ORCID Profile
0000-0002-5471-6288
Current Organisation
University of Adelaide
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Publisher: Elsevier BV
Date: 03-2015
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.JSBMB.2017.09.005
Abstract: Previous studies have shown that 1α,25-dihydroxyvitamin D
Publisher: American Chemical Society (ACS)
Date: 25-01-2021
Publisher: MDPI AG
Date: 12-04-2018
DOI: 10.3390/MPS1020014
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.JSBMB.2012.11.016
Abstract: In osteoblast cultures, 1,25-dihydroxyvitamin D (1,25D) has been shown to play either catabolic or anabolic roles on differentiation and mineralisation. We have employed osteoblast-like cells extracted from neonatal mouse calvariae and cells derived from juvenile mouse long bones to compare the biological effects of 1,25D on differentiation and mineralisation in vitro. 1,25D exerts differential effects on osteoblast-like cells depending on their stage of maturation and possibly their skeletal origin. This article is part of a Special Issue entitled 'Vitamin D Workshop'.
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.ACTBIO.2019.01.047
Abstract: Periprosthetic osteolysis is a major cause of implant failure in total hip replacements. Aseptic loosening caused by osteolytic lesions is associated with the production of bioactive wear particles from the articulations of implants. Wear particles infiltrate the surrounding tissue of implants, promoting inflammation as well as bone resorption. Osteocytes have been shown to both regulate physiological osteoclastogenesis and directly remodel their perilacunar bone matrix by the process of osteocytic osteolysis. We hypothesise that osteocytes respond to wear debris of orthopaedic implant materials by adopting a pro-catabolic phenotype and thus contribute to periprosthetic osteolysis through the known pathways of bone loss. Osteocyte responses to particles derived from clinically relevant materials, ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (XLPE) and metal alloys, Ti6Al4V and CoCrMo, were examined in vitro in human primary osteocyte-like cultures. Osteocyte-like cells exposed to both polyethylene and metal wear particle types showed upregulated expression of catabolic markers associated with osteocytic osteolysis, MMP13, carbonic anhydrase 2 (CA2) and cathepsin K (CTSK). In addition, pro-osteoclastogenesis markers RANKL and M-CSF were induced, as well as the expression of pro-inflammatory cytokines, IL-6 and TNFα, albeit with different kinetics. These findings suggest a previously unrecognised action of wear particles of multiple orthopaedic materials on osteocytes, and suggest a multifaceted role for osteocytes in periprosthetic osteolysis. STATEMENT OF SIGNIFICANCE: This study addresses periprosthetic osteolysis, a major clinical problem leading to aseptic loosening of orthopaedic implants. It is well accepted that wear particles of polyethylene and of other implant materials stimulate the activity of bone resorbing osteoclasts. Our recent work provided evidence that commercial particles of ultra-high molecular weight polyethylene (UHMWPE) stimulated osteocytes to adopt a bone catabolic state. In this study we demonstrate for the first time that particles derived from materials in clinical use, conventional UHMWPE, highly cross-linked polyethylene (XLPE), and Ti6Al4V and CoCrMo metal alloys, all stimulate human osteocyte activities of osteocyte-regulated osteoclastogenesis, osteocytic osteolysis, proinflammatory responses, osteocyte apoptosis, albeit to varying extents. This study provides further mechanistic insight into orthopaedic wear particle mediated bone disease in terms of the osteocyte, the most abundant and key controlling cell type in bone.
