Myostatin Enhances the Invasion and Adhesion of the Rheumatoid Arthritis Synovial Fibroblasts and the Transmigration of CD4 ⁺ Th Cells

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation of the synovial joint, leading to pain and joint destruction. Myostatin (MSTN), a member of the TGF-β superfamily, plays a critical role as a negative regulator of skeletal muscle growth, and recent studies have shown upregulation of MSTN expression in the synovial tissues of RA patients, suggesting the potential role of MSTN in the pathogenesis of the disease. We hypothesized that MSTN regulates the RA synovial fibroblasts (RASFs) invasion/adhesion and immune cell infiltration. For cell invasion assay, the immortalized RASF cells (MH7A) and healthy synovial fibroblasts (HSFs) were treated with MSTN (0, 10, and 20 ng/ml) and TGFβ (20 ng/ml) in a cell invasion chamber for 24 h at 5% CO 2 and 37° C. A transwell migration assay measured the transmigration of CD4 + Th cells. RASFs or HSFs were stimulated with MSTN (0, 10, and 20 ng/ml) for 24 h, and the conditioned culture medium (CCM) was collected. CXCL-1 and IL-17 were blocked by anti-CXCL1 or anti-IL17 antibodies (8 μg/ml). Transmigration of CD4 + Th cells was performed for 6 h at 37° C and 5% CO 2, and the cells were stained for immunofluorescence. Data were analyzed using the Kruskal-Wallis rank sum test and Dunn’s multiple comparison test. Results showed that 20 ng/ml MSTN significantly increased RASF cell invasion with 2.3-fold compared with non-treated RASFs, but HSF cell invasion was not observed by MSTN or TGF-β treatment. The results of the transmigration assay demonstrated that CD4 + Th cell transmigration was significantly increased dose-dependently in RASF CCM stimulated with MSTN. The CD4 + Th cell transmigration was significantly decreased in CXCL1-blocked CCM compared to IL17-blocked CCM with 10.3-fold and 7.9-fold decrease in 20 and 10 ng/ml MSTN-stimulated RASF CCM, respectively. CD4 + Th cell transmigration did not happen in MSTN-stimulated HSF CCM. In summary, our findings show that MSTN significantly enhances the invasiveness of RASFs and CD4 + Th cell migration. Furthermore, results show for the first time that CXCL1 is crucial in mediating CD4 + Th cell migration in response to MSTN stimulation. Thus, this study highlights the potential of MSTN as a therapeutic target for mitigating RASF invasion and adhesion and CD4 + Th cell transmigration in RA. This study was funded by NIH 5R01AR043521-29 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.