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. Heart tissues were collected from P14 control and Cend1-KO mice and subjected to RNA sequencing

背景：通过激活心肌细胞增殖以改善心脏再生，在修复病变心脏领域具有巨大应用潜力。本团队近期研究表明，赖氨酸特异性去甲基化酶1（LSD1，Lysine-specific demethylase 1）对Cend1转录的依赖型表观遗传抑制，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信号轴在心脏再生与修复中的潜在作用。方法：本研究采用心肌细胞特异性Lsd1敲除或过表达小鼠、Cend1全基因敲除（Cend1null）小鼠以及心肌细胞特异性Cend1过表达小鼠，以明确LSD1-CEND1信号轴在实验性心脏损伤后再生过程中的功能。分别对新生小鼠与成年小鼠实施心尖切除术或左前降支冠状动脉结扎术，构建心脏损伤模型。通过超声心动图与Masson三色染色分别评估心脏功能与组织病理学特征。利用RNA测序（RNA sequencing）、定量实时聚合酶链反应（qRT-PCR，quantitative real-time polymerase chain reaction）、蛋白质印迹法（Western blotting）以及免疫染色技术检测分子水平的变化。结果：心肌细胞特异性Lsd1敲除会阻碍新生小鼠的心脏再生，而过表达Lsd1则呈现相反效应。RNA测序结果显示，Cend1作为心肌细胞周期增殖的关键抑制因子，是心脏再生过程中Lsd1缺失诱导上调最为显著的基因。心肌细胞特异性Cend1过表达会抑制新生小鼠心脏再生，而Cend1全基因敲除小鼠则表现出相反的表型。Cend1缺失可引发与心肌细胞增殖增强、新生血管生成以及巨噬细胞活化相关的基因表达改变。进一步研究发现，当使用Cend1全基因敲除小鼠开展实验时，Lsd1缺失导致的心脏再生缺陷不再出现。此外，本研究发现无论是过表达Lsd1还是敲除Cend1，均可促进成年小鼠实验性心肌梗死模型的心脏再生与修复，并改善其心脏功能。本研究收集了出生后14天（P14）的野生型对照小鼠与Cend1敲除（Cend1-KO）小鼠的心脏组织，进行RNA测序分析。