Abstract P351: Grayscale Texture Feature Angular Second Moment Correlates With Collagen Alignment in Carotid Artery Plaques

Introduction: Grayscale (GS) texture features that examine homogeneity and echogenicity have been used to identify vulnerable plaques with in vivo ultrasound imaging have been shown to correlate with plaque tissue composition. However, the relationship of collagen fiber organization to GS texture features extracted from in vivo images is a novel idea to provide additional information about plaque structure. We hypothesize that collagen fiber alignment is clinically relevant to identify vulnerable plaques. The objective of this feasibility study was to use multiscale imaging (in vivo ultrasound and high resolution optical microscopy) to determine how GS texture features are related to plaque collagen structure. Methods: Participants (n=6) scheduled for clinically indicated carotid endarterectomy underwent in vivo carotid ultrasound imaging with texture feature extraction (spatial gray level dependence matrices method for calculating angular second moment [SGLDM-ASM] and grayscale median value [GSM]). Plaque specimens were sent to histopathology and stained with H&E. The collagen fibers in the fibrous cap of the plaque histopathology slides were imaged with liquid crystal based polarization microscopy and quantified using an established software tool (CurveAlign). Correlations between collagen alignment coefficient (range 0-1, 1 represents perfectly aligned fibers) and the texture feature SGLDM-ASM (a measure of homogeneity, higher values are more homogenous) and GSM (a measure of echogenicity higher values are more echogenic) were examined. Results: Participants were mean (SD) 72.5 (6.1) years of age, had 71.67 (8.16) percent stenosis. The mean SGLDM-ASM was 0.0017 (0.0023), the mean SD GSM was 73.13 (30.98). SGLDM-ASM was significantly correlated to collagen alignment (r=0.83; p=0.028). There was no significant correlation detected between GSM and collagen alignment (r=-0.43;p=0.38). Conclusion: Results of this study indicate the potential role for using high resolution optical microscopy with ultrasound to characterize collagen fiber alignment in plaques with measures of homogeneity. Future studies are needed to see how multiscale imaging can be used to inform in vivo imaging for identification of vulnerable plaque features.

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Mechanical properties of tissue formed in vivo are affected by 3D-bioplotted scaffold microarchitecture and correlate with ECM collagen fiber alignment

Connective Tissue Research ◽

10.1080/03008207.2019.1624733 ◽

2019 ◽

Vol 61 (2) ◽

pp. 190-204 ◽

Cited By ~ 2

Author(s):

Pedro Huebner ◽

Paul B. Warren ◽

Daniel Chester ◽

Jeffrey T. Spang ◽

Ashley C. Brown ◽

...

Keyword(s):

Mechanical Properties ◽

Collagen Fiber ◽

Fiber Alignment ◽

Collagen Fiber Alignment

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Microstructural and Mechanical Properties of the Anterolateral Ligament (ALL) of the Knee

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120s00442 ◽

2020 ◽

Vol 8 (7_suppl6) ◽

pp. 2325967120S0044

Author(s):

Ryan Castile ◽

Spencer Lake ◽

Robert Brophy ◽

Ronak Patel

Keyword(s):

