title: Different healing rates of bone autografts, syngeneic grafts, and allografts in an experimental rat model.
abstract: Matching of donors and recipients for tissue antigens is vitally important for successful transplantation of essentially all organs and tissues, the major exception being bone. The importance of tissue-typing for the healing of bone allografts remains, however, a controversial issue as development of both humoral and cell-mediated immunity against the grafted bone has been observed in some experimental systems. In the present study, we compared the healing patterns of frozen antigen-mismatched allografts, frozen antigen-matched allografts (syngeneic grafts), and fresh cortical bone autografts in an experimental rat model. Histomorphometry of the graft-host interface revealed that new bone formation started significantly earlier in autografts than in allografts or syngeneic grafts. By 2 weeks, the level of new bone formation in the syngeneic grafts had reached that in autografts. Antigen-mismatched allografts, however, continued to exhibit a retarded formation of new bone throughout the union process. These histomorphometric observations were confirmed by molecular biologic analyses for the mRNA levels of type I collagen, which increased earlier and reached a higher level in autografts than in allografts. Use of syngeneic grafts resulted in a longer persistence of type I collagen mRNA expression in the healing tissue than in antigen-mismatched allografts. No apparent differences were seen between allografts and autografts in the expression of type III collagen. No cartilage-specific type II collagen mRNA was observed, indicating that antigen-mismatching or preservation by freezing did not alter the basic mechanism of the interface healing process, although it did slow down the beginning of the process. The experiments suggest that a major antigen mismatch between donor and recipient affects the temporal gene expression of extracellular bone matrix and delays new bone formation at the graft-host interface of cortical bone allografts.
authors.affiliation: Department of Surgery, University of Turku, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Virolainen
authors.forename: E
authors.initials: E
authors.lastname: Vuorio
authors.forename: H T
authors.initials: HT
authors.lastname: Aro
mesh_terms: D000818:Animals; D016025:Bone Transplantation / Q000276:immunology*; D003094:Collagen / Q000737:chemistry; D004195:Disease Models, Animal; D015870:Gene Expression; D006650:Histocompatibility Testing; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D011919:Rats, Inbred Strains; D014182:Transplantation, Autologous; D014184:Transplantation, Homologous; D014185:Transplantation, Isogeneic; D014945:Wound Healing / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D003094:Collagen