Locomotor function shapes the passive mechanical properties and operating lengths of muscle

Locomotor muscles often perform diverse roles, functioning as motors that produce mechanical energy, struts that produce force and brakes that dissipate mechanical energy. In many vertebrate muscles, these functions are not mutually exclusive and a single muscle often performs a range of mechanically diverse tasks. This functional diversity has obscured the relationship between a muscle's locomotor function and its mechanical properties. I use hopping in toads as a model system for comparing muscles that primarily produce mechanical energy with muscles that primarily dissipate mechanical energy. During hopping, hindlimb muscles undergo active shortening to produce mechanical energy and propel the animal into the air, whereas the forelimb muscles undergo active lengthening to dissipate mechanical energy during landing. Muscles performing distinct mechanical functions operate on different regions of the force–length curve. These findings suggest that a muscle's operating length may be shaped by potential trade-offs between force production and sarcomere stability. In addition, the passive force–length properties of hindlimb and forelimb muscles vary, suggesting that passive stiffness functions to restrict the muscle's operating length in vivo . These results inform our understanding of vertebrate muscle variation by providing a clear link between a muscle's locomotor function and its mechanical properties.

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Toughening mechanisms for the attachment of architectured materials: The mechanics of the tendon enthesis

10.1101/2021.05.17.444505 ◽

2021 ◽

Author(s):

Mikhail Golman ◽

Adam C Abraham ◽

Iden Kurtaliaj ◽

Brittany P Marshall ◽

Yizhong Jenny Hu ◽

...

Keyword(s):

Mechanical Properties ◽

Mouse Model ◽

Energy Absorption ◽

Protein Denaturation ◽

Simultaneous Observation ◽

In Vivo Models ◽

Trade Offs ◽

Wide Range ◽

Architectured Materials

Architectured materials offer tailored mechanical properties but are limited in engineering applications due to challenges in maintaining toughness across their attachments. The enthesis connects tendon and bone, two vastly different architectured materials, and exhibits toughness across a wide range of loadings. Understanding the mechanisms by which this is achieved could inform the development of engineered attachments. Integrating experiments, simulations, and novel imaging that enabled simultaneous observation of mineralized and unmineralized tissues, we identified putative mechanisms of enthesis toughening in a mouse model and then manipulated these mechanisms via in vivo control of mineralization and architecture. Imaging uncovered a fibrous architecture within the enthesis that controls trade-offs between strength and toughness. In vivo models of pathology revealed architectural adaptations that optimize these trade-offs through cross-scale mechanisms including nanoscale protein denaturation, milliscale load-sharing, and macroscale energy absorption. Results suggest strategies for optimizing architecture for tough bimaterial attachments in medicine and engineering.

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In vivo measurement of the anisotropic mechanical properties of human skin by indentation test

Mechanics of Materials ◽

10.1016/j.mechmat.2021.103851 ◽

2021 ◽

pp. 103851

Author(s):

Lei Zhou ◽

Shibin Wang ◽

Jian Zhang ◽

Jialin Wang ◽

Chuanwei Li

Keyword(s):

Mechanical Properties ◽

Human Skin ◽

Indentation Test ◽

In Vivo Measurement ◽

Anisotropic Mechanical Properties

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Concomitant control of mechanical properties and degradation in resorbable elastomer-like materials using stereochemistry and stoichiometry for soft tissue engineering

Nature Communications ◽

10.1038/s41467-020-20610-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Mary Beth Wandel ◽

Craig A. Bell ◽

Jiayi Yu ◽

Maria C. Arno ◽

Nathan Z. Dreger ◽

...

