Transcriptional regulatory mechanisms that govern embryonic stem cell fate

Transplantation of human cord blood-derived multipotent stem cells (CB-SCs) enhances the recovery of Parkinson in rats

Earlier published research showed that cord blood-derived multipotent stem cells (CB-SCs) exhibited the intrinsic expression of specific transcription factors (e.g., En1, Nurr1 and Wnt1) and seems to be induced to form dopamine neurons in vitro. In this research, we further investigated the therapeutic potential of CB-SCs in 6-hydroxydopamine lesioned Parkinson's disease (PD) rats. The results of PCR analysis showed that CB-SCs could express transcription factors associated with pluripotentiality and dopaminergic differentiation (e.g., Klf4, c-Myc, Nanog, Sox2, Ngn2, and Nurr1). After being transplanted into the striatum and substantia nigra of PD rats, most of CB-SCs (>90%) developed a fate commitment to dopaminergic differentiation, expressed as the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT). The improvement effect of cell transplantation on dyskinesia in PD rats was better than that in sham control group. Moreover, higher levels of TH protein in brain homogenates further demonstrated that there were more surviving dopamine neurons in the brain of transplanted PD rats. Study concluds, CB SCS transplantation could promote the regeneration of dopamine neurons and behavioral recovery of PD rats.

Proof of Concept on Functionality Improvement of Mesenchymal Stem-Cells, in Postmenopausal Osteoporotic Women Treated with Teriparatide (PTH1-34), After Suffering Atypical Fractures

Osteoporosis long-term treatment with nitrogen-containing bisphosphonates, has been associated with uncommon adverse effects, as atypical femoral fractures (AFF). Thus, treatment with teriparatide (TPTD; fragment of human parathyroid hormone; PTH_1-34) has been proposed for such patients. Besides its anabolizing effect on bone, TPTD may affect stem-cell mobilization and expansion. Bone marrow mononuclear cells (BMMNC) were isolated from five women that had suffered AFF associated to bisphosphonate treatment, before and after 6 months of TPTD therapy. The presence of mesenchymal stromal cells (CD73, CD90 and CD105 positive cells), gene expression of NANOG, SOX2 and OCT4, proliferation, senescence and capacity to differentiate into osteoblasts and adipocytes were analyzed. After TPTD treatment, BMMNC positive cells for CD73, CD90 and CD105 increased from 6.5 to 37.5% (p < 0.05); NANOG, SOX2 and OCT4 were upregulated, being statistically significant for NANOG (p < 0.05), and cells increased proliferative capacity more than 50% at day 7 (p < 0.05). Senescence was reduced 2.5-fold (p < 0.05), increasing differentiation capacity into osteoblasts and adipocytes, with more than twice mineralization capacity of extracellular matrix or fat-droplet formation (p < 0.05), respectively. Results show that TPTD treatment caused BMMNC "rejuvenation", increasing the number of cells in a more undifferentiated stage, with higher differentiation potency. This effect may favor TPTD anabolic action on bone in such patients with AFF, increasing osteoblast precursor cells. Such response could also arise in other osteoporotic patients treated with TPTD, without previous AFF. Furthermore, our data suggest that TPTD effect on stromal cells may have clinical implications for bone-regenerative medicine. Further studies may deepen on this potential.

MEK1 signaling promotes self-renewal and tumorigenicity of liver cancer stem cells via maintaining SIRT1 protein stabilization

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death. This high mortality has been commonly attributed to the presence of residual cancer stem cells (CSCs). Meanwhile, MEK1 signaling is regarded as a key molecular in HCC maintenance and development. However, nobody has figured out the particular mechanisms that how MEK1 signaling regulates liver CSCs self-renewal. In this study, we show that inhibition or depletion of MEK1 can significantly decrease liver CSCs self-renewal and tumor growth both in vitro and vivo conditions. Furthermore, we demonstrate that MEK1 signaling promotes liver CSCs self-renewal and tumorigenicity by maintaining SIRT1 level. Mechanistically, MEK1 signaling keeps SIRT1 protein stabilization through activating SIRT1 ubiquitination, which inhibits proteasomal degradation. Clinical analysis shows that patients co-expression of MEK1 and SIRT1 are associated with poor survival. Our finding indicates that MEK1-SIRT1 can act as a novel diagnostic biomarker and inhibition of MEK1 may be a viable therapeutic option for targeting liver CSCs treatment.

Cell cycle and pluripotency: Convergence on octamer‑binding transcription factor 4 (Review)

Embryonic stem cells (ESCs) have unlimited expansion potential and the ability to differentiate into all somatic cell types for regenerative medicine and disease model studies. Octamer-binding transcription factor 4 (OCT4), encoded by the POU domain, class 5, transcription factor 1 gene, is a transcription factor vital for maintaining ESC pluripotency and somatic reprogramming. Many studies have established that the cell cycle of ESCs is featured with an abbreviated G1 phase and a prolonged S phase. Changes in cell cycle dynamics are intimately associated with the state of ESC pluripotency, and manipulating cell-cycle regulators could enable a controlled differentiation of ESCs. The present review focused primarily on the emerging roles of OCT4 in coordinating the cell cycle progression, the maintenance of pluripotency and the glycolytic metabolism in ESCs.

