Figure 2. Functions of microRNAs in the cardiovascular system.

(A) Table summarizing microRNA functions in myocardium and vasculature. + indicates that the process is promoted by the indicated microRNA, – indicates the pathophysiologic process is prevented by the indicated microRNA. Information on microRNAs that promote or impair cardiac function, after their elevation or inhibition, is provided in the respective column. (B) Exemplary microRNAs that control targets involved in cell-to-cell communication in the cardiovascular system (information compiled from studies cited in Table 1). (C) Paracrine roles of exemplary secreted microRNAs in the cardiovascular system. Atheroprotective effects are exerted by extracellular miR-126-3p (184) and miR-143-3p/miR-145-3p, proangiogenic effects are exerted by exosomal miR-143-3p, miR-222-5p, miR-92a-3p, and miR-214-3p, whereas miR-320-3p confers the opposite effect. The passenger (3′) strand of miR-21 is enriched in exosomes from cardiac fibroblasts, promoting cardiac myocyte hypertrophy (156), whereas the miR-21 guide strand, released by endometrial mesenchymal stem cells, is cardioprotective by promoting cell survival and angiogenesis (157). In the retrograde direction, several microRNAs of myocardial origin promote the mobilization of progenitor cells in bone marrow (102). miR-223-3p is delivered by platelets and regulates differentiation and proliferation of vascular SMCs (193). For an overview on these and other cardiovascular microRNAs with proposed paracrine function, see refs. 99–101. EC, endothelial cell; SMC, smooth muscle cell.