Transplantation of embryonic stem (ES) cells into the ischemic and infarcted heart has proven to repopulate cardiac cell populations, attenuate structural cardiac remodeling, and rescue cardiac function. Unfortunately, the pluripotency of ES cells increases risk of teratoma formation in vivo. Exosomes, smaller in comparison to ES cells, are cell free carriers of miRNA, proteins, and lipids, and do not suggest risk of teratoma formation. Exosomes have been proposed to mediate and attenuate regeneration following myocardial infarction (MI), however, the role of exosomes derived from ES cells (ES-Exo) in activating resident cardiac stem cells (CSCs) to undergo cardiac differentiation is not established. In the present study, Stem cell antigen 1 positive (Sca-1+ve) CSCs were isolated, incubated with exosomes, and evaluated for differentiation into the major heart cell types in vitro. Observations of in vitro cardiac differentiation were further established in an in vivo model of MI. Ligation of the coronary artery, or a sham surgery was performed in C57BL/6 mice 8-12 weeks of age. Mice were split among four study groups: sham, MI, MI + H9c2-Exo (a cell line control), & MI + ES-Exo. ES-Exo were transplanted via intramyocardial (IM) injection immediately following coronary artery ligation. At day 14 (D14), chocardiography was used to evaluate cardiac function. Differentiation into the major heart cells was determined by sarcomeric α-actin (cardiomyocytes) and smooth muscle α-actin (vascular smooth muscle cells) immunostaining. Hematoxylin and Eosin and Masson’s Trichrome staining assessed cardiomyocyte hypertrophy and fibrosis, respectively. Immunostaining for major heart cellular markers revealed significant activation of resident Sca-1+ve CSCs to undergo cardiac differentiation after ES-Exo treatment. Cardiomyocyte hypertrophy and myocardial fibrosis were significantly increased following coronary artery ligation. Results from histological staining revealed significantly decreased levels of hypertrophy and fibrosis in hearts transplanted with ESExo following coronary ligation. In summary, our findings advocate ES-Exo as a viable treatment option to repopulate the myocardium with viable heart cells, attenuate cardiac remodeling, and rescue cardiac function.
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Master of Science (M.S.)
College of Medicine
Length of Campus-only Access
Masters Thesis (Campus-only Access)
Hammond, Jamillah, "Embryonic Stem Cell Derived Exosomes Enhance Cardiac Stem Cell Differentiation into Heart Cells" (2018). Electronic Theses and Dissertations. 6036.