IVF子代脐血中APOE上调的机制及其对远期心血管功能影响的机理研究

Epidemiological data indicate that IVF offspring are at an increased risk of cardiovascular abnormalities, however the mechanism remains unclear. A possible explanation could be that the IVF procedures altered DNA methylation in the offspring. Our previous proteomic study found that, compared to that of fetus born from natural pregnancies, APOE expression level was significantly higher in cord blood serum of IVF fetus. DNA methylation patterns affected serum APOE expression level, which further influenced cardiovascular function, thus we hypothesize: IVF upregulated serum APOE levels in offspring via changing APOE gene methylation patterns, and in turn affected the long-term cardiovascular function. In this study, we will investigate the DNA methylation alteration in the organs secreting higher level of APOE in IVF mice model, then observe the recovery phenotype after normalizing the gene methylation, in order to elucidate the mechanism of higher serum APOE levels in IVF offspring. Then we observe the effect of higher serum APOE levels on the structure and function of cardiovascular system in IVF offspring via IVF knockout mice. After that, we will explore its molecular mechanism from the aspect of lipid metabolism, vascular oxidative stress and inflammation stress. This study is to illustrate the mechanism of higher serum APOE level in IVF offspring and its long-term effect on cardiovascular dysfunction, which is beneficial for the improvement of assisted reproductive technology procedures and the safety of the offspring.

据报道IVF子代心血管异常的风险增高，机制尚不清楚，IVF改变子代相关DNA甲基化可能是机制之一。我们前期研究发现，对比自然妊娠胎儿，IVF胎儿脐血清中载脂蛋白E（APOE）表达显著增高。APOE表达量受其DNA甲基化模式的影响，其血清浓度影响心血管功能。由此提出假说：IVF通过改变APOE基因甲基化模式，上调子代血清APOE，进而影响远期心血管功能。本研究拟利用IVF小鼠模型，观察分泌APOE增高的器官其DNA甲基化的改变，及干预后表型逆转情况，阐明IVF子代血清APOE上调的机制；利用APOE基因敲除小鼠，评估IVF子代APOE上调对心脏、血管结构和功能的影响；进一步从脂代谢、血管氧化应激及炎症反应三个方面探讨IVF子代APOE上调影响心血管的分子机制。本研究阐述IVF致子代血清APOE上调及远期心血管结构与功能异常的相关机制，对改进辅助生殖技术，提高辅助生殖安全性有重要意义。

背景：..全世界IVF子代数量迅速增加，据报道其心血管异常风险增高。目前年龄最大IVF后代尚未到老年期，对IVF远期心血管异常评估意义重大。我们前期研究发现,对比自然妊娠胎儿,IVF胎儿脐血清中载脂蛋白E(APOE)表达显著增高。本研究拟通过IVF小鼠模型，研究IVF子代远期心血管功能异常，探索APOE异常表达对IVF子代心血管功能的影响机理。..方法：.建立IVF子代小鼠模型，以自然妊娠子代小鼠为对照组。ELISA比较两组不同周龄血清APOE表达差异。比较两组小鼠6周、12周及41-56周体重、血压、血脂、血糖，并利用彩色超声评估心血管结构功能，体外灌注老年鼠取材称重脏器。7周雄性IVF和对照小鼠尾静脉注射APOE超表达及阴参腺相关病毒（AAV-APOE、AAV-NULL），检测心血管结构和功能差异。..结果：.各周龄小鼠IVF组比对照组体重均增高，血压、脉搏及空腹血糖无显著差异，老年鼠甘油三酯IVF组显著下降。IVF老年雌鼠糖耐量实验60及90分钟血糖显著增高。心血管超声显示IVF子代6周小鼠心血管结构功能指标对比对照组存在差异，雌鼠比雄鼠差异更明显；12周IVF小鼠对比6周小鼠，差异指标明显减少；41周雌性小鼠心脏超声指标比对照组无显著差异，而雄性老年鼠心功能（EF%，FS%等）显著下降，且肺动脉流速及压力显著下降。两组血清APOE差异表达，超表达APOE后，心脏结构功能指标组间均无差异；颈总、冠状及肺动脉相关指标（对照+AAV-NULL）组较其他组别显著增高。..结论：.IVF子代小鼠与自然妊娠小鼠相比,大部分指标无差异，老年雌鼠糖代谢异常。IVF对心血管结构功能的影响随着小鼠成年后逐渐减小，老年雌鼠和对照组相似，而老年雄鼠心血管功能显著减退。IVF小鼠APOE上调影响子代血管功能，对心脏结构功能无影响，远期影响需进一步评估。..意义：. 本研究反映小鼠心血管功能随着年龄的变化过程，揭示了APOE可能作用机制。本研究提示IVF雄性后代老年期需加强心血管监测，预防心血管事件发生。