References of "Geris, Liesbet"
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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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See detailModelling of in vitro mesenchymal stem cell cultivation, chondrogenesis and osteogenesis
Geris, Liesbet ULg; Peiffer, Véronique; Demol, Jan et al

in Journal of Biomechanics (2008, July), 41

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See detailMathematical modelling of atrophic non-union and its treatment
Geris, Liesbet ULg; Vander Sloten, Jos; VanOosterwyck, Hans

in Proceedings of the International symposium on Biomechanics and Biology of Bone Healing (2008)

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See detailA mechanobioregulatory model for the study of bone fracture healing
Geris, Liesbet ULg; Gerisch, A.; Weiner, R. et al

in Proceedings of the European Conference on Mathematical and Theoretical Biology (2008)

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See detailDevelopment of a mechanobiological model of bone formation in orthodontic tooth movement
Van Schepdael, A.; Geris, Liesbet ULg; Vander Sloten, Jos

in Proceedings of the European Conference on Mathematical and Theoretical Biology (2008)

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See detailMathematical modelling of bone regeneration during fracture healing
Geris, Liesbet ULg; VanderSloten@mech.kuleuven.be, Jos; VanOosterwyck, Hans

in proceedings of the OPTEC Topical Workshop on Parameter Estimation in Differential Equations (2008)

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See detailA mathematical model of bone regeneration including angiogenesis: relevance for tissue engineering strategies
Van Oosterwyck, Hans; Vander Sloten, Jos; Geris, Liesbet ULg

in European Cells and Materials (2008), Vol. 14(Suppl. 1,), 29

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See detailAn integrated mathematical modelling framework for the study of bone fracture healing
Geris, Liesbet ULg; Vander Sloten, Jos; Van Oosterwyck, Hans

in Journal of Biomechanics (2008), 41

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See detailMathematical modelling of bone regeneration including angiogenesis: design of treatment strategies for atrophic non-unions
Geris, Liesbet ULg; Vander Sloten, Jos; Van Oosterwyck, Hans

in Proceedings of the 54th Annual Meeting of the Orthopaedic Research Society (2008)

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See detailComputational modelling of peri-implant bone healing considering cell-biomaterial interactions
Amor, Nadya; Geris, Liesbet ULg; Vander Sloten, Jos et al

in Arbor, Ann (Ed.) Proceedings of the North American Congress on Biomechanics (2008)

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See detailMathematical modeling of fracture healing: coupling between mechanics, angiogenesis and osteogenesis
Geris, Liesbet ULg; Vander Sloten, Jos; VanOosterwyck, Hans

in IFMBE Proceedings 22 (2008)

Both mechanical and biological factors play an important role in normal as well as impaired fracture healing. This study aims to provide a mathematical framework in which both regulatory mechanisms are ... [more ▼]

Both mechanical and biological factors play an important role in normal as well as impaired fracture healing. This study aims to provide a mathematical framework in which both regulatory mechanisms are included and angiogenesis is explicitly incorporated. To illustrate the added value of such a framework, a coupled mechanobioregulatory model was proposed. This model was based on a previously developed bioregulatory model [1], using a simple coupling between mechanics and biology whereby certain parameters of the bioregulatory model were made dependent on local mechanical stimuli. As a first example, in this study, the proliferation of osteoblasts and endothelial cells were made dependent on the local fluid flow [2]. Various loading situations, ranging from non-loading to overloading, were simulated. Simulations of adverse mechanical circumstances predicted the formation of avascular nonunions, a result that was corroborated by various experimental observations. This model allows testing various hypotheses concerning the nature of the mechanical stimulus influencing the healing process, as well as the most important cellular processes influenced by mechanical loading. It is one of the first models that provides an explicit coupling between mechanical and angiogenic factors. As both factors have been identified to play a key role in the occurrence of delayed and nonunions, the model allows to further explore their etiology and treatment. [less ▲]

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See detailModelling of peri-implant osteogenesis by means of a fracture healing mode
Amor, Nadia; Geris, Liesbet ULg; Vander Sloten, Jos et al

in Journal of Biomechanics (2008), 41(S1), 289

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See detailComputational modelling of peri-implant healing
Amor, Nadia; Geris, Liesbet ULg; Vander Sloten, Jos et al

in Middleton, J.; Jones, M. L.; Shrive, N. (Eds.) Proceedings of the 8th interantional symposium on Computer Methods in Biomechanics and Biomedical Engineering (2008)

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See detailApplication of mechanoregulatory models to simulate peri-implant tissue formation in an in vivo bone chamber
Geris, Liesbet ULg; Vandamme, Katleen; Naert, Ignace et al

in Journal of Biomechanics (2008), 41(1), 145-154

Several mechanoregulatory tissue differentiation models have been proposed over the last decade. Corroboration of these models by comparison with experimental data is necessary to determine their ... [more ▼]

