The Effects of Geometry and Static Boundary Conditions on Microvessel Outgrowth in a 3D Model of Angiogenesis

2010 ◽  
Author(s):  
Clayton J. Underwood ◽  
Laxminarayanan Krishnan ◽  
Lowell T. Edgar ◽  
Steve Maas ◽  
James B. Hoying ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Direct Relationship ◽  
3D Model ◽  
Mechanical Strain ◽  
Matrix Stiffness ◽  
Collagen Gels ◽  
3D Collagen ◽  
In Vitro Angiogenesis

We reported previously that, in addition to mechanical strain, a constrained boundary condition alone can alter the organization of microvessel outgrowth during in vitro angiogenesis [1]. After 6 days of culture in vitro, microvessels aligned parallel to the long axis of rectangular 3D collagen gels that had constrained edges on the ends. However, unconstrained cultures did not show any alignment of microvessels. The ability to direct microvessel outgrowth during angiogenesis has significant implications for engineering prevascularized grafts and tissues in vitro, therefore an understanding of this process is important. Since there is direct relationship between the ability of endothelial cells to contract 3D gels and matrix stiffness [2], we hypothesize that some constrained boundary conditions will increase the apparent matrix stiffness and in turn will limit gel contraction, prevent microvessel alignment, and reduce microvessel outgrowth. The objective of this study was to compare microvessel growth and alignment under several different static boundary conditions.

Quantification of Temporal Collagen and Microvessel Alignment Induced by Anchored Boundary Conditions During Angiogenesis

2009 ◽  
Author(s):  
Clayton J. Underwood ◽  
Laxminarayanan Krishnan ◽  
Allen Fung ◽  
Shawn Reese ◽  
James B. Hoying ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Mechanical Strain ◽  
Collagen Matrix ◽  
In Vitro Angiogenesis

Previously we have found that in addition to mechanical strain, an anchored boundary condition alone can alter the organization of microvessel outgrowth during in vitro angiogenesis [1]. Microvessels were found to align parallel to the long axis of the anchored gel construct after 6 days in vitro. However, unanchored cultures did not show alignment of microvessels. This ability to control the direction of angiogenesis has immense implications for engineering prevascularized grafts and tissues in vitro, therefore an understanding of this process is important. The goal of this study was to first determine whether or not the underlying collagen matrix aligns similar to microvessels, and second to determine the timing of this alignment.

scholarly journals An Active Chemo-mechanical Model to Predict Adhesion and Microenvironmental Regulation of 3D Cell Shapes

2020 ◽  
Author(s):  
Xingyu Chen ◽  
Veronika te Boekhorst ◽  
Eoin McEvoy ◽  
Peter Friedl ◽  
Vivek B. Shenoy
Keyword(s):  
Cell Types ◽  
Matrix Stiffness ◽  
Collagen Gels ◽  
Collagen Matrices ◽  
Feedback Model ◽  
3D Microenvironment ◽  
The Matrix ◽  
Cell Shapes ◽  
Quantitative Understanding ◽  
3D Collagen

AbstractCell shapes are known to regulate cytoskeletal organization, stiffness and the ability of cells to migrate and proliferate. Yet a quantitative understanding of the fundamental biochemical and biophysical mechanisms that determine the cell shapes is currently not available. In this study, we developed a chemo-mechanical feedback model to predict how adhesions and the properties of the 3D microenvironment regulate cell shapes. We find that the cells in 3D collagen matrices remain round or adopt an elongated shape depending on the density of active integrins, the level of contractility regulated by mechanosensitive signaling pathways and the density and mechanics of the matrix. While the formation of actin fibers that run along the cell body mediated by integrins and matrix stiffness drive elongation of cells, the cortical and membrane tension resist elongation. Based on the competition between these mechanisms, we derive phase diagrams for cell shape in the space spanned by the density of active adhesions and the level of biochemical signaling that controls contractility. Our predictions are validated by studying the shapes of HT1080 cells cultured in collagen gels of varying densities and using pharmacological treatments to regulate adhesions and contractility. The predictions of the model are found to be in excellent agreement with our experiments and data reported on a number of cell types in the literature.

scholarly journals 0383 : In vitro 3D model of in vitro angiogenesis using human endothelial cells and pericytes

2015 ◽  
Vol 7 (2) ◽  
pp. 148
Author(s):  
Ester Garcia-Valiente ◽  
Elsa Vanhecke ◽  
Laurent Muller ◽  
Bruno Peault ◽  
Germain Stéphane
Keyword(s):  
Endothelial Cells ◽  
3D Model ◽  
Human Endothelial Cells ◽  
In Vitro Angiogenesis

