Inhibition of DYRK1a Enhances Cardiomyocyte Cycling After Myocardial Infarction

Background: DYRK1a (dual-specificity tyrosine phosphorylation-regulated kinase 1a) contributes to the control of cycling cells, including cardiomyocytes. However, the effects of inhibition of DYRK1a on cardiac function and cycling cardiomyocytes after myocardial infarction (MI) remain unknown. Methods: We investigated the impacts of pharmacological inhibition and conditional genetic ablation of DYRK1a on endogenous cardiomyocyte cycling and left ventricular systolic function in ischemia-reperfusion (I/R) MI using alpha MHC-MerDreMer-Ki67p-RoxedCre::Rox-Lox-tdTomato-eGFP (RLTG) (denoted alpha DKRC::RLTG) and alpha MHC-Cre::Fucci2aR::DYRK1a(flox/flox) mice. Results: We observed that harmine, an inhibitor of DYRK1a, improved left ventricular ejection fraction (39.5 +/- 1.6% and 29.1 +/- 1.6%, harmine versus placebo, respectively), 2 weeks after I/R MI. Harmine also increased cardiomyocyte cycling after I/R MI in alpha DKRC::RLTG mice, 10.8 +/- 1.5 versus 24.3 +/- 2.6 enhanced Green Fluorescent Protein (eGFP)+ cardiomyocytes, placebo versus harmine, respectively, P=1.0x10(-)(3). The effects of harmine on left ventricular ejection fraction were attenuated in alpha DKRC::DTA mice that expressed an inducible diphtheria toxin in adult cycling cardiomyocytes. The conditional cardiomyocyte-specific genetic ablation of DYRK1a in alpha MHC-Cre::Fucci2aR::DYRK1a(flox/flox) (denoted DYRK1a k/o) mice caused cardiomyocyte hyperplasia at baseline (210 +/- 28 versus 126 +/- 5 cardiomyocytes per 40x field, DYRK1a k/o versus controls, respectively, P=1.7x10(-)(2)) without changes in cardiac function compared with controls, or compensatory changes in the expression of other DYRK isoforms. After I/R MI, DYRK1a k/o mice had improved left ventricular function (left ventricular ejection fraction 41.8 +/- 2.2% and 26.4 +/- 0.8%, DYRK1a k/o versus control, respectively, P=3.7x10(-2)). RNAseq of cardiomyocytes isolated from alpha MHC-Cre::Fucci2aR::DYRK1a(flox/flox) and alpha MHC-Cre::Fucci2aR mice after I/R MI or Sham surgeries identified enrichment in mitotic cell cycle genes in alpha MHC-Cre::Fucci2aR::DYRK1a(flox/flox) compared with alpha MHC-Cre::Fucci2aR. Conclusions: The pharmacological inhibition or cardiomyocyte-specific ablation of DYRK1a caused baseline hyperplasia and improved cardiac function after I/R MI, with an increase in cell cycle gene expression, suggesting the inhibition of DYRK1a may serve as a therapeutic target to treat MI.