Hes1 stimulates transcriptional activity of Runx2 by increasing protein stabilization during osteoblast differentiation

A human organoid drug screen identifies α2-adrenergic receptor signaling as a therapeutic target for cartilage regeneration

Directed differentiation of stem cells toward chondrogenesis in vitro and in situ to regenerate cartilage suffers from off-target differentiation and hypertrophic tendency. Here, we generated a cartilaginous organoid system from human expanded pluripotent stem cells (hEPSCs) carrying a COL2A1mCherry and COL10A1eGFP double reporter, enabling real-time monitoring of chondrogenesis and hypertrophy. After screening 2,040 FDA-approved drugs, we found that α-adrenergic receptor (α-AR) antagonists, especially phentolamine, stimulated chondrogenesis but repressed hypertrophy, while α2-AR agonists reduced chondrogenesis and induced hypertrophy. Phentolamine prevented cartilage degeneration in hEPSC cartilaginous organoid and human cartilage explant models and stimulated microfracture-activated endogenous skeletal stem cells toward hyaline-like cartilage regeneration without fibrotic degeneration in situ. Mechanistically, α2-AR signaling induced hypertrophic degeneration via cyclic guanosine monophosphate (cGMP)-dependent secretory leukocyte protease inhibitor (SLPI) production. SLPI-deleted cartilaginous organoid was degeneration resistant, facilitating large cartilage defect healing. Ultimately, targeting α2-AR/SLPI was a promising and clinically feasible strategy to regenerate cartilage via promoting chondrogenesis and repressing hypertrophy.

HES1 is required for mouse fetal hematopoiesis

BACKGROUND

Hematopoiesis in mammal is a complex and highly regulated process in which hematopoietic stem cells (HSCs) give rise to all types of differentiated blood cells. Previous studies have shown that hairy and enhancer of split (HES) repressors are essential regulators of adult HSC development downstream of Notch signaling.

METHODS

In this study, we investigated the role of HES1, a member of HES family, in fetal hematopoiesis using an embryonic hematopoietic specific Hes1 conditional knockout mouse model by using phenotypic flow cytometry, histopathology analysis, and functional in vitro colony forming unit (CFU) assay and in vivo bone marrow transplant (BMT) assay.

RESULTS

We found that loss of Hes1 in early embryonic stage leads to smaller embryos and fetal livers, decreases hematopoietic stem progenitor cell (HSPC) pool, results in defective multi-lineage differentiation. Functionally, fetal hematopoietic cells deficient for Hes1 exhibit reduced in vitro progenitor activity and compromised in vivo repopulation capacity in the transplanted recipients. Further analysis shows that fetal hematopoiesis defects in Hes1fl/flFlt3Cre embryos are resulted from decreased proliferation and elevated apoptosis, associated with de-repressed HES1 targets, p27 and PTEN in Hes1-KO fetal HSPCs. Finally, pharmacological inhibition of p27 or PTEN improves fetal HSPCs function both in vitro and in vivo.

CONCLUSION

Together, our findings reveal a previously unappreciated role for HES1 in regulating fetal hematopoiesis, and provide new insight into the differences between fetal and adult HSC maintenance.

Genetic models for lineage tracing in musculoskeletal development, injury, and healing

Musculoskeletal development and later post-natal homeostasis are highly dynamic processes, marked by rapid structural and functional changes across very short periods of time. Adult anatomy and physiology are derived from pre-existing cellular and biochemical states. Consequently, these early developmental states guide and predict the future of the system as a whole. Tools have been developed to mark, trace, and follow specific cells and their progeny either from one developmental state to the next or between circumstances of health and disease. There are now many such technologies alongside a library of molecular markers which may be utilized in conjunction to allow for precise development of unique cell 'lineages'. In this review, we first describe the development of the musculoskeletal system beginning as an embryonic germ layer and at each of the key developmental stages that follow. We then discuss these structures in the context of adult tissues during homeostasis, injury, and repair. Special focus is given in each of these sections to the key genes involved which may serve as markers of lineage or later in post-natal tissues. We then finish with a technical assessment of lineage tracing and the techniques and technologies currently used to mark cells, tissues, and structures within the musculoskeletal system.

Repurposing sarecycline for osteoinductive therapies: an in vitro and ex vivo assessment

INTRODUCTION

Tetracyclines (TCs) embrace a class of broad-spectrum antibiotics with unrelated effects at sub-antimicrobial levels, including an effective anti-inflammatory activity and stimulation of osteogenesis, allowing their repurposing for different clinical applications. Recently, sarecycline (SA)-a new-generation molecule with a narrower antimicrobial spectrum-was clinically approved due to its anti-inflammatory profile and reduced adverse effects verified with prolonged use. Notwithstanding, little is known about its osteogenic potential, previously verified for early generation TCs.

MATERIALS AND METHODS

Accordingly, the present study is focused on the assessment of the response of human bone marrow-derived mesenchymal stromal cells (hBMSCs) to a concentration range of SA, addressing the metabolic activity, morphology and osteoblastic differentiation capability, further detailing the modulation of Wnt, Hedgehog, and Notch signaling pathways. In addition, an ex vivo organotypic bone development system was established in the presence of SA and characterized by microtomographic and histochemical analysis.

