# bFGF-Mediated Inhibition of Astrocytes’ Optogenetic Activation Impairs Neuronal Repair in Female Rats After Stroke

## TL;DR

This study shows that optogenetic activation of astrocytes helps male rats recover from stroke but not female rats, possibly due to higher levels of bFGF in females.

## Contribution

The study reveals gender-specific differences in astrocyte-mediated brain repair after stroke and identifies bFGF as a potential inhibitor in females.

## Key findings

- Male rats showed improved recovery after astrocyte optogenetic activation, while female rats did not.
- bFGF levels increased in female rats after stroke and optogenetic stimulation, inhibiting astrocyte activation.
- Higher bFGF in females may explain the reduced effectiveness of optogenetic therapy in post-stroke recovery.

## Abstract

Astrocyte activation and gender differences play critical roles in the prognosis following stroke. Recent studies have shown that optogenetic technology can promote brain repair after stroke by activating astrocytes in male rats. However, it remains unclear whether gender differences influence the efficacy of optogenetic activation of astrocytes in regulating post-stroke brain repair and its underlying mechanisms. In this study, we activated astrocytes in the ipsilateral cortex of adult glial fibrillary acidic protein-channelrhodopsin 2-enhanced yellow fluorescent protein (GFAP-ChR2-EYFP) transgenic Sprague Dawley rats using optogenetic stimulation at 24, 36, 48, and 60 h after inducing photothrombosis stroke. Neurobehavioral tests, cresyl violet staining, RT-qPCR, Western blot, and immunofluorescence analysis were performed on both female and male rats. Our results showed that male rats exhibited significant improvements in behavioral scores and reduction in infarct size after optogenetic activation of astrocytes at three days post-stroke (p < 0.05), whereas no significant changes were observed in female rats. Additionally, in female rats, the expression of basic fibroblast growth factor (bFGF) increased after ischemic stroke and astrocytic optogenetic stimulation (p < 0.05), leading to enhanced endothelial cell proliferation compared to male rats (p < 0.05). In vitro experiments further demonstrated that the astrocyte activation was inhibited in the presence of bFGF (p < 0.05). These findings suggest that the increase in bFGF levels in females following stroke may inhibit the optogenetic activation of astrocytes, thereby attenuating the therapeutic effect of astrocyte activation on post-stroke brain repair. This study provides important insights into the gender-specific roles of astrocytes in the acute phase of ischemic stroke.