EFFECT OF COOLING RATE AND ITS INTERACTION WITH PREFREEZE AND POSTTHAW TISSUE-CULTURE ON THE IN-VITRO AND IN-VIVO FUNCTION OF CRYOPRESERVEDPANCREATIC-ISLETS

Rapid cooling destroys passenger lymphoid cells during cryopreservatio n. We now describe improved in vivo survival of rat islets after rapid cooling by adding pre-freeze tissue culture. Islets were equilibrated with 2M dimethylsulphoxide, cooled at 0.3-degrees, 20-degrees, or 70- degrees-C/min, and stored at -196-degrees-C. The culture was kept at 3 7-degrees-C for 2 or 72 h before and/or after preservation. When coole d at 0.3-degrees-C/min, keeping the culture for 72 h gave the highest proportion of dye-excluding cells, but more than 50% were viable under all culture conditions. Islets cooled at 20-degrees or 70-degrees-C/m in (rapidly) required 72 h of culture for a survival rate of more than 50%. When islets were cultured for 72 h before cryopreservation, thei r in vitro insulin secretory ability was similar to that of slowly coo led islets and they were able to sustain normoglycaemia in diabetic an imals, although more islets were needed. Extended tissue culture befor e freezing improves the survival of rapidly cooled islets and is there fore important for combined immunomodulation and cryopreservation.