Phenotypic characterization of mononuclear cells following anorganic bovine bone implantation in rats

The purpose of this study was to measure inflammatory changes associated with implantation of anorganic bovine bone and bovine bone/collagen composite grafts, and to compare the response to that obtained following grafting with hydroxyapatite. Anorganic bovine bone, either with or without bovine collagen, as well as granular and block forms of synthetic hydroxyapatite, were implanted subcutaneously in Wistar rats. Saline and turpentine oil were used as controls. Biopsies were obtained after 3 days and at 1, 2, 4, 6, and 8 weeks. A panel of 6 monoclonal antibodies was used to detect monocytes, several distinct macrophage subsets, Ia-antigen expression, and T- and B-lymphocytes. Cells identified by each antibody were counted after immunocytochemical staining, and sera obtained 6 weeks after grafting were used in immunoblotting assays to detect antibodies to bovine serum proteins and collagen. Anorganic bovine bone, bovine bone/collagen, and hydroxyapatite all produced a transient macrophage infiltrate that was maximum 3 days after implantation, but resolved to normal levels within 6 to 8 weeks. Lymphocyte infiltration was not elicited by any bovine graft material, and antibodies to bovine serum proteins or type I collagen were not detected in any of the animals examined. These data indicate that a systemic or local immune response does not develop following implantation with anorganic bovine bone or with anorganic bovine bone/collagen materials. It appears appropriate to explore further the merits of these materials for periodontal regenerative procedures.