Induction of longitudinal fiber alignment in collagen gel with static mechanical loading

2019 ◽  
Vol 2019.32 (0) ◽  
pp. 2D33
Author(s):  
Ryota KAWAMURA ◽  
Eijiro MAEDA ◽  
Takeo MATSUMOTO
Keyword(s):  
Mechanical Loading ◽  
Collagen Gel ◽  
Fiber Alignment ◽  
Static Mechanical ◽  
Longitudinal Fiber

scholarly journals Experimental and Modeling Study of Collagen Scaffolds with the Effects of Crosslinking and Fiber Alignment

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Bin Xu ◽  
Ming-Jay Chow ◽  
Yanhang Zhang
Keyword(s):  
Magnetic Particles ◽  
Type I Collagen ◽  
Collagen Gel ◽  
Collagen Type I ◽  
Mechanical Tests ◽  
Type I ◽  
Collagen Scaffolds ◽  
Fiber Alignment ◽  
Biaxial Tensile ◽  
Anisotropic Mechanical Properties

Collagen type I scaffolds are commonly used due to its abundance, biocompatibility, and ubiquity. Most applications require the scaffolds to operate under mechanical stresses. Therefore understanding and being able to control the structural-functional integrity of collagen scaffolds becomes crucial. Using a combined experimental and modeling approach, we studied the structure and function of Type I collagen gel with the effects of spatial fiber alignment and crosslinking. Aligned collagen scaffolds were created through the flow of magnetic particles enmeshed in collagen fibrils to mimic the anisotropy seen in native tissue. Inter- and intra- molecular crosslinking was modified chemically with Genipin to further improve the stiffness of collagen scaffolds. The anisotropic mechanical properties of collagen scaffolds were characterized using a planar biaxial tensile tester and parallel plate rheometer. The tangent stiffness from biaxial tensile test is two to three orders of magnitude higher than the storage moduli from rheological measurements. The biphasic nature of collagen gel was discussed and used to explain the mechanical behavior of collagen scaffolds under different types of mechanical tests. An anisotropic hyperelastic constitutive model was used to capture the characteristics of the stress-strain behavior exhibited by collagen scaffolds.

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

2007 ◽  
Vol 129 (5) ◽  
pp. 642-650 ◽  
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.

scholarly journals Microscale Fiber Network Alignment Affects Macroscale Failure Behavior in Simulated Collagen Tissue Analogs

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Mohammad F. Hadi ◽  
Victor H. Barocas
Keyword(s):  
Type I Collagen ◽  
Soft Tissues ◽  
Collagen Gel ◽  
Aortic Aneurysms ◽  
Failure Behavior ◽  
Fe Model ◽  
Type I ◽  
Fiber Network ◽  
Fiber Alignment ◽  
Damage And Failure

A tissue's microstructure determines its failure properties at larger length scales, however, the specific relationship between microstructure and macroscopic failure in native and engineered soft tissues (such as capsular ligaments, aortic aneurysms, or vascular grafts) has proven elusive. In this study, variations in the microscale fiber alignment in collagen gel tissue analogs were modeled in order to understand their effects on macroscale damage and failure outcomes. The study employed a multiscale finite-element (FE) model for damage and failure in collagen-based materials. The model relied on microstructural representative volume elements (RVEs) that consisted of stochastically-generated networks of discrete type-I collagen fibers. Fiber alignment was varied within RVEs and between layers of RVEs in a macroscopic FE model of a notched dogbone geometry. The macroscale stretch and the microscale response of fibers for each of the differently aligned cases were compared as the dogbone was uniaxially extended to failure. Networks with greater fiber alignment parallel to the direction of extension failed at smaller strains (with a 6–22% reduction in the Green strain at failure), however, at greater grip forces (a 28–60% increase) than networks with fibers aligned perpendicular to the extension. Alternating layers of crisscrossed network alignments (aligned ±45 deg to the direction of extension) failed at smaller strains but at greater grip forces than those created using one fiber alignment type. In summary, variations in microscale structure via fiber alignment produced different macroscale failure trends. To conclude, these findings may be significant in the realm of tissue engineering and in soft tissue biomechanics.

scholarly journals In vivo tibiofemoral cartilage strain mapping under static mechanical loading using continuous GRASP‐MRI

2019 ◽  
Vol 51 (2) ◽  
pp. 426-434
Author(s):  
Rajiv G. Menon ◽  
Marcelo V.W. Zibetti ◽  
Ravinder R. Regatte
Keyword(s):  
Mechanical Loading ◽  
Strain Mapping ◽  
Static Mechanical

OCT Detects Collagen Fiber Alignment in Human Cadaveric Lumbar Facet Capsular Ligament During Mechanical Loading

