Improved quantity and in vivo function of islets isolated by reduced pressure-controlled injection of collagenase in a rat model.

In islet transplantation, insufficient yield is a major obstacle to one-donor/one-recipient transplant. Collagenase, which is injected via a pancreatic duct to separate islets from acini, can so easily distribute into the islet core that it may result in disruption of islets. The purpose of this study was to evaluate the superiority of reduced pressure-controlled collagenase injection (RPCI) at 80 mmHg on islet isolation to injection at 180 mmHg by examining in vivo transplant experiments besides the yield and the glucose stimulation test in a rat model. Lewis rat pancreases were distended with collagenase solution at 80 mmHg pressure as the RPCI group (group 1) and at 180 mmHg (group 2), followed by isolation. The yield in group 1 (1100 +/- 160 islets with 2750 +/- 530 IEQ) was significantly higher than that in group 2 (900 +/- 130 islets with 1570 +/- 350 IEQ, p < 0.01) due to the significant difference of the number of islets sized >150 microm in diameter, although the purity was not significantly different between the two groups. Stimulation indices in the glucose stimulation tests were 2.88 +/- 1.12 in group 1 and 1.93 +/- 0.62 in group 2 (p < 0.05). The cure rate by transplantation of 100 islets to diabetic nude mice in group 1 (8/10) was significantly higher than that in group 2 (3/10, p < 0.05). In a syngenic transplant model of 90% of islets isolated from one donor, the cure rates were 100% and 67% in groups I and 2, respectively (NS). The area under the curve on the graph of IPGTT on postoperative day 28 in group I was significantly smaller than that in group 2 (p < 0.05). In conclusion, our data show that RPCI at 80 mmHg could contribute to consistently high islet yield and in vivo function in a rat model. It was suggested that the current human protocol should be reviewed from this viewpoint.