Static Magnetic Field Effect on Cell Alignment, Growth, and Differentiation in Human Cord-Derived Mesenchymal Stem Cells

Effect of static magnetic field on gene expression of human umbilical cord mesenchymal stem cells by transcriptome analysis

PURPOSE

Static magnetic fields (SMFs) induce various biological reactions and have been applied in the biological therapy of diseases, especially in combination with mesenchymal stem cells (MSCs) and tissue engineering. However, the underlying influence of SMFs on MSCs gene expression remains largely unclear. In this study, we aim to investigate the effects of SMFs on gene expression of human MSCs.

MATERIALS AND METHODS

We exposed human MSCs to two different intensities (0.35 ​T and 1.0 ​T) of SMFs and observed the effects of SMFs on cell morphology. Subsequently, RNA-sequencing was performed to explore the gene expression changes.

RESULTS

Compared with control group cells, no significant differences in cell morphology were observed under a phase contrast inverted microscope, but the transcriptome of SMF-exposed MSCs were significantly changed in both 0.35 ​T and 1.0 ​T groups and the differential expressed genes are involved in multiple pathways, such as ubiquitin mediated proteolysis, TNF signaling pathway, NF-kappa B signaling pathway, TGF-beta signaling pathway, metabolic pathways, and apoptosis, which regulate the biological functions of MSCs.

CONCLUSIONS

SMFs stimulation could affect the gene expression of human MSCs and the biological effects vary by the different intensities of SMFs. These data offer the molecular foundation for future application of SMFs in stem cell technology as well as tissue engineering medicine.

Design and characterisation of a cell exposure system with high magnetic field homogeneity: RILZ coils

In vitro studies requiring controlled exposure to low-frequency electromagnetic fields employ exposure systems with different geometries and configurations, the Helmholtz configuration being one of the most widely used. This configuration has limitations in the homogeneity of the spatial distribution of the magnetic field intensity values. We present the design, manufacturing, and characterisation of a new coil system, called RILZ configuration, which improves the distribution of magnetic field intensity values in the three dimensions of space for three different heights in comparison with the traditional circular coils in Helmholtz configuration. In addition, a comparative study of the cellular response in CT2A cultures exposed to a magnetic field of 50 Hz and 100 µT for 48 hrs is performed with both exposure systems. The results of the study show reduced values of deviation from the central value of magnetic field intensity using the RILZ coil system. These differences are statistically significant compared to the Helmholtz configuration for the three Cartesian directions: x (p < 0.01), y (p < 0.01), z (p < 0.01). In addition, the intensity values for three different heights are statistically significantly correlated using the RILZ coil system (p < 0.01). The differences in cell behaviour are also statistically significant between the two systems (p < 0.01) and may be directly related to the differences found in the distribution of intensity values between the two systems. This study highlights the importance of the homogeneity of the magnetic field intensity generated by the exposure systems used and offers an effective solution to control the magnetic field exposure parameters in vitro assays.

Static magnetic fields in regenerative medicine

All organisms on Earth live in the weak but ubiquitous geomagnetic field. Human beings are also exposed to magnetic fields generated by multiple sources, ranging from permanent magnets to magnetic resonance imaging (MRI) in hospitals. It has been shown that different magnetic fields can generate various effects on different tissues and cells. Among them, stem cells appear to be one of the most sensitive cell types to magnetic fields, which are the fundamental units of regenerative therapies. In this review, we focus on the bioeffects of static magnetic fields (SMFs), which are related to regenerative medicine. Most reports in the literature focus on the influence of SMF on bone regeneration, wound healing, and stem cell production. Multiple aspects of the cellular events, including gene expression, cell signaling pathways, reactive oxygen species, inflammation, and cytoskeleton, have been shown to be affected by SMFs. Although no consensus yet, current evidence indicates that moderate and high SMFs could serve as a promising physical tool to promote bone regeneration, wound healing, neural differentiation, and dental regeneration. All in vivo studies of SMFs on bone regeneration and wound healing have shown beneficial effects, which unravel the great potential of SMFs in these aspects. More mechanistic studies, magnetic field parameter optimization, and clinical investigations on human bodies will be imperative for the successful clinical applications of SMFs in regenerative medicine.

