Institute of Women, Children and Reproductive Health, Shandong University, Jinan, 250012, Shandong, China.
State Key Laboratory of Reproductive Medicine and Offspring Health, Shandong University, Jinan, 250012, Shandong, China.
Cell Commun Signal. 2024 Jan 23;22(1):61. doi: 10.1186/s12964-023-01463-z.
During human early placentation, a proportion of extravillous trophoblasts (EVTs) migrate to the maternal decidua, differentiating into endovascular EVTs to remodel spiral arteries and ensure the establishment of blood circulation at the maternal-fetal interface. Inadequate EVT migration and endovascular differentiation are closely associated with adverse pregnancy outcomes such as miscarriage. Activin A and fibronectin are both secretory molecules abundantly expressed at the maternal-fetal interface. Activin A has been reported to regulate EVT biological functions. However, whether fibronectin mediates activin A-promoted EVT migration and acquisition of endothelial-like phenotype as well as the underlying molecular mechanisms remain unknown. Additionally, the role of fibronectin in pregnancy establishment and maintenance warrants further investigation.
Primary and immortalized (HTR8/SVneo) human EVTs were used as in vitro study models. Cultured human first-trimester chorionic villous explants were utilized for ex vivo validation. A local fibronectin knockdown model in ICR mouse uteri, achieved by nonviral in vivo transfection with small interfering RNA (siRNA) targeting fibronectin 1 (si-Fn1), was employed to explore the roles of fibronectin in the establishment and maintenance of early pregnancy.
Our results showed that activin A treatment significantly induced fibronectin 1 (FN1) mRNA expression and fibronectin protein production, which is essential for human trophoblast migration and endothelial-like tube formation. Both basal and activin A-upregulated fibronectin expression were abolished by the TGF-β type I receptor inhibitor SB431542 or siRNA-mediated knockdown of activin receptor-like kinase (ALK4) or SMAD4. Moreover, activin A-increased trophoblast migration and endothelial-like tube formation were attenuated following the depletion of fibronectin. Fibronectin knockdown via intrauterine siRNA administration reduced CD31 and cytokeratin 8 (CK8) expression at the maternal-fetal interface, resulting in a decrease in the number of implantation sites and embryos.
Our study demonstrates that activin A promotes trophoblast cell migration and acquisition of endothelial-like phenotype via ALK4-SMAD2/3-SMAD4-mediated fibronectin upregulation. Furthermore, through a local fibronectin knockdown model in mouse uteri, we found that the absence of fibronectin at the maternal-fetal interface impedes endovascular migration of trophoblasts and decidual vascularization, thereby interfering with early embryo implantation and the maintenance of pregnancy. These findings provide novel insights into placental development during early pregnancy establishment and contribute to the advancement of therapeutic approaches for managing pregnancy complications related to trophoblast dysfunction.
在人类早期胎盘形成过程中，一部分绒毛外滋养细胞（EVT）迁移到母体蜕膜，分化为血管内 EVT，重塑螺旋动脉，确保在母体-胎儿界面建立血液循环。EVT 迁移和血管内分化不足与流产等不良妊娠结局密切相关。激活素 A 和纤维连接蛋白都是在母体-胎儿界面大量表达的分泌分子。已有报道称激活素 A 调节 EVT 的生物学功能。然而，纤维连接蛋白是否介导激活素 A 促进 EVT 迁移和获得内皮样表型以及潜在的分子机制尚不清楚。此外，纤维连接蛋白在妊娠建立和维持中的作用值得进一步研究。
原代和永生化（HTR8/SVneo）人 EVT 被用作体外研究模型。培养的人早孕绒毛绒毛外植体用于离体验证。通过非病毒体内转染针对纤维连接蛋白 1（FN1）的小干扰 RNA（siRNA），在 ICR 小鼠子宫中建立局部纤维连接蛋白敲低模型，以探讨纤维连接蛋白在早期妊娠建立和维持中的作用。
我们的结果表明，激活素 A 处理显著诱导纤维连接蛋白 1（FN1）mRNA 表达和纤维连接蛋白蛋白产生，这对于人滋养细胞迁移和内皮样管形成是必需的。TGF-β 型 I 受体抑制剂 SB431542 或激活素受体样激酶（ALK4）或 SMAD4 的 siRNA 介导敲低均消除了基础和激活素 A 上调的纤维连接蛋白表达。此外，纤维连接蛋白耗竭后，激活素 A 诱导的滋养细胞迁移和内皮样管形成减弱。宫内 siRNA 给药导致纤维连接蛋白敲低，导致母胎界面 CD31 和细胞角蛋白 8（CK8）表达减少，导致着床部位和胚胎数量减少。
我们的研究表明，激活素 A 通过 ALK4-SMAD2/3-SMAD4 介导的纤维连接蛋白上调促进滋养细胞迁移和获得内皮样表型。此外，通过在小鼠子宫中建立局部纤维连接蛋白敲低模型，我们发现母胎界面缺乏纤维连接蛋白会阻碍滋养细胞的血管内迁移和蜕膜血管化，从而干扰早期胚胎着床和妊娠的维持。这些发现为早期妊娠建立过程中的胎盘发育提供了新的见解，并为管理与滋养细胞功能障碍相关的妊娠并发症的治疗方法的发展做出了贡献。
