An automated approach for three-dimensional quantification of fibrillar structures in optically cleared soft biological tissues

Abstract

We present a novel approach allowing for a simple, fast and automated morphological analysis of three-dimensional image stacks (z-stacks) featuring fibrillar structures from optically cleared soft biological tissues. Five nonatherosclerotic tissue samples from human abdominal aortas were used to outline the multi-purpose methodology, applicable to various tissue types. It yields a three-dimensional orientational distribution of relative amplitudes, representing the original collagen fibre morphology, identifies regions of isotropy where no preferred fibre orientations are observed and determines structural parameters throughout anisotropic regions for the analysis and numerical modelling of biomechanical quantities such as stress and strain. Our method combines optical tissue clearing with second-harmonic generation imaging, Fourier-based image analysis and maximum-likelihood estimation for distribution fitting. With a new sample preparation method for arteries, we present, for the first time to our knowledge, a continuous three-dimensional distribution of collagen fibres throughout the entire thickness of the aortic wall, revealing novel structural and organizational insights into the three arterial layers.

Computational method for excluding fibers under compression in modeling soft fibrous solids

“…Specifically, in human arterial walls the collagen fibers are not perfectly aligned but are dispersed around a mean direction. Such a fiber dispersion has been observed in, for example, human arterial walls [1][2][3][4][5], the myocardium [6,7], corneas [8,9] and articular cartilage [10]. In particular, recent extensive experimental results [4] have shown that the collagen fiber dispersion in each of the layers of (healthy) human thoracic and abdominal aortas and iliac arteries is non-symmetric, in contrast to the rotationally symmetric fiber dispersion assumed in previous studies; see, for example, [11].…”

Modelling non-symmetric collagen fibre dispersion in arterial walls

“…To inform the modelling process, second-harmonic generation, for example, in combination with optical clearing [49] is a powerful technique for obtaining collagen fibre dispersion data from various types of tissues.…”

An exponential constitutive model excluding fibres under compression: Application to extension–inflation of a residually stressed carotid artery

“…In many of these tissues the collagen fibers are distributed around a mean direction in the reference configuration in the ground substance within which the fibers are embedded [1,[5][6][7][8].…”