Responses of Bone Cells to Biomechanical Forces in Vitro

1999 ◽  
Vol 13 (1) ◽  
pp. 93-98 ◽  
Author(s):  
E.H. Burger ◽  
J. Klein-Nulend
Keyword(s):  
Nitric Oxide ◽  
Mechanical Loading ◽  
Cell Biology ◽  
Cellular Response ◽  
Fluid Shear Stress ◽  
Bone Structure ◽  
Bone Cells ◽  
Bone Adaptation

In this paper, we review recent studies of the mechanism by which mechanical loading of bone is transduced into cellular signals of bone adaptation. Current biomechanical theory and in vivo as well as in vitro experiments agree that the three-dimensional network of osteocytes and bone-lining cells provides the cellular basis for mechanosensing in bone, leading to adaptive bone (re)modeling. They also agree that flow of interstitial fluid through the lacunar-canalicular porosity of bone, as a result of mechanical loading, most likely provides the stimulus for mechanosensing, and informs the bone cellular network about the adequacy of the existing bone structure. Important signaling molecules involved in in vivo adaptive bone formation, as well as in in vitro cellular response to fluid flow, are nitric oxide and prostaglandins. The expression of key enzymes for nitric oxide and prostaglandin production in bone cells is altered by fluid shear stress in vitro. Together, these studies have increased our understanding of the cell biology underlying Wolff's Law. This may lead to new strategies for combating disuse-related osteoporosis, and may also be of use in understanding and predicting the long-term integration of bone-replacing implants.

scholarly journals Rapid Fabrication of Microfluidic Devices for Biological Mimicking: A Survey of Materials and Biocompatibility

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 346
Author(s):  
Hui Ling Ma ◽  
Ana Carolina Urbaczek ◽  
Fayene Zeferino Ribeiro de Souza ◽  
Paulo Augusto Gomes Garrido Carneiro Leão ◽  
Janice Rodrigues Perussi ◽  
...  
Keyword(s):  
Shear Stress ◽  
Cell Viability ◽  
Cellular Response ◽  
Fluid Shear Stress ◽  
Umbilical Vein ◽  
Microfluidic Devices ◽  
In Vitro Assays ◽  
Stress Effect

Microfluidics is an essential technique used in the development of in vitro models for mimicking complex biological systems. The microchip with microfluidic flows offers the precise control of the microenvironment where the cells can grow and structure inside channels to resemble in vivo conditions allowing a proper cellular response investigation. Hence, this study aimed to develop low-cost, simple microchips to simulate the shear stress effect on the human umbilical vein endothelial cells (HUVEC). Differentially from other biological microfluidic devices described in the literature, we used readily available tools like heat-lamination, toner printer, laser cutter and biocompatible double-sided adhesive tapes to bind different layers of materials together, forming a designed composite with a microchannel. In addition, we screened alternative substrates, including polyester-toner, polyester-vinyl, glass, Permanox® and polystyrene to compose the microchips for optimizing cell adhesion, then enabling these microdevices when coupled to a syringe pump, the cells can withstand the fluid shear stress range from 1 to 4 dyne cm2. The cell viability was monitored by acridine orange/ethidium bromide (AO/EB) staining to detect live and dead cells. As a result, our fabrication processes were cost-effective and straightforward. The materials investigated in the assembling of the microchips exhibited good cell viability and biocompatibility, providing a dynamic microenvironment for cell proliferation. Therefore, we suggest that these microchips could be available everywhere, allowing in vitro assays for daily laboratory experiments and further developing the organ-on-a-chip concept.

scholarly journals Osteoblast and Osteoclast Activity Affect Bone Remodeling Upon Regulation by Mechanical Loading-Induced Leukemia Inhibitory Factor Expression in Osteocytes

