Development of a novel digestion chamber for human and porcine islet isolation.

BACKGROUND: The current technique of human pancreas digestion for islet isolation relies on selective distribution of collagenase delivered via the pancreatic duct to produce digestion and removal of peri-acinar fibrous tissue. However, the collagenase has relatively little effect on the interlobular fibrous tissue, which must therefore be broken down by mechanical means within the digestion chamber so as to release the contained acini and islets. The current way of achieving this in the Ricordi chamber is to place five or six stainless steel balls within the chamber and shake vigorously. The shaking presumably breaks down the interlobular fibrous tissue by a combination of shear force induced by the movement of tissue through the shaking process, assisted by numerous blows from the steel balls. Intuitively, one would expect some islets would be destroyed rather than released by such a battering. METHODS: In an attempt to improve the efficiency of islet isolation we have designed a new digestion/filtration chamber that consists of a glass cylinder, sealed with Teflon plates holding in mesh filters at each end, secured in place by a central threaded tie-rod and external knurled nuts. A ring-shaped piston within the cylinder can be pushed up and down the travel by two rods passing out through sealed ports in the Teflon disk at one end and connected to an external handle. The handle is used to gently push the piston up and down the travel of the cylinder, which pushes the fluid and tissue through the central lumen of the ring-piston. A series of hooks attached to the central tie-rod catch the fibrous strands of the passing tissue; the shearing forces produced cause disruption by a process thought to be similar to teasing the tissue apart with fine forceps. RESULTS: A series of initial experiments with human pancreas showed the prototype to be too large, causing temperature control problems, and a redesigned smaller chamber was produced, maintaining the crucial design features. Experience processing five human pancreata has now demonstrated that in three of five pancreata the new chamber produced a good yield (>200,000 I.E.) of remarkably well separated and intact islets, the entire dispersion process being under 1 hour. However, in two isolations the collagenase digestion was poor, with few free islets. A copy of the new chamber (reserved for porcine work only) has been produced, as well as a copy of the Ricordi chamber. We have confirmed that the new chamber can isolate porcine islets in large numbers (>5000 islets/g pancreas [n = 2], but note that pig islets are small). CONCLUSION: These preliminary studies are sufficiently encouraging to justify further direct comparison with the Ricordi chamber for the purpose of animal and human islet isolation.

Transplantation of mouse pancreatic islets into primates--in vivo and in vitro evaluation.

BACKGROUND: Islets transplanted from other species to man has the potential to cure diabetes but whether islets are subject to hyperacute rejection after xenotransplantation is contentious. We transplanted mouse pancreatic islets of mouse beneath the primate renal capsule and assessed natural xenoantibody binding, complement activation and cell lysis in vitro. METHODS: Freshly isolated mouse islets were transplanted in a blood clot under the renal capsule of cynolmogus monkeys. The graft was removed after 24 hr for histological and ultrastructural analysis. Freshly isolated mouse pancreatic islets were analyzed in vitro by immunohistochemistry for Gal(alpha1,3)Gal and Von Willebrand factor expression and for IgG, IgM, C3, C4, and C5b-9 binding after incubation in 100% human serum. Complement mediated cell lysis was evaluated by 51Cr release assays after incubation of islets for 4 hr in human serum, plasma, and lymph with and without added neutrophils. RESULTS: Mouse islets transplanted under the renal capsule of cynomolgus monkeys were destroyed within 24 hr by a process involving necrosis with neutrophil and mononuclear cell infiltration. Gal(alpha1,3)Gal was strongly positive on only 10% of islet cells. After islet incubation in 100% human serum before frozen section, human IgG and IgM, C3, C4, and C5b-9 was deposited on islets with increased intensity in the periphery. Measurement of 51Cr release from labeled fresh islets after four hours incubation in 100% human serum showed 17% lysis and was not changed by addition of neutrophils. CONCLUSION: These results indicate that mouse islets in a primate recipient undergo rapid destruction by a process that has features similar to hyperacute rejection in vascularized organs and we propose the same term be used.