衰老对骨髓基质干细胞刺激心肌梗死后心脏前体细胞群重建的影响及机制研究

The therapeutic effect of mesenchymal stem cells (MSCs) from aged donors for myocardial infarction (MI) is impaired. The underlying mechanisms remains unknown. In the previous studies, we reported that pigment epithelium derived factor (PEDF) secreted by MSCs played an important role in MI. Moreover,the up-regulated PEDF expression in aged MSCs blunted its therapeutic effects, but the mechanism is unclear. PEDF is the first identified paracrine factor of MSCs that is detrimental for the recovery of MI, which indicates its crucial role in regulating MI. It is recently reported that restitution of cardiac progenitor cells (CPCs) greatly contributed to the recovery of MI. We have demonstrated that the proliferation and apoptosis of CPCs were notably affected by PEDF; comparing with younger MSCs, transplantion of aged MSCs following MI diminished the quantity of CPCs and inhibited the differentiation of CPCs to cardiomyocytes . Therefore, we propose our hypothesis that PEDF secreted by MSCs regulates the microenvironment of CPCs. Increased PEDF level in aged MSCs hinders the restitution of CPCs. The present project is aimed to investigate the underlying molecular mechanisms of the blunted effect of aged MSCs in restituting of CPCs after MI at molecular, cellular and in vivo levels, and to certify the feasibility of PEDF being the target in improving the stimulatory function of aged MSCs for restitution of CPCs, and finally to provide novel therapeutic strategies for MI treatment.

来源于衰老个体的基质干细胞（MSCs）对心肌梗死（MI）疗效下降，但机制不明。我们首先发现MSCs分泌色素上皮衍生因子(PEDF)对MI有重要调控作用，衰老MSCs高表达PEDF是其疗效下降的重要原因。PEDF是首个被证明不利于MI恢复的MSCs旁分泌信号，因此更值得关注。新近研究表明MI后心脏前体细胞群(CPCs)的重建对MI恢复至关重要。我们初步证明PEDF显著影响CPCs增殖凋亡；与年轻MSCs相比，MI后给予衰老MSCs使CPCs的数量和向心肌分化明显减少，有力提示MSCs分泌PEDF可调控CPCs微环境；衰老MSCs高分泌PEDF使MI后CPCs重建受抑制是其疗效下降的重要机制。本课题以PEDF为切入点，在分子、细胞和在体水平研究衰老MSCs对MI后CPCs重建的影响及关键分子机制，证实PEDF为靶点可提高衰老MSCs对CPCs重建的刺激作用，进而改善疗效，为MI治疗提供新思路。

干细胞治疗心肌梗死(MI)的关键机制是什么？如何有效提高干细胞治疗MI的疗效？这些是尚未完全阐明的重要科学问题。我们前期研究发现基质干细胞(MSCs)分泌的多功能蛋白—色素上皮衍生因子(PEDF)在MI的治疗中扮演关键角色。近年国际上研究干细胞疗法治疗MI的发展趋势出现两个引人关注的新观点：1.认为外源性的MSCs在MI的病理过程中主要是扮演“组织者”(organizer)的角色—其通过旁分泌信号调节MI部位内源性细胞的微环境，影响他们的生物学行为，进而促进疾病恢复；2.成体哺乳动物心脏在损伤后具有远超出人们原先认为的再生能力，心脏原位的前体细胞(CPCs)对损伤后的组织修复过程中至关重要。MI后心脏原位CPCs的增殖与分化对MI的恢复有重要贡献。在此研究背景中，本项目受国家自然科学基金资助围绕PEDF的作用机制，特别是对CSCs的调控作用开展了系列研究，取得以下新发现：. 1.证明色素上皮衍生因子(PEDF)广泛存在于CPCs微环境(niche)中，心肌梗死后注入年轻或衰老的MSCs显著改变CPCs niche中的PEDF含量，注入衰老MSCs后MI区域的PEDF是注入年轻MSCs后的1.6倍；2.心肌细胞与CPCs表达PEDF受体-磷脂酶A2(PLA2)；3.PEDF促进CSCs在氧化应激损伤下的生存；4.MSCs与CPCs共培养试验发现MSCs高表达PEDF可促进CPCs向心肌细胞分化；5.PEDF本身不诱导CPCs向心肌细胞分化，但PEDF显著增强向心肌细胞分化中的CPCs的分化效应；6.PEDF可通过Notch信号途径增强CPCs向心肌细胞的分化作用。（具体数据见报告正文）. 通过本项目的研究，进一步证明了PEDF是对MI病理过程的关键调控蛋白，心肌细胞与CSCs是PEDF的重要效应细胞，PEDF可通过PLA2受体与Notch信号通路发挥生物学作用，PEDF可作为心肌缺血损伤的重要干预靶点。本研究对认识MI的病理调控机制以及临床转化治疗有重要意义。本课题已发表SCI论文4篇，中文核心期刊论文2篇，取得了预期研究结果。课题承担人获中华医学会中华医学科技一等奖1项，中华医学会厄尔巴肯青年科学家奖1项。课题培养博士后1名，博士研究生1名，硕士研究生2名。