In contrast to the extensive experience culturing vascular smooth muscle cells, little is known about the culture behavior of gastrointestinal smooth muscle cells. In this work, we have studied smooth muscle cells from bovine gallbladder muscularis in culture. Properties reflecting their state of differentiation, including cellular morphology, multicellular arrangements, intermediate filament protein expression, and content of contractile proteins, were studied after dispersed cell preparations were placed into short- and long-term culture on a variety of substrates. Immunocytochemical analysis of intact healthy gallbladder wall demonstrated that the muscularis smooth muscle cells express actin and the intermediate filament protein desmin, while being vimentin-negative. In this tissue they are, however, surrounded by sheets of vimentin-positive fibroblasts. Optimal microdissection of mucosa and serosa from the muscularis therefore still produced a combination of smooth muscle cells and fibroblasts; however, multiple strategies for enriching the yield and purity of muscularis smooth muscle cells for culture were partially successful. Like vascular smooth muscle cells in culture, these visceral smooth muscle cells rapidly underwent morphological dedifferentiation, losing their contactile phenotype. By 5 days in culture, the desmin-positive muscle cells took on a spread, fibroblast-like morphology, likely representing modulation to a proliferative, dedifferentiated state. After long-term culture, the muscle cells were observed to regain some markers of differentiation, but they were never observed to attain complete morphological and functional redifferentiation.
Expression of the smooth-muscle proteins α-smooth-muscle actin and calponin, and of the intermediate filament protein desmin are parameters of cardiomyocyte maturation in the prenatal rat heart
