Fresh islets are more effective for islet transplantation than cultured islets.

For clinical islet transplantation, isolated islets deteriorate rapidly in culture, although culturing islets prior to transplantation provides flexibility for evaluation of isolated islets and pretreatment of patients. In the present study, we compared human fresh islets to cultured islets with in vitro and in vivo assays. After culture for 24, 48, and 72 h, islet yield significantly decreased from 2,000 to 1,738 ± 26 (13% loss), 1,525 ± 30 (24% loss), or 1,298 ± 18 IEQ (35% loss), respectively. The ATP contents were significantly higher in the 6-h cultured group (near fresh group) than in 48-h culture groups. The stimulation index was relatively higher in the 6-h cultured group than in 48-h cultured group. Human islets with or without culture were transplanted into diabetic nude mice. The attainability of posttransplantation normoglycemia was significantly higher in fresh group than in the culture groups. Intraperitoneal glucose tolerance testing (IPGTT) showed that the blood glucose levels of mice transplanted with fresh islets were significantly lower than with cultured islets at 30, 60, 90, and 120 min after injection. These data suggest that human islet transplantation without culture could avoid the deterioration of islets during culture and improve the outcome of islet transplantation. Based on these data, we have transplanted fresh islets without culture for our current clinical islet transplantation protocol.