Circulating smooth muscle progenitor cells in arterial remodeling

► Bone marrow-derived mononuclear cells (BMMCs) acquire a smooth muscle cell-(SMC) like phenotype in vitro. ► BMMCs account for 'SMC-like macrophages' in vivo. ► 'Trans-differentiation' of BMMCs into definitive SMCs in vivo is rare, if it occurs at all. ► BMMCs contribute to arterial remodeling by paracrine effects.