（GFAP+CD248+）双阳性细胞的发现及其在脑I/R血脑屏障损伤中的作用机制

血脑屏障（BBB）损伤是脑梗死防治研究的关键科学问题，阐明BBB损伤及修复机制具有重要临床意义。既往研究发现周细胞在维持BBB完整性中具有重要作用，通过前体细胞分化成周细胞可减小BBB损伤，但在脑I/R环境下是否存在周细胞的前体细胞尚不清楚。我们前期采用单细胞测序对I/R梗死周边区细胞进行检测，发现了同时表达星形胶质细胞标记GFAP和周细胞标记CD248的新细胞亚群，并在体外实验证实通过补充轴突导向因子1（Ntn1）可促进其向周细胞转化。据此我们提出假设：（GFAP+CD248+）双阳性细胞极可能通过Ntn1向周细胞转化，在脑梗死BBB损伤中发挥保护作用。为此本项目拟检测上述双阳性细胞的时空表达特征，明确Ntn1促进双阳性细胞向周细胞分化的作用机制，阐明双阳性细胞向周细胞分化对I/R的保护作用。该研究从周细胞来源角度发现补充周细胞的新靶点，为脑梗死临床治疗提供新策略。

Blood-brain barrier (BBB) damage is a key scientific issue in the prevention and treatment of cerebral infarction. It is urgent to clarify the mechanism of BBB damage and repair in cerebral infarction. Pericytes play a key role in maintaining the integrity of the BBB. After cerebral ischemia-reperfusion (I/R), pericytes are lost in large quantities, leading to the destruction of BBB integrity but the regulatory mechanism is not yet clear. We used single-cell sequencing technology to detect the cell types on the side of the I/R infarction and found a new cell sub-substance expressing both the astrocyte marker GFAP and the pericyte marker CD248. Furthermore, we found that supplementation of netrin-1 (Ntn1) can promote the transformation of the （GFAP+CD248+）double-positive cells into pericytes in vitro experiments. Based on these results, we put forward the hypothesis: (GFAP+CD248+) double-positive cells play a protective role in the integrity of BBB in cerebral infarction by pericytes transforming with Ntn1. Therefore, this project intends to detect the temporal and spatial expression characteristics of the （GFAP+CD248+）double-positive cells, to clarify the mechanism of Ntn1 promoting the differentiation of double-positive cells into pericytes, and to clarify the protective effect of double-positive cells on I/R from the differentiation of double-positive cells into pericytes. This study will reveal the source of pericytes in the I/R process, discover new targets to supplement pericytes, and provide new strategies for clinical treatment of cerebral infarction.