Improved method of human islet isolation for young donors.

Background: Although islet transplantation using young donors is more effective than older donors, islet isolation from young donor is notoriously difficult. This may relate to islet ontogeny and collagen composition in the young pancreas. Therefore, we examined whether a high concentration of collagenase could improve the separation of islets from exocrine tissues resulting in an high islet yield.

Methods: We used six human pancreata from brain-dead donors of less than 30 years old. Islet isolation was performed based on the Edmonton protocol with modifications. All pancreata were digested with Collagenase NB1 Premium Grade (Serva). The pancreas was expanded by injecting either 200 mL of cold collagenase solution (2.5 mg/mL, standard group, n = 3) or 100 mL of solution (5 mg/mL, new group, n = 3) in a controlled manner under low pressure for 5 minutes. Then the pressure was raised for another 5 minutes. The following procedure and evaluation were performed based on the Edmonton protocol.

Results: Phase II time in the new group was significantly shorter than the standard group. The ratio of embedded islets in the new group was significantly lower than the standard group. The postpurification islet equivalents per pancreas weight (IEQ/g) and the recovery rate in the new group were higher than the standard group, but not significantly. There was no significant difference in the postpurification purity, viability, and final tissue volume.

Conclusion: Our simple modification with an initially concentrated collagenase preparation using a syringe significantly improved the ratio of embedded islets, resulting in a higher yield from young donors.