RESULTS

hBMSCs cultured with SA presented a significantly increased metabolic activity compared to control, with an indistinguishable cell morphology. Moreover, RUNX2 expression was upregulated 2.5-fold, and ALP expression was increased around sevenfold in the presence of SA. Further, GLI2 expression was significantly upregulated, while HEY1 and HNF1A were downregulated, substantiating Hedgehog and Notch signaling pathways' modulation. The ex vivo model developed in the presence of SA presented a significantly enhanced collagen deposition, extended migration areas of osteogenesis, and an increased bone mineral content, substantiating an increased osteogenic development.

CONCLUSION

Summarizing, SA is a promising candidate for drug repurposing within therapies envisaging the enhancement of bone healing/regeneration.

Research Methodology and Mechanisms of Action of Current Orthopaedic Implant Coatings

Orthopedic implants are crucial interventions that are gaining greater importance in modern medicine to restore function to commonly affected joints. Each implantation carries the risk of implant-associated infection and loosening of the implant due to improper integration with soft tissue. Coating strategies have been developed to aid the growth of bone into the implant (osteointegration) and prevent biofilm formation to avoid infection. In this review, primary articles highlighting recent developments and advancements in orthopedic implant coating will be presented. Additionally, the methodology of the articles will be critiqued based on this research criteria: establishment of function on a theoretical basis, validation of coating function, and potential next steps/improvements based on results. A theoretical basis based on understanding the mechanisms at play of these various coatings allows for systems to be developed to tackle the tasks of osteointegration, subversion of infection, and avoidance of cytotoxicity. The current state of research methodology in coating design focuses too heavily on either osteointegration or the prevention of infection, thus, future development in medical implant coating needs to investigate the creation of a coating that accomplishes both tasks. Additionally, next steps and improvements to systems need to be better highlighted to move forward when problems arise within a system. Research currently showcasing new coatings is performed primarily in vitro and in vivo. More clinical trials need to be performed to highlight long-term sustainability, the structural integrity, and the safety of the implant.

GRWD1 affects the proliferation, apoptosis, invasion and migration of triple negative breast cancer through the Notch signaling pathway

Breast cancer is a highly heterogeneous tumor, among which triple negative breast cancer (TNBC) is the most invasive and prone to recurrence and metastasis. The present study aimed to investigate the regulatory mechanisms of glutamate-rich WD-repeat-containing protein 1 (GRWD1) in TNBC cells. The expression of GRWD1 in the normal human breast epithelial cells and human breast cancer cells was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. The transfection effects of small interfering RNA (siRNA)-GRWD1 and overexpression (Ov)-Notch1 were also confirmed by RT-qPCR and western blotting. The proliferation, apoptosis, invasion and migration of transfected cells were in turn analyzed by Cell Counting Kit-8, 5-Ethynyl-2'-deoxyuridine, Matrigel and wound healing assays. The expression of proteins related to proliferation, apoptosis, metastasis, epithelial-mesenchymal transition and the Notch signaling pathway was detected by western blotting. As a result, GRWD1 expression was upregulated in breast cancer cells and was revealed to be highest in MDA-MB-231 and HCC1937 cells. GRWD1 knockdown suppressed TNBC cell proliferation, invasion and migration and promoted TNBC cell apoptosis. Furthermore, the expression of Notch1 and Notch4 was inhibited by GRWD1 knockdown. The expression of downstream genes of the Notch signaling pathway Hes1, Hes5, Hey1, Hey2, p21, c-Myc, cyclin D1, human epidermal growth factor 2 receptor and NF-κB were all suppressed after siRNA-GRWD1 transfection. However, Notch1 overexpression reversed the effect of GRWD1 knockdown on biological behaviors of TNBC cells. In conclusion, GRWD1 knockdown could suppress the proliferation, invasion and migration and promoted apoptosis of TNBC cells through inhibiting the Notch signaling pathway.

Regulation and Role of Transcription Factors in Osteogenesis

Bone is a dynamic tissue constantly responding to environmental changes such as nutritional and mechanical stress. Bone homeostasis in adult life is maintained through bone remodeling, a controlled and balanced process between bone-resorbing osteoclasts and bone-forming osteoblasts. Osteoblasts secrete matrix, with some being buried within the newly formed bone, and differentiate to osteocytes. During embryogenesis, bones are formed through intramembraneous or endochondral ossification. The former involves a direct differentiation of mesenchymal progenitor to osteoblasts, and the latter is through a cartilage template that is subsequently converted to bone. Advances in lineage tracing, cell sorting, and single-cell transcriptome studies have enabled new discoveries of gene regulation, and new populations of skeletal stem cells in multiple niches, including the cartilage growth plate, chondro-osseous junction, bone, and bone marrow, in embryonic development and postnatal life. Osteoblast differentiation is regulated by a master transcription factor RUNX2 and other factors such as OSX/SP7 and ATF4. Developmental and environmental cues affect the transcriptional activities of osteoblasts from lineage commitment to differentiation at multiple levels, fine-tuned with the involvement of co-factors, microRNAs, epigenetics, systemic factors, circadian rhythm, and the microenvironments. In this review, we will discuss these topics in relation to transcriptional controls in osteogenesis.

