Linear and nonlinear viscoelastic modeling of ovine aortic biomechanical properties under in vivo and ex vivo conditions

Acellular nerve allografts (ANGs) represent a promising alternative in nerve repair. Our aim is to improve the structural and biomechanical properties of biocompatible Sondell (SD) and Roosens (RS) based ANGs using genipin (GP) as a crosslinker agent ex vivo. The impact of two concentrations of GP (0.10% and 0.25%) on Wistar rat sciatic nerve-derived ANGs was assessed at the histological, biomechanical, and biocompatibility levels. Histology confirmed the differences between SD and RS procedures, but not remarkable changes were induced by GP, which helped to preserve the nerve histological pattern. Tensile test revealed that GP enhanced the biomechanical properties of SD and RS ANGs, being the crosslinked RS ANGs more comparable to the native nerves used as control. The evaluation of the ANGs biocompatibility conducted with adipose-derived mesenchymal stem cells cultured within the ANGs confirmed a high degree of biocompatibility in all ANGs, especially in RS and RS-GP 0.10% ANGs. Finally, this study demonstrates that the use of GP could be an efficient alternative to improve the biomechanical properties of ANGs with a slight impact on the biocompatibility and histological pattern. For these reasons, we hypothesize that our novel crosslinked ANGs could be a suitable alternative for future in vivo preclinical studies.

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In Vivo and ex Vivo Approaches to Studying the Biomechanical Properties of Healing Wounds in Rat Skin

Journal of Biomechanical Engineering ◽

10.1115/1.4025109 ◽

2013 ◽

Vol 135 (10) ◽

Cited By ~ 14

Author(s):

Clare Y. L. Chao ◽

Gabriel Y. F. Ng ◽

Kwok-Kuen Cheung ◽

Yong-Ping Zheng ◽

Li-Ke Wang ◽

...

Keyword(s):

Wound Healing ◽

Ex Vivo ◽

Normal Skin ◽

Biomechanical Properties ◽

Skin Wound ◽

Sprague Dawley ◽

Rat Skin ◽

Mechanical Stiffness ◽

Air Jet

An evaluation of wound mechanics is crucial in reflecting the wound healing status. The present study examined the biomechanical properties of healing rat skin wounds in vivo and ex vivo. Thirty male Sprague-Dawley rats, each with a 6 mm full-thickness circular punch biopsied wound at both posterior hind limbs were used. The mechanical stiffness at both the central and margins of the wound was measured repeatedly in five rats over the same wound sites to monitor the longitudinal changes over time of before wounding, and on days 0, 3, 7, 10, 14, and 21 after wounding in vivo by using an optical coherence tomography-based air-jet indentation system. Five rats were euthanized at each time point, and the biomechanical properties of the wound tissues were assessed ex vivo using a tensiometer. At the central wound bed region, the stiffness measured by the air-jet system increased significantly from day 0 (17.2%), peaked at day 7 (208.3%), and then decreased progressively until day 21 (40.2%) as compared with baseline prewounding status. The biomechanical parameters of the skin wound samples measured by the tensiometer showed a marked reduction upon wounding, then increased with time (all p < 0.05). On day 21, the ultimate tensile strength of the skin wound tissue approached 50% of the normal skin; while the stiffness of tissue recovered at a faster rate, reaching 97% of its prewounded state. Our results suggested that it took less time for healing wound tissues to recover their stiffness than their maximal strength in rat skin. The stiffness of wound tissues measured by air-jet could be an indicator for monitoring wound healing and contraction.

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Biomechanical Properties of the Equine Third Metacarpal Bone: In Vivo Quantitative Ultrasonography Versus Ex Vivo Compression and Bending Techniques

Journal of Equine Veterinary Science ◽

10.1016/j.jevs.2014.12.016 ◽

2015 ◽

Vol 35 (3) ◽

pp. 198-205 ◽

Cited By ~ 3

Author(s):

Maria J. Fradinho ◽

Ana C. Vale ◽

Nuno Bernardes ◽

Rui M. Caldeira ◽

Maria Fátima Vaz ◽

...

Keyword(s):

Ex Vivo ◽

Biomechanical Properties ◽

Metacarpal Bone ◽

Quantitative Ultrasonography

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High Pulsatile Load Decreases Arterial Stiffness: An ex vivo Study

Frontiers in Physiology ◽

10.3389/fphys.2021.741346 ◽

2021 ◽

Vol 12 ◽

Author(s):

Cédric H. G. Neutel ◽

Giulia Corradin ◽

Pauline Puylaert ◽

Guido R. Y. De Meyer ◽

Wim Martinet ◽

...