2020 ◽  
Vol 7 ◽  
Author(s):  
Jingke Du ◽  
Jiancheng Yang ◽  
Zihao He ◽  
Junqi Cui ◽  
Yiqi Yang ◽  
...  
Keyword(s):  
Bone Remodeling ◽  
Mechanical Loading ◽  
Leukemia Inhibitory Factor ◽  
Fluid Shear Stress ◽  
Bone Structure ◽  
Inhibitory Factor ◽  
Tartrate Resistant Acid Phosphatase ◽  
Osteoclast Activity ◽  
Microgravity Simulation

PurposeBone remodeling is affected by mechanical stimulation. Osteocytes are the primary mechanical load-sensing cells in the bone, and can regulate osteoblast and osteoclast activity, thus playing a key role in bone remodeling. Further, bone mass during exercise is also regulated by Leukemia inhibitory factor (LIF). This study aimed to investigate the role of LIF in the mechanical response of the bone, in vivo and in vitro, and to elucidate the mechanism by which osteocytes secrete LIF to regulate osteoblasts and osteoclasts.MethodsA tail-suspension (TS) mouse model was used in this study to mimic muscular disuse. ELISA and immunohistochemistry were performed to detect bone and serum LIF levels. Micro-computed tomography (CT) of the mouse femurs was performed to measure three-dimensional bone structure parameters. Fluid shear stress (FSS) and microgravity simulation experiments were performed to study mechanical stress-induced LIF secretion and its resultant effects. Bone marrow macrophages (BMMs) and bone mesenchymal stem cells (BMSCs) were cultured to induce in vitro osteoclastogenesis and osteogenesis, respectively.ResultsMicro-CT results showed that TS mice exhibited deteriorated bone microstructure and lower serum LIF expression. LIF secretion by osteocytes was promoted by FSS and was repressed in a microgravity environment. Further experiments showed that LIF could elevate the tartrate-resistant acid phosphatase activity in BMM-derived osteoclasts through the STAT3 signaling pathway. LIF also enhanced alkaline phosphatase staining and osteogenesis-related gene expression during the osteogenic differentiation of BMSCs.ConclusionMechanical loading affected LIF expression levels in osteocytes, thereby altering the balance between osteoclastogenesis and osteogenesis.

scholarly journals Cytoskeleton reorganization of spreading cells on micro-patterned islands: a functional model

2010 ◽  
Vol 368 (1920) ◽  
pp. 2629-2652 ◽  
Author(s):  
Y. Loosli ◽  
R. Luginbuehl ◽  
J. G. Snedeker
Keyword(s):  
Cell Biology ◽  
Cellular Response ◽  
Cell Model ◽  
Numerical Models ◽  
Mechanistic Model ◽  
Functional Model ◽  
Cell Spreading ◽  
Cellular Interaction

Predictive numerical models of cellular response to biophysical cues have emerged as a useful quantitative tool for cell biology research. Cellular experiments in silico can augment in vitro and in vivo investigations by filling gaps in what is possible to achieve through ‘wet work’. Biophysics-based numerical models can be used to verify the plausibility of mechanisms regulating tissue homeostasis derived from experiments. They can also be used to explore potential targets for therapeutic intervention. In this perspective article we introduce a single cell model developed towards the design of novel biomaterials to elicit a regenerative cellular response for the repair of diseased tissues. The model is governed by basic mechanisms of cell spreading (lamellipodial and filopodial extension, formation of cell–matrix adhesions, actin reinforcement) and is developed in the context of cellular interaction with functionalized substrates that present defined points of potential adhesion. To provide adequate context, we first review the biophysical underpinnings of the model as well as reviewing existing cell spreading models. We then present preliminary benchmarking of the model against published experiments of cell spreading on micro-patterned substrates. Initial results indicate that our mechanistic model may represent a potentially useful approach in a better understanding of cell interactions with the extracellular matrix.

scholarly journals Altered aggrecan synthesis correlates with cell and nucleus structure in statically compressed cartilage

