Current status of beta-cell replacement therapy (pancreas and islet transplantation) for treatment of diabetes mellitus

Islet transplantation improved penile tissue fibrosis in a rat model of type 1 diabetes

BACKGROUND

Glycaemic control is one of the most effective strategies for the treatment of diabetes-related erectile dysfunction (DMED). Compared to conventional anti-diabetic drugs and insulin, islet transplantation is more effective in the treatment of diabetic complications. The aim of this study was to investigate the efficacy of islet transplantation for reversing advanced-stage DMED in rats and to observe its influence on corpus cavernosum fibrosis.

METHODS

Wistar rats were intraperitoneally injected with streptozotocin to establish a diabetes model. After 12 weeks, the rats were divided into 4 groups: diabetic, insulin, islet transplantation, and normal control. Following supplementation, the changes in blood glucose and weight were determined sequentially. Penile erectile function was evaluated by apomorphine experiments in the fourth week, and the penile corpus cavernosum was also collected for assessment by Masson staining, immunohistochemistry and Western blot to observe the spongy tissue and the related cellular changes at the molecular level.

RESULTS

Islet transplantation significantly ameliorated penile erectile function in advanced-stage diabetic rats. The ratio of corpus cavernosum smooth muscle cells to fibroblasts and the expression level of α-SMA in the islet transplantation group were significantly higher than those in the diabetic and insulin groups. In addition, the expression levels of TGF-β1, p-Samd2, and connective tissue growth factor (CTGF) in the islet transplantation and insulin groups were much lower than those in the diabetic group, while those in the islet transplantation group were significantly lower than those in the insulin group.

CONCLUSIONS

Our findings strongly suggest that islet transplantation can promote the regeneration of smooth muscle cells and ameliorate corpus cavernosum fibrosis to restore its normal structure in advanced-stage diabetic rats. The possible mechanism of ameliorating corpus cavernosum fibrosis by islet transplantation may be associated with improvement of the hyperglycaemic status in diabetic rats, thereby inhibiting the TGF-β1/Samd2/CTGF pathway.

The Influence of Stabilized Deconjugated Ursodeoxycholic Acid on Polymer-Hydrogel System of Transplantable NIT-1 Cells

PURPOSE

The encapsulation of pancreatic β-cells in biocompatible matrix has generated great interest in diabetes treatment. Our work has shown improved microcapsules when incorporating the bile acid ursodeoxycholic acid (UDCA), in terms of morphology and cell viability although cell survival remained low. Thus, the study aimed at incorporating the polyelectrolytes polyallylamine (PAA) and poly-l-ornithine (PLO), with the polymer sodium alginate (SA) and the hydrogel ultrasonic gel (USG) with UDCA and examined cell viability and functionality post microencapsulation.

METHODS

Microcapsules without (control) and with UDCA (test) were produced using 1% PLO, 2.5% PAA, 1.8% SA and 4.5% USG. Pancreatic β-cells were microencapsulated and the microcapsules' morphology, surface components, cellular and bile acid distribution, osmotic and mechanical stability as well as biocompatibilities, insulin production, bioenergetics and the inflammatory response were tested.

RESULTS

Incorporation of UDCA at 4% into a PLO-PAA-SA formulation system increased cell survival (p < 0.01), insulin production (p < 0.01), reduced the inflammatory profile (TNF-α, IFN-ϒ, IL-6 and IL-1β; p < 0.01) and improved the microcapsule physical and mechanical strength (p < 0.01).

CONCLUSIONS

β-cell microencapsulation using 1% PLO, 2.5% PAA, 1.8% SA, 4.5% USG and the bile acid UDCA (4%) has good potential in cell transplantation and diabetes treatment.

Transplantation of insulin-producing cells differentiated from human periosteum-derived progenitor cells ameliorate hyperglycemia in diabetic mice

BACKGROUND

Periosteum-derived progenitor cells (PDPCs) isolated from the adult periosteum can differentiate into several specific cell types. In this study, we examined the characteristics of human PDPCs and insulin-producing cells (IPCs) differentiated from PDPCs and their ability to ameliorate hyperglycemia when transplanted into streptozotocin-induced nonobese diabetic-severe combined immunodeficiency diabetic mice.

METHODS

Periosteum-derived progenitor cells were isolated from patients, expanded in culture, and subjected to a three-step differentiation protocol to produce IPCs. The expression of immunogenic, pluripotent, and pancreatic markers was examined, and glucose-stimulated insulin release in vitro was also assessed. Insulin-producing cells that differentiated from PDPCs were transplanted under the kidney capsule of streptozotocin-induced diabetic mice, and glucose levels and glucose tolerance were measured.

RESULTS

We found that PDPCs expressed the mesenchymal stem cell markers CD73, CD90, and CD105 and the pluripotent markers, octamer-binding transcription factor 4 and Nanog, but not sex-determining region Y-box 2 or Rex1. Periosteum-derived progenitor cells expressed human leukocyte antigen-ABC but did not express human leukocyte antigen-DR or the costimulatory molecules CD80 and CD86. Differentiated IPCs expressed pancreatic hormones (insulin, glucagon, somatostatin, and glucose transporter 2), hormone processing, and secretion molecules (prohormone convertase-1 and convertase-2, Kir6.2), and pancreatic transcription factors (neurogenin 3, pancreatic and duodenal homeobox 1, sex-determining region Y-box 17). When IPCs were stimulated with glucose in vitro, insulin secretion was elevated. Transplantation of IPCs under the kidney capsules of diabetic mice improved hyperglycemia and glucose tolerance. Human insulin was detected in the serum and kidney sections of mice transplanted with IPCs differentiated from PDPCs.

