Restoration of interstitial cells of Cajal and pacemaker activity via cellular transplantation

The experiments described in this dissertation examine the feasibility of using transplantation techniques to establish Interstitial cells of Cajal (ICC) and functional pacemaker electrical activity in the gastrointestinal tract, of an animal model previous shown to be lacking this characteristic behavior.;Interstitial cells of Cajal (ICC) at the level of the myenteric plexus (ICC-MY) are now established as critical elements in the regulation of gastrointestinal (GI) motility, having been implicated in playing crucial roles as pacemakers throughout the GI tract. In this role ICC-MY act to initiate and conduct electrical slow waves to the adjacent, electrically coupled smooth muscle. In doing so ICC act to organize and pace the contractile ability of the GI tract.;W/Wv mutants, harboring a deficiency in Kit signaling, have been characterized as lacking ICC-MY networks in the small intestine resulting in electrical quiescence.;This well characterized loss of function provides an ideal model environment to analyze the feasibility of cellular transplantation as a means to establish ICC and pacemaker activity in previously devoid regions.;This dissertation outlines 2 transplantation methods as a possible means of restoring function to W/Wv small intestine, both in vivo, via bone marrow transplantation and within organotypic cultures via allotransplantation.;Using immunohistochemical, molecular and electrophysiological techniques, we have demonstrated, the presence and development of ICC at the level of the myenteric plexus, increases in total Kit protein expression, and the functional establishment of pacemaker activity within W/Wv small intestine, as a consequence of transplantation.;Allotransplantation within organotypic cultures revealed the development of clustered ICC networks, displaying a mature phenotype, together with a time dependent development of slow wave activity similar to that observed in wild type intestinal tissues. Bone marrow transplantation revealed the development of ICC at the level of the myenteric plexus however these cells appear to lack the ability to develop into functional networks which elicit slow wave activity.;Theses studies raise interesting questions as to the developmental mechanisms and origins of ICC post transplantation and the microenvironmental factors, which regulate ICC growth within the myenteric plexus region.;In summary, the development of ICC networks into tissues normally devoid of these cells and the generation of robust slow waves demonstrates for the first time the feasibility of transplantation to restore functional pacemaker activity. These findings provide preliminary evidence that cellular transplantation of ICC may provide a means to alleviate gastrointestinal motility disorders.