Keyword(s):

Arterial Stiffness ◽

Blood Vessel ◽

Pulse Pressure ◽

Ex Vivo ◽

Strong Predictor ◽

Biomechanical Properties ◽

Aortic Tissue ◽

Infrarenal Aorta ◽

Pulsatile Load

Measuring arterial stiffness has recently gained a lot of interest because it is a strong predictor for cardiovascular events and all-cause mortality. However, assessing blood vessel stiffness is not easy and the in vivo measurements currently used provide only limited information. Ex vivo experiments allow for a more thorough investigation of (altered) arterial biomechanical properties. Such experiments can be performed either statically or dynamically, where the latter better corresponds to physiological conditions. In a dynamic setup, arterial segments oscillate between two predefined forces, mimicking the diastolic and systolic pressures from an in vivo setting. Consequently, these oscillations result in a pulsatile load (i.e., the pulse pressure). The importance of pulse pressure on the ex vivo measurement of arterial stiffness is not completely understood. Here, we demonstrate that pulsatile load modulates the overall stiffness of the aortic tissue in an ex vivo setup. More specifically, increasing pulsatile load softens the aortic tissue. Moreover, vascular smooth muscle cell (VSMC) function was affected by pulse pressure. VSMC contraction and basal tonus showed a dependence on the amplitude of the applied pulse pressure. In addition, two distinct regions of the aorta, namely the thoracic descending aorta (TDA) and the abdominal infrarenal aorta (AIA), responded differently to changes in pulse pressure. Our data indicate that pulse pressure alters ex vivo measurements of arterial stiffness and should be considered as an important variable in future experiments. More research should be conducted in order to determine which biomechanical properties are affected due to changes in pulse pressure. The elucidation of the underlying pulse pressure-sensitive properties would improve our understanding of blood vessel biomechanics and could potentially yield new therapeutic insights.

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Exploring the Biomechanical Properties of the Human Cornea In Vivo Based on Corvis ST

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.771763 ◽

2021 ◽

Vol 9 ◽

Author(s):

Di Zhang ◽

Haixia Zhang ◽

Lei Tian ◽

Yan Zheng ◽

Caiyun Fu ◽

...

Keyword(s):

Viscoelastic Properties ◽

Strain Energy ◽

Biomechanical Properties ◽

Human Cornea ◽

Corvis St ◽

First Order ◽

Healthy Humans ◽

Nonlinear Viscoelastic ◽

Work Done

Purpose: The aim of this study was to provide a method to determine corneal nonlinear viscoelastic properties based on the output data of corneal visualization Scheimpflug technology (Corvis ST).Methods: The Corvis ST data from 18 eyes of 12 healthy humans were collected. Based on the air-puff pressure and the corneal displacement from the Corvis ST test of normal human eyes, the work done by the air-puff attaining the whole corneal displacement was obtained. By applying a visco-hyperelastic strain energy density function of the cornea, in which the first-order Prony relaxation function and the first-order Ogden strain energy were employed, the corneal strain energy during the Corvis ST test was calculated. Then the work done by the air-puff attaining the whole corneal displacement was completely regarded as the strain energy of the cornea. The identification of the nonlinear viscoelastic parameters was carried out by optimizing the sum of difference squares of the work and the strain energy using the genetic algorithm.Results: The visco-hyperelastic model gave a good fit to the data of corneal strain energy with time during the Corvis ST test (R2 > 0.95). The determined Ogden model parameter μ ranged from 0.42 to 0.74 MPa, and α ranged from 32.76 to 55.63. The parameters A and τ in the first-order Prony function were 0.09–0.36 and 1.21–1.95 ms, respectively.Conclusion: It is feasible to determine the corneal nonlinear viscoelastic properties based on the corneal contour information and air-puff pressure of the Corvis ST test.

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In vivo assessment of spinal cord elasticity using shear wave ultrasound in dogs

Journal of Neurosurgery Spine ◽

10.3171/2018.2.spine171195 ◽

2018 ◽

Vol 29 (4) ◽

pp. 461-469 ◽

Cited By ~ 2

Author(s):

Amro Al-Habib ◽

Abdulrahman Albakr ◽

Abdullah Al Towim ◽

Metab Alkubeyyer ◽

Abdullah Abu Jamea ◽

...

Keyword(s):

Spinal Cord ◽

Shear Wave ◽

Dura Mater ◽

Ex Vivo ◽

Shear Wave Elastography ◽

Biomechanical Properties ◽

Tissue Elasticity ◽

Pia Mater ◽

Balloon Compression

OBJECTIVEEvaluation of living tissue elasticity has wide applications in disease characterization and prognosis prediction. Few previous ex vivo attempts have been made to characterize spinal cord elasticity (SCE). Recently, tissue elasticity assessment has been clinically feasible using ultrasound shear wave elastography (SWE). The current study aims to characterize SCE in healthy dogs, in vivo, utilizing SWE, and to address SCE changes during compression.METHODSTen Greyhound dogs (mean age 14 months; mean weight 14.3 kg) were anesthetized and tracheally intubated, with hemodynamic and neurological monitoring. A 3-level, midcervical laminectomy was performed. SCE was assessed at baseline. Next, 8- and 13-mm balloon compressions were sequentially applied ventral to the spinal cord.RESULTSThe mean SCE was 18.5 ± 7 kPa. Elasticity of the central canal, pia mater, and dura mater were 21.7 ± 9.6 kPa, 26.1 ± 14.8 kPa, and 63.2 ± 11.5 kPa, respectively. As expected, the spinal cord demonstrated less elasticity than the dura mater (p < 0.0001) and pia mater (trend toward significance p = 0.08). Notably, the 13-mm balloon compression resulted in a stiffer spinal cord than at baseline (233 ± 73 kPa versus 18.5 ± 7 kPa, p < 0.0001) and 8-mm balloon compression (233 ± 73 kPa versus 185 ± 68 kPa, p < 0.048).CONCLUSIONSIn vivo SCE evaluation using SWE is feasible and comparable to earlier reports, as demonstrated by physical sectioning of the spinal cord. The compressed spinal cord is stiffer than a free spinal cord, with a linear increase in SCE with increasing mechanical compression. Knowledge of the biomechanical properties of the spinal cord including SCE has potential implications for disease management and prognosis.

