CXCL12/CXCR4 signaling coordinates trophoblast, immune, vascular, and metabolic programming during early placentation in sheep.

Abstract

Successful placentation requires coordinated regulation of trophoblast differentiation, immune tolerance, vascular remodeling, and nutrient transport during the peri-implantation period. The chemokine ligand CXCL12 and its receptor CXCR4 are expressed at the fetal-maternal interface and implicated in trophoblast migration, immune regulation, and angiogenesis, but their in vivo role in early placental functional development remains unclear. The objective of this study was to determine whether suppression of CXCL12/CXCR4 signaling during implantation alters placental programming in sheep. Ewes received intrauterine infusion of CXCR4 antagonist AMD3100 from Day 12-19 of pregnancy, and tissues were collected on Day 20. Pregnancy rates were not affected by treatment; however, pregnancy-associated glycoprotein abundance was increased in treated ewes, indicating altered trophoblast differentiation. Inhibiting CXCR4 reduced expression of angiogenic factors including vascular endothelial growth factor A, placental growth factor, fms-like tyrosine kinase-1, and angiopoietin-1 in endometrium, consistent with impaired vascular development. Suppression of CXCR4 also shifted immune signaling toward a pro-inflammatory profile, with increased interferon-gamma and interleukin-12 and decreased transforming growth factor beta. In addition, expression of glucose and amino acid transporters, including SLC2A1, SLC2A3, SLC38, and SLC7 family members, was altered in fetal membranes and endometrium, accompanied by increased autophagy marker LC3B-II, suggesting metabolic stress. These findings demonstrate that CXCL12/CXCR4 signaling is not required for conceptus attachment but is important for coordinated development of vascular, immune, and metabolic pathways during early placentation. Disruption of this axis produces molecular changes consistent with placental insufficiency, supporting a central role for CXCL12/CXCR4 in establishing functional placental capacity.