Abstract: Objective To investigate the effect of tanshinone Ⅱ -A (TSⅡ -A) on regulatory T(Treg) / helper T cell 17 (Th17) in osteoarthritis (OA) cartilage degeneration rats, and its regulation on the expression of Toll like receptor 4 (TLR4) signaling pathway related genes. Methods The rat OA model was constructed by injecting papain into the joint cavity, rats then were dividedinto 3 groups for drug intervention: TS Ⅱ -A low-dose group ( TS Ⅱ -A-L), TS Ⅱ -A high-dosegroup (TSⅡ -A-H), and glucosamine sulfate (DGS) group as positive control. Enzyme linked immunosorbent assay was used to detect the levels of tumor crossing factor-α (TNF-α) and interleukin-6 ( IL-6) in serum. TUNEL assay was used to detect the cell apoptosis in rat cartilage tissues. Flow cytometry was used to detect the proportion of Treg and Th17 in spleen tissues. qRT-PCRwas used to detect the mRNA expression levels of TLR4, myeloid differentiation factor 88(MyD88), nuclear factor κB ( NF-κB), aggrecan, Collagen Ⅱ , forkhead / winged helix transcription factor 3 (Foxp3), IL-17, B cell lymphoma-2 (Bcl-2), and Bcl-2 associated x protein(Bax) in rat knee joint cartilage tissues. Western blotting assay was used to detect the expressionlevels of TLR4, MyD88, p-NF-κB, Bcl-2 and Bax in the cartilage tissues. Results The proportion of Treg cells, and the expression levels of aggrecan, Collagen Ⅱ , Foxp3, and Bcl-2 in theOA group were significantly decreased, and the levels of TNF-α and IL-6, the cell apoptosis rate,the proportion of Th17 cells, and the expression levels of IL-17, TLR4, MyD88, p-NF-κB andBax were significantly increased when compared with those in the Sham group. The proportion of Tregcells, and the expression levels of aggrecan, Collagen Ⅱ , Foxp3, and Bcl-2 in the TSⅡ -A-Lgroup, TSⅡ -A-H group, and DGS group were significantly increased, and the levels of TNF-αand IL-6, the cell apoptosis rate, the proportion of Th17 cells, and the expression levels of IL-17,TLR4, MyD88, p-NF-κB and Bax were significantly decreased when compared with those in theOA group. The proportion of Treg cells and the expression levels of aggrecan, Collagen Ⅱ , Foxp3,and Bcl-2 in the TSⅡ -A-H group and the DGS group were significantly increased, and the levels ofTNF-α and IL-6, the cell apoptosis rate, the proportion of Th17 cells, and the expression levels ofIL-17, TLR4, MyD88, p-NF-κB and Bax were significantly decreased when compared with thosein the TSⅡ -A-L group ( all P < 0. 05). No statistically significance in those above indexes werefound between the TSⅡ -A-H group and the DGS group (P> 0. 05). Conclusion Tanshinone Ⅱ -A(TSⅡ -A) could significantly inhibit the expression of TLR4, MyD88, p-NF-κB and reduce thecell apoptosis rate in the articular cartilage tissues of OA rats, which may be related to the improvement of Treg / Th17 imbalance in rats.

Key words: tanshinoneⅡ-A, osteoarthritis, regulatory T cells, Th17 cells, Toll-like receptor 4