Immunohistochemical localization of inducible nitric oxide synthase in synovial tissue of human temporomandibular joints with internal derangement

The expression and distribution of inducible nitric oxide synthase (iNOS) w as examined in 12 samples of human temporomandibular joint (TMJ) with inter nal derangement (ID) and four control specimens. In the diseased joints, st rong or definite iNOS reactivity was expressed in synovial lining and endot helial cells; weaker activity was present in synovial fibroblasts. In contr ast, although there was weak expression of iNOS in synovial fibroblasts and endothelial cells in the two control specimens, there was no iNOS staining in the synovial lining cell layers. This original report that iNOS is expr essed in the synovial tissue of the temporomandibular joint indicates that nitric oxide is produced locally at least in the synovial lining in these j oints when affected by internal derangement. (C) 2000 Elsevier Science Ltd. All rights reserved.