A tantalum-containing zirconium-based metallic glass with superior endosseous implant relevant properties.

Zirconium-based metallic glasses (Zr-MGs) are demonstrated to exhibit high mechanical strength, low elastic modulus and excellent biocompatibility, making them promising materials for endosseous implants. Meanwhile, tantalum (Ta) is also well known for its ideal corrosion resistance and biological effects. However, the metal has an elastic modulus as high as 186 GPa which is not comparable to the natural bone (10-30 GPa), and it also has a relative high cost. Here, to fully exploit the advantages of Ta as endosseous implants, a small amount of Ta (as low as 3 at. %) was successfully added into a Zr-MG to generate an advanced functional endosseous implant, Zr58Cu25Al14Ta3 MG, with superior comprehensive properties. Upon carefully dissecting the atomic structure and surface chemistry, the results show that amorphization of Ta enables the uniform distribution in material surface, leading to a significantly improved chemical stability and extensive material-cell contact regulation. Systematical analyses on the immunological, angiogenesis and osteogenesis capability of the material are carried out utilizing the next-generation sequencing, revealing that Zr58Cu25Al14Ta3 MG can regulate angiogenesis through VEGF signaling pathway and osteogenesis via BMP signaling pathway. Animal experiment further confirms a sound osseointegration of Zr58Cu25Al14Ta3 MG in achieving better bone-implant-contact and inducing faster peri-implant bone formation.

Changes in sulfur in soybean rhizosphere soil and the response of microbial flora in a continuous cropping system mediated by Funneliformis mosseae.

Soybean is an S-loving crop, and continuous cropping might cause soil sulfur shortage. The primary objectives of this study are to determine whether Funneliformis mosseae (F. mosseae) can enhance the content of available S in S-deficient soil and thereby improve the sulfur utilization rate in soybean. The experiment used Heinong 48 (HN48), a soybean variety with a vast planting area in Heilongjiang Province, and F. mosseae was inoculated in the soil of soybean that had been continuously cropped for 0 and 3 years. The results of the barium sulfur turbidimetric assay show that the sulfur content in the soil and soybean was reduced by continuous cropping and increased by inoculation with F. mosseae; the results of the macro-genome sequencing technology, show that the diversity and abundance of bacteria in the soil was decreased by continuous cropping and increased by inoculation with F. mosseae. The sulfur-oxidizing bacteria (SOB) activity and sulfur-related gene expression levels were lower in the continuous crop group compared to the control group and higher in the F.mosseae-inoculated group compared to the control group. Continuous cropping reduced the sulfur content and ratio of soybean rhizosphere soil, affecting soil flora activity and thus soybean growth; F. mosseae inoculation increased the sulfur content of soybean root-perimeter soil and plants, increased the diversity and abundance of rhizosphere soil microorganisms, increased the expression of genes for sulfur transport systems, sulfur metabolism, and other metabolic functions related to elemental sulfur, and increased the species abundance and metabolic vigor of most SOB. In summary, continuous cropping inhibits soil sulfur uptake and utilization in soybean while the inoculation with F. mosseae can significantly improve this situation. This study offers a theoretical research foundation for using AMF as a bio-fungal agent to enhance soil sulfur use. It also supports the decrease of chemical fertilizers, their substitution, and the protection of native soil.

The Source and Distribution of Tetracycline Antibiotics in China: A Review.

In recent years, antibiotics have been listed as a new class of environmental pollutants. Tetracycline antibiotics (TCs) used in human medical treatment, animal husbandry and agricultural production are the most widely used antibiotics. Due to their wide range of activities and low cost, their annual consumption is increasing. TCs cannot be completely metabolized by humans and animals. They can be abused or overused, causing the continuous accumulation of TCs in the ecological environment and potential negative effects on non-target organisms. These TCs may spread into the food chain and pose a serious threat to human health and the ecology. Based on the Chinese environment, the residues of TCs in feces, sewage, sludge, soil and water were comprehensively summarized, as well as the potential transmission capacity of air. This paper collected the concentrations of TCs in different media in the Chinese environment, contributing to the collection of a TC pollutant database in China, and facilitating the monitoring and treatment of pollutants in the future.

