P-66: Optimization of Human Luteinizing Hormone Expression in CHO Cells Culture by Stepwise Reduction in Serum Concentration

Background: Mammalian Cell lines are the main expression system for the production of recombinant therapeutic proteins. Optimization of cell culture condition is performed via alteration in different parameter. Cell culture media plays an important role in cell cycle because of compounds such as amino acids, vitamins, inorganic salts, glucose, and serum as a source of growth factors, trace elements, and attachment factors. But serum is an ill-defined mixture of compounds that may contain endotoxins, microbial contaminants, and growth inhibiting factors and is also expensive part of cell culture. So, efforts are directed towards reducing serum concentration in cell culture. Materials and Methods: In this study, the recombinant CHO-C111 cells transfected with human LH (luteinizing hormone) gene were cultured in DMEM medium containing 15, 10, 5, 3 and 1% FBS (fetal bovine serum) respectively. Then, approximately equal number of cells (9×106) in each medium was used for protein extraction and Bradford assay. SDS-PAGE and western blotting techniques were performed to confirm protein expression. Untransfected CHOC111 cells were used as a negative control and recombinant LH (Lutropin) as a positive control. Results: There was no significant difference in cell growth in different concentrations of serum, because in all mediums, 9×106 cells were collected after about four days. Using Bradford assay, it was observed that the protein concentration was approximately equal. Despite using the equal amount of protein, western blotting showed that maximum productivity was in medium with 15% serum. Conclusion: Higher concentrations of serum in medium caused higher level of LH expression, but because of disadvantages of serum in cell culture, it seems that the use of alternative or reduction in serum concentration is in favor of protein expression.