Abstract P384: Distinct Roles Of Cellular And Extracellular TRNA-derived Small RNAs In Myocardial Fibrosis

Heart failure (HF) remains the leading cause of morbidity and mortality in the US, affecting approximately 6.2 million Americans with an anticipated 46% increase in overall prevalence by 2030. Myocardial fibrosis, defined as increased cardiac fibroblast (CF) activation and excessive extracellular matrix (ECM) deposition, is a leading contributor to the progression of adverse heart remodeling that leads to HF. Despite this clinical importance, no FDA-approved antifibrotic drug is available to prevent the development of HF. There is therefore an urgent need to understand pathways important in myocardial fibrosis that can be targeted with novel therapies. Non-coding RNAs, particularly miRNAs and lincRNAs, have emerged as promising novel biomarkers or therapeutic targets for myocardial fibrosis. As an emerging category of small regulatory non-coding RNAs that was discovered only a decade ago, tRNA-derived small RNAs (tDRs), have been shown to play important roles in cancer and neurological disorders. However, the knowledge of tDRs in myocardial remodeling remains scarce. Here, by using a recently developed tDR sequencing technique, called ARM-seq, we have discovered the unique extracellular tDR fragmentation profile and created an atlas of stress-specific cellular and extracellular tDR signatures in both CFs and cardiomyocytes (CMs). Notably, we identified a nutritional deprivation-induced cellular tRNA-Asp-GTC-3’tDR (cl-tRNA-Asp-GTC-3’tDR) that demonstrates potent antifibrotic effects. In vitro mechanistic studies and transcriptome analysis suggest that the lysosome-localized cl-tRNA-Asp-GTC-3’tDR inhibits CF activation through targeting ECM deposition program and cellular response to TGFβ stimulus and the G-quadruplex motifs are required for its functionality. Meanwhile, a related extracellular tDR derived from the same canonical tRNA, ex-tRNA-Asp-GTC-3’tDR, which has two additional nucleotides at both 5’ and 3’ end of cl-tRNA-Asp-GTC-3’tDR, is specifically enriched in the extracellular vesicles derived from CFs and CMs. Our pilot data suggest that the secretion of ex-tRNA-Asp-GTC-3’tDR may be required for maintaining the homeostasis of CFs and CMs. Importantly, we found that cardiac ischemia significantly decreases the circulating ex-tRNA-Asp-GTC-3’tDR level in both cell culture models and human patients during cardiopulmonary bypass surgery or following acute coronary syndrome. Together, our findings identify a cellular tDR that represents an attractive therapeutic target against myocardial fibrosis and an extracellular tDR with the same origin that has a distinct function and may be translated into novel biomarkers for cardiac ischemia.