Bio-activating ultrafine grain titanium: RNA sequencing reveals enhanced mechano-activation of osteoconduction on nanostructured substrates

Titanium is essentially absent from biological systems yet reliably integrates into bone. To achieve osseointegration, titanium must activate biological processes without entering cells, defining it as a bio-activating material. Nanostructuring bulk titanium reduces grain size, increases strength, and improves other quantifiable physical properties, including cytocompatibility. The biological processes activated by increasing grain boundary availability were detected with total RNA-sequencing in mouse pre-osteoblasts grown for 72 hours on nanometrically smooth substrates of either coarse grain or nanostructured ultrafine grain titanium. The average grain boundary length under cells on the conventional coarse grain substrates is 273.0 μm, compared to 70,881.5 μm for cells adhered to the nanostructured ultrafine grain substrates; a 260-fold difference. Cells on both substrates exhibit similar expression profiles for genes whose products are critical for mechanosensation and transduction of cues that trigger osteoconduction. Biological process Gene Ontology term enrichment analysis of differentially expressed genes reveals that cell cycle, chromatin modification, telomere maintenance, and RNA metabolism processes are upregulated on ultrafine grain titanium. Processes related to immune response, including apoptosis, are downregulated. Tumor-suppressor genes are upregulated while tumor-promoting genes are downregulated. Upregulation of genes involved in chromatin remodeling and downregulation of genes under the control of the peripheral circadian clock implicate both processes in the transduction of mechanosensory information. Non-coding RNAs may also play a role in the response. Merging transcriptomics with well-established mechanobiology principles generates a unified model to explain the bio-activating properties of titanium. The modulation of processes is accomplished through chromatin remodeling in which the nucleus responds like a rheostat to grain boundary concentration. This convergence of biological and materials science reveals a pathway toward understanding the biotic-abiotic interface and will inform the development of effective bio-activating and bio-inactivating materials.

Ozone ultrafine bubble water induces the cellular signaling involved in oxidative stress responses in human periodontal ligament fibroblasts

Periodontitis is a chronic inflammatory disease caused by oral microorganisms in the subgingival biofilm. Stable aqueous ozone ultrafine bubble water (OUFBW) has recently begun to be used as an antiseptic in the treatment of periodontitis. The effectiveness of OUFBW is thought to depend on the bactericidal actions of dissolved ozone exerted via its oxidizing effect. On the other hand, the effects of ozone on the periodontal tissues are largely unknown. In this paper we examined the cellular responses after OUFBW treatment. Human primary periodontal ligament fibroblasts (hPDLFs) or Ca9-22 human gingival epithelial cells were treated with OUFBW or UV-inactivated OUFBW. The production of reactive oxygen species (ROS), the activation of mitogen-activated protein kinase (MAPK) and the nuclear factor-kappa B (NF-κB) activation were analyzed. The transcript profiles of hPDLFs after OUFBW treatment were also analyzed by RNA sequencing (RNA-seq). Our results showed that OUFBW induces oxidative stress by generating ROS, which, in turn, activated the MAPK pathway. OUFBW triggered activation of c-Fos, a major component of the transcription factor activator protein 1 (AP-1), and also nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), which possessed a high sensitivity to oxidative stress. The results of RNA-seq analysis revealed that the numerous genes involved in oxidative stress responses or MAPK signaling pathway were up-regulated after OUFBW treatment. Investigation of the signaling pathways activated by OUFBW highlights another aspect of the biological roles of OUFBW, in addition to its bactericidal activity, in the treatment of periodontitis.

Biodegradable polymer promotes osteogenic differentiation in immortalized and primary osteoblast-like cells

Biodegradable polymers have been broadly used as agents that can complex with and deliver osteoinductive agents, but osteoinductivity of the polymers themselves has been rarely studied. Here we report the osteoinductivity of poly(4-hydroxy-L-proline ester) (PHPE), a biodegradable cationic polymer with cell penetrating properties. Under physiological conditions, PHPE degrades into trans-4-hydroxy-L-proline (trans-Hyp), a non-coded amino acid with essential functions in collagen fibril formation and fibril stability. Treatment of SaOS-2 osteoblast-like cells and hFOB 1.19 primary osteoblast cells with PHPE promoted earlier collagen nodule formation and mineralization of the extracellular matrix compared to untreated cells, even when mineralization activators were absent in the growth medium. Our results indicate that PHPE is a potential osteoinductive agent in vitro that can favor bone regeneration. Moreover, this osteoinductive property could be partly attributed to the degradation product trans-Hyp, which could recapitulate some, but not all of the osteogenic activity. The primary findings of this study can be summarized as follows: treatment of cells with PHPE led to (1) the induction of COL1A1 expression, collagen synthesis and secretion in osteoblast-like cells, (2) mineralization of the ECM in both SaOS-2 and hFOB 1.19 primary osteoblasts, and (3) induction of BMP2 gene and protein expression in osteoblast-like cells, which can promote mineralization of the ECM and regeneration of the bone tissue. Our results suggest that PHPE is a non-cytotoxic polymer and can be potentially used to overcome collagenopathies such as osteogenesis imperfecta.

