Static magnetic fields enhance dental pulp stem cell proliferation by activating the p38 mitogen-activated protein kinase pathway as its putative mechanism

Stimuli-responsive biomaterials: smart avenue toward 4D bioprinting

3D bioprinting is an advanced technology combining cells and bioactive molecules within a single bioscaffold; however, this scaffold cannot change, modify or grow in response to a dynamic implemented environment. Lately, a new era of smart polymers and hydrogels has emerged, which can add another dimension, e.g., time to 3D bioprinting, to address some of the current approaches' limitations. This concept is indicated as 4D bioprinting. This approach may assist in fabricating tissue-like structures with a configuration and function that mimic the natural tissue. These scaffolds can change and reform as the tissue are transformed with the potential of specific drug or biomolecules released for various biomedical applications, such as biosensing, wound healing, soft robotics, drug delivery, and tissue engineering, though 4D bioprinting is still in its early stages and more works are required to advance it. In this review article, the critical challenge in the field of 4D bioprinting and transformations from 3D bioprinting to 4D phases is reviewed. Also, the mechanistic aspects from the chemistry and material science point of view are discussed too.

Using a static magnetic field to attenuate the severity in COVID-19-invaded lungs

Two important factors affecting the progress of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are the S-protein binding function of ACE2 receptors and the membrane fluidity of host cells. This study aimed to evaluate the effect of static magnetic field (SMF) on S-protein/ACE2 binding and cellular membrane fluidity of lung cells, and was performed in vitro using a Calu-3 cell model and in vivo using an animal model. The ability of ACE2 receptors to bind to SARS-CoV-2 spike protein on host cell surfaces under SMF stimulation was evaluated using fluorescence images. Host lung cell membrane fluidity was tested using fluorescence polarization to determine the effects of SMF. Our results indicate that 0.4 T SMF can affect binding between S-protein and ACE2 receptors and increase Calu-3 cell membrane fluidity, and that SMF exposure attenuates LPS-induced alveolar wall thickening in mice. These results may be of value for developing future non-contact, non-invasive, and low side-effect treatments to reduce disease severity in COVID-19-invaded lungs.

Effects of Sapindus mukorossi Seed Oil on Bone Healing Efficiency: An Animal Study

Natural products have attracted great interest in the development of tissue engineering. Recent studies have demonstrated that unsaturated fatty acids found in natural plant seed oil may exhibit positive osteogenic effects; however, few in vivo studies have focused on the use of plant seed oil for bone regeneration. The aim of this study is to investigate the effects of seed oil found in Sapindus mukorossi (S. mukorossi) on the osteogenic differentiation of mesenchymal stem cells and bone growth in artificial bone defects in vivo. In this study, Wharton-jelly-derived mesenchymal stem cells (WJMSCs) were co-cultured with S. mukorossi seed oil. Cellular osteogenic capacity was assessed using Alizarin Red S staining. Real-time PCR was carried out to evaluate ALP and OCN gene expression. The potential of S. mukorossi seed oil to enhance bone growth was assessed using an animal model. Four 6 mm circular defects were prepared at the parietal bone of New Zealand white rabbits. The defects were filled with hydrogel and hydrogel-S. mukorossi seed oil, respectively. Quantitative analysis of micro-computed tomography (Micro-CT) and histological images was conducted to compare differences in osteogenesis between oil-treated and untreated samples. Although our results showed no significant differences in viability between WJMSCs treated with and without S. mukorossi seed oil, under osteogenic conditions, S. mukorossi seed oil facilitated an increase in mineralized nodule secretion and upregulated the expression of ALP and OCN genes in the cells (p < 0.05). In the animal study, both micro-CT and histological evaluations revealed that new bone formation in artificial bone defects treated with S. mukorossi seed oil were nearly doubled compared to control defects (p < 0.05) after 4 weeks of healing. Based on these findings, it is reasonable to suggest that S. mukorossi seed oil holds promise as a potential candidate for enhancing bone healing efficiency in bone tissue engineering.

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.

Enhancing bone tissue engineering using iron nanoparticles and magnetic fields: A focus on cytomechanics and angiogenesis in the chicken egg chorioallantoic membrane model

AIM

To evaluate the potential of iron nanoparticles (FeNPs) in conjunction with magnetic fields (MFs) to enhance osteoblast cytomechanics, promote cell homing, bone development activity, and antibacterial capabilities, and to assess their in vivo angiogenic viability using the chicken egg chorioallantoic membrane (CAM) model.

SETTINGS AND DESIGN

Experimental study conducted in a laboratory setting to investigate the effects of FeNPs and MFs on osteoblast cells and angiogenesis using a custom titanium (Ti) substrate coated with FeNPs.

MATERIALS AND METHODS

A custom titanium (Ti) was coated with FeNPs. Evaluations were conducted to analyze the antibacterial properties, cell adhesion, durability, physical characteristics, and nanoparticle absorption associated with FeNPs. Cell physical characteristics were assessed using protein markers, and microscopy, CAM model, was used to quantify blood vessel formation and morphology to assess the FeNP-coated Ti's angiogenic potential. This in vivo study provided critical insights into tissue response and regenerative properties for biomedical applications.

STATISTICAL ANALYSIS

Statistical analysis was performed using appropriate tests to compare experimental groups and controls. Significance was determined at P < 0.05.

RESULTS

FeNPs and MFs notably improved osteoblast cell mechanical properties facilitated the growth and formation of new blood vessels and bone tissue and promoted cell migration to targeted sites. In the group treated with FeNPs and exposed to MFs, there was a significant increase in vessel percentage area (76.03%) compared to control groups (58.11%), along with enhanced mineralization and robust antibacterial effects (P < 0.05).

CONCLUSION

The study highlights the promising potential of FeNPs in fostering the growth of new blood vessels, promoting the formation of bone tissue, and facilitating targeted cell migration. These findings underscore the importance of further investigating the mechanical traits of FeNPs, as they could significantly advance the development of effective bone tissue engineering techniques, ultimately enhancing clinical outcomes in the field.