Luteolin and apigenin activate the Oct-4/Sox2 signal via NFATc1 in human periodontal ligament cells

Identifying small molecules to activate the Oct-4/Sox2-derived pluripotency network represents a hopeful and safe method to pluripotency without genetic manipulation. Luteolin and apigenin, two major bioactive flavonoids, enhance reprogramming efficiency and increase expression of Oct-4/Sox2/c-Myc, albeit the detailed mechanism regulating pluripotency in dental-derived cells remains unknown. In the present study, to elucidate the effect of luteolin/apigenin on pluripotency of periodontal ligament cells (PDLCs) through interaction with downstream signals, we examined cell cycle, proliferation, apoptosis, expression of Oct-4/Sox2/c-Myc, and multilineage differentiation of PDLCs with luteolin/apigenin treatment. Moreover, we profiled the differentially expressed pluripotency genes by PCR arrays. Our results demonstrated that luteolin/apigenin restrained cell proliferation, increased apoptosis, and arrested PDLCs in G2/M and S phase. Luteolin and apigenin activated expression of Oct-4, Sox2, and c-Myc in a time- and dose-dependent pattern, and repressed lineage-specific differentiation. PCR arrays profiled multiple signals in PDLCs with luteolin/apigenin treatment, among which NFATc1 was the major upregulated gene. Notably, blocking of the NFATc1 signal with INCA-6 significantly decreased mRNA and protein expression of Oct-4, Sox2, and c-Myc in PDLCs with luteolin/apigenin treatment, indicating that NFATc1 may act as an upstream modulator of Oct-4/Sox2 signal. Taken together, this study showed that luteolin and apigenin effectively maintain pluripotency of PDLCs through activation of Oct-4/Sox2 signal via NFATc1.

YAP1 Regulates OCT4 Activity and SOX2 Expression to Facilitate Self-Renewal and Vascular Mimicry of Stem-Like Cells

Non-small cell lung cancer (NSCLC) is highly correlated with smoking and has very low survival rates. Multiple studies have shown that stem-like cells contribute to the genesis and progression of NSCLC. Our results show that the transcriptional coactivator yes-associated protein 1 (YAP1), which is the oncogenic component of the Hippo signaling pathway, is elevated in the stem-like cells from NSCLC and contributes to their self-renewal and ability to form angiogenic tubules. Inhibition of YAP1 by a small molecule or depletion of YAP1 by siRNAs suppressed self-renewal and vascular mimicry of stem-like cells. These effects of YAP1 were mediated through the embryonic stem cell transcription factor, Sox2. YAP1 could transcriptionally induce Sox2 through a physical interaction with Oct4; Sox2 induction occurred independent of TEAD2 transcription factor, which is the predominant mediator of YAP1 functions. The binding of Oct4 to YAP1 could be detected in cell lines as well as tumor tissues; the interaction was elevated in NSCLC samples compared to normal tissue as seen by proximity ligation assays. YAP1 bound to Oct4 through the WW domain, and a peptide corresponding to this region could disrupt the interaction. Delivery of the WW domain peptide to stem-like cells disrupted the interaction and abrogated Sox2 expression, self-renewal, and vascular mimicry. Depleting YAP1 reduced the expression of multiple epithelial-mesenchymal transition genes and prevented the growth and metastasis of tumor xenografts in mice; overexpression of Sox2 in YAP1 null cells rescued these functions. These results demonstrate a novel regulation of stem-like functions by YAP1, through the modulation of Sox2 expression.

Monitoring Stemness in Long-Term hESC Cultures by Real-Time PCR

Human embryonic stem cells (hESC) involve long-term cultures that must remain undifferentiated. The real-time PCR (RT-PCR) technique allows the relative quantification of target genes, including undifferentiation and differentiation markers when referred to a housekeeping control with the addition of a calibrator that serves as an internal control to compare different lots of reactions during the time. The main aspects will include a minimal number of cells to be analyzed, genes to be tested, and how to choose the appropriate calibrator sample and the reference gene. In this chapter, we present how to apply the RT-PCR technique, protocols for its performance, experimental setup, and software analysis, as of the gene expression of hESC lines in consecutive passages for long-term culture surveillance.

Astrocyte-like cells differentiated from a novel population of CD45-positive cells in adult human peripheral blood

We have previously reported a novel CD45-positive cell population called peripheral blood insulin-producing cells (PB-IPCs) and its unique potential for releasing insulin in vitro. Despite the CD45-positive phenotype and self-renewal ability, PB-IPCs are distinguished from hemopoietic and endothelial progenitor cells (EPCs) by some characteristics, such as a CD34-negative phenotype and different culture conditions. We have further identified the gene profiles of the embryonic and neural stem cells, and these profiles include Sox2, Nanog, c-Myc, Klf4, Notch1 and Mash1. After treatment with all-trans retinoic acid (ATRA) in vitro, most PB-IPCs exhibited morphological changes that included the development of elongated and branched cell processes. In the process of induction, the mRNA expression of Hes1 was robustly upregulated, and a majority of cells acquired some astrocyte-associated specific phenotypes including anti-glial fibrillary acidic protein (GFAP), CD44, Glutamate-aspartate transporter (GLAST) and S100β. In spite of the deficiency of glutamate uptaking, the differentiated cells significantly relaxed the regulation of the expression of brain-derived neurotrophic factor (BDNF) mRNA. This finding demonstrates that PB-IPCs could be induced into a population of astrocyte-like cells and enhanced the neurotrophic potential when the state of proliferation was limited by ATRA, which implies that this unique CD45+ cell pool may have a protective role in some degenerative diseases of the central nervous system (CNS).