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Item type:Publication, Access status: with files , Osteoidosis leads to altered differentiation and function of osteoclasts(Wiley-Blackwell, 2020-04-13); ; ; ; In patients with osteomalacia, a defect in bone mineralization leads to changed characteristics of the bone surface. Considering that the properties of the surrounding matrix influence function and differentiation of cells, we aimed to investigate the effect of osteoidosis on differentiation and function of osteoclasts. Based on osteomalacic bone biopsies, a model for osteoidosis in vitro (OIV) was established. Peripheral blood mononuclear cells were differentiated to osteoclasts on mineralized surfaces (MS) as internal control and on OIV. We observed a significantly reduced number of osteoclasts and surface resorption on OIV. Atomic force microscopy revealed a significant effect of the altered degree of mineralization on surface mechanics and an unmasking of collagen fibres on the surface. Indeed, coating of MS with RGD peptides mimicked the resorption phenotype observed in OIV, suggesting that the altered differentiation of osteoclasts on OIV might be associated with an interaction of the cells with amino acid sequences of unmasked extracellular matrix proteins containing RGD sequences. Transcriptome analysis uncovered a strong significant up-regulation of transmembrane glycoprotein TROP2 in osteoclastic cultures on OIV. TROP2 expression on OIV was also confirmed on the protein level and found on the bone surface of patients with osteomalacia. Taken together, our results show a direct influence of the mineralization state of the extracellular matrix surface on differentiation and function of osteoclasts on this surface which may be important for the pathophysiology of osteomalacia and other bone disorders with changed ratio of osteoid to bone.Publicationtype: Journal ArticleScopus© Citations 6 149 160 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Biodegradable poly (lactic acid-co-glycolic acid) scaffolds as carriers for geneticallymodified fibroblasts(Public Library of Science (PLoS), 2017-04-05); ; ; ; Recent advances in gene delivery into cells allow improved therapeutic effects in gene therapy trials. To increase the bioavailability of applied cells, it is of great interest that transfected cells remain at the application site and systemic spread is minimized. In this study, we tested clinically used biodegradable poly(lactic acid-co-glycolic acid) (PLGA) scaffolds (Vicryl & Ethisorb) as transient carriers for genetically modified cells. To this aim, we used human fibroblasts and examined attachment and proliferation of untransfected cells on the scaffolds in vitro, as well as the mechanical properties of the scaffolds at four time points (1, 3, 6 and 9 days) of cultivation. Furthermore, the adherence of cells transfected with green fluorescent protein (GFP) and vascular endothelial growth factor (VEGF165) and also VEGF165 protein secretion were investigated. Our results show that human fibroblasts adhere on both types of PLGA scaffolds. However, proliferation and transgene expression capacity were higher on Ethisorb scaffolds most probably due to a different architecture of the scaffold. Additionally, cultivation of the cells on the scaffolds did not alter their biomechanical properties. The results of this investigation could be potentially exploited in therapeutic regiments with areal delivery of transiently transfected cells and may open the way for a variety of applications of cell-based gene therapy, tissue engineering and regenerative medicine.Publicationtype: Journal ArticleScopus© Citations 8 358 308 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Matrix demineralisation leads to altered differentiation and function of osteoclasts(Public Library of Science (PLoS), 2015); ; ; ; Publicationtype: Journal Article4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Three-dimensional quantification of calcium salt-composite resorption (CSC) in vitro by micro-computed tomography (Micro-CT)The commonly applied cell-based, two-dimensional (2D) in vitro resorption assays for biomaterials are limited in a variety of cases, including high initial roughness of material surface, uncontrollable solubilization (or resorption) of the entire material surface, or complex three-dimensional (3D) structure of the bioactive material itself. All these make the accurate assessment and successful selection of the optimal bone substitute material difficult. In vivo, micro-computed tomography (micro-CT) has been widely applied for the analysis of bone physiology and pathology, as well as for the 3D analysis of scaffolds for bone tissue engineering. In this study, we show that micro-CT can also be applied for the in vitro analysis of osteoclast-mediated resorption of biomaterials. For our experiments, we chose a calcium salt-composite (composite of calcium sulphate (CSC), calcium carbonate, glycerin-1,2,3-tripalmiate), which evades common 2D in vitro resorption analysis as a result of its high surface roughness and material composition. Human osteoclasts were differentiated from precursor cells on the surface of the material for 28 days. Cells were analyzed for expression of tartrate-resistant acid phosphatase 5b (TRAP5b), multinuclearity, and size. Volumetric analysis of resorption was performed by micro-CT. Multinucleated osteoclasts developed on the surface of the material. TRAP5b expression of the cells on CSC was comparable with TRAP5b expression of cells cultivated on dentin for the first 3 weeks of culture. At day 28, TRAP5b expression, cell number, and size of the TRAP+ cells were reduced on the CSC when compared with cells on dentin. Volumetric anaylsis by micro-CT showed a strong cellular effect on resorption of CSC. We consider micro-CT to be a promising technique for 3D quantification of cell-based resorption that will allow the study of cellular resorption of materials in vitro, which were up to now confined to animal experimental analysis. © 2014 The Minerals, Metals & Materials Society.Publicationtype: Journal Article3 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Bioresorption and degradation of biomaterialsThe human body is a composite structure, completely constructed of biodegradable materials. This allows the cells of the body to remove and replace old or defective tissue with new material. Consequently, artificial resorbable biomaterials have been developed for application in regenerative medicine. We discuss here advantages and disadvantages of these bioresorbable materials for medical applications and give an overview of typically used metals, ceramics and polymers. Methods for the quantification of bioresorption in vitro and in vivo are described. The next challenge will be to better understand the interface between cell and material and to use this knowledge for the design of " intelligent" materials that can instruct the cells to build specific tissue geometries and degrade in the process.Publicationtype: Journal Article4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , High amplitude direct compressive strain enhances mechanical properties of scaffold-free tissue-engineered cartilage(2011); ; ; ; Schüttler, DanielAdult cartilage has a limited healing capacity. Damages resulting from disease or injury increase over time and cause severe pain. One approach to reinstate the cartilage function is tissue engineering (TE). However, the generation of TE cartilage is time consuming and expensive and its properties are so far suboptimal. As in vivo cartilage is subject to loading, it is assumed that mechanical stimulation may enhance the quality of TE cartilage. In this study the short-term influence of variable compressive strain amplitudes on mechanical and biochemical properties of scaffold-free TE cartilage was investigated. Primary porcine chondrocytes were isolated, proliferated, redifferentiated, and transferred onto hydroxyapatite carriers, resulting in scaffold-free cartilage-carrier constructs. These constructs were placed in a custom-made bioreactor. Compression amplitudes of 5%, 10%, and 20% were applied. In each experiment four constructs were loaded with dynamic compression (3000 cycles/day, 1 Hz) for 14 days and four constructs served as unloaded control. The cartilage was evaluated biochemically, histological, and mechanically. No difference in glycosaminoglycan or collagen content between the loaded and the control groups was found. However, a positive correlation between compression amplitude and normalized Young's modulus was detected (R2=0.59, p<0.001). The highest compression amplitude of 20% had the strongest positive effect on the mechanical properties of the TE cartilage (Young's modulus increase of 241±28% compared to unloaded control). The data presented suggest that preconditioning with higher load amplitudes might be an attractive way of generating stiffer tissue and may help accelerating the cultivation of mechanically competent TE cartilage. © 2011 Mary Ann Liebert, Inc.Publicationtype: Journal Article5