TRPV1 and osteoarthritis: Engler et al. showed an increased gene and protein expression of IL-6 in cultured synovial fibroblasts from osteoarthritis (OA) and rheumatoid arthritis (RA) patients in response to the TRPV1 agonist capsaicin, suggesting a possible non-neuronal role for TRPV1 in OA and RA pain [51].