Transplantation of mesenchymal stem cells from human umbilical cord versus human umbilical cord blood for peripheral nerve regeneration

BACKGROUND： Mesenchymal stem cells （MSCs） appear to be a good alternative to Schwann cells in the treatment of peripheral nerve injury. Fetal stem cells, like umbilical cord blood （UCB） and umbilical cord （UC） stem cells, have several advantages over adult stem cells. OBJECTIVE： To assess the effects of UC-derived MSCs （UCMSCs） and UCB-derived MSCs （UCBMSCs） in repair of sciatic nerve defects. DESIGN, TIME AND SETTING： A randomized controlled animal experiment was performed at the laboratory of Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital, from July to December 2009. MATERIALS： UCMSCs were provided by the Research Institute of Biotechnology, Dongguk University. UCBMSCs were provided by the Laboratory of Stem Cells and Tumor Biology, College of Veterinary Medicine, Seoul National University. Dulbecco＇s modified Eagle＇s medium （DMEM） was purchased from Gibco-BRL, USA. METHODS： Seven-week-old Sprague-Dawley rats were randomly and evenly divided into three groups： DMEM, UCBMSCs, and UCMSCs. A 10-mm defect in the left sciatic nerve was constructed in all rats. DMEM （15 μL） containing 1×10^6 UCBMSCs or UCMSCs was injected into the gap between nerve stumps, with the surrounding epineurium as a natural conduit. For the DMEM group, simple DMEM was injected. MAIN OUTCOME MEASURES： At 7 weeks after sciatic nerve dissection, dorsal root ganglia neurons were labeled by fluorogold retrograde labeling. At 8 weeks, electrophysiology and histomorphometry were performed. At 2, 4, 6, and 8 weeks after surgery, sciatic nerve function was evaluated using gait analysis. RESULTS： The UCBMSCs group and the UCMSCs group exhibited similar sciatic nerve function and electrophysiological indices, which were better than the DMEM group, as measured by gait analysis （P 〈 0.05）. Fluorogold retrograde labeling of sciatic nerve revealed that the UCBMSCs group demonstrated a higher number of labeled neurons; however, the differences were not significant. Histomorphometric indices were similar in the UCBMSCs and UCMSCs groups, and total axon counts, particularly axon density （P 〈 0.05）, were significantly greater in the UCBMSCs and UCMSCs groups than in the DMEM group. CONCLUSION： Transplanting either UCBMSCs or UCMSCs into axotomized sciatic nerves could accelerate and promote sciatic nerve regeneration over 8 weeks. Both treatments had similar effects on nerve regeneration.

Low-frequency pulsed electromagnetic field pretreated bone marrow-derived mesenchymal stem cells promote the regeneration of crush-injured rat mental nerve

Bone marrow-derived mesenchymal stem cells （BMSCs） have been shown to promote the regeneration of injured peripheral nerves. Pulsed electromagnetic field （PEMF） reportedly promotes the proliferation and neuronal differentiation of BMSCs. Low-frequency PEMF can induce the neuronal differentiation of BMSCs in the absence of nerve growth factors. This study was designed to investigate the effects of low-frequency PEMF pretreatment on the proliferation and function of BMSCs and the effects of low-frequency PEMF pre-treated BMSCs on the regeneration of injured peripheral nerve using in vitro and in vivo experiments.In in vitro experiments, quantitative DNA analysis was performed to determine the proliferation of BMSCs, and reverse transcription-polymerase chain reaction was performed to detect S100 （Schwann cell marker）, glial fibrillary acidic protein （astrocyte marker）, and brain-derived neurotrophic factor and nerve growth factor （neurotrophic factors） mRNA expression. In the in vivo experiments, rat models of crush-injured mental nerve established using clamp method were randomly injected with low-frequency PEMF pretreated BMSCs, unpretreated BMSCs or PBS at the injury site （1 × 106 cells）. DiI-labeled BMSCs injected at the injury site were counted under the fluorescence microscope to determine cell survival. One or two weeks after cell injection, functional recovery of the injured nerve was assessed using the sensory test with von Frey filaments. Two weeks after cell injection, axonal regeneration was evaluated using histomorphometric analysis and retrograde labeling of trigeminal ganglion neurons. In vitro experiment results revealed that low-frequency PEMF pretreated BMSCs proliferated faster and had greater mRNA expression of growth factors than unpretreated BMSCs. In vivo experiment results revealed that compared with injection of unpretreated BMSCs, injection of low-frequency PEMF pretreated BMSCs led to higher myelinated axon count and axon density and more DiI-labeled neurons in the trigeminal ganglia, contributing to rapider functional recovery of injured mental nerve. These findings suggest that low-frequency PEMF pretreatment is a promising approach to enhance the efficacy of cell therapy for peripheral nerve injury repair.

