Glycosaminoglycans Modulate Long-Range Mechanical Communication Between Cells in Collagen Networks

AbstractCells can sense and respond to mechanical forces in fibrous extracellular matrices (ECM) over distances much greater than their size. This phenomenon, termed long-range force transmission, is enabled by the realignment (buckling) of collagen fibers along directions where the forces are tensile (compressive). However, whether other key structural components of the ECM, in particular glycosaminoglycans (GAGs), can affect the efficiency of cellular force transmission remains unclear. Here we developed a theoretical model of force transmission in collagen networks with interpenetrating GAGs, capturing the competition between tension-driven collagen-fiber alignment and the swelling pressure induced by GAGs. Using this model, we show that the swelling pressure provided by GAGs increases the stiffness of the collagen network by stretching the fibers in an isotropic manner. We found that the GAG-induced swelling pressure can help collagen fibers resist buckling as the cells exert contractile forces. This mechanism impedes the alignment of collagen fibers and decreases long-range cellular mechanical communication. We experimentally validated the theoretical predictions by comparing collagen fiber alignment between cellular spheroids cultured on collagen gels versus collagen-GAG co-gels. We found significantly less alignment of collagen in collagen-GAG co-gels, consistent with the prediction that GAGs can prevent collagen fiber alignment. The roles of GAGs in modulating force transmission uncovered in this work can be extended to understand pathological processes such as the formation of fibrotic scars and cancer metastasis, where cells communicate in the presence of abnormally high concentrations of GAGs.Statement of significanceGlycosaminoglycans (GAGs) are carbohydrates that are expressed ubiquitously in the human body and are among the key macromolecules that influence development, homeostasis, and pathology of native tissues. Abnormal accumulation of GAGs has been observed in metabolic disorders, solid tumors, and fibrotic tissues. Here we theoretically and experimentally show that tissue swelling caused by the highly polar nature of GAGs significantly affects the mechanical interactions between resident cells by altering the organization and alignment of the collagenous extracellular matrix. The roles of GAGs in modulating cellular force transmission revealed here can guide the design of biomaterial scaffolds in regenerative medicine and provides insights on the role of cell-cell communication in tumor progression and fibrosis.

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Long Range Force Transmission in Fibrous Matrices Enabled by Tension-Driven Alignment of Fibers

10.1101/048579 ◽

2016 ◽

Cited By ~ 1

Author(s):

Hailong Wang ◽

A.S. Abhilash ◽

Christopher S. Chen ◽

Rebecca G. Wells ◽

Vivek B. Shenoy

Keyword(s):

Long Range ◽

Cell Shape ◽

Collagen Fiber ◽

Constitutive Law ◽

Force Transmission ◽

Collagen Matrices ◽

Fiber Alignment ◽

Aspect Ratios ◽

Range Force ◽

Collagen Fiber Alignment

AbstractCells can sense and respond to mechanical signals over relatively long distances across fibrous extracellular matrices. Recently proposed models suggest that long-range force transmission can be attributed to the nonlinear elasticity or fibrous nature of collagen matrices, yet the mechanism whereby fibers align remains unknown. Moreover, cell shape and anisotropy of cellular contraction are not considered in existing models, although recent experiments have shown that they play crucial roles. Here, we explore all of the key factors that influence long-range force transmission in cell-populated collagen matrices: alignment of collagen fibers, responses to applied force, strain stiffening properties of the aligned fibers, aspect ratios of the cells, and the polarization of cellular contraction. A constitutive law accounting for mechanically-driven collagen fiber reorientation is proposed. We systematically investigate the range of collagen fiber alignment using both finite element simulations and analytical calculations. Our results show that tension-driven collagen fiber alignment plays a crucial role in force transmission. Small critical stretch for fiber alignment, large fiber stiffness and fiber strain-hardening behavior enable long-range interaction. Furthermore, the range of collagen fiber alignment for elliptical cells with polarized contraction is much larger than that for spherical cells with diagonal contraction. A phase diagram showing the range of force transmission as a function of cell shape and polarization and matrix properties is presented. Our results are in good agreement with recent experiments, and highlight the factors that influence long-range force transmission, in particular tension-driven alignment of fibers. Our work has important relevance to biological processes including development, cancer metastasis and wound healing, suggesting conditions whereby cells communicate over long distances.

