Mechanically Induced Calcium Release From Bone Matrix Triggers Intracellular Ca2+ Signalling in Osteoblasts: A Novel Mechanotransduction Mechanism

2011 ◽  
Author(s):  
Xuanhao Sun ◽  
Vipuil Kishore ◽  
Kateri Fites ◽  
Ozan Akkus
Keyword(s):  
Fluid Flow ◽  
Hydrostatic Pressure ◽  
Calcium Release ◽  
Bone Cells ◽  
Bone Matrix ◽  
Bone Adaptation ◽  
Exact Form ◽  
Flow Shear ◽  
Damage Repair ◽  
Physical Stimuli

Bone cells are responsible for sensing and converting the mechanical signals into cellular signals to drive bone adaptation and damage repair [1]. Cell-mediated repair of bone is reported to be in preferential association with regions filled with microdamage [2]. Although different theories have been proposed for mechanisms involved in those processes (such as substrate deformation, fluid flow shear, and hydrostatic pressure in mechanotransduction [3], or microcrack and osteocyte apoptosis in damage detection [4]), knowledge on the exact form of physical stimuli which trigger bone cells, especially in critically loaded regions of bone, is still elusive.

Substrate Deformation Levels Associated With Routine Physical Activity Are Less Stimulatory to Bone Cells Relative to Loading-Induced Oscillatory Fluid Flow

2000 ◽  
Vol 122 (4) ◽  
pp. 387-393 ◽  
Author(s):  
J. You ◽  
C. E. Yellowley ◽  
H. J. Donahue ◽  
Y. Zhang ◽  
Q. Chen ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Matrix Protein ◽  
Bone Cells ◽  
Mrna Level ◽  
Bone Matrix ◽  
Bone Cell ◽  
Bone Adaptation ◽  
Physical Activities ◽  
Substrate Strain

Although it is well accepted that bone tissue metabolism is regulated by external mechanical loads, it remains unclear to what load-induced physical signals bone cells respond. In this study, a novel computer-controlled stretch device and parallel plate flow chamber were employed to investigate cytosolic calcium Ca2+i mobilization in response to a range of dynamic substrate strain levels (0.1–10 percent, 1 Hz) and oscillating fluid flow (2 N/m2, 1 Hz). In addition, we quantified the effect of dynamic substrate strain and oscillating fluid flow on the expression of mRNA for the bone matrix protein osteopontin (OPN). Our data demonstrate that continuum strain levels observed for routine physical activities (<0.5 percent) do not induce Ca2+i responses in osteoblastic cells in vitro. However, there was a significant increase in the number of responding cells at larger strain levels. Moreover, we found no change in osteopontin mRNA level in response to 0.5 percent strain at 1 Hz. In contrast, oscillating fluid flow predicted to occur in the lacunar–canalicular system due to routine physical activities (2 N/m2, 1 Hz) caused significant increases in both Ca2+i and OPN mRNA. These data suggest that, relative to fluid flow, substrate deformation may play less of a role in bone cell mechanotransduction associated with bone adaptation to routine loads. [S0148-0731(00)01204-8]

scholarly journals The Effect of Fluid Flow Shear Stress and Substrate Stiffness on Yes-Associated Protein (YAP) Activity and Osteogenesis in Murine Osteosarcoma Cells

Cancers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 3128
Author(s):  
Thomas R. Coughlin ◽  
Ali Sana ◽  
Kevin Voss ◽  
Abhilash Gadi ◽  
Upal Basu-Roy ◽  
...  
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Bone Cells ◽  
Bone Cancer ◽  
Substrate Stiffness ◽  
Flow Shear ◽  
Fluid Movement ◽  
Flow Shear Stress ◽  
Fluid Flow Shear Stress ◽  
New Treatments

Osteosarcoma (OS) is an aggressive bone cancer originating in the mesenchymal lineage. Prognosis for metastatic disease is poor, with a mortality rate of approximately 40%; OS is an aggressive disease for which new treatments are needed. All bone cells are sensitive to their mechanical/physical surroundings and changes in these surroundings can affect their behavior. However, it is not well understood how OS cells specifically respond to fluid movement, or substrate stiffness—two stimuli of relevance in the tumor microenvironment. We used cells from spontaneous OS tumors in a mouse engineered to have a bone-specific knockout of pRb-1 and p53 in the osteoblast lineage. We silenced Sox2 (which regulates YAP) and tested the effect of fluid flow shear stress (FFSS) and substrate stiffness on YAP expression/activity—which was significantly reduced by loss of Sox2, but that effect was reversed by FFSS but not by substrate stiffness. Osteogenic gene expression was also reduced in the absence of Sox2 but again this was reversed by FFSS and remained largely unaffected by substrate stiffness. Thus we described the effect of two distinct stimuli on the mechanosensory and osteogenic profiles of OS cells. Taken together, these data suggest that modulation of fluid movement through, or stiffness levels within, OS tumors could represent a novel consideration in the development of new treatments to prevent their progression.

