Antioxidants N-acetylcysteine (NAC) and 2-mercaptoethanol (2-ME) affect the survival and differentiative potential of cholinergic precursors from the embryonic septal nuclei and basal forebrain: involvement of ras signaling

β-mercaptoethanol promotes osteogenesis of human mesenchymal stem cells via sirt1-ERK pathway

Human umbilical cord-derived mesenchymal stem cells (hUMSCs) hold strong self-renewal capacity and low immunogenicity, which have attracted attention as potential candidates for bone repair and regeneration. However, insufficient osteogenic differentiation markedly hinders the clinical applications of hUMSCs. In the present study, the effect of β-mercaptoethanol (BME), a small molecule antioxidant which has been identified to regulate cell proliferation and differentiation, on osteogenic differentiation of hUMSCs and underlying signaling mechanism were investigated. The results indicated that under osteogenic induction conditions, BME treatment increased the alkaline phosphatase (ALP) activity and promoted calcium mineralization in hUMSCs. The gene and protein expression of osteogenesis-related markers such as ALP, osteopontin (OPN), osteocalcin (OCN) and collagen type I (COLI) were also significantly up-regulated. Besides, BME promoted the protein expression of silent information regulator type 1 (sirt1) and stimulated the activation of extracellular signal-related kinase (ERK), contributing to increased Runx2 expression. Furthermore, blocking the expression of sirt1 attenuated BME-enhanced ERK phosphorylation and osteogenic differentiation of hUMSCs. These results indicated that BME accelerated osteogenic differentiation of hUMSCs by activating the sirt1-ERK signaling pathway, thereby providing insights into the development of MSCs-based bone regeneration strategies.

Trans-Differentiation of Human Dental Pulp Stem Cells Into Cholinergic-Like Neurons Via Nerve Growth Factor

Introduction:

Cell therapy has been widely considered as a therapeutic approach for neurodegenerative diseases and nervous system damage. Cholinergic neurons as one of the most important neurons that play a significant role in controlling emotions, mobility, and autonomic systems. In this study, Human Dental Pulp Stem Cells (hDPSCs) were differentiated into the cholinergic neurons by β-mercaptoethanol in the preinduction phase and also by the nerve growth factor (NGF) in the induction phase.

Methods:

The hDPSCs were evaluated for CD73, CD31, CD34, and Oct-4. Concentration-time relationships for NGF were assessed by evaluating the viability rate of cells and the immune response to nestin, neurofilament 160, microtubule-associated protein-2, and choline acetyltransferase.

Results:

The hDPSCs had a negative response to CD34 and CD31. The optimal dose for the NGF was 50 ng/mL seven days after the induction when the highest percentage of expressing markers for the Cholinergic neurons (ChAT) was detected.

Conclusion:

The results of this study provided a method for producing cholinergic neurons by hDPSCs, which can be used in cytotherapy for degenerative diseases of the nervous system and also spinal cord injury.

Comparative analysis of three different protocols for cholinergic neuron differentiation in vitro using mesenchymal stem cells from human dental pulp

A decrease in the activity of choline acetyltransferase, the enzyme responsible for acetylcholine synthesis in the cholinergic neurons cause neurological disorders involving a decline in cognitive abilities, such as Alzheimer's disease. Mesenchymal stem cells (MSCs) can be used as an efficient therapeutic agents due to their neuronal differentiation potential. Different source derived MSCs may have different differentiation potential under different inductions. Various in vitro protocols have been developed to differentiate MSCs into specific neurons but the comparative effect of different protocols utilizing same source derived MSCs, is not known. To address this issue, dental pulp derived MSCs (DPSCs) were differentiated into cholinergic neurons using three different protocols. In protocol I, DPSCs were pre-induced with serum-free ADMEM containing 1 mM of β-mercaptoethanol for 24 h and then incubated with 100 ng/ml nerve growth factor (NGF) for 6 days. Under protocol II, DPSCs were cultured in serum-free ADMEM containing 15 µg/ml of D609 (tricyclodecan-9-yl-xanthogenate) for 4 days. Under protocol III, the DPSCs were cultured in serum-free ADMEM containing 10 ng/ml of basic fibroblast growth factor (bFGF), 50 µM of forskolin, 250 ng/ml of sonic hedgehog (SHH), and 0.5 µM of retinoic acid (RA) for 7 days. The DPSCs were successfully trans-differentiated under all the protocols, exhibited neuron-like morphologies with upregulated cholinergic neuron-specific markers such as ChAT, HB9, ISL1, BETA-3, and MAP2 both at mRNA and protein levels in comparison to untreated cells. However, protocol III-induced cells showed the highest expression of the cholinergic markers and secreted the highest level of acetylcholine.