1996 ◽  
Vol 109 (2) ◽  
pp. 499-508 ◽  
Author(s):  
M.D. Buschmann ◽  
E.B. Hunziker ◽  
Y.J. Kim ◽  
A.J. Grodzinsky
Keyword(s):  
Mechanical Loading ◽  
Cellular Response ◽  
Functional Adaptation ◽  
Cartilage Explants ◽  
Spatial Inhomogeneity ◽  
Cartilage Tissue ◽  
Nucleus Structure ◽  
Nucleus Volume

Previous studies have shown that static equilibrium compression of cartilage tissue in vivo and in vitro decreases chondrocyte synthesis of aggrecan molecules. In order to identify mechanisms of cellular response to loading, we have investigated alterations in cell and nucleus structure and the accompanying changes in the synthesis of aggrecan in statically compressed cartilage explants. Using glutaraldehyde fixation and quantitative autoradiography of compressed and radiolabeled cartilage disks we spatially localized newly synthesized aggrecan. Using stereological tools to analyze these same specimens we estimated the cell and nucleus volume, surface area and directional radii. We found that aggrecan synthesis was reduced overall in compressed tissue disks. However, the compression induced a spatial (radial) inhomogeneity in aggrecan synthesis which was not present in uncompressed disks. This spatial inhomogeneity appeared to be directly related to mechanical boundary conditions and the manner in which the load was applied and, therefore, may represent a spatially specific functional adaptation to mechanical loading. Coincident with reduced aggrecan synthesis, we observed reductions in cell and nucleus volume and radii in the direction of compression which were in approximate proportion to the reduction in tissue thickness. Cell and nucleus dimensions perpendicular to the direction of compression did not change significantly. Therefore the observed deformation of the cell and nucleus in statically compressed cartilage approximately followed the dimensional changes imposed on external specimen surfaces. The strong correlation observed between local changes in aggrecan synthesis and alterations in cell and nucleus structure also lend support to certain hypotheses regarding the intracellular signal transduction pathways that may be important in the biosynthetic response of chondrocytes to mechanical loading.

scholarly journals Establishment of a fluorescent reporter of RNA-polymerase II activity to identify dormant cells

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Rasmus Freter ◽  
Paola Falletta ◽  
Omid Omrani ◽  
Mahdi Rasa ◽  
Katharine Herbert ◽  
...  
Keyword(s):  
Stem Cell ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Cell Biology ◽  
Cellular Response ◽  
Cell Activity ◽  
Isolation And Characterization ◽  
Dormant Cells

AbstractDormancy, a reversible quiescent cellular state characterized by greatly reduced metabolic activity, protects from genetic damage, prolongs survival and is crucial for tissue homeostasis and cellular response to injury or transplantation. Dormant cells have been characterized in many tissues, but their identification, isolation and characterization irrespective of tissue of origin remains elusive. Here, we develop a live cell ratiometric fluorescent Optical Stem Cell Activity Reporter (OSCAR) based on the observation that phosphorylation of RNA Polymerase II (RNApII), a hallmark of active mRNA transcription elongation, is largely absent in dormant stem cells from multiple lineages. Using the small intestinal crypt as a model, OSCAR reveals in real time the dynamics of dormancy induction and cellular differentiation in vitro, and allows the identification and isolation of several populations of transcriptionally diverse OSCARhigh and OSCARlow intestinal epithelial cell states in vivo. In particular, this reporter is able to identify a dormant OSCARhigh cell population in the small intestine. OSCAR therefore provides a tool for a better understanding of dormant stem cell biology.

