Pax5 Negatively Regulates Osteoclastogenesis through Downregulation of Blimp1

Paired box protein 5 (Pax5) is a crucial transcription factor responsible for B-cell lineage specification and commitment. In this study, we identified a negative role of Pax5 in osteoclastogenesis. The expression of Pax5 was time-dependently downregulated by receptor activator of nuclear factor kappa B (RANK) ligand (RANKL) stimulation in osteoclastogenesis. Osteoclast (OC) differentiation and bone resorption were inhibited (68.9% and 48% reductions, respectively) by forced expression of Pax5 in OC lineage cells. Pax5 led to the induction of antiosteoclastogenic factors through downregulation of B lymphocyte-induced maturation protein 1 (Blimp1). To examine the negative role of Pax5 in vivo, we generated Pax5 transgenic (Pax5Tg) mice expressing the human Pax5 transgene under the control of the tartrate-resistant acid phosphatase (TRAP) promoter, which is expressed mainly in OC lineage cells. OC differentiation and bone resorption were inhibited (54.2–76.9% and 24.0–26.2% reductions, respectively) in Pax5Tg mice, thereby contributing to the osteopetrotic-like bone phenotype characterized by increased bone mineral density (13.0–13.6% higher), trabecular bone volume fraction (32.5–38.1% higher), trabecular thickness (8.4–9.0% higher), and trabecular number (25.5–26.7% higher) and decreased trabecular spacing (9.3–10.4% lower) compared to wild-type control mice. Furthermore, the number of OCs was decreased (48.8–65.3% reduction) in Pax5Tg mice. These findings indicate that Pax5 plays a negative role in OC lineage specification and commitment through Blimp1 downregulation. Thus, our data suggest that the Pax5–Blimp1 axis is crucial for the regulation of RANKL-induced osteoclastogenesis.

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Blockade of IL-6 alleviates bone loss induced by modeled microgravity in mice

Canadian Journal of Physiology and Pharmacology ◽

10.1139/cjpp-2019-0632 ◽

2020 ◽

Vol 98 (10) ◽

pp. 678-683

Author(s):

Baorong He ◽

Xinhua Yin ◽

Dingjun Hao ◽

Xuefang Zhang ◽

Zhen Zhang ◽

...

Keyword(s):

Bone Loss ◽

Mrna Expression ◽

Volume Fraction ◽

Femoral Diaphysis ◽

Tartrate Resistant Acid Phosphatase ◽

Mineral Density ◽

Trabecular Thickness ◽

Modeled Microgravity ◽

Protein Levels ◽

Hind Limb Suspension

This study investigated the effects of blockade of IL-6 on bone loss induced by modeled microgravity (MG). Adult male mice were exposed to hind-limb suspension (HLS) and treated with IL-6-neutralizing antibody (IL-6 nAb) for 4 weeks. HLS in mice led to upregulation of IL-6 expression in both sera and femurs. IL-6 nAb treatment in HLS mice significantly alleviated bone loss, evidenced by increased bone mineral density of whole tibia, trabecular thickness and number, bone volume fraction of proximal tibiae, and ultimate load and stiffness of femoral diaphysis. IL-6 nAb treatment in HLS mice significantly enhanced levels of osteocalcin in sera and reduced levels of deoxypyridinoline. In MC3T3-E1 cells exposed to MG in vitro, IL-6 nAb treatment increased mRNA expression and activity of alkaline phosphatase, mRNA expression of osteopontin and runt-related transcription factor 2, and protein levels of osteoprotegerin and decreased protein levels of receptor activator of the NF-κB ligand. In RAW254.7 cells exposed to MG, IL-6 nAb treatment downregulated mRNA expression of cathepsin K and tartrate-resistant acid phosphatase (TRAP) and reduced numbers of TRAP-positive multinucleated osteoclasts. In conclusion, blockade of IL-6 alleviated the bone loss induced by MG.

