氧感受器PHD2介导干细胞旁分泌促进组织血管新生的核心作用研究

Cell therapy has great potential of promoting neovascularization and tissue regeneration，thus displays promising prospects in plastic and reconstructive surgery. However, the mechanisums of angiogenic cell therapy is still unclear. Most scientists believe that the therapeutic effect is mainly due to the cytokines secreted from the implanted cells. Our previous studies disvovered that after cell implantation, the level of angiogenic growth factor in the target tissue continuous to increase over time. However, we also observed that, as other authors reported, the cell number declined greatly after implantation. This paradox made us to presume that the majority of cytokines we detected from the harvested tissue is not derived from the implanted cells, but from the host tissue. The implanted cells probably exert their therapeutic effects via triggering the angiogenic potential of the host tissue. But in which way does this happen remains unclear. Deduce from the known fact that hypoxia induces neovascularization via PHD2 regulated HIF-1a pathway, as well as the recent discovery that PHD2 regulates tumor neovascularization, we speculate that the prolyl hydroxylase domain-2 (PHD2), which controls oxygen homeostasis and neovascularization of mammals, plays a key role in mediating therapeutic effects of the angiogenic cell therapies. The implanted cells may exert their funtion by regulating PHD2 level of the host tissue to trigger a cascade of reactions similar to the response to hypoxia, therefore results in better neovascularization of the host tissue. The aim of this study is to confirm this hyothesis by blocking PHD2-HIF-1a pathway in the cell transplantation animal models and the in vitro co-culture systems. Therefore help us better understand the mechanisms of angiogenic cell therapies.

近年发现干细胞治疗具有促进移植物血管化和组织再生的作用，在整复外科领域显示了强大的应用前景，但对它的机制目前尚不清楚，极大地妨碍了它的临床转化。多数学者认为植入的细胞旁分泌细胞因子起了主要作用。最新的研究证实，氧分子感受器PHD2是触发肿瘤及缺氧诱导的血管新生过程的"总开关"；本课题组在前期研究中也发现，组织移植模型应用干细胞治疗后，局部VEGF、bFGF、EGF等HIF-1a的效应蛋白水平均上调,而HIF-1a受PHD2调控，因此提出PHD2可能是介导干细胞旁分泌治疗作用的核心分子。本项目拟通过皮瓣/下肢缺血动物模型和体外细胞共培养模型，分别独立检测种子细胞和靶组织的因子水平，借助基因干扰工具，逐步论证PHD2及其下游的HIF-1α通路是如何介导干细胞移植后通过旁分泌促进组织血管化的过程，揭示PHD2在细胞治疗机理中的核心作用及发挥作用的方式，为细胞治疗的临床转化研究提供完整的理论基础。

组织移植物的再血管化是移植物成活的关键，细胞治疗是促进组织血管化的有效手段，但是其伦理及安全性等问题限制了它的临床转化，对其机理的深入研究有助于我们开发更为安全有效、简便低廉的方式来促进组织血管化。促进组织血管化不仅对于整复外科，在血管外科、心脑血管疾病治疗等等领域，也有巨大的潜在利用价值。本项目立足于血管化调控的中心环节——PHD2分子，从细胞治疗促进组织血管化的机理入手，论证了PHD2分子在这一过程中的核心作用，体外及体内实验研究都证实，干细胞治疗通过抑制受体靶组织细胞的PHD2表达水平进而促进了血管化进程。在这一发现基础上，项目组进一步设计了利用PHD2抑制剂去铁胺来促进组织血管化，在预构皮瓣动物模型中观察到了预构皮瓣的成活率显著提高，为PHD2抑制剂在整复外科的临床应用打下了实验基础，也为促进组织血管化提供了新的思路和方向。