Gli1 labels progenitors during chondrogenesis in postnatal mice.

Skeletal growth promoted by endochondral ossification is tightly coordinated by self-renewal and differentiation of chondrogenic progenitors. Emerging evidence has shown that multiple skeletal stem cells (SSCs) participate in cartilage formation. However, as yet, no study has reported the existence of common long-lasting chondrogenic progenitors in various types of cartilage. Here, we identify Gli1+ chondrogenic progenitors (Gli1+ CPs), which are distinct from PTHrP+ or FoxA2+ SSCs, are responsible for the lifelong generation of chondrocytes in the growth plate, vertebrae, ribs, and other cartilage. The absence of Gli1+ CPs leads to cartilage defects and dwarfishness phenotype in mice. Furthermore, we show that the BMP signal plays an important role in self-renewal and maintenance of Gli1+ CPs. Deletion of Bmpr1α triggers Gli1+ CPs quiescence exit and causes the exhaustion of Gli1+ CPs, consequently disrupting columnar cartilage. Collectively, our data demonstrate that Gli1+ CPs are common long-term chondrogenic progenitors in multiple types of cartilage and are essential to maintain cartilage homeostasis.

Roles of the cytoskeleton in human diseases.

Recently, researches have revealed the key roles of the cytoskeleton in the occurrence and development of multiple diseases, suggesting that targeting the cytoskeleton is a viable approach for treating numerous refractory diseases. The cytoskeleton is a highly structured and complex network composed of actin filaments, microtubules, and intermediate filaments. In normal cells, these three cytoskeleton components are highly integrated and coordinated. However, the cytoskeleton undergoes drastic remodeling in cytoskeleton-related diseases, causing changes in cell polarity, affecting the cell cycle, leading to senescent diseases, and influencing cell migration to accelerate cancer metastasis. Additionally, mutations or abnormalities in cytoskeletal proteins and their related proteins are closely associated with several congenital diseases. Therefore, this review summarizes the roles of the cytoskeleton in cytoskeleton-related diseases as well as its potential roles in disease treatment to provide insights regarding the physiological functions and pathological roles of the cytoskeleton.

Effects of different physical factors on osteogenic differentiation.

Osteoblasts are essential for bone formation and can perceive external mechanical stimuli, which are translated into biochemical responses that ultimately alter cell phenotypes and respond to environmental stimuli, described as mechanical transduction. These cells actively participate in osteogenesis and the formation and mineralisation of the extracellular bone matrix. This review summarises the basic physiological and biological mechanisms of five different physical stimuli, i.e. light, electricity, magnetism, force and sound, to induce osteogenesis; further, it summarises the effects of changing culture conditions on the morphology, structure and function of osteoblasts. These findings may provide a theoretical basis for further studies on bone physiology and pathology at the cytological level and will be useful in the clinical application of bone formation and bone regeneration technology.

Attenuates of NAD+ impair BMSC osteogenesis and fracture repair through OXPHOS.

BACKGROUND: Controlling the adipo-osteogenic lineage commitment of bone marrow mesenchymal stem cell (BMSC) in favor of osteogenesis is considered a promising approach for bone regeneration and repair. Accumulating evidence indicates that oxidative phosphorylation (OXPHOS) is involved in regulating cell fate decisions. As an essential cofactor for OXPHOS, nicotinamide adenine dinucleotide (NAD) has been shown to correlate with the differentiation of stem cells. However, whether NAD manipulates BMSC lineage commitment through OXPHOS remains elusive. Therefore, it is critical to investigate the potential role of NAD on energy metabolism in mediating BMSC lineage commitment. METHODS: In this study, the mitochondrial respiration and intracellular NAD+ level were firstly compared between osteogenic and adipogenic cells. For validating the role of NAD in mitochondrial OXPHOS, the inhibitor of NAD+ salvage pathway FK866 and activator P7C3 were used to manipulate the NAD+ level during osteogenesis. Furthermore, a murine femur fracture model was established to evaluate the effect of FK866 on bone fracture repair. RESULTS: We elucidated that osteogenic committed BMSCs exhibited increased OXPHOS activity and a decreased glycolysis accompanied by an elevated intracellular NAD+ level. In contrast, adipogenic committed BMSCs showed little change in OXPHOS but an upregulated activity in glycolysis and a decline in intracellular NAD+ level in vitro. Moreover, attenuates of NAD+ via salvage pathway in BMSCs diminished osteogenic commitment due to mitochondria dysfunction and reduced activity of OXPHOS. The cells were rescued by supplementing with nicotinamide mononucleotide. In addition, treatment with NAD+ inhibitor FK866 impaired bone fracture healing in vivo. CONCLUSION: Our data reveals NAD+-mediated mitochondrial OXPHOS is indispensable for osteogenic commitment in BMSCs and bone repair, which might provide a potential therapeutic target for bone repair and regeneration.

