720 Comparing transcriptional signatures of fetal hofbauer cells derived from bulk versus single-Cell RNA sequencing approaches

Abstract

Fetal Hofbauer Cells (HBC) play an instrumental role in the maintenance of a healthy pregnancy and in response to infection. Single-cell RNA sequencing (scRNAseq) has recently identified potential markers of HBC (Vento-Tormo, Nature, 2018). However, it is unknown whether these transcriptional signatures are congruent with profiles obtained from bulk RNA sequencing (bRNAseq) of purified cell populations. Here we compared the results from these two different approaches to transcriptomic studies. This is a comparative study of results from a publicly available scRNAseq database that analyzed first trimester placentas and bRNAseq data generated by our group analyzing term placentas from normal pregnancies. In the bRNAseq analysis, maternal intervillous monocytes (MIM) and HBC were purified using targeted isolation techniques. Differentially expressed genes in paired samples were identified using LIMMA and compared to a list of 30 proposed HBC markers. Transcript levels were normalized against the mean expression in MIM for each gene to determine relative gene expression; normalized expression values were compared with the 30 markers. HBC:MIM expression ratios were also calculated in paired samples. 19 of 30 (63%) HBC markers defined by scRNAseq were also identified by bRNAseq (adjusted p-value<0.01). Hierarchical clustering demonstrated that HBC and MIM samples clustered separately and that all markers were more highly expressed in HBC, with the exception of DAB2 (Fig 1). Analysis of HBC:MIM expression ratios in paired samples, also demonstrated low relative expression of DAB2 in HBC. ATP1B1, LGMN, NINJ1, and EGFL7 showed higher expression in HBC which was consistent between patient samples (Fig 2). Results from scRNAseq and bRNAseq approaches showed >60% concordance in the identification of HBC markers, despite differences in gestational age and approach. Future studies are needed to validate the use of these potential biomarkers of HBCs, which will serve as important tools in understanding the role of these cells in placental disease.View Large Image Figure ViewerDownload Hi-res image Download (PPT)