MiR-9 promotes the neural differentiation of mouse bone marrow mesenchymal stem cells via targeting zinc finger protein 521

Microchip encapsulation and microRNA-7 overexpression of trabecular meshwork mesenchymal stem/stromal cells improve motor function after spinal cord injury

Manipulation of stem cells and microencapsulation through microfluidic chips has shown more promising results in treating complex conditions, such as spinal cord injury (SCI), than traditional treatments. This study aimed to investigate the potency of neural differentiation and its therapeutic role in SCI animal model of trabecular meshwork mesenchymal stem/stromal cells (TMMSCs) via miR-7 overexpression and microchip-encapsulated. TMMSCs are transduced with miR-7 via a lentiviral vector (TMMSCs-miR-7[+]) and encapsulated in alginate-reduced graphene oxide (alginate-rGO) hydrogel via a microfluidic chip. Neuronal differentiation of transduced cells in hydrogel (3D) and tissue cultures plate (2D) was assessed by expressing specific mRNAs and proteins. Further evaluation is being carried out through 3D and 2D TMMSCs-miR-7(+ and -) transplantation into the rat contusion SCI model. TMMSCs-miR-7(+) encapsulated in the microfluidic chip (miR-7-3D) increased nestin, β-tubulin III, and MAP-2 expression compared with 2D culture. Moreover, miR-7-3D could improve locomotor behavior in contusion SCI rats, decrease cavity size, and increase myelination. Our results revealed that miR-7 and alginate-rGO hydrogel were involved in the neuronal differentiation of TMMSCs in a time-dependent manner. In addition, the microfluidic-encapsulated miR-7 overexpression TMMSCs represented a better survival and integration of the transplanted cells and the repair of SCI. Collectively, the combination of miR-7 overexpression and encapsulation of TMMSCs in hydrogels may represent a promising new treatment for SCI.

Enhanced ZNF521 expression induces an aggressive phenotype in human ovarian carcinoma cell lines

Epithelial ovarian carcinoma (EOC) is the most lethal gynecological tumor, that almost inevitably relapses and develops chemo-resistance. A better understanding of molecular events underlying the biological behavior of this tumor, as well as identification of new biomarkers and therapeutic targets are the prerequisite to improve its clinical management. ZNF521 gene amplifications are present in >6% of OCs and its overexpression is associated with poor prognosis, suggesting that it may play an important role in OC. Increased ZNF521 expression resulted in an enhancement of OC HeyA8 and ES-2 cell growth and motility. Analysis of RNA isolated from transduced cells by RNA-Seq and qRT-PCR revealed that several genes involved in growth, proliferation, migration and tumor invasiveness are differentially expressed following increased ZNF521 expression. The data illustrate a novel biological role of ZNF521 in OC that, thanks to the early and easy detection by RNA-Seq, can be used as biomarker for identification and treatment of OC patients.

Synergistic effect of miR-9 overexpression and electrical induction on differentiation of conjunctiva mesenchymal stem cells into photoreceptor-like cells

A variety of genes and materials can induce the differentiation of stem cells. The purpose of this work was to investigate the effect of microRNA-9 (miR-9) overexpression and electrical induction on the photoreceptor differentiation of Conjunctiva Mesenchymal Stem Cells (CJMSCs). In this study, an electroconductive scaffold (silk fibroin polymer (SF) and reduced graphene oxide (rGo) nanoparticles) was fabricated by electrospinning method, and its characteristics such as diameter, graphene distribution, compound, conductivity, and toxicity were evaluated by scanning and transmission electron microscopy (SEM and TEM), FTIR, electrochemical impedance spectroscopy, and MTT assay. The cells were transduced by a lentiviral vector carrying miR-9, then electrical induction was implied on mir-9-CJMSCs, cultivated on the fabricated scaffold, and the expressions of neural and photoreceptor marker genes were evaluated by RT-qPCR. A uniform, smooth appearance with lower diameter, uniform distribution of rGo nanoparticles across the fibers, and lower resistance were shown in SF-rGo fibrous scaffold. After electrical stimulation, lower and higher expression of neural marker genes and photoreceptor marker genes (Rhodopsin, PKC) were documented, respectively. Finally, we proposed that the combinational approach of miR-9 overexpression and electrical induction leads CJMSCs to photoreceptor-like cells.

Selenium enhances the expression of miR-9, miR-124 and miR-29a during neural differentiation of bone marrow mesenchymal stem cells

BACKGROUND

Selenium (Se) is a trace element that plays important role in antioxidant defense in the brain. Sodium selenite (Na₂SeO₃) is an inorganic salt of Se which has an antioxidant function. In the present study, we investigated the effect of Sodium selenite on the expression of important neuronal microRNAs during neural differentiation of bone marrow-derived stem cells (BMSCs).

