Elucidating the endocrine regulation of cardiac regeneration in vertebrates

摘要 器官再生潜力在本体论和胚胎学上是不同的。而低等脊椎动物和 新生哺乳动物保持强大的心脏再生能力，成年哺乳动物通常解决 心脏损伤是通过纤维化而不是再生。然而，导致损失的潜在机制 这种在进化和发展中看似有利特征仍然是个谜。哺乳动物心脏 由于心肌细胞细胞周期退出和多倍化而失去再生潜力。使用 心肌细胞倍性作为再生潜力的指标，我们筛选了23种哺乳动物， 发现裸鼹鼠（NMR），Heterocephalus glaber，具有异常高的二倍体 心肌细胞百分比我们发现了心肌细胞倍性与 标准代谢，主要由甲状腺激素（TH）调节的生理参数。血清 对于哺乳动物来说，核磁共振中的TH异常低，初步证据表明核磁共振心肌细胞 可以扩散。此外，我们还观察到TH抑制可增强小鼠心肌细胞的 增殖和降低倍性，而外源性TH抑制斑马鱼心肌细胞增殖。 因此，我们假设NMR具有增强的心脏再生潜力，并且不同的NMR具有不同的心脏再生能力。 核磁共振、小鼠和斑马鱼中的TH水平有助于其独特的心脏再生 潜力我们的目标#1将在体外和体内评估NMR心脏再生潜力。目的 #2将确定TH抑制是否增强成年小鼠的心脏再生。目标3将测试是否 外源性TH抑制斑马鱼心脏再生。TH对心脏功能影响的研究 再生可以产生新的见解的分子控制器官再生潜力， 发展和演变。

ABSTRACT Organ regenerative potential varies ontologically and phylogenetically. While lower vertebrates and neonatal mammals retain robust capacities for heart regeneration, adult mammals generally resolve cardiac injury through fibrosis, not regeneration. However, the underlying mechanisms driving loss of such a seemingly advantageous trait in evolution and development remain enigmatic. Mammalian hearts lose regenerative potential due to cardiomyocyte cell-cycle withdrawal and polyploidization. Using cardiomyocyte ploidy as an indicator of regenerative potential, we screened 23 mammalian species and identified the Naked-Mole Rat (NMR), Heterocephalus glaber, as having an unusually high diploid cardiomyocyte percentage. We uncovered a robust correlation between cardiomyocyte ploidy and standard metabolism, a physiological parameter primarily regulated by thyroid hormone (TH). Serum TH in NMRs is unusually low for a mammal, and preliminary evidence suggests NMR cardiomyocytes can proliferate. Additionally, we have observed that TH inhibition enhances mouse cardiomyocyte proliferation and reduces ploidy, while exogenous TH inhibits cardiomyocyte proliferation in zebrafish. Thus, we hypothesize that NMRs possess enhanced cardiac regenerative potential and that the distinct TH levels in NMRs, mice, and zebrafish contribute to their distinct cardiac regenerative potentials. Our Aim #1 will assess NMR cardiac regenerative potential in vitro and in vivo. Aim #2 will determine if TH inhibition enhances cardiac regeneration in adult mice. Aim #3 will test whether exogenous TH inhibits cardiac regeneration in zebrafish. Studying the influence of TH over cardiac regeneration could yield novel insights into the molecular control of organ regenerative potential in development and evolution.