A custom image-based analysis tool for quantifying elastin and collagen micro-architecture in the wall of the human aorta from multi-photon microscopy

Abstract

The aorta possesses a micro-architecture that imparts and supports a high degree of compliance and mechanical strength. Alteration of the quantity and/or arrangement of the main load-bearing components of this micro-architecture the elastin and collagen fibers leads to mechanical, and hence functional, changes associated with aortic disease and aging. Therefore, in the future, the ability to rigorously characterize the wall fiber micro-architecture could provide insight into the complicated mechanisms of aortic wall remodeling in aging and disease. Elastin and collagen fibers can be observed using state-of-the-art multi-photon microscopy. Image-analysis algorithms have been effective at characterizing fibrous constructs using various microscopy modalities. The objective of this study was to develop a custom MATLAB-language automated image-based analysis tool to describe multiple parameters of elastin and collagen micro-architecture in human soft fibrous tissue samples using multi-photon microscopy images. Human aortic tissue samples were used to develop the code. The tool smooths, cleans and equalizes fiber intensities in the image before segmenting the fibers into a binary image. The binary image is cleaned and thinned to a fiber skeleton representation of the image. The developed software analyzes the fiber skeleton to obtain intersections, fiber orientation, concentration, porosity, diameter distribution, segment length and tortuosity. In the future, the developed custom image-based analysis tool can be used to describe the micro-architecture of aortic wall samples in a variety of conditions. While this work targeted the aorta, the software has the potential to describe the architecture of other fibrous materials, tube-like networks and connective tissues.

Aging of the skeletal muscle extracellular matrix drives a stem cell fibrogenic conversion

“…From the SHG images, the collagen fibril orientation and tortuosity were analyzed using a customized algorithm (Takanari et al ., 2013; Koch et al ., 2014). Structural alterations in collagen fiber alignment (Courtney et al ., 2006) and/or tortuosity (Stella et al ., 2010b) affect the ECM degree of mechanical anisotropy and can provide important insight into the biologic basis for age‐related alterations in ECM mechanical properties.…”

Failure of the Porcine Ascending Aorta: Multidirectional Experiments and a Unifying Microstructural Model

“…Network parameters were selected to reflect the biological roles of each component and were adjusted to match the experimental results. This approach was successful in matching a wide range of tissue mechanical tests, including one-radial extension to failure-that was not used during the fitting process, and it has the potential to be extended to the more disorganized (and thus more complex) architecture of the aneurysm, especially as better imaging and image-based modeling methods emerge [67,68]. The work of Pal et al [61] represents an excellent example of this approach, developing a theoretical model of peel failure based on known structure.…”

Characterizing liver capsule microstructure via in situ bulge test coupled with multiphoton imaging

“…In particular, many studies aim to understand the extension and reorganization mechanisms of collagenous structures on different tissues such as tendons (Sasaki and Odajima, 1996;Screen et al, 2004), skin (Brown, 1973), connective tissue (Liao et al, 2005;Purslow et al, 1998), or arteries (Keyes et al, 2013;Rezakhaniha et al, 2012;Wang et al, 2013). Indeed, the changes in the microstructure at the fiber level can impact greatly the mechanical properties of the tissue and thus its functional purpose, affecting cell environment and behavior, leading to diseases or disorders (Engler et al, 2006;Koch et al, 2014;Pizzo et al, 2005;Robertson et al, 2012). The identification of the relationship between microstructure and mechanical behavior needs coupling mechanical tests with microstructural observation which turns out to be challenging.…”