Date of Award

Fall 10-21-2024

Embargo Period

11-6-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Regenerative Medicine and Cell Biology

College

College of Graduate Studies

First Advisor

Ge Tao

Second Advisor

Henry Sucov

Third Advisor

Russell Norris

Fourth Advisor

Kristine Deleon-Pennell

Fifth Advisor

Danyelle Townsend

Abstract

Cardiovascular diseases (CVDs) are the leading cause of death in the United States, and heart attack occurs every 40 seconds in the US. A myocardial infarction (MI), or heart attack, results in ischemic injury and cardiomyocyte (CM) death. Mature mammalian CM renewal in the heart is insufficient to repopulate the lost tissue. However, the neonatal mouse heart retains its regenerative capacity through the first week of life, providing a valuable model to identifying regenerative factors.

Recent work by our lab revealed that the main mechanism of CM death in the heart post-MI is ferroptosis. In this study, we investigate the effects of ferroptosis by subjecting regenerative postnatal day 1 (P1) and non-regenerative postnatal day 7 (P7) mice to permanent left anterior descending coronary artery occlusion (LAD-O) and treatment with Ferrostatin-1 (Fer-1), a commercially available ferroptosis inhibitor. Echocardiography and histology revealed impaired cardiac function accompanied by an insignificant increase in infarct size. Immunostaining showed decreased endothelial cell (EC) density alongside reduced macrophage infiltration and M2 polarization. Flow cytometry of ventricular tissue confirmed the macrophage phenotype.

To elucidate CM-derived signaling, we differentiated human induced pluripotent stem cells (hiPSCs) into CMs (iCMs). iCMs were exposed to either Erastin or Staurosporine to induce ferroptosis or apoptosis. Human umbilical vein endothelial cells (HUVECs) were treated with conditioned media from treated iCMs for assays characterizing survival, migration, proliferation, and tube formation. HUVECs treated with conditioned media from ferroptotic iCMs exhibited increased survival and angiogenic activity over apoptotic iCM conditioned media treated HUVECs.

Cytokine array analysis allowed characterization of the ferroptotic iCM secretome, leading to the identification of a potential mechanism involving interleukin-19 (IL-19). We utilized computational modeling of publicly available single-cell RNA sequencing data to predict signaling networks between subpopulations of CMs, ECs, and macrophages that included IL-19. Further, IL-19 administration in P7 LAD-O mice lead to improved EC density and proliferation in the infarct, decreased CM ferroptosis, and improved cardiac function.

This project has led to a better understanding of the beneficial effects ferroptotic cardiomyocytes exert on cardiac remodeling after MI, and the role that regulated CM death plays on the wound healing process.

Rights

Copyright is held by the author. All rights reserved.

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