Production of Recombinant Human Leukemia Inhibitory Factor (lif) in a Mammalian Cell Bioreactor: A First Approach
The development of chemically well defined media is a demanding task in order to create the optimal conditions for the in-vitro stem cell (SC) proliferation and differentiation. Mammalian cell culture has become the dominant technology for the production of recombinant proteins for clinical applications due proper protein folding, assembly and post-translational modifications with superior quality and efficacy than when expressed in other hosts such as bacteria, plants and yeasts (Hacker et al. 2009). This work aims the large-scale production of recombinant human Leukemia Inhibitory Factor (r-hLIF) expressed in mammalian cells in the absence of serum. LIF is a secreted globular and monomeric glycoprotein with a molecular weight of 32 to 62 kDa. It has a wide array of actions, including acting as a stimulus for platelet formation, proliferation of some hematopoietic cells, bone formation, adipocyte lipid transport, neuronal survival and formation, and acute phase production by hepatocytes (Metcalf 2003). HEK293-EBNA cells were successfully expanded in 100 mL spinner-flask at agitation rates of 80 rpm and a feeding-regime (FR) of 25% medium renewal every 24 h. Then, scale-up to a mechanically-stirred bioreactor and a working volume of 1 L with fully controlled parameters was achieved. The data presented seems to predict that considerable volume changes in the suspension culture system of HEK293 cells may have a negative effect in cellular growth leading to a decrease in cell density and an increase in the heterogeneity of cell aggregate size-distribution. Thus, a variable FR, apparently good in terms of nutrient refresh, can provide additional variables that can affect autocrine factors concentration in the bulk and, consequently, affect maximum cell density and specific productivities. Overall, this work will allow the establishment of a versatile platform for the production of a wide range of recombinant proteins to be used in stem cell culture in a cost-effective way.