Effect of Low-Magnitude, High-Frequency Mechanical Stimulation on BMD Among Young Childhood Cancer Survivors: A Randomized Clinical Trial

Whole Body Vibration Therapy for Children with Disabilities: A Survey of Potential Risks and Benefits

The purpose of this report is to remind providers of the potential risks of Whole Body Vibration Therapy (WBVT) for children with disabilities. We reviewed the current state of knowledge and learned that WBVT may have potential risk of injury for some children. To the best of our knowledge this review is the first to clarify WBVT risks. We believe WBVT may have therapeutic value but we recommend caution and offer suggestions for future research.

External devices increasing bone quality in animals: A systematic review

Background: Osteoporosis can reduce bone quality and increase the risk of fractures. In addition to pharmacological approaches, physical activity, and implanted devices, external devices can also be detected in the literature as a technique to strengthen bones. This type of intervention arises to be particularly promising because it minimizes the invasiveness of therapy. Methods: A systematic review of the technologies involved in such devices was carried out to identify the most fruitful ones in improving bone quality. This review, according to the PRISMA Statement, focuses on studies involving animals, and excludes pharmaceutical approaches. Findings: The animal models and devices used, their settings, interventions, outcomes measured, and consequent effect on bone quality are reported for each detected technology. Ultrasound and laser arose to be the most studied technologies in the literature, even if they have yet to be proved to have a significant effect on bone quality. Interpretation: External devices for bone quality improvement offer a non-invasive approach that causes minimum discomfort to the patient. This review aimed to detect which technologies reported in the literature significantly affect bone quality. The results showed that several technologies are currently used to improve bone quality. However, each study measures different outcomes and uses different measurement methods, device settings, and interventions. This lack of standardization and the reduced number of articles found do not allow for proper quantitative comparisons.

Increased deformations are dispensable for cell mechanoresponse in engineered bone analogs mimicking aging bone marrow

Aged individuals and astronauts experience bone loss despite rigorous physical activity. Bone mechanoresponse is in-part regulated by mesenchymal stem cells (MSCs) that respond to mechanical stimuli. Direct delivery of low intensity vibration (LIV) recovers MSC proliferation in senescence and simulated microgravity models, indicating that age-related reductions in mechanical signal delivery within bone marrow may contribute to declining bone mechanoresponse. To answer this question, we developed a 3D bone marrow analog that controls trabecular geometry, marrow mechanics and external stimuli. Validated finite element (FE) models were developed to quantify strain environment within hydrogels during LIV. Bone marrow analogs with gyroid-based trabeculae of bone volume fractions (BV/TV) corresponding to adult (25%) and aged (13%) mice were printed using polylactic acid (PLA). MSCs encapsulated in migration-permissive hydrogels within printed trabeculae showed robust cell populations on both PLA surface and hydrogel within a week. Following 14 days of LIV treatment (1g, 100 Hz, 1 hour/day), type-I collagen and F-actin were quantified for the cells in the hydrogel fraction. While LIV increased all measured outcomes, FE models predicted higher von Mises strains for the 13% BV/TV groups (0.2%) when compared to the 25% BV/TV group (0.1%). Despite increased strains, collagen-I and F-actin measures remained lower in the 13% BV/TV groups when compared to 25% BV/TV counterparts, indicating that cell response to LIV does not depend on hydrogel strains and that bone volume fraction (i.e. available bone surface) directly affects cell behavior in the hydrogel phase independent of the external stimuli. Overall, bone marrow analogs offer a robust and repeatable platform to study bone mechanobiology.

Determinants of bone parameters in young paediatric cancer survivors: the iBoneFIT project

BACKGROUND

Bone health is remarkably affected by endocrine side effects due to paediatric cancer treatments and the disease itself. We aimed to provide novel insights into the contribution of independent predictors of bone health in young paediatric cancer survivors.

METHODS

This cross-sectional multicentre study was carried out within the iBoneFIT framework in which 116 young paediatric cancer survivors (12.1 ± 3.3 years old; 43% female) were recruited. The independent predictors were sex, years from peak height velocity (PHV), time from treatment completion, radiotherapy exposure, region-specific lean and fat mass, musculoskeletal fitness, moderate-vigorous physical activity and past bone-specific physical activity.

RESULTS

Region-specific lean mass was the strongest significant predictor of most areal bone mineral density (aBMD), all hip geometry parameters and Trabecular Bone Score (β = 0.400-0.775, p ≤ 0.05). Years from PHV was positively associated with total body less head, legs and arms aBMD, and time from treatment completion was also positively associated with total hip and femoral neck aBMD parameters and narrow neck cross-sectional area (β = 0.327-0.398, p ≤ 0.05; β = 0.135-0.221, p ≤ 0.05), respectively.

CONCLUSION

Region-specific lean mass was consistently the most important positive determinant of all bone parameters, except for total hip aBMD, all Hip Structural Analysis parameters and Trabecular Bone Score.

IMPACT

The findings of this study indicate that region-specific lean mass is consistently the most important positive determinant of bone health in young paediatric cancer survivors. Randomised clinical trials focused on improving bone parameters of this population should target at region-specific lean mass due to the site-specific adaptations of the skeleton to external loading following paediatric cancer treatment. After paediatric cancer diagnosis, years from peak height velocity (somatic maturity) is critical for bone development.

[Differentiation of stem cells regulated by biophysical cues]

Stem cells have been regarded with promising application potential in tissue engineering and regenerative medicine due to their self-renewal and multidirectional differentiation abilities. However, their fate is relied on their local microenvironment, or niche. Recent studied have demonstrated that biophysical factors, defined as physical microenvironment in which stem cells located play a vital role in regulating stem cell committed differentiation. In vitro, synthetic physical microenvironments can be used to precisely control a variety of biophysical properties. On this basis, the effect of biophysical properties such as matrix stiffness, matrix topography and mechanical force on the committed differentiation of stem cells was further investigated. This paper summarizes the approach of mechanical models of artificial physical microenvironment and reviews the effects of different biophysical characteristics on stem cell differentiation, in order to provide reference for future research and development in related fields.

Robotic Intracellular Pressure Measurement Using Micropipette Electrode

Intracellular pressure, a key physical parameter of the intracellular environment, has been found to regulate multiple cell physiological activities and impact cell micromanipulation results. The intracellular pressure may reveal the mechanism of these cells' physiological activities or improve the micro-manipulation accuracy for cells. The involvement of specialized and expensive devices and the significant damage to cell viability that the current intracellular pressure measurement methods cause significantly limit their wide applications. This paper proposes a robotic intracellular pressure measurement method using a traditional micropipette electrode system setup. First, the measured resistance of the micropipette inside the culture medium is modeled to analyze its variation trend when the pressure inside the micropipette increases. Then, the concentration of KCl solution filled inside the micropipette electrode that is suitable for intracellular pressure measurement is determined according to the tested electrode resistance-pressure relationship; 1 mol/L KCl solution is our final choice. Further, the measurement resistance of the micropipette electrode inside the cell is modeled to measure the intracellular pressure through the difference in key pressure before and after the release of the intracellular pressure. Based on the above work, a robotic measurement procedure of the intracellular pressure is established based on a traditional micropipette electrode system. The experimental results on porcine oocytes demonstrate that the proposed method can operate on cells at an average speed of 20~40 cells/day with measurement efficiency comparable to the related work. The average repeated error of the relationship between the measured electrode resistance and the pressure inside the micropipette electrode is less than 5%, and no observable intracellular pressure leakage was found during the measurement process, both guaranteeing the measurement accuracy of intracellular pressure. The measured results of the porcine oocytes are in accordance with those reported in related work. Moreover, a 90% survival rate of operated oocytes was obtained after measurement, proving limited damage to cell viability. Our method does not rely on expensive instruments and is conducive to promotion in daily laboratories.

Effect of exercise on bone health in children and adolescents with cancer during and after oncological treatment: A systematic review and meta-analysis

Background: Although regular physical activity and exercise programs might improve bone health caused by oncological treatment and the disease itself, it remains unknown the pooled effect of exercise interventions following frequency, intensity, time and type prescriptions.

