Methods of Protein Production Using Anti-Senescence Compounds CROSS REFERENCE TO RELATED APPLICATIONS This application is copending with, shares at least one common inventor with, and claims priority to United States provisional patent application number 60/913,382, filed April 23,2007, the contents of which are hereby incorporated by reference in their entirety. BACKGROUND OF INVENTION This disclosure relates generally to the production of proteins in mammalian cell cultures. Particularly this disclosure relates to culturing mammalian cells in the presence of an anti-senescence compound, e.g. camosine, to maintain viability and increase productivity with superior quality. Culturing cells has produced many protein products. These products, such as hybridoma-produced monoclonal antibodies, can be used for therapeutic, research or other applications. Animal cells, notably mammalian cells, are often used to produce proteins. Unfortunately, using animal celts causes the production process to be time consuming and costly. Adding a chemical agent to a cell culture medium can increase cell productivity by inducing cells to produce a product, thereby increasing overall yield. The optimal agent to use varies depending on a nun4)er of Actors, including the desired protein product and cell type. Similar factors also affect the amount of the chosen agent added and when the agent is added to the cell culture medium. Examples of agents are alkanoic acids or salts, urea derivatives, or dimethylsulphoxide (DMSO). Chemical agents, such as sodium butyrate, can have diverse effects on protein production. The addition of an agent can increase the specific productivity of the cells, but also have cytotoxic effects and can inhibit cell grovy^ and viability. As cells produce a protein, typically, the protein is secreted into the cell culture medium. The specific protein, however, is not the only matter in the medium; high molecular weight aggregates, acidic species, and other materials are also often in the medium, which can make the process of purification more laborious and costly. Techniques and methods are available to improve product quality, enabling more efficient protein purification; including, among others, altering the conditions of the bioreactor or using a different cell line, l-lowever, there nevertheless remains a need in the field for protein production techniques and methods that lead to improved purification processes. Therelbre, what is needed is a chemical agent that is added to the cell culture medium that can enhance the expression of a protein of interest while maintaining high cell viability. What is further needed is an agent that increases the product quality of the protein by decreasing the amount of high molecular weight aggregates and acidic species in the ceil culture medium. SUMMARY OF THE INVENTION In certain embodiments, the present disclosure relates to a process for enhanced production of a protein product. For example, in certain embodiments, the present invention provides methods of culturing host cells expressing a protein of interest in a medium comprising an anti-senescence compound such that overall production of the protein of interest is enhanced. In certain embodiments, such an anti-senescence compound comprises camosine. In certain embodiments, the present invention provides compositions that enhance production of a protein of interest. Any of a variety of proteins may be produced in accordance with the methods and compositions of the present invention. For example, in certain embodiments, methods and compositions of the present invention are used to produce an antibody, in certain embodiments, methods and compositions of the present invention are used to produce a receptor, optionally linked to one or more additional protein moieties. For example, methods and compositions of the present invention may be used to produce a TNFR fusion protein. In certain embodiments, the present invention provides a cell culture medium comprising an anti-senescence compound that enhances production of a protein of interest expressed in a host cell. In certain embodiments, such an anti-senescence compound comprises camosine. In certain emtxxliments, genetically manipulated host cells are combined with an inoculum medium to form a cell culture medium, which is grown in a bioreactor. During a production run of the desired protein product, conditions of the bioreactor may be altered and/or supplements may be added in order to increase the productivity and/or maintain viability. Supplements may include a feed medium and/or one or more additives such as in the instant disclosure, camosine and/or other anti-senescence compounds. Mammalian host cells, for example, Chinese hamster ovary (CHO) cells, can experience a reductbn in viability nearing the end of a production run in a bioreactor. It has been discovered that the additbn of an anti-senescence agent, such as camosine and analogs thereof, to a cell culture medium helps maintain a higher viable cell number and cell viability until the protein is harvested. In addition, methods for increasing productivity, such as altering the temperature after the growth phase and/or during the production phase of the production run may be used in accordance with the present invention. To give but one example, during the production of a protein product, specifically the antibody for growth differentiation factor-d (GDF-8), the temperature was shifted downwards to help initiate and increase the productivity. In certain embodiments, addition of an anti-senescence compound such as camosine helps increase the productivity of the cell culture. In certain embodiments, an anti-senescence compound may be added before, during and/or after such a temperature shift. It has also been discovered that the addition of an anti-senescence compound such as camosine to a cell culture medium increases the overall quality of protein product. During the production of the protein, high molecular weight aggregates, along with other unwanted species, are in the cell culture medium. The addition of camosine decreases the amount of high molecular aggregates and increases product quality. In certain embodiments, addition of an anti-senescence compound other than camosine decreases accumulatbn of such high molecular weight aggregates and improves product quality. In certain embodiments, camosine is added in combination with one or more additional anti-senescence compounds. The concentration of anti-senescence compound (e.g., camosine) added to the cell culture medium can vary depending on many Actors of the process, including, for example, the cell type, the desired product, and the conditions of the bioreactor, among others. Also, camosine can be substituted with its analogues; acetyl-camosine, homo-camosine, anserine, and beta-alanine. In certain embodiments, camosine is provided in combination with one or more other anti-senescence compounds. In certain embodiments, the concentration of anti-senescence agent (e.g., camosine) in a cell culture medium is about 5 mM to about 100 mM. In certain embodiments, the concentration is about 10 mM to about 40 mM. In certain embodiments, the concentration is about 20 mM. Any suitable culture procedures and inoculum medium may be used to culture the cells in the process of protein production. Both serum and serum li"ee media may be used. In addition, cultunng methods may be used to culture the cells as appropriate for the specific cell type and protein product. Such procedures are known and understood by those of ordinary skill in the cell culture art. Other features and advantages of the disclosure will be apparent finom the following descriptton, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure la. Effect of Camosine on Acklic Peaks for MYO-29. :   Figure 1 b. Effect of Camosine on High Molecular Weight Aggregates. Figure 1c. Effect of Camosine Additions on Different Days on Acidic Peaks. j   Figure Id. Effect of Camosine Additions on Different Days on High Molecular Weight Aggregates. Figure 2a. Effect of Camosine on Daily Viable Cell Density. Figure 2b. Effect of Camosine on Daily Cell Viability. Figure 2c. Effect of Camosine on Daily Titer. Figure 2d. Effect of Camosine on Cumulative Specific Cellular Productivity. The bars on days 12 and 14 represent, from left to right: Control A D10 Feed, 20 mM Camosine D10 Feed, Control B D10 Feed, 20 mM Camosine (No D10 Feed), and Control C (No D10 Feed). Figure 2e. Effect of Camosine on High Molecular Weight Aggregates. The bars on days 12 and 14 represent, from left to right: Control A D10 Feed, 20 mM Camosine D10 Feed, Control B D10 Feed, 20 rvM Camosine (No D10 Feed), and Control