Fibroblast Growth Factor 2 Modulates Endotheliogenesis of Human Adipose Tissue Derived Stem Cells

Background: Adipose-derived stem cells (ASCs) are a potential adult mesenchymal stem cell source for restoring endothelial function in critical limb ischemia patients. Fibroblast growth factors (FGF) play a major role in angiogenesis and wound healing. The purpose of this study was to evaluate the effects of FGF and VEGF on human ASCs proliferation, migration and potential endothelial differentiation regards to their use as endothelial cell (EC) substitutes.

Methods: ASCs were isolated from clinical lipoaspirates and cultured in M199 medium with FBS (10%), FGF2 (10ng/ml), VEGF (50ng/ml) or combinations of FGF2 and VEGF. Cell proliferation rates, viability, and migration were measured by growth curves, MTT and scratch assays. For cell attachment determinations, ASCs were seeded onto scaffold (small intestinal submucosa) for 5d. Endothelial differentiation capabilities of ASC were confirmed by expression of EC specific markers using qPCR, immunofluorescence staining and cord formation on Matrigel. PD173074, a selective inhibitor of FGF receptor, was used to confirm the importance of FGF signaling.

Results: Increased proliferation rates were observed in ASCs treated with FGF2 when compared to ASCs cultured with VEGF and control groups (3.2 fold, p<0.05). In comparison with controls, FGF2 showed increased ASC migration (relative scratch width, p<0.01). FGF2-treated ASCs seeded onto the SIS scaffold for 5d exhibited increased attachment rates compared to ASCs cultured with VEGF (1.7 fold, p<0.01). After 10 days exposed to FGF, ASCs expressed EC-markers (CD31, vWF mRNA) and formed cords upon Matrigel. Cultured ASCs with FGF2 and VEGF increased eNOS mRNA and protein levels when compared to ASCs cultured with FGF2 or VEGF alone. Furthermore, blockade of FGF signaling with PD173074 blocked ASC EC differentiation potential.

Conclusions: Our results indicate that: 1) FGF is an ASC promoter for proliferation, migration, attachment and endothelial differentiation; 2) FGF and VEGF have a co-stimulatory effect on ASC endotheliogenesis; and 3) FGF signaling mediates ASC EC differentiation. These results suggest that ASCs with enhanced FGF2 signaling may potentially be used for tissue engineering and cell-based therapies in critical limb ischemia patients.