The Characterization of Inducible Nitric Oxide Synthase (iNOS) in the Interface Tissue Obtained from Failed Cementless Total Hip Arthroplasty with Femoral Osteolysis

The expression of human inducible NO synthase (iNOS) and membrane-bound interleukin (IL)-6 receptor (mIL-6R) were investigated immunohistologically in relation to the abnormal activation and infiltration mechanism of macrophages in interface tissues surrounding the femoral component of failed cementless total hip arthroplasty (THA). Gene expression of these cytokines at the lesion site was investigated using the reverse transcription-polymerase chain reaction (RT-PCR) method, and mRNAs for iNOS and mIL-6R were found to be expressed in the interface tissue surrounding the femoral component of failed cementless THA. Immunohistochemical investigation revealed the presence of iNOS and mIL-6 R. These results suggest that iNOS and mIL-6R play a role in the focal osteolysis observed in patients with failed cementless hip prostheses. Moreover, iNOS and mIL-6R were expressed in almost identical cells in an autocrine manner, indicating that when iNOS expression is enhanced, mIL-6R expression is also enhanced.