Ghrelin抑制胸腺脂肪细胞生成的分子调控网络研究

Adipose-related thymic involution results in a progressively decline in T cell output and immunity. Previous studies have showed that ghrelin can suppress thymic adipogenesis, but the molecular mechanisms have not yet been clear. In order to elucidate the regulatory mechanisms underlieing thymic adiposity and molecular regulatory network involved in ghrelin suppressing thymic adipogenesis, this work aims to investigate the effects of ghrelin on expression of adipogenesis-related signal transduction elements, transcription factors, transcriptional cofactors (coactivators and corepressors), microRNAs(miRNAs) and adipocyte-specific markers in thymus after intraperitoneally administration of ghrelin to mice and during induced differentiation of thymic mesenchymal stem cells to adipocytes after administration of ghrelin in vitro, and constructing thymic mesenchymal stem cells overexpressing ghrelin and blocking related signal pathway molecules via RNA interference by real time-PCR, western blot, miRNAs microarray assay. It means to establish a foundation for ghrelin as an immunopotentiator clinically to suppress thymic involution or to promote its regeneration, developing novel ideas and strategies for strengthening or recovering thymic immune function, and to provide a useful guidance for questing new appropriate therapeutic targets of energy metabolic syndromes such as obesity in human and companion animals and for regulateing adipose tissue development to improve meat quality in livestocks.

胸腺脂肪性退化导致T细胞产量和免疫力下降。前期研究表明Ghrelin能够抑制胸腺脂肪细胞生成，但其分子机理尚未阐明。本项目拟通过小鼠体内注射Ghrelin、体外诱导胸腺间充质干细胞分化为脂肪细胞过程中添加Ghrelin、构建过表达Ghrelin的胸腺间充质干细胞模型及采用RNAi阻断相关信号通路分子表达后，应用荧光定量PCR、蛋白质印迹和基因芯片技术研究Ghrelin对脂肪细胞生成相关的信号转导分子、转录因子、转录辅助因子、microRNAs和脂肪细胞特异标志物表达的影响；从而阐明Ghrelin抑制胸腺脂肪细胞生成的分子调控网络，揭示胸腺脂肪性退化的调控机理；为临床应用Ghrelin作为免疫增强剂抑制胸腺退化或促进其再生奠定理论基础，开辟增强或恢复胸腺免疫功能的新思路和新策略，并为人类和伴侣动物的肥胖症等能量代谢综合征寻找新的治疗靶标以及调控家畜的脂肪组织发育从而改善肉质等提供借鉴和参考。

胸腺随年龄增长而逐渐发生脂肪性退化，导致T细胞产生减少，机体免疫力下降。本项目建立了小鼠和鸡的胸腺及脂肪组织间充质干细胞的分离培养纯化鉴定方法，为开展间充质干细胞的深入研究与应用奠定了基础；研究了Ghrelin对间充质干细胞和前脂肪细胞增殖分化为脂肪细胞及其相关信号转导分子、转录因子、microRNAs和脂肪细胞特异性标志基因表达的影响，对胸腺退化与再生的影响等；从小鼠和鸡的胸腺及脂肪组织中筛选出了一些与脂肪细胞生成相关的microRNAs，发现Ghrelin能够调节一些microRNAs的表达；重点研究了miR-195a-5p、miR-181-5p、miR-125b-5p、miR-92a-3p、miR-26a-5p、miR-23b-3p等对小鼠前脂肪细胞和胸腺上皮细胞增殖分化的影响，为探讨以microRNAs为靶点抑制胸腺年龄性脂肪性退化的方法以及治疗肥胖症等奠定了基础。