Xenotransplantation of adult porcine islets in diabetic mice. A study of UVB irradiation, cryopreservation and immunosuppression on graft survival time

Effect of ultraviolet B (302 nm) irradiation on viability, metabolic and detoxification functions of goat hepatocytes--in vitro study

The object of the present study was to investigate the effect(s) of UV-B irradiation on the functional integrity, metabolic and detoxifying capacity of the isolated goat hepatocytes. Isolated goat hepatocytes were subjected to UV-B irradiation invitro for 0, 250, 500, 1250, 2500 and 7500 Joules/m2 which correspond to the irradiation time of 0, 1, 2, 5, 10 and 30 min. Cells were then analysed for Viability (Trypan blue exclusion test [TBE], 3-[4,5-dimethylthiozol-2yl]-2,5-diphenyltetrazolium bromide [MTT] assay, Membrane integrity (Lactate dehydrogenase [LDH] leakage, Lipid peroxidation) Detoxification (Ureagenesis, Cytochrome P450 activity [CYP450, Diazepam metabolism] and Glutathione-S-Transferase [GST] activity. The results show that there was no difference in functional, metabolic as well as detoxifying parameters of the hepatocytes when irradiated from 0-1250 Joules/m2, whereas a significant alteration was appreciable in the parameters such as LDH leakage, lipid peroxidation, and CYP450 activity when irradiated beyond 1250 Joules/m2. Our present findings suggest that the biologically compatible and feasible dose of UV-B irradiation for xenotransplantation appears to be 1250 Joules/m2.

Differential responses of UV-B irradiation on the viability and intracellular calcium influx in goat hepatocytes-in vitro effect

Ultraviolet-B (UV-B) irradiation in the range of 280-320nm has shown to be a promising immunomodulatory tool in xenogenic hepatocyte transplantation. Most of the studies documenting the effect(s) of UV-B irradiation on hepatic transplantation have been carried out in small model systems with very little information available in larger animals. The aim of the present investigation was to study in vitro the effect(s) of UV-B irradiation (302 nm) at 0, 250, 500, 1250 and 2500 J/m2 on the viability and cellular responses in the isolated goat hepatocytes. The results showed that the cells irradiated at 0, 250, 500, 1250 and 2500 J/m2 demonstrated a viability of 90-95%. However, intracellular [Ca2+]i influx as quantitated by Flu 3-acetete showed a significant increase with irradiation as observed in confocal microscope. The intracellular pH (quantitated by the flourescence of BCCEF) although tend to show an increase with UV-B irradiation was not statistically significant. The present observations suggest that there is a modulation in the intracellular [Ca2+]i concentration within the hepatocytes at higher dose of UV-B irradiation without altering the viability of hepatocytes. These observations are significant for the xenotransplantation of cells.

Characterization of secretory and morphologic properties of primary cultured endocrine cells from porcine pancreata

We characterized morphologic and secretory properties of porcine pancreatic endocrine cells in primary culture obtained by autolytic preparation without any exogenous proteolytic enzymes. The endocrine cells exhibited a neuron-like shape, and insulin granules were accumulated at the terminal of the processes. Thus derived endocrine cells survived in culture medium containing nicotinamide and remained sensitive to glucose for at least 6 weeks after preparations. The cells responded well to physiologic concentrations of glucose, and high K+ depolarization and the antidiabetic sulfonylureas, tolbutamide, and glibenclamide also elicited the release. With high glucose, insulin release was markedly potentiated by forskolin, glucagon, glucagon-like peptide-1, and arginine and inhibited by somatostatin, the Ca2+ channel blocker nitrendipine, and the ATP-sensitive K+ channel opener diazoxide. Epinephrine had dual effects on the release by glucose; enhanced within a low nanomolar range and inhibited at 1 micromol/L. However, the cells were unresponsive to leucine. Such secretory sensitivities to nutrients, hormones, and pharmacologic agents, and long survival rate (as long as 5-6 weeks) of these cells suggest to us therefore that derived endocrine cells may be useful for xenotransplantation of pancreatic beta cells for treatment of insulin-dependent diabetes mellitus.