Wnt7b Inhibits Osteoclastogenesis via AKT Activation and Glucose Metabolic Rewiring.

The imbalance between bone formation and bone resorption causes osteoporosis, which leads to severe bone fractures. It is known that increases in osteoclast numbers and activities are the main reasons for increasing bone resorption. Although extensive studies have investigated the regulation of osteoclastogenesis of bone marrow macrophages (BMMs), new pharmacological avenues still need to be unveiled for clinical purpose. Wnt ligands have been widely demonstrated as stimulators of bone formation; however, the inhibitory effect of the Wnt pathway in osteoclastogenesis is largely unknown. Here, we demonstrate that Wnt7b, a potent Wnt ligand that enhances bone formation and increases bone mass, also abolishes osteoclastogenesis in vitro. Importantly, enforced expression of Wnt in bone marrow macrophage lineage cells significantly disrupts osteoclast formation and activity, which leads to a dramatic increase in bone mass. Mechanistically, Wnt7b impacts the glucose metabolic process and AKT activation during osteoclastogenesis. Thus, we demonstrate that Wnt7b diminishes osteoclast formation, which will be beneficial for osteoporosis therapy in the future.

GPX7 Facilitates BMSCs Osteoblastogenesis via ER Stress and mTOR Pathway.

Emerging evidence indicates extensive oxidative stress is a consequence of obesity which impairs bone formation. Glutathione peroxidase 7 (GPX7) is a conserved endoplasmic reticulum (ER) retention protein, lacking of which causes accumulation of reactive oxygen species (ROS) and promotes adipogenesis. Since the imbalance between osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cell (BMSC) leads to severe bone diseases such as osteoporosis, it is critical to investigate the potential protective role of Gpx7 in osteogenesis. Here, we provide evidence that deficiency of Gpx7 reduces osteogenesis, but increases adipogenesis in both human BMSCs (hBMSCs) and mouse mesenchymal stem cell line. Interestingly, further studies indicate this defect can be alleviated by the ER stress antagonist, but not the ROS inhibitor, unveiling an unexpected finding that, unlike adipogenesis, lacking of Gpx7 inhibits osteogenesis mediating by induced ER stress instead of enhanced ROS. Furthermore, the mTOR signalling pathway is found down-regulation during osteogenic differentiation in Gpx7-deficient condition, which can be rescued by relief of ER stress. Taken together, for the first time we identify a novel function of Gpx7 in BMSCs' osteogenic differentiation and indicate that Gpx7 may protect against osteoporotic deficits in humans through ER stress and mTOR pathway interplay.

Investigating biological effects of multidimensional carboxylated carbon-based nanomaterials on human lung A549 cells revealed via non-targeted metabolomics approach.

