# Sema3dhi Fibroblasts Promote Acute Kidney Injury Fibrotic Progression Through Confining Endothelial Cell Migration

## TL;DR

This study shows how a specific type of fibroblast promotes kidney injury progression by limiting blood vessel growth, offering a new treatment target.

## Contribution

Identifies Sema3dhi fibroblasts as key drivers of fibrosis by inhibiting endothelial cell migration through Sema3d signaling.

## Key findings

- Sema3dhi fibroblasts increase after kidney injury and correlate with fewer endothelial cells.
- Sema3d secreted by these fibroblasts impairs endothelial cell migration and angiogenesis.
- Reducing Sema3d with AAV9-shRNA alleviates renal fibrosis in mice.

## Abstract

Acute kidney injury (AKI) often leads to incomplete recovery of renal function, progressing to chronic kidney disease (CKD). Key pathological features in the AKI-CKD transition include microvascular rarefaction and fibrosis. However, the direct effects of activated fibroblasts on microvasculature and endothelial cells remain unclear. We constructed a single-cell RNA sequencing (scRNA-seq) database from unilateral ischemia reperfusion injury (uIRI) mouse model and identified five heterogeneous fibroblast subpopulations, with C0-Sema3dhi fibroblasts significantly increasing post-injury and correlating with reduced endothelial cells. Conditioned medium from Sema3dhi-NRK49F cells inhibited focal adhesion formation and induced cytoskeletal collapse in human umbilical vein endothelial cells (HUVECs), preventing migration and angiogenesis. Mechanistically, Sema3dhi fibroblasts secrete Sema3d, activating the endothelial Plexin D1 receptor, leading to Arf6 activation and integrin β1 internalization, thus suppressing endothelial function. Systemic administration of Sema3d-shRNA using adeno-associated virus serotype 9 (AAV9) effectively reduced Sema3d levels and significantly alleviated renal fibrosis in mice. The presence of SEMA3D+ fibroblasts was confirmed by analyzing human scRNA-seq data and through immunofluorescence staining of kidney sections from patients with kidney diseases. This study reveals new target for mitigating renal fibrosis and microvascular loss, suggesting that targeting the Sema3d signaling pathway may provide a novel strategy for preventing AKI fibrotic progression.