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Collagen Fiber Alignment Does Not Explain Mechanical Anisotropy in Fibroblast Populated Collagen Gels

Journal of Biomechanical Engineering ◽

10.1115/1.2768104 ◽

2007 ◽

Vol 129 (5) ◽

pp. 642-650 ◽

Cited By ~ 42

Author(s):

Stavros Thomopoulos ◽

Gregory M. Fomovsky ◽

Preethi L. Chandran ◽

Jeffrey W. Holmes

Keyword(s):

Mechanical Behavior ◽

Network Model ◽

Continuum Model ◽

Collagen Fiber ◽

Collagen Gel ◽

Mechanical Anisotropy ◽

Collagen Gels ◽

Fiber Alignment ◽

High Degree ◽

Collagen Fiber Alignment

Many load-bearing soft tissues exhibit mechanical anisotropy. In order to understand the behavior of natural tissues and to create tissue engineered replacements, quantitative relationships must be developed between the tissue structures and their mechanical behavior. We used a novel collagen gel system to test the hypothesis that collagen fiber alignment is the primary mechanism for the mechanical anisotropy we have reported in structurally anisotropic gels. Loading constraints applied during culture were used to control the structural organization of the collagen fibers of fibroblast populated collagen gels. Gels constrained uniaxially during culture developed fiber alignment and a high degree of mechanical anisotropy, while gels constrained biaxially remained isotropic with randomly distributed collagen fibers. We hypothesized that the mechanical anisotropy that developed in these gels was due primarily to collagen fiber orientation. We tested this hypothesis using two mathematical models that incorporated measured collagen fiber orientations: a structural continuum model that assumes affine fiber kinematics and a network model that allows for nonaffine fiber kinematics. Collagen fiber mechanical properties were determined by fitting biaxial mechanical test data from isotropic collagen gels. The fiber properties of each isotropic gel were then used to predict the biaxial mechanical behavior of paired anisotropic gels. Both models accurately described the isotropic collagen gel behavior. However, the structural continuum model dramatically underestimated the level of mechanical anisotropy in aligned collagen gels despite incorporation of measured fiber orientations; when estimated remodeling-induced changes in collagen fiber length were included, the continuum model slightly overestimated mechanical anisotropy. The network model provided the closest match to experimental data from aligned collagen gels, but still did not fully explain the observed mechanics. Two different modeling approaches showed that the level of collagen fiber alignment in our uniaxially constrained gels cannot explain the high degree of mechanical anisotropy observed in these gels. Our modeling results suggest that remodeling-induced redistribution of collagen fiber lengths, nonaffine fiber kinematics, or some combination of these effects must also be considered in order to explain the dramatic mechanical anisotropy observed in this collagen gel model system.

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Collagen Fiber Alignment and Maximum Principle Strain in the Axillary Pouch Predict Location of Failure During Uniaxial Extension

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19044 ◽

2010 ◽

Author(s):

Carrie A. Voycheck ◽

Patrick J. McMahon ◽

Richard E. Debski

Keyword(s):

