# Damage-induced pyroptosis drives endogenous thymic regeneration by activating the purinergic receptor P2Y2

## TL;DR

This study shows that thymic regeneration after damage is driven by pyroptosis in thymocytes, which activates P2Y2 receptors to promote immune recovery.

## Contribution

The novel finding is that pyroptosis in thymocytes triggers P2Y2-mediated thymic regeneration, identifying P2Y2 as a potential therapeutic target.

## Key findings

- CD4+ CD8+ thymocytes undergo pyroptosis after radiation, releasing ATP into the thymic microenvironment.
- Extracellular ATP activates P2Y2 on thymic epithelial cells, upregulating FOXN1 and promoting regeneration.
- P2Y2 agonists like UTPγS accelerate TEC regeneration in vivo after acute damage.

## Abstract

T cell recovery is critical following damage, such as hematopoietic cell transplantation (HCT), with increased reconstitution associated with improved clinical outcomes. Endogenous thymic regeneration, a crucial process for restoring immune competence following cytoreductive therapies such as HCT conditioning, is often delayed, limiting T cell reconstitution. Fully understanding the molecular mechanisms driving regeneration is therefore crucial for uncovering therapeutic targets that can be exploited to enhance thymic function. Here, we identified that CD4+ CD8+ thymocytes rapidly and acutely undergo lytic cell death, specifically pyroptosis, following acute damage caused by ionizing radiation, and release damage-associated molecular patterns (DAMPS) into the thymic microenvironment, including ATP. Extracellular ATP stimulates the P2Y2 purinergic receptor on thymic epithelial cells (TECs)—a stromal cell crucial for supporting T cell development—resulting in the upregulation FOXN1, the master TEC transcription factor. Targeting the P2Y2 receptor with a P2Y2 agonist, UTPγS, promotes rapid regeneration of the TEC compartment in vivo following acute damage. These findings reveal a novel damage-sensing mechanism employed by the thymus where thymocytes adopt an alternative cell death mechanism which promotes thymic repair via P2Y2 signaling in TECs. This work identifies P2Y2 as a promising therapeutic target for enhancing thymus regeneration and improving immune recovery after HCT.