Although islet isolation techniques have been improved overtime, protocols and products are not completely standardized. It is known that following transplantation (Tx) from 30 to 60 % of the islet mass is lost. In our study we have investigated 1) the role of size as a factor affecting islet engraftment and 2) potential procedural manipulation to improve the number of smaller islets. Methods: C57/BL10 mice were used as donors and recipients in a syngeneic islet transplant model. Isolated islets were divided by size (large, >300 um; medium 150-300 um; small, <150 um). Each size was transplanted in chemically induced diabetic mice as full (600 IEq), suboptimal (400 IEq) and marginal mass (200IEq). Control animals received all sizes islets in all three masses. Engraftment was defined as reversal of diabetes by day 7 post-Tx. When superiority of smaller islets was observed, strategies of over-digestion and fragmentation were adopted during isolation in the attempt to improve islet engraftment. Results: Smaller islets were significantly superior in engraftment as compared to medium, large and control (all sizes) groups. In all masses success decreased as islet sizes increased.

When larger islets were fragmented, a significant decrease in islet functionality was observed. When the entire preparation was slightly over-digested, an increase in engraftment was observed when compared to control (all sizes) groups.

Conclusion: Smaller islets are superior in engraftment following islet Tx. Fragmentation of larger islets resulted in a significant decrease in functionality. Islet isolations can be performed with slight over-digestion resulting in a shift toward smaller islets and better engraftment.

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