Circulating smooth muscle progenitors and atherosclerosis.

Atherosclerosis is a chronic inflammatory disease of the arterial wall; during the transition from primitive fatty streaks to more complex lesions, smooth muscle cells play a pivotal role. According to the canonical view, smooth muscle cells migrate from tunica media and contribute to the development of neointima and the fibrous cap. New evidences suggest that bone marrow-derived smooth muscle progenitors might contribute to both neointima formation and fibrous cap development. In this review, we discuss the controversial identity and origin of circulating smooth muscle progenitors by focusing on the methodological clues for their isolation. Furthermore, we examine the potential contribution of smooth muscle progenitors in the development/progression of atherosclerotic lesions.