Pericytes are contractile cells that extend along the vasculature to mediate key homeostatic functions of endothelial barriers within the body. In the central nervous system (CNS), pericytes are important contributors to the structure and function of the neurovascular unit, which includes endothelial cells, astrocytes and neurons. The understanding of pericytes has been marred by an inability to accurately distinguish pericytes from other stromal cells with similar expression of identifying markers. Evidence is now growing in favor of pericytes being actively involved in both CNS homeostasis and pathology of neurological diseases, including multiple sclerosis, spinal cord injury, and Alzheimer's disease among others. In this review, we discuss the current understanding on the characterization of pericytes, their roles in maintaining the integrity of the blood–brain barrier, and their contributions to neuroinflammation and neurorepair. Owing to its plethora of surface receptors, pericytes respond to inflammatory mediators such as CCL2 (monocyte chemoattractant protein‐1) and tumor necrosis factor‐α, in turn secreting CCL2, nitric oxide, and several cytokines. Pericytes can therefore act as promoters of both the innate and adaptive arms of the immune system. Much like professional phagocytes, pericytes also have the ability to clear up cellular debris and macromolecular plaques. Moreover, pericytes promote the activities of CNS glia, including in maturation of oligodendrocyte lineage cells for myelination. Conversely, pericytes can impair regenerative processes by contributing to scar formation. A better characterization of CNS pericytes and their functions would bode well for therapeutics aimed at alleviating their undesirable properties and enhancing their benefits.

中文翻译：

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超越屏障功能：周细胞在稳态和神经炎症调节中的作用。

周细胞是沿着脉管系统延伸以介导体内内皮屏障的关键稳态功能的收缩细胞。在中枢神经系统 (CNS) 中，周细胞是神经血管单元（包括内皮细胞、星形胶质细胞和神经元）的结构和功能的重要贡献者。由于无法准确区分周细胞与具有相似识别标记表达的其他基质细胞，因此对周细胞的理解受到了损害。现在越来越多的证据支持周细胞积极参与中枢神经系统稳态和神经系统疾病的病理学，包括多发性硬化症、脊髓损伤和阿尔茨海默病等。在这篇综述中，我们讨论了目前对周细胞特征的理解，它们在维持血脑屏障完整性方面的作用，以及它们对神经炎症和神经修复的贡献。由于其表面受体过多，周细胞对炎症介质如 CCL2（单核细胞趋化蛋白-1）和肿瘤坏死因子-α 产生反应，进而分泌 CCL2、一氧化氮和几种细胞因子。因此，周细胞可以作为免疫系统先天性和适应性臂的启动子。就像专业的吞噬细胞一样，周细胞也具有清除细胞碎片和大分子斑块的能力。此外，周细胞促进中枢神经系统胶质细胞的活动，包括用于髓鞘形成的少突胶质细胞系细胞的成熟。相反，周细胞可以通过促进疤痕形成来损害再生过程。