Novel, high-frequency, low-strain mechanical loading for premenopausal women with low bone mass: early findings

A Tympanic Piezo-Bioreactor Modulates Ion Channel-Associated Mechanosignaling to Stabilize Phenotype and Promote Tenogenesis in Human Tendon-Derived Cells

Preserving the function of human tendon-derived cells (hTDCs) during cell expansion is a significant challenge in regenerative medicine. In this study, a non-genetic approach is introduced to control the differentiation of hTDCs using a newly developed tympanic bioreactor. The system mimics the functionality of the human tympanic membrane, employing a piezoelectrically tuned acoustic diaphragm made of polyvinylidene fluoride-co-trifluoroethylene and boron nitride nanotubes. The diaphragm is vibrationally actuated to deliver targeted electromechanical stimulation to hTDCs. The results demonstrate that the system effectively maintains the tendon-specific phenotype of hTDCs, even under conditions that typically induce nonspecific differentiation, such as osteogenesis. This stabilization is achieved by modulating integrin-mediated mechanosignaling via ion channel-regulated calcium activity, potentially by TREK-1 and PIEZO1, yet targeted studies are required for confirmation. Finally, the system sustains the activation of key differentiation pathways (bone morphogenetic protein, BMP) while downregulating osteogenesis-associated (mitogen-ctivated protein kinase, MAPK and wingless integrated, WNT) pathways and upregulating Focal Adhesion Kinase (FAK) signaling. This approach offers a finely tunable, dose-dependent control over hTDC differentiation, presenting significant potential for non-genetic approaches in cell therapy, tendon tissue engineering, and the regeneration of other mechanosensitive tissues.

Influence of 40 Hz and 100 Hz Vibration on SH-SY5Y Cells Growth and Differentiation-A Preliminary Study

(1) Background: A novel bioreactor platform of neuronal cell cultures using low-magnitude, low-frequency (LMLF) vibrational stimulation was designed to discover vibration influence and mimic the dynamic environment of the in vivo state. To better understand the impact of 40 Hz and 100 Hz vibration on cell differentiation, we join biotechnology and advanced medical technology to design the nano-vibration system. The influence of vibration on the development of nervous tissue on the selected cell line SH-SY5Y (experimental research model in Alzheimer’s and Parkinson’s) was investigated. (2) Methods: The vibration stimulation of cell differentiation and elongation of their neuritis were monitored. We measured how vibrations affect the morphology and differentiation of nerve cells in vitro. (3) Results: The highest average length of neurites was observed in response to the 40 Hz vibration on the collagen surface in the differentiating medium, but cells response did not increase with vibration frequency. Also, vibrations at a frequency of 40 Hz or 100 Hz did not affect the average density of neurites. 100 Hz vibration increased the neurites density significantly with time for cultures on collagen and non-collagen surfaces. The exposure of neuronal cells to 40 Hz and 100 Hz vibration enhanced cell differentiation. The 40 Hz vibration has the best impact on neuronal-like cell growth and differentiation. (4) Conclusions: The data demonstrated that exposure to neuronal cells to 40 Hz and 100 Hz vibration enhanced cell differentiation and proliferation. This positive impact of vibration can be used in tissue engineering and regenerative medicine. It is planned to optimize the processes and study its molecular mechanisms concerning carrying out the research.

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.

Low magnitude high frequency vibrations expedite the osteogenesis of bone marrow stem cells on paper based 3D scaffolds

Anabolic effects of low magnitude high frequency (LMHF) vibrations on bone tissue were consistently shown in the literature in vivo, however in vitro efforts to elucidate underlying mechanisms are generally limited to 2D cell culture studies. Three dimensional cell culture platforms better mimic the natural microenvironment and biological processes usually differ in 3D compared to 2D culture. In this study, we used laboratory grade filter paper as a scaffold material for studying the effects of LHMF vibrations on osteogenesis of bone marrow mesenchymal stem cells in a 3D system. LMHF vibrations were applied 15 min/day at 0.1 g acceleration and 90 Hz frequency for 21 days to residing cells under quiescent and osteogenic conditions. mRNA expression analysis was performed for alkaline phosphatase (ALP) and osteocalcin (OCN) genes, Alizarin red S staining was performed for mineral nodule formation and infrared spectroscopy was performed for determination of extracellular matrix composition. The highest osteocalcin expression, mineral nodule formation and the phosphate bands arising from the inorganic phase was observed for the cells incubated in osteogenic induction medium with vibration. Our results showed that filter paper can be used as a model scaffold system for studying the effects of mechanical loads on cells, and LMHF vibrations induced the osteogenic differentiation of stem cells.