A Novel Technique to Align the Intraoral Scans to the Virtual Articulator and Set the Patient-Specific Sagittal Condylar Inclination.

Customized cast orientations and parameter settings of the virtual articulator according to the patient's condyles are indispensable parts of today's digital workflows in prosthodontics. This article describes a digital technique to align the intraoral scans to a virtual articulator by using a facial scanner to locate the patient's cutaneous landmarks of the arbitrary hinge axis and the reference plane, and to customize the sagittal condylar inclination of the virtual articulator through a digital protrusive interocclusal record and a dental computer-aided design software program. It enables individual cast orientations and virtual articulator parameter settings without conventional facebow transferring and bite registration procedures and can be easily integrated with most virtual articulator systems on the market to allow clinicians and technicians to work in a complete digital workflow and facilitate customized treatment planning and dental prosthesis fabrication.

DNA demethylase ALKBH1 promotes adipogenic differentiation via regulation of HIF-1 signaling.

DNA N6-adenine methylation (6mA), as a novel adenine modification existing in eukaryotes, shows essential functions in embryogenesis and mitochondrial transcriptions. ALKBH1 is a demethylase of 6mA and plays critical roles in osteogenesis, tumorigenesis, and adaptation to stress. However, the integrated biological functions of ALKBH1 still require further exploration. Here, we demonstrate that knockdown of ALKBH1 inhibits adipogenic differentiation in both human mesenchymal stem cells (hMSCs) and 3T3-L1 preadipocytes, while overexpression of ALKBH1 leads to increased adipogenesis. Using a combination of RNA-seq and N6-mA-DNA-IP-seq analyses, we identify hypoxia-inducible factor-1 (HIF-1) signaling as a crucial downstream target of ALKBH1 activity. Depletion of ALKBH1 leads to hypermethylation of both HIF-1α and its downstream target GYS1. Simultaneous overexpression of HIF-1α and GYS1 restores the adipogenic commitment of ALKBH1-deficient cells. Taken together, our data indicate that ALKBH1 is indispensable for adipogenic differentiation, revealing a novel epigenetic mechanism that regulates adipogenesis.

Control of osteocyte dendrite formation by Sp7 and its target gene osteocrin.

Some osteoblasts embed within bone matrix, change shape, and become dendrite-bearing osteocytes. The circuitry that drives dendrite formation during "osteocytogenesis" is poorly understood. Here we show that deletion of Sp7 in osteoblasts and osteocytes causes defects in osteocyte dendrites. Profiling of Sp7 target genes and binding sites reveals unexpected repurposing of this transcription factor to drive dendrite formation. Osteocrin is a Sp7 target gene that promotes osteocyte dendrite formation and rescues defects in Sp7-deficient mice. Single-cell RNA-sequencing demonstrates defects in osteocyte maturation in the absence of Sp7. Sp7-dependent osteocyte gene networks are associated with human skeletal diseases. Moreover, humans with a SP7R316C mutation show defective osteocyte morphology. Sp7-dependent genes that mark osteocytes are enriched in neurons, highlighting shared features between osteocytic and neuronal connectivity. These findings reveal a role for Sp7 and its target gene Osteocrin in osteocytogenesis, revealing that pathways that control osteocyte development influence human bone diseases.

METTL3-Mediated m6 A mRNA Methylation Modulates Tooth Root Formation by Affecting NFIC Translation.

N6-methyladenosine (m6 A), as a eukaryotic mRNA modification catalyzed by methyltransferase METTL3, is involved in various processes of development or diseases via regulating RNA metabolism. However, the effect of METTL3-mediated m6 A modification in tooth development has remained elusive. Here we show that METTL3 is prevalently expressed in odontoblasts, dental pulp cells, dental follicle cells, and epithelial cells in Hertwig's epithelial root sheath during tooth root formation. Depletion of METTL3 in human dental pulp cells (hDPCs) impairs proliferation, migration, and odontogenic differentiation. Furthermore, conditional knockout of Mettl3 in Osterix-expressing cells leads to short molar roots and thinner root dentin featured by decreased secretion of pre-dentin matrix and formation of the odontoblast process. Mechanistically, loss of METTL3 cripples the translational efficiency of the key root-forming regulator nuclear factor I-C (NFIC). The odontogenic capacity of METTL3-silenced hDPCs is partially rescued via overexpressing NFIC. Our findings suggest that m6 A methyltransferase METTL3 is crucial for tooth root development, uncovering a novel epigenetic mechanism in tooth root formation. © 2020 American Society for Bone and Mineral Research (ASBMR).