An Overview of Protocols for the Neural Induction of Dental and Oral Stem Cells In Vitro

To date, various adult stem cells have been identified within the oral cavity, including dental pulp stem cells, dental follicle stem cells, stem cells from apical papilla, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, and mesenchymal stem cells from the gingiva. All of these possess neurogenic potential due to their common developmental origin from the embryonic neural crest. Besides the relative ease of isolation of these adult stem cells from readily available biological waste routinely produced during dental treatment, these cells also possess the advantage of immune compatibility in autologous transplantation. In recent years, much interest has been focused on the derivation of neural lineages from these adult stem cells for therapeutic applications in the brain, spinal cord, and peripheral nerve regeneration. In addition, there are also promising nontherapeutic applications of stem cell-derived neurons in pharmacological and toxicological screening of neuroactive drugs, and for in vitro modeling of neurodevelopmental and neurodegenerative diseases. Hence, this review will critically examine the diverse array of in vitro neural induction protocols that have been devised for dental and oral-derived stem cells. These protocols are defined not only by the culture milieu comprising the basal medium plus growth factors, small molecules, and other culture supplements but also by the substrata/surface coatings utilized, the presence of multiple culture stages, the total culture duration, the initial seeding density, and whether the spheroid/neurosphere formation is being utilized to recapitulate the three-dimensional neural differentiation microenvironment that is naturally present physiologically in vivo.

A new multistep induction protocol for the transdifferentiation of bone marrow stromal stem cells into GABAergic neuron-like cells

BACKGROUND

Bone marrow stromal stem cells (BMSC) are appropriate source of multipotent stem cells that are ideally suited for use in various cell-based therapies. It can be differentiated into neuronal-like cells under appropriate conditions. This study examined the effectiveness of co-stimulation of creatine and retinoic acid in increasing the differentiation of BMSC into GABAergic neuron-like cells (GNLC).

METHODS

BMSC isolated from the femurs and tibias of adult rats were cultured in DMEM/F12 medium supplemented with 10% FBS, pre-induced using β-mercaptoethanol β-ME) and induced using retinoic acid (RA) and creatine. Immunostaining of neurofilament 200 kDa, neurofilament 160 kDa, nestin, fibronectin, Gamma-amino butyric acid (GABA) and glutamic acid decarboxylase (GAD) 65/67 were used to evaluate the transdifferentiation of BMSC into GNLC and to evaluate the effectiveness of pre-induction and induction assays. The expression of genes that encode fibronectin, octamer-binding transcription factor 4 (Oct-4), GAD 65/67 and the vesicular GABA transporter was examined in BMSC and GNLC by using RT-PCR assays during transdifferentiation of BMSC into GLNC.

RESULTS

Co-stimulation with RA and creatine during the induction stage doubled the rates of GABAergic differentiation compared with induction using creatine alone, resulting in a 71.6% yield for GLNC. RT-PCR showed no expression of Oct-4 and fibronectin after the induction stage.

CONCLUSION

The results of this study showed that the application of β-ME, RA, and creatine induced the transdifferentiation of BMSC into GLNC.

Transdifferentiation of bone marrow stromal cells into cholinergic neuronal phenotype: a potential source for cell therapy in spinal cord injury

BACKGROUND AIMS

Cholinergic neurons are very important cells in spinal cord injuries because of the deficits in motor, autonomic and sensory neurons. In this study, bone marrow stromal cells (BMSC) were evaluated as a source of cholinergic neurons in a rat model of contusive spinal cord injury.