Objective: This systematic review and meta-analysis aimed to synthesise evidence regarding the effectiveness of exercise interventions on bone health in children and adolescents with cancer during and after oncological treatment.

Methods: A systematic search was conducted in the MEDLINE (via PubMed), Web of Science and Scopus databases from November 2021 to January 2022. Randomised controlled trials (RCTs) and non-RCTs reporting pre-post changes of the effectiveness of exercise interventions on DXA-measured bone parameters in young population (1–19 years) during or after oncological treatment were included. Pooled (ESs) and 95% confidence intervals (95%CIs) were calculated. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed.

Results: A total of eight trials with 341 participants were included. The meta-analyses did not reveal a statistically significant increase in whole body areal bone mineral density (ES = 0.10; 95%CI: −0.14, 0.34), lumbar spine (ES = 0.03; 95%CI: −0.21, 0.26) or femoral neck (ES = 0.10; 95%CI: −0.37, 0.56). Similarly, during the oncological treatment phase the ES was 0.04 (95%CI: −0.17, 0.25) and after the ES was 0.07 (95%CI: −0.20, 0.33).

Conclusion: To date, exercise interventions have been inappropriate and therefore, ineffective to illustrate any beneficial effect on bone health in children and adolescents with cancer during and after oncological treatment.

Systematic Review Registration: PROSPERO registration number: CRD42022310876

Low-Magnitude Mechanical Signals Combined with Zoledronic Acid Reduce Musculoskeletal Weakness and Adiposity in Estrogen-Deprived Mice

Combination treatment of Low-Intensity Vibration (LIV) with zoledronic acid (ZA) was hypothesized to preserve bone mass and muscle strength while reducing adipose tissue accrual associated with complete estrogen (E ₂ )-deprivation in young and skeletally mature mice. Complete E ₂ -deprivation (surgical-ovariectomy (OVX) and daily injection of aromatase inhibitor (AI) letrozole) were performed on 8-week-old C57BL/6 female mice for 4 weeks following commencement of LIV administration or control (no LIV), for 28 weeks. Additionally, 16-week-old C57BL/6 female E ₂ -deprived mice were administered ±LIV twice daily and supplemented with ±ZA (2.5 ng/kg/week). By week 28, lean tissue mass quantified by dual-energy X-ray absorptiometry was increased in younger OVX/AI+LIV(y) mice, with increased myofiber cross-sectional area of quadratus femorii. Grip strength was greater in OVX/AI+LIV(y) mice than OVX/AI(y) mice. Fat mass remained lower in OVX/AI+LIV(y) mice throughout the experiment compared with OVX/AI(y) mice. OVX/AI+LIV(y) mice exhibited increased glucose tolerance and reduced leptin and free fatty acids than OVX/AI(y) mice. Trabecular bone volume fraction and connectivity density increased in the vertebrae of OVX/AI+LIV(y) mice compared to OVX/AI(y) mice; however, this effect was attenuated in the older cohort of E ₂ -deprived mice, specifically in OVX/AI+ZA mice, requiring combined LIV with ZA to increase trabecular bone volume and strength. Similar improvements in cortical bone thickness and cross-sectional area of the femoral mid-diaphysis were observed in OVX/AI+LIV+ZA mice, resulting in greater fracture resistance. Our findings demonstrate that the combination of mechanical signals in the form of LIV and anti-resorptive therapy via ZA improve vertebral trabecular bone and femoral cortical bone, increase lean mass, and reduce adiposity in mice undergoing complete E ₂ -deprivation. One Sentence Summary: Low-magnitude mechanical signals with zoledronic acid suppressed bone and muscle loss and adiposity in mice undergoing complete estrogen deprivation.

TRANSLATIONAL RELEVANCE

Postmenopausal patients with estrogen receptor-positive breast cancer treated with aromatase inhibitors to reduce tumor progression experience deleterious effects to bone and muscle subsequently develop muscle weakness, bone fragility, and adipose tissue accrual. Bisphosphonates (i.e., zoledronic acid) prescribed to inhibit osteoclast-mediated bone resorption are effective in preventing bone loss but may not address the non-skeletal effects of muscle weakness and fat accumulation that contribute to patient morbidity. Mechanical signals, typically delivered to the musculoskeletal system during exercise/physical activity, are integral for maintaining bone and muscle health; however, patients undergoing treatments for breast cancer often experience decreased physical activity which further accelerates musculoskeletal degeneration. Low-magnitude mechanical signals, in the form of low-intensity vibrations, generate dynamic loading forces similar to those derived from skeletal muscle contractility. As an adjuvant to existing treatment strategies, low-intensity vibrations may preserve or rescue diminished bone and muscle degraded by breast cancer treatment.

Effect of a physical activity intervention on lower body bone health in childhood cancer survivors: A randomized controlled trial (SURfit)

It remains controversial whether physical activity promotes bone health in childhood cancer survivors (CCS). We aimed to assess the effect of a one-year general exercise intervention on lower body bone parameters of CCS. CCS ≥16 years at enrollment, <16 years at diagnosis and ≥5 years in remission were identified from the national Childhood Cancer Registry. Participants randomized to the intervention group were asked to perform an additional ≥2.5 hours of intense physical activity/week, controls continued exercise as usual. Bone health was assessed as a secondary trial endpoint at baseline and after 12-months. We measured tibia bone mineral density (BMD) and morphology by peripheral quantitative computed tomography and lumbar spine, hip and femoral neck BMD by dual-energy x-ray absorptiometry. We performed intention-to-treat, per protocol, and an explorative subgroup analyses looking at low BMD using multiple linear regressions. One hundred fifty-one survivors (44% females, 7.5 ± 4.9 years at diagnosis, 30.4 ± 8.6 years at baseline) were included. Intention-to-treat analysis revealed no differences in changes between the intervention and control group. Per protocol analyses showed evidence for an improvement in femoral neck and trabecular BMD between 1.5% and 1.8% more in participants being compliant with the exercise program. Trabecular BMD increased 2.8% more in survivors of the intervention group with BMD z-score ≤-1 compared to those starting at z-score >-1. A nonstandardized personalized exercise programs might not be specific enough to promote bone health in CCS, although those compliant and those most in need may benefit. Future trials should include bone stimulating exercise programs targeting risk groups with reduced bone health and motivational features to maximize compliance.

Spectral characterization of cell surface motion for mechanistic investigations of cellular mechanobiology

Understanding the specific mechanisms responsible for anabolic and catabolic responses to static or dynamic force are largely poorly understood. Because of this, most research groups studying mechanotransduction due to dynamic forces employ an empirical approach in deciding what frequencies to apply during experiments. While this has been shown to elucidate valuable information regarding how cells respond under controlled provocation, it is often difficult or impossible to determine a true optimal frequency for force application, as many intracellular complexes are involved in receiving, propagating, and responding to a given stimulus. Here we present a novel adaptation of an analytical technique from the fields of civil and mechanical engineering that may open the door to direct measurement of mechanobiological cellular frequencies which could be used to target specific cell signaling pathways leveraging synergy between outside-in and inside-out mechanotransduction approaches. This information could be useful in identifying how specific proteins are involved in the homeostatic balance, or disruption thereof, of cells and tissue, furthering the understanding of the pathogenesis and progression of many diseases across a wide variety of cell types, which may one day lead to the development of novel mechanobiological therapies for clinical use.

The bone-muscle connection in breast cancer: implications and therapeutic strategies to preserve musculoskeletal health

Breast cancer and its therapies frequently result in significant musculoskeletal morbidity. Skeletal complications include bone metastases, pain, bone loss, osteoporosis, and fracture. In addition, muscle loss or weakness occurring in both the metastatic and curative setting is becoming increasingly recognized as systemic complications of disease and treatment, impacting quality of life, responsiveness to therapy, and survival. While the anatomical relationship between bone and muscle is well established, emerging research has led to new insights into the biochemical and molecular crosstalk between the skeletal and muscular systems. Here, we review the importance of both skeletal and muscular health in breast cancer, the significance of crosstalk between bone and muscle, and the influence of mechanical signals on this relationship. Therapeutic exploitation of signaling between bone and muscle has great potential to prevent the full spectrum of musculoskeletal complications across the continuum of breast cancer.