Calcium Efflux From Bone Matrix in Response to Mechanical Loading

2011 ◽  
Author(s):  
Xuanhao Sun ◽  
Eric S. McLamore ◽  
D. Marshall Porterfield ◽  
Ozan Akkus
Keyword(s):  
Hydrostatic Pressure ◽  
Cell Surface ◽  
Bone Cells ◽  
Bone Matrix ◽  
Mechanical Stimulus ◽  
Calcium Efflux ◽  
Fluid Shear ◽  
Mechanical Environment ◽  
Surface Receptors ◽  
Cellular Events

Bone is known for its ability to self-repair the microdamage and actively adapt to its mechanical environment, both of which are under the coordination of bone cells. Mechanical cues are sensed by cells and converted into cellular events in a process called mechanotransduction [1]. Most theories of mechanotransduction are based on direct stimulus of cell surface receptors by substrate deformation, fluid shear and/or hydrostatic pressure [2]. Yet, mechanical stimulus may come to affect cell response indirectly, via pathways which alter the pericellular niche. Such indirect pathways of mechanotransduction are not well-investigated for bone.

Physiological Levels of Substrate Deformation Are Less Stimulatory to Bone Cells Compared to Fluid Flow

1999 ◽  
Author(s):  
Jun You ◽  
Clare E. Yellowley ◽  
Henry J. Donahue ◽  
Christopher R. Jacobs
Keyword(s):  
Fluid Flow ◽  
Matrix Protein ◽  
Bone Cells ◽  
Bone Matrix ◽  
Biological Response ◽  
Bone Cell ◽  
Osteoblastic Cells ◽  
Physiological Strain ◽  
Substrate Strain

Abstract It is believed that bone cells can sense mechanical loading and alter bone external shape and internal structure to efficiently support the load bearing demands placed upon it. However, the mechanism by which bone cells sense and respond to their mechanical environment is still poorly understood. In particular, the load-induced signals to which bone cells respond, e.g. fluid flow, substrate deformation, electrokinetic effects etc., are unclear. Furthermore, there are few studies focused on the effects of physiological strain (strain &lt; 0.5%, Burr, 1996; Owan, 1997) on bone cells. The goal of this study was to investigate cytosolic Ca2+ mobilization (a very early signaling event) in response to different substrate strains (physiological or supra-physiological strains), and to distinguish the effects of substrate strain from those of fluid flow by applying precisely controlled strain without induced fluid flow. In addition, we quantified the effect of physiologically relevant fluid flow (Cowin, 1995) and substrate stretch on the expression of mRNA for the bone matrix protein osteopontin (OPN). A computer controlled stretch device was employed to apply different substrate strains, 0.1%, 1%, 5% and 10%. A parallel plate flow chamber was used to test cell responses to steady and oscillating flows (20dyn/cm2, 1Hz). Our data demonstrate that physiological strain (&lt; 0.5%) does not induce [Ca2+]i responses in primary rat osteoblastic cells (ROB) in vitro. However, there was a significant (p &lt; 0.05) increase in the number of responding cells at supra-physiological strains of 1, 5, and 10% suggesting that the cells were capable of a biological response. Similar results for human fetal osteoblastic cells (hFOB 1.19) and osteocyte-like cells (ML0-Y4) were obtained. Furthermore, compared to physiological substrate deformation, physiological fluid flow induced greater [Ca2+]i responses for hFOB cells, and these [Ca2+]i responses were quantitatively similar to those obtained for 10% substrate strain. Moreover we found no change in osteopontin mRNA expression after 0.5% strain stretch. Conversely, physiological oscillating flow (20dyn/cm2, 1Hz) caused a significant increase in osteopontin mRNA. These data suggest that, relative to fluid flow, substrate deformation may play less of a role in bone cell mechanotransduction.

Oscillatory Bone Fluid Flow and its Role in Initiating Remodeling in the Absence of Matrix Strain

2001 ◽  
Author(s):  
Yixian Qin ◽  
Anita Saldanha ◽  
Tamara Kaplan
Keyword(s):  
Fluid Flow ◽  
Cellular Response ◽  
Fluid Shear Stress ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Streaming Potential ◽  
Bone Adaptation ◽  
Interstitial Fluid Flow ◽  
Bone Fluid Flow ◽  
Matrix Deformation

Abstract Load-generated intracortical fluid flow is proposed to be an important mediator for regulating bone mass and morphology [1]. Although the mechanism of cellular response to induced flow parameters, i.e., fluid pressure, pressure gradient, velocity, and fluid shear stress, are not yet clear, interstitial fluid flow driven by loading may be necessary to explain the adaptive response of bone, which is either coupled with load-induced strain magnitude or independent with matrix strain per se [2]. It has been demonstrated that load-induced intracortical fluid flow is contributed by both bone matrix deformation and induced intramedullary (IM) pressure [3]. To examine the hypothesis of fluid flow generated adaptation, it is necessary to test the mechanism under the circumstances of solely fluid induced bone adaptation in the absence of matrix deformation. While our previous data has demonstrated that bone fluid flow and its associated streaming potential product can be influenced by the dynamic IM pressure quantitatively [4], the objective of this study was to evaluate fluid induced bone adaptation in an avian ulna model using oscillatory IM fluid pressure loading in the absence of bone matrix strain. The potential fluid pathway was measured in the model.