METHODS

Mesenchymal stem cells were collected from rat bone marrow and cultured in the Dulbecco's Modified Eagle Medium (DMEM) medium. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay was conducted to determine the toxicity of Na₂SeO₃. For neural induction, BMSCs were divided into control, Na₂SeO₃ containing (10 ng/mL) and Na2SeO₃ free groups and cultured in DMEM medium supplemented with Isobutyl-l-methylxanthine (IBMX), Fibroblast growth factor 2 (FGF2), B27, Retinoic acid, and brain derived neurotrophic factor (BDNF) for 14 days. At the end of the differentiation, immunostaining against Microtubule associated protein 2 (Map-2) and Choline acetyltransferase (ChAT) proteins was performed. Also, the total RNA is extracted from control and neural differentiated cells using a special kit, and the expression of miR-9, miR-124, and miR-29a was analyzed using real-time polymerase chain reaction (RT-PCR).

RESULTS

Increasing Na₂SeO₃ concentrations had increasing toxicity; therefore, the concentration of 10 ng/mL was used as a supplement during neural differentiation. Examination of the expression of Map-2 and ChAT proteins showed that Na₂SeO₃ increased the expression of them and consequently the neuronal differentiation of BMSCs. Na₂SeO₃ also significantly increased the expression of miR-9, miR-124, and miR-29a in BMSCs undergoing neuronal differentiation.

CONCLUSIONS

Our results suggest that the protective effect of selenium on neural differentiation of stem cells may be mediated through neuron specific microRNAs. This result further highlights the importance of selenium supplementation in preventing neuronal diseases.

Regulatory Role of microRNAs Targeting the Transcription Co-Factor ZNF521 in Normal Tissues and Cancers

Powerful bioinformatics tools have provided a wealth of novel miRNA–transcription factor networks crucial in controlling gene regulation. In this review, we focus on the biological functions of miRNAs targeting ZNF521, explaining the molecular mechanisms by which the dysregulation of this axis contributes to malignancy. ZNF521 is a stem cell-associated co-transcription factor implicated in the regulation of hematopoietic, neural, and mesenchymal stem cells. The aberrant expression of ZNF521 transcripts, frequently associated with miRNA deregulation, has been detected in several tumors including pancreatic, hepatocellular, gastric, bladder transitional cell carcinomas as well as in breast and ovarian cancers. miRNA expression profiling tools are currently identifying a multitude of miRNAs, involved together with oncogenes and TFs in the regulation of oncogenesis, including ZNF521, which may be candidates for diagnostic and prognostic biomarkers of cancer.

An Overview of Mesenchymal Stem Cell-based Therapy Mediated by Noncoding RNAs in the Treatment of Neurodegenerative Diseases

Mesenchymal stem cells (MSCs) have become a promising tool for neurorestorative therapy of neurodegenerative diseases (NDDs), which are mainly characterized by the progressive and irreversible loss of neuronal structure and function in the central or peripheral nervous system. Recently, studies have reported that genetic manipulation mediated by noncoding RNAs (ncRNAs) can increase survival and neural regeneration of transplanted MSCs, offering a new strategy for clinical translation. In this review, we summarize the potential role and regulatory mechanism of two major types of ncRNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), during the neurogenesis of MSCs with gene expression profile analyses. We also overview the realization of MSC-based therapy mediated by ncRNAs in the treatment of spinal cord injury, stroke, Alzheimer's disease and peripheral nerve injury. It is expected that ncRNAs will become promising therapeutic targets for NDD on stem cells, while the underlying mechanisms require further exploration.

Recent Progress in Engineering Mesenchymal Stem Cell Differentiation

Due to the ability to differentiate into variety of cell types, mesenchymal stem cells (MSCs) hold promise as source in cell-based therapy for treating injured tissue and degenerative diseases. The potential use of MSCs to replace or repair damaged tissues may depend on the efficient differentiation protocols to derive specialized cells without any negative side effects. Identification of appropriate cues that support the lineage-specific differentiation of stem cells is critical for tissue healing and cellular therapy. Recently, a number of stimuli have been utilized to direct the differentiation of stem cells. Biochemical stimuli such as small molecule, growth factor and miRNA have been traditionally used to regulate the fate of stem cells. In recent years, many studies have reported that biophysical stimuli including cyclic mechanical strain, fluid shear stress, microgravity, electrical stimulation, matrix stiffness and topography can also be sensed by stem cells through mechanical receptors, thus affecting the stem cell behaviors including their differentiation potential. In this paper, we review all the most recent literature on the application of biochemical and biophysical cues on regulating MSC differentiation. An extensive literature search was done using electronic database (Medline/Pubmed). Although there are still some challenges that need to be taken into consideration before translating these methods into clinics, biochemical and biophysical stimulation appears to be an attractive method to manipulate the lineage commitment of MSCs.

