The promyelotic leukemia zinc finger promotes osteoblastic differentiation of human mesenchymal stem cells as an upstream regulator of CBFA1

Supramolecular Composite Hydrogel Loaded with CaF2 Nanoparticles Promotes the Recovery of Periodontitis Bone Resorption

Treatments to reduce periodontal inflammation and rescue periodontitis bone resorption have been of interest to researchers. Bone tissue engineering materials have been gradually used in the treatment of bone defects, but periodontal bone tissue regeneration still faces challenges. Considering the biocompatibility factor, constructing bionic scaffolds with natural extracellular matrix properties is an ideal therapeutic pathway. Based on the pathological mechanism of periodontitis, in this study, short peptide and nanometer inorganic particles were comingled to construct NapKFF-nano CaF2 supramolecular composite hydrogels with different ratios. Material characterization experiments confirmed that the composite hydrogel had suitable mechanical properties and a three-dimensional structure that can function in the resorption region of the alveolar bone and provide spaces for cell proliferation and adhesion. The release of low concentrations of fluoride and calcium ions has been shown to have positive biological effects in both in vivo and in vitro experiments. Vitro experiments confirmed that the composite hydrogel had good biocompatibility and promoted osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Microbiological experiments confirmed that the composite hydrogel inhibited the activity of periodontal pathogenic bacteria. In animal studies, composite hydrogel applied to periodontitis rats in vivo can effectively repair alveolar bone resorption. This composite hydrogel has a simple preparation method and is inexpensive to produce, yet it has antibacterial and osteogenesis-promoting incremental effects, which makes it well suited for the treatment of periodontitis bone resorption, providing a new strategy for periodontal bone tissue engineering.

Establishment of Murine Pregnancy Requires the Promyelocytic Leukemia Zinc Finger Transcription Factor

Using an established human primary cell culture model, we previously demonstrated that the promyelocytic leukemia zinc finger (PLZF) transcription factor is a direct target of the progesterone receptor (PGR) and is essential for progestin-dependent decidualization of human endometrial stromal cells (HESCs). These in vitro findings were supported by immunohistochemical analysis of human endometrial tissue biopsies, which showed that the strongest immunoreactivity for endometrial PLZF is detected during the progesterone (P4)-dominant secretory phase of the menstrual cycle. While these human studies provided critical clinical support for the important role of PLZF in P4-dependent HESC decidualization, functional validation in vivo was not possible due to the absence of suitable animal models. To address this deficiency, we recently generated a conditional knockout mouse model in which PLZF is ablated in PGR-positive cells of the mouse (Plzf d/d). The Plzf d/d female was phenotypically analyzed using immunoblotting, real-time PCR, and immunohistochemistry. Reproductive function was tested using the timed natural pregnancy model as well as the artificial decidual response assay. Even though ovarian activity is not affected, female Plzf d/d mice exhibit an infertility phenotype due to an inability of the embryo to implant into the Plzf d/d endometrium. Initial cellular and molecular phenotyping investigations reveal that the Plzf d/d endometrium is unable to develop a transient receptive state, which is reflected at the molecular level by a blunted response to P4 exposure with a concomitant unopposed response to 17-β estradiol. In addition to a defect in P4-dependent receptivity, the Plzf d/d endometrium fails to undergo decidualization in response to an artificial decidual stimulus, providing the in vivo validation for our earlier HESC culture findings. Collectively, our new Plzf d/d mouse model underscores the physiological importance of the PLZF transcription factor not only in endometrial stromal cell decidualization but also uterine receptivity, two uterine cellular processes that are indispensable for the establishment of pregnancy.

The role of zinc finger proteins in the fate determination of mesenchymal stem cells during osteogenic and adipogenic differentiation

Zinc finger proteins (ZFPs) constitute a crucial group of transcription factors widely present in various organisms. They act as transcription factors, nucleases, and RNA-binding proteins, playing significant roles in cell differentiation, growth, and development. With extensive research on ZFPs, their roles in the determination of mesenchymal stem cells (MSCs) fate during osteogenic and adipogenic differentiation processes have become increasingly clear. ZFP521, for instance, is identified as an inhibitor of the Wnt signaling pathway and RUNX2's transcriptional activity, effectively suppressing osteogenic differentiation. Moreover, ZFP217 contributes to the inhibition of adipogenic differentiation by reducing the M6A level of the cell cycle regulator cyclin D1 (CCND1). In addition, other ZFPs can also influence the fate of mesenchymal stem cells (MSCs) during osteogenic and adipogenic differentiation through various signaling pathways, transcription factors, and epigenetic controls, participating in the subsequent differentiation and maturation of precursor cells. Given the prevalent occurrence of osteoporosis, obesity, and related metabolic disorders, a comprehensive understanding of the regulatory mechanisms balancing bone and fat metabolism is essential, with a particular focus on the fate determination of MSCs in osteogenic and adipogenic differentiation. In this review, we provide a detailed summary of how zinc finger proteins influence the osteogenic and adipogenic differentiation of MSCs through different signaling pathways, transcription factors, and epigenetic mechanisms. Additionally, we outline the regulatory mechanisms of ZFPs in controlling osteogenic and adipogenic differentiation based on various stages of MSC differentiation.

M6A Demethylase Inhibits Osteogenesis of Dental Follicle Stem Cells via Regulating miR-7974/FKBP15 Pathway

N6-methyladenosine (m6A) is the most abundant RNA modification, regulating gene expression in physiological processes. However, its effect on the osteogenic differentiation of dental follicle stem cells (DFSCs) remains unknown. Here, m6A demethylases, the fat mass and obesity-associated protein (FTO), and alkB homolog 5 (ALKBH5) were overexpressed in DFSCs, followed by osteogenesis assay and transcriptome sequencing to explore potential mechanisms. The overexpression of FTO or ALKBH5 inhibited the osteogenesis of DFSCs, evidenced by the fact that RUNX2 independently decreased calcium deposition and by the downregulation of the osteogenic genes OCN and OPN. MiRNA profiling revealed that miR-7974 was the top differentially regulated gene, and the overexpression of m6A demethylases significantly accelerated miR-7974 degradation in DFSCs. The miR-7974 inhibitor decreased the osteogenesis of DFSCs, and its mimic attenuated the inhibitory effects of FTO overexpression. Bioinformatic prediction and RNA sequencing analysis suggested that FK506-binding protein 15 (FKBP15) was the most likely target downstream of miR-7974. The overexpression of FKBP15 significantly inhibited the osteogenesis of DFSCs via the restriction of actin cytoskeleton organization. This study provided a data resource of differentially expressed miRNA and mRNA after the overexpression of m6A demethylases in DFSCs. We unmasked the RUNX2-independent effects of m6A demethylase, miR-7974, and FKBP15 on the osteogenesis of DFSCs. Moreover, the FTO/miR-7974/FKBP15 axis and its effects on actin cytoskeleton organization were identified in DFSCs.

Stem Cell Membrane-Encapsulated Zeolitic Imidazolate Framework-8: A Targeted Nano-Platform for Osteogenic Differentiation

Mesenchymal stem cells (MSCs) have been recognized as one of the most promising pharmaceutical multipotent cells, and a key step for their wide application is to safely and efficiently regulate their activities. Various methods have been proposed to regulate the directional differentiation of MSCs during tissue regeneration, such as nanoparticles and metal ions. Herein, nanoscale zeolitic imidazolate framework-8 (ZIF-8), a Zn-based metal-organic framework, is modified to direct MSCs toward an osteoblast lineage. Specifically, ZIF-8 nanoparticles are encapsulated using stem cell membranes (SCMs) to mimic natural molecules and improve the biocompatibility and targeted ability toward MSCs. SCM/ZIF-8 nanoparticles adjust the sustained release of Zn²⁺ , and promote their specific internalization toward MSCs. The internalized SCM/ZIF-8 nanoparticles show excellent biocompatibility, and increase MSCs' osteogenic potentials. Moreover, RNA-sequencing results elucidate that the activated cyclic adenosine 3,5-monophosphate (cAMP)-PKA-CREB signaling pathway can be dominant in accelerating osteogenic differentiation. In vivo, SCM/ZIF-8 nanoparticles greatly promote the formation of new bone tissue in the femoral bone defect detected by 3D micro-CT, hematoxylin and eosin staining, and Masson staining after 4 weeks. Overall, the SCM-derived ZIF-8 nanostructures achieve the superior targeting ability, biocompatibility, and enhanced osteogenesis, providing a constructive design for tissue repair.

