Department of Cellular Neurophysiology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czech Republic.
Department of Microscopy, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czech Republic.
Neuroscience. 2018 Dec 1;394:127-143. doi: 10.1016/j.neuroscience.2018.10.028. Epub 2018 Oct 24.
Transient receptor potential vanilloid type 4 (TRPV4) channels are involved in astrocyte volume regulation; however, only limited data exist about its mechanism in astrocytes in situ. We performed middle cerebral artery occlusion in adult mice, where we found twice larger edema 1 day after the insult in trpv4 mice compared to the controls, which was quantified using magnetic resonance imaging. This result suggests disrupted volume regulation in the brain cells in trpv4 mice leading to increased edema formation. The aim of our study was to elucidate whether TRPV4 channel-based volume regulation occurs in astrocytes in situ and whether the disrupted volume regulation in trpv4 mice might lead to higher edema formation after brain ischemia. For our experiments, we used trpv4 mice crossed with transgenic mice expressing enhanced green fluorescent protein (EGFP) under the control of the glial fibrillary acidic protein promoter, which leads to astrocyte visualization by EGFP expression. For quantification of astrocyte volume changes, we used two-dimensional (2D) and three-dimensional (3D) morphometrical approaches and a quantification algorithm based on fluorescence intensity changes during volume alterations induced by hypotonicity or by oxygen-glucose deprivation. In contrast to in vitro experiments, we found little evidence of the contribution of TRPV4 channels to volume regulation in astrocytes in situ in adult mice. Moreover, we only found a rare expression of TRPV4 channels in adult mouse astrocytes. Our data suggest that TRPV4 channels are not involved in astrocyte volume regulation in situ; however, they play a protective role during the ischemia-induced brain edema formation.
瞬时受体电位香草酸亚型 4（TRPV4）通道参与星形胶质细胞体积调节；然而，目前关于原位星形胶质细胞中 TRPV4 通道的机制仅有有限的数据。我们在成年小鼠中进行了大脑中动脉闭塞，发现 TRPV4 小鼠在损伤后 1 天的脑水肿比对照组大两倍，这一结果通过磁共振成像进行了量化。这一结果表明 TRPV4 小鼠的脑细胞体积调节受损，导致脑水肿形成增加。我们的研究目的是阐明 TRPV4 通道介导的体积调节是否发生在原位星形胶质细胞中，以及 TRPV4 小鼠的体积调节受损是否会导致脑缺血后更高的水肿形成。为了进行实验，我们使用了与表达增强型绿色荧光蛋白（EGFP）的转基因小鼠杂交的 TRPV4 小鼠，该蛋白在胶质纤维酸性蛋白启动子的控制下表达，从而通过 EGFP 表达来可视化星形胶质细胞。为了定量星形胶质细胞体积变化，我们使用了二维（2D）和三维（3D）形态计量学方法以及基于体积变化期间荧光强度变化的定量算法，这些体积变化是由低渗或氧葡萄糖剥夺引起的。与体外实验相反，我们发现 TRPV4 通道对成年小鼠原位星形胶质细胞体积调节的贡献证据很少。此外，我们只发现成年小鼠星形胶质细胞中 TRPV4 通道的罕见表达。我们的数据表明，TRPV4 通道不参与原位星形胶质细胞的体积调节；然而，它们在缺血性脑水肿形成过程中发挥保护作用。
