Early-life mucosal T cells direct intestinal stem cell fate via a coordinated developmental program

Area of Science:

• Immunology
• Developmental Biology
• Gastroenterology

Background:

• The fetal immune system is dynamic, with T lymphocytes being a major population in the fetal small intestine (SI) by the second trimester.
• The specific roles of these fetal SI T cells in intestinal development and stem cell function remain largely undefined.

Purpose of the Study:

• To investigate the functional roles of early-life (fetal and neonatal) versus adult small intestine (SI) T cells in promoting intestinal stem cell renewal and differentiation.
• To explore the potential of fetal T cells in restoring regenerative capacity in organoids from adult or necrotizing enterocolitis (NEC) affected infants.

Main Methods:

• Established an ex vivo co-culture system using 3D SI organoids from various ages co-cultured with mucosal T cells from fetal, neonatal, or adult SI donors.
• Assessed organoid generation as a metric of stem cell renewal and analyzed stem cell differentiation pathways.
• Investigated the role of T cell-derived soluble factors versus physical interactions and T cell localization to the stem cell niche.

Main Results:

• Homeostatic fetal and neonatal SI T cells uniquely promoted organoid generation and upregulated cell cycle-associated gene programs, indicating enhanced stem cell renewal.
• Early-life T cells directed intestinal stem cell differentiation towards the secretory lineage, a function absent in adult SI T cells and cord blood T cells.
• Fetal T cells restored regenerative states in adult or NEC organoids, and T cell localization to the stem cell niche was crucial for supporting fetal stem cell function via Notch, Wnt, and growth factor signaling.

Conclusions:

• Fetal and neonatal SI T cells possess developmentally specialized, non-immune functions critical for intestinal development, balancing stem cell self-renewal and differentiation.
• T cells play a coordinated role in a developmental immune-epithelial axis, influencing stem cell fate and potentially offering therapeutic avenues for intestinal regeneration.
• Dysfunctional T cell responses may contribute to pathologies like necrotizing enterocolitis (NEC), highlighting the importance of early-life immune interactions in intestinal health.