Ginsenoside Rg3 enhances islet cell function and attenuates apoptosis in mouse islets.

BACKGROUND: The transplantation of isolated islets is thought to be an attractive approach for curative treatment of diabetes mellitus. Panax ginseng has been used in oriental countries for its pharmacologic effects, such as antidiabetic and antiinflammatory activities. 20(S)-ginsenoside Rg3 (Rg3), an active ingredient of ginseng saponins, has been reported to enhance insulin secretion-stimulating and antiapoptotic activities in pancreatic beta cells. We performed this study to examine the hypothesis that preoperative Rg3 administration can enhance islet cell function and antiapoptosis before islet transplantation. METHODS: Balb/c mice were randomly divided into 2 groups according to the administration of Rg3 after islet isolation. Mouse islets were cultured in medium supplemented with or without Rg3. In vitro, islet viability and function were assessed. After treatment of islets with a cytokine cocktail (tumor necrosis factor α, interferon-γ, and interleukin-1ß), cell viability, function, and apoptosis were assessed. RESULTS: Cell viability was similar between the 2 groups. Islets cultured in medium supplemented with Rg3 showed 2.3-fold higher glucose-induced insulin secretion than islets cultured in medium without Rg3. After treatment with a cytokine cocktail, glucose-induced insulin release, total insulin content of islets, and apoptosis were significantly improved in Rg3-treated islets compared with cytokine-treated islets. Cytokine-treated islets produced significantly higher levels of nitric oxide (NO) than islets treated with Rg3. CONCLUSIONS: These results suggest that preoperative Rg3 administration enhanced islet function before islet transplantation and attenuated both cytokine-induced damage associated with NO production and apoptosis. Rg3 administration might be a prospective management to enhanced islet function and ameliorate early inflammation after transplantation.

Experimental microencapsulation of porcine and rat pancreatic islet cells with air-driven droplet generator and alginate.

Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of type 1 diabetes mellitus without immunosuppression. This strategy is based on the principle that foreign cells are protected from the host immune system by an artificial membrane. The aim of this study was to establish an ideal condition of microencapsulation using an air-driven droplet generator and alginate in vitro. The optimal conditions for islet encapsulation were an alginate inflow rate of 10 mL/h, CO2 flow rate of 2.0 L/min in a concentration of 2% alginate. For 2.5% alginate, the alginate inflow rate of 20 mL/h, CO2 flow rate 3.0 L/min was ideal; alginate inflow rate of 40 mL/h, CO2 flow rate of 4.0 L/min showed good microcapsules at 3% alginate. Viability of encapsulated islets was greater than 90%. In terms of insulin secretion, encapsulated islets secreted insulin in response to glucose in static culture medium. However, there was no normal response to low or high glucose challenge with a stimulation index less than 2.0. Microencapsulation of pig islets was successfully performed with air-driven droplet generator and alginate in vitro. Further studies about biocompatibility and glucose control in vivo may provide a useful tool for treatment of patients with diabetes mellitus.

Improved islet yields after purification following the novel endogenous trypsin inhibitor and histidine-tryptophan-ketoglutarate treatment in pigs.

BACKGROUND: Adult porcine islet xenotransplantation into humans is greatly diminished by the difficulty to isolate islets because of their fragility. The goal of this study was to improve the efficacy of islet yields using endogenous trypsin inhibitor and histidine-tryptophan-ketoglutarate (HTK) perfusate. METHOD: We compared two porcine islet isolation protocols: Eurocollins solution for in situ pancreas perfusion without use of an endogenous trypsin inhibitor versus HTK solution including endogenous trypsin inhibitor for pancreas perfusion. RESULTS: Endogenous trypsin inhibitor and HTK strategies significantly improved total islet yield, recovery, and islet index after purification (P < .05), whereas unpurified islet yield did not increase. An average of 228,000 +/- 95,000 islet equivalents (IEQ) (n = 20) purified islets were obtained in the first group compared with 115,000 +/- 56,000 IEQ (n = 18) in the second group. The average islet index was significantly increased in the first group compared with the second group before and after purification: before: 0.28 versus 0.49 versus after: 0.25 versus 0.4 (P < .05). At this time, islet purity, viability, and stimulation index did not show a significant difference between groups. CONCLUSION: Our study showed that endogenous trypsin inhibitor and HTK strategies significantly improved purified islet isolation efficacy because of reduction of islet fragility.

Protective effect of alpha-melanocyte-stimulating hormone on pancreas islet cell against peripheral blood mononuclear cell-mediated cytotoxicity in vitro.

The alpha-melanocyte-stimulating hormone (alpha-MSH) has been shown to interact with various cells of the immune and inflammatory systems and down-regulate either the production or the action of proinflammatory cytokines. In this study, we investigated the potential of alpha-MSH to prevent pancreatic islet cells from cytotoxic injury by inflammatory cytokines released from peripheral blood mononuclear cells (PBMCs) in rats. Pancreatic islets were cocultured with PBMCs in a transwell system during stimulation by phorbol myristic acid and ionomycin. alpha-MSH (50 nmol/L) was added to PBMCs for 2 hours before coculture. Viability and apoptosis of islets were observed by the 3-(4,5-dimethylthiazole-2-yl)-, 5-diphenyltrazolium bromide assay and flow cytometry. We measured inflammatory cytokines and nitric oxide (NO). Insulin release from islets cocultured with mononuclear cells was checked as the metric of islet function. In comparison to the control group, the viability of islets with alpha-MSH-treated mononuclear cells was increased and apoptosis reduced significantly. Inflammatory cytokines, such as tumor necrosis factor-alpha and interleukin-1beta, were significantly reduced among the alpha-MSH-treated group. NO production in the alpha-MSH-treated group was decreased significantly. Insulin secretory function of the islets recovered in conditions of alpha-MSH treatment. This study demonstrated that alpha-MSH protected pancreatic islet cells from PBMC-mediated cytotoxicity and preserved insulin secretory function. This treatment may have the potential to improve graft survival in clinical islet transplantation.