Notch signaling negatively regulates BMP9-induced osteogenic differentiation of mesenchymal progenitor cells by inhibiting JunB expression

Although interaction between BMP and Notch signaling has been demonstrated to be crucial for osteogenic differentiation of mesenchymal stem cells (MSCs), the precise molecular mechanism remains unknown. Here, we show that Notch intracellular domain (NICD) overexpression inhibits BMP9-induced C3H10T1/2 cell osteogenesis in vivo and in vitro. Our results show that activated Notch signaling results in down-regulation of Runx2 and early osteogenesis differentiation factors, without affecting p-Smad1/5/8 expression, and that blocking Notch signaling with DAPT (N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester) significantly increases p-Smad1/5/8 expression. Interestingly, Notch signaling also regulates the cell cycle by increasing PCNA (proliferation cell nuclear antigen) and CyclinD1 expression. Furthermore, similar results were obtained by ectopic bone formation and histological analyses, indicating that Notch signaling activation significantly inhibits BMP9-induced MSC osteogenic, cartilage and adipogenic differentiation. Moreover, we are the first to show that Notch regulates by suppressing JunB synthesis and that the negative effect of Notch is partially reversed by treatment with the JunB activator TPA (12-O-tetradeca-noylphorbol-13-acetate). Our findings demonstrate that Notch signaling significantly enhances cell proliferation but inhibits MSC osteogenic differentiation induced by BMP9 via JunB protein suppression rather than by BMP/Smad signaling regulation.

Notch pathway is active during osteogenic differentiation of human bone marrow mesenchymal stem cells induced by pulsed electromagnetic fields

Pulsed electromagnetic fields (PEMFs) have been used to treat bone diseases, particularly nonunion healing. Although it is known that PEMFs promote the osteogenic differentiation of human mesenchymal stem cells (hMSCs), to date PEMF molecular mechanisms remain not clearly elucidated. The Notch signalling is a highly conserved pathway that regulates cell fate decisions and skeletal development. The aim of this study was to investigate if the known PEMF-induced osteogenic effects may involve the modulation of the Notch pathway. To this purpose, during in vitro osteogenic differentiation of bone marrow hMSCs in the absence and in the presence of PEMFs, osteogenic markers (alkaline phosphatase activity, osteocalcin and matrix mineralization), the messenger ribonucleic acid expression of osteogenic transcription factors (Runx2, Dlx5, Osterix) as well as of Notch receptors (Notch1-4), their ligands (Jagged1, Dll1 and Dll4) and nuclear target genes (Hes1, Hes5, Hey1, Hey2) were investigated. PEMFs stimulated all osteogenic markers and increased the expression of Notch4, Dll4, Hey1, Hes1 and Hes5 in osteogenic medium compared to control. In the presence of DAPT and SAHM1, used as Notch pathway inhibitors, the expression of the osteogenic markers, including Runx2, Dlx5, Osterix, as well as Hes1 and Hes5 were significantly inhibited, both in unexposed and PEMF-exposed hMSCs. These results suggest that activation of Notch pathway is required for PEMFs-stimulated osteogenic differentiation. These new findings may be useful to improve autologous cell-based regeneration of bone defects in orthopaedics.

Hes4: A potential prognostic biomarker for newly diagnosed patients with high-grade osteosarcoma

BACKGROUND

Prognostic biomarkers for osteosarcoma (OS) at the time of diagnosis are lacking. Necrotic response of OS to preoperative chemotherapy correlates with survival and is determined 3-4 months after diagnosis. The purpose of this study is to identify biomarkers that will stratify patients into good or poor responders to chemotherapy at diagnosis and determine the role of potential biomarkers in OS pathogenesis.

PROCEDURE

Because OS may be caused by disruptions of osteogenic differentiation, and the Notch pathway is one regulator of bone development, we examined the link between Notch effectors, OS differentiation, and OS outcome. We probed the R2: Genomics Analysis and Visualization Platform for RNA expression levels of Notch targets in mixed high-grade OS pretreatment biopsies. We used human OS cell lines in vitro and in mice to determine the role of the Notch target hairy/enhancer of split 4 (Hes4) in OS.

RESULTS

We found that in OS patients, high expression of Hes4 is correlated with decreased metastasis-free and overall survival. Human OS cells that overexpress Hes4 are more immature and have an increased invasive capacity in vitro. This was not universal to all Notch effectors, as Hes1 overexpression induced opposing effects. When injected into NSG mice, Hes4-overexpressing OS cells produced significantly larger, more lytic tumors and significantly more metastases than did control cells.

CONCLUSIONS

Hes4 overexpression promotes a more aggressive tumor phenotype by preventing osteoblastic differentiation of OS cells. Hes4 expression may allow for the stratification of patients into good or poor responders to chemotherapy at diagnosis.

Hairy/enhancer of Split Homologue-1 Suppresses Vascular Endothelial Growth Factor-induced Angiogenesis via Downregulation of Osteopontin Expression

Angiogenesis plays a critical role in the progression and vulnerability of atherosclerotic plaques; however, the orchestration of angiogenesis in atherosclerotic plaque formation remains unclear. The results of microarray analysis, real-time PCR and immunohistochemical analyses showed that Hairy/enhancer of split homologue-1 (Hes-1) expression was significantly decreased, while that of osteopontin (OPN) was increased, in atherosclerotic plaques. Meanwhile, immunofluorescence results demonstrated that both Hes-1 and OPN were expressed in endothelial cells (ECs) of neovessels in atherosclerotic plaques. The results of an in vitro study showed that Hes-1 was downregulated, while OPN was upregulated, in a time- and dose-dependent manner in human umbilical vein endothelial cells (HUVECs) by VEGF treatment. In addition, Hes-1 knockdown was found to have transcriptional promotion effect on OPN expression in HUVECs and enhance OPN-induced angiogenesis in response to VEGF. On the contrary, Hes-1 overexpression inhibited OPN expression in HUVECs and reduced angiogenesis in vitro and in vivo. The results of this study suggest that decreased Hes-1 expression in atherosclerotic plaques exaggerate VEGF-induced angiogenesis by upregulating OPN. Therefore, restoring Hes-1 expression and inhibiting OPN expression may be a promising strategy to prevent vulnerable plaque formation in patients with atherosclerosis.