BONE ADAPTATION AND REGENERATION – NEW DEVELOPMENTS

2012 ◽  
Vol 17 ◽  
pp. 34-43 ◽  
Author(s):  
JENNEKE KLEIN-NULEND ◽  
ROMMEL GAUD BACABAC
Keyword(s):  
Bone Formation ◽  
Cell Signaling ◽  
Mechanical Loading ◽  
Bone Structure ◽  
Bone Cells ◽  
Mechanical Energy ◽  
Bone Adaptation ◽  
Mechanical Stimuli ◽  
Waste Products ◽  
Local Bone

Bone is a dynamic tissue that is constantly renewed and adapts to its local loading environment. Mechanical loading results in adaptive changes in bone size and shape that strengthen bone structure. The mechanisms for adaptation involve a multistep process called mechanotransduction, which is the ability of resident bone cells to perceive and translate mechanical energy into a cascade of structural and biochemical changes within the cells. The transduction of a mechanical signal to a biochemical response involves pathways within the cell membrane and cytoskeleton of the osteocytes, the professional mechansensor cells of bone. During the last decade the role of mechanosensitive osteocytes in bone metabolism and turnover, and the lacuno-canalicular porosity as the structure that mediates mechanosensing, is likely to reveal a new paradigm for understanding the bone formation response to mechanical loading, and the bone resorption response to disuse. Strain-derived fluid flow of interstitial fluid through the lacuno-canalicular porosity seems to mechanically activate the osteocytes, as well as ensures transport of cell signaling molecules, nutrients and waste products. Cell-cell signaling from the osteocyte sensor cells to the effector cells (osteoblasts or osteoclasts), and the effector cell response – either bone formation or resorption, allow an explanation of local bone gain and loss as well as remodeling in response to fatigue damage as processes supervised by mechanosensitive osteocytes. The osteogenic activity of cultured bone cells has been quantitatively correlated with varying stress stimulations highlighting the importance of the rate of loading. Theoretically a possible mechanism for the stress response by osteocytes is due to strain amplification at the pericellular matrix. Single cell studies on molecular responses of osteocytes provide insight on local architectural alignment in bone during remodeling. Alignment seems to occur as a result of the osteocytes sensing different canalicular flow patterns around cutting cone and reversal zone during loading, thus determining the bone's structure. Disturbances in architecture and permeability of the 3D porous network will affect transduction of mechanical loads to the mechanosensors. Uncovering the cellular and mechanical basis of the osteocyte's response to loading represents a significant challenge to our understanding of cellular mechanotransduction and bone remodeling. In view of the importance of mechanical stress for maintaining bone strength, mechanical stimuli have great potential for providing a therapeutic approach for bone (re)generation.

scholarly journals PKC-δ deficiency in B cells displays osteopenia accompanied with upregulation of RANKL expression and osteoclast–osteoblast uncoupling

2020 ◽  
Vol 11 (9) ◽  
Author(s):  
Shangfu Li ◽  
Qiuli Liu ◽  
Depeng Wu ◽  
Tianwei He ◽  
Jinbo Yuan ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Bone Structure ◽  
Bone Cells ◽  
Osteoclast Differentiation ◽  
Bone Homeostasis ◽  
Osteoblast Proliferation ◽  
And Function

Abstract PKC-δ is an important molecule for B-cell proliferation and tolerance. B cells have long been recognized to play a part in osteoimmunology and pathological bone loss. However, the role of B cells with PKC-δ deficiency in bone homeostasis and the underlying mechanisms are unknown. We generated mice with PKC-δ deletion selectively in B cells by crossing PKC-δ-loxP mice with CD19-Cre mice. We studied their bone phenotype using micro-CT and histology. Next, immune organs were obtained and analyzed. Western blotting was used to determine the RANKL/OPG ratio in vitro in B-cell cultures, ELISA assay and immunohistochemistry were used to analyze in vivo RANKL/OPG balance in serum and bone sections respectively. Finally, we utilized osteoclastogenesis to study osteoclast function via hydroxyapatite resorption assay, and isolated primary calvaria osteoblasts to investigate osteoblast proliferation and differentiation. We also investigated osteoclast and osteoblast biology in co-culture with B-cell supernatants. We found that mice with PKC-δ deficiency in B cells displayed an osteopenia phenotype in the trabecular and cortical compartment of long bones. In addition, PKC-δ deletion resulted in changes of trabecular bone structure in association with activation of osteoclast bone resorption and decrease in osteoblast parameters. As expected, inactivation of PKC-δ in B cells resulted in changes in spleen B-cell number, function, and distribution. Consistently, the RANKL/OPG ratio was elevated remarkably in B-cell culture, in the serum and in bone specimens after loss of PKC-δ in B cells. Finally, in vitro analysis revealed that PKC-δ ablation suppressed osteoclast differentiation and function but co-culture with B-cell supernatant reversed the suppression effect, as well as impaired osteoblast proliferation and function, indicative of osteoclast–osteoblast uncoupling. In conclusion, PKC-δ plays an important role in the interplay between B cells in the immune system and bone cells in the pathogenesis of bone lytic diseases.