Publisher: Hindawi Limited
Date: 17-01-2019
DOI: 10.1155/2019/9838167
Abstract: The process of osteoblast switching to alternative mesenchymal phenotypes is incompletely understood. In this study, we tested the ability of the osteoblast reosteocyte osteogenic cell line, MLO-A5, to also differentiate into either adipocytes or chondrocytes. MLO-A5 cells expressed a subset of skeletal stem cell markers, including Sca-1, CD44, CD73, CD146, and CD166. Confluent cultures of cells underwent differentiation within 3 days upon the addition of osteogenic medium. The same cultures were capable of undergoing adipogenic and chondrogenic differentiation under lineage-appropriate culture conditions, evidenced by lineage-specific gene expression analysis by real-time reverse-transcription-PCR, and by Oil Red O and alcian blue (pH 2.5) staining, respectively. Subcutaneous implantation of MLO-A5 cells in a gel foam into NOD SCID mice resulted in a woven bone-like structure containing embedded osteocytes and regions of cartilage-like tissue, which stained positive with both alcian blue (pH 2.5) and safranin O. Together, our findings show that MLO-A5 cells, despite being a strongly osteogenic cell line, exhibit characteristics of skeletal stem cells and display mesenchymal lineage plasticity in vitro and in vivo . These unique characteristics suggest that this cell line is a useful model with which to study aging and disease-related changes to the mesenchymal lineage composition of bone.
Publisher: Cold Spring Harbor Laboratory
Date: 29-10-2020
DOI: 10.1101/2020.10.29.360024
Abstract: Osteocyte produced fibroblast growth factor 23 (FGF23) is the key regulator of serum phosphate (Pi) homeostasis. The interplay between parathyroid hormone (PTH), FGF23 and other proteins that regulate FGF23 production and serum Pi levels is complex and incompletely characterised. Evidence suggests that the protein product of the SOST gene, sclerostin (SCL), also a PTH target and also produced by osteocytes, plays a role in FGF23 expression, however the mechanism for this effect is unclear. Part of the problem of understanding the interplay of these mediators is the complex multi-organ system that achieves Pi homeostasis in vivo . In the current study, we sought to address this using a unique cell line model of the osteocyte, IDG-SW3, known to express FGF23 at both the mRNA and protein levels. In cultures of differentiated IDG-SW3 cells, both PTH 1-34 and recombinant human (rh) SCL remarkably induced Fgf23 mRNA expression dose-dependently within 3 hours. Both rhPTH 1-34 and rhSCL also strongly induced C-terminal FGF23 protein secretion. Secreted intact FGF23 levels remained unchanged, consistent with constitutive post-translational cleavage of FGF23 in this cell model. Both rhPTH 1-34 and rhSCL treatments significantly suppressed mRNA levels of Phex, Dmp1 and Enpp1 mRNA, encoding putative negative regulators of FGF23 levels, and induced Galnt3 mRNA expression, encoding N-acetylgalactosaminyl-transferase 3 (GalNAc-T3), which protects FGF23 from furin-like proprotein convertase-mediated cleavage. The effect of both rhPTH 1-34 and rhSCL was antagonised by pre-treatment with the NF-κβ signalling inhibitors, BAY11 and TPCK. RhSCL also stimulated FGF23 mRNA expression in ex vivo cultures of human bone. These findings provide evidence for the direct regulation of FGF23 expression by sclerostin. Locally expressed sclerostin via the induction of FGF23 in osteocytes thus has the potential to contribute to the regulation of Pi homeostasis.
Publisher: Wiley
Date: 13-07-2018
DOI: 10.1002/JOR.24057
Abstract: We investigated if time between injury and surgery affects cancellous bone properties in patients suffering tibial plateau fractures (TPF), in terms of structural integrity and gene expression controlling bone loss. A cohort of 29 TPF, operated 1–17 days post‐injury, had biopsies from the fracture and an equivalent contralateral limb site, at surgery. S les were assessed using micro‐computed tomography and real‐time RT‐PCR analysis for the expression of genes known to be involved in bone remodeling and fracture healing. Significant decreases in the injured vs control side were observed for bone volume fraction (BV/TV, −13.5 ± 6.0%, p = 0.011), trabecular number (Tb.N, −10.5 ± 5.9%, p = 0.041) and trabecular thickness (Tb.Th, −4.6 ± 2.5%, p = 0.033). Changes in these parameters were more evident in patients operated 5–17 days post‐injury, compared to those operated in the first 4 days post‐injury. A significant negative association was found between Tb.Th ( r = −0.54, p 0.01) and BV/TV ( r = −0.39, p 0.05) in relation to time post‐injury in the injured limb. Both BV/TV and Tb.Th were negatively associated with expression of key molecular markers of bone resorption, CTSK , ACP5 , and the ratio of RANKL : OPG mRNA. These structure/gene expression relationships did not exist in the contralateral tibial plateau of these patients. This study demonstrated that there is a significant early time‐dependent bone loss in the proximal tibia after TPF. This bone loss was significantly associated with altered expression of genes typically involved in the process of osteoclastic bone resorption but possibly also bone resorption by osteocytes. The mechanism of early bone loss in such fractures should be a subject of further investigation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2865–2875, 2018.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7TB03251J
Abstract: 3D printing technology combined with electrochemical nano-structuring and HA modification is a promising approach for the fabrication of Ti implants with improved osseointegration.
