Abstract Body: Objectives: Moyamoya Disease (MMD) is a complex cerebrovascular disease marked by progressive narrowing in the cerebral arteries. Previous studies have suggested that dysregulated genes in the peripheral blood of MMD patients are involved in extracellular matrix organization and immune responses. However, the mechanism by which the immune response contributes to MMD progression is unclear. In this study we investigated the immune landscape in the peripheral blood mononuclear cells (PBMCs) of MMD patients using single-cell RNA sequencing (scRNA-seq).

Methods: Blood samples were collected from 3 bilateral MMD patients and 2 healthy controls. PBMCs were isolated and processed for 10x single-cell RNA sequencing. Immune cell heterogeneity and differentially expressed genes (DEGs) in each cell type were identified. Top biological pathways were determined using Ingenuity Pathway Analysis (IPA). Flow cytometry with an 11-fluorochrome panel was use to validate key immune populations and fluorescence-activated cell sorting (FACS) was used to isolate specific immune populations for transcriptome analysis.

Results: Preliminary analysis revealed notable increase of cell percentages in certain cell types in MMD, such as CD8+T (9.21% vs 7.11%), B cells (6.94% vs 3.45%) and CD4+NKT (5.78% vs 3.22%), and decrease in CD8+NKT (9.59% vs 15.74%), compared to controls. Higher transcriptome dynamics were observed in certain cell type in MMD, with 2402 DEGs in classical monocytes, 1379 DEGs in CD4+T, 1312 DEGs in CD8+NKT and 997 DEGs in B cells. Interestingly, many cell types, except for classical and non-classical monocytes, displayed a higher number of downregulated DEGs in MMD, particularly in T cells, B cells, and NKT cells. Pathway analysis indicated that CD4+T, CD8+NKT, and B cells show predicted inhibition in several pathways, including T cell receptor and mTOR signaling, interleukins and CXCR4 signaling, as well as cell surface interactions at the vascular wall.

Conclusion: These preliminary findings point to a distinct immunological profile in MMD, suggesting significant alterations in both immune cell activity and interaction within the vascular environment. Ongoing studies utilize FACS to validate specific immune populations and their transcriptomes in a larger cohort. These findings reveal unique transcriptomic signatures of peripheral blood immune cells in MMD and highlight key immune cell types that may contribute to its pathogenesis.