Role of the exosomes on the epigenetic modulation of myocardial plasticity in a rodent model of myocardial infarction

Introduction: The communication between fibroblasts and cardiomyocytes underlies the pathological cardiac hypertrophy induced by angiotensin-II (AngII), which contributes to heart failure. Fibroblast-derived exosomes (F-Exo) have been implicated in mediating AngII-induced cardiomyocyte hypertrophy. However, how release of anti-hypertrophic F-Exo is induced, remains an unanswered issue. Sulforaphane (SFN), a naturally occurring isothiocyanate extracted from cruciferous vegetables, attenuates AngII-induced cardiomyocytes hypertrophy. We tested the effects of SFN on the release of anti-hypertrophic F-Exo in vitro. Methods: Murine embryo fibroblasts were treated with non-toxic dose of SFN (3μM/7 days). Intact F-Exo were isolated from cell culture media by differential centrifugation. F-Exo were quantified by Western blot using CD63. Hypertrophy of HL-1 cardiomyocytes was induced by AngII (100nM/12h). Cell viability was assessed by MTT assay. Cell surface area, an indicator of cell hypertrophy, was measured after 3 or 24h incubation with 30μg exosomes isolated from SFN-treated (SFN-F-Exo) or untreated (F-Exo, control) fibroblasts. Uptake by HL-1 of DiA-labeled exosomes was measured under rest or AngII. Exosomal content of Maspin, a protease inhibitor with function of inhibitor of histone deacetylase 1, was assessed by Western blot. Results: Treatment with F-Exo significantly increased HL-1 viability by 53% under stress compared to control. Stressed HL-1 treated for 24h with SFN-F-Exo displayed cell surface area similar to resting cells, but not those treated with F-Exo. Stressed HL-1 exhibited a ~3-fold increase in SFN-F-Exo uptake rather than F-Exo. SFN-F-Exo are enriched in Maspin. F-exo or F-exo-sfn have been injected in the myocardium of infarcted male rats. Transthoracic echocardiography was performed 2 and 28 days after myocardial infarction to study cardiac function . Heart tissue was collected from each rat. By histological analysis we examined scar size and cardiac hypertrophy in the remote and border zone of infarction. Summary/conclusion: SFN increases the uptake of F-Exo which display the ability to prevent AngII-induced cardiomyocytes hypertrophy. Higher content of Maspin in SFN-F-Exo suggests that modulation of exosomal uptake and hypertrophy in stressed cardiomyocytes may be epigenetically driven. We are still analizing results from in vivo experiments.