C (No D10 Feed). Figure 3a. Effect of Different Concentrations of Camosine on Viable Cell Density. Figure 3b. Effect of Different Concentrations of Camosine on Daily Cell Viability. Figure 3c. Effect of Different Concentrations of Camosine on Daily Titer. Figure 3d. Effect of Different Concentrations of Camosine on Cumulative Specific Cellular Productivity. The bars represent, from left to right: Control P2. Control P5, 20 mM Camosine, and 40 mM Camosine. Figure 3e. Effect of Different Concentrations of Camosine on High Molecular Weight Aggregates. The bars represent, from left to right: Control P2, Control P5, 20 mM Camosine, and 40 mM Camosine. Figure 4. Viable Cell Density Profiles of a Chinese Hamster Ovary (CHO) Cell Line Producing Recombinant TNFR Fusion Protein Grown in Media Containing or Lacking Camosine. The Control Condition is the Average of 4 Control Bioreactor Runs. Figure 5. Cell Viability Profiles of a Chinese Hamster Ovary (CHO) Cell Line Producing Recombinant TNFR Fusion Protein Grown in Media Containing or Lacking Camosine. The Control Condition is the Average of 4 Control Bioreactor Runs. Figure 6. Effect of Camosine on the Percentage of Aggregated/Misfolded TNFR Fusion Protein. The Control Condition is the Average of 4 Control Bioreactor Runs. Figure 7. Effect of Camosine on the Percentage of High Molecular Weight (HMW) Aggregates Produced by a Chinese Hamster Ovary (CHO) Cell Line Producing Recombinant TNFR Fusion Protein. The Control Condition is the Average of 4 Control Bioreactor Runs. Figure 8. Product Titer Profiles of a Chinese Hamster Ovary (CHO) Cell Line Producing Recombinant TNFR Fusion Protein Grown in Media Containing or Lacking Camosine. The Control Condition Is the Average of 4 Control Bioreactor Runs. Figure 9. Specific Cellular Productivity Profiles of a Chinese Hamster Ovary (CHO) Cell Line Producing Recombinant TNFR Fuskjn Protein Grown in Media Containing or Lacking Camosine. The Control Condition is the Average of 4 Control Bioreactor Runs. Figure 10. Total Sialylafion Profiles, Expressed as a Percentage of the Reference Material, of Recombinant TNFR Fusion Protein Produced by a Chinese Hamster Ovary (CHO) Ceil Line Grown in Media Containing or Lacking Camosine. The Control Condition is the Average of 4 Control Bioreactor Runs. Figure 11. Distributbn of Sialylated N-linked Oligosaccharides, Expressed as a Percentage of Total N-Linked Oligosaccharides, of Recombinant TNFR Fusion Protein Produced by a Chinese Hamster Ovary (CHO) Cell Line Grown in Media Containing or Lacking Camosine. The Control Condition is the Average of 4 Control Bioreactor Runs. DEFINITIONS Following long-standing convention, the temns "a" and "an" mean "one or more" when used in this application, including the claims. Even though the invention has been described with a certain degree of particularity, it is evident that many alternatives, modrficatbns, and variations will be apparent to those skilled in the art in light of the disclosure. Accordingly, it is intended that all such alternatives, nxxlifications, and variations, which fall within the spirit and scope of the invention, be embraced by the defined claims. The term "anti-senescence compound" as used herein refers to any agent or compound that, when added to a cell culture, promotes viability, growth, and/or lifespan of a cell grown therein. In certain emtxxJiments, use of such an anti-senescence compound in cell culture results in increased titer, increased cell specific productivity, inaeased cell viability, increased integrated viable cell density, decreased accumulation of high molecular weight aggregates, and/or decreased accumulation of acidic species than would be observed under othenvise identical culture conditions that lack the anti-senescence compound. Non-limiting examples of anti-senescence compounds that may be used in accordance with methods and compositons of the present invention include camosine, acetyl-camosine, homo-camosine, anserine, and t>eta-alanine. In certain embodiments, two or more anti-senescence compounds may be used in accordance with compositions and methods of the present invention. The phrase "host cell" refers to cells which are capable of being genetically manipulated and/or are capable of growth and survival in a cell culture medium. Typically, the cells can express a large quantity of an endogenous or heterologous protein of interest and can either retain the protein or secrete it into the cell culture medium Host cells are typically "mammalian cells," which comprise the nonlimiting examples of vertebrate cells, including baby hamster kidney (BHK), Chinese hamster ovary (CHO), human kkJney (293), nomial fetal rhesus diploid (FRhL-2), and murine myeloma (e.g., SP2/0 and NSO) cells. One of ordinary skill in the art will be aware of other host cells that may be used in accordance with methods and compositions of the present invention. The term "cell culture medium" refers to a solution containing nutrients to support cell survival under conditions in which cells can grow and produce a desired protein. The phrases "inoculation medium" or "inoculum medium" refer to a solution or sut)stance containing nutrients in which a culture of cells is initiated. In certain embodiments a "feed medium" contains similar nutrients as the inoculation medium, but is a solution or substance with which the cells are fed after initiatk)n of the culture. In certain embodiments, a feed medium contains one or more components not present in an inoculation medium. In certain embodiments, a feed medium lacks one or more components present in an inoculation medium. A person of ordinary skill in the cell culture art will know without undue experimentation what components make-up the inoculation and feed mediums. Typically, these solutions provkJe essential and non-essential amino ackJs, vitamins, energy sources, lipids, and trace elements required by a cell for growth and survival. In certain embodiments, an inoculation medium, a feed medium or both comprise an anti-senescence compound. The term "cell culture characteristic" as used herein refers to an observable and/or measurable characteristic of a cell culture. Methods and compositions of the present invention are advantageously used to improve one or more cell culture characteristics. In certain embodiments, improvement of a cell culture characteristic comprises increasing the magnitude of a cell culture characteristic. In certain embodiments, improvement of a cell culture characteristic comprises decreasing the magnitude of a cell culture characteristic. As non-limiting examples, a cell culture characteristic may be titer, cell specific productivity, cell viability, integrated viable cell density, accumulation of high molecular weight aggregates, and/or accumulation of acidic species. One of ordinary skill in the art will be aware of other cell culture characteristics that may be improved using methods and compositions of the present invention. The term "defined medium" as used herein refers to a medium in which the composition of the medium is both known and controlled. Defined media do not contain complex additives such as serum or hydroiysates that contain unknown and/or uncontrolled components. The term "complex medium" as used herein refers to a medium that contains at least one component whose identity or quantity is either unknown or uncontrolled. The phrase "cell line" refers to, generally, primary host cells that express a protein of interest. In some embodiments, the cells have been transfected with exogenous DNA coding for a desired protein and/or containing control sequences that activate expression of linked sequences, whether endogenous or heterologous. In certain embodiments, cells derived finom such genetically modified cells form a cell line and are placed in a cell culture medium to grow and produce the protein product. In certain embodiments, a cell line comprises primary host cells that have not been transfected with exogenous DNA and express an endogenous protein of interest. The "growth phase" of a cell culture medium refers to the period when the cells are undergoing rapid divisron and growing exponentially, or close to exponentially. Typically, cells are cultured in conditions optimized for cell growth for generally 1-4 days. Growth phase conditions may include a temperature at about ZS"C to 42*C, generally about ZJ"C. The length of the growth phase and the culture conditions in the growth phase can vary but are generally known to a person of ordinary skill in the cell culture art. In certain embodiments, a cell culture medium in a growth phase is supplemented with a feed medium. The transitkjn phase" occurs during the