Reorganization of structural proteins in vascular smooth muscle cells grown in collagen gel and basement membrane matrices (Matrigel): A comparison with their in situ counterparts

When smooth muscle cells are enzyme-dispersed from tissues they lose their original filament architecture and extracellular matrix surrounds. They the n reorganize their structural proteins to accommodate a 2-D growth environm ent when seeded onto culture dishes. The aim of the present study was to de termine the expression and reorganization of the structural proteins in rab bit aortic smooth muscle cells seeded into 3-D collagen gel and Matrigel (a basement membrane matrix). It was shown that smooth muscle cells seeded in both gels gradually reorganize their structural proteins into an architect ure similar to that of their in vivo counterparts. At the same time, a grad ual decrease in levels of smooth muscle-specific contractile proteins (main ly smooth muscle myosin heavy chain-2) and an increase in p-nonmuscle actin occur, independent of both cell growth and extracellular matrix components . Thus, smooth muscle cells in 3-D extracellular matrix culture and in vivo have a similar filament architecture in which the contractile proteins suc h as actin, myosin, and alpha -actinin are organized into longitudinally ar ranged "myofibrils" and the vimentin-containing intermediate filaments form a meshed cytoskeletal network, However, the myofibrils reorganized in vitr o contain less smooth muscle-specific and more nonmuscle contractile protei ns. (C) 2001 Academic Press.