Functional significance of nerve growth factor and its receptor (TrkA) in inflammatory arthritis

Excerpt

We read the article by Barthel and colleagues [1] in this issue of Arthritis Research & Therapy with great interest. They reported that neurotrophin receptors/ligands and specifically nerve growth factor (NGF) and NGF receptor (NGF-R) (TrkA and p75) are expressed in synovial fluid (SF) cells and synovial tissue (ST) of patients with rheumatoid arthritis (RA) or spondyloarthritis (SpA). The authors also looked for the cellular source of NGF and demonstrated that the T cells and monocytes/macrophages derived from SF of patients with RA/SpA are enriched with NGF. Furthermore, they reported that ST-derived fibroblast-like synoviocytes (FLSs) did not produce NGF in vitro. In a recent publication, we observed similarly that NGF levels in SF were significantly higher in patients with psoriatic arthritis (PsA) (365.5 ± 85.2 pg/mL) or RA (120 ± 35 pg/mL) than in patients with osteoarthritis (OA) (30 ± 6 pg/mL) [2]. However, in regard to the source of NGF, we observed that FLSs produced a significant amount of NGF. Here, we would like to share our observations about the NGF/TrkA system in human FLSs and its function. …