Effects of Whole-Body Vibration on Breast Cancer Bone Metastasis and Vascularization in Mice

We evaluated whether whole-body vibration (WBV) prevented bone loss induced by breast cancer (BC) metastasis and the involvement of bone marrow vasculature. One day after orthotopic transplantation of mammary 4T1 tumor cells, 8-week-old BALB/c mice were subjected to 0.3 g/90 Hz vertical vibration for 20 min/day for 5 days/week (BC-WBV) or sham-handled (BC-Sham) over 3 weeks. Age-matched intact mice (Intact) were also sham-handled. Both tibiae were harvested from BC-WBV (n = 7), BC-Sham (n = 9), and Intact (n = 5) mice for bone structure imaging by synchrotron radiation-based computed tomography (SRCT) and hematoxylin and eosin staining, whereas right tibiae were harvested from other BC-WBV and BC-Sham (n = 6 each) mice for vascular imaging by SRCT. Tumor cells were similarly widespread in the marrow in BC-WBV and BC-Sham mice. In BC-Sham mice, cortical bone volume, trabecular volume fraction, trabecular thickness, trabecular number density, and bone mineral density were smaller, and marrow volume and trabecular separation were larger than in Intact mice. However, although trabecular thickness was smaller in BC-WBV than Intact mice, the others did not differ between the two groups. Serum osteocalcin tended to be higher in BC-WBV than BC-Sham mice. Compared with BC-Sham mice, BC-WBV mice had a smaller vessel diameter, a trend of a larger vessel number density, and smaller vessel diameter heterogeneity. In conclusion, WBV mitigates bone loss in BC bone metastasis, which may be partly due to increased bone anabolism. The alteration of marrow vasculature appears to be favorable for anti-tumor drug delivery. Further studies are needed to clarify the multiple actions of WBV on bone, tumor, and marrow vasculature and how they contribute to bone protection in BC metastasis.

Whole-body vibration training for inpatient children and adolescents receiving chemotherapy for first cancer diagnosis: an exploratory feasibility study

Whole-body vibration (WBV) is a feasible and potentially beneficial exercise strategy for managing neuromuscular impairments like decreased strength or flexibility, mobility limitations and bone health in pediatric cancer survivors. However, as starting rehabilitation as early as possible is recommended to preserve physical function, this study investigated the feasibility of WBV for patients receiving cancer treatment for first cancer diagnosis. Eleven patients (various types of cancer, ages 7–17) participated in the supervised WBV intervention concomitant to acute cancer treatment, which involved chemotherapy. Training was implemented as part of a general exercise program and offered 3 days per week during hospitalization (warm-up, four progressive training exercises comprising 60–120 s, 21–27 Hz, 2 mm peak-to-peak-displacement). Feasibility, which was defined as the absence of WBV-related serious adverse events leading to study dropout, was primarily evaluated. Training documentation was additionally analyzed. As a main result, no serious adverse events leading to study dropout were reported. However, two incidents of bleeding (adverse events) were observed in patients with bleeding tendencies and low platelets (thrombocytes < 30,000/μL). After adjusting the platelet count threshold for WBV participation to 30,000/μL, no further incidents occurred. Moreover, due to WBV-related side effects like physical exhaustion, 11% of all training sessions had to be stopped and another 11% required reductions in the vibration load. Patients participated in 48% of the planned sessions. While main reasons for non-attendance were medical issues (35%), only few WBV sessions were missed, not completed or needed modifications due to motivational issues. Consequently, WBV seems to be feasible for inpatient pediatric patients receiving chemotherapy for first cancer diagnosis, given a sufficiently high platelet count of at least 30,000/μL. Although WBV tolerance and training motivation appear high, patient’s reduced medical condition during hospitalization can negatively impact training progression and attendance. Future research is required to confirm our findings on feasibility and to assess efficiency of WBV training for pediatric cancer patients receiving cancer treatment.

Bone health in glucocorticoid-treated childhood acute lymphoblastic leukemia

Glucocorticoids (GCs) are widely used in the treatment of childhood acute lymphoblastic leukemia (ALL), but their long-term use is also associated with bone-related morbidities. Among others, growth deficit, decreased bone mineral density (BMD) and increased fracture rate are well-documented and severely impact quality of life. Unfortunately, no efficient treatment for the management of bone health impairment in patients and survivors is currently available. The overall goal of this review is to discuss the existing data on how GCs impair bone health in pediatric ALL and attempts made to minimize these side effects.

At the nuclear envelope of bone mechanobiology

The nuclear envelope and nucleoskeleton are emerging as signaling centers that regulate how physical information from the extracellular matrix is biochemically transduced into the nucleus, affecting chromatin and controlling cell function. Bone is a mechanically driven tissue that relies on physical information to maintain its physiological function and structure. Disorder that present with musculoskeletal and cardiac symptoms, such as Emery-Dreifuss muscular dystrophies and progeria, correlate with mutations in nuclear envelope proteins including Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, Lamin A/C, and emerin. However, the role of nuclear envelope mechanobiology on bone function remains underexplored. The mesenchymal stem cell (MSC) model is perhaps the most studied relationship between bone regulation and nuclear envelope function. MSCs maintain the musculoskeletal system by differentiating into multiple cell types including osteocytes and adipocytes, thus supporting the bone's ability to respond to mechanical challenge. In this review, we will focus on how MSC function is regulated by mechanical challenges both in vitro and in vivo within the context of bone function specifically focusing on integrin, β-catenin and YAP/TAZ signaling. The importance of the nuclear envelope will be explored within the context of musculoskeletal diseases related to nuclear envelope protein mutations and nuclear envelope regulation of signaling pathways relevant to bone mechanobiology in vitro and in vivo.

Bone mineral density surveillance for childhood, adolescent, and young adult cancer survivors: evidence-based recommendations from the International Late Effects of Childhood Cancer Guideline Harmonization Group

Childhood, adolescent, and young adult cancer survivors are at increased risk of reduced bone mineral density. Clinical practice surveillance guidelines are important for timely diagnosis and treatment of these survivors, which could improve bone mineral density parameters and prevent fragility fractures. Discordances across current late effects guidelines necessitated international harmonisation of recommendations for bone mineral density surveillance. The International Late Effects of Childhood Cancer Guideline Harmonization Group therefore established a panel of 36 experts from ten countries, representing a range of relevant medical specialties. The evidence of risk factors for very low and low bone mineral density and fractures, surveillance modality, timing of bone mineral density surveillance, and treatment of very low and low bone mineral density were evaluated and critically appraised, and harmonised recommendations for childhood, adolescent, and young adult cancer survivors were formulated. We graded the recommendations based on the quality of evidence and balance between potential benefits and harms. Bone mineral density surveillance is recommended for survivors treated with cranial or craniospinal radiotherapy and is reasonable for survivors treated with total body irradiation. Due to insufficient evidence, no recommendation can be formulated for or against bone mineral density surveillance for survivors treated with corticosteroids. This surveillance decision should be made by the survivor and health-care provider together, after careful consideration of the potential harms and benefits and additional risk factors. We recommend to carry out bone mineral density surveillance using dual-energy x-ray absorptiometry at entry into long-term follow-up, and if normal (Z-score > -1), repeat when the survivor is aged 25 years. Between these measurements and thereafter, surveillance should be done as clinically indicated. These recommendations facilitate evidence-based care for childhood, adolescent, and young adult cancer survivors internationally.

Suppression of cancer-associated bone loss through dynamic mechanical loading

Patients afflicted with or being treated for cancer constitute a distinct and alarming subpopulation who exhibit elevated fracture risk and heightened susceptibility to developing secondary osteoporosis. Cancer cells uncouple the regulatory processes central for the adequate regulation of musculoskeletal tissue. Systemically taxing treatments to target tumors or disrupt the molecular elements driving tumor growth place considerable strain on recovery efforts. Skeletal tissue is inherently sensitive to mechanical forces, therefore attention to exercise and mechanical loading as non-pharmacological means to preserve bone during treatment and in post-treatment rehabilitative efforts have been topics of recent focus. This review discusses the dysregulation that cancers and the ensuing metabolic dysfunction that confer adverse effects on musculoskeletal tissues. Additionally, we describe foundational mechanotransduction pathways and the mechanisms by which they influence both musculoskeletal and cancerous cells. Functional and biological implications of mechanical loading at the tissue and cellular levels will be discussed, highlighting the current understanding in the field. Herein, in vitro, translational, and clinical data are summarized to consider the positive impact of exercise and low magnitude mechanical loading on tumor-bearing skeletal tissue.

