References of "Geris, Liesbet"
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See detailContrast enhanced nanoCT for 3D quantitative and spatial analysis of in vitro manufactured extracellular matrix in metallic tissue engineering scaffolds
Sonnaert, Maarten; Papantoniou, Ioannis; Geris, Liesbet ULg et al

in Abstract book User Meeting Bruker MicroCT 2013 (2013)

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See detailMicro-CT evaluation of the effect of material, donor and implantation site variability on the bone forming capacity of progenitor cell/CaP-collagen constructs implanted ectopically in nude mice
Van Hove, Astrid; Geeroms, Carla; Maréchal, Marina et al

in Abstract book User Meeting Bruker MicroCT 2013 (2013)

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See detailThree dimensional characterization of tissue-engineered constructs by contrast enhanced nanofocus computed tomography.
Papantoniou, Ioannis; Sonnaert, Maarten; Geris, Liesbet ULg et al

in Tissue engineering. Part C, Methods (2013)

In order to successfully implement tissue engineered (TE) constructs as part of a clinical therapy, it is necessary to first develop and validate quality control tools that will ensure accurate and ... [more ▼]

In order to successfully implement tissue engineered (TE) constructs as part of a clinical therapy, it is necessary to first develop and validate quality control tools that will ensure accurate and consistent TE construct release specifications. Hence advanced methods to monitor TE construct properties need to be further developed. In this study we showed proof of concept for contrast enhanced nanofocus computed tomography (CE-nanoCT) as a 'whole-construct' imaging technique with non-invasive potential that enables 3D visualization and quantification of in vitro engineered extracellular matrix (ECM) in TE constructs. In particular we performed a 3D quantitative and qualitative structural and spatial assessment of the in vitro engineered ECM, formed during static and perfusion bioreactor cell culture in 3D TE scaffolds, using two contrast agents, namely Hexabrix(R) and phosphotungstic acid (PTA). CE-nanoCT image data were validated by comparison to Live/Dead viability/cytotoxicity and picrosirius red staining data, and to the net dry weight of the TE constructs. When using Hexabrix(R) as contrast agent, ECM volume fitted linearly with net dry ECM weight independent from the flow rate used. When using PTA as contrast agent, CE-nanoCT data showed pronounced distinction between flow conditions when compared to both net dry weight and picrosirius red staining data although linearity was maintained, indicating culture-specific structural ECM differences. This was attributed to the binding specificity of this contrast agent. This novel type of information can contribute to optimize bioreactor culture conditions and potentially critical quality characteristics of TE constructs such as ECM quantity and homogeneity, facilitating the gradual transformation of 'TE constructs' in well characterized 'TE products'. [less ▲]

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See detailMechanobiological modeling can explain orthodontic tooth movement: three case studies.
Van Schepdael, An ULg; Vander Sloten, J.; Geris, Liesbet ULg

in Journal of Biomechanics (2013), 46(3), 470-7

Progress in medicine and higher expectation of quality of life has led to a higher demand for several dental and medical treatments. This increases the occurrence of situations in which orthodontic ... [more ▼]

Progress in medicine and higher expectation of quality of life has led to a higher demand for several dental and medical treatments. This increases the occurrence of situations in which orthodontic treatment is complicated by pathological conditions, medical therapies and drugs. Together with experiments, computer models might lead to a better understanding of the effect of pathologies and medical treatment on tooth movement. This study uses a previously presented mechanobiological model of orthodontic tooth displacement to investigate the effect of pathologies and (medical) therapies on the result of orthodontic treatment by means of three clinically relevant case studies looking at the effect of estrogen deficiency, the effect of OPG injections and the influence of fluoride intake. When less estrogen was available, the model predicted bone loss and a rise in the number of osteoclasts present at the compression side, and a faster bone resorption. These effects were also observed experimentally. Experiments disagreed on the effect of estrogen deficiency on bone formation, while the mechanobiological model predicted very little difference between the pathological and the non-pathological case at formation sites. The model predicted a decrease in tooth movement after OPG injections or fluoride intake, which was also observed in experiments. Although more experiments and model analysis is needed to quantitatively validate the mechanobiological model used in this study, its ability to conceptually describe several pathological conditions is an important measure for its validity. [less ▲]

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See detailMechanisms of cell migration in the adult brain: modelling subventricular neurogenesis.
Van Schepdael, An ULg; Ashbourn, J. M. A.; Beard, R. et al

in Computer Methods in Biomechanics & Biomedical Engineering (2013)

Neurogenesis has been the subject of active research in recent years. Although the majority of neurons form during the embryonic period, neurogenesis continues in restricted regions of the mammalian brain ... [more ▼]