Keyword(s):

Mechanical Properties ◽

Drug Delivery ◽

Soft Tissue ◽

Tissue Regeneration ◽

Biological Tissues ◽

Soft Tissue Regeneration ◽

Soft Tissue Engineering ◽

Degradation Properties ◽

Enhance Cell Adhesion

AbstractComplex biological tissues are highly viscoelastic and dynamic. Efforts to repair or replace cartilage, tendon, muscle, and vasculature using materials that facilitate repair and regeneration have been ongoing for decades. However, materials that possess the mechanical, chemical, and resorption characteristics necessary to recapitulate these tissues have been difficult to mimic using synthetic resorbable biomaterials. Herein, we report a series of resorbable elastomer-like materials that are compositionally identical and possess varying ratios of cis:trans double bonds in the backbone. These features afford concomitant control over the mechanical and surface eroding degradation properties of these materials. We show the materials can be functionalized post-polymerization with bioactive species and enhance cell adhesion. Furthermore, an in vivo rat model demonstrates that degradation and resorption are dependent on succinate stoichiometry in the elastomers and the results show limited inflammation highlighting their potential for use in soft tissue regeneration and drug delivery.

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Injectable non-leaching tissue-mimetic bottlebrush elastomers as an advanced platform for reconstructive surgery

Nature Communications ◽

10.1038/s41467-021-23962-8 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Erfan Dashtimoghadam ◽

Farahnaz Fahimipour ◽

Andrew N. Keith ◽

Foad Vashahi ◽

Pavel Popryadukhin ◽

...

Keyword(s):

Mechanical Properties ◽

Reconstructive Surgery ◽

Biomedical Applications ◽

The Body ◽

Surrounding Tissue ◽

Curing Time ◽

Materials Used ◽

Significant Health

AbstractCurrent materials used in biomedical devices do not match tissue’s mechanical properties and leach various chemicals into the body. These deficiencies pose significant health risks that are further exacerbated by invasive implantation procedures. Herein, we leverage the brush-like polymer architecture to design and administer minimally invasive injectable elastomers that cure in vivo into leachable-free implants with mechanical properties matching the surrounding tissue. This strategy allows tuning curing time from minutes to hours, which empowers a broad range of biomedical applications from rapid wound sealing to time-intensive reconstructive surgery. These injectable elastomers support in vitro cell proliferation, while also demonstrating in vivo implant integrity with a mild inflammatory response and minimal fibrotic encapsulation.

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Zn-Containing Membranes for Guided Bone Regeneration in Dentistry

Polymers ◽

10.3390/polym13111797 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1797

Author(s):

Manuel Toledano ◽

Marta Vallecillo-Rivas ◽

María T. Osorio ◽

Esther Muñoz-Soto ◽

Manuel Toledano-Osorio ◽

...

Keyword(s):

Mechanical Properties ◽

Bone Regeneration ◽

Bone Healing ◽

Bone Repair ◽

Complex Modulus ◽

Bacterial Colonization ◽

Guided Bone Regeneration ◽

M2 Macrophage

Barrier membranes are employed in guided bone regeneration (GBR) to facilitate bone in-growth. A bioactive and biomimetic Zn-doped membrane with the ability to participate in bone healing and regeneration is necessary. The aim of the present study is to state the effect of doping the membranes for GBR with zinc compounds in the improvement of bone regeneration. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken, focusing on the antibacterial effects, physicochemical and biological properties of Zn-loaded membranes. Bioactivity, bone formation and cytotoxicity were analyzed. Microstructure and mechanical properties of these membranes were also determined. Zn-doped membranes have inhibited in vivo and in vitro bacterial colonization. Zn-alloy and Zn-doped membranes attained good biocompatibility and were found to be non-toxic to cells. The Zn-doped matrices showed feasible mechanical properties, such as flexibility, strength, complex modulus and tan delta. Zn incorporation in polymeric membranes provided the highest regenerative efficiency for bone healing in experimental animals, potentiating osteogenesis, angiogenesis, biological activity and a balanced remodeling. Zn-loaded membranes doped with SiO2 nanoparticles have performed as bioactive modulators provoking an M2 macrophage increase and are a potential biomaterial for promoting bone repair. Zn-doped membranes have promoted pro-healing phenotypes.

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Fibronectin Adsorption on Electrospun Synthetic Vascular Grafts Attracts Endothelial Progenitor Cells and Promotes Endothelialization in Dynamic In Vitro Culture

Cells ◽

10.3390/cells9030778 ◽

2020 ◽

Vol 9 (3) ◽

pp. 778 ◽

Cited By ~ 4

Author(s):

Ruben Daum ◽

Dmitri Visser ◽

Constanze Wild ◽

Larysa Kutuzova ◽

Maria Schneider ◽

...

