Weber Cj

Pancreatic islet transplantation in cynomolgus monkeys: initial studies and evidence that cyclosporine impairs glucose tolerance in normal monkeys

Using a model of streptozotocin-induced, ketosis-prone, insulin-dependent diabetes mellitus (IDDM) in the cynomolgus monkey, we performed 11 intraportal transplants of collagenase-digested, Ficoll-purified pancreatic islets (9 ABO-compatible allografts and 2 concordant baboon xenografts). Islets were pretreated with ultraviolet-B irradiation and recipients received cyclosporine A immunosuppression. Two grafts never functioned, five grafts showed evidence of partial function, and four grafts (three allografts and one xenograft) showed evidence of good function, with the animals independent of exogenous insulin with morning fasting blood glucose levels less than 200 mg/dl. Because two grafts functioned only after CsA was either tapered or discontinued, we performed a related study that showed that therapeutic doses of CsA (morning trough serum level 150-250 ng/ml) impaired intravenous glucose tolerance tests (IVGTT) of normal monkeys and may contributed to graft dysfunction in our islet transplantation model. The results show that there is a decrease in release of serum insulin during an IVGTT leading to impairment of glucose utilization, while serum glucagon remains unaffected. After cessation of CsA, the IVGTT did not return to normal for 28 days. Oral glucose tolerance tests were unaffected in CsA-treated monkeys. These initial studies show that the streptozotocin-diabetic monkey is a valuable model to study IDDM and islet transplantation in nonhuman primates. We also confirm studies in rodents, dogs, and sheep by showing that CsA partially inhibits beta cell function in normal monkeys.

Pancreatic islet transplantation. Induction of graft acceptance by ultraviolet irradiation of donor tissue.

The effect of ultraviolet (UV) irradiation on the immunogenicity of rat pancreatic islets was examined in allograft and xenograft models. Direct UV irradiation (900 J/m2) of Lewis islets, isolated and hand-picked, does not alter pancreatic islet endocrine function in isograft experiments and results in indefinite islet allograft survival in streptozocin diabetic ACT rats without chronic immunosuppression. Direct UV irradiation, at an appropriate dose, also leads to indefinite islet xenograft survival of Lewis islets in B10-BR diabetic mice and prolonged survival of rat islets in Balb/C mice. When direct UV irradiation of islet allografts did not result in indefinite islet allograft prolongation [Wistar/Furth (W/F) to diabetic Lewis], the addition of brief peritransplant immunosuppression with cy-closporine (days 0, +1, and +2) resulted in permanent acceptance of islet allografts, a result not achieved by cyclosporine alone. The effectiveness of UV irradiation in abrogating islet allograft rejection in several experimental models is supported by in vitro studies showing that UV irradiation of stimulator cells, peripheral blood lymphocytes, splenocytes, and isolated rat dendritic cells abolishes any significant stimulation by such cells of totally histoincompatible thoracic duct responder lymphocytes. In vitro nonreactivity of mixed lymphocyte culture (MLC) with UV-irradiated stimulator cells and in vivo permanent allograft acceptance are reversed by the addition of a small number of untreated donor-type dendritic cells to either the MLC or the recipient bearing the permanent graft. The authors suggest that the primary effect of UV irradiation on immune alteration of islet allografts and xenografts is due to induction of a major metabolic change in the dendritic cells in the graft. This then leads to defective antigen presentation and results in either permanent or prolonged allograft and xenograft acceptance, depending on the degree of MLC stimulation between the islet donor and the diabetic recipient.

Localized ischemic colitis in a young woman with diabetes

Ischemic colitis involving a limited segment of the proximal transverse colon in a young diabetic woman was identified and treated. Important clinical, radiographic, and histopathologic findings are detailed.

Hypogastrinemia in streptozotocin diabetes with islet transplantation-reconstitution☆

Gastrin is present in normal mammalian pancreatic islets, as well as in the antrum and duodenum. Serum gastrin levels are responsive to many physiologic and pharmacologic factors including hyperglycemia, somatostatin, and glucagon. To evaluate the effects of streptozotocin diabetes and islet transplantation on gastrin homeostasis, young, adult, male Lewis rats underwent streptozotocin diabetes alone (N = 14), diabetes plus intraperitoneal islet isografts (N = 22), or sham operation alone (N = 18). Streptozotocin reduced fasting gastrin immunoreactivity (107 pg/ml +/- 26 mean +/- SEM) compared to controls (256 pg/ml +/- 31) (P less than 0.001). Islet isotransplantation resulted in restoration of fasting gastrin immunoreactivity (230 pg/ml +/- 19) to levels significantly greater than diabetics (P less than 0.001) and comparable to control animals (P = NS). Normalization of serum gastrin levels occurred within one month of transplantation and persisted for up to 14 months. In addition, media from cultures of 4/7 dispersed neonatal rat pancreas cultures contained gastrin immunoreactivity. Streptozotocin diabetes produces hypogastrinemia; intraperitoneal islet isotransplantation normalizes fasting gastrin immunoreactivity. Rat islet culture medium contains gastrin-like immunoreactivity. Pancreatic islets would appear to produce or control a portion of circulating gastrin immunoreactivity.

Organ culture of human parathyroid glands: Effects of catecholamines☆

Normal and adenomatous human parathyroid glands were studied in organ culture to determine basal secretory rates of cyclic AMP and parathyroid hormone as well as sensitivity to β-adrenergic catecholamines. Basal cyclic AMP secretion was relatively constant over 4 weeks but parathyroid hormone secretion declined. Both normal and adenomatous tissue were stimulated to secrete cyclic AMP and parathyroid hormone in the presence of the β agonist, isoproterenol. Half-maximal stimulation for adenomas occurred at 1 μM. Propranolol, a β-adrenergic inhibitor, completely prevented the response, with half-maximal inhibition occurring at 0.1 μM. Under basal conditions, normal explants secreted significantly more cyclic AMP and parathyroid hormone than adenomas. The results indicate that both normal and adenomatous human parathyroid glands can be maintained in organ culture for up to 4 weeks and that β-adrenergic catecholamines can stimulate the secretion of cyclic AMP and parathyroid hormone.

Pancreatic polypeptide (PP) immunoreactivity in human parathyroid culture media.

Media from cultures of normal and abnormal human parathyroid fragments were assayed for parathyrin (PTH) and pancreatic polypeptide (PP) using sensitive radioimmunoassays. PP immunoreactivity was present in media (Day 6-7 in vitro) from cultures of 3/10 adenomas and 6/6 3 degrees hyperplastic glands (mean = 126. fmole/mg protein/day) (range = 6.-675.), and was not suppressed by 0 leads to 3 mM calcium challenge. PP was undetectable in media from cultures of one parathyroid carcinoma, one 1 degree hyperplasia, and one normal parathyroid. Medium C-terminal PTH levels were quite variable (26.-2,545,000. pg/mg protein/day). Presence of PP immunoreactivity in media from cultures of some hyperplastic parathyroids and some parathyroid adenomas suggests that PP may be released from these tissues in vitro. The significance of elevated PP levels in the MEA syndromes may be of special clinical relevance to this observation.