References of "Geris, Liesbet"
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See detailTowards a quantitative understanding of oxygen tension and cell density evolution in fibrin hydrogels
Demol, Jan; Lambrechts, Dennis; Geris, Liesbet ULg et al

in Biomaterials (2010), 32(1), 107-118

The in vitro culture of hydrogel-based constructs above a critical size is accompanied by problems of unequal cell distribution when diffusion is the primary mode of oxygen transfer. In this study, an ... [more ▼]

The in vitro culture of hydrogel-based constructs above a critical size is accompanied by problems of unequal cell distribution when diffusion is the primary mode of oxygen transfer. In this study, an experimentally informed mathematical model was developed to relate cell proliferation and death inside fibrin hydrogels to the local oxygen tension in a quantitative manner. The predictive capacity of the resulting model was tested by comparing its outcomes to the density, distribution and viability of human periosteum derived cells (hPDCs) that were cultured inside fibrin hydrogels in vitro. The model was able to reproduce important experimental findings, such as the formation of a multilayered cell sheet at the hydrogel periphery and the occurrence of a cell density gradient throughout the hydrogel. In addition, the model demonstrated that cell culture in fibrin hydrogels can lead to complete anoxia in the centre of the hydrogel for realistic values of oxygen diffusion and consumption. A sensitivity analysis also identified these two parameters, together with the proliferation parameters of the encapsulated cells, as the governing parameters for the occurrence of anoxia. In conclusion, this study indicates that mathematical models can help to better understand oxygen transport limitations and its influence on cell behaviour during the in vitro culture of cellseeded hydrogels. [less ▲]

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See detailIn vivo, in vitro, in silico: computational tools for tissue engineering
Van Oosterwyck, Hans; Truscello, S.; Demol, Jan et al

in proceedings of the 2nd International Conference on Innovation for Sustainable Production i-SUP (2010)

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See detailOptimizing The Micro-Environment In A Tissue Engineering Scaffold: A Computational Approach
Van Oosterwyck, Hans; Truscello, S.; Demol, J. et al

in proceedings of the Materialise World Conference (2010)

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See detailMathematical modelling of cell aggregates for bone tissue engineering using continuum methods
Geris, Liesbet ULg; Clarke, T.; Ashbourn, J.

in Middleton, J.; Jacobs, C.; Walker, B. (Eds.) et al 9th International symposium on Computer Methods in Biomechanics and Biomedical Engineering (2010)

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See detailExperimental and computational study of the correlation between oxygen tension, cell viability and proliferation in fibrin hydrogels
Demol, J.; Lambrechts, D.; Geris, Liesbet ULg et al

in Proceedings of the 17th conference of the European Society of Biomechanics (2010)

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See detailNumerical simulation of two-dimensional and three-dimensional axisymmetric advection-diffusion systems with complex geometries using finite-volume methods
Ashbourn, J. M. A.; Geris, Liesbet ULg; Gerisch, A. et al

in Proceedings : Mathematical, Physical & Engineering Sciences (2010), 466(2118), 1621-1643

A finite-volume method has been developed that can deal accurately with complicated, curved boundaries for both two-dimensional and three-dimensional axisymmetric advection-diffusion systems. The ... [more ▼]

A finite-volume method has been developed that can deal accurately with complicated, curved boundaries for both two-dimensional and three-dimensional axisymmetric advection-diffusion systems. The motivation behind this is threefold. Firstly, the ability to model the correct geometry of a situation yields more accurate results. Secondly, smooth geometries eliminate corner singularities in the calculation of, for example, mechanical variables and thirdly, different geometries can be tested for experimental applications. An example illustrating each of these is given: fluid carrying a dye and rotating in an annulus, bone fracture healing in mice, and using vessels of different geometry in an ultracentrifuge. [less ▲]

