Periodic Reporting for period 2 - ForceMorph (The integration of cell signalling and mechanical forces in vascular morphology )
Reporting period: 2019-09-01 to 2021-02-28
Arteries comprise two cell types: endothelial cells, which line the lumen of the vessel, and vascular smooth muscle cells, which form a thicker cell layer around the endothelial cells. Vascular smooth muscle cells can exist in different forms, ranging from a contractile type typically present in normal, healthy vessels and a synthetic form present predominantly in arteries actively remodeling their structure in response to injury, inflammation or abnormal mechanical forces. A main regulator of the switch between the different vascular smooth muscle cell types is the Notch signaling pathway. It functions through cell-cell contacts and has a major role in both development and maintenance of vascular tissue. Accordingly, manipulation of this signaling pathway has potential in treatment of arterial diseases and engineering of vascular tissue grafts. To use this potential, we need to understand how mechanical forces in arteries control Notch and how Notch and mechanics together regulate vessel structure and remodeling.
The overall goals of the project are to develop new physiologically relevant tools for vascular studies, to decipher how mechanical cues affect Notch signaling between arterial cell layers and to better understand how signaling and mechanics together control vascular form and function. The novelty of the project is in its wide interdisciplinary approach where newly engineered devices, computational modelling, animal studies and cell biological experiments are combined. The project has also three detailed objectives. Firstly, the creation and use of a novel 3D Artery-on-Chip device mimicking the cell organization and mechanical environment present in a real-life vessel. The second aim is to create computational models able to predict how the combination of signaling and changing mechanical conditions controls vessel remodeling in health and disease. The third objective is to use animal models to understand how signaling perturbations and blood flow dynamics affect artery structure.
We have generated both a 1D and a 2D computational model of mechanosensitive Notch signaling in the artery wall. The models predict the fate of vascular smooth muscle cells in a vessel wall of increasing thickness while taking into account Notch signaling changes induced by mechanical cues. To create the 1D model, we performed stretch experiments on vascular cells to determine changes in Notch-related gene expression and incorporated these results into an existing computational framework. The model revealed a switch-type behavior where at a certain wall thickness smooth muscle cells transition from an actively dividing synthetic form to a contractile form, guided by Notch signaling status. Importantly, the model successfully predicted vessel thickness at different arterial locations in individuals from different age groups when given information on the mechanical stress conditions in the vasculature of these individuals. The subsequent 2D model builds upon the 1D model by taking a higher number of neighboring cells into consideration. This is of importance as the Notch pathway relies upon direct cell-cell contacts for activation.
Additionally, we have combined animal work, cell biological laboratory experiments and computational modeling to identify vimentin, an important structural component of vascular cells, as a mediator of mechanosensitive Notch signaling and arterial remodeling. We used genetically modified mice deficient of vimentin to show that this protein regulates vascular smooth muscle cell state via Notch signaling and is involved in controlling vascular remodeling in response to increased mechanical stress. Using computational simulations, we were able to predict the specific Notch signaling events involved in adverse remodeling of vimentin-deficient arteries. We have also shown the central Notch signaling component Jagged to be sensitive to mechanical changes.