Mechanical forces in IntraCranial aneurysm: Understanding the role of Rho proteins signaling – MICRO

To understand how mechanical forces in blood vessels control cell function, we use in vitro models in which cells are cultured in special compartments that allow us to model these forces. We thus reproduce the friction forces associated with blood flow and the stretching of the vessel wall associated with heartbeats. We can reproduce “physiological” or “pathological” forces present in certain vascular pathologies such as intracranial aneurysms. Using imaging and molecular biology techniques, we then study which signaling pathways are modulated under these experimental conditions. Once we have identified interesting molecular targets, we combine an in vitro approach, where we produce cells that no longer express our target in order to understand its exact role (two targets for this project), and an in vivo approach where we produce a mouse model that no longer expresses our target (one target for this project) to understand its involvement in blood vessel formation and intracranial aneurysm development.

Major results of the project

This project identified two new proteins sensitive to mechanical forces in blood vessels: ARHGEF18 and NET1. ARHGEF18 responds to friction forces associated with blood flow, while NET1 responds to stretching of the vessel wall. ARHGEF18 helps maintain the barrier function of blood vessels in the brain, limiting blood leakage outside the vessels. ARHGEF18 also enables good vessel dilation and helps regulate blood pressure. NET1 enables vascular cells to maintain their contractile capacity. These discoveries provide a better understanding of how vessel cells respond to mechanical forces and open up new avenues for understanding what happens when intracranial aneurysms form.

Scientific output and patents since the start of the project

This project has resulted in a publication in an international peer-reviewed journal (Batta SPR et al. Cell Rep. 2025 Mar 25;44(3):115288) and will be the subject of two further publications in the coming months (work on NET1, Mrad MA et al. BioRxiv Dec 01. 2025; and work on the role of ARHGEF18 in intracranial aneurysms). The work carried out and the tools developed during this project also contributed to two other parallel studies on the role of two other proteins in intracranial aneurysms (C. Baron-Menguy, et al. BioRxiv Jan 14. 2025 and M. Freneau, R. Blanchet et al. MedRxiv Feb 02. 2024, accepted in Cardiovascular Research).

Factual information

This project is a fundamental research project led by a young researcher, Dr. Anne-Clémence Vion. The project began in March 2022 and lasted 42 months. It received €302,000 in funding from the ANR.

In summary, the objective to identify novel mechanosensitive RhoGEFs in vascular cells was successfully accomplished. The functions of these proteins in vascular biology and physiology have been well-established. A breakthrough was made for each protein studied: first, although ARHGEF18 had been studied in the past, no endothelial-specific role had been described. The only work that had been done stated that its role in this cell type was dispensable thanks to work done during embryogenesis. Our findings have demonstrated the critical role of this protein in endothelial cells during both the postnatal period and adulthood, underscoring its importance in regulating permeability and immune surveillance. Furthermore, our research reveals an unexpected association of ARHEGF18 with hypertension, a major contributing factor to IA. Secondly, NET1, on its own, is the first stretch-sensitive RhoGEF reporter in vascular smooth muscle cells.

thr forst short-term perspective of MICRO is to ascertain the protective function of ARHGEF18 in IA formation. This investigation will be conducted over the course of the following two years. The subsequent logical progression in this research would be to develop inhibitors/activators for NET1 or ARHGEF18. My team has strong experience in creating pharmacological inhibitors of Rho GTPases (Dr Sauzeau), some of which are specific to GEF interactions with their GTPase.

IA is a pathology for which there is a crucial lack of diagnostic tools to predict rupture and a lack of non-invasive treatment. This fundamental research constitutes the initial step in the process of future clinical discoveries, reduction of the societal impact and cost of IA, and instills hope in patients.

Intracranial aneurysm is a silent cerebrovascular abnormality characterized by a local dilation and thinning of the wall of a cerebral arteries that affects 3% of the population. Its rupture is unpredictable and results in a subarachnoid hemorrhage, fatal in 40% of cases, or leaving patients with neurological disability if not. Currently, there are neither diagnostic tools to predict the risk of rupture nor treatments to prevent or limit the formation and the progression of an intracranial aneurysm. Understanding the mechanisms involved is therefore a major challenge for improving disease evaluation and patient management. Intracranial aneurysm preferentially arises at arterial bifurcation of the circle of Willis, where vascular cells are exposed to large variation of mechanical stimuli, suggesting that it may result from the inability of the arterial wall to adapt properly to these hemodynamic conditions. With this proposal, my aim is to discover the molecular mechanisms involved in the defective response to mechanical stresses of intracranial arteries underlying intracranial aneurysm formation.