Biology subjects

Rego, B. V.

Publications and source records attributed to Rego, B. V..

4 recordsLinked to original sources

bioRxiv2023

A fast, robust method for quantitative assessment of collagen fibril architecture from transmission electron micrographs

Collagen is the most abundant protein in mammals; it exhibits a hierarchical organization and provides structural support to a wide range of soft tissues, including blood vessels. The architecture of collagen fibrils dictates vascular stiffness and strength, and changes therein can contribute to disease progression. While transmission electron microscopy (TEM) is routinely used to examine collagen fibrils under normal and pathological conditions, computational tools that enable fast and minimally subjective quantitative assessment remain lacking. In the present study, we describe a novel semi-automated image processing and statistical modeling pipeline for segmenting individual collagen fibrils from TEM images and quantifying key metrics of interest, including fibril crosssectional area and aspect ratio. For validation, we show illustrative results for adventitial collagen in the thoracic aorta from three different mouse models.

bioengineering↗

bioRxiv2022

Compensatory aortic remodeling in Marfan syndrome protects against sexually dimorphic rupture during a BAPN challenge

Transmural rupture of the aorta is responsible for significant morbidity and mortality; it occurs when wall stress exceeds local wall strength. Amongst other conditions, the aortic root and ascending aorta become vulnerable to dissection and rupture in Marfan syndrome, a connective tissue disorder that results in a progressive fragmentation and degradation of the elastic fibers of the aortic wall. Whereas competent elastic fibers are critical for aortic functionality, cross-linked collagen fibers endow the aorta with its stiffness and strength. In this paper, we contrast progressive degeneration of the ascending aorta in male and female Marfan and wild-type mice, with and without chronic exposure to a potent inhibitor of lysyl oxidase ({beta}-aminopropionitrile, or BAPN), to examine effects of extracellular matrix cross-linking in aortic dilatation and rupture. We found a strong sexual dimorphism in aortic dilatation in Marfan mice and aortic rupture in wild-type mice, but also a compensatory remodeling of the aorta that protected the Marfan aorta against lethal rupture despite a strong BAPN challenge. This compensation appears to be mediated via increased lysyl oxidase in the female and especially male Marfan aorta, resulting in improved collagen fiber stability and integrity, particularly of fibril bundles in the adventitia.

bioengineering↗

bioRxiv2021

Uncertainty quantification in subject-specific estimation of local vessel mechanical properties

Quantitative estimation of local mechanical properties remains critically important in the ongoing effort to elucidate how blood vessels establish, maintain, or lose mechanical homeostasis. Recent advances based on panoramic digital image correlation (pDIC) have made high-fidelity 3D reconstructions of small-animal (e.g., murine) vessels possible when imaged in a variety of quasi-statically loaded configurations. While we have previously developed and validated inverse modeling approaches to translate pDIC-measured surface deformations into biomechanical metrics of interest, our workflow did not heretofore include a methodology to quantify uncertainties associated with local point estimates of mechanical properties. This limitation has compromised our ability to infer biomechanical properties on a subject-specific basis, such as whether stiffness differs significantly between multiple material locations on the same vessel or whether stiffness differs significantly between multiple vessels at a corresponding material location. In the present study, we have integrated a novel uncertainty quantification and propagation pipeline within our inverse modeling approach, relying on empirical and analytic Bayesian techniques. To demonstrate the approach, we present illustrative results for the ascending thoracic aorta from three mouse models, quantifying uncertainties in constitutive model parameters as well as circumferential and axial tangent stiffness. Our extended workflow not only allows parameter uncertainties to be systematically reported, but also facilitates both subject-specific and group-level statistical analyses of the mechanics of the vessel wall.

bioengineering↗

bioRxiv2019

Mitral valve leaflet response to ischemic mitral regurgitation: From gene expression to tissue remodeling

AimsIschemic mitral regurgitation is frequently observed following myocardial infarction and is associated with higher mortality and poor clinical prognosis if left untreated. Accumulating evidence suggests that mitral valve leaflets actively remodel post-myocardial infarction, yet the cellular mechanisms underlying these responses and how this affects tissue function remain largely unknown. We sought to elucidate mitral valve remodeling post myocardial infarction at the tissue, cellular, and transcriptomic levels. Methods and ResultsThe mechanical behavior of ovine mitral valve leaflets pre- and 8 weeks post- myocardial infarction reveal a significant decrease in radial direction extensibility, which essentially eliminated the mechanical anisotropy typically observed in healthy mitral valves. Quantitative histology and ultrastructural assessment by transmission electron microscopy revealed altered leaflet composition and architecture at 8 weeks post-myocardial infarction. Assessment of the mitral valve interstitial cell nuclear aspect ratio, a metric of cellular deformation, revealed that they were on average rounder following myocardial infarction. RNA sequencing indicated that YAP-induced genes were elevated at 4 weeks post-myocardial infarction and genes related to extracellular matrix organization were some of the most downregulated in sheep with IMR compared to sheep without ischemic mitral regurgitation at 4 weeks post-myocardial infarction. Additionally, RNA sequencing revealed the possible recruitment of immune cells in this remodeling process due to the drastic elevation of CXCL9 and CLEC10A. ConclusionsOur multiscale assessment revealed significant mechanical and microstructural changes due to myocardial infarction. RNA sequencing provided a baseline for global gene expression changes in response to myocardial infarction with and without ischemic mitral regurgitation and suggests YAP-induced mechanotransduction, altered expression of extracellular matrix-related genes, and recruitment of immune cells as mechanisms contributing to altered mitral valve biomechanics post-myocardial infarction.

bioengineering↗