孕期尼古丁暴露所致子代和孙代关节软骨发育不良的表观遗传机制

It has been observed that nicotine could affect the female fetal cartilage development and augment the susceptibility of adult osteoarthropathy in the offspring even grand offspring. The results of our preliminary experiments showed that the proliferation of fetal chondrocytes were reduced. However, the mechanism of this critical process and its epigenetic effect is still a mystery. Wnt signaling pathway was proved to participate the cell proliferation, fetal cartilage development and epigenetic. The high level of glucocorticoid (GC) in fetal blood induced by prenatal nicotine exposure (PNE) could inhibit the Wnt pathway. Thus we speculated that the PNE might suppress the proliferation of fetal chondrocyte and modify the histone code through Wnt pathway. To confirm this speculation, our group plans to detect the status of Wnt pathway, the cell proliferation and histone code in the fetal cartilage and ovaries after the PNE. We will analyze the proliferation ability, Wnt pathway activation and histone code of the fetal chondrocyte after the stimulation by GC or nicotine. We will also perform the function loss-gain experiments to determine how Wnt pathway and cell proliferation ability are altered by GC, then elucidate the mechanism how environment factor affects the fetal chondrocyte proliferation and offer an potential therapy target for the development originated adult osteoarthritis.

研究证实，孕期尼古丁暴露可影响胎软骨发育导致雌性子代甚至孙代成年骨软骨疾病的易感性增高。本团队预实验发现此时胎儿软骨细胞增殖被抑制，但这种抑制及其表观遗传调节的机制仍不明确且尚未见报道。Wnt通路被证实参与了细胞的增殖、胎软骨发育以及表观遗传现象。孕期尼古丁暴露导致的胎血糖皮质激素升高可能抑制Wnt通路的活性。因此，我们推测孕期尼古丁暴露通过高糖皮质激素影响Wnt通路改变了增殖关键基因CyclinD1启动子组蛋白乙酰化状态抑制了胎软骨细胞的增殖。本课题组拟检测尼古丁暴露后胎儿软骨和卵巢内Wnt通路的活性、CyclinD1启动子组蛋白乙酰化和胎软骨细胞增殖状态揭示Wnt通路和胎软骨细胞增殖的相关性，拟用胎软骨细胞行功能抑制和获得实验明确细胞增殖受抑制的具体机制，从而探索孕期尼古丁暴露引起子代孙代软骨发育不良的表观遗传机制，并为治疗发育源性的成年关节疾病提供新的思路。

吸烟一直被公认为胎儿期不良环境刺激中的重要一种，有系统分析表明我国孕妇二手烟的暴露率在38.9%到75.1%之间。研究显示，尼古丁被孕期母体摄入后可以触发很多成年疾病易感性的宫内编程。本研究中，我们发现孕期尼古丁暴露可导致子代甚至孙代胎儿关节软骨细胞数量较正常明显下降，细胞内增殖相关基因表达明显降低。然而细胞实验证实尼古丁对于软骨细胞增殖并没有影响。团队既往的研究表明，孕期尼古丁暴露可以明显增高母体血和胎血中糖皮质激素的表达，因此我们进一步检验了糖皮质激素对于软骨细胞增殖的效应发现，糖皮质激素作用后软骨细胞增殖能力下降、增殖相关基因表达和其组蛋白乙酰化水平降低，同时该变化由Wnt经典通路中的GSK-3β所介导。我们予以孕期接受了尼古丁暴露的大鼠Wnt经典通路激活剂BIO摄入，成功逆转其子代和孙代的关节软骨细胞增殖能力的下降。由于关节软骨基质更新速度极慢，软骨在受损时难以自行修复，因而软骨本身的发育状况决定了成年后软骨对疾病的抵抗力，胎儿时期软骨发育不佳的个体成年后在相关危险因素的作用下更易出现关节疾病。因此，对孕期尼古丁暴露所致软骨发育不良机制的挖掘，为我们对发育相关的关节疾病，如退行性骨性关节炎的早期预防以及早期干预提供了理论基础，并为治疗发育相关的成年关节疾病提供可能的靶点。