Human umbilical cord blood-derived mesenchymal stem cells promote regeneration of crush-injured rat sciatic nerves

Several studies have demonstrated that human umbilical cord blood-derived mesenchymal stem cells can promote neural regeneration following brain injury. However, the therapeutic effects of human umbilical cord blood-derived mesenchymal stem cells in guiding peripheral nerve regeneration remain poorly understood. This study was designed to investigate the effects of human umbilical cord blood-derived mesenchymal stem cells on neural regeneration using a rat sciatic nerve crush injury model. Human umbilical cord blood-derived mesenchymal stem cells （1 ~ 106） or a PBS control were injected into the crush-injured segment of the sciatic nerve. Four weeks after cell injection, brain-derived neurotrophic factor and tyrosine kinase receptor B mRNA expression at the lesion site was increased in comparison to control. Furthermore, sciatic function index, Fluoro Gold-labeled neuron counts and axon density were also significantly increased when compared with control. Our results indicate that human umbilical cord blood-derived mesenchvmal stem cells promote the functinnal r~.RcJv^rv nf P.n I^h-inillr^4 ~r^i~tit, n^r~e

Recombinant human fibroblast growth factor-2 promotes nerve regeneration and functional recovery after mental nerve crush injury

Several studies have shown that fibroblast growth factor-2 （FGF2） can directly affect axon regeneration after peripheral nerve damage. In this study, we performed sensory tests and histological analyses to study the effect of recombinant human FGF-2 （rhFGF2） treatment on damaged mental nerves. The mental nerves of 6-week-old male Sprague-Dawley rats were crush-injured for 1 minute and then treated with 10 or 50 μg/mL rhFGF2 or PBS in crush injury area with a mini Osmotic pump. Sensory test using von Frey filaments at 1 week revealed the presence of sensory degeneration based on decreased gap score and increased difference score. However, at 2 weeks, the gap score and difference score were significantly rebounded in the mental nerve crush group treated with 10 μg/mL rhFGF2. Interestingly, treatment with 10 μg/mL rhFGF had a more obviously positive effect on the gap score than treatment with 50 μg/mL rhFGF2. In addition, retrograde neuronal tracing with Dil revealed a significant increase in nerve regeneration in the trigeminal ganglion at 2 and 4 weeks in the rhFGF2 groups （10 μg/mL and 50 μg/mL） than in the PBS group. The 10 μg/mL rhFGF2 group also showed an obviously robust regeneration in axon density in the mental nerve at 4 weeks. Our results demonstrate that 10 μg/mL rhFGF induces mental nerve regeneration and sensory recovery after mental nerve crush injury.

Human periodontal ligament stem cells repair mental nerve injury

Human periodontal ligament stem cells are easily accessible and can differentiate into Schwann cells. We hypothesized that human periodontal ligament stem cells can be used as an alternative source for the autologous Schwann cells in promoting the regeneration of injured peripheral nerve. To validate this hypothesis, human periodontal ligament stem cells （1 × 106） were injected into the crush-injured left mental nerve in rats. Simultaneously, autologous Schwann cells （1 × 106） and PBS were also injected as controls. Real-time reverse transcriptase polymerase chain reaction showed that at 5 days after injection, mRNA expression of low affinity nerve growth factor receptor was sig-nificantaly increased in the left trigeminal ganglion of rats with mental nerve injury. Sensory tests, histomorphometric evaluation and retrograde labeling demonstrated that at 2 and 4 weeks after in-jection, sensory function was significantly improved, the numbers of retrograde labeled sensory neurons and myelinated axons were significantly increased, and human periodontal ligament stem cells and autologous Schwann cells exhibited similar therapeutic effects. These findings suggest that transplantation of human periodontal ligament stem cells show a potential value in repair of mental nerve injury.