Several mechanoregulatory tissue differentiation models have been proposed over the last decade. Corroboration of these models by comparison with experimental data is necessary to determine their predictive power. So far, models have been applied with various success rates to different experimental set-ups investigating mainly secondary fracture heating. In this study, the mechanoregulatory models are applied to simulate the implant osseointegration process in a repeated sampling in vivo bone chamber, placed in a rabbit tibia. This bone chamber provides a mechanically isolated environment to study tissue differentiation around titanium implants loaded in a controlled manner. For the purpose of this study, bone formation around loaded cylindrical and screw-shaped implants was investigated. Histologically, no differences were found between the two implant geometries for the global amount of bone formation in the entire chamber. However, a significantly larger amount of bone-to-implant contact was observed for the screw-shaped implant compared to the cylindrical implant. In the simulations, a larger amount of bone was also predicted to be in contact with the screw-shaped implant. However, other experimental observations could not be predicted. The simulation results showed a distribution of cartilage, fibrous tissue and (im)mature bone, depending on the mechanoregulatory model that was applied. In reality, no cartilage was observed. Adaptations to the differentiation models did not lead to a better correlation between experimentally observed and numerically predicted tissue distribution patterns. The hypothesis that the existing mechanoregulatory models were able to predict the patterns of tissue formation in the in vivo bone chamber could not be fully sustained. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailAngiogenesis in bone fracture healing: a bioregulatory model.
Geris, Liesbet ULg; Gerisch, Alf; Sloten, Jos Vander et al

in Journal of Theoretical Biology (2008), 251(1), 137-58

The process of fracture healing involves the action and interaction of many cells, regulated by biochemical and mechanical signals. Vital to a successful healing process is the restoration of a good ... [more ▼]

The process of fracture healing involves the action and interaction of many cells, regulated by biochemical and mechanical signals. Vital to a successful healing process is the restoration of a good vascular network. In this paper, a continuous mathematical model is presented that describes the different fracture healing stages and their response to biochemical stimuli only (a bioregulatory model); mechanoregulatory effects are excluded here. The model consists of a system of nonlinear partial differential equations describing the spatiotemporal evolution of concentrations and densities of the cell types, extracellular matrix types and growth factors indispensable to the healing process. The model starts after the inflammation phase, when the fracture callus has already been formed. Cell migration is described using not only haptokinetic, but also chemotactic and haptotactic influences. Cell differentiation is controlled by the presence of growth factors and sufficient vascularisation. Matrix synthesis and growth factor production are controlled by the local cell and matrix densities and by the local growth factor concentrations. Numerical simulations of the system, using parameter values based on experimental data obtained from literature, are presented. The simulation results are corroborated by comparison with experimental data from a standardised rodent fracture model. The results of sensitivity analyses on the parameter values as well as on the boundary and initial conditions are discussed. Numerical simulations of compromised healing situations showed that the establishment of a vascular network in response to angiogenic growth factors is a key factor in the healing process. Furthermore, a correct description of cell migration is also shown to be essential to the prediction of realistic spatiotemporal tissue distribution patterns in the fracture callus. The mathematical framework presented in this paper can be an important tool in furthering the understanding of the mechanisms causing compromised healing and can be applied in the design of future fracture healing experiments. [less ▲]

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See detailA coupled mechanobioregulatory model for the simulation of peri-implant bone formation in an in vivo bone chamber
Geris, Liesbet ULg; Vandamme, K.; Duyck, J. et al

in Proceedings of the second thematic workshop of the European Society of Biomechanics on Finite Element modelling in Biomechanis and Mechanobiology (2007, August)

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See detailMathematical modeling of bone regeneration during fracture healing and implant osseointegration
Geris, Liesbet ULg

Doctoral thesis (2007)

Despite the extensive body of literature on bone regeneration, many questions remain on e.g. the regulatory mechanisms and potential treatment strategies of pathological regeneration cases. The hypothesis ... [more ▼]

Despite the extensive body of literature on bone regeneration, many questions remain on e.g. the regulatory mechanisms and potential treatment strategies of pathological regeneration cases. The hypothesis underlying this work states that mathematical models of bone regeneration can make a substantial contribution to this domain by proposing pathological regeneration mechanisms and designing therapies, which can subsequently be tested experimentally. In the first part of this work, existing mechanoregulatory and bioregulatory models of bone regeneration are implemented and applied to both implant osseointegration and fracture healing set-ups. A quantitative comparison with experimental results is performed. Thorough sensitivity analyses are carried out to assess the influence of various modelling aspects on the simulation outcome. Shortcomings of these models are identified and suggestions for improvements are made. In the second part of this work, a novel bioregulatory model of bone regeneration is developed in which several of the previously defined shortcomings are addressed. This model includes key aspects of the regeneration process such as intramembranous and endochondral ossification, angiogenesis and directed cell motion. The results obtained with this novel model are corroborated both qualitatively and quantitatively by comparison with experimental data for normal fracture healing. Cases of pathological fracture healing are simulated and experimentally testable therapeutic strategies are implemented. The last part of this work describes the establishment of a mathematical framework, based on the previously developed bioregulatory model, in which the regulatory influence of both biological and mechanical factors is combined. This is the first model of bone regeneration in which the coupling between mechanical loading and angiogenesis is made in an explicit and mechanistic manner. Several examples are given to illustrate the added value of this approach in simulating normal and pathological bone regeneration. In summary, this work demonstrates the potential of mathematical models in advancing the knowledge on bone regeneration and designing treatment strategies for pathological healing cases. [less ▲]

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See detailInfluence of immediate loading and implant design on bone formation
Vandamme, K.; Naert, Ignace; Geris, Liesbet ULg et al

in Proceedings of the 85th General Session & Exhibition of the IADR (2007)

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