Mesenchymal stem cells (MSCs) are immunosuppressive and have been used to facilitate tissue repair in the context of allogeneic implantation. However, xenogeneic cell transplantation has not been fully explored. The present study investigated the feasibility of xenogeneic MSCs implantation in mice. MSCs were harvested from the bone marrow of GFP rats (Green Fluorescent Protein transgenic rats), and cultured as previously described. 1 million GFP MSCs were loaded onto the synthetic HA/TCP porous Skelite blocks and implanted intramuscularly into the quadriceps of the MF1 and SCID mice. After 11 weeks, the implants were harvested and processed for histology examination. Upon termination, the mononuclear cells from the peripheral blood of each animal were also collected for mixed lymphocyte culture to examine lymphocyte proliferation potential and T-cell mediated cell lysis (cytotoxic) assays. In the SCID mice, there was sparse osteoid tissue formation in the implants, whereas only dense connective tissues were seen in the implants of the MF1 mice. Osteocalcin mRNA expression was confirmed in the osteoid tissues in the implants from the SCID mice, but it was not detected in the MF1 mice by RT in situ PCR examination. Cells of GFP-rat origin were observed in both the MF1 and SCID mice (more so in the SCID mice) after 11 weeks implantation, which were confirmed by positive immunostaining of anti-GFP antibody. In the MF1 mice after 11 weeks xenogeneic MSCs implantation, the rate of lymphocyte proliferation was significantly increased when mixed with the GFP-MSCs compared to that of mixed lymphocyte culture assays in the SCID or MF1 mice without xenogeneic MSCs implantation, suggesting that implantation of xenoge-neic MSCs has promoted host anti-graft immunogenic responses towards to otherwise immunosuppressive MSCs. In conclusion, xenogeneic rat MSCs transplanted in immunocompetent mice has survived for prolonged period, but their function was comprised to certain extent and this may be due to the increased host anti-graft immune sensitization after exposed to the xenogeneic MSCs.
Fifty-five patients undergoing isolated acetabular revisions in fifty-seven hips were available for review. In thirty-three of fifty-seven hips there was no significant acetabular deficiency; of the remaining twenty-four hips twenty underwent allograft reconstruction and four autogenous bone grafting. Mean follow-up was four years with a range of three to seven years; there have been no femoral loosening, and three further surgical procedures for hip instability. All acetabular components at last review were soundly fixed with the exception of one patient who underwent excision arthroplasty at twelve months for deep infection. The purpose of this study was to review the functional outcome and the fate of the femoral stem and revised acetabular component following isolated ace-tabular revision. Findings of the current study demonstrate that isolated acetabular revision does not compromise the final functional nor radiographic outcome in acetabular revision in appropriately selected patients; the fate of the femoral component is not adversely influenced by this procedure. There is no need to remove the femoral component at the time of acetabular revision if the femoral component is well fixed and stable by pre- and intra-operative assessment. Prospectively entered data on fifty-seven hips (fifty-five patients) who have undergone isolated acetabular revision without femoral revision was available for review. All patients were assessed pre-operatively and post-operatively on an annual basis by means of physical examination, x-ray, SF-36 and WOMAC questionnaires. In thirty-three of fifty-seven hips there was no significant acetabular deficiency; of the remaining twenty-four hips, one had a segmental defect, thirteen had a cavitary defect and ten had a combined segmental and cavitary defect. Osteolysis existed in the proximal femur of two hips. Bone grafting in twenty-four hips consisted of morselized allograft in nine; combined structural and morselized allograft used in eleven and autogenous bone used in four acetabular defects. Autogenous bone grafting was done in two femoral osteolytic lesions. Mean follow-up was four years with a range of three to seven years. The mean duration of arthroplasty prior to revision was fourteen years (range four to twenty-three years). There were no nerve palsies, vascular injuries or intra-operative fractures in this patient group. All ace-tabular components at latest review were soundly fixed with the exception of one patient who underwent excision arthroplasty at twelve months for deep infection. Twenty-one of the twenty-four hips with bone grafting demonstrated positive radiographic signs of incorporation; the remaining threehips have a stable interface but no evidence of bone ingrowth. Three of the fifty-seven hips presented with hip dislocations after revision arthroplasty; two were managed by closed reduction; the third by open reduction and soft tissue repair.