Comprehensive analysis of microRNAs in the mantle central and mantle edge provide insights into shell formation in pearl oyster Pinctada fucata martensii

MicroRNAs (miRNAs) are a class of non-coding RNA molecules with post-transcriptional regulatory activity in various biological processes. Pearl oyster Pinctada fucata martensii is one of the main species cultured for marine pearl production in China and Japan. In this study, we constructed two small RNA libraries of mantle central (MC) and mantle edge (ME) from P. f. martensii and obtained 24,175,537 and 21,593,898 clean reads, respectively. A total of 258 miRNAs of P. f. martensii (Pm-miRNA) were identified, and 93 differentially expressed miRNAs (DEMs) including 49 known Pm-miRNAs and 44 novel Pm-miRNAs were obtained from the MC and ME. The target transcripts of these DEMs were obviously enriched in neuroactive ligand-receptor interaction pathway, and others. After over-expression of Pm-miR-124 and Pm-miR-9a-5p in the MC by mimic injection into the muscle of P. f. martensii, nacre exhibited a disorderly growth as detected by scanning electron microscopy. Pm-nicotinic acetylcholine receptor alpha subunit, Pm-neuropeptide Y and Pm-chitin synthase were investigated as the targets of Pm-miR-124; and Pm-tumor necrosis factor receptor associated factor 2 and Pm-chitin synthase were investigated as the targets of Pm-miR-9a-5p. These predicted target transcripts were down-regulated after the over-expression of Pm-miR-124 and Pm-miR-9a-5p in MC. This study comprehensively analyzed the miRNAs in mantle tissues to enhance our understanding of the regulatory mechanism underlying shell formation.

ZNF521 which is downregulated by miR-802 suppresses malignant progression of Hepatocellular Carcinoma through regulating Runx2 expression

Zinc finger protein 521 (ZNF521) plays an important role in the tumor development and process. However, its regulatory role in hepatocellular carcinoma (HCC) remains unclear. In this study, we demonstrated for the first time that ZNF521 mRNA and protein was down-regulated in HCC tissues and cell lines. Down-regulated ZNF521 expression was significantly associated with malignant prognostic features, including advanced TNM stage and large tumor size. For 5-year survival, ZNF521 served as a potential prognostic marker of HCC patients. Moreover, ZNF521 inhibited cell proliferation, colony formation and cell viability through Runx2 transcriptional inhibition and AKT phosphorylation pathway. Moreover, we demonstrated that ZNF521 expression was regulated by miR-802. In HCC tissues. MiR-802 has an inverse correlation with ZNF521 expression. In conclusion, we demonstrate for the first time that ZNF521 is down-regulated in HCC tissues and inhibits HCC growth through Runx2 transcriptional inhibition and AKT inactivation, which was regulated by miR-802, suggesting the potential therapeutic value for HCC.

miR-762 regulates the proliferation and differentiation of retinal progenitor cells by targeting NPDC1

Retinal degenerations, which lead to irreversible decline in visual function, are still no effective recovery treatments. Currently, retinal progenitor cell (RPC) transplantation therapy is expected to provide a new approach to treat these diseases; however, the limited proliferation capacity and differentiation potential toward specific retinal neurons of RPCs hinder their potential clinical applications. microRNAs have been reported to serve as important regulators in the cell fate determination of stem/progenitor cells. In this study, our data demonstrated that miR-762 inhibited NPDC1 expression to positively regulate RPC proliferation and suppress RPC neuronal differentiation. Furthermore, the knockdown of miR-762 upregulated NPDC1 expression in RPCs, leading to the inhibition of RPC proliferation and the increase in neuronal differentiation. Moreover, NPDC1 could rescue anti-miR-762-induced RPC proliferation deficiency and the inhibitory effect of miR-762 on RPC differentiation. In conclusion, our study demonstrated that miR-762 plays a crucial role in regulating RPC proliferation and differentiation by directly targeting NPDC1, which is firstly reported that microRNAs positively regulate RPC proliferation and negatively regulate RPC differentiation, which provides a comprehensive understanding of the molecular mechanisms that dominate RPC proliferation and differentiation in vitro.

