scholarly journals Tissue Folding by Mechanical Compaction of the Mesenchyme

2017 ◽  
Author(s):  
Alex J. Hughes ◽  
Hikaru Miyazaki ◽  
Maxwell C. Coyle ◽  
Jesse Zhang ◽  
Matthew T. Laurie ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Ex Vivo ◽  
Cell Contractility ◽  
Element Modeling ◽  
Mechanical Compaction ◽  
Complex Shapes ◽  
Collagen Alignment ◽  
Tissue Interfaces

SUMMARYMany tissues fold during development into complex shapes. Engineering this process in vitro would represent an important advance for tissue engineering. We use embryonic tissue explants, finite element modeling, and 3D cell patterning techniques to show that a mechanical compaction of the ECM during mesenchymal condensation can drive tissue folding along programmed trajectories. The process requires cell contractility, generates strains at nearby tissue interfaces, and causes specific patterns of collagen alignment around and between condensates. Aligned collagen fibers support elevated tensions that promote the folding of interfaces along paths that can be predicted by finite element modeling. We demonstrate the robustness and versatility of this strategy for sculpting tissue interfaces by directing the morphogenesis of a variety of folded tissue forms from engineered patterns of mesenchymal condensates. These studies provide insight into the active mechanical properties of the embryonic mesenchyme and establish entirely new strategies for more robustly directing tissue morphogenesis ex vivo, without genetic engineering.

scholarly journals RBIO-04. NEW THERAPEUTIC DELIVERY METHODS FOR TUMOR-TREATING FIELDS FOR HIGHER EFFICACY

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii192-ii193
Author(s):  
Kristen Carlson ◽  
Zeev Bomzon ◽  
Jeffrey Arle
Keyword(s):  
Finite Element ◽  
Animal Models ◽  
Field Strength ◽  
Finite Element Modeling ◽  
Tumor Resection ◽  
Electrode Arrays ◽  
Delivery Methods ◽  
Element Modeling ◽  
Tumor Treating Fields

Abstract Tumor-treating fields (TTFields) are the fourth modality of glioblastoma (GBM) treatment and in conjunction with chemotherapy can increase overall survival of GBM patients up to 60 months. However, in vitro and in animal models TTFields show 100% efficacy on a variety of tumor cell types including GBM cells when field strength is 4 V/cm, versus ~2 V/cm that is the clinical delivery target, TTFields are delivered transcranially. TTFields finite element modeling studies, supported by similar transcranial electric stimulation studies, show that the principal obstacle to delivering 4 V/cm is the electrically resistive skull. Our modeling shows the biophysics is more complicated than these findings. For instance, electrically-conductive cerebrospinal fluid regions surrounding the grey matter and in ventricles shunt electric current from anode to cathode, hindering delivery of the current required to produce 4 V/cm at the tumor/peritumor target. Thus, we consider two new delivery methods for TTFields. First, the transcranial array can be made more focal and directional, following modeling and development of electrode arrays used in spinal cord and deep brain stimulation. Our finite element modeling shows that similarly-designed TTFields electrode arrays can deliver field strength focally to a tumor target approaching 4 V/cm. Second, pre- or post-resection, TTFields can be delivered via electrode arrays surgically placed in the tumor or tumor resection cavity (intra-tumoral delivery), circumventing the resistive skull and CSF shunting effects. Such intra-tumoral arrays can deliver 4 V/cm to the tumor/peritumor region, opening up the potential to replicate clinically the 100% efficacy of TTFields in vitro and in animal models. Thus, new TTFields delivery may lead to unlimited survival of GMB patients via a side-effect free treatment modality.

scholarly journals Finding the ideal biomaterial for aortic valve repair with ex vivo porcine left heart simulator and finite element modeling

2014 ◽  
Vol 148 (4) ◽  
pp. 1739-1745.e1 ◽  
Author(s):  
Hadi Daood Toeg ◽  
Ovais Abessi ◽  
Talal Al-Atassi ◽  
Laurent de Kerchove ◽  
Gebrine El-Khoury ◽  
...  
Keyword(s):  
Finite Element ◽  
Aortic Valve ◽  
Finite Element Modeling ◽  
Ex Vivo ◽  
Aortic Valve Repair ◽  
Left Heart ◽  
Valve Repair ◽  
Element Modeling ◽  
The Ideal

scholarly journals A 3-D Constitutive Model for Finite Element Analyses of Agarose with a Range of Gel Concentrations

2020 ◽  
Author(s):  
Xiaogang Wang ◽  
Ronald K. June ◽  
David M. Pierce
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Finite Element Modeling ◽  
Computational Models ◽  
Model Parameters ◽  
Optimization Approach ◽  
Widespread Application ◽  
Element Modeling ◽  
High Stiffness

AbstractHydrogels have seen widespread application across biomedical sciences and there is considerable interest in using hydrogels, including agarose, for creating in vitro three-dimensional environments to grow cells and study mechanobiology and mechanotransduction. Recent advances in the preparation of agarose gels enable successful encapsulation of viable cells at gel concentrations as high as 5%. Agarose with a range of gel concentrations can thus serve as an experimental model mimicking changes in the 3-D microenvironment of cells during disease progression and can facilitate experiments aimed at probing the corresponding mechanobiology, e.g. the evolving mechanobiology of chondrocytes during the progression of osteoarthritis. Importantly, whether stresses (forces) or strains (displacement) drive mechanobiology and mechanotransduction is currently unknown. We can use experiments to quantify mechanical properties of hydrogels, and imaging to estimate microstructure and even strains; however, only computational models can estimate intra-gel stresses in cell-seeded agarose constructs because the required in vitro experiments are currently impossible. Finite element modeling is well-established for (computational) mechanical analyses, but accurate constitutive models for modeling the 3-D mechanical environments of cells within high-stiffness agarose are currently unavailable. In this study we aimed to establish a 3-D constitutive model of high-stiffness agarose with a range of gel concentrations. We applied a multi-step, physics-based optimization approach to separately fit subsets of model parameters and help achieve robust convergence. Our constitutive model, fitted to experimental data on progressive stress-relaxations, was able to predict reaction forces determined from independent experiments on cyclical loading. Our model has broad applications in finite element modeling aimed at interpreting mechanical experiments on agarose specimens seeded with cells, particularly in predicting distributions of intra-gel stresses. Our model and fitted parameters enable more accurate finite element simulations of high-stiffness agarose constructs, and thus better understanding of experiments aimed at mechanobiology, mechanotransduction, or other applications in tissue engineering.

Exact First Order Finite Element Modeling for Eddy Current NDE

1991 ◽  
Vol 3 (1) ◽  
pp. 235-253 ◽  
Author(s):  
L. D. Philipp ◽  
Q. H. Nguyen ◽  
D. D. Derkacht ◽  
D. J. Lynch ◽  
A. Mahmood
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Eddy Current ◽  
Element Modeling ◽  
First Order ◽  
Eddy Current Nde
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