Surface-roughened current collectors for anode-free all-solid-state batteries

Anode-free all-solid-state batteries(AFASSBs), composed of a fully lithiated cathode and a bare current collector(CC) that eliminates excess lithium, can maximize the energy density(because of a compact cell configuration) and improve the safety of solid-state systems. Although significant progress has been made by modifying CCs in liquid-based anode-free batteries, the role of CCs and the mechanism of Li formation on CCs in AFASSBs are still unexplored. Here, we systematically investigate the effect of the surface roughness of the CCs on the Li plating/stripping behavior in AFASSBs. The results show that the moderately roughened CC substantially improves the Coulombic efficiency and cycle stability of AFASSBs owing to the increased contact points between the solid electrolyte and the roughened CC. In contrast, the excessively roughened CC deteriorates the performance owing to the contact loss.Moreover, an ex situ interface analysis reveals that the roughened surface of the CC could suppress the interfacial degradation during the Li ion extraction from a sulfide solid electrolyte to a CC. This provides an indication to the origin that hinders the electrochemical performance of AFASSBs. These findings show the potential for the application of surface-engineered CCs in AFASSBs and provide guidelines for designing advanced CCs.

Peripheral nerve regeneration with cotransplantation of umbilical cord mesenchymal stem cells and Schwann cells in rat sciatic nerve defect

Previous research has demonstrated that cotransplantation of umbilical cord mesenchymal stem cells （UCMSCs） and Schwann cells （SCs） can repair spinal nerve injury, but few studies have investigated their use in peripheral nerve regeneration. In the present study, we cotransplanted UCMSCs and SCs to repair 5-mm left sciatic nerve defects in rats, and compared the effects of UCMSCs ＋ SCs transplantation with UCMSCs or SCs transplantation alone. After UCMSCs ＋ SCs transplantation, nerve conduction velocity of the left sciatic nerve and gait were both improved. Retrograde tracing analysis demonstrated that the mean count of fluorogold-labeled neurons, as well as the mean axon count and axon density, were significantly greater in the left sciatic nerve after UCMSCs ＋ SCs transplantation, compared with UCMSCs or SCs transplantation alone. Improvements in conduction velocity and increased sheath thickness in the left sciatic nerve were similar after UCMSCs transplantation and UCMSCs ＋ SCs transplantation. These findings suggest that UCMSCs transplantation can promote the repair of sciatic nerve defects to some extent, but that combined UCMSCs ＋ SCs transplantation has a significantly greater regenerative effect.

Construction of recombinant human nerve growth factor beta adenovirus and evaluation of its function An in vitro and in vivo study

Exogenous delivery of nerve growth factor （NGF） promotes neural regeneration. However, the short half-life limits delivery efficacy. Therefore, a long-term, efficient, local delivery tool or scheme is needed. The purpose of this study was to construct a functioning, recombinant, adenoviral vector carrying human NGF-β （hNGF-β） DNA, and to measure expression of the constructed vector in vitro and in vivo. rhNGF-β adenoviral vector containing full-length hNGF-β cDNA was generated by homologous recombination in Escherichia CoIL The rhNGF-β adenovirus was packaged and amplified in human embryonic kidney HEK293 cells. Transformation efficiency, expression and function of rhNGF-β adenovirus for primary Schwann cells, Schwann cell lines, human embryonic kidney HEK 293 cells, CRH myoblasts, and NIH3T3 fibroblasts were evaluated. Subsequently, expression of rhNGF-β adenovirus at the peripheral nerve of rat was also assessed. Recombinant adenoviral vector carrying hNGF-β was successfully constructed and confirmed by restriction endonuclease analysis and DNA sequence analysis. Green fluorescent protein expression was observed in 90% of rhNGF-β adenovirus-infected cells （primary Schwann cells, Schwann cell line, human embryonic kidney HEK 293 cells, CRH myoblasts, and NIH3T3 fibroblasts） compared with non-infected cells. Total mRNA isolated from rhNGF-β adenovirus-infected cells exhibited strong expression. Maximum NGF release was induced by primary cultured Schwann cells at 4 days after infection, which steadily continued for 14 days. PC-12 cells exposed to media conditioned with rhNGF-β adenovirus-infected Schwann cells exhibited increased neurite extension. In vivo experiment revealed that the injected rhNGF-β adenovirus was transfected into the cells at the injected site and promoted expression of NGF, p75NTR and brain derived neurotrophic factor at the sciatic nerve and dorsal root ganglia.