Recent perspectives on the association between osteonecrosis and bone mineral density decline in childhood acute lymphoblastic leukemia

The attention to treatment-related toxicity has increased since the survival of children with acute lymphoblastic leukemia (ALL) has improved significantly over the past few decades. Intensive ALL treatment schedules including corticosteroids and asparaginase have been shown to give rise to skeletal abnormalities such as osteonecrosis and low bone mineral density (BMD), which may lead to debilitating sequelae in survivors. Although osteonecrosis and low BMD are different entities with suggested separate pathophysiological mechanisms, recent studies indicate that osteonecrosis is associated with accelerated BMD decline. Common underlying mechanisms for osteonecrosis and BMD decline are considered, such as an enhanced sensitivity to corticosteroids in children who suffer from both osteonecrosis and low BMD. In addition, restriction of weight-bearing activities, which is generally advised in patients with osteonecrosis, could aggravate BMD decline. This induces a clinical dilemma, since bone stimulation is important to maintain BMD but alternative interventions for osteonecrosis are limited. Furthermore, this recent finding of accelerated BMD decline in children with osteonecrosis emphasizes the need to develop effective preventive measures for osteonecrosis, which may include targeting BMD decline.

Feasibility of a combined supervised and home-based whole-body vibration intervention in children after inpatient oncological treatment

Purpose

Reduced physical performance due to therapy-related dysfunctions in children diagnosed with cancer contributes to insufficient physical activity levels. It is therefore essential that relevant functions are restored. Whole-body vibration (WBV) training, a neuromuscular stimulating exercise intervention, could have the potential to target those functions adequately. Therefore, the aim of this study was to evaluate the feasibility of a combined supervised and home-based WBV intervention with children after inpatient oncological treatment.

Methods

Eight children aged 6–21 years were included after cessation of their inpatient oncological treatment. They performed a 12-week WBV training including one supervised and two home-based sessions per week according to a standardized training protocol. Feasibility, adherence and compliance to the vibration protocol were documented. Subjective benefits and satisfaction were assessed using a questionnaire.

Results

Study participants attended 84.03 ± 13.09% of WBV sessions. No serious adverse events occurred. Some patients reported side effects partially resulting in modifications of the vibration protocol by therapists. Almost all children regarded the intervention as beneficial.

Conclusion

A combined supervised and home-based WBV intervention with children after inpatient oncological treatment is feasible and safe. The beneficial potential regarding relevant sensory and motor dysfunctions is now to be investigated.

Trial registration number and date of registration

DRKS00014713 15.05.2018

Effect of Low-Intensity Vibration on Bone Strength, Microstructure, and Adiposity in Pre-Osteoporotic Postmenopausal Women: A Randomized Placebo-Controlled Trial

There has been evidence that cyclical mechanical stimulation may be osteogenic, thus providing opportunities for nonpharmacological treatment of degenerative bone disease. Here, we applied this technology to a cohort of postmenopausal women with varying bone mineral density (BMD) T-scores at the total hip (-0.524 ± 0.843) and spine (-0.795 ± 1.03) to examine the response to intervention after 1 year of daily treatment with 10 minutes of vibration therapy in a randomized double-blinded trial. The device operates either in an active mode (30 Hz and 0.3 g) or placebo. Primary endpoints were changes in bone stiffness at the distal tibia and marrow adiposity of the vertebrae, based on 3 Tesla high-resolution MRI and spectroscopic imaging, respectively. Secondary outcome variables included distal tibial trabecular microstructural parameters and vertebral deformity determined by MRI, volumetric and areal bone densities derived using peripheral quantitative computed tomography (pQCT) of the tibia, and dual-energy X-ray absorptiometry (DXA)-based BMD of the hip and spine. Device adherence was 83% in the active group (n = 42) and 86% in the placebo group (n = 38) and did not differ between groups (p = .7). The mean 12-month changes in tibial stiffness in the treatment group and placebo group were +1.31 ± 6.05% and -2.55 ± 3.90%, respectively (group difference 3.86%, p = .0096). In the active group, marrow fat fraction significantly decreased after 12 months of intervention (p = .0003), whereas no significant change was observed in the placebo group (p = .7; group difference -1.59%, p = .029). Mean differences of the changes in trabecular bone volume fraction (p = .048) and erosion index (p = .044) were also significant, as was pQCT-derived trabecular volumetric BMD (vBMD; p = .016) at the tibia. The data are commensurate with the hypothesis that vibration therapy is protective against loss in mechanical strength and, further, that the intervention minimizes the shift from the osteoblastic to the adipocytic lineage of mesenchymal stem cells. © 2020 American Society for Bone and Mineral Research (ASBMR).

A long-term trajectory of bone mineral density in childhood cancer survivors after discontinuation of treatment: retrospective cohort study

Low bone mineral density (BMD) was diagnosed in 24% of childhood cancer survivors (CCS), whereas very low BMD was relatively uncommon at 8%. We suggest that low BMD in CCS may become alleviated over time. Stem cell transplantation, radiotherapy, and underweight were the strongest independent predictors of decreased BMD.

PURPOSE

Childhood cancer survivors (CCS) are at risk of premature bone loss, although published studies are inconsistent. The objective of this study was to evaluate the prevalence and pattern of low bone mineral density (BMD) in short- and long-term CCS, and to determine clinical factors affecting skeleton after anticancer treatment.

METHODS

This retrospective study was conducted in a cohort of 326 children and young adult CCS (147 females) who completed anticancer treatment. BMD was determined by dual-energy X-ray absorptiometry (DXA). Low BMD was defined as a Z-score ≤ - 1.0, and the very low BMD as a Z-score ≤ - 2.0. Additionally, the changes in BMD over time were studied in 123 CCS who had been re-examined by DXA during follow-up.

RESULTS

Median age at diagnosis was 7.27 years (range, 4.4-10.6); median time between end of treatment and DXA was 6.12 (range, 4.0-22.0). Low BMD was found in 24% of CCS, while very low BMD was relatively uncommon (8%). Based on multivariate analysis, the following were significantly associated with low BMD at the follow-up: hematopoietic stem cell transplantation (OR 3.13, 95% CI 1.02-9.63), head and neck radiotherapy (OR 2.54, 95% CI 1.32-4.90), and body weight below the standard reference (OR 3.57, 95% CI 1.24-10.23). The time-related trajectory showed an improvement (BMD_LS) or stabilization (BMD_TB) in Z-scores values.

CONCLUSION

These data based on serial DXA measurements, encompassing a long-lasting observation period, show that CCS may not be at risk of premature bone loss in young adulthood. However, it is unknown how the scenario for skeletal mass is until the CCS will achieve older or postmenopausal age.

Analysis of mechanotransduction dynamics during combined mechanical stimulation and modulation of the extracellular-regulated kinase cascade uncovers hidden information within the signalling noise

Osteoporosis is a bone disease characterized by brittle bone and increased fracture incidence. With ageing societies worldwide, the disease presents a high burden on health systems. Furthermore, there are limited treatments for osteoporosis with just two anabolic pharmacological agents approved by the US Food and Drug Administration. Healthy bones are believed to be maintained via an intricate relationship between dual biochemical and mechanical (bio-mechanical) stimulations. It is widely considered that osteoporosis emerges as a result of disturbances to said relationship. The mechanotransduction process is key to this balance, and disruption of its dynamics in bone cells plays a role in osteoporosis development. Nonetheless, the exact details and mechanisms that drive and secure the health of bones are still elusive at the cellular and molecular scales. This study examined the dual modulation of mechanical stimulation and mechanotransduction activation dynamics in an osteoblast (OB). The aim was to find patterns of mechanotransduction dynamics demonstrating a significant change that can be mapped to alterations in the OB responses, specifically at the level of gene expression and osteogenic markers such as alkaline phosphatase. This was achieved using a three-dimensional hybrid multiscale computational model simulating mechanotransduction in the OB and its interaction with the extracellular matrix, combined with a numerical analytical technique. The model and the analysis method predict that within the noise of mechanotransduction, owing to modulation of the bio-mechanical stimulus and consequent gene expression, there are unique events that provide signatures for a shift in the system's dynamics. Furthermore, the study uncovered molecular interactions that can be potential drug targets.

