Islet Graft Assessment in the Edmonton Protocol

Abstract

The success of the Edmonton Protocol for islet transplantation has provided new hope in the treatment of type 1 diabetes. This study reports on the assessment of 83 human islet grafts transplanted using the Edmonton Protocol since 1999. Cellular composition, as assessed by immunohistochemistry, showed a lower islet purity (ϳ40%) than has been reported in previous studies using dithizone staining to quantitate islet equivalents. Furthermore, grafts were found to contain substantial populations of exocrine and ductal tissue. Total cellular insulin transplanted was 8,097.6 ؎ 3,164.4 g/patient, and was significantly lower in bottom gradient layer grafts than top gradient layer or whole/combined grafts (P < 0.0005). A static incubation test for islet function gave a stimulation index of 3-4, although this measure did not correlate with posttransplant metabolic outcome. Furthermore, we confirmed a previously reported trend in which donor age affects islet yield and purity. It is important to note that a significant positive correlation was observed between the number of islet progenitor (ductal-epithelial) cells transplanted and long-term metabolic success as assessed an by intravenous glucose tolerance test at ϳ2 years posttransplant. In summary, careful assessment of islet graft composition is needed in a clinical transplantation program to accurately estimate islet purity and assess the contribution of other cell types present, such as islet progenitor cells.

Sustained insulin secretory response in human islets co-cultured with pancreatic duct-derived epithelial cells within a rotational cell culture system

“…The results of recent clinical trials in islet transplantation suggest that improved graft survival correlates, to an extent, with the presence of unprocessed exocrine material inadvertently co-transplanted with human islet cells [22]. This material may provide a pool of progenitor cells with the capacity to differentiate to insulin-secreting cells and thus increase the functional beta cell mass.…”

“…In the present investigation we sought to determine whether appropriate glucose signalling and insulin secretion could be restored in culture by re-establishing cellular interactions between islets and non-endocrine components of the human pancreas. Specifically, we aimed to re-introduce the influences exerted by pancreatic ductal epithelial cells (DECs), which are considered to be a potential source of trophic factors [19], ECM components [20] and beta cell progenitors [21] thought to contribute to sustained graft survival following islet transplantation [22].…”

The impact of the mTOR inhibitor sirolimus on the proliferation and function of pancreatic islets and ductal cells

“…We have recently shown that islet recipients who receive greater numbers of ductal cells within islet grafts have better graft function at 2 years post transplant as measured by acute insulin response to glucose [19]. Since ductal progenitors within the grafts may contribute to long-term graft function, it is important to determine the effect of immunosuppressive agents on these cells.…”

“…Since ductal progenitors within the grafts may contribute to long-term graft function, it is important to determine the effect of immunosuppressive agents on these cells. Indeed, long-term immunosuppression may reduce graft function either by direct drug effects on the beta cells themselves or by effects on ductal cell progenitors that are transplanted with the islets (ductal cells form 20-30% of islet grafts) [19].…”

Filtration is a time-efficient option to Histopaque, providing good-quality islets in mouse islet isolation

“…However, islets in this work were healthy, with a SI between 2 and 20 (Carter et al 2009) not showing any harmful effect of Histopaque on the islets, as supported also by more recent studies performed with Ficoll-based gradients (McCall et al 2011;Mita et al 2010;Lamb et al 2011), nor were any statistical differences between methods observed. However, although GSIS is an important predictor of islet function it does not have a correlation with clinical transplantation outcomes (Ricordi et al 2001;Street et al 2004). Therefore, islets obtained by filtration (with the lowest GSIS and the highest viability) may recover once transplanted and improve their functionality in vivo (Papas et al 2009).…”