Droplet Based Measurements of Mechanical Forces and Material Properties, In Vivo and In Vitro

Observations of crack damage in the tooth structure from in vivo studies and in vitro experimental thermal cycling studies were combined with numerical analysis techniques to identify and isolate the influence of thermal stresses an the creation and propagation of cracks in teeth. The factors considered in this study included: (a) variations in tooth type or geometry (molar, bicuspid, etc.), (b) tooth age, (c) material properties of the tooth, (d) the magnitude of the change in the temperature of the environment surrounding the tooth, and (e) the thermal resistance between the tooth and the medium surrounding the tooth.

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Force-dependent vinculin binding to talin in live cells: a crucial step in anchoring the actin cytoskeleton to focal adhesions

AJP Cell Physiology ◽

10.1152/ajpcell.00122.2013 ◽

2014 ◽

Vol 306 (6) ◽

pp. C607-C620 ◽

Cited By ~ 57

Author(s):

Hiroaki Hirata ◽

Hitoshi Tatsumi ◽

Chwee Teck Lim ◽

Masahiro Sokabe

Keyword(s):

Actin Cytoskeleton ◽

Focal Adhesions ◽

Living Cells ◽

Live Cells ◽

Mechanical Forces ◽

Actin Network ◽

Crucial Step

Mechanical forces play a pivotal role in the regulation of focal adhesions (FAs) where the actin cytoskeleton is anchored to the extracellular matrix through integrin and a variety of linker proteins including talin and vinculin. The localization of vinculin at FAs depends on mechanical forces. While in vitro studies have demonstrated the force-induced increase in vinculin binding to talin, it remains unclear whether such a mechanism exists at FAs in vivo. In this study, using fibroblasts cultured on elastic silicone substrata, we have examined the role of forces in modulating talin-vinculin binding at FAs. Stretching the substrata caused vinculin accumulation at talin-containing FAs, and this accumulation was abrogated by expressing the talin-binding domain of vinculin (domain D1, which inhibits endogenous vinculin from binding to talin). These results indicate that mechanical forces loaded to FAs facilitate vinculin binding to talin at FAs. In cell-protruding regions, the actin network moved backward over talin-containing FAs in domain D1-expressing cells while it was anchored to FAs in control cells, suggesting that the force-dependent vinculin binding to talin is crucial for anchoring the actin cytoskeleton to FAs in living cells.

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Growth factors are released by mechanically wounded endothelial cells.

The Journal of Cell Biology ◽

10.1083/jcb.109.2.811 ◽

1989 ◽

Vol 109 (2) ◽

pp. 811-822 ◽

Cited By ~ 294

Author(s):

P L McNeil ◽

L Muthukrishnan ◽

E Warder ◽

P A D'Amore

Keyword(s):

Endothelial Cells ◽

Plasma Membrane ◽

Growth Factors ◽

Growth Factor ◽

Mechanical Forces ◽

Fibroblast Growth ◽

Growth Promoting ◽

Transient Plasma

Growth factors may be required at sites of mechanical injury and normal wear and tear in vivo, suggesting that the direct action of mechanical forces on cells could lead to growth factor release. Scraping of cells from the tissue culture substratum at 37 degrees C was used to test this possibility. We show that scraping closely mimics in vitro both the transient plasma membrane wounds observed in cells subject to mechanical forces in vivo (McNeil, P. L., and S. Ito. 1989. Gastroenterology. 96:1238-1248) and the transient plasma membrane wounds shown here to occur in endothelial cells under normal culturing conditions. Scraping of endothelial cells from the culturing substratum released into the culture medium a potent growth-promoting activity for Swiss 3T3 fibroblasts. Growth-promoting activity was released rapidly (within 5 min) after scraping but was not subsequently degraded by the endothelial cells for at least 24 h thereafter. A greater quantity of growth-promoting activity was released by cells scraped 4 h after plating than by those scraped 4 or 7 d afterwards. Thus release is not due to scraping-induced disruption of extracellular matrix. Release was only partially cold inhibitable, was poorly correlated with the level of cell death induced by scraping, and did not occur when cells were killed with metabolic poisons. These results suggest that mechanical disruption of plasma membrane, either transient or permanent, is the essential event leading to release. A basic fibroblast growth factor-like molecule and not platelet-derived growth factor appears to be partially responsible for the growth-promoting activity. We conclude that one biologically relevant route of release of basic fibroblast growth factor, a molecule which lacks the signal peptide sequence for transport into the endoplasmic reticulum, could be directly through mechanically induced membrane disruptions of endothelial cells growing in vivo and in vitro.

