Frequency of mononuclear diploid cardiomyocytes underlies natural variation in heart regeneration
Related Experiment Video
Updated: Feb 25, 2026
Simultaneous Assessment of Cardiomyocyte DNA Synthesis and Ploidy: A Method to Assist Quantification of Cardiomyocyte Regeneration and Turnover
Published on: May 23, 2016
Michaela Patterson1, Lindsey Barske1, Ben Van Handel1
1Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
Abstract:
Adult mammalian cardiomyocyte regeneration after injury is thought to be minimal. Mononuclear diploid cardiomyocytes (MNDCMs), a relatively small subpopulation in the adult heart, may account for the observed degree of regeneration, but this has not been tested. We surveyed 120 inbred mouse strains and found that the frequency of adult mononuclear cardiomyocytes was surprisingly variable (>7-fold). Cardiomyocyte proliferation and heart functional recovery after coronary artery ligation both correlated with pre-injury MNDCM content. Using genome-wide association, we identified Tnni3k as one gene that influences variation in this composition and demonstrated that Tnni3k knockout resulted in elevated MNDCM content and increased cardiomyocyte proliferation after injury. Reciprocally, overexpression of Tnni3k in zebrafish promoted cardiomyocyte polyploidization and compromised heart regeneration. Our results corroborate the relevance of MNDCMs in heart regeneration. Moreover, they imply that intrinsic heart regeneration is not limited nor uniform in all individuals, but rather is a variable trait influenced by multiple genes.
Insights
Adult mammalian hearts have limited regeneration. This study found that mononuclear diploid cardiomyocytes (MNDCMs) vary significantly between individuals, influencing heart repair after injury. Genetic factors like Tnni3k impact this regenerative capacity.
Area of Science:
- Cardiovascular Biology
- Regenerative Medicine
- Genetics
Background:
- Adult mammalian cardiomyocyte regeneration is considered minimal.
- Mononuclear diploid cardiomyocytes (MNDCMs) are a small subpopulation potentially involved in heart regeneration.
- The variability and role of MNDCMs in adult heart repair remain largely untested.
Purpose of the Study:
- To investigate the variability of adult mononuclear diploid cardiomyocytes (MNDCMs) across different mouse strains.
- To determine the correlation between pre-injury MNDCM content and cardiomyocyte proliferation and functional recovery after heart injury.
- To identify genetic factors influencing MNDCM frequency and their impact on heart regeneration.
Main Methods:
- Surveyed 120 inbred mouse strains to quantify adult mononuclear cardiomyocyte frequency.
- Induced coronary artery ligation in mice to assess cardiomyocyte proliferation and heart functional recovery.
- Utilized genome-wide association studies to identify genes affecting MNDCM composition.
- Performed Tnni3k gene knockout in mice and overexpression in zebrafish to study its role in cardiomyocyte proliferation and regeneration.
Main Results:
- Significant inter-strain variability (>7-fold) in adult mononuclear cardiomyocyte frequency was observed.
- Pre-injury MNDCM content positively correlated with cardiomyocyte proliferation and heart functional recovery post-injury.
- The gene Tnni3k was identified as influencing MNDCM composition; its knockout increased MNDCMs and cardiomyocyte proliferation.
- Tnni3k overexpression in zebrafish led to increased cardiomyocyte polyploidization and impaired heart regeneration.
Conclusions:
- Mononuclear diploid cardiomyocytes (MNDCMs) play a crucial role in adult mammalian heart regeneration.
- Intrinsic heart regeneration is not uniform but a variable trait influenced by genetic factors.
- The gene Tnni3k is a key regulator of cardiomyocyte cell cycle status and heart regenerative potential.
