DataSheet1_Impaired autophagy with augmented apoptosis in a Th1/Th2-imbalanced placental micromilieu is associated with spontaneous preterm birth.PDF

Background: Despite decades of research, the pathogenesis of spontaneous preterm birth (PTB) remains largely unknown. Limited currently available data on PTB pathogenesis are based on rodent models, which do not accurately reflect the complexity of the human placenta across gestation. While much study has focused on placental infection and inflammation associated with PTB, two key potentially important cellular events in the placenta—apoptosis and autophagy—remained less explored. Understanding the role of these processes in the human placenta may unravel currently ill-understood processes in the pathomechanism of PTB.
Methods: To address this necessity, we conducted qRT-PCR and ELISA assays on placental villous tissue from 20 spontaneous preterm and 20 term deliveries, to assess the inter-relationships between inflammation, apoptosis, and autophagy in villous tissue in order to clarify their roles in the pathogenesis of PTB.
Results: We found disrupted balance between pro-apoptotic BAX and anti-apoptotic BCL2 gene/protein expression in preterm placenta, which was associated with significant reduction of BCL2 and increase of BAX proteins along with upregulation of active CASP3 and CASP8 suggesting augmented apoptosis in PTB. In addition, we detected impaired autophagy in the same samples, evidenced by significant accumulation of autophagosome cargo protein p62/SQSTM1 in the preterm villous placentas, which was associated with simultaneous downregulation of an essential autophagy gene ATG7 and upregulation of Ca2+-activated cysteine protease CAPN1. Placental aggregation of p62 was inversely correlated with newborn birth weight, suggesting a potential link between placental autophagy impairment and fetal development. These two aberrations were detected in a micromilieu where the genes of the Th2 cytokines IL10 and IL13 were downregulated, suggesting an alteration in the Th1/Th2 immune balance in the preterm placenta.
Conclusion: Taken together, our observations suggest that impaired autophagy and augmented apoptosis in a Th1/Th2 imbalanced placental micro-environment may be associated with the pathogenesis of spontaneous PTB.

研究背景：尽管已开展数十年相关研究，但自发性早产（spontaneous preterm birth, PTB）的发病机制仍未完全阐明。当前可获取的PTB发病机制相关数据多基于啮齿类动物模型，此类模型无法准确反映妊娠全程人类胎盘的复杂生理状态。既往研究多聚焦于与PTB相关的胎盘感染与炎症反应，但胎盘中另外两项潜在关键细胞事件——细胞凋亡（apoptosis）与细胞自噬（autophagy）——的相关探索仍相对匮乏。明确上述过程在人类胎盘中的作用，或可揭示当前尚未阐明的PTB发病通路。
研究方法：为解决上述研究空白，本研究对20例自发性早产产妇及20例足月分娩产妇的胎盘绒毛组织开展实时定量逆转录聚合酶链反应（quantitative real-time polymerase chain reaction, qRT-PCR）与酶联免疫吸附测定（enzyme-linked immunosorbent assay, ELISA）实验，以评估绒毛组织中炎症反应、细胞凋亡与细胞自噬之间的相互关联，进而明确三者在PTB发病机制中的作用。
研究结果：本研究发现，早产产妇胎盘中促凋亡蛋白BAX与抗凋亡蛋白BCL2的基因及蛋白表达平衡被打破：BCL2蛋白表达水平显著降低，BAX蛋白表达水平显著升高，同时活化的CASP3与CASP8表达上调，提示PTB患者胎盘组织细胞凋亡水平升高。此外，本研究在同一批样本中检测到自噬功能受损，表现为早产产妇胎盘绒毛组织中自噬底物蛋白p62/SQSTM1显著聚集，这一现象与核心自噬基因ATG7的表达下调及钙离子激活的半胱氨酸蛋白酶CAPN1表达上调同时存在。胎盘组织中p62的聚集水平与新生儿出生体重呈负相关，提示胎盘自噬功能受损与胎儿发育之间存在潜在关联。在上述两项异常改变对应的胎盘微环境中，2型辅助性T细胞（Th2）细胞因子IL10与IL13的基因表达均出现下调，提示早产产妇胎盘组织的Th1/Th2免疫平衡发生紊乱。
研究结论：综上，本研究结果提示，在Th1/Th2免疫失衡的胎盘微环境中，胎盘组织自噬功能受损与细胞凋亡增强或与自发性PTB的发病机制相关。