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Integrin signaling's potential for mediating gene expression in hypertrophying skeletal muscle

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.1.337 ◽

2000 ◽

Vol 88 (1) ◽

pp. 337-343 ◽

Cited By ~ 73

Author(s):

James A. Carson ◽

Lei Wei

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Signaling Pathway ◽

Mechanical Load ◽

Integrin Signaling ◽

Mechanical Forces ◽

Growth Factor Signaling ◽

Muscle Gene

Overloaded skeletal muscle undergoes dramatic shifts in gene expression, which alter both the phenotype and mass. Molecular biology techniques employing both in vivo and in vitro hypertrophy models have demonstrated that mechanical forces can alter skeletal muscle gene regulation. This review's purpose is to support integrin-mediated signaling as a candidate for mechanical load-induced hypertrophy. Research quantifying components of the integrin-signaling pathway in overloaded skeletal muscle have been integrated with knowledge regarding integrins role during development and cardiac hypertrophy, with the hope of demonstrating the pathway's importance. The role of integrin signaling as an integrator of mechanical forces and growth factor signaling during hypertrophy is discussed. Specific components of integrin signaling, including focal adhesion kinase and low-molecular-weight GTPase Rho are mentioned as downstream targets of this signaling pathway. There is a need for additional mechanistic studies capable of providing a stronger linkage between integrin-mediated signaling and skeletal muscle hypertrophy; however, there appears to be abundant justification for this type of research.

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Cross-linking Electrospun Polydioxanone-Soluble Elastin Blends: Material Characterization

Journal of Engineered Fibers and Fabrics ◽

10.1177/155892500800300101 ◽

2008 ◽

Vol 3 (1) ◽

pp. 155892500800300 ◽

Cited By ~ 6

Author(s):

Michael J. McClure ◽

Scott A. Sell ◽

Catherine P. Barnes ◽

Whitney C. Bowen ◽

Gary L. Bowlin

Keyword(s):

Femoral Artery ◽

Material Properties ◽

In Vivo Studies ◽

Uniaxial Tensile ◽

Cross Linking ◽

Materials Testing ◽

Uniaxial Tensile Testing ◽

The Cross

The purpose of this study was to establish whether material properties of elastin co-electrospun with polydioxanone (PDO) would change over time in both the uncross-linked state and the cross-linked state. First, uncross-linked scaffolds were placed in phosphate buffered saline (PBS) for three separate time periods: 15 minutes, 1 hour, and 24 hours, and subsequently tested using uniaxial materials testing. Several cross-linking reagents were then investigated to verify their ability to crosslink elastin: 1–ethyl-3–(dimethylaminopropyl)-carbodiimide (EDC), ethylene glycol diglycidyl ether (EGDE), and genipin. Uniaxial tensile testing was performed on scaffolds cross-linked with EDC and genipin, yielding results that warranted further investigation for PDO-elastin blends. Material properties of the cross-linked scaffolds were then found within range of both pig femoral artery and human femoral artery. These results demonstrate PDO-elastin blends could potentially be favorable as vascular grafts, thus warranting future in vitro and in vivo studies.

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CXCL1, CCL2, and CCL5 modulation by microbial and biomechanical signals in periodontal cells and tissues—in vitro and in vivo studies

Clinical Oral Investigations ◽

10.1007/s00784-020-03244-1 ◽

2020 ◽

Vol 24 (10) ◽

pp. 3661-3670 ◽

Cited By ~ 4

Author(s):

Birgit Rath-Deschner ◽

Svenja Memmert ◽

Anna Damanaki ◽

Marjan Nokhbehsaim ◽

Sigrun Eick ◽

...