period when the cell culture medium is being shifted from conditions consistent with the growth phase to conditions consistent with the production phase. During the transition phase, factors like temperature, among others, are often changed. In certain embodiments, a cell culture medium in a transition phase is supplemented with a feed medium. The "production phase" occurs after both the growth phase and the transition phase. The exponential growth of the cells has ended and protein production is the principal otjjective. The cell culture medium can be supplemented to initiate production. In certain emtx)diments, a cell culture medium in a production phase is supplemented with a feed medium. In addition, the temperature of the cell culture medium during the productbn phase may be lower, generally, than during the growth phase, which typically encourages production. The production phase continues until a desired endpoint is achieved. The phrase "viable cell density" refers to the total number of cells that are sun/iving in the cell culture medium in a particular volume, generally per ml. The phrase "cell viability" refers to number of cells, which are alive compared to the total number of cells, both dead and alive, expressed as a percentage. Integrated Viable Cell Density", "IVCD": The terms "integrated viable cell density" or IVCD" as used herein refer to the average density of viable cells over the course of the culture multiplied by the amount of time the culture has run. When the amount of protein produced is proportional to the number of viable cells present over the course of the culture, integrated viable cell density is a useful tool for estimating the amount of protein produced over the course of the culture. The temi "high molecular weight aggregates" refers to generally mis-folded proteins or an improper association of at least two polypeptides. The association may arise by any method including, but not limited to, covalent, non-covalent, disulfide, or nonreducible cross linking, in certain embodiments, methods and compositions of the present invention are advantageously utilized to reduce the accumulation of high molecular weight aggregates. The phrase "antbxidant" refers to a compound that can prevent oxidative damage to lipids, proteins, DNA and other essential macromolecules by blocking free radicals. "Therapeutic protein": A "therapeutic protein" is a protein or peptide that has a bnlogical effect on a region in the body on which it acts or on a region of the txxjy on which it remotely acts via intermediates. A therapeutic protein can be, for example, a secreted protein, such as, an antibody, an antigen-binding fragment of an antibody, a soluble receptor, a receptor fusion, a cytokine, a growth factor, an enzyme, or a clotting factor, as described in more detail herein below. The above list of proteins is merely exemplary in nature, and is not intended to be a limiting recitation. One of ordinary skill in the art will understand that any protein may be used in accordance with the present invention and will be able to select the particular protein to be produced based as needed. As used in the specification, the terms polypeptide, protein and peptide are synonymous and are used interchangeably. Accordingly, as used herein, the size of a protein, peptide or polypeptide generally comprises more than 2 amino acids. For example, a protein, peptide or polypeptide can comprise from about 2 to about 20 amino acids, fix>m about 20 to about 40 amino acids, from about 40 to about 100 amino acids, from about 100 amino acids to about 200 amino acids, from about 200 amino acids to about 300 amino acids, and so on. As used herein, an amino acid refers to any naturally occurring amino acid, any amino acid derivative or any amino acid mimic known in the art. In certain embodiments, the residues of the protein or peptide are sequential, without any non-amino acid intenrupting the sequence of amino acid residues. In other embodiments, the sequence may comprise one or more non-amino acid moieties. In particular embodiments, the sequence of residues of the prote^ or peptide may be interrupted by one or more non-amino acid moieties. "Antibody": The term "antibody" is used to refer to any antibody-like molecule that has an antigen binding region, and includes antibody fragments such as Fab", Fab, F(ab").sub.2, single domain antitxxjies (DABs), Fv, scFv (single chain Fv), and the like. Techniques for preparing and using various antibody-based constructs and fragments are well known in the art. Means for preparing and characterizing antitxxlies are also well known in the art (See, e.g., Hariow and Lane, Antibodies: A Laboratory Manual, Cold Spring Hart)or Laboratory, 1988; incorporated herein by reference). For example, an antibody can include at least one, and preferably two full-length heavy chains, and at least one, and preferably two light chains. The term "antibody" as used herein includes an antibody fragment or a variant molecule such as an antigen-binding fi^gment (e.g., an Fab, F(ab")2, Fv, a single chain Fv fragment, a heavy chain fragment (e.g., a camelid VHH) and a binding domain-immunoglobuiin fusion (e.g., SMIP™). The antibody can be a monoclonal or single-specificity antibody. The antibody can also be a human, humanized, chimeric, CDR-grafted, or in vitro generated antibody. In yet other embodiments, the antibody has a heavy chain constant region chosen from, e.g., lgG1, lgG2, lgG3, or lgG4. In another embodiment, the antibody has a light chain chosen from, e.g., kappa or lambda. In one embodiment, the constant region is altered, e.g., mutated, to modify the properties of the antibody (e.g., to increase or decrease one or more of: Fc receptor binding, antibody glycosylation, the number of cysteine residues, effector cell function, or complement function). Typically, the antibody specifically binds to a predetermined antigen, e.g., an antigen associated with a disorder, e.g., a neurodegenerative, metabolic, inflammatory, autoimmune and/or a malignant disorder. Small Modular ImmunoPharmaceuticals (SMIP™) provide an example of a variant molecule comprising a binding domain polypeptide. SMIPs and their uses and applications are disclosed in, e.g., U.S. Published Patent Application. Nos. 2003/0118592, 2003/0133939, 2004/0058445, 2005/0136049, 2005/0175614, 2005/0180970. 2005/0186216, 2005/0202012, 2005/0202023, 2005/0202028, 2005/0202534, and 2005/0238646, and related patent family members thereof, all of which are hereby incoqwrated by reference herein in their entireties. Single domain antibodies can include antibodies whose complementary determining regions are part of a single domain polypeptide. Examples include, but are not limited to, heavy chain antibodies, antitxxjies naturally devoid of light chains, single domain antibodies derived from conventional 4-chain antibodies, engineered antitxxJies and single domain scaffolds other than those derived from antibodies. Single domain antibodies may be any of the art, or any future single domain antibodies. Single domain antibodies may be derived from any species including, but not limited to mouse, human, camel, llama, goat, rabbit, bovine. According to one aspect of the invention, a single domain antitxxJy as used herein is a naturally occurring single domain antibody known as heavy chain antibody devoid of light chains. Such single domain antibodies are disclosed in WO 9404678 for example. For clarity reasons, this variable domain derived from a heavy chain antitxxJy naturally devoid of light chain is known herein as a VHH or nanotxxjy to distinguish it from the conventional VH of four chain immunoglobulins. Such a VHH molecule can be derived from antibodies raised in Camelidae species, for example in camel, llama, dromedary, alpaca and guanaco. Other species besides CamelkJae may produce heavy chain antibodies naturally devoid of light chain; such VHHs are within the scope of the invention. Examples of binding fragments encompassed within the term "antigen-binding fragmenf of an antibody include (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL and CH1 domains; (ii) a F(ab")2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VH and CH1 domains; (iv) a Fv fragment consisting of the VL and VH domains of a single arm of an antibody, (v) a dAb fragment, which consists of a VH domain; (vi) a camelid or camelized variable domain, e.g., a VHH domain; (vii) a single chain Fv (scFv); (viii) a bispecific antibody; and (ix) one or more fragments of an immunoglobulin molecule fused to an Fc region. Furthemiore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regons pair to form monovalent molecules (known as single chain Fv (scFv); see, e.g.. Bird et al. (1988) Science 242:423-26; Huston et al. (1988) Proc. Natl. Acad. Sci. U.S.A. 85:5879-83). Such single chain antibodies are also intended to t>e encompassed within the term "antigen-binding firagmenf of an antibody. These antibody fragments are obtained using conventional techniques known to those skilled in the art, and the fragments are evaluated for function in the same manner as are intact antibodies. Other than "bispecific" or "bifunctional" antibodies, an antibody is understood to have each of its binding sites identical. A "bispecific" or "bifunctonal antibody" is an artificial hybrid antibody having two different heavy/light chain pairs and two different binding sites. Bispecific antibodies can be produced by a variety of methods including fusion of hybridomas or linking of Fab" fragments. See, e.g., Songsivilai & Lachmann, Clin. Exp. Immunol. 