Human mesenchymal stromal cells are mechanosensitive to vibration stimuli

Biomaterials regulates BMSCs differentiation via mechanical microenvironment

Bone mesenchymal stem cells (BMSCs) are crucial for bone tissue regeneration, the mechanical microenvironment of hard tissues, including bone and teeth, significantly affects the osteogenic differentiation of BMSCs. Biomaterials may mimic the microenvironment of the extracellular matrix and provide mechanical signals to regulate BMSCs differentiation via inducing the secretion of various intracellular factors. Biomaterials direct the differentiation of BMSCs via mechanical signals, including tension, compression, shear, hydrostatic pressure, stiffness, elasticity, and viscoelasticity, which can be transmitted to cells through mechanical signalling pathways. Besides, biomaterials with piezoelectric effects regulate BMSCs differentiation via indirect mechanical signals, such as, electronic signals, which are transformed from mechanical stimuli by piezoelectric biomaterials. Mechanical stimulation facilitates achieving vectored stem cell fate regulation, while understanding the underlying mechanisms remains challenging. Herein, this review summarizes the intracellular factors, including translation factors, epigenetic modifications, and miRNA level, as well as the extracellular factor, including direct and indirect mechanical signals, which regulate the osteogenic differentiation of BMSCs. Besides, this review will also give a comprehensive summary about how mechanical stimuli regulate cellular behaviours, as well as how biomaterials promote the osteogenic differentiation of BMSCs via mechanical microenvironments. The cellular behaviours and activated signal pathways will give more implications for the design of biomaterials with superior properties for bone tissue engineering. Moreover, it will also provide inspiration for the construction of bone organoids which is a useful tool for mimicking in vivo bone tissue microenvironments.

Characterization of Mechanical and Cellular Effects of Rhythmic Vertical Vibrations on Adherent Cell Cultures

This paper presents an innovative experimental setup that employs the principles of audio technology to subject adherent cells to rhythmic vertical vibrations. We employ a novel approach that combines three-axis acceleration measurements and particle tracking velocimetry to evaluate the setup's performance. This allows us to estimate crucial parameters such as root mean square acceleration, fluid flow patterns, and shear stress generated within the cell culture wells when subjected to various vibration types. The experimental conditions consisted of four vibrational modes: No Vibration, Continuous Vibration, Regular Pulse, and Variable Pulse. To evaluate the effects on cells, we utilized fluorescence microscopy and a customized feature extraction algorithm to analyze the F-actin filament structures. Our findings indicate a consistent trend across all vibrated cell cultures, revealing a reduction in size and altered orientation (2D angle) of the filaments. Furthermore, we observed cell accumulations in the G1 cell cycle phase in cells treated with Continuous Vibration and Regular Pulse. Our results demonstrate a negative correlation between the magnitude of mechanical stimuli and the size of F-actin filaments, as well as a positive correlation with the accumulations of cells in the G1 phase of the cell cycle. By unraveling these analyses, this study paves the way for future investigations and provides a compelling framework for comprehending the intricate cellular responses to rhythmic mechanical stimulation.

Mechanotransduction in Mesenchymal Stem Cells (MSCs) Differentiation: A Review

Mechanotransduction is the process by which physical force is converted into a biochemical signal that is used in development and physiology; meanwhile, it is intended for the ability of cells to sense and respond to mechanical forces by activating intracellular signals transduction pathways and the relative phenotypic adaptation. It encompasses the role of mechanical stimuli for developmental, morphological characteristics, and biological processes in different organs; the response of cells to mechanically induced force is now also emerging as a major determinant of disease. Due to fluid shear stress caused by blood flowing tangentially across the lumen surface, cells of the cardiovascular system are typically exposed to a variety of mechanotransduction. In the body, tissues are continuously exposed to physical forces ranging from compression to strain, which is caused by fluid pressure and compressive forces. Only lately, though, has the importance of how forces shape stem cell differentiation into lineage-committed cells and how mechanical forces can cause or exacerbate disease besides organizing cells into tissues been acknowledged. Mesenchymal stem cells (MSCs) are potent mediators of cardiac repair which can secret a large array of soluble factors that have been shown to play a huge role in tissue repair. Differentiation of MSCs is required to regulate mechanical factors such as fluid shear stress, mechanical strain, and the rigidity of the extracellular matrix through various signaling pathways for their use in regenerative medicine. In the present review, we highlighted mechanical influences on the differentiation of MSCs and the general factors involved in MSCs differentiation. The purpose of this study is to demonstrate the progress that has been achieved in understanding how MSCs perceive and react to their mechanical environment, as well as to highlight areas where more research has been performed in previous studies to fill in the gaps.

Design, Fabrication, and Characterization of a Multimodal Reconfigurable Bioreactor for Bone Tissue Engineering

In the past decades, bone tissue engineering developed and exploited many typologies of bioreactors, which, besides providing proper culture conditions, aimed at integrating those bio‐physical stimulations that cells experience in vivo, to promote osteogenic differentiation. Nevertheless, the highly challenging combination and deployment of many stimulation systems into a single bioreactor led to the generation of several unimodal bioreactors, investigating one or at mostly two of the required biophysical stimuli. These systems miss the physiological mimicry of bone cells environment, and often produced contrasting results, thus making the knowledge of bone mechanotransduction fragmented and often inconsistent. To overcome this issue, in this study we developed a perfusion and electroactive‐vibrational reconfigurable stimulation bioreactor to investigate the differentiation of SaOS‐2 bone‐derived cells, hosting a piezoelectric nanocomposite membrane as cell culture substrate. This multimodal perfusion bioreactor is designed based on a numerical (finite element) model aimed at assessing the possibility to induce membrane nano‐scaled vibrations (with ~12 nm amplitude at a frequency of 939 kHz) during perfusion (featuring 1.46 dyn cm⁻² wall shear stress), large enough for inducing a physiologically‐relevant electric output (in the order of 10 mV on average) on the membrane surface. This study explored the effects of different stimuli individually, enabling to switch on one stimulation at a time, and then to combine them to induce a faster bone matrix deposition rate. Biological results demonstrate that the multimodal configuration is the most effective in inducing SaOS‐2 cell differentiation, leading to 20‐fold higher collagen deposition compared to static cultures, and to 1.6‐ and 1.2‐fold higher deposition than the perfused‐ or vibrated‐only cultures. These promising results can provide tissue engineering scientists with a comprehensive and biomimetic stimulation platform for a better understanding of mechanotransduction phenomena beyond cells differentiation.

VIABILITY OF 3T3-L1 PREADIPOCYTES IS MODULATED BY THE APPLIED FREQUENCY BUT NOT THE EXPOSURE DURATION OF LOW INTENSITY VIBRATORY STIMULATION

Mechanical forces are the integral determinants in cell and tissue homeostasis and regeneration, and they can affect numerous biological process from proliferation to fate determination. Mechanical forces that possess low magnitude and high frequency characteristics are also known as low intensity vibrations (LIVs). These signals were studied widely on many cell types for regenerative purposes, however most of these studies select components of LIV signals (e.g., magnitude, frequency, duration, etc.) arbitrarily. Here, we addressed the effect of LIV applied frequency, LIV daily exposure time and fate induction on the viability of preadipocyte 3T3-L1 cells. For this, we performed a frequency sweep that was ranging from 30[Formula: see text]Hz to 120[Formula: see text]Hz with 15[Formula: see text]Hz increments applied for 5, 10 or 20[Formula: see text]min during quiescent growth or adipogenesis for up to 10 days. Results suggest that the applied frequency and fate induction was an important determinant of cell viability while daily exposure time had no effect. These findings contribute to the effort of optimizing a relevant mechanical stimulus that can inhibit adipogenesis.