Publisher: Frontiers Media SA
Date: 03-11-2021
DOI: 10.3389/FCIMB.2021.781022
Abstract: Infectious osteomyelitis associated with periprosthetic joint infections is often recalcitrant to treatment and has a high rate of recurrence. In the case of Staphylococcus aureus , the most common pathogen in all forms of osteomyelitis, this may be attributed in part to residual intracellular infection of host cells, yet this is not generally considered in the treatment strategy. Osteocytes represent a unique cell type in this context due to their abundance, their formation of a syncytium throughout the bone that could facilitate bacterial spread and their relative inaccessibility to professional immune cells. As such, there is potential value in studying the host-pathogen interactions in the context of this cell type in a replicable and scalable in vitro model. Here, we examined the utility of the human osteosarcoma cell line SaOS2 differentiated to an osteocyte-like stage (SaOS2-OY) as an intracellular infection model for S. aureus . We demonstrate that S. aureus is capable of generating stable intracellular infections in SaOS2-OY cells but not in undifferentiated, osteoblast-like SaOS2 cells (SaOS2-OB). In SaOS2-OY cells, S. aureus transitioned towards a quasi-dormant small colony variant (SCV) growth phenotype over a 15-day post-infection period. The infected cells exhibited changes in the expression of key immunomodulatory mediators that are consistent with the infection response of primary osteocytes. Thus, SaOS2-OY is an appropriate cell line model that may be predictive of the interactions between S. aureus and human osteocytes, and this will be useful for studying mechanisms of persistence and for testing the efficacy of potential antimicrobial strategies.
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.MCE.2015.06.021
Abstract: Sclerostin, the SOST gene product, is a negative regulator of bone formation and a positive regulator of bone resorption. In this study, treatment of human primary osteoblasts, including cells differentiated to an osteocyte-like stage, with 1α,25-dihydroxyvitaminD3 (1,25D) resulted in the dose-dependent increased expression of SOST mRNA. A similar effect was observed in human trabecular bone s les cultured ex vivo, and in osteocyte-like cultures of differentiated SAOS2 cells. Treatment of SAOS2 cells with 1,25D resulted in the production and secretion of sclerostin protein. In silico analysis of the human SOST gene revealed a single putative DR3-type vitamin D response element (VDRE) at position -6216 bp upstream of the transcription start site (TSS). This sequence was confirmed to have strong VDRE activity by luciferase reporter assays and electrophoretic mobility shift analysis (EMSA). Sequence substitution in the VDR/RXR half-sites abolished VDRE reporter activity and binding of nuclear proteins. A 6.3 kb fragment of the human proximal SOST promoter demonstrated responsiveness to 1,25D. The addition of the evolutionary conserved region 5 (ECR5), a known bone specific enhancer region, ahead of the 6.3 kb fragment increased basal promoter activity but did not increase 1,25D responsiveness. Site-specific mutagenesis abolished the responsiveness of the 6.3 kb promoter to 1,25D. We conclude that 1,25D is a direct regulator of human SOST gene and sclerostin protein expression, extending the pathways of control of sclerostin expression. At least some of this responsiveness is mediated by the identified classical VDRE however the nature of the transcriptional regulation by 1,25D warrants further investigation.
