Viability and recovery of frozen-thawed human islets and in vivo quality control by xenotransplantation

Cryopreservation of islets of Langerhans offers advantages for the transpla ntation into diabetic patients. In this study two different methods of cryo preservation were compared with respect to islet viability and recovery aft er cryostorage. It was also investigated whether human islet survival in mi ce was affected by cryopreservation. Aliquots of human islets were cryopres erved conventionally or vitrified, respectively. After rapid thawing, islet viability and islet equivalent (IEQ) recovery rate were determined. Aliquo ts of freshly isolated or conventionally cryopreserved islets were transpla nted beneath the kidney capsule of non-diabetic C57BL/6 mice. After three d ays renal insulin content was determined. Islet cell viability was 17.3+/-8 .0% for vitrified and 51.8+/-3.0% for conventionally cryopreserved islets; the recovery rate was 84.8+/-12.2% and 92.8+/-12.4%, respectively. Insulin recovery after transplantation was 25.6+/-7.3% for fresh and 24.1+/-7.4% fo r cryopreserved islets. This study suggests that the conventional method of cryopreservation is superior to vitrification with respect to islet viabil ity after thawing. We found no significant difference between fresh and cry opreserved islets with respect to insulin recovery after transplantation in to mice.