Magneto-mechanical stimulation modulates osteocyte fate via the ECM-integrin-CSK axis and wnt pathway

The effects and mechanisms of electromagnetic fields on bone remodeling: From clinical to laboratory

Electromagnetic fields (EMFs) are physical fields generated by electrically charged objects, and play a vital role in the growth and development of living organisms. Bone is a highly dynamic structure that undergoes a constant remodeling process. From 1962 to 1977, Bassett discovered the piezoelectric effect in bone tissue and found that EMFs accelerated osteogenesis, promoted tibial fracture healing in dogs, and had positive effects in clinical trials. Since then, EMFs have been increasingly studied in bone remodeling disorders as a non-invasive physical therapy. This review summarizes clinical trials and laboratory studies on EMF interventions in bone remodeling disorders over the past few decades, outlining the effects of EMFs on various bone cells and their underlying molecular mechanisms. In addition, we propose issues in current studies and give an outlook on the research and application of EMFs as a non-invasive physical therapy.

The translational potential of this article

This article systematically reviews the research ranging from biological and physical mechanisms to medical applications of EMFs on bone remodeling and related diseases, identifies key challenges in future basic research, and proposes new strategies for developing novel medical equipment and advancing clinical applications in this field. These insights contribute to the advancement of non-invasive physical therapies in orthopedics.

Deciphering mechanical cues in the microenvironment: from non-malignant settings to tumor progression

The tumor microenvironment functions as a dynamic and intricate ecosystem, comprising a diverse array of cellular and non-cellular components that precisely orchestrate pivotal tumor behaviors, including invasion, metastasis, and drug resistance. While unraveling the intricate interplay between the tumor microenvironment and tumor behaviors represents a tremendous challenge, recent research illuminates a crucial biological phenomenon known as cellular mechanotransduction. Within the microenvironment, mechanical cues like tensile stress, shear stress, and stiffness play a pivotal role by activating mechanosensitive effectors such as PIEZO proteins, integrins, and Yes-associated protein. This activation initiates cascades of intrinsic signaling pathways, effectively linking the physical properties of tissues to their physiological and pathophysiological processes like morphogenesis, regeneration, and immunity. This mechanistic insight offers a novel perspective on how the mechanical cues within the tumor microenvironment impact tumor behaviors. While the intricacies of the mechanical tumor microenvironment are yet to be fully elucidated, it exhibits distinct physical attributes from non-malignant tissues, including elevated solid stresses, interstitial hypertension, augmented matrix stiffness, and enhanced viscoelasticity. These traits exert notable influences on tumor progression and treatment responses, enriching our comprehension of the multifaceted nature of the microenvironment. Through this innovative review, we aim to provide a new lens to decipher the mechanical attributes within the tumor microenvironment from non-malignant contexts, broadening our knowledge on how these factors promote or inhibit tumor behaviors, and thus offering valuable insights to identify potential targets for anti-tumor strategies.

Moderate static magnetic field regulates iron metabolism and salvage bone loss caused by iron accumulation

Objective

Clinical studies, epidemiological investigations and animal experiments have demonstrated that iron overload lead to bone loss, especially postmenopausal osteoporosis. As a physiotherapy tool, electromagnetic fields already used in clinical treatment of osteoporosis and participates in bone remodeling by affecting the iron metabolism of organisms. As an electromagnetic field with constant magnetic flux density and direction, the mechanism of static magnetic field (SMF) regulating iron metabolism remains unclear. Therefore, the aim of this study was to investigate the effects of moderate static magnetic field (MMF) on iron metabolism and bone metabolism in postmenopausal osteoporosis and HAMP-deficient mouse models, and to elucidate the underlying mechanisms.

Methods

Firstly, the effects of MMF on bone metabolism and iron metabolism in 22 postmenopausal osteoporosis participants were evaluated by comparing the changes of bone mineral density (BMD) and serum ferritin before and after treatment. Secondly, 10-week-old male C57BL/6 HAMP +/+ and HAMP -/- mice were randomly divided into four groups, namely GMF-HAMP +/+ group and MMF-HAMP +/+ group, GMF-HAMP -/- group and MMF-HAMP -/- group (n = 8/group). The MMF-treated mice were exposed daily to MMF, while the remaining group was exposed to geomagnetic field (GMF) for 8 weeks. BMD was scanned and bone tissues were collected for mechanical, structural and histological analysis. In addition, analysis of serum and tissue iron content evaluated the regulation of systemic iron metabolism by MMF. Finally, the effects of MMF on the differentiation of primary macrophages and primary osteoblasts were evaluated in vitro.

