[Exploring mechanism of Yiqi Huoluo Formula in improving bone destruction in rheumatoid arthritis via...

This study aims to investigate whether Yiqi Huoluo Formula(YQHLF) exerts anti-bone destruction effects in rheumatoid arthritis(RA) by regulating the fibroblast growth factor receptor 1(FGFR1)/extracellular signal-regulated kinase(ERK)/nuclear factor of activated T-cells cytoplasmic 1(NFATc1) pathway. Forty SD rats were randomly allocated to normal control group, model group, low-, medium-, and high-dose YQHLF groups, and specific FGFR1 inhibitor(PD173074) groups, with eight rats per group. Collagen-induced arthritis(CIA) rat model was established in all groups except for the normal control group. Following modeling, rats in all groups were treated with the corresponding drug and saline intervention for 28 d. During the intervention, the paw thickness of rats in each group was measured, and the arthritis index(AI) was scored on days 0, 7, 14, 21, 28, and 35 after the second immunization, respectively. The changes in limb grip strength of rats before and after treatment were evaluated by using a grip strength meter. Histopathological changes in ankle joints of rats were examined via hematoxylin-eosin(HE) staining, while tartrate-resistant acid phosphatase(TRAP) staining was used to measure the number of osteoclasts(OC) in the ankle joint bone tissue. The levels of inflammatory factors in serum of rats, such as interleukin(IL)-1β, IL-6, tumor necrosis factor-α(TNF-α), and so on, were determined by enzyme-linked immunosorbent assay(ELISA). Western blot was performed to detect the protein expressions of FGFR1, phosphorylated(p)-ERK/ERK ratio, and NFATc1 in tissue of rats, and immunohistochemistry was employed to detect the protein expressions of cathepsin K(CTSK) and matrix metalloproteinase-9(MMP-9) in synovial tissue of rats. Compared with those in the normal group, the rats in model group showed significantly increased paw thickness and AI(P<0.01), alongside significantly decreased grip strength(P<0.01). Ankle joints in the model group exhibited rough cartilage surfaces, increased number and disordered arrangement of synovial cells, and moderate inflammatory cell infiltration. Furthermore, the number of OC in ankle joints was increased(P<0.01), and the protein expression levels of FGFR1, p-ERK/ERK, NFATc1, MMP-9, and CTSK in synovial tissue were significantly upregulated(P<0.01). Compared with those in model group, the rats in medium-, high-dose YQHLF groups and PD173074 group showed significantly reduced paw thickness and AI(P<0.05, P<0.01) and increased grip strength(P<0.01). These treatments alleviated cartilage damage, synovial hyperproliferation, and inflammatory infiltration, with more regular cell arrangement and reduced matrix hyperplasia. Additionally, the number of OC in ankle joint bone tissue was decreased(P<0.01), and the protein expression levels of FGFR1, p-ERK/ERK, NFATc1, MMP-9, and CTSK in synovial tissue were significantly downregulated(P<0.05, P<0.01). These findings suggest that YQHLF may alleviate bone destruction in CIA rats by downregulating the FGFR1/ERK/NFATc1 pathway and inhibiting OC differentiation and inflammatory responses.