Bone marrow mesenchyrnal stem cells (BMSC) can differentiate into diverse cell types,including adipogenic,osteogenic,chondrogenic and myogenic lineages.There are lots of BMSC accumulated in atherosclerosis vessels and differentiate into VSMC.However,it is unclear whether VSMC originated from BMSC (BMSC-SMC) could remodel the vessel in newtunica intima or promote the pathogenesis of atherosclerosis.In this study,BMSC were differentiated into VSMC in response to the transforming growth factor β (TGF-β) and shown to express a number of VSMC markers,such as a-smooth muscle actin (α-SMA) and smooth muscle myosin heavy chainl (SM-MHC1).BMSC-SMC became foam cells after treatment with 80 mg/L ox-LDL for 72 hours.Ox-LDL could upregulate scavenger receptor class A 1(SR-A) but downregulate the ATP-binding cassette transporter A1 (ABCA1) and caveolin-1protein expression,suggesting that modulating relative protein activity contributes to smooth muscle foam cell formation in BMSC-SMC.Furthermore,we found that BMSC-SMC have some biological characteristics that are similar to VSMC,such asthe ability of proliferation and secretion of extracellular matrix,but,at the same time,retain some biological characteristics of BMSC,such as a high level of migration.These results suggest that BMSC-SMC could be induced to foam cells and be involved in the development of atherosclerosis.