The impact of electrical charge on the viability and physiology of dendritic cells

Glioblastoma U-87 cell electrotaxis is hindered by doxycycline with a concomitant reduction in the matrix metallopeptidase-9 expression

Electric fields (EF) play an essential role in cancer cell migration. Numerous cancer cell types exhibit electrotaxis under direct current electric fields (dcEF) of physiological electric field strength (EFs). This study investigated the effects of doxycycline on the electrotactic responses of U87 cells. After EF stimulation, U87 cells migrated toward the cathode, whereas doxycycline-treated U87 cells exhibited enhanced cell mobility but hindered cathodal migration. We further investigated the expression of the metastasis-correlated proteins matrix metallopeptidase-2 (MMP-2) and MMP-9 in U87 cells. The levels of MMP-2 in the cells were not altered under EF or doxycycline stimulation. In contrast, the EF stimulation greatly enhanced the levels of MMP-9 and then repressed in doxycycline-cotreated cells, accompanied by reduced cathodal migration. Our results demonstrated that an antibiotic at a non-toxic concentration could suppress the enhanced cell migration accelerated by EF of physiological strength. This finding may be applied as an anti-metastatic treatment for cancers.

Cochlear implant-based electric-acoustic stimulation modulates neural stem cell-derived neural regeneration

Cochlear implantation is considered to be the best therapeutic method for profound sensorineural hearing loss, but insufficient numbers of functional spiral ganglion neurons hinder the clinical effects of cochlear implantation. Stem cell transplantation has the potential to provide novel strategies for spiral ganglion neuron regeneration after injury. However, some obstacles still need to be overcome, such as low survival and uncontrolled differentiation. Several novel technologies show promise for modulating neural stem cell behaviors to address these issues. Here, a device capable of electrical stimulation was designed by combining a cochlear implant with a graphene substrate. Neural stem cells (NSCs) were cultured on the graphene substrate and subjected to electrical stimulation transduced from sound waves detected by the cochlear implant. Cell behaviors were studied, and this device showed good biocompatibility for NSCs. More importantly, electric-acoustic stimulation with higher frequencies and amplitudes induced NSC death and apoptosis, and electric-acoustic stimulation could promote NSCs to proliferate and differentiate into neurons only when low-frequency stimulation was supplied. The present study provides experimental evidence for understanding the regulatory role of electric-acoustic stimulation on NSCs and highlights the potentials of the above-mentioned device in stem cell therapy for hearing loss treatment.

Doxycycline inhibits electric field-induced migration of non-small cell lung cancer (NSCLC) cells

Adenocarcinoma, large cell carcinoma and squamous cell carcinoma are the most commonly diagnosed subtypes of non-small cell lung cancers (NSCLC). Numerous lung cancer cell types have exhibited electrotaxis under direct current electric fields (dcEF). Physiological electric fields (EF) play key roles in cancer cell migration. In this study, we investigated electrotaxis of NSCLC cells, including human large cell lung carcinoma NCI-H460 and human lung squamous cell carcinoma NCI-H520 cells. Non-cancerous MRC-5 lung fibroblasts were included as a control. After dcEF stimulation, NCI-H460 and NCI-H520 cells, which both exhibit epithelial-like morphology, migrated towards the cathode, while MRC-5 cells, which have fibroblast-like morphology, migrated towards the anode. The effect of doxycycline, a common antibiotic, on electrotaxis of MRC-5, NCI-H460 and NCI-H520 cells was examined. Doxycycline enhanced the tested cells’ motility but inhibited electrotaxis in the NSCLC cells without inhibiting non-cancerous MRC-5 cells. Based on our finding, further in-vivo studies could be devised to investigate the metastasis inhibition effect of doxycycline in an organism level.