Relationships of Bone Mineral Density to Whole Body Mass, Fat Mass and Fat-free Mass in Long-term Survivors of Acute Lymphoblastic Leukemia in Childhood

Body size influences bone mineral density (BMD) in health. Relationships of BMD with body mass index, fat mass (FM), fat-free mass, and appendicular lean mass were explored in acute lymphoblastic leukemia (ALL) survivors (n=75; 41 males; 45 standard risk ALL) >10 years from diagnosis. Dual energy radiograph absorptiometry performed body composition analysis. Relationships were assessed by regression analyses and Pearson correlation coefficients (r). Twenty subjects (26.3%) were osteopenic; lumbar spine (LS) BMD Z score <-1.00. Age at diagnosis, sex, ALL risk-category, type of post-induction steroid or cranial radiation did not correlate with LS or whole body (WB) BMD. Body mass index correlated significantly with LS BMD (r=0.333, P=0.004) and WB BMD (r=0.271, P=0.033). FM index (FM/height²) Z score showed no significant correlation with LS or WB BMD. Fat-free mass index Z score correlated strongly with LS BMD (r=0.386, P=0.013) and WB BMD (r=0.605, P<0.001) in males but not in females. The appendicular lean mass index, a surrogate for skeletal muscle mass, correlated significantly with LS BMD (r=0.367, P=0.018) and WB BMD (r=0.604, P<0.001) in males but not in females. Future studies to evaluate interventions to enhance BMD focused on improving body composition particularly skeletal muscle mass are warranted.

Exercise and Diet: Uncovering Prospective Mediators of Skeletal Fragility in Bone and Marrow Adipose Tissue

PURPOSE OF REVIEW

To highlight recent basic, translational, and clinical works demonstrating exercise and diet regulation of marrow adipose tissue (MAT) and bone and how this informs current understanding of the relationship between marrow adiposity and musculoskeletal health.

RECENT FINDINGS

Marrow adipocytes accumulate in the bone in the setting of not only hypercaloric intake (calorie excess; e.g., diet-induced obesity) but also with hypocaloric intake (calorie restriction; e.g., anorexia), despite the fact that these states affect bone differently. With hypercaloric intake, bone quantity is largely unaffected, whereas with hypocaloric intake, bone quantity and quality are greatly diminished. Voluntary running exercise in rodents was found to lower MAT and promote bone in eucaloric and hypercaloric states, while degrading bone in hypocaloric states, suggesting differential modulation of MAT and bone, dependent upon whole-body energy status. Energy status alters bone metabolism and bioenergetics via substrate availability or excess, which plays a key role in the response of bone and MAT to mechanical stimuli. Marrow adipose tissue (MAT) is a fat depot with a potential role in-as well as responsivity to-whole-body energy metabolism. Understanding the localized function of this depot in bone cell bioenergetics and substrate storage, principally in the exercised state, will aid to uncover putative therapeutic targets for skeletal fragility.

Childhood Cancer Survivorship: Daily Challenges

Survivors of childhood cancer are at risk of experiencing fatigue, pain, lower levels of physical activity, increased engagement in risky health behavior, and poor social adjustment, after finishing treatment. Risks are more pronounced for survivors of specific diagnoses or receiving specific treatment protocols. Interventions to address these outcomes are in their infancy. Future research should focus on exploring the antecedents and consequences of these outcomes. In the meantime, researchers and cancer centers should attempt to provide high-quality and accessible health information to survivors through various media outlets to encourage healthy behaviors.

Mechanical suppression of breast cancer cell invasion and paracrine signaling to osteoclasts requires nucleo-cytoskeletal connectivity

Exercise benefits the musculoskeletal system and reduces the effects of cancer. The effects of exercise are multifactorial, where metabolic changes and tissue adaptation influence outcomes. Mechanical signals, a principal component of exercise, are anabolic to the musculoskeletal system and restrict cancer progression. We examined the mechanisms through which cancer cells sense and respond to low-magnitude mechanical signals introduced in the form of vibration. Low-magnitude, high-frequency vibration was applied to human breast cancer cells in the form of low-intensity vibration (LIV). LIV decreased matrix invasion and impaired secretion of osteolytic factors PTHLH, IL-11, and RANKL. Furthermore, paracrine signals from mechanically stimulated cancer cells, reduced osteoclast differentiation and resorptive capacity. Disconnecting the nucleus by knockdown of SUN1 and SUN2 impaired LIV-mediated suppression of invasion and osteolytic factor secretion. LIV increased cell stiffness; an effect dependent on the LINC complex. These data show that mechanical vibration reduces the metastatic potential of human breast cancer cells, where the nucleus serves as a mechanosensory apparatus to alter cell structure and intercellular signaling.

The effect of an online exercise programme on bone health in paediatric cancer survivors (iBoneFIT): study protocol of a multi-centre randomized controlled trial

BACKGROUND

New approaches on paediatric cancer treatment aim to maintain long-term health. As a result of radiotherapy, chemotherapy or surgery, paediatric cancer survivors tend to suffer from any chronic health condition. Endocrine dysfunction represents one of the most common issues and affects bone health. Exercise is key for bone mass accrual during growth, specifically plyometric jump training. The iBoneFIT study will investigate the effect of a 9-month online exercise programme on bone health in paediatric cancer survivors. This study will also examine the effect of the intervention on body composition, physical fitness, physical activity, calcium intake, vitamin D, blood samples quality of life and mental health.

METHODS

A minimum of 116 participants aged 6 to 18 years will be randomized into an intervention (n = 58) or control group (n = 58). The intervention group will receive an online exercise programme and diet counselling on calcium and vitamin D. In addition, five behaviour change techniques and a gamification design will be implemented in order to increase the interest of this non-game programme. The control group will only receive diet counselling. Participants will be assessed on 3 occasions: 1) at baseline; 2) after the 9 months of the intervention; 3) 4 months following the intervention. The primary outcome will be determined by dual energy X-ray absorptiometry (DXA) and the hip structural analysis, trabecular bone score and 3D-DXA softwares. Secondary outcomes will include anthropometry, body composition, physical fitness, physical activity, calcium and vitamin D intake, blood samples, quality of life and mental health.

DISCUSSION

Whether a simple, feasible and short in duration exercise programme can improve bone health has not been examined in paediatric cancer survivors. This article describes the design, rationale and methods of a study intended to test the effect of a rigorous online exercise programme on bone health in paediatric cancer survivors. If successful, the iBoneFIT study will contribute to decrease chronic health conditions in this population and will have a positive impact in the society.

TRIAL REGISTRATION

Prospectively registered in isrctn.com: isrctn61195625 . Registered 2 April 2020.

High impact physical activity and bone health of lower extremities in childhood cancer survivors: A cross-sectional study of SURfit

Childhood cancer survivors (CCS) are at risk of reduced bone health and premature osteoporosis. As physical activity with high impact loading (IL-PA) is known to promote bone health, we compared bone densitometry and microstructure between groups of CCS who performed different amounts of physical activities in their daily life. We used baseline data of a single-center PA trial including 161 CCS from the Swiss Childhood Cancer Registry, aged <16 at diagnosis, ≥16 at study and ≥5 years since diagnosis. Lower body bone health was assessed with peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA). Daily IL-PA (duration in activities >2 g acceleration and numbers of vertical impacts/hr >2 g) was captured using hip-worn accelerometers (1-3 weeks). For both IL-PA approaches, we formed low, middle and high activity groups based on tertiles. Bone health of the high and middle active groups was compared to the low active group. 63% of CCS had indication of at least one bone mineral density z-score ≤ -1 measured by pQCT or DXA. The high IL-PA group performing 2.8 min/day or 19.1 impact peaks/hr > 2 g (median) showed about 3-13% better microstructural and densitometric bone health as compared to the low IL-PA group with 0.38 min/day or 0.85 peaks/hr > 2 g. Just a few minutes and repetitions of high IL-PA as easily modifiable lifestyle factor may be sufficient to improve bone health in adult CCS. Future longitudinal research is needed to better understand pattern and dosage of minimal impact loading needed to strengthen bone in growing and adult CCS.

