Nano-topography sensing by osteoclasts.
TL;DR: It was observed that steps or sub-micrometer cracks on the smooth surface stimulate local ring formation, raising the possibility that similar imperfections on bone surfaces may stimulate local osteoclast resorptive activity.
Abstract: Bone resorption by osteoclasts depends on the assembly of a specialized, actin-rich adhesive ‘sealing zone’ that delimits the area designed for degradation. In this study, we show that the level of roughness of the underlying adhesive surface has a profound effect on the formation and stability of the sealing zone and the associated F-actin. As our primary model substrate, we use ‘smooth’ and ‘rough’ calcite crystals with average topography values of 12 nm and 530 nm, respectively. We show that the smooth surfaces induce the formation of small and unstable actin rings with a typical lifespan of ~8 minutes, whereas the sealing zones formed on the rough calcite surfaces are considerably larger, and remain stable for more than 6 hours. It was further observed that steps or sub-micrometer cracks on the smooth surface stimulate local ring formation, raising the possibility that similar imperfections on bone surfaces may stimulate local osteoclast resorptive activity. The mechanisms whereby the physical properties of the substrate influence osteoclast behavior and their involvement in osteoclast function are discussed.
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TL;DR: Sustained disruptions in tensional homeostasis can be caused by alterations in the extracellular matrix, allowing it to serve as a mechanically based memory-storage device that can perpetuate a disease or restore normal tissue behaviour.
Abstract: All cells exist within the context of a three-dimensional microenvironment in which they are exposed to mechanical and physical cues. These cues can be disrupted through perturbations to mechanotransduction, from the nanoscale-level to the tissue-level, which compromises tensional homeostasis to promote pathologies such as cardiovascular disease and cancer. The mechanisms of such perturbations suggest that a complex interplay exists between the extracellular microenvironment and cellular function. Furthermore, sustained disruptions in tensional homeostasis can be caused by alterations in the extracellular matrix, allowing it to serve as a mechanically based memory-storage device that can perpetuate a disease or restore normal tissue behaviour.
875 citations
Cites background from "Nano-topography sensing by osteocla..."
...On a more specific level, the spatial presentation of ECM ligands, such as fibronectin, vitronectin, laminin and collagen, and the nanotopography of the ECM, control integrin organization, adhesion assembly, and signal transduction to direct cell behaviou...
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TL;DR: These cell adhesions play crucial roles in cell migration, proliferation, and determination of cell fate, and are mediated by membrane receptors such as the integrins, as well as many other components that comprise the adhesome.
Abstract: Cell adhesions mediate important bidirectional interactions between cells and the extracellular matrix. They provide an interactive interface between the extracellular chemical and physical environment and the cellular scaffolding and signaling machinery. This dynamic, reciprocal regulation of intracellular processes and the matrix is mediated by membrane receptors such as the integrins, as well as many other components that comprise the adhesome. Adhesome constituents assemble themselves into different types of cell adhesion structures that vary in molecular complexity and change over time. These cell adhesions play crucial roles in cell migration, proliferation, and determination of cell fate.
507 citations
Cites background from "Nano-topography sensing by osteocla..."
...Cells can also respond to the micro- or even nano-topography of a surface to which they adhere (Curtis and Wilkinson 1997; Cukierman et al. 2001; Geiger et al. 2001; Baharloo et al. 2005; Grossner-Schreiber et al. 2006; Vogel et al. 2006; Geblinger et al. 2010)....
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...They can assemble into large, belt-like superstructures, and are implicated in matrix-modulating activities (e.g., bone resorption by osteoclasts (Geblinger et al. 2010) and matrix invasion by a variety of cancer cells (Gimona et al. 2008)....
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...2006), regulating their dynamic properties (Geblinger et al. 2010), and modulating their signaling activity....
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...Cells can also respond to the micro-topography or even nano-topography of a surface to which they adhere (Curtis and Wilkinson 1997; Cukierman et al. 2001; Geiger et al. 2001; Baharloo et al. 2005; Grossner-Schreiber et al. 2006; Vogel et al. 2006; Geblinger et al. 2010)....
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...…surface features that are known to play a role in guiding the formation of matrix adhesions (Cukierman et al. 2001; Geiger et al. 2001; Baharloo et al. 2005; Grossner-Schreiber et al. 2006), regulating their dynamic properties (Geblinger et al. 2010) and modulating their signaling activity....
