DataSheet1_Enhancing autophagy and energy metabolism in the meniscus can delay the occurrence of PTOA in ACLT rat.PDF

Osteoarthritis (OA) is a progressive degenerative joint disease characterized by the destruction of the articular cartilage, meniscus and the like. Autophagy and cellular energy metabolism are the mechanisms by which cells maintain homeostasis. However, little is known about the effects of autophagy and cellular energy metabolism on meniscus degeneration, and the pathogenesis of posttraumatic osteoarthritis (PTOA) after the meniscal injury is rarely reported. Therefore, this study aimed to investigate the relationship between changes in autophagy and cellular energy metabolism in the meniscus following anterior cruciate ligament transection (ACLT) and PTOA induced by subsequent articular cartilage injury. In this study, we use a combination of cell experiments in vitro and animal experiments in vivo. On the one hand, cell experiment results show that inhibiting the mTORC1 signaling pathway by inhibiting the phosphorylation of S6K and AKT proteins in meniscal cells will lead to the increase of Beclin1, LC-3B, ATG12, ULK1, P62, and activate autophagy-related signaling pathways, which in turn protects the extracellular matrix component COL1 of meniscal cells from degradation by catabolic factor MMP13. In addition, it increased the generation of mitochondrial membrane potential in meniscal cells, increased the expression of anti-apoptotic factor BCL-XL, decreased the expression of pro-apoptotic factors BAD and BAX, and reduced the apoptosis of meniscal cells. More importantly, under the stimulation of inflammatory factor IL-1β, the secretion of meniscus cells can reduce the elevated levels of MMP13 and Adamts5 caused by chondrocytes affected by IL-1β. On the other hand, the results of animal experiments in vivo further proved the validity of the results of the cell experiments, and also proved that the meniscus injury did prior to the articular cartilage degeneration after ACLT. In conclusion, this study suggests that the meniscus prior to articular cartilage damage during the development of PTOA after ACLT, and that promoting autophagy and energy metabolism of meniscal cells may be a potential therapeutic target for delaying PTOA.

骨关节炎（Osteoarthritis, OA）是一类以关节软骨、半月板等结构破坏为特征的进行性退行性关节疾病。自噬与细胞能量代谢是细胞维持稳态的核心机制，但目前关于自噬及细胞能量代谢对半月板退变的影响尚不明晰，半月板损伤后继发创伤后骨关节炎（posttraumatic osteoarthritis, PTOA）的发病机制也鲜有报道。为此，本研究旨在探讨前交叉韧带横断术（anterior cruciate ligament transection, ACLT）后半月板组织中自噬与细胞能量代谢的变化，及其与后续关节软骨损伤诱导的创伤后骨关节炎的关联。本研究采用体外细胞实验与体内动物实验相结合的研究方案。一方面，体外细胞实验结果显示：通过抑制半月板细胞中S6K与AKT蛋白的磷酸化水平以阻断mTORC1信号通路，可上调Beclin1、LC-3B、ATG12、ULK1及P62的表达，激活自噬相关信号通路，进而保护半月板细胞外基质组分Ⅰ型胶原（COL1）免受分解代谢因子基质金属蛋白酶13（MMP13）的降解；此外，该处理可提升半月板细胞的线粒体膜电位水平，上调抗凋亡因子BCL-XL的表达，下调促凋亡因子BAD与BAX的表达，最终减少半月板细胞的凋亡。更重要的是，在炎性因子白细胞介素1β（IL-1β）的刺激下，半月板细胞的分泌功能可缓解IL-1β作用下软骨细胞所诱导的MMP13与Adamts5水平升高。另一方面，体内动物实验结果进一步验证了体外细胞实验结论的可靠性，同时证实前交叉韧带横断术后，半月板损伤早于关节软骨退变。综上，本研究表明在前交叉韧带横断术后创伤后骨关节炎的进展过程中，半月板损伤早于关节软骨损伤；而促进半月板细胞的自噬与能量代谢，或可成为延缓创伤后骨关节炎进展的潜在治疗靶点。