Long-term islet storage would facilitate many aspects of islet research and clinical islet transplantation. Collagenase-isolated, Ficoll-purified islets from eight cadaveric pancreases were stored in liquid nitrogen for 44 ± 9 days after dimethyl sulfoxide equilibration and slow cooling. Rapid rewarming and 48 h of culture preceded repeat evaluation of recovery by islet counts, insulin extraction, and glucose-stimulated perifusion. Islet recovery was 94 ± 4% by count and 90 ± 22% by insulin extraction immediately after thawing. After an additional 48 h in culture, recovery was 74 ± 12% by insulin extraction and 79% by quantitative perifusion culture. Perifusion demonstrated normal baseline and first-phase insulin secretion with decreased secondphase insulin secretion after cryopreservation. Insulinstained sections and electron microscopy revealed preserved islet morphology and ultrastructure. Granulated islets with preserved morphology were recovered 14 days after renal subcapsular xenografting into nude mice. This study demonstrates high recovery and good functional activity of human islets after prolonged cryopreservation.

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