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]

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.

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.

Tissue Strain Transduction and Amplification at the Osteocyte as a Result of Microstructural Changes in the Bone Matrix

2007 ◽  
Author(s):  
Amber Rath Bonivtch ◽  
Lynda F. Bonewald ◽  
Daniel P. Nicolella
Keyword(s):  
Bone Cells ◽  
Bone Matrix ◽  
Mechanical Strain ◽  
Bone Cell ◽  
Cellular Level ◽  
Tissue Strain ◽  
Biological Responses ◽  
Spatial Level

It is well known that bone adapts to changes in its mechanical environment and that this adaptation is controlled at the cellular level through the coordinated actions of osteoblasts, osteocytes, and osteoclasts. Osteocytes make up over 90% of all bone cells [1], and are hypothesized to be the mechanosensors in bone [2] that mediate the effects of bone loading through their extensive communication network. The application of force to the skeletal system produces several potential stimuli for osteocyte function including hydrostatic pressure, fluid flow-induced shear stress, and bone tissue strain. Previously, the basis used for studying the stimulatory effects of mechanical strain on bone cell biological responses in vitro has been the direct measurement of bone strain in humans during various physical activities [3,4]. The limitation of applying this strain magnitude data to cells in vitro, however, is that the in vivo strain gage measurements represent continuum measures of bone deformation. Clearly, at the spatial level of bone cells, cortical bone is not a continuum and microstructural inhomogeneities will result in inhomogeneous microstructural strain fields; local tissue strains will be magnified in association with microstructural features [5,6]. It is unclear as to how much of these magnified strains will be directly transmitted to the osteocyte itself. Additionally, if the osteocyte has the ability to alter its perilacunar environment [7], it is unknown what effect do these changes have on the strain that is transmitted to the osteocyte and cell process.

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.

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.

scholarly journals Protocol of Co-Culture of Human Osteoblasts and Osteoclasts to Test Biomaterials for Bone Tissue Engineering

2022 ◽  
Vol 5 (1) ◽  
pp. 8
Author(s):  
Giorgia Borciani ◽  
Giorgia Montalbano ◽  
Nicola Baldini ◽  
Chiara Vitale-Brovarone ◽  
Gabriela Ciapetti
Keyword(s):  
Tissue Engineering ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Bone Cells ◽  
Bone Cell ◽  
Seeding Density ◽  
Bone Homeostasis ◽  
Bone Microenvironment

New biomaterials and scaffolds for bone tissue engineering (BTE) applications require to be tested in a bone microenvironment reliable model. On this assumption, the in vitro laboratory protocols with bone cells represent worthy experimental systems improving our knowledge about bone homeostasis, reducing the costs of experimentation. To this day, several models of the bone microenvironment are reported in the literature, but few delineate a protocol for testing new biomaterials using bone cells. Herein we propose a clear protocol to set up an indirect co-culture system of human-derived osteoblasts and osteoclast precursors, providing well-defined criteria such as the cell seeding density, cell:cell ratio, the culture medium, and the proofs of differentiation. The material to be tested may be easily introduced in the system and the cell response analyzed. The physical separation of osteoblasts and osteoclasts allows distinguishing the effects of the material onto the two cell types and to evaluate the correlation between material and cell behavior, cell morphology, and adhesion. The whole protocol requires about 4 to 6 weeks with an intermediate level of expertise. The system is an in vitro model of the bone remodeling system useful in testing innovative materials for bone regeneration, and potentially exploitable in different application fields. The use of human primary cells represents a close replica of the bone cell cooperation in vivo and may be employed as a feasible system to test materials and scaffolds for bone substitution and regeneration.

scholarly journals The Anchorage of Bone Cells onto an Yttria-Stabilized Zirconia Surface with Mild Nano-Micro Curved Profiles

2020 ◽  
Vol 8 (4) ◽  
pp. 127
Author(s):  
Susanne Staehlke ◽  
Armin Springer ◽  
Thomas Freitag ◽  
Jakob Brief ◽  
J. Barbara Nebe
Keyword(s):  
Matrix Protein ◽  
Bone Cells ◽  
Cell Attachment ◽  
Yttria Stabilized Zirconia ◽  
Extracellular Matrix Protein ◽  
Cell Phenotype ◽  
Ros Generation ◽  
Stabilized Zirconia ◽  
Dental Surgery

The high biocompatibility, good mechanical properties, and perfect esthetics of ceramic dental materials motivate investigation into their suitability as an endosseous implant. Osseointegration at the interface between bone and implant surface, which is a criterion for dental implant success, is dependent on surface chemistry and topography. We found out earlier that osteoblasts on sharp-edged micro-topographies revealed an impaired cell phenotype and function and the cells attempted to phagocytize these spiky elevations in vitro. Therefore, micro-structured implants used in dental surgery should avoid any spiky topography on their surface. The sandblasted, acid-etched, and heat-treated yttria-stabilized zirconia (cer.face®14) surface was characterized by scanning electron microscopy and energy dispersive X-ray. In vitro studies with human MG-63 osteoblasts focused on cell attachment and intracellular stress level. The cer.face 14 surface featured a landscape with nano-micro hills that was most sinusoidal-shaped. The mildly curved profile proved to be a suitable material for cell anchorage. MG-63 cells on cer.face 14 showed a very low reactive oxygen species (ROS) generation similar to that on the extracellular matrix protein collagen I (Col). Intracellular adenosine triphosphate (ATP) levels were comparable to Col. Ceramic cer.face 14, with its sinusoidal-shaped surface structure, facilitates cell anchorage and prevents cell stress.