79:315-321 (1990); Kostelny et al., J. Immunol. 148,1547-1553 (1992). The phrase "bioreactor" refers to a vessel in which a cell culture medium can be contained and internal conditions of which can be controlled during the culturing period, e.g., pH and temperature. A fed batch culture" refers to a method of culturing cells in which cells are first inoculated in a bk)reactor with an inoculum medium. The cell culture medium is then supplemented at one or more points throughout the production run with a feed medium containing nutritional components and/or other supplements. A "batch culture" refers to a method of culturing cells in which cells are inoculated in a bioreactor with all the necessary nutrients and supplements for the entirety of the production run. No nutrient additions are made to the cell culture medium throughout the duration of the production. A "perfusion culture" refers to a method of culturing cells that is different from a batch or fed-batch culture method, in which the culture is not terminated, or is not necessarily terminated, prior to isolating and/or purifying an expressed protein of interest, and in which new nutrients and other components are periodically or continuously added to the culture, during which the expressed protein is periodically or continuously harvested. The composition of the added nutrients may be changed during the course of the cell culture, depending on the needs of the cells, the requirements for optimal protein production, and/or any of a variety of other factors known to those of ordinary skill in the art. The phrase "expression" refers to the transcription and the translatton that occurs within a host cell. The level of expression relates, generally, to the amount of protein being produced by the host cell. "Cell specific productivity", and the like, refer to the specific, as in per cell, product expression rate. The cell specific productivity is generally measured in micrograms of protein produc»d per 10® cells per day or in picograms of protein produced per 10® cells per day. The tenn "titer" as used herein refers to the total amount of recombinantly expressed protein produced by a cell culture in a given amount of medium volume. Titer is typically expressed in units of milligrams or micrograms of protein per milliliter of medium. One of skill in the art will recognize that the methods disclosed herein may be used to culture many of the well-known mammalian cells routinely used and cultured in the art, i.e., the methods disclosed herein are not limited to use with only the instant disclosure. DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION It has been discovered that using an anti-senescence compound such as camosine modifies the viability and productivity of a cell culture. For example, addition of camosine maintains cell viability, and improves productivity of cells, and improves product quality of the desired protein product. Camosine is an antioxidant and an anti-senescence compound that is also a naturally occun-ing dipeptide present at high levels (up to 20 mM) in musde and nerve tissues in animals. Being an antioxidant, camosine also is a free radical scavenger and glycatlon inhibitor. Generally, camosine transforms reactive species into non-reactive species thereby protecting proteins, DNA, and other essential macromdecules. As an anti-senescence compound, camosine can extend the lifespan of human diploid fibroblasts and human fetal lung (primary cell lines) at a concentration of 20 mM in culture media. The present invention encompasses the surprising finding that it is advantageous to use an anti-senescence compound (including, but not limited to. camosine) in cell culture to produce a protein of interest. In certain emtxxjiments, using such an anti-senescence compound in cell culture to produce a protein of interest results in one or more improved cell culture characteristics including, but not limited to, increased titer, increased cell specific productivity, increased cell viability, increased integrated viable cell density, decreased accumulation of high molecular weight aggregates, and/or decreased accumulation of acidic species. It has been demonstrated that camosine is cytotoxic to human or rodent transformed and neoplastic cells in Minimal Essential Medium (MEM, Sigma), which has lower glucose levels, but not in Dulbecco"s Modified Eagle"s Medium (DMEM, Sigma), which contains ImM pyruvate. (Holliday et al. Biochemistry (Moscow), 65:843-848,846). In addition, dialyzed fetal calf seaim with low molecular weight compounds removed increased the cytotoxic effects of camosine. Id. It was also determined that 1mM oxaloacetate and 1 mM of o-ketoglutarate had comparable effects as pyruvate, neither of which are components of the inoculum or feed mediums used with the camosine examples. Id. Sodium pyruvate, however, is an original component in the inoculum medium at a concentration of 0.5 mM, not for camosine additions but rather to better mimic in vivo conditions in a bioreactor system and as a potential altemate energy source. The inoculum medium is also semm free, which would imply that camosine would have cytotoxic effects. According to the reference, the addition of camosine to a cell culture medium would have similar cytotoxic effects as seen in the MEM medium in Holliday. By utilizing methods and/or compositions of the present invention, such cytotoxicity is reduced or eliminated and cell viability and protein production are improved. In certain embodiments, camosine is provided in a cell culture medium at a concentration of between about 5 mM and about 100 mM. In certain emtxxliments, camosine is provided in a cell culture medium at a concentration of about 10 mM to about 40 mM, for example at a concentration of about 20 mM. In certain embodiments, camosine is provided in a cell culture medium at a concentration of about 5,6, 7, 8, 9,10,11,12,13. 14,15, 16,17,18,19. 20, 21, 22. 23, 24, 25, 26, 27, 28, 29, 30, 31. 32, 33, 34, 35, 36, 37, 38, 39, 40.41, 42, 43, 44, 45,46. 47,48. 49, 50, 55, 60. 65, 70. 75. 80, 85, 90, 95.100 mM. or higher. In certain embodiments, such concentrations of camosine are achieved in cell culture by adding camosine at multiple times during the cell culture process, for example, in one or more feed media. The concentration of camosine utilized depends on the cell culture medium and the cell line being used, among other factors, including the desired effiects being sought on the cell line or product. Analogs of camosine, e.g. acetyl-camosine, homo-camosine, anserine, and t)eta-alanine, may also be provided in a cell culture medium for a similar effect. One or more of these analogs may be provided in a cell culture medium. In certain embodiments, such analogs are provided in a cell culture medium that lacks camosine. In certain embodiments, such analogs are provided in a cell culture medium in combination with camosine. In certain embodiments, such analogs are providedataconcentrationofabout5,6,7, 8,9,10.11,12,13,14,15,16,17,18,19, 20, 21. 22, 23. 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39. 40. 41. 