Maximum Principle ◽

Collagen Fiber ◽

Glenohumeral Joint ◽

External Rotation ◽

Uniaxial Extension ◽

Supraspinatus Tendon ◽

Collagen Fibers ◽

Fiber Alignment ◽

Glenohumeral Ligament ◽

Collagen Fiber Alignment

The glenohumeral joint is frequently dislocated in the anterior direction causing injury to the anteroinferior (axillary pouch, anterior band of the inferior glenohumeral ligament (AB-IGHL)) capsule. [1, 2] When unloaded, the axillary pouch consists of randomly oriented collagen fibers. These fibers play a pertinent role in its function to resist loading in multiple directions during dislocation at the extreme ranges of motion. [3] Maximum principle strain directions in the anteroinferior capsule have been shown to align with the AB-IGHL during increasing external rotation, suggesting that the collagen fibers may become more aligned with loading as well. [4] In addition, at positions of increased external rotation, the peak maximum principle strains in the capsule correspond to the location of a common capsular failure known as the Bankart lesion. [4] Further, an increase in collagen fiber alignment with load in the supraspinatus tendon has been shown in the toe region of the load-elongation curve. [5] Therefore, it was hypothesized that increases in the collagen fiber alignment and maximum principle strain would correlate with the location of tissue failure. The objective of this work was to determine the collagen fiber alignment and maximum principle strain in the axillary pouch during uniaxial extension to failure and to determine if these parameters could predict the location of tissue failure.

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Quantitative mapping of collagen fiber alignment in thick tissue samples using transmission polarized-light microscopy

Journal of Biomedical Optics ◽

10.1117/1.jbo.21.7.071111 ◽

2016 ◽

Vol 21 (7) ◽

pp. 071111 ◽

Cited By ~ 6

Author(s):

Dmitry D. Yakovlev ◽

Marina E. Shvachkina ◽

Maria M. Sherman ◽

Andrey V. Spivak ◽

Alexander B. Pravdin ◽

...

Keyword(s):

Light Microscopy ◽

Collagen Fiber ◽

Polarized Light ◽

Polarized Light Microscopy ◽

Tissue Samples ◽

Fiber Alignment ◽

Quantitative Mapping ◽

Collagen Fiber Alignment

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Collagen Fiber Alignment and Maximum Principal Strain in the Glenohumeral Capsule Predict Location of Failure During Uniaxial Extension

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53492 ◽

2011 ◽

Author(s):

Kelvin Luu ◽

Carrie A. Voycheck ◽

Patrick J. McMahon ◽

Richard E. Debski

Keyword(s):

Collagen Fiber ◽

Glenohumeral Joint ◽

Uniaxial Extension ◽

Principal Strain ◽

Fiber Alignment ◽

Glenohumeral Ligament ◽

Maximum Principal Strain ◽

Inferior Glenohumeral Ligament ◽

Glenohumeral Capsule ◽

Collagen Fiber Alignment

The glenohumeral joint is frequently dislocated causing injury to the glenohumeral capsule (axillary pouch (AP), anterior band of the inferior glenohumeral ligament (AB-IGHL), posterior band of the inferior glenohumeral ligament (PB-IGHL), posterior (Post), and anterosuperior region (AS)). [1, 2] The capsule is a passive stabilizer to the glenohumeral joint and primarily functions to resist dislocation during extreme ranges of motion. [3] When unloaded, the capsule consists of randomly oriented collagen fibers, which play a pertinent role in its function to resist loading in multiple directions. [4] The location of failure in only the axillary pouch has been shown to correspond with the highest degree of collagen fiber orientation and maximum principle strain just prior to failure. [4, 5] However, several discrepancies were found when comparing the collagen fiber alignment between the AB-IGHL, AP, and PB-IGHL. [3,6,7] Therefore, the objective was to determine the collagen fiber alignment and maximum principal strain in five regions of the capsule during uniaxial extension to failure and to determine if these parameters could predict the location of tissue failure. Since the capsule functions as a continuous sheet, we hypothesized that maximum principal strain and peak collagen fiber alignment would correspond with the location of tissue failure in all regions of the glenohumeral capsule.

