MAGED1 is a negative regulator of bone remodeling in mice

Dynamic expression of Mage-D1 in rat dental germs and potential role in mineralization of ectomesenchymal stem cells

Mage-D1 (MAGE family member D1) is involved in a variety of cell biological effects. Recent studies have shown that Mage-D1 is closely related to tooth development, but its specific regulatory mechanism is unclear. The purpose of this study was to investigate the expression pattern of Mage-D1 in rat dental germ development and its differential mineralization ability to ectomesenchymal stem cells (EMSCs), and to explore its potential mechanism. Results showed that the expression of Mage-D1 during rat dental germ development was temporally and spatially specific. Mage-D1 promotes the proliferation ability of EMSCs but inhibits their migration ability. Under induction by mineralized culture medium, Mage-D1 promotes osteogenesis and tooth-forming ability. Furthermore, the expression pattern of Mage-D1 at E19.5 d rat dental germ is similar to p75 neurotrophin receptor (p75NTR), distal-less homeobox 1 (Dlx1) and msh homeobox 1 (Msx1). In addition, Mage-D1 is binding to p75NTR, Dlx1, and Msx1 in vitro. These findings indicate that Mage-D1 is play an important regulatory role in normal mineralization of teeth. p75NTR, Dlx1, and Msx1 seem to be closely related to the underlying mechanism of Mage-D1 action.

Piperlongumine Inhibits Titanium Particles-Induced Osteolysis, Osteoclast Formation, and RANKL-Induced Signaling Pathways

Wear particle-induced aseptic loosening is the most common complication of total joint arthroplasty (TJA). Excessive osteoclast formation and bone resorptive activation have been considered to be responsible for extensive bone destruction and prosthesis failure. Therefore, identification of anti-osteoclastogenesis agents is a potential therapy strategy for the treatment of aseptic loosening and other osteoclast-related osteolysis diseases. In the present study, we reported, for the first time, that piperlongumine (PL), a key alkaloid compound from Piper longum fruits, could significantly suppress the formation and activation of osteoclasts. Furthermore, PL effectively decreased the mRNA expressions of osteoclastic marker genes such as tartrate-resistant acid phosphatase (TRAP), calcitonin receptor (CTR), and cathepsin K (CTSK). In addition, PL suppressed the receptor activator of nuclear factor-κB ligand (RANKL)-induced activations of MAPKs (ERK, JNK and p38) and NF-κB, which down-regulated the protein expression of nuclear factor of activated T-cells cytoplasmic 1 (NFATc1). Using a titanium (Ti) particle-induced calvarial osteolysis model, we demonstrated that PL could ameliorate Ti particle-induced bone loss in vivo. These data provide strong evidence that PL has the potential to treat osteoclast-related diseases including periprosthetic osteolysis (PPO) and aseptic loosening.

VELCRO-IP RNA-seq reveals ribosome expansion segment function in translation genome-wide

Roles for ribosomal RNA (rRNA) in gene regulation remain largely unexplored. With hundreds of rDNA units positioned across multiple loci, it is not possible to genetically modify rRNA in mammalian cells, hindering understanding of ribosome function. It remains elusive whether expansion segments (ESs), tentacle-like rRNA extensions that vary in sequence and size across eukaryotic evolution, may have functional roles in translation control. Here, we develop variable expansion segment-ligand chimeric ribosome immunoprecipitation RNA sequencing (VELCRO-IP RNA-seq), a versatile methodology to generate species-adapted ESs and to map specific mRNA regions across the transcriptome that preferentially associate with ESs. Application of VELCRO-IP RNA-seq to a mammalian ES, ES9S, identified a large array of transcripts that are selectively recruited to ribosomes via an ES. We further characterize a set of 5′ UTRs that facilitate cap-independent translation through ES9S-mediated ribosome binding. Thus, we present a technology for studying the enigmatic ESs of the ribosome, revealing their function in gene-specific translation.

