Eun Na Kim ¹ Hee Young Seok ² Joon Seo Lim ³ Jiwon Koh ¹ Jeong Mo Bae ¹ Chong Jai Kim ⁴ You Jung Ok ⁵ Jae-Sung Choi ⁵ Chung-Hyun Cho ^6* Se Jin Oh ^5*

• ¹ Department of Pathology, College of Medicine, Seoul National University, Seoul, Seoul, Republic of Korea
• ² Department of Transdisciplinary Research and Collaboration, Genomics Core Facility, Seoul National University Hospital, Seoul, Republic of Korea
• ³ Asan Medical Center, College of Medicine, University of Ulsan, SONGPA-GU, Seoul, Republic of Korea
• ⁴ Department of Pathology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Republic of Korea
• ⁵ Seoul Metropolitan Government - Seoul National University Boramae Medical Center, Seoul, Republic of Korea
• ⁶ Department of Pharmacology, College of Medicine, Seoul National University, Seoul, Republic of Korea

Background: We investigated the effects of C-reactive protein (CRP) deposition on the vessel walls in abdominal aortic aneurysm (AAA) by analyzing spatially resolved changes in gene expression. Our aim was to elucidate the pathways that contribute to disease progression. Methods: AAA specimens from surgically resected FFPE tissues were categorized into the AAA-high CRP (serum CRP ≥ 0.1 mg/dL, diffuse&strong IHC; n=7 [12 cores]) and AAA-low CRP (serum CRP < 0.1 mg/dL, weak IHC; n=3 [5 cores]) groups. Normal aorta specimens obtained during heart transplantation were used as the control group (n=3 [6 cores]). Spatially resolved whole transcriptomic analysis was performed, focusing on CD68-positive macrophages, CD45-positive lymphocytes, and αSMA-positive vascular smooth muscle cells. Results: Spatial whole transcriptomic analysis revealed significant differential expression of 1086, 1629, and 1281 genes between high CRP and low CRP groups within CD68, CD45, and αSMA-positive cells, respectively. Gene ontology (GO) analysis of CD68-positive macrophages identified clusters related to inflammation, apoptosis, and immune response, with STAT3 implicated across three processes. Notably, genes involved in blood vessel diameter maintenance were significantly downregulated in the high CRP group. GO analysis of lymphocytes showed upregulation of leukocyte rolling and the apoptosis pathway, while in smooth muscle cells, genes associated with NF-κB signaling and JNK pathway were upregulated, and those related to blood pressure regulation were downregulated in the high CRP group. Discussion: CRP deposition was associated with significant transcriptomic changes in macrophages, lymphocytes, and vascular smooth muscle cells in AAA, suggesting its potential role in promoting pro-inflammatory and apoptotic processes, as well as contributing to the degradation of vascular structure and elasticity.