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In vivo microcomputed tomography evaluation of rat alveolar bone and root resorption during orthodontic tooth movement

The Angle Orthodontist ◽

10.2319/031312-219.1 ◽

2012 ◽

Vol 83 (3) ◽

pp. 402-409 ◽

Cited By ~ 22

Author(s):

Nan Ru ◽

Sean Shih-Yao Liu ◽

Li Zhuang ◽

Song Li ◽

Yuxing Bai

Keyword(s):

Alveolar Bone ◽

Tooth Movement ◽

Root Resorption ◽

Volume Fraction ◽

Orthodontic Tooth Movement ◽

Bone Volume ◽

Structure Model ◽

Bone Volume Fraction ◽

Trabecular Thickness

ABSTRACT Objective: To observe the real-time microarchitecture changes of the alveolar bone and root resorption during orthodontic treatment. Materials and Methods: A 10 g force was delivered to move the maxillary left first molars mesially in twenty 10-week-old rats for 14 days. The first molar and adjacent alveolar bone were scanned using in vivo microcomputed tomography at the following time points: days 0, 3, 7, and 14. Microarchitecture parameters, including bone volume fraction, structure model index, trabecular thickness, trabecular number, and trabecular separation of alveolar bone, were measured on the compression and tension side. The total root volume was measured, and the resorption crater volume at each time point was calculated. Univariate repeated measures analysis of variance with Bonferroni corrections were performed to compare the differences in each parameter between time points with significance level at P < .05. Results: From day 3 to day 7, bone volume fraction, structure model index, trabecular thickness, and trabecular separation decreased significantly on the compression side, but the same parameters increased significantly on the tension side from day 7 to day 14. Root resorption volume of the mesial root increased significantly on day 7 of orthodontic loading. Conclusions: Real-time root and bone resorption during orthodontic movement can be observed in 3 dimensions using in vivo micro-CT. Alveolar bone resorption and root resorption were observed mostly in the apical third on day 7 on the compression side; bone formation was observed on day 14 on the tension side during orthodontic tooth movement.

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Antiosteoporosis Effect ofRadix ScutellariaeExtract on Density and Microstructure of Long Bones in Tail-Suspended Sprague-Dawley Rats

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2013/753703 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Chen-Rui Li ◽

Guang-Wei Zhang ◽

Yin-Bo Niu ◽

Ya-Lei Pan ◽

Yuan-Kun Zhai ◽

...

Keyword(s):

Bone Mineral Density ◽

Bone Mineral ◽

Volume Fraction ◽

Bone Microarchitecture ◽

Osteoclast Differentiation ◽

Hindlimb Unloading ◽

Mineral Density ◽

Bone Volume Fraction ◽

Trabecular Thickness ◽

Radix Scutellariae

Radix Scutellariae (RS), a medicinal herb, is extensively employed in traditional Chinese medicines and modern herbal prescriptions. Two major flavonoids in RS were known to induce osteoblastic differentiation and inhibit osteoclast differentiation, respectively. This study aimed to investigate the effect ofRadix Scutellariaeextract (RSE) against bone loss induced by mechanical inactivity or weightlessness. A hindlimb unloading tail-suspended rat model (TS) was established to determine the effect of RSE on bone mineral density and bone microarchitecture. Treatment of RSE at 50 mg/kg/day and alendronate (ALE) at 2 mg/kg/day as positive control for 42 days significantly increased the bone mineral density and mechanical strength compared with TS group. Enhanced bone turnover markers by TS treatment were attenuated by RSE and ALE administration. Deterioration of bone trabecula induced by TS was prevented. Moreover, both treatments counteracted the reduction of bone volume fraction, trabecular thickness and number, and connectivity density. In conclusion, RSE was demonstrated for the first time to prevent osteoporosis induced by TS treatment, which suggests the potential application of RSE in the treatment of disuse-induced osteoporosis.