Results

In clinical trial, MMF decreased serum ferritin levels in postmenopausal osteoporosis patients, which was negatively correlated with changes in lumbar BMD. In vivo, the results showed that HAMP-deficient mice were accompanied by iron overload, along with reduced lumbar vertebra bone mass and bone quality. MMF improved the bone mass, microstructure and biomechanical properties of lumbar vertebrae in HAMP -/- mice. In vitro, MMF reduced the number and differentiation of osteoclasts in HAMP -/- mice, and promoted primary osteoblast differentiation by activating Wnt/β-catenin signaling pathway. Further, MMF also reduced the iron ion conversion and enhanced the antioxidant system of HAMP -/- mice. These data suggested that MMF could regulate iron metabolism and salvage bone loss caused by iron accumulation.

Conclusions

The clinical trial and laboratory results suggested that MMF intervention has a protective effect on bone loss caused by iron metabolism disorders.

Translational potential of this article

Translational potential of this article: This study demonstrated the feasibility and potential effectiveness of MMF in the treatment of postmenopausal osteoporosis patients, demonstrating for the first time that MMF can reduce bone loss in mice with inherited iron metabolism abnormalities. It was suggested that MMF plays an important role in iron metabolism disorders or as an alternative therapy to ameliorate osteoporosis caused by iron accumulation.

Effects of 16.8-22.0 T high static magnetic fields on the development of zebrafish in early fertilization

OBJECTIVES

Despite some existing studies on the safety of high static magnetic fields (SMFs), the effects of ultra-high SMFs above 20.0 T for embryonic development in early pregnancy are absent. The objective of this study is to evaluate the influence of 16.8-22.0 T SMF on the development of zebrafish embryos, which will provide important information for the future application of ultra-high field magnetic resonance imaging (MRI).

METHODS

Two-hour exposure to homogenous (0 T/m) 22.0 T SMF, or 16.8 T SMFs with 123.25 T/m spatial gradient of opposite magnetic force directions was examined in the embryonic development of 200 zebrafish. Their body length, heart rate, spontaneous tail-wagging movement, hatching and survival rate, photomotor response, and visual motor response (VMR) were analyzed.

RESULTS

Our results show that these ultra-high SMFs did not significantly affect the general development of zebrafish embryos, such as the body length or spontaneous tail-wagging movement. However, the hatching rate was reduced by the gradient SMFs (p < 0.05), but not the homogenous 22.0 T SMF. Moreover, although the zebrafish larva activities were differentially affected by these ultra-high SMFs (p < 0.05), the expression of several visual and neurodevelopmental genes (p < 0.05) was generally downregulated in the eyeball.

CONCLUSIONS

Our findings suggest that exposure to ultra-high SMFs, especially the gradient SMFs, may have adverse effects on embryonic development, which should cause some attention to the future application of ultra-high field MRIs.

CLINICAL RELEVANCE STATEMENT

As technology advances, it is conceivable that very strong magnetic fields may be adapted for use in medical imaging. Possible dangers associated with these higher Tesla fields need to be considered and evaluated prior to human use.

KEY POINTS

Ultra-High static magnetic field may affect early embryonic development. High strength gradient static magnetic field exposure impacted zebrafish embryonic development. The application of very strong magnetic fields for MR technologies needs to be carefully evaluated.

Insights and implications of sexual dimorphism in osteoporosis

Osteoporosis, a metabolic bone disease characterized by low bone mineral density and deterioration of bone microarchitecture, has led to a high risk of fatal osteoporotic fractures worldwide. Accumulating evidence has revealed that sexual dimorphism is a notable feature of osteoporosis, with sex-specific differences in epidemiology and pathogenesis. Specifically, females are more susceptible than males to osteoporosis, while males are more prone to disability or death from the disease. To date, sex chromosome abnormalities and steroid hormones have been proven to contribute greatly to sexual dimorphism in osteoporosis by regulating the functions of bone cells. Understanding the sex-specific differences in osteoporosis and its related complications is essential for improving treatment strategies tailored to women and men. This literature review focuses on the mechanisms underlying sexual dimorphism in osteoporosis, mainly in a population of aging patients, chronic glucocorticoid administration, and diabetes. Moreover, we highlight the implications of sexual dimorphism for developing therapeutics and preventive strategies and screening approaches tailored to women and men. Additionally, the challenges in translating bench research to bedside treatments and future directions to overcome these obstacles will be discussed.