ST2 + T-Regulatory Cells in Renal Inflammation and Fibrosis after Ischemic Kidney Injury

Abstract

Key Points:

1. IL-33/ST2 alarmin pathway regulates inflammation, fibrosis, and resolution of ischemia-reperfusion injury of kidneys.

2. ST2 regulates the transcriptome of T-regulatory cells related to suppressive and reparative functions.

3. The secretome of ST2⁺ T-regulatory cells regulates hypoxic injury in an amphiregulin-dependent manner.

Background: Inflammation is a major cause of kidney injury. IL-1 family cytokine IL-33 is released from damaged cells and modulates the immune response through its receptor ST2 expressed on many cell types, including regulatory T cells (Tregs). Although a proinflammatory role of IL-33 has been proposed, exogenous IL-33 expanded Tregs and suppressed renal inflammation. However, the contribution of endogenous IL-33/ST2 for the role of Tregs in the resolution of kidney injury has not been investigated.

Methods: We used murine renal ischemia-reperfusion injury and kidney organoids (KDOs) to delineate the role of the ST2 and amphiregulin (AREG) specifically in Tregs using targeted deletion. Bulk and single-cell RNA sequencing were performed on flow-sorted Tregs from spleen and CD4 T cells from postischemic kidneys, respectively. The protective role of ST2-sufficient Tregs was analyzed using a novel coculture system of syngeneic KDOs and Tregs under hypoxic conditions.

Results: Bulk RNA sequencing of splenic and single-cell RNA sequencing of kidney CD4 T cells showed that ST2⁺ Tregs are enriched for genes related to Treg proliferation and function. Genes for reparative factors, such as Areg, were also enriched in ST2⁺ Tregs. Treg-specific deletion of ST2 or AREG exacerbated kidney injury and fibrosis in the unilateral ischemia-reperfusion injury model. In coculture studies, wild-type but not ST2-deficient Tregs preserved hypoxia-induced loss of kidney organoid viability, which was restored by AREG supplementation.

Conclusions: Our study identified the role of the IL-33/ST2 pathway in Tregs for resolution of kidney injury. The transcriptome of ST2⁺ Tregs was enriched for reparative factors including Areg. Lack of ST2 or AREG in Tregs worsened kidney injury. Tregs protected KDOs from hypoxia in a ST2- and AREG-dependent manner.