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The Incorporation of Platelet-rich Plasma into Calcium Phosphate Cement Enhances Bone Regeneration in Osteoporosis

January 2018 - Pain Physician ◽

10.36076/ppj.2014/17/e737 ◽

2014 ◽

Vol 6;17 (6;12) ◽

pp. E737-E745

Author(s):

Kyung-Hoon Kim

Keyword(s):

Bone Regeneration ◽

Trabecular Bone ◽

Volume Fraction ◽

Platelet Rich Plasma ◽

Bone Volume ◽

Filler Materials ◽

Trabecular Bone Volume ◽

Mineral Density ◽

Bone Volume Fraction ◽

Trabecular Thickness

Background: Polymethyl methacrylate (PMMA) bone cement is widely used for osteoplasty. However, previous studies have demonstrated the adverse effects of PMMA due to its excessive stiffness and heat production. Recently, calcium phosphate cement (CPC) that overcomes those negative effects has been successfully applied in osteoplasty. The potential problem of CPC is markedly less initial stiffness. It leads to progressive, repeated collapse in the treated vertebra before CPC has been replaced by new bone that would provide substantial improvement in compressive strength and stiffness. The activated platelets in platelet-rich plasma (PRP) release a high concentration of growth factors which play an important role in bone healing. Objective: To investigate whether PRP could accelerate the osteoconduction of CPC and enhance the bone strength of the treated vertebra in an animal model. Study Design: Controlled animal study. Setting: Laboratory animal study, Methods: Thirty-two female Sprague-Dawley rats were ovariectomized at 8 weeks of age. After 3 months, they were randomly divided into 4 groups and received cement augmentation in the fifth caudal spine with different filler materials; sham-operated rats (S), PMMA (P), CPC (C), and CPC + PRP (CP). Bone mineral density (BMD) and trabecular type-associated morphological parameters, including trabecular bone volume fraction and trabecular thickness in the augmented caudal spine, were evaluated by micro-computed tomography (mirco-CT) 2 weeks after the cementoplasty. Histological analysis was also performed to compare the bone regeneration. Results: The trabecular bone volume fraction in the CP group was significantly greater than those of all the other groups. Trabecular thickness was higher in the CP group than the S and P groups. This augmented trabecular structure in the CP group accordingly showed higher BMD. Histological evaluations showed significantly more bone regeneration in the CP group. Limitations: There has been a concern that the effect of PRP would be dependent on the species, and might show different results in humans. Baseline values of micro-CT analysis were not measured, which could have provided exact evidence of the changes in trabecular microarchitecture parameters and cement resorption profiles. Finally, caudal vertebrae with filler materials used in biological study should have been compared by their mechanical properties using biomechanical evaluations for a more coherent study, which was not possible due to technical problems. Conclusions: Incorporating PRP into CPC could accelerate osteoconduction in the augmented vertebra leading to improvement of trabecular bone microarchitecture and BMD in rats. Key words: Bone mineral density, calcium phosphates, cementoplasty, histology, osteoconduction, osteoporosis, platelet-rich plasma, polymethyl methacrylate, vertebra

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Healing Cranial Defects with AdRunx2-transduced Marrow Stromal Cells

Journal of Dental Research ◽

10.1177/154405910708601213 ◽

2007 ◽

Vol 86 (12) ◽

pp. 1207-1211 ◽

Cited By ~ 45

Author(s):

Z. Zhao ◽

Z. Wang ◽

C. Ge ◽

P. Krebsbach ◽

R.T. Franceschi

Keyword(s):