Alpha-ketoglutarate ameliorates age-related osteoporosis via regulating histone methylations.

Age-related osteoporosis is characterized by the deterioration in bone volume and strength, partly due to the dysfunction of bone marrow mesenchymal stromal/stem cells (MSCs) during aging. Alpha-ketoglutarate (αKG) is an essential intermediate in the tricarboxylic acid (TCA) cycle. Studies have revealed that αKG extends the lifespan of worms and maintains the pluripotency of embryonic stem cells (ESCs). Here, we show that the administration of αKG increases the bone mass of aged mice, attenuates age-related bone loss, and accelerates bone regeneration of aged rodents. αKG ameliorates the senescence-associated (SA) phenotypes of bone marrow MSCs derived from aged mice, as well as promoting their proliferation, colony formation, migration, and osteogenic potential. Mechanistically, αKG decreases the accumulations of H3K9me3 and H3K27me3, and subsequently upregulates BMP signaling and Nanog expression. Collectively, our findings illuminate the role of αKG in rejuvenating MSCs and ameliorating age-related osteoporosis, with a promising therapeutic potential in age-related diseases.

AFF1 inhibits adipogenic differentiation via targeting TGM2 transcription.

OBJECTIVES: AF4/FMR2 family member 1 (AFF1), known as a central scaffolding protein of super elongation complex (SEC), regulates gene transcription. We previously reported that AFF1 inhibited osteogenic differentiation of human mesenchymal stromal/stem cells (hMSCs). However, its role in adipogenic differentiation has not been elucidated. MATERIALS AND METHODS: hMSCs and 3T3-L1 pre-adipocytes were cultured and induced for adipogenic differentiation. Small interfering RNAs (siRNAs) were applied to deplete AFF1 while lentiviruses expressing HA-Aff1 were used for overexpression. Oil Red O staining, triglyceride (TAG) quantification, quantitative real-time PCR (qPCR), Western blot analysis, immunofluorescence staining, RNA sequencing (RNA-seq) analysis and ChIP-qPCR were performed. To evaluate the adipogenesis in vivo, BALB/c nude mice were subcutaneously injected with Aff1-overexpressed 3T3-L1 pre-adipocytes. RESULTS: AFF1 depletion leads to an enhanced adipogenesis in both hMSCs and 3T3-L1 pre-adipocytes. Overexpression of Aff1 in 3T3-L1 cells results in the reduction of adipogenic differentiation and less adipose tissue formation in vivo. Mechanistically, AFF1 binds to the promoter region of Tgm2 gene and regulates its transcription. Overexpression of Tgm2 largely rescues adipogenic differentiation of Aff1-deficient cells. CONCLUSIONS: Our data indicate that AFF1 inhibits adipogenic differentiation by regulating the transcription of TGM2.

In silico genome-wide identification of m6A-associated SNPs as potential functional variants for periodontitis.

Genetic variation is considered to affect the N6 -methyladenosine (m6A) RNA transcript modification, which is the most prevalent posttranscriptional messenger RNA modification. This study aimed to identify m6A-associated single-nucleotide polymorphisms (m6A-SNPs) that may affect m6A methylation from numerous periodontitis (PD) SNPs. We identified an abundance of m6A-SNPs by analyzing raw data of published PD genome-wide association studies and m6A-SNPs list from the m6AVar database. Other evidence was found in public databases for expression quantitative trait loci (eQTL) and differential gene expression analysis. Accordingly, 1938 m6A-SNPs were identified, 104 of which appeared to be associated with PD (p < .05) while 65 showed eQTL signals. Lastly, the leading SNP rs2723183 (p = 3.93E-07) was predicted to regulate local gene IL-37 expression in PD (p = 2.64E-05; in GSE10334) and change regulatory motif RXRA. In summary, dozens of PD-associated m6A-SNPs were identified and their possible functions were demonstrated in this study.