Impact of Local Vibration Training on Neuromuscular Activity, Muscle Cell, and Muscle Strength: A Review

This paper presents a review of studies on the effects of local vibration training (LVT) on muscle strength along with the associated changes in neuromuscular and cell dynamic responses. Application of local/direct vibration can significantly change the structural properties of muscle cell and can improve muscle strength. The improvement is largely dependent on vibration parameters such as amplitude and frequency. The results of 20 clinical studies reveal that electromyography (EMG) and maximal voluntary contraction (MVC) vary depending on vibration frequency, and studies using frequencies of 28-30 Hz reported greater increases in muscle activity in terms of EMG (rms) value and MVC data than the studies using higher frequencies. A greater muscle activity can be related to the recruitment of large motor units due to the application of local vibration. A greater increase in EMG (rms) values for biceps and triceps during extension than flexion under LVT suggests that types of muscles and their functions play an important role. Although a number of clinical trials and animal studies have demonstrated positive effects of vibration on muscle, an optimum training protocol has not been established. An attempt is made in this study to investigate the optimal LVT conditions on different muscles through review and analysis of published results in the literature pertaining to the changes in the neuromuscular activity. Directions for future research are discussed with regard to identifying optimal conditions for LVT and better understanding of the mechanisms associated with effects of vibration on muscles.

The role of micro-vibration parameters in inflammatory responses of macrophages cultured on biphasic calcium phosphate ceramics and the resultant influence on osteogenic differentiation of mesenchymal stem cells

Although in vitro studies have shown that biomaterials and mechanical stimuli can mediate inflammatory responses or regulate osteogenesis of MSCs, the underlying behaviour of the inflammatory response of macrophages on biomaterials mediated by mechanical stimuli, which regulates osteogenesis, is relatively unknown. Thus, it is imperative to explore the role of bionic mechanical stimulation in the biomaterial-mediated inflammatory response of macrophages. In this study, we used osteoinductive biphasic calcium phosphate (BCP) ceramics as the model biomaterial and chose micro-vibration stimulation (MVs) with three variable parameters (frequency, magnitude, and time). Based on orthogonal experiments, nine combinations of MVs parameters were generated, and their effects on the BCP-mediated macrophage inflammatory response were investigated. MVs significantly affected the gene expression and cytokine secretion of macrophages grown on BCP ceramics and further influenced the behaviour of bone marrow mesenchymal stem cells (BMMSCs) in a paracrine manner. Moreover, frequency seemed to be the most dominant factor (compared with magnitude and time) in regulating the inflammatory response of macrophages. The optimal combination of MVs parameters (frequency 10 Hz, magnitude 0.45 g, and time 60 min) could induce a healing-associated M2 phenotype, as evidenced by the downregulated pro-inflammatory gene (Il-1β, and Tnf-α) expression, the upregulated anti-inflammatory gene (Il10) expression, and the inhibited pro-inflammatory cytokine (Il-1β and Tnf-α) secretion of macrophages grown on BCP ceramics, and its conditioned medium (CM) could further promote osteogenic differentiation of BMMSCs. These findings provide valuable insights into the mechanical stimulus-mediated macrophage inflammatory response and osteogenesis in the presence of osteoinductive BCP ceramics and allow accurate evaluation of the biological performance of biomaterials in vitro, in order to optimize bone substitute materials to achieve the desired clinical performance.

[Research on the nature of micromovement and the biomechanical staging of fracture healing]

Objective

To explore the nature of micromovement and the biomechanical staging of fracture healing.

Methods

Through literature review and theoretical analysis, the difference in micromovement research was taken as the breakthrough point to try to provide a new understanding of the role of micromovement and the mechanical working mode in the process of fracture healing.

Results

The process of fracture healing is the process of callus generation and connection. The micromovement is the key to start the growth of callus, and the total amount of callus should be matched with the size of the fracture space. The strain at the fracture end is the key to determine the callus connection. The strain that can be tolerated by different tissues in the fracture healing process will limit the micromovement. According to this, the fracture healing process can be divided into the initiation period, perfusion period, contradiction period, connection period, and physiological period, i.e., the biomechanical staging of fracture healing.

Conclusion

Biomechanical staging of fracture healing incorporates important mechanical parameters affecting fracture healing and introduces the concepts of time and space, which helps to understand the role of biomechanics, and its significance needs further clinical test and exploration.

Remote-Controlled 3D Porous Magnetic Interface toward High-Throughput Dynamic 3D Cell Culture

Mechanical stimuli have been shown to play a large role in cellular behavior, including cellular growth, differentiation, morphology, homeostasis, and disease. Therefore, developing bioreactor systems that can create complex mechanical environments for both tissue engineering and disease modeling drug screening is appealing. However, many of existing systems are restricted because of their bulky size with external force generators, destructive microenvironment control, and low throughput. These shortcomings have preceded to the utilization of magnetic stimuli responsive materials, given their untethered, fast, and tunable actuation potential at both the microscale and macroscale level, for seamless integration into cell culture wells and microfluidic systems. Nevertheless, magnetic soft materials for cell culture have been limited due to the inability to develop well-defined 3D structures for more complex and physiological relevant mechanical actuation. Herein, we introduce a facile fabrication process to develop magnetic-PDMS (polydimethylsiloxane) porous composite designs with both well-defined and controllable microlevel and macrolevel features to dynamically manipulate 3D cell-laden gel at the scale. The intrinsic stiffness of the magnetic-PDMS porous composites is also modulated to control the deformation potential to mimic physiological relevant strain levels, with 2.89-11% observed in magnetic actuation studies. High cell viability was achieved with the culturing of both human adipose stem cells (hADMSCs) and human umbilical cord mesenchymal stem cells (hUCMSCs) in 3D cell-laden gel interfaced with the magnetic-PDMS porous composite. Also, the highly interconnected porous network of the magnetic-PDMS composites facilitated free diffusion throughout the porous structure showcasing the potential of a multisurface contact 3D porous magnetic structure in both reservoir and 96-well plate insert designs for more complex dynamic mechanical actuation. In conclusion, these studies provide a means for establishing a biocompatible, tunable magnetic-PDMS porous composite with fast and programmable dynamic strain potential making it a suitable platform for high-throughput, dynamic 3D cell culture.

Effects of Extracellular Osteoanabolic Agents on the Endogenous Response of Osteoblastic Cells

The complex multidimensional skeletal organization can adapt its structure in accordance with external contexts, demonstrating excellent self-renewal capacity. Thus, optimal extracellular environmental properties are critical for bone regeneration and inextricably linked to the mechanical and biological states of bone. It is interesting to note that the microstructure of bone depends not only on genetic determinants (which control the bone remodeling loop through autocrine and paracrine signals) but also, more importantly, on the continuous response of cells to external mechanical cues. In particular, bone cells sense mechanical signals such as shear, tensile, loading and vibration, and once activated, they react by regulating bone anabolism. Although several specific surrounding conditions needed for osteoblast cells to specifically augment bone formation have been empirically discovered, most of the underlying biomechanical cellular processes underneath remain largely unknown. Nevertheless, exogenous stimuli of endogenous osteogenesis can be applied to promote the mineral apposition rate, bone formation, bone mass and bone strength, as well as expediting fracture repair and bone regeneration. The following review summarizes the latest studies related to the proliferation and differentiation of osteoblastic cells, enhanced by mechanical forces or supplemental signaling factors (such as trace metals, nutraceuticals, vitamins and exosomes), providing a thorough overview of the exogenous osteogenic agents which can be exploited to modulate and influence the mechanically induced anabolism of bone. Furthermore, this review aims to discuss the emerging role of extracellular stimuli in skeletal metabolism as well as their potential roles and provide new perspectives for the treatment of bone disorders.

