5 results on '"Wagermaier, Wolfgang"'
Search Results
2. The small world of osteocytes: connectomics of the lacuno-canalicular network in bone
- Author
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Kollmannsberger, Philip, Kerschnitzki, Michael, Repp, Felix, Wagermaier, Wolfgang, Weinkamer, Richard, and Fratzl, Peter
- Subjects
biomaterials ,bone ,mechanobiology ,networks ,osteocytes ,image analysis ,FOS: Physical sciences ,Quantitative Biology - Tissues and Organs ,Biological Physics (physics.bio-ph) ,ddc:570 ,FOS: Biological sciences ,Physics - Biological Physics ,Tissues and Organs (q-bio.TO) - Abstract
Osteocytes and their cell processes reside in a large, interconnected network of voids pervading the mineralized bone matrix of most vertebrates. This osteocyte lacuno-canalicular network (OLCN) is believed to play important roles in mechanosensing, mineral homeostasis, and for the mechanical properties of bone. While the extracellular matrix structure of bone is extensively studied on ultrastructural and macroscopic scales, there is a lack of quantitative knowledge on how the cellular network is organized. Using a recently introduced imaging and quantification approach, we analyze the OLCN in different bone types from mouse and sheep that exhibit different degrees of structural organization not only of the cell network but also of the fibrous matrix deposited by the cells. We define a number of robust, quantitative measures that are derived from the theory of complex networks. These measures enable us to gain insights into how efficient the network is organized with regard to intercellular transport and communication. Our analysis shows that the cell network in regularly organized, slow-growing bone tissue from sheep is less connected, but more efficiently organized compared to irregular and fast-growing bone tissue from mice. On the level of statistical topological properties (edges per node, edge length and degree distribution), both network types are indistinguishable, highlighting that despite pronounced differences at the tissue level, the topological architecture of the osteocyte canalicular network at the subcellular level may be independent of species and bone type. Our results suggest a universal mechanism underlying the self-organization of individual cells into a large, interconnected network during bone formation and mineralization., New Journal of Physics, 19, ISSN:1367-2630
- Published
- 2017
3. Scanning texture analysis of lamellar bone using microbeam synchrotron X-ray radiation.
- Author
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Wagermaier, Wolfgang, Gupta, Himadri S., Gourrier, Aurélien, Paris, Oskar, Roschger, Paul, Burghammer, Manfred, Riekel, Christian, and Fratzl, Peter
- Subjects
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BONES , *APATITE , *SYNCHROTRON radiation , *OPTICAL diffraction , *CRYSTAL texture , *OPTICAL resolution - Abstract
Texture analysis with microbeam scanning diffraction enables the local mapping of three-dimensional crystallite orientation in heterogeneous natural and synthetic materials. Cortical (compact) bone is an example of a hierarchically structured biocomposite, which is built mainly of cylindrical osteons, having a lamellar texture at the micrometre level. In this work, a combination of microbeam synchrotron X-ray texture analysis with thin sections of osteonal bone is used to measure the three-dimensional distribution of the c-axis orientation of the mineral apatite in bone with positional resolution of 1 µm. The data reduction procedure needed to go from the stereographic projection of X-ray intensity to the determination of the local orientation of mineralized collagen fibrils is described. The procedure can be applied to other mineralized tissues (such as trabecular bone and chitin) with micrometre scale and biologically controlled fibrillar texture. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
