Retinoic Acid-Mediated Signaling Regulates Allantoic and Fetoplacental Vascularization

The placenta is vital for fetal development, and altered placental vascularization underlies prevalent disorders, including fetal growth restriction, prematurity, and pregnancy complications. Impaired placental vascularization is associated with Vitamin A deficiency, but mechanisms are undefined. To investigate this, we used retinoic acid (RA)-deficient Raldh2?/? embryos, and found they exhibit placental endothelial hyperproliferation and impaired arterial-venous remodeling, which were rescued by providing all-trans-RA (ATRA) via maternal diet. Single cell RNA sequencing of E9.5 Raldh2+/+, Raldh2?/?,and Raldh2?/?+ATRA placental cells, and functional assays, revealed that RA regulates endothelial growth and vascular remodeling via Notch signaling. Overall design: Placentas from E9.5 embryos that were WT Raldh2, KO Raldh2, WT Raldh2 (from ATRA fed moms), and KO Raldh2 (from ATRA fed moms) were enzymatically digested into a single cell suspension, depleted of CD45+ cells and enriched for CD31+ cells to increase the number of ECs using microbeads. 5% of all other placental cells were spiked back and analyzed using scRNA-seq.