Possible Mechanisms for the Effects of Sound Vibration on Human Health

This paper presents a narrative review of research literature to “map the landscape” of the mechanisms of the effect of sound vibration on humans including the physiological, neurological, and biochemical. It begins by narrowing music to sound and sound to vibration. The focus is on low frequency sound (up to 250 Hz) including infrasound (1–16 Hz). Types of application are described and include whole body vibration, vibroacoustics, and focal applications of vibration. Literature on mechanisms of response to vibration is categorized into hemodynamic, neurological, and musculoskeletal. Basic mechanisms of hemodynamic effects including stimulation of endothelial cells and vibropercussion; of neurological effects including protein kinases activation, nerve stimulation with a specific look at vibratory analgesia, and oscillatory coherence; of musculoskeletal effects including muscle stretch reflex, bone cell progenitor fate, vibration effects on bone ossification and resorption, and anabolic effects on spine and intervertebral discs. In every category research on clinical applications are described. The conclusion points to the complexity of the field of vibrational medicine and calls for specific comparative research on type of vibration delivery, amount of body or surface being stimulated, effect of specific frequencies and intensities to specific mechanisms, and to greater interdisciplinary cooperation and focus.

Influence of Low-Magnitude High-Frequency Vibration on Bone Cells and Bone Regeneration

Bone is a mechanosensitive tissue for which mechanical stimuli are crucial in maintaining its structure and function. Bone cells react to their biomechanical environment by activating molecular signaling pathways, which regulate their proliferation, differentiation, and matrix production. Bone implants influence the mechanical conditions in the adjacent bone tissue. Optimizing their mechanical properties can support bone regeneration. Furthermore, external biomechanical stimulation can be applied to improve implant osseointegration and accelerate bone regeneration. One promising anabolic therapy is vertical whole-body low-magnitude high-frequency vibration (LMHFV). This form of vibration is currently extensively investigated to serve as an easy-to-apply, cost-effective, and efficient treatment for bone disorders and regeneration. This review aims to provide an overview of LMHFV effects on bone cells in vitro and on implant integration and bone fracture healing in vivo. In particular, we review the current knowledge on cellular signaling pathways which are influenced by LMHFV within bone tissue. Most of the in vitro experiments showed that LMHFV is able to enhance mesenchymal stem cell (MSC) and osteoblast proliferation. Furthermore, osteogenic differentiation of MSCs and osteoblasts was shown to be accelerated by LMHFV, whereas osteoclastogenic differentiation was inhibited. Furthermore, LMHFV increased bone regeneration during osteoporotic fracture healing and osseointegration of orthopedic implants. Important mechanosensitive pathways mediating the effects of LMHFV might be the Wnt/beta-catenin signaling pathway, the estrogen receptor (ER) signaling pathway, and cytoskeletal remodeling.

Low magnitude high frequency vibration promotes chondrogenic differentiation of bone marrow stem cells with involvement of β-catenin signaling pathway

OBJECTIVE

Mesenchymal stem cells (MSCs) are well known to have the capability to form bone and cartilage, and chondrogenesis derived from MSCs is reported to be affected by mechanical stimuli. This research aimed to study the effects of low magnitude high frequency (LMHF) vibration on the chondrogenic differentiation of bone marrow-derived MSCs (BMSCs) which were cultured with chondrogenic medium, and to investigate the role of β-catenin cascade in this process.

METHODS

Rat bone marrow-derived MSCs (BMSCs) were isolated and randomized into vibration and static cultures. The effect of vibration on BMSCs proliferation, differentiation and chondrogenic potential was assessed at the protein level.

RESULTS

LMHFV did not affect the proliferation of BMSCs. However, this was accompanied by increased markers of chondrogenesis. The protein expression of chondrocyte-specific markers of Aggrecan, Sox9, and BMP7 were upregulated and Collagen X was decreased by LMHF vibration introduced at the chondrogenic differentiation in vitro. Specifically, thicker blue-stained particles were observed in Alcian Blue staining and the level of glycosaminoglycan were significantly increased respectively in the vibration culture group by 56.5 % and 93.6 % on the 7th and 14th day. The expression and nuclear translocation of β-catenin were activated in a significant manner. And inhibition of GSK-3β activity with Licl rearranged and intensified the cytoskeleton affected by vibration stimulation.

CONCLUSIONS

Our data demonstrated that LMHF mechanical vibration promotes BMSCs chondrogenic differentiation and implies β-catenin signal acts as an essential mediator in the mechano-biochemical transduction and subsequent transcriptional regulation in the process of chondrogenesis.

Graphene Oxide Scaffold Stimulates Differentiation and Proangiogenic Activities of Myogenic Progenitor Cells

The physiological process of muscle regeneration is quite limited due to low satellite cell quantity and also the inability to regenerate and reconstruct niche tissue. The purpose of the study was to examine whether a graphene oxide scaffold is able to stimulate myogenic progenitor cell proliferation and the endocrine functions of differentiating cells, and therefore, their active participation in the construction of muscle tissue. Studies were carried out using mesenchymal cells taken from 6-day-old chicken embryos and human umbilical vein endothelial cells (HUVEC) were used to assess angiogenesis. The graphene scaffold was readily colonized by myogenic progenitor cells and the cells dissected from heart, brain, eye, and blood vessels did not avoid the scaffold. The scaffold strongly induced myogenic progenitor cell signaling pathways and simultaneously activated proangiogenic signaling pathways via exocrine vascular endothelial growth factor (VEGF) secretion. The present study revealed that the graphene oxide (GO) scaffold initiates the processes of muscle cell differentiation due to mechanical interaction with myogenic progenitor cell.

Joint construction of micro-vibration stimulation and BCP scaffolds for enhanced bioactivity and self-adaptability tissue engineered bone grafts

The bone defects caused by trauma and disease have become a major difficulty in the treatment of clinical bone defects, and bone tissue engineering has become a promising treatment strategy. It was found that mechanical stimulation regulated the development of bone constructs by affecting the distribution and differentiation of cells on them. In this study, tissue-engineered bone grafts with enhanced bioactivity and self-adaptability were constructed by BMSCs and biphasic calcium phosphate (BCP) scaffolds under periodic micro-vibration stimulation (MVS) with a frequency of 40 Hz and a magnitude of 0.3 g. The results of the material characterization indicated that the BCP scaffolds created a more favourable osteogenic micro-environment with promoted calcium ion release, protein adsorption and mineralization deposition under the micro-vibration stimulation. The in vitro results showed that the apoptosis of BMSCs increased significantly on day 1, but from day 3 on, the proliferation increased and apoptosis decreased. Cells were evenly distributed on the scaffolds, exhibiting tight adhesion in a flat-shape and distinct matrix mineralization. F-actin and ALP expression significantly increased and meanwhile osteogenesis-related genes including Runx2, Col-I, ALP, and OCN were significantly up-regulated. Western blotting results suggested that the ERK1/2 and Wnt/β-catenin signalling pathways were involved in the osteogenic behaviour of BMSCs induced by MVS. In vivo experiments showed that grafts had stronger osteoinduction and mechanical adaptability. Taken together, this study suggested that micro-vibration stimulation combined with BCP scaffolds with good osteoinduction could be a promising approach for constructing tissue engineered bone grafts with enhanced bioactivity, mechanical adaptability, and bone regeneration repair capability.

