Figure 1. Dynamics of fibroblast-mediated exosome secretion and pivotal miRs involved in cardiac hypertrophy.
Following cardiac stress, fibroblasts secrete miR-enriched exosomes, which are enriched with miR-21*. Cardiomyocytes take up the fibroblast-secreted exosomes, which release miR-21*. Targeted knockdown of SORBS2 and PDLIM5 by miR-21* promotes hypertrophy. Many miRs that regulate hypertrophy have been identified and can be considered as tissue specific, circulating, and secreted. Among the latter, only miR-21* has been detected in pericardial fluid in the context of cardiac hypertrophy (21).