MSCs源性外泌体(exosomes)通过投递let-7f促进HIBD血管新生及其机制探讨

Perinatal brain injury is an important factors cause of neonatal death and postnatal neuropathy, among which hypoxic ischemic brain injury (HIBD) is the most common lesion. Therapeutic angiogenesis is an important process by which new blood vessels generate from existing vascular endothelial cells in order to deliver nutrients and oxygen to hypoxic-ischemic injury organs and tissues. Many studies have suggested that paracrine factors play an important role in MSCs mediated angiogenesis. MSCs can positively affect their environment via secreted exosomes to orchestrate interactions within the cellular milieu to promote angiogenesis. We previously found that exosomes derived from MSCs promoted angiogenesis in vitro and associated with exosomal higher level of let-7f. However, the exact mechanisms and characteristics of exosomes on angiogenesis are still unknown. It is recognized that miRNAs are key regulators of angiogenesis. Exosomes are nanosized (30 to100 nm) bi-lipid-layered vesicles containing proteins, mRNAs, and miRNAs. These molecules can be transferred to the recipient cells and modulate their function. On the basis of the preliminary data, we proposed a hypothesis and sought to explore the molecular mechanisms of promoting angiogenesis by exosomes derived from MSCs from the aspect of miRs. We will take endogenous encapsulated let-7f of exosomes as the keypoint and HIBD as therapy target. We will demonstrate the promoting effects of exosomes to angiogenesis using both in vitro and in vivo angiogenic models. Additionally, the specific target of let-7f will be verified by luciferase reporter assay and the downstream molecular signaling pathway also will be investigated. In all, we will systematically investigate the the promoting effects of exosomes to angiogenesis and explore the potential molecular mechanisms. The study can provide reliable experimental basis for exosomal therapy using in hypoxic-ischemic nervous diseases including HIBD.

围产期脑损伤是引起新生儿死亡和导致出生后神经系统病变的重要原因，其中缺氧缺血性脑损伤（HIBD）是最常见的一种病变。治疗性血管新生（therapeutic angiogenesis）是治疗缺氧缺血性组织器官损伤的有效手段。MSCs分泌的外泌体（exosomes，exo）介导的旁分泌调控在MSCs促血管新生过程中起重要作用。我们前期结果显示MSCs源性exo能明显促进体外血管新生，并与exo所包涵携带的miRNA let-7f密切相关。在此基础上提出课题假设，以exo中高表达的let-7f为切入点，通过体外血管新生研究模型和HIBD动物模型，分别从体内外证实exo对血管新生的促进作用，明确exo投递的let-7f的确切作用；再到体外证实let-7f具体靶点和下游分子信号，系统全面地研究MSCs源性exo促进血管新生的分子机制，为exo治疗HIBD等缺氧缺血神经损伤性疾病提供可靠的实验依据。

缺氧缺血性脑损伤（HIBD）是最常见的围产期脑损伤，可引起新生儿死亡及导致出生后神经系统损伤后遗症。治疗性血管新生（therapeutic angiogenesis）通过促进损伤脑组织的血管再生，可有效促进脑组织神经功能修复。本课题以纳米级大小的MSCs源性exosomes作为研究对象，exosomes是很好的靶向治疗的载体，其包涵的mRNA和miRNAs等分子参与细胞间信号转导、调控靶细胞功能。本研究通过体内外实验证实exosomes介导了其包涵的let-7f的投递作用，exosomes通过对let-7f的靶向投递作用促进了血管新生及HIBD损伤后神经功能恢复；进一步证实exosomes投递的let-7f作用的直接靶点为THBS1，并检测到THBS1下游信号分子sGC和cGK-I的相应变化。本实验揭示MSCs源性exosomes对HIBD血管新生的促进作用及潜在的miRNA信号调控机理，为exosomes治疗HIBD等缺氧缺血神经损伤性疾病提供可靠的实验依据。