ZIF-8 modified multifunctional injectable photopolymerizable GelMA hydrogel for the treatment of periodontitis

Periodontitis is a chronic inflammatory disease caused by plaque that leads to alveolar bone resorption. In the treatment of periodontitis, it is necessary to reduce the bacterial load and promote alveolar bone regeneration. In this study, zeolitic imidazolate framework-8 (ZIF-8) is used in the treatment of periodontitis, and an injectable photopolymerizable ZIF-8/gelatin methacryloyl (GelMA) composite hydrogel (GelMA-Z) is constructed. We confirm that ZIF-8 nanoparticles are successfully loaded into GelMA, which demonstrates fluidity and photopolymerizability. GelMA-Z continuously releases Zn²⁺ and shows good cytocompatibility. In vitro, GelMA-Z can effectively upregulate the expression of osteogenesis-related genes and proteins, increase alkaline phosphatase activity, promote extracellular matrix mineralization by rat bone mesenchymal stem cells, and exert an obvious antibacterial effect against Porphyromonas gingivalis. In vivo, GelMA-Z reduces the bacterial load, relieves inflammation and promotes alveolar bone regeneration in a rat model. The above results show that GelMA-Z has potential prospects in the treatment of periodontitis. STATEMENT OF SIGNIFICANCE: Various methods have been explored for the treatment of periodontitis. However, current regiments have difficulty achieving ideal alveolar bone regeneration. In this study, we constructed a zeolitic imidazolate framework-8 (ZIF-8)/gelatin methacryloyl (GelMA) composite hydrogel (GelMA-Z). (1) The injectable and photopolymerizable GelMA-Z showed biocompatibility in vitro and in vivo. (2) GelMA-Z continually released zinc ions to promote the osteogenic differentiation of bone mesenchymal stem cells and kill bacteria in vitro. (3) In a rat model, the GelMA-Z pregel solution was used to fill the periodontal pocket and then crosslinked by UV exposure. GelMA-Z can stably remain in the periodontal pocket to reduce the bacterial load, relieve inflammation and promote alveolar bone regeneration. In conclusion, GelMA-Z has great potential for use in the treatment of periodontitis, especially in promoting alveolar bone regeneration.

Biomimetic Metal-Organic Frameworks as Targeted Vehicles to Enhance Osteogenesis

Although engineered nanoparticles loaded with specific growth factors are used to regulate differentiation of stem cells, the low loading efficiency and biocompatibility are still great challenges in tissue repair. A nature-inspired biomimetic delivery system with targeted functions is attractive for enhancing cell activity and controlling cell fate. Herein, a stem cell membrane (SCM)-wrapped dexamethasone (DEX)-loaded zeolitic imidazolate framework-8 (ZIF-8) is constructed, which integrates the synthetic nanomaterials with native plasma membrane, to achieve efficient DEX delivery and DEX-mediated bone repair. The DEX@ZIF-8-SCM enables high DEX loading capacity, modulates the sustained release, and facilitates the specific uptake of mesenchymal stem cells (MSCs), owing to the porous property of ZIF-8 and the innate targeting capability of SCM. The endocytosed DEX@ZIF-8-SCM shows high cytocompatibility and greatly enhances the osteogenic differentiation of MSCs. Furthermore, RNA-sequencing data reveal that the phosphoinositide 3-kinase (PI3K)-Akt signaling pathways are activated and dominantly involved in the accelerated osteogenesis. In the bone defect model, the administrated DEX@ZIF-8-SCM exerts excellent biocompatibility and effectively promotes bone regeneration. Overall, the SCM-derived biomimetic nanoplatform achieves targeted delivery, excellent biosafety, and enhanced osteogenic differentiation and bone repair, which provides a new and valid strategy for treating various tissue injuries.

PLZF and its fusion proteins are pomalidomide-dependent CRBN neosubstrates

Pomalidomide and lenalidomide are immunomodulatory agents that were derived from thalidomide. Cereblon (CRBN) is a common direct target of thalidomide and related compounds and works as a Cullin Ring 4 E3 ubiquitin ligase (CRL4) with DDB1, CUL4, and ROC1. The substrate specificity of CRL4^CRBN is modulated by thalidomide-related compounds. While lenalidomide is approved for the treatment of several diseases including multiple myeloma, 5q- syndrome, mantle cell lymphoma, and follicular lymphoma, pomalidomide is approved only for the treatment of lenalidomide-resistant multiple myeloma. Here we show that PLZF/ZBTB16 and its fusion proteins are pomalidomide-dependent neosubstrates of CRL4^CRBN. PLZF joins to RARα or potentially other partner genes, and the translocation causes leukemias, such as acute promyelocytic leukemia and T-cell acute lymphoblastic leukemia. We demonstrate that pomalidomide treatment induces PLZF-RARα degradation, resulting in antiproliferation of leukemic cells expressing PLZF-RARα. This study highlights a potential therapeutic role of pomalidomide as a degrader of leukemogenic fusion proteins.

Bioinformatics Analysis Identified miR-584-5p and Key miRNA-mRNA Networks Involved in the Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Human periodontal ligament cells (PDLCs) play an important role in periodontal tissue stabilization and function. In the process of osteogenic differentiation of PDLSCs, the regulation of molecular signal pathways are complicated. In this study, the sequencing results of three datasets on GEO were used to comprehensively analyze the miRNA-mRNA network during the osteogenic differentiation of PDLSCs. Using the GSE99958 and GSE159507, a total of 114 common differentially expressed genes (DEGs) were identified, including 62 up-regulated genes and 52 down-regulated genes. GO enrichment analysis was performed. The up-regulated 10 hub genes and down-regulated 10 hub genes were screened out by protein-protein interaction network (PPI) analysis and STRING in Cytoscape. Similarly, differentially expressed miRNAs (DEMs) were selected by limma package from GSE159508. Then, using the miRwalk website, we further selected 11 miRNAs from 16 DEMs that may have a negative regulatory relationship with hub genes. In vitro RT-PCR verification revealed that nine DEMs and 18 hub genes showed the same trend as the RNA-seq results during the osteogenic differentiation of PDLSCs. Finally, using miR-584-5p inhibitor and mimics, it was found that miR-584-5p negatively regulates the osteogenic differentiation of PDLSCs in vitro. In summary, the present results found several potential osteogenic-related genes and identified candidate miRNA-mRNA networks for the further study of osteogenic differentiation of PDLSCs.

Using CRISPR/Cas9 engineering to generate a mouse with a conditional knockout allele for the promyelocytic leukemia zinc finger transcription factor

The promyelocytic leukemia zinc finger (PLZF) transcription factor mediates a wide-range of biological processes. Accordingly, perturbation of PLZF function results in a myriad of physiologic defects, the most conspicuous of which is abnormal skeletal patterning. Although whole body knockout of Plzf in the mouse (Plzf KO ) has significantly expanded our understanding of Plzf function in vivo, a conditional knockout mouse model that enables tissue or cell-type specific ablation of Plzf has not been developed. Therefore, we used CRISPR/Cas 9 gene editing to generate a mouse model in which exon 2 of the murine Plzf gene is specifically flanked (or floxed) by LoxP sites (Plzf f/f ). Crossing our Plzf f/f mouse with a global cre-driver mouse to generate the Plzf d/d bigenic mouse, we demonstrate that exon 2 of the Plzf gene is ablated in the Plzf d/d bigenic. Similar to the previously reported Plzf KO mouse, the Plzf d/d mouse exhibits a severe defect in skeletal patterning of the hindlimb, indicating that the Plzf f/f mouse functions as designed. Therefore, studies in this short technical report demonstrate that the Plzf f/f mouse will be useful to investigators who wish to explore the role of the Plzf transcription factor in a specific tissue or cell-type.

