Mammalian cell culture disadvantages

Despite these disadvantages, the major benefit of transgenic technology offers a means to produce proteins at a very low cost. Mammalian cell culture systems are often used for expression of recombinant human proteins (rHP), as the latter can only be obtained in a biologically active conformation when produced in such cells. However, this approach has limited production capacity and is expensive. In contrast, the production of rHP in milk of transgenic cattle is a safe and less-expensive alternative with the advantage of better protein output (Brink et al., 2000). 

Mammalian cell cultures have been used as the basis of several systemsin detect ng the potential carcinogenic activity of chemicals. Basically, two general approaches have been utilized continuous cell lines and primary cell cultures. Cell lines have the advantage of ease of use, in that cultures do not have to be obtained fresh from animals prior to each test, but may be maintained for months to years by proper subculturing techniques. They have the disadvantage of possessing one or more "transformed" characteristics (e.g., immortality). In some cases cell lines may also lack certain enzyme systems required for metabolic activation of chemicals. Some of the cell lines used for transformation assays include the murine (BALB/3T3) A31 system ( ), and the baby kidney-21 (BHK-21) systems (43). 

Spontaneous mutations in mammalian cell cultures lead to an accumulation of mutant cells in the population, provided that the mutant cells are not at a selective disadvantage under the in vitro conditions. The spontaneous mutation rate per cell per division at different loci can be estimated by various methods, including the Po method in the fluctuation test (Luria and Delbriick, 1943). For example, in hamster cells the spontaneous forward mutation rate to azaguanine resistance was estimated as 1.5 x 10 per cell per generation the spontaneous reverse mutation rate from glutamine auxotrophy to prototrophy was estimated as 1.4 X 10 per cell per generation (Chu et al.y 19696). 

The genetic manipulation of animal cells allows the production of therapeutic proteins in animal cell culture systems. Mammalian cells such as Chinese hamster ovarian cells and baby hamster kidney cells are commonly used. These mammalian hosts produce recombinant proteins that have almost identical properties to those made by human cells. However, the use of mammalian cells does have disadvantages. As noted earlier, they are expensive to use. This is influenced by their more complex nutritional requirements, their slower growth, and their increased susceptibility to physical damage (Walsh, 2003). 

The growth of mammalian cell lines requires a chemically defined liquid basal medium which is traditionally supplemented with 10% (by volume) bovine serum to provide supplements of growth factors. Although bovine (or other animal) serum provides excellent growth support for cells in culture, there are significant disadvantages in using serum as a an additive to hybridoma cultures. These include ... 

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