The biological responses of multidimensional carboxylated carbon-based nanomaterials (c-CBNs), including carboxylated graphene, carbon nanotube, and fullerene, on human lung A549 cells were investigated by using metabolomics technology. The structure and components of c-CBNs were characterized, and their biological effects were evaluated through cell apoptosis and viability analysis. Additionally, the metabolomics analysis of the nanomaterial-cell interaction system was performed using the established platform combining liquid chromatography-mass spectrometry (LC-MS) with the bioinformatics system. Results revealed that all tested c-CBNs demonstrated some biological effects in our cell model. However, significant metabolomic alterations induced by c-CBNs were also observed mainly in amino acids, organic acids, glycerophospholipids, and glycerolipids. Further, under the tested concentrations, the multiple dimensions of c-CBNs played a major role in determining the metabolic process in various interaction modes. This study provides an advanced alternative for evaluating metabolic effects of multidimensional nanomaterials through metabolomics technology considering the association between dimension and metabolic characteristics.

Self-supervised Learning of Detailed 3D Face Reconstruction.

In this paper, we present an end-to-end learning framework for detailed 3D face reconstruction from a single image1. Our approach uses a 3DMM-based coarse model and a displacement map in UV-space to represent a 3D face. Unlike previous work addressing the problem, our learning framework does not require supervision of surrogate ground-truth 3D models computed with traditional approaches. Instead, we utilize the input image itself as supervision during learning. In the first stage, we combine a photometric loss and a facial perceptual loss between the input face and the rendered face, to regress a 3DMM-based coarse model. In the second stage, both the input image and the regressed texture of the coarse model are unwrapped into UV-space, and then sent through an image-toimage translation network to predict a displacement map in UVspace. The displacement map and the coarse model are used to render a final detailed face, which again can be compared with the original input image to serve as a photometric loss for the second stage. The advantage of learning displacement map in UV-space is that face alignment can be explicitly done during the unwrapping, thus facial details are easier to learn from large amount of data. Extensive experiments demonstrate the superiority of the proposed method over previous work.

Wnt7b-induced Sox11 functions enhance self-renewal and osteogenic commitment of bone marrow mesenchymal stem cells.

As a profoundly anabolic regulator of bone, Wnt7b is well acknowledged to enhance osteoblast activities. Here, we report that bone marrow mesenchymal stem cells (BMSCs) are another important population responding to Wnt7b. In this study, we systematically investigated the in vivo role of Wnt7b in BMSCs using transgenic mice, high-throughput RNA-seq, immunohistochemistry, RT-qPCR, and in situ hybridization. These methods led us to uncover that Sox11 is induced via Wnt7b in BMSCs. Colony formation assay, flow cytometry, EdU incorporation labeling, RT-qPCR, and Western blot were conducted to detect the self-renewal capacity of BMSCs. Alkaline phosphatase staining, alizarin red staining, and ex vivo BMSCs transplantation were utilized to detect the osteogenic ability of BMSCs. ChIP-qPCR, shRNAs, and immunofluorescence staining were utilized to investigate the underlying mechanisms. Consequently, bone-derived Wnt7b was found to decrease in osteoporosis and elevate in bone fracture healing. During bone fracture healing, Wnt7b was particularly expressed in the mesenchymal cells residing within healing frontiers. RNA-seq data of Wnt7b-overexpressed bones uncovered the significant upregulation of Sox11. Histological results further unveiled that Sox11 is specifically increased in BMSCs. Wnt7b-induced Sox11 was demonstrated to reinforce both self-renewal and osteogenic differentiation of BMSCs. Mechanistically, Wnt7b activates the Ca2+ -dependent Nfatc1 signaling to directly induce Sox11 transcription, which in turn activates the transcriptions of both proliferation-related transcription factors (Ccnb1 and Sox2) and osteogenesis-related factors (Runx2, Sp7) in BMSCs. It is intriguing that this Wnt7b-Sox11 signaling in BMSCs is ß-Catenin-independent. Overall, this study provides brand new insights of Wnt7b in bone formation, namely, Wnt7b can enhance both self-renewal and osteogenic differentiation of BMSCs via inducing Sox11. These findings present a new crosstalk between Wnt and Sox signaling in BMSCs.

The role of Wnt7B in the mediation of dentinogenesis via the ERK1/2 pathway.

