OBJECTIVE To explore the mechanism by which cryptotanshinone improves synovial fibrosis in rats with knee osteoarthritis(KOA) via regulating the p38 MAPK signaling pathway.

METHODS Using network pharmacology to screen common targets and key signaling pathways between cryptotanshinone and KOA, and validating the binding activity through molecular docking. A KOA rat model was established by anterior cruciate ligament transection method. Rats in the low- and high-concentration groups received oral administration of cryptotanshinone(20, 60 mg·kg⁻¹·d⁻¹). The agonist group received intraperitoneal injection of the p38 MAPK agonist anisomycin(5.0 mg·kg⁻¹) combined with high-concentration cryptotanshinone. Synovial tissue was extracted post-treatment. The degree of synovial fibrosis was evaluated by HE and Masson staining. The expression levels of TGF-β, α-SMA, and Collagen Ⅰ in synovial tissue were detected by immunohistochemistry. Serum concentrations of inflammatory factors IL-1β and TNF-α in rat were quantified by ELISA. The mRNA and protein expression of key molecules including TGF-β, α-SMA, Collagen Ⅰ, and p38 MAPK in synovial tissue were determined by qPCR and Western blotting.

RESULTS Through network pharmacology analysis, cryptotanshinone exerted its effects via the MAPK signaling pathway, demonstrating strong binding affinity with core targets. Compared to the sham-operated group, the model group exhibited significantly thickened synovial lining layers with disorganized cellular arrangement. The sub-synovial layer showed extensive inflammatory cell infiltration accompanied by diffuse collagen fiber deposition. The proportion of TGF-β, α-SMA, and Collagen I protein-positive areas markedly increased. Serum levels of IL-1β and TNF-α were elevated. The expression of fibrosis-related proteins(TGF-β, α-SMA, Collagen Ⅰ) and their corresponding mRNAs, as well as p38 MAPK protein and its mRNA, and p-p38 MAPK protein in synovial tissue, were all significantly upregulated. Compared with the model group, rats in the cryptotanshinone group showed markedly improved pathological alterations in synovial tissue, with significant reversal of all the above quantitative indicators. Moreover, the high-concentration group exhibited more pronounced effects than the low-concentration group.

CONCLUSION Cryptotanshinone can improve synovial fibrosis in KOA rats, with a more pronounced effect at higher concentrations. The mechanism may involve the suppression of the p38 MAPK signaling pathway.