Spatially-resolved nanometer-scale measurement of cartilage extracellular matrix mobility

Abstract

Objective: Tissues have complex structures, comprised of solid and fluid phases. Improved understanding of interactions between joint fluid and extracellular matrix (ECM) is required in models of cartilage mechanics. X-ray photon correlation spectroscopy (XPCS) directly measures nanometer-scale dynamics, and thus can provide insight into biofluid-biosolid interactions in cartilage. This study applies XPCS to evaluate dynamic interactions between intact cartilage and biofluids.Design: Cartilage biopsies were collected from bovine femoral condyles. During XPCS measurements, cartilage samples were exposed to different fluids: deionized water, PBS, synovial fluid, or sonicated synovial fluid. ECM-biofluid interactions were also assessed at different length scales and different depths from the cartilage surface.Results: Using SA-XPCS, cartilage ECM mobility was detected at length scales from 50 to 207 nm. As length scale decreased, time scale for autocorrelation decay decreased, suggesting smaller ECM components are more mobile. ECM dynamics were slowed by dehydrating the sample, demonstrating XPCS assesses matrix mobility in hydrated environments. At all length scales, the matrix was more mobile in deionized water and slowest in synovial fluid. Using the 207 nm length scale assessment, ECM dynamics in synovial fluid were fastest at the cartilage surface and progressively slowed as depth into the sample increased, demonstrating XPCS can assess spatial distribution of ECM dynamics. Finally, ECM mobility increased for sonicated synovial fluid.

pyXPCSviewer: an open-source interactive tool for X-ray photon correlation spectroscopy visualization and analysis

“…XPCS can provide meaningful information from samples with extremely low scattering intensities (Sheyfer et al, 2022;Lurio et al, 2021;Partain et al, 2021), but doing so requires averaging of XPCS results from hundreds or sometimes even thousands of repeating measurements to achieve the signalto-noise ratio (SNR) of g 2 sufficient for quantitative analysis (Zhang et al, 2021). To avoid prolonged X-ray exposure and mitigate the beam damage, such repeated measurements are usually performed on different locations of the sample, which makes the averaging of the results susceptible to spatial heterogeneity of the sample.…”

Liquid platelet-rich fibrin produced via horizontal centrifugation decreases the inflammatory response and promotes chondrocyte regeneration in vitro

“…Previous studies have demonstrated that high molecular weight HA not only has the ability to suppress inflammation but also inhibits nitric oxide-induced apoptosis and dedifferentiation of articular chondrocytes in osteoarthritis (Peng et al, 2010;Partain et al, 2021). Therefore, HA may play an important role in downregulating the Il-1β expression and may be more efficient for aggrecan expression than PRF alone.…”