Regulatory Effect of Kdm6b on Chondrocyte Metabolism in Mouse Cartilage Injury Repair Model

In order to study the expression of lysine-specific demethylase 6B, Kdm6b in differentiation of chondrocyte and chondrogenesis and the regulation effect of Kdm6b on chondrocyte anabolism, a mouse model of osteochondral defects was established in this study. The mice were subjected to antibiotic treatment and intestinal microbiota reconstruction by the method of specific knock out Kdm6b of embryonic cartilage. The mice were divided into Col2al-CreER Kdm6b experimental group and Kdm6b control group and then the destabilization of the medial meniscus operation was performed to model osteoarthritis in mice, which accelerated the abnormal metabolism of cartilage. In addition, transgenic mice with induced chondrocyte specific knockout of Kdm6b were constructed and embryonic samples were collected to study the effects of Kdm6b knockout on cartilage development. At the same time, the proliferation and apoptosis of chondrocytes after kdm6b gene knockout were also studied based on the obvious abnormalities in embryonic chondrogenesis. The results showed that 3 weeks after the mouse osteochondral defect modelling surgery, the mice in the Col2al-CreER; Kdm6b group still had an area without complete healing in the femoral trochle defect, while the defect areas in the Kdm6b group of mice were completely filled. After 12 weeks of mouse osteoarthritis modelling, mice in the Kdm6b group showed cartilage staining loss and cartilage defect. The mice in the Col2al-CreER Kdm6b group were more severe, and even a large area of wear and destruction of the cartilage layer appeared. However, after the growth plate thickness of mice in the Col2al-CreER Kdm6b group was observed, it was found that there was no statistical significance compared with the Kdm6b control group. qRT-PCR analysis showed that compared with the Kdm6b control group, the Col10al gene expression in the primary chondrocytes of the Col2a1-CreER Kdm6b group was significantly decreased. In addition, qRT-PCR and Western Blot sequencing verified that the expressions of Sox9, Col2al, Acan and other proteins related to anabolism were significantly reduced after Kdm6b knockout. Therefore, it can be concluded that Kdm6b directly regulated the expression of genes related to chondrocyte anabolism, and Kdm6b knockout could inhibit the anabolism of chondrocytes, impair the synthesis of cartilage matrix, and accelerate the progress of osteoarthritis.