-
[show abstract]
[hide abstract]
ABSTRACT: This study reports the morphology and in vitro function of fetal porcine proislets (FPP) after cryopreservation or culture and the in vivo effects of frozen-thawed FPP in comparison to cultured FPP on the glucose metabolism after transplantation into nude mice rendered diabetic by streptozotocin (STZ). Furthermore, the morphology and the in vitro function of removed grafts is examined in an in vitro:ex vivo model and the in vitro and in vivo effects of FPP of the diabetogenic substance, STZ, is assessed. The data demonstrate that cryopreservation has no adverse effects on the morphology and in vitro function of FPP when compared to cultured FPP. Frozen-thawed FPP are equally effective to normalize blood glucose levels in nude mice rendered diabetic by streptozotocin. Histological and in vitro:ex vivo examination of the removed graft revealed that the extent of differentiation and proliferation in vivo of cryopreserved FPP is comparable with that of cultured FPP. Streptozotocin is not toxic (diabetogenic) to FPP, neither in vitro nor in vivo. We conclude that cryopreserved fetal porcine proislets, easily yielded and pooled from pregnant sows bred in a microbiologically controlled environment, may be a potential source for future xenotransplantation in Type 1 diabetic humans.
Xenotransplantation 11/2008; 2(3):133 - 138. · 2.33 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The enzymatic dissociation of acinar tissue by collagenase is a substantial step in the isolation of pancreatic islets. Although essential collagenase components have been purified, the variability in the activity of different batches limits long-term reproducibility of isolation success. The utilization of purified recombinant proteases would solve this problem. In the present study, pancreases from multiorgan donors were dissociated by means of digestion-filtration using either Liberase HI (n = 51) or a recombinant collagenase blend (n = 25). No significant differences were found regarding islet yield before and after purification, the percent of exocrine-attached islets, and final purity. However, the ratio between islet equivalents and islet numbers indicated a lesser fragmentation in islets isolated with recombinant collagenase (P < 0.01). In contrast, viability was slightly higher in islets isolated with Liberase (92.3 +/- 0.8 vs. 85.6 +/- 2.9%; P < 0.05). Insulin release during static glucose incubation was not different between experimental groups. Islet transplantation into diabetic nude mice resulted in sustained normoglycemia in either group until the graft was removed. These results demonstrated that viable human islets can be isolated using recombinant collagenase. Final optimization of this enzyme blend would offer continuous reproducibility of isolation success.
Diabetes 05/2003; 52(5):1143-6. · 8.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Background. Because of its anatomical and physiological similarities to humans, the pig appears to be a suitable large animal model for preclinical studies of islet transplantation. The aim of this study was to investigate islet auto- and allotransplantation in a pig model with diabetes induced by total pancreatectomy.
Methods. Porcine islets were isolated by a continuous digestion-filtration device at 32°C and purified by a discontinuous iso-osmolar Ficoll-sodium-diatrizoate gradient on a Cobe 2991. The purified islets were autografted into the liver or the renal subcapsular space. The liver appears to be a more suitable site for the islet grafts than the renal subcapsular space, and the minimal amount of islets for reversal of diabetes is >5µl/kg of body weight.
Results. Persistent normoglycemia (fasting blood glucose level: 72.4±44.38 mg/dl) with a normal insulin secretion response to glucose stimulation was successfully achieved in five of six diabetic pigs by implanting a sufficient islet mass into the liver. Triple-drug immunosuppressive therapy with cyclosporine, azathioprine, and prednisolone did not prevent porcine islet allografts from experiencing early failure. However, the addition of 15-deoxyspergualin to the triple-drug immunosuppressive regimen significantly prolonged the function of the islet allografts. When antithymocyte globulin was added to the above-mentioned immunosuppressive drug regimen, the normoglycemic period was prolonged to more than 1 month (fasting blood glucose level: 75.4±17 mg/dl).
Conclusion. We conclude that autotransplantation with a sufficient islet mass can induce normoglycemia with a normal insulin secretion response to glucose stimulation in pancreatectomized diabetic pigs and that allotransplantation can be successfully achieved when 15-deoxyspergualin and antithymocyte globulin are combined with the triple-drug immunosuppression described above. However, this immunosuppressive protocol results in a high rate of infectious complications.
Transplantation 07/1998; 66(2):200-204. · 4.00 Impact Factor