4. Scanning X-ray imaging with small-angle scattering contrast.
- Author
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Gourrier, Aurelien, Wagermaier, Wolfgang, Burghammer, Manfred, Lammie, Donna, Gupta, Himadri S., Fratzl, Peter, Riekel, Christian, Wess, Tim J., and Paris, Oskar
- Subjects
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X-ray scattering , *SCANNING electron microscopy , *TRANSMISSION electron microscopy , *EGGSHELLS , *X-ray optics , *NANOSTRUCTURED materials - Abstract
An X-ray scanning imaging technique using the integrated intensity of the small-angle X-ray scattering (SAXS) signal is presented. The technique is based on two-dimensional scanning of a thin sample section with an X-ray microbeam, collecting SAXS patterns at every scanning step using a two-dimensional detector. The integrated intensity within pre-defined regions of interest of the SAXS patterns is used to image bulk nanostructural features in the specimen with micrometre resolution which are usually not accessible by other methods such as light microscopy or scanning electron microscopy. The possibilities and limitations of the method are discussed with particular emphasis on the sources of contrast in the SAXS region for three biological specimens: cortical bone, eggshell and hair. Two main sources of image contrast are identified in the form of orientation effects for strongly anisotropic systems like cortical bone and differences in the local volume fraction of the scattering entities in eggshell. Moreover, other parameters than the integrated intensity can be quantitatively deduced from the SAXS patterns, for instance, the mean thickness of mineral platelets in bone or the strain distributions in a hair deformed plastically by microindentation. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
5. Der Effekt mechanischer Belastung auf die Knochenkrankheit in einem Modell des multiplen Myeloms
- Author
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Rummler, Maximilian, Fleck, Claudia, Willie, Bettina, Technische Universität Berlin, and Wagermaier, Wolfgang
- Subjects
mechanical loading ,Krebs ,mechanische Belastung ,mechanobiology ,bone ,Mechanobiologie ,Material-Charakterisierung ,Myelom ,myeloma ,Knochen ,cancer ,ddc:610 ,610 Medizin und Gesundheit ,material characterisation - Abstract
Multiple myeloma is a cancer of white blood cells which migrate to the bone marrow. In the bone marrow cavity these malignant cells interact with the present bone cells and over activate osteoclasts while simultaneously suppressing osteoblasts. These interactions lead to catastrophically bone loss, visible in radiographs as characteristic lesions within the cortex of bone. This progressed disease state is called multiple myeloma bone disease. While there are anti-resorptive therapies for the bone disease, till this day there is no anabolic treatment. A promising nonpharmacological therapy to prevent bone loss or even form new bone and therefore decrease fracture risk are physical stimuli such as exercise. While exercise is known to be beneficial to bone in healthy patients, it is largely unknown how physical stimuli effect multiple myeloma bone disease and if it is a valid therapeutic approach. Moreover, it is unknown how physical stimuli in the presence of multiple myeloma and even multiple myeloma itself influence the material quality of bone. The overall aim of this work was to investigate how controlled in vivo loading affects the bone mass, the microstructure, bone formation and resorption and the material quality in the presence of multiple myeloma. To obtain these answers, a wide range of material characterisation techniques were used. An axial compressive loading model was used to apply super-physiological loads to the tibiae of young, tumor bearing mice. The first aim was to study the effect of additional mechanical loading on the cortical and trabecular bone mass, microstructure and bone formation and resorption in the metaphyseal region of tumor injected tibia. The obtained results showed that in vivo loading can counteract the deleterious effects of the tumor. In tumor injected loaded mice, the cortical and trabecular bone mass was maintained as well as the microstructure in comparison to the nonloaded tumor injected mice. Furthermore, bone formation was increased in response to loading in those tumor bearing mice, while the resorption was not influenced. An interesting result was that the injection of either the tumor cells or a phosphate buffered saline solution led to a healing response in the tibia and subsequently to higher bone formation. However, loading did not seem to influence the material quality of bone. All parameters measure in loaded tumor bearing mice did not differ from nonloaded tumor bearing mice. Thus, the tumor does not alter the quality of the newly formed cortical bone, since