Applicability of Low-intensity Vibrations as a Regulatory Factor on Stem and Progenitor Cell Populations

Persistent and transient mechanical loads can act as biological signals on all levels of an organism. It is therefore not surprising that most cell types can sense and respond to mechanical loads, similar to their interaction with biochemical and electrical signals. The presence or absence of mechanical forces can be an important determinant of form, function and health of many tissue types. Along with naturally occurring mechanical loads, it is possible to manipulate and apply external physical loads on tissues in biomedical sciences, either for prevention or treatment of catabolism related to many factors, including aging, paralysis, sedentary lifestyles and spaceflight. Mechanical loads consist of many components in their applied signal form such as magnitude, frequency, duration and intervals. Even though high magnitude mechanical loads with low frequencies (e.g. running or weight lifting) induce anabolism in musculoskeletal tissues, their applicability as anabolic agents is limited because of the required compliance and physical health of the target population. On the other hand, it is possible to use low magnitude and high frequency (e.g. in a vibratory form) mechanical loads for anabolism as well. Cells, including stem cells of the musculoskeletal tissue, are sensitive to high frequency, lowintensity mechanical signals. This sensitivity can be utilized not only for the targeted treatment of tissues, but also for stem cell expansion, differentiation and biomaterial interaction in tissue engineering applications. In this review, we reported recent advances in the application of low-intensity vibrations on stem and progenitor cell populations. Modulation of cellular behavior with low-intensity vibrations as an alternative or complementary factor to biochemical and scaffold induced signals may represent an increase of capabilities in studies related to tissue engineering.

A systematic review of the exercise effect on bone health: the importance of assessing mechanical loading in perimenopausal and postmenopausal women

OBJECTIVE

The aims of this systematic review were to determine the general effects of exercise on areal bone mineral density (BMD) in perimenopausal and postmenopausal women, and to provide information on the most suitable bone-loading exercise regimens that may improve bone health in this population group.

METHODS

A computerized, systematic literature search was performed in the electronic databases PubMed, Web of Science, CINAHL, SPORTDiscus, and The Cochrane Library, from January 2005 to November 2015, to identify all randomized controlled trials related to exercise in perimenopausal and postmenopausal women. The initial search identified 915 studies, with a final yield of 10 studies. Only randomized controlled trials that examined the effects of exercise programs longer than 24 weeks in women aged 35 to 70 years were included. The 10 studies quantified at least BMD and described training variables adequately (training period, frequency, volume, intensity).

RESULTS

Ten studies with moderate quality evidence (6.4 ± 1.8 points, range 4-9) were included. Significant changes in lumbar and femoral neck BMD were found mainly with high-impact exercise and whole body vibration interventions.

CONCLUSIONS

While training effects must be interpreted with caution because of the heterogeneity of the protocols and exercises performed, this systematic review confirmed the effectiveness of impact exercises combined with other forms of training (vibration or strength training) to preserve BMD in perimenopausal and postmenopausal women. Despite the results possibly not representing a general dose-response relationship, we highlight the importance of quantifying loading intensity and frequency by means of accelerometry as these parameters are determinants for bone adaptation.

Low magnitude high frequency vibration promotes adipogenic differentiation of bone marrow stem cells via P38 MAPK signal

Low magnitude high frequency vibration (LMHFV) has been mainly reported for its influence on the musculoskeletal system, particularly the bone tissue. In the bone structure, osteogenic activity is the main focus of study with regards to LMHFV. However, adipogenesis, another important mode of differentiation in the bone marrow cavity that might be affected by LMHFV, is much less researched. Furthermore, the molecular mechanism of how LMHFV influences adipogenesis still needs to be understood. Here, we tested the effect of LMHFV (0.3g, 40 Hz, amplitude: 50μm), 15min/d, on multipotent stem cells (MSCs), which are the common progenitors of osteogenic, chondrogenic, adipogenic and myogenic cells. It is previously shown that LMHFV promotes osteogenesis of MSCs. In this study, we further revealed its effect on adipo-differentiation of bone marrow stem cells (BMSCs) and studied the underlying signaling pathway. We found that when treated with LMHFV, the cells showed a higher expression of PPARγ, C/EBPα, adiponectin and showed more oil droplets. After vibration, the protein expression of PPARγ increased, and the phosphorylation of p38 MAPK was enhanced. After treating cells with SB203580, a specific p38 inhibitor, both the protein level of PPARγ illustrated by immunofluorescent staining and the oil droplets number, were decreased. Altogether, this indicates that p38 MAPK is activated during adipogenesis of BMSCs, and this is promoted by LMHFV. Our results demonstrating that specific parameters of LMHFV promotes adipogenesis of MSCs and enhances osteogenesis, highlights an unbeneficial side effect of vibration therapy used for preventing obesity and osteoporosis.

