Transcriptional heterogeneity of stemness phenotypes in the ovarian epithelium

Abstract

The ovarian surface epithelium (OSE) is a monolayer of epithelial cells covering the surface of the ovary. During ovulation, the OSE is ruptured to allow release of the oocyte. This wound is quickly repaired, but mechanisms of this repair are poorly understood. The contribution of tissue-resident stem cells in the homeostasis of several epithelial tissues is widely accepted, such as the intestinal epithelium, airway epithelium, and skin, but their involvement in OSE maintenance is unclear. While putative stem cell populations in the OSE have been described, how they are regulated is poorly defined. We show that traits associated with stem cells (stemness) can be increased in OSE following exposure to the cytokine TGFB1, overexpression of the transcription factor Snai1, or deletion of Brca1. By assessing the gene expression profiles of these populations, we show that stemness is often linked to mesenchymal-associated gene expression and higher activation of ERK signalling, but it is not consistently dependent on their activation. Expression profiles of these populations are extremely context specific, suggesting that stemness may not correspond to a single, distinct population, but rather is a heterogenous state that can possibly emerge from diverse environmental cues. Together, these findings support that the OSE may not require distinct stem cell populations for long-term maintenance, and may achieve this through transient dedifferentiation into a stem-like state.