CONCLUSION

These results suggest that IPCs differentiated from PDPCs might be an alternative source of β cells for treating diabetes.

A stirred microchamber for oxygen consumption rate measurements with pancreatic islets

Improvements in pancreatic islet transplantation for treatment of diabetes are hindered by the absence of meaningful islet quality assessment methods. Oxygen consumption rate (OCR) has previously been used to assess the quality of organs and primary tissue for transplantation. In this study, we describe and characterize a stirred microchamber for measuring OCR with small quantities of islets. The device has a titanium body with a chamber volume of about 200 microL and is magnetically stirred and water jacketed for temperature control. Oxygen partial pressure (pO(2)) is measured by fluorescence quenching with a fiber optic probe, and OCR is determined from the linear decrease of pO(2) with time. We demonstrate that measurements can be made rapidly and with high precision. Measurements with betaTC3 cells and islets show that OCR is directly proportional to the number of viable cells in mixtures of live and dead cells and correlate linearly with membrane integrity measurements made with cells that have been cultured for 24 h under various stressful conditions.

Immune modification of rat islet by methoxy-polyethylene glycol

AIM: To investigate the insulin secretion changes of rat islets after immune modification of methoxy-polyethylene glycol (mPEG).

METHODS: The islets isolated from Wistar rats were divided into control group and mPEG-treated groups (with 200, 300 and 400 g/L mPEG, respectively). After culture for 24 h, the viability of islets was detected by dithizone staining, and insulin secretion function was examined by glucose stimulation test. The islets from different groups were mixed with splenic lymphocyte from SD rats to evaluate the immunogenicity.

RESULTS: The viability of islets or the insulin secretion function in the three treatment groups was not significantly different from that in the control group. However, the cytoxicity rates in mPEG-treated groups were markedly lower than those in the control group (24.7%, 14.8%, 21.4% vs 69.5%, t = 2.378, 2.584, 2.472, all P < 0.05). Furthermore, the cytoxicity in the islets treated with 300 g/L mPEG was the lowest (14.8% vs 24.7%, 21.4%, t = 2.285, 2.383, both P < 0.05).

CONCLUSION: mPEG can mask the immunogenicity of rat islets while hardly affect the viability and insulin secretion.

Beneficial effects of nerve growth factor on islet transplantation

OBJECTIVE

Development of the Edmonton protocol was a pivotal contribution to clinical islet transplantation (ITx). Persistent limitations to ITx include insufficient supply and posttransplant functional failure of islets. In this study, nerve growth factor (NGF) was used to enhance both cultured and transplanted beta-cell function, thus achieving prolonged graft survival.

METHODS

Fluorescence microscopy with ethidium bromide and SYTO green staining was used to evaluate balb/c mouse islet viability. Islets were syngeneically transplanted under the kidney capsule of recipients with streptozotocin-induced diabetes. Intraperitoneal glucose tolerance was used to test posttransplant function.

RESULTS

Improved viability was found in murine islets cultured for 48 hours in 500 ng/mL NGF (P < .05). A submarginal islet mass (260 islet equivalents/recipient) was used for ITx. The NGF-culture resulted in prolonged islet survival (24.7 days vs 5.5 days without NFG culture, n = 6). Intravenous injection of NGF (6 mug) on the day of transplant and postoperative days (POD) 1 + 2 prolonged islet survival from 4.1 days (no treatment) to 13.2 days (n = 6). Glucose tolerance testing performed at posttransplant day 4 showed improvement at 60 and 120 minutes in recipients treated intravenously with NGF (blood glucose of 95 +/- 15 vs 210 +/- 78 and 57 +/- 6 vs 176 +/- 70 mg/dL, respectively).

CONCLUSION

NGF may improve beta-cell function and result in prolonged survival of both cultured and transplanted islets.

Prospective and challenges of islet transplantation for the therapy of autoimmune diabetes

Pancreatic islet cell transplantation is an attractive treatment of type 1 diabetes (T1D). The success enhanced by the Edmonton protocol has fostered phenomenal progress in the field of clinical islet transplantation in the past 5 years, with 1-year rates of insulin independence after transplantation near 80%. Long-term function of the transplanted islets, however, even under the Edmonton protocol, seems difficult to accomplish, with only 10% of patients maintaining insulin independence 5 years after transplantation. These results differ from the higher metabolic performance achieved by whole pancreas allotransplantation, and autologous islet cell transplantation, and form the basis for a limited applicability of islet allografts to selected adult patients. Candidate problems in islet allotransplantation deal with alloimmunity, autoimmunity, and the need for larger islet cell masses. Employment of animal islets and stem cells, as alternative sources of insulin production, will be considered to face the problem of human tissue shortage. Emerging evidence of the ability to reestablish endogenous insulin production in the pancreas even after the diabetic damage occurs envisions the exogenous supplementation of islets to patients also as a temporary therapeutic aid, useful to buy time toward a possible self-healing process of the pancreatic islets. All together, islet cell transplantation is moving forward.