OBJECTIVES: This study investigates the role of Wnt7b in mouse dentin formation. DESIGN: C57BL/6 mouse tooth germs at different developmental stages were collected to measure the expression of Wnt7b by immunohistochemical staining. The morphology of mandibles of Dmp1-cre;ROSA26-Wnt7b transgenic mice and ROSA26-Wnt7b littermates was analyzed by Micro-CT and HE staining. The ultramicrostructure of dentin was scanned with an electron microscope. Primary mouse dental papillae cells (MDPCs) and odontoblastic cell line (A11) were cultured and infected with adenovirus to overexpress Wnt7b. Cell proliferation and cell apoptosis were evaluated using CCK-8 and flow cytometry. Osteogenic differentiation of MDPCs and A11 was assessed by Alizarin red staining, and qPCR detection of osteogenic gene expression. The activation of signaling pathways was measured by the use of western blot analysis. The ERK1/2 inhibitor was used to test the effect of Wnt7b regulated cell differentiation. RESULTS: Wnt7b was expressed principally in the mouse odontoblast layer after the early bell stage. In transgenic mice, Wnt7b was over-expressed in tooth mesenchyme, with a thinner predentin layer and thicker intertubular dentin. Both the micro-hardness value and the Ca/Pi ratio of dentin of transgenic mice were higher. Wnt7b promoted proliferation and mineralization of MDPCs and A11. The protein level of p-ERK1/2 was found to be higher in A11 infected with Ad-Wnt7b. The ERK signaling pathway inhibitor partly rescued the Wnt7b-induced differentiation of A11. CONCLUSIONS: Wnt7b enhances dentinogenesis by increasing the proliferation and differentiation of dental mesenchymal cells partly through ERK1/2 pathway.

NUMB maintains bone mass by promoting degradation of PTEN and GLI1 via ubiquitination in osteoblasts.

The adaptor protein NUMB is involved in asymmetric division and cell fate determination and recognized as an antagonist of Notch. Previous studies have proved that Notch activation in osteoblasts contributes to a high bone mass. In this study,  however, an osteopenic phenotype was found in 9-week-old mice using osteoblastic specific Col1a1-2.3-Cre to ablate both Numb and its homologue Numbl . The trabecular bone mass decreased dramatically while the cortical bone mass was unaffected. Here, the Notch signal was not activated, while the tensin homologue deleted on human chromosome 10 (PTEN), which dephosphorylates phosphatidylinositide 3-kinases, was elevated, attenuating protein kinase B (Akt). The ubiquitination assay revealed that NUMB may physiologically promote PTEN ubiquitination in the presence of neural precursor cell-expressed developmentally downregulated protein 4-1. In addition, the deficiency of Numb/Numbl also activated the Hedgehog pathway through GLI1. This process was found to improve the ratio of the receptor activator of nuclear factor-kB ligand to osteoprotegerin, which enhanced the differentiation of osteoclasts and bone resorption . In conclusion, this study provides an insight into  new functons of   NUMB and NUMBL on bone homeostasis.

Visual Osteoclast Fusion via A Fluorescence Method.

Osteoclasts are multinucleated giant cells. Fusion is an essential element in the formation of osteoclasts. However, the exact cellular events and mechanisms remain largely unknown because of limited and insufficient methods for observing fusion process. In this work, a fluorescence reporter strategy was established to monitor osteoclast fusion. After fusing with cells expressing Cre recombinase, those cells with double fluorescence switch its expression from red to green fluorescent protein. The effect of RANKL and PTH on osteoclast fusion were both quantitatively and visually detected utilizing this strategy. Furthermore, a combination of this strategy with a technique of fluorescence-activated cell sorting revealed two different populations of fused osteoclasts, tdTomato+ GFP+ cells (TG cells) and GFP+ cells (G cells). The results argue for the potential of combining this technique with other bio-technologies to gain more information about osteoclast fusion. Overall, these data demonstrated that this visual fluorescence switch strategy is useful for further analysis of osteoclast fusion mechanisms.

Microenvironmental Stiffness Regulates Dental Papilla Cell Differentiation: Implications for the Importance of Fibronectin-Paxillin-ß-Catenin Axis.