Keyword(s):

Tooth Movement ◽

Orthodontic Tooth Movement ◽

In Vivo Studies ◽

Mechanical Forces ◽

Rt Pcr ◽

Mechanical Signals ◽

Periodontal Infection ◽

Experimental Periodontitis

Abstract Objectives This study was established to investigate whether the chemokines CXCL1, CCL2, and CCL5 are produced in periodontal cells and tissues and, if so, whether their levels are regulated by microbial and/or mechanical signals. Materials and methods The chemokine expression and protein levels in gingival biopsies from patients with and without periodontitis were analyzed by RT-PCR and immunohistochemistry. The chemokines were also analyzed in gingival biopsies from rats subjected to experimental periodontitis and/or orthodontic tooth movement. Additionally, chemokine levels were determined in periodontal fibroblasts exposed to the periodontopathogen Fusobacterium nucleatum and mechanical forces by RT-PCR and ELISA. Results Higher CXCL1, CCL2, and CCL5 levels were found in human and rat gingiva from sites of periodontitis as compared with periodontally healthy sites. In the rat experimental periodontitis model, the bacteria-induced upregulation of these chemokines was significantly counteracted by orthodontic forces. In vitro, F. nucleatum caused a significant upregulation of all chemokines at 1 day. When the cells were subjected simultaneously to F. nucleatum and mechanical forces, the upregulation of chemokines was significantly inhibited. The transcriptional findings were paralleled at protein level. Conclusions This study provides original evidence in vitro and in vivo that the chemokines CXCL1, CCL2, and CCL5 are regulated by both microbial and mechanical signals in periodontal cells and tissues. Furthermore, our study revealed that biomechanical forces can counteract the stimulatory actions of F. nucleatum on these chemokines. Clinical relevance Mechanical loading might aggravate periodontal infection by compromising the recruitment of immunoinflammatory cells.

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The Development of Physiological Compliant Abdominal Aortic Aneurysm Models for In Vitro Flow Studies

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206608 ◽

2009 ◽

Author(s):

Timothy J. Corbett ◽

Barry J. Doyle ◽

Anthony Callanan ◽

Tim M. McGloughlin

Keyword(s):

Abdominal Aortic Aneurysm ◽

Aortic Aneurysm ◽

Material Properties ◽

Abdominal Aortic Aneurysms ◽

Aortic Aneurysms ◽

Flow Loop ◽

The Past ◽

Abdominal Aortic

A vast amount of experimental research has been undertaken in the past decade to investigate different aspects of preoperative and postoperative abdominal aortic aneurysms (AAAs). Much of this research has been based on the use of mock arteries in an in vitro flow loop to mimic the behaviour of the abdominal aorta in vivo [1]. These models should be reproducible, have consistent material properties, consistent thickness and be physiological in behaviour.

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Alteration of Bone’s Nonlinear Elastic and Viscoelastic Nanomechanical Properties Is Triggered by Low Intensity Pulsed Ultrasound

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206711 ◽

2009 ◽

Author(s):

Suzanne Ferreri ◽

Yi-Xian Qin

Keyword(s):

Mechanical Strength ◽

Material Properties ◽

Signal Intensity ◽

In Vivo Studies ◽

Dynamic Mechanical ◽

Mechanical Signals ◽

Ultrasound Signal ◽

Ultrasound Signals

Dynamic mechanotransduction, particularly under high frequency, low amplitude signals, has been proven effective in mediating bone loss and improving mechanical strength for tissues affected by estrogen deficient osteopenia. Ultrasound, which behaves as an alternating pressure wave in bone, may offer an effective, non-invasive technology for delivery of anabolic signals. In vitro, dynamic mechanical signals delivered using ultrasound have been shown to increase osteoblast proliferation [1], and in vivo studies have established ultrasound as an effective treatment for delayed and non-union fractures [2]. Previously, we showed that ultrasound signals similar to those currently used in a clinical setting for fracture healing were effective in mediating decreases in bone volume and mechanical strength at the millimeter length-scale in response to estrogen deficient osteopenia [3]. Due to bone’s inherent viscoelasticity and the dynamic nature of the applied ultrasound signals, it is particularly important to consider both elastic and viscous components of bone’s adaptive response to applied loads. In light of these findings, the goal of this study was to determine the role of therapeutic ultrasound signal intensity in modulating changes in bone’s nanoscale elastic and viscoelastic material properties associated with estrogen deficient osteopenia. We hypothesize that bone is sensitive to dynamic mechanical signals delivered via ultrasound and that bone’s tissue level nano-scale material properties, particularly nonlinear viscoelastic properties, are sensitive to ultrasound signal intensity.