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.

Effects of whole body vibration and resistance training on bone mineral density and anthropometry in obese postmenopausal women

Objective. The aim of this study was to evaluate the impact of two exercise programs, whole body vibration and resistance training on bone mineral density (BMD) and anthropometry in obese postmenopausal women. Material and Methods. Eighty Egyptian obese postmenopausal women were enrolled in this study; their age ranged from 50 to 68 years. Their body mass index ranged (30-36 kg/m(2)). The exercise prescription consisted of whole body vibration (WBV) and resistance training. Bone mineral density (BMD) and anthropometrical parameters were measured at the beginning and at the end of the study. Changes from baseline to eight months in BMD and anthropometric parameters were investigated. Results. BMD at the greater trochanter, at ward's triangle, and at lumbar spine were significantly higher after physical training, using both WBV and resistive training. Moreover, both exercise programs were effective in BMI and waist to the hip ratio. Simple and multiple regression analyses showed significant associations between physical activity duration and BMD at all sites. The highest values of R (2) were found for the models incorporating WBV plus BMI. Conclusion. The study suggests that both types of exercise modalities had a similar positive effect on BMD at all sites in obese postmenopausal women. Significant association was noted between physical activity and anthropometric variables and BMD measures at all sites.

p38-MAPK signaling pathway is not involved in osteogenic differentiation during early response of mesenchymal stem cells to continuous mechanical strain

Mechanical stimuli play a significant role in the regulation of bone remodeling during orthodontic tooth movement. However, the correlation between mechanical strain and bone remodeling is still poorly understood. In this study, we used a model of continuous mechanical strain (CMS) on bone mesenchymal stem cells (BMSCs) to investigate the proliferation and osteogenic differentiation of BMSCs and the mechanism of mechano-transduction. A CMS of 10 % at 1 Hz suppressed the proliferation of BMSCs and induced early osteogenic differentiation within 48 h by activating Runx2 and increasing alkaline phosphatase (ALP) activity and mRNA expression of osteogenesis-related genes (ALP, collagen type I, and osteopontin). Regarding mitogen-activated protein kinase (MAPK) activation, CMS induced phased phosphorylation of p38 consisting of a rapid induction of p38 MAPK at 10 min and a rapid decay after 1 h. Furthermore, the potent p38 inhibitor SB203580 blocked the induction of p38 MAPK signaling, but had little effect on subsequent osteogenic events. These results demonstrate that mechanical strain may act as a stimulator to induce the differentiation of BMSCs into osteoblasts, which is a vital function for bone formation in orthodontic tooth movement. However, activation of the p38 signaling pathway may not be involved in this process.

Whole Body Vibration Training is Osteogenic at the Spine in College-Age Men and Women

Osteoporosis is a chronic skeletal disease characterized by low bone mass which is currently challenging the American health care system. Maximizing peak bone mass early in life is a cost-effective method for preventing osteoporosis. Whole body vibration (WBV) is a novel exercise method with the potential to increase bone mass, therefore optimizing peak bone and decreasing the risk for osteoporotic fracture. The aim of this investigation was to evaluate changes in bone mineral density at the hip, spine, and whole body in college-age men and women who underwent a WBV training protocol. Active men (n=6) and women (n=4), ages 18-22 participated in the WBV training; while an additional 14 volunteers (1 male, 13 female) served as controls. All participants completed baseline and follow-up questionnaires to assess health history, physical activity, dietary intake, and menstrual history. The WBV training program, using a Vibraflex 550, incorporated squats, stiff-leg dead lifts, stationary lunges, push-up holds, bent-over rows, and jumps performed on the platform, and occurred 3 times a week, for 12 weeks. Dual energy x-ray absorptiometry (Hologic Explorer, Waltham, MA, USA) was used to assess bone mineral density (BMD, g/cm(2)). A two-tailed, t-test identified significantly different changes in BMD between the WBV and control groups at the lateral spine (average change of 0.022 vs. -0.015 g/cm(2)). The WBV group experienced a 2.7% and 1.0% increase in BMD in the lateral spine and posterior-anterior spine while the control group decreased 1.9% and 0.9%, respectively. Results indicate that 12 weeks of WBV training was osteogenic at the spine in college-age men and women.