Recombinant growth differentiation factor 11 impairs fracture healing through inhibiting chondrocyte differentiation.

Growth differentiation factor 11 (GDF11), a secreted member of the transforming growth factor-ß (TGF-ß) superfamily, has been reported to have the capacity to reverse age-related pathologic changes and regulate organ regeneration after injury; however, the role of GDF11 in fracture healing and bone repair is still unclear. Here, we established a fracture model in 12-week-old male mice to observe two healing states: the cartilaginous callus and bony callus formation phases. Our results showed that recombinant GDF11 (rGDF11) injection inhibits cartilaginous callus maturation and hard callus formation, thereby impairing fracture healing in vivo. In vitro, rGDF11 administration inhibited chondrocyte differentiation and maturation by phosphorylating SMAD2/3 protein and inhibiting RUNX2 expression. Notably, inhibition of TGF-ß activity by a SMAD-specific inhibitor attenuated GDF11 effects. Thus, our study demonstrates that, rather than acting as a rejuvenating agent, rGDF11 impairs fracture healing by inhibiting chondrocyte differentiation and maturation.

Mettl3-mediated m6A RNA methylation regulates the fate of bone marrow mesenchymal stem cells and osteoporosis.

N6-methyladenosine (m6A) is the most abundant epigenetic modification in eukaryotic mRNAs and is essential for multiple RNA processing events during mammalian development and disease control. Here we show that conditional knockout of the m6A methyltransferase Mettl3 in bone marrow mesenchymal stem cells (MSCs) induces pathological features of osteoporosis in mice. Mettl3 loss-of-function results in impaired bone formation, incompetent osteogenic differentiation potential and increased marrow adiposity. Moreover, Mettl3 overexpression in MSCs protects the mice from estrogen deficiency-induced osteoporosis. Mechanistically, we identify PTH (parathyroid hormone)/Pth1r (parathyroid hormone receptor-1) signaling axis as an important downstream pathway for m6A regulation in MSCs. Knockout of Mettl3 reduces the translation efficiency of MSCs lineage allocator Pth1r, and disrupts the PTH-induced osteogenic and adipogenic responses in vivo. Our results demonstrate the pathological outcomes of m6A mis-regulation in MSCs and unveil novel epitranscriptomic mechanism in skeletal health and diseases.

Ubiquitin-specific protease USP34 controls osteogenic differentiation and bone formation by regulating BMP2 signaling.

The osteogenic differentiation of mesenchymal stem cells (MSCs) is governed by multiple mechanisms. Growing evidence indicates that ubiquitin-dependent protein degradation is critical for the differentiation of MSCs and bone formation; however, the function of ubiquitin-specific proteases, the largest subfamily of deubiquitylases, remains unclear. Here, we identify USP34 as a previously unknown regulator of osteogenesis. The expression of USP34 in human MSCs increases after osteogenic induction while depletion of USP34 inhibits osteogenic differentiation. Conditional knockout of Usp34 from MSCs or pre-osteoblasts leads to low bone mass in mice. Deletion of Usp34 also blunts BMP2-induced responses and impairs bone regeneration. Mechanically, we demonstrate that USP34 stabilizes both Smad1 and RUNX2 and that depletion of Smurf1 restores the osteogenic potential of Usp34-deficient MSCs in vitro Taken together, our data indicate that USP34 is required for osteogenic differentiation and bone formation.

Marrow Adipose Tissue: Its Origin, Function, and Regulation in Bone Remodeling and Regeneration.

Marrow adipose tissue (MAT) is a unique fat depot in the bone marrow and exhibits close relationship with hematopoiesis and bone homeostasis. MAT is distinct from peripheral adipose tissue in respect of its heterogeneous origin, site-specific distribution, and complex and perplexing function. Though MAT is indicated to function in hematopoiesis, skeletal remodeling, and energy metabolism, its explicit characterization still requires further research. In this review, we highlight recent advancement made in MAT regarding the origin and distribution of MAT, the local interaction with bone homeostasis and hematopoietic niche, the systemic endocrine regulation of metabolism, and MAT-based strategies to enhance bone formation.

