Cardiac Repair of Severe Heart Failure by Human Heart- or Skeletal Muscle-Derived Multipotent Stem Cells

最近的研究表明，来自成人心脏的心脏干细胞（CSCs）可以产生功能性心肌细胞；然而，确定的表面标记物来确定CSCs的明确单一实体和调节其生长的分子机制仍然未知。在这里，我们展示了一种单细胞沉积分析，从成人心脏中分离出单独选择的CSCs，并研究其增殖和存活所需的信号。克隆增殖的CSCs表达具有胚胎干细胞（ES）和间充质细胞样特征的干细胞抗原-1 (Sca-1)，并与端粒酶逆转录酶（TERT）相关。使用在TERT启动子控制下表达GFP报告基因的转基因，我们证明了来自心脏的TERT^<GFP+>组分被用于表达Sca-1的细胞。CSCs中Sca-1转录物的敲低通过Akt失活导致体外扩增和凋亡延迟。我们还发现，直接细胞移植到缺血心肌后，持续的CSC增殖和存活需要Sca-1上调分泌的旁分泌效应物，从而增加新血管生成并限制心脏凋亡，因此，Sca-1可能是促进CSC增殖和存活的重要成分，直接促进早期移植，并间接影响CSC移植后晚期心血管分化。

Recent studies have shown that cardiac stem cells (CSCs) from the adult heart can give rise to functional cardiomyocytes; however, the definite surface markers to identify a definitive single entity of CSCs and the molecular mechanisms regulating their growth have remained unknown. Here we demonstrate a single-cell deposition analysis to isolate individually selected CSCs from adult hearts and investigate the signals required for their proliferation and survival. Clonally proliferated CSCs express stem cell antigen-1 (Sca-1) with embryonic stem (ES) cell-and mesenchymal cell-like characteristics and are associated with telomerase reverse transcriptase (TERT). Using a transgene that expresses a GFP reporter under the control of the TERT promoter, we demonstrated that TERT^<GFP+> fractions from the heart were entiched for cell expressing Sca-1. Knockdown of Sca-1 transcripts in CSCs led to retarded ex vivo expansion and apoptosis through Akt inactivation. We also show that ongoing CSC proliferation and survival after direct cell-grafting into ischemic myocardium require Sca-1 to upregulate the secreted paracrine effectors that augment neoangiogenesis and limit cardiac apoptosis, Thus, Sca-1 might bean essential component that promotes CSC proliferation and survival to directly facilitate early engraftment, and that indirectly exerts the effects on late cardiovascular differentiation after CSC transplantation.