The stem cell-associated transcription co-factor, ZNF521, interacts with GLI1 and GLI2 and enhances the activity of the Sonic hedgehog pathway

ZNF521 is a transcription co-factor with recognized regulatory functions in haematopoietic, osteo-adipogenic and neural progenitor cells. Among its diverse activities, ZNF521 has been implicated in the regulation of medulloblastoma (MB) cells, where the Hedgehog (HH) pathway, has a key role in the development of normal cerebellum and of a substantial fraction of MBs. Here a functional cross-talk is shown for ZNF521 with the HH pathway, where it interacts with GLI1 and GLI2, the major HH transcriptional effectors and enhances the activity of HH signalling. In particular, ZNF521 cooperates with GLI1 and GLI2 in the transcriptional activation of GLI (glioma-associated transcription factor)-responsive promoters. This synergism is dependent on the presence of the N-terminal, NuRD-binding motif in ZNF521, and is sensitive to HDAC (histone deacetylase) and GLI inhibitors. Taken together, these results highlight the role of ZNF521, and its interaction with the NuRD complex, in determining the HH response at the level of transcription. This may be of particular relevance in HH-driven diseases, especially regarding the MBs belonging to the SHH (sonic HH) subgroup where a high expression of ZNF521 is correlated with that of HH pathway components.

Micrornas at the Interface between Osteogenesis and Angiogenesis as Targets for Bone Regeneration

Bone formation and regeneration is a multistep complex process crucially determined by the formation of blood vessels in the growth plate region. This is preceded by the expression of growth factors, notably the vascular endothelial growth factor (VEGF), secreted by osteogenic cells, as well as the corresponding response of endothelial cells, although the exact mechanisms remain to be clarified. Thereby, coordinated coupling between osteogenesis and angiogenesis is initiated and sustained. The precise interplay of these two fundamental processes is crucial during times of rapid bone growth or fracture repair in adults. Deviations in this balance might lead to pathologic conditions such as osteoarthritis and ectopic bone formation. Besides VEGF, the recently discovered important regulatory and modifying functions of microRNAs also support this key mechanism. These comprise two principal categories of microRNAs that were identified with specific functions in bone formation (osteomiRs) and/or angiogenesis (angiomiRs). However, as hypoxia is a major driving force behind bone angiogenesis, a third group involved in this process is represented by hypoxia-inducible microRNAs (hypoxamiRs). This review was focused on the identification of microRNAs that were found to have an active role in osteogenesis as well as angiogenesis to date that were termed "CouplingmiRs (CPLGmiRs)". Outlined representatives therefore represent microRNAs that already have been associated with an active role in osteogenic-angiogenic coupling or are presumed to have its potential. Elucidation of the molecular mechanisms governing bone angiogenesis are of great relevance for improving therapeutic options in bone regeneration, tissue-engineering, and the treatment of bone-related diseases.

Zinc Finger Protein 521 Regulates Early Hematopoiesis through Cell-Extrinsic Mechanisms in the Bone Marrow Microenvironment

Zinc finger protein 521 (ZFP521), a DNA-binding protein containing 30 Krüppel-like zinc fingers, has been implicated in the differentiation of multiple cell types, including hematopoietic stem and progenitor cells (HSPC) and B lymphocytes. Here, we report a novel role for ZFP521 in regulating the earliest stages of hematopoiesis and lymphoid cell development via a cell-extrinsic mechanism. Mice with inactivated Zfp521 genes (Zfp521^-/-) possess reduced frequencies and numbers of hematopoietic stem and progenitor cells, common lymphoid progenitors, and B and T cell precursors. Notably, ZFP521 deficiency changes bone marrow microenvironment cytokine levels and gene expression within resident HSPC, consistent with a skewing of hematopoiesis away from lymphopoiesis. These results advance our understanding of ZFP521's role in normal hematopoiesis, justifying further research to assess its potential as a target for cancer therapies.

MicroRNA-664a-5p promotes neuronal differentiation of SH-SY5Y cells

MicroRNAs (miRNAs) belong to a class of small noncoding RNAs that play important roles in the translational regulation of gene expression. A number of miRNAs are known to act as key regulators of diverse processes such as neuronal differentiation. In this study, we have attempted to identify novel miRNAs related to neuronal differentiation via microarray analysis in the human neuronal differentiation model neuroblastoma SH-SY5Y cells. We identified 15 up-regulated and eight down-regulated miRNAs in SH-SY5Y cells treated with all-trans retinoic acid to induce differentiation. We further showed that one of the up-regulated miRNAs, miR-664a-5p, promoted neuronal differentiation of SH-SY5Y cells. These findings enhance our understanding of the miRNAs involved in the process of neurogenesis and, in particular, highlight an important role of miR-664a-5p in SH-SY5Y cell neuronal differentiation. Further studies will be required to confirm the function of miR-664-5p in neuronal development and disease and to identify its relevant target genes.

