Qualitative Changes in Cortical Thymic Epithelial Cells Drive Postpartum Thymic Regeneration

Area of Science:

• Immunology
• Developmental Biology
• Endocrinology

Background:

• Pregnancy involves significant thymic involution, a process where the thymus shrinks, which is rapidly reversed after childbirth.
• Thymic epithelial cells (TECs) are crucial for regulating thymopoiesis, the process of T-cell development within the thymus.
• Understanding the mechanisms behind postpartum thymic regeneration is essential for comprehending immune system recovery after pregnancy.

Purpose of the Study:

• To investigate the sequential phenotypic and transcriptomic changes in TECs during the postpartum period.
• To identify the specific molecular mechanisms that trigger and orchestrate postpartum thymic regeneration.

Main Methods:

• Purification of distinct TEC subsets.
• Flow cytometry analyses to assess cell populations.
• Deep RNA-sequencing to analyze gene expression profiles at various time points before and after parturition.

Main Results:

• Pregnancy-induced thymic involution does not involve a decrease in TEC numbers.
• A significant depletion of thymocyte subsets (beyond DN1 stage) occurs during pregnancy.
• Cortical TECs (cTECs) exhibit significant transcriptomic changes, particularly in the expression of *Foxn1* and related genes essential for thymopoiesis, correlating with thymocyte number variations.
• Medullary TECs (mTECs) show minimal changes early postpartum but respond later to thymocyte expansion.

Conclusions:

• Postpartum thymic regeneration is primarily orchestrated by early, specific transcriptomic alterations in cTECs, rather than changes in TEC numbers.
• The identified gene expression changes in cTECs are key drivers of thymic recovery following pregnancy.