Growth characteristics and cytoskeletal organization of cultured smooth muscle cells from human primary stenosing and restenosing lesions

Abstract

Growth characteristics of human plaque cells selectively extracted from advanced primary stenosing and fresh restenosing lesions by percutaneous transluminal atherectomy were studied in vitro. Cells were isolated either by explant technique or by enzymatic disaggregation, and they were identified as smooth muscle cells (SMC) by positive reaction with antibodies against α-smooth muscle actin. Endothelial cells were not found in the atherectomized tissue. The cells of primary stenosing tissue (ps-SMC) exhibited a significantly low growth rate (0.16±0.04 population doublings per day) in comparison to the cells of restenosing lesions (re-SMC, 0.64±0.15 population doublings per day). Furthermore, ps-SMC became senescent and remained quiescent after two passages, whereas re-SMC retained a high proliferative activity and became quiescent by passage 8 to 10. Both types of cells responded to increasing serum concentrations in a dose-dependent manner. Ps-SMC failed to respond to purified platelet-derived growth factor (PDGF) and a mitogen mixture isolated from bovine brain (ECGF), but their proliferative activity was increased by the addition of re-SMC-conditioned culture medium. Despite their high basic growth rate, the proliferative activity of re-SMC was significantly stimulated by PDGF and ECGF in a dose-dependent manner. PS-SMC and re-SMC populations consisted of two distinct subpopulations, which could be discriminated by cell size measurements and cell adhesion: 1) relatively small (cell diameter, 18.6±5 μm), low-adhesive, predominant cells, and 2) enlarged (cell diameter, 27.1 ± 3 μm), high-adhesive, fibroblast-like cells with abundant microfilaments. Neither ps-SMC or re-SMC stained with antibodies against desmin, but did express vimentin. The organization patterns of vimentin and tubulin were unaltered in comparison to each other and to smooth muscle cells cultured from the media of nonatherosclerotic human arteries.