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 Reduces Intracellular ROS Levels and Protects Cells Against Peroxide-Induced Damage: Suggested Roles for Catalase

A feature in neurodegenerative disorders is the loss of neurons, caused by several factors including oxidative stress induced by reactive oxygen species (ROS). In this work, static magnetic field (SMF) was applied in vitro to evaluate its effect on the viability, proliferation, and migration of human neuroblastoma SH-SY5Y cells, and on the toxicity induced by hydrogen peroxide (H2O2), tert-butyl hydroperoxide (tBHP), H2O2/sodium azide (NaN3) and photosensitized oxidations by photodynamic therapy (PDT) photosensitizers. The SMF increased almost twofold the cell expression of the proliferation biomarker Ki-67 compared to control cells after 7 days of exposure. Exposure to SMF accelerated the wound healing of scratched cell monolayers and significantly reduced the H2O2-induced and the tBHP-induced cell deaths. Interestingly, SMF was able to revert the effects of NaN3 (a catalase inhibitor), suggesting an increased activity of catalase under the influence of the magnetic field. In agreement with this hypothesis, SMF significantly reduced the oxidation of DCF-H2, indicating a lower level of intracellular ROS. When the redox imbalance was triggered through photosensitized oxidation, no protection was observed. This observation aligns with the proposed role of catalase in cellular proctetion under SMF.  Exposition to SMF should be further validated in vitro and in vivo as a potential therapeutic approach for neurodegenerative disorders.

Ultra-high static magnetic fields cause immunosuppression through disrupting B-cell peripheral differentiation and negatively regulating BCR signaling

To increase the imaging resolution and detection capability, the field strength of static magnetic fields (SMFs) in magnetic resonance imaging (MRI) has significantly increased in the past few decades. However, research on the side effects of high magnetic field is still very inadequate and the effects of SMF above 1 T (Tesla) on B cells have never been reported. Here, we show that 33.0 T ultra-high SMF exposure causes immunosuppression and disrupts B cell differentiation and signaling. 33.0 T SMF treatment resulted in disturbance of B cell peripheral differentiation and antibody secretion and reduced the expression of IgM on B cell membrane, and these might be intensity dependent. In addition, mice exposed to 33.0 T SMF showed inhibition on early activation of B cells, including B cell spreading, B cell receptor clustering and signalosome recruitment, and depression of both positive and negative molecules in the proximal BCR signaling, as well as impaired actin reorganization. Sequencing and gene enrichment analysis showed that SMF stimulation also affects splenic B cells' transcriptome and metabolic pathways. Therefore, in the clinical application of MRI, we should consider the influence of SMF on the immune system and choose the optimal intensity for treatment.

Static Magnetic Fields Promote Generation of Muscle Lineage Cells from Pluripotent Stem Cells and Myoblasts

Static magnetic fields (SMFs) exhibit numerous biological effects and regulate the proliferation and differentiation of several adult stem cells. However, the role of SMFs in the self-renewal maintenance and developmental potential of pluripotent embryonic stem cells (ESCs) remains largely uninvestigated. Here, we show that SMFs promote the expression of the core pluripotent markers Sox2 and SSEA-1. Furthermore, SMFs facilitate the differentiation of ESCs into cardiomyocytes and skeletal muscle cells. Consistently, transcriptome analysis reveals that muscle lineage differentiation and skeletal system specification of ESCs are remarkably strengthened by SMF stimuli. Additionally, when treated with SMFs, C2C12 myoblasts exhibit an increased proliferation rate, improved expression of skeletal muscle markers and elevated myogenic differentiation capacity compared with control cells. Together, our data show that SMFs effectively promote muscle cell generation from pluripotent stem cells and myoblasts. The noninvasive and convenient physical stimuli can be used to increase the production of muscle cells in regenerative medicine and the manufacture of cultured meat in cellular agriculture.

Effects of different physical factors on osteogenic differentiation

Osteoblasts are essential for bone formation and can perceive external mechanical stimuli, which are translated into biochemical responses that ultimately alter cell phenotypes and respond to environmental stimuli, described as mechanical transduction. These cells actively participate in osteogenesis and the formation and mineralisation of the extracellular bone matrix. This review summarises the basic physiological and biological mechanisms of five different physical stimuli, i.e. light, electricity, magnetism, force and sound, to induce osteogenesis; further, it summarises the effects of changing culture conditions on the morphology, structure and function of osteoblasts. These findings may provide a theoretical basis for further studies on bone physiology and pathology at the cytological level and will be useful in the clinical application of bone formation and bone regeneration technology.

Magnetic Bone Tissue Engineering: Reviewing the Effects of Magnetic Stimulation on Bone Regeneration and Angiogenesis

Bone tissue engineering emerged as a solution to treat critical bone defects, aiding in tissue regeneration and implant integration. Mainly, this field is based on the development of scaffolds and coatings that stimulate cells to proliferate and differentiate in order to create a biologically active bone substitute. In terms of materials, several polymeric and ceramic scaffolds have been developed and their properties tailored with the objective to promote bone regeneration. These scaffolds usually provide physical support for cells to adhere, while giving chemical and physical stimuli for cell proliferation and differentiation. Among the different cells that compose the bone tissue, osteoblasts, osteoclasts, stem cells, and endothelial cells are the most relevant in bone remodeling and regeneration, being the most studied in terms of scaffold-cell interactions. Besides the intrinsic properties of bone substitutes, magnetic stimulation has been recently described as an aid in bone regeneration. External magnetic stimulation induced additional physical stimulation in cells, which in combination with different scaffolds, can lead to a faster regeneration. This can be achieved by external magnetic fields alone, or by their combination with magnetic materials such as nanoparticles, biocomposites, and coatings. Thus, this review is designed to summarize the studies on magnetic stimulation for bone regeneration. While providing information regarding the effects of magnetic fields on cells involved in bone tissue, this review discusses the advances made regarding the combination of magnetic fields with magnetic nanoparticles, magnetic scaffolds, and coatings and their subsequent influence on cells to reach optimal bone regeneration. In conclusion, several research works suggest that magnetic fields may play a role in regulating the growth of blood vessels, which are critical for tissue healing and regeneration. While more research is needed to fully understand the relationship between magnetism, bone cells, and angiogenesis, these findings promise to develop new therapies and treatments for various conditions, from bone fractures to osteoporosis.

Temporospatial Expression of Neuropeptide Substance P in Dental Pulp Stem Cells During Odontoblastic Differentiation in Vitro and Reparative Dentinogenesis in Vivo

INTRODUCTION

Substance P (SP) is a neuropeptide released from the nervous fibers in response to injury. In addition to its association with pain and reactions to anxiety and stress, SP exerts various physiological functions by binding to the neurokinin-1 receptor (NK1R). However, the expression and role of SP in reparative dentinogenesis remain elusive. Here, we explored whether SP is involved in odontoblastic differentiation during reparative dentinogenesis.

