Transforming growth factor-beta 1 and 2 in the synovial-like interface membrane between implant and bone in loosening of total hip arthroplasty.

OBJECTIVE: Development of a synovial-like membrane in the implant-bone or cement-bone interface has been linked to aseptic loosening of total hip arthroplasties (THA). This tissue consists of a fibrous stroma containing blood vessels and macrophages, but with relatively few lymphocytes, compared to "autoimmune" rheumatoid synovitis. Our aim was to examine transforming growth factor-beta (TGF-beta) in the synovial-like membrane of the interface and pseudocapsular tissue of loose THA and compare it to control knee synovial membrane.
METHODS: Twenty samples obtained from 10 patients with loose THA at revisions performed for aseptic loosening and 10 samples of knee synovial membrane as controls were analyzed for TGF-beta expression using rabbit antihuman TGF-beta 1 and TGF-beta 2 IgG in immunohistochemical staining. Results were quantitated by a semi-automatic VIDAS image analysis system.
RESULTS: Immunoperoxidase staining disclosed TGF-beta in macrophages and fibroblasts and also in some vascular endothelial cells and in occasional lymphocytes. Image analysis showed an increased number of positive cells/mm2 of both TGF-beta 1 (2327 +/- 212 vs 946 +/- 136; p < 0.01) and TGF-beta 2 (2292 +/- 594 vs 311 +/- 113; p < 0.01) compared to the control tissue. Increased expression of both TGF-beta 1 and TGF-beta 2 was also shown in the pseudocapsule (3210 +/- 585 and 1796 +/- 214). Use of cement or type of alloy did not seem to have any great effect on local expression of TGF-beta.
CONCLUSION: Profibrotic and immunosuppressive TGF-beta are increased in the synovial-like membrane in periprosthetic tissues around loose hip prostheses. They may play a role in the formation, maintenance, and growth of the interface tissue, and thus in the aseptic loosening of THA.