Determining the Stiffness of ECM Fibers Using Space-Time Image Correlation Spectroscopy

Arias, Joshua Daniel

Decade-spanning research has shown that the microenvironment surrounding cells, which includes the extracellular matrix (ECM), plays an important role in development, angiogenic disease, and cancer. ECM research has posited a direct relationship between changes in cell development and the local stiffness of ECM fibers. Being able to measure the relative quantitative stiffness of these fibers can help clarify the exact roles the ECM plays in cell development, as well as act as a prognostic tool for cancer and angiogenic disease, to name a few. The objectives of this study, then, are to (1) develop an effective way of visualizing these ECM fibers so that we could (2) develop a working method of determining the relative stiffness of ECM fibers using Spatio-Temporal Image Correlation Spectroscopy (STICS). Selective Plane Illumination Microscopy (SPIM) is a new, powerful method of imaging given its large field of view, high image resolution, fast collection times, and ability to make 3D models of samples in space and time. SPIM works by illuminating a single plane within a sample, which eliminates all other noise above and below the plane to allow image sectioning. Spatio-Temporal Image Correlation Spectroscopy is a mathematically-based method of determining the persistence length of fibers through image post-processing. A MATLAB STICS algorithm will cross-correlate a pixel in a SPIM image with every other pixel in order to “track” the motion, or lack thereof, of a defined fiber in three-dimensional space and time. These results will then be compared with those of active microrheology (AMR) under similar conditions, in order to prove whether this new method is valid and equivalent to that of AMR.