METHODS

Dental pulp stem cells (DPSCs) were isolated from healthy human dental pulp tissues and subjected to odontoblastic differentiation. The expression of SP and NK1R during odontoblastic differentiation was investigated in vitro. The effects of SP on odontoblastic differentiation of DPSCs were evaluated using alizarin red staining, alkaline phosphatase staining, and real-time polymerase chain reaction. After direct pulp capping with mineral trioxide aggregate, the expression of SP and NK1R during reparative dentin formation in rats were identified using histological and immunohistochemical staining.

RESULTS

SP and NK1R expression increased during the odontoblastic differentiation of DPSCs. SP translocated to the nucleus when DPSCs were exposed to differentiation medium. NK1R was always present in the nuclei of DPSCs and odontoblast-like cells. Additionally, we discovered that 10^-8 M SP marginally enhanced the odontoblastic differentiation of DPSCs, and that these effects could be impaired by the NK1R antagonist. Furthermore, SP and NK1R were expressed in odontoblast-like and dental pulp cells during reparative dentin formation in vivo.

CONCLUSIONS

SP contributes to odontoblastic differentiation during reparative dentin formation by binding to the NK1R.

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.

Insights into the Molecular Mechanisms Regulating Cell Behavior in Response to Magnetic Materials and Magnetic Stimulation in Stem Cell (Neurogenic) Differentiation

Magnetic materials and magnetic stimulation have gained increasing attention in tissue engineering (TE), particularly for bone and nervous tissue reconstruction. Magnetism is utilized to modulate the cell response to environmental factors and lineage specifications, which involve complex mechanisms of action. Magnetic fields and nanoparticles (MNPs) may trigger focal adhesion changes, which are further translated into the reorganization of the cytoskeleton architecture and have an impact on nuclear morphology and positioning through the activation of mechanotransduction pathways. Mechanical stress induced by magnetic stimuli translates into an elongation of cytoskeleton fibers, the activation of linker in the nucleoskeleton and cytoskeleton (LINC) complex, and nuclear envelope deformation, and finally leads to the mechanical regulation of chromatin conformational changes. As such, the internalization of MNPs with further magnetic stimulation promotes the evolution of stem cells and neurogenic differentiation, triggering significant changes in global gene expression that are mediated by histone deacetylases (e.g., HDAC 5/11), and the upregulation of noncoding RNAs (e.g., miR-106b~25). Additionally, exposure to a magnetic environment had a positive influence on neurodifferentiation through the modulation of calcium channels' activity and cyclic AMP response element-binding protein (CREB) phosphorylation. This review presents an updated and integrated perspective on the molecular mechanisms that govern the cellular response to magnetic cues, with a special focus on neurogenic differentiation and the possible utility of nervous TE, as well as the limitations of using magnetism for these applications.

Evidence of the static magnetic field effects on bone-related diseases and bone cells

Static magnetic fields (SMFs), magnetic fields with constant intensity and orientation, have been extensively studied in the field of bone biology both fundamentally and clinically as a non-invasive physical factor. A large number of animal experiments and clinical studies have shown that SMFs have effective therapeutic effects on bone-related diseases such as non-healing fractures, bone non-union of bone implants, osteoporosis and osteoarthritis. The maintenance of bone health in adults depends on the basic functions of bone cells, such as bone formation by osteoblasts and bone resorption by osteoclasts. Numerous studies have revealed that SMFs can regulate the proliferation, differentiation, and function of bone tissue cells, including bone marrow mesenchymal stem cells (BMSCs), osteoblasts, bone marrow monocytes (BMMs), osteoclasts, and osteocytes. In this paper, the effects of SMFs on bone-related diseases and bone tissue cells are reviewed from both in vivo studies and in vitro studies, and the possible mechanisms are analyzed. In addition, some challenges that need to be further addressed in the research of SMF and bone are also discussed.

Biological Impact of γ-Fe2O3 Magnetic Nanoparticles Obtained by Laser Target Evaporation: Focus on Magnetic Biosensor Applications

The biological activity of γ-Fe2O3 magnetic nanoparticles (MNPs), obtained by the laser target evaporation technique, was studied, with a focus on their possible use in biosensor applications. The biological effect of the MNPs was investigated in vitro on the primary cultures of human dermal fibroblasts. The effects of the MNPs contained in culture medium or MNPs already uptaken by cells were evaluated for the cases of the fibroblast’s proliferation and secretion of cytokines and collagen. For the tests related to the contribution of the constant magnetic field to the biological activity of MNPs, a magnetic system for the creation of the external magnetic field (having no commercial analogues) was designed, calibrated, and used. It was adapted to the size of standard 24-well cell culture plates. At low concentrations of MNPs, uptake by fibroblasts had stimulated their proliferation. Extracellular MNPs stimulated the release of pro-inflammatory cytokines (Interleukin-6 (IL-6) and Interleukin-8 (IL-8) or chemokine (C-X-C motif) ligand 8 (CXCL8)) in a concentration-dependent manner. However, the presence of MNPs did not increase the collagen secretion. The exposure to the uniform constant magnetic field (H ≈ 630 or 320 Oe), oriented in the plane of the well, did not cause considerable changes in fibroblasts proliferation and secretion, regardless of presence of MNPs. Statistically significant differences were detected only in the levels of IL-8/CXCL8 release.

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.

Influencing factors of pulp-dentin complex regeneration and related biological strategies

Regenerative endodontic therapy (RET) utilizing tissue engineering approach can promote the regeneration of pulp-dentin complex to restore pulp vascularization, neuralization, immune function and tubular dentin, therefore the regenerated pulp-dentin complex will have normal function. Multiple factors may significantly affect the efficacy of RET, including stem cells, biosignaling molecules and biomaterial scaffolds. Stem cells derived from dental tissues (such as dental pulp stem cells) exhibit certain advantages in RET. Combined application of multiple signaling molecules and activation of signal transduction pathways such as Wnt/β-catenin and BMP/Smad play pivotal roles in enhancing the potential of stem cell migration, proliferation, odontoblastic differentiation, and nerve and blood vessel regeneration. Biomaterials suitable for RET include naturally-derived materials and artificially synthetic materials. Artificially synthetic materials should imitate natural tissues for biomimetic modification in order to realize the temporal and spatial regulation of pulp-dentin complex regeneration. The realization of pulp-dentin complex regeneration depends on two strategies: stem cell transplantation and stem cell homing. Stem cell homing strategy does not require the isolation and culture of stem cells in vitro, so is better for clinical application. However, in order to achieve the true regeneration of pulp-dentin complex, problems related to improving the success rate of stem cell homing and promoting their proliferation and differentiation need to be solved. This article reviews the influencing factors of pulp-dentin complex regeneration and related biological strategies, and discusses the future research direction of RET, to provide reference for clinical translation and application of RET.

