Fibroblast growth factor 2 (FGF-2) – also known as basic fibroblast growth factor (bFGF) – has a broad range of physiological roles, including regulation of cell proliferation and differentiation. FGF-2 is used to support the maintenance of embryonic stem cells and proliferation and differentiation of induced pluripotent and mesenchymal stem cells. [1-3]
FGF-2 is inherently unstable and prone to proteolytic degradation and aggregation. This fundamental biochemical instability, and therefore low half-life in culture media (<10 h), is an important contribution to the need for frequent media changes and challenges in improving homogeneity during stem cell proliferation and subsequent differentiation. To improve the stability of FGF-2 for stem cell and cultivated meat applications, an optimal set of nine amino acid substitutions that stabilize FGF-2 were identified. The biological activity of wild-type FGF-2 is <50% after 10h incubation with conditioned media. In contrast, no reduction in FGF2-G3 biological activity is observed after >7 days incubation with conditioned media at 37 oC.
It is generally accepted that best practice is to use growth factors from the target species for reasons of consumer acceptance, regulatory considerations and species-specific activity including differences in receptor binding and efficacy in some cases. Some growth factor protein sequences are highly conserved and 100% identical across species. There is currently a lack of commercial availability of cultured-meat and fish relevant species-specific growth factors, so often human proteins, or indeed bovine serum, are used as a surrogate. It’s advisable to determine the conservation of protein sequence when selecting appropriate growth factors and switch to species-specific proteins if feasible.