This EAGER award funded by the Biotechnology, Biochemical and Biomass Engineering Program in the CBET Division of NSF will be used to develop a computational framework to model subcellular remodeling that will take into account the active cellular mechanosensing, turn over of cytoskeletal constituents, and kinetics of key molecules associated with cell-substrate and cell-cell interactions. This computational framework will enable researchers to explore the biological complexity associated with mechanosensing and how biophysical cues from the cellular enviroment modulate cellular processes and cell phenotype.
Intellectual Merit. Previous researchers have investigated mechanosensitive cellular behavior by focusing on the effects of mechanical states (stress, strain, stiffness) which are independent of the cell. In contrast, in this work a more active mechanism will be examined by which the cell feels the physical environment, i.e., the cell actively applies traction and senses the response of the substrate. The computational model developed in this work will use a constrained mixture approach to account for the pre-stress and turnover of subcellular components and their interactions with key molecules in the cell-substrate and cell-cell interfaces. The computational model will also include substratum in the computational domain such that interactions between the cytoskeletal remodeling and the deformation of the substrate are taken into account.
Broader Impact. If successful, the computational tool will enable researchers to integrate quantitative measurements from experiments into the computational model to elucidate the cellular processes modulated by various mechanical and soluble cues. This study will also impact the tissue engineering and clinical communities by providing a predictive model that can be used in the design of engineered tissues and development of pharmaceutical treatment of diseases. From an educational standpoint, the project will provide a broad exposure to the students with an opportunity to integrate knowledge bases from vastly different fields. The PI has supported both (female and minority) undergraduate students and high school teachers from an existing NSF RET site program. The PI has been and will be actively engaged in K-12 education, RET, and public outreach programs such as Grandparents University. The outcomes of the research will be incorporated into these activities and the computational biomechanics course that the PI will be developing. The computational model and outcomes of this proposal will be disseminated through the web, in addition to traditional modes, such as journal publications and presentations at scientific meetings.
Mechanical cues in the cellular environment play important roles in guiding various cell behaviors, such as cell alignment, differentiation and synthesis of extracellular matrix. The grant aims to integrate a computational framework to model subcellular remodeling that takes into account the active cellular mechanosensing, turnover of cytoskeleton constituents, and kinetics of key molecules associated with cell-substrate and cell-extracellular matrix. Main activities and findings In contrast to other studies, we created a static, pre-stretched, anisotropic surface in which the cells were seeded on the substrate. In the first project, we hypothesized that the cell senses the physical environment through a more active mechanism, namely, even without external forces the cell can actively apply traction and sense an increased stiffness in the stretched direction and align in that direction. To test the hypothesis, we applied pre-stretch induced anisotropy by employing the theory of small deformation superimposed on large and predicted the effective stiffness in the stretch direction as well as its perpendicular direction. The results showed mesenchymal stem cells (MSC) aligned in the pre-stretched direction, and the cell alignment and morphology were dependent on the prestretch magnitude (Fig. 1. MSC orientation for pre-stretch). In addition, the pre-stretched surface demonstrated an ability to promote early myoblast differentiation of the MSC. This study is the first report on MSC alignment on a statically pre-stretched surface. Vascular smooth muscle tone and collagen turnover is critical for vascular adaptation of arteries in normal physiological conditions. Recently many studies used constrained mixture approaches in which vascular walls are assumed to be made up of different constitutes. In the second project, we develop a biochemomechanical model that incorporates subcellular regulation and collagen synthesis and removal for changes in wall shear stress, wall tension, and growth factors and inhibitors (Fig. 2. a schematic drawing). In the computations, we study possible ranges of the kinetic parameters in collagen synthesis and several possible functions of degradation, and study their consequences and, then, narrow the possible relations between collagen turnover and arterial adaptation as well as provide guidelines for further experiments. The results suggested that both of synthesis and degradation rates should be tightly regulated by the mechanical stresses (wall stress and shear stress). Intellectual merit and broad impacts The cell orientation induced by the pre-stretch induced anisotropy could provide insight into tissue engineering applications involving cells that aligned in vivo in the absence of dynamic mechanical stimuli. We also believe that the biochemomodel in our analysis will be beneficial to cardiovascular researchers, in the sense that it could be used as a tool for studying the vascular adaptation such as aneurysms and hypertension in human brain for patients and hemodynamics disorders. By further investigating the stress-mediated subcellular growth and remodeling that help to understand the cellular behavior (morphological change, synthesis and degradation rate, and phenotype changes) for tissue engineering and clinical interventions. Those projects from the EAGER funding were studying a more active mechanism of cellular mechanotransduction, by which the cell feels the physical environment, i.e., the cell actively applies traction and senses the response of the substrate. The computational tool will enable us to integrate quantitative measurements from experiments into the computational model to elucidate the cellular processes modulated by various mechanical and soluble cues. This study impacts the tissue engineering and clinical communities by providing a predictive model that can be used in the design of engineered tissues and development of pharmaceutical treatment of diseases. From an educational aspect, the project provided a broad exposure to the students with an opportunity to integrate knowledge bases from vastly different fields. The PI has supported both (female and minority) undergraduate students and high school teachers from an existing NSF RET site program. The PI has been actively engaged in K-12 education, RET, and public outreach programs such as Grandparents University. The outcomes of the research were incorporated into these activities and the computational biomechanics course as well as publications.