Revealing hidden information in osteoblast's mechanotransduction through analysis of time patterns of critical events

BACKGROUND

Mechanotransduction in bone cells plays a pivotal role in osteoblast differentiation and bone remodelling. Mechanotransduction provides the link between modulation of the extracellular matrix by mechanical load and intracellular activity. By controlling the balance between the intracellular and extracellular domains, mechanotransduction determines the optimum functionality of skeletal dynamics. Failure of this relationship was suggested to contribute to bone-related diseases such as osteoporosis.

RESULTS

A hybrid mechanical and agent-based model (Mech-ABM), simulating mechanotransduction in a single osteoblast under external mechanical perturbations, was utilised to simulate and examine modulation of the activation dynamics of molecules within mechanotransduction on the cellular response to mechanical stimulation. The number of molecules and their fluctuations have been analysed in terms of recurrences of critical events. A numerical approach has been developed to invert subordination processes and to extract the direction processes from the molecular signals in order to derive the distribution of recurring events. These predict that there are large fluctuations enclosing information hidden in the noise which is beyond the dynamic variations of molecular baselines. Moreover, studying the system under different mechanical load regimes and altered dynamics of feedback loops, illustrate that the waiting time distributions of each molecule are a signature of the system's state.

CONCLUSIONS

The behaviours of the molecular waiting times change with the changing of mechanical load regimes and altered dynamics of feedback loops, presenting the same variation of patterns for similar interacting molecules and identifying specific alterations for key molecules in mechanotransduction. This methodology could be used to provide a new tool to identify potent molecular candidates to modulate mechanotransduction, hence accelerate drug discovery towards therapeutic targets for bone mass upregulation.

Quantitative ultrasound imaging monitoring progressive disuse osteopenia and mechanical stimulation mitigation in calcaneus region through a 90-day bed rest human study

Background

Osteoporosis parallels aging and functional mechanical unloading (e.g., space flight and bed rest), jeopardizing mineral density, microstructure, and integrity of bone and leading to an increased risk of fracture. A way to combat this deterioration is to harness the sensitivity of bone to mechanical signals.

Objective

This study evaluates the longitudinal effect of a dynamic mechanical loading through the heel on human bone in vivo during 90-day bed rest, monitored by quantitative ultrasound (QUS) imaging and dual-energy X-ray absorptiometry (DXA) in localized regions of interests, i.e., calcaneus.

Methods

A total of 29 bed rest individuals were evaluated (11 control and 18 treatment) with a brief (10-minute) daily low-intensity (0.3g), high-frequency (30Hz) dynamic mechanical stimulation countermeasure through vibrational inhibition bone erosion (VIBE). Both QUS and DXA detected longitudinal bone density and quality changes.

Results

Ultrasound velocity (UV) decreased in the control group and increased in the group treated with low-intensity loading. The UV increased by 1.9% and 1.6% at 60- and 90-day bed rest (p=0.01) in VIBE over control groups. A trend was found in broadband ultrasound attenuation (BUA), with a VIBE benefit of 1.8% at day 60 and 0.5% at day 90 in comparison with control (p=0.5). Bone mineral density (BMD) assessed by DXA decreased -4.50% for control individuals and -2.18% for VIBE individuals, showing a moderate effect of the mechanical intervention (p=0.19). Significant correlations between QUS and DXA were observed, with a combined BUA and UV vs. BMD: r²=0.70.

Conclusion

These results indicated that low-intensity, high-frequency loading has the potential to mitigate regional bone loss induced by long-term bed rest and that QUS imaging may be able to assess the subtle changes in bone alteration.

Translational potential of this article

Quantitative ultrasound has shown the efficacy of noninvasively assessing bone mass and structural properties in cadaver and isolated trabecular bone samples. While its ability in measuring in vivo bone quality and density is still unclear, a scanning confocal ultrasound imaging is developed and can perform an instant assessment for the subtle changes of such bone loss. This ultrasound imaging modality can potentially be used in the clinical assessment of bone mass. Moreover, physical stimulation has shown the ability to prevent bone loss induced by functional disuse and estrogen deficiency in animal models. However, its treatment capability is unclear. This study has shown that low-magnitude mechanical signals, introduced using low-intensity vibration (LIV), can mitigate regional bone loss caused by functional disuse. Thus localized mechanical treatment, and the quantitative ultrasound imaging have shown translational potential to noninvasively attenuate bone loss, and assess bone mass in the clinic, e.g., in an extreme condition such as long-term space mission, and long-term bedrest such as in case of spinal cord injury.

Dietary and Exercise Interventions for Pediatric Oncology Patients: The Way Forward

This review focuses on diet and exercise interventions that have been conducted in pediatric cancer and pediatric stem cell transplant patients. It examines the different reasons for conducting lifestyle interventions with attention to the different outcome measurements and feasibility of these measures with an argument toward a need for standardization to move the field forward.

Combating osteoporosis and obesity with exercise: leveraging cell mechanosensitivity

Osteoporosis, a condition of skeletal decline that undermines quality of life, is treated with pharmacological interventions that are associated with poor adherence and adverse effects. Complicating efforts to improve clinical outcomes, the incidence of obesity is increasing, predisposing the population to a range of musculoskeletal complications and metabolic disorders. Pharmacological management of obesity has yet to deliver notable reductions in weight and debilitating complications are rarely avoided. By contrast, exercise shows promise as a non-invasive and non-pharmacological method of regulating both osteoporosis and obesity. The principal components of exercise - mechanical signals - promote bone and muscle anabolism while limiting formation and expansion of fat mass. Mechanical regulation of bone and marrow fat might be achieved by regulating functions of differentiated cells in the skeletal tissue while biasing lineage selection of their common progenitors - mesenchymal stem cells. An inverse relationship between adipocyte versus osteoblast fate selection from stem cells is implicated in clinical conditions such as childhood obesity and increased marrow adiposity in type 2 diabetes mellitus, as well as contributing to skeletal frailty. Understanding how exercise-induced mechanical signals can be used to improve bone quality while decreasing fat mass and metabolic dysfunction should lead to new strategies to treat chronic diseases such as osteoporosis and obesity.

Long-Term Endocrine and Metabolic Consequences of Cancer Treatment: A Systematic Review

The number of patients surviving ≥5 years after initial cancer diagnosis has significantly increased during the last decades due to considerable improvements in the treatment of many cancer entities. A negative consequence of this is that the emergence of long-term sequelae and endocrine disorders account for a high proportion of these. These late effects can occur decades after cancer treatment and affect up to 50% of childhood cancer survivors. Multiple predisposing factors for endocrine late effects have been identified, including radiation, sex, and age at the time of diagnosis. A systematic literature search has been conducted using the PubMed database to offer a detailed overview of the spectrum of late endocrine disorders following oncological treatment. Most data are based on late effects of treatment in former childhood cancer patients for whom specific guidelines and recommendations already exist, whereas current knowledge concerning late effects in adult-onset cancer survivors is much less clear. Endocrine sequelae of cancer therapy include functional alterations in hypothalamic-pituitary, thyroid, parathyroid, adrenal, and gonadal regulation as well as bone and metabolic complications. Surgery, radiotherapy, chemotherapy, and immunotherapy all contribute to these sequelae. Following irradiation, endocrine organs such as the thyroid are also at risk for subsequent malignancies. Although diagnosis and management of functional and neoplastic long-term consequences of cancer therapy are comparable to other causes of endocrine disorders, cancer survivors need individually structured follow-up care in specialized surveillance centers to improve care for this rapidly growing group of patients.

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.

Whole-body vibration in children with disabilities demonstrates therapeutic potentials for pediatric cancer populations: a systematic review

PURPOSE

Low levels of physical activity often observed in pediatric oncology might be attributed to various functional deficits, especially those of the lower limbs as these affect gait, mobility, and, consequently, physical activity. In the past few years, whole-body vibration (WBV) has emerged as a new therapy modality for improving physical functioning. Although WBV is increasingly applied in children with disabilities, its impact on lower limb function in pediatric cancer patients and survivors has not yet been investigated.

