Shaoyang Xibi Decoction improves cholesterol accumulation to delay the progression of knee osteoarthritis by regulating the LXRα-ABCA1/ABCG1 signaling pathway

Objective Our study focuses on observing the therapeutic effects of Shaoyang Xibi Decoction on a rat model of knee osteoarthritis and exploring its underlying mechanisms. Methods (1) A rat model of osteoarthritis was established using the modified HULTH method. The experiment was divided into the following groups for intervention: sham operation group, model group, meloxicam group, Shaoyang Xibi decoction low-dose group, Shaoyang Xibi decoction medium-dose group, and Shaoyang Xibi decoction high-dose group. Rats' pain sensation and motor function were evaluated by gait analysis. Cartilage tissue morphology was observed with toluidine blue and safranin O/fast green staining. The levels of inflammatory factors in rat serum were detected by ELISA, and the cholesterol content in rats' knee cartilage was measured by the total cholesterol assay. (2) Rat knee cartilage cells were isolated and cultured in vitro. They were identified using toluidine blue staining. A chondrocyte cholesterol accumulation model was prepared using a cholesterol-β-cyclodextrin complex, and FILIPIN fluorescent staining was employed for identification. Interventions were then carried out using rat medicated serum, LXR-α agonists, and LXR-α inhibitors. The groups included the following: blank group, model group, Shaoyang Xibi group, inhibitor group, agonist group, Shaoyang Xibi + inhibitor group, and Shaoyang Xibi + agonist group. The levels of inflammatory cytokines in the supernatants of the cartilage cells were measured by ELISA, and the total cholesterol content in the cartilage cells was determined using a total cholesterol detection method. (3) Preparation of rat knee osteoarthritis models and chondrocyte cholesterol accumulation models was conducted. Rats were divided into the following groups: sham surgery group, model group, meloxicam group, Shaoyang Xibi Decoction low dose group, Shaoyang Xibi Decoction medium dose group, and Shaoyang Xibi Decoction high dose group. Cells were divided into the following groups: blank group, model group, Shaoyang Xibi Decoction group, inhibitor group, agonist group, Shaoyang Xibi Decoction + inhibitor group, and Shaoyang Xibi Decoction + agonist group. Immunohistochemistry was used to detect the expression of type II collagen in knee joint cartilage, and Western blot and qPCR were used to detect the expression of LXR-α, ABCA1, ABCG1, and chondrogenic matrix synthesis-related molecules COL10, ACAN, SOX9, COL2 in cartilage tissue and chondrocytes. Results (1) Gait analysis results show that after intervention with Shaoyang Xibi Decoction, there is alleviation of pain in rats, enhancement of motor function recovery ( P  < 0.05), and toluidine blue and safranin-fast green staining suggests that Shaoyang Xibi Decoction can protect the cartilage structure. ELISA and cholesterol tests indicate that Shaoyang Xibi Decoction can reduce the expression of inflammatory factors in rats with knee osteoarthritis and improve the cholesterol accumulation in rat knee cartilage ( P  < 0.05). (2) Successful isolation and in vitro culturing of chondrocytes from SD rat knee joints were achieved. FILIPIN fluorescence staining results indicate that the construction of a cholesterol accumulation model in rat chondrocytes was successful. ELISA and cholesterol detection results show that Shaoyang Xibi Decoction can reduce the release of inflammatory factors in chondrocytes and alleviate the accumulation of cholesterol in chondrocytes ( P  < 0.05). (3) Immunohistochemistry, Western blot, and qPCR results demonstrate that Shaoyang Xibi Decoction can promote the expression of cartilage matrix synthesis molecules such as COL10, ACAN, SOX9, and COL2 ( P  < 0.05). Western blot and qPCR results show that Shaoyang Xibi Decoction can enhance the expression of LXR-α and increase the expression of cholesterol reverse transport-related molecules ABCA1 and ABCG1 ( P  < 0.05). Conclusion The Shaoyang Xibi Decoction can activate the LXR-α-ABCA1/ABCG1 Signaling Pathway to promote cholesterol efflux from chondrocytes. This, in turn, enhances the expression of matrix synthesis-related molecules, thereby delaying the progression of knee osteoarthritis in rats. It effectively alleviates pain and improves the motor function of rats with knee osteoarthritis.