42,43, 44, 45, 46,47.48, 49, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,100 mM, or higher. In certain embodiments, in order to produce a protein of interest, initially, host cells are transfected or transformed with exogenous DNA coding for a protein to supply transformed cells, which constitutively produce the desired protein product. In certain embodiments, a nucleic acid molecule introduced into the cell encodes the protein desired to be expressed according to the present invention. In certain embodiments, a nucleic acid molecule contains a regulatory sequence or encodes a gene product that induces or enhances the expression of the desired protein by the cell. As a non-limiting example. such a gene product may be a transcription factor that increases expression of the protein of interest. In certain embodiments, a nucleic acid that directs expression of a protein is stably introduced into the host cell. In certain embodiments, a nucleic acid that directs expressbn of a protein is transiently introduced into the host cell. One of ordinary skill in the art will be able to choose whether to stably or transiently introduce the nucleic acid into the cell based on experimental, commercial or other needs. A gene encoding a protein of interest may optionally be linked to one or more regulatory genetic control elements. In some embodiments, a genetk; control element directs constitutive expression of the protein. In some embodiments, a genetic control element that provkles inducible expression of a gene encoding the protein of interest can be used. Use of an inducible genetk; control element (e.g., an inducible promoter) allows for modulation of the prxxJuction of the protein in the cell. Non-limiting examples of potentially useful inducible genetic control elements for use in eukaryotic cells include hormone- regulated elements (see e.g., Mader, S. and White, J.H., Proc. Natl. Acad. Sci. USA 90:5603-5607,1993), synthetic ligand-regulated elements (see, e.g. Spencer, D.M. et al.. Science 262:1019-1024,1993) and ionizing radiation-regulated elements (see e.g., Manome, Y. et al.. Biochemistry 32:10607-10613,1993; Datta, R. et al., Proc. Natl. Acad. Sci. USA 89:10149-10153,1992). Additkinal cell-specific or other regulatory systems known in the art may be used in accordance with methods and compositions described herein. Any host cell susceptible to cell culture, and to expressk)n of proteins, may be utilized in accordance with the present invention. Tlie host cells are generally mammalian cells, more particularly animal cells, such as Chinese hamster ovary (CHO) cells. Other non-limiting examples of mammalian cells that may be used in accordance with the present invention include BALB/c mouse myekama line (NSO/I, ECACC No: 85110503); human retinoWasts (PER.C6 (CnjCell, Leiden, The Netherlands)); monkey kidney CV1 line transfonmed by SV40 (COS-7, ATCC CRL 1651); human embryonic kidney line (293 or 293 cells subcloned for growth in suspensk>n culture, Graham et al., J. Gen Virol., 36:59 (1977)); baby hamster kidney cells (BHK, ATCC CCL 10); Chinese hamster ovary cells +/-DHFR (CHO, Uriaub and Chasin. Proc. Natl. Acad. Sci. USA, 77:4216 (1980)); mouse Sertoli cells (TM4, Mather, Btol. Reprod., 23:243-251 (1980)); monkey kidney cells (CV1 ATCC CCL 70); Atirican green monkey kidney cells (VERO-76, ATCC CRL-1 587); human cervical carcinoma cells (HeLa, ATCC CCL 2); canine kidney cells (MDCK, ATCC CCL 34); buffalo rat liver cells (BRL 3A. ATCC CRL 1442); human lung cells (W138. ATCC CCL 75); human liver cells (Hep G2, HB 8065); mouse mammary tumor (MMT 060562, ATCC CCL51); TRI cells (Mather et al.. Annals N.Y. Acad. Sci.. 383:44-68 (1982)); MRC 5 cells; FS4 cells; and a human hepatoma line (Hep G2). Polvoeotides Any polypeptkje that is expressible in a host cell may be produced in accordance with the present invention. The polypeptide may be expressed from a gene that is endogenous to the host cell, or from a heterologous gene that is introduced into the host cell. The polypeptkje may be one that occurs in nature, or may alternatively have a sequence that was engineered or selected by the hand of man. A polypeptide to be produced according to the present inventk}n may be assembled from polypeptkje fragments that individually occur in nature. Additionally or alternatively, the engineered polypeptide may include one or more fragments that are not naturally occurring. Proteins or peptides may be made by any technique loiown to those of skill in the art, including the expression of proteins, polypeptides or peptides through standard molecular bblogical techniques, the isolation of proteins or peptides from natural sources, or the chemical synthesis of proteins or peptides. The coding regions for known genes may be amplified and/or expressed using the techniques disclosed herein or as would be known to those of ordinary skill in the art. Alternatively, various commercial preparations of proteins, polypeptides and peptides are known to those of skill in the art. :   Therapeutic proteins that may desirably be expressed in accordance with the present invention will often be selected on the basis of an interesting or useful biological or chemical activity. For example, the present invention may be employed to express any pharmaceutrcally or commercially relevant enzyme, clotting factor, receptor, antibody, hormone, regulatory factor, antigen, binding agent, etc. The following list of therapeutic proteins that can be produced according to the present invention is merely exemplary in nature, and is not intended to be a limiting recitation. One of ordinary skill in the art will understand that any polypeptide may be expressed in accordance with the present invention and will be able to select the particular polypeptkje to be produced based on his or her particular needs. Fusion Proteins Fusion proteins generally have all or a substantial portion of a targeting peptide, linked at the N- or C-terminus, to all or a portbn of a second polypeptide or protein. For example, fusions may employ leader sequences from other species to pemnit the recombinant expression of a protein in a heterologous host. Another useful fusion includes the addition of an immunologically active domain, such as an antibody epitope, to facilitate purification of the fusion protein. A fusion protein can include a targeting nwiety, e.g., a soluble receptor fragment or a I"lgand, and an immunoglobulin chain, an Fc fragment, a heavy chain constant regions of the various isotypes, including for example: lgG1, lgG2, lgG3, lgG4, IgM, lgA1, lgA2, IgO, and IgE. For example, the fusion protein can include the extracellular domain of a receptor, and, e.g., fused to, a human immunoglobulin Fc chain (e.g., human lgG1 or human lgG4, or a mutated form thereof). In one embodiment, the human Fc sequence has been mutated at one or more amino acids, e.g., mutated at residues 254 and 257 from the wild type sequence to reduce Fc receptor binding. The fusion proteins may additionally include a linker sequence joining the first moiety to the second moiety, e.g., the immunoglobulin fragment. For example, the fusion protein can include a peptide linker, e.g., a peptide linker of about 4 to 20, more preferably, 5 to 10, amino ackjs in length; in certain embodiments, the peptkje linker is 8 amino ackds in length. For example, the fusion protein can include a peptide linker having the formula (Ser-Gly-Gly-Gly-Gly)y wherein y is 1, 2, 3,4, 5. 6,7, or 8. In other embodiments, additional amino ackj sequences can be added to the N- or C-temiinus of the fusion protein to facilitate expression, steric flexibility, detection and/or isolation or purification. Inclusion of a cleavage site at or near the fusion junctnn will facilitate removal of the extraneous polypeptkJe after purificatKtn. Other useful fusons include linking of functional domains, such as active sites from enzymes, glycosylation domains, cellular targeting signals or transmembrane regions. Examples of proteins or peptides that may be incorporated into a fusion protein include cytostatic proteins, cytocidal proteins, pro-apoptosis agents, anti-angiogenic agents, hormones, cytokines, growth factors, peptide doigs, antibodies, Fab fragments antibodies, antigens, receptor proteins, enzymes, lectins, MHC proteins, cell adhesion proteins and binding proteins. Methods of generating fusion proteins are well known to those of skill in the art. Such proteins can be produced, for example, by chemical attachment using bifunctional cross-linking reagents, by de novo synthesis of the complete fuson protein, or by attachment of a DNA sequence encoding the targeting peptkle to a DNA sequence encoding the second peptide or protein, followed by expression of the intact fliskjn protein. Antibodies Antitxjdies are proteins that have the ability to specifically bind a particular antigen. Given the large number of antibodies currently in use or under investigation as pharmaceutrcal or other commercial agents, production of antibodies in accordance with the present inventton is of particular interest. For example, the present invention may be used to produce antibodies in a cell culture wherein the misfolding and/or aggregatbn of the produced antibodies are reduced. [00t}2)   In certain embodiments, methods and/or compositions of the present invention are emptoyed to produce an antibody against growth