Abstract Body: Background: Moyamoya disease (MMD) is a rare progressive cerebrovascular disease that can lead to strokes. A hallmark of MMD is the thickening of the intima arterial layer, leading to the narrowing of arteries that supply oxygen to the brain. However, the mechanism of MMD is largely unknown. To address this, we investigated the histological characteristics and performed spatial transcriptomics on the principal cell types in the blood vessels - endothelial cells (EC) and vascular smooth muscle cells (VSMC), in middle cerebral artery (MCA) and superficial temporal artery (STA) samples.
Methods: STA and/or MCA were collected during surgical bypass to treat MMD in patients or other vascular diseases (Control STA). MCA and STA samples were sectioned and stained for endothelial cells (CD31), vascular smooth muscle cells (αSMA), actin filaments (phalloidin), and nuclear staining (Hoechst33342). Sections were imaged with Zeiss laser scanning microscope (LSM800) and analyzed with ImageJ for quantification. An additional set of adjacent sections were processed for Nanostring Spatial Transcriptomics.
Results: Immunohistochemistry staining for CD31 and α-SMA revealed marked differences in the intima and media layers in the STA between MMD and control. In the MMD STA, αSMA expression was found in both the media and the intima layers, in contrast to control STA where αSMA expression was localized mostly in media layer. Furthermore, morphology of VSMCs in MMD STA differed significantly; control STA mostly displayed a contractile phenotype with elongated, spindle-shaped cells, whereas MMD STA exhibited a synthetic phenotype with shorter, cobblestone appearance. Furthermore, phalloidin staining showed greater intensity in MMD STA and MCA compared to control. Quantification of intima layer thickness showed significant increased intima thickness in MMD STA. Spatial transcriptome of these vessels have been processed to identify gene expression differences in these arterial layers.
Conclusions: Our findings showed morphological differences in MMD STA VSMCs, indicating a shift towards synthetic phenotype associated with increased cellular proliferation and reduced contractility. The increased phalloidin staining in MMD STA and MCA aligns with this synthetic phenotype, reflecting more robust cytoskeleton remodeling. Ongoing studies include analysis of transcriptome changes across different layers in MMD arteries to identify key molecular changes driving these pathological features.