Dispersed pancreatic graft cryopreservation in the dog: In vivo assessment of preservation protocols

Dispersed canine pancreatic grafts were cryopreserved and the in vivo function was studied following intrasplenic autotransplantation. Four protocols were employed, examining the effects of cooling and thawing rates and cryoprotectant (dimethylsulfoxide) concentration on graft survival. The degree of graft injury by each protocol was assessed by examining the requirement for exogenous insulin following transplantation. Cooling at 5 degrees C/min and thawing at 80 degrees C/min allowed three successful grafts from seven when thawed at 80 degrees C/min using 1.4 or 2 M Me2SO but only one success from eight when thawed at 8 degrees C/min. Of the seven experiments where successful preservation was achieved graft injury was estimated as less than 50% in four but for three it was probably greater than 50%. Each protocol exhibited considerable variability of islet survival. When sufficient islet mass was transplanted to restore fasting euglycaemia, graft function, as assessed by glucose-stimulated insulin release and intravenous glucose disposal, was identical to fresh grafts. Successful graft implantation, however, does not guarantee indefinite survival as six of seven grafts in this study became exhausted within 13 months of implantation.