Evaluation of cryopreservation techniques of pancreatic fragments and islets in vitro and in vivo.

We evaluated cryopreservation techniques for pancreatic fragments and islets using rat tissue. After equilibration in 10% dimethyl sulfoxide (Me2SO), the tissue was frozen in a programmable freezer at 1 degree C/min down to -40 degrees C and at 3 degrees C/min down to -71 degrees C. The islets, when thawed, released abundant insulin in the presence of as little as 3.3 mM glucose, much more so than non-frozen islets did. Three additional procedures, prefreezing and post-thawing culture and the stepwise dilution of the Me2SO, lowered the non-specific insulin release of the thawed islets and improved their insulin response to 16.7 mM glucose. Thawed pancreatic fragments subjected to these additional procedures, transplanted into the peritoneal cavity of streptozotocin-induced diabetic rats, reduced their hyperglycemia significantly. The thawed fragments and islets did not differ from their corresponding non-frozen controls in 3H-leucine incorporation. The maintenance of tissue function was not satisfactory. However, our observations indicate that culturing pancreatic tissue before freezing and after thawing and the stepwise dilution of the cryoprotective agent reduce the damage induced by freezing the tissue.