Evaluation of the Efficacy of Intramuscular Islet Autograft After Extensive Pancreatectomy

Overview

The liver may not be an optimal site for islet transplantation due to obstacles by an instant blood-mediated inflammatory response, and low revascularization of transplanted islets. Therefore, intramuscular islet transplantation offers an attractive alternative, based on its simplicity, enabling easier access for noninvasive graft imaging and cell explantation.

The field of β cell replacement therapies has progressed extensively over the last decades. It is well established that successful intraportal islet transplantation can restore endogenous β cell function to subjects with type 1 diabetes mellitus. In fact, when the graft function is optimal, insulin independence can be consistently prolonged for up to 5 years in 50% of patients. Several factors influence the outcome and performance of the graft upon implantation. For instance, preclinical studies have confirmed the significant differences in utilizing several sites for the implantation of islet grafts, but the most utilized clinical approach is embolization into the liver. However, it has become evidently clear that the liver may not be the optimal environment as a recipient site for pancreatic islets, owing not only to immunologic, but also to anatomic and physiologic factors that may promote a decline in islet function. Moreover, intrahepatic islet infusion is often associated with an immediate blood- mediated inflammatory reaction , thrombosis and hepatic tissue ischemia with elevated blood liver enzymes. In addition, the cross-talk between activated coagulation and inflammatory mediators after implantation, dramatically affects islet cell survival and engraftment, resulting in β cell dysfunction or death, depicting primary nonfunction as a consequence of reduced functional islet mass. This intrahepatic environment appears to potently impair the metabolic functions of transplanted islets. Furthermore, the complications associated with graft recovery within the hepatic site, will further limit its potential applications in exploiting insulin-secreting cells obtained from alternative cell sources. These include xenogenic islets, immortalized β cell lines, embryonic stem cells, or adult progenitor cells, including β cell encapsulation. Restoration of β cell function is a highly desirable goal for patients with unstable diabetes; therefore, the search for an alternative site that is safer for islet transplantation is imperative. In man, autotransplantation of minced tissue into striated muscle following blunt dissection has been successfully used in parathyroid surgery for several decades. Initially demonstrated in rodents in the early 1980s, intramuscular islet transplantation (IMIT) has rarely been considered as a clinically feasible implantation site. This study want to provide direct evidence of the feasibility and function of autologous islets transplanted in the muscle

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