Mechanical impact stimulation platform tailored for high-resolution light microscopy

High frequency (HF) mechanical vibration has been used in vitro to study the cellular response to mechanical stimulation and induce stem cell differentiation. However, detailed understanding of the effect of the mechanical cues on cellular physiology is lacking. To meet this limitation, we have designed a system, which enables monitoring of living cells by high-resolution light microscopy during mechanical stimulation by HF vibration or mechanical impacts. The system consists of a commercial speaker, and a 3D printed sample vehicle and frame. The speaker moves the sample in the horizontal plane, allowing simultaneous microscopy. The HF vibration (30–200 Hz) performances of two vehicles made of polymer and aluminum were characterized with accelerometer. The mechanical impacts were characterized by measuring the acceleration of the aluminum vehicle and by time lapse imaging. The lighter polymer vehicle produced higher HF vibration magnitudes at 30–50 Hz frequencies than the aluminum vehicle. However, the aluminum vehicle performed better at higher frequencies (60–70 Hz, 90–100 Hz, 150 Hz). Compatibility of the system in live cell experiments was investigated with epithelial cells (MDCKII, expressing Emerald-Occludin) and HF (0.56Gpeak,30 Hz and 60 Hz) vibration. Our findings indicated that our system is compatible with high-resolution live cell microscopy. Furthermore, the epithelial cells were remarkable stable under mechanical vibration stimulation. To conclude, we have designed an inexpensive tool for the studies of cellular biophysics, which combines versatile in vivo like mechanical stimuli with live cell imaging, showing a great potential for several cellular applications.

Design, construction and characterisation of a novel nanovibrational bioreactor and cultureware for osteogenesis

In regenerative medicine, techniques which control stem cell lineage commitment are a rapidly expanding field of interest. Recently, nanoscale mechanical stimulation of mesenchymal stem cells (MSCs) has been shown to activate mechanotransduction pathways stimulating osteogenesis in 2D and 3D culture. This has the potential to revolutionise bone graft procedures by creating cellular graft material from autologous or allogeneic sources of MSCs without using chemical induction. With the increased interest in mechanical stimulation of cells and huge potential for clinical use, it is apparent that researchers and clinicians require a scalable bioreactor system that provides consistently reproducible results with a simple turnkey approach. A novel bioreactor system is presented that consists of: a bioreactor vibration plate, calibrated and optimised for nanometre vibrations at 1 kHz, a power supply unit, which supplies a 1 kHz sine wave signal necessary to generate approximately 30 nm of vibration amplitude, and custom 6-well cultureware with toroidal shaped magnets incorporated in the base of each well for conformal attachment to the bioreactor’s magnetic vibration plate. The cultureware and vibration plate were designed using finite element analysis to determine the modal and harmonic responses, and validated by interferometric measurement. This helps ensure that the vibration plate and cultureware, and thus collagen and MSCs, all move as a rigid body, avoiding large deformations close to the resonant frequency of the vibration plate and vibration damping beyond the resonance. Assessment of osteogenic protein expression was performed to confirm differentiation of MSCs after initial biological experiments with the system, as well as atomic force microscopy of the 3D gel constructs during vibrational stimulation to verify that strain hardening of the gel did not occur. This shows that cell differentiation was the result of the nanovibrational stimulation provided by the bioreactor alone, and that other cell differentiating factors, such as stiffening of the collagen gel, did not contribute.

Cell adhesion and culture medium dependent changes in the high frequency mechanical vibration induced proliferation, osteogenesis, and intracellular organization of human adipose stem cells

High frequency (HF) mechanical vibration appears beneficial for in vitro osteogenesis of mesenchymal stem cells (MSCs). However, the current mechanobiological understanding of the method remains insufficient. We designed high-throughput stimulators to apply horizontal or vertical high magnitude HF (HMHF; 2.5 G_peak, 100 Hz) vibration on human adipose stem cells (hASCs). We analyzed proliferation, alkaline phosphatase (ALP) activity, mineralization, and effects on the actin cytoskeleton and nuclei using immunocytochemical stainings. Proliferation was studied on a standard tissue culture plastic (sTCP) surface and on an adhesion supporting tissue culture plastic (asTCP) surface in basal (BM) and osteogenic (OM) culture medium conditions. We discovered that the improved cell adhesion was a prerequisite for vibration induced changes in the proliferation of hASCs. Similarly, the adhesion supporting surface enabled us to observe vibration initiated ALP activity and mineralization changes in OM condition. The horizontal vibration increased ALP activity, while vertical stimulation reduced ALP activity. However, mineralization was not enhanced by the HMHF vibration. We performed image-based analysis of actin and nuclei to obtain novel data of the intracellular-level responses to HF vibration in BM and OM conditions. Our quantitative results suggest that actin organizations were culture medium and stimulation direction dependent. Both stimulation directions decreased OM induced changes in nuclear size and elongation. Consequently, our findings of the nuclear deformations provide supportive evidence for the involvement of the nuclei in the mechanocoupling of HF vibration. Taken together, the results of this study enhanced the knowledge of the intracellular mechanisms of HF vibration induced osteogenesis of MSCs.

Vibration enhances osteoclastogenesis by inducing RANKL expression via NF-κB signaling in osteocytes

To shorten the duration of orthodontic treatment it is important not only to reduce risks such as dental caries, periodontal disease, and root resorption, but also to decrease pain and discomfort caused by a fixed appliance. Several studies have investigated the effect of vibration applied to fixed appliances to accelerate tooth movement. Although it was reported that vibration accelerates orthodontic tooth movement by enhancing alveolar bone resorption, the underlying cellular and molecular mechanisms remain unclear. In this study, we investigated the effects of vibration on osteoclastogenesis in vitro and in vivo. Vibration applied to pre-osteoclast cell line RAW264.7 cells enhanced cell proliferation but did not affect their differentiation into osteoclasts. Osteocytes in bone are known to be mechanosensitive and to act as receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL). Therefore, in the present study, vibration was applied to cells from the osteocyte-like cell line MLO-Y4. In MLO-Y4 cells, vibration induced phosphorylation of the inhibitor of NF-κB (IκB) and caused nuclear localization of NF-κB p65. Additionally, vibration increased RANKL mRNA expression, but did not affect osteoprotegerin (OPG) mRNA expression in MLO-Y4 cells, thus resulting in an increased RANKL/OPG ratio. Consistent with these findings, vibration applied during experimental tooth movement increased NF-κB activation and RANKL expression in osteocytes on the compression side of alveolar bone in vivo, whereas vibration had no such effects on the tension side. Furthermore, in a co-culture of MLO-Y4 cells and RAW264.7 cells, vibration applied to MLO-Y4 cells enhanced osteoclastogenesis. These findings suggest that vibration could accelerate orthodontic tooth movement by enhancing osteoclastogenesis through increasing the number of pre-osteoclasts and up-regulating RANKL expression in osteocytes on the compression side of alveolar bone via NF-κB activation.