Guided Axon Growth by Gradients of Adhesion in Collagen Gels

2008 ◽  
Author(s):  
Harini G. Sundararaghavan ◽  
Gary A. Monteiro ◽  
David I. Shreiber
Keyword(s):  
Spinal Cord ◽  
Collagen Gel ◽  
Axon Growth ◽  
Neurite Growth ◽  
Gradient System ◽  
Spinal Cord Regeneration ◽  
Collagen Gels ◽  
Direct Growth ◽  
3D Collagen

During development, neurites are directed by gradients of attractive and repulsive soluble (chemotactic) cues and substrate-bound adhesive (haptotactic) cues. Many of these cues have been extensively researched in vitro, and incorporated into strategies for nerve and spinal cord regeneration, primarily to improve the regenerative environment. To enhance and direct growth, we have developed a system to create 1D gradients of adhesion through a 3D collagen gel using microfluidics. We test our system using collagen grafted with bioactive peptide sequences, IKVAV and YIGSR, from laminin — an extra-cellular matrix (ECM) protein known to strongly influence neurite outgrowth. Gradients are established from ∼0.37mg peptide/mg collagen – 0, and ∼0.18 mg peptide/mg collagen – 0 of each peptide and tested using chick dorsal root ganglia (DRG). Neurite growth is evaluated 5 days after gradient formation. Neurites show increased growth in the gradient system when compared to control and biased growth up the gradient of peptides. Growth in YIGSR-grafted collagen increased with steeper gradients, whereas growth in IKVAV-grafted collagen decreased with steeper gradients. These results demonstrate that neurite growth can be enhanced and directed by controlled, immobilized, haptotactic gradients through 3D scaffolds, and suggest that including these gradients in regenerative therapies may accelerate nerve and spinal cord regeneration.

Microfluidic Generation of Adhesion Gradients Through 3D Collagen Gels: Implications for Neural Tissue Engineering

2008 ◽  
Author(s):  
Harini G. Sundararaghavan ◽  
Gary A. Monteiro ◽  
David I. Shreiber
Keyword(s):  
Spinal Cord ◽  
Collagen Gel ◽  
Neurite Growth ◽  
Gradient System ◽  
Spinal Cord Regeneration ◽  
Collagen Gels ◽  
Direct Growth ◽  
3D Collagen ◽  
Regenerative Therapies

During development, neurites are directed by gradients of attractive and repulsive soluble (chemotactic) cues and substrate-bound adhesive (haptotactic) cues. Many of these cues have been extensively researched in vitro, and incorporated into strategies for nerve and spinal cord regeneration, primarily to improve the regenerative environment. To enhance and direct growth, we have developed a system to create 1D gradients of adhesion through a 3D collagen gel using microfluidics. We test our system using collagen grafted with bioactive peptide sequences, IKVAV and YIGSR, from laminin — an extra-cellular matrix (ECM) protein known to strongly influence neurite outgrowth [1, 2]. Gradients are established from 0.14 mg/ml–0, and 0.07 mg/ml–0 of each peptide and tested using chick dorsal root ganglia (DRG). Neurite growth is evaluated 5 days after gradient formation. Neurites show increased growth in the gradient system when compared to control and biased growth up the gradient of peptides. These results demonstrate that neurite growth can be enhanced and directed by controlled, immobilized, haptotactic gradients through 3D scaffolds, and suggest that including these gradients in regenerative therapies may accelerate nerve and spinal cord regeneration.

scholarly journals Driving Native-like Zonal Enthesis Formation in Engineered Ligaments Using Mechanical Boundary Conditions and β-Tricalcium Phosphate

2021 ◽  
Author(s):  
M. Ethan Brown ◽  
Jennifer L Puetzer
Keyword(s):  
Boundary Conditions ◽  
Tricalcium Phosphate ◽  
Culture System ◽  
Great Promise ◽  
Cell Phenotype ◽  
Collagen Gels ◽  
Zonal Organization

