Substance P receptor (NK₁) gene expression in synovial tissue in rheumatoid arthritis and osteoarthritis

Abstract

The distribution of messenger RNA coding for substance P receptor (NK₁) in rheumatoid synovia and the relationship between signal intensity of NK₁ mRNA and clinical parameters of disease activity were investigated. The synovia from 10 patients with rheumatoid arthritis (RA) and 7 patients with osteoarthritis was investigated by in situ hybridization histochemistry. In rheumatoid synovia, strong hybridization signal of NK₁ mRNA was detected in 80% of the cells in both the lining layer and the interstitial layer. Moreover, the signal intensities of NK₁ mRNA positively correlated with serum C-reactive protein levels and radiographic grade of joint destruction. These results provide histochemical evidence that rheumatoid synoviocytes strongly express NK₁ gene, and the positive relation of the signal intensity of NK₁ mRNA with CRP and radiographic severity suggests that the facilitation of NK₁ gene expression in rheumatoid synovium relate the disease progression of RA. Kiyoshi Sakai, Department of Orthopedic Surgery, Faculty of Medicine, Toyama Medical and Pharmaceutical University 2630 Sugitani, Toyama City, 930-01 Japan