differentiation factor-8 (GDF-6). Nonlimiting examples of GDF-8 antibodies include Myo29, Myo28, and Myo22. In certain embodiments, GDF-8 antibodies produced in accordance with the present teachings are produced in the form of human IgG isotopes. In certain embodiments, methods and/or compositions of the present invention are employed to produce a MY02g antibody such as described in international patent application, publication number WO 2004/037861, entitled Neutralizing Antibodies Against GDF-8 and Uses Thereof, incorporated herein by reference in its entirety. Other representative commercially available therapeutic proteins that can be produced in accordance with the present invention include, for example, AVASTIN [Bevacizumab], CAMPATH [Alemtuzumab], ERBITUX [Cetuximab], HERCEPTIN [TRASTUZUMAB], HUMIRA [Adalimumabl, LUCENTIS [Ranibizumab], MYLOTARG feemtuzumab ozogamicin], MYCSCINT [Imicromab Penetate], PROSTASCINT [Capromab Pendetide], RAPTIVA [Efalizumab], REMiCADE [infliximab], REOPRO [Abciximab], RITUXAN [Rituximab], SIMULECST [Basilximab], SOLIRIS [Eculizumab], SYNAGIS [Palivizumab], TYSABRI [Natalizumab], VECTIBIX [Panitumumab], VERLUMA [Nofetumomab], XOLAIR [Omalizumab], ZANAPAX [Dadizumab], ZEVALIN [Ibritumomab Tiuxetan], etc. In certain embodiments, the monoclonal, chimeric, or humanized antibodies described above contain amino acid residues that do not naturally occur in any antibody in any species in nature. These foreign residues can be utilized, for example, to confer novel or modified specificity, affinity or effector function on the monoclonal, chimeric or humanized antibody. Clotting Factors Clotting factors have been shown to be effective as phanmaceutical and/or commercial agents. Hemophilia B is a disorder in which the blood of the sufferer is unable to clot. Thus, any small wound that results in bleeding is potentially a life-threatening event. Given the importance of recombinant clotting factors in the treatment of diseases such as hemophilia, production of clotting factors in accordance with the present invention is of particular interest. In certain embodiments, the present invention may be used to produce dotting factors in a cell culture wherein the misfolding and/or aggregation of the produced clotting factors are reduced. For example, Coagulation Factor IX (Factor IX or "FIX") is a single-chain glycoprotein whose deficiency results in Henrx)philia B. FIX is synthesized as a single chain zymogen that can be activated to a two-chain serine protease (Factor IXa) by release of an activation peptide. The catalytic domain of Factor IXa is located in the heavy chain (see Chang et al., J. Clin. Invest., 100:4,1997, incorporated herein by reference in its entirety). Other clotting factors that can t>e produced in accordance with the present invention include tissue factor, and von Willebrands factor and/or commercially available blood-dotting Actors. Representative commerdally available blood-clotting factors that can be produced in accordance with the present invention include, for example, ALTEPLASE [Tissue Plasminogen Activator; t-PA], BENEFIX [Factor IX]. HEMOFIL [Antihemophilic Factor; Factor XIII], RECOMBINATE (Recombinant Antihemophiliac Factor), etc. Enzymes Another class of polypeptides that have been shown to be effective as pharmaceutical and/or commercial agents and that can desirably be produced according to the teachings of the present invention includes enzymes. Given the importance of recombinant enzymes in the treatment of diseases and other commercial and pharmaceutical uses, production of enzymes in accordance with the present invention is of particular interest. For example, the present invention may be used to produce enzymes in a cell culture wherein the misfolding and/or aggregation of the produced enzymes are reduced. Representative commercially available enzymes that can be produced in accordance with the present invention include, for example, ACTIVASE [Recombinant alteplase], CEREDASE [Ajglucerase], CERE2YME [Imiglucerase], PULMOZYME [DNase], etc. Growth Factors and Other Signaling Molecules Another class of polypeptides that have been shown to be effective as pharmaceutical and/or commercial agents and that can desirably be produced according to the teachings of the present invention includes growth factors and other signaling molecules. Growth factors are often glycoproteins that are secreted by cells and bind to and activate receptors on other cells, initiating a metalxilic or developmental change in the receptor cell. Given the biological importance of growth factors and other signaling molecules and their importance as potential therapeutic agents, production of these molecules in accordance with the present invention is of particular interest. For example, the present invention may be used to produce growth factors or other signaling molecules in a cell culture wherein the misfolding and/or aggregation of the produced growth factors or other signaling molecules are reduced. Non-limiting examples of mammalian growth factors and other signaling molecules include cytokines; epidermal growth factor (EGF); platelet-derived growth factor (PDGF); fibroblast growth factors (FGFs) such as aFGF and bFGF; transforming growth factors (TGFs) such as TGF-alpha and TGF-beta, including TGF-beta 1, TGF-beta 2, TGF- beta 3. TGF-beta 4. or TGF-beta 5; insulin-like growth factor-l and -II (IGF-I and IGF-II); des(1-3) -IGF-I (brain IGF-I), insulin-like growth factor binding proteins; CD proteins such as CD-3, CD-4, CD-8, and CD-19; erythropoietin (representative commercially available erythropoietins include, for example, ARANESEP [darbepoetin]; CEA-SCAN [Arcitumomab], EPOGEN [epoetin alfa]; PROCRIT [epoetin alfa]), etc.); osteoinductive factors; immunotoxins; a bone morphogenetic protein (BMP); an interferon such as interferon-alpha, -beta, and -gamma (representative commercially available interferons include, for example, ACTIMUNNE [Interferon gamma-1b], AVONEX [Interferon beta-1a]. REBIF [Interferon beta-1a], BETASERON [Interferon beta-1b]). etc.); colony stimulating Actors (CSFs), e.g., M-CSF, GM-CSF, and G-CSF (other representative commercially available colony stimulating factors include, tor example, GRANUCYTE, Lenograstim, LEUKINE [Sargramostim]), etc.); interleukins (TLs), e.g., IL-1 to IL-10; tumor necrosis factor (TNF) alpha and beta; insulin A-chain; insulin B-chain; proinsulin; follicle stimulating honnone; calcitonin; luteinizing hormone; glucagon; clotting factors such as factor VIIIC, factor IX, tissue ^ctor, and von Willebrands factor; antj-dotting factors such as Protein C; atrial natriuretic factor; lung surfactant; a plasminogen activator, such as urokinase or human urine or tissue-type plasminogen activator (t-PA); bombesin; thrombin, hemopoietic growth factor; enkephalinase; RANTES (regulated on activation normally T-cell expressed and secreted); human macrophage inflammatory protein (MIP-1-alpha); mullerian-inhibiting substance; relaxin A-chain; relaxin B-chain; prorelaxin; mouse gonadotropin-associated peptide; neurotrophic Actors such as bone-derived neurotrophic factor (BDNF), neurotrophin-3. -4, -5, or -6 (NT-3, NT-4, NT-5, or NT-6), or a nerve growth factor such as NGF-beta. One of ordinary skill in the art will be aware of other growth factors or signaling molecules that can be expressed in accordance with methods and compositions of the present invention. Receptors Another class of polypeptides that have been shown to be effective as pharmaceutical and/or commercial agents and that can desirably be produced according to the teachings of the present invention includes receptors. Given the biological importance of receptors and their importance as potential therapeutic agents, production of these molecules in accordance with the present invention is of particular interest. For example, the present invention may be used to produce receptors in a cell culture wherein the misfblding and/or aggregation of the produced receptors are reduced. Receptors are typically trans-membrane glycoproteins that function by recognizing an extra-cellular signaling ligand. Receptors often have a protein kinase domain in addition to the ligand recognizing domain. This protein kinase domain initiates a signal:ng pathway by phosphorylating target intracellular molecules upon binding the ligand, heading to developmental or metabolic changes within the cell. In certain embodiments, an extracellular domain of a transmembrane receptor is produced in accordance with methods and systems disclosed herein. In certain embodiments, an intracellular domain of a transmembrane receptor is produced in accordance with methods and systems disclosed herein. In certain embodiments, tumor necrosis factor inhibitors, in the fonm of tumor necrosis factor alpha and beta receptors (TNFR-1; EP 417.563 published Mar. 20.1991; and TNFR-2, EP 417,014 published Mar. 20,1991, each of which is incorporated herein by reference in its entirety) are expressed in accordance with systems and methods of the present invention (for review, see Naismith and Sprang, J Inflamm. 