Effects of electrical stimulation on cell proliferation and apoptosis

The application of exogenous electrical stimulation (ES) to cells in order to manipulate cell apoptosis and proliferation has been widely investigated as a possible method of treatment in a number of diseases. Alteration of the transmembrane potential of cells via ES can affect various intracellular signaling pathways which are involved in the regulation of cellular function. Controversially, several types of ES have proved to be effective in both inhibiting or inducing apoptosis, as well as increasing proliferation. However, the mechanisms through which ES achieves this remain fairly unclear. The aim of this review was to comprehensively summarize current findings from in vitro and in vivo studies on the effects of different types of ES on cell apoptosis and proliferation, highlighting the possible mechanisms through which ES induced these effects and define the optimum parameters at which ES can be used. Through this we hope to provide a greater insight into how future studies can most effectively use ES at the clinical trial stage.

Pulsed DC Electric Field-Induced Differentiation of Cortical Neural Precursor Cells

We report the differentiation of neural stem and progenitor cells solely induced by direct current (DC) pulses stimulation. Neural stem and progenitor cells in the adult mammalian brain are promising candidates for the development of therapeutic neuroregeneration strategies. The differentiation of neural stem and progenitor cells depends on various in vivo environmental factors, such as nerve growth factor and endogenous EF. In this study, we demonstrated that the morphologic and phenotypic changes of mouse neural stem and progenitor cells (mNPCs) could be induced solely by exposure to square-wave DC pulses (magnitude 300 mV/mm at frequency of 100-Hz). The DC pulse stimulation was conducted for 48 h, and the morphologic changes of mNPCs were monitored continuously. The length of primary processes and the amount of branching significantly increased after stimulation by DC pulses for 48 h. After DC pulse treatment, the mNPCs differentiated into neurons, astrocytes, and oligodendrocytes simultaneously in stem cell maintenance medium. Our results suggest that simple DC pulse treatment could control the fate of NPCs. With further studies, DC pulses may be applied to manipulate NPC differentiation and may be used for the development of therapeutic strategies that employ NPCs to treat nervous system disorders.

A non-aggressive, highly efficient, enzymatic method for dissociation of human brain-tumors and brain-tissues to viable single-cells

Background

Conducting research on the molecular biology, immunology, and physiology of brain tumors (BTs) and primary brain tissues requires the use of viably dissociated single cells. Inadequate methods for tissue dissociation generate considerable loss in the quantity of single cells produced and in the produced cells’ viability. Improper dissociation may also demote the quality of data attained in functional and molecular assays due to the presence of large quantities cellular debris containing immune-activatory danger associated molecular patterns, and due to the increased quantities of degraded proteins and RNA.

Results

Over 40 resected BTs and non-tumorous brain tissue samples were dissociated into single cells by mechanical dissociation or by mechanical and enzymatic dissociation. The quality of dissociation was compared for all frequently used dissociation enzymes (collagenase, DNase, hyaluronidase, papain, dispase) and for neutral protease (NP) from Clostridium histolyticum. Single-cell-dissociated cell mixtures were evaluated for cellular viability and for the cell-mixture dissociation quality. Dissociation quality was graded by the quantity of subcellular debris, non-dissociated cell clumps, and DNA released from dead cells. Of all enzymes or enzyme combinations examined, NP (an enzyme previously not evaluated on brain tissues) produced dissociated cell mixtures with the highest mean cellular viability: 93 % in gliomas, 85 % in brain metastases, and 89 % in non-tumorous brain tissue. NP also produced cell mixtures with significantly less cellular debris than other enzymes tested. Dissociation using NP was non-aggressive over time—no changes in cell viability or dissociation quality were found when comparing 2-h dissociation at 37 °C to overnight dissociation at ambient temperature.

Conclusions

The use of NP allows for the most effective dissociation of viable single cells from human BTs or brain tissue. Its non-aggressive dissociative capacity may enable ambient-temperature shipping of tumor pieces in multi-center clinical trials, meanwhile being dissociated. As clinical grade NP is commercially available it can be easily integrated into cell-therapy clinical trials in neuro-oncology. The high quality viable cells produced may enable investigators to conduct more consistent research by avoiding the experimental artifacts associated with the presence dead cells or cellular debris.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-016-0262-y) contains supplementary material, which is available to authorized users.

