Topographical arrangement of α- and β-cells within neo-islet tissues engineered by islet cell sheet transplantation...

We established a procedure to engineer therapeutic neo-islets in subcutaneous spaces in mice by transplanting contiguous layers of islet cell sheets. In this study, we investigated the cellular arrangements of α and β within these engineered neo-islets in vivo as a function of time after sheet transplantation.

Temperature-responsive culture dishes optimized for dispersed islet cell culture were prepared by covalently immobilizing a temperature-responsive polymer poly(N-isopropylacrylamide) (PIPAAm) on plastic dishes followed by laminin-5 coating. Dispersed islet cells obtained from Lewis rats were plated onto the PIPAAm dishes. After reaching confluence at day 2, islet cells were harvested as uniformly spread islet cell sheets by lowering the culture temperature from 37°C to 20°C for 20 minutes. Islet sheet transplantation was performed to creat neo-islet tissues in the subcutaneous spaces of SCID mice with streptozotocin-induced diabetes. This neo-islet engineering approach successfully lowered mouse blood glucose levels, achieving euglycemia at day 5 and thereafter. Histologic analyses of samples obtained at day 4 revealed that neo-islet tissues in the subcutaneous spaces showed heterogeneous cellular alignment of α and β cells. In contrast, analyses of samples at days 14 and 60 revealed α and β cells predominantly located at the peripheral and central parts of the engineered tissues, respectively.

Reassembly of α and β cells occurred in neo-islet tissues engineered by sheet transplantation. The unique cellular arrangements in neo-islet tissues, which were similar to those in naïve pancreatic islets, may contribute to their longevity and long-term function.