Myostatin regulates the expression of inflammatory cytokines and chemokines, invasion of rheumatoid arthritis synovial fibroblasts, and the CD4+ Th cells’ transmigration

Abstract

Rheumatoid arthritis synovial fibroblast cells (RASFs), which are present in the rheumatoid synovium, play a pivotal role in the destructive process of RA. Myostatin (MSTN), a regulator of skeletal muscle mass, is highly expressed in the synovium of RA. However, its function in RASFs during the progression of RA remains poorly understood. We hypothesized that MSTN regulates the expression of inflammatory cytokines, chemokines, and matrix metalloproteinases (MMPs), RASF cell invasion, and immune cell transmigration. The immortalized MH7A cells (RASFs) and healthy synovial fibroblasts (HSFs) were treated with MSTN (0, 10, and 20 ng/mL) for 0, 24, and 48 h. Then, the secretion and expression of inflammatory cytokines (IL-8, IL-17, TNF-, IL-6, IL-23, IFN-, IFN-) and chemokines (CCL2, CCL20, CXCL13, CXCL1) were measured by ELISA, RT-qPCR, and western blots. Furthermore, RASFs and HSFs were treated with TNF-, IL-17, IFN-, IFN-, CCL2, and CXCL1 (0 and 20 ng/mL) for 24 h to examine their effects on MSTN. The impact of MSTN on the proliferation of Thy-1(CD90)+ RASFs and HSFs was analyzed by immunofluorescence. CD4+ Th cell transmigration under MSTN-treated RASF and HSF culture medium was measured using a transwell transmigration assay. MSTN-treated RASF and HSF cell invasion was also measured. The RASF phenotype differs from the HSFs, exhibiting high cell proliferation and elevated expression of cytokines and chemokines. MSTN treatment (20 ng/mL) significantly increased the secretion and expression of inflammatory cytokines and chemokines, with CXCL1 being the highest induction by MSTN in RASFs. IFN- and IL-17 significantly increased MSTN expression in RASFs. MSTN did not affect the proliferation of Thy-1(CD90)+ RASF and HSF cells. Current results demonstrate a cross-stimulation between MSTN and inflammatory cytokines and chemokines. MSTN significantly increased RASF cell invasion and CD4+ Th cell transmigration. Blocking CXCL1 and IL-17 significantly decreased the CD4+ Th cell transmigration, and the decrease in CD4+ Th cell transmigration by CXCL1 blocking was much more significant than that by IL-17, underscoring the critical role of CXCL1 signaling in immune cell infiltration. This study highlights the potential of MSTN as a therapeutic target for mitigating inflammation in RA.