PLZF targets developmental enhancers for activation during osteogenic differentiation of human mesenchymal stem cells

The PLZF transcription factor is essential for osteogenic differentiation of hMSCs; however, its regulation and molecular function during this process is not fully understood. Here, we revealed that the ZBTB16 locus encoding PLZF, is repressed by Polycomb (PcG) and H3K27me3 in naive hMSCs. At the pre-osteoblast stage of differentiation, the locus lost PcG binding and H3K27me3, gained JMJD3 recruitment, and H3K27ac resulting in high expression of PLZF. Subsequently, PLZF was recruited to osteogenic enhancers, influencing H3K27 acetylation and expression of nearby genes important for osteogenic function. Furthermore, we identified a latent enhancer within the ZBTB16/PLZF locus itself that became active, gained PLZF, p300 and Mediator binding and looped to the promoter of the nicotinamide N-methyltransferase (NNMT) gene. The increased expression of NNMT correlated with a decline in SAM levels, which is dependent on PLZF and is required for osteogenic differentiation.

Gene expression of TWIST1 and ZBTB16 is regulated by methylation modifications during the osteoblastic differentiation of mesenchymal stem cells

BACKGROUND

Osteoblastic differentiation of mesenchymal stem cells (MSCs) is the principal stage during the restoration and regeneration of bone tissue. Epigenetic modifications such as DNA methylation play a key role in the differentiation process of stem cells. In this study, the methylation status of the promoter region of ZBTB16 and Twist1 genes and their role in controlling osteoblastic differentiation in MSCs was investigated during the osteoblastic differentiation of MSCs.

METHODS

The MSCs were cultured under standard conditions and differentiated into the osteoblasts. We had three treatment groups including 5-azacytidine (methylation inhibitor), metformin (Twist-inhibitor), and procaine (Wnt/β-catenin inhibitor) and a non-treated group (control). Methylation level of DNA in the promoter regions was monitored by methylation specific-quantitative polymerase chain reaction (PCR). Also, the mRNA levels of key genes in osteoblastic differentiation were measured using real-time PCR.

RESULTS

ZBTB16 gene expression was upregulated, and promoter methylation was decreased. For Twist1 messenger RNA (mRNA) level decreased and promoter methylation increased during osteoblastic differentiation of MSCs. 5-Azacytidine caused a significant reduction in methylation and increased the mRNA expression of ZBTB16 and Twist1. Metformin repressed the Twist1 expression, and therefore osteoblastic differentiation was increased. On the opposite side, procaine could block the WNT/β-catenin signaling pathway, as a consequence the gene expression of key genes involved in osteoblastic differentiation was declined.

CONCLUSION

We found that methylation of DNA in the promoter region of ZBTB16 and Twist1 genes might be one of the main mechanisms that controlling the gene expression during osteoblastic differentiation of MSCs. Also, we could find an association between regulation of Twist1 and ZBTB16 genes and osteoblastic differentiation in MSCs by showing the relation between their expression and some key genes involved in osteoblastic differentiation. In addition, we found a connection between the Twist1 expression level and osteoblastic differentiation by using a Twist-inhibitor (metformin).

ZBTB16 and metabolic syndrome: a network perspective

Metabolic syndrome is a prevalent, complex condition. The search for genetic determinants of the syndrome is currently undergoing a paradigm enhancement by adding systems genetics approaches to association studies. We summarize the current evidence on relations between an emergent new candidate, zinc finger and BTB domain containing 16 (ZBTB16) transcription factor and the major components constituting the metabolic syndrome. Information stemming from studies on experimental models with altered Zbtb16 expression clearly shows its effect on adipogenesis, cardiac hypertrophy and fibrosis, lipid levels and insulin sensitivity. Based on current evidence, we provide a network view of relations between ZBTB16 and hallmarks of metabolic syndrome in order to elucidate the potential functional links involving the ZBTB16 node. Many of the identified genes interconnecting ZBTB16 with all or most metabolic syndrome components are linked to immune function, inflammation or oxidative stress. In summary, ZBTB16 represents a promising pleiotropic candidate node for metabolic syndrome.

Changes of signal transductivity and robustness of gene regulatory network in the carcinogenesis of leukemic subtypes via microarray sample data

Mutation accumulation and epigenetic alterations in genes are important for carcinogenesis. Because leukemogenesis-related signal pathways have been investigated and microarray sample data have been produced in acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and normal cells, systems analysis in coupling pathways becomes possible.

Based on system modeling and identification, we could construct the coupling pathways and their associated gene regulatory networks using microarray sample data. By applying system theory to the estimated system model in coupling pathways, we can then obtain transductivity sensitivity, basal sensitivity and error sensitivity of each protein to identify the potential impact of genetic mutations, epigenetic alterations and the coupling of other pathways from the perspective of energy, respectively. By comparing the results in AML, MDS and normal cells, we investigated the potential critical genetic mutations and epigenetic alterations that activate or repress specific cellular functions to promote MDS or AML leukemogenesis. We suggested that epigenetic modification of β-catenin and signal integration of CSLs, AP-2α, STATs, c-Jun and β-catenin could contribute to cell proliferation at AML and MDS. Epigenetic regulation of ERK and genetic mutation of p53 could lead to the repressed apoptosis, cell cycle arrest and DNA repair in leukemic cells. Genetic mutation of JAK, epigenetic regulation of ERK, and signal integration of C/EBPα could result in the promotion of MDS cell differentiation. According to the results, we proposed three drugs, decitabine, genistein, and monorden for preventing AML leukemogenesis, while three drugs, decitabine, thalidomide, and geldanamycin, for preventing MDS leukemogenesis.

ZBTB16 as a Downstream Target Gene of Osterix Regulates Osteoblastogenesis of Human Multipotent Mesenchymal Stromal Cells

Human multipotent mesenchymal stromal cells (hMSCs) possess the ability to differentiate into osteoblasts, and they can be utilized as a source for bone regenerative therapy. Osteoinductive pretreatment, which induces the osteoblastic differentiation of hMSCs in vitro, has been widely used for bone tissue engineering prior to cell transplantation. However, the molecular basis of osteoblastic differentiation induced by osteoinductive medium (OIM) is still unknown. Therefore, we used a next-generation sequencer to investigate the changes in gene expression during the osteoblastic differentiation of hMSCs. The hMSCs used in this study possessed both multipotency and self-renewal ability. Whole-transcriptome analysis revealed that the expression of zinc finger and BTB domain containing 16 (ZBTB16) was significantly increased during the osteoblastogenesis of hMSCs. ZBTB16 mRNA and protein expression was enhanced by culturing the hMSCs with OIM. Small interfering RNA (siRNA)-mediated gene silencing of ZBTB16 decreased the activity of alkaline phosphatase (ALP); the expression of osteogenic genes, such as osteocalcin (OCN) and bone sialoprotein (BSP), and the mineralized nodule formation induced by OIM. siRNA-mediated gene silencing of Osterix (Osx), which is known as an essential regulator of osteoblastic differentiation, markedly downregulated the expression of ZBTB16. In addition, chromatin immunoprecipitation (ChIP) assays showed that Osx associated with the ZBTB16 promoter region containing the GC-rich canonical Sp1 sequence, which is the specific Osx binding site. These findings suggest that ZBTB16 acts as a downstream transcriptional regulator of Osx and can be useful as a late marker of osteoblastic differentiation. J. Cell. Biochem. 117: 2423-2434, 2016. © 2016 Wiley Periodicals, Inc.

Identification of Novel EZH2 Targets Regulating Osteogenic Differentiation in Mesenchymal Stem Cells

Histone three lysine 27 (H3K27) methyltransferase enhancer of zeste homolog 2 (EZH2) is a critical epigenetic modifier, which regulates gene transcription through the trimethylation of the H3K27 residue leading to chromatin compaction and gene repression. EZH2 has previously been identified to regulate human bone marrow-derived mesenchymal stem cells (MSC) lineage specification. MSC lineage specification is regulated by the presence of EZH2 and its H3K27me3 modification or the removal of the H3K27 modification by lysine demethylases 6A and 6B (KDM6A and KDM6B). This study used a bioinformatics approach to identify novel genes regulated by EZH2 during MSC osteogenic differentiation. In this study, we identified the EZH2 targets, ZBTB16, MX1, and FHL1, which were expressed at low levels in MSC. EZH2 and H3K27me3 were found to be present along the transcription start site of their respective promoters. During osteogenesis, these genes become actively expressed coinciding with the disappearance of EZH2 and H3K27me3 on the transcription start site of these genes and the enrichment of the active H3K4me3 modification. Overexpression of EZH2 downregulated the transcript levels of ZBTB16, MX1, and FHL1 during osteogenesis. Small interfering RNA targeting of MX1 and FHL1 was associated with a downregulation of the key osteogenic transcription factor, RUNX2, and its downstream targets osteopontin and osteocalcin. These findings highlight that EZH2 not only acts through the direct regulation of signaling modules and lineage-specific transcription factors but also targets many novel genes important for mediating MSC osteogenic differentiation.

