Oxidized low density lipoprotein-induced transdifferentiation of bone marrow-derived smooth muscle-like cells into foam-like cells in vitro.

Oxidized-low density lipoprotein (ox-LDL) is believed to contribute to atherogenesis in part by being taken up into smooth muscle cells (SMC) via specific scavenger receptors; however, it is not clear whether ox-LDL receptor(s) are expressed in bone marrow-derived smooth muscle-like cells (SMLCs) and whether they play a role in the process of SMLC development. Therefore, we examined the ox-LDL-induced transdifferentiation of SMLCs that is mediated by lectin-like ox-LDL receptor-1 (LOX-1). Smooth muscle progenitor cells (SMPCs) from bone marrow mesenchymal stem cells (BMSCs) were isolated using a tissue-specific promoter sorting method with a mouse SM22_ promoter (_480 bp)/green fluorescent protein recombinant plasmid. The SMPCs were myocardin+CD105+KDR+CD45(-)CD34(-), but did not express SMC-specific markers alpha-smooth muscle actin (alpha-SMA), SM22, smooth muscle myosin heavy chain (SM-MHC) and smoothelin. After long-term culture with platelet-derived growth factor-BB (PDGF-BB), SMPCs expressed alpha-SMA, SM22 and SM-MHC and differentiated into SMLCs. When SMLCs were incubated with different concentrations of ox-LDL, LOX-1 expression on the surface of SMLCs gradually increased with the increase of the ox-LDL concentration, but myocardin and SMC-specific marker genes decreased, accordingly. Furthermore, receptor-mediated endocytosis was enhanced and lipid droplets accumulated in the cytoplasm of SMLCs. A subpopulation of myocardin+CD105+KDR+CD45(-)CD34(-) SMPCs exist in BMSCs that can differentiate into SMLCs under induction with PDGF-BB. Moreover, LOX-1 contributes to the ox-LDL-induced transdifferentiation of bone marrow-derived SMLCs into foam-like cells.