Fibrocartilaginous entheses are structurally complex tissues that translate load from elastic ligaments to stiff bone via complex zonal organization with gradients in organization, mineralization, and cell phenotype. Currently, these gradients, necessary for long-term mechanical function, are not recreated in soft tissue-to-bone healing or engineered replacements, leading to high failure rates. Previously, we developed a culture system which guides ligament fibroblasts to develop aligned native-sized collagen fibers using high density collagen gels and mechanical boundary conditions. These constructs hold great promise as ligament replacements, however functional ligament-to-bone attachments, or entheses, are required for long-term function in vivo. The objective of this study was to investigate the effect of compressive mechanical boundary conditions and the addition of beta tricalcium phosphate (βTCP), a known osteoconductive agent, on the development of zonal ligament-to-bone entheses. We found that compressive boundary clamps, that restrict cellular contraction and produce a zonal tensile-compressive environment, guide ligament fibroblasts to produce 3 unique zones of collagen organization, and zonal accumulation of glycosaminoglycans (GAGs), type II and type X collagen by 6 weeks of culture, ultimately resulting in similar organization and composition as immature bovine entheses. Further, βTCP under the clamp enhanced the maturation of these entheses, leading to increased GAG accumulation, sheet-like mineralization, and significantly improved tensile moduli, suggesting the initiation of endochondral ossification. This culture system produced some of the most organized entheses to date, closely mirroring early postnatal enthesis development, and provides an in vitro platform to better understand the cues that drive enthesis maturation in vivo.

A Numerical Analysis of the Hemodynamic Functionality of Human Coronary Stenosis Under Different Physiologic Conditions and Boundary Condition Formulations

2019 ◽  
Author(s):  
Iyad Fayssal ◽  
Fadl Moukalled
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Functional Significance ◽  
Diffusion Flux ◽  
Computational Effort ◽  
Patient Specific ◽  
Computational Domain ◽  
Artery Disease ◽  
Outflow Boundary

Abstract Coronary artery disease (CAD) is among the foremost causes for human death worldwide. This study aims at investigating the performance of different boundary condition model types to characterize CAD functional significance. In addition, alternate models to estimate FFR using any different combination of boundary conditions at inlet and outlet were analyzed. In the first type of boundary condition, an outflow resistance model is used combined with a fixed pressure at inlet. In the second model of boundary conditions, constant pressure values are imposed at the domain inlet and outlet/s sections. In the third model, a zero diffusion flux is applied at outlet with a pre-specified flow rate at inlet. Numerical simulations performed on healthy and stenosed idealized and physiological arterial models revealed the superiority of the first type of boundary condition to directly capture the level of ischemia in diseased arteries. However, in this model, special numerical treatment at the outflow boundary is needed to dampen pseudo numerical reflections entering the computational domain. Alternative simple methods are developed to tackle the problem incurred in the second and third types of boundary condition types. The alternate models are effective for carrying extensive parametric studies with minimal computational effort. The new developed methods allow results generated via generic simulations under any specified boundary condition type to correctly estimate CAD functional significance. The obtained surrogate models account for the effects of the patient-specific physiologic parameters and can be easily incorporated without modifying existing CFD codes. Moreover, where it is unfeasible to experimentally incorporate the downstream effects of a given diseased arterial segment, an important aspect the alternative models provide is that they can be easily adopted by experimentalists through building in-vitro arterial models to assess the functional significance of the obstruction caused by the disease and its relation to any given patient specific physiologic parameter.

scholarly journals Image-based Characterization of 3D Collagen Networks and the Effect of Embedded Cells

2019 ◽  
Vol 25 (4) ◽  
pp. 971-981 ◽  
Author(s):  
Vanesa Olivares ◽  
Mar Cóndor ◽  
Cristina Del Amo ◽  
Jesús Asín ◽  
Carlos Borau ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Activity ◽  
Three Dimensional ◽  
Collagen Fibers ◽  
Collagen Gels ◽  
Culture Dish ◽  
Collagen Concentration ◽  
A Cell ◽  
3D Collagen

AbstractCollagen microstructure is closely related to the mechanical properties of tissues and affects cell migration through the extracellular matrix. To study these structures, three-dimensional (3D) in vitro collagen-based gels are often used, attempting to mimic the natural environment of cells. Some key parameters of the microstructure of these gels are fiber orientation, fiber length, or pore size, which define the mechanical properties of the network and therefore condition cell behavior. In the present study, an automated tool to reconstruct 3D collagen networks is used to extract the aforementioned parameters of gels of different collagen concentration and determine how their microstructure is affected by the presence of cells. Two different experiments are presented to test the functionality of the method: first, collagen gels are embedded within a microfluidic device and collagen fibers are imaged by using confocal fluorescence microscopy; second, collagen gels are directly polymerized in a cell culture dish and collagen fibers are imaged by confocal reflection microscopy. Finally, we investigate and compare the collagen microstructure far from and in the vicinities of MDA-MB 23 cells, finding that cell activity during migration was able to strongly modify the orientation of the collagen fibers and the porosity-related values.

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