Research Projects

Investigating the Molecular Determinants of Cell and Tissue Mechanical Properties

Sustaining and generating mechanical forces is a normal part of physiology for mammalian tissue: Intestinal epithelia are stretched during peristaltic movements in the gut, lung alveoli deform during breathing and skin epidermal layers provide a mechanical barrier to the external environment. Mechanical integrity and force transmission in even the simplest tissues is critical to their proper function. This is particularly apparent in diseased states where point mutations to cytoskeletal or junctional proteins result in tissue mechanical failure such as blistering, cracking and hemorrhaging. Characterizing the mechanical properties of single cells and simple tissues from a materials science and engineering perspective could lead to a better understanding of diseases of cell and tissue fragility. The lab is currently interested in understanding the mechanical properties of cells in a number of different systems and tissues including the kidney, gut, skin and blood.

One of the major determinants of cell mechanical properties is a filament forming protein called actin. Actin filaments are assembled into distinct higher order structures (including bundles, meshes and cables) by an array of specialized binding and crosslinking proteins. The organization of actin filaments within each structure is directly linked to its function through the ability to generate specific mechanical forces. For example, aligned bundles of actin filaments in stress fibers pull on the extracellular matrix, and dendritic actin networks push the leading edge of migrating cells forwards. Missense mutations to actin crosslinking proteins are associated with a number of diseases including familial Focal Segmental Glomerulosclerosis (FSG), Periventricular nodular heterotopia (PVNH), Myofibrillar and Distal Myopathies, many of which present with symptoms associated with compromised cellular force generation and tissue fragility. Understanding how actin filaments are organized into distinct force generating structures through the activity of filament crosslinking proteins is therefore interesting and important from both a biophysical and clinical perspective. The lab takes a multidisciplinary approach to understanding how actin filaments are organized into force generating structures using tools such as machine learning for image analysis and purification of actin regulatory proteins to characterize their behavior in vitro.

A significant focus of our work is on understanding how cytoskeletal proteins such as actin and intermediate filament proteins endow cells and tissues with their mechanical characteristics. We study actin organization using optical microscopy and live cell imaging shown below. (publication)

In collaboration with the Impact Mechanics Lab at Carleton University, we are investigating the role of cytoskeletal proteins expressed in cells in the central nervous system in traumatic brain injury. One of these proteins, Glial fibrillary acidic protein (GFAP), expressed in C6 glioblastoma cells is shown in green the image below.

Building Tools to Study Biology

The length scale of a single cell or simple tissue is on the order of tens to hundreds of micrometers. In order to study the mechanical properties of samples on this length scale, we can adapt and shrink down common tools for mechanical testing. Additional constraints on making these measurements are that the sample is alive and needs to be kept in conditions that are as close to physiologically relevant as possible. Engineering tools for studying biological systems presents an intriguing problem and often requires creative solutions. The lab uses established techniques such as Optical Microscopy and Atomic Force Microscopy but also develops new tools that provide quantitative measurements of the behavior of biological samples in a controlled environment, across a range of length scales.

Our lab has developed a home built Atomic Force Microscope that can be used to measure the mechanical properties of single cells and simple tissues (publication).

We engineer the mechanical properties of the cellular microenvironment in order to understand how cells adapt and respond to mechanical signals, using custom strategies for fabricating substrates with different mechanical and physical characteristics (publication).

To investigate cellular responses to mechanical strain amplitude and strain rate, we have built our own mechanical testing setup for subjecting neurons and astrocytes to pathological loading conditions associated with Traumatic Brain Injury.

Engineering Protein, Cell and Tissue Mechanical Properties for Regenerative Medicine

One size fits all therapies often have varying success in treating patients. An exciting and active area of research is to design and engineer the properties of cells and tissues for personalized medicine. In the CTELab we are interested in engineering tissue mechanical characteristics for therapies such as skin grafts and replacement tissues where they physical properties of the engineered tissue can be customized for each condition and patient. This approach requires a wholistic understanding of cell and tissue mechanics from the molecular level (nanometer), to cell (micrometer), tissue and organ (millimeter) scale. To address this challenge, we start from the bottom up, engineering protein function and then measuring changes at the cell and tissue level with our custom tools and optical microscopy approaches.

As part of this work we use our expertise in molecular biology to modify actin binding and regulatory proteins to control cell shape and mechanics. These tools can be verified using single molecule optical microscopy and in vitro binding assays (publication).

Single molecule TIRF microscopy video showing individual binding events (white dots) as a fluorescently labelled actin binding domain interacts with actin filaments (not shown) on the surface of a coverslip.

Engineering Education

Creating an inclusive environment in the lab and the classroom is paramount for success. The CTE lab has active research projects in the area of engineering education and developing novel devices for laboratory experiments and experiential learning.