no significant differences have been found in bone composition. However, the injection itself altered the material composition of bone, foremost in increased matrix mineralization and crystal size of the hydroxyapatite crystals in the bone matrix. The reason for this effect remains unclear, since the injected solution or the healing response of bone could cause such changes in material quality. Taken together, the presented results provide a broader understanding of the influence of additional mechanical stimuli in the presence of multiple myeloma. It can be concluded that mechanical stimulation can counteract the bone disease and therefore diminish or mitigate the deleterious bone loss. Furthermore, newly formed bone does not seem to lack quality. Therefore, mechanical stimulation could be a viable option as an adjuvant therapy in patients suffering from multiple myeloma bone disease., Das multiple Myelom beschreibt bösartig entartete antikörperproduzierende Zellen, welche ins Knochenmark wandern und dort ihre Nische finden. Diese entarteten Zellen interagieren mit den dort präsenten Knochenzellen und hyperaktivieren Osteoklasten bei gleichzeitiger Suppression der Osteoblasten. Diese Interaktionen führen zu einem katastrophalen Knochenverlust, sichtbar in Röntgenaufnahmen als charakteristische Läsionen im Kortex der befallenen Knochen. Die so vorangeschrittene Krankheit wird mit antiresorptiven Medikamenten behandelt, aber bis zum heutigen Tag gibt es keine Behandlung zum Wiederaufbau des Knochens. Eine vielversprechende nicht-medikamentöse Therapie, um Knochenverlust vorzubeugen oder neuen Knochen aufzubauen und dementsprechend das Frakturrisiko zu senken, ist mechanische Stimulation. Es ist bekannt, dass sportliche Betätigung bei Gesunden positive Auswirkung auf die Knochenmasse hat. Es ist jedoch unklar, ob dies auch für Patienten mit multiplen Myelom gilt und ein therapeutischer Ansatz sein könnte. Weiterhin ist es unklar, inwiefern physikalische Stimuli die Materialqualität des Knochens bei Patienten mit multiplem Myelom beeinflussen. Das vorrangige Ziel dieser Arbeit war zu untersuchen, wie die kontrollierte mechanische Belastung in vivo die Knochenmasse, -mikrostruktur, -formation und -resorption und die Materialeigenschaften des Knochens bei gleichzeitiger Präsenz eines multiplen Myeloms beeinflusst. Dafür wurden verschiedene Methoden zur Materialcharakterisierung angewandt. Ein mechanisches Belastungsmodell mit axialer Kompression wurde benutzt, um superphysiologische Belastung in der Tibia von jungen, tumortragenden Mäusen zu induzieren. Als erstes wurde der Effekt der zusätzlichen mechanischen Belastung auf kortikale und trabekuläre Knochenmasse, -mikrostruktur und Knochenformation und -resorption in der Metaphyse der tumortragenden Tibia untersucht. Die in vivo Ergebnisse zeigen, dass die mechanische Belastung den schädlichen Auswirkungen des Tumors entgegenwirken kann. Im Vergleich zu nicht mechanisch belasteten tumorinjizierten Mäusen, war die kortikale und trabekuläre Knochenmasse erhalten und die Mikrostruktur erheblich verbessert. In diesen mechanisch belasteten tumorinjizierten Mäusen war die Knochenformation erhöht. Ein Einfluss auf die Knochenresorption konnte nicht nachgewiesen werden. Dass durch die direkte Injektion von Tumorzellen oder Phosphatlösung in die Tibia ein Heilungsprozess im Knochen ausgelöst wurde, was auch zu einer erhöhten Knochenmasse führte, ist ein überraschendes Ergebnis. Weitere materialcharakteristische Untersuchungen zeigten, dass mechanische Belastung nicht zu Veränderungen in der Materialqualität von kortikalem Knochen führten. Alle in tumorinjizierten und mechanisch belasteten Mäusen untersuchten Parameter waren nicht verändert im Vergleich zu mechanisch nichtbelasteten tumorinjizierten Mäusen. Der Tumor beeinflusste also nicht die Qualität von neugebildetem kortikalem Knochen. Die Injektion als solche aber beeinflusste die Materialzusammensetzung des Knochens. Hauptsächlich konnte eine Erhöhung der Mineralisierung der Knochenmatrix sowie der Dicke der Hydroxyapatitkristalle nachgewiesen werden. Die Mechanismen dieser Veränderung bleiben unklar, jedoch könnte der beobachtete Heilungsprozess zu solchen Veränderungen in der Materialzusammensetzung führen. Zusammenfassend ermöglichen die präsentierten Ergebnisse ein besseres Verständnis des Einflusses mechanischer Belastung auf Knochen mit präsentem multiplen Myelom. Es kann geschlussfolgert werden, dass mechanische Stimulation dem schädlichen Einfluss des multiplen Myeloms auf den Knochen und damit auch dem Knochenverlust entgegenwirken kann. Weiterhin scheint der neugebildete Knochen nicht kompromittiert. Daher könnte mechanische Stimulation eine mögliche adjuvante Therapieoption bei Patienten mit multiplem Myelom darstellen.
- Published
- 2020
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