CXCR4 signaling at the ovine fetal–maternal interface regulates vascularization, CD34+ cell presence, and autophagy in the endometrium†

Abstract

Placenta development is characterized by extensive angiogenesis and vascularization but if these processes are compromised placental dysfunction occurs, which is the underlying cause of pregnancy complications such as preeclampsia and intrauterine growth restriction. Dysregulation of placental angiogenesis has emerged as one of the main pathophysiological features in the development of placental insufficiency and its clinical consequences. The signaling axis initiated by chemokine ligand 12 (CXCL12) and its receptor CXCR4 stimulates angiogenesis in other tissues, and may be central to placental vascularization. We hypothesized that CXCL12-CXCR4 signaling governs the pro-angiogenic placental microenvironment by coordinating production of central angiogenic factors and receptors and regulates endometrial cell survival essential for placental function and subsequent fetal longevity. The CXCR4 antagonist, AMD3100, was used to elucidate the role of CXCL12-CXCR4 signaling regarding uteroplacental vascular remodeling at the fetal–maternal interface. On day 12 postbreeding, osmotic pumps were surgically installed and delivered either AMD3100 or PBS into the uterine lumen ipsilateral to the corpus luteum. On day 20, endometrial tissues were collected, snap-frozen in liquid nitrogen, and uterine horn cross sections preserved for immunofluorescent analysis. In endometrium from ewes receiving AMD3100 infusion, the abundance of select angiogenic factors was diminished, while presence of CD34+ cells increased compared to control ewes. Ewes receiving AMD3100 infusion also exhibited less activation of Akt/mTOR signaling, and elevated LC3B-II, a marker of cellular autophagy in endometrium. This study suggests that CXCL12-CXCR4 signaling governs placental homeostasis by serving as a critical upstream mediator of vascularization and cell viability, thereby ensuring appropriate placental development.

Inhibition of the C-X-C Motif Chemokine 12 (CXCL12) and Its Receptor CXCR4 Reduces Utero-Placental Expression of the VEGF System and Increases Utero-Placental Autophagy

“…Similar to previous reports, the negative impact to placental vascularization early in gestation when CXCR4 is antagonized remains evident in placenta several days after treatments subsided. VEGFA abundance was diminished in fetal (COT) and maternal (CAR) placenta on day 35, but unlike our previous studies, FLT1 levels did not differ (15,16). Instead, production of the other VEGFA receptor, KDR, tended to decrease in maternal placenta after suppressing CXCL12-CXCR4.…”

“…The current study suppressed CXCL12-CXCR4 signaling at the fetal-maternal interface for 14 days whereas previous studies antagonized CXCR4 for 7 days, which may account for the differences in the production of the different VEGF receptors in the studies. Taken together, it appears that CXCL12-CXCR4 signaling regulates many components of the VEGFA pathway at the fetal-maternal interface including VEGFA and both receptors (15,16) and thus may be a key upstream regulator of the placental VEGFA angiogenic axis in the placenta.…”

“…To determine if diminished CXCL12-CXCR4 signaling at the fetal-maternal interface during implantation and initial placental vascularization results in long-term detrimental effects to the placenta, we suppressed CXCL12-CXCR4 at the fetal-maternal interface for 14 days starting on day 12 of gestation (days [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and then collected placental tissues on day 35 of gestation, 9 days after treatment delivery to uterus had stopped. Placental growth, vascularization, cell survival, and relevant signaling pathways were evaluated in fetal and maternal placenta on day 35 of gestation.…”

“…Using an in vivo sheep model in combination with in vitro methods, we have gained insight into CXCL12-induced actions during conceptus attachment and initial placentation. Suppressing CXCL12/CXCR4 signaling during the small window of conceptus implantation diminishes placental vascularization, induces autophagy, and dampens the inflammatory placental environment (13)(14)(15)(16). Moreover, we recently published evidence demonstrating that suppressing CXCL12-induced actions at the fetal-maternal interface reduces trophoblast invasion into maternal endometrium and delays uterine remodeling (13).…”

Role of Vascular Endothelial Growth Factor (VEGF) in Human Embryo Implantation: Clinical Implications

“…VEGFR-1 and VEGFR-2 were found to be overexpressed in the placenta from patients suffering from PE [130]. Placentation is a process with extensive angiogenesis in order to establish an appropriate vascular network between mother and fetus [137][138][139]. VEGF mediates angiogenesis and has an anti-apoptotic effect on vascular endothelium cells [2].…”