The effect of 8 mos of twice-weekly low- or higher intensity whole body vibration on risk factors for postmenopausal hip fracture

OBJECTIVE

Whole body vibration is a potential therapy for age-related loss of musculoskeletal competence. Vibration has improved bone in animal models, but evidence in humans is limited. Relative efficacy of low- vs. high-intensity whole body vibration is also unknown. Our goal was to observe the effect of brief low- and higher intensity whole body vibration on risk factors for hip fracture in postmenopausal women.

DESIGN

We used an 8-mo randomized controlled trial design to examine the influence of twice-weekly low-intensity whole body vibration (15 mins, 30 Hz, 0.3 g) or higher intensity whole body vibration (2 × 3 mins, 12.5 Hz, 1 g) on anthropometrics, bone (whole body, hip, spine, forearm, and heel), muscle (wall squat and chair rise), and balance (tandem walk and single leg stance). Physical activity, daily calcium, and compliance were recorded. Effects were examined by repeated-measures analysis of covariance, controlling for age, height, weight, calcium, physical activity, compliance, and baseline values.

RESULTS

Forty-seven women (71.5 ± 9.0 yrs) completed the trial. There were no between-group differences in any measure at 8 mos, but within-group effects were evident. Controls lost bone at the trochanter (-6%, P = 0.03) and lumbar spine (-6.6%, P = 0.02), whereas whole body vibration groups did not. Whole body vibration subjects improved wall squat (up to 120%, P = 0.004) and chair rise performance (up to 10.5%, P = 0.05).

CONCLUSIONS

Eight mos of twice-weekly whole body vibration may reduce bone loss at the hip and spine and improve lower limb muscle function. These changes may translate to a decreased risk of falls and hip fracture.

Efeitos dos recursos eletrofísicos na osteoporose: uma revisão da literatura

OBJETIVO: Fazer uma revisão bibliográfica a respeito dos efeitos dos principais recursos eletrofísicos utilizados na aceleração do metabolismo ósseo e no tratamento da osteoporose. ANTECEDENTES: A Organização Mundial da Saúde (OMS) define a osteoporose como doença esquelética sistêmica caracterizada por diminuição da massa óssea e deterioração microarquitetural do tecido ósseo, com consequente aumento da fragilidade óssea e susceptibilidade à fratura. Vários tratamentos medicamentosos e não medicamentosos vêm sendo desenvolvidos na tentativa de aumentar a massa óssea e prevenir a osteoporose. Dentro desse contexto, os recursos eletrofísicos vêm tendo um papel de destaque, como recursos que apresentam um potencial osteogênico, capazes de estimular a proliferação de osteoblastos e biomodular o metabolismo ósseo. ESTRATÉGIA DE PESQUISA: Foram consultadas as bases de dados: The Cochrane Library, MEDLINE, Embase, LILACS, SciELO, referências dos artigos identificados, e contato com especialisas em laser, entre os anos de 1983 e 2009. CRITÉRIOS DE SELEÇÃO: Foram incluídos estudos experimentais e ensaios clínicos randomizados que avaliaram os efeitos dos recursos eletrofísicos na osteoporose. RECOMPILAÇÃO E ANÁLISE DE DADOS: Dois revisores selecionaram independentemente os estudos, avaliaram sua qualidade metodológica dos estudos e coletaram os dados. RESULTADOS: Todos os recursos eletrofísicos citados neste artigo se mostraram eficazes na estimulação do metabolismo ósseo. No entanto, a grande maioria dos estudos realizados evidenciam esses efeitos através de estudos in vitro e estudos experimentais com cobaias. Cabe ressaltar que trabalhos como esses são raros em seres humanos. Baseado nos achados desta revisão pode ser sugerido que os recursos eletrofísicios como o laser terapêutico, o ultrassom, campos eletromagnéticos e plataformas vibratórias são recursos que tem um potencial osteogênico entretanto mais estudos são necessários para definir os efeitos dos mesmos em humanos, bem como, protocolos mais eficazes de tratamento. CONCLUSÃO: A partir deste levantamento bibliográfico, fica evidente que os recursos eletrofísicos apresentam um grande potencial osteogênico, porém, a maior parte dos estudos é in vitro. São necessários mais estudos in vivo, definindo, assim, melhores parâmetros e doses, para que sejam utilizados no tratamento da osteoporose.