47(1-2):1-7,1995-96, incorporated herein by reference in its entirety). According to some embodiments, a tumor necrosis factor inhibitor comprises a soluble TNF receptor. In certain embodiments, a tumor necrosis factor inhibitor comprises a soluble TNFR fused to any portion of an immunoglobulin protein, including the Fc region of an immunoglobulin. In certain embodiments, TNF inhibitors of the present invention are soluble forms of TNFR I and TNFR II. In certain embodiments, TNF inhibitors of the present invention are soluble TNF binding proteins. In certain embodiments, the TNF inhibitors of the present invention are TNFR-Fc, for example, etanercept. As used herein, "etanercept," refers to a TNFR-Fc, which is a dimer of two molecules of the extracellular portion of the p75 TNF-a receptor, each molecule consisting of a 235 amino acid Fc portion of human IgGI. In accordance with the invention, an anti-senescence compound, such as camosine, is used to decrease the amount of misfolded and/or aggregated protein during the production of TNFR-Fc. In some embodiments, receptors to be produced in accordance with the present invention are receptor tyrosine Idnases (RTKs). The RTK family includes receptors that are crucial for a variety of functions numerous cell types (see, e.g., Yarden and Ullrich, Ann. Rev. Biochem. 57:433-478.1988; Ullrich and Schlessinger, Cell 61:243-254,1990. each of which is incorporated herein by reference). Non-limiting examples of RTKs include tumor necrosis fector alpha and beta receptors, members of the fibroblast growth factor (FGF) receptor femily, memtjers of the epidermal growth factor receptor (EGF) family, platelet derived growth factor (PDGF) receptor, tyrosine kinase with immunoglobulin and EGF honwlogy domains-1 (TIE-1) and TIE-2 receptors (Sato et al., Nature 376(6535):70-74, 1995, incorporated herein by reference in its entirety) and c-Met receptor, some of which have been suggested to promote angiogenesis, directly or indirectly (Mustonen and Alitalo, J. Cell Bol. 129:895-898,1995). Other non-limiting examples of RTK"s include fetal liver kinase 1 (FLK-1) (sometimes referred to as kinase insert domain-containing receptor (KDR) (Terman et al.. Oncogene 6:1677-83,1991) or vascular endothelial cell growth factor receptor 2, VEGFR-2), fms-like tyrosine kinase-1 (Flt-1) (DeVries et al. Science 255;989-991,1992; Shibuya et al.. Oncogene 5:519-524,1990), sometimes refen^ to as vascular endothelial cell growth ^ctor receptor 1 (VEGFR-1), neurx>pilin-1, endoglin, endosialin, and Axl. Those of ordinary skill in the art will be aware of other receptors that can be expressed in accordance with the present invention. In certain emtxxJiments, the receptor to be produced in accordance with the present invention is a G-pnotein coupled receptor (GPCR). GPCRs are a major target for drug action and development. In fact, receptors have led to more than half of the currently known drugs (Drews, Nature Biotechnology, 14:1516,1996) and GPCRs represent the most important target for therapeutic intervention with 30% of clinically prescribed drugs either antagonizing or agonizing a GPCR (Milligan, G. and Rees, S., TIPS, 20:118-124, 1999). Since these receptors have an established, proven history as therapeutic targets, production of GPCRs in accordance with the present invention is also of particular interest. In general, practitioners of the present invention will select their protein or polypeptide of Interest, and will know its precise amino acid sequence. Any given polypeptide that is to be expressed in accordance with the present invention will have its own particular characteristks and may influence the cell density or viability of the cultured cells, and may be expressed at tower levels than another polypeptide or protein grown under identical culture conditions. One of ordinary skill in the art will be able to appropriately modify inventive media and methods described herein in order to optimize cell growth, titer, folding or any other property of a given expressed polypeptide or protein. One of ordinary skill in the art will be aware of other useful and/or desirable proteins that may be expressed in accordance with methods and compositions of the present invention. Cell lines may be cultured using a variety of techniques to produce the desired protein product. The cell culture can be done on a small or large scale, depending on the purpose of the cell culture medium or use of the product. For example, cells may be grown in a btoreactor. In certain embodiments, the volume of the bioreactor is at least 1 liter and may be 10.100, 250, 500,1,000. 2,500, 5,000, 8,000,10,000,12,000 liters or more, or any volume in between. In additbn, bioreactors that may be used include, but are not limited to. a stirred tank bioreactor. fluidized bed reactor, hollow fiber bk>reactor, or roller bottle. The systems can also operate either in a batch, fed-batch, or continuous/perfusion mode. The bioreactor and mode in which to control and monitor the cell culture medium will be known to one of ordinary skill in the cell culture art. In the instant example, the system utilized is a stirred tank bioreactor and operated in fed-batch mode. The bk>reactor is generally seeded with an inoculum medium and a chosen cell line, for example a TNFR fusion protein cell line, which may be transfected to stably express and produce the desired protein product. Commercially available medium such as Minimal Essential Medium (MEM, Sigma), Ham"s F10 (Sigma), or Dulbecco"s Modified Eagle"s Medium (OMEM, Sigma) may be used as the base medium. These base mediums may then be supplemented with amino acids, vitamins, trace elements, and/or other components to produce the inoculum or feed mediums used during the production run. In certain embodiments, a base medium is altered to permit robust growth of cells, to increase cell viability, to increase cell productivity, to increase integrated viable cell density, and/or to improve the quality of the produced protein in the presence of camosine. For example, a base medium may be supplemented with pyaivate, oxaloacetate and/or a-ketoglutarate. One of ordinary skill in the art will be able to alter a base medium for use with methods and compositions of the present invention without undue experimentation. In certain embodiments, cells are cultured in any of a variety of chemically defined media containing an anti-senescence compound, wherein the components of the media are both known and controlled. For example, defined media typically do not contain complex additives such as serum or hydrolysates. In certain emtxxjiments, cells are cultured in any of a variety of complex media containing an anti-senescence compound, in which not all components of the medium are known and/or controlled. In certain embodiments, such an anti-senescence compound comprises camosine. The conditions of the btoreactor are controlled typically, with the pH set between about 6.5 to about 7.5. The pH is adjusted using an acid, generally CO2, or a base, such as sodium bicarbonate. The dissolved oxygen is controlled between about 5 and 90% of air saturation, and the temperature is held between SO"C to 42°C, during the growth phase. A person of ordinary skill in the cell culture art can modify the conditions of the bioreactor based upon the cell line and methods being employed to achieve the desired results without undue experimentation. Compositions and methods of the present invention may be used with any cell culture method or system that is amenable to the expression of proteins. For example, cells expressing a protein of interest may be grown in batch or fed-batch cultures, wherein the culture is terminated after sufficient expression of the protein, after which the expressed protein is harvested and optionally purified. Alternatively, cells expressing a protein of interest may be grown in perfusion cultures, wherein the culture is not terminated and new nutrients and other components are periodically or continuously added to the culture, during which the expressed protein is periodically or continuously harvested. After the cells are seeded they go through a growth phase during which the number of cells generally increases exponentially. During the growth phase, the temperature or temperature range of the cell culture will be selected based primarily on the temperatures or range of temperatures at which the cell culture remains viable, at which a high level of protein is produced, at which production or accumulation of metabolic waste products is minimized, and/or any combination of these or other factors deemed important by the practitioner. As one non-limiting example, CHO cells grow well and produce high levels or protein at approximately SZ"^C. In general, most mammalian cells grow well and/or can produce high levels or protein within a range of about 25°C to 42""C, although methods taught by the present disclosure are not limited to these temperatures. Certain mammalian cells grow well and/or can produce high levels of protein within the range of at>out ZS"C to 40°C. In certain embodiments, the cell culture is grown at a temperature of 20,21,22,23, 24, 25. 