Media type: E-Article Title: Interface membrane fibroblasts around aseptically loosened endoprostheses express MMP‐13 Contributor: Wagner, Susanne; Gollwitzer, Hans; Wernicke, Dirk; Langer, Rupert; Siebenrock, Klaus A.; Hofstetter, Willy imprint: Wiley, 2008 Published in: Journal of Orthopaedic Research Language: English DOI: 10.1002/jor.20494 ISSN: 0736-0266; 1554-527X Keywords: Orthopedics and Sports Medicine Origination: Footnote: Description: <jats:title>Abstract</jats:title><jats:p>The objective of this article was to assess whether matrix metalloproteinase‐13 (MMP‐13) is produced by cells of the peri‐implant interface tissues and to further characterize these cells. Tissue specimens were collected from the bone–prosthesis interface at the time of revision surgery of clinically loosened hip and knee arthroplasties (<jats:italic>n</jats:italic> = 27). Synovial tissues from osteoarthritic patients and young patients with mild joint deformity were used as controls (<jats:italic>n</jats:italic> = 6). Tissue samples were fixed in 4% PFA, decalcified with EDTA, and embedded in paraffin. Sections (4 µm) were stained with hematoxylin/eosin and for the osteoclastic marker enzyme tartrate resistant acid phosphatase. Monocytes/macrophages were characterized with a monoclonal antibody against CD68 and mRNAs encoding MMP‐13 and α<jats:sub>1</jats:sub> collagen I (COL1A1) were detected by <jats:italic>in situ</jats:italic> hybridization. Cells expressing transcripts encoding MMP‐13 were found in 70% of the interface tissues. These cells colocalized with a cell population expressing COL1A1 mRNA, and were fibroblastic in appearance. MMP‐13 expressing cells were found in the close vicinity of osteoclasts and multinuclear giant cells. No signals for transcripts encoding MMP‐13 were detected in multinuclear giant cells or in osteoclasts. Control tissues were negative for transcripts encoding MMP‐13 mRNA. Fibroblasts of the interface from aseptically loosened endoprostheses selectively express MMP‐13. By the expression and the release of MMP‐13, these fibroblastic cells may contribute to the local degradation of the extracellular matrix and to bone resorption. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:143–152, 2008</jats:p>