NGF and rheumatoid arthritis: The NGF mRNA expression levels as determined in ST biopsies were found to be significantly higher in RA (mean expression level 1.6 ± 1.2 SD) as compared with SpA (mean expression level 0.7 ± 0.3 SD) patients (P = 0.02) indicating that NGF is produced locally, at least in the arthritic synovium of RA patients (Figure 3).