Traditional herbal medicines,Fuling,Baizhu,and Danggui,promote the proliferation of human Schwann cells

Enhancing Schwann cell proliferation may be beneficial for peripheral nerve repair and nerve regeneration. A traditional herbal formula composed of Fuling （poria cocos）, Baizhu （Atractylodes macrocephala）, and Danggui （Angelica sinensis） （FBD） improves neuronal survival and growth, and FBD may promote the secretion of brain-derived neurotrophic factor. However, the mechanism underlying Schwann cell proliferation remains unclear. We tested whether FBD enhanced the proliferation of human Schwann cells. FBD （20 ug/mL） increased Schwann cell viability and survival and increased the number of cells at G2/M and S phases. FBD also increased nerve growth factor and brain-derived neurotrophic factor expression in Schwann cells, with maximum efficacy at 20 ug/mL.

Blockade of PD-L1/PD-1 signaling promotes osteo-/odontogenic differentiation through Ras activation

The programmed cell death ligand 1(PD-L1)and its receptor programmed cell death 1(PD-1)deliver inhibitory signals to regulate immunological tolerance during immune-mediated diseases.However,the role of PD-1 signaling and its blockade effect on human dental pulp stem cells(h DPSCs)differentiation into the osteo-/odontogenic lineage remain unknown.We show here that PD-L1 expression,but not PD-1,is downregulated during osteo-/odontogenic differentiation of h DPSCs.Importantly,PD-L1/PD-1 signaling has been shown to negatively regulate the osteo-/odontogenic differentiation of h DPSCs.Mechanistically,depletion of either PD-L1 or PD-1 expression increased ERK and AKT phosphorylation levels through the upregulation of Ras enzyme activity,which plays a pivotal role during h DPSCs osteo-/odontogenic differentiation.Treatment with nivolumab(a human anti-PD-1 monoclonal antibody),which targets PD-1 to prevent PD-L1 binding,successfully enhanced osteo-/odontogenic differentiation of h DPSCs through enhanced Ras activity-mediated phosphorylation of ERK and AKT.Our findings underscore that downregulation of PD-L1 expression accompanies during osteo-/odontogenic differentiation,and h DPSCs-intrinsic PD-1 signaling inhibits osteo-/odontogenic differentiation.These findings provide a significant basis that PD-1 blockade could be effective immunotherapeutic strategies in h DPSCs-mediated dental pulp regeneration.

RIOX1-demethylated cGAS regulates ionizing radiation-elicited DNA repair

Exposure to radiation causes DNA damage;hence, continuous surveillance and timely DNA repair are important for genome stability. Epigenetic modifications alter the chromatin architecture, thereby affecting the efficiency of DNA repair. However, how epigenetic modifiers coordinate with the DNA repair machinery to modulate cellular radiosensitivity is relatively unknown. Here, we report that loss of the demethylase ribosomal oxygenase 1(RIOX1) restores cell proliferation and reduces cell death after exposure to ionizing radiation. Furthermore, RIOX1 depletion enhances homologous recombination(HR) repair but not nonhomologous endjoining(NHEJ) repair in irradiated bone marrow cells and oral mucosal epithelial cells. Mechanistic study demonstrates that RIOX1 removes monomethylation at K491 of cyclic GMP-AMP synthase(c GAS) to release c GAS from its interaction with the methyl-lysine reader protein SAGA complex-associated factor 29(SGF29), which subsequently enables c GAS to interact with poly(ADP-ribosyl)ated poly(ADP-ribose) polymerase 1(PARP1) at DNA break sites, thereby blocking PARP1-mediated recruitment of Timeless. High expression of RIOX1 maintains c GAS K491 me at a low level, which impedes HR repair and reduces cellular tolerance to ionizing radiation. This study highlights a novel RIOX1-dependent mechanism involved in the non-immune function of c GAS that is essential for the regulation of ionizing radiation-elicited HR repair.

