Gelatinolytic and collagenolytic activity in periprosthetic tissues from loose hip endoprostheses

Objective. To study the contribution of different members of the metallopro teinases (MMP) family in gelatinolytic and collagenolytic potential, namely dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg (DNP-S) sensitive proteoly tic activity, in loose total hip arthroplasty (THA) endoprostheses. Methods. Periprosthetic tissues and fluid samples were collected from patie nts subjected to hip endoprosthesis replacement. DNP-S sensitive proteolyti c activity was evaluated by the degradation of synthetic DNP-S and reverse phase high performance liquid chromatography, while gelatinolytic activity was assessed by gelatin zymography. The isolation and separation of gelatin ases was performed by gelatin- and concanavalin A-Sepharose affinity chroma tographies and the identification of collagenases by immunoblot analysis. Results. High gelatinolytic activity was observed in all periprosthetic tis sue extracts and fluid samples. All samples also exhibited DNP-S degrading activity, without pretreatment by activating agents. Upon fractionation of MMP by gelatin-Sepharose affinity chromatography it was found that the gela tin-unbound collagenases are exclusively responsible for DNP-S degrading ac tivity. Activated species of both MMP-1 and 13 were detected inmost samples , but not the soluble form of MT1-MMP. Separation of gelatinases from each other and treatment with 4-aminophenylmercuric acetate (APMA) revealed that both enzymes mainly existed in complex with tissue inhibitor of metallopro teinase (TIMP). Conclusion. MMP-1 and MMP-13, which exist in activated form, could be respo nsible for the DNPS-degrading activity in periprosthetic tissues and fl;ids , while the gelatinases do not contribute in this potential, since they mai nly exist in complex with TIMP. The 2 collagenases may play a key role in t he loosening of THA endoprostheses.