Regional extracellular matrix remodeling: multiscale imaging and mechanics.

Project Summary Cells have a dynamic and reciprocal relationship with their extracellular matrix (ECM). Cells synthesize, degrade, and rearrange local ECM proteins and molecules even as the physical properties of the ECM, (including its stiffness, density, and orientation), regulate cell phenotype, behavior, and communication. Disease and injury disrupt this dynamic relationship causing cells to produce local patterns of ECM remodeling that can be pathologic, such as fibrosis, or inadequate, leading to tearing or a persistent wound. Understanding ECM heterogeneity represents a key opportunity to enhance knowledge of how disease and injury develop and progress. Therefore, my research program focuses on increasing the rigor and reproducibility of approaches to capture ECM remodeling. Specifically, we ask (1) how do ECM geometry and structure vary regionally at multiple scales? and (2) how does heterogeneity influence a tissue’s local and global load-bearing function? My research program answers these questions by addressing critical limitations in the visualization and mechanical characterization of heterogeneous ECM. Although groundbreaking techniques have emerged that enable micro and even nano-scale ECM imaging, a crucial tradeoff is field of view or sample size. For example, laser scanning microscopy provides unparalleled visualization of collagen, the most abundant ECM protein in the human body, capturing fiber dimensions and morphology with clarity far beyond traditional microscopy. However, it covers, at most, a couple hundred microns in each direction. Therefore, a critical challenge in applying high-resolution imaging to heterogeneous pathologic samples involves selecting this micron-sized imaging window from the centimeters of available tissue. Our group is at the forefront of increasing rigor and repeatability in this field, advancing low-resolution imaging, image segmentation, and analysis automation. Another barrier to investigating ECM heterogeneity is the lack of experimental protocols and analysis tools to quantify spatial variations in mechanical properties . Inverse methods have addressed technical challenges in this area but face limited adoption due to their complex mathematical techniques and specialized codes. We will address this gap using a novel experimental system to generate a repository of full-field measurements on a range of heterogenous samples. Then, we will create sample-specific finite element models using a popular open-source software and encourage the inverse mechanics community to outperform us. To study pathologic remodeling under highly controlled conditions, we will also build a specialized clamping system that connects cell-seeded tissue-engineered constructs to our mechanical and quantitative polarized light testing systems. Our research program addresses specific challenges in quantifying regional differences in ECM remodeling to address fundamental questions about how pathology develops and progresses. Ultimately, insights from this program will improve disease detection and prognostication as well as localized treatment.