Sensory innervation and inflammatory cytokines in hypertrophic synovia associated with pain transmission in osteoarthritis of the hip: a case-control study.

Abstract

To clarify the sensory innervation and inflammatory cytokines in hypertrophic synovia associated with pain transmission in OA of the hip. A piece of the synovium was extracted during reconstruction surgery in 50 patients with OA of the hip as an inflammatory synovium and in 12 patients with femoral neck fracture as a normal synovium. Each sample was immersed in fixative solution, sectioned on a cryostat, and then processed for immunohistochemistry using antibodies as follows: neuron-specific class III β-tubulin (TuJ-1) as a general marker for nerve fibres, calcitonin gene-related peptide (CGRP) for sensory nerve fibres, nuclear factor κB (NF-κB) for the protein complex controlling the transcription of DNA in cellular responses to painful stimuli, and TNF-α for cytokines involved in acute inflammation. The number of immunopositive cells and fibres were counted using a fluorescence microscope. In the inflammatory synovium of OA of the hip, TuJ-1 was positive in 46% (23 hips). Of those positive for TuJ-1, 78% (18 hips) were also positive for CGRP, but 22% (5 hips) were negative for CGRP. NF-κB was positive in 68% (34 hips). Of those positive for NF-κB, 76% (26 hips) were also positive for TNF-α, but 24% (8 hips) were negative for TNF-α. In normal synovia, all four substances were negative. We suggest sensory innervation and inflammatory cytokines in hypertrophic synovia are associated with nociception in OA of the hip. University Hospital Medical Information Network, www.umin.ac.jp, UMIN000001335.