Graphene scaffolds in progressive nanotechnology/stem cell-based tissue engineering of the nervous system

Although graphene/stem cell-based tissue engineering has recently emerged and has promisingly and progressively been utilized for developing one of the most effective regenerative nanomedicines, it suffers from low differentiation efficiency, low hybridization after transplantation and lack of appropriate scaffolds required in implantations without any degrading in functionality of the cells. In fact, recent studies have demonstrated that the unique properties of graphene can successfully resolve all of these challenges. Among various stem cells, neural stem cells (NSCs) and their neural differentiation on graphene have attracted a lot of interest, because graphene-based neuronal tissue engineering can promisingly realize the regenerative therapy of various incurable neurological diseases/disorders and the fabrication of neuronal networks. Hence, in this review, we further focused on the potential bioapplications of graphene-based nanomaterials for the proliferation and differentiation of NSCs. Then, various stimulation techniques (including electrical, pulsed laser, flash photo, near infrared (NIR), chemical and morphological stimuli) which have recently been implemented in graphene-based stem cell differentiations were reviewed. The possibility of degradation of graphene scaffolds (NIR-assisted photodegradation of three-dimensional graphene nanomesh scaffolds) was also discussed based on the latest achievements. The biocompatibility of graphene scaffolds and their probable toxicities (especially after the disintegration of graphene scaffolds and distribution of its platelets in the body), which is still an important challenge, were reviewed and discussed. Finally, the initial recent efforts for fabrication of neuronal networks on graphene materials were presented. Since there has been no in vivo application of graphene in neuronal regenerative medicine, we hope that this review can excite further and concentrated investigations on in vivo (and even in vitro) neural proliferation, stimulation and differentiation of stem cells on biocompatible graphene scaffolds having the potential of degradability for the generation of implantable neuronal networks.

Near infrared laser stimulation of human neural stem cells into neurons on graphene nanomesh semiconductors

Reduced graphene oxide nanomeshes (rGONMs), as p-type semiconductors with band-gap energy of ∼ 1 eV, were developed and applied in near infrared (NIR) laser stimulation of human neural stem cells (hNSCs) into neurons. The biocompatibility of the rGONMs in growth of hNSCs was found similar to that of the graphene oxide (GO) sheets. Proliferation of the hNSCs on the GONMs was assigned to the excess oxygen functional groups formed on edge defects of the GONMs, resulting in superhydrophilicity of the surface. Under NIR laser stimulation, the graphene layers (especially the rGONMs) exhibited significant cell differentiations, including more elongations of the cells and higher differentiation of neurons than glia. The higher hNSC differentiation on the rGONM than the reduced GO (rGO) was assigned to the stimulation effects of the low-energy photoexcited electrons injected from the rGONM semiconductors into the cells, while the high-energy photoelectrons of the rGO (as a zero band-gap semiconductor) could suppress the cell proliferation and/or even cause cell damages. Using conventional heating of the culture media up to ∼ 43 °C (the temperature typically reached under the laser irradiation), no significant differentiation was observed in dark. This further confirmed the role of photoelectrons in the hNSC differentiation.

