# Reconstitution of the cellular niche requirements for primordial germ cell-like cell progression in humans

## TL;DR

Researchers found that human primordial germ cell-like cells can mature and avoid dedifferentiation when cultured in specific human cellular niches, such as reconstituted fetal ovaries or amnion-like cell aggregates.

## Contribution

This study demonstrates that human-specific cellular niches can support the progression of hPGCLCs without relying on mouse-derived cells.

## Key findings

- hPGCLCs in reconstituted fetal ovaries upregulated germ cell markers and initiated meiosis.
- hPGCLCs co-cultured with amnion-like cells showed less dedifferentiation and acquired migratory characteristics.
- Stem cell factor (SCF) was essential for hPGCLC survival in both niche environments.

## Abstract

Human primordial germ cell-like cells (hPGCLCs) can be specified from human-induced pluripotent stem cells (hiPSCs), offering a valuable model for human germ cell development. However, further maturation steps of hPGCLCs rely on mouse feeders, or co-culture with mouse gonadal somatic cells. Exposure of hPGCLCs to human cellular niche has not been attempted. Here, we co-cultured female hPGCLCs in two distinct niche compartments. In reconstituted fetal ovary (rOv) culture, human fetal germ cells proliferated and initiated meiosis, while hPGCLCs upregulated gonadal germ cell markers such as DDX4. Additionally, hPGCLCs were supported and matured into migratory hPGCLCs in 3D co-culture with amnion-like cells (AMLCs). Compared to rOv, hPGCLCs in PGCLC/AMLC aggregates were less prone to dedifferentiate. In both niches, stem cell factor (SCF) was crucial for the survival of hPGCLCs. Together, this work underscores that a shift in niche is required for the further germ cell development of hPGCLCs.

•Reconstituted human fetal ovaries (rOvs) support meiosis entry of fetal germ cells•The rOvs support hPGCLCs to upregulate gonadal germ cell markers•hPGCLCs show less dedifferentiation in amnion-like cell aggregates compared to rOvs•SCF is not required for survival of fetal germ cells, but crucial for hPGCLCs

Reconstituted human fetal ovaries (rOvs) support meiosis entry of fetal germ cells

The rOvs support hPGCLCs to upregulate gonadal germ cell markers

hPGCLCs show less dedifferentiation in amnion-like cell aggregates compared to rOvs

SCF is not required for survival of fetal germ cells, but crucial for hPGCLCs

Chuva de Sousa Lopes and colleagues used in vitro reconstituted human fetal ovaries (rOvs) as cellular niche to mature human primordial germ cell-like cells (hPGCLCs). hPGCLCs in rOvs matured but were prone to dedifferentiate. By contrast, hPGCLCs cultured with amnion-like cells were maintained without dedifferentiation and acquired migratory fate. In both systems, SCF was crucial for the survival of hPGCLCs.