Regulation of heart regeneration by LSD1 through suppressing CEND1

Background: Improving heart regeneration through reactivating cardiomyocyte proliferation holds a great potential for repairing diseased hearts. We recently reported that LSD1-dependent epigenetic repression of Cend1 transcription is prerequisite for cardiomyocyte proliferation and mouse heart development. This study interrogates the potential role of this LSD1-CEND1 axis in heart regeneration and repair. Methods: The cardiomyocyte-specific Lsd1 knockout or overexpression mice, Cend1null mice and cardiomyocyte-specific Cend1 overexpression mice were used to determine the role of LSD1-CEND1 axis in heart regeneration after experimental injuries. Neonatal and adult mice were subjected to apical resection or left anterior descending coronary artery ligation, respectively, to establish cardiac injury models. Echocardiography and Masson staining were employed to assess cardiac function and histopathology, respectively. The molecular changes were determined using RNA sequencing, quantitative RT-PCR, Western blotting and immunostaining. Results: Cardiomyocyte-specific deletion impeded neonatal heart regeneration, while overexpression of Lsd1 had the opposite effect. RNA sequencing revealed that Cend1, a crucial suppressor of cardiomyocyte cycling, was the most significantly elevated gene induced by Lsd1 loss during heart regeneration. Cardiomyocyte-specific Cend1 overexpression hindered neonatal heart regeneration, while Cend1 loss in nullizygous mice had the opposite effect. Cend1 deletion resulted in gene expression alterations associated with enhanced cardiomyocyte proliferation, neovascularization, and macrophage activation. Furthermore, the cardiac regeneration defect caused by Lsd1 loss was not observed when experiments were performed with mice that were nullizyogus for Cend1. Moreover, we found that either Lsd1 overexpression or Cend1 deletion could promote heart regeneration and repair, and improve cardiac function following experimental myocardial infraction in adult mice. Overall design: Heart tissues were collected from P14 control and Cend1-KO mice and subjected to RNA sequencing

研究背景：通过重新激活心肌细胞（cardiomyocyte）增殖以改善心脏再生，在病变心脏的修复中具有巨大应用潜力。本课题组此前报道，依赖于LSD1的Cend1转录表观遗传抑制是心肌细胞增殖与小鼠心脏发育的必要前提。本研究旨在探究该LSD1-CEND1轴在心脏再生与修复中的潜在作用。研究方法：本研究使用心肌细胞特异性Lsd1敲除或过表达小鼠、Cend1纯合敲除（Cend1null）小鼠以及心肌细胞特异性Cend1过表达小鼠，以明确LSD1-CEND1轴在实验性心脏损伤后再生过程中的作用。分别对新生小鼠与成年小鼠实施心尖切除术与左前降支冠状动脉结扎术，以构建心脏损伤模型。采用超声心动图与马松染色分别评估心脏功能与组织病理学变化。通过RNA测序、定量实时逆转录聚合酶链反应（qRT-PCR）、蛋白质印迹法（Western blotting）与免疫染色检测分子水平变化。研究结果：心肌细胞特异性Lsd1敲除会阻碍新生小鼠心脏再生，而过表达Lsd1则可产生相反效果。RNA测序结果显示，作为心肌细胞周期关键抑制因子的Cend1，是心脏再生过程中Lsd1缺失诱导上调最显著的基因。心肌细胞特异性Cend1过表达会抑制新生小鼠心脏再生，而Cend1纯合敲除小鼠则呈现相反表型。Cend1缺失可导致与心肌细胞增殖增强、血管新生以及巨噬细胞活化相关的基因表达谱改变。进一步实验发现，当使用Cend1纯合敲除小鼠开展实验时，Lsd1缺失引发的心脏再生缺陷表型消失。此外，本研究发现，在成年小鼠的实验性心肌梗死模型中，过表达Lsd1或敲除Cend1均可促进心脏再生与修复，并改善心脏功能。实验整体设计：收集出生后14天（P14）野生型对照小鼠与Cend1敲除（Cend1-KO）小鼠的心脏组织，进行RNA测序。