Characteristics of coronary smooth muscle cells and adventitial fibroblasts

Background-Recent findings suggesting the involvement of adventitial cells in coronary repair have raised questions regarding the phenotypic "plastici ty" of medial, smooth muscle cells (SMCs). Accordingly, the aims of the pre sent study were to examine the characteristics of coronary medial and adven titial cells and to compare the responses of coronary and noncoronary SMCs to stimulation. Methods and Results-Enzymatically isolated coronary SMCs (human and porcine ) were distinct from noncoronary SMCs, showing poor adhesion and spreading, as well as lower proliferation, collagen synthesis, and LDL degradation. S everal extracellular matrix components (Matrigel, collagen I and IV, lamini n, vitronectin, fibronectin) or growth factors (epidermal growth factor, pl atelet-derived growth factor-BE, insulin growth factor-1, interleukin-1 alp ha) failed to augment the adhesion or proliferation of coronary SMCs to the levels observed in noncoronary SMCs. Unlike coronary SMCs, coronary fibrob lasts demonstrated high adhesion, proliferation, collagen synthesis, and av id LDL metabolism. Limited responses of coronary SMCs were associated with sustained expression of differentiation markers (alpha-smooth muscle actin, h-caldesmon, and smooth muscle myosin heavy chain), whereas noncoronary SM Cs showed marked phenotypic heterogeneity. Conclusions-Coronary SMCs appeared to maintain highly differentiated phenot ype in response to stimulation, whereas coronary adventitial fibroblasts de monstrated several characteristics that are essential during vascular repai r. Coronary SMCs, however, were distinct from noncoronary medial cells, whi ch displayed greater phenotypic heterogeneity and versatility in culture. W e postulate that the mechanism of vascular repair may differ among vascular beds, pointing to the importance of coronary artery-specific investigation s in vascular biology.