The positional identity of iPSC-derived neural progenitor cells along the anterior-posterior axis is controlled in a dosage-dependent manner by bFGF and EGF

Postsynaptic structure formation of human iPS cell-derived neurons takes longer than presynaptic formation during neural differentiation in vitro

The generation of mature synaptic structures using neurons differentiated from human-induced pluripotent stem cells (hiPSC-neurons) is expected to be applied to physiological studies of synapses in human cells and to pathological studies of diseases that cause abnormal synaptic function. Although it has been reported that synapses themselves change from an immature to a mature state as neurons mature, there are few reports that clearly show when and how human stem cell-derived neurons change to mature synaptic structures. This study was designed to elucidate the synapse formation process of hiPSC-neurons. We propagated hiPSC-derived neural progenitor cells (hiPSC-NPCs) that expressed localized markers of the ventral hindbrain as neurospheres by dual SMAD inhibition and then differentiated them into hiPSC-neurons in vitro. After 49 days of in vitro differentiation, hiPSC-neurons significantly expressed pre- and postsynaptic markers at both the transcript and protein levels. However, the expression of postsynaptic markers was lower than in normal human or normal rat brain tissues, and immunostaining analysis showed that it was relatively modest and was lower than that of presynaptic markers and that its localization in synaptic structures was insufficient. Neurophysiological analysis using a microelectrode array also revealed that no synaptic activity was generated on hiPSC-neurons at 49 days of differentiation. Analysis of subtype markers by immunostaining revealed that most hiPSC-neurons expressed vesicular glutamate transporter 2 (VGLUT2). The presence or absence of NGF, which is required for the survival of cholinergic neurons, had no effect on their cell fractionation. These results suggest that during the synaptogenesis of hiPSC-neurons, the formation of presynaptic structures is not the only requirement for the formation of postsynaptic structures and that the mRNA expression of postsynaptic markers does not correlate with the formation of their mature structures. Technically, we also confirmed a certain level of robustness and reproducibility of our neuronal differentiation method in a multicenter setting, which will be helpful for future research. Synapse formation with mature postsynaptic structures will remain an interesting issue for stem cell-derived neurons, and the present method can be used to obtain early and stable quality neuronal cultures from hiPSC-NPCs.

Efficient One-Step Induction of Human Umbilical Cord-Derived Mesenchymal Stem Cells (UC-MSCs) Produces MSC-Derived Neurospheres (MSC-NS) with Unique Transcriptional Profile and Enhanced Neurogenic and Angiogenic Secretomes

Cell therapy has emerged as a promising strategy for treating neurological diseases such as stroke, spinal cord injury, and various neurodegenerative diseases, but both embryonic neural stem cells and human induced Pluripotent Stem Cell- (iPSC-) derived neural stem cells have major limitations which restrict their broad use in these diseases. We want to find a one-step induction method to transdifferentiate the more easily accessible Umbilical Cord-Derived Mesenchymal Stem Cells (UC-MSCs) into neural stem/progenitor cells suitable for cell therapy purposes. In this study, UC-MSCs were induced to form neurospheres under a serum-free suspension culture with Epidermal Growth Factor- (EGF-) and basic Fibroblast Growth Factor- (bFGF-) containing medium within 12 hours. These MSC-derived neurospheres can self-renew to form secondary neurospheres and can be readily induced to become neurons and glial cells. Real-time PCR showed significantly upregulated expression of multiple stemness and neurogenic genes after induction. RNA transcriptional profiling study showed that UC-MSC-derived neurospheres had a unique transcriptional profile of their own, with features of both UC-MSCs and neural stem cells. RayBio human growth factor cytokine array analysis showed significantly upregulated expression levels of multiple neurogenic and angiogenic growth factors, skewing toward a neural stem cell phenotype. Thus, we believe that these UC-MSC-derived neurospheres have amenable features of both MSCs and neural stem/progenitor cells and have great potential in future stem cell transplantation clinical trials targeting neurological disorders.

[Culture and identification of tumor stem cells from surgically resected colorectal cancer tissues]

OBJECTIVE

To obtain cancer stem cells (CSCs) from surgically resected colorectal cancer specimens and identify their stem cell characteristics.

