The mechanical properties of human adipose tissues and their relationships to the structure and composition of the extracellular matrix

Adipose tissue (AT) expansion in obesity is characterized by cellular growth and continuous extracellular matrix (ECM) remodeling with increased fibrillar collagen deposition. It is hypothesized that the matrix can inhibit cellular expansion and lipid storage. Therefore, it is important to fully characterize the ECM's biomechanical properties and its interactions with cells. In this study, we characterize and compare the mechanical properties of human subcutaneous and omental tissues, which have different physiological functions. AT was obtained from 44 subjects undergoing surgery. Force/extension and stress/relaxation data were obtained. The effects of osmotic challenge were measured to investigate the cellular contribution to tissue mechanics. Tissue structure and its response to tensile strain were determined using nonlinear microscopy. AT showed nonlinear stress/strain characteristics of up to a 30% strain. Comparing paired subcutaneous and omental samples ( n = 19), the moduli were lower in subcutaneous: initial 1.6 ± 0.8 (means ± SD) and 2.9 ± 1.5 kPa ( P = 0.001), final 11.7 ± 6.4 and 32 ± 15.6 kPa ( P < 0.001), respectively. The energy dissipation density was lower in subcutaneous AT ( n = 13): 0.1 ± 0.1 and 0.3 ± 0.2 kPa, respectively ( P = 0.006). Stress/relaxation followed a two-exponential time course. When the incubation medium was exchanged for deionized water in specimens held at 30% strain, force decreased by 31%, and the final modulus increased significantly. Nonlinear microscopy revealed collagen and elastin networks in close proximity to adipocytes and a larger-scale network of larger fiber bundles. There was considerable microscale heterogeneity in the response to strain in both cells and matrix fibers. These results suggest that subcutaneous AT has greater capacity for expansion and recovery from mechanical deformation than omental AT.

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Multiscale Mechanical Simulations of Cell Compacted Collagen Gels

Journal of Biomechanical Engineering ◽

10.1115/1.4024460 ◽

2013 ◽

Vol 135 (7) ◽

Cited By ~ 27

Author(s):

Maziar Aghvami ◽

V. H. Barocas ◽

E. A. Sander

Keyword(s):

Mechanical Properties ◽

Extracellular Matrix ◽

Mechanical Stimulation ◽

Collagen Gel ◽

Theoretical Models ◽

Isometric Tension ◽

Collagen Gels ◽

Ecm Remodeling ◽

Engineered Tissues ◽

Mechanical Models

Engineered tissues are commonly stretched or compressed (i.e., conditioned) during culture to stimulate extracellular matrix (ECM) production and to improve the mechanical properties of the growing construct. The relationships between mechanical stimulation and ECM remodeling, however, are complex, interdependent, and dynamic. Thus, theoretical models are required for understanding the underlying phenomena so that the conditioning process can be optimized to produce functional engineered tissues. Here, we continue our development of multiscale mechanical models by simulating the effect of cell tractions on developing isometric tension and redistributing forces in the surrounding fibers of a collagen gel embedded with explants. The model predicted patterns of fiber reorganization that were similar to those observed experimentally. Furthermore, the inclusion of cell compaction also changed the distribution of fiber strains in the gel compared to the acellular case, particularly in the regions around the cells where the highest strains were found.

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Lung tissue mechanics and extracellular matrix composition in a murine model of silicosis

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.4.1400 ◽

2001 ◽

Vol 90 (4) ◽

pp. 1400-1406 ◽

Cited By ~ 47

Author(s):

Débora S. Faffe ◽

Gabriela H. Silva ◽

Pedro M. P. Kurtz ◽

Elnara M. Negri ◽

Vera L. Capelozzi ◽

...

Keyword(s):

Mechanical Properties ◽

Extracellular Matrix ◽

Lung Tissue ◽

Elastic System ◽

Elastic Fiber ◽

Dynamic Mechanical Properties ◽

Tissue Mechanics ◽

Matrix Composition ◽

Elastic Fibers ◽

Oxytalan Fibers

The dynamic mechanical properties of lung tissue and its contents of collagen and elastic fibers were studied in strips prepared from mice instilled intratracheally with saline (C) or silica [15 (S15) and 30 days (S30) after instillation]. Resistance, elastance, and hysteresivity were studied during oscillations at different frequencies on S15 and S30. Elastance increased from C to silica groups but was similar between S15 and S30. Resistance was augmented from C to S15 and S30 and was greater in S30 than in S15 at higher frequencies. Hysteresivity was higher in S30 than in C and S15. Silica groups presented a greater amount of collagen than did C. Elastic fiber content increased progressively along time. This increment was related to the higher amount of oxytalan fibers at 15 and 30 days, whereas elaunin and fully developed elastic fibers were augmented only at 30 days. Silicosis led not only to pulmonary fibrosis but also to fibroelastosis, thus assigning a major role to the elastic system in the silicotic lung.

