# Dysregulation of Rho‐Associated Coiled‐Coil Protein Kinase1 Depletes Neural Stem Cell Pool and Impairs Hippocampal Neurogenesis After Traumatic Brain Injury

## TL;DR

ROCK1 protein overactivity after brain injury harms stem cells and brain cell growth, leading to cognitive issues.

## Contribution

ROCK1's role in impairing neurogenesis after TBI is identified, with potential therapeutic implications.

## Key findings

- ROCK1 is upregulated in neural stem cells after TBI, causing their depletion and impaired neurogenesis.
- ROCK1 inhibition or knockout rescues neurogenic deficits and improves cognitive function in TBI mice.
- ROCK1 impairs neurogenesis via AKT hyperphosphorylation, forming a ROCK1-AKT signaling axis.

## Abstract

Traumatic brain injury (TBI) represents a global health burden, often resulting in persistent neurological deficits due to impaired hippocampal neurogenesis. Nevertheless, the temporal progression of post‐TBI neurogenesis and its molecular mechanisms remain elusive. To investigate the mechanism of impaired hippocampal neurogenesis and neurological deficits following TBI. Single‐cell RNA sequencing (scRNA‐seq) was employed to explore the mechanism of abnormal hippocampal neurogenesis after TBI in mice. Antagonists and conditional gene knockout (CKO) strategies were applied to dissect the molecular function of target genes. Here, we found that neural stem cells (NSCs) were hyperactivated as observed in Nestin‐GFP reporter mice in hippocampus during the early phases of TBI, followed by progressive depletion of the NSC pool, impaired neurogenesis, and the onset of progressive cognitive dysfunction. ScRNA‐seq transcriptomic analysis revealed sustained upregulation of Rho‐associated coiled‐coil protein kinase 1 (ROCK1) in hippocampal NSCs post‐TBI. Pharmacological inhibition of ROCK1 or ROCK1 CKO rescued chronic neurogenic deficits and improved cognitive functions in TBI mice. Mechanistically, ROCK1 dysregulation impaired neurogenesis via aberrant AKT hyperphosphorylation, establishing a unidirectional ROCK1‐AKT signalling axis in adult hippocampal neurogenesis. Our findings position ROCK1 as a pivotal regulator of the post‐TBI NSC pool hyperactivation and aberrant neurogenesis and propose targeted kinase inhibition strategies as a potential therapy to mitigate abnormal neurogenesis in TBI patients.

Following TBI, hippocampal neurogenesis in mice is impaired and affects cognitive function. This impairment is associated with the upregulation of p‐AKT/AKT mediated by ROCK1.