Abstract 12609: A Novel Cell Ablation Strategy Defines the Regenerative Potential of the Embryonic Mouse Heart
Background: Recent studies demonstrate that the regenerative potential of a mammalian heart declines rapidly after birth. However, the ability of an embryonic heart to regenerate after injury has not been explored in detail. We tested the hypothesis that embryonic mouse hearts exhibit a robust mechanism for regeneration following extensive cell loss.
Methods and Results: We developed a novel strategy to quantitatively ablate defined fractions of embryonic cardiac progenitor cells (CPCs) or cardiomyocytes (CMs) by combining blastocyst microinjection technology with a Cre-Lox based lineage-marking approach to generate chimeric mouse embryos with fractional cell loss during embryogenesis. Using the Nkx2.5-Cre and ROSA26-flox-GFPStop-diphtheria toxin A (DTA) alleles to ablate CPCs at embryonic day 7.5 (e7.5), we found the number of surviving e10.5 embryos with up to 50% CPC ablation was similar to unablated controls, but declined dramatically with higher degrees of ablation (p≤0.01). This result was confirmed by a reverse complementation experiment whereby Nkx2.5-Cre;ROSA26-floxGFPStop-DTA embryonic stem (ES) cells were injected into wild type blastocysts. These findings demonstrate that the embryonic heart is capable of supporting ~50% CPC loss during development, presumably from compensation and replacement by the remaining unablated cells. To address whether developing CMs are capable of myocardial cell replacement, we introduced cardiomyocyte-specific α-myosin heavy chain-Cre;ROSA26-flox-GFPStop-DTA ES cells into wild type blastocysts to fractionally ablate embryonic cardiomyocytes. We found, remarkably, that ablation of ~50% of embryonic cardiomyocytes was also well tolerated. Furthermore, embryos that underwent up to ~50% CPC or CM ablation can survive into adulthood and are indistinguishable from control mice with respect to cardiac chamber size, myocyte number, and overall cardiac function.
Conclusions: Our study reveals that mammalian embryonic hearts possess remarkable ability to regenerate following ablation of CPCs or immature CMs and defines an upper limit for this process. Identification of the mechanisms involved in embryonic heart regeneration may lead to improved strategies for adult cardiac injury repair.
- Cardiac regeneration
- Cardiac development
- Stem/progenitor cells
- Regenerative medicine stem cells
- © 2013 by American Heart Association, Inc.