Abstract
Background: Electromagnetic field therapy is gaining attention for its potential in treating bone disorders, with Extracorporeal Magnetotransduction Therapy (EMTT) emerging as an innovative approach. EMTT offers a higher oscillation frequency and magnetic field strength compared to traditional Pulsed Electromagnetic Field (PEMF) therapy, showing promise in enhancing fracture healing and non-union recovery. However, the mechanisms underlying these effects remain unclear. Results: This study demonstrates that EMTT significantly enhances osteoblast bone formation at multiple levels, from gene expression to extracellular matrix mineralization. Key osteoblastogenesis regulators, including SP7 and RUNX2, and bone-related genes such as COL1A1, ALPL, and BGLAP, were upregulated, with expression levels surpassing those of the control group by over sevenfold (p < 0.001). Enhanced collagen synthesis and mineralization were confirmed by von Kossa and Alizarin Red staining, indicating increased calcium and phosphate deposition. Additionally, calcium imaging revealed heightened calcium influx, suggesting a cellular mechanism for EMTT’s osteogenic effects. Importantly, EMTT did not compromise cell viability, as confirmed by live/dead staining and WST-1 assays. Conclusion: This study is the first to show that EMTT can enhance all phases of osteoblastogenesis and improve the production of critical mineralization components, offering potential clinical applications in accelerating fracture healing, treating osteonecrosis, and enhancing implant osseointegration.
1. Introduction
Bone consists of approximately 60% mineral (inorganic), 30% organic material, and 10% water, with the organic component predominantly comprised of type I collagen (COL1A1) [1]. Research has consistently demonstrated that the collagen matrix acts as a scaffold for bone mineral deposition [2]. The collagen-rich extracellular matrix (ECM) undergoes mineralization through the deposition of hydroxyapatite [3]. Chemically, the inorganic material comprises ionic calcium (Ca2+) and inorganic phosphate (Pi). Pyrophosphate (PPi), consisting of two inorganic Pi groups, is one of the most potent mineralization inhibitors [4]. Therefore, the hydrolysis of PPi is critical for the mineralization process. Alkaline phosphatase (ALP), often regarded as a marker for bone metabolism, plays a pivotal role in regulating ECM mineralization [5]. Moreover, phosphatase orphan 1 (PHOSPHO1) and nucleoside pyrophosphohydrolase-1 (NPP1), encoded by the ENPP1 gene, are additional vital PPi/Pi ratio regulators, modulating the mineralization process [6].
Osteoblasts are the primary bone-forming cells. Besides ALP and a significant amount of type I collagen, osteoblasts produce osteocalcin (OCN). OCN and its gene (BGLAP) are widely trusted indicators in scientific research for measuring osteoblastic activity [7].
Osteoblast differentiation, termed osteoblastogenesis, progresses through three phases: proliferation, matrix maturation, and mineralization [8]. The transition of osteoprogenitors from proliferation to ECM maturation is orchestrated by RUNX2, leading to the expression of bone-related genes. Simultaneously, Osterix (SP7) plays a guiding role in osteoblast differentiation [9].
Constituting over 95% of all bone cells, osteocytes play a central role in regulating bone formation and mineralization [10]. Specific proteins, uniquely expressed in osteocytes, serve essential functions in maintaining phosphate homeostasis. These include phosphate-regulating genes with PHEX (phosphate-regulating neutral endopeptidase on chromosome x) and MEPE (matrix extracellular phosphoglycoprotein) [10].
Since the initial discovery of a potential piezoelectric effect in bones in 1957, extensive research has been devoted to investigating the modulation of bone formation through the application of electric fields [11]. Following approval by the Food and Drug Administration (FDA) in 1979, numerous devices have been developed to produce a distinct form of electromagnetic wave therapy known as pulsed electromagnetic field (PEMF). Demonstrating promising potential in enhancing bone repair, electromagnetic wave therapy has been effectively utilized to address various osteogenic disorders. This includes the successful treatment of fractures, particularly non-union fractures, as well as mitigating bone loss linked to osteoporosis or radiation exposure [12,13]. Although some studies propose that PEMF influences osteoblastogenesis and cell proliferation, the effectiveness of PEMF therapy in influencing bone formation remains unclear and inconclusive [14]. Intracellular calcium transients are widely recognized as crucial in regulating osteoblast proliferation and differentiation, thereby playing a fundamental role in bone formation. Numerous studies suggest that calcium is pivotal in enhancing osteoblastogenesis triggered by magnetic field exposure [13,15].
Most PEMF devices can generate magnetic field strengths ranging from 1 mT to 10 mT [16]. A recent advancement in electromagnetic field therapy is Extracorporeal Magnetotransduction Therapy (EMTT), which sets itself apart from PEMF by using high-intensity electromagnetic fields with a strength reaching up to 150 mT. These physical parameters facilitate a more substantial biological impact, promising a new therapeutic approach to managing bone disorders [17]. Since EMTT is a relatively novel form of electromagnetic wave therapy, there is limited available evidence regarding its effectiveness. Yet, a few case reports have demonstrated enhanced bone healing [18,19]. EMTT has been successfully used to treat non-unions and lower back pain [18,20]. Clinical practitioners have characterized it as a significant advancement in treating complex bone disorders and chronic inflammatory conditions [17].
To date, only a single cellular study has been conducted, offering potential insights into the osteogenic effects of EMTT. The in vitro analysis was performed on human bone marrow mesenchymal stem cells (MSCs) and revealed increased vascular endothelial growth factor (VEGF) levels and upregulation of bone formation-specific genes such as COL1A1 and ALP [21]. These findings imply the potential benefits of EMTT in bone fracture healing through the modulation of bone metabolism and angiogenesis mechanisms.
For the first time, this study represents a cellular investigation, providing essential biological insights into the observed acceleration of bone formation through EMTT stimulation. We specifically examined the effects of EMTT stimulation on the proliferation, differentiation, and mineralization of primary human osteoblasts (hOBs).
To ensure the clarity of our study’s conclusions, we rigorously maintained identical experimental conditions throughout. This involved employing consistent stimulation and cultivation protocols, including standardized EMTT physical parameters (level 8, 8 Hz, 30 min).
Continue reading: https://pmc.ncbi.nlm.nih.gov/articles/PMC11505246/