Role of DNA and RNA N6-Adenine Methylation in Regulating Stem Cell Fate.

BACKGROUND: Epigenetic modifications have been evidenced to participate in eukaryotic stem cell fate decision. Among the most studied, 5-methylcytosine (m5C) and its derivatives are wellestablished epigenetic codes that play important roles in stem cell pluripotency and differentiation. Based on improved detection techniques, recent studies have succeeded in defining N6-adenine methylation (m6A) in eukaryotic DNA and RNA. The abundant m6A methylation in RNA was shown to be involved in multiple cellular metabolisms while the presence and functional potential of DNA m6A methylation in different species advanced our knowledge in the m6A-mediated biological processes. CONCLUSION: m6A modification has been observed during embryogenesis and has been proposed to fine-tune stem cell regulation. The m6A methyltransferases and demethylases work together to control the dynamic state of m6A marks in genomic DNA and RNA to ensure proper cell fate transition and determination, which are vital to the development and survival of eukaryotes.

Effect of FK-506 (tacrolimus) therapy on bone healing of titanium implants: a histometric and biomechanical study in mice.

Immunosuppressive agents have been recognized as a factor affecting bone metabolism. The aim of the present study was to evaluate the influence of FK-506 administration on the healing of bone around titanium implants. Thirty-two male mice were randomly allocated to two groups: the FK-506 group (n = 16 mice), which received subcutaneous administration of FK-506 (1 mg kg-1 d-1 ); and the control group (n = 16 mice), which received saline solution by the same route of administration. After 2 wk, one titanium implant with sandblasted/acid-etched surface was placed in the femur. The therapy continued until the mice were killed 2 and 4 wk after surgery. The femurs with implants were evaluated by biomechanical testing and histologic analysis. The bone-implant contact (BIC) and bone volume (BV/TV) within a 100-µm-wide circumferential zone lateral to the implant surface were histomorphometrically analyzed. Compared with the control group, the FK-506 group showed significantly lower BIC and BV/TV at both 2 and 4 wk. Biomechanical tests showed that FK-506 significantly impaired the strength of bone-implant integration at both 2 and 4 wk postoperatively. Our data indicate that immunosuppressive therapy with FK-506 negatively affects the fixation of titanium implants.

A Novel Nanosilver/Nanosilica Hydrogel for Bone Regeneration in Infected Bone Defects.

Treating bone defects in the presence of infection is a formidable clinical challenge. The use of a biomaterial with the dual function of bone regeneration and infection control is a novel therapeutic approach to this problem. In this study, we fabricated an innovative, dual-function biocomposite hydrogel containing nanosilver and nanosilica (nAg/nSiO2) particles and evaluated its characteristics using FT-IR, SEM, swelling ratio, and stiffness assays. The in vitro antibacterial analysis showed that this nAg/nSiO2 hydrogel inhibited both Gram-positive and Gram-negative bacteria. In addition, this nontoxic material could promote osteogenic differentiation of rat bone marrow stromal cells (BMSCs). We then created infected bone defects in rat calvaria in order to evaluate the function of the hydrogel in vivo. The hydrogel demonstrated effective antibacterial ability while promoting bone regeneration in these defects. Our results indicate that this nAg/nSiO2 hydrogel has the potential to both control infection and to promote bone healing in contaminated defects.

N(6)-Methyladenosine Methyltransferases and Demethylases: New Regulators of Stem Cell Pluripotency and Differentiation.

The discovery of mammalian N(6)-methyladenosine (m(6)A) methyltransferases and demethylases has enriched our knowledge of the dynamic regulation of the most prevalent posttranscriptional RNA modification, m(6)A methylation. This reversible methylation process of adding and removing m(6)A marks on RNA has been shown to have broad biological functions in fine tuning cellular processes and gene expression. Recent studies have revealed a critical role for the currently known m(6)A methyltransferases and demethylases in regulating the pluripotency and differentiation of stem cells. These data establish a novel dimension in epigenetic regulation at the RNA level to affect mammalian cell fate.