Effects of Magnetite Nanoparticles and Static Magnetic Field on Neural Differentiation of Pluripotent Stem Cells

Neurodevelopmental processes of pluripotent cells, such as proliferation and differentiation, are influenced by external natural forces. Despite the presence of biogenic magnetite nanoparticles in the central nervous system and constant exposure to the Earth's magnetic fields and other sources, there is scant knowledge regarding the role of electromagnetic stimuli in neurogenesis. Moreover, emerging applications of electrical and magnetic stimulation to treat neurological disorders emphasize the relevance of understanding the impact and mechanisms behind these stimuli. Here, the effects of magnetic nanoparticles (MNPs) in polymeric coatings and the static external magnetic field (EMF) were investigated on neural induction of murine embryonic stem cells (mESCs) and human induced pluripotent stem cells (hiPSCs). The results show that the presence of 0.5% MNPs in collagen-based coatings facilitates the migration and neuronal maturation of mESCs and hiPSCs in vitro. Furthermore, the application of 0.4 Tesla EMF perpendicularly to the cell culture plane, discernibly stimulates proliferation and guide fate decisions of the pluripotent stem cells, depending on the origin of stem cells and their developmental stage. Mechanistic analysis reveals that modulation of ionic homeostasis and the expression of proteins involved in cytostructural, liposomal and cell cycle checkpoint functions provide a principal underpinning for the impact of electromagnetic stimuli on neural lineage specification and proliferation. These findings not only explore the potential of the magnetic stimuli as neural differentiation and function modulator but also highlight the risks that immoderate magnetic stimulation may affect more susceptible neurons, such as dopaminergic neurons.

Melatonin enhances osteogenic differentiation of dental pulp mesenchymal stem cells by regulating MAPK pathways and promotes the efficiency of bone regeneration in calvarial bone defects

Background

Mesenchymal stem cell (MSC)-based tissue engineering plays a major role in regenerative medicine. However, the efficiency of MSC transplantation and survival of engrafted stem cells remain challenging. Melatonin can regulate MSC biology. However, its function in the osteogenic differentiation of dental pulp-derived MSCs (DPSCs) remains unclear. We investigated the effects and mechanisms of melatonin on the osteogenic differentiation and bone regeneration capacities of DPSCs.

Methods

The biological effects and signaling mechanisms of melatonin with different concentrations on DPSCs were evaluated using a proliferation assay, the quantitative alkaline phosphatase (ALP) activity, Alizarin red staining, a real-time polymerase chain reaction, and a western blot in vitro cell culture model. The in vivo bone regeneration capacities were assessed among empty control, MBCP, MBCP + DPSCs, and MBCP + DPSCs + melatonin preconditioning in four-created calvarial bone defects by using micro-computed tomographic, histological, histomorphometric, and immunohistochemical analyses after 4 and 8 weeks of healing.

Results

In vitro experiments revealed that melatonin (1, 10, and 100 μM) significantly and concentration-dependently promoted proliferation, surface marker expression (CD 146), ALP activity and extracellular calcium deposition, and osteogenic gene expression of DPSCs (p < 0.05). Melatonin activated the protein expression of ALP, OCN, and RUNX-2 and inhibited COX-2/NF-κB expression. Furthermore, the phosphorylation of mitogen-activated protein kinase (MAPK) p38/ERK signaling was significantly increased in DPSCs treated with 100 μM melatonin, and their inhibitors significantly decreased osteogenic differentiation. In vivo experiments demonstrated that bone defects implanted with MBCP bone-grafting materials and melatonin-preconditioned DPSCs exhibited significantly greater bone volume fraction, trabecular bone structural modeling, new bone formation, and osteogenesis-related protein expression than the other three groups at 4 and 8 weeks postoperatively (p < 0.05).

Conclusions

These results suggest that melatonin promotes the proliferation and osteogenic differentiation of DPSCs by regulating COX-2/NF-κB and p38/ERK MAPK signaling pathways. Preconditioning DPSCs with melatonin before transplantation can efficiently enhance MSCs function and regenerative capacities.

The Review of Bioeffects of Static Magnetic Fields on the Oral Tissue-Derived Cells and Its Application in Regenerative Medicine

Magnets have been widely used in dentistry for orthodontic tooth movement and denture retention. Nevertheless, criticisms have arisen regarding the biosafety of static magnetic field (SMF) effects on surrounding tissues. Various controversial pieces of evidence have been discussed regarding SMFs on cellular biophysics, but little consensus has been reached, especially in the field of dentistry. Thus, the present paper will first review the safe use of SMFs in the oral cavity and as an additive therapy to orthodontic tooth movement and periodontium regeneration. Then, studies regarding SMF-incorporated implants are reviewed to investigate the advantageous effects of SMFs on osseointegration and the underlying mechanisms. Finally, a review of current developments in dentistry surrounding the combination of magnetic nanoparticles (MNPs) and SMFs is made to clarify potential future clinical applications.

Comparison of Osteogenic Potentials of Dental Pulp and Bone Marrow Mesenchymal Stem Cells Using the New Cell Transplantation Platform, CellSaic, in a Rat Congenital Cleft-Jaw Model

Scaffolds stimulate cell proliferation and differentiation and play major roles in providing growth and nutrition factors in the repair of bone defects. We used the recombinant peptide Cellnest™ to prepare the three-dimensional stem cell complex, CellSaic, and evaluated whether CellSaic containing rat dental pulp stem cells (rDPSCs) was better than that containing rat bone marrow stem cells (rBMSCs). rDPSC-CellSaic or rBMSC-CellSaic, cultured with or without osteogenic induction medium, formed the experimental and control groups, respectively. Osteoblast differentiation was evaluated in vitro and transplanted into a rat model with a congenital jaw fracture. Specimens were collected and evaluated by microradiology and histological analysis. In the experimental group, the amount of calcium deposits, expression levels of bone-related genes (RUNX2, ALP, BSP, and COL1), and volume of mineralized tissue, were significantly higher than those in the control group (p < 0.05). Both differentiated and undifferentiated rDPSC-CellSaic and only the differentiated rBMSC-CellSaic could induce the formation of new bone tissue. Overall, rBMSC-CellSaic and rDPSC-CellSaic made with Cellnest™ as a scaffold, provide excellent support for promoting bone regeneration in rat mandibular congenital defects. Additionally, rDPSC-CellSaic seems a better source for craniofacial bone defect repair than rBMSC-CellSaic, suggesting the possibility of using DPSCs in bone tissue regenerative therapy.