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TL;DR: Nanotopography is examined as a means to guide differentiation, and its application is described in the context of different subsets of stem cells, with a particular focus on skeletal (mesenchymal) stem cells.
Abstract: Stem cells have the capacity to differentiate into various lineages, and the ability to reliably direct stem cell fate determination would have tremendous potential for basic research and clinical therapy. Nanotopography provides a useful tool for guiding differentiation, as the features are more durable than surface chemistry and can be modified in size and shape to suit the desired application. In this paper, nanotopography is examined as a means to guide differentiation, and its application is described in the context of different subsets of stem cells, with a particular focus on skeletal (mesenchymal) stem cells. To address the mechanistic basis underlying the topographical effects on stem cells, the likely contributions of indirect (biochemical signal-mediated) and direct (force-mediated) mechanotransduction are discussed. Data from proteomic research is also outlined in relation to topography-mediated fate determination, as this approach provides insight into the global molecular changes at the level of the functional effectors.
349 citations
Cites background from "Nano-topography sensing by osteocla..."
...diverse cell types including fibroblasts [18, 22], osteoblasts [23], osteoclasts [24, 25], endothelial [15], smooth muscle [26], epithelial [27, 28], and epitenon cells [16]....
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TL;DR: An overview of the field is provided, with special focus on current developments such as intracellular transport processes, ultrastructural analysis, the possible involvement of invadosomes in disease, and the tentative identification of invadoomes in 3D environments and in vivo.
Abstract: Podosomes and invadopodia, collectively known as invadosomes, are cell-matrix contacts in a variety of cell types, such as monocytic cells or cancer cells, that have to cross tissue barriers. Both structures share an actin-rich core, which distinguishes them from other matrix contacts, and are regulated by a multitude of signaling pathways including RhoGTPases, kinases, actin-associated proteins, and microtubule-dependent transport. Invadosomes recruit and secrete proteinases and are thus able to lyse extracellular matrix components. They are therefore considered to be potential key structures in proteolytic cell invasion in both physiological and pathological settings. This review provides an overview of the field, with special focus on current developments such as intracellular transport processes, ultrastructural analysis, the possible involvement of invadosomes in disease, and the tentative identification of invadosomes in 3D environments and in vivo.
346 citations
TL;DR: This comprehensive review will focus on how networks of ECM proteins function to regulate osteoclast- and osteoblast-mediated bone remodeling and the clinical significance of these networks on normal bone and as they relate to pathologies of bone mass and geometry will be considered.
223 citations
References
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TL;DR: Major advances have been made recently in the understanding of the cell biology and molecular biology of the osteoclast, as well as the role that the marrow microenvironment plays in regulating osteOClast formation and bone resorption.
Abstract: I. Introduction BONE is a dynamic tissue that constantly undergoes remodeling. Bone remodeling is a coupled process in which bone resorption is normally followed by new bone formation. During early life, bone formation exceeds bone resorption with a net increase in bone mass, while late in life, bone resorption exceeds bone formation with net loss of bone. During some pathological processes, such as in patients with advanced stages of multiple myeloma, bone remodeling is uncoupled, and bone resorption is not followed by new bone formation. The primary cell responsible for bone resorption is the multinucleated osteoclast. Although many questions still remain unanswered about the factors that regulate osteoclast formation and osteoclastic bone resorption, major advances have been made recently in our understanding of the cell biology and molecular biology of the osteoclast, as well as the role that the marrow microenvironment plays in regulating osteoclast formation and bone resorption.
519 citations
TL;DR: Using quartz crystal microbalance with dissipation and ellipsometry, it is shown that during adsorption of fibrinogen on evaporated tantalum films the saturation uptake increases with increasing root-mean-square roughness beyond the accompanying increase in surface area.
Abstract: Using quartz crystal microbalance with dissipation and ellipsometry, we show that during adsorption of fibrinogen on evaporated tantalum films the saturation uptake increases with increasing root-mean-square roughness (from 2.0 to 32.9 nm) beyond the accompanying increase in surface area. This increase is attributed to a change in the geometrical arrangement of the fibrinogen molecules on the surface. For comparison, the adsorption of a nearly globular protein, bovine serum albumin, was studied as well. In this case, the adsorption was less influenced by the roughness. Simple Monte Carlo simulations taking into account surface roughness and the anisotropic shape of fibrinogen reproduce the experimentally observed trend.
499 citations
"Nano-topography sensing by osteocla..." refers background in this paper
...The latter mechanism could be expected, considering the fact that rough surfaces characterized by high surface energy usually show stronger protein adsorption (Kang and Lee, 2007; Rechendorff et al., 2006)....
