Kuo Tung-Tai, Wang Vicki, Wu Jui-Sheng, Chen Yuan-Hao, Tseng Kuan-Yin
Department of Neurological Surgery, Tri-Service General Hospital, Taipei, Taiwan.
Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan.
Front Mol Neurosci. 2021 May 28;14:639145. doi: 10.3389/fnmol.2021.639145. eCollection 2021.
The specific role of peri-infarct microglia and the timing of its morphological changes following ischemic stroke are not well understood. Valproic acid (VPA) can protect against ischemic damage and promote recovery. In this study, we first determined whether a single dose of VPA after stroke could decrease infarction area or improve functional recovery. Next, we investigated the number and morphological characteristic of peri-infarct microglia at different time points and elucidated the mechanism of microglial response by VPA treatment. Male Sprague-Dawley rats were subjected to distal middle cerebral artery occlusion (dMCAo) for 90 min, followed by reperfusion. Some received a single injection of VPA (200 mg/kg) 90 min after the induction of ischemia, while vehicle-treated animals underwent the same procedure with physiological saline. Infarction volume was calculated at 48 h after reperfusion, and neurological symptoms were evaluated. VPA didn't significantly reduce infarct volume but did ameliorate neurological deficit at least partially compared with vehicle. Meanwhile, VPA reduced dMCAo-induced elevation of IL-6 at 24 h post-stroke and significantly decreased the number of CD11b-positive microglia within peri-infarct cortex at 7 days. Morphological analysis revealed that VPA therapy leads to higher fractal dimensions, smaller soma size and lower circularity index of CD11b-positive cells within peri-infarct cortex at both 2 and 7 days, suggesting that VPA has core effects on microglial morphology. The modulation of microglia morphology caused by VPA might involve HDAC inhibition-mediated suppression of galectin-3 production. Furthermore, qPCR analysis of CD11b-positive cells at 3 days post-stroke suggested that VPA could partially enhance M2 subset polarization of microglia in peri-infarct cortex. Analysis of VPA-induced changes to gene expressions at 3 days post-stroke implies that these alternations of the biomarkers and microglial responses are implicated in the upregulation of wound healing, collagen trimmer, and extracellular matrix genes within peri-infarct cortex. Our results are the first to show that a low dose of VPA promotes short-term functional recovery but does not alter infarct volume. The decreases in the expression of both IL-6 and galectin-3 might influence the morphological characteristics and transcriptional profiles of microglia and extracellular matrix remodeling, which could contribute to the improved recovery.
梗死灶周围小胶质细胞的具体作用及其在缺血性中风后形态变化的时间尚不清楚。丙戊酸（VPA）可以预防缺血性损伤并促进恢复。在本研究中，我们首先确定中风后单次给予VPA是否可以减小梗死面积或改善功能恢复。接下来，我们研究了不同时间点梗死灶周围小胶质细胞的数量和形态特征，并阐明了VPA治疗引起小胶质细胞反应的机制。雄性Sprague-Dawley大鼠接受大脑中动脉远端闭塞（dMCAo）90分钟，然后再灌注。一些大鼠在缺血诱导后90分钟接受单次注射VPA（200mg/kg），而接受载体治疗的动物用生理盐水进行相同的操作。在再灌注后48小时计算梗死体积，并评估神经症状。与载体相比，VPA没有显著减小梗死体积，但至少部分改善了神经功能缺损。同时，VPA降低了中风后24小时dMCAo诱导的IL-6升高，并在7天时显著减少了梗死灶周围皮质内CD11b阳性小胶质细胞的数量。形态学分析表明，VPA治疗导致梗死灶周围皮质内CD11b阳性细胞在2天和7天时具有更高的分形维数、更小的胞体大小和更低的圆形度指数，表明VPA对小胶质细胞形态具有核心作用。VPA引起的小胶质细胞形态调节可能涉及HDAC抑制介导的半乳糖凝集素-3产生的抑制。此外，中风后3天对CD11b阳性细胞的qPCR分析表明，VPA可以部分增强梗死灶周围皮质中小胶质细胞的M2亚群极化。对中风后3天VPA诱导的基因表达变化的分析表明这些生物标志物和小胶质细胞反应的改变与梗死灶周围皮质内伤口愈合、胶原蛋白修剪和细胞外基质基因的上调有关。我们的结果首次表明低剂量的VPA促进短期功能恢复，但不改变梗死体积。IL-6和半乳糖凝集素-3表达水平的降低可能影响小胶质细胞的形态特征和转录谱以及细胞外基质重塑，这可能有助于改善恢复。