Multicellular Spheroids Formation on Hydrogel Enhances Osteogenic/Odontogenic Differentiation of Dental Pulp Stem Cells Under Magnetic Nanoparticles Induction

Introduction

Promotion odontogenic differentiation of dental pulp stem cells (DPSCs) is essential for dentin regeneration. Physical cellular microenvironment is of critical importance for stem cells differentiation and influences the function of other biological/chemical factors to differentiation.

Methods

Based on adjusting the mechanical/interfacial properties of hydrogels, multicellular spheroids (MCSs) of DPSCs generated through self-organization. The spheroids were characterized by immunofluorescent staining and flow cytometry. Quantitative real-time polymerase chain reaction, alkaline phosphatase (ALP) activity assay, ALP staining and Alizarin Red S staining were performed to evaluate the osteogenic/odontogenic differentiation of DPSCs with or without magnetic iron oxide nanoparticles (IONPs) induction.

Results

MCSs of DPSCs exhibited a significant upregulation of E-cadherin and N-cadherin and enriched CD146 positive subpopulation, along with a stronger osteogenic/odontogenic differentiation ability. Moreover, DPSCs spheroids showed more substantial osteogenic differentiation tendency than the classical two-dimensional cultured DPSCs under the stimulation of magnetic IONPs.

Conclusion

Three-dimensional spheroids culture of DPSCs based on composite viscoelastic materials combined with mechanical/magnetic stimulation may provide a theoretical basis for the subsequent development of dentin or bone regeneration technology.

Effect of magnetic graphene oxide on cellular behaviors and osteogenesis under a moderate static magnetic field

The biological behaviors of magnetic graphene oxide (MGO) in a static magnetic field (SMF) are unknown. The current study is to investigate the cellular behaviors, osteogenesis and the mechanism in BMSCs treated with MGO combined with an SMF. Results showed that the synthetic MGO particles were bio-compatible and could significantly improve the osteogenesis of BMSCs under SMFs, as verified by elevated alkaline phosphatase activity, mineralized nodule formation, and expressions of mRNA and protein levels. Under SMF at the same intensity, the addition of graphene oxide to Fe₃O₄ could increase the osteogenic ability of BMSCs. The Wnt/β-catenin pathway was indicated to be related to the MGO-driven osteogenic behavior of the BMSCs under SMF. Taken together, our findings suggested that MGO under an SMF could promote osteogenesis in BMSCs through the Wnt/β-catenin pathway and hence should attract more attention for practical applications in bone tissue regeneration.

Electromagnetic field-assisted cell-laden 3D printed poloxamer-407 hydrogel for enhanced osteogenesis

3D bioprinted hydrogel has gained enormous attention, especially in tissue engineering, owing to its attractive structure and excellent biocompatibility. In this study, we demonstrated that 3D bioprinted cell-laden 'thermoresponsive' poloxamer-407 (P407) gels have the potential to stimulate osteogenic differentiation of apical papilla stem cells (SCAPs) under the influence of low voltage-frequency (5 V-1 Hz, 0.62 mT) electromagnetic fields (EMFs). SCAPs were initially used for cell-laden 3D printing to biomimic the apical papilla of human teeth. The developed hydrogel exhibited higher mechanical strength as well as good printability, showing high-quality micro-architecture. Moreover, the as-printed hydrogels (5 mm × 5 mm) were loaded with plasminogen activator inhibitor-1 (PAI-1) for testing the combined effect of PAI-1 and EMFs on SCAP differentiation. Interestingly, the 3D hydrogels showed improved viability and differentiation of SCAPs under EMFs' influence as examined by live/dead assay and alizarin Red-S staining, respectively. Therefore, our results confirmed that P407 hydrogels are non-toxic for encapsulation of SCAPs, yielding high cell viability and accelerate the cell migration potential. The 3D hydrogels with PAI-1 exhibited high mRNA expression levels for osteogenic/odontogenic gene markers (ALP, Col-1, DSPP, and DMP-1) vis-à-vis control after 14 days of in vitro culture. Our findings suggest that 3D bioprinted P407 hydrogels are biocompatible for SCAP encapsulation, and the applied low voltage-frequency EMFs could effectively improve dental tissue regeneration, particularly for oral applications.

Magnetic Properties of Iron Oxide Nanoparticles Do Not Essentially Contribute to Ferrogel Biocompatibility

Two series of composite polyacrylamide (PAAm) gels with embedded superparamagnetic Fe₂O₃ or diamagnetic Al₂O₃ nanoparticles were synthesized, aiming to study the direct contribution of the magnetic interactions to the ferrogel biocompatibility. The proliferative activity was estimated for the case of human dermal fibroblast culture grown onto the surfaces of these types of substrates. Spherical non-agglomerated nanoparticles (NPs) of 20-40 nm in diameter were prepared by laser target evaporation (LTE) electrophysical technique. The concentration of the NPs in gel was fixed at 0.0, 0.3, 0.6, or 1.2 wt.%. Mechanical, electrical, and magnetic properties of composite gels were characterized by the dependence of Young's modulus, electrical potential, magnetization measurements on the content of embedded NPs. The fibroblast monolayer density grown onto the surface of composite substrates was considered as an indicator of the material biocompatibility after 96 h of incubation. Regardless of the superparamagnetic or diamagnetic nature of nanoparticles, the increase in their concentration in the PAAm composite provided a parallel increase in the cell culture proliferation when grown onto the surface of composite substrates. The effects of cell interaction with the nanostructured surface of composites are discussed in order to explain the results.

The Role of Small Extracellular Vesicles Derived from Lipopolysaccharide-preconditioned Human Dental Pulp Stem Cells in Dental Pulp Regeneration

INTRODUCTION

Regenerative endodontics has created a desirable shift in the treatment paradigm despite current limitations of regenerative outcomes. Mesenchymal stem cells (MSCs) facilitate tissue regeneration and repair in a mild inflammatory environment. Small extracellular vesicles (sEVs) derived from MSCs play an imperative role in the paracrine modulation of regenerative responses modulated by MSCs. However, it remains unknown whether MSCs enhance dental pulp regeneration or whether this enhancement is mediated by sEVs in a mild inflammatory environment. The present study aimed to elucidate the effects of sEVs originated from lipopolysaccharide (LPS)-preconditioned human dental pulp stem cells (hDPSCs) on dental pulp regeneration.