The Promyelocytic Leukemia Zinc Finger Transcription Factor Is Critical for Human Endometrial Stromal Cell Decidualization

Progesterone, via the progesterone receptor (PGR), is essential for endometrial stromal cell decidualization, a cellular transformation event in which stromal fibroblasts differentiate into decidual cells. Uterine decidualization supports embryo implantation and placentation as well as subsequent events, which together ensure a successful pregnancy. Accordingly, impaired decidualization results not only in implantation failure or early fetal miscarriage, but also may lead to potential adverse outcomes in all three pregnancy trimesters. Transcriptional reprogramming on a genome-wide scale underlies progesterone dependent decidualization of the human endometrial stromal cell (hESC). However, identification of the functionally essential signals encoded by these global transcriptional changes remains incomplete. Importantly, this knowledge-gap undercuts future efforts to improve diagnosis and treatment of implantation failure based on a dysfunctional endometrium. By integrating genome-wide datasets derived from decidualization of hESCs in culture, we reveal that the promyelocytic leukemia zinc finger (PLZF) transcription factor is rapidly induced by progesterone and that this induction is indispensable for progesterone-dependent decidualization. Chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq) identified at least ten progesterone response elements within the PLZF gene, indicating that PLZF may act as a direct target of PGR signaling. The spatiotemporal expression profile for PLZF in both the human and mouse endometrium offers further support for stromal PLZF as a mediator of the progesterone decidual signal. To identify functional targets of PLZF, integration of PLZF ChIP-Seq and RNA Pol II RNA-Seq datasets revealed that the early growth response 1 (EGR1) transcription factor is a PLZF target for which its level of expression must be reduced to enable progesterone dependent hESC decidualization. Apart from furnishing essential insights into the molecular mechanisms by which progesterone drives hESC decidualization, our findings provide a new conceptual framework that could lead to new avenues for diagnosis and/or treatment of adverse reproductive outcomes associated with a dysfunctional uterus.

Promyelocytic leukemia zinc finger mediates glucocorticoid-induced cell cycle arrest in the chondroprogenitor cell line ATDC5

Glucocorticoids (GCs) affect the proliferation of growth plate chondrocytes. In this study, we investigated the role of the GC-inducible promyelocytic leukemia zinc finger (PLZF) gene in chondrocyte differentiation by using the chondrogenic cell line ATDC5. PLZF overexpression suppressed cell cycle progression (p < 0.01) and promoted differentiation into hypertrophic chondrocytes by inducing mRNA expression of alkaline phosphatase (p < 0.01), and the cyclin-dependent kinase (CDK) inhibitor p21 (p < 0.01). In contrast, PLZF knockdown impaired differentiation into hypertrophic chondrocytes and promoted cell cycle progression (p < 0.01). Treatment with the GC analogue dexamethasone (10(-6) M) suppressed cell cycle progression in ATDC5 cells. PLZF shRNA attenuated dexamethasone-induced cell cycle arrest (p < 0.01) by downregulating the mRNA expression of the CDK inhibitors p21 and p57 (p < 0.01). These results clearly indicated that PLZF promoted differentiation into hypertrophic chondrocytes and mediated dexamethasone-induced cell cycle arrest by regulating CDK inhibitors.

Expression of plzfa in embryo and adult of medaka Oryzias latipes

In this study, a homologous gene named plzfa was identified and characterized in medaka Oryzias latipes. Oryzias latipes plzfa was detected in all the tissues including brain, gill, muscle, liver, intestine, kidney, spleen, testis and ovary using reverse transcriptase (RT)-PCR. plzfa was detected in the oocytes of the ovary and in the spermatogonia and somitic cells of the testis by in situ hybridization. plzfa had a maternal origin with continuous and dynamic expression during embryonic development. plzfa was observed in the brain, neural rod and sensor organs including the eyes, ears and nose during embryogenesis. plzfa was also detected in the neural crest, somite, pectoral fin, intestine and skin. These results indicate that plzfa is a pleiotropic gene that may play major roles in various tissues.

Degenerative Cervical Myelopathy: Epidemiology, Genetics, and Pathogenesis

STUDY DESIGN

Review.

OBJECTIVE

To formally introduce "degenerative cervical myelopathy" (DCM) as the overarching term to describe the various degenerative conditions of the cervical spine that cause myelopathy. Herein, the epidemiology, pathogenesis, and genetics of conditions falling under this hypernym are carefully described.

SUMMARY OF BACKGROUND DATA

Nontraumatic, degenerative forms of cervical myelopathy represent the commonest cause of spinal cord impairment in adults and include cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, and degenerative disc disease. Unfortunately, there is neither a specific term nor a specific diagnostic International Classification of Diseases, Tenth Revision code to describe this collection of clinical entities. This has resulted in the inconsistent use of diagnostic terms when referring to patients with myelopathy due to degenerative disease of the cervical spine.

METHODS

Narrative review.

RESULTS

The incidence and prevalence of myelopathy due to degeneration of the spine are estimated at a minimum of 41 and 605 per million in North America, respectively. Incidence of cervical spondylotic myelopathy-related hospitalizations has been estimated at 4.04/100,000 person-years, and surgical rates seem to be rising. Pathophysiologically, myelopathy results from static compression, spinal malalignment leading to altered cord tension and vascular supply, and dynamic injury mechanisms. Occupational hazards, including transportation of goods by weight bearing on top of the head, and other risk factors may accelerate DCM development. Potential genetic factors include those related to MMP-2 and collagen IX for degenerative disc disease, and collagen VI and XI for ossification of the posterior longitudinal ligament. In addition, congenital anomalies including spinal stenosis, Down syndrome, and Klippel-Feil syndrome may predispose to the development of DCM.

CONCLUSION

Although DCMs can present as separate diagnostic entities, they are highly interrelated, frequently manifest concomitantly, present similarly from a clinical standpoint, and seem to be in part a response to compensate and improve stability due to progressive age and wear of the cervical spine. The use of the term "degenerative cervical myelopathy" is advocated.

LEVEL OF EVIDENCE

5.

Genome-wide gene expression profiles of dental follicle stem cells

OBJECTIVE

Dental stem cells (SCs) will be increasingly used for bone regeneration in the future. Recently, dental follicle cells (DFCs) from retained human third molars have been isolated and characterized as osteogenic progenitors. Although these results are promising for regenerative dentistry, molecular processes during osteogenic differentiation are not yet well understood.

MATERIALS AND METHODS

This study compared DFCs before and during osteogenic differentiation. ALP activity was measured and cells were stained with alizarin red. Real-time RT-PCRs for osteogenic markers were done. The genome-wide expression profile was evaluated using a microarray.

RESULTS

DFCs showed strong mineralization and increased expression of osteogenic marker genes during osteogenic differentiation. A microarray analysis showed regulated genes before and in the process of osteogenic differentiation (day 7). Several regulated genes in DFCs were associated with skeletal development. Bioinformatic analysis revealed a number of factors associated with dental follicle osteogenic differentiation. Osteogenic differentiation affected expression levels of the transcriptional regulators FOXC2 and ZNF219.

