Tissue engineering requires large numbers of cells with enhanced differentiation properties. Thus, the effect of expansion conditions must be explored. Human and rat marrow-derived mesenchymal stem cells (hMSCs and rMSCs, respectively) were comparatively culture expanded through seven passages in the presence of either fibroblast growth factor-2 (FGF-2) or platelet-derived growth factor BB (PDGF-BB). Proliferation of both hMSCs and rMSCs was enhanced by FGF-2 and PDGF-BB. Population doubling times for hMSCs were 2.4 days for control and 1.75 and 2.0 days for FGF-2 and PDGF-BB, respectively, and 3.25, 3.06, and 2.95 days for rMSCs. Supplementation with FGF-2 during cell expansion resulted in significantly greater in vivo bone formation for hMSCs. Use of PDGF-BB resulted in greater bone formation than that observed for control conditions, but the differences were only significant for P1. For rMSCs, significant increases in bone formation were noted in either FGF-2 or PDGF-BB expanded cells implanted at P4 or P7, but not for P1. Under in vitro osteogenic stimulation, calcium content was elevated and bone matrix deposition was enhanced for P1 and P7 rMSCs expanded with FGF-2. Although culture conditions, including FBS, were held constant, these observations suggest that medium must be optimized separately for each species of MSCs.
Keywords: FGF-2; PDGF-BB; mesenchymal stem cells.