MicroRNA let-7f-5p regulates neuronal differentiation of rat bone marrow mesenchymal stem cells by targeting Par6α

Par6α (partitioning defective 6 homologue alpha), a component of the Par3/Par6/aPKC complex, was recently shown to be essential for axon specification during neuronal development. However, the biological functions and regulatory mechanisms of Par6α in the mesenchymal stem cell (MSC) differentiation process have not been investigated. In this study, we found that the expression of let-7f-5p was downregulated during differentiation of bone marrow-derived MSCs to neuron-like cells. Interestingly, Par6α was predicted to be a target gene of let-7f-5p by computerized analysis and the luciferase reporter assay. Using gain- and loss-of-function approaches, we found that expression of Par6α was inversely correlated with let-7f-5p levels during differentiation (p < 0.05). By silencing Par6α using siRNAs, we demonstrated that Par6α was necessary for MSC neuronal differentiation. Altogether, our studies proved that inhibition of let-7f-5p facilitates induction of MSCs into neuron-like cells by directly targeting Par6α.

Osthole Stimulated Neural Stem Cells Differentiation into Neurons in an Alzheimer's Disease Cell Model via Upregulation of MicroRNA-9 and Rescued the Functional Impairment of Hippocampal Neurons in APP/PS1 Transgenic Mice

Alzheimer's disease (AD) is the most serious neurodegenerative disease worldwide and is characterized by progressive cognitive impairment and multiple neurological changes, including neuronal loss in the brain. However, there are no available drugs to delay or cure this disease. Consequently, neuronal replacement therapy may be a strategy to treat AD. Osthole (Ost), a natural coumarin derivative, crosses the blood-brain barrier and exerts strong neuroprotective effects against AD in vitro and in vivo. Recently, microRNAs (miRNAs) have demonstrated a crucial role in pathological processes of AD, implying that targeting miRNAs could be a therapeutic approach to AD. In the present study, we investigated whether Ost could enhance cell viability and prevent cell death in amyloid precursor protein (APP)-expressing neural stem cells (NSCs) as well as promote APP-expressing NSCs differentiation into more neurons by upregulating microRNA (miR)-9 and inhibiting the Notch signaling pathway in vitro. In addition, Ost treatment in APP/PS1 double transgenic (Tg) mice markedly restored cognitive functions, reduced Aβ plague production and rescued functional impairment of hippocampal neurons. The results of the present study provides evidence of the neurogenesis effects and neurobiological mechanisms of Ost against AD, suggesting that Ost is a promising drug for treatment of AD or other neurodegenerative diseases.

Deep sequencing reveals complex mechanisms of microRNA regulation during retinoic acid-induced neuronal differentiation of mesenchymal stem cells

Retinoic acid (RA) has an important role in nervous system development; exogenous RA could induce stem cells towards neural lineage cells. However, the miRNA regulation mechanism and biological process of this induction require further exploration. In this study, using high-throughput sequencing results, we evaluated the microRNA profiles of neurally differentiated adipose-derived mesenchymal stem cells (ASCs), summarized several crucial microRNAs that profoundly contributed to the differentiation process, and speculated that several miRNAs were likely to mimic RA or other factors to induce the neuronal differentiation of stem cells. The GO terms and KEGG PATHWAY in the DAVID tool were used to elucidate the biological process of RA induction. Finally, we described a network for clarifying the relationship among the miRNAs, target genes and signaling pathways. These findings will be beneficial for understanding the induction mechanism and supporting the application of RA in stem cell transformation.

Combination of RNA Interference and Stem Cells for Treatment of Central Nervous System Diseases

RNA interference (RNAi), including microRNAs, is an important player in the mediation of differentiation and migration of stem cells via target genes. It is used as a potential strategy for gene therapy for central nervous system (CNS) diseases. Stem cells are considered vectors of RNAi due to their capacity to deliver RNAi to other cells. In this review, we discuss the recent advances in studies of RNAi pathways in controlling neuronal differentiation and migration of stem cells. We also highlight the utilization of a combination of RNAi and stem cells in treatment of CNS diseases.

