Introduction: Bone xenografts from pig to human appear to be an alternative to resolve the shortage of bone autologous and allografts. However, the major obstacle of pig-to-human xenotransplantation is the interaction between human natural anti-Gal antibody and the alpha-Gal epitope abundantly expressed on pig endothelium. It was important to investigate the expression of alpha-Gal epitopes in porcine bone tissue to look for an ideal method to remove the alpha-Gal epitopes.
Methods: The cortical and trabecular bone were retrieved from five pigs. After the soft tissues and periosteum were removed, the blood and marrow cavity were cleaned with phosphate-buffered solution. All 5 mm x 5 mm x 5 mm samples were imbedded in paraffin and methyl methacrylate resin for histological sections. The mouse IgM M86 monoclonal antibody, which was highly specific for alpha-Gal epitopes, was used to document alpha-Gal epitope expression by immunostaining of tissues and immunofluorescence.
Results: Gal-positive immunostaining and immunofluorescence were observed on the surface of osteocytes and Haversian canals. There was a significant difference in Gal expression between cortical and trabecular bone tissues. There was no Gal expression in the extracellular matrix of bone.
Conclusions: Major alpha-Gal epitopes were on the surface of osteocytes of porcine bone tissues. A method should be used to damage the osteocytes and eliminate the alpha-Gal epitopes to avoid the xenogenic rejection in xenotransplantation of porcine bone tissues.