The significance of culture for successful cryopreservation of isolated pancreatic islets of Langerhans.

It was the aim of the present study to investigate the significance of culture before and after freeze-thawing of isolated mouse pancreatic islets. To evaluate the impact of culture before freezing (5 degrees C/min; 2 M dimethyl sulfoxide), islets were frozen either directly after isolation or after 2, 4, or 7 days of culture in medium RPMI 1640. The culture period after thawing was 7 days. Islets immediately frozen exhibited virtually no (pro)insulin biosynthesis and also a severe inhibition of glucose-stimulated insulin release. The precultured (2-7 days), frozen islets synthesized and released insulin at rates comparable to those of nonfrozen, cultured islets. Studies of the effects of culture after freeze-thawing were performed after a 3-day culture period prior to freezing. The (pro)insulin biosynthetic rates did not differ between islets cultured for 0-7 days after thawing. There was an apparent increase of glucose-stimulated insulin release when the islets were cultured for more than 2 days after thawing. It may be that the decreased viability of islets frozen immediately after isolation was due to minor cell damage induced by the collagenase incubation. During culture the islets may recover and become more resistant to freeze-damage. The beneficial effect of culture after thawing may reflect the loss of damaged cells, which otherwise would influence the results of the viability tests.