Abstract
Pericardial fluid (PF) plays physiological and pathological roles through paracrine signalling within the microenvironment of the heart. These paracrine effects are mediated by exosomes released by various cells that carry cargo and host cell markers. Among the various cargoes, microRNAs (miRNAs) within exosomes play a critical role in their functionality. miRNAs are non-coding RNAs that regulate gene expression post-transcriptionally. Diabetes-induced dysregulation of miRNAs in the heart is associated with increased apoptosis and reduced functionality. PF exosomes have been shown to contain cardiac-specific miRNAs; however, their alterations in response to diabetes are unknown. This study aimed to examine the molecular and functional roles of PF exosomes and their miRNAs in diabetic hearts.
PF exosomes from diabetic and non-diabetic individuals undergoing coronary artery bypass graft surgery at Dunedin Public Hospital were isolated and analysed using a NanoString n-counter to obtain miRNA profiles. Following further validation, two miRNAs were chosen for therapeutic modulation studies using an in vitro model of type-2 diabetes, incorporating both insulin resistance and hyperglycaemia. As exosomes contain a complex mix of cargoes that collectively modulate cellular functions, the functional role of whole PF exosomes was assessed.
NanoString analysis identified 798 miRNAs, of which 57 were significantly altered in diabetic PF exosomes. The overexpression of miRNA-181a-5p and miRNA-206 in diabetic PF exosomes was confirmed. Therapeutic modulation of miRNA-181a-5p showed inconclusive results. However, therapeutic downregulation of miRNA-206 improved cardiomyocyte survival by target protein restoration. Functional assessment of whole exosomes indicated PF exosomes to increase cardiomyocyte apoptosis and endothelial cell migration, while diabetic PF exosomes impaired endothelial cell angiogenesis.
These results provide novel evidence of altered miRNA profiles in diabetic PF exosomes. Although the molecular and functional roles of individual miRNAs altered in PF exosomes require further study, the molecular alterations in diabetic PF exosomes have downstream effects on recipient cell function.