# Tubule-derived CCN1 drives renal repair via αvβ5-STAT6-ARG1-dependent reprogramming of macrophages

## TL;DR

This study shows that CCN1, a protein produced by kidney tubules, helps repair kidney damage by reprogramming macrophages through a specific signaling pathway.

## Contribution

The study identifies a novel tubular-immune communication pathway involving CCN1, αvβ5, STAT6, and ARG1 in renal repair after injury.

## Key findings

- CCN1 promotes pro-repair macrophage differentiation via the αvβ5-STAT6-ARG1 pathway.
- RTEC-derived CCN1 enhances kidney repair and epithelial proliferation in ischemia-reperfusion injury.
- Integrin αvβ5 is a direct CCN1-binding partner mediating macrophage reprogramming.

## Abstract

Macrophages play a critical role in injury and repair following acute kidney injury (AKI), but their regulatory mechanisms remain incompletely understood. Cellular communication network factor 1 (CCN1), a secreted matricellular protein and early biomarker of AKI, may regulate macrophage function during kidney injury. In this study, we first investigated CCN1’s interaction with macrophages in a murine model of ischemia-reperfusion (I/R)-induced AKI. The role of CCN1 was further investigated using recombinant protein administration, a renal tubular epithelial cell (RTEC)-specific CCN1 knockdown mouse model via adeno-associated virus, and in vitro studies with bone marrow-derived macrophages (BMDMs). We found that in response to injury, RTECs upregulated and secreted CCN1, which colocalized with infiltrating F4/80+ macrophages. RTEC-specific CCN1 knockdown exacerbated renal injury and reduced macrophage infiltration, as confirmed by H&E, KIM-1 and F4/80 staining. Transcriptomic profiling of kidney tissues revealed that CCN1 expression was associated with immune cell infiltration, particularly macrophages, while RNA-seq analysis of BMDMs demonstrated that CCN1 promoted pro-repair arginase1 (Arg1)+ macrophage differentiation and activated the STAT6 signaling pathway. BayesPrism deconvolution further confirmed the enrichment of Arg1hi macrophages following CCN1 treatment. Co-immunoprecipitation coupled with mass spectrometry identified integrin αvβ5 as a direct CCN1-binding partner mediating STAT6/ARG1 activation. Functionally, CCN1-treated macrophages enhanced RTECs' proliferation in vitro and in vivo, an effect abolished by ARG1 inhibition or macrophage depletion. In conclusion, CCN1 regulates macrophages via the αvβ5-STAT6-ARG1 axis to promote tubular epithelial proliferation and improve kidney function in I/R-AKI, highlighting a novel tubular-immune communication pathway and potential therapeutic targets for ischemic AKI.