Expression of carbohydrate xenoantigens on porcine peripheral nerve.

Background: The use of thin easily revascularized cutaneous nerve autografts, which has been the gold standard, or the alternative use of nerve allografts or artificial grafts for nerve reconstructing have all their pros and cons. Nerve xenotransplantation may offer a potential alternative. In a potential pig to human nerve xenograft transplantation set-up several porcine antigen barriers have to be considered such as carbohydrate antigens system like the blood group A/O, the Galalpha1-3Gal (alphaGal) and the Hanganutziu-Deicher (HD) antigens. The swine leukocyte protein antigens system may also have to bee considered. The knowledge of the antigen expression on pig peripheral nerves is today limited. The present study describes the distribution of glycolipid based carbohydrate xenoantigens in ischiadicus nerve from blood group A and O pigs.
Methods: Glycolipid fractions were separated on thin layer chromatography plates and immunostained with human AB sera, biotinylated Griffonia simplicifolia isolectin B4, monoclonal antibodies reacting with the HD antigen and with blood group A antigens based on different core saccharide structures. In addition, the subcellular distribution of alphaGal and HD antigens were studied by light- and electron-microscopical immunohistochemistry. The total amount of neutral glycolipids was 15 mg/g tissue for both blood group A and O nerves with mono-glycosylceramides as the dominating component.
Results and Conclusions: The total amount of acidic glycolipids (gangliosides and sulpholipids) was 9 mg/g tissue for both the blood group O and A nerves with sulphatides as the dominating components. Analyses of the glycolipid fractions showed strong expression of both the alphaGal and the HD antigens in nerves from both blood group A and O pigs. In addition, small amounts of blood group A antigens were expressed in nerves from blood group A pigs. Staining of neutral glycolipids from blood group A pigs using monoclonal antibodies reacting with A antigen having different core structures suggested that the A epitope expressed on pig ischiadicus nerves is based on the type 1 core chain structure. Light and electron microscopical studies on the alphaGal and HD-antigen distribution revealed that the neural cells were alphaGal antigen negative. Endothelial cells of blood vessels, and lymphatic and perineural cells expressed alphaGal antigen. Both endothelial cells and myelinized axons revealed positively labelled for the HD antigen.