Static magnetic field: A potential tool of controlling stem cells fates for stem cell therapy in osteoporosis

Osteoporosis is a kind of bone diseases characterized by dynamic imbalance of bone formation and bone absorption, which is prone to fracture, and seriously endangers human health. At present, there is a lack of highly effective drugs for it, and the existing measures all have some side effects. In recent years, mesenchymal stem cell therapy has brought a certain hope for osteoporosis, while shortcomings such as homing difficulty and unstable therapeutic effects limit its application widely. Therefore, it is extremely urgent to find effective and reliable means/drugs for adjuvant stem cell therapy or develop new research techniques. It has been reported that static magnetic fields(SMFs) has a certain alleviating and therapeutic effect on varieties of bone diseases, also promotes the proliferation and osteogenic differentiation of mesenchymal stem cells derived from different tissues to a certain extent. Basing on the above background, this article focuses on the key words "static/constant magnetic field, mesenchymal stem cell, osteoporosis", combined literature and relevant contents were studied to look forward that SMFs has unique advantages in the treatment of osteoporosis with mesenchymal stem cells, which can be used as an application tool to promote the progress of stem cell therapy in clinical application.

Static Magnetic Fields Regulate T-Type Calcium Ion Channels and Mediate Mesenchymal Stem Cells Proliferation

The static magnetic fields (SMFs) impact on biological systems, induce a variety of biological responses, and have been applied to the clinical treatment of diseases. However, the underlying mechanisms remain largely unclear. In this report, by using human mesenchymal stem cells (MSCs) as a model, we investigated the biological effect of SMFs at a molecular and cellular level. We showed that SMF exposure promotes MSC proliferation and activates the expression of transcriptional factors such as FOS (Fos Proto-Oncogene, AP-1 Transcription Factor Subunit) and EGR1 (Early Growth Response 1). In addition, the expression of signal-transduction proteins p-ERK1/2 and p-JNK oscillate periodically with SMF exposure time. Furthermore, we found that the inhibition of the T-type calcium ion channels negates the biological effects of SMFs on MSCs. Together, we revealed that the SMFs regulate T-type calcium ion channels and mediate MSC proliferation via the MAPK signaling pathways.

Magnetic exposure using Samarium Cobalt (SmCO5) increased proliferation and stemness of human Umbilical Cord Mesenchymal Stem Cells (hUC-MSCs)

Despite the extensive reports on the potential hazard of magnetic field (MF) exposures on humans, there are also concurrently reported on the improved proliferative property of stem cells at optimum exposure. However, the effect on mesenchymal stem cells (MSCs) remains unknown. Therefore, we aimed to investigate the impact of induced static MF (SMF) on human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) using Samarium Cobalt (SmCO5). At passage 3, hUC-MSCs (1 × 10⁴) were exposed to 21.6 mT SMF by a direct exposure (DE) showed a significantly higher cell count (p < 0.05) in the growth kinetics assays with the shortest population doubling time relative to indirect exposure and negative control. The DE group was committed into the cell cycle with increased S phase (55.18 ± 1.38%) and G2/M phase (21.75 ± 1.38%) relative to the NC group [S-phase (13.54 ± 2.73%); G2/M phase (8.36 ± 0.28%)]. Although no significant changes were observed in the immunophenotype, the DE group showed an elevated expression of pluripotency-associated markers (OCT4, SOX2, NANOG, and REX1). These results suggest that the MFs could potentially induce proliferation of MSCs, a promising approach to promote stem cells propagation for clinical therapy and research without compromising the stemness of hUC-MSCs.

Magnetic stimulation of the angiogenic potential of mesenchymal stromal cells in vascular tissue engineering

The growing prevalence of vascular diseases worldwide has emphasized the need for novel tissue-engineered options concerning the development of vascularized 3D constructs. This study reports, for the first time, the use of external magnetic fields to stimulate mesenchymal stromal cells (MSCs) to increase the production of vascular endothelial growth factor-A (VEGF-A). Polyvinylalcohol and gelatin-based scaffolds, containing iron oxide nanoparticles, were designed for optimal cell magnetic stimulation. While the application of static magnetic fields over 24 h did not impact on MSCs proliferation, viability and phenotypic identity, it significantly increased the production of VEGF-A and guided MSCs morphology and alignment. The ability to enhance MSCs angiogenic potential was demonstrated by the increase in the number of new vessels formed in the presence of MSCs conditioned media through in vitro and in vivo models. Ultimately, this study uncovers the potential to manipulate cellular processes through short-term magnetic stimulation.

