title: Effects of reduction in the alpha-gal antigen on bony union: a model of xenobone graft using GalT knockout mouse.
abstract: BACKGROUND
  Among the bone graft sources used currently, the availability of autografts is limited and allografts are expensive. Therefore, xenobone grafts have drawn attention as a new source of bone grafts, although immunologic rejection issues are unresolved. This study used a GalT knockout mouse model to investigate the effects of reducing the alpha-gal epitope using alpha-galactosidase on the union of porcine xenobone grafts.
  
  
  METHODS
  Sixty-eight alpha-gal knockout C57/BL6 mice and eight wild-type mice were used. The mice were divided into five groups: In group 1 (26 alpha-gal knockout mice), an alpha-galactosidase-treated porcine xenograft was transplanted into the mouse femur to reduce antigenicity, and intramedullary fixation was performed. In group 2 (26 alpha-gal knockout mice), a non-treated porcine xenobone graft was performed. In group 3 (eight alpha-gal knockout C57/BL6 mice), syngenic bone grafts were performed. In group 4 (eight wild-type C57/BL6 mice), syngenic bone grafts were performed. In group 5 (eight C57/BL6 alpha-gal knockout mice), a bone defect model was obtained by maintaining the gap of the osteotomy site. Groups 3, 4, and 5 were used for positive and negative control groups. Qualitative immunohistochemical analysis of the porcine bone was performed to detect the presence of the alpha-gal epitope in groups 1 and 2. The concentration of the anti-alpha-gal antibody was evaluated using a quantitative enzyme-linked immunosorbent assay (ELISA) at the time of sacrifice (3, 4, and 5 weeks after the operation). Histologic and radiologic results (Goldberg method) for the bone union were compared.
  
  
  RESULTS
  The qualitative immunohistochemical analysis showed that the alpha-gal epitope was reduced when xenobone grafts were treated with alpha-galactosidase. Compared with group 2, group 1 showed a low anti-alpha-gal antibody concentration in the ELISA results. In group 2, the anti-alpha-gal antibody concentration increased with time. Group 1 showed significantly better histologic union than group 2, but the amount of radiologic union was similar in the two groups.
  
  
  CONCLUSIONS
  Alpha-galactosidase treatment of a porcine xenobone graft can reduce the alpha-gal epitope. This reduction in the antigen could significantly reduce the humoral immune response to the alpha-gal antigen in C57/BL6 alpha-gal knockout mice, leading to significant improvements in histologic union. This study provides a relevant GalT knockout mouse model for detecting the effects of alpha-gal epitope reduction by alpha-galactosidase on the union of porcine xenobone grafts.
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Moon Seok
authors.initials: MS
authors.lastname: Park
authors.forename: Tae Gyun
authors.initials: TG
authors.lastname: Kim
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Chin Youb
authors.initials: CY
authors.lastname: Chung
authors.forename: Soon-Sun
authors.initials: SS
authors.lastname: Kwon
authors.forename: Il-Hee
authors.initials: IH
authors.lastname: Yoon
authors.forename: Chung-Gyu
authors.initials: CG
authors.lastname: Park
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D016025:Bone Transplantation / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005819:Genetic Markers; D006084:Graft Rejection / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control*; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000276:immunology / Q000627:therapeutic use*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013977:Tibia / Q000637:transplantation*; D014183:Transplantation, Heterologous / Q000379:methods*; D016896:Treatment Outcome; D000519:alpha-Galactosidase / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D015415:Biomarkers; D005819:Genetic Markers; D007166:Immunosuppressive Agents; D000519:alpha-Galactosidase
keywords: alpha-gal; mouse; porcine xenobone graft; union