CONCLUSION

In conclusion, the results yielded new objectives for further studies on transcription factors like FOXC2 or ETV1 and their role in dental SCs during osteogenic differentiation.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

Downregulation of PLZF in human hepatocellular carcinoma and its clinical significance

Promyelocytic leukemia zinc finger (PLZF) acts as a tumor-suppressor gene in a series of cancers including prostate, melanoma, colon cancer and leukemia. However, its role in hepatocellular carcinoma (HCC) has not yet been illustrated. The present study aimed to investigate the expression and epigenetic regulation of PLZF as well as its clinical significance in HCC. We found that the expression of PLZF was significantly downregulated in HCC samples at both the RNA level (P<0.001) and protein level compared with these levels in adjacent normal tissues. The relative expression level of PLZF was also positively correlated with the ALP level (P=0.026) noted in the HCC patients. However, hypermethylation was only detected in one out of 5 paired HCC samples, indicating that methylation of the selected promoter region (from -1702 to -1388) may not be the major regulatory mechanism for the downregulation of PLZF in HCC. A receiver operating characteristic (ROC) curve was created to evaluate the diagnostic value for differentiating between HCC and benign diseases. The area under the ROC curve (AUC) for indicating the value of PLZF as an HCC biomarker was 0.794 (95% CI, 0.697-0.892; P<0.001). Taken together, our results suggest that PLZF may play an important role in HCC development and may be a potential biomarker for the diagnosis of HCC.

Dexamethasone-related osteogenic differentiation of dental follicle cells depends on ZBTB16 but not Runx2

Dental follicle cells (DFCs) can be artificially differentiated into mineralizing cells. With a dexamethasone-based differentiation protocol, transcription factors ZBTB16 and NR4A3 are highly upregulated but Runx2 and other osteogenic marker genes are not. Previous studies have suggested the involvement of a Runx2-independent differentiation pathway. The objective of this study is to further elucidate this mechanism. Differentiation of DFCs was examined by alkaline phosphatase (ALP) staining and ALP activity measurement, by Alizarin Red S staining and by real-time reverse transcription plus the polymerase chain reaction. ZBTB16 was overexpressed by using a transient transfection method. Resulting genome-wide gene expression changes were assessed by microarray. ZBTB16 and Runx2 were inhibited by short interfering RNA transfection. Promoter binding of ZBTB16 was evaluated by chromatin immunoprecipitation. Downregulation of Runx2 had no effect on dexamethasone-induced differentiation but was effective on BMP2-induced differentiation. Downregulation of ZBTB16, however, impaired dexamethasone-induced differentiation. Genes that were upregulated by dexamethasone induction were also upregulated by ZBTB16 overexpression. Genes that were not upregulated during dexamethasone-induced differentiation were also not regulated by ZBTB16 overexpression. ZBTB16 bound directly to the promoter regions of osterix and NR4A3 but not that of Runx2. Overexpression of ZBTB16 led to changes in the gene expression profile, whereby upregulated genes were overrepresented in osteogenesis-associated biological processes. Our findings suggest that, in DFCs, a Runx2-independent differentiation mechanism exists that is regulated by ZBTB16.

Long-term tumor necrosis factor treatment induces NFκB activation and proliferation, but not osteoblastic differentiation of adipose tissue-derived mesenchymal stem cells in vitro

The pro-inflammatory cytokine tumor necrosis factor (TNF) is well known to induce differentiation of bone matrix-resorbing osteoclasts from hematopoietic stem cells. However, the impact of TNF on differentiation of bone matrix-forming osteoblasts from mesenchymal stem cells (MSC) was only fragmentarily studied so far. Therefore, we investigated what impact long-term TNF treatment has on osteoblastic differentiation of MSC isolated from the adipose tissue (ASC) in vitro. In summary, we found continuous TNF exposure to induce the nuclear factor of kappa B pathway in ASC as well as secretion of the pro-inflammatory chemokine interleukin 8, but not the mitogen-activated protein kinase and the apoptosis pathway in ASC. Moreover, TNF neither induced nor inhibited osteoblastic differentiation of ASC, but strongly increased their proliferation rate. In that manner, pro-inflammatory conditions in vivo may generate significantly increased numbers of progenitor cells, and ASC especially, in conjunction with external stimuli, may contribute to the events of ectopic ossification observed in chronic inflammatory diseases. The substantiation of the translation of our in vitro findings to the disease context encourages further in vivo studies.

Promyelocytic leukemia zinc-finger induction signs mesenchymal stem cell commitment: identification of a key marker for stemness maintenance?

Introduction

Mesenchymal stem cells (MSCs) are an attractive cell source for cartilage and bone tissue engineering given their ability to differentiate into chondrocytes and osteoblasts. However, the common origin of these two specialized cell types raised the question about the identification of regulatory pathways determining the differentiation fate of MSCs into chondrocyte or osteoblast.

Methods

Chondrogenesis, osteoblastogenesis, and adipogenesis of human and mouse MSC were induced by using specific inductive culture conditions. Expression of promyelocytic leukemia zinc-finger (PLZF) or differentiation markers in MSCs was determined by RT-qPCR. PLZF-expressing MSC were implanted in a mouse osteochondral defect model and the neotissue was analyzed by routine histology and microcomputed tomography.

Results

We found out that PLZF is not expressed in MSCs and its expression at early stages of MSC differentiation is the mark of their commitment toward the three main lineages. PLZF acts as an upstream regulator of both Sox9 and Runx2, and its overexpression in MSC enhances chondrogenesis and osteogenesis while it inhibits adipogenesis. In vivo, implantation of PLZF-expressing MSC in mice with full-thickness osteochondral defects resulted in the formation of a reparative tissue resembling cartilage and bone.

Conclusions

Our findings demonstrate that absence of PLZF is required for stemness maintenance and its expression is an early event at the onset of MSC commitment during the differentiation processes of the three main lineages.

ZBTB16 induces osteogenic differentiation marker genes in dental follicle cells independent from RUNX2

BACKGROUND

Dental follicle cells (DFCs) are neural crest cell-derived cells and the genuine precursor cells of cementoblast and alveolar osteoblasts. After osteogenic differentiation, expression levels of the transcription factor zinc factor and BTB domain containing 16 (ZBTB16) were significantly increased. ZBTB16 is associated with the process of osteogenic differentiation in bone marrow-derived mesenchymal stem cells and crucial for the expression of the osteogenic transcription factor runt-related transcription factor 2 (RUNX2). It is proposed that ZBTB16 plays also a crucial role for the differentiation of DFCs into osteoblasts.

METHODS

In this study, the differentiation of DFCs by alkaline phosphatase (ALP) activity measurement, alizarin red staining, and electron-dispersive x-ray spectrometry (EDX) analysis is investigated. The expression of ZBTB16 during osteogenic differentiation and the expression of osteogenic differentiation markers were assessed by real-time reverse transcription polymerase chain reaction. Glucocorticoid stimulation was inhibited using RU486 (11β-[p-(Dimethylamino)phenyl]-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one), and ZBTB16 was overexpressed via transient transfection of an expression vector.

RESULTS

After the initiation of osteogenic differentiation, ZBTB16 levels were increased highly in DFCs, whereas RUNX2 was expressed constitutively only. An EDX analysis verified the differentiation of DFCs into osteoblast-like cells because clusters of mineralization consisted of hydroxyapatite. ZBTB16 induced the expression of nuclear receptor subfamily 4, group A, member 3; osteocalcin; and stanniocalcin 1 (STC1) but not of RUNX2 and ALP in DFCs. STC1 was upregulated in DFCs downstream of ZBTB16 and after the osteogenic differentiation. The overexpression of STC1 in DFCs increased the expression of ZBTB16 and specific markers for biomineralization.

CONCLUSIONS

The present study shows that ZBTB16 induced the expression of osteogenic differentiation markers independently of RUNX2. Moreover, STC1 is a new candidate for the evaluation of late mechanisms of osteogenic differentiation downstream of ZBTB16.

PLZF mediates the PTEN/AKT/FOXO3a signaling in suppression of prostate tumorigenesis

Promyelocytic leukemia zinc finger (PLZF) protein expression is closely related to the progression of human cancers, including prostate cancer (PCa). However, the according context of a signaling pathway for PLZF to suppress prostate tumorigenesis remains greatly unknown. Here we report that PLZF is a downstream mediator of the PTEN signaling pathway in PCa. We found that PLZF expression is closely correlated with PTEN expression in a cohort of prostate cancer specimens. Interestingly, both PTEN rescue and phosphoinositide 3-kinase (PI3K) inhibitor LY294002 treatment increase the PLZF expression in prostate cancer cell lines. Further, luciferase reporter assay and chromatin immunoprecipitation assay demonstrate that FOXO3a, a transcriptional factor phosphorylated by PI3K/AKT, could directly bind to the promoter of PLZF gene. These results indicate that PTEN regulates PLZF expression by AKT/FOXO3a. Moreover, our animal experiments also demonstrate that PLZF is capable of inhibiting prostate tumorigenesis in vivo. Taken together, our study defines a PTEN/PLZF pathway and would shed new lights for developing therapeutic strategy of prostate cancer.