Notch Signaling and the Skeleton

Notch 1 to 4 receptors are important determinants of cell fate and function, and Notch signaling plays an important role in skeletal development and bone remodeling. After direct interactions with ligands of the Jagged and Delta-like families, a series of cleavages release the Notch intracellular domain (NICD), which translocates to the nucleus where it induces transcription of Notch target genes. Classic gene targets of Notch are hairy and enhancer of split (Hes) and Hes-related with YRPW motif (Hey). In cells of the osteoblastic lineage, Notch activation inhibits cell differentiation and causes cancellous bone osteopenia because of impaired bone formation. In osteocytes, Notch1 has distinct effects that result in an inhibition of bone resorption secondary to an induction of osteoprotegerin and suppression of sclerostin with a consequent enhancement of Wnt signaling. Notch1 inhibits, whereas Notch2 enhances, osteoclastogenesis and bone resorption. Congenital disorders of loss- and gain-of-Notch function present with severe clinical manifestations, often affecting the skeleton. Enhanced Notch signaling is associated with osteosarcoma, and Notch can influence the invasive potential of carcinoma of the breast and prostate. Notch signaling can be controlled by the use of inhibitors of Notch activation, small peptides that interfere with the formation of a transcriptional complex, or antibodies to the extracellular domain of specific Notch receptors or to Notch ligands. In conclusion, Notch plays a critical role in skeletal development and homeostasis, and serious skeletal disorders can be attributed to alterations in Notch signaling.

A smart fluorescence nanoprobe for the detection of cellular alkaline phosphatase activity and early osteogenic differentiation

In the past decades, biomaterials were designed to induce stem cell toward osteogenic differentiation. However, conventional methods for evaluation osteogenic differentiation all required a process of cell fixation or lysis, which induce waste of a large number of cells. In this study, a fluorescence nanoprobe was synthesized by combining phosphorylated fluoresceinamine isomer I (FLA) on the surface of mesoporous silica-coated superparamagnetic iron oxide (Fe3O4@mSiO2) nanoparticles. In the presence of alkaline phosphatase (ALP), the phosphorylated FLA on the nanoprobe would be hydrolyzed, resulting in a fluorescence recovery of FLA. During early osteogenic differentiation, a high-level expression of cellular ALP was induced, which accelerated the hydrolysis of phosphorylated FLA, resulting in an enhancement of cellular fluorescence intensity. This fluorescence nanoprobe provides us a rapid and non-toxic method for the detection of cellular ALP activity and early osteogenic differentiation.

Hes1: a key role in stemness, metastasis and multidrug resistance

Hes1 is one mammalian counterpart of the Hairy and Enhancer of split proteins that play a critical role in many physiological processes including cellular differentiation, cell cycle arrest, apoptosis and self-renewal ability. Recent studies have shown that Hes1 functions in the maintenance of cancer stem cells (CSCs), metastasis and antagonizing drug-induced apoptosis. Pathways that are involved in the up-regulation of Hes1 level canonically or non-canonically, such as the Hedgehog, Wnt and hypoxia pathways are frequently aberrant in cancer cells. Here, we summarize the recent data supporting the idea that Hes1 may have an important function in the maintenance of cancer stem cells self-renewal, cancer metastasis, and epithelial-mesenchymal transition (EMT) process induction, as well as chemotherapy resistance, and conclude with the possible mechanisms by which Hes1 functions have their effect, as well as their crosstalk with other carcinogenic signaling pathways.

Global increase in O-linked N-acetylglucosamine modification promotes osteoblast differentiation

The balance between bone formation and bone resorption is maintained by osteoblasts and osteoclasts, and an imbalance in this bone metabolism leads to osteoporosis. Here, we found that osteoblast differentiation in MC3T3-E1 cells is promoted by the inactivation of O-linked β-N-acetylglucosaminidase (O-GlcNAcase) and suppressed by the inactivation of O-GlcNAc transferase, as indicated by extracellular matrix calcification. The expression of osteogenic genes such as alp, ocn, and bsp during osteoblast differentiation was positively regulated in a O-GlcNAc glycosylation-dependent manner. Because it was confirmed that Ets1 and Runx2 are the two key transcription factors responsible for the expression of these osteogenic genes, their transcriptional activity might therefore be regulated by O-GlcNAc glycosylation. However, osteoclast differentiation of RAW264 cells, as indicated by the expression and activity of tartrate-resistant acid phosphatase, was unaffected by the inactivation of either O-GlcNAcase or O-GlcNAc transferase. Our findings suggest that an approach to manipulate O-GlcNAc glycosylation could be useful for developing the therapeutics for osteoporosis.