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See detailA cell based modelling framework for skeletal tissue engineering applications
Geris, Liesbet ULg; Van Liedekerke, Paul; Smeets, Bart et al

in Journal of Biomechanics (2010), 43(5), 887-892

In this study, a cell based lattice free modelling framework is proposed to study cell aggregate behaviour in bone tissue engineering applications. The model encompasses cell-to-cell and cell environment ... [more ▼]

In this study, a cell based lattice free modelling framework is proposed to study cell aggregate behaviour in bone tissue engineering applications. The model encompasses cell-to-cell and cell environment interactions such as adhesion, repulsion and drag forces. Oxygen, nutrients, waste products, growth factors and inhibitors are explicitly represented in the model influencing cellular behaviour. Furthermore, a model for cell metabolism is incorporated representing the basic enzymic reactions of glycolysis and the Krebs cycle. Various types of cell death such as necrosis, apoptosis and anoikis are implemented. Finally, an explicit model of the cell cycle controls the proliferation process, taking into account the presence or absence of various metabolites, sufficient space and mechanical stress. Several examples are presented demonstrating the potential of the modelling framework. The behaviour of a synchronised cell aggregate under ideal circumstances is simulated, clearly showing the different stages of the cell cycle and the resulting growth of the aggregate. Also the difference in aggregate development under ideal (normoxic) and hypoxic conditions is simulated, showing hypoxia induced necrosis mainly in the centre of the aggregate grown under hypoxic conditions. The next step in this research will be the application of this modelling framework to specific experimental set-ups for bone tissue engineering applications. (C) 2009 Elsevier Ltd. All rights reserved. [less ▲]

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See detailIn silico design of treatment strategies in wound healing and bone fracture healing
Geris, Liesbet ULg; Schugart, R.; Van Oosterwyck, H.

in Philosophical Transactions : Mathematical, Physical & Engineering Sciences (2010), 368(1920), 2683-2706

Wound and bone fracture healing are natural repair processes initiated by trauma. Over the last decade, many mathematical models have been established to investigate the healing processes in silico, in ... [more ▼]

Wound and bone fracture healing are natural repair processes initiated by trauma. Over the last decade, many mathematical models have been established to investigate the healing processes in silico, in addition to ongoing experimental work. In recent days, the focus of the mathematical models has shifted from simulation of the healing process towards simulation of the impaired healing process and the in silico design of treatment strategies. This review describes the most important causes of failure of the wound and bone fracture healing processes and the experimental models and methods used to investigate and treat these impaired healing cases. Furthermore, the mathematical models that are described address these impaired healing cases and investigate various therapeutic scenarios in silico. Examples are provided to illustrate the potential of these in silico experiments. Finally, limitations of the models and the need for and ability of these models to capture patient specificity and variability are discussed. [less ▲]

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See detailA single cell-based modelling framework for bone tissue engineering
Geris, Liesbet ULg; Van Liedekerke, Paul; Smeets, Bart et al

in Proceedings of the 17th conference of the European Society of Biomechanics (2010)

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See detailA hybrid model for the simulation of angiogenesis during bone fracture healing
Geris, Liesbet ULg; Peiffer, Veronique; Gerisch, Alf et al

in Proceedings of the 17th conference of the European Society of Biomechanics (2010)

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See detailA mathematical model describing the biology of orthodontic tooth movement
Van Schepdael, A.; Vander Sloten, Jos; Geris, Liesbet ULg

in Goh Cho Hong, James; Teck Lim, Chwee (Eds.) proceedings of the 6th world congress on biomechanics (2010)

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See detailCrosstalk Modeling of Wnt, BMP and ERK Pathways during osteochondrogenic differentiation
Geris, Liesbet ULg; Vandeput, Maarten; Roberts, Scott et al

in proceedings of the International Symposium on Biomechanics and Biology of Bone Regeneration “From Functional Assessment To Guided Tissue Formation (2009, November)