Stromal Cells ◽

Volume Fraction ◽

Marrow Stromal Cells ◽

Osteogenic Potential ◽

Specific Gene ◽

Mineral Density ◽

Bone Volume Fraction ◽

Calvarial Defects

Marrow stromal cells (MSCs) include stem cells capable of forming all mesenchymal tissues, including bone. However, before MSCs can be successfully used in regeneration procedures, methods must be developed to stimulate their differentiation selectively to osteoblasts. Runx2, a bone-specific transcription factor, is known to stimulate osteoblast differentiation. In the present study, we tested the hypothesis that Runx2 gene therapy can be used to heal a critical-sized defect in mouse calvaria. Runx2-engineered MSCs displayed enhanced osteogenic potential and osteoblast-specific gene expression in vitro and in vivo. Runx2-expressing cells also dramatically enhanced the healing of critical-sized calvarial defects and increased both bone volume fraction and bone mineral density. These studies provide a novel route for enhancing osteogenesis that may have future therapeutic applications for craniofacial bone regeneration.

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Triptolide Prevents Bone Destruction in the Collagen-Induced Arthritis Model of Rheumatoid Arthritis by Targeting RANKL/RANK/OPG Signal Pathway

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2013/626038 ◽

2013 ◽

Vol 2013 ◽

pp. 1-12 ◽

Cited By ~ 16

Author(s):

Chunfang Liu ◽

Yanqiong Zhang ◽

Xiangying Kong ◽

Liuluan Zhu ◽

Jian Pang ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Mononuclear Cells ◽

Volume Fraction ◽

Bone Destruction ◽

Signal Pathway ◽

Therapeutic Effects ◽

Mineral Density ◽

Collagen Induced Arthritis ◽

Bone Volume Fraction ◽

Trabecular Thickness

Focal bone destruction within inflamed joints is the most specific hallmark of rheumatoid arthritis (RA). Our previous study indicated that the therapeutic efficiency of triptolide in RA may be due partially to its chondroprotective and anti-inflammatory effects. However, its roles in bone destruction are still unclear. In this study, our data firstly showed the therapeutic effects of triptolide on severity of arthritis and arthritis progression in collagen-induced arthritis (CIA) mice. Then, by micro-CT quantification, triptolide treatment significantly increased bone mineral density, bone volume fraction, and trabecular thickness and decreased trabecular separation of inflamed joints. Interestingly, triptolide treatment could prevent the bone destruction by reducing the number of osteoclasts in inflamed joints, reducing the expression of receptor activator of NF-κB (RANK) ligand (RANKL) and RANK, increasing the expression of osteoprotegerin (OPG), at both mRNA and protein levels, and decreasing the ratio of RANKL to OPG in sera and inflamed joints of CIA mice, which were further confirmed in the coculture system of human fibroblast-like synovial and peripheral blood mononuclear cells. These findings offer the convincing evidence for the first time that triptolide may attenuate RA partially by preventing the bone destruction and inhibit osteoclast formation by regulating RANKL/RANK/OPG signal pathway.

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Comparison of Trabecular Bone Mineral Density Measurement Using Hounsfield Unit and Trabecular Microstructure in Orthodontic Patients Using Cone-Beam Computed Tomography

Applied Sciences ◽

10.3390/app11031028 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1028

Author(s):

Tae-Hyun Kim ◽

Dong-Yul Lee ◽

Seok-Ki Jung

Keyword(s):

Bone Mineral Density ◽

Bone Mineral ◽

Volume Fraction ◽

Cervical Vertebra ◽

Hounsfield Unit ◽

Mineral Density ◽

Bone Volume Fraction ◽

Trabecular Thickness ◽

Trabecular Microstructure ◽

Trabecular Number

The aim of this study was to measure the bone mineral density of specific regions of maxilla, mandible, and first cervical vertebra using the Hounsfield unit and trabecular microstructure pattern analysis and to compare the two methods. In this study, cone-beam computed tomography (CBCT) images were obtained from 58 patients. Trabecular thickness, trabecular number, trabecular separation, and bone volume fraction were measured in 484 regions for trabecular microstructure parameters and Hounsfield unit was measured for the grayscale value. There was no difference in bone mineral density between the right and left side in every site and between males and females. Trabecular thickness and trabecular number were high in the order of anterior base of the maxilla, mandibular body, first cervical vertebra, and mandibular condyle. Bone volume fraction and Hounsfield unit were high in the order of anterior base of the maxilla, mandibular body, mandibular condyle, and first cervical vertebra (p < 0.05). Trabecular thickness, trabecular number, and bone volume fraction was positively correlated to the Hounsfield unit, and trabecular separation was negatively correlated to the Hounsfield unit (p < 0.005). This study suggests that it is possible to compare the bone mineral density of trabecular bone in various sites using the Hounsfield unit and trabecular microstructure pattern analysis.

