MFG-E8改善“无症状性”颈动脉狭窄介导的认知功能障碍及其机制研究

Cerebral white matter damage is a critical component of “asymptomatic” carotid stenosis-mediated cognitive impairment. Pathological findings include the accumulation of myelin debris in the injury white matter site. Clearance of myelin debris by microglia promptly could promote the repairment of injured white matter. In the preliminary study, we have identified that MFG-E8, a miroglial phagocytosis associated protein, was significantly decreased in the cerebral white matter of bilateral carotid artery stenosis (BCAS) mice. Intracerebroventricular injection of exogenous rmMFG-E8 could improve BCAS induced working memory deficits. In this study, we aim to: 1) comfirm the effect of MFG-E8 on asymptomatic carotid stenosis-mediated white matter damage and cognitive dysfunction; 2) investigate whether the effect of MFG-E8 on cerebral white matter could be related to microglia phagocyting myelin debris and remyelination; 3) further explore the mechanism of MFG-E8 promoting microglia phagocytosis of myelin fragments. We hope our findings will provide a new theoretical basis for the study of mechanism of asymptomatic carotid stenosis-mediated cognitive dysfunction and provide an effective therapeutic target for future clinical transformation.

脑白质损伤是“无症状性”颈动脉狭窄介导的认知功能障碍的重要病因，病理可见受累白质部位髓鞘碎片堆积，小胶质细胞及时吞噬这些髓鞘碎片，可促进受损白质的修复。我们前期研究发现，在双侧颈动脉狭窄（BCAS）介导认知障碍模型小鼠的脑白质中，小胶质细胞吞噬相关蛋白MFG-E8表达明显下降，侧脑室注射外源性rmMFG-E8可改善模型小鼠的认知障碍。本课题拟采用mfge8-/-小鼠，通过行为学、病理、分子等技术，从整体到细胞水平，明确MFG-E8对无症状性颈动脉狭窄介导的脑白质损伤和认知功能障碍的改善作用；研究其对脑白质损伤的改善是否与增强小胶质细胞清除髓鞘碎片、促进髓鞘再生有关，并进一步探索MFG-E8促进小胶质细胞吞噬髓鞘碎片的机制。期望通过本课题的研究，为无症状性颈动脉狭窄介导的认知功能障碍的机制研究提供新的理论基础，为未来的临床转化提供有效的治疗靶点。

“无症状性”重度颈动脉狭窄虽未发生脑缺血事件，但确是认知功能下降的独立危险因素，脑白质损伤是无症状性颈动脉狭窄介导的认知功能下降的重要原因。小胶质细胞及时吞噬白质损伤累积的髓鞘碎片，可促进白质修复。我们前期研究发现，在双侧颈动脉狭窄（BCAS）介导认知障碍模型小鼠的脑白质中，小胶质细胞吞噬相关蛋白MFG-E8表达明显下降，侧脑室注射外源性rmMFG-E8可改善模型小鼠的认知障碍。本研究中，我们采用WT和MFG-E8-/-小鼠制备BCAS模型，通过行为学测定发现，MFG-E8敲除加重了BCAS引起的认知功能障碍，并通过荧光染色和电镜技术验证了MFG- E8缺失加重了白质损害及髓鞘微结构的破坏；我们通过体内外实验发现，MFG- E8可增强小胶质细胞的吞噬功能，并促进少突胶质祖细胞向成熟少突胶质细胞分化；此外，我们采用选择性αVβ3/αVβ5受体抑制剂验证了MFG-E8通过αVβ3/αVβ5/Rac1通路促进小胶质细胞的吞噬功能。在本研究中，我们首次发现了在BCAS模型中MFG- E8通过增强小胶质细胞吞噬髓鞘碎片的能力，从而促进少突胶质祖细胞分化为产髓鞘的成熟少突胶质细胞，促进白质修复，从而改善BCAS后的认知功能障碍，为治疗无症状性颈动脉狭窄介导的认知功能损害提供治疗靶点。