Bone marrow-derived endothelial progenitor cell line responds to PDGF and differentiates into vascular cells

Endothelial progenitor cells (EPC) express CD34, Flk-1 and CD133 and differentiate into endothelial cells (EC) where neovascularization occurs. Recently, we established a conditionally immortalized bone marrow EPC-derived EC line, TR-BME, from temperature sensitive-SV40 T-antigen gene transgenic rats. TR-BME forms a network in Matrigel and expresses EPC markers. To analyze the difference between EPC and mature EC, we identified EPC-specific genes by means of subtractive hybridization between TR-BME and brain capillary EC line, TR-BBB as a mature EC model. There was no significant difference between TR-BME and TR-BBB in the expression of EC marker. In contrast, the expression of smooth muscle cells (SMC) markers was higher in TR-BME than in TR-BBB. Moreover, the expression of contractile SMC markers was increased in the absence of the EC growth factors, such as vascular endothelial growth factor. The expression of synthetic SMC markers was increased by the addition of PDGF-BB. The SMC derived from TR-BME showed an altered phenotype, from contractile type to synthetic type, when they were cultured in the absence of PDGF-BB. These results show that TR-BME cells express higher levels of SMC markers as compared with mature EC, and can differentiate into contractile- and synthetic-type SMC.