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Extracellular Matrix in Cardiac Tissue Mechanics and Physiology: Role of Collagen Accumulation

10.5772/intechopen.96585 ◽

2021 ◽

Author(s):

Kristen LeBar ◽

Zhijie Wang

Keyword(s):

Heart Failure ◽

Mechanical Properties ◽

Extracellular Matrix ◽

Pressure Overload ◽

Volume Overload ◽

Tissue Mechanics ◽

Functional Changes ◽

Collagen Accumulation ◽

Heart Failure Progression

The extracellular matrix (ECM) forms a mesh surrounding tissue, made up of fibrous and non-fibrous proteins that contribute to the cellular function, mechanical properties of the tissue and physiological function of the organ. The cardiac ECM remodels in response to mechanical alterations (e.g., pressure overload, volume overload) or injuries (e.g., myocardial infarction, bacterial infection), which further leads to mechanical and functional changes of the heart. Collagen, the most prevalent ECM protein in the body, contributes significantly to the mechanical behavior of myocardium during disease progression. Alterations in collagen fiber morphology and alignment, isoform, and cross-linking occur during the progression of various cardiac diseases. Acute or compensatory remodeling of cardiac ECM maintains normal cardiac function. However, chronic or decompensatory remodeling eventually results in heart failure, and the exact mechanism of transition into maladaptation remains unclear. This review aims to summarize the primary role of collagen accumulation (fibrosis) in heart failure progression, with a focus on its effects on myocardial tissue mechanical properties and cellular and organ functions.

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Physical and functional cell-matrix uncoupling in a developing tissue under tension

10.1101/306696 ◽

2018 ◽

Cited By ~ 1

Author(s):

Amsha Proag ◽

Bruno Monier ◽

Magali Suzanne

Keyword(s):

Mechanical Properties ◽

Extracellular Matrix ◽

Crucial Role ◽

Myosin Ii ◽

Tissue Mechanics ◽

Mechanical Tension ◽

Cell Matrix ◽

Independent Mechanism ◽

Ecm Degradation ◽

Envelope Layer

AbstractTissue mechanics play a crucial role in organ development. It relies on cells and extracellular matrix (ECM) mechanical properties, but also on their reciprocal interaction. The relative physical contribution of cells and ECM to morphogenesis is poorly understood. Here, we dissected the mechanics of the envelope of the Drosophila developing leg, an epithelium submitted to a number of mechanical stresses: first stretched, it is then torn apart and withdrawn to free the leg. During stretching, we found that mechanical tension is entirely borne by the ECM at first, then by the cellular monolayer as soon as they detach themselves from one another. Then, each envelope layer is removed by an independent mechanism: while ECM withdraws following local proteolysis, cellular monolayer withdrawal is independent of ECM degradation and driven by an autonomous myosin-II-dependent contraction. These results reveal a physical and functional cell-matrix uncoupling that could timely control tissue dynamics during development.

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Time-Course Changes of Extracellular Matrix Encoding Genes Expression Level in the Spinal Cord Following Contusion Injury—A Data-Driven Approach

International Journal of Molecular Sciences ◽

10.3390/ijms22041744 ◽

2021 ◽

Vol 22 (4) ◽

pp. 1744

Author(s):

Andrea Bighinati ◽

Zahra Khalajzeyqami ◽

Vito Antonio Baldassarro ◽

Luca Lorenzini ◽

Maura Cescatti ◽

...

Keyword(s):

Gene Expression ◽

Spinal Cord ◽

Spinal Cord Injury ◽

Extracellular Matrix ◽

Time Course ◽

Post Injury ◽

Active Lesion ◽

Ecm Remodeling ◽

Cord Injury ◽

Data Driven Approach

The involvement of the extracellular matrix (ECM) in lesion evolution and functional outcome is well recognized in spinal cord injury. Most attention has been dedicated to the “core” area of the lesion and scar formation, while only scattered reports consider ECM modification based on the temporal evolution and the segments adjacent to the lesion. In this study, we investigated the expression profile of 100 genes encoding for ECM proteins at 1, 8 and 45 days post-injury, in the spinal cord segments rostral and caudal to the lesion and in the scar segment, in a rat model. During both the active lesion phases and the lesion stabilization, we observed an asymmetric gene expression induced by the injury, with a higher regulation in the rostral segment of genes involved in ECM remodeling, adhesion and cell migration. Using bioinformatic approaches, the metalloproteases inhibitor Timp1 and the hyaluronan receptor Cd44 emerged as the hub genes at all post-lesion times. Results from the bioinformatic gene expression analysis were then confirmed at protein level by tissue analysis and by cell culture using primary astrocytes. These results indicated that ECM regulation also takes place outside of the lesion area in spinal cord injury.

