PSVI-1 - Elucidating the effects of the CXCL12/CXCR4 axis through hematological changes in sheep during gestation

Abstract: The placenta, an organ that develops during pregnancy is essential for transporting nutrients and oxygen to the developing offspring. Formation of the placenta is characterized by many physiological and hematological changes necessary for a healthy gestation. Improper placentation causes placental insufficiency which increases fetal mortality and poor postnatal health and performance. Causes of placental insufficiency are poorly understood, however evidence indicates immune factors including the chemokine ligand 12 (CXCL12) and its receptor (CXCR4) regulate several processes central to placentation and white blood cells (WBC) play essential roles by promoting trophoblast invasion and supporting artery remodeling. We previously demonstrated suppressing CXCL12/CXCR4 signaling at the fetal-maternal interface during implantation diminishes placental vascularization, reduces trophoblast invasion, and creates an excessively inflammatory placental environment. Building on these studies, we hypothesized the negative impacts early in gestation would result in compromised placental development and altered hematological parameters during gestation. Identifying key hematological changes or inflammatory markers in a complete blood count analysis during pregnancy might provide diagnostic clues to placental insufficiency at early stages of pregnancy. Our objective was to determine if disrupting the CXCL12/CXCR4 axis during implantation results in an altered hematological profile or serum progesterone (P4) concentrations. Using an in-vivo sheep model osmotic pumps were surgically installed to deliver treatments into the uterine lumen on day 12 of gestation. Pumps delivered either CXCR4 inhibitor (AMD3100) at (1X, 1.5X, or 3X dose), CXCL12 at (low or high dose), or PBS (control) into the uterus over the course of 14 days. Blood samples were collected via jugular venipuncture daily from days 11 to 16 of gestation, every two days from days 18 to 30, and weekly from day 35 to 135 and analyzed within 2 h of collection for a complete blood count using the Abaxis VetScan HM5. Serum was also collected and P4 levels were quantified by radioimmunoassay. Manipulating the CXCL12/CXCR4 axis during early gestation did not affect (P = 0.98) systemic circulating progesterone values during days tested, but neutrophils, lymphocytes, WBCs, and platelets increased indicated systemic inflammation. Of the hematological parameters tested, WBC counts were significantly elevated (P < 0.05) in the 3X AMD3100 treatment group and neutrophils and lymphocytes tended (P < 0.1) to increase compared to control. Our results reveal suppressing CXCL12/CXCR4 signaling during early gestation creates an inflammatory response reflected in circulation. A greater understanding of hematological changes and endometrial interactions involved in placentation in sheep is necessary to elucidate the causes of placental insufficiency and recurrent pregnancy loss. Future research will investigate if circulating markers indicative of placental dysfunction exist which may lead to methods to improve fertility, pregnancy outcomes, and fetal health.