Organ Culture of Fetal Mouse and Fetal Human Pancreatic Islets for Allografting

In organ culture of fetal human and fetal murine pancreas under “conventional” conditions (10% CO₂ in air), the islet cells of both species survive, proliferate and function but the acinar tissue rapidly degenerates. Fetal mouse islet cells also survive in 90% CO₂ but nonendocrine cells, including fibroblasts and macrophages, degenerate. Fetal mouse islets grown in 90% O₂ show diminished immunogenicity when transplanted into recipients differing across the entire MHC, but a reduced allograft response by the host is frequently still present in the absence of immunosuppresslon. Fetal human islets, grown in 10% C0₂ in air, produce insulin in vitro for prolonged periods, and as xenografts, differentiate under the kidney capsule of athymlc mice, suggesting that under appropriate conditions both in vitro and in vivo, the fetal human islets can survive. However, fetal human pancreatic cells of all types are highly susceptible to high oxygen concentrations and are rapidly killed. Because of the susceptibility of fetal human pancreas to oxygen, conditions for the culture of fetal human islets for allotransplantation may need to be modified from those tolerated by fetal mouse islets. Fetal human islets may be a useful source of transplant material in human insulin-dependent diabetes, but it is likely that tissue matching and immunosuppression may be required in addition to modification of islet immunogenicity by prior organ culture.