Leppek et al. develop a pulldown technology employing chimeric yeast ribosomes, VELCRO-IP RNA-seq, to map interactions between ribosomal RNA (rRNA) and mRNAs genome-wide with positional precision. They find that expansion segments (ESs), the extended rRNA tentacles of the ribosome, specifically bind 5′ UTR elements to enable cap-independent translation of select mRNAs.

Knockout of NRAGE promotes autophagy-related gene expression and the periodontitis process in mice

BACKGROUND AND OBJECTIVE

Neurotrophin receptor-interacting MAGE homologue (NRAGE) plays a crucial role in the regulation of bone metabolism. The present study investigated the regulation role of NRAGE on autophagy activation and periodontitis process during experimental periodontitis.

MATERIALS AND METHODS

Six-week-old wild-type (WT) and NRAGE-/- mice were randomly divided into three time points in the periodontitis groups (0, 2, and 4 weeks). Histopathological changes were determined using the tooth mobility, hematoxylin and eosin (H&E) staining, and micro-computed tomography (micro-CT). Osteoclasts activation and number were investigated using tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemistry, and real-time quantitative PCR (RT-PCR). The level of autophagy-related gene expression was measured using immunohistochemistry, immunofluorescence, and RT-PCR.

RESULTS

H&E staining and Micro-CT showed that the destruction of the alveolar bone was considerably more severe in the NRAGE-/- group than the WT group after ligation. Tooth mobility in the NRAGE-/- group was obviously higher than that in the WT group. The activation and number of osteoclasts and the level of autophagy-related gene expression in NRAGE-/- group were significantly higher than that in WT group.

CONCLUSIONS

The present study showed that knockout of NRAGE induced autophagy-related gene expression and accelerated the process of periodontitis disease via increasing the activity and differentiation of osteoclast.

MAGE genes in the kidney: identification of MAGED2 as upregulated during kidney injury and in stressed tubular cells

BACKGROUND

Mutations in Melanoma Antigen-encoding Gene D2 (MAGED2) promote tubular dysfunction, suggesting that MAGE proteins may play a role in kidney pathophysiology. We have characterized the expression and regulation of MAGE genes in normal kidneys and during kidney disease.

METHODS

The expression of MAGE genes and their encoded proteins was explored by systems biology multi-omics (kidney transcriptomics and proteomics) in healthy adult murine kidneys and following induction of experimental acute kidney injury (AKI) by a folic acid overdose. Changes in kidney expression during nephrotoxic AKI were validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blot and immunohistochemistry. Factors regulating gene expression were studied in cultured tubular cells.

RESULTS

Five MAGE genes (MAGED1, MAGED2, MAGED3, MAGEH1, MAGEE1) were expressed at the mRNA level in healthy adult mouse kidneys, as assessed by RNA-Seq. Additionally, MAGED2 was significantly upregulated during experimental AKI as assessed by array transcriptomics. Kidney proteomics also identified MAGED2 as upregulated during AKI. The increased kidney expression of MAGED2 mRNA and protein was confirmed by qRT-PCR and western blot, respectively, in murine folic acid- and cisplatin-induced AKI. Immunohistochemistry located MAGED2 to tubular cells in experimental and human kidney injury. Tubular cell stressors [serum deprivation and the inflammatory cytokine tumour necrosis factor-like weak inducer of apoptosis (TWEAK)] upregulated MAGED2 in cultured tubular cells.

CONCLUSIONS

MAGED2 is upregulated in tubular cells in experimental and human kidney injury and is increased by stressors in cultured tubular cells. This points to a role of MAGED2 in tubular cell injury during kidney disease that should be dissected by carefully designed functional approaches.

Phillyrin Attenuates Osteoclast Formation and Function and Prevents LPS-Induced Osteolysis in Mice

As the sole cell type responsible for bone resorption, osteoclasts play a pivotal role in a variety of lytic bone diseases. Suppression of osteoclast formation and activation has been proposed as an effective protective therapy for new bone. In this study, we reported for the first time that phillyrin (Phil), an active ingredient extracted from forsythia, significantly inhibited RANKL-induced osteoclastogenesis and bone resorption in vitro and protected against lipopolysaccharide-induced osteolysis in vivo. Further molecular investigations demonstrated that Phil effectively blocked RANKL-induced activations of c-Jun N-terminal kinase and extracellular signal-regulated kinase, which suppressed the expression of c-Fos and nuclear factor of activated T-cells cytoplasmic 1. Taken together, these data suggested that Phil might be a potential antiosteoclastogenesis agent for treating osteoclast-related bone lytic diseases.

