A COMPARISON OF MEDIA SUPPLEMENT METHODS FOR THE EXTENDED CULTURE OF HUMAN ISLET TISSUE

Background. The preservation of sufficient quantities of islets for hu man transplantation has proven to be a tenacious problem for researche rs and transplant programs. Beyond the variables associated with islet procurement, there is the problem of tissue storage before transplant ation. Cryopreservation has been adopted as a method for long-term isl et storage that allows for recovery of viable tissue. However, there i s significant tissue loss during the process and the possibility that long-term viability may be compromised. An alternate method of prolong ed culture at 24 degrees C was initially introduced as a means of redu cing islet antigenicity. Although successful in the short term, prolon ged culture with serum-based media has also resulted in a significant loss of tissue. In this study, we report the successful use of an ITS Premix-supplemented serum-free media for prolonged islet culture and its comparison to fetal bovine serum-supplemented media and to cryopre servation. Methods. Pancreata were procured from cadaveric organ donor s, and islets were isolated using our own modification of the automate d method of Ricordi. Aliquots from a series of human islet isolations were cultured in parallel in (A) CMRL + ITS (serum-free media; SFM) or (B) CMRL + 10% fetal bovine serum (standard media) and compared with cryopreserved and thawed tissue. Results. Our results show that SFM al lows for the long-term culture of islet tissue. For time points up to 2 months, islets cultured in SFM showed recovery ratios greater than t hose for standard serum-supplemented media. At 1 week and 1 month, isl et recovery ratios were greater for SFM-cultured islets than for cryop reserved tissue. Viability studies confirmed that the SFM-cultured isl ets were able to respond to glucose stimulation (stimulation index 0.8 -21.2). Additionally, in vivo results using cultured islets in a patie nt demonstrated good islet function, with a 1-month stimulation index of 4.02 in response to an intravenous glucose tolerance test. Conclusi on. We conclude that this culture modification represents a method by which functional islet tissue can be maintained in long-term culture a nd successfully transplanted.