Keyword(s):

Mechanical Properties ◽

Cell Activation ◽

Vascular Endothelial Cells ◽

Endothelial Progenitor ◽

Advanced Therapy Medicinal Product ◽

Endothelial Colony Forming Cells ◽

Advanced Therapy ◽

Custom Made

Appropriate mechanical properties and fast endothelialization of synthetic grafts are key to ensure long-term functionality of implants. We used a newly developed biostable polyurethane elastomer (TPCU) to engineer electrospun vascular scaffolds with promising mechanical properties (E-modulus: 4.8 ± 0.6 MPa, burst pressure: 3326 ± 78 mmHg), which were biofunctionalized with fibronectin (FN) and decorin (DCN). Neither uncoated nor biofunctionalized TPCU scaffolds induced major adverse immune responses except for minor signs of polymorph nuclear cell activation. The in vivo endothelial progenitor cell homing potential of the biofunctionalized scaffolds was simulated in vitro by attracting endothelial colony-forming cells (ECFCs). Although DCN coating did attract ECFCs in combination with FN (FN + DCN), DCN-coated TPCU scaffolds showed a cell-repellent effect in the absence of FN. In a tissue-engineering approach, the electrospun and biofunctionalized tubular grafts were cultured with primary-isolated vascular endothelial cells in a custom-made bioreactor under dynamic conditions with the aim to engineer an advanced therapy medicinal product. Both FN and FN + DCN functionalization supported the formation of a confluent and functional endothelial layer.

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Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading

European Journal of Applied Physiology ◽

10.1007/s00421-013-2758-9 ◽

2013 ◽

Vol 114 (3) ◽

pp. 499-509 ◽

Cited By ~ 7

Author(s):

Ola Eiken ◽

Igor B. Mekjavic ◽

Roger Kölegård

Keyword(s):

Mechanical Properties ◽

Blood Pressure ◽

Blood Pressure Regulation ◽

Pressure Regulation ◽

Pressure Loading ◽

Loading And Unloading

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Gender Difference in Architectural and Mechanical Properties of Medial Gastrocnemius–Achilles Tendon Unit In Vivo

Life ◽

10.3390/life11060569 ◽

2021 ◽

Vol 11 (6) ◽

pp. 569

Author(s):

Liqin Deng ◽

Xini Zhang ◽

Songlin Xiao ◽

Baofeng Wang ◽

Weijie Fu

Keyword(s):

Mechanical Properties ◽

Gender Differences ◽

Gender Difference ◽

Achilles Tendon ◽

Medial Gastrocnemius ◽

Regular Exercise ◽

Training Experience ◽

Exercise Habits ◽

Vertical Stiffness

This study aims to explore whether gender differences exist in the architectural and mechanical properties of the medial gastrocnemius–Achilles tendon unit (gMTU) in vivo. Thirty-six healthy male and female adults without training experience and regular exercise habits were recruited. The architectural and mechanical properties of the gMTU were measured via an ultrasonography system and MyotonPRO, respectively. Independent t-tests were utilized to quantify the gender difference in the architectural and mechanical properties of the gMTU. In terms of architectural properties, the medial gastrocnemius (MG)’s pennation angle and thickness were greater in males than in females, whereas no substantial gender difference was observed in the MG’s fascicle length; the males possessed Achilles tendons (ATs) with a longer length and a greater cross-sectional area than females. In terms of mechanical properties, the MG’s vertical stiffness was lower and the MG’s logarithmic decrement was greater in females than in males. Both genders had no remarkable difference in the AT’s vertical stiffness and logarithmic decrement. Gender differences of individuals without training experience and regular exercise habits exist in the architectural and mechanical properties of the gMTU in vivo. The MG’s force-producing capacities, ankle torque, mechanical efficiency and peak power were higher in males than in females. The load-resisting capacities of AT were greater and the MG strain was lesser in males than in females. These findings suggest that males have better physical fitness, speed and performance in power-based sports events than females from the perspective of morphology and biomechanics.

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