Control of Oriented Extracellular Matrix Similar to Anisotropic Bone Microstructure

2014 ◽  
Vol 783-786 ◽  
pp. 72-77 ◽  
Author(s):  
Takayoshi Nakano ◽  
Aira Matsugaki ◽  
Takuya Ishimoto ◽  
Mitsuharu Todai ◽  
Ai Serizawa ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Bone Tissue ◽  
Bone Cells ◽  
Crystal Surface ◽  
Early Stage ◽  
Bone Microstructure ◽  
Bone Cell ◽  
Collagen Fibers

Bone microstructure is dominantly composed of anisotropic extracellular matrix (ECM) in which collagen fibers and epitaxially-oriented biological apatite (BAp) crystals are preferentially aligned depending on the bone anatomical position, resulting in exerting appropriate mechanical function. The regenerative bone in bony defects is however produced without the preferential alignment of collagen fibers and the c-axis of BAp crystals, and subsequently reproduced to recover toward intact alignment. Thus, it is necessary to produce the anisotropic bone-mimetic tissue for the quick recovery of original bone tissue and the related mechanical ability in the early stage of bone regeneration. Our group is focusing on the methodology for regulating the arrangement of bone cells, the following secretion of collagen and the self-assembled mineralization by oriented BAp crystallites. Cyclic stretching in vitro to bone cells, principal-stress loading in vivo on scaffolds, step formation by slip traces on Ti single crystal, surface modification by laser induced periodic surface structure (LIPSS), anisotropic collagen substrate with the different degree of orientation, etc. can dominate bone cell arrangement and lead to the construction of the oriented ECM similar to the bone tissue architecture. This suggests that stress/strain loading, surface topography and chemical anisotropy are useful to produce bone-like microstructure in order to promote the regeneration of anisotropic bone tissue and to understand the controlling parameters for anisotropic osteogenesis induction.

scholarly journals Increased serum and bone matrix levels of transforming growth factor β1 in patients with GH deficiency in response to GH treatment

2011 ◽  
Vol 165 (3) ◽  
pp. 393-400 ◽  
Author(s):  
Thor Ueland ◽  
Tove Lekva ◽  
Kari Otterdal ◽  
Tuva B Dahl ◽  
Nicoleta Cristina Olarescu ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cortical Bone ◽  
Transforming Growth Factor ◽  
Bone Cells ◽  
Gh Deficiency ◽  
Bone Matrix ◽  
Transforming Growth Factor Β1 ◽  
Gh Treatment

ObjectivePatients with adult onset GH deficiency (aoGHD) have secondary osteoporosis, which is reversed by long-term GH substitution. Transforming growth factor β1 (TGFβ1 or TGFB1) is abundant in bone tissue and could mediate some effects of GH/IGFs on bone. We investigated its regulation by GH/IGF1in vivoandin vitro.Design and methodsThe effects of GH substitution (9–12 months, placebo controlled) on circulating and cortical bone matrix contents of TGFβ1 were investigated in patients with aoGHD. The effects of GH/IGF1 on TGFβ1 secretion in osteoblasts (hFOB), adipocytes, and THP-1 macrophages as well as the effects on release from platelets were investigatedin vitro.ResultsIn vivoGH substitution increased TGFβ1 protein levels in cortical bone and serum.In vitro, GH/IGF1 stimulation induced a significant increase in TGFβ1 secretion in hFOB. In contrast, no major effect of GH/IGF1 on TGFβ1 was found in adipocytes and THP-1 macrophages. Finally, a minor modifying effect on SFLLRN-stimulated platelet release of TGFβ1 was observed in the presence of IGF1.ConclusionGH substitution increases TGFβ1in vivoandin vitro, and this effect could contribute to improved bone metabolism during such therapy, potentially reflecting direct effect of GH/IGF1 on bone cells.

Gap Junctions and Osteoblast-like Cell Gene Expression in Response to Fluid Flow

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Michael G. Jekir ◽  
Henry J. Donahue
Keyword(s):  
Fluid Flow ◽  
Gap Junctions ◽  
Gap Junction ◽  
Bone Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mrna Levels ◽  
Mechanical Stimuli ◽  
Junctional Communication ◽  
Osteogenic Response

Bone formation occurs in vivo in response to mechanical stimuli, but the signaling pathways involved remain unclear. The ability of bone cells to communicate with each other in the presence of an applied load may influence the overall osteogenic response. The goal of this research was to determine whether inhibiting cell-to-cell gap junctional communication between bone-forming cells would affect the ensemble cell response to an applied mechanical stimulus in vitro. In this study, we investigated the effects of controlled oscillatory fluid flow (OFF) on osteoblastic cells in the presence and the absence of a gap-junction blocker. MC3T3-E1 Clone 14 cells in a monolayer were exposed to 2h of OFF at a rate sufficient to create a shear stress of 20dynes∕cm2 at the cell surface, and changes in steady-state mRNA levels for a number of key proteins known to be involved in osteogenesis were measured. Of the five proteins investigated, mRNA levels for osteopontin (OPN) and osteocalcin were found to be significantly increased 24h postflow. These experiments were repeated in the presence of 18β-glycyrrhetinic acid (BGA), a known gap-junction blocker, to determine whether gap-junction intercellular communication is necessary for this response. We found that the increase in OPN mRNA levels is not observed in the presence of BGA, suggesting that gap junctions are involved in the signaling process. Interestingly, enzyme linked immunosorbent assay data showed that levels of secreted OPN protein increased 48h postflow and that this increase was unaffected by the presence of intact gap junctions.

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