Flow-Induced Crystallization of Collagen: A Potentially Critical Mechanism in Early Tissue Formation

Abstract

The type I collagen monomer is one of nature's most exquisite and prevalent structural tools. Its 300 nm triple-helical motifs assemble into tough extracellular fibers that transition seamlessly across tissue boundaries and exceed cell dimensions by up to 4 orders of magnitude. In spite of extensive investigation, no existing model satisfactorily explains how such continuous structures are generated and grown precisely where they are needed (aligned in the path of force) by discrete, microscale cells using materials with nanoscale dimensions. We present a simple fiber drawing experiment, which demonstrates that slightly concentrated type I collagen monomers can be “flow-crystallized” to form highly oriented, continuous, hierarchical fibers at cell-achievable strain rates (<1 s−1) and physiologically relevant concentrations (∼50 μM). We also show that application of tension following the drawing process maintains the structural integrity of the fibers. While mechanical tension has been shown to be a critical factor driving collagen fibril formation during tissue morphogenesis in developing animals, the precise role of force in the process of building tissue is not well understood. Our data directly couple mechanical tension, specifically the extensional strain rate, to collagen fibril assembly. We further derive a “growth equation” which predicts that application of extensional strains, either globally by developing muscles or locally by fibroblasts, can rapidly drive the fusion of already formed short fibrils to produce long-range, continuous fibers. The results provide a pathway to scalable connective tissue manufacturing and support a mechano-biological model of collagen fibril deposition and growth in vivo.

From Tendon Injury to Collagen-based Tendon Regeneration: Overview and Recent Advances

“…Another interesting, yet simple technique, has been reported by Paten et al (2016) [212]. They were able to draw centimeter-long collagen fibers with a diameter around 50 μm, just by poking a collagen solution drop left a few minutes under dry nitrogen atmosphere with a glass micro-needle ( Figure 10).…”

Human Corneal Fibroblast Pattern Evolution and Matrix Synthesis on Mechanically Biased Substrates

“…Our recent work suggests that shearing or extensional strain applied to condensed collagen solutions in the direction of cell motion is the most likely driver of collagen crystallization. 77 …”

Surface-modified substrates for the Langmuir-Blodgett deposition of patterned ultra-thin and highly oriented collagen coatings

“…Collagen alignment in films is accomplished by magnetic or electrical fields, the application of stress/strain and the Langmuir-Blodgett/Schaefer technology (Narayanan et al, 2014;Pastorino et al, 2014;Chaubaroux et al, 2015;Sorkio et al, 2015;Nam et al, 2016;Bonfrate et al, 2017). Thick films and membranes are fabricated via micro fluidics, stress/strain, extrusion/compacting (Riching et al, 2014;Banglmaier et al, 2015;Nam et al, 2016), while for scaffolds the fabrication can be based on electro spinning, freeze drying, electrochemical treatment, micro fluidics and 'crowding" of collagen (English et al, 2012;Kishore et al, 2012;Saeidi et al, 2012;Younesi et al, 2014;Thomas et al, 2016;Islam et al, 2016;Paten et al, 2016;Ryan et al, 2017).…”