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Magnetic Resonance Elastography of the Mouse Brain In Vivo

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-175375 ◽

2007 ◽

Author(s):

Stefan M. Atay ◽

Philip V. Bayly

Keyword(s):

Magnetic Resonance ◽

Shear Modulus ◽

Mouse Brain ◽

Ex Vivo ◽

Magnetic Resonance Elastography ◽

Dynamic Shear Modulus ◽

Dynamic Shear ◽

High Deformation ◽

Nonlinear Viscoelastic

In the current study we apply the magnetic resonance elastography (MRE) technique to estimate the dynamic shear modulus of mouse brain tissue in vivo. The frequency used (1200 Hz) is well above those reported previously [1]. Estimates of dynamic shear modulus range from 12,600–14,800 N/m2 at 1200 Hz. These data are strictly relevant only to small oscillations at this specific frequency, but these values are obtained at high frequencies (and thus high deformation rates) and non-invasively throughout the brain. These data complement measurements of nonlinear viscoelastic properties obtained by others at slower rates, either ex vivo or invasively.

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Reverberant Shear Wave Elastography: A Multi-Modal and Multi-Scale Approach to Measure the Viscoelasticity Properties of Soft Tissues

Frontiers in Physics ◽

10.3389/fphy.2020.606793 ◽

2021 ◽

Vol 8 ◽

Author(s):

Juvenal Ormachea ◽

Fernando Zvietcovich

Keyword(s):

Wave Propagation ◽

Shear Wave ◽

Acoustic Waves ◽

Guided Waves ◽

Soft Tissues ◽

Ex Vivo ◽

Surface Acoustic Waves ◽

Shear Wave Elastography ◽

Biomechanical Properties

There are a variety of approaches used to create elastography images. Techniques based on shear wave propagation have received significant attention. However, there remain some limitations and problems due to shear wave reflections, limited penetration in highly viscous media, requirements for prior knowledge of wave propagation direction, and complicated propagation in layers where surface acoustic waves and guided waves are dominant. To overcome these issues, reverberant shear wave elastography (RSWE) was proposed as an alternative method which applies the concept of a narrow-band diffuse field of shear waves within the tissue. Since 2017, the RSWE approach has been implemented in ultrasound (US) and optical coherence tomography (OCT). Specifically, this approach has been implemented in these imaging modalities because they are similar in image formation principles and both share several approaches to estimate the biomechanical properties in tissues. Moreover, they cover different spatial-scale and penetration depth characteristics. RSWE has shown promising results in the elastic and viscoelastic characterization of multiple tissues including liver, cornea, and breast. This review summarizes the 4-year progress of the RSWE method in US and OCT. Theoretical derivations, numerical simulations, and applications in ex vivo and in vivo tissues are shown. Finally, we emphasize the current challenges of RSWE in terms of excitation methods and estimation of biomechanical parameters for tissue-specific cases and discuss future pathways for the in vivo and in situ clinical implementations.

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DYNAMIC OPTICAL COHERENCE ELASTOGRAPHY: A REVIEW

Journal of Innovative Optical Health Sciences ◽

10.1142/s1793545810001180 ◽

2010 ◽

Vol 03 (04) ◽

pp. 221-233 ◽

Cited By ~ 36

Author(s):

XING LIANG ◽

VASILICA CRECEA ◽

STEPHEN A. BOPPART

Keyword(s):

Quantitative Methods ◽

Ex Vivo ◽

Biomechanical Properties ◽

Biological Tissues ◽

Internal Dynamic ◽

Optical Coherence ◽

Real Time Processing ◽

Tissue Changes ◽

Application Fields

With the development of optical coherence tomography, the application optical coherence elastography (OCE) has gained more and more attention in biomechanics for its unique features including micron-scale resolution, real-time processing, and non-invasive imaging. In this review, one group of OCE techniques, namely dynamic OCE, are introduced and discussed including external dynamic OCE mapping and imaging of ex vivo breast tumor, external dynamic OCE measurement of in vivo human skin, and internal dynamic OCE including acoustomotive OCE and magnetomotive OCE. These techniques overcame some of the major drawbacks of traditional static OCE, and broadened the OCE application fields. Driven by scientific needs to engineer new quantitative methods that utilize the high micron-scale resolution achievable with optics, results of biomechanical properties were obtained from biological tissues. The results suggest potential diagnostic and therapeutic clinical applications. Results from these studies also help our understanding of the relationship between biomechanical variations and functional tissue changes in biological systems.

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