心肌梗死后HIF1α/Pim1信号轴对心脏干细胞增殖和迁移的影响

Improvement of the ability of stem cells in cell survival, proliferation and migration is one of the key unsolved problems regarding the cell.therapy based on stem cell transplantation in the treatment of myocardial infarction (MI). Very recently, we have found that the maintenance of the activity of Pim1, a serine/threonine kinase, is crucial for the cardiac stem cell (CSC) proliferation and migration. Additionally, MI may induce Pim1 to re-express in CSC, and the results of bioinformatics analysis revealed that there were several hypoxic response elements (HREs) special for hypoxia-induced factor 1α (HIF1α) in the 5’ non-coding region of Pim1 gene. These preliminary experiment results suggest that HIF1α may induce Pim1 to express post MI, that is the activation of HIF1α/Pim1 signaling, which is beneficial for the CSC proliferation and migration in vitro, and plays a cardioprotection role in myocardial injury in vivo. In this project, we aim to establish the Pim1 gene knock-out mice, after the CSCs were isolated from the Pim1 knock-out mice and associated wild type mice, the mechanism of activation of HIF1α/Pim1 signaling and its contribution to the biofunction of CSC in vitro and in vivo were investigated. We expect that the activation of HIF1α/Pim1 signaling may enhance the proliferation and migration of CSC in vitro, and lead to the restoration of the cardiac function post MI in vivo. The outcomes of this proposal would enforce our previous research, and provide a novel experimental basis for the progression of regeneration medicine regarding repair the injured heart based on the CSC trsnsplatation.

提高干细胞的存活、增殖及趋化能力是干细胞移植治疗心肌梗死（MI）中亟待解决的难题之一。近期我们发现丝/苏氨酸激酶Pim1 活性的维持对心脏干细胞（CSC）的增殖和迁移至关重要；低氧可诱导CSC 中Pim1 再表达；生物信息学分析发现Pim1 基因5'端具有多个低氧反应因子1α（HIF1α）的反应元件。上述结果提示MI 后可能通过建立HIF1α/Pim1信号系统从而对CSC 的增殖及迁移产生影响，因而在MI 后的心肌保护中发挥重要的作用。本项目通过构建Pim1 基因敲除小鼠，着重探讨HIF1α/Pim1信号轴对CSC增殖和迁移的影响及其可能分子机制。预期HIF1α/Pim1信号的活化体外可促进CSC 的增殖和迁移能力，体内可有效促进移植的CSC 参与MI 损伤后心功能的修复。项目的实施将深化前期研究，为基于CSC 移植治疗MI 的再生医学提供新的实验依据。

本研究团队在实际围绕CSC工作开展的过程中发现采用Anversa P实验室的方法分离成年鼠心脏c-Kit+的细胞相对困难且增殖缓慢，严重影响实验的进程。因而，本项目采用成年鼠骨髓c-Kit+细胞来代替成年鼠心脏c-Kit+细胞作为细胞模型。结果发现低氧刺激可使c-Kit+ BMSCs中Pim1表达上调，同时伴随着c-Kit+BMSCs的分化；并阐明了在此过程中HIF1α对Pim1的调节作用，为c-Kit+ BMSCs临床应用提供实验室依据。