# Combinatory differentiation of human induced pluripotent stem cells generates functional thymic epithelium driving dendritic cell and CD4/CD8 T cell development

## TL;DR

This study develops a method to grow functional thymic tissue in the lab using stem cells, enabling the production of T cells and dendritic cells for research and potential therapies.

## Contribution

A novel in vitro thymic organoid model is developed to support multilineage differentiation including T and dendritic cells from human iPSCs.

## Key findings

- Modulating signaling pathways generates progenitors that mature into medullary and cortical thymic epithelial cells.
- 3D thymic organoids support the differentiation of CD4+ and CD8+ T cells from hematopoietic progenitors.
- Dendritic cell populations also emerge in the thymic organoid model, indicating multilineage differentiation.

## Abstract

The thymus educates thymocytes through a selection process mediated by thymic epithelial cells (TECs). Recent advances have made the generation of T lymphocytes from induced pluripotent stem cells (iPSc) a promising therapeutic strategy. However, current approaches often fail to replicate the thymic niche, leading to impaired T cell generation. Here we address the production of functional mature iPSc-derived TECs supporting in vitro T cell generation. We optimize thymic lineage differentiation through an unbiased multifactorial experimental design. By modulating specific signaling pathways, we generate progenitors that mature into medullary and cortical TECs. Co-culture with primary hematopoietic progenitors in a 3D thymic organoid setup induces their differentiation into CD4+ and CD8+ T cells. Importantly, thymic organoids support multilineage differentiation, with dendritic cell populations also emerging. Thus, the presented thymic organoid model provides a practical platform for studying thymic cellular interactions and thymopoiesis in vitro, and opens further research perspectives towards cell-based therapies.

In vitro methods for thymic organoid cultures are useful to examine requirements for T cell development and for generating large numbers of cells for therapeutic purposes. Here the authors use human induced pluripotent stem cells, differentiate these into thymic epithelial organoid cultures and utilise haematopoietic progenitors to show development of T cells in vitro.