脂肪干细胞微泡携带let-7促血管新生作用及其机制探讨

There have been many reports about the transplantation of adipose-derived stem cells in repairing injured myocardium, but the exactly mechanisms have not been fully elucidated; Recently, some studies suggest that ADSC secrete paracrine factors that have proangiogenic effect may be an important research approch. Microvesicles secreted from many cell types have biologic activity because it can deliver many molecules from cell cytoplasm. Previous studies from our laboratory have revealed that microvesicles of ADSC are rich in microRNA let-7 and when deprived of microvesicles from ADSC conditioned medium, the proangiogenic effect decreased. Based on the effect of let-7 on angiogenesis and the important functions of microvesicle in cell-to-cell communication, we infer that microvesicles of ADSC deliver let-7 to targeted cells (HUVEC) and exert proangiogenic effect, it may be a key, but recently unknown mechanism in repairing injured myocardium. Based on this, we propose to confirm microvesicles of ADSC having proangiogenic effect by using laser cofocal microscopy, flow cytometry, HUVEC cell proliferation, invasion and tube formation experiments. we confirm microvesicles have proangiogenic effect because of the let-7 in it by establishing luciferase experiment, RNAi and other molecular biological methods. Try to elucidate the effect and mechanism of ADSC paracrine factors on angiogenesis from an new angle and enrich the theory of ADSC transplantation in reparing injured myocardium.

脂肪干细胞(ADSC)移植修复心肌损伤的研究多有报道，其确切机制尚有待阐明。近来研究提示从ADSC旁分泌因子促血管新生作用切入是重要的研究思路。微泡是多种细胞生理性分泌的囊泡状小体，它因携带多种源细胞成分而具有重要生物活性。我们前期研究发现ADSC分泌富含let-7的微泡，而且去除微泡，其条件培养基原本具有的促血管新生作用明显减弱。基于let-7在促血管新生中的作用，以及微泡新近被发现的重要功能，我们推测，ADSC来源微泡携带let-7发挥促血管新生作用，是未被认知却作用关键的修复心肌损伤的机制。本研究拟通过激光共聚焦及流式细胞术，血管内皮细胞增殖、迁移和管样结构形成实验证实ADSC微泡具有促血管新生作用；采用荧光素酶实验、 RNAi等分子生物学方法证实微泡通过传递let-7发挥促血管新生作用。以期从新的角度阐明ADSC旁分泌促血管新生作用及其机制，丰富ADSC移植修复心肌损伤理论的内涵。

脂肪干细胞促血管新生作用主要是因为其定向分化和旁分泌细胞因子作用，本课题通过对新近发现的细胞外排物——微泡具有携带生物活性分子活性，探讨脂肪干细胞源微泡是否具有促血管新生作用。通过激光共聚焦、细胞迁移和管样结构形成等证实了脂肪干细胞微泡可促进血管新生作用，并且证实脂肪干细胞微泡内具有生物活性分子let-7和VEGF等。该课题的重要结果主要包括：脂肪干细胞微泡miRNA的检测结果、激光共聚焦证实微泡可作用于血管内皮细胞等。该课题科学意义主要在于证实了脂肪干细胞除了可通过分泌可溶性细胞因子作用于血管内皮外，还可通过微泡起作用，而且微泡内含有具有重要生物活性分子，对于以后脂肪干细胞的相关研究提供新的方向及思路，从新的角度阐明ADSC旁分泌促血管新生作用及其机制，丰富ADSC移植修复心肌损伤理论的内涵。