Transcriptional regulation of the proto-oncogene Zfp521 by SPI1 (PU.1) and HOXC13

The mouse zinc‐finger gene Zfp521 (also known as ecotropic viral insertion site 3; Evi3; and ZNF521 in humans) has been identified as a B‐cell proto‐oncogene, causing leukemia in mice following retroviral insertions in its promoter region that drive Zfp521 over‐expression. Furthermore, ZNF521 is expressed in human hematopoietic cells, and translocations between ZNF521 and PAX5 are associated with pediatric acute lymphoblastic leukemia. However, the regulatory factors that control Zfp521 expression directly have not been characterized. Here we demonstrate that the transcription factors SPI1 (PU.1) and HOXC13 synergistically regulate Zfp521 expression, and identify the regions of the Zfp521 promoter required for this transcriptional activity. We also show that SPI1 and HOXC13 activate Zfp521 in a dose‐dependent manner. Our data support a role for this regulatory mechanism in vivo, as transgenic mice over‐expressing Hoxc13 in the fetal liver show a strong correlation between Hoxc13 expression levels and Zfp521 expression. Overall these experiments provide insights into the regulation of Zfp521 expression in a nononcogenic context. The identification of transcription factors capable of activating Zfp521 provides a foundation for further investigation of the regulatory mechanisms involved in ZFP521‐driven cell differentiation processes and diseases linked to Zfp521 mis‐expression.

MiR-9 promotes osteoblast differentiation of mesenchymal stem cells by inhibiting DKK1 gene expression

The aim of this study is to investigate the role of miR-9 and its mechanism on the osteoblast differentiation of mesenchymal stem cells. Real-time PCR and western blotting were used to study gene expression. Assay of Alkaline phosphatase activity and alizarin red staining were used to examine osteoblast differentiation. Transfection of miR-9 mimics or lent-shmiR-9 was used to modulate the level of miR-9 in C2C12. Overexpression of miR-9 in C2C12 cells stimulated alkaline phosphatase activity and osteoblast mineralization, as well as the expression of osteoblast marker genes Col I, Ocn and Bsp. Gene silencing of miR-9 in C2C12 resulted in the suppression of alkaline phosphatase activity and osteoblast mineralization, as well as the expression of Col I, Ocn and Bsp. DKK1 mRNA was not affected by miR-9 overexpression, however, DKK1 protein was significantly decreased. Moreover, DKK1 3'-UTR mediated transcriptional luciferase activity was also significantly suppressed by miR-9 overexpression. DKK1 mRNA was not affected by miR-9 gene silencing, however, DKK1 protein was significantly stimulated. Moreover, DKK1 3'-UTR mediated transcriptional luciferase activity was significantly stimulated by miR-9 gene silencing, and suppressed by miR-9 overexpression, however, DKK1 3'-UTR mutant mediated luciferase activity was unaffected. The siRNA derived gene silencing of DKK1 blocked the inhibiting effect of shmiR-9 on the expression of alkaline phosphatase; and blocked the inhibiting effect of shmiR-9 on the expression of ColI, Ocn and Bsp. MiR-9 promotes osteoblast differentiation of mesenchymal cell C2C12 by suppressing the gene expression of DKK1.

The Role of microRNAs in Animal Cell Reprogramming

Our concept of cell reprogramming and cell plasticity has evolved since John Gurdon transferred the nucleus of a completely differentiated cell into an enucleated Xenopus laevis egg, thereby generating embryos that developed into tadpoles. More recently, induced expression of transcription factors, oct4, sox2, klf4, and c-myc has evidenced the plasticity of the genome to change the expression program and cell phenotype by driving differentiated cells to the pluripotent state. Beyond these milestone achievements, research in artificial cell reprogramming has been focused on other molecules that are different than transcription factors. Among the candidate molecules, microRNAs (miRNAs) stand out due to their potential to control the levels of proteins that are involved in cellular processes such as self-renewal, proliferation, and differentiation. Here, we review the role of miRNAs in the maintenance and differentiation of mesenchymal stem cells, epimorphic regeneration, and somatic cell reprogramming to induced pluripotent stem cells.

