Mononuclear Diploid Atrial Cardiomyocytes as a Model to develop Cardiac Regenerative Therapies
Description: Regenerative hearts including those of zebrafish, axolotl, and neonatal mice, have largely mononuclear (MN) diploid (D) cardiomyocytes (CMs). Polyploidy is considered a barrier to cell cycle re-entry and proliferation. A hypothesis in the field is that increasing number of MND CMs can facilitate heart regeneration. In adult human heart, VCMs are largely MN, with 30% being MND. Thus, the substantial proportion of human MND VCMs suggests an important reservoir of VCMs that might be tapped for regeneration. We recently showed that MND ventricular (V) CMs of infarct and border zones more readily undergo polyploidization in response to MI injury than their polyploid counterparts. In contrast to highly binucleated and polyploid adult mouse VCMs, we have found that a majority (74%) of adult mouse atrial (A) CMs are MND. This observation suggests that mouse adult ACMs provide an excellent model to gain insights into cell cycle regulation of MND CMs. Therefore, we have performed time course and pulse-chase EdU labeling, which demonstrated that DNA synthesis in mouse LA CMs results in polyploidization in more than 10% of LA CMs post MI. To gain insight into factors which prevent MND CM proliferation, we will perform single nuclei RNA-sequencing (snRNA-seq) and assay for transposase-accessible chromatin using sequencing (snATAC-seq) analyses to compare gene regulatory networks operative in distinct populations of MND ACMs undergoing distinct states of cell cycle activity both during development and post MI. We anticipate that bioinformatics analyses will define key pathways blocking proliferation in adult MND CMs. Candidate pathways can then be genetically manipulated to examine their role on proliferation of MND CMs. In this regard, our preliminary studies have shown that the DNA damage response (DDR) is selectively upregulated in cell cycle active ACMs post MI. Our overall hypothesis is that comparison of gene regulatory networks in MND ACMs with distinct cell cycle activities during development or post MI will identify key pathways as targets to promote proliferation of MND CMs and heart regeneration post MI. Accordingly, our Specific Aims are: 1. To perform snATAC-seq and snRNA-seq on ACMs in various states of cell cycle activation, and to perform comparative bioinformatics analyses to gain insight into candidate target pathways to achieve proliferation of adult MND CMs. 2. To investigate the role of the DDR factor ATR on ACM cell cycle activity post MI.
Funder: American Heart Association
Amount: $300,000
Funding type: research
Funder scheme: Transformational Project Award
Start date: 2024-07-01
End date: 2027-06-30
Investigators: Sylvia Evans, Sylvia Evans
Institution: The Regents of the University of California, San Diego
Subfield: Molecular Biology
Domain: Life Sciences
Funded outputs count: 2
Funder award ID: 24TPA1288908
OpenAlex ID: G2149457031