METHODS

Colorectal cancer tissue specimen obtained from a patient undergoing radical resection of colorectal cancer were implanted in nude mice, and the xenograft was harvested 1 month later to obtain purified tumor cells by enzyme digestion and adherent culture. The CSCs were screened by limiting dilution method and serum-free culture to identify their phenotypes. Soft agar colony assay was used to assess the proliferative ability of the CSCs and human colorectal cancer cell line SW480. The tumorigenic ability of the isolated CSCs and SW480 cells was evaluated by observing their subcutaneous tumor formation in nude mice. Western blotting and immunofluorescence assay were used to detect the immunophenotype of the CSCs and SW480 cells.

RESULTS

The primary cultured CSCs from clinical specimens of colorectal cancer underwent differentiation in the presence of serum in the culture. Soft agar colony formation assay showed that the CSCs had a colony formation rate above 50%, significantly higher than the rate of colorectal cancer SW480 cells (4.41%; P < 0.01). In nude mice, subcutaneous injection of 500 CSCs was sufficient to result in subcutaneous tumor formation, while the injection of 500 SW480 cells failed to form any subcutaneous tumors. The CSCs expressed CD133 and CD44 but not CK7, while SW480 cells expressed CK7 but not CD133 or CD44.

CONCLUSIONS

CSCs can be derived by primary culture of cancer cells obtained from surgically resected colorectal cancer tissue followed by serum-free culture, and the CSCs obtained have self-renewal and differentiation abilities.

An adherent-cell depletion technique to generate human neural progenitors and neurons

Existing methodologies to produce human neural stem cells and neurons from embryonic stem cells frequently involve multistep processes and the use of complex and expensive media components, cytokines or small molecules. Here, we report a simple technique to generate human neuroepithelial progenitors and neurons by periodic mechanical dissection and adherent-cell depletion on regular cell-culture grade plastic surfaces. This neural induction technique does not employ growth factors, small molecules or peptide inhibitors, apart from those present in serum-free supplements. Suggestive of their central nervous system origin, we found that neural progenitors formed by this technique expressed radial glia markers, and, when differentiated, expressed TUBB3, RBFOX3 (NeuN) and serotonin, but not markers for peripheral neurons. With these data, we postulate that incorporation of periodic mechanical stimuli and plastic surface-mediated cell selection could improve and streamline existing human neuron production protocols.

The involvement of mitochondrial fission in maintenance of the stemness of bone marrow mesenchymal stem cells

IMPACT STATEMENT

How to maintain the stemness of bone marrow mesenchymal stem cells (BMSCs) in cultures is a long-standing question. The present study found that mitochondrial dynamics affects the stemness of BMSCs in cultures and the retaining of mitochondrial fission enhances the stemness of BMSCs. This work thus provides a novel insight into strategic approaches to maintain the stemness of BMSCs in cultures in relation to the clinical application of bone-marrow stem cells.

Antagonism between the transcription factors NANOG and OTX2 specifies rostral or caudal cell fate during neural patterning transition

During neurogenesis, neural patterning is a critical step during which neural progenitor cells differentiate into neurons with distinct functions. However, the molecular determinants that regulate neural patterning remain poorly understood. Here we optimized the "dual SMAD inhibition" method to specifically promote differentiation of human pluripotent stem cells (hPSCs) into forebrain and hindbrain neural progenitor cells along the rostral-caudal axis. We report that neural patterning determination occurs at the very early stage in this differentiation. Undifferentiated hPSCs expressed basal levels of the transcription factor orthodenticle homeobox 2 (OTX2) that dominantly drove hPSCs into the "default" rostral fate at the beginning of differentiation. Inhibition of glycogen synthase kinase 3β (GSK3β) through CHIR99021 application sustained transient expression of the transcription factor NANOG at early differentiation stages through Wnt signaling. Wnt signaling and NANOG antagonized OTX2 and, in the later stages of differentiation, switched the default rostral cell fate to the caudal one. Our findings have uncovered a mutual antagonism between NANOG and OTX2 underlying cell fate decisions during neural patterning, critical for the regulation of early neural development in humans.