Ezh2 Regulates Cartilase Development And Homeostasis

Osteoarthritis(OA)is the most widely affected degenerative chronic osteoarthrosis in the world,seriously affecting the quality of life of patients and leading to huge social and economic costs.It is characterized by pain and functional limitations caused by the degradation of articular cartilage.Epigenetics refers to genetic modification by DNA methylation,histone modification,chromatin remodeling,and microRNA(miRNA)without altering the DNA sequence.Among them,EZH2(Enhancer of Zeste Homo log 2),as a specific methylase,trimethylated lysine on histone H3 to participate in epigenetic regulation.More and more studies have revealed that epigenetics plays an important role in the development of osteoarthritis.To explore the effects and mechanisms of Ezh2 in skeletal development and osteoarthritis,we conducted this study.To explore the effects and mechanisms of Ezh2 in skeletal development and osteoarthritis,we conducted the research of this topic.In this study,we first performed Ezh2 conditional knockout using the Col2a1-CreERT2;Ezh2f/f mice to study the effect of Ezh2 cartilage-specific knockout on endochondral ossification of embryonic and puberty mice.Using GEO(GENE EXPRESSION OMNIBUS)data analysis and osteoarthritis model of C57BL/6J mice,we observed the expression of Ezh2 in human osteoarthritic cartilage in vitro and in mice.Further,in order to explore its expression in arthritis patients,we used histological techniques to analyze 66 articular cartilage samples of OA patients and 5 normal human samples,and found Ezh2-positive subpopulations in patients with osteoarthritis.Next,the Ezh2 was knocked out in adult mice using Col2a1-CreERT2;Ezh2f/f mice,and its effect on the pathological development of osteoarthritis and osteochondral defects was observed.The mechanism of Ezh2 in chondrocytes was obtained by analyzing the RNA-Seq data of mouse primary cells and human osteoarthritis samples.Finally,the mechanism was verified by q-PCR and cell scratch assay.Through the above studies,we found that Ezh2 cartilage-specific knockout during embryonic stage would lead to embryonic shortening malformation,and the cartilage proliferative zone presented a deformity of chondrocytes into clumps.Ezh2 cartilage knockout in adolescent would increase cartilage anabolism.In osteoarthritic isolated chondrocytes,the expression level of Ezh2 was increased.Similarly,in the osteoarthritis model of C57BL/6J mice,EZH2 expression was increased compared with the sham groups.The histological results of the human osteoarthritis sample revealed the presence of EZH2-positive subpopulations in patients with osteoarthritis,and this subgroup exhibited worse pathology of osteoarthritis.Using the pathological model of Col2a1-CreERT2;Ezh2f/f mice,we found that in osteoarthritis and osteochondral defect models,conditional cartilage-specific knockout of Ezh2 would aggravate the pathological development.RNA-Seq data from mouse primary cells and human OA samples suggested that Ezh2 affected chondrocytes via TNF pathway,particularly TNFSF13B.The results of qRT-PCR showed that the expression of Tnfsf13b decreased after Ezh2 knockout,and the scratch test and qRT-PCR further verified the effect of Ezh2 on cell damage repair and hypertrophic ossification by TNFSF13B.And we also explored the mechanism under it.In summary,this study revealed that Ezh2 affected the development and pathological processes of the skeletal system.In patients with osteoarthritis,there were subgroups of EZH2 positive with clinical manifestations,and Ezh2 may affect the pathological development of osteoarthritis through TNFSF13B.