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Kindlin-2 regulates skeletal homeostasis by modulating PTH1R in mice

Signal Transduction and Targeted Therapy ◽

10.1038/s41392-020-00328-y ◽

2020 ◽

Vol 5 (1) ◽

Author(s):

Xuekun Fu ◽

Bo Zhou ◽

Qinnan Yan ◽

Chu Tao ◽

Lei Qin ◽

...

Keyword(s):

Bone Mass ◽

Volume Fraction ◽

Bone Marrow Cells ◽

Bone Matrix ◽

Osteoblastic Cells ◽

Mineral Density ◽

Bone Volume Fraction ◽

Ovariectomized Mice

AbstractIn vertebrates, the type 1 parathyroid hormone receptor (PTH1R) is a critical regulator of skeletal development and homeostasis; however, how it is modulated is incompletely understood. Here we report that deleting Kindlin-2 in osteoblastic cells using the mouse 10-kb Dmp1-Cre largely neutralizes the intermittent PTH-stimulated increasing of bone volume fraction and bone mineral density by impairing both osteoblast and osteoclast formation in murine adult bone. Single-cell profiling reveals that Kindlin-2 loss increases the proportion of osteoblasts, but not mesenchymal stem cells, chondrocytes and fibroblasts, in non-hematopoietic bone marrow cells, with concomitant depletion of osteoblasts on the bone surfaces, especially those stimulated by PTH. Furthermore, haploinsufficiency of Kindlin-2 and Pth1r genes, but not that of either gene, in mice significantly decreases basal and, to a larger extent, PTH-stimulated bone mass, supporting the notion that both factors function in the same genetic pathway. Mechanistically, Kindlin-2 interacts with the C-terminal cytoplasmic domain of PTH1R via aa 474–475 and Gsα. Kindlin-2 loss suppresses PTH induction of cAMP production and CREB phosphorylation in cultured osteoblasts and in bone. Interestingly, PTH promotes Kindlin-2 expression in vitro and in vivo, thus creating a positive feedback regulatory loop. Finally, estrogen deficiency induced by ovariectomy drastically decreases expression of Kindlin-2 protein in osteocytes embedded in the bone matrix and Kindlin-2 loss essentially abolishes the PTH anabolic activity in bone in ovariectomized mice. Thus, we demonstrate that Kindlin-2 functions as an intrinsic component of the PTH1R signaling pathway in osteoblastic cells to regulate bone mass accrual and homeostasis.

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Pregnane X receptor knockout mice display osteopenia with reduced bone formation and enhanced bone resorption

Journal of Endocrinology ◽

10.1677/joe-10-0208 ◽

2010 ◽

Vol 207 (3) ◽

pp. 257-263 ◽

Cited By ~ 30

Author(s):

Kotaro Azuma ◽

Stephanie C Casey ◽

Masako Ito ◽

Tomohiko Urano ◽

Kuniko Horie ◽

...

