ISG15 signalling in coronary microvascular endothelial cells as a key determinant of adverse remodelling in diabetic cardiomyopathy

Abstract

Objective: Type 2 diabetes mellitus (T2DM) is a progressive metabolic disorder associated with increased cardiovascular risk. Diabetic cardiomyopathy (DCM), characterised by subclinical diastolic dysfunction, microvascular injury, and heightened susceptibility to cardiac stress, is a major contributor to chronic heart failure. Preventive and therapeutic strategies for DCM remain limited due to incomplete understanding of its underlying mechanisms. Emerging evidence implicates endothelial microvascular dysfunction as a central pathogenic process. This PhD thesis aimed to identify key pathological signalling pathways driving coronary microvascular endothelial dysfunction in DCM.

Methods: Differential gene expression analyses were performed on cardiac tissue from an established mouse model of DCM using single nuclei and total RNA sequencing. Integration with the human cardiac cell atlas identified capillary endothelial-enriched genes, which were analysed using Ingenuity Pathway Analysis to identify pathogenic pathways, highlighting interferon signalling. Key pathway intermediates were examined in human cardiac microvascular endothelial cells (HCMECs) exposed to high glucose to model diabetes-associated endothelial dysfunction, with endothelial junctional integrity as the primary functional endpoint. ISG15 was selected for further investigation using pharmacological inhibition of JAK/STAT signalling, ISG15 siRNA knockdown in vitro, and siRNA nanoparticle targeting in vivo.

Results: Integrated transcriptomic and protein analyses identified ISG15 as a central mediator of endothelial interferon signalling in experimental diabetes with translational relevance for DCM. In vitro studies confirmed ISG15 as a key driver of hyperglycemia induced endothelial inflammation and dysfunction, which were attenuated by JAK/STAT inhibition and ISG15 silencing. Endothelial ISG15 expression also promoted cardiac fibroblast differentiation through altered cytokine secretion, implicating paracrine signalling in pathological remodelling. In vivo ISG15 siRNA nanoparticle delivery reduced adverse structural and functional remodelling in DCM mice. Conclusion: ISG15 is a key regulator of interferon-mediated endothelial microvascular dysfunction in DCM. Targeting ISG15 represents a promising therapeutic strategy to limit cardiac remodelling and functional decline in DCM.