Analysis of cardiomyocyte clonal expansion during mouse heart development and injury

Abstract

The cellular mechanisms driving cardiac tissue formation remain poorly understood, largely due to the structural and functional complexity of the heart. It is unclear whether newly generated myocytes originate from cardiac stem/progenitor cells or from pre-existing cardiomyocytes that re-enter the cell cycle. Here, we identify the source of new cardiomyocytes during mouse development and after injury. Our findings suggest that cardiac progenitors maintain proliferative potential and are the main source of cardiomyocytes during development; however, the onset of αMHC expression leads to reduced cycling capacity. Single-cell RNA sequencing reveals a proliferative, “progenitor-like” population abundant in early embryonic stages that decreases to minimal levels postnatally. Furthermore, cardiac injury by ligation of the left anterior descending artery was found to activate cardiomyocyte proliferation in neonatal but not adult mice. Our data suggest that clonal dominance of differentiating progenitors mediates cardiac development, while a distinct subpopulation of cardiomyocytes may have the potential for limited proliferation during late embryonic development and shortly after birth.

Surviving Acute Organ Failure: Cell Polyploidization and Progenitor Proliferation

“…When acute ischemic injury occurs in the heart, cardiomyocyte progenitors can proliferate but this ability declines with age in mammalian hearts ( Figure 3) [19,22,[52][53][54]57,58]. Indeed, neonatal murine hearts can regenerate efficiently after injury [59], mirroring what happens in lower vertebrates (Figure 3) [60][61][62].…”

“…Progenitors are a small subset of parenchymal cells that reside inside adult organs in a more immature structural and functional differentiation state, and hence, do not contribute to organ function, and maintain the capacity to quickly undergo mitosis and to self-renew by asymmetric division (Figure 1) [6,[21][22][23][24]. In adult liver, heart, and kidney such progenitors have been identified as resident diploid parenchymal cells with the capacity to self-renew and differentiate in order to replace lost cells ( Figure 1) [5,7,8].…”

“…However, recent studies have demonstrated a low but constant rate of cardiomyocyte turnover in the adult mammalian heart [46][47][48][49]. Newly generated cardiomyocytes originate from a subpopulation of pre-existing cardiomyocytes that retain their proliferative capacity throughout adulthood [19,22,[46][47][48][49][50]. Several studies have suggested that these may represent a population of cardiomyocyte progenitors [19,22,51,52].…”

“…Newly generated cardiomyocytes originate from a subpopulation of pre-existing cardiomyocytes that retain their proliferative capacity throughout adulthood [19,22,[46][47][48][49][50]. Several studies have suggested that these may represent a population of cardiomyocyte progenitors [19,22,51,52]. Cardiomyocyte progenitors were identified in the adult mouse and human heart by using a variety of approaches: (i) the expression of surface markers such as c-Kit [51,53] or Sca1 (even if no human ortholog exists) [54]; (ii) the demonstration of physiological properties such as the ability to efflux Hoechst dye [55] or to form cardiospheres in culture [56], and (iii) by lineage tracing at a single-cell level [22,52].…”

Spatiotemporal Gene Coexpression and Regulation in Mouse Cardiomyocytes of Early Cardiac Morphogenesis

“…The introduction of single cell RNA-seq technology has started to overcome this limitation. It revolutionizes the studies of gene regulation in embryonic developments by providing a systematic and highthroughput way to profile the expression of hundreds to thousands of cells simultaneously, resulting in the discovery of new cell types, cell state transitions and functions, as well as gene markers that are associated with unique cells populations and functions (Chen, Chakravarty et al, 2016, DeLaughter, Bick et al, 2016, Gladka, Molenaar et al, 2018, Li, Xu et al, 2016, Liu, Wang et al, 2017, See, Tan et al, 2017, Sereti, Nguyen et al, 2018, Skelly, Squiers et al, 2018.…”