Conversion of Human Fibroblasts to Stably Self-Renewing Neural Stem Cells with a Single Zinc-Finger Transcription Factor

Direct conversion of somatic cells into neural stem cells (NSCs) by defined factors holds great promise for mechanistic studies, drug screening, and potential cell therapies for different neurodegenerative diseases. Here, we report that a single zinc-finger transcription factor, Zfp521, is sufficient for direct conversion of human fibroblasts into long-term self-renewable and multipotent NSCs. In vitro, Zfp521-induced NSCs maintained their characteristics in the absence of exogenous factor expression and exhibited morphological, molecular, developmental, and functional properties that were similar to control NSCs. In addition, the single-seeded induced NSCs were able to form NSC colonies with efficiency comparable with control NSCs and expressed NSC markers. The converted cells were capable of surviving, migrating, and attaining neural phenotypes after transplantation into neonatal mouse and adult rat brains, without forming tumors. Moreover, the Zfp521-induced NSCs predominantly expressed rostral genes. Our results suggest a facilitated approach for establishing human NSCs through Zfp521-driven conversion of fibroblasts.

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ZFP521 can directly convert human fetal, neonatal, and adult fibroblasts into NSCs

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iNSCs exhibit NSC properties, i.e., markers, long-term self-renewal, and tripotency

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ZFP521-iNSCs predominantly express rostral markers

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Single-seeded ZFP521-iNSCs are clonogenically comparable with control NSCs

Genetic Engineering of Mesenchymal Stem Cells for Regenerative Medicine

Mesenchymal stem cells (MSCs), which can be obtained from various organs and easily propagated in vitro, are one of the most extensively used types of stem cells and have been shown to be efficacious in a broad set of diseases. The unique and highly desirable properties of MSCs include high migratory capacities toward injured areas, immunomodulatory features, and the natural ability to differentiate into connective tissue phenotypes. These phenotypes include bone and cartilage, and these properties predispose MSCs to be therapeutically useful. In addition, MSCs elicit their therapeutic effects by paracrine actions, in which the metabolism of target tissues is modulated. Genetic engineering methods can greatly amplify these properties and broaden the therapeutic capabilities of MSCs, including transdifferentiation toward diverse cell lineages. However, cell engineering can also affect safety and increase the cost of therapy based on MSCs; thus, the advantages and disadvantages of these procedures should be discussed. In this review, the latest applications of genetic engineering methods for MSCs with regenerative medicine purposes are presented.

MicroRNAs and their potential therapeutic applications in neural tissue engineering

The inherent poor regeneration capacity of nerve tissues, especially in the central nervous system, poses a grand challenge for neural tissue engineering. After injuries, the local microenvironment often contains potent inhibitory molecules and glial scars, which do not actively support axonal regrowth. MicroRNAs can direct fate of neural cells and are tightly controlled during nerve development. Thus, RNA interference using microRNAs is a promising method to enhance nerve regeneration. Although the physiological roles of microRNA expression levels in various cellular activities or disease conditions have been extensively investigated, the translational use of these understanding for neural tissue engineering remains limited. This review aims to highlight essential microRNAs that participate in cellular behaviors within the adult nervous system and their potential therapeutic applications. In addition, possible delivery methods are also suggested for effective gene silencing in neural tissue engineering.

MicroRNA-9 promotes the neuronal differentiation of rat bone marrow mesenchymal stem cells by activating autophagy

MicroRNA-9 (miR-9) has been shown to promote the differentiation of bone marrow mesenchymal stem cells into neuronal cells, but the precise mechanism is unclear. Our previous study confirmed that increased autophagic activity improved the efficiency of neuronal differentiation in bone marrow mesenchymal stem cells. Accumulating evidence reveals that miRNAs adjust the autophagic pathways. This study used miR-9-1 lentiviral vector and miR-9-1 inhibitor to modulate the expression level of miR-9. Autophagic activity and neuronal differentiation were measured by the number of light chain-3 (LC3)-positive dots, the ratio of LC3-II/LC3, and the expression levels of the neuronal markers enolase and microtubule-associated protein 2. Results showed that LC3-positive dots, the ratio of LC3-II/LC3, and expression of neuron specific enolase and microtubule-associated protein 2 increased in the miR-9⁺ group. The above results suggest that autophagic activity increased and bone marrow mesenchymal stem cells were prone to differentiate into neuronal cells when miR-9 was overexpressed, demonstrating that miR-9 can promote neuronal differentiation by increasing autophagic activity.

miR-29a modulates neuronal differentiation through targeting REST in mesenchymal stem cells

OBJECTIVE

To investigate the modulation of microRNAs (miRNAs) upon the neuronal differentiation of mesenchymal stem cells (MSCs) through targeting RE-1 Silencing Factor (REST), a mature neuronal gene suppressor in neuronal and un-neuronal cells.

