Date of Award

Fall 12-19-2025

Embargo Period

12-1-2030

Document Type

Dissertation - MUSC Only

Degree Name

Doctor of Philosophy (PhD)

Department

Regenerative Medicine and Cell Biology

College

College of Graduate Studies

First Advisor

Henry Sucov

Abstract

The development of heart failure after myocardial infarction (MI) is driven by the failure of CMs to regenerate after injury, resulting in replacement with a stiff, fibrotic scar and impairing overall cardiac contractility. Fetal CMs are characteristically diploid and regenerative, while adult CMs are polyploid and nonregenerative. Increased polyploidy in postmitotic CMs remains a significant barrier to regeneration in the adult heart. Previously, through the analysis of multiple mouse strains, our lab has shown that Tnni3k, a cardiac specific kinase, increases polyploidy in the adult heart. The mechanisms that regulate CM polyploidization are unknown but could be due to a multitude of changes including reactive oxygen species (ROS) production from the influx of O2 after birth, metabolism changes, and ROS production from neighboring cells. ROS is essential in cardiac development and works to promote maturation and facilitate cell signaling. Yet, previous studies have shown that the postnatal increase in ROS triggers CM cell cycle exit. Since Tnni3k has been implicated in this process, here we investigated if Tnni3k converges with ROS, potentially through a ROS responsive protein, to induce CM polyploidization. To test this, glucose oxidase (GO) was used to increase H2O2, followed by measurement of Tnni3k activity in vitro. Results indicate that Tnni3k autophosphorylation is increased by extracellular H2O2, and that extracellular ROS is a mediator of CM MN frequency, suggesting that redox signaling could be signaling through Tnni3k activation. Additionally, we identify a misinterpretation in the literature, and further show that Tnni3k interacts with two cytoplasmic Prdxs, Prdx1 and Prdx2. We provide evidence that these interactions are dependent on extracellular H2O2 and demonstrate that a mixed disulfide intermediate forms between Tnni3k and Prdx2. Finally, we show that Prdx2 activity increases Tnni3k activity, identifying a novel signaling axis that could be a potential therapeutic target. These findings reveal a potential new mechanism by which excess ROS could induce CM cell cycle exit and polyploidization, providing insight into how cellular redox state influences CM regenerative potential.

Rights

Copyright is held by the author. All rights reserved.

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