METHODS

To establish whether there is evidence that WBV may be beneficial for pediatric cancer patients and survivors, this review summarizes current data on WBV studies among children with disabilities and extracts relevant information for the pediatric cancer population. Two independent reviewers performed a systematic literature search following the PRISMA guidelines.

RESULTS

Nine studies were included in the analysis. Results demonstrate that WBV is a safe, highly compliant, and effective approach in cohorts of children with disabilities. The largest effects of WBV were observed in lower extremity muscle mass and strength, balance control, gait, and walking ability. Furthermore, we were able to develop first recommendations for WBV protocols.

CONCLUSIONS

WBV seems to be feasible and effective for improving parameters that may be relevant to the pediatric cancer population. Efforts are needed to conduct first WBV interventions in children with cancer proving the effects. The developed recommendations for WBV protocols might help to implement these intervention studies.

Whole-Body Vibration Training Designed to Improve Functional Impairments After Pediatric Inpatient Anticancer Therapy: A Pilot Study

PURPOSE

To assess a whole-body vibration (WBV) intervention for children after cancer treatment.

METHODS

Eleven children after inpatient anticancer therapy participated in a 12-week supervised WBV intervention, which consisted of one 9- to 13-minute WBV session per week, with 5 to 9 minutes' overall vibration time. Feasibility was defined as the ability to participate in WBV training without reporting adverse events. The number of offered and completed training sessions, program acceptance, and measures of function were assessed.

RESULTS

Nine participants completed the WBV intervention without any WBV-related adverse events. The adherence rate was 87.96%. Only minor side effects were reported and there was general program acceptance. We found indications that WBV has positive effects on knee extensor strength and active ankle dorsiflexion range of motion.

CONCLUSIONS

WBV was feasible, safe, and well received among children after inpatient anticancer therapy. No health deteriorations were observed. Positive effects need to be confirmed in future trials.

Physical stimulations and their osteogenesis-inducing mechanisms

Physical stimulations such as magnetic, electric and mechanical stimulation could enhance cell activity and promote bone formation in bone repair process via activating signal pathways, modulating ion channels, regulating bonerelated gene expressions, etc. In this paper, bioeffects of physical stimulations on cell activity, tissue growth and bone healing were systematically summarized, which especially focused on their osteogenesis-inducing mechanisms. Detailedly, magnetic stimulation could produce Hall effect which improved the permeability of cell membrane and promoted the migration of ions, especially accelerating the extracellular calcium ions to pass through cell membrane. Electric stimulation could induce inverse piezoelectric effect which generated electric signals, accordingly up-regulating intracellular calcium levels and growth factor synthesis. And mechanical stimulation could produce mechanical signals which were converted into corresponding biochemical signals, thus activating various signaling pathways on cell membrane and inducing a series of gene expressions. Besides, bioeffects of physical stimulations combined with bone scaffolds which fabricated using 3D printing technology on bone cells were discussed. The equipments of physical stimulation system were described. The opportunities and challenges of physical stimulations were also presented from the perspective of bone repair.

Modifying bone mineral density, physical function, and quality of life in children with acute lymphoblastic leukemia

BACKGROUND

The early effects of childhood acute lymphoblastic leukemia (ALL) include decreased physical function, bone mineral density (BMD/g/cm2 ), and health-related quality of life (HRQL). We assessed the capacity of a physical therapy and motivation-based intervention, beginning after diagnosis and continuing through the end of treatment, to positively modify these factors.

PROCEDURE

A 2.5-year randomized controlled trial of 73 patients aged 4-18.99 years within 10 days of ALL diagnosis assessed BMD at baseline (T0 ) and end of therapy (T3 ), strength, range of motion, endurance, motor skills, and HRQL at baseline (T0 ), 8 (T1 ), 15 (T2 ), and 135 (T3 ) weeks.

RESULTS

There were no significant changes between groups (intervention, n = 33; usual care, n = 40) in BMD (P = 0.059) at T3 or physical function and HRQL at T0 -T3 . While BMD declined in both the intervention (T0  = -0.21, T3  = -0.55) and usual care (T0  = -0.62, T3  = -0.78) groups, rates of decline did not differ between groups (P = 0.56). Univariate analysis (n = 73) showed associations of higher T3 bone density with body mass index T1 (P = 0.01), T2 (P = <0.0001), T3 (P = 0.01), T3 ankle flexibility/strength (P = 0.001), and T2 parent (P = 0.02)/T0 child (P = 0.03) perceptions of less bodily pain.

CONCLUSIONS

The intervention delivered during treatment was not successful in modifying BMD, physical function, or HRQL. Physical activity, at the level and intensity required to modify these factors, may not be feasible during early treatment owing to the child's responses to the disease and treatment. Future studies will consider intervention implementation during late maintenance therapy, extending into survivorship.

Low-intensity vibration increases cartilage thickness in obese mice

Obesity is associated with an elevated risk of osteoarthritis (OA). We examined here whether high fat diet administered in young mice, compromised the attainment of articular cartilage thickness. Further, we sought to determine if low-intensity vibration (LIV) could protect the retention of articular cartilage in a mouse model of diet-induced obesity. Five-week-old, male, C57BL/6 mice were separated into three groups (n = 10): Regular diet (RD), High fat diet (HF), and HF + LIV (HFv; 90 Hz, 0.2g, 30 min/d, 5 d/w) administered for 6 weeks. Additionally, an extended HF diet study was run for 6 months (LIV at 15 m/d). Articular cartilage and subchondral bone morphology, and sulfated GAG content were quantified using contrast agent enhanced μCT and histology. Gene expression within femoral condyles was quantified using real-time polymerase chain reaction. Contrary to our hypothesis, HF cartilage thickness was not statistically different from RD. However, LIV increased cartilage thickness compared to HF, and the elevated thickness was maintained when diet and LIV were extended into adulthood. RT-PCR analysis showed a reduction of aggrecan expression with high fat diet, while application of LIV reduced the expression of degradative MMP-13. Further, long-term HF diet resulted in subchondral bone thickening, compared to RD, providing early evidence of OA pathology-LIV suppressed the thickening, such that levels were not significantly different from RD. These data suggest that dynamic loading, via LIV, protected the retention of cartilage thickness, potentially resulting in joint surfaces better suited to endure the risks of elevated loading that parallel obesity. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:751-759, 2018.

Bone mineral density in children with acute lymphoblastic leukemia

BACKGROUND

Children with acute lymphoblastic leukemia (ALL) can develop reduced bone mineral density (BMD). However, data from patients who received treatment on a frontline regimen without cranial irradiation are limited, and no genome-wide analysis has been reported.

METHODS

Lumbar BMD was evaluated by quantitative computed tomography at diagnosis, after 120 weeks of continuation therapy, and after 2 years off therapy in pediatric patients with ALL (ages 2-18 years at diagnosis) who were treated on the St. Jude Total XV Protocol. Clinical, pharmacokinetic, and genetic risk factors associated with decreased BMD Z-scores were evaluated.

RESULTS

The median BMD Z-score in 363 patients was 0.06 at diagnosis, declined to -1.08 at week 120, but partly recovered to -0.72 after 2 years off therapy; BMD in patients with low BMD Z-scores at diagnosis remained low after therapy. Older age (≥10 years vs 2-9.9 years at diagnosis; P < .001), a higher BMD Z-score at diagnosis (P = .001), and a greater area under the plasma drug concentration-time curve for dexamethasone in weeks 7 and 8 of continuation therapy (P = .001) were associated with a greater decrease in BMD Z-score from diagnosis to week 120. Single-nucleotide polymorphisms in 2 genes important in osteogenesis and bone mineralization (COL11A1 [reference single-nucleotide polymorphism rs2622849]; P = 2.39 × 10^-7 ] and NELL1 [rs11025915]; P = 4.07 × 10^-6 ]) were associated with a decreased BMD Z-score. NELL1 (P = .003) also was associated with a greater dexamethasone area under the plasma drug concentration-time curve.