The mechanical stiffness of substrates is recognized to be an important physical cue in the microenvironment of local cellular residents in mammalian species due to their great capacity in regulating cell behavior. Dental papilla cells (DPCs) play an important role in the field of dental tissue engineering for their stem cell-like properties. Therefore, it is essential to provide the suitable microenvironment by combining with the physical cues of biomaterials for DPCs to carry out the function of effective tissue regeneration. However, how the substrate stiffness influences the odontogenic differentiation of DPCs is still unclear. Thus, we fabricated poly(dimethylsiloxane) substrates with varied stiffness for cell behavior. Both cell morphology and focal adhesion were shown to have significant changes in response to varied stiffness. Paxillin, an important protein adapter of focal adhesion kinase protein, was shown to interact with both ectoplasmic fibronectin and cytoplasmic ß-catenin by coimmunoprecipitation. The resultant changes of ß-catenin by varied stiffness were confirmed by immunofluorescent stain and western blotting. Further, the higher quantity nuclear translocation of ß-catenin and the less phospho-ß-catenin on the stiff substrate were detected. This nuclear translocation in the stiff substrate finally led to an increased mineralization of DPCs relative to the soft substrate detected by Von Kossa and Alizarin Red stain. Taken together, this work not only points out that the substrate stiffness can regulate the odontogenic differentiation potential of DPCs via fibronectin/paxillin/ß-catenin pathway but also provides significant consequence for biomechanical control of cell behavior in cell-based tooth tissue regeneration.

Evidence for excessive osteoclast activation in SIRT6 null mice.

SIRT6 is a NAD-dependent histone 3 deacetylase. SIRT6 null mice have been reported suffering osteopenia. However, the role of SIRT6 in bone resorption is still not well understood. In this study, we focused on the role of SIRT6 in osteoclast. We performed histological analysis on the femur, spine, alveolar bone and even tail of mutant mice, and found the bone mass is sharply decreased while the osteoclast activity is significantly increased. These phenotypes were further demonstrated by the osteoclast differentiation in cell-cultures with TRAP staining and Pit Resorption Assay. We next found the proliferation activity of mutant osteoclast precursors was increased, which might account for the enhanced osteoclast formation. The concentration of tartrate-resistant acid phosphatase 5b, a marker of osteoclast differentiation, was significantly higher in the mutant mice than control. Besides, the osteoclastogenic and NF-κB signaling related genes were significantly up-regulated. Moreover, osteoblast/osteoclast co-culture demonstrated that SIRT6 regulated osteoclast mainly through osteoblast paracrine manner, rather than osteoclast-autonomous behavior. Together, the enhanced osteoclast activation in SIRT6 null mice might be regulated by the hyperactive NF-κB signaling and the enhanced proliferation activity of osteoclast precursors through osteoblast paracrine manner at the cellular level.

Reporter Mice Used for Dentinogenesis Study.

BACKGROUND: Dentinogenesis is a long and complex process not only in tooth development, but also throughout the lifespan. Reporter mice provided us a preferred model to study the dentin formation with characteristics of high sensitivity, visualization, and reliability, which makes the long-term and intricate period of dentinogenesis much clear. With the advent of different gene reporters, genetic engineering methods, and tissue specific promoters, various reporter mice can be created to solve different problems. OBJECTIVE: To understand the fundamental concepts and characteristics to use the reporter mice for dentinogenesis study. RESULTS: This review introduced the frequently used gene-based reporters, genetic engineering technologies, dentinogenesis-related promoters and the reporter mice commonly used in the dentin study, with the purpose of obtaining a better application of reporter mice and gaining more details about dentinogenesis. CONCLUSION: Reporter mice is a convenient and reliable model for studying dentinogenesis.

Evaluation of Three Block Anesthesia Methods for Pain Management During Mandibular Third Molar Extraction: A Meta-analysis.