The in vitro engineering of tissues may be achieved by mimicking in vivo tissue development. Although multiple skeletal tissue engineering applications already exist, the underlying mechanisms at protein ... [more ▼]

The in vitro engineering of tissues may be achieved by mimicking in vivo tissue development. Although multiple skeletal tissue engineering applications already exist, the underlying mechanisms at protein level are often poorly understood. Growth factors and protein pathways precisely navigate mesenchymal stem cells trough the correct cascades. A detailed understanding of these cascades will enable us to develop efficient and robust production methods, which are required for large scale tissue engineering applications. Multiple studies hypothesize that the Wnt/β-catenin pathway acts as a switching mechanism to determine the differential fate of esenchymal cells in osteoblasts or chondrocytes during skeletogenesis. The concentration of β-catenin is a key factor in this mechanism. Wnt upregulates the productionof β-catenin which in turn upregulates Runx2 and downregulates Sox9. High concentrations of Runx2 relative to Sox9 lead to osteoblasts, while the opposite situation leads to chondrocytes. Crosstalks of the Wnt pathway with other pathways such as that of BMP and ERK expand the amount of factors that can influence β-catenin, turning the linear signaling cascade into a complex network with multiple starting conditions. A mathematical model was derived from literature describing the pathways of BMP, Wnt and ERK as well as various crosstalks between these pathways that were suggested in literature. CellDesigner™ was used to formulate, solve and visualize the Ordinary Differential Equations describing the temporal evolution of the various model constituents. Multiple starting conditions (various concentrations of BMP, Wnt and ERK) were examined to clarify the crosstalk effect. Modeling various crosstalks proposed in literature resulted in a mutual inhibitory effect between Wnt and BMP signaling, an effect independently described in literature. Experiments are ongoing to corroborate the model predictions. [less ▲]

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See detailDesign of treatment strategies for an atrophic nonunion case in fracture healing
Geris, Liesbet ULg; Vander Sloten, Jos; Van Oosterwyck, Hans

in proceedings of the IVth International Conference on Computational Bioengineering (2009)

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See detailMathematical modeling of bone regeneration during fracture healing
Geris, Liesbet ULg; Vander Sloten, Hans; Van Oosterwyck, Hans

in proceedings of the National Conference on Theoretical and Applied Mechanics (2009)

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See detailModelling at the biological/biomechanical interface: fracture healing case studies
Geris, Liesbet ULg

in Exploring the biological/biomechanics interface (2009)

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See detailThe biology of bone formation in orthodontic tooth movement: a mathematical model
van Schepdael, A.; Vander Sloten, Jos; Geris, Liesbet ULg

in Proceedings of the International Conference on Mathematical Biology 2009 (2009)

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See detailNumerical simulation of bone regeneration in a bone chamber.
Geris, Liesbet ULg; Vandamme, K.; Naert, I. et al

in Journal of Dental Research (2009), 88(2), 158-63

While mathematical models are able to capture essential aspects of biological processes like fracture healing and distraction osteogenesis, their predictive capacity in peri-implant osteogenesis remains ... [more ▼]

While mathematical models are able to capture essential aspects of biological processes like fracture healing and distraction osteogenesis, their predictive capacity in peri-implant osteogenesis remains uninvestigated. We tested the hypothesis that a mechano-regulatory model has the potential to predict bone regeneration around implants. In an in vivo bone chamber set-up allowing for controlled implant loading (up to 90 microm axial displacement), bone tissue formation was simulated and compared qualitatively and quantitatively with histology. Furthermore, the model was applied to simulate excessive loading conditions. Corresponding to literature data, implant displacement magnitudes larger than 90 microm predicted the formation of fibrous tissue encapsulation of the implant. In contradiction to findings in orthopedic implant osseointegration, implant displacement frequencies higher than 1 Hz did not favor the formation of peri-implant bone in the chamber. Additional bone chamber experiments are needed to test these numerical predictions. [less ▲]