CONCLUSIONS

BMD Z-scores decreased during therapy, especially in patients who had clinical, pharmacokinetic, and genetic risk factors. Early recognition of BMD changes and strategies to optimize bone health are essential. Cancer 2018;124:1025-35. © 2017 American Cancer Society.

Mechanical forces direct stem cell behaviour in development and regeneration

Stem cells and their local microenvironment, or niche, communicate through mechanical cues to regulate cell fate and cell behaviour and to guide developmental processes. During embryonic development, mechanical forces are involved in patterning and organogenesis. The physical environment of pluripotent stem cells regulates their self-renewal and differentiation. Mechanical and physical cues are also important in adult tissues, where adult stem cells require physical interactions with the extracellular matrix to maintain their potency. In vitro, synthetic models of the stem cell niche can be used to precisely control and manipulate the biophysical and biochemical properties of the stem cell microenvironment and to examine how the mode and magnitude of mechanical cues, such as matrix stiffness or applied forces, direct stem cell differentiation and function. Fundamental insights into the mechanobiology of stem cells also inform the design of artificial niches to support stem cells for regenerative therapies.

The Efficacy of Low-intensity Vibration to Improve Bone Health in Patients with End-stage Renal Disease Is Highly Dependent on Compliance and Muscle Response

RATIONAL AND OBJECTIVES

Low intensity vibration (LIV) may represent a nondrug strategy to mitigate bone deficits in patients with end-stage renal disease.

MATERIALS AND METHODS

Thirty end-stage renal patients on maintenance hemodialysis were randomized to stand for 20 minutes each day on either an active or placebo LIV device. Analysis at baseline and completion of 6-month intervention included magnetic resonance imaging (tibia and fibula stiffness; trabecular thickness, number, separation, bone volume fraction, plate-to-rod ratio; and cortical bone porosity), dual-energy X-ray absorptiometry (hip and spine bone mineral density [BMD]), and peripheral quantitative computed tomography (tibia trabecular and cortical BMD; calf muscle cross-sectional area).

RESULTS

Intention-to-treat analysis did not show any significant changes in outcomes associated with LIV. Subjects using the active device and with greater than the median adherence (70%) demonstrated an increase in distal tibia stiffness (5.3%), trabecular number (1.7%), BMD (2.3%), and plate-to-rod ratio (6.5%), and a decrease in trabecular separation (-1.8%). Changes in calf muscle cross-sectional area were associated with changes in distal tibia stiffness (R = 0.85), trabecular bone volume/total volume (R = 0.91), number (R = 0.92), and separation (R = -0.94) in the active group but not in the placebo group. Baseline parathyroid hormone levels were positively associated with increased cortical bone porosity over the 6-month study period in the placebo group (R = 0.55) but not in the active group (R = 0.01). No changes were observed in the nondistal tibia locations for either group except a decrease in hip BMD in the placebo group (-1.7%).

CONCLUSION

Outcomes and adherence thresholds identified from this pilot study could guide future longitudinal studies involving vibration therapy.

Pharmacologic Calcitriol Inhibits Osteoclast Lineage Commitment via the BMP-Smad1 and IκB-NF-κB Pathways

Vitamin D is involved in a range of physiological processes and its active form and analogs have been used to treat diseases such as osteoporosis. Yet how vitamin D executes its function remains unsolved. Here we show that the active form of vitamin D calcitriol increases the peak bone mass in mice by inhibiting osteoclastogenesis and bone resorption. Although calcitriol modestly promoted osteoclast maturation, it strongly inhibited osteoclast lineage commitment from its progenitor monocyte by increasing Smad1 transcription via the vitamin D receptor and enhancing BMP-Smad1 activation, which in turn led to increased IκBα expression and decreased NF-κB activation and NFATc1 expression, with IκBα being a Smad1 target gene. Inhibition of BMP type I receptor or ablation of Bmpr1a in monocytes alleviated the inhibitory effects of calcitriol on osteoclast commitment, bone resorption, and bone mass augmentation. These findings uncover crosstalk between the BMP-Smad1 and RANKL-NF-κB pathways during osteoclastogenesis that underlies the action of active vitamin D on bone health. © 2017 American Society for Bone and Mineral Research.

Low intensity vibration mitigates tumor progression and protects bone quantity and quality in a murine model of myeloma

Myeloma facilitates destruction of bone and marrow. Since physical activity encourages musculoskeletal preservation we evaluated whether low-intensity vibration (LIV), a means to deliver mechanical signals, could protect bone and marrow during myeloma progression. Immunocompromised-mice (n=25) were injected with human-myeloma cells, while 8 (AC) were saline-injected. Myeloma-injected mice (LIV; n=13) were subjected to daily-mechanical loading (15min/d; 0.3g @ 90Hz) while 12 (MM) were sham-handled. At 8w, femurs had 86% less trabecular bone volume fraction (BV/TV) in MM than in AC, yet only a 21% decrease in LIV was observed in comparison to AC, reflecting a 76% increase versus MM. Cortical BV was 21% and 15% lower in MM and LIV, respectively, than in AC; LIV showing 30% improvement over MM. Similar outcomes were observed in the axial skeleton, showing a 35% loss in MM with a 27% improved retention of bone in the L5 of LIV-treated mice as compared to MM. Transcortical-perforations in the femur from myeloma-induced osteolysis were 9× higher in MM versus AC, reduced by 57% in LIV. Serum-TRACP5b, 61% greater in MM versus AC, rose by 33% in LIV compared to AC, a 45% reduction in activity when compared to MM. Histomorphometric analyses of femoral trabecular bone demonstrated a 70% elevation in eroded surfaces of MM versus AC, while measures in LIV were 58% below those in MM. 72% of marrow in the femur of MM mice contained tumor, contrasted by a 31% lower burden in LIV. MM mice (42%) presented advanced-stage necrosis of tibial marrow while present in just 8% of LIV. Myeloma infiltration inversely correlated to measures of bone quality, while LIV slowed the systemic, myeloma-associated decline in bone quality and inhibited tumor progression through the hindlimbs.

Exercise Regulation of Marrow Adipose Tissue

Despite association with low bone density and skeletal fractures, marrow adipose tissue (MAT) remains poorly understood. The marrow adipocyte originates from the mesenchymal stem cell (MSC) pool that also gives rise to osteoblasts, chondrocytes, and myocytes, among other cell types. To date, the presence of MAT has been attributed to preferential biasing of MSC into the adipocyte rather than osteoblast lineage, thus negatively impacting bone formation. Here, we focus on understanding the physiology of MAT in the setting of exercise, dietary interventions, and pharmacologic agents that alter fat metabolism. The beneficial effect of exercise on musculoskeletal strength is known: exercise induces bone formation, encourages growth of skeletally supportive tissues, inhibits bone resorption, and alters skeletal architecture through direct and indirect effects on a multiplicity of cells involved in skeletal adaptation. MAT is less well studied due to the lack of reproducible quantification techniques. In recent work, osmium-based 3D quantification shows a robust response of MAT to both dietary and exercise intervention in that MAT is elevated in response to high-fat diet and can be suppressed following daily exercise. Exercise-induced bone formation correlates with suppression of MAT, such that exercise effects might be due to either calorie expenditure from this depot or from mechanical biasing of MSC lineage away from fat and toward bone, or a combination thereof. Following treatment with the anti-diabetes drug rosiglitazone - a PPARγ-agonist known to increase MAT and fracture risk - mice demonstrate a fivefold higher femur MAT volume compared to the controls. In addition to preventing MAT accumulation in control mice, exercise intervention significantly lowers MAT accumulation in rosiglitazone-treated mice. Importantly, exercise induction of trabecular bone volume is unhindered by rosiglitazone. Thus, despite rosiglitazone augmentation of MAT, exercise significantly suppresses MAT volume and induces bone formation. That exercise can both suppress MAT volume and increase bone quantity, notwithstanding the skeletal harm induced by rosiglitazone, underscores exercise as a powerful regulator of bone remodeling, encouraging marrow stem cells toward the osteogenic lineage to fulfill an adaptive need for bone formation. Thus, exercise represents an effective strategy to mitigate the deleterious effects of overeating and iatrogenic etiologies on bone and fat.