Globularity and language-readiness: generating new predictions by expanding the set of genes of interest

This study builds on the hypothesis put forth in Boeckx and Benítez-Burraco (2014), according to which the developmental changes expressed at the levels of brain morphology and neural connectivity that resulted in a more globular braincase in our species were crucial to understand the origins of our language-ready brain. Specifically, this paper explores the links between two well-known 'language-related' genes like FOXP2 and ROBO1 implicated in vocal learning and the initial set of genes of interest put forth in Boeckx and Benítez-Burraco (2014), with RUNX2 as focal point. Relying on the existing literature, we uncover potential molecular links that could be of interest to future experimental inquiries into the biological foundations of language and the testing of our initial hypothesis. Our discussion could also be relevant for clinical linguistics and for the interpretation of results from paleogenomics.

Notch signaling in chondrocytes modulates endochondral ossification and osteoarthritis development

Here we examined the involvement of Notch signaling in the endochondral ossification process, which is crucial for osteoarthritis (OA) development. Intracellular domains of Notch1 and -2 were translocated into the nucleus of chondrocytes with their differentiation in mouse limb cartilage and in mouse and human OA articular cartilage. A tissue-specific inactivation of the Notch transcriptional effector recombination signal binding protein for Ig kappa J (RBPjκ) in chondroprogenitor cells of SRY-box containing gene 9 (Sox9)-Cre;Rbpj(fl/fl) mouse embryos caused an impaired terminal stage of endochondral ossification in the limb cartilage. The RBPjκ inactivation in adult articular cartilage after normal skeletal growth using type II collagen (Col2a1)-Cre(ERT);Rbpj(fl/fl) mice by tamoxifen injection caused resistance to OA development in the knee joint. Notch intracellular domain with the effector RBPjκ stimulated endochondral ossification through induction of the target gene Hes1 in chondrocytes. Among the Notch ligands, Jagged1 was strongly induced during OA development. Finally, intraarticular injection of N-[N-(3,5-diflurophenylacetate)-L-alanyl]-(S)-phenylglycine t-butyl ester (DAPT), a small compound Notch inhibitor, to the mouse knee joint prevented OA development. The RBPjκ-dependent Notch signaling in chondrocytes modulates the terminal stage of endochondral ossification and OA development, representing an extracellular therapeutic target of OA.

Scanning probe-enabled nanocombinatorics define the relationship between fibronectin feature size and stem cell fate

We report the development of a powerful analytical method that utilizes a tilted elastomeric pyramidal pen array in the context of a scanning probe lithography experiment to rapidly prepare libraries having as many as 25 million features over large areas with a range of feature sizes from the nano- to microscale. This technique can be used to probe important chemical and biological processes, opening up the field of nanocombinatorics. In a proof-of-concept investigation of mesenchymal stem cell (MSC) differentiation, combinatorial patterns first enabled a rapid and systematic screening of MSC adhesion, as a function of feature size, while uniform patterns were used to study differentiation with statistically significant sample sizes. Without media containing osteogenic-inducing chemical cues, cells cultured on nanopatterned fibronectin substrates direct MSC differentiation towards osteogenic fates when compared to nonpatterned fibronectin substrates. This powerful and versatile approach enables studies of many systems spanning biology, chemistry, and engineering areas.

USP1 deubiquitinates ID proteins to preserve a mesenchymal stem cell program in osteosarcoma

Inhibitors of DNA binding (IDs) antagonize basic-helix-loop-helix (bHLH) transcription factors to inhibit differentiation and maintain stem cell fate. ID ubiquitination and proteasomal degradation occur in differentiated tissues, but IDs in many neoplasms appear to escape degradation. We show that the deubiquitinating enzyme USP1 promotes ID protein stability and stem cell-like characteristics in osteosarcoma. USP1 bound, deubiquitinated, and thereby stabilized ID1, ID2, and ID3. A subset of primary human osteosarcomas coordinately overexpressed USP1 and ID proteins. USP1 knockdown in osteosarcoma cells precipitated ID protein destabilization, cell-cycle arrest, and osteogenic differentiation. Conversely, ectopic USP1 expression in mesenchymal stem cells stabilized ID proteins, inhibited osteoblastic differentiation, and enhanced proliferation. Consistent with USP1 functioning in normal mesenchymal stem cells, USP1-deficient mice were osteopenic. Our observations implicate USP1 in preservation of the stem cell state that characterizes osteosarcoma and identify USP1 as a target for differentiation therapy.

Musashi1 and hairy and enhancer of split 1 high expression cells derived from embryonic stem cells enhance the repair of small-intestinal injury in the mouse

BACKGROUND

Embryonic stem cells have great plasticity. In this study, we repaired impaired small intestine by transplanting putative intestinal epithelial stem cells (Musashi1 and hairy and enhancer of split 1 high expression cells) derived from embryonic stem cells.

METHODS

The differentiation of definitive endoderm in embryoid bodies, derived from male ES-E14TG2a cells by the hanging-drop method, was monitored to define a time point for maximal induction of putative intestinal epithelial stem cells by epidermal growth factor. Furthermore, to evaluate the regenerative potential of intestinal epithelium, these putative stem cells were engrafted into NOD/SCID mice and female mice with enteritis. Donor cells were located by SRY DNA in situ hybridization.

RESULTS

The results revealed that definitive endodermal markers were highly expressed in 5-day embryoid bodies. These embryoid body cells were induced into putative intestinal epithelial stem cells on the 5th day of epidermal growth factor administration. Grafts from these cells consisted of adenoid structures and nonspecific structural cells with strong expression of small-intestinal epithelial cell markers. In situ hybridization revealed that the donor cells could specifically locate in damaged intestinal epithelium, contribute to epithelial structures, and enhance regeneration.