Neurogenesis has been the subject of active research in recent years. Although the majority of neurons form during the embryonic period, neurogenesis continues in restricted regions of the mammalian brain well into adulthood. In rodent brains, neuronal migration is present in the rostral migratory stream (RMS), connecting the subventricular zone to the olfactory bulb (OB). The migration in the RMS is characterised by a lack of dispersion of neuroblasts into the surrounding tissues and a highly directed motion towards the OB. This study uses a simple mathematical model to investigate several theories of migration of neuroblasts through the RMS proposed in the literature, including chemo-attraction, chemorepulsion, general inhibition and the presence of a migration-inducing protein. Apart from the general inhibition model, all the models were able to provide results in good qualitative correspondence with the experimental observations. [less ▲]

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See detailAnalytical determination of stress patterns in the periodontal ligament during orthodontic tooth movement.
Van Schepdael, An ULg; Geris, Liesbet ULg; Vander Sloten, Jos

in Medical Engineering & Physics (2013), 35(3), 403-10

A dedicated software package that allows simulation of tooth movement can lead to shortening of the treatment program in orthodontics. A first step in the development of this software is the modelling of ... [more ▼]

A dedicated software package that allows simulation of tooth movement can lead to shortening of the treatment program in orthodontics. A first step in the development of this software is the modelling of the movement of a single tooth. Forces applied to the crown of the tooth are transmitted to the alveolar bone through the periodontal ligament, stretching, and compressing the ligament, eventually resulting in tooth movement. This paper presents an analytical model that predicts stresses and strains inside this ligament by approximating the shape of the root as an elliptic paraboloid. The model input consists of 2 material parameters and 4 geometrical parameters. To assess the accuracy of the model a finite element model (FEM) was constructed to compare the results and the influence of the eccentricity of the root was studied. The results show that the model is able to successfully describe the global behavior of the PDL and, except at a region near the alveolar crest, the differences between analytical and FEM results are small. In contrast to FEM, the analytical model does not require setting up a 3D-model and creating a mesh, allowing for significantly lower computational times and reducing cost when implementing in clinical practice. [less ▲]

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See detailTo heal or not to heal: a multiscale model of the influence of oxygen during bone fracture healing.
Carlier, Aurélie ULg; Geris, Liesbet ULg; Van Oosterwyck, Hans

Poster (2012, October 24)

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See detailA multiscale model of sprouting angiogenesis during fracture healing.
Carlier, Aurélie ULg; Geris, Liesbet ULg; Van Oosterwyck, Hans

Conference (2012, September 18)

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See detailA Dynamic Graph Model of Endochondral Ossification can assess the Importance of Biological Actors in Differentiation
Kerkhofs, Johan ULg; Van Oosterwyck, Hans; Geris, Liesbet ULg

Conference (2012, September 18)

Cell-based tissue engineering constructs are a promising avenue for the treatment of long bone defects since they provide the primordial ingredients for bone regeneration. The construct provides the ... [more ▼]

Cell-based tissue engineering constructs are a promising avenue for the treatment of long bone defects since they provide the primordial ingredients for bone regeneration. The construct provides the appropriate micro-environment through the carrier, cells to form tissue and chemical cues to kick start the natural bone forming process. Clearly this approach will benefit from a more comprehensive appreciation of how cell populations and the microenvironment provided by the carrier can impact on bone formation in all its complexities. A cornucopia of studies of developmental biology have revealed many biological actors that together form a central network that orchestrates cell behaviour during this process and assures its robustness. This knowledge can be brought to bear specifically in the form of a mathematical model of endochondral ossification, the dominant type of ossification. This model can facilitate the understanding of how growth factors and transcription factors influence cell fate decisions and consequently answer the question whether they can boost bone healing. The model formalism accommodates the qualitative information that is typically available in developmental studies. The network comprises 46 nodes and 161 interactions, shown to be important in endochondral ossification. To simulate network dynamics in discrete time the normalized value of each gene is determined by additive functions where all interactions are assumed to be equally powerful. Furthermore, each species is represented by a fast variable (activity level, as determined by post translation modifications) which is assumed to be in equilibrium with a slow variable (mRNA) at all times. Through a Monte Carlo approach the importance of each node in the stability of chondrocytic phenotypes (proliferating, hypertrophic) is assessed. The hypertrophic state, driven by Runx2, is more stable than the proliferating chondrocyte. This higher stability seems to be conferred by faster reactions that favor the hypertrophic phenotype. In addition, the results point out that some transcription factors are necessary for the induction of a certain phenotype, whereas other transcription factors are required to maintain the phenotype, but are not necessary capable of inducing it. Overall, the model allows the importance of several important factors in the fate decision of mesenchymal cells to be quantitatively assessed based mainly on topological information. [less ▲]

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See detailMultiscale modeling of in the influence of oxygen during bone fracture healing.
Carlier, Aurélie ULg; Van Gastel, Nick; Carmeliet, Geert et al