How the Morphology of Osteocytes Contributes to their Mechanotransduction near Microdamage

2015 ◽  
Vol 1724 ◽  
Author(s):  
Elisa Budyn ◽  
Morad Bensidhoum ◽  
Patrick Tauc ◽  
Eric Deprez ◽  
Herve Petite
Keyword(s):  
Numerical Model ◽  
Mechanical Loading ◽  
Bone Cells ◽  
Mechanical Load ◽  
Allograft Bone ◽  
Top Down ◽  
Human Donor ◽  
Fresh Bone

ABSTRACTA dual experimental and numerical top-down approach is applied to investigate the link between osteocyte morphology and mechanical perception of their environment at the progenitor and mature stages. The numerical model is based on explicit tissue morphology discretization to identify bone diffuse damage at the cellular scale. The in vitro experimental model presents a live allograft bone system where a patient progenitor or mature osteocytes were reseeded in fresh human donor cortical bone tissues subjected to mechanical loading. The live systems behaved mechanically as fresh bone and the cells spatially reorganized in vitro as in vivo. The system under mechanical load also showed an adaptation of the calcium membrane transport rate to the expected in vivo mechanical load detected by bone cells at different stages of differentiation.

scholarly journals In Vitro and In Vivo Anti-Inflammatory Effects of Sulfated Polysaccharides Isolated from the Edible Brown Seaweed, Sargassum fulvellum

Marine Drugs ◽  
2021 ◽  
Vol 19 (5) ◽  
pp. 277
Author(s):  
Lei Wang ◽  
Hye-Won Yang ◽  
Ginnae Ahn ◽  
Xiaoting Fu ◽  
Jiachao Xu ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Brown Seaweed ◽  
Sulfated Polysaccharides ◽  
Raw 264.7 ◽  
Raw 264.7 Macrophages ◽  
Sargassum Fulvellum ◽  
Pharmaceutical Industries ◽  
Anti Inflammatory

In the present study, the in vitro and in vivo anti-inflammatory effects of the sulfated polysaccharides isolated from Sargassum fulvellum (SFPS) were evaluated in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages and zebrafish. The results indicated that SFPS improved the viability of LPS-stimulated RAW 264.7 macrophages from 80.02 to 86.80, 90.09, and 94.62% at the concentration of 25, 50, and 100 µg/mL, respectively. Also, SFPS remarkably and concentration-dependently decreased the production levels of inflammatory molecules including nitric oxide (NO), tumor necrosis factor-alpha, prostaglandin E2, interleukin-1 beta, and interleukin-6 in LPS-treated RAW 264.7 macrophages. In addition, SFPS significantly inhibited the expression levels of cyclooxygenase-2 and inducible nitric oxide synthase in LPS-treated RAW 264.7 macrophages. Furthermore, the in vivo test results indicated that SFPS improved the survival rate of LPS-treated zebrafish from 53.33 to 56.67, 60.00, and 70.00% at the concentration of 25, 50, and 100 µg/mL, respectively. In addition, SFPS effectively reduced cell death, reactive oxygen species, and NO levels in LPS-stimulated zebrafish. Taken together, these results suggested that SFPS possesses strong in vitro and in vivo anti-inflammatory activities, and could be used as an ingredient to develop anti-inflammatory agents in the functional food and pharmaceutical industries.

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