Recovery of stem cell proliferation by low intensity vibration under simulated microgravity requires LINC complex

Mesenchymal stem cells (MSC) rely on their ability to integrate physical and spatial signals at load bearing sites to replace and renew musculoskeletal tissues. Designed to mimic unloading experienced during spaceflight, preclinical unloading and simulated microgravity models show that alteration of gravitational loading limits proliferative activity of stem cells. Emerging evidence indicates that this loss of proliferation may be linked to loss of cellular cytoskeleton and contractility. Low intensity vibration (LIV) is an exercise mimetic that promotes proliferation and differentiation of MSCs by enhancing cell structure. Here, we asked whether application of LIV could restore the reduced proliferative capacity seen in MSCs that are subjected to simulated microgravity. We found that simulated microgravity (sMG) decreased cell proliferation and simultaneously compromised cell structure. These changes included increased nuclear height, disorganized apical F-actin structure, reduced expression, and protein levels of nuclear lamina elements LaminA/C LaminB1 as well as linker of nucleoskeleton and cytoskeleton (LINC) complex elements Sun-2 and Nesprin-2. Application of LIV restored cell proliferation and nuclear proteins LaminA/C and Sun-2. An intact LINC function was required for LIV effect; disabling LINC functionality via co-depletion of Sun-1, and Sun-2 prevented rescue of cell proliferation by LIV. Our findings show that sMG alters nuclear structure and leads to decreased cell proliferation, but does not diminish LINC complex mediated mechanosensitivity, suggesting LIV as a potential candidate to combat sMG-induced proliferation loss.

Efficacy of mechanical vibration in regulating mesenchymal stem cells gene expression

This study aimed at investigating the expression of osteoblast and chondrocyte-related genes in mesenchymal stem cells (MSCs), derived from rabbit adipose tissue, under mechanical vibration. The cells were placed securely on a vibrator's platform and subjected to 300 Hz of sinusoidal vibration, with a maximum amplitude of 10 μm, for 45 min per day, and for 14 consequent days, in the absence of biochemical reagents. The negative control group was placed in the conventional culture medium with no mechanical loading. The expression of osteoblast and chondrocyte-related genes was investigated using real-time polymerase chain reaction (real-time PCR). In addition, F-actin fiber structure and alignment with the help of actin filament fluorescence staining were evaluated, and the level of metabolic activity of MSCs was determined by the methyl thiazolyl tetrazolium assay. The real-time PCR study showed a significant increase of bone gene expression in differentiated cells, compared with MSCs (P < 0.05). On the other hand, the level of chondrocyte gene expression was not remarkable. Applying mechanical vibration enhanced F-actin fiber structure and made them aligned in a specific direction. It was also found that during the differentiation process, the metabolic activity of the cells increased (P < 0.05). The results of this work are in agreement with the well-accepted fact that the MSCs, in the absence of growth factors, are sensitive to low-amplitude, high-frequency vibration. Outcomes of this work can be applied in cell therapy and tissue engineering, when regulation of stem cells is required.

Experimental and Numerical Design and Evaluation of a Vibration Bioreactor using Piezoelectric Patches

In this present study, we propose a method for exposing biological cells to mechanical vibration. The motive for our research was to design a bioreactor prototype in which in-depth in vitro studies about the influence of vibration on cells and their metabolism can be performed. The therapy of cancer or antibacterial measures are applications of interest. In addition, questions about the reaction of neurons to vibration are still largely unanswered. In our methodology, we used a piezoelectric patch (PZTp) for inducing mechanical vibration to the structure. To control the vibration amplitude, the structure could be excited at different frequency ranges, including resonance and non-resonance conditions. Experimental results show the vibration amplitudes expected for every frequency range tested, as well as the vibration pattern of those excitations. These are essential parameters to quantify the effect of vibration on cell behavior. Furthermore, a numerical model was validated with the experimental results presenting accurate results for the prediction of those parameters. With the calibrated numerical model, we will study in greater depth the effects of different vibration patterns for the abovementioned cell types.

The effect of low-magnitude, high-frequency vibration on poly(ethylene glycol)-microencapsulated mesenchymal stem cells

Low-magnitude, high-frequency vibration has stimulated osteogenesis in mesenchymal stem cells when these cells were cultured in certain types of three-dimensional environments. However, results of osteogenesis are conflicting with some reports showing no effect of vibration at all. A large number of vibration studies using three-dimensional scaffolds employ scaffolds derived from natural sources. Since these natural sources potentially have inherent biochemical and microarchitectural cues, we explored the effect of low-magnitude, high-frequency vibration at low, medium, and high accelerations when mesenchymal stem cells were encapsulated in poly(ethylene glycol) diacrylate microspheres. Low and medium accelerations enhanced osteogenesis in mesenchymal stem cells while high accelerations inhibited it. These studies demonstrate that the isolated effect of vibration alone induces osteogenesis.

Emerging Strategies for Stem Cell Lineage Commitment in Tissue Engineering and Regenerative Medicine

Stem cells have transformed the fields of tissue engineering and regenerative medicine, and their potential to further advance these fields cannot be overstated. The stem cell niche is a dynamic microenvironment that determines cell fate during development and tissue repair following an injury. Classically, stem cells were studied in isolation of their microenvironment; however, contemporary research has produced a myriad of evidence that shows the importance of multiple aspects of the stem cell niche in regulating their processes. In the context of tissue engineering and regenerative medicine studies, the niche is an artificial environment provided by culture conditions. In vitro culture conditions may involve coculturing with other cell types, developing specific biomaterials, and applying relevant forces to promote the desired lineage commitment. Considerable advance has been made over the past few years toward directed stem cell differentiation; however, the unspecific differentiation of stem cells yielding a mixed population of cells has been a challenge. In this review, we provide a systematic review of the emerging strategies used for lineage commitment within the context of tissue engineering and regenerative medicine. These strategies include scaffold pore-size and pore-shape gradients, stress relaxation, sonic and electromagnetic effects, and magnetic forces. Finally, we provide insights and perspectives into future directions focusing on signaling pathways activated during lineage commitment using external stimuli.

Effect of two months whole body vibration on hoof growth rate in the horse: A pilot study

Hoof problems are commonly seen in veterinary practice and manipulation of hoof growth rate can be practical and beneficial for that matter. The purpose of this research was to evaluate the effect of whole body vibration (WBV) on hoof growth rate of front feet in the horse. The study was an experimental, single subject, repeated measure design, with all horses serving as control and treatment. Ten horses were subject to WBV, 30 min, twice daily, five days a week, for 60 days in addition to their regular exercise routine. Hoof growth was measured from the reference hairline down to a horizontal groove in both front feet at 30-day (monthly) intervals starting 30 days before the start of treatment (WBV) up until 60 days post cessation of the treatment (WBV). The data analysis was carried out, by applying several paired t-tests to the mean 30-day hoof growth before, during, and after treatment (WBV). A significant mean increase in hoof growth was seen after 30 days WBV (p < 0.001) as well as after 60 days WBV (p = 0.001) with the increase occurring mainly during the first 30 days of WBV. No prolonged effect on hoof growth rate was seen after cessation of WBV. These results indicate that whole body vibration can be used as a non-invasive, safe and non labor-intensive therapeutic modality to accelerate hoof growth in the horse.

