Abstract 795: Integrin-alpha1/beta1 and PDGF Receptor Pathways Coordinately Mediate Stem Cell Differentiation into Smooth Muscle Cells
Background: Embryonic stem (ES) cells can differentiate into smooth muscle cells (SMC) that can be used for tissue engineering and repair of damaged organs. However, little is known about the molecular mechanisms of differentiation in these cells.
Methods and Results: In the present study, we found collagen IV can promote ES cells to differentiate into Sca-1+ progenitor and SMC. Pretreatment of ES cell with antibodies against collagen IV significantly inhibited SMC marker expression. To further elucidate the effect of collagen IV on the induction and maintenance of SMC differentiation, Sca-1+ progenitor cells were isolated with magnetic beads, and placed into collagen-IV-coated flasks and cultured in DM medium with or without PDGF-BB for 6 to 90 days. Both immunostaining and FACS analyses revealed that majority of these cells were positive for SMC-specific markers. Pretreatment of Sca-1+ progenitor with antibodies against integrin alpha1/beta1, alphav /beta1, but not alpha1/beta3 and alphav/ beta3, inhibited focal adhesion kinase (FAK) and paxillin phosphorylation, and resulted in a marked inhibition of SMC differentiation. Various tyrosine kinase inhibitors, and specific siRNA for PI3K and PDGF receptor-beta significantly inhibited SMC marker expression.
Conclusions: Taken together, we demonstrate for the first time that collagen IV plays a crucial role in the early stage of SMC differentiation, and that integrin (alpha1/beta1 and alphav/beta1)-FAK-PI3K-MAPK and PDGFR-beta signaling pathways are coordinately involved in SMC differentiation.