Proliferation and extracellular matrix synthesis of smooth muscle cells cultured from human coronary atherosclerotic and restenotic lesions

Objectives. The purpose of this study was to examine the proliferative capacity and extracellular matrix synthesis of human coronary plaque cells in vitro. Background. Common to both primary atherosclerosis and restenosis are vascular smooth muscle cell proliferation and production of extracellular matrix proteins. The applicability to humans of experimental animal models of these processes has been questioned. Methods. Primary atherosclerotic and restenotic lesions were excised by percutaneous directional coronary atherectomy in 93 patients. Smooth muscle cells were cultivated by an explant technique and identified by their morphology in culture, ultrastructural features under electron microscopy and immunostaining using monoclonal antibodies to smooth muscle cell alpha-actin. Proliferation in secondary culture was assessed with growth curves and the synthesis of collagen and sulfated glycosaminoglycans by the incorporation of 3H-proline and 35S-sulfate, respectively. These studies were also performed in cells derived from human umbilical artery media. Results. Success rates for primary (45%) and secondary (12%) culture of coronary cells were not influenced by clinical variables or lesion category. Primary culture success was improved by the presence of organized thrombus in the plaque and in relation to increased maximal cell density of the atherectomy specimen. Restenotic cells displayed more rapid growth than did cells of primary atherosclerotic origin, which grew in a manner similar to that of umbilical artery cells. Mean calculated population-doubling for the three cell groups were 52 h (95% confidence interval [CI] 48 to 58 h), 71 h (95% CI 62 to 83 h) and 74 h (95% CI 65 to 84 h), respectively. Restenotic and primary atherosclerotic cells did not differ in the synthesis of collagen ([mean ± SEM] 0.034 ± 0.004 vs. 0.033 ± 0.004 nmol isotope· μg protein−1, p = NS) or sulfated glycosaminoglycans (11.47 ± 1.07 vs. 15.37 ± 3.10 nmol isotope· μg protein−1, p = NS), but the coronary cells synthesized significantly more collagen and sulfated glycosaminoglycans than did umbilical artery cells (0.019 ± 0.004 and 5.43 ± 1.00 nmol isotope· μg protein−1, respectively, both p < 0.05). Conclusions. These data indicate that increased smooth muscle cell proliferation contributes to coronary restenosis in humans and support the concept that the extracellular matrix synthesis of adult smooth muscle cells is important to lesion formation.