Effects of duration of cold storage and gestational age on the insulin secretory capacity of human fetal pancreatic islets.

Studies were performed on human fetal pancreatic tissue to determine viability after long-term cold storage at 0 degrees to 2 degrees C and the effect of gestational age on in vitro insulin secretory capacity. Viability expressed by the insulin secretory capacity was assessed by insulin responses to 2 successive 1 hr static batch incubations. The first incubation (F1) was in low glucose (2mM) medium while the second incubation (F2) included 25 mM glucose and 1 mM 3-isobutyl-1-methylxanthine (IBMX) as potentiator. The fractional stimulatory ratio (FSR defined as F2/F1) and trypan exclusion rates of isolated fetal islets were used as indexes of viability. Cold storage at 0 degrees to 2 degrees C of whole pancreata for period up to 144 hr was not found to alter insulin secretory capacity (FSR-values), but the percentage of dead islets indicated by trypan blue uptake increased. Microscopic examination of dithizone stained pancreatic islets showed intact and well demarcated variable sized islets. Histologically, islets showed well preserved endocrine cells after cold storage for 18 hr followed by culture for 48 hr. Fetal islets isolated from pancreata of 16-18 weeks gestational age were found to have a 2-fold increase in FSR-values when compared to islets isolated from pancreata of 19-24 weeks gestational age. These experiments document the feasibility of obtaining human fetal islet tissue for transplantation at centers widely separated from the site of transplantation. The implication of the enhanced insulin secretory response of islets obtained between 16-18 weeks gestational age remains to be defined.