Mechanical Properties ◽

Elastic Moduli ◽

Collagen Fiber ◽

Microstructural Analysis ◽

Microstructural Properties ◽

Fiber Alignment ◽

Data Points ◽

Mechanical And Microstructural Properties ◽

Collagen Alignment ◽

Collagen Fiber Alignment

Objectives: The anterolateral ligament (ALL) of the knee has recently emerged as a potential contributor to rotational stability of the knee, with growing interest in ALL reconstruction as a supplement to anterior cruciate ligament reconstruction. The prevalence of the ALL in the knee has varied in anatomic dissection and imaging studies, raising questions about its importance as a knee stabilizer. The purpose of this study was to assess the microstructural and mechanical properties of the anterolateral knee, to better understand the ALL structure compared to the surrounding anterolateral capsule (ALC) and lateral collateral ligament (LCL). A polarized light imaging technique was used to quantify collagen fiber alignment simultaneously with measurement of tensile mechanical properties. Our primary hypothesis was that there is no difference in the microstructural and mechanical properties between the ALL and ALC. Our secondary hypothesis was that the properties of the LCL are different from the ALL and ALC. Methods: Twenty-five knee specimens from sixteen donors (five males, eleven females; mean age 45.6 +/- 6.4; age range 35-59 years; mean BMI 26.5 +/- 8.4) were obtained as determined by a priori power analysis. The anatomic technique to dissect the anterolateral knee structures was performed as described previously. Three tissue samples (LCL, ALL, and ALC) were harvested (Fig. 1). The ALL was taken as a quadrilateral piece of tissue starting posterior/proximal from the lateral femoral epicondyle and ending at the lateral border of Gerdy’s tubercle. During gross dissection, the knee was assessed for the presence or absence of a distinct visible and palpable structure within the area defined as the ALL. Harvested samples were thinned to approximately 1-mm thick using a freezing-stage sliding microtome. Cross-sectional area was measured using a 3D laser scanning system. Four 0.8-mm diameter aluminum beads were attached to the sample surface to enable strain measurement. Mechanical testing was performed with preconditioning followed by both a stress-relaxation test and a quasi-static ramp to failure. Microstructural analysis was performed using transmitted circularly-polarized incident light and a high-resolution, division-of-focal-plane polarization camera. The average degree of linear polarization (AVG DoLP; i.e., mean strength of collagen alignment) and standard deviation of the angle of polarization (STD AoP; i.e., degree of variation in collagen angle orientation) were calculated for the region of interest of each sample. Statistical analysis was performed using Kruskal-Wallis test (assuming nonparametric data) with Dunn’s correction for multiple comparisons. Results: Mechanical analysis of elastic moduli for the toe- and linear-region of the stress-strain curves showed no difference between the ALL and ALC but were significantly higher for the LCL (p<0.0001; Fig. 2). Microstructural analysis of the ALL and ALC during quasi-static ramp to failure showed no difference in AVG DoLP and STD AoP values at all strain levels (Fig. 3). Larger DoLP values (i.e., stronger collagen fiber alignment) were observed for the LCL than both the ALL and ALC (p<0.0001). Larger STD AoP values (i.e., more variation in collagen orientation) were observed for the ALL and ALC compared to the LCL (p<0.0001; Fig. 3). When looking at correlations between mechanical and microstructural properties (Fig. 4), we found clustering of the LCL data points at high linear modulus and AVG DoLP while the ALL and ALC data points were clustered together. Similarly, we found clustering of the LCL at high linear modulus and low STD AoP while the ALL and ALC were clustered together. Only three of 25 knee specimens (12%) were observed to have a distinct, ligamentous structure in the region of the ALL. Interestingly, these distinct ALL samples (outlined in black on figures) showed relatively larger elastic moduli, higher AVG DoLP, and lower STD AoP (i.e., uniform and organized collagen alignment) across the stress-strain curve compared to samples harvested from knees without a distinct ALL. The distinct ALL tissues were also seen clustered near the LCL data points in the correlation plots. Conclusions: Overall, there were no differences in the mechanical and microstructural properties between the ALL and ALC, while the LCL demonstrated different properties compared to both the ALL and ALC. Both the ALC and ALL show significantly weaker collagen fiber alignment and more variation in the direction of collagen fiber alignment compared to the LCL. These findings suggest that the ALL has similar properties to capsule (i.e., ALC). However, when a distinct ALL was present at dissection (12%), the data indicates stronger and more uniform collagen alignment suggestive of more ligament-type qualities. Further research is needed to more precisely define the prevalence and properties of distinct ALLs in the knee.

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In-Situ Deformation of the Aortic Valve Interstitial Cell Nucleus Under Diastolic Loading

Journal of Biomechanical Engineering ◽

10.1115/1.2801670 ◽

2007 ◽

Vol 129 (6) ◽

pp. 880-889 ◽

Cited By ~ 67

Author(s):

Hsiao-Ying Shadow Huang ◽

Jun Liao ◽

Michael S. Sacks

Keyword(s):

Aortic Valve ◽

Collagen Fiber ◽

Structural Integrity ◽

Tissue Level ◽

Fe Model ◽

Mechanical Stimuli ◽

Fiber Alignment ◽

Collagen Fiber Alignment

Within the aortic valve (AV) leaflet resides a population of interstitial cells (AVICs), which serve to maintain tissue structural integrity via protein synthesis and enzymatic degradation. AVICs are typically characterized as myofibroblasts, exhibit phenotypic plasticity, and may play an important role in valve pathophysiology. While it is known that AVICs can respond to mechanical stimuli in vitro, the level of in vivo AVIC deformation and its relation to local collagen fiber reorientation during the cardiac cycle remain unknown. In the present study, the deformation of AVICs was investigated using porcine AV glutaraldehyde fixed under 0–90mmHg transvalvular pressures. The resulting change in nuclear aspect ratio (NAR) was used as an index of overall cellular strain, and dependencies on spatial location and pressure loading levels quantified. Local collagen fiber alignment in the same valves was also quantified using small angle light scattering. A tissue-level finite element (FE) model of an AVIC embedded in the AV extracellular matrix was also used explore the relation between AV tissue- and cellular-level deformations. Results indicated large, consistent increases in AVIC NAR with transvalvular pressure (e.g., from mean of 1.8 at 0mmHg to a mean of 4.8 at 90mmHg), as well as pronounced layer specific dependencies. Associated changes in collagen fiber alignment indicated that little AVIC deformation occurs with the large amount of fiber straightening for pressures below ∼1mmHg, followed by substantial increases in AVIC NAR from 4mmHgto90mmHg. While the tissue-level FE model was able to capture the qualitative response, it also underpredicted the extent of AVIC deformation. This result suggested that additional micromechanical and fiber-compaction effects occur at high pressure levels. The results of this study form the basis of understanding transvalvular pressure-mediated mechanotransduction within the native AV and first time quantitative data correlating AVIC nuclei deformation with AV tissue microstructure and deformation.

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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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