Static Magnetic Stimulation Induces Changes in the Oxidative Status and Cell Viability Parameters in a Primary Culture Model of Astrocytes

Astrocytes play an important role in the central nervous system function and may contribute to brain plasticity response during static magnetic fields (SMF) brain therapy. However, most studies evaluate SMF stimulation in brain plasticity while few studies evaluate the consequences of SMF at the cellular level. Thus, we here evaluate the effects of SMF at 305 mT (medium-intensity) in a primary culture of healthy/normal cortical astrocytes obtained from neonatal (1 to 2-day-old) Wistar rats. After reaching confluence, cells were daily subjected to SMF stimulation for 5 min, 15 min, 30 min, and 40 min during 7 consecutive days. Oxidative stress parameters, cell cycle, cell viability, and mitochondrial function were analyzed. The antioxidant capacity was reduced in groups stimulated for 5 and 40 min. Although no difference was observed in the enzymatic activity of superoxide dismutase and catalase or the total thiol content, lipid peroxidation was increased in all stimulated groups. The cell cycle was changed after 40 min of SMF stimulation while 15, 30, and 40 min led cells to death by necrosis. Mitochondrial function was reduced after SMF stimulation, although imaging analysis did not reveal substantial changes in the mitochondrial network. Results mainly revealed that SMF compromised healthy astrocytes' oxidative status and viability. This finding reveals how important is to understand the SMF stimulation at the cellular level since this therapeutic approach has been largely used against neurological and psychiatric diseases.

Low magnetic field promotes recombinant human BMP-2-induced bone formation and influences orientation of trabeculae and bone marrow-derived stromal cells

Effects of high magnetic fields [MFs, ≥ 1 T (T)] on osteoblastic differentiation and the orientation of cells or matrix proteins have been reported. However, the effect of low MFs (< 1 T) on the orientation of bone formation is not well known. This study was performed to verify the effects of low MFs on osteoblastic differentiation, bone formation, and orientation of both cells and newly formed bone. An apparatus was prepared with two magnets (190 mT) aligned in parallel to generate a parallel MF. In vitro, bone marrow-derived stromal cells of rats were used to assess the effects of low MFs on cell orientation, osteoblastic differentiation, and mineralization. A bone morphogenetic protein (BMP)-2-induced ectopic bone model was used to elucidate the effect of low MFs on microstructural indices, trabecula orientation, and the apatite c-axis orientation of newly formed bone. Low MFs resulted in an increased ratio of cells oriented perpendicular to the direction of the MF and promoted osteoblastic differentiation in vitro. Moreover, in vivo analysis demonstrated that low MFs promoted bone formation and changed the orientation of trabeculae and apatite crystal in a direction perpendicular to the MF. These changes led to an increase in the mechanical strength of rhBMP-2-induced bone. These results suggest that the application of low MFs has potential to facilitate the regeneration of bone with sufficient mechanical strength by controlling the orientation of newly formed bone.

Static magnetic field-enhanced osteogenic differentiation of human umbilical cord-derived mesenchymal stem cells via matrix vesicle secretion

METHODS

In methodology, WJMSCs were treated with a 0.4-T SMF. The cell viability was tested using the MTT assay. For the osteogenic analysis, the alkaline phosphatase activity assay and alizarin red S staining were performed. The osteogenic-related gene expression of ALP, BMP-2, and Runx2 was examined using real-time polymerase chain reaction. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy was used to analyze matrix vesicle secretion.

RESULTS

The cell viability showed no significant difference between the SMF-treated group and the sham-exposed cells. However, the SMF-treated group exhibited significantly more mineralized nodule formation and higher ALP activity than their control counterparts (p < .05). The expressions of osteogenic-related markers, ALP, BMP-2, and Runx2, were also significantly higher in the SMF-treated WJMSCs. The scanning electron microscopy results showed much more matrix vesicle secretion in the SMF-treated cells than in the sham-treated cells. A mineralized sheath was noted in the SMF-treated cells, along with a sporadic accumulation of spherical mineralized deposits on the cell surface.

CONCLUSIONS

The results suggest that 0.4-T SMF treatment enhances the osteogenesis of WJMSCs at the early-to-middle stage of osteogenic differentiation by increasing the matrix vesicle secretion and mineralization.