Improvement in islet yield from obese donors for human islet transplants

Background. The feasibility of human islet transplantations has been firmly established. To increase the number of islet transplants, the suitability of pancreases from organ donors considered inappropriate for pancreas transplantations must be evaluated. Methods. We isolated islets from 114 human cadaver donor pancreases by the automated Ricordi method, followed by purification using continuous-density gradients. We divided the pancreases into two groups by donor body mass index (BMI)-group 1: n=51, BMI of 30 or more; group 2: n=63, BMI of less than 30. We compared the results of human islet isolation, in vitro potency assays, and a nude mouse bioassay. Results. In group 1 (vs. group 2), we found a significantly higher mean pancreas weight (109.5±30.7 vs. 90.6±24.0 g; P=0.0002); higher mean islet equivalents/pancreas, after digestion (442,565±238,741 vs. 289,860±158,995; P<0.0001) and after purification (319,129±164, 002 vs. 215,753±126,089; P=0.0002); and a higher islet isolation success rate-defined as isolations yielding more than 300,000 islet equivalents/ pancreas, with purities of more than 50% (37.3% [19 of 51 pancreases] vs. 15.9% [10 of 63]; P=0.009). Our in vitro potency assays and bioassay uncovered no differences between the two groups. Notably, all except one of the donor BMIs for the successful isolations in group 2 exceeded 26; the mean donor BMI for the successful isolations (27.3±3.0, n=10) was significantly higher than for the unsuccessful isolations (24.8±3.3, n=53) (P=0.03). Conclusions. Pancreases from both overweight (BMI ≥26 but <30) and obese (BMI ≥30) cadaver donors are suitable for islet isolation and transplantations. Their use could increase the size of the islet donor pool.