Knockdown of NRAGE induces odontogenic differentiation by activating NF-κB signaling in mouse odontoblast-like cells

PURPOSE

Neurotrophin receptor-interacting MAGE homologue (Nrage) plays an important role in bone development and the metabolism of normal skeletal structures. Our previous study showed that Nrage inhibited the odontogenic differentiation of mouse dental pulp cells. However, the potential roles and mechanism of Nrage in regulating odontogenic differentiation are unknown. The aim of this study was to investigate the molecular mechanism of Nrage in odontogenic differentiation of mouse odontoblast-like cells.

MATERIALS AND METHODS

Endogenous expression of Nrage was stably downregulated by lentivirus-mediated shRNA. Mineralized nodules formation was detected by alizarin red S staining. Dmp-1, Dspp, and ALP mRNA and protein levels were detected by qRT-PCR and western blotting, respectively. In addition, ALPase activity was detected. Confocal microscopy and co-immunoprecipitation (co-IP) were used to analyze the interactions between NRAGE and NF-κB signaling molecules. An IKK inhibitor was also used in the study.

RESULTS

NRAGE expression in odontoblasts was downregulated during mouse first maxillary molar development. Moreover, NRAGE expression was downregulated during odontogenic differentiation of odontoblast-like cells. NRAGE knockdown significantly upregulated DMP1 and DSP expression, increased ALPase activity, and promoted mineralized nodule formation. In addition, NRAGE knockdown increased the translocation of NF-κB1 to the nucleus and phosphorylation levels of p65. Co-IP results showed that NRAGE bound to IKKβ. Most importantly, the promoting effect of Nrage knockdown on odontoblastic differentiation was reduced after treatment with an IKK inhibitor.

CONCLUSIONS

Our data confirmed that NRAGE is an important regulator of odontogenic differentiation of odontoblasts by inhibiting the NF-κB signaling pathway through binding to IKKβ.

ABBREVIATIONS

Nrage: neurotrophin receptor-interacting MAGE homologue; DSP: dentin sialophospho protein; DMP-1: dentin matrix protein-1; BMP: bone morphogenetic protein; Wnt: wingless; NF-κB: nuclear factor of activated B cells; DAPI: 4',6-diamidino-2-phenylindole; KO: knockout; DPCs: dental pulp cells; AA: ascorbic acid; β-Gly: β-glycerophosphate; Dex: dexamethasone; co-IP: co-immunoprecipitation; IκB: inhibitor of NF-κB; IKK: IκB kinase.

Jatrorrhizine Hydrochloride Suppresses RANKL-Induced Osteoclastogenesis and Protects against Wear Particle-Induced Osteolysis

Wear particle-induced aseptic prosthetic loosening is a major complication associated with total joint arthroplasty (TJA). A growing body of evidence suggests that receptor activator of nuclear factor κ-B ligand (RANKL)-stimulated osteoclastogenesis and bone resorption are responsible for peri-implant loosening. Thus, agents which attenuate excessive osteoclast differentiation and function have been considered to offer therapeutic potential for prolonging the life of TJA implants. Jatrorrhizine hydrochloride (JH), a major protoberberine alkaloid isolated from the traditional Chinese herb Coptis chinensis, has been reported to have antimicrobial, antitumor, and antihypercholesterolemic and neuroprotective activities. However, its effects on osteoclast biology remain unknown. Here, we found that JH inhibited RANKL-induced osteoclast formation and bone resorption in vitro and exerted protection against titanium (Ti) particle-induced osteolysis in vivo. Biochemical analysis demonstrated that JH suppressed RANKL-induced activation of MAPKs (p38 and ERK) which down-regulated the production of NFATc1 and NFATc1-regulated osteoclastic marker genes, such as TRAP, CTR and CTSK. Collectively, our findings suggest that JH may be a promising anti-osteoclastogenesis agent for treating periprosthetic osteolysis or other osteoclast-related osteolytic diseases.