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See detailIn silico biology of bone modelling and remodelling: regeneration.
Geris, Liesbet ULg; Vander Sloten, J.; Van Oosterwyck, H.

in Philosophical Transactions : Mathematical, Physical & Engineering Sciences (2009), 367(1895), 2031-53

Bone regeneration is the process whereby bone is able to (scarlessly) repair itself from trauma, such as fractures or implant placement. Despite extensive experimental research, many of the mechanisms ... [more ▼]

Bone regeneration is the process whereby bone is able to (scarlessly) repair itself from trauma, such as fractures or implant placement. Despite extensive experimental research, many of the mechanisms involved still remain to be elucidated. Over the last decade, many mathematical models have been established to investigate the regeneration process in silico. The first models considered only the influence of the mechanical environment as a regulator of the healing process. These models were followed by the development of bioregulatory models where mechanics was neglected and regeneration was regulated only by biological stimuli such as growth factors. The most recent mathematical models couple the influences of both biological and mechanical stimuli. Examples are given to illustrate the added value of mathematical regeneration research, specifically in the in silico design of treatment strategies for non-unions. Drawbacks of the current continuum-type models, together with possible solutions in extending the models towards other time and length scales are discussed. Finally, the demands for dedicated and more quantitative experimental research are presented. [less ▲]

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See detailBiomaterial Surface Characteristics Modulate the Outcome of Bone Regeneration around Endosseous Oral Implants: In Silico Modeling
Amor, Nadya; Geris, Liesbet ULg; Vander Sloten, Jos et al

in Miller, Karol; Nielsen, Poul M.F. (Eds.) MICCAI 2009 Workshop Proceedings (2009)

Experimental investigations have demonstrated the importance of platelets and their activation for bone regeneration around oral implants. This study aimed to numerically demonstrate the key role of ... [more ▼]

Experimental investigations have demonstrated the importance of platelets and their activation for bone regeneration around oral implants. This study aimed to numerically demonstrate the key role of activated platelets which is controlled by implant surface characteristics. The cellular activities involved in the process of peri-implant endosseous healing can be represented by migration, proliferation, differentiation, removal, extracellular matrix synthesis and degradation, and growth factor production/release and decay. These activities are described by a system of highly coupled non-linear partial differential equations of taxis–diffusion–reaction type. Moreover, cell–biomaterial interactions were treated by including surface-specific model parameters. A well-designed in vivo model that looked at healing around oral implants with different surface properties was selected from literature to validate the results. Numerical simulations agreed well with the experimentally observed healing response and demonstrated that platelet-related model parameters, which were dependent on implant surface characteristics, modulate the pattern of healing. [less ▲]

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See detailModelling the early phases of bone regeneration around an endosseous oral implant
Amor, N.; Geris, Liesbet ULg; Vander Sloten, J. et al

in Computer Methods in Biomechanics & Biomedical Engineering (2009), 12(4), 459-468

The objective of this study was to see whether a mathematical model of fracture healing was able to mimic bone formation around an unloaded screw-shaped titanium implant as it is well-believed that both ... [more ▼]

The objective of this study was to see whether a mathematical model of fracture healing was able to mimic bone formation around an unloaded screw-shaped titanium implant as it is well-believed that both processes exhibit many biological similarities. This model describes the spatio-temporal evolution of cellular activities, ranging from mesenchymal stem cell migration, proliferation, differentiation to bone formation, which are initiated and regulated by the growth factors present at the peri-implant site. For the simulations, a finite volume code was used and adequate initial and boundary conditions were applied. Two sets of analyses have been performed, in which either initial and boundary condition or model parameter values were changed with respect to the fracture healing model parameter values. For a number of combinations, the spatio-temporal evolution of bone density was well-predicted. However reducing cell proliferation rate and increasing osteoblast differentiation and osteogenic growth factor synthesis rates, the simulation results were in agreement with the experimental data. [less ▲]

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