Biology subjects

de Moraes, P. A. D.

Publications and source records attributed to de Moraes, P. A. D..

3 recordsLinked to original sources

bioRxiv2025

Spatiotemporal mapping of microscale stiffness during collagen polymerization and crosslinking by optical multifrequency time-harmonic elastography

Optical multifrequency time-harmonic elastography (OMTHE) was used for rapid mechanical characterization of extra-cellular matrix-derived collagen networks at micrometer resolution. OMTHE was optimized for point-wise shear wave excitation in small sample volumes and compared to tabletop magnetic resonance elastography (ttMRE) and optical intensity changes. Dynamic stiffening due to the fluid-gel transition during collagen polymerization and chemical crosslinking using glutaraldehyde was tracked by shear waves speed (SWS) at vibration frequencies between 3 and 10 kHz and frame rates up to 4 kHz. During collagen polymerization, after an initial lag phase, SWS increased on average 6 {+/-} 3 min earlier than optical density, suggesting that a load-bearing percolating fiber network was established before fibril thickening enhanced light scattering. In contrast, chemical crosslinking showed a lag-free, diffusion-driven SWS increase from 1.7 {+/-} 0.4 m/s to 2.5 {+/-} 0.5 m/s, matching the relative SWS change from ground-truth ttMRE. In conclusion, OMTHE provides a unique research tool that quantifies biomechanical property changes in small biological samples with spatiotemporal resolutions of micrometers and seconds. Key Results- Point-excitation OMTHE at microscopic resolution maps dynamic stiffness changes in collagen gels during polymerization and crosslinking at high frame rates. - Polymerization and crosslinking of collagen show distinct time courses with polymerization being in the order of minutes ahead of crosslinking. - Collagen stiffening due to polymerization precedes changes in optical density as seen by light microscopy.

biophysics↗

bioRxiv2025

Liver Viscosity Decreases Before the Onset of Fibrosis in Metabolic Dysfunction-Associated 1 Steatohepatitis (MASH)

Background and AimMetabolic dysfunction-associated steatohepatitis (MASH) is an increasingly prevalent condition worldwide, associated with biomechanical liver changes and detectable by magnetic resonance elastography (MRE). This study explored the pathophysiological features and their biomechanical manifestations at different stages of MASH in a mouse dietary model. MethodsUsing MRE on a clinical 3 Tesla MRI scanner, we measured liver stiffness, viscosity, fat fraction and water diffusion in 45 male mice. These values were correlated with histopathology and proteomics analyses to further characterize the liver microstructural and metabolic changes during MASH progression. ResultsWe found in a high-fat, low amino-acid model that early MASH was marked by fat accumulation and increasing inflammatory activity, while later stages showed a reduction in fat despite persistent inflammation. These changes in microstructure were associated with biomechanical adaptations, including a progressive decrease in hepatic viscosity and the water diffusion. Notably, viscosity was inversely correlated with lobular inflammation, cell adhesion, antioxidant activity, and metabolic adaptations such as enhanced ketone body synthesis. These findings, which precede the onset of fibrosis and tissue stiffening, show that tissue viscosity is highly sensitive to early microstructural and metabolic alterations in MASH. ConclusionSteatosis and inflammation significantly alter liver biophysical properties, particularly viscosity, in a mouse dietary model of MASH, even in the absence of fibrosis. These findings suggest that viscosity is a potential early and clinically translatable biomarker for the development and progression of MASH.

biophysics↗

bioRxiv2025

Longitudinal in vivo MR elastography reveals whole-liver viscoelastic involvement in a murine model of hepatocellular carcinoma

Cancer cells actively shape their microenvironment and adapt the physical and biomechanical properties of the host tissue. However, for organs like the liver, especially in vivo, it remains unclear at what rate and spatial extent macroscopic viscoelastic properties change during formation of a cancer-permissive environment. Using clinical multifrequency magnetic resonance elastography (MRE) in a mouse model of hepatocellular carcinoma (HCC), we identified surprisingly early and large-scale viscoelasticity changes leading to whole-liver biomechanical involvement stretching far beyond the local cancer microenvironment. Widespread liver softening began two weeks after HCC inoculation, followed by a decrease in tissue viscosity and fluidity two weeks later, preceding any macroscopic evidence of local tumor growth. In contrast, local lesions with stiff-rigid biomechanical properties were not detectable by standard MRI and MRE until five to six weeks post-injection. Furthermore, tumor viscoelasticity correlated with that of the host liver, also suggesting a possible widespread adaptation of the biomechanical properties beyond the tumor margins and its local niche during early liver colonization. The observed large-scale viscoelastic signature, detectable just two weeks after tumor cells injection, could serve as a non-invasive imaging biomarker to inform physicians about tumor niche formation and liver cancer progression long before any macroscopic manifestation of solid tumors.

biophysics↗