Pigment epithelium-derived factor enhances differentiation and mineral deposition of human mesenchymal stem cells

Abstract

Pigment epithelium-derived factor (PEDF) is a potent antiangiogenic factor found in a wide variety of tissues. Recent findings indicated that lack of PEDF leads to osteogenesis imperfecta type VI whose hallmark is a defect in mineralization. We investigated the effects of PEDF on human mesenchymal stem cells (hMSCs) and signaling pathways through which PEDF displays its activities in hMSCs. hMSCs incubated in a medium supplemented with PEDF induced expression of osteoblastic-related genes. In addition, PEDF induced alkaline phosphatase (ALP) activity in MSCs at 14 days of incubation in maintenance medium; hMSCs incubated in osteogenic medium in presence of PEDF expressed 19% more ALP activity (35.6556±1.827 U/mg protein, p5.041 than cells incubated in the same medium without PEDF supplementation (29.9566±2.100 U/lg protein). hMSCs incubated in osteogenic medium in presence of PEDF deposited 50% more mineral (2.1086±0.306 OD/ml per well per 1×104 cells per square centimeter, p5.017) than MSCs incubated in absence of the protein (1.3986±0.098 OD/ml per well per 1 × 104 cells per square centimeter) as determined by Alizarin Red quantitation. Reduction in PEDF expression in MSCs by siRNA led to decreased ALP activity (33.5526±2.009 U/ng protein of knockdown group vs. 39.2696±3.533 U/ng protein of scrambled siRNA group, p5.039) and significant reduction in mineral deposition (0.65460±050 OD/ml per well per 1×104 cells per square centimeter of knockdown group vs. 1.15260±132 OD/ml per well per 1×104 cells per square centimeter of wildtype group, p5.010). Decreased ALP activity and mineral deposition were restored by supplementation with exogenous PEDF protein. PEDF activated ERK and AKT signaling pathways in MSCs to induce expression of osteoblastic-related genes. These data suggest that PEDF is involved in MSCs osteoblastic differentiation. © AlphaMed Press.