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Stress relaxation in tunable gels

Soft Matter ◽

10.1039/d1sm00091h ◽

2021 ◽

Author(s):

Chiara Raffaelli ◽

Wouter G Ellenbroek

Keyword(s):

Mechanical Properties ◽

Drug Delivery ◽

Tissue Engineering ◽

Stress Relaxation

Hydrogels are a staple of biomaterials development. Optimizing their use in e.g. drug delivery or tissue engineering requires a solid understanding of how to adjust their mechanical properties. Here, we...

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Evolution of Meniscal Biomechanical Properties with Growth: An Experimental and Numerical Study

Bioengineering ◽

10.3390/bioengineering8050070 ◽

2021 ◽

Vol 8 (5) ◽

pp. 70

Author(s):

Marco Ferroni ◽

Beatrice Belgio ◽

Giuseppe M. Peretti ◽

Alessia Di Giancamillo ◽

Federica Boschetti

Keyword(s):

Mechanical Properties ◽

Stress Relaxation ◽

Developmental Stage ◽

Mechanical Response ◽

Numerical Study ◽

Numerical Models ◽

Mechanical Stimulus ◽

Specific Response ◽

Mechanical Parameters ◽

Biochemical Analyses

The menisci of the knee are complex fibro-cartilaginous tissues that play important roles in load bearing, shock absorption, joint lubrication, and stabilization. The objective of this study was to evaluate the interaction between the different meniscal tissue components (i.e., the solid matrix constituents and the fluid phase) and the mechanical response according to the developmental stage of the tissue. Menisci derived from partially and fully developed pigs were analyzed. We carried out biochemical analyses to quantify glycosaminoglycan (GAG) and DNA content according to the developmental stage. These values were related to tissue mechanical properties that were measured in vitro by performing compression and tension tests on meniscal specimens. Both compression and tension protocols consisted of multi-ramp stress–relaxation tests comprised of increasing strains followed by stress–relaxation to equilibrium. To better understand the mechanical response to different directions of mechanical stimulus and to relate it to the tissue structural composition and development, we performed numerical simulations that implemented different constitutive models (poro-elasticity, viscoelasticity, transversal isotropy, or combinations of the above) using the commercial software COMSOL Multiphysics. The numerical models also allowed us to determine several mechanical parameters that cannot be directly measured by experimental tests. The results of our investigation showed that the meniscus is a non-linear, anisotropic, non-homogeneous material: mechanical parameters increase with strain, depend on the direction of load, and vary among regions (anterior, central, and posterior). Preliminary numerical results showed the predominant role of the different tissue components depending on the mechanical stimulus. The outcomes of biochemical analyses related to mechanical properties confirmed the findings of the numerical models, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint. During maturation, the increase in compressive moduli could be explained by cell differentiation from fibroblasts to metabolically active chondrocytes, as indicated by the found increase in GAG/DNA ratio. The changes of tensile mechanical response during development could be related to collagen II accumulation during growth. This study provides new information on the changes of tissue structural components during maturation and the relationship between tissue composition and mechanical response.

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Age related extracellular matrix and interstitial cell phenotype in pulmonary valves

Scientific Reports ◽

10.1038/s41598-020-78507-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Shaohua Wu ◽

Vikas Kumar ◽

Peng Xiao ◽

Mitchell Kuss ◽

Jung Yul Lim ◽

...

Keyword(s):

Mechanical Properties ◽

Extracellular Matrix ◽

Heart Valve ◽

Cell Phenotype ◽

Primary Concern ◽

Ross Operation ◽

Extracellular Matrix Components ◽

Matrix Components

AbstractHeart valve disease is a common manifestation of cardiovascular disease and is a significant cause of cardiovascular morbidity and mortality worldwide. The pulmonary valve (PV) is of primary concern because of its involvement in common congenital heart defects, and the PV is usually the site for prosthetic replacement following a Ross operation. Although effects of age on valve matrix components and mechanical properties for aortic and mitral valves have been studied, very little is known about the age-related alterations that occur in the PV. In this study, we isolated PV leaflets from porcine hearts in different age groups (~ 4–6 months, denoted as young versus ~ 2 years, denoted as adult) and studied the effects of age on PV leaflet thickness, extracellular matrix components, and mechanical properties. We also conducted proteomics and RNA sequencing to investigate the global changes of PV leaflets and passage zero PV interstitial cells in their protein and gene levels. We found that the size, thickness, elastic modulus, and ultimate stress in both the radial and circumferential directions and the collagen of PV leaflets increased from young to adult age, while the ultimate strain and amount of glycosaminoglycans decreased when age increased. Young and adult PV had both similar and distinct protein and gene expression patterns that are related to their inherent physiological properties. These findings are important for us to better understand the physiological microenvironments of PV leaflet and valve cells for correctively engineering age-specific heart valve tissues.

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