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.JSBMB.2015.12.006
Abstract: The osteocyte expressed gene SOST encodes sclerostin, a potent negative regulator of bone formation and inducer of bone resorption. We have recently demonstrated that the human SOST gene is positively regulated in response to 1α,25-dihydroxyvitamin D
Publisher: European Cells and Materials
Date: 08-10-2021
DOI: 10.22203/ECM.V042A19
Abstract: Osteomyelitis associated with periprosthetic joint infection (PJI) signals a chronic infection and the need for revision surgery. An osteomyelitic bone exhibits distinct morphological features, including evidence for osteolysis and an accelerated bone remodelling into poorly organised, poor-quality bone. In addition to immune cells, various bone cell-types have been implicated in the pathology. The present study sought to determine the types of bone-cell activities in human PJI bones. Acetabular biopsies from peri-implant bone from patients undergoing revision total hip replacement (THR) for chronic PJI (with several identified pathogens) as well as control bone from the same patients and from patients undergoing primary THR were analysed. Histological analysis confirmed that PJI bone presented increased osteoclastic activity compared to control bone. Analysis of osteocyte parameters showed no differences in osteocyte lacunar area between the acetabular bone taken from PJI patients or primary THR controls. Analysis of bone matrix composition using Masson’s trichrome staining and second-harmonic generation microscopy revealed widespread lack of mature collagen, commonly surrounding osteocytes, in PJI bone. Increased expression of known collagenases, such as matrix metallopeptidase (MMP) 13, MMP1 and cathepsin K (CTSK), was measured in infected bone compared to non-infected bone. Human bone and cultured osteocyte-like cells experimentally exposed to Staphylococcus aureus exhibited strongly upregulated expression of MMP1, MMP3 and MMP13 compared to non-exposed controls. In conclusion, the study identified previously unrecognised bone-matrix changes in PJI caused by multiple organisms deriving from osteocytes. Histological examination of bone collagen composition may provide a useful adjunct diagnostic measure of PJI.
Publisher: American Society for Microbiology
Date: 02-05-2018
Abstract: Periprosthetic joint infection (PJI) is a potentially devastating complication of orthopedic joint replacement surgery. PJI with associated osteomyelitis is particularly problematic and difficult to cure. Whether viable osteocytes, the predominant cell type in mineralized bone tissue, have a role in these infections is not clear, although their involvement might contribute to the difficulty in detecting and clearing PJI. Here, using Staphylococcus aureus , the most common pathogen in PJI, we demonstrate intracellular infection of human-osteocyte-like cells in vitro and S. aureus adaptation by forming quasi-dormant small-colony variants (SCVs). Consistent patterns of host gene expression were observed between in vitro -infected osteocyte-like cultures, an ex vivo human bone infection model, and bone s les obtained from PJI patients. Finally, we confirm S. aureus infection of osteocytes in clinical cases of PJI. Our findings are consistent with osteocyte infection being a feature of human PJI and suggest that this cell type may provide a reservoir for silent or persistent infection. We suggest that elucidating the molecular/cellular mechanism(s) of osteocyte-bacterium interactions will contribute to better understanding of PJI and osteomyelitis, improved pathogen detection, and treatment. IMPORTANCE Periprosthetic joint infections (PJIs) are increasing and are recognized as one of the most common modes of failure of joint replacements. Osteomyelitis arising from PJI is challenging to treat and difficult to cure and increases patient mortality 5-fold. Staphylococcus aureus is the most common pathogen causing PJI. PJI can have subtle symptoms and lie dormant or go undiagnosed for many years, suggesting persistent bacterial infection. Osteocytes, the major bone cell type, reside in bony caves and tunnels, the lacuno-canalicular system. We report here that S. aureus can infect and reside in human osteocytes without causing cell death both experimentally and in bone s les from patients with PJI. We demonstrate that osteocytes respond to infection by the differential regulation of a large number of genes. S. aureus adapts during intracellular infection of osteocytes by adopting the quasi-dormant small-colony variant (SCV) lifestyle, which might contribute to persistent or silent infection. Our findings shed new light on the etiology of PJI and osteomyelitis in general.