Flash photo stimulation of human neural stem cells on graphene/TiO2 heterojunction for differentiation into neurons

For the application of human neural stem cells (hNSCs) in neural regeneration and brain repair, it is necessary to stimulate hNSC differentiation towards neurons rather than glia. Due to the unique properties of graphene in stem cell differentiation, here we introduce reduced graphene oxide (rGO)/TiO2 heterojunction film as a biocompatible flash photo stimulator for effective differentiation of hNSCs into neurons. Using the stimulation, the number of cell nuclei on rGO/TiO2 increased by a factor of ~1.5, while on GO/TiO2 and TiO2 it increased only ~48 and 24%, respectively. Moreover, under optimum conditions of flash photo stimulation (10 mW cm(-2) flash intensity and 15.0 mM ascorbic acid in cell culture medium) not only did the number of cell nuclei and neurons differentiated on rGO/TiO2 significantly increase (by factors of ~2.5 and 3.6), but also the number of glial cells decreased (by a factor of ~0.28). This resulted in a ~23-fold increase in the neural to glial cell ratio. Such highly accelerated differentiation was assigned to electron injection from the photoexcited TiO2 into the cells on the rGO through Ti-C and Ti-O-C bonds. The role of ascorbic acid, as a scavenger of the photoexcited holes, in flash photo stimulation was studied at various concentrations and flash intensities.

Enhanced maturation and function of dendritic cells using hydrogel coated plate and antigen electroporation

Dendritic cells (DCs) are potent antigen-presenting cells that can be matured in vitro from immature dendritic cells (iDCs) in the presence of several biological agents such as cytokine cocktail, CD40L, TNF-a and antigen loading, which are necessary and achieved using various protocols, such as lipofection, passive pulse or electroporation. However, these DCs maturation protocols may cause with a significant loss of cells because of cellular attachment and spreading during culturing. Some biomaterials that influence adhesion and development of cells have been used in cell culture techniques, and it was thought that they might be applied on the culture of DCs. In this study, we used polyHEMA, which is a hydrogel coating biomaterial that prevents DCs from adherence, and investigated whether hydrogel coating affects the maturation of iDCs. The efficiency in the generation of mDCs was improved through hydrogel coating procedure and a dendritic cell maturation marker, CD83, was significantly increased in hydrogel-coated culture condition. The antigen-loaded mDCs from electroporation were further expressed the CD83. The mDCs generated in the hydrogel-coated culture condition showed more, longer and thicker dendrites, and produced more amounts of cytokines such as IL-12 and IFN-γ. Therefore, it was suggested that the hydrogel-coated culture condition could improve function of mDCs. Cheol-Hun Son and Jae-Ho Bae contributed equally to this work.

Effective clinical-scale production of dendritic cell vaccines by monocyte elutriation directly in medium, subsequent culture in bags and final antigen loading using peptides or RNA transfection

Dendritic cell (DC) vaccination approaches are advancing fast into the clinic. The major obstacle for further improvement is the current lack of a simple functionally "closed" system to generate standardized monocyte-derived (mo) DC vaccines. Here, we significantly optimized the use of the Elutra counterflow elutriation system to enrich monocytic DC precursors by (1) developing an algorithm to avoid red blood cell debulking and associated monocyte loss before elutriation, and (2) by elutriation directly in culture medium rather than phosphate-buffered saline. Upon elutriation the bags containing the collected monocytes are simply transferred into the incubator to generate DC progeny as the final "open" washing step is no longer required. Elutriation resulted in significantly more (> or = 2-fold) and purer DC than the standard gradient centrifugation/adherence-based monocyte enrichment, whereas morphology, maturation markers, viability, migratory capacity, and T cell stimulatory capacity were identical. Subsequently, we compared RNA transfection, as this is an increasingly used approach to load DC with antigen. Elutra-derived and adherence-derived DC could be electroporated with similar, high efficiency (on average >85% green fluorescence protein positive), and appeared also equal in antigen expression kinetics. Both Elutra-derived and adherence-derived DC, when loaded with the MelanA peptide or electroporated with MelanA RNA, showed a high T cell stimulation capacity, that is, priming of MelanA-specific CD8+ T cells. Our optimized Elutra-based procedure is straightforward, clearly superior to the standard gradient centrifugation/plastic adherence protocol, and now allows the generation of large numbers of peptide-loaded or RNA-transfected DC in a functionally closed system.