Attenuation of Cardiomyocyte Hypertrophy Via Inhalation of Isosteviol-Loaded Exosome in Mice

Isosteviol has been investigated with a cardio-treating effect on cardiomyocyte hypertrophy. However, its hydrophilicity suppressed its efficient cellular uptake for targeting the heart. Exosomes were seen as delivery vesicles with excellent histocompatibility; thus, an isosteviol-loaded exosome (Istv-exo) was prepared for cardiopulmonary delivery in this study. For in vivo evaluation, the Istv-exo and isosteviol saline solution was used for inhalation or intragastric administration on Sprague–Dawley rats for an assay of dynamic distribution. The higher biodistribution of Istv-exo in the lung and heart has been confirmed by the dynamic content curve. Istv-exo/isosteviol solution was administered by inhalation/intragastrically to Myh6^-/- mice, a cardiomyocyte hypertrophy model, to explore the therapeutic effect. The heart function of the mice was measured using echocardiography and in situ imaging was used to analyze the morphology of the heart. The higher level of left ventricular internal dimension, ejection fraction, and cardiac output in echocardiography indicated that Istv-exo enhanced improvement of myocardial function. The attenuation of cardiomyocyte hypertrophy in mice treated with inhalation of Istv-exo determined that it contributed to the reversal of pathological hypertrophy phenotypes. Wheat germ agglutinin staining confirmed that cardiomyocyte hypertrophy was reversed to varying degrees in the Istv-exo, intragastrical isosteviol, and positive control groups. Hematoxylin and eosin staining exhibited the enlarging left ventricular and thinning ventricular wall of the treated mice. Drastically less collagen fiber was observed in the positive control group and Istv-exo group. The inhalation administration of isosteviol-loaded exosomes may be better in therapy for cardiomyocyte hypertrophy than intragastric usage of isosteviol.