Inhibition of PPARγ, adipogenesis and insulin sensitivity by MAGED1

Peroxisome proliferator-activated receptor-γ (PPARγ) is a master regulator of adipogenesis and a target of the thiazolidinedione (TZD) class of antidiabetic drugs; therefore, identifying novel regulators of PPARγ action in adipocytes is essential for the future development of therapeutics for diabetes. MAGE family member D1 (MAGED1), by acting as an adaptor for ubiquitin-dependent degradation pathways and a co-factor for transcription, plays an important role in neural development, cell differentiation and circadian rhythm. Here, we showed that MAGED1 expression was downregulated during adipogenesis and loss of MAGED1 promoted preadipocyte proliferation and differentiation in vitro. MAGED1 bound to PPARγ and suppressed the stability and transcriptional activity of PPARγ. Compared to WT littermates, MAGED1-deficient mice showed increased levels of PPARγ protein and its target genes, more CD29+CD34+Sca-1+ adipocyte precursors and hyperplasia of white adipose tissues (WATs). Moreover, MAGED1-deficient mice developed late-onset obesity as a result of decreased energy expenditure and physical activity. However, these mice were metabolically healthy as shown by improved glucose clearance and insulin sensitivity, normal levels of serum lipids and enhanced secretion of adipokines such as leptin and adiponectin. Taken together, our data identify MAGED1 as a novel negative regulator of PPARγ activity, adipogenesis and insulin sensitivity in mice. MAGED1 might therefore serve as a novel pharmaceutical target to treat obesity-associated insulin resistance.

Differential time-dependent transcriptional changes in the osteoblast lineage in cortical bone associated with sclerostin antibody treatment in ovariectomized rats

Inhibition of sclerostin with sclerostin antibody (Scl-Ab) results in stimulation of bone formation on cancellous (Cn), endocortical (Ec), and periosteal (Ps) surfaces in rodents and non-human primates. With long-term dosing of Scl-Ab, the increase in bone formation is not sustained, attenuating first on Cn surfaces and later on Ec and Ps surfaces. In Cn bone, the attenuation in bone formation (self-regulation) is associated with transcriptional changes in the osteocyte (OCy) that would limit mitogenesis and are sustained with continued dosing. The expression changes in Cn OCy occur coincident with a decrease in osteoprogenitor (OP) numbers that may directly or indirectly be a consequence of the transcriptional changes in the OCy to limit OP proliferation. To characterize the Scl-Ab–mediated changes in cortical (Ct) bone and compare these changes to Cn bone, densitometric, histomorphometric, and transcriptional analyses were performed on femur diaphyses from aged ovariectomized rats. Animals were administered 50 mg/kg/wk of Scl-Ab or vehicle for up to 6 months (183 days), followed by a treatment-free period (up to 126 days). Scl-Ab increased Ct mass and area through day 183, which declined slightly when treatment was discontinued. Ps and Ec bone formation was sustained through the dosing on both Ct surfaces, with evidence of a decline in bone formation only at day 183 on the Ec surface. This is in contrast to Cn bone, where reduced bone formation was observed after day 29. TaqMan analysis of 60 genes with functional roles in the bone using mRNA isolated from laser capture micro-dissection samples enriched for Ec osteoblasts and Ct OCy suggest a pattern of gene expression in Ct bone that differed from Cn, especially in the OCy, and that corresponded to observed differences in the timing of phenotypic changes. Notable with Scl-Ab treatment was a “transcriptional switch” in Ct OCy at day 183, coincident with the initial decline in bone formation on the endocortex. A consistent sustained increase of expression for most genes in response to Scl-Ab was observed from day 8 through day 85 at the times of maximal bone formation on both Ct surfaces; however, at day 183, this increase was reversed, with expression of these genes generally returning to control values or decreasing compared to vehicle. Genes exhibiting this pattern included Wnt inhibitors Sost and Dkk1, though both had been up-regulated until the end of dosing in Cn OCy. Changes in cell cycle genes such as Cdkn1a and Ndrg1 in Ct OCy suggested up-regulation of p53 signaling, as observed in Cn OCy; however, unlike in Cn bone, p53 signaling was not associated with decreased bone formation and was absent at day 183, when bone formation began to decline on the Ec surface. These data demonstrate involvement of similar molecular pathways in Ct and Cn bone in response to Scl-Ab but with a different temporal relationship to bone formation and suggest that the specific mechanism underlying self-regulation of Scl-Ab–induced bone formation may be different between Cn and Ct bone.

