CRYOPRESERVATION OF PURIFIED BOVINE ISLETS OF LANGERHANS

In this study, bovine islets were isolated by collagenase digestion an d density gradient purification, equilibrated stepwise with 3 M dimeth ylsulfoxide at 24 degrees C, nucleated at -150 degrees C, slow cooled at 0.25 degrees C/min down to -40 degrees C, and finally stored at -15 0 degrees C. After variable periods of time, the islets were quickly t hawed at 37 degrees C, and dimethylsulfoxide was removed by 0.75 M suc rose. Postthawing recovery was 86+/-6% islet equivalents. Histology co nfirmed the identity and morphological integrity of the islets. Insuli n release from the frozen-thawed islets was 0.13+/-0.03 mu U/is/min at 3.3 mmol/L glucose and increased significantly (0.27+/-0.04 mu U/is/m in, P<0.05) at 25 mmol/L glucose. Encapsulated, cryopreserved islets r eversed hyperglycemia in diabetic mice after 6-8 days following implan tation. Therefore, the method described in this paper permitted succes sful cryopreservation of bovine islets of proven in vitro and in vivo viability.