Highlighting the impact of aging on type I collagen: label-free investigation using confocal reflectance microscopy and diffuse reflectance spectroscopy in 3D matrix model.

Marie Guilbert,Anne Koenig,Blandine Roig,François Perraut,Christine Terryn,Olivier Piot,Ganesh D Sockalingum,Pierre Jeannesson,Michel Manfait,Roselyne Garnotel,Jean-Marc Dinten

doi:10.18632/oncotarget.7385

Abstract

During aging, alterations of extracellular matrix proteins contribute to various pathological phenotypes. Among these alterations, type I collagen cross-linking and associated glycation products accumulation over time detrimentally affects its physico-chemical properties, leading to alterations of tissue biomechanical stability. Here, different-age collagen 3D matrices using non-destructive and label-free biophotonic techniques were analysed to highlight the impact of collagen I aging on 3D constructs, at macroscopic and microscopic levels. Matrices were prepared with collagens extracted from tail tendons of rats (newborns, young and old adults) to be within the physiological aging process. The data of diffuse reflectance spectroscopy reveal that aging leads to an inhibition of fibril assembly and a resulting decrease of gel density. Investigations by confocal reflectance microscopy highlight poor-fibrillar structures in oldest collagen networks most likely related to the glycation products accumulation. Complementarily, an infrared analysis brings out marked spectral variations in the Amide I profile, specific of the peptidic bond conformation and for carbohydrates vibrations as function of collagen-age. Interestingly, we also highlight an unexpected behavior for newborn collagen, exhibiting poorly-organized networks and microscopic features close to the oldest collagen. These results demonstrate that changes in collagen optical properties are relevant for investigating the incidence of aging in 3D matrix models.

Highlights

The aging process constitutes a field of major interest in our society since it represents a progressive, irreversible, and multidimensional mechanism affecting all people
The gel formation for the oldest collagen is faster, but the decrease of gel density indicates an inhibition of fibril assembly with aging
Our data show the potential of the combination of diffuse reflectance spectroscopy (DRS) and confocal reflectance microscopy (CRM) methodologies to characterize the changes occurring in 3D matrices as a function of collagen age

Summary

Introduction

The aging process constitutes a field of major interest in our society since it represents a progressive, irreversible, and multidimensional mechanism affecting all people. Modifications of extracellular matrix (ECM) components affect tissue biomechanical properties in vivo, leading to a decline of both tissue integrity and function [3, 4] Among these matrix compounds, type I collagen represents the most abundant long-life protein in humans, and the key fibrillar structural component of several tissues such as skin, bone, or tendon [5]. Its structure consists of three parallel polypeptide strands (two-α1 and one-α2 chains) coiled together into a rightwww.impactjournals.com/oncotarget handed triple helix; triple helices assemble into supramolecular structures corresponding to collagen fibrils and fibers [6, 7] This scaffold is fundamental for tissue integrity in governing their biomechanical properties, thermal stability, mechanical strength, and interactions with other biomolecules and cells [8, 9]. Networks of type I collagen can be obtained in vitro, and 3D matrices have been largely developed as collagen tissue substitutes in cell biology or tissue engineering [10, 11]

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