2012 ◽  
Author(s):  
Amy A. Claeson ◽  
Yi-Jou Yeh ◽  
Taner Akkin ◽  
Beth A. Winkelstein ◽  
David J. Nuckley ◽  
...  
Keyword(s):  
Mechanical Loading ◽  
Collagen Fiber ◽  
Facet Joint ◽  
Spinous Process ◽  
Posterior Portion ◽  
Fiber Alignment ◽  
Capsular Ligament ◽  
Articular Process ◽  
Lumbar Facet ◽  
Collagen Fiber Alignment

The lumbar facet capsular ligament (FCL) is a highly collagenous structure that functions to constrain lumbar spinal motion. Two FCLs are found at each level of the spine, flanking the spinous process. The ligament spans from the inferior articular process (IAP) of the superior vertebra to the superior articular process (SAP) of the inferior vertebra forming the posterior portion of the facet capsule (Figure 1). Along with the anteriorly located ligamentum flavum, the FCL contains the synovial fluid that lubricates the facet joint. The facet capsule is highly innervated [1] and may be involved in low back pain or proprioception. Thus, changes in collagen fiber alignment from mechanical loading may activate mechanoreceptors leading to proprioception or nociceptors leading to pain.

Dupuytren's Contracture and Microvessels

1981 ◽  
Vol 39 ◽  
pp. 470-471
Author(s):  
C. W. Klscher ◽  
D. Speer
Keyword(s):  
Hypertrophic Scar ◽  
Active Form ◽  
Scar Tissue ◽  
Vascular Supply ◽  
Fiber Bundles ◽  
Dupuytren’S Contracture ◽  
Palmar Fascia ◽  
Immune Disease ◽  
Dupuytren's Contracture ◽  
Longitudinal Fiber

Dupuytren's Contracture is a nodular proliferation of the longitudinal fiber bundles of palmar fascia with its attendant contraction. The factors attributed to its etiology have included trauma, diabetes, alcoholism, arthritis, and auto-immune disease. The tissue has been observed by electron microscopy and found to contain myofibroblasts.Dupuytren's Contracture constitutes a scar, and as such, excessive collagen can be observed, along with an active form of fibroblast.Previous studies of the hypertrophic scar have led us to propose that integral in the initiation and sustenance of scar tissue is a profusion of microvascular regeneration, much of which becomes and remains occluded producing a hypoxia which stimulates fibroblast synthesis. Thus, when considering a study of Dupuytren's Contracture, we predicted finding occluded microvessels at or near the fascial scarring focus.Three cases of Dupuytren's Contracture yielded similar specimens, which were fixed in Karnovskys fluid for 2 to 20 days. Upon removal of the contracture bands care was taken to include the contiguous fatty and areolar tissue which contain the vascular supply and to identify the junctional area between old and new fascia.

Facilitated migration of cells from a transected peripheral nerve over collagen fibers: in vivo observations

1989 ◽  
Vol 47 ◽  
pp. 888-889
Author(s):  
Arthur J. Wasserman ◽  
Azam Rizvi ◽  
George Zazanis ◽  
Frederick H. Silver
Keyword(s):  
Sciatic Nerve ◽  
Peripheral Nerve ◽  
Collagen Gel ◽  
Collagen Fibers ◽  
Control Group ◽  
Guide Tube ◽  
Sprague Dawley ◽  
Silicone Tube ◽  
Thin Sections

In cases of peripheral nerve damage the gap between proximal and distal stumps can be closed by suturing the ends together, using a nerve graft, or by nerve tubulization. Suturing allows regeneration but does not prevent formation of painful neuromas which adhere to adjacent tissues. Autografts are not reported to be as good as tubulization and require a second surgical site with additional risks and complications. Tubulization involves implanting a nerve guide tube that will provide a stable environment for axon proliferation while simultaneously preventing formation of fibrous scar tissue. Supplementing tubes with a collagen gel or collagen plus extracellular matrix factors is reported to increase axon proliferation when compared to controls. But there is no information regarding the use of collagen fibers to guide nerve cell migration through a tube. This communication reports ultrastructural observations on rat sciatic nerve regeneration through a silicone nerve stent containing crosslinked collagen fibers.Collagen fibers were prepared as described previously. The fibers were threaded through a silicone tube to form a central plug. One cm segments of sciatic nerve were excised from Sprague Dawley rats. A control group of rats received a silicone tube implant without collagen while an experimental group received the silicone tube containing a collagen fiber plug. At 4 and 6 weeks postoperatively, the implants were removed and fixed in 2.5% glutaraldehyde buffered by 0.1 M cacodylate containing 1.5 mM CaCl2 and balanced by 0.1 M sucrose. The explants were post-fixed in 1% OSO4, block stained in 1% uranyl acetate, dehydrated and embedded in Epon. Axons were counted on montages prepared at a total magnification of 1700x. Montages were viewed through a dissecting microscope. Thin sections were sampled from the proximal, middle and distal regions of regenerating sciatic plugs.

Sign in / Sign up

Export Citation Format

Share Document