Li Sen, Keung Wendy, Cheng Heping, Li Ronald A
Stem Cell & Regenerative Medicine Consortium, LKS Faculty of Medicine, University of Hong Kong, Hong Kong.
Dr. Li Dak-Sum Research Centre, The University of Hong Kong, Pokfulam, Hong Kong.
Stem Cells Int. 2019 Apr 1;2019:8765752. doi: 10.1155/2019/8765752. eCollection 2019.
The loss of nonregenerative, terminally differentiated cardiomyocytes (CMs) due to aging or diseases is generally considered irreversible. Human pluripotent stem cells (hPSCs) can self-renew while maintaining their pluripotency to differentiate into all cell types, including ventricular (V) cardiomyocytes (CMs), to provide a potential unlimited source of CMs for heart disease modeling, drug/cardiotoxicity screening, and cell-based therapies. In the human heart, cytosolic Ca signals are well characterized but the contribution of nuclear Ca is essentially unexplored. The present study investigated nuclear Ca signaling in hPSC-VCMs. Calcium transient or sparks in hPSC-VCMs were measured by line scanning using a spinning disc confocal microscope. We observed that nuclear Ca, which stems from unitary sparks due to the diffusion of cytosolic Ca that are mediated by RyRs on the nuclear reticulum, is functional. Parvalbumin- (PV-) mediated Ca buffering successfully manipulated Ca transient and stimuli-induced apoptosis in hPSC-VCMs. We also investigated the effect of Ca on gene transcription in hPSC-VCMs, and the involvement of nuclear factor of activated T-cell (NFAT) pathway was identified. The overexpression of Ca-sensitive, nuclear localized Ca/calmodulin-dependent protein kinase II (CaMKII ) induced cardiac hypertrophy through nuclear Ca/CaMKIIB/HDAC4/MEF2 pathway. These findings provide insights into nuclear Ca signal in hPSC-VCMs, which may lead to novel strategies for maturation as well as improved systems for disease modeling, drug discovery, and cell-based therapies.
由于衰老或疾病导致的不可再生、终末分化的心肌细胞（CMs）的丧失通常被认为是不可逆的。人类多能干细胞（hPSCs）可以自我更新，同时保持其多能性以分化为所有细胞类型，包括心室（V）心肌细胞（CMs），从而为心脏病建模、药物/心脏毒性筛选和基于细胞的治疗提供潜在的无限CMs来源。在人类心脏中，胞质钙信号已得到充分表征，但核钙的作用基本上未被探索。本研究调查了hPSC-VCMs中的核钙信号。使用旋转盘共聚焦显微镜通过线扫描测量hPSC-VCMs中的钙瞬变或钙火花。我们观察到，核钙源于核内质网上由兰尼碱受体（RyRs）介导的胞质钙扩散产生的单个钙火花，并且具有功能。小清蛋白（PV）介导的钙缓冲成功地调控了hPSC-VCMs中的钙瞬变和刺激诱导的细胞凋亡。我们还研究了钙对hPSC-VCMs基因转录的影响，并确定了活化T细胞核因子（NFAT）途径的参与。钙敏感的、定位于核的钙/钙调蛋白依赖性蛋白激酶II（CaMKII）的过表达通过核钙/CaMKIIB/组蛋白去乙酰化酶4（HDAC4）/肌细胞增强因子2（MEF2）途径诱导心脏肥大。这些发现为hPSC-VCMs中的核钙信号提供了见解，这可能会带来新的成熟策略以及改进的疾病建模、药物发现和基于细胞的治疗系统。
