Single-cell transcriptomics of pathological pregnancies

Pregnancy is a complicated process involving various anatomical and physiological changes to provide a suitable environment for fetal development, to meet the increased metabolic demands, and to prepare for labor. While most pregnancies and births are uneventful, all pregnancies are at risk of complications. No less than 15% of all pregnant women develop a potentially lifethreatening complication or may also experience an unpleasant outcome. Conventional sequencing has been widely used in this field for diagnoses and treatment planning. However, it lacks the precise resolution to identify transcriptomic variation between the nearby cell types. Single-cell RNA sequencing is a novel approach that through single-cell isolation, transcript capturing, and development and sequencing of expression libraries allows the assessments of fundamental biological properties of cell populations and biological systems at unprecedented resolution. The single-cell sequencing technology is a powerful tool for investigating cell distribution and cell-to-cell relationships in human reproduction. Since 2016, the technique has contributed to the discovery of many transcriptomic atlases of human embryos, placenta, decidua, and endometrium and the identification of various crucial regulatory pathways in fetal development. Here, we briefly describe the application of single-cell RNA sequencing in the studies of physiological processes and pathological mechanisms of pregnancy.