Mechanical stresses influence biological form and function. For normal functions, tissues must maintain stress at a preferred level a process known as tensional homeostasis. Various factors including injuries, diet, aging and genetic risk factors may disrupt tensional homeostasis, and loss of homeostasis promotes the progression of diseases including atherosclerosis, formation of aneurysm balloons, acute lung injury, and cancer. Although it is widely believed that tensional homeostasis traverses a wide range of length scales and that even single cells in isolation are capable of maintaining tensional homeostasis, preliminary data indicate that isolated cells are not capable of maintaining tensional homeostasis and that intercellular cooperation is required. This award will investigate how intercellular cooperation contributes to tensional homeostasis and to determine the underlying biophysical and biochemical mechanisms. The project will focus on homeostasis in vascular endothelial cells since vascular diseases are linked to a loss of tensional homeostasis. Results from this study will have a transformative impact on our understanding of the functional link between loss of tensional homeostasis and progression of diseases such as atherosclerosis and aneurysm. Furthermore, results of our study may provide insight into diseases such as cancer where the loss of tensional homeostasis is a hallmark of disease progression. The work will involve both undergraduate and graduate students and will be integrated into coursework.
The dominant paradigm in vascular biology is that tensional homeostasis exists across multiple length (and time) scales through the feedback control of intracellular mechanics and signaling in response to the externally imposed stresses. However, preliminary data from this study revealed that isolated cells could not maintain tensional homeostasis, whereas confluent multicellular clusters could, suggesting that cell-cell interactions might be necessary for homeostasis. This leads to a working hypothesis that direct cell-cell interactions are required for maintaining tensional homeostasis in the endothelium. This is accomplished either via mechanical interdependence between adjacent cells, or via molecular crosstalk between adherens junctions and focal adhesions. To test this hypothesis, traction forces in cellular clusters and in individual cells will be measured using a micropattern traction microscopy system that was developed by the PIs. This technique utilizes multiple, distinct adhesion ligands and is compatible with substrate strain application mimicking the stretch conditions in vivo, application of shear flow mimicking vascular wall shear stress, tunable substrate rigidity, and high resolution microscopy to measure cellular traction forces with less than 1 nN accuracy.