A patient's pain during mandibular third molar extraction often creates problems for a dental surgeon and can also cause immense patient discomfort, such as decreased quality of life, serious complications, or even danger to the patients' lives. Effective pain management is therefore of great importance. Conventional block anesthesia method often fails to control such pain completely during an operation. Therefore, two available alternatives, Gow-Gates (G-G) and Vazirani-Akinosi (V-A) methods, have been developed. However, the results of current studies regarding their effectiveness and safety are somewhat ambiguous. The use of G-G and V-A techniques is therefore restricted. This study did a comprehensive review of the relevant research and finally 7 RCTs were included. The results of this meta-analysis indicate that both G-G and V-A techniques have a lower risk of positive aspiration. G-G technique also evidenced a higher success rate than the conventional method. V-A was faster while the G-G technique in contrast had a slower onset time than the conventional technique. In terms of the measurement of analgesic success, however, the V-A method was statistically indistinguishable from conventional techniques. These findings will hopefully endow clinicians with the knowledge required to make appropriate choices for effective anesthesia during lower third molar extraction.

[Isolation and identification of aerobic and facultative anaerobic bacteria in the oral cavity].

OBJECTIVE: To establish a systematic method for isolation and identification of aerobic and facultative anaerobic bacteria in the oral cavity. METHODS: Samples of the saliva, dental plaque and periapical granulation tissue were collected from 20 subjects with healthy oral condition and from 8 patients with different oral diseases. The bacteria in the samples were identified by morphological identification, VITEK automatic microorganism identification and 16s rRNA gene sequencing. RESULTS: VITEK automatic microorganism identification and 16s rRNA gene sequencing showed an agreement rate of 22.39% in identifying the bacteria in the samples. We identified altogether 63 bacterial genus (175 species), among which Streptococcus, Actinomyces and Staphylococcus were the most common bacterial genus, and Streptococcus anginosus, Actinomyces oris, Streptococcus mutans and Streptococcus mitis were the most common species. Streptococcus anginosus was commonly found in patients with chronic periapical periodontitis. Streptococcus intermedius and Staphylococcus aureus were common in patients with radiation caries, and in patients with rampant caries, Streptococcus mutans was found at considerably higher rate than other species. CONCLUSION: Aerobic and facultative anaerobic bacteria are commonly found in the oral cavity, and most of them are gram-positive. 16s rRNA gene sequencing is more accurate than VITEK automatic microorganism identification in identifying the bacteria.

Suitability of IS6110-RFLP and MIRU-VNTR for differentiating spoligotyped drug-resistant mycobacterium tuberculosis clinical isolates from Sichuan in China.

Genotypes of Mycobacterium tuberculosis complex (MTBC) vary with the geographic origin of the patients and can affect tuberculosis (TB) transmission. This study was aimed to further differentiate spoligotype-defined clusters of drug-resistant MTBC clinical isolates split in Beijing (n = 190) versus non-Beijing isolates (n = 84) from Sichuan region, the second high-burden province in China, by IS6110-restriction fragment length polymorphism (RFLP) and 24-locus MIRU-VNTRs. Among 274 spoligotyped isolates, the clustering ratio of Beijing family was 5.3% by 24-locus MIRU-VNTRs versus 2.1% by IS6110-RFLP, while none of the non-Beijing isolates were clustered by 24-locus MIRU-VNTRs versus 9.5% by IS6110-RFLP. Hence, neither the 24-locus MIRU-VNTR was sufficient enough to fully discriminate the Beijing family, nor the IS6110-RFLP for the non-Beijing isolates. A region adjusted scheme combining 12 highly discriminatory VNTR loci with IS6110-RFLP was a better alternative for typing Beijing strains in Sichuan than 24-locus MIRU-VNTRs alone. IS6110-RFLP was for the first time introduced to systematically genotype MTBC in Sichuan and we conclude that the region-adjusted scheme of 12 highly discriminative VNTRs might be a suitable alternative to 24-locus MIRU-VNTR scheme for non-Beijing strains, while the clusters of the Beijing isolates should be further subtyped using IS6110-RFLP for optimal discrimination.