Multi-Scale Micro-Mechanical Poroelastic Modeling of Fluid Flow in Cortical Bone

Materials ◽  
2004 ◽  
Author(s):  
Colby C. Swan ◽  
Hyung-Joo Kim
Keyword(s):  
Fluid Flow ◽  
Cortical Bone ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Flow Characteristics ◽  
Bone Adaptation ◽  
Circular Cylinders ◽  
Shear Stresses ◽  
Fluid Flow Characteristics

To explore the potential role that load-induced fluid flow plays as a mechano-transduction mechanism in bone adaptation, a lacunar-canalicular scale bone poroelasticity model is developed and exercised. The model uses micromechanics to homogenize the pericanalicular bone matrix, a system of straight circular cylinders in the bone matrix through which bone fluids can flow, as a locally anisotropic poroelastic medium. In this work, a simplified two-dimensional model of a periodic array of lacunae and their surrounding systems of canaliculi is developed and exercised to quantify local fluid flow characteristics in the vicinity of a single lacuna. When the cortical bone model is loaded, microscale stress and strain concentrations occur in the vicinity of individual lacunae and give rise to microscale spatial variations in the pore fluid pressure field. Consequently, loading of cortical bone can induce fluid flow in the canaliculi and exchange of fluid between canaliculi and lacunae. For realistic bone morphology parameters, and a range of loading frequencies, fluid pressures and fluid-solid shear stresses in the canalicular bone are computed and the associated energy dissipation in the models compared to that measured in physical in vitro experiments on human cortical bone. For realistic volume fractions of canaliculi, deformation-induced fluid flow is found to have a much larger characteristic time constant than deformation-induced flow in the Haversian system.

Integrin receptor-mediated mobilisation of intranuclear calcium in rat osteoclasts

1993 ◽  
Vol 105 (1) ◽  
pp. 61-68 ◽  
Author(s):  
G. Shankar ◽  
I. Davison ◽  
M.H. Helfrich ◽  
W.T. Mason ◽  
M.A. Horton
Keyword(s):  
Cell Function ◽  
Bone Cells ◽  
Dynamic Equilibrium ◽  
Bone Matrix ◽  
Ion Concentration ◽  
Calcium Signal ◽  
Free Calcium ◽  
Integrin Receptor ◽  
Vitronectin Receptor ◽  
Alpha V Beta 3

Cell-matrix interactions have been shown to play an important role in regulating cell function and behaviour. In bone, where calcified matrix formation and resorption events are required to be in dynamic equilibrium, regulation of adhesive interactions between bone cells and their matrix is critical. The present study focuses on the osteoclast, the bone resorbing cell, as well as integrins, which are cell surface adhesion receptors that mediate osteoclast attachment to bone matrix. In osteoclasts, the most abundant integrin receptor is the vitronectin receptor (VNR, alpha v beta 3). The objective of the study was to investigate changes in intracellular calcium, a regulator of osteoclast function, following addition of peptides that bind integrins, in particular the alpha v beta 3 form of the vitronectin receptor (VNR), which is highly expressed in osteoclasts. The study demonstrated a unique spatial localisation of the calcium signal in response to cell membrane receptor occupancy by integrin ligands in rat osteoclasts. Addition of peptides with the Arg-Gly-Asp (RGD) sequence such as BSP-IIA, GRGDSP and GRGDS to rat osteoclasts evoked an immediate increase in free calcium ion concentration [Ca2+]i, localised to the nuclei and to the thin cytoplasmic skirt. These responses were inhibited by F11, a monoclonal antibody to the rat integrin beta 3 chain, as well as echistatin, a snake venom shown to colocalise with the alpha v chain in osteoclasts, suggesting that the calcium signal is mediated by the alpha v beta 3 form of VNR.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of Osteocyte Deformation Resulting From Fluid Flow Induced Shear Stress

1999 ◽  
Author(s):  
Daniel P. Nicolella ◽  
Eugene Sprague ◽  
Lynda Bonewald
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Flow Rate ◽  
Bone Cells ◽  
Individual Cell ◽  
Analysis Techniques ◽  
Sheer Stress ◽  
Increased Sensitivity ◽  
Cell Strains ◽  
Substrate Strain

Abstract It has been shown that bone cells are more responsive to fluid flow induced shear stress as compared to applied substrate strain (Owan, et al., 1997, Smalt, et al., 1997). Using novel micromechanical analysis techniques, we have measured individual cell strains resulting from 10 minutes of continuous fluid flow at a flow rate that produces a shear stress of 15 dyne/cm2. Individual cell strains varied widely from less than 1.0% to over 25% strain within the same group of cells. The increased sensitivity of cells to fluid flow induced shear stress may be attributed to much greater cellular deformations resulting from fluid flow induced sheer stress.

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