26.27, 28, 29, 30, 31. 32, 33, 34, 35, 36, 37, 38, 39, 40, 41. 42, 43,44, or 45°C at one or wore times during the growth phase. Those of ordinary skill in the art will be able to select appropriate temperature or temperature range in which to grow cells, depending on the needs of the cells and the production requirements of the practitioner. Following the growth phase is a transition phase during which the cells adapt to any changes occurring in the surroundings, such as a temperature change. The changes occurring are typically parameters for the production phase. In the instant examples, on day 4, the temperature decreased from alx)ut 37°C to atx)ut 31 °C. The temperature shift, however, can occur more than once and does not need to necessarily go in the downward directton. Moreover, the transition phase and the temperature shift can occur on any day during the production run. Although most methods of production include multi-phase processes, camosine also may be utilized in a single-phase process. When shifting the temperature of the culture, the temperature shift may be relatively gradual. For example, it may take several hours or days to complete the temperature change. Alternatively, the temperature shift may be relatively abrupt. The temperature may be steadily inaeased or decreased during the culture process. Altematively, the temperature may be increased or decreased by discrete amounts at various times during the culture process. The subsequent temperature(s) or temperature range(s) may be lower than or higher than the initial or previous temperature(s) or temperature range(s). One of ordinary skill in the art will understand that multiple discrete temperature shifts are encompassed in these embodiments. For example, the temperature may be shifted once (either to a higher or tower temperature or temperature range), the cells maintained at this temperature or temperature range for a certain period of time, after which the temperature may be shifted again to a new temperature or temperature range, which may be either higher or lower than the temperature or temperature range of the previous temperature or temperature range. The temperature of the culture after each discrete shift may be constant or may be maintained within a certain range of temperatures. Finally, there is the production phase where the cell number does not substantially increase, but rather the cells produce the desired protein product. One of ordinary skill in the art will understand, however, that in certain embodiments, cells may continue to grow and increase in number during the production phase. During this phase the environment of the bioreactor is controlled at conditions in which the cells are more likely to be productive. For example, the temperature is generally held at a temperature different than that of the grov^h phase, which is conducive to the production of a protein product, e.g. 31 °C. Throughout the production run, the cells may be fed a feed medium containing nutrients and supplements the cells may need. For example, in certain cases, it may be beneficial or necessary to supplement the cell culture during the subsequent production phase with nutrients or other medium components that have been depleted or metabolized by the cells. As non-limiting examples, it may be beneficial or necessary to supplement the cell culture with hormones and/or other growth factors, particular ions (such as sodium, chloride, calcium, magnesium, and phosphate), buffers, vitamins, nucleosides or nucleotides, trace elements (inorganic compounds usually present at very low final concentrations), amino acids, lipids, or glucose or other energy source. These supplementary components may all be added to the cell culture at one time, or they may be provided to the cell culture in a series of additnns. In certain embodiments, an anti-senescence compound is provided in a feed medium at one or more times during the production phase. According to certain embodiments, use of an anti-senescence compound, e.g. camosine, in the cell culture medium during the production phase, whether provided in an inoculation medium or a feed medium, increases cell viability and/or specific protein production, thus improving the overall yield of produced protein. Aspects of a protein production process are determined by one of ordinary skill in the cell culture art. The parameters such as seed density, duration of the production culture, operating conditions during harvest, among others, including those mentioned above are functions of the cell line and the cell culture medium. Therefore, the parameters can be determined without undue experimentation by a person of ordinary skill in the cell culture art. As with the temperature or temperature range during the growth phase, the temperature or temperature range of the cell culture during the production phase will be selected based primarily on the temperature or temperature range at which the cell culture remains viable, at which a high level of protein is produced, at which production or accumulation of metabolk: waste products is minimized, and/or any combination of these or other factors deemed important by the practitioner. In general, most mammalian cells remain viable and produce high levels or protein within a range of about 25°C to 42°C, although methods taught by the present disclosure are not limited to these temperatures. In certain embodiments, mammalian cells remain viable and produce high levels or protein within a range of about 25°C to SS"C. In certain embodiments, the cell culture is grown at a temperature of 20, 21, 22, 23. 24, 25, 26. 27, 28, 29, 30. 31. 32, 33. 34. 35, 36, 37, 38, 39, 40,41,42,43,44, or 45°C at one or more times during the production phase. Those of ordinary skill in the art will be able to select appropriate temperature(s) or temperature range(s) in which to grow cells during the production phase, depending on the particular needs of the cells and the particular production requirements of the practitioner. The cells may be grown for any anwunt of time, depending on the needs of the practitioner and the requirement of the cells themselves. In certain embodiments, batch or fed-batch cultures are temiinated once the culture achieves one or more relevant culture conditions, as detemnined by the needs of the practitioner. In certain embodiments, batch or fed-batch cultures are terminated once the expressed protein reaches a sufficiently high titer, once the cell density reaches a sufficiently high level, once the expressed protein reaches a sufficiently high cell density, and/or to prevent undesirable production or accumulation of metabolic waste products (e.g., lactate and/or ammonium). One of ordinary skill in the art will be aware of other relevant culture conditions that may be used to determine when a batch or fed-batch culture should be tenminated, based on experimental, commercial, and/or other conskjerations. in certain embodiments, following a production run, the protein product is recovered from the cell culture medium and further isolated using traditbnal separation techniques. For example, the protein may initially be separated by centrifugation, retaining the supernatant containing the protein. Additionally or alternatively, the protein product may be bound to the surtece of the host cell. In such embodiments, the media is removed and the host cells expressing the protein are lysed as a first step in the purification process. Lysis of mammalian host cells can be achieved by any number of means known to those of ordinary skill in the art, including physical dismption by glass beads and exposure to high pH conditions. Using conventional protein purification methods, the protein may be additionally isolated. Methods by which to isolate and purify the desired protein product are i