CONCLUSIONS

In conclusion, the Musashi1 and hairy and enhancer of split 1 high expression cells, derived from mouse embryonic stem cells, locate predominantly in impaired small-intestinal epithelium after transplantation and contribute to epithelial regeneration.

HES1 (hairy and enhancer of split 1) is a determinant of bone mass

HES1 (hairy and enhancer of split) is a transcription factor that regulates osteoblastogenesis in vitro. The skeletal effects of HES1 misexpression were studied. Transgenic mice where a 3.6-kilobase fragment of the collagen type 1 α1 promoter directs HES1 overexpression were created. Transgenics were osteopenic due to decreased osteoblast function in female and increased bone resorption in male mice. HES1 impaired osteoblastogenesis in vitro, and transgenic osteoblasts enhanced the resorptive activity of co-cultured osteoclast precursors. Mice homozygous for a Hes1 loxP-targeted allele were bred to transgenics, where the paired-related homeobox gene enhancer or the osteocalcin promoter direct Cre recombinase expression to inactivate Hes1 in the limb bud or in osteoblasts. To avoid genetic compensation, Hes1 was inactivated in the context of the global deletion of Hes3 and Hes5. Hes3 and Hes5 null mice had no skeletal phenotype. Hes1 inactivation in the limb bud increased femoral length and trabecular number. Hes1 inactivation in osteoblasts increased trabecular bone volume, number, and connectivity due to increased mineral apposition rate and suppressed bone resorption. Hes1 inactivation in vitro increased alkaline phosphatase expression and suppressed the resorptive activity of co-cultured osteoclast precursors. In conclusion, by inhibiting osteoblast function and inducing bone resorption, HES1 is an intracellular determinant of bone mass and structure.

Jagged1 functions downstream of Twist1 in the specification of the coronal suture and the formation of a boundary between osteogenic and non-osteogenic cells

The Notch pathway is crucial for a wide variety of developmental processes including the formation of tissue boundaries. That it may function in calvarial suture development and figure in the pathophysiology of craniosynostosis was suggested by the demonstration that heterozygous loss of function of JAGGED1 in humans can cause Alagille syndrome, which has craniosynostosis as a feature. We used conditional gene targeting to examine the role of Jagged1 in the development of the skull vault. We demonstrate that Jagged1 is expressed in a layer of mesoderm-derived sutural cells that lie along the osteogenic-non-osteogenic boundary. We show that inactivation of Jagged1 in the mesodermal compartment of the coronal suture, but not in the neural crest compartment, results in craniosynostosis. Mesodermal inactivation of Jagged1 also results in changes in the identity of sutural cells prior to overt osteogenic differentiation, as well as defects in the boundary between osteogenic and non-osteogenic compartments at the coronal suture. These changes, surprisingly, are associated with increased expression of Notch2 and the Notch effector, Hes1, in the sutural mesenchyme. They are also associated with an increase in nuclear β-catenin. In Twist1 mutants, Jagged1 expression in the suture is reduced substantially, suggesting an epistatic relationship between Twist1 and Jagged1. Consistent with such a relationship, Twist1-Jagged1 double heterozygotes exhibit a substantial increase in the severity of craniosynostosis over individual heterozygotes. Our results thus suggest that Jagged1 is an effector of Twist1 in coronal suture development.

Id4, a new candidate gene for senile osteoporosis, acts as a molecular switch promoting osteoblast differentiation

Excessive accumulation of bone marrow adipocytes observed in senile osteoporosis or age-related osteopenia is caused by the unbalanced differentiation of MSCs into bone marrow adipocytes or osteoblasts. Several transcription factors are known to regulate the balance between adipocyte and osteoblast differentiation. However, the molecular mechanisms that regulate the balance between adipocyte and osteoblast differentiation in the bone marrow have yet to be elucidated. To identify candidate genes associated with senile osteoporosis, we performed genome-wide expression analyses of differentiating osteoblasts and adipocytes. Among transcription factors that were enriched in the early phase of differentiation, Id4 was identified as a key molecule affecting the differentiation of both cell types. Experiments using bone marrow-derived stromal cell line ST2 and Id4-deficient mice showed that lack of Id4 drastically reduces osteoblast differentiation and drives differentiation toward adipocytes. On the other hand knockdown of Id4 in adipogenic-induced ST2 cells increased the expression of Pparγ2, a master regulator of adipocyte differentiation. Similar results were observed in bone marrow cells of femur and tibia of Id4-deficient mice. However the effect of Id4 on Pparγ2 and adipocyte differentiation is unlikely to be of direct nature. The mechanism of Id4 promoting osteoblast differentiation is associated with the Id4-mediated release of Hes1 from Hes1-Hey2 complexes. Hes1 increases the stability and transcriptional activity of Runx2, a key molecule of osteoblast differentiation, which results in an enhanced osteoblast-specific gene expression. The new role of Id4 in promoting osteoblast differentiation renders it a target for preventing the onset of senile osteoporosis.

