Maintenance of morphology and function of canine proximal colon smooth muscle in organ culture.

We have determined that serum source plays a critical role in optimizing conditions for an organ culture model of canine proximal colon. Previous studies using equine serum in the medium have shown that some properties of canine colonic smooth muscle can be maintained in organ culture. However, many characteristics of the tissue were altered by the culture conditions. The aims of the present study were to determine whether serum isolated from canine blood would improve the preservation of physiological properties of canine proximal colon in organ culture. Strips of canine colonic smooth muscle were cultured in 10% canine serum medium, and electrical, mechanical, morphological, and molecular analyses were performed after 0, 3, and 6 days in culture. Unlike organ culture in equine serum, in which Na+-K+-adenosinetriphosphatase (Na+-K+-ATPase) expression declined, culture in canine serum maintained Na+-K+-ATPase expression, and resting membrane potential of smooth muscle cells along the submucosal surface of the circular muscle in cultured tissue remained unchanged during the culture period. Increased sensitivity in the contractile response to acetylcholine, previously observed with tissues cultured in equine serum, was not observed. However, the mechanical performance of the muscle (maximal contractile activity) declined over time in culture. Ultrastructural organization of cellular organelles and myofilaments remained intact in the majority of cells; however, some cells possessed regions devoid of contractile filaments. The results of these studies suggest that organ cultured strips of smooth muscle may provide a useful tool for evaluating electrical and mechanical events in conjunction with molecular analysis of functional components.