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Dissertation
From cardiac development to regeneration: a new murine model to study the role of cardiogenic transcription factors
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2024
DOI: 10.25820/etd.007736
Abstract
During the development of an embryo, the heart is the first organ to emerge. The process of heart formation is a well-conversed process from lower vertebrates to humans. How the heart develops has been of interest to the scientific community for over a hundred years. Some of the first anatomists were able to identify clinical cases of what would later become known as congenital heart defects (CHDs). Today, CHDs are the most common birth defect, occurring in 1 in 100 live births. Through advancements in genetics and molecular biology research, the underpinnings of the CHDs were unveiled. These causal genes, specifically transcription factors, have been at the forefront of research into the developmental programs that promote cardiogenesis.On the opposite end, cardiovascular disease (CVD) in adults is the leading cause of mortality in the world. Like development, understanding how CVDs arise has been an area of active study. However, the broad range of CVDs has implicated many causal genes and environmental factors. Advancements in research and treatments have improved patient outcomes exponentially. The end goal of these treatments is to find novel methods to regenerate cardiac muscle, which has been lost or damaged. The theorized goal of cardiac regeneration has, to date, not translated to routine clinical practice.
One hypothesis for cardiac regeneration is to investigate the molecular mechanism that dictates cardiogenesis. Thus, in the case of CVDs, the activated developmental program will promote new cardiac muscle growth and restore heart function. The work within this thesis challenges this hypothesis.
Here, using a new mouse model to study embryonic cardiac development, has revealed an unfound role for transcription factors (TFs) Tbx5, Gata4, and Mef2c. These factors share a
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common microRNA regulator, the miR-200 family. Using mice that express an RNA inhibitor to miR-200 caused increased expression of Tbx5, Gata4, and Mef2c during development. The increased expression resulted in the activation of downstream target genes. Employment of single nuclei (sn) Multi-Omic sequencing (RNAseq and ATACseq) of embryonic hearts, found a new cardiomyocyte cell population in hearts with reduced miR-200 expression. Bioinformatic analysis revealed this new population to possess “progenitor-like” qualities. Further investigation of the cardiomyocyte population unraveled how inhibiting miR-200 allows its presence. This new population, with “progenitor-like” qualities, was hypothesized to have a role in aiding cardiac regeneration following an ischemic injury/myocardial infarction.
In a mouse model of ischemic injury/myocardial infarct, inhibiting miR-200 was found to lead to rapid, sustained, and efficient cardiac regeneration. By 3 weeks following the injury, inhibitor mice had significantly increased heart function and reversed chamber dilation. The rate of recovery has been seen in only a few published studies and could be described as “too good to be true.” By 9 weeks, inhibitor mice have regained full heart function, and show no signs of ischemic injury. Molecularly, inhibiting miR-200 increased express of Tbx5, Gata4, and Mef2c. Additionally, the “progenitor-like” population of cardiomyocytes was present post-injury, suggesting a role in regeneration. The ability of inhibitor mice to regenerate post-MI opens to door to potential clinical therapeutic for patients.
Details
- Title: Subtitle
- From cardiac development to regeneration: a new murine model to study the role of cardiogenic transcription factors
- Creators
- Riley James Leonard
- Contributors
- Brad A Amendt (Advisor)John F Engelhardt (Committee Member)Martine Dunnwald (Committee Member)Ling Yang (Committee Member)Eric van Otterloo (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Anatomy and Cell Biology
- Date degree season
- Summer 2024
- DOI
- 10.25820/etd.007736
- Publisher
- University of Iowa
- Number of pages
- xix, 304 pages
- Copyright
- Copyright 2024 Riley James Leonard
- Comment
- This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: https://www.lib.uiowa.edu/sc/contact/
- Language
- English
- Date submitted
- 03/22/2024
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 266-304).
- Public Abstract (ETD)
Today, congenital heart defects (CHDs) are the most common birth defects, while cardiovascular disease (CVD) in adults is the leading cause of mortality in the world. Through advancements in genetics and molecular biology research, the underpinnings of CHDs and CVDs have been unveiled. However, there is still much yet undiscovered that regulates heart development and disease. Though patient care and treatments are exponentially improving, the theorized goal of cardiac regeneration has, to date, not translated to routine clinical practice.
To gain more insight into heart development and disease, a new mouse model to study embryonic development and cardiac regeneration has revealed a new role for microRNA (miR) in these processes. The miR-200 family is expressed during embryonic heart development and disease. The new mouse model inhibits the expression of the miR-200 family causing increased expression of its downstream targets. Inhibitor embryos had heart development phenotypes reminiscent of clinical CHD cases. Deployment of high-throughput sequencing revealed at a cellular level the increased expression of factors preventing heart development from progressing.
Studying the mouse model to inhibit miR-200 in adult CVD, proven to be overall beneficial to health. In a model of the CVD ischemic injury/myocardial infarct, inhibiting miR-200 was found to lead to rapid, sustained, and efficient cardiac regeneration. By 9 weeks, inhibitor mice had regained full heart function and showed no signs of ischemic injury. Inhibiting miR-200 caused activation of developmental pathways which are thought to aid regeneration. These results open the door to potential clinical therapeutic for patients.
- Academic Unit
- Anatomy and Cell Biology; Craniofacial Anomalies Research Center
- Record Identifier
- 9984697847502771
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