Increased bone marrow adiposity is observed in the bone marrow of senile osteoporosis patients. This is caused by unbalanced differentiation of mesenchymal stem cells (MSCs) into osteoblast or adipocyte. Previous reports have indicated that several transcription factors play important roles in determining the direction of MSCs differentiation into osteoblast or adipocyte. So far, little is known about the overall dynamics and regulation of transcription factor expression changes leading to the imbalance of osteoblast and adipocyte differentiation inside the bone marrow. We have performed genome-wide gene expression analyses during the differentiation of MSCs into osteoblast or adipocyte. We identified basic helix-loop-helix transcription factor family member Id4 as a leading candidate controlling the differentiation toward adipocyte or osteoblast. Suppression of Id4 expression in MSCs repressed osteoblast differentiation and increased adipocyte differentiation. In contrast, overexpression of Id4 in MSCs promoted osteoblast differentiation and attenuated adipocyte differentiation. Moreover, Id4-mutant mice showed abnormal accumulation of lipid droplets in bone marrow and impaired bone formation activity. In summary, we have demonstrated a molecular function of Id4 in osteoblast differentiation. The findings revealed that Id4 is a molecular switch enhancing osteoblast differentiation at the expense of adipocyte differentiation.

Down-regulation of Notch1 by gamma-secretase inhibition contributes to cell growth inhibition and apoptosis in ovarian cancer cells A2780

The release of Notch intracellular domain (NICD) is mediated by gamma-secretase. gamma-Secretase inhibitors have been shown to be potent inhibitors of NICD. We hypothesized that Notch1 is acting as an oncogene in ovarian cancer and that inhibition of Notch1 would lead to inhibition of cell growth and apoptotic cell death in ovarian cancer cells. In this study, expressions of Notch1 and hes1 in four human ovarian cancer (A2780, SKOV3, HO-8910, and HO-8910PM), and one ovarian surface (IOSE 144) cell lines were detected by Western blot and quantitative real-time RT-PCR. The effects of gamma-secretase inhibition (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester, DAPT) were measured by MTT assay, flow cytometry, ELISA and colony-forming assay. Our results showed that Notch1 and hes1 were found in all the four human ovarian cancer and IOSE 144 cell lines, and they were significantly higher in ovarian cancer cells A2780 compared to another four ovarian cells. Down-regulation of Notch1 expression by DAPT was able to substantially inhibit cell growth, induce G1 cell cycle arrest and induce cell apoptosis in A2780 in dose- and time-dependent manner. In addition, hes1 was found to be down-regulated in dose- and time-dependent manner by DAPT in A2780. These results demonstrate that treatment with DAPT leads to growth inhibition and apoptosis of A2780 cells in dose- and time-dependent manner. These findings also support the conclusion that blocking of the Notch1 activity by gamma-secretase inhibitors represents a potentially attractive strategy of targeted therapy for ovarian cancer.

Distinct transcriptional profiles characterize bone microenvironment mesenchymal cells rather than osteoblasts in relationship with multiple myeloma bone disease

OBJECTIVE

Multiple myeloma (MM) is characterized by a high incidence of osteolytic bone lesions, which have been previously correlated with the gene expression profiles of MM cells. The aim of this study was to investigate the transcriptional patterns of cells in the bone microenvironment and their relationships with the presence of osteolysis in MM patients.

MATERIALS AND METHODS

Both mesenchymal (MSC) and osteoblastic (OB) cells were isolated directly from bone biopsies of MM patients and controls to perform gene expression profiling by microarrays and real-time polymerase chain reaction on selected bone-related genes.

RESULTS

We identified a series of upregulated and downregulated genes that were differentially expressed in the MSC cells of osteolytic and nonosteolytic patients. Comparison of the osteolytic and nonosteolytic samples also showed that the MSC cells and OB had distinct transcriptional patterns. No significantly modulated genes were found in the OBs of the osteolytic and nonosteolytic patients.

CONCLUSIONS

Our data suggest that the gene expression profiles of cells of the bone microenvironment are different in MM patients and controls, and that MSC cells, but not OBs, have a distinct transcriptional pattern associated with the occurrence of bone lesions in MM patients. These data support the idea that alterations in MSC cells may be involved in MM bone disease.

The Notch-responsive transcription factor Hes-1 attenuates osteocalcin promoter activity in osteoblastic cells

Notch signaling plays a key role in osteoblast differentiation. A major transcriptional downstream regulator of this pathway is the helix-loop-helix (HLH) transcription factor Hairy/Enhancer of Split 1 (Hes-1). Here we investigated the function of Hes-1 in osteoblastic cells. Endogenous Hes-1 gene expression decreases during progression of bone cell phenotype development in MC3T3-E1 osteoblasts suggesting that it is a negative regulator of osteoblast differentiation. Forced expression of Hes-1 inhibits osteocalcin (OC) mRNA levels, and luciferase assays indicate that Hes-1 directly represses OC promoter activity. In vitro and in vivo protein/DNA interaction assays reveal that recombinant Hes-1 binds specifically to an E-box in the proximal promoter of the OC gene. Deletion of the Hes-1 WRPW domain (MHes-1) that recruits the co-repressor Groucho abrogates repression of OC promoter activity by Hes-1, but also blocks Hes-1 binding to the promoter. The latter result suggests that exogenous Hes-1 may be recruited to the OC promoter by both protein/DNA and protein/protein interactions. We conclude that the Notch-responsive Hes-1 protein is capable of repressing OC gene transcription in osteoblastic cells through an E-box in the proximal promoter. Hes-1 may contribute to osteoblast growth and differentiation by controlling basal bone-specific transcription directly through interactions with transcriptional regulators that are known to bind to the OC gene promoter.