METHODS

All sEVs were isolated from hDPSCs cultured with or without LPS (ie, N-sEVs and L-sEVs, respectively). The effect of N-sEVs and L-sEVs on proliferation, migration, angiogenesis, and differentiation of rat bone marrow MSCs was identified in vitro. Moreover, N-sEVs or L-sEVs were implanted into rat pulpless root canal models, and the regenerated tissue in root canals was assessed via hematoxylin-eosin staining, Masson staining, and immunohistochemistry after 30 days of transplantation.

RESULTS

Both N-sEVs and L-sEVs could modulate BMSC proliferation, migration, angiogenesis, and differentiation. Both kinds of sEVs enhanced the structure of the regenerated tissue closer to that of a normal dental pulp in vivo. L-sEVs had a more significant effect than N-sEVs.

CONCLUSIONS

sEVs released by hDPSCs in a mild inflammatory microenvironment are capable of facilitating the regeneration of dental pulp through functional healing instead of scar healing, which has potential applications in regenerative endodontics.

Stem Cell-based Dental Pulp Regeneration: Insights From Signaling Pathways

Deep caries, trauma, and severe periodontitis result in pulpitis, pulp necrosis, and eventually pulp loss. However, no clinical therapy can regenerate lost pulp. A novel pulp regeneration strategy for clinical application is urgently needed. Signaling transduction plays an essential role in regulating the regenerative potentials of dental stem cells. Cytokines or growth factors, such as stromal cell-derived factor (SDF), fibroblast growth factor (FGF), bone morphogenetic protein (BMP), vascular endothelial growth factor (VEGF), WNT, can promote the migration, proliferation, odontogenic differentiation, pro-angiogenesis, and pro-neurogenesis potentials of dental stem cells respectively. Using the methods of signaling modulation including growth factors delivery, genetic modification, and physical stimulation has been applied in multiple preclinical studies of pulp regeneration based on cell transplantation or cell homing. Transplanting dental stem cells and growth factors encapsulated into scaffold regenerated vascularized pulp-like tissue in the root canal. Also, injecting a flowable scaffold only with chemokines recruited endogenous stem/progenitor cells for pulp regeneration. Notably, dental pulp regeneration has gradually developed into the clinical phase. These findings enlightened us on a novel strategy for structural and functional pulp regeneration through elaborate modulation of signaling transduction spatially and temporally via clinically applicable growth factors delivery. But challenges, such as the adverse effects of unphysiological signaling activation, the controlled drug release system, and the safety of gene modulation, are necessary to be tested in future works for promoting the clinical translation of pulp regeneration.

Stimuli-Responsive Biomaterials: Scaffolds for Stem Cell Control

Stem cell fate is closely intertwined with microenvironmental and endogenous cues within the body. Recapitulating this dynamic environment ex vivo can be achieved through engineered biomaterials which can respond to exogenous stimulation (including light, electrical stimulation, ultrasound, and magnetic fields) to deliver temporal and spatial cues to stem cells. These stimuli-responsive biomaterials can be integrated into scaffolds to investigate stem cell response in vitro and in vivo, and offer many pathways of cellular manipulation: biochemical cues, scaffold property changes, drug release, mechanical stress, and electrical signaling. The aim of this review is to assess and discuss the current state of exogenous stimuli-responsive biomaterials, and their application in multipotent stem cell control. Future perspectives in utilizing these biomaterials for personalized tissue engineering and directing organoid models are also discussed.

Moderate SMFs attenuate bone loss in mice by promoting directional osteogenic differentiation of BMSCs

Background

Osteoporosis is a common metabolic bone disease without effective treatment. Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to differentiate into multiple cell types. Increased adipogenic differentiation or reduced osteogenic differentiation of BMSCs might lead to osteoporosis. Whether static magnetic fields (SMFs) might influence the adipo-osteogenic differentiation balance of BMSCs remains unknown.

Methods

The effects of SMFs on lineage differentiation of BMSCs and development of osteoporosis were determined by various biochemical (RT-PCR and Western blot), morphological (staining and optical microscopy), and micro-CT assays. Bioinformatics analysis was also used to explore the signaling pathways.

Results

In this study, we found that SMFs (0.2–0.6 T) inhibited the adipogenic differentiation of BMSCs but promoted their osteoblastic differentiation in an intensity-dependent manner. Whole genomic RNA-seq and bioinformatics analysis revealed that SMF (0.6 T) decreased the PPARγ-mediated gene expression but increased the RUNX2-mediated gene transcription in BMSCs. Moreover, SMFs markedly alleviated bone mass loss induced by either dexamethasone or all-trans retinoic acid in mice.

Conclusions

Taken together, our results suggested that SMF-based magnetotherapy might serve as an adjunctive therapeutic option for patients with osteoporosis.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13287-020-02004-y.

The effect of electromagnetic fields on survival and proliferation rate of dental pulp stem cells

Aims: Extremely low-frequency electromagnetic fields (ELF-EMF) can affect biological systems and alter some cell functions like proliferation rate. Dental pulp tissue is known as a source of multipotent stromal stem cells (MSCs), which can be obtained by a less invasive and more available process compared to bone marrow-derived stem cells (BMSCs). This study aimed to consider the effect of ELF-EMF on proliferation rates of human dental pulp stem cells (hDPSCs).Material and methods: ELF-EMF was generated by a system including autotransformer, multi-meter, solenoid coils, teslameter and its probe. The effect of ELF-EMF with the intensity of 0.5 and 1 mT and 50 Hz on the proliferation rate of hDPSCs was assessed in 20 and 40 min per day for 7 days. MTT assay and DAPI test were used to determine the growth and proliferation of DPSCs.Results: Based on MTT, ELF-EMF has maximum effect with the intensity of 1 mT for 20 min/day on the proliferation of hDPSCs. The survival and proliferation rate in all exposure groups were significantly higher than the control group. Based on the data obtained from MTT and DAPI assay, the number of viable cells in the group exposed to 1 mT for 20 min/day was higher than other groups (p < .05).Conclusions: Regarding to the results of this study, 0.5 and 1 mT ELF-EMF can enhance survival and proliferation rates of hDPSCs.