Vibration loading promotes osteogenic differentiation of bone marrow-derived mesenchymal stem cells via p38 MAPK signaling pathway

Low magnitude high frequency vibration (LMHFV) exhibits effectively anabolic effects on the bone tissue, and can promote osteogenic differentiation of mesenchymal stem cells (MSCs) in vitro. The role of p38 MAPK signaling in LMHFV-induced osteogenesis remains unclear. In this current study, LMHFV loading was applied to BMSCs in vitro, and cell proliferation, alkaline phosphatase (ALP), matrix mineralization, as well as osteogenic genes expression were assayed. The mechanism of mechanical signal transduction was analysed using PCR array, qRT-PCR and Western blot. LMHFV increased cell proliferation in the growth medium, while inhibited proliferation in the osteogenic medium. ALP activity, matrix mineralization and osteogenic genes expression of Runx2, Col-I, ALP, OPN and OC were increased by LMHFV. p38 and MKK6 genes expression, and p38 phosphorylation were promoted in LMHFV-induced osteogenesis. Inhibition of p38 MAPK with SB203580 and targeted p38 siRNA blunted the increased ALP activity and osteogenic genes expression by LMHFV. These findings suggest that LMHFV promotes osteogenic differentiation of BMSCs, and p38 MAPK signaling shows an important function in LMHFV-induced osteogenesis.

Strain and Vibration in Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into any mesenchymal tissue, including bone, cartilage, muscle, and fat. MSC differentiation can be influenced by a variety of stimuli, including environmental and mechanical stimulation, scaffold physical properties, or applied loads. Numerous studies have evaluated the effects of vibration or cyclic tensile strain on MSCs towards developing a mechanically based method of differentiation, but there is no consensus between studies and each investigation uses different culture conditions, which also influence MSC fate. Here we present an overview of the response of MSCs to vibration and cyclic tension, focusing on the effect of various culture conditions and strain or vibration parameters. Our review reveals that scaffold type (e.g., natural versus synthetic; 2D versus 3D) can influence cell response to vibration and strain to the same degree as loading parameters. Hence, in the efforts to use mechanical loading as a reliable method to differentiate cells, scaffold selection is as important as method of loading.

Synergistic acceleration of experimental tooth movement by supplementary high-frequency vibration applied with a static force in rats

Several recent prospective clinical trials have investigated the effect of supplementary vibration applied with fixed appliances in an attempt to accelerate tooth movement and shorten the duration of orthodontic treatment. Among them, some studies reported an increase in the rate of tooth movement, but others did not. This technique is still controversial, and the underlying cellular and molecular mechanisms remain unclear. In the present study, we developed a new vibration device for a tooth movement model in rats, and investigated the efficacy and safety of the device when used with fixed appliances. The most effective level of supplementary vibration to accelerate tooth movement stimulated by a continuous static force was 3 gf at 70 Hz for 3 minutes once a week. Furthermore, at this optimum-magnitude, high-frequency vibration could synergistically enhance osteoclastogenesis and osteoclast function via NF-κB activation, leading to alveolar bone resorption and finally, accelerated tooth movement, but only when a static force was continuously applied to the teeth. These findings contribute to a better understanding of the mechanism by which optimum-magnitude high-frequency vibration accelerates tooth movement, and may lead to novel approaches for the safe and effective treatment of malocclusion.

The Effect of Low-Magnitude Low-Frequency Vibrations (LMLF) on Osteogenic Differentiation Potential of Human Adipose Derived Mesenchymal Stem Cells

Introduction

In the current study, we investigated the effect of low magnitude, low frequency (LMLF) mechanical vibrations on the osteogenic differentiation potential of human adipose derived mesenchymal stem cells (hASC), taken from elderly patients.

Methods

During 21 days in osteogenic culture medium, cells were periodically exposed to three different frequencies (25, 35 and 45 Hz) of continuous sinusoidal oscillation, using a vibration generator. We measured cell proliferation, cell morphology, calcium and phosphorus deposition using Almar Blue assay, fluorescence microscopy, scanning electron microscopy, and a EDX detector, respectively. Osteogenic differentiation was measured by assessing protein and mRNA levels. Osteogenesis was confirmed by detection of specific markers with alkaline phosphatase and enzyme-linked immunosorbent assays for: bone morphogenetic protein 2 (BMP-2), osteocalcin (OCL) and osteopontin (OPN).

Results

We found that 25 Hz vibrations had the greatest impact on hASC morphology, ultrastructure, and proliferation. We observed the formation of osteocyte- and hydroxyapatite-like structures, an increased quantity of calcium and phosphorus deposits, and increased differentiation in the stimulated groups.

Conclusions

Our findings suggest that LMLF vibrations could be used to enhance cell-based therapies for treatment of bone deficits, particularly in elderly patients, where the need is greatest.

The effect of biomechanical stimulation on osteoblast differentiation of human jaw periosteum-derived stem cells

Background

This study was to investigate the effect of biomechanical stimulation on osteoblast differentiation of human periosteal-derived stem cell using the newly developed bioreactor.

Methods

Human periosteal-derived stem cells were harvested from the mandible during the extraction of an impacted third molar. Using the new bioreactor, 4% cyclic equibiaxial tension force (0.5 Hz) was applied for 2 and 8 h on the stem cells and cultured for 3, 7, and 14 days on the osteogenic medium. Biochemical changes of the osteoblasts after the biomechanical stimulation were investigated. No treatment group was referred to as control group.

Results

Alkaline phosphatase (ALP) activity and ALP messenger RNA (mRNA) expression level were higher in the strain group than those in the control group. The osteocalcin and osteonectin mRNA expressions were higher in the strain group compared to those in the control group on days 7 and 14. The vascular endothelial growth factor (VEGF) mRNA expression was higher in the strain group in comparison to that in the control group. Concentration of alizarin red S corresponding to calcium content was higher in the strain group than in the control group.

Conclusions

The study suggests that cyclic tension force could influence the osteoblast differentiation of periosteal-derived stem cells under optimal stimulation condition and the force could be applicable for tissue engineering.

[Influences of vibration on rapid osteogenic response of osteoblasts]

OBJECTIVE

This study investigated the rapid response of osteoblasts, which were derived from low-magnitude high-frequency vibration (LMHFV). Refractory period-derived memory response was also observed.

METHODS

MC3T3-E1 cells were incubated and received LMHFV stimulation (0.49 g, 40 Hz) for 30 min. After application of LMHFV, mRNA levels of earlier osteogenic differentiation markers Runt-related transcription factor 2 (Runx2), collagen typeⅠ(Col-Ⅰ), and alkaline phosphatase (ALP) were immediately detected by real-time fluorescence quantitative polymerase chain reaction in the absence or presence of antioxidant. Simultaneously, concentrations of mitochondrial reactive oxygen species (ROS) and average mitochondrial length were also measured.

RESULTS

Osteoblasts in the vibration group showed decreased gene expressions of Runx2, Col-Ⅰ, and ALP (P<0.01) and increased levels of mitochondrial ROS (P<0.01) and shortened mitochondria (P<0.01), whereas antioxidant treatment resulted in recovery from changes in the above indicators (P<0.01).

CONCLUSIONS

LMHFV can downregulate mRNA levels of early osteogenic differentiation markers, promote ROS generation, and mitochondrial fission. 
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The effect of local application of low-magnitude high-frequency vibration on the bone healing of rabbit calvarial defects-a pilot study

Background

The objective of this pilot study was to evaluate the effect of local application of low-magnitude high-frequency vibration (LMHFV) on the bone healing of rabbit calvarial defects that were augmented with different grafting materials and membranes.

