Cryopreservation of rat islets of Langerhans: a comparison of two techniques

Although a number of different protocols have been described for the cryopreservation of pancreatic islets of Langerhans, most involve equilibration with 2 M Me2SO followed by slow cooling and fast warming. This paper compares two methods with identical equilibration protocols: one with cooling at 0.25 degree C/min to -40 degrees C prior to transferring to liquid nitrogen and subsequent warming at 200 degrees C/min and sucrose dilution of Me2SO (Method A) and the other with cooling at 0.3 degree C/min to -70 degrees C prior to transferring to liquid nitrogen and warming at 50 degrees C/min followed by stepwise dilution of Me2SO (Method B). Islet viability was assessed by syngeneic transplantation to the renal subcapsular space of streptozotocin-induced diabetic rats. Seven hundred fifty fresh islets in the size range 100-200 microns consistently reversed diabetes (blood glucose < 10 mmol/liter) whereas 1000 Method A cryopreserved islets and 2000 Method B cryopreserved islets were required. Cryopreservation by either method resulted in impaired islet function compared to that of fresh islets, although this functional loss could be partially compensated by the transplantation of greater numbers of cryopreserved islets.