METHODS

BMSC were isolated from adult rats and transdifferentiated into cholinergic neuronal cells. The BMSC were pre-induced with beta-mercaptoethanol (BME), while the induction was done with nerve growth factor (NGF). Neurofilament (NF)-68, -160 and -200 immunostaining was used for evaluating the transdifferentiation of BMSC into a neuronal phenotype. NeuroD expression, a marker for neuroblast differentiation, and Oct-4 expression, a marker for stemness, were evaluated by reverse transcriptase (RT)-polymerase chain reaction (PCR). Choline acetyl transferase (ChAT) immunoreactivity was used for assessing the cholinergic neuronal phenotype. Anti-microtubule-associated protein-2 (MAP-2) and anti-synapsin I antibodies were used as markers for the tendency for synptogenesis. Finally, the induced cells were transplanted into the contused spinal cord and locomotion was evaluated with the Basso-Beattie-Bresnahan (BBB) test.

RESULTS

At the induction stage, there was a decline in the expression of NF-68 associated with a sustained increase in the expression of NF-200, NF-160, ChAT and synapsin I, whereas MAP-2 expression was variable. Transplanted cells were detected 6 weeks after their injection intraspinally and were associated with functional recovery.

CONCLUSIONS

The transdifferentiation of BMSC into a cholinergic phenotype is feasible for replacement therapy in spinal cord injury.

Induction of mesenchymal stem cells leads to HSP72 synthesis and higher resistance to oxidative stress

The phenomenon of neuronal transdifferentiation performed on bone marrow mesenchymal stem cells (MSCs) has been criticized by recent studies indicating that acquired neuron-like morphology of induced MSCs is caused by cellular stress. Therefore, to test this hypothesis we have investigated whether exposure of rat MSCs (rMSCs) to chemical inducer 2 mM beta-mercaptoethanol (BME) for 1-3 h followed by 24 h incubation leads to HSP72 synthesis, thus suggesting higher resistance of rMSCs to oxidative damage. Present data from immunohistochemistry clearly indicate development of time-dependent sub-cellular HSP72 distribution, initially seen in nuclei at 1 h followed by its translocation to surrounding central cytoplasm and processes at 2-3 h after BME stimulation. Western blot (WB) analysis confirmed the expression of HSP72 protein in induced rMSCs at both stimulation periods. Furthermore, preconditioned rMSCs with BME for 1 h expressing HSP72 positivity at 24 h showed higher resistance (78 +/- 10% of survival cells) to oxidative stress caused by 1 mM H(2)O(2) when compared to those preconditioned for 3 h (59 +/- 8% of survival cells) or control-unconditioned rMSCs exposed to the same stressor conditions (56 +/- 6% of survival cells). Thus, the cellular protection was lost if the duration of BME preconditioning was increased as far as possible (3 h) (while still remaining sub-lethal). This suggests that exposure of rMSCs to the optimal concentration of BME (2 mM) during optimal induction period (1 h) mediate their protection and increases resistance to oxidative injury, while over crossing these limits is in-effective. In addition, our findings confirm that cultured rMSCs remain competent to be preconditioned by BME, through a pathway that may increase the antioxidant balance or involve activation of HSP72 protein induced tolerance.

The neuronal differentiation process involves a series of antioxidant proteins

Involvement of individual antioxidant proteins (AOXP) and antioxidants in the differentiation process has been already reported. A systematic search strategy for detecting differentially regulated AOXP in neuronal differentiation, however, has not been published so far. The aim of this study was to provide an analytical tool identifying AOXP and to generate a differentiation-related AOXP expressional pattern. The undifferentiated N1E-115 neuroblastoma cell line was switched into a neuronal phenotype by DMSO treatment and used for proteomic experiments: We used two-dimensional gel electrophoresis followed by unambiguous mass spectrometrical (MALDI-TOF-TOF) identification of proteins to generate a map of AOXP. 16 AOXP were unambiguously determined in both cell lines; catalase, thioredoxin domain-containing protein 4 and hypothetical glutaredoxin/glutathione S-transferase C terminus-containing protein were detectable in the undifferentiated cells only. Five AOXP were observed in both, undifferentiated and differentiated cells and thioredoxin, thioredoxin-like protein p19, thioredoxin reductase 1, superoxide dismutases (Mn and Cu-Zn), glutathione synthetase, glutathione S-transferase P1 and Mu1 were detected in differentiated cells exclusively. Herein a differential expressional pattern is presented that reveals so far unpublished antioxidant principles involved in neuronal differentiation by a protein chemical approach, unambiguously identifying AOXP. This finding not only shows concomitant determination of AOXP but also serves as an analytical tool and forms the basis for design of future studies addressing AOXP and differentiation per se.

Induction of bone marrow stromal cells to neurons: differentiation, transdifferentiation, or artifact?

