Fetal Cell Senescence Signals Initiation of Parturition

 描述(由申请人提供)：足月胎儿细胞衰老是对氧化应激(OS)的自然生理反应，氧化应激(OS)是成熟胎儿增加代谢需求的结果。早产的各种危险因素与OS诱导的衰老有关。我们的初步数据表明，胎儿细胞衰老导致Alarmin HMGB1(一种非组蛋白蛋白)从细胞核转移到胞浆。在那里，它被乙酰化修饰并通过胞吐释放(“游离的”HMGB1)或被包裹在外体中(30-100 nm颗粒)，通过多囊内小体与质膜融合形成并挤出。分泌的HMGB1在母胎组织中起促炎细胞因子的作用。在胎膜中，它通过TLR2介导的p38MAPK激活，促进胎儿细胞衰老和相关的“无菌”炎症反应。在心肌细胞中，HMGB1激活p38MAPK，导致孕激素受体(PR)亚型A上调，COX-2表达增加，心肌细胞炎症。HMGB1还建立了一个正的OS反馈环，加速了羊膜细胞的老化。我们的核心假设是，从衰老的胎膜中分泌的HMGB1，无论是通过扩散还是通过外体运输，都会通过p38MAPK激活子宫肌层，进而增加PR-A/PR-B的比例，导致功能性孕酮退出并引发分娩。这一假设将在两个具体目标中得到检验。具体目标1将确定在人类怀孕和分娩过程中，OS如何刺激胎儿膜细胞来源的HMGB1分泌，作为游离蛋白质或包装在外体中并输出。具体目标2将确定胎膜细胞对OS的反应中产生的游离或外体HMGB1如何诱导功能性孕酮退出和子宫肌层收缩。原代和转化的人羊膜、绒毛滋养层细胞和子宫肌层细胞，以及胎膜和子宫肌层器官培养，将暴露在OS诱导剂中。使用分子和细胞生物学方法，我们将量化OS诱导的胎儿细胞衰老、HMGB1释放、外体包装、外体-HMGB1分泌方向、p38MAPK信号、PR异构体转换和肌层激活。此外，我们将量化来自足月和早产(PTB)的储存的母胎生物体液(羊水、外周和母体子宫静脉血浆以及胎儿脐带血浆)中Exosome-HMGB1的浓度，以将它们的分布与明确的妊娠结局相关联。这项研究将评估一种新的胎儿-母体信号机制，该机制可以触发分娩以响应胎儿的OS。新途径和生物分子的识别将为筛选、诊断和降低肺结核的风险提供新的靶点。

 DESCRIPTION (provided by applicant): Fetal cell senescence at term is a natural physiologic response to oxidative stress (OS) that occurs as a result of increased metabolic demands by the maturing fetus. Various risk factors for preterm labor are associated with OS-induced senescence. Our pilot data suggest that fetal cell senescence causes the alarmin HMGB1 (a non-histone protein) to translocate from the nucleus to the cytosol. There it is modified by acetylation and released via exocytosis ("free" HMGB1) or encapsulated in exosomes, (30-100 nm particles) formed and extruded by multivesicular endosome fusion with the plasma membrane. Secreted HMGB1 functions as a proinflammatory cytokine in feto-maternal tissues. In the fetal membranes, it augments fetal cell senescence and an associated 'sterile' inflammatory reaction through TLR2-mediated p38 MAPK activation. In myocytes, HMGB1 activates p38 MAPK, resulting in upregulation of progesterone receptor (PR) isoform A and increased COX-2 expression and myocyte inflammation. A positive OS feedback loop is also established by HMGB1, accelerating amniocyte aging. Our core hypothesis posits that HMGB1 secreted from senescing fetal membranes, either by diffusion or transported via exosomes, causes myometrial activation through p38 MAPK, which in turn increases the ratio of PR-A to PR-B, leading to functional progesterone withdrawal and triggering the onset of labor. This hypothesis will be tested in 2 specific aims. Specific Aim 1 will determine how OS stimulates fetal membrane cell-derived HMGB1 secretion, as free protein or packaged and exported in exosomes, during human pregnancy and parturition. Specific Aim 2 will determine how free- or exosome-HMGB1 produced by fetal membrane cells in response to OS induces functional progesterone withdrawal and myometrial contractility. Primary and transformed human amnion, chorionic trophoblast, and myometrial cells, as well as fetal membrane and myometrial organ cultures, will be exposed to OS-inducing agents. Using molecular and cellular biological approaches we will quantitate OS-induced fetal cell senescence, HMGB1 release, exosome packaging, direction of exosome-HMGB1 secretion, signaling via p38 MAPK, PR isoform switching, and myometrial activation. Additionally, we will quantify the concentrations of exosome-HMGB1 in our banked feto-maternal biologic fluids (amniotic fluid, peripheral and maternal uterine venous plasma, and fetal cord plasma) from term and preterm births (PTB) to correlate their distribution with defined pregnancy outcomes. This study will evaluate a new feto-maternal signaling mechanism that triggers parturition in response to fetal OS. Identification of novel pathways and biomolecules should provide new targets to screen, diagnose, and reduce the risk of PTB.