Mechanical vibration preserves bone structure in rats treated with glucocorticoids

Glucocorticoids are an important cause of secondary osteoporosis in humans, which decreases bone quality and leads to fractures. Mechanical stimulation in the form of low-intensity and high-frequency vibration seems to be able to prevent bone loss and to stimulate bone formation. The objective of this study was to evaluate the effects of mechanical vibration on bone structure in rats treated with glucocorticoids. Thirty 3-month-old adult male Wistar rats were randomized to three groups: control (C), glucocorticoid (G), and glucocorticoid with vibration (GV). The G and GV groups received 3.5mg/kg/day of methylprednisolone 5 days/week for a duration of 9 weeks, and the C group received vehicle (saline solution) during the same period. The GV group was vibrated on a special platform for 30 min per day, 5 days per week during the experiment. The platform was set to provide a vertical acceleration of 1 G and a frequency of 60 Hz. Skeletal bone mass was evaluated by total body densitometry (DXA). Fracture load threshold, undecalcified bone histomorphometry, and bone volume were measured in tibias. Glucocorticoids induced a significantly lower weight gain (-9.7%) and reduced the bone mineral content (-9.2%) and trabecular number (-41.8%) and increased the trabecular spacing (+98.0%) in the G group, when compared to the control (C). Vibration (GV) was able to significantly preserve (29.2%) of the trabecular number and decrease the trabecular spacing (+26.6%) compared to the G group, although these parameters did not reach C group values. The fracture load threshold was not different between groups, but vibration significantly augmented the bone volume of the tibia by 21.4% in the GV group compared to the C group. Our study demonstrated that low-intensity and high-frequency mechanical vibration was able to partially inhibit the deleterious consequences of glucocorticoids on bone structure in rats.

Effects of low-amplitude, high-frequency vibrations on proliferation and differentiation of SAOS-2 human osteogenic cell line

The aim of the work was to understand the consequences of low-amplitude, high-frequency vibrations on proliferation and differentiation of SAOS-2 cells (sarcoma osteogenetic), an osteoblastic and tumorigenic cell line. We realized a bioreactor composed of an eccentric motor that produces a displacement of 11 mm at frequencies between 1 and 120 Hz on a plate connected to the motor. The cultures of SAOS-2 cells were fixed on the plate, and the linear acceleration provoked by the motor to the cultures was measured. We used 30 Hz as stimulating frequency after a preliminary test on the effect of different frequencies on differentiation of cells. Afterward, SAOS-2 cells were stimulated with 30 Hz for different durations, every day for 4 days. The expression of some genes involved in the differentiation process was analyzed first with a reverse transcriptase-polymerase chain reaction and afterward with a real-time polymerase chain reaction on the most expressed genes. Moreover, the proliferation of cells was evaluated. The results suggest a strong increase in the expression of the genes involved in tissue differentiation in the treated groups with respect to the controls. On the other hand, the proliferation seems to be slowed down, so probably the acceleration perceived by the mechanosensors of the cells changes the cellular cycle by blocking the duplication to early differentiate toward bone tissue.

Progressive bone mineral content loss in children with intractable epilepsy treated with the ketogenic diet

BACKGROUND

The ketogenic diet (KD) is a high-fat, low-carbohydrate, and protein diet that effectively treats intractable epilepsy (IE).

OBJECTIVE

The purpose of this study was to measure the change in bone mineral content (BMC) in children with IE treated with the KD for 15 mo.

DESIGN

Prepubertal children >or=5 y of age with IE were eligible. A 4:1 ketogenic diet was maintained for 15 mo, and whole-body and spine BMCs were measured with dual-energy X-ray absorptiometry. Z scores were generated by comparing the children with IE with a cohort of 847 healthy children. Other measurements included demographics, anthropometry, serum 25-hydroxyvitamin D (25-OHD), intact parathyroid hormone, electrolytes, and dietary intake. All measurements were performed at baseline and at 3, 6, 12, and 15 mo. Longitudinal mixed effects models were used to analyze change in BMC over time.

RESULTS

Twenty-five children (9 girls, 16 boys) with IE [age (x +/- SD): 7.3 +/- 1.9 y] participated. Growth and bone health status were suboptimal as were serum 25-OHD concentrations and dietary intake of calcium and vitamin D. Whole-body and spine BMC-for-age both declined by 0.6 z score/y and whole-body and spine BMC-for-height declined 0.7 z score/y and 0.4 z score/y, respectively. Height declined 0.5 z score/y. Body mass index (BMI; in kg/m(2)) z score, age, and ambulation were positive predictors of BMC, which declined sharply over 15 mo of KD treatment.

CONCLUSION

Bone health in children with IE was poor, particularly for younger nonambulatory children with low BMI status. The KD resulted in progressive loss of BMC. The mechanism is unclear. Further studies are needed.