The expression of substance P in human temporomandibular joint samples: an immunohistochemical study

The expression of neuropeptide substance P was examined in 18 human temporomandibular joint (TMJ) samples with internal derangement of the TMJ, and in 10 control specimens. The examination was carried out using an immunohistological technique, using paraffin-embedded tissue and specific anti-human substance P polyclonal antibody. We noted five characteristic distribution patterns of substance P expression: at the nerves' fibre bundles in the connective tissues of the anterior and/or posterior attachment; around the blood vessels in the attachments; at the margin of the TMJ disc and synovial membrane layer; on the surface of hypertrophic synovial membranes with inflammation and proliferation; and around the newly formed capillaries in the TMJ discs. In TMJs with internal derangement associated with severe pain, we found distinct substance P expression in most of the specimens. The expression was particularly intense at the margin of the TMJ disc and synovial membrane layer, on the surface of hypertrophic synovial membranes and around the newly formed capillaries in the TMJ discs. The clinical symptoms of internal derangement of the TMJ are thought to be associated with the degree of synovitis. We conclude that the expression of substance P seems to be closely related to histopathological changes of the human TMJ with internal derangement.