367 Spatial Transcriptomics to Characterize Aneurysm Initiation at the Basilar Terminus in a Flow-Driven Rabbit Model of Intracranial Aneurysm

INTRODUCTION: We have routinely used the rabbit bilateral common carotid artery (CCA) model to study the effect of hemodynamics on vascular biology during intracranial aneurysm (IA) formation. METHODS: A New Zealand white rabbit underwent bilateral CCA ligation to increase flow in the basilar artery (BA) and initiate IA at the BT. After 24h, the BA and BT were dissected and 10-micron frozen sections were collected onto Capture Slides for spatial sequencing on the 10X Visium platform. Reads were aligned to the rabbit genome and counts were quantified using the Cell Ranger Spatial pipeline. Spots on intima and media were identified on histology in the Loupe browser. Differentially expressed genes were identified by modified F-test (p-value<0.1 ). RESULTS: Comparing expression in eutrophic vs dystrophic intima (BA vs BT), 101 genes were differentially expressed (81 higher, 20 lower at BT). In the media, 335 genes were differentially expressed (294 higher, 41 lower at BT). Potential upstream (endothelial derived) regulators of smooth-muscle cells were predicted from the medially-expressed genes using Ingenuity Pathway Analysis (IPA; Qiagen Inc) (significance, z>2). Key genes in networks of potential interactions were generated in IPA for differentially expressed intimal genes at the BA and BT (significance, p-score>21). This suggested that TGFβ1 signaling pathway could mediate dystrophic remodeling. Correlation analysis revealed 486 gene pairs (involving 97 intimal genes) whose expression were correlated between intima and media. One of the intimal genes with the most media correlates was BMP4, a member of the TGF-β superfamily. CONCLUSIONS: Correlative expression analysis of intimal/medial genes can reveal novel signals that may regulate flow-induced arterial remodeling. IPA and correlation analysis implicate TGF-β superfamily in dystrophic remodeling.