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In our brain, there are different types of nerve cells, including neurons and various types of glial cells. In the past, glial cells were considered to be the "glue" of the brain, providing connection, support, and protection for neurons, hence the name. However, new research has shown that their roles extend beyond this, playing a crucial part in the development of many brain diseases. Neurons consist of a large, star-like cell body and a long, trunk-like extension called an axon. Axons are wrapped in a protective layer called the myelin sheath, formed by oligodendrocytes. The myelin sheath protects neurons and supports their normal physiological activities, such as signal transmission, thus maintaining our daily physiological functions, including walking, talking, and various movements.

Microglia are another type of glial cell in the brain. Their primary function is to clear daily metabolic substances in the brain through phagocytosis while also secreting different cytokines and growth factors to regulate and support other nerve cells, including maintaining the integrity of the myelin tissue. The abnormal accumulation of metabolic substances in the brain can lead to various neurological diseases, such as Alzheimer's and Parkinson's. Therefore, the normal function of microglia is crucial for protecting brain health. However, many neurological diseases involve inflammation in the brain, and under inflammatory conditions, microglia not only engulf harmful metabolic products but also attack healthy myelin tissue, causing damage and loss of the myelin sheath. This process is a major pathological feature of several neurological diseases, with multiple sclerosis being the most common example. The loss of myelin can lead to a range of clinical symptoms, including muscle weakness, movement disorders, fatigue, spasms, sensory abnormalities, urinary incontinence, and impaired vision.

In my doctoral research thesis, I found that a signaling molecule called TGF-β is essential for maintaining the normal function of microglia and preserving brain health. If microglia cannot detect this signal, they become abnormally activated and attack the myelin, resulting in a series of behavioral abnormalities and disease symptoms. Experiments with mice showed that female and older mice are more sensitive to the lack of TGF-β signaling, resulting in more severe disease symptoms.

Furthermore, other factors, such as brain inflammation, can directly cause myelin loss or indirectly attack myelin by activating microglia. Damaged myelin no longer protects neurons or maintains their normal function, and the accumulation of myelin debris around exposed axons hinders new myelin regeneration. This demonstrates that microglia can have both protective and harmful effects in our brain. Researchers are therefore studying new therapeutic approaches to regulate microglia, reducing their harmful effects in disease states while maintaining their beneficial physiological functions. In my doctoral thesis, I also explored and proposed some novel treatment strategies. In one of my studies, I used a mouse model of brain inflammation and found that a compound extracted from a plant called the "happy tree" could inhibit the activation of microglia in an inflamed brain environment, thereby reducing their damage to normal myelin tissue. In another study, I used a mouse model with extensive myelin damage and discovered that capsaicin, the main component of chili peppers, could promote microglial clearance of myelin debris, thus creating a better environment for the growth of new myelin.

In conclusion, microglia are essential for maintaining the health of the myelin sheath. My doctoral research revealed the specific molecular mechanisms on which microglia rely to maintain myelin integrity and provided potential therapeutic strategies for modulating microglial function.

在我们的大脑中有不同的神经细胞类型，包括称为神经元的神经细胞和不同类型的神经胶质细胞。在过去神经胶质细胞被认为是脑内的胶水，起到连接、支持和保护神经元的作用，故而得名。但是新的研究已经证明他们的作用不仅于此，并且在许多脑内疾病的发病过程中起到很关键的作用。神经元包含一个大的类似五角星形状的胞体和一个长的树干样形状的胞体延长部分，称为轴突。轴突被由少突胶质细胞形成的称为髓鞘的保护层包裹。髓鞘的包裹可以保护神经元，支持神经元的正常生理活动如神经信号的传导等，从而维持我们日常生活中的各项生理功能，包括行走、说话以及各类运动等等。

小胶质细胞是大脑中的另一类神经胶质细胞，它的主要生理功能是通过吞噬作用清除大脑中日常产生的代谢物质，同时也会分泌不同的细胞因子和营养因子对其它神经细胞起到调节和支持作用，包括对髓鞘组织完整性的维护。代谢物质和其它有害物质在脑内的异常累积会导致不同的神经系统疾病，比如阿兹海默症和帕金森症等等。因此，小胶质细胞功能的正常与否对于保护大脑的健康至关重要。然而，在许多神经系统疾病中都存在脑内炎症，而在炎症环境下，小胶质细胞不仅吞噬有害的代谢产物，也会攻击正常的髓鞘组织，导致髓鞘组织的破坏和脱落。这一过程正是一些神经系统疾病的主要病理过程，其中以多发性硬化这一疾病最为常见。髓鞘脱落会导致一系列的临床症状，包括肌肉无力、运动障碍、疲劳、抽搐、感觉异常、小便失禁、视力受损等。

在我的博士研究论文中，我发现一个叫做TGF-β的信号对于维持小胶质细胞的正常功能和维护大脑健康非常重要。如果小胶质细胞无法检测到该信号，它们会被异常地激活并且攻击髓鞘，从而产生一系列的行为异常和疾病症状。通过小鼠实验研究发现，雌性小鼠和大龄小鼠对于TGF-β信号缺失更为敏感，所产生的疾病症状也更为严重。

此外，脑内炎症等其他因素也可直接引起髓鞘损失或通过激活小胶质细胞间接攻击髓鞘。受损的髓鞘不再具有保护神经元、维持神经元正常功能的作用，并且损伤后脱落的髓鞘碎片会聚集在裸露的轴突周围，阻碍新的髓鞘再生。由此可见，小胶质细胞对于在我们大脑中既可以起到保护性作用，也可以产生有害的后果。

因此，科研人员正在研究新的用于调节小胶质细胞的治疗手段，以减少它们在疾病状态下的危害性，并同时保持甚至促进它们有益的生理功能。在我的博士论文中，我也探讨并提出了一些新的治疗策略。在我的一项研究中，我使用小鼠脑内炎症的模型，发现一类提取自喜树的化合物可以抑制脑内炎症状态下小胶质细胞的激活，从而减少它们对正常髓鞘组织的伤害。而在另一项研究中，我使用了一个产生大量髓鞘损伤的小鼠模型，发现辣椒的主要成分辣椒素能够促进小胶质细胞对髓鞘碎片的清除，从而为新的髓鞘生成创造了更好的再生环境。

综上所述，小胶质细胞对髓鞘的健康十分重要。我的博士论文研究揭示了小胶质细胞维持髓鞘完整性所依赖的具体分子机制，通过调节小胶质细胞功能提供为脑内脱髓鞘相关疾病提供了潜在的治疗策略。