IDENTIFICATION OF DISTINCT MOLECULAR PHENOTYPES IN CULTURED GASTROINTESTINAL SMOOTH-MUSCLE CELLS

Background & Aims: Cultured gastrointestinal smooth muscle cells have been shown to dedifferentiate and reinitiate their myogenic program in vitro. The aim of this study was to determine whether the cellular ph enotypes observed in vitro were similar to those previously characteri zed in vivo. Methods: Differential isoactin expression was examined in primary cultures of intestinal smooth muscle cells (ISMCs) by Norther n blot and immunohistochemical analysis. Cellular phenotype was determ ined for cultured ISMCs grown at high density, at low density, in the presence and absence of serum supplementation, and on several distinct substrates including collagen type IV, laminin, fibronectin, and plas tic. Results: The unique patterns of isoactin protein and gene express ion observed in cultured ISMCs indicate that distinct cellular phenoty pes were present in vitro. The production and maintenance of these dis tinct smooth muscle cell phenotypes was dependent on cell density, ser um supplementation, and substrate used. Conclusions: Cultured ISMCs ap pear to recapitulate a portion of their in vivo myogenic program in vi tro, providing a unique opportunity for the molecular mechanisms contr olling gastrointestinal smooth muscle myogenesis and pathogenesis to b egin to be identified.