Background. Culturing human islets in Memphis serum-free media (M-SFM) is associated with excellent postculture recovery, in vitro function, and in vivo survival. The authors investigate the possibility of preserving islet function for extended periods (6 months) in culture and describe the in vitro and in vivo functional outcomes associated with these extended culture times. Methods. Human islets isolated from three cadaveric donor organs were cultured in M-SFM for 1, 3, or 6 months before transplantation under the kidney capsule of nonobese diabetic (NOD)-severe combined immunodeficiency (SCID) mice. In vitro function was measured by static incubation at the time of transplantation. In vivo function was assessed by measuring human insulin and C-peptide production, and by the ability of 6-month cultured islets to cure streptozotocin-induced diabetes in this mouse model. Results. Islet recovery ratios after 1 month in culture ranged from 85% to 88% and declined to 28% to 53% after 6 months of culture (P<0.01). Insulin stimulation indices did not differ among the fresh or the 6-month cultured preparations. All preparations cultured for 1 to 3 months functioned in the NOD-SCID mice. After 6 months of culture, two of the three preparations demonstrated in vivo function and were able to cure streptozotocin-induced diabetes. Conclusions. These data demonstrate that human islets can be cultured in M-SFM for extended periods and still retain in vitro and in vivo function and the ability to cure experimental diabetes. The ability to maintain islets in culture for prolonged periods is an important step toward the development of islet tissue repositories and distribution centers.
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