Effects of Sapindus mukorossi Seed Oil on Proliferation, Osteogenetic/Odontogenetic Differentiation and Matrix Vesicle Secretion of Human Dental Pulp Mesenchymal Stem Cells

Stem cells have attracted great interest in the development of tissue engineering. However, the self-regeneration and multi-differentiation capabilities of stem cells are easily impaired during cell transplantation. Recent studies have demonstrated that Sapindus mukorossi (S. mukorossi) seed oil has various positive biological effects. However, it is not yet clear whether S. mukorossi seed oil can increase the growth and differentiation of dental pulp mesenchymal stem cells (DPSCs). The aim of this study is to investigate the effects of S. mukorossi seed oil on the proliferation and differentiation of DPSCs. DPSCs with and without S. mukorossi seed oil, respectively, were evaluated and compared. The viabilities of the cells were assessed by MTT tests. The osteogenetic and odontogenetic capacities of the DPSCs were tested using Alizarin red S staining and alkaline phosphatase (ALP) activity assays. In addition, real-time PCR was performed to examine the gene expression of ALP, BMP-2 and DMP-1. Finally, extracellular matrix vesicle secretion was detected via scanning electron microscopy. No significant difference was observed in the viabilities of the DPSCs with and without S. mukorossi seed oil, respectively. However, under osteogenic and odontogenic induction, S. mukorossi seed oil increased the secretion of mineralized nodules and the ALP activity of the DPSCs (p < 0.05). The ALP gene expression of the differentiation-induced DPSCs was also enhanced. Finally, a greater secretion of extracellular matrix vesicles was detected in the DPSCs following odontogenic induction complemented with S. mukorossi seed oil. Overall, the present results show that S. mukorossi seed oil promotes the osteogenic/odontogenic differentiation and matrix vesicle secretion of DPSCs.

Effects of Constant Magnetic Field to the Proliferation Rate of Human Fibroblasts Grown onto Different Substrates: Tissue Culture Polystyrene, Polyacrylamide Hydrogel and Ferrogels γ-Fe2O3 Magnetic Nanoparticles

The static magnetic field was shown to affect the proliferation, adhesion and differentiation of various types of cells, making it a helpful tool for regenerative medicine, though the mechanism of its impact on cells is not completely understood. In this work, we have designed and tested a magnetic system consisting of an equidistant set of the similar commercial permanent magnets (6 × 4 assay) in order to get insight on the potential of its experimental usage in the biological studies with cells culturing in a magnetic field. Human dermal fibroblasts, which are widely applied in regenerative medicine, were used for the comparative study of their proliferation rate on tissue culture polystyrene (TCPS) and on the polyacrylamide ferrogels with 0.00, 0.63 and 1.19 wt % concentrations of γ-Fe₂O₃ magnetic nanoparticles obtained by the well-established technique of laser target evaporation. We used either the same batch as in previously performed but different biological experiments or the same fabrication conditions for fabrication of the nanoparticles. This adds special value to the understanding of the mechanisms of nanoparticles contributions to the processes occurring in the living systems in their presence. The magnetic field increased human dermal fibroblast cell proliferation rate on TCPS, but, at the same time, it suppressed the growth of fibroblasts on blank gel and on polyacrylamide ferrogels. However, the proliferation rate of cells on ferrogels positively correlated with the concentration of nanoparticles. Such a dependence was observed both for cell proliferation without the application of the magnetic field and under the exposure to the constant magnetic field.

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.

Comparing the Osteogenic Potentials and Bone Regeneration Capacities of Bone Marrow and Dental Pulp Mesenchymal Stem Cells in a Rabbit Calvarial Bone Defect Model

The bone regeneration efficiency of bone marrow mesenchymal stem cells (BMSCs) and dental pulp mesenchymal stem cells (DPSCs) combined with xenografts in the craniofacial region remains unclear. Accordingly, this study commenced by comparing the cell morphology, cell proliferation, trilineage differentiation, mineral synthesis, and osteogenic gene expression of BMSCs and DPSCs in vitro. Four experimental groups (empty control, Bio-Oss only, Bio-Oss+BMSCs, and Bio-Oss+DPSCs) were then designed and implanted in rabbit calvarial defects. The BMSCs and DPSCs showed a similar morphology, proliferative ability, surface marker profile, and trilineage-differentiation potential in vitro. However, the BMSCs exhibited a higher mineral deposition and expression levels of osteogenic marker genes, including alkaline phosphatase (ALP), runt related transcription factor 2 (RUNX2), and osteocalcin (OCN). In the in vivo studies, the bone volume density in both MSC groups was significantly greater than that in the empty control or Bio-Oss only group. Moreover, the new bone formation and Collagen I / osteoprotegerin protein expressions of the scaffold+MSC groups were higher than those of the Bio-Oss only group. Finally, the Bio-Oss+BMSC and Bio-Oss+DPSC groups had a similar bone mineral density, new bone formation, and osteogenesis-related protein expression. Overall, the DPSCs seeded on Bio-Oss matched the bone regeneration efficacy of BMSCs in vivo and hence appear to be a promising strategy for craniofacial defect repair in future clinical applications.

Strategies to enhance efficacy of SPION-labeled stem cell homing by magnetic attraction: a systemic review with meta-analysis

Stem cells possess a promising potential in the clinical field. The application and effective delivery of stem cells to the desired target organ or site of injury plays an important role. This review describes strategies on understanding the effective delivery of stem cells labeled with superparamagnetic iron oxide nanoparticles (SPION) using an external magnet to enhance stem cell migration in vivo and in vitro. Fourteen total publications among 174 articles were selected. Stem cell type, SPION characteristics, labeling time, and magnetic force in vivo are considered important factors affecting the effective delivery of stem cells to the homing site. Most papers reported that the efficiency was increased when magnet is applied compared to those without. Ten studies analyzed the homing competency of SPION-labeled MSCs in vitro by observing the migration of the cell toward the external magnet. In cell-based experiments, the mechanism of magnetic attraction, the kind of nanoparticles, and various stem cells were studied well. Meta-analysis has shown the mean size of nanoparticles and degree of recovery or regeneration of damaged target organs upon in vivo studies. This strategy may provide a guideline for designing studies involving stem cell homing and further expand stem cell.