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Piezo1 links mechanical forces to red blood cell volume

eLife ◽

10.7554/elife.07370 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 186

Author(s):

Stuart M Cahalan ◽

Viktor Lukacs ◽

Sanjeev S Ranade ◽

Shu Chien ◽

Michael Bandell ◽

...

Keyword(s):

Blood Cell ◽

Calcium Influx ◽

Mechanical Stretch ◽

Conditional Knockout ◽

Volume Control ◽

Mechanical Forces ◽

Gardos Channel

Red blood cells (RBCs) experience significant mechanical forces while recirculating, but the consequences of these forces are not fully understood. Recent work has shown that gain-of-function mutations in mechanically activated Piezo1 cation channels are associated with the dehydrating RBC disease xerocytosis, implicating a role of mechanotransduction in RBC volume regulation. However, the mechanisms by which these mutations result in RBC dehydration are unknown. In this study, we show that RBCs exhibit robust calcium entry in response to mechanical stretch and that this entry is dependent on Piezo1 expression. Furthermore, RBCs from blood-cell-specific Piezo1 conditional knockout mice are overhydrated and exhibit increased fragility both in vitro and in vivo. Finally, we show that Yoda1, a chemical activator of Piezo1, causes calcium influx and subsequent dehydration of RBCs via downstream activation of the KCa3.1 Gardos channel, directly implicating Piezo1 signaling in RBC volume control. Therefore, mechanically activated Piezo1 plays an essential role in RBC volume homeostasis.

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Adding exogenous biglycan or decorin improves tendon formation for equine peritenon and tendon proper cells in vitro

BMC Musculoskeletal Disorders ◽

10.1186/s12891-020-03650-2 ◽

2020 ◽

Vol 21 (1) ◽

Author(s):

Monica Y. Pechanec ◽

Tannah N. Boyd ◽

Keith Baar ◽

Michael J. Mienaltowski

Keyword(s):

Material Properties ◽

Quantitative Polymerase Chain Reaction ◽

Tendon Repair ◽

Three Dimensional ◽

Collagen Content ◽

Matrix Assembly ◽

Post Injury ◽

Transmission Electron

Abstract Background Tendon injuries amount to one of the leading causes of career-ending injuries in horses due to the inability for tendon to completely repair and the high reinjury potential. As a result, novel therapeutics are necessary to improve repair with the goal of decreasing leg lameness and potential reinjury. Small leucine-rich repeat proteoglycans (SLRPs), a class of regulatory molecules responsible for collagen organization and maturation, may be one such therapeutic to improve tendon repair. Before SLRP supplementation can occur in vivo, proper evaluation of the effect of these molecules in vitro needs to be assessed. The objective of this study was to evaluate the effectiveness of purified bovine biglycan or decorin on tendon proper and peritenon cell populations in three-dimensional tendon constructs. Methods Equine tendon proper or peritenon cell seeded fibrin three-dimensional constructs were supplemented with biglycan or decorin at two concentrations (5 nM or 25 nM). The functionality and ultrastructural morphology of the constructs were assessed using biomechanics, collagen content analysis, transmission electron microscopy (TEM), and gene expression by real time – quantitative polymerase chain reaction (RT-qPCR). Results SLRP supplementation affected both tendon proper and peritenon cells-seeded constructs. With additional SLRPs, material and tensile properties of constructs strengthened, though ultrastructural analyses indicated production of similar-sized or smaller fibrils. Overall expression of tendon markers was bolstered more in peritenon cells supplemented with either SLRP, while supplementation of SLRPs to TP cell-derived constructs demonstrated fewer changes in tendon and extracellular matrix markers. Moreover, relative to non-supplemented tendon proper cell-seeded constructs, SLRP supplementation of the peritenon cells showed increases in mechanical strength, material properties, and collagen content. Conclusions The SLRP-supplemented peritenon cells produced constructs with greater mechanical and material properties than tendon proper seeded constructs, as well as increased expression of matrix assembly molecules. These findings provide evidence that SLRPs should be further investigated for their potential to improve tendon formation in engineered grafts or post-injury.

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