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TL;DR: Findings suggest a role for contractility in the generation of matrix adhesion diversity, and particularly informative was fluorescence ratio imaging, comparing the local labeling intensities of different plaque molecules, including vinculin, paxillin, tensin and phosphotyrosine-containing proteins.
Abstract: In this study we have examined for molecular heterogeneity of cell-matrix adhesions and the involvement of actomyosin contractility in the selective recruitment of different plaque proteins. For this purpose, we have developed a novel microscopic approach for molecular morphometry, based on automatic identification of matrix adhesions, followed by quantitative immunofluorescence and morphometric analysis. Particularly informative was fluorescence ratio imaging, comparing the local labeling intensities of different plaque molecules, including vinculin, paxillin, tensin and phosphotyrosine-containing proteins. Ratio imaging revealed considerable molecular heterogeneity between and within adhesion sites. Most striking were the differences between focal contacts, which are vinculin- and paxillin-rich and contain high levels of phosphotyrosine, and fibrillar adhesions, which are tensin-rich and contain little or no phosphotyrosine. Ratio imaging also revealed considerable variability in the molecular substructure of individual focal contacts, pointing to a non-uniform distribution of phosphotyrosine and the different plaque constituents. Studying the quantitative relationships between the various components of the submembrane plaque indicated that the levels of vinculin, paxillin and phosphotyrosine in adhesion sites are positively correlated with each other and negatively correlated with the levels of tensin. Tyrosine phosphorylation of focal contacts was highly sensitive to cellular contractility, and was diminished within 5 minutes after treatment with the kinase inhibitor H-7, an inhibitor of actomyosin contractility. This was followed by the loss of paxillin and vinculin from the focal adhesions. Tensin-rich fibrillar adhesions were relatively insensitive to H-7 treatment. These findings suggest a role for contractility in the generation of matrix adhesion diversity.
484 citations
"Nano-topography sensing by osteocla..." refers methods in this paper
...Temporal ratio images were produced as previously described (Zamir et al., 1999)....
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TL;DR: A mechanism for the patterning of podosomes in osteoclasts is provided and a turnover of actin inside the podosome is revealed, showing that an additional step of differentiation, requiring microtubule integrity, stabilizes the podsomes at the periphery of the cell in large circular patterns.
Abstract: Podosomes, small actin-based adhesion structures, differ from focal adhesions in two aspects: their core structure and their ability to organize into large patterns in osteoclasts. To address the mechanisms underlying these features, we imaged live preosteoclasts expressing green fluorescent protein-actin during their differentiation. We observe that podosomes always form inside or close to podosome groups, which are surrounded by an actin cloud. Fluorescence recovery after photobleaching shows that actin turns over in individual podosomes in contrast to cortactin, suggesting a continuous actin polymerization in the podosome core. The observation of podosome assemblies during osteoclast differentiation reveals that they evolve from simple clusters into rings that expand by the continuous formation of new podosomes at their outer ridge and inhibition of podosome formation inside the rings. This self-organization of podosomes into dynamic rings is the mechanism that drives podosomes at the periphery of the cell in large circular patterns. We also show that an additional step of differentiation, requiring microtubule integrity, stabilizes the podosome circles at the cell periphery to form the characteristic podosome belt pattern of mature osteoclasts. These results therefore provide a mechanism for the patterning of podosomes in osteoclasts and reveal a turnover of actin inside the podosome.
443 citations
"Nano-topography sensing by osteocla..." refers result in this paper
...Interestingly, when nocodazole, which destroys microtubules, was added to osteoclasts adhering to rough surfaces, it induced the formation of smaller, more dynamic rings (supplementary material Movie 6), in line with the findings of Destaing et al. (Destaing et al., 2003)....
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TL;DR: A surface-modification process is developed to produce roughness gradients that cover a wide range of roughness values on one substratum, allowing for systematic investigations ofroughness on cell behavior.
443 citations
"Nano-topography sensing by osteocla..." refers background in this paper
...…cell proliferation, gene expression and cell viability (Bershadsky et al., 2006a; Chen et al., 1997; Diener et al., 2005; Discher et al., 2005; Engler et al., 2006; Geiger et al., 2009; Kunzler et al., 2007; Lo et al., 2000; Roach et al., 2007; Saltel et al., 2004; Vogel and Sheetz, 2006)....
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