Impact of bacteria and bacterial components on osteogenic and adipogenic differentiation of adipose-derived mesenchymal stem cells

Adult mesenchymal stem cells (MSC) are present in several tissues, e.g. bone marrow, heart muscle, brain and subcutaneous adipose tissue. In invasive infections MSC get in contact with bacteria and bacterial components. Not much is known about how bacterial pathogens interact with MSC and how contact to bacteria influences MSC viability and differentiation potential. In this study we investigated the impact of three different wound infection relevant bacteria, Escherichia coli, Staphylococcus aureus, and Streptococcus pyogenes, and the cell wall components lipopolysaccharide (LPS; Gram-negative bacteria) and lipoteichoic acid (LTA; Gram-positive bacteria) on viability, proliferation, and osteogenic as well as adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells (adMSC). We show that all three tested species were able to attach to and internalize into adMSC. The heat-inactivated Gram-negative E. coli as well as LPS were able to induce proliferation and osteogenic differentiation but reduce adipogenic differentiation of adMSC. Conspicuously, the heat-inactivated Gram-positive species showed the same effects on proliferation and adipogenic differentiation, while its cell wall component LTA exhibited no significant impact on adMSC. Therefore, our data demonstrate that osteogenic and adipogenic differentiation of adMSC is influenced in an oppositional fashion by bacterial antigens and that MSC-governed regeneration is not necessarily reduced under infectious conditions.

Effect of compressive force on human osteoblast-like cells and bone remodelling: an in vitro study

OBJECTIVE

The aim of this study was to determine the effect of continuous compressive force (CF) on expression by human alveolar bone-derived osteoblasts (HOBs) of some specific molecules involved in bone remodelling.

DESIGN

HOBs were cultured with or without CF (control, 2.0, 4.0gcm(-2)) for 1, 3 and 7 days. Expression of alkaline phosphatase (ALP), type I collagen (Col I), osteopontin (OPN), osteocalcin (OCN), transcription factor Runx2, receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG) and prostaglandin E2 (PGE2) was analysed by real-time-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and/or immunostaining.

RESULTS

The results revealed that CF upregulated ALP and Col I expression at both messenger RNA (mRNA) and protein levels but did not affect expression of OPN and OCN mRNA. Runx2 mRNA was inhibited by CF, which also altered the expression of molecules involved in osteoclastogenesis, by enhancing RANKL expression and suppressing OPG expression. At 4.0gcm(-2) of CF, the expression of RANKL and PGE2 was significantly upregulated.

CONCLUSION

The results suggest that initial application of CF on HOBs can simultaneously affect expression of markers related to both osteogenesis and osteoclastogenesis.

Distinct signal transduction pathways downstream of the (P)RR revealed by microarray and ChIP-chip analyses

The (pro)renin receptor ((P)RR) signaling is involved in different pathophysiologies ranging from cardiorenal end-organ damage via diabetic retinopathy to tumorigenesis. We have previously shown that the transcription factor promyelocytic leukemia zinc finger (PLZF) is an adaptor protein of the (P)RR. Furthermore, recent publications suggest that major functions of the (P)RR are mediated ligand-independently by its transmembrane and intracellular part, which acts as an accessory protein of V-ATPases. The transcriptome and recruitmentome downstream of the V-ATPase function and PLZF in the context of the (P)RR are currently unknown. Therefore, we performed a set of microarray and chromatin-immunoprecipitation (ChIP)-chip experiments using siRNA against the (P)RR, stable overexpression of PLZF, the PLZF translocation inhibitor genistein and the specific V-ATPase inhibitor bafilomycin to dissect transcriptional pathways downstream of the (P)RR. We were able to identify distinct and overlapping genetic signatures as well as novel real-time PCR-validated target genes of the different molecular functions of the (P)RR. Moreover, bioinformatic analyses of our data confirm the role of (P)RŔs signal transduction pathways in cardiovascular disease and tumorigenesis.

Transcriptional regulatory cascades in Runx2-dependent bone development

The development of the musculoskeletal system is a complex process that involves very precise control of bone formation and growth as well as remodeling during postnatal life. Although the understanding of the transcriptional mechanisms of osteogenesis has increased considerably, the molecular regulatory basis, especially the gene regulatory network of osteogenic differentiation, is still poorly understood. This review provides the reader with an overview of the key transcription factors that govern bone formation, highlighting their function and regulation linked to Runt-related transcription factor 2 (Runx2). Runx2 as the master transcription factor of osteoblast differentiation, Twist, Msh homeobox 2 (Msx2), and promyelocytic leukemia zinc-finger protein (PLZF) acting upstream of Runx2, Osterix (Osx) acting downstream of Runx2, and activating transcription factor 4 (ATF4) and zinc-finger protein 521 (ZFP521) acting as cofactors of Runx2 are discussed, and their relevance for tissue engineering is presented. References are provided for more in-depth personal study.

Comparison of the differentiation potential of neural crest derived progenitor cells from apical papilla (dNC-PCs) and stem cells from exfoliated deciduous teeth (SHED) into mineralising cells

OBJECTIVE

Recently, cells from the apical papilla of retained human third molars (dental neural crest-derived progenitor cells, dNC-PCs) have been isolated and characterised as multipotent progenitor cells. Nonetheless, molecular processes during differentiation into mineralising cells are still unknown. This study evaluated the osteogenic/odontogenic differentiation of dNC-PCs under in vitro conditions and compared these cells with already known odontoblast precursor cells (dental stem cells from exfoliated human deciduous teeth, SHED).

METHODS

The differentiation of dNC-PCs and SHED under in vitro conditions was verified by Alizarin red staining (mineralisation), alkaline phosphatase activity and the expression of osteogenic/odontogenic markers (RT-PCRs). The genome wide expression-profiles were investigated with Affymetrix DNA-microarrays and the cell migration with a gel spot cell migration assay.

RESULTS

In our study dNC-PCs differentiated like SHED in mineralising cells. The expression of odontoblast markers suggested that dNC-PCs and SHED differentiated into different types of odontoblasts. This supposition was supported by genome wide gene expression profiles of dNC-PCs and SHED after cell differentiation. Typical biological processes of undifferentiated cells, for example "mitosis", were regulated in dNC-PCs. In SHED biological processes like "response to wounding" or "cell migration" were regulated, which are associated with replacement odontoblasts and their precursors. Moreover, a gel-spot assay revealed that SHED migrated faster than dNC-PCs.

CONCLUSION

Our results suggest that dNC-PCs are precursors for primary odontoblasts, whereas SHED differentiate into replacement odontoblasts. These different odontogenic differentiation potentials of dNC-PCs and SHED have to be considered for cellular therapies and tissue engineering approaches in the future.

Runx2 haploinsufficiency ameliorates the development of ossification of the posterior longitudinal ligament

Ossification of the Posterior Longitudinal Ligament (OPLL) is a disease that is characterized by the ectopic calcification of the ligament; however, the pathogenesis of OPLL remains to be investigated. We attempted to identify the in vivo role of Runx2, a master regulator of osteoblast differentiation and skeletal mineralization, in the pathogenesis of OPLL. The expression of Runx2 in the ligament was examined using in situ hybridization and immunohistochemistry and by monitoring the activity of a LacZ gene that was inserted into the Runx2 gene locus. To investigate the functional role of Runx2, we studied ENPP1^ttw/ttw mice, a mouse model of OPLL, that were crossed with heterozygous Runx2 mice to decrease the expression of Runx2, and we performed histological and quantitative radiological analyses using 3D-micro CT. Runx2 was expressed in the ligament of wild-type mice. The induction of Runx2 expression preceded the development of ectopic calcification in the OPLL-like region of the ENPP1^ttw/ttw mice. Runx2 haploinsufficiency ameliorated the development of ectopic calcification in the ENPP1^ttw/ttw mice. Collectively, this study demonstrated that Runx2 is expressed in an OPLL-like region, and its elevation is a prerequisite for developing the complete OPLL-like phenotype in a mouse model of OPLL.

