Conservation at the uterine-placental interface

The hemochorial placentation site is characterized by a dynamic interplay between trophoblast cells and maternal cells. These cells cooperate to establish an interface required for nutrient delivery to promote fetal growth. In the human, trophoblast cells penetrate deep into the uterus. This is not a consistent feature of hemochorial placentation and has hindered the establishment of suitable animal models. The rat represents an intriguing model for investigating hemochorial placentation with deep trophoblast cell invasion. In this study, we used single cell RNA sequencing to characterize the transcriptome of the invasive trophoblast cell lineage, as well as other cell populations within the rat uterine-placental interface during early (gestation day, gd, 15.5) and late (gd 19.5) stages of intrauterine trophoblast cell invasion. We identified a robust set of transcripts that define invasive trophoblast cells, as well as transcripts that distinguished endothelial, smooth muscle, natural killer, and macrophage cells. Invasive trophoblast, immune, and endothelial cell populations exhibited distinct spatial relationships within the uterine-placental interface. Furthermore, the maturation stage of invasive trophoblast cell development could be determined by assessing gestation-stage dependent changes in transcript expression. Finally, and most importantly, expression of a prominent subset of rat invasive trophoblast cell transcripts is conserved in the invasive extravillous trophoblast cell lineage of the human placenta. These findings provide foundational data to identify and interrogate key conserved regulatory mechanisms essential for development and function of an important compartment within the hemochorial placentation site that is essential for a healthy pregnancy. Rat uterine-placental interface (UPI) tissues were dissected on gd 15.5 and 19.5 . Dissected UPI compartments from wild type placentation sites were minced and enzymatically digested into a single cell suspension. Samples were further processed for scRNA-seq by Chromium Single Cell RNA-seq (10X Genomics). Single cell suspensions were prepared by enzymatic digestion of the uterine-placental interface. Single cell libraries were then constructed using the 10X Genomics platform and sequenced with an Illumina NovaSeq 6000 system. Computational analysis with the Cell-Ranger pipeline led to the identification a number of unique cell clusters defined by their transcript profiles, samples were analyzed.