Identification of Circulating Gene Expression Signatures of Intracranial Aneurysm in Peripheral Blood Mononuclear Cells

Vincent M Tutino,Kenneth V Snyder,Hamidreza Rajabzadeh-Oghaz,Haley R Zebraski,Adnan H Siddiqui,James N Jarvis,Konrad Bach,Kerry E Poppenberg,Maxim Mokin,Muhammad Waqas

doi:10.3390/diagnostics11061092

Vincent M Tutino, Kenneth V Snyder + Show 8 more

Open Access

https://doi.org/10.3390/diagnostics11061092

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Abstract

Peripheral blood mononuclear cells (PBMCs) play an important role in the inflammation that accompanies intracranial aneurysm (IA) pathophysiology. We hypothesized that PBMCs have different transcriptional profiles in patients harboring IAs as compared to IA-free controls, which could be the basis for potential blood-based biomarkers for the disease. To test this, we isolated PBMC RNA from whole blood of 52 subjects (24 with IA, 28 without) and performed next-generation RNA sequencing to obtain their transcriptomes. In a randomly assigned discovery cohort of n = 39 patients, we performed differential expression analysis to define an IA-associated signature of 54 genes (q < 0.05 and an absolute fold-change ≥ 1.3). In the withheld validation dataset, these genes could delineate patients with IAs from controls, as the majority of them still had the same direction of expression difference. Bioinformatics analyses by gene ontology enrichment analysis and Ingenuity Pathway Analysis (IPA) demonstrated enrichment of structural regulation processes, intracellular signaling function, regulation of ion transport, and cell adhesion. IPA analysis showed that these processes were likely coordinated through NF-kB, cytokine signaling, growth factors, and TNF activity. Correlation analysis with aneurysm size and risk assessment metrics showed that 4/54 genes were associated with rupture risk. These findings highlight the potential to develop predictive biomarkers from PBMCs to identify patients harboring IAs.

Highlights

Intracranial aneurysms (IAs) are pathological outpouchings within cerebral vasculature that are present in about 3–6% of the general population [1,2]
To determine if differentially expressed genes could separate patients with IAs from controls in an independent cohort, we evaluated their expression in the validation cohort that consisted of 25% of all samples
As aberrant RNA expression in circulating Peripheral blood mononuclear cells (PBMCs) may be aggravated in cases of larger or more developed IAs, we explored the relationship between expression of differentially expressed genes (DEGs) and IA risk

Summary

Introduction

Intracranial aneurysms (IAs) are pathological outpouchings within cerebral vasculature that are present in about 3–6% of the general population [1,2]. Clinical reports and animal model studies have shown that IA pathology is dominated by inflammation [1,12,13,14]. Reports have shown increased neutrophil-to-lymphocyte ratios in patients with larger, more progressed IAs, and with ruptured aneurysms, suggesting a role for peripheral activation of immune cells and systemic innate inflammatory responses during IA [18,19]. Macrophages have been recognized as the main contributor to inflammation in IA [22,23] Studies of both ruptured and unruptured IA tissue have reported increased presence of T cells, B cells, and macrophages within the vascular walls of IAs, and even more so in ruptured ones [24,25]. Animal models have demonstrated that both the depletion of macrophages and the inhibition of monocyte chemoattractants are associated with a reduced aneurysm formation [26,27]

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