Methods

Four calvarial defects were created in each of two New Zealand rabbits and filled with the following materials: biphasic calcium phosphate (BCP), deproteinized bovine bone mineral covered with a non-cross-linked collagen membrane (BO/BG), biphasic calcium phosphate covered with a strontium hydroxyapatite-containing collagen membrane (BCP/SR), and non-cross-linked collagen membrane (BG). Four defects in one rabbit served as a control, while the other was additionally subjected to the local LMHFV protocol of 40 Hz, 16 min per day. The rabbits were sacrificed 1 week after surgery. Histomorphometric analysis was performed to determine the percentages of different tissue compartments.

Results

Compared to the control defects, the higher percentage of osteoid tissue was found in LMHFV BG defects (35.3 vs. 19.3%), followed by BCP/SR (17.3 vs. 2.0%) and BO/BG (9.3 vs. 1.0%). The fraction occupied by the residual grafting material varied from 40.3% in BO/BG to 22.3% in BCP/SR LMHFV defects. Two-way models revealed that material type was only significant for the osteoid (P= 0.045) and grafting material (P = 0.001) percentages, while the vibration did not provide any statistical significance for all histomorphometric outcomes (P > 0.05).

Conclusion

Local application of LMHFV did not appear to offer additional benefit in the initial healing phase of rabbit calvarial defects. Histomorphometric measurements after 1 week of healing demonstrated more pronounced signs of early bone formation in both rabbits that were related with material type and independent of LMHFV.

Mechanobiology of bone remodeling and fracture healing in the aged organism

Bone can adapt to changing load demands by mechanically regulated bone remodeling. Osteocytes, osteoblasts, and mesenchymal stem cells are mechanosensitive and respond to mechanical signals through the activation of specific molecular signaling pathways. The process of bone regeneration after fracture is similarly and highly regulated by the biomechanical environment at the fracture site. Depending on the tissue strains, mesenchymal cells differentiate into fibroblasts, chondrocytes, or osteoblasts, determining the course and the success of healing. In the aged organism, mechanotransduction in both intact and fractured bones may be altered due to changed hormone levels and expression of growth factors and other signaling molecules. It is proposed that altered mechanotransduction may contribute to disturbed healing in aged patients. This review explains the basic principles of mechanotransduction in the bone and the fracture callus and summarizes the current knowledge on aging-induced changes in mechanobiology. Furthermore, the methods for external biomechanical stimulation of intact and fractured bones are discussed with respect to a possible application in the elderly patient.

Low-magnitude, high-frequency vibration promotes the adhesion and the osteogenic differentiation of bone marrow-derived mesenchymal stem cells cultured on a hydroxyapatite-coated surface: The direct role of Wnt/β-catenin signaling pathway activation

The positive effect of low-magnitude, high‑frequency (LMHF) vibration on implant osseointegration has been demonstrated; however, the underlying cellular and molecular mechanisms remain unknown. The aim of this study was to explore the effect of LMHF vibration on the adhesion and the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) cultured on hydroxyapatite (HA)-coated surfaces in an in vitro model as well as to elucidate the molecular mechanism responsible for the effects of LMHF vibration on osteogenesis. LMHF vibration resulted in the increased expression of fibronectin, which was measured by immunostaining and RT-qPCR. Stimulation of BMSCs by LMHF vibration resulted in the rearrangement of the actin cytoskeleton with more prominent F-actin. Moreover, the expression of β1 integrin, vinculin and paxillin was notably increased following LMHF stimulation. Scanning electron microscope observations revealed that there were higher cell numbers and more extracellular matrix attached to the HA-coated surface in the LMHF group. Alkaline phosphatase activity as well as the expression of osteogenic-specific genes, namely Runx2, osterix, collagen I and osteocalcin, were significantly elevated in the LMHF group. In addition, the protein expression of Wnt10B, β-catenin, Runx2 and osterix was increased following exposure to LMHF vibration. Taken together, the findings of this study indicate that LMHF vibration promotes the adhesion and the osteogenic differentiation of BMSCs on HA-coated surfaces in vitro, and LMHF vibration may directly induce osteogenesis by activating the Wnt/β‑catenin signaling pathway. These data suggest that LMHF vibration enhances the osseointegration of bone to a HA-coated implant, and provide a scientific foundation for improving bone-implant osseointegration through the application of LMHF vibration.

Cell Mechanosensitivity to Extremely Low-Magnitude Signals Is Enabled by a LINCed Nucleus

A cell's ability to recognize and adapt to the physical environment is central to its survival and function, but how mechanical cues are perceived and transduced into intracellular signals remains unclear. In mesenchymal stem cells (MSCs), high-magnitude substrate strain (HMS, ≥2%) effectively suppresses adipogenesis via induction of focal adhesion (FA) kinase (FAK)/mTORC2/Akt signaling generated at FAs. Physiologic systems also rely on a persistent barrage of low-level signals to regulate behavior. Exposing MSC to extremely low-magnitude mechanical signals (LMS) suppresses adipocyte formation despite the virtual absence of substrate strain (<0.001%), suggesting that LMS-induced dynamic accelerations can generate force within the cell. Here, we show that MSC response to LMS is enabled through mechanical coupling between the cytoskeleton and the nucleus, in turn activating FAK and Akt signaling followed by FAK-dependent induction of RhoA. While LMS and HMS synergistically regulated FAK activity at the FAs, LMS-induced actin remodeling was concentrated at the perinuclear domain. Preventing nuclear-actin cytoskeleton mechanocoupling by disrupting linker of nucleoskeleton and cytoskeleton (LINC) complexes inhibited these LMS-induced signals as well as prevented LMS repression of adipogenic differentiation, highlighting that LINC connections are critical for sensing LMS. In contrast, FAK activation by HMS was unaffected by LINC decoupling, consistent with signal initiation at the FA mechanosome. These results indicate that the MSC responds to its dynamic physical environment not only with "outside-in" signaling initiated by substrate strain, but vibratory signals enacted through the LINC complex enable matrix independent "inside-inside" signaling.

Combination treatment with whole body vibration and a kidney-tonifying herbal Fufang prevent osteoporosis in ovariectomized rats

OBJECTIVE

To assess the ability of whole body vibration (WBV) with the kidney-tonifying herbal Fufang (Bushen Zhuanggu Granules, BZG) to prevent osteoporosis in ovariectomized rats.

METHODS

Fifty 6-month-old female Sprague Dawley rats were divided into five groups: sham-operated (SHAM), ovariectomized (OVX), OVX with WBV (OVX + WBV), OVX with BZG (OVX + BZG), OVX with both WBV and BZG (OVX + WBV + BZG). The SHAM group received normal saline. After 12 weeks of treatment, the rats were killed, their serum concentrations of osteopontin (OPN), receptor activator of nuclear factor kappa-B ligand RANKL and bone turnover markers assayed and bone mineral density (BMD), histomorphometry and bone strength evaluated.

