Abstract 16880: Exosomes From Dilated Cardiomyocytes Activate Fibrosis

In dilated cardiomyopathy (DCM), exaggerated fibrosis reduces tissue compliance and accelerates the progression to heart failure. However, the mechanisms for fibrotic remodeling in DCM are not well understood. Exosomes are small extracellular vesicles that function as intercellular messengers. Our hypothesis is that exosomes from hypertrophic stimulated DCM cardiomyocytes activate fibrosis in the heart. We utilized iPSCs reprogrammed from DCM patients and healthy control individuals (CTL) to differentiate them into cardiomyocytes (iCMs). iCMs were stimulated by Angiotensin II, and conditioned media were collected to isolate exosomes thereafter. Fibroblasts were treated with CTL-exosomes and DCM-exosomes respectively in vitro. Meanwhile, we injected exosomes into the mouse hearts in vivo. Fibrotic markers and protein expression were examined by western blot and histology. Additionally, we also analyzed the microRNA profiles in the DCM-exosomes and CTL-exosomes by small RNA sequencing. The microRNAs expressions in exosomes were also confirmed by RT-PCR. We found DCM exosomes treatment significantly upregulated extracellular matrix proteins expressions in fibroblasts. Collagen I, collagen III, and CTGF were significantly upregulated in DCM exosomes treatment group compared to CTL exosomes treatment group. Intramyocardial injection of DCM exosomes into wild type mice (CD-1) caused impaired ejection fraction after 7 days compared to CTL exosomes injection (DCM = 51.5 ± 6.21%*, CTL =64.6 ± 3.99%; * = P < 0.05). Picro sirius red staining for extracellular matrix showed significant increase of fibrosis in DCM exosome injection group, compared to CTL exosomes and PBS group (DCM = 3.08 ± 0.24%*, CTL = 0.087 ± 0.02%, PBS = 0.053 ± 0.01%; * = P < 0.05). Next-generation sequencing of these exosomes exhibited upregulation of a group microRNAs in the DCM exosomes. microRNA-103a upregulation was confirmed in DCM exosomes. Overexpression microRNA-103a resulted in fibroblast activation and upregulation of Col I, Col III, and CTGF expression in vitro. Our findings uncovered a critical role for exosomal microRNA (microRNA-103a) mediating pathological fibrotic remodeling in DCM.