Publications (9) View all
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Article: The identification of genetic pathways involved in vascular adaptations after physical deconditioning versus exercise training in humans.
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ABSTRACT: Physical inactivity and exercise training result in opposite adaptations of vascular structure. However, the molecular mechanisms behind these adaptations are not completely understood. Therefore, we used a unique study design to examine both vascular characteristics of the superficial femoral artery (using ultrasound) and gene expression levels (from a muscle biopsy) in human models for physical deconditioning and exercise training. First, we compared able-bodied controls (n=6) with spinal cord-injured (SCI) individuals (n=8) to assess the effects of long-term deconditioning. Subsequently, able-bodied controls underwent short-term lower limb deconditioning using 3 weeks of unilateral limb suspension. SCI individuals were examined before and after 6 weeks functional electrical stimulation exercise training. Baseline diameter and hyperemic flow were lower after short- and long-term deconditioning and higher after exercise training, whilst intima-media thickness/lumen ratio was increased with short- and long-term deconditioning and decreased with exercise training. Regarding gene expression levels of vasculature-related genes, we found that groups of genes including the vascular endothelial growth factor (VEGF) pathway, transforming growth factor beta 1 (TGFB1), and extracellular matrix (ECM) proteins strongly related with vascular adaptations in humans. This approach resulted in the identification of important genes that may be involved in vascular adaptations after physical deconditioning and exercise.Experimental physiology 10/2012; · 3.17 Impact Factor -
Article: The expression of genes involved in fatty acid transport and insulin signaling is altered by physical inactivity and exercise training in human skeletal muscle.
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ABSTRACT: Physical deconditioning is associated with the development of chronic diseases, including type 2 diabetes and cardiovascular disease. Exercise training effectively counteracts these developments, but the underlying mechanisms are largely unknown. To gain more insight in these mechanisms, muscular gene expression levels were assessed after physical deconditioning and after exercise training of the lower limbs in humans using gene expression microarrays. In order to exclude systemic effects, we used human models for local physical inactivity (three weeks of unilateral limb suspension) and for local exercise training (six weeks of functional electrical stimulation exercise of the extremely deconditioned legs of individuals with a spinal cord injury). The most interesting subset of genes, those downregulated after deconditioning as well as upregulated after exercise training, contained 18 genes related to both the 'insulin action' and 'adipocytokine signaling' pathway. Of these genes, the three with strongest up/downregulation were the muscular fatty acid binding protein 3 (FABP3), the fatty acid oxidizing enzyme hydroxyacyl-CoA dehydrogenase (HADH), and the mitochondrial fatty acid transporter solute carrier 25 family member A20 (SLC25A20). The expression levels of these genes were confirmed using RT-qPCR. The results of the present study indicate an important role for a decreased transport and metabolism of fatty acids which provides a link between physical activity levels and insulin signaling in relation to physical (in)activity.AJP Endocrinology and Metabolism 09/2012; · 4.75 Impact Factor -
Article: Repair of surgically created diaphragmatic defect in rat with use of a crosslinked porous collagen scaffold.
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ABSTRACT: Large defects in congenital diaphragmatic hernia are closed by patch repair, which is associated with a high complication risk and reherniation rate. New treatment modalities are warranted. We evaluated the feasibility of using an acellular biodegradable collagen bioscaffold for a regenerative medicine approach to close a surgically created diaphragmatic defect in a rat model. Scaffold degradation, cellular ingrowth and regeneration of the diaphragm were studied. In 25 rats, a subcostal incision was made and one third of the right hemidiaphragm was resected. Crosslinked porous type I collagen scaffolds (Ø ~ 14 mm) were sutured into the lesion. Rats were sacrificed at 2, 4, 8, 12 or 24 weeks after scaffold implantation. Implants were evaluated macroscopically and (immuno)histologically. Survival after surgery was 88% with no evidence of reherniation. Histological examination showed that the collagen scaffold degraded slowly and new collagen, elastin and mesothelium were deposited. Blood vessels were observed primarily at the outer borders of the scaffold; their number gradually increased in time. Muscle fibres were found on the scaffold covering up to 10% of the defect. Macroscopically, adhesion of the scaffold to the liver was observed. Use of a collagen scaffold to close a surgically created diaphragmatic defect is feasible, with evidence of new tissue formation. The use of crosslinked collagen scaffolds allows targeted modification; e.g. addition of growth factors to further stimulate growth of muscle cells. Copyright © 2012 John Wiley & Sons, Ltd.Journal of Tissue Engineering and Regenerative Medicine 05/2012; · 3.28 Impact Factor -
Article: Construction of a microstructured collagen membrane mimicking the papillary dermis architecture and guiding keratinocyte morphology and gene expression.
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ABSTRACT: A papillary-structured collagen fibril membrane is created, mimicking the 3D-architecture of the human papillary dermis. Primary human keratinocytes cultured to confluency on papillar-structured films are compared to keratinocytes cultured on flat membranes. Microscopical evaluation reveals the presence of morphologically distinct cells at the base of the papillar structures that are not observed on flat membranes. Gene expression microarrays and RT-qPCR indicate that these cells are in a more proliferative/migrational state, whereas cells on flat membranes have a more differentiated expression profile. Immunohistochemical stainings confirm these results. In conclusion, specific collagen architecture can direct keratinocyte behavior, and this may be used to further improve skin regeneration.Macromolecular Bioscience 03/2012; 12(5):675-91. · 3.89 Impact Factor -
Article: A comparison of seven methods to analyze heparin in biomaterials: quantification, location, and anticoagulant activity.
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ABSTRACT: Glycosaminoglycans, like heparin, are frequently incorporated in biomaterials because of their capacity to bind and store growth factors and because of their hydrating properties. Heparin is also often used in biomaterials for its anticoagulant activity. Analysis of biomaterial-bound heparin is challenging because most assays are based on heparin in solution. In this study, seven different methods were probed to analyze heparin covalently attached to collagen scaffolds. For each method, the basic mechanism and the advantages and disadvantages are given. An analysis by the factor Xa assay and the Farndale assay clearly indicated that the amount of immobilized heparin cannot be determined correctly when the scaffold is intact. Scaffolds had to be proteolytically digested or acid treated to obtain reliable measurements. Methods used to quantify the amount of bound heparin included a hexosamine assay, an uronic acid assay, a Farndale assay, agarose gel electrophoresis, and immuno-dot blot analysis. Location and semiquantification of heparin were accomplished by immunofluorescence. Although all assays had their advantages and disadvantages, the hexosamine assay turned out to be the most robust and is recommended as the preferred assay to quantify the amount of heparin bound to scaffolds. It is applicable to all scaffolds that are acid hydrolyzable. This study may allow researchers in the field to select the most appropriate method to analyze glycosaminoglycans in biomaterials.Tissue Engineering Part C Methods 03/2011; 17(6):669-76. · 4.64 Impact Factor
