Event

Title: Endothelial Junction Remodeling as a Multiscale System: Molecular Mechanisms, Temporal Structure, and Spatial Coordination

Committee members:
Dr. Kimberly M. Stroka, Chair
Dr. Katharina Maisel
Dr. Alisa Morss Clyne
Dr. Helim Aranda-Espinoza

Dr. Behtash Babadi, Dean's Representative

Abstract:

Endothelial barrier dysfunction, which results in abnormal leakage of fluid and molecules from blood vessels into surrounding tissues, compromises vascular homeostasis and exacerbates disease severity in conditions like cancer and stroke. Despite many studies drawing connections between the remodeling of endothelial cell junctions and monolayer leakage, mechanisms governing this process remain incompletely understood. These junctions are increasingly recognized as dynamic structures, yet many current approaches rely on fixed-cell analyses rather than capturing their behavior in live cells. While these approaches provide important mechanistic insights, their inability to capture how junctions evolve over time and coordinate across cells limits our understanding of junction remodeling as a dynamic process and constrains the development of effective strategies to modulate barrier function in disease.

This dissertation develops a multiscale framework to investigate endothelial junction remodeling across molecular, temporal, and spatial scales. To determine how known molecular mechanisms of junction remodeling contribute to barrier dysfunction, we first used everolimus, a clinically used rapamycin analog, as a model barrier-disrupting stimulus to probe junctional responses. Quantitative analysis of fixed-cell imaging revealed that everolimus-induced junction remodeling is mediated by endocytic trafficking and actin reorganization, consistent with established pathways of barrier disruption.

Building on this mechanistic foundation, quantitative analysis of live-cell imaging revealed that junction remodeling occurs across distinct slow and rapid timescales that conventional time-domain metrics (e.g., rates of change) compress, limiting their resolution. Therefore, we developed a workflow using frequency-domain analysis, which not only preserved multi-timescale behavior but also allowed us to identify distinct dynamics of stable versus disrupted junctions. Extending this approach, we then quantified the coordination of junction dynamics between connected endothelial cells using correlation- and information-based metrics. Here we show that coordination between neighboring and distant cells follows coordinated patterns that are disrupted under disease-like conditions.

Together, this work shows that endothelial junction remodeling is governed by multiscale dynamics and coordinated behavior not captured by traditional approaches. By establishing a quantitative framework for studying endothelial junction dynamics and integrating metrics to capture their coordination, this work advances our understanding of the endothelial barrier as a dynamic and coordinated system and how it is altered when disrupted.