Keyword(s):

Bone Resorption ◽

Bone Formation ◽

Volume Fraction ◽

Pregnane X Receptor ◽

Bending Test ◽

Bone Homeostasis ◽

Micro Computed Tomography ◽

Mineral Density ◽

Bone Volume Fraction ◽

Trabecular Bones

The steroid and xenobiotic receptor (SXR) and its murine ortholog pregnane X receptor (PXR) are nuclear receptors that are expressed mainly in the liver and intestine where they function as xenobiotic sensors. In addition to its role as a xenobiotic sensor, previous studies in our laboratories and elsewhere have identified a role for SXR/PXR as a mediator of bone homeostasis. Here, we report that systemic deletion of PXR results in marked osteopenia with mechanical fragility in female mice as young as 4 months old. Bone mineral density (BMD) of PXR knockout (PXRKO) mice was significantly decreased compared with the BMD of wild-type (WT) mice. Micro-computed tomography analysis of femoral trabecular bones revealed that the three-dimensional bone volume fraction of PXRKO mice was markedly reduced compared with that of WT mice. Histomorphometrical analysis of the trabecular bones in the proximal tibia showed a remarkable reduction in bone mass in PXRKO mice. As for bone turnover of the trabecular bones, bone formation is reduced, whereas bone resorption is enhanced in PXRKO mice. Histomorphometrical analysis of femoral cortical bones revealed a larger cortical area in WT mice than that in PXRKO mice. WT mice had a thicker cortical width than PXRKO mice. Three-point bending test revealed that these morphological phenotypes actually caused mechanical fragility. Lastly, serum levels of phosphate, calcium, and alkaline phosphatase were unchanged in PXRKO mice compared with WT. Consistent with our previous results, we conclude that SXR/PXR promotes bone formation and suppresses bone resorption thus cementing a role for SXR/PXR as a key regulator of bone homeostasis.

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Raloxifene inhibits the overexpression of TGF-β1 in cartilage and regulates the metabolism of subchondral bone in rats with osteoporotic osteoarthritis

Bosnian Journal of Basic Medical Sciences ◽

10.17305/bjbms.2020.5142 ◽

2020 ◽

Author(s):

Shao-Hua Ping ◽

Fa-Ming Tian ◽

Hao Liu ◽

Qi Sun ◽

Li-Tao Shao ◽

...

Keyword(s):

Subchondral Bone ◽

Transforming Growth Factor Beta ◽

Transforming Growth Factor ◽

Volume Fraction ◽

Clinical Indication ◽

Tartrate Resistant Acid Phosphatase ◽

Mineral Density ◽

Bone Volume Fraction ◽

Ovx Rats ◽

Tgf Β1

Overexpression of transforming growth factor-beta 1 (TGF-β1) and subchondral bone remodelling play key roles in osteoarthritis (OA). Raloxifene (RAL) reduces the serum level of TGF-β1 in postmenopausal women. However, the effect of RAL on TGF-β1 expression in articular cartilage is still unclear. Therefore, we aimed to investigate the protective effect of RAL on osteoporotic osteoarthritis via affecting TGF-β1 expression in cartilage and the metabolism of subchondral bone. Osteoporotic osteoarthritis was induced by a combination of anterior cruciate transection (ACLT) and ovariectomy (OVX). Rats were divided into five groups (n = 12): The sham group, the ACLT group, the OVX group, the ACLT + OVX group, and the RAL group (ACLT + OVX + RAL, 6.25 mg/kg/day for 12 weeks). Assessment was performed by histomorphology, microcomputed tomography (micro-CT) scan, immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining. We found that severe cartilage degeneration was shown in the ACLT + OVX group. The histomorphological scores, the levels of TGF-β1, and its related catabolic enzymes and osteoclasts numbers in the ACLT + OVX group were higher than those in other groups (p < 0.05). Furthermore, structure model index (SMI) and trabecular spacing (Tb.Sp) were decreased (p < 0.05), while bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular number (Tb.N) were increased by RAL compared with the ACLT + OVX group (p < 0.05). Our findings demonstrated that RAL in clinical doses retards the development of osteoporotic osteoarthritis by inhibiting the overexpression of TGF-β1 in cartilage and regulating the metabolism of subchondral bone. These results provide support for RAL in the expansion of clinical indication for prevention and treatment in postmenopausal osteoarthritis.

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