The promyelocytic leukemia zinc finger protein: two decades of molecular oncology

The promyelocytic leukemia zinc finger (PLZF) protein, also known as Zbtb16 or Zfp145, was first identified in a patient with acute promyelocytic leukemia, where a reciprocal chromosomal translocation t(11;17)(q23;q21) resulted in a fusion with the RARA gene encoding retinoic acid receptor alpha. The wild-type Zbtb16 gene encodes a transcription factor that belongs to the POK (POZ and Krüppel) family of transcriptional repressors. In addition to nine Krüppel-type sequence-specific zinc fingers, which make it a member of the Krüppel-like zinc finger protein family, the PLZF protein contains an N-terminal BTB/POZ domain and RD2 domain. PLZF has been shown to be involved in major developmental and biological processes, such as spermatogenesis, hind limb formation, hematopoiesis, and immune regulation. PLZF is localized mainly in the nucleus where it exerts its transcriptional repression function, and many post-translational modifications affect this ability and also have an impact on its cytoplasmic/nuclear dissociation. PLZF achieves its transcriptional regulation by binding to many secondary molecules to form large multi-protein complexes that bind to the regulatory elements in the promoter region of the target genes. These complexes are also capable of physically interacting with its target proteins. Recently, PLZF has become implicated in carcinogenesis as a tumor suppressor gene, since it regulates the cell cycle and apoptosis in many cell types. This review will examine the major advances in our knowledge of PLZF biological activities that augment its value as a therapeutic target, particularly in cancer and immunological diseases.

The transcription factor DLX3 regulates the osteogenic differentiation of human dental follicle precursor cells

The transcription factor DLX3 plays a decisive role in bone development of vertebrates. In neural-crest derived stem cells from the dental follicle (DFCs), DLX3 is differentially expressed during osteogenic differentiation, while other osteogenic transcription factors such as DLX5 or RUNX2 are not highly induced. DLX3 has therefore a decisive role in the differentiation of DFCs, but its actual biological effects and regulation are unknown. This study investigated the DLX3-regulated processes in DFCs. After DLX3 overexpression, DFCs acquired a spindle-like cell shape with reorganized actin filaments. Here, marker genes for cell morphology, proliferation, apoptosis, and osteogenic differentiation were significantly regulated as shown in a microarray analysis. Further experiments showed that DFCs viability is directly influenced by the expression of DLX3, for example, the amount of apoptotic cells was increased after DLX3 silencing. This transcription factor stimulates the osteogenic differentiation of DFCs and regulates the BMP/SMAD1-pathway. Interestingly, BMP2 did highly induce DLX3 and reverse the inhibitory effect of DLX3 silencing in osteogenic differentiation. However, after DLX3 overexpression in DFCs, a BMP2 supplementation did not improve the expression of DLX3 and the osteogenic differentiation. In conclusion, DLX3 influences cell viability and regulates osteogenic differentiation of DFCs via a BMP2-dependent pathway and a feedback control.

Zinc-finger protein 145, acting as an upstream regulator of SOX9, improves the differentiation potential of human mesenchymal stem cells for cartilage regeneration and repair

OBJECTIVE

Human mesenchymal stem cells (hMSCs) represent one of the most promising stem cell therapies for traumatic injury and age-related degenerative diseases involving cartilage. However, few genetic factors regulating chondrogenesis of MSCs have been identified. One study showed that zinc-finger protein 145 (ZNF145), a transcription factor, was up-regulated during 3-lineage differentiation of hMSCs. The present study was undertaken to validate whether this novel transcription factor is useful for the repair and regeneration of cartilage.

METHODS

Human MSCs were transfected with lentiviral short hairpin RNA (for small interfering RNA knockdown of ZNF145) and a lentiviral vector for overexpression of ZNF145, and the effects of ZNF145 on chondrogenesis were studied using quantitative polymerase chain reaction and immunostaining. Microarray and transient expression analyses were used to determine whether ZNF145 is a factor operating upstream of SOX9. Allogeneic transplantation of hMSCs into osteochondral defects in rats was performed to determine the effects of ZNF145 on repair of cartilage in vivo.

RESULTS

Small interfering RNA-mediated gene silencing of ZNF145 slowed down chondrogenesis, whereas overexpression of ZNF145 enhanced chondrogenesis. Global gene expression profiling showed up-regulated gene expression in ZNF145-overexpressing MSCs, and transient overexpression of ZNF145 enhanced the expression of SOX9, suggesting that ZNF145 acts as a factor upstream of SOX9, the master regulator of chondrogenesis. Moreover, allogeneic transplantation of hMSCs into osteochondral defects of rat knees showed that ZNF145-overexpressing MSCs repaired cartilage defects better and earlier than empty control MSCs.

CONCLUSION

These findings suggest that ZNF145 gene therapy may be a very useful strategy for improving the quality of cartilage regeneration and repair.

Recent highlights on bone stem cells: a report from Bone Stem Cells 2009, and not only…

The use of stem cells has opened new prospects for the treatment of orthopaedic conditions characterized by large bone defects. However, many issues still exist to which answers are needed before routine, large-scale application becomes possible. Bone marrow stromal cells (MSC), which are clonogenic, multipotential precursors present in the bone marrow stroma, are generally employed for bone regeneration. Stem cells with multilineage differentiation similar to MSC have also been demonstrated in adipose tissue, peripheral blood, umbilical cord and amniotic fluid. Each source presents its own advantages and drawbacks. Unfortunately, no unique surface antigen is expressed by MSC, and this hampers simple MSC enrichment from heterogeneous populations. MSC are identified through a combination of physical, morphological and functional assays. Different in vitro and in vivo models have been described for the research on bone stem cells. These models should predict the in vivo bone healing capacity of MSC and if the induced osteogenesis is similar to the physiological one. Although stem cells offer an exciting possibility of a renewable source of cells and tissues for replacement, orthopaedic applications often represent case reports whereas controlled randomized trials are still lacking. Further biological aspects of bone stem cells should be elucidated and a general consensus on the best models, protocols and proper use of scaffolds and growth factors should be achieved.

Evaluation of the delivery of mesenchymal stem cells into the root canal space of necrotic immature teeth after clinical regenerative endodontic procedure

INTRODUCTION

Immature teeth with open apices treated with conventional nonsurgical root canal treatment often have a poor prognosis as a result of the increased risk of fracture and susceptibility to recontamination. Regenerative endodontics represents a new treatment modality that focuses on reestablishment of pulp vitality and continued root development. This clinical procedure relies on the intracanal delivery of a blood clot (scaffold), growth factors (possibly from platelets and dentin), and stem cells. However, to date, the clinical presence of stem cells in the canal space after this procedure has not been demonstrated. The purpose of this clinical study was to evaluate whether regenerative endodontic procedures are able to deliver stem cells into the canal space of immature teeth in young patients and to identify the possible tissue origin for these cells.

METHODS

After informed consent, the first appointment consisted of NaOCl irrigation and treatment with a triple antibiotic paste. One month later, the root canal space was irrigated with sterile saline, and bleeding was evoked with collection of samples on paper points. Real-time reverse-transcription polymerase chain reaction and immunocytochemistry were conducted to compare the gene transcripts and proteins found in the root canal sample with levels found in the systemic circulation.

RESULTS

Molecular analyses of blood collected from the canal system indicated the significant accumulation of transcripts for the stem cell markers CD73 and CD105 (up to 600-fold), compared with levels found in the systemic blood. Furthermore, this effect was selective because there was no change in expression of the differentiation markers ALK-P, DSPP, ZBTB16, and CD14. Histologic analyses demonstrated that the delivered cells expressed both CD105 and STRO-1, markers for a subpopulation of mesenchymal stem cells.

CONCLUSIONS

Collectively, these findings demonstrate that the evoked-bleeding step in regenerative procedures triggers the significant accumulation of undifferentiated stem cells into the canal space where these cells might contribute to the regeneration of pulpal tissues seen after antibiotic paste therapy of the immature tooth with pulpal necrosis.

Genetic differences in the osteogenic differentiation potency according to the classification of ossification of the posterior longitudinal ligament of the cervical spine

STUDY DESIGN

We categorized the four types of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine into two groups. We biochemically investigated the genetic differences in the osteogenic differentiation potency between the two groups.