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Rapid Quantification of 3D Collagen Fiber Alignment and Fiber Intersection Correlations with High Sensitivity

PLoS ONE ◽

10.1371/journal.pone.0131814 ◽

2015 ◽

Vol 10 (7) ◽

pp. e0131814 ◽

Cited By ~ 19

Author(s):

Meng Sun ◽

Alexander B. Bloom ◽

Muhammad H. Zaman

Keyword(s):

Collagen Fiber ◽

High Sensitivity ◽

Fiber Alignment ◽

3D Collagen ◽

Collagen Fiber Alignment ◽

Rapid Quantification

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Effect of Preconditioning on Collagen Fiber Recruitment: Inhomogeneous Properties of Rat Supraspinatus Tendon

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19089 ◽

2010 ◽

Author(s):

Kristin S. Miller ◽

Lena Edelstein ◽

Louis J. Soslowsky

Keyword(s):

Mechanical Properties ◽

Collagen Fiber ◽

Insertion Site ◽

Supraspinatus Tendon ◽

Fiber Alignment ◽

Rigorous Evaluation ◽

Structural Alterations ◽

Testing Protocol ◽

Inhomogeneous Properties ◽

Collagen Fiber Alignment

Cyclic preconditioning is a commonly accepted initial component of any tendon testing protocol. Preconditioning provides tendons with a consistent “history” and stress-strain results become repeatable allowing for rigorous evaluation and comparison. While it is widely accepted that preconditioning is important, changes that occur during preconditioning are not well understood. Micro-structural alterations, such as re-arrangement of collagen fibers, is one proposed mechanism of preconditioning [1,4]. However, this mechanism has not been examined. Therefore, the objective of this study is to locally measure: 1) fiber re-alignment during preconditioning, stress relaxation and tensile testing and 2) corresponding mechanical properties, to address mechanisms of preconditioning as well as tissue nonlinearity and inhomogeneity in the rat supraspinatus tendon. We hypothesize that 1) fiber re-alignment will be greatest in the toe region, but will also occur during preconditioning and 2) mechanical properties and initial collagen fiber alignment will be greater in the midsubstance location of the tendon compared to the tendon-to-bone insertion site.

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Collagen Fiber Re-Alignment and Mechanical Properties in a Mouse Supraspinatus Tendon Model: Examining Changes With Age and Location

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80017 ◽

2012 ◽

Cited By ~ 1

Author(s):

Kristin S. Miller ◽

Brianne K. Connizzo ◽

Elizabeth Feeney ◽

Louis J. Soslowsky

Keyword(s):

Mechanical Properties ◽

Collagen Fiber ◽

Mechanical Load ◽

Mechanical Test ◽

Insertion Site ◽

Supraspinatus Tendon ◽

Tissue Response ◽

Mechanical Stimuli ◽

Fiber Alignment ◽

Collagen Fiber Alignment

One postulated mechanism of tendon structural response to mechanical load is collagen fiber re-alignment. Recently, where collagen fiber re-alignment occurs during a tensile mechanical test has been shown to vary by tendon age and location in a postnatal developmental mouse supraspinatus tendon (SST) model [1]. It is thought that as the tendon matures and its collagen fibril network, collagen cross-links and collagen-matrix interactions develop, its ability to respond quickly to mechanical stimuli hastens [1]. Additionally, the insertion site and midsubstance of postnatal SST may develop differently and at different rates, providing a potential explanation for differences in fiber re-alignment behaviors at the insertion site and midsubstance at postnatal developmental time points [1]. However, collagen fiber re-alignment behavior, in response to mechanical load at a mature age and in comparison to developmental ages, have not been examined. Therefore, the objectives of this study are to locally measure: 1) fiber re-alignment during preconditioning and tensile mechanical testing and 2) to compare local differences in collagen fiber alignment and corresponding mechanical properties to address tissue response to mechanical load in the mature and postnatal developmental mouse SST. We hypothesize that 1) 90 day tendons will demonstrate the largest shift in fiber re-alignment during preconditioning, but will also re-align during the toe- and linear-regions. Additionally, we hypothesize that 2) mechanical properties and initial collagen fiber alignment will be greater in the midsubstance of the tendon compared to the tendon-to-bone insertion site at 90 days, 3) that mechanical properties will increase with age, and that 4) collagen fiber organization at the insertion site will decrease with age.

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