Poster (2012, September 17)

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See detailMultiscale modeling of sprouting angiogenesis: tip cells are selected for the top.
Carlier, Aurélie ULg; Geris, Liesbet ULg; Van Oosterwyck, Hans

Poster (2012, September 05)

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See detailMathematical Level-Set Modelling of Cell Growth on 3D Surfaces
Guyot, Yann ULg; Papatoniou, Ioannis; Chai, Yoke Chin et al

Poster (2012, September)

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See detailMultiscale modelling of the influence of VEGF on sprouting angiogenesis.
Carlier, Aurélie ULg; Geris, Liesbet ULg; Van Oosterwyck, Hans

Poster (2012, July 06)

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See detailBridging the Gap: A Theoretical Model of Mechanotransduction Through ERK Signalling
Kerkhofs, Johan ULg; Geris, Liesbet ULg; Bosmans, Bart et al

Conference (2012, July 02)

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See detailTip cells at the top: a multiscale model of sprouting angiogenesis.
Carlier, Aurélie ULg; Geris, Liesbet ULg; Van Oosterwyck, Hans

Conference (2012, July 01)

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See detailRelating the Chondrocyte Gene Network to Growth Plate Morphology: From Genes to Phenotype
Kerkhofs, Johan ULg; Roberts, Scott J; Luyten, Frank P et al

in PLoS ONE (2012)

During endochondral ossification, chondrocyte growth and differentiation is controlled by many local signalling pathways. Due to crosstalks and feedback mechanisms, these interwoven pathways display a ... [more ▼]

During endochondral ossification, chondrocyte growth and differentiation is controlled by many local signalling pathways. Due to crosstalks and feedback mechanisms, these interwoven pathways display a network like structure. In this study, a large-scale literature based logical model of the growth plate network was developed. The network is able to capture the different states (resting, proliferating and hypertrophic) that chondrocytes go through as they progress within the growth plate. In a first corroboration step, the effect of mutations in various signalling pathways of the growth plate network was investigated. [less ▲]

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See detailCoupling Cell Mechanics and Intracellular Signalling: Mechanotransduction through ERK
Kerkhofs, Johan ULg; Geris, Liesbet ULg; Bosmans, Bart et al

in Middleton, John (Ed.) The Proceedings of the 10th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering. Hotel Berlin, Berlin, Germany, April 7th – 11th, 2012 pages:0-0 (2012, April 12)

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See detailTip cells at the top: multiscale modeling of angiogenesis during fracture healing
Carlier, Aurélie ULg; Geris, Liesbet ULg; Van Oosterwyck, Hans

in Computer Methods in Biomechanics and Biomedical Engineering (CMBBE) - Proceedings (2012, April)

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See detailMOSAIC: a multiscale model of osteogenesis and sprouting angiogenesis with lateral inhibition of endothelial cells.
Carlier, Aurélie ULg; Geris, Liesbet ULg; Bentley, Katie et al

in PLoS Computational Biology (2012), 8(10), 1002724

The healing of a fracture depends largely on the development of a new blood vessel network (angiogenesis) in the callus. During angiogenesis tip cells lead the developing sprout in response to ... [more ▼]

The healing of a fracture depends largely on the development of a new blood vessel network (angiogenesis) in the callus. During angiogenesis tip cells lead the developing sprout in response to extracellular signals, amongst which vascular endothelial growth factor (VEGF) is critical. In order to ensure a correct development of the vasculature, the balance between stalk and tip cell phenotypes must be tightly controlled, which is primarily achieved by the Dll4-Notch1 signaling pathway. This study presents a novel multiscale model of osteogenesis and sprouting angiogenesis, incorporating lateral inhibition of endothelial cells (further denoted MOSAIC model) through Dll4-Notch1 signaling, and applies it to fracture healing. The MOSAIC model correctly predicted the bone regeneration process and recapitulated many experimentally observed aspects of tip cell selection: the salt and pepper pattern seen for cell fates, an increased tip cell density due to the loss of Dll4 and an excessive number of tip cells in high VEGF environments. When VEGF concentration was even further increased, the MOSAIC model predicted the absence of a vascular network and fracture healing, thereby leading to a non-union, which is a direct consequence of the mutual inhibition of neighboring cells through Dll4-Notch1 signaling. This result was not retrieved for a more phenomenological model that only considers extracellular signals for tip cell migration, which illustrates the importance of implementing the actual signaling pathway rather than phenomenological rules. Finally, the MOSAIC model demonstrated the importance of a proper criterion for tip cell selection and the need for experimental data to further explore this. In conclusion, this study demonstrates that the MOSAIC model creates enhanced capabilities for investigating the influence of molecular mechanisms on angiogenesis and its relation to bone formation in a more mechanistic way and across different time and spatial scales. [less ▲]

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