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.MCE.2015.06.005
Abstract: While vitamin D supplementation is common, the anabolic mechanisms that improve bone status are poorly understood. Under standard mineralising conditions including media ionised calcium of 1.1 mM, 1,25-dihydroxyvitamin D3 (1,25D) enhanced differentiation and mineral deposition by the mature osteoblast re-osteocyte cell line, MLO-A5. This effect was markedly increased with a higher ionised calcium level (1.5 mM). Gene expression analyses revealed that 1,25D-induced mineral deposition was associated with induction of Enpp1 mRNA, coding for nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) and NPP1 protein levels. Since MLO-A5 cells express abundant alkaline phosphatase that was not further modified by 1,25D treatment or exposure to increased calcium, this finding suggested that the NPP1 production of pyrophosphate (PPi) may provide alkaline phosphatase with substrate for the generation of inorganic phosphate (Pi). Consistent with this, co-treatment with Enpp1 siRNA or a NPP1 inhibitor, PPADS, abrogated 1,25D-induced mineral deposition. These data demonstrate that 1,25D stimulates osteoblast differentiation and mineral deposition, and interacts with the extracellular calcium concentration. 1,25D regulates Enpp1 expression, which presumably, in the context of adequate tissue non-specific alkaline phosphatase activity, provides Pi to stimulate mineralisation. Our findings suggest a mechanism by which vitamin D with adequate dietary calcium can improve bone mineral status.
Publisher: MDPI AG
Date: 08-07-2022
DOI: 10.3390/BIOM12070960
Abstract: The regulation of vitamin D3 actions in humans occurs mainly through the Cytochrome P450 24-hydroxylase (CYP24A1) enzyme activity. CYP24A1 hydroxylates both 25-hydroxycholecalciferol (25(OH)D3) and 1,25-dihydroxycholecalciferol (1,25(OH)2D3), which is the first step of vitamin D catabolism. An abnormal status of the upregulation of CYP24A1 occurs in many diseases, including chronic kidney disease (CKD). CYP24A1 upregulation in CKD and diminished activation of vitamin D3 contribute to secondary hyperparathyroidism (SHPT), progressive bone deterioration, and soft tissue and cardiovascular calcification. Previous studies have indicated that CYP24A1 inhibition may be an effective strategy to increase endogenous vitamin D activity and decrease SHPT. This study has designed and synthesized a novel C-24 O-methyloxime analogue of vitamin D3 (VD1-6) to have specific CYP24A1 inhibitory properties. VD1-6 did not bind to the vitamin D receptor (VDR) in concentrations up to 10−7 M, assessed by a VDR binding assay. The absence of VDR binding by VD1-6 was confirmed in human embryonic kidney HEK293T cultures through the lack of CYP24A1 induction. However, in silico docking experiments demonstrated that VD1-6 was predicted to have superior binding to CYP24A1, when compared to that of 1,25(OH)2D3. The inhibition of CYP24A1 by VD1-6 was also evident by the synergistic potentiation of 1,25(OH)2D3-mediated transcription and reduced 1,25(OH)2D3 catabolism over 24 h. A further indication of CYP24A1 inhibition by VD1-6 was the reduced accumulation of the 24,25(OH)D3, the first metabolite of 25(OH)D catabolism by CYP24A1. Our findings suggest the potent CYP24A1 inhibitory properties of VD1-6 and its potential for testing as an alternative therapeutic candidate for treating SHPT.
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.JSBMB.2016.03.004
Abstract: Clinical and animal data indicate that serum 25-hydroxyvitamin D
No related grants have been discovered for Dongqing Yang.