Islet isolation and transplantation techniques in the primate.

Aspects of islet transplantation in the primate have been investigated using a model of autotransplantation of islets in the monkey after total pancreatectomy. The results showed that the subcapsule of the kidney was not a good site for implantation of relatively impure islet preparations, or of purified islet preparations if the mass of tissue implanted was marginal. The spleen was a much better site for the islet implantation, allowing fasting normoglycemia in many of the animals. The results of histologic examination of the spleen four to six weeks after intrasplenic islet transplantation showed good preservation of islet morphologic features, with numerous islets scattered throughout the spleen. Cells secreting insulin, glucagon and somatostatin were present in approximately normal proportions. Transplantation of islets into the portal vein produced good short and long term function. A number of grafts failed between four and 18 months, this failure being related to the function demonstrated at six weeks by intravenous glucose tolerance tests. Animals with poor initial function tended to fail early. However, those with good initial function continued to gain weight and remain normoglycemic up to 2.5 years, providing encouragement to improve further the yield and purity of the islet preparation as well as seeking more efficient techniques for islet implantation.