Rationale:
Rheumatoid arthritis (RA) is a prototype of inflammatory
arthritis in which synovial fibroblasts (SFs) play key roles in cartilage and bone destruction through
tumor-like proliferation, migration, invasion and
inflammation. This study aimed to research
forkhead box protein C1 (FoxC1) and
microRNA (miR)-141-3p, which modulate pathological changes in the synovial membrane, to find possible strategies for treating RA. Methods: FoxC1, β-
catenin and miR-141-3p gene expression in synovial tissues and SFs was quantified by real-time PCR; FoxC1 and β-
catenin protein levels were evaluated by immunohistochemistry, immunofluorescence, and Western blotting. We transiently transfected human SFs with FoxC1 and β-
catenin overexpression and silencing vectors and assessed proliferation, migration, invasion and
inflammation by cell function and
enzyme-linked
immunosorbent assays. We also assessed downstream signaling activation using immunofluorescence, real-time PCR and Western blotting. Double
luciferase, coimmunoprecipitation and
chromatin immunoprecipitation assays were used to verify miR-141-3p, FoxC1 and β-
catenin gene and
protein combinations. Finally, the
therapeutic effects of FoxC1 silencing and miR-141-3p overexpression were evaluated in
type II collagen-induced
arthritis (CIA) rats. Results: We found that FoxC1 expression was significantly upregulated in synovium and SFs in both RA patients and rats with
collagen-induced arthritis (CIA). FoxC1 overexpression increased β-
catenin messenger RNA (
mRNA) and
protein levels and upregulated
cyclin D1, c-Myc,
fibronectin and
matrix metalloproteinase 3 (MMP3)
mRNA and
protein expression in RA SFs (RASFs). In contrast, FoxC1 knockdown reduced β-
catenin mRNA and
protein levels as well as
cyclin D1, c-Myc, and
fibronectin mRNA and
protein levels in RASFs. Furthermore, altering FoxC1 expression did not significantly change GSK3β and pGSK3β levels. FoxC1 overexpression promoted proliferation, migration, invasion and proinflammatory
cytokine (
interleukin (IL)-1β, IL-6, and
tumor necrosis factor-α (TNF-α)) production and reduced anti-inflammatory
cytokine (IL-10) levels in RASFs. FoxC1 bound to the β-
catenin promoter, and β-
catenin mediated the FoxC1-induced pathological changes. We also observed downregulated
microRNA (miR)-141-3p expression in SFs from both RA patients and CIA rats and further found that miR-141-3p bound to the FoxC1
3'UTR and suppressed FoxC1 expression. Intra-ankle miR-141-3p agomir or FoxC1-specific
siRNA injection hindered CIA development in rats. Conclusions: FoxC1 and miR-141-3p participate in RA pathogenesis by mediating
inflammation and SF proliferation, migration, and invasion and thus could be novel targets for RA
therapy as a nonimmunosuppressive approach.