RESULTS

Concentrations of OPN were significantly lower in the SHAM, OVX + WBV and OVX + WBV + BZG groups at 12 weeks, whereas concentrations of RANKL had decreased significantly in the SHAM, OVX + WBV, OVX + BZG and OVX + WBV + BZG groups. In the OVX + WBV, OVX + BZG and OVX + WBV + BZG groups the amount of bone turnover had been significantly antagonized. Compared with OVX group, BMD, % trabecular area (Tb.Ar), number of trabeculae (Tb.N) and assessed biomechanical variables were higher in OVX+WBV group, whereas and BMD, %Tb.Ar, Tb.N, maximal load and yield load were higher in the OVX + BZG group. All tested indices were significantly lower in the OVX + WBV and OVX + BZG groups than in the OVX + WBV + BZG group.

CONCLUSION

Either WBV or BZG alone prevents OVX-induced bone loss. However, BZG enhances the effect of WBV by further enhancing BMD, bone architecture and strength.

Effect of low-level mechanical vibration on osteogenesis and osseointegration of porous titanium implants in the repair of long bone defects

Emerging evidence substantiates the potential of porous titanium alloy (pTi) as an ideal bone-graft substitute because of its excellent biocompatibility and structural properties. However, it remains a major clinical concern for promoting high-efficiency and high-quality osseointegration of pTi, which is beneficial for securing long-term implant stability. Accumulating evidence demonstrates the capacity of low-amplitude whole-body vibration (WBV) in preventing osteopenia, whereas the effects and mechanisms of WBV on osteogenesis and osseointegration of pTi remain unclear. Our present study shows that WBV enhanced cellular attachment and proliferation, and induced well-organized cytoskeleton of primary osteoblasts in pTi. WBV upregulated osteogenesis-associated gene and protein expression in primary osteoblasts, including OCN, Runx2, Wnt3a, Lrp6 and β-catenin. In vivo findings demonstrate that 6-week and 12-week WBV stimulated osseointegration, bone ingrowth and bone formation rate of pTi in rabbit femoral bone defects via μCT, histological and histomorphometric analyses. WBV induced higher ALP, OCN, Runx2, BMP2, Wnt3a, Lrp6 and β-catenin, and lower Sost and RANKL/OPG gene expression in rabbit femora. Our findings demonstrate that WBV promotes osteogenesis and osseointegration of pTi via its anabolic effect and potential anti-catabolic activity, and imply the promising potential of WBV for enhancing the repair efficiency and quality of pTi in osseous defects.

Preclinical models for in vitro mechanical loading of bone-derived cells

It is well established that bone responds to mechanical stimuli whereby physical forces are translated into chemical signals between cells, via mechanotransduction. It is difficult however to study the precise cellular and molecular responses using in vivo systems. In vitro loading models, which aim to replicate forces found within the bone microenvironment, make the underlying processes of mechanotransduction accessible to the researcher. Direct measurements in vivo and predictive modeling have been used to define these forces in normal physiological and pathological states. The types of mechanical stimuli present in the bone include vibration, fluid shear, substrate deformation and compressive loading, which can all be applied in vitro to monolayer and three-dimensional (3D) cultures. In monolayer, vibration can be readily applied to cultures via a low-magnitude, high-frequency loading rig. Fluid shear can be applied to cultures in multiwell plates via a simple rocking platform to engender gravitational fluid movement or via a pump to cells attached to a slide within a parallel-plate flow chamber, which may be micropatterned for use with osteocytes. Substrate strain can be applied via the vacuum-driven FlexCell system or via a four-point loading jig. 3D cultures better replicate the bone microenvironment and can also be subjected to the same forms of mechanical stimuli as monolayer, including vibration, fluid shear via perfusion flow, strain or compression. 3D cocultures that more closely replicate the bone microenvironment can be used to study the collective response of several cell types to loading. This technical review summarizes the methods for applying mechanical stimuli to bone cells in vitro.

On the possible role of protein vibrations in information processing in the brain: three Russian dolls

Until recently it was held that the neurocomputations conducted by the brain involved only whole neurons as the operating units. This may however represent only a part of the mechanism. This theoretical and academic position article reviews the considerable evidence that allosteric interactions between proteins (as extensively described by Fuxe et al., 2014), and in particular protein vibrations in neurons, form small scale codes that are involved as parts of the complex information processing systems of the brain. The argument is then developed to suggest that the protein allosteric and vibration codes (that operate at the molecular level) are nested within a medium scale coding system whose computational units are organelles (such as microtubules). This medium scale code is nested in turn inside a large scale coding system, whose computational units are individual neurons. The hypothesis suggests that these three levels interact vertically in both directions thus materially increasing the computational capacity of the brain. The whole hierarchy is thus similar to three nested Russian dolls. This theoretical development may be of use in the design of experiments to test it.

Adult Stem Cell Responses to Nanostimuli

Adult or mesenchymal stem cells (MSCs) have been found in different tissues in the body, residing in stem cell microenvironments called "stem cell niches". They play different roles but their main activity is to maintain tissue homeostasis and repair throughout the lifetime of an organism. Their ability to differentiate into different cell types makes them an ideal tool to study tissue development and to use them in cell-based therapies. This differentiation process is subject to both internal and external forces at the nanoscale level and this response of stem cells to nanostimuli is the focus of this review.

Vibration stimuli and the differentiation of musculoskeletal progenitor cells: Review of results in vitro and in vivo

Due to the increasing burden on healthcare budgets of musculoskeletal system disease and injury, there is a growing need for safe, effective and simple therapies. Conditions such as osteoporosis severely impact on quality of life and result in hundreds of hours of hospital time and resources. There is growing interest in the use of low magnitude, high frequency vibration (LMHFV) to improve bone structure and muscle performance in a variety of different patient groups. The technique has shown promise in a number of different diseases, but is poorly understood in terms of the mechanism of action. Scientific papers concerning both the in vivo and in vitro use of LMHFV are growing fast, but they cover a wide range of study types, outcomes measured and regimens tested. This paper aims to provide an overview of some effects of LMHFV found during in vivo studies. Furthermore we will review research concerning the effects of vibration on the cellular responses, in particular for cells within the musculoskeletal system. This includes both osteogenesis and adipogenesis, as well as the interaction between MSCs and other cell types within bone tissue.

Acoustic-frequency vibratory stimulation regulates the balance between osteogenesis and adipogenesis of human bone marrow-derived mesenchymal stem cells

Osteoporosis can be associated with the disordered balance between osteogenesis and adipogenesis of bone marrow-derived mesenchymal stem cells (BM-MSCs). Although low-frequency mechanical vibration has been demonstrated to promote osteogenesis, little is known about the influence of acoustic-frequency vibratory stimulation (AFVS). BM-MSCs were subjected to AFVS at frequencies of 0, 30, 400, and 800 Hz and induced toward osteogenic or adipogenic-specific lineage. Extracellular matrix mineralization was determined by Alizarin Red S staining and lipid accumulation was assessed by Oil Red O staining. Transcript levels of osteogenic and adipogenic marker genes were evaluated by real-time reverse transcription-polymerase chain reaction. Cell proliferation of BM-MSCs was promoted following exposure to AFVS at 800 Hz. Vibration at 800 Hz induced the highest level of calcium deposition and significantly increased mRNA expression of COL1A1, ALP, RUNX2, and SPP1. The 800 Hz group downregulated lipid accumulation and levels of adipogenic genes, including FABP4, CEBPA, PPARG, and LEP, while vibration at 30 Hz supported adipogenesis. BM-MSCs showed a frequency-dependent response to acoustic vibration. AFVS at 800 Hz was the most favorable for osteogenic differentiation and simultaneously suppressed adipogenesis. Thus, acoustic vibration could potentially become a novel means to prevent and treat osteoporosis.