Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session V09: Mechanics and Structure of Filament Networks: Tissues and CytoskeletonInvited Live
|
Hide Abstracts |
Sponsoring Units: DSOFT Chair: Alex Levine, University of California; Christoph Schmidt, Duke University |
Thursday, March 18, 2021 3:00PM - 3:36PM Live |
V09.00001: The role of the Nonlinear plastic response of fibrous networks for organoid growth Invited Speaker: Andreas Bausch Branching morphogenesis is an essential process during organ development in all type of species, but the mechanisms governing its execution differ depending on cell types and extracellular matrices. An outstanding organ of interest to study branching morphogenesis is the human mammary gland since it undergoes most of its development postnatally during puberty. To mimic realistic conditions related to the human mammary gland we use a 3D organotypic collagen assay in which freshly isolated primary human mammary epithelial cells generate ductal structures with multiple branching points. We conducted long-term live-cell imaging over several days to reveal the dynamics of organoid formation. Extension of ducts correlated with large deformation of the surrounding matrix, imaged by tracking embedded fluorescent beads. We identify the hihlgy nonlinear plastic response of the collagen to govern the branching morphogenesis. |
Thursday, March 18, 2021 3:36PM - 4:12PM Live |
V09.00002: Finite-element Brownian dynamics simulations of biopolymer filament bundles and networks Invited Speaker: Maximilian Grill Cross-linked, semiflexible filaments form bundles and networks, which are ubiquitous, load-bearing structures in the cytoskeleton and extracellular matrix. We perform large-scale numerical simulations of such complex, three-dimensional fibrous systems in order to explore their fundamental mechanical properties. This is enabled by our efficient, mesoscopic modeling approach, which uses nonlinear beam finite elements to model the filaments, and additionally includes stochastic thermal forces and viscous drag to account for their Brownian dynamics. The random binding and unbinding of cross-linker molecules is based on given reaction rates and a preferred binding length and orientation. |
Thursday, March 18, 2021 4:12PM - 4:48PM Live |
V09.00003: Quenched and topological disorder in filament networks and kinked bundles Invited Speaker: Valentin Slepukhin The filament networks are common in the living world, from the intracellular cytoskeleton in our cells to the extracellular matrix outside them. These filament networks typically include highly cross-linked bundles of nearly parallel filaments. In this talk, I explore the structure and mechanics of cross-linked filament bundles focusing on the role of quenched defects in bundles. |
Thursday, March 18, 2021 4:48PM - 5:24PM Live |
V09.00004: Mechanical criticality, nonlinearity, fracturing, and topological edge modes in fiber networks Invited Speaker: Xiaoming Mao Disordered networks of crosslinked fibers capture the essential structure of many materials in nature, such as the cytoskeleton and extracellular matrix as networks of biopolymers, and manmade materials such as hydrogels and aerogels. In this talk, we will discuss a number of remarkable mechanical properties of fiber networks, starting from Maxwell's counting of numbers of degrees of freedom and constraints, which places these fiber networks close to a special mechanical critical point, the so called "isostatic point", leading to highly sensitive changes of elastic properties [1]. We will then proceed to discuss how this point also controls the significant strain-stiffening behavior of these fiber networks in the nonlinear regime [2], as well as special critical phenomena when these materials fail under stress [3]. Moreover, we will show that in two dimensions, floppy modes in these fiber networks are controlled by a topological winding number. Interestingly, when a small active stress changes the network geometry, floppy modes in fiber networks can localize at opposite edges of the network, strongly affects mechanical properties of the network from local stiffness to signal transmission [4]. These unusual mechanical phenomena reveal great potential for both controlling fiber networks in nature such as tissue engineering, and creating new materials with sensitive, topologically protected, mechanical properties. |
Thursday, March 18, 2021 5:24PM - 6:00PM Live |
V09.00005: Cells utilize strain hardening and crosslinking to establish their extracellular niche in fibrous tissue Invited Speaker: Elliot Botvinick Bulk measurements of ECM stiffness are commonly used in mechanobiology. However, peri-cellular stiffness can be quite heterogenous and divergent from the bulk properties. Here, we use optical tweezers active microrheology (AMR) to quantify how two different cell lines embedded in 1.0 and 1.5 mg/ml type 1 collagen (T1C) establish dissimilar patterns of peri-cellular stiffness. We found that dermal fibroblasts (DFs) increase local stiffness of 1.0 mg/ml T1C hydrogels, but surprisingly do not alter stiffness of 1.5 mg/ml T1C hydrogels. In contrast, MDA-MB-231 cells (MDAs) predominantly do not stiffen T1C hydrogels, as compared to cell-free controls. Results suggest that MDAs adapt to the bulk ECM stiffness, while DFs regulate local stiffness to levels they intrinsically “prefer”. Further, cells were subjected to treatments, that were previously shown to alter migration, proliferation and contractility of DFs and MDAs. Following treatment, both cell lines established different levels of stiffness magnitude and anisotropy, which were dependent on the cell line, T1C concentration and treatment. In summary, our findings demonstrate that AMR reveals otherwise masked mechanical properties such as spatial gradients and anisotropy, which are known to affect cell behavior at the macro-scale. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700