# Stiff matrix drives microglial cell migration through Piezo1/Ca2+/AKT/cofilin signaling axis-regulated F-actin reassembly

## TL;DR

Stiff brain tissue promotes microglial cell movement through a chain of signals involving Piezo1, calcium, AKT, and cofilin, which helps reorganize cell structures.

## Contribution

The study identifies a novel signaling pathway (Piezo1/Ca2+/AKT/cofilin) linking matrix stiffness to microglial migration.

## Key findings

- Stiff substrates increased microglial migration and Piezo1 expression.
- Blocking Piezo1 or Ca2+ reduced F-actin reassembly and cell migration.
- AKT activation and cofilin dephosphorylation were key in promoting F-actin reassembly.

## Abstract

The local stiffness of brain tissues increases in pathological states, and then, drives microglial cells to migrate towards stiffer areas for their functioning, but the underlying mechanism is still unclear. Herein, we investigated the role and mechanism of the mechanosensitive Piezo1 channel in matrix stiffness regulation of microglial cell migration using BV2 microglial cell line and mouse primary microglial cells growing on soft (500 Pa) and stiff (20 kPa) polyacrylamide (PA) hydrogels. Compared with soft substrates, stiff substrates promoted cell migration, upregulated the Piezo1 expression, raised intracellular Ca2+ concentration ([Ca2+]i) and favored F-actin reassembly. Cell migration and F-actin assembly were suppressed by inhibiting the Piezo1 channel, reducing the [Ca2+]i or inhibiting PI3K/AKT. In addition, stiff substrates induced AKT activation that was reversed by blocking the Piezo1 channel or preventing an increase in [Ca2+]i. Finally, stiff substrates induced a Piezo1-, Ca2+- and AKT-dependent decrease in the phosphorylation level of cofilin, which promotes cofilin severing F-actin, increases G-actin levels and further enhances F-actin reassembly, thereby promoting microglial cell migration. Collectively, our study has revealed that stiff matrix regulates drives microglial cell migration through the Piezo1/Ca2+/AKT/cofilin signaling axis-regulated F-actin reassembly. Our findings provide new insights into the mechanisms underlying tissue stiffness regulation of microglial cells occurring in neurological disorders.