Electroacupuncture enhances CSPCs proliferation in an FGFR4-mediated manner to ameliorate osteoarthritis-associated pain and cartilage degeneration.

BACKGROUND

Osteoarthritis (OA) is an age-related degenerative joint disease for which there are no effective therapies. Although electroacupuncture (EA) has emerged as a potentially effective therapeutic intervention for OA, the underlying mechanisms are not yet fully understood. Cartilage-derived stem/progenitor cells (CSPCs) are known to play a critical role in cartilage repair; however, whether CSPCs contribute to the therapeutic effects of EA has not been well characterized. Accordingly, this study aimed to investigate the involvement of CSPCs in mediating the therapeutic efficacy of EA in OA and to explore the associated mechanisms.

METHODS

CSPCs (CD44+CD90+CD45-) obtained from cartilage specimens of OA mice in EA or control groups were examined based on bulk RNA sequencing. Molecules involved in the functions of CSPCs were investigated through in vitro and in vivo experiments. The effects of fibroblast growth factor receptor 4 (FGFR4) on CSPCs proliferation induced by EA were determined via intraarticular injection of adenoviruses (AAVs) with the targeted inhibition of FGFR4 in chondrocytes of Gremlin 1-creERT mice. Immunofluorescence, immunohistochemistry, Western blot, chromatin immunoprecipitation, and luciferase reporter analyses were used for determining the associated molecular and cellular mechanisms.

RESULTS

Our results indicated that EA intervention alleviated pain behaviors and cartilage degeneration in OA mice, along with upregulated proliferation of CSPCs. An EA-induced increment of FGFR4 played a protective role by inducing CSPCs proliferation. The targeted inhibition of FGFR4 in CSPCs suppressed the efficacy of EA treatment in OA mice. Mechanistically, EA intervention may promote the proliferation of CSPCs via activation of the Ca2+/phosphorylated-calmodulin-dependent protein kinase II (p-CaMKII)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Moreover, FGFR4 expression was induced via direct binding of STAT3 on the Fgfr4 promoter in CSPCs following EA intervention in OA mice.

CONCLUSIONS

Our findings in this study provide valuable insights into the molecular and cellular mechanisms underlying the effects of EA on pain and cartilage degeneration in OA mice. EA may enhance CSPCs' function via the Ca2+/STAT3/FGFR4 signaling pathway in the OA mice model, providing possible novel targets for treating chronic aging-related OA diseases.