# Profiling the cell-specific small non-coding RNA transcriptome of the human placenta

## TL;DR

This study profiles small non-coding RNA expression in different cell types of the human placenta, revealing cell-specific patterns and differences across development stages.

## Contribution

The first exploration of the sncRNA transcriptome in bulk placental villi and major placental cell types using FACS-sorted samples.

## Key findings

- Samples clustered primarily by cell type lineage after normalization for technical variables.
- Mean expression of 115 sncRNAs differed by cell type, though no sncRNAs were uniquely expressed by a single cell type.
- Some sncRNA-CpG pairs showed high correlation (R2 ± 0.6), but overall sncRNA and DNA methylation correlation was not significant.

## Abstract

The human placenta is the composite of multiple cell types, each which contributes uniquely to placental function. Small non-coding RNAs (sncRNAs) are regulators of gene expression and can be cell-specific. The sncRNA transcriptome of individual placental cell types has not yet been investigated due to difficulties in their procurement and isolation. Using a custom sequencing method, we explored the expression of seven sncRNA species (miRNA, piRNA, rRNA, scaRNA, snRNA, snoRNA, tRNA) from whole chorionic villi and four major sample-matched FACS-sorted cell type (cytotrophoblast, stromal, endothelial, Hofbauer) samples from 9 first trimester and 17 term placentas. After normalization for technical variables, samples clustered primarily by cell type lineage. No sncRNAs were uniquely expressed by cell type, however, mean expression differed by cell type for 115 sncRNAs. Known placentally-expressed sncRNAs showed differing expression by cell type and trimester. Expression of few sncRNAs varied by sex. Lastly, sample-matched sncRNA expression and DNA methylation correlation was not significant, although high correlation (> R2 ± 0.6) was observed for some sncRNA-CpG pairs. This study represents the first exploration of the sncRNA transcriptome of bulk placental villi and placental cell types, informing about the expression and regulatory patterns underlying human placental development.