METHODS

Rat bone marrow derived-MSCs were induced into neuron-like cells (MSC-NCs) by DMSO and BHA in vitro. The expression of neuron specific enolase (NSE), microtubule-associated protein tau (Tau), REST and its target genes, including synaptosomal-associated protein 25 (SNAP25) and L1 cell adhesion molecular (L1CAM), were detected in MSCs and MSC-NCs. miRNA array analysis was conducted to screen for the upregulated miRNAs after neuronal differentiation. TargetScan was used to predict the relationship between these miRNAs and REST gene, and dual luciferase reporter assay was applied to validate it. Gain and loss of function experiments were used to study the role of miR-29a upon neuronal differentiation of MSCs. The knockdown of REST was conducted to show that miR-29a affected this process through targeting REST.

RESULTS

MSCs were induced into neuron-like cells which presented neuronal cell shape and expressed NSE and Tau. The expression of REST declined and the expression of SNAP25 and L1CAM increased upon the neuronal differentiation of MSCs. Among 14 upregulated miRNAs, miR-29a was validated to target REST gene. During the neuronal differentiation of MSCs, miR-29a inhibition blocked the downregulation of REST, as well as the upregulation of SNAP25, L1CAM, NSE and Tau. REST knockdown rescued the effect of miR-29a inhibition on the expression of NSE and Tau. Meanwhile, miR-29a knockin significantly decreased the expression of REST and increased the expression of SNAP25 and L1CMA in MSCs, but did not significantly affect the expression of NSE and Tau.

CONCLUSION

miR-29a regulates neurogenic markers through targeting REST in mesenchymal stem cells, which provides advances in neuronal differentiation research and stem cell therapy for neurodegenerative diseases.

A positive feedback mechanism that regulates expression of miR-9 during neurogenesis

MiR-9, a neuron-specific miRNA, is an important regulator of neurogenesis. In this study we identify how miR-9 is regulated during early differentiation from a neural stem-like cell. We utilized two immortalized rat precursor clones, one committed to neurogenesis (L2.2) and another capable of producing both neurons and non-neuronal cells (L2.3), to reproducibly study early neurogenesis. Exogenous miR-9 is capable of increasing neurogenesis from L2.3 cells. Only one of three genomic loci capable of encoding miR-9 was regulated during neurogenesis and the promoter region of this locus contains sufficient functional elements to drive expression of a luciferase reporter in a developmentally regulated pattern. Furthermore, among a large number of potential regulatory sites encoded in this sequence, Mef2 stood out because of its known pro-neuronal role. Of four Mef2 paralogs, we found only Mef2C mRNA was regulated during neurogenesis. Removal of predicted Mef2 binding sites or knockdown of Mef2C expression reduced miR-9-2 promoter activity. Finally, the mRNA encoding the Mef2C binding partner HDAC4 was shown to be targeted by miR-9. Since HDAC4 protein could be co-immunoprecipitated with Mef2C protein or with genomic Mef2 binding sequences, we conclude that miR-9 regulation is mediated, at least in part, by Mef2C binding but that expressed miR-9 has the capacity to reduce inhibitory HDAC4, stabilizing its own expression in a positive feedback mechanism.

Abnormal behaviors and developmental disorder of hippocampus in zinc finger protein 521 (ZFP521) mutant mice

Zinc finger protein 521 (ZFP521) regulates a number of cellular processes in a wide range of tissues, such as osteoblast formation and adipose commitment and differentiation. In the field of neurobiology, it is reported to be an essential factor for transition of epiblast stem cells into neural progenitors in vitro. However, the role of ZFP521 in the brain in vivo still remains elusive. To elucidate the role of ZFP521 in the mouse brain, we generated mice lacking exon 4 of the ZFP521 gene. The birth ratio of our ZFP521Δ/Δ mice was consistent with Mendel's laws. Although ZFP521Δ/Δ pups had no apparent defect in the body and were indistinguishable from ZFP521+/+ and ZFP521+/Δ littermates at the time of birth, ZFP521Δ/Δ mice displayed significant weight reduction as they grew, and most of them died before 10 weeks of age. They displayed abnormal behavior, such as hyper-locomotion, lower anxiety and impaired learning, which correspond to the symptoms of schizophrenia. The border of the granular cell layer of the dentate gyrus in the hippocampus of the mice was indistinct and granular neurons were reduced in number. Furthermore, Sox1-positive neural progenitor cells in the dentate gyrus and cerebellum were significantly reduced in number. Taken together, these findings indicate that ZFP521 directly or indirectly affects the formation of the neuronal cell layers of the dentate gyrus in the hippocampus, and thus ZFP521Δ/Δ mice displayed schizophrenia-relevant symptoms. ZFP521Δ/Δ mice may be a useful research tool as an animal model of schizophrenia.