Figure 1. Co-culture of MSCs and EPCs decreased level of PDGF-BB and increases proportion of PDGFR-β+ MSCs. The co-culture cells were sorted into co-MSCs (R1, CD90+) and co-EPCs (R2, CD90-) by FACS (A). Flow cytometry revealed that R1 cells expressed the mesenchymal stem cell markers CD44, CD73 and CD90, but not hematopoietic or endothelial markers CD11b and CD31. R2 cells expressed hematopoietic and endothelial markers CD31, CD34 and vWF, but not mesenchymal stem cell markers CD45 and CD90. Real-time PCR revealed that after co-culture, the expression level of PDGF-BB in co-EPCs significantly decreased. Results are mean ± SD from three independent experiments (C). Correspondingly, the expression level of PDGFR-β in co-MSCs increased obviously. Results are mean ± SD from three independent experiments (D). In addition, flow cytometry revealed that detection of PDGFR-β decreased in co-MSCs due to combination of PDGF-BB and PDGFR-β (E). **P<0.01.