OBJECTIVE

To investigate the genetic differences in the osteogenic differentiation potency according to the OPLL classification.

SUMMARY OF BACKGROUND DATA

Clinical studies on OPLL have revealed that the risk of progression of the ossification area is greatest for continuous and mixed type OPLL. However, until now, these four types of OPLL have been studied as a single condition.

METHODS

We categorized the four types of OPLL into the OPLL continuous (continuous or mixed type) and OPLL segmental groups (segmental or circumscribed type). Paraspinal ligaments were aseptically obtained from OPLL patients during surgery. The fibroblast-like cells that migrated from the explants were used for experiments. The cells were placed in a 60-mm culture dishes for total ribonucleic acid preparation and 12 well microplates for alkaline phosphatase (ALP) activity staining. After cultures reached confluence, the cells were cultured in osteogenic medium. The messenger ribonucleic acid expression of bone morphogenetic protein-2 (BMP-2), osterix, tumor necrosis factor-α-stimulated gene-6, and ALP was analyzed by quantitative real time-polymerase chain reaction. Osteogenic differentiation of fibroblast-like cells was determined by histochemically detecting ALP production.

RESULTS

After osteogenic induction, BMP-2 expression increased in the OPLL continuous and segmental groups. Osterix expression increased in the OPLL continuous group only. Tumor necrosis factor-α-stimulated gene-6 expression was suppressed in the OPLL continuous and segmental groups. ALP expression as well as ALP activity staining was higher in the OPLL continuous group than in the OPLL segmental group. CONCLUSION.: The study revealed genetic differences in the osteogenic differentiation potency between the OPLL continuous and segmental groups. We propose to distinguish OPLL continuous group from segmental group in biochemical studies on OPLL.

Mesenchymal Stem Cells

Stem cells have two features: the ability to differentiate along different lineages and the ability of self-renewal. Two major types of stem cells have been described, namely, embryonic stem cells and adult stem cells. Embryonic stem cells (ESC) are obtained from the inner cell mass of the blastocyst and are associated with tumorigenesis, and the use of human ESCs involves ethical and legal considerations. The use of adult mesenchymal stem cells is less problematic with regard to these issues. Mesenchymal stem cells (MSCs) are stromal cells that have the ability to self-renew and also exhibit multilineage differentiation. MSCs can be isolated from a variety of tissues, such as umbilical cord, endometrial polyps, menses blood, bone marrow, adipose tissue, etc. This is because the ease of harvest and quantity obtained make these sources most practical for experimental and possible clinical applications. Recently, MSCs have been found in new sources, such as menstrual blood and endometrium. There are likely more sources of MSCs waiting to be discovered, and MSCs may be a good candidate for future experimental or clinical applications. One of the major challenges is to elucidate the mechanisms of differentiation, mobilization, and homing of MSCs, which are highly complex. The multipotent properties of MSCs make them an attractive choice for possible development of clinical applications. Future studies should explore the role of MSCs in differentiation, transplantation, and immune response in various diseases.

Transcriptomes and Proteomes of Dental Follicle Cells

Ectomesenchymal dental stem cells could be feasible tools for dental tissue engineering. Dental follicle cells are a promising example, since they are capable of differentiation into various dental tissue cells, such as osteoblasts or cementoblasts. However, cellular mechanisms of cell proliferation and differentiation are not understood in detail. Basic knowledge of these molecular processes may shorten the time before ectomesenchymal dental stem cells can be exploited for bone augmentation in regenerative medicine. Recent developments in proteomics and transcriptomics have made information about genome-wide expression profiles accessible, which can aid in clarifying molecular mechanisms of cells. This review describes the transcriptomes and proteomes of dental follicle cells before and after differentiation, and compares them with differentially expressed populations from dental tissue or bone marrow.

NF-kappaB activation stimulates osteogenic differentiation of mesenchymal stem cells derived from human adipose tissue by increasing TAZ expression

Tumor necrosis factor-alpha (TNF-alpha) is a skeletal catabolic agent that stimulates osteoclastogenesis and inhibits osteoblast function. Although TNF-alpha inhibits the mineralization of osteoblasts, the effect of TNF-alpha on mesenchymal stem cells (MSC) is not clear. In this study, we determined the effect of TNF-alpha on osteogenic differentiation of stromal cells derived from human adipose tissue (hADSC) and the role of NF-kappaB activation on TNF-alpha activity. TNF-alpha treatment dose-dependently increased osteogenic differentiation over the first 3 days of treatment. TNF-alpha activated ERK and increased NF-kappaB promoter activity. PDTC, an NF-kappaB inhibitor, blocked the osteogenic differentiation induced by TNF-alpha and TLR-ligands, but U102, an ERK inhibitor, did not. Overexpression of miR-146a induced the inhibition of IRAK1 expression and inhibited basal and TNF-alpha- and TLR ligand-induced osteogenic differentiation. TNF-alpha and TLR ligands increased the expression of transcriptional coactivator with PDZ-binding motif (TAZ), which was inhibited by the addition of PDTC. A ChIP assay showed that p65 was bound to the TAZ promoter. TNF-alpha also increased osteogenic differentiation of human gastroepiploic artery smooth muscle cells. Our data indicate that TNF-alpha enhances osteogenic differentiation of hADSC via the activation of NF-kappaB and a subsequent increase of TAZ expression.

Gene expression profiles of dental follicle cells before and after osteogenic differentiation in vitro

Recently, osteogenic precursor cells were isolated from human dental follicles, which differentiate into cementoblast- or osteoblast-like cells under in vitro conditions after the induction with dexamethasone or insulin. However, mechanisms for osteogenic differentiation are not understood in detail. In a previous study, real-time RT-PCR results demonstrated molecular mechanisms in dental follicle cells (DFCs) during osteogenic differentiation that are different from those in bone-marrow-derived mesenchymal stem cells. We analysed gene expression profiles in DFCs before and after osteogenic differentiation with the Affymetrix GeneChip(R) Human Gene 1.0 ST Array. Transcripts of 98 genes were up-regulated after differentiation. These genes could be clustered into subcategories such as cell differentiation, cell morphogenesis, and skeletal development. Osteoblast-specific transcription factors like osterix and runx2 were constitutively expressed in differentiated DFCs. In contrast, the transcription factor ZBTB16, which promotes the osteoblastic differentiation of mesenchymal stem cells as an up-stream regulator of runx2, was differentially expressed after differentiation. Transcription factors NR4A3, KLF9 and TSC22D3, involved in the regulation of cellular development, were up-regulated as well. In conclusion, we present the first transcriptome of human DFCs before and after osteogenic differentiation. This study sheds new light on the complex mechanism of osteogenic differentiation in DFCs.

Endothelial cells influence the osteogenic potential of bone marrow stromal cells

Background

Improved understanding of the interactions between bone cells and endothelial cells involved in osteogenesis should aid the development of new strategies for bone tissue engineering. The aim of the present study was to determine whether direct communication between bone marrow stromal cells (MSC) and human umbilical vein endothelial cells (EC) could influence the osteogenic potential of MSC in osteogenic factor-free medium.

Methods

After adding EC to MSC in a direct-contact system, cell viability and morphology were investigated with the WST assay and immnostaining. The effects on osteogenic differentiation of adding EC to MSC was systematically tested by the using Superarray assay and results were confirmed with real-time PCR.

Results

Five days after the addition of EC to MSC in a ratio of 1:5 (EC/MSC) significant increases in cell proliferation and cellular bridges between the two cell types were detected, as well as increased mRNA expression of alkaline phosphatase (ALP). This effect was greater than that seen with addition of osteogenic factors such as dexamethasone, ascorbic acid and β-glycerophosphate to the culture medium. The expression of transcription factor Runx2 was enhanced in MSC incubated with osteogenic stimulatory medium, but was not influenced by induction with EC. The expression of Collagen type I was not influenced by EC but the cells grown in the osteogenic factor-free medium exhibited higher expression than those cultured with osteogenic stimulatory medium.

Conclusion

These results show that co-culturing of EC and MSC for 5 days influences osteogenic differentiation of MSC, an effect that might be independent of Runx2, and enhances the production of ALP by MSC.