Funding Acknowledgements Type of funding sources: None. Background Intracranial aneurysm (IA) rupture is a common cause of hemorrhagic stroke. IAs are present in 3 to 5% of the general population and the annual rupture rate of an IA has been estimated to 1%. Once formed, an IA can rupture immediately, grow before rupturing, or remain stable. Predicting the evolution of an unruptured IA is very difficult. Indeed, the biology of the IA wall is complex and the precise biomechanical processes leading to aneurysm wall rupture are not yet known. While the contribution of wall shear stress in IA disease has been demonstrated in several studies, the role of cyclic circumferential stretch (CCS) remains poorly understood. Purpose The levels of CCS in saccular IAs are unknown but are generally considered very low or even absent. The goal of our study was to investigate the transcriptional response of endothelial cells (ECs) to absence of CCS and the potential impact on the endothelium function. Methods Human umbilical veins ECs (HUVECs) from 6 different donors were exposed to physiological CCS levels for cerebral arteries (6% stretch) or to aneurysmal CCS (0%) for 48h using the Flexcell strain unit FX-5000T, and unbiased transcriptomics were performed. The expression of selected genes was confirmed by qPCR. Results As a validation of our methodology, we verified the induction of eNOS phosphorylation after exposure of the ECs to physiological CCS. Stretched EC samples display a high similarity between each other while EC samples under aneurysmal CCS were spread-out on a multidimensional scaling plot. The differential gene expression of ECs exposed to aneurysmal or physiological CCS revealed 51 up-regulated genes and 49 down-regulated genes in absence of CCS. The gene set enrichment analysis identified 70 up-regulated and 38 down-regulated pathways in HUVECs exposed to aneurysmal CCS. Up-regulated pathways were involved in oxidative stress, angiogenic and inflammatory pathways, and the down-regulated pathways in proliferation and extracellular matrix-receptor interactions. We confirmed by qPCR the down-regulation by aneurysmal CCS of Gja4 and Gja5, genes coding for the gap junction proteins Connexin37 (Cx37) and Connexin40 (Cx40), respectively. Connexins (Cxs) are crucial proteins for endothelial homeostasis, vascular function, endothelial cell cycle regulation and inflammation, and their role in the context of IA disease will be further studied. Conclusion Our results indicate that physiological CCS prevents large deviation in ECs and regulate the expression of genes essential for maintaining vascular homeostasis. The down-regulation of endothelial Cx37 and Cx40 under aneurysmal CSS may contribute to the endothelial dysfunction associated with IA progression. Further investigation may help to better define the role of Cxs in aneurysmal disease and to understand the significance of absence of CCS in IA disease progression.

中文翻译：

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动脉瘤循环周向拉伸影响参与血管稳态的内皮基因的表达

资金确认 资金来源类型：无。背景颅内动脉瘤 (IA) 破裂是出血性中风的常见原因。IA 存在于 3% 至 5% 的普通人群中，IA 的年破裂率估计为 1%。一旦形成，IA 可以立即破裂、在破裂前生长或保持稳定。预测未破裂的 IA 的演变非常困难。事实上，IA 壁的生物学是复杂的，导致动脉瘤壁破裂的精确生物力学过程尚不清楚。虽然在几项研究中已经证明了壁剪切应力在 IA 疾病中的作用，但循环圆周拉伸 (CCS) 的作用仍然知之甚少。目的 囊状 IA 中的 CCS 水平未知，但通常被认为非常低或什至不存在。我们研究的目的是研究内皮细胞 (EC) 对 CCS 缺失的转录反应以及对内皮功能的潜在影响。方法 使用 Flexcell 应变单元 FX-5000T 将来自 6 个不同供体的人脐静脉 ECs (HUVECs) 暴露于脑动脉生理 CCS 水平（6% 拉伸）或动脉瘤 CCS（0%）48 小时，并进行无偏转录组学. 通过 qPCR 确认所选基因的表达。结果作为对我们方法的验证，我们验证了在 ECs 暴露于生理 CCS 后 eNOS 磷酸化的诱导。拉伸的 EC 样本显示出彼此之间的高度相似性，而动脉瘤 CCS 下的 EC 样本在多维比例图上展开。暴露于动脉瘤或生理 CCS 的 ECs 的差异基因表达揭示了在没有 CCS 的情况下 51 个上调基因和 49 个下调基因。基因集富集分析确定了暴露于动脉瘤 CCS 的 HUVEC 中的 70 条上调和 38 条下调通路。上调途径涉及氧化应激、血管生成和炎症途径，以及增殖和细胞外基质-受体相互作用中的下调途径。我们通过 qPCR 证实了 Gja4 和 Gja5 的动脉瘤 CCS 下调，这些基因分别编码间隙连接蛋白 Connexin37 (Cx37) 和 Connexin40 (Cx40)。连接蛋白 (Cxs) 是内皮稳态、血管功能、内皮细胞周期调节和炎症的关键蛋白，以及它们在 IA 疾病中的作用将得到进一步研究。结论 我们的结果表明生理 CCS 可防止 ECs 的大偏差并调节维持血管稳态所必需的基因的表达。动脉瘤 CSS 下内皮 Cx37 和 Cx40 的下调可能导致与 IA 进展相关的内皮功能障碍。进一步的研究可能有助于更好地确定 Cxs 在动脉瘤疾病中的作用，并了解 CCS 在 IA 疾病进展中的重要性。动脉瘤 CSS 下内皮 Cx37 和 Cx40 的下调可能导致与 IA 进展相关的内皮功能障碍。进一步的研究可能有助于更好地确定 Cxs 在动脉瘤疾病中的作用，并了解 CCS 在 IA 疾病进展中的重要性。动脉瘤 CSS 下内皮 Cx37 和 Cx40 的下调可能导致与 IA 进展相关的内皮功能障碍。进一步的研究可能有助于更好地确定 Cxs 在动脉瘤疾病中的作用，并了解 CCS 在 IA 疾病进展中的重要性。