Background. A major unmet challenge is to reduce the islet mass needed for insulin independence in type 1 diabetic recipients after islet transplantation. The recombinant homodimer of human annexin V, diannexin, has completed a Phase II Clinical Trial in Kidney Transplantation (NCT00615966).Methods. We developed a marginal islet mass transplantation model (10-12 islets per gram of recipient body weight) and investigated whether diannexin prevents beta-cell apoptosis and improves islet graft function. Diannexin was administered to islet cell donors shortly before pancreas harvest, added to isolation reagents, and infused into recipients at the time of transplantation and repeated daily until day 4.Results. In the syngeneic marginal islet mass transplantation model, the median time needed to achieve normoglycemia was reduced from 17.0 days among untreated controls to 3.5 days among diannexin-treated recipients (P = 0.004). Histologic analysis of islet grafts harvested on day 3 posttransplantation revealed decreased macrophage (44.7% +/- 9.8% vs. 19.2% +/- 3.2%, P = 0.007) and T-cell infiltration (25.9% +/- 5.5% vs. 9.1% +/- 1.1%, P = 0.004), and a lower rate of islet cell apoptosis (20.5% +/- 2.8% vs. 7.6% +/- 2.3%, P = 0.01) with diannexin treatment. Expression profiling of the islet grafts showed significantly lower levels of mRNA for the proapoptotic molecule Bid, but higher levels of interleukin-6, interferon-gamma, and immunosuppressive cytokine interleukin-10.Conclusions. Our findings demonstrate that diannexin improves the early function of marginal mass islet grafts, and its effects are associated with reductions in inflammatory cell infiltration and beta-cell death by apoptosis after islet transplantation.