Differentiation of stem cells toward a neuronal lineage normally involves a gradually progressive restriction in developmental potential and is regulated by a diverse set of specific and temporally precise genetic events. However, recent studies have indicated that both rodent and human bone marrow stromal cells (MSCs) can be rapidly (within minutes to hours) induced to differentiate into neurons in vitro by relatively simple chemical means (using beta-mercaptoethanol [BME] or dimethylsulfoxide [DMSO] and butylated hydroxyanisol [BHA]; Woodbury et al. [ 2000] J. Neurosci. Res. 61:364-370). The ability to transdifferentiate an easily accessible cell source into neurons could have substantial potential for promoting neural repair. We therefore explored the potential of simple chemical methods to transdifferentiate other cell types, including primary rat fibroblasts, primary human keratinocytes, HEK293 cells, rat PC-12 cells, and as positive control rat bone marrow stromal (BMS) cells. Surprisingly, all cells except for keratinocytes adopted at least partial "neuron-like" pyramidal cell morphology with fine-cellular extensions resembling neurites upon stimulation with BME or DMSO/BHA. However, time-lapse microscopy indicated that the chemical exposure of MSCs did not result in new neurite growth but rather cellular shrinkage, with retraction of the majority of existing cell extensions, leaving only few, fine neurite-like processes. To determine whether the chemically induced transdifferentiation resulted from simple cellular toxicity, MSCs were exposed to various stressors, including detergents, high-molarity sodium chloride, and extremes of pH. In all cases, cellular shrinkage and adoption of pseudoneuronal morphology were observed. Concomitantly with cellular shrinkage, apparent increases in immunolabeling for the neuronal markers NSE and NeuN were detected in the cell soma that could not be confirmed by RT-PCR. Furthermore, blockade of protein synthesis with cycloheximide did not prevent cells from adopting "neuron-like" morphology after chemical induction. Thus, morphological changes and increases in immunolabeling for certain cellular markers upon "chemical induction" of MSCs are likely the result of cellular toxicity, cell shrinkage, and changes in the cytoskeleton and do not represent regulated steps in a complicated cellular differentiation process.

Transformation of human umbilical mesenchymal cells into neurons in vitro

Neuronal transplantation has provided a promising approach for treating neurodegenerative diseases. Recently, efforts have been directed at in vitro induction of various stem cells to transform into neurons. We report the first successful quantities in an in vitro attempt at directing the transformation into neurons of human umbilical mesenchymal cells, which are capable of rapid proliferation in vitro and are easily available. When cultured in neuronal conditioned medium, human umbilical mesenchymal cells started to express neuron-specific proteins such as NeuN and neurofilament (NF) on the 3rd day and exhibited retraction of the cell body, elaboration of processes, clustering of cells and expression of functional mRNA responsible for the synthesis of subunits of the kainate receptor and glutamate decarboxylase on the 6th day. Between the 9th and 12th days, the percentage of human umbilical mesenchymal cells expressing NF was as high as 87%, while functionality was demonstrated by glutamate invoking an inward current. At this stage, cells were differentiated into mature neurons in the post mitosis phase.

Effects of chronic acetyl-L-carnitine treatment on brain lipid hydroperoxide level and passive avoidance learning in senescence-accelerated mice

In the present study, we examined the effects of acetyl-L-carnitine (ALC) on the brain lipid hydroperoxide level and on passive avoidance performance in senescence-acceleration-prone 8 mice (SAMP8). Mice were treated intraperitoneally with either saline or ALC (100 or 400 mg/kg) three times a week up to 4 months of age (starting at 3 weeks of age). In 4-month-old SAMP8, the deficit in learning and memory seen in saline-treated controls was significantly ameliorated in 400 mg/kg ALC-treated SAMP8, and the brain lipid hydroperoxide level was significantly lower in the 400 mg/kg ALC-treated group than in the saline-treated controls. Administration of 100 mg/kg ALC to SAMP8 did not have significant effect on learning and memory performance or on the brain lipid hydroperoxide level (by comparison with the saline-treated controls). These results suggest that ALC has antioxidant activity towards oxidative stress, and that the improvement in cognitive ability seen with ALC may occur through an amelioration of cellular dysfunction via an inhibition of the increase in lipid hydroperoxidation observed in the brain tissue of untreated SAMP8.