Selective Cdk9 inhibition resolves neutrophilic inflammation and enhances cardiac regeneration in larval zebrafish

Abstract

Sustained neutrophilic inflammation is detrimental for cardiac repair and associated with adverse outcomes following myocardial infarction (MI). An attractive therapeutic strategy to treat MI is to reduce or remove infiltrating neutrophils to promote downstream reparative mechanisms. CDK9 inhibitor compounds enhance the resolution of neutrophilic inflammation, however, their effects on cardiac repair/regeneration are unknown. Our laboratory has devised a cardiac injury model to investigate inflammatory and regenerative responses in larval zebrafish using heartbeat-synchronised light sheet fluorescence microscopy. We used this model to test two clinically approved CDK9 inhibitors, AT7519 and Flavopiridol, examining their effects on neutrophils, macrophages and cardiomyocyte regeneration. We found AT7519 and Flavopiridol resolve neutrophil infiltration by inducing reverse migration from the cardiac lesion. While continuous exposure to AT7519 or Flavopiridol caused adverse phenotypes, transient treatment accelerated neutrophil resolution while avoiding these effects. Transient treatment with AT7519, but not Flavopiridol, augmented wound-associated macrophage polarisation, which enhanced macrophage-dependent cardiomyocyte number expansion and the rate of myocardial wound closure. Using cdk9−/- knockout mutants we showed AT7519 is a selective CDK9 inhibitor, revealing the potential of such treatments to promote cardiac repair/regeneration.

CDK9 binds and activates SGK3 to promote cardiac repair after injury via the GSK-3β/β-catenin pathway

“…Inhibition of CDK9 impairs the accumulation of neutrophils after injury and inhibits the recruitment of macrophages, thus hindering the repair of zebrafish heart damage. In contrast, transient inhibition of CDK9 can show positive effects (2-h window period) ( 21 ). In this study, we found that the expression pattern of CDK9 was consistent with the gradual loss of myocardial regenerative capacity in vivo , so we speculated that CDK9 might be a key regulator of myocardial regeneration.…”

Regenerative neurogenesis: the integration of developmental, physiological and immune signals

“…Resolution of the neutrophil reaction also supports regeneration in other organ systems. For example, in the larval heart, transient treatment with a Cdk9 inhibitor accelerates reverse migration of neutrophils and subsequent polarisation of macrophages towards a pro-regenerative phenotype (Kaveh et al, 2021; reviewed by Simões and Riley, 2022). Hence, any global treatments that interfere with macrophage function may indirectly influence stem/progenitor cell behaviour because neutrophil abundance or activation state is changed.…”

A curious case of cyclin-dependent kinases in neutrophils

“…A small-molecule multi-CDK inhibitor, AT7519, inhibits RNA polymerase II phosphorylation carried out by CDK7 and 9. 124 Kaveh et al 125…”

“…A small‐molecule multi‐CDK inhibitor, AT7519, inhibits RNA polymerase II phosphorylation carried out by CDK7 and 9 124 . Kaveh et al 125 . have shown that in zebrafish, treatment with this inhibitor or flavopiridol resolves neutrophil infiltration by inducing reverse migration from the cardiac lesion in a cardiac injury model.…”