Analysis of structural effects of sickle cell disease on brain vasculature of mice using three-dimensional quantitative phase imaging

Abstract

Although the molecular origins of sickle cell disease (SCD) have been extensively studied, the effects of SCD on the vasculature-which can influence blood clotting mechanisms, pain crises, and strokes-are not well understood. Improving this understanding can yield insight into the mechanisms and wide-ranging effects of this devastating disease. Aim:We aim to demonstrate the ability of a label-free 3D quantitative phase imaging technology, called quantitative oblique back-illumination microscopy (qOBM), to provide insight into the effects of SCD on brain vasculature. Approach:Using qOBM, we quantitatively analyze the vasculature of freshly excised, but otherwise unaltered, whole mouse brains. We use Townes sickle transgenic mice, which closely recapitulate the pathophysiology of human SCD, and sickle cell trait mice as controls. Two developmental time points are studied: 6-week-old mice and 20-week-old mice. Quantitative structural and biophysical parameters of the vessels (including the refractive index (RI), which is linearly proportional to dry mass) are extracted from the high-resolution images and analyzed.Results: qOBM reveals structural differences in the brain blood vessel thickness (thinner for SCD in particular brain regions) and the RI of the vessel wall (higher and containing a larger variation throughout the brain for SCD). These changes were only significant in 20-week-old mice. Further, vessel breakages are observed in SCD mice at both time points. The vessel wall RI distribution near these breaks, up to 350 μm away from the breaking point, shows an erratic behavior characterized by wide RI variations. Vessel diameter, tortuosity, texture within the vessel, and structural fractal patterns are found to not be statistically different. As with vessel breaks, we also observe blood vessel blockages only in mice brains with SCD.Conclusions: qOBM provides insight into the biophysical and structural composition of brain blood vessels in mice with SCD. Data suggest that the RI may be an indirect indicator of vessel rigidity, vessel strength, and/or tensions, which change with SCD. Future ex vivo and in vivo studies with qOBM could improve our understanding of SCD.

Real-time in-vivo volumetric quantitative phase imaging with a compact handheld probe

“…Beyond static imaging, the system's real-time functionality allows for the dynamic visualization of cellular and tissue behaviors, enabling the observation of possible physiological dynamics and interactions. Further, dynamic analysis and functional imaging with qOBM are possible [6][7][8], which opens up new opportunities for 3D, label-free, in-vivo imaging.…”

Label-free functional analysis of root-associated microbes with dynamic quantitative oblique back-illumination microscopy

“…Lastly, while DqOBM provides the label-free functional imaging of bacterial cells in roots, the penetration depth of qOBM has been shown to be limited to 200 m in tissues 28 . Therefore, it will not be able to penetrate deep into the natural environment of roots, such as soil.…”

“…While this methodology has been utilized to observe eukaryotic cells (i.e. blood cells 26 , cell cultures 18 , 25 , and neuronal tissues 17 , 27 , 28 ), this paper provides a novel use of functional qOBM imaging to study bacterial cells.

Figure 1 ( A ) Overview of the qOBM imaging approach which consists of an inverted brightfield microscope with epi-illumination.

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Experimental assessment of the optical transfer function for quantitative oblique back-illumination microscopy

“…Quantitative oblique back-illumination microscopy (qOBM) is an innovative technology enabling quantitative phase imaging (QPI) in thick scattering samples such as brain, [3][4][5][6] blood collection bag 7,8 or organoids. 9 Unlike traditional laser setups, qOBM utilizes four partially coherent light sources (LEDs), offering higher resolution and eliminating speckle noise.…”