Abstract
The delivery of therapeutic long non-coding RNAs (lncRNA) to the heart by extracellular vesicles (EVs) is promising for heart repair. H19, a lncRNA acting as a major regulator of gene expression within the cardiovascular system, is alternatively spliced, but the loading of its different splice variants into EVs and their subsequent uptake by recipient cardiac cells remain elusive. Here, we dissected the cellular expression of H19 splice variants and their loading into EVs secreted by Wharton-Jelly mesenchymal stromal/stem cells (WJ-MSCs). We demonstrated that overexpression of the mouse H19 gene in WJ-MSCs induces the expression of H19 splice variants at different levels. Interestingly, EVs isolated from the H19-transfected WJ-MSCs (EV-H19) showed similar expression levels for all tested splice variant sets. In vitro, we further demonstrated that EV-H19 was taken up by cardiomyocytes, fibroblasts, and endothelial cells (ECs). Finally, analysis of EV tropism in living rat myocardial slices indicated that EVs were internalized mostly by cardiomyocytes and ECs. Collectively, our results indicated that EVs can be loaded with different lncRNA splice variants and successfully internalized by cardiac cells.