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Sclerostin antibody stimulates bone formation that attenuates over time.

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Attenuation (self-regulation) is delayed in cortical versus cancellous bone.

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Self-regulation coincides with transcriptional changes in cortical osteocytes.

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Response of Wnt inhibitors differs between cortical and cancellous bone.

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Results suggest a distinct mechanism for self-regulation in cortical bone.

Carnosic acid inhibits inflammation response and joint destruction on osteoclasts, fibroblast-like synoviocytes, and collagen-induced arthritis rats

The discovery of new therapeutic drugs with the ability of preventing inflammation and joint destruction with less adverse effects is urgently needed for rheumatoid arthritis (RA). Carnosic acid (CA), a major phenolic compound isolated from the leaves of Rosemary (Rosmarinus officinalis L.), has been reported to have antioxidative and antimicrobial properties. However, its effects on RA have not been elucidated. Here, we investigated the effects of CA on osteoclasts and fibroblast-like synoviocytes in vitro and on collagen-induced arthritis (CIA) in Wistar rats in vivo. Our in vitro and in vivo studies showed that CA suppressed the expression of pro-inflammatory cytokines including TNFɑ, IL-1β, IL-6, IL-8, IL-17 and MMP-3, and downregulated the production of RANKL. More importantly, we observed that CA inhibited osteoclastogenesis and bone resorption in vitro and exerted therapeutic protection against joint destruction in vivo. Further biochemical analysis demonstrated that CA suppressed RANKL-induced activations of NF-κB and MAPKs (JNK and p38) leading to the downregulation of NFATc1. Taken together, our findings provide the convincing evidence that rosemary derived CA is a promising natural compound for the treatment of RA.

p75 neurotrophin receptor regulates differential mineralization of rat ectomesenchymal stem cells

OBJECTIVES

The aim of this study was to investigate whether p75NTR (p75 neurotrophin receptor) regulates differential mineralization capacity of rEMSCs (rat ectomesenchymal stem cells) and underlying mechanisms associated with Mage-D1 (melanoma-associated antigens-D1).

MATERIALS AND METHODS

Immunohistochemical staining of p75NTR in developing tooth germs was performed on E12.5d (embryonic 12.5 days) and E19.5d (embryonic 19.5 days). E12.5d EMSCs and E19.5d EMSCs were isolated in the same pregnant Sprague-Dawley rats from embryonic maxillofacial processes and tooth germs. p75NTR small-interfering RNA, p75NTR overexpression plasmid, Mage-D1 small-interfering RNA and recombined rat NGF were used to transfect cells.

RESULTS

p75NTR was expressed in epithelial-mesenchymal interaction areas at E12.5d and E19.5d tooth germ development stages. E19.5d EMSCs had higher p75NTR expression levels and differential mineralization capacity but lower levels of cell proliferation. Under induction by mineralized culture medium, the potential of differential mineralization had identical trends in regulation of p75NTR in EMSCs; Mage-D1 did not fluctuate and TrkA was not expressed. Binding of p75NTR and Mage-D1 were detected. Mage-D1 knockdown significantly down-regulated expression of related genes, which NGF could not rescue.

CONCLUSION

p75NTR participated in tooth germ development stages and mediated differential mineralization of EMSCs. p75NTR played a critical role in regulating the potential of differential mineralization of EMSCs. Mage-D1 seemed to act as a bridge in the underlying mechanism of effects of p75NTR.