References of "Carmeliet, G"
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See detailMechanisms of ectopic bone formation by human osteoprogenitor cells on CaP biomaterial carriers.
Chai, Y. C.; Roberts, S. J.; Desmet, E. et al

in Biomaterials (2012)

Stem cell-based strategies for bone regeneration, which use calcium phosphate (CaP)-based biomaterials in combination with developmentally relevant progenitor populations, have significant potential for ... [more ▼]

Stem cell-based strategies for bone regeneration, which use calcium phosphate (CaP)-based biomaterials in combination with developmentally relevant progenitor populations, have significant potential for clinical repair of skeletal defects. However, the exact mechanism of action and the stem cell-host-material interactions are still poorly understood. We studied if pre-conditioning of human periosteum-derived cells (hPDCs) in vitro could enhance, in combination with a CaP-based biomaterial carrier, ectopic bone formation in vivo. By culturing hPDCs in a biomimetic calcium (Ca(2+)) and phosphate (P(i)) enriched culture conditions, we observed an enhanced cell proliferation, decreased expression of mesenchymal stem cell (MSC) markers and upregulation of osteogenic genes including osterix, Runx2, osteocalcin, osteopontin, and BMP-2. However, the in vitro pre-conditioning protocols were non-predictive for in vivo ectopic bone formation. Surprisingly, culturing in the presence of Ca(2+) and P(i) supplements resulted in partial or complete abrogation of in vivo ectopic bone formation. Through histological, immunohistochemical and microfocus X-ray computed tomography (muCT) analysis of the explants, we found that in situ proliferation, collagen matrix deposition and the mediation of osteoclastic activity by hPDCs are associated to their ectopic bone forming capacity. These data were validated by the multivariate analysis and partial least square regression modelling confirming the non-predictability of in vitro parameters on in vivo ectopic bone formation. Our series of experiments provided further insights on the stem cell-host-material interactions that govern in vivo ectopic bone induction driven by hPDCs on CaP-based biomaterials. [less ▲]

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See detailNumerical simulation and experimental validation of murine fracture healing
Geris, Liesbet ULg; Gerisch, A.; Maes, C. et al

in Proceedings of the fifth national day on biomedical engineering (2005)

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See detailNumerical simulation and experimental validation of murine fracture healing
Geris, Liesbet ULg; Gerisch, A.; Maes, C. et al

in Proceedings of the European Conference on Mathematical and Theoretical Biology (2005)

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See detailThe pro- or antiangiogenic effect of plasminogen activator inhibitor 1 is dose dependent
Devy, L.; Blacher, Silvia ULg; Grignet-Debrus, Christine ULg et al

in FASEB Journal (2002), 16(2), 147-54

Plasminogen activator inhibitor 1 (PAI-1) is believed to control proteolytic activity and cell migration during angiogenesis. We previously demonstrated in vivo that this inhibitor is necessary for ... [more ▼]

Plasminogen activator inhibitor 1 (PAI-1) is believed to control proteolytic activity and cell migration during angiogenesis. We previously demonstrated in vivo that this inhibitor is necessary for optimal tumor invasion and vascularization. We also showed that PAI-1 angiogenic activity is associated with its control of plasminogen activation but not with the regulation of cell-matrix interaction. To dissect the role of the various components of the plasminogen activation system during angiogenesis, we have adapted the aortic ring assay to use vessels from gene-inactivated mice. The single deficiency of tPA, uPA, or uPAR, as well as combined deficiencies of uPA and tPA, did not dramatically affect microvessel formation. Deficiency of plasminogen delayed microvessel outgrowth. Lack of PAI-1 completely abolished angiogenesis, demonstrating its importance in the control of plasmin-mediated proteolysis. Microvessel outgrowth from PAI-1(-/-) aortic rings could be restored by adding exogenous PAI-1 (wild-type serum or purified recombinant PAI-1). Addition of recombinant PAI-1 led to a bell-shaped angiogenic response clearly showing that PAI-1 is proangiogenic at physiological concentrations and antiangiogenic at higher levels. Using specific PAI-1 mutants, we could demonstrate that PAI-1 promotes angiogenesis at physiological (nanomolar) concentrations through its antiproteolytic activity rather than by interacting with vitronectin. [less ▲]

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See detailThe Plasminogen Activator Inhibitor PAI-1 Controls in Vivo Tumor Vascularization by Interaction with Proteases, Not Vitronectin. Implications for Antiangiogenic Strategies
Bajou, Khalid ULg; Masson, Véronique ULg; Gerard, R. D. et al

in Journal of Cell Biology (2001), 152(4), 777-84

The plasminogen (Plg)/plasminogen activator (PA) system plays a key role in cancer progression, presumably via mediating extracellular matrix degradation and tumor cell migration. Consequently, urokinase ... [more ▼]

The plasminogen (Plg)/plasminogen activator (PA) system plays a key role in cancer progression, presumably via mediating extracellular matrix degradation and tumor cell migration. Consequently, urokinase-type PA (uPA)/plasmin antagonists are currently being developed for suppression of tumor growth and angiogenesis. Paradoxically, however, high levels of PA inhibitor 1 (PAI-1) are predictive of a poor prognosis for survival of patients with cancer. We demonstrated previously that PAI-1 promoted tumor angiogenesis, but by an unresolved mechanism. We anticipated that PAI-1 facilitated endothelial cell migration via its known interaction with vitronectin (VN) and integrins. However, using adenoviral gene transfer of PAI-1 mutants, we observed that PAI-1 promoted tumor angiogenesis, not by interacting with VN, but rather by inhibiting proteolytic activity, suggesting that excessive plasmin proteolysis prevents assembly of tumor vessels. Single deficiency of uPA, tissue-type PA (tPA), uPA receptor, or VN, as well as combined deficiencies of uPA and tPA did not impair tumor angiogenesis, whereas lack of Plg reduced it. Overall, these data indicate that plasmin proteolysis, even though essential, must be tightly controlled during tumor angiogenesis, probably to allow vessel stabilization and maturation. These data provide insights into the clinical paradox whereby PAI-1 promotes tumor progression and warrant against the uncontrolled use of uPA/plasmin antagonists as tumor angiogenesis inhibitors. [less ▲]

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