TISSUE INHIBITOR OF METALLOPROTEINASE-1, COLLAGENOLYTIC AND GELATINOLYTIC ACTIVITY IN LOOSE HIP ENDOPROSTHESES

Objective, To study tissue inhibitor of metalloproteinase 1 (TIMP-1) i n relation to collagenolytic and gelatinolytic potential, namely dinit rophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg (DNP-S) sensitive proteolyt ic activity, in loose total hip arthroplasty (THA) endoprostheses. Met hods. Tissue localization of TIMP-1 was investigated immunohistochemic ally. TIMP-1 level of the periprosthetic tissues and fluid samples fro m 9 loose THA endoprostheses was measured by competitive ELISA, and DN P-S sensitive collagenolytic and gelatinolytic potential was evaluated by the degradation of synthetic DNP-S and reverse phase high performa nce liquid chromatography. Results. Immunohistochemical analysis revea led moderate to marked immunoreactivity of TIMP-1 in pseudosynovial li ning cells, and weak to moderate immunoreactivity often in monocyte/ma crophages, endothelial cells, and fibroblasts in both interface tissue s between bone and implant and pseudocapsular tissues around the artif icial joints. TIMP-1 level was low in interface tissue samples (795 +/ - 203 ng/ml) compared to pseudosynovial fluid samples (2026 +/- 584 ng /ml). Degradation rate of the substrate was higher in interface tissue samples (56 +/- 6%) than in pseudocapsular tissue samples (32 +/- 4%) and pseudosynovial fluid samples (6 +/- 2%). Conclusion. Low TIMP-1 l evel combined with high percentage of degradation of synthetic substra te DNP-S leads to high collagenolytic and gelatinolytic activity in in terface tissue samples. This may in part explain the weakening of peri prosthetic connective tissue. Weakening Combined with cyclic mechanica l loading may lead to loosening of THA endoprostheses.