Preparation of single-cell suspensions from the human placenta.

Single-cell RNA-sequencing (scRNA-seq) allows the characterization of cellular composition and interactions in complex tissues. An essential prerequisite for scRNA-seq is the preparation of high-quality single-cell suspensions. So far, no protocols have been described for preparing such suspensions from the placenta, an essential organ for fetal development and a site of maternal-fetal immune interaction. Here we describe a protocol for the preparation of high-quality single-cell suspensions from human placental tissues-namely, the basal plate, placental villi and chorioamniotic membranes. The protocol outlines the collection of tissues from the placenta, tailored dissociation procedures for each tissue, and the cryopreservation of single-cell suspensions for multiplex sequencing library preparation. The protocol can be performed by a qualified investigator with basic working knowledge of placental structure. Moreover, the single-cell suspensions generated by using this protocol are compatible with droplet-based scRNA-seq technology, such as the 10x Genomics Chromium system. This protocol reliably produces single-cell suspensions from the placental tissues with high yield and viability for scRNA-seq. This protocol takes ~6 h to complete from tissue collection to cryopreservation of single-cell suspensions, and an additional 2 h for thawing of cryopreserved single cells.