Established Thymic Epithelial Progenitor/Stem Cell-Like Cell Lines Differentiate into Mature Thymic Epithelial Cells and Support T Cell Development

Pengfei Chen,Yarui Du,Juanjuan Su,Jun Zhang,Yufang Shi,Guoliang Xu,Ulrich Siebenlist,Xiaoren Zhang,Yu Zhan,Elias T Zambidis

doi:10.1371/journal.pone.0075222

Abstract

Common thymic epithelial progenitor/stem cells (TEPCs) differentiate into cortical and medullary thymic epithelial cells (TECs), which are required for the development and selection of thymocytes. Mature TEC lines have been widely established. However, the establishment of TEPC lines is rarely reported. Here we describe the establishment of thymic epithelial stomal cell lines, named TSCs, from fetal thymus. TSCs express some of the markers present on tissue progenitor/stem cells such as Sca-1. Gene expression profiling verifies the thymic identity of TSCs. RANK stimulation of these cells induces expression of autoimmune regulator (Aire) and Aire-dependent tissue-restricted antigens (TRAs) in TSCs in vitro. TSCs could be differentiated into medullary thymic epithelial cell-like cells with exogenously expressed NF-κB subunits RelB and p52. Importantly, upon transplantation under the kidney capsules of nude mice, TSCs are able to differentiate into mature TEC-like cells that can support some limited development of T cells in vivo. These findings suggest that the TSC lines we established bear some characteristics of TEPC cells and are able to differentiate into functional TEC-like cells in vitro and in vivo. The cloned TEPC-like cell lines may provide useful tools to study the differentiation of mature TEC cells from precursors.

Highlights

The epithelial architecture in the thymus acts as a shelter fostering the expansion, maturation and selection of T lymphocytes [1,2]
Other markers are used to distinguish Medullary thymic epithelial cells (mTECs) from Cortical thymic epithelial cells (cTECs). mTECs are positive for Ulex europaeus agglutinin-1 (UEA-1), autoimmune regulator (Aire), ER-TR5 and MTS10, whereas cTECs are positive for ER
One recent study reported that cultured clonogenic thymic epithelial cells (TECs) have the capacity to organize into structures that closely resemble a thymus but can irreversibly adopt the fate of hair follicle multipotent stem cells, indicating that they might be thymic epithelial progenitor/stem cells (TEPCs) lines

Summary

Introduction

The epithelial architecture in the thymus acts as a shelter fostering the expansion, maturation and selection of T lymphocytes [1,2]. The thymus contains thymic epithelial cells that form a complex three-dimensional meshwork structure organized in anatomically distinct cortical and medullary compartments. Cortical thymic epithelial cells (cTECs) provide the differentiation signal, regulate the directional migration and population expansion of immature T lymphocytes, and positively select CD4+CD8+ thymocytes, which are capable of recognizing self-major histocompatibility complex (MHC). Patterns of keratin expression have been described as markers of TEC subsets [1]. Other markers are used to distinguish mTECs from cTECs. mTECs are positive for Ulex europaeus agglutinin-1 (UEA-1), Aire, ER-TR5 and MTS10, whereas cTECs are positive for ER-

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