Single-cell analysis of human ovarian cortex identifies distinct cell populations but no oogonial stem cells

Abstract

The human ovary orchestrates sex hormone production and undergoes monthly structural changes to release mature oocytes. The outer lining of the ovary (cortex) has a key role in defining fertility in women as it harbors the ovarian reserve. It has been postulated that putative oogonial stem cells exist in the ovarian cortex and that these can be captured by DDX4 antibody isolation. Here, we report single-cell transcriptomes and cell surface antigen profiles of over 24,000 cells from high quality ovarian cortex samples from 21 patients. Our data identify transcriptional profiles of six main cell types; oocytes, granulosa cells, immune cells, endothelial cells, perivascular cells, and stromal cells. Cells captured by DDX4 antibody are perivascular cells, not oogonial stem cells. Our data do not support the existence of germline stem cells in adult human ovaries, thereby reinforcing the dogma of a limited ovarian reserve.

The ovarian stroma as a new frontier

“…In contrast, localization of CYP17A1 shifted from exclusively the theca interna in control mice to patches in the interstitial stroma in DHT-treated mice, supporting a potential role for the stroma in androgen production following certain perturbations (Candelaria et al 2019). Singlecell RNA sequencing studies have also demonstrated subpopulations of stromal cells expressing CYP17A1 and STAR (Wagner et al 2020, Wang et al 2020. Although stromal cells have demonstrated varied hormone production and responsiveness, definitive characterization of these dynamics and their functional significance remains to be established (Fig.…”

“…Other studies have used DCN and LUM to identify populations of human theca/stroma cells (Fan et al 2019). Higher expression in some of the human cells considered to be stroma was demonstrated for markers PDGFRA, DCN, COL1A1, COL6A1, STAR, and/or CYP17A1 (Wagner et al 2020). A different study delineated nonhuman primate ovarian stroma by expression of TCF21, COL1A2, and/ or STAR (Wang et al 2020).…”

“…Additionally, postnatal DDX4-expressing cells generated using a Rosa26 rbw/+ ;Ddx4-Cre fluorescent reporter mouse were not seen to be mitotically active nor participating in follicular renewal (Zhang et al 2012). A recent single-cell sequencing study isolated human Abcam DDX4-positive cells and concluded these cells were perivascular cells rather than oogonial stem cells (Wagner et al 2020). In contrast, cell line establishment of female germline stem cells has been described using cells from human ovarian cortical tissue fragments present in follicular aspirates, which differentiated into oocyte-like cells (Ding et al 2016).…”

“…They classified a majority of cells (83%) as stroma, noting shared expression of mesodermal lineage markers (PDGFRA, DCN), ECM proteins (COL1A1, COL6A1), as well as expression of STAR and CYP17A1 by some cells in the stromal cluster. Although they isolated many stromal cells, their study mainly focused on discerning whether cells isolated using the Abcam DDX4 antibody were oogonial stem cells (Wagner et al 2020). A single-cell transcriptomic study of ovarian aging in nonhuman primate ovaries identified seven ovarian cell types, including oocytes, granulosa cells, stromal cells, smooth muscle cells, endothelial cells, Natural Killer T cells, and macrophages (Wang et al 2020).…”

Safeguarding Female Reproductive Health Against Endocrine Disrupting Chemicals—The FREIA Project

“…At birth, a baby girl has per ovary approximately 300,000 primordial follicles containing immature eggs or oocytes, which constitutes the ovarian reserve [13]. The human ovarian reserve is finite, as was recently demonstrated by the lack of oocyte stem cells in single-cell analyses of adult human ovaries, demonstrating that lost oocytes cannot be replaced [14]. This clearly shows that the number of oocytes is a major limiting factor in human reproduction.…”