Static Magnetic Field (SMF) as a Regulator of Stem Cell Fate - New Perspectives in Regenerative Medicine Arising from an Underestimated Tool

Tissue engineering and stem cell-based therapies are one of the most rapidly developing fields in medical sciences. Therefore, much attention has been paid to the development of new drug-delivery systems characterized by low cytotoxicity, high efficiency and controlled release. One of the possible strategies to achieve these goals is the application of magnetic field and/or magnetic nanoparticles, which have been shown to exert a wide range of effects on cellular metabolism. Static magnetic field (SMF) has been commonly used in medicine as a tool to increase wound healing, bone regeneration and as a component of magnetic resonance technique. However, recent data shed light on deeper mechanism of SMF action on physiological properties of different cell populations, including stem cells. In the present review, we focused on SMF effects on stem cell biology and its possible application as a tool for controlled drug delivery. We also highlighted the perspectives, in which SMF can be used in future therapies in tissue engineering due to its easy application and a wide range of possible effects on cells and organisms.

Novel magnetic calcium phosphate-stem cell construct with magnetic field enhances osteogenic differentiation and bone tissue engineering

Superparamagnetic iron oxide nanoparticles (IONPs) are promising bioactive additives to fabricate magnetic scaffolds for bone tissue engineering. To date, there has been no report on osteoinductivity of IONP-incorporated calcium phosphate cement (IONP-CPC) scaffold on stem cells using an exterior static magnetic field (SMF). The objectives of this study were to: (1) develop a novel magnetic IONP-CPC construct for bone tissue engineering, and (2) investigate the effects of IONP-incorporation and SMF application on the proliferation, osteogenic differentiation and bone mineral synthesis of human dental pulp stem cells (hDPSCs) seeded on IONP-CPC scaffold for the first time. The novel magnetic IONP-CPC under SMF enhanced the cellular performance of hDPSCs, yielding greater alkaline phosphatase activities (about 3-fold), increased expressions of osteogenic marker genes, and more cell-synthesized bone minerals (about 2.5-fold), compared to CPC control and nonmagnetic IONP-CPC. In addition, IONP-CPC induced more active osteogenesis than CPC control in rat mandible defects. These results were consistent with the enhanced cellular performance by magnetic IONP in media under SMF. Moreover, nano-aggregates were detected inside the cells by transmission electron microscopy (TEM). Therefore, the enhanced cell performance was attributed to the physical forces generated by the magnetic field together with cell internalization of the released magnetic nanoparticles from IONP-CPC constructs.

Magnetic field and nano-scaffolds with stem cells to enhance bone regeneration

Novel strategies utilizing magnetic nanoparticles (MNPs) and magnetic fields are being developed to enhance bone tissue engineering efficacy. This article first reviewed cutting-edge research on the osteogenic enhancements via magnetic fields and MNPs. Then the current developments in magnetic strategies to improve the cells, scaffolds and growth factor deliveries were described. The magnetic-cell strategies included cell labeling, targeting, patterning, and gene modifications. MNPs were incorporated to fabricate magnetic composite scaffolds, as well as to construct delivery systems for growth factors, drugs and gene transfections. The novel methods using magnetic nanoparticles and scaffolds with magnetic fields and stem cells increased the osteogenic differentiation, angiogenesis and bone regeneration by 2-3 folds over those of the controls. The mechanisms of magnetic nanoparticles and scaffolds with magnetic fields and stem cells to enhance bone regeneration were identified as involving the activation of signaling pathways including MAPK, integrin, BMP and NF-κB. Potential clinical applications of magnetic nanoparticles and scaffolds with magnetic fields and stem cells include dental, craniofacial and orthopedic treatments with substantially increased bone repair and regeneration efficacy.

Use of 0.4-Tesla static magnetic field to promote reparative dentine formation of dental pulp stem cells through activation of p38 MAPK signalling pathway

AIM

To investigate whether static magnetic fields (SMFs) have a positive effect on the migration and dentinogenesis of dental pulp stem cells (DPSCs) to promote reparative dentine formation.

METHODOLOGY

In vitro scratch assays and a traumatic pulp exposure model were performed to evaluate the effect of 0.4-Tesla (T) SMF on DPSC migration. The cytoskeletons of the DPSCs were identified by fluorescence immunostaining and compared with those of a sham-exposed group. Dentinogenic evaluation was performed by analysing the expressions of DMP-1 and DSPP marker genes using a quantitative real-time polymerase chain reaction (qRT-PCR) process. Furthermore, the formation of calcified deposits was examined by staining the dentinogenic DPSCs with Alizarin Red S dye. Finally, the role played by the p38 MAPK signalling pathway in the migration and dentinogenesis of DPSCs under 0.4-T SMF was investigated by incorporating p38 inhibitor (SB203580) into the in vitro DPSC experiments. The Student's t-test and the Kruskal-Wallis test followed by Dunn's post hoc test with a significance level of P < 0.05 were used for statistical analysis.

RESULTS

The scratch assay results revealed that the application of 0.4-T SMF enhanced DPSCs migration towards the scratch wound (P < 0.05). The cytoskeletons of the SMF-treated DPSCs were found to be aligned perpendicular to the scratch wound. After 20 days of culture, the SMF-treated group had a greater number of out-grown cells than the sham-exposed group (nonmagnetized control). For the SMF-treated group, the DMP-1 (P < 0.05) and DSPP genes (P < 0.05), analysed by qRT-PCR, exhibited a higher expression. The distribution of calcified nodules was also found to be denser in the SMF-treated group when stained with Alizarin Red S dye (P < 0.05). Given the incorporation of p38 inhibitor SB203580 into the DPSCs, cell migration and dentinogenesis were suppressed. No difference was found between the SMF-treated and sham-exposed cells (P > 0.05).

CONCLUSION

0.4-T SMF enhanced DPSC migration and dentinogenesis through the activation of the p38 MAPK-related pathway.

The role of hesperetin on osteogenesis of human mesenchymal stem cells and its function in bone regeneration

Hesperetin has been suggested to be involved in bone strength. We aimed to investigate the effects of hesperetin on the osteogenic differentiation of human mesenchymal stem cells and its related mechanisms. We showed that hesperetin promoted osteogenic differentiation of human mesenchymal stem cells in vitro. It potentially exerts its effects via the ERK and Smad signaling pathways. Using a rat osteotomy model, we showed that human mesenchymal stem cells combined with a hesperetin/gelatin sponge scaffold resulted in accelerated fracture healing in vivo. Due to the low cost of hesperetin, it could be used as a growth factor for bone tissue engineering or surgical fracture treatment.