mRNA expression of matrix metalloproteinases and tissue inhibitors of metalloproteinase in interface tissue around implants in loosening total hip arthroplasty.

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) play an important role in tissue destruction and remodeling. Nine samples of cement interface tissues from nine patients who had failed cemented total hip arthroplasty (THA) were obtained for revision of THA and analyzed on mRNA expression of MMPs and TIMPs. The preoperative serial radiographic examinations revealed an apparent clear zone around all implants. We excluded septic loosening as one of the factors affecting THA. Three samples were obtained from three different sites of the acetabular interface tissue in each patient. After extraction of total RNA from 27 samples, we used the reverse-transcriptional polymerase chain reaction (RT-PCR). mRNA of MMP-1, -2, -3, -9, and TIMP-1 and -2 was detected in the interface tissue. MMP-10 mRNA was not detected, yet MMP-1 and MMP-3 mRNA were commonly observed. TIMP-2 mRNA was also strongly expressed compared to TIMP-1. It was thus demonstrated that MMPs and TIMPs were produced locally in the cemented tissue of THA loosening. These findings may suggest that MMPs and TIMPs expressed around the implants play a critical role in the progression of aseptic loosening of THA.