Simulation study on short channel double-gate junctionless field-effect transistors

We study the characteristics of short channel double-gate(DG) junctionless(JL) FETs by device simulation. OutputⅠ-Ⅴcharacteristic degradations such as an extremely reduced channel length induced subthreshold slope increase and the threshold voltage shift due to variations of body doping and channel length have been systematically analyzed.Distributions of electron concentration,electric field and potential in the body channel region are also analyzed.Comparisons with conventional inversion-mode(IM) FETs,which can demonstrate the advantages of JL FETs,have also been performed.

Effect of Palladium Nanoparticles on Photocatalytic Characteristics of N doped Titania Catalyst

To improve the photocatalytic efficiency of TiO2nanotubular catalyst,N doped and Pd decorated titania nanotubes was successfully synthesized via anodizing,hydrazine hydrate treatment and photoreduction of Pd ions.The small Pd nanoparticles were precipitated on TiO2nanotubes through photoreduction of Pd ions,and its distribution is relatively homogeneous.From X-ray photoelectron spectrometry（XPS） result,the N 1s spectrum represents two peaks with binding energy at 399.7 and 400.7 eV,which suggests that the nitrogen elements doped by hydrazine hydrate treatment are located in interstitial sites of the TiO2crystalline structure.For N doped TiO2nanotubes with Pd particles,a high photocurrent was detected due to increase of interface charge carrier separation rate.Moreover,N doped and Pd decorated TiO2nanotubes exhibited much higher dye destruction efficiency and rate constant due to the synergistic effect of the N dopant and the Pd deposition on TiO2nanotubes.

Modeling of subthreshold characteristics for undoped and doped deep nanoscale short channel double-gate MOSFETs

A model of subthreshold characteristics for both undoped and doped double-gate （DG） MOSFETs has been proposed. The models were developed based on solution of 2-D Poisson＇s equation using variable separa- tion technique. Without any fitting parameters, our proposed models can exactly reflect the degraded subthreshold characteristics due to nanoscale channel length. Also, design parameters such as body thickness, gate oxide thick- ness and body doping concentrations can be directly reflected from our models. The models have been verified by comparing with device simulations＇ results and found very good agreement.

Graphene electrode with tunable charge transport in thin-film transistors

Graphene, a single atomic layer of sp2-hybridized carbon, has immense potential as a transparent conducting material in electronic applications owing to its superior properties, including optical transparency and high conductivity. Particularly, the tunable work function of graphene enables the integration of graphene electrodes with various electronic devices. To achieve high performance in graphene-based devices, effective charge transport between the graphene electrode and the semiconducting material needs to be optimized; this is closely related to the modulation of the Schottky barrier （SB）. In this study, we investigate the ~nable charge transport properties as a function of graphene doping in n-channel thin-film transistors （TFTs） in terms of the electrical characteristics and low-frequency noise （LFN） behaviors. Alkali metal carbonates tuned the work function of graphene, resulting in a dramatic decrease in the SB and an improvement of the carrier injection in n-channel TFTs. The electrical performance of the TFTs was evaluated by extraction of the field-effect mobilities and ratio of contact resistance to total resistance. Furthermore, the level of contact noise created by the barrier height fluctuation and relative contribution of channel noise and contact noise in the TFTs was investigated by LFN measurements to demonstrate the ~nable charge transport. Our findings therefore provide new insights into the tunable charge transport mechanism in graphene-based devices and reveal the immense potential of graphene as electrodes in high performance flexible and transparent displays.

Effects of Microstructure of Aluminum Substrate on Ordered Nanopore Arrays in Anodic Alumina

The effects of microstructure of aluminum substrate on regular nanopore arrangement in anodic alumina layer were investigated. The dissimilar microstructure and texture on aluminum sheets were prepared by various cold rollings and heat treatments, and anodic alumina nanoporous layers were fabricated by two step anodizing method at 40 V in oxalic acid solution. For the aluminum sheets with similar surface texture and annealing condition except purity, the regularity of the nanopore arrangement on the anodic alumina layer increased with purity of aluminum substrate. The difference of surface texture on AI sheets is not critical parameter for formation of ordered nanopore array compared with purity and heat treatment of substrate aluminum. The investigation suggested that the purity and reasonable annealing temperature of aluminum substrate are very important process to obtain the highly-ordered nanopore array on anodic alumina layer.