The Role Of TET2 Mediated DNA Demethylation In Pathological Myocardial Remodeling And Its Mechanisms

Background:Heart failure refers to the change of cardiac function and structure under the action of various factors,resulting in cardiac circulatory disorder syndrome.It is the final stage of the development of heart diseases,while the current therapy still cannot reverse heart failure effectively.Cardiac remodeling is the basic pathophysiological process of heart failure,which is characterized by myocardial hypertrophy and cardiac fibrosis.DNA methylation modification has been proved to participate in heart diseases.Ten-Eleven Translocation-2（TET2）is a key demethylation enzyme that restores the methylated DNA by catalyzing 5-methylcytosine to 5-hydroxymethylcytosine.In this study,we investigate the role of TET2 in cardiac remodeling.Methods:We determined the expression of TET2 in mouse and human hypertrophic hearts by western blot and immunohistochemistry（IHC）.The expression of TET2 in human umbilical vein endothelial cells was modified by siRNA and adenovirus respectively.The mesenchymal phenotypes were evaluated by qPCR,Western blot,IHC and flow cytometry.Cdh5-CreERT2/TET2^flox/flox;Rosa26-mTmG+/-mice were developed and used for transverse aortic constriction（TAC）-induced cardiac hypertrophy model.Cardiac function and fibrosis were evaluated by serial echocardiography,HE and Masson staining.Vitamin C that could mimic TET2restoration,was intraperitoneally injected to observe its effect on cardiac remodeling.Furthermore,RNA sequencing and whole-genome bisulfite sequencing（WGBS）were used to explore DNA methylation and down-stream gene expression after TET2knocked down.Results:TET2 was abundant in endothelial cells but decreased in hypertrophic hearts.TET2 knockdown in endothelial cells triggered endothelial-to-mesenchymal transition（End MT）,while overexpression of TET2 inhibited the End MT.In vivo,endothelial cells in hypertrophic hearts of TAC had elevated expression of fibroblast markers such as vimentin.Moreover,hearts of Cdh5-Cre ERT2/TET2flox/flox mice showed more severe hypertrophy and impaired function than controls in the TAC model.Vitamin C could partially restore cardiac function and inhibit myocardial fibrosis.RNA sequencing and WGBS revealed that the modification of methylation of EGLN3played an important role in End MT as the downstream gene of TET2.Conclusions:The deficiency of TET2 promotes endothelial-to-mesenchymal transition and cardiac fibrosis.Vitamin C can enhance TET2-dependent DNA demethylation,thus preventing End MT and improving cardiac remodeling.EGLN3works as the downstream gene of TET2 involved in End MT.