A comparison of three methods of decellularization of pig corneas to reduce immunogenicity

·AIM: To investigate whether decellularization using different techniques can reduce immunogenicity of the cornea, and to explore the decellularized cornea as a scaffold for cultured corneal endothelial cells(CECs).Transplantation of decellularized porcine corneas increases graft transparency and survival for longer periods compared with fresh grafts.·METHODS: Six-month-old wild-type pig corneas were cut into 100-200 μm thickness, and then decellularized by three different methods: 1) 0.1% sodium dodecyl sulfate(SDS); 2) hypoxic nitrogen(N2); and 3) hypertonic NaCl. Thickness and transparency were assessed visually. Fresh and decellularized corneas were stained with hematoxylin/eosin(H&E), and for the presence of galactose-α1,3-galactose(Gal) and N-glycolylneuraminic acid(NeuGc, a nonGal antigen). Also, a human IgM/IgG binding assay was performed. Cultured porcine CECs were seeded on the surface of the decellularized cornea and examined after H&E staining.· RESULTS: All three methods of decellularization reduced the number of keratocytes in the stromal tissue by 】80% while the collagen structure remained preserved. No remaining nuclei stained positive for Gal or NeuGc, and expression of these oligosaccharides on collagen was also greatly decreased compared to expression on fresh corneas. Human IgM/IgG binding to decellularized corneal tissue was considerably reduced compared to fresh corneal tissue. The cultured CECs formed a confluent monolayer on the surface of decellularized tissue.· CONCLUSION: Though incomplete, the significant reduction in the cellular component of the decellularized cornea should be associated with a significantly reduced in vivo immune response compared to fresh corneas.

The potential of genetically-engineered pigs in providing an alternative source of organs and cells for transplantation

There is a critical shortage of organs, cells, and corneas from deceased human donors worldwide. There are also shortages of human blood for transfusion. A potential solution to all of these problems is the transplantation of organs, cells, and corneas from a readily available animal species, such as the pig, and the transfusion of red blood cells from pigs into humans. However, to achieve these ends, major immunologic and other barriers have to be overcome. Considerable progress has been made in this respect by the genetic modification of pigs to protect their tissues from the primate immune response and to correct several molecular incompatibilities that exist between pig and primate. These have included knockout of genes responsible for the expression of major antigenic targets for primate natural anti-pig antibodies, insertion of human complement- and coagulation-regulatory transgenes, and knockdown of swine leukocyte antigens that stimulate the primate＇s adaptive immune response. As a result of these manipulations, the administration of novel immunosuppressive agents, and other innovations, pig hearts have now functioned in baboons for 6-8 months, pig islets have maintained normoglycemia in diabetic monkeys for 〉 1 year, and pig corneas have maintained transparency for several months. Clinical trials of pig islet trans- plantation are already in progress. Future developments will involve further genetic manipulations of the organ- source pig, with most of the genes that are likely to be beneficial already identified.

Induction of diabetes in cynomolgus monkey with one shot of analytical grade streptozotocin

Backgrounds:Streptozotocin(STZ)-induced diabetic monkey is a wide used preclinical animal model for the investigation of diabetes such as islet transplantation and development of diabetic drugs.There are serious side effects of this method,including nausea,emesis,weight loss,liver damage,renal failure,and metabolic acidosis.In order to reduce the side effects,diabetic monkeys were induced using clinicalgrade STZ.However,clinical-grade STZ is not available in China.Here,we establised a method by using 100 mg/kg analytical-grade STZ to induce complete diabetes in cynomolgus monkey without generating adverse effects to liver and renal.Methods:Three cynomolgus monkeys were used in this study.100 mg/kg STZ dissolved in normal saline and infused through vein line in 5 minutes after indwelling catheter in the carotid artery and jugular vein.After the STZ administration,blood glucose levels were examined every 1 or 2 hours in the first 48 hours.Then,blood glucose levels were examined twice per day during the first week after the STZ injection.Insulin and C-peptide levels were measured by ELISA.Blood chemistry of hepatic and renal function tests were performed.Insulin and glucagon expression in the islet of diabetic monkey and normal monkey were examined by immunohistochemistry assays.Results:The stimulated C-peptide level(Intravenous glucose tolerance test)which is less than 0.5 ng/mL,the triphasic blood glucose response and the destroyed β cell suggested the complete induction of diabetes model.No apparent adverse effects were observed including no signs of vomiting and toxicity after STZ injection.Conclusion:In summary,we established a safe and reproducible STZ-induced diabetic cynomolgus monkey model for islet transplantation which will be used to develop novel approaches for the treatment of diabetes.