Myosin in cultured vascular smooth muscle cells: immunofluorescence and immunochemical studies of alterations in antigenic expression.

Abstract

Vascular smooth muscle cells (VSMC) in the rat mesenteric artery show specific immunofluorescent staining with antisera against purified human uterine myosin (ASMM) but not human platelet myosin (APM). However, in primary cultures produced by enzymatic dissociation of this vessel, VSMC stain specifically with both ASMM and APM within 5 h after plating and throughout growth to confluence (4-10 d). In confluent cultures, APM staining remains bright while ASMM staining is reduced in intensity in most cells. In contrast, cellular myosin content, determined by quantitative SDS PAGE, is comparable in confluent and growing cultures. Immunoprecipitation of high salt extracts of cultured VSMC with ASMM and APM yields myosins with the same mobilities on SDS PAGE. When serial, exhaustive precipitations are performed with one antiserum, followed by reprecipitation with the other, myosin in subconfluent and confluent VSMC cultures is exhaustively precipitated by either antiserum, thus indicating complete immunological cross-reactivity. These results might be explained by synthesis of a new myosin isoform reactive with both ASMM and APM. However, the development of APM staining in cultured VSMC did not require protein synthesis. Therefore, it is more likely that the changes in immunofluorescent staining observed in vitro reflect conformational alterations, perhaps related to cytoskeletal rearrangements. These changes in myosin antigenic expression may be relevant to the problem of VSMC phenotypic modulation both in vitro and in vivo.

Replication of smooth muscle cells in vascular disease.

“…This has been confirmed by Thyberg et al (1983Thyberg et al ( , 1985. However, Alexander and his colleagues have reported smooth muscle cells that retain the ability to contract after serial passage (Larson et al, 1984a(Larson et al, , 1984b. This may be related to the observation of Chamley et al (1974) that about 5% of smooth muscle cells do not change to the synthetic state, but remain contractile, or else the correlation of morphology with the ability to divide may not be absolute.…”

Actin expression in smooth muscle cells of rat aortic intimal thickening, human atheromatous plaque, and cultured rat aortic media.

“…The migration distance from the origin is indicated (in centimeters) on the edges of A. The anodic (+) side for each electrophoretic direction is given in A (for details see reference 19 (5,29). Again it will be of interest to know whether changes of myosin expression in vitro (and possibly in vivo) are correlated with changes of actin expression under the same conditions.…”

Structural determinants of the capacity of heparin to inhibit the proliferation of vascular smooth muscle cells. II. Evidence for a pentasaccharide sequence that contains a 3-O-sulfate group.

“…5): (a) a 4,500-D product derived from the controlled depolymerization of commercial heparin, and (b) a 2,500-D product also derived from controlled depolymerization of commercial heparin. These products have significant activity against Factor Xa (Yin et al, 1973) but almost no activity against Factor IIa (Larsen et al, 1978), and are antithrombotic. These were compared to a 7,000-11,000-D non-anticoagulant, non-antithrombotic heparin prepared by ion exchange chromatography (Sache et al, 1982).…”