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Jucht AE, Scholz CC. PHD1-3 oxygen sensors in vivo-lessons learned from gene deletions. Pflugers Arch 2024; 476:1307-1337. [PMID: 38509356 PMCID: PMC11310289 DOI: 10.1007/s00424-024-02944-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2024] [Revised: 03/02/2024] [Accepted: 03/07/2024] [Indexed: 03/22/2024]
Abstract
Oxygen sensors enable cells to adapt to limited oxygen availability (hypoxia), affecting various cellular and tissue responses. Prolyl-4-hydroxylase domain 1-3 (PHD1-3; also called Egln1-3, HIF-P4H 1-3, HIF-PH 1-3) proteins belong to the Fe2+- and 2-oxoglutarate-dependent dioxygenase superfamily and utilise molecular oxygen (O2) alongside 2-oxoglutarate as co-substrate to hydroxylate two proline residues of α subunits of the dimeric hypoxia inducible factor (HIF) transcription factor. PHD1-3-mediated hydroxylation of HIF-α leads to its degradation and inactivation. Recently, various PHD inhibitors (PHI) have entered the clinics for treatment of renal anaemia. Pre-clinical analyses indicate that PHI treatment may also be beneficial in numerous other hypoxia-associated diseases. Nonetheless, the underlying molecular mechanisms of the observed protective effects of PHIs are only partly understood, currently hindering their translation into the clinics. Moreover, the PHI-mediated increase of Epo levels is not beneficial in all hypoxia-associated diseases and PHD-selective inhibition may be advantageous. Here, we summarise the current knowledge about the relevance and function of each of the three PHD isoforms in vivo, based on the deletion or RNA interference-mediated knockdown of each single corresponding gene in rodents. This information is crucial for our understanding of the physiological relevance and function of the PHDs as well as for elucidating their individual impact on hypoxia-associated diseases. Furthermore, this knowledge highlights which diseases may best be targeted by PHD isoform-selective inhibitors in case such pharmacologic substances become available.
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Affiliation(s)
- Agnieszka E Jucht
- Institute of Physiology, University of Zurich, Zurich, 8057, Switzerland
| | - Carsten C Scholz
- Institute of Physiology, University Medicine Greifswald, Friedrich-Ludwig-Jahn-Str. 15a, 17475, Greifswald, Germany.
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2
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Muralidharan A, Gomez GA, Kesavan C, Pourteymoor S, Larkin D, Tambunan W, Sechriest VF, Mohan S. Sex-Specific Effects of THRβ Signaling on Metabolic Responses to High Fat Diet in Mice. Endocrinology 2024; 165:bqae075. [PMID: 38935021 PMCID: PMC11237353 DOI: 10.1210/endocr/bqae075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 06/11/2024] [Accepted: 06/21/2024] [Indexed: 06/28/2024]
Abstract
Thyroid hormone (TH) plays a crucial role in regulating the functions of both bone and adipose tissue. Given that TH exerts its cholesterol-lowering effects in hepatic tissue through the TH receptor-β (TRβ), we hypothesized that TRβ agonist therapy using MGL3196 (MGL) would be effective in treating increased adiposity and bone loss in response to a 12-week high-fat diet (HFD) in adult C57BL/6J mice. Transcriptional and serum profiling revealed that HFD-induced leptin promoted weight gain in both males and females, but MGL only suppressed leptin induction and weight gain in males. In vitro studies suggest that estrogen suppresses MGL activity in adipocytes, indicating that estrogen might interfere with MGL-TRβ function. Compared to systemic adiposity, HFD reduced bone mass in male but not female mice. Paradoxically, MGL treatment reversed macroscopic bone mineral density loss in appendicular bones, but micro-CT revealed that MGL exacerbated HFD-induced trabecular bone loss, and reduced bone strength. In studies on the mechanisms for HFD effects on bone, we found that HFD induced Rankl expression in male femurs that was blocked by MGL. By ex vivo assays, we found that RANKL indirectly represses osteoblast lineage allocation of osteoprogenitors by induction of inflammatory cytokines TNFα, IL-1β, and CCL2. Finally, we found that MGL functions in both systemic adiposity and bone by nongenomic TRβ signaling, as HFD-mediated phenotypes were not rescued in TRβ147F knockout mice with normal genomic but defective nongenomic TRβ signaling. Our findings demonstrate that the negative effects of HFD on body fat and bone phenotypes are impacted by MGL in a gender-specific manner.
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Affiliation(s)
- Aruljothi Muralidharan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Gustavo A Gomez
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Chandrasekhar Kesavan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Sheila Pourteymoor
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Destiney Larkin
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - William Tambunan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - V Franklin Sechriest
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
- Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
- Department of Biochemistry, Loma Linda University, Loma Linda, CA 92354, USA
- Department of Orthopedic Surgery, Loma Linda University, Loma Linda, CA 92354, USA
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Chen N, Wu RW, Lam Y, Chan WC, Chan D. Hypertrophic chondrocytes at the junction of musculoskeletal structures. Bone Rep 2023; 19:101698. [PMID: 37485234 PMCID: PMC10359737 DOI: 10.1016/j.bonr.2023.101698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 06/12/2023] [Accepted: 07/01/2023] [Indexed: 07/25/2023] Open
Abstract
Hypertrophic chondrocytes are found at unique locations at the junction of skeletal tissues, cartilage growth plate, articular cartilage, enthesis and intervertebral discs. Their role in the skeleton is best understood in the process of endochondral ossification in development and bone fracture healing. Chondrocyte hypertrophy occurs in degenerative conditions such as osteoarthritis. Thus, the role of hypertrophic chondrocytes in skeletal biology and pathology is context dependent. This review will focus on hypertrophic chondrocytes in endochondral ossification, in which they exist in a transient state, but acting as a central regulator of differentiation, mineralization, vascularization and conversion to bone. The amazing journey of a chondrocyte from being entrapped in the extracellular matrix environment to becoming proliferative then hypertrophic will be discussed. Recent studies on the dynamic changes and plasticity of hypertrophic chondrocytes have provided new insights into how we view these cells, not as terminally differentiated but as cells that can dedifferentiate to more progenitor-like cells in a transition to osteoblasts and adipocytes, as well as a source of skeletal stem and progenitor cells residing in the bone marrow. This will provide a foundation for studies of hypertrophic chondrocytes at other skeletal sites in development, tissue maintenance, pathology and therapy.
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Affiliation(s)
- Ning Chen
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
| | - Robin W.H. Wu
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
| | - Yan Lam
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
| | - Wilson C.W. Chan
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
- Department of Orthopaedics Surgery and Traumatology, The University of Hong Kong-Shenzhen Hospital (HKU-SZH), Shenzhen 518053, China
| | - Danny Chan
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, China
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Rundle CH, Gomez GA, Pourteymoor S, Mohan S. Sequential application of small molecule therapy enhances chondrogenesis and angiogenesis in murine segmental defect bone repair. J Orthop Res 2023; 41:1471-1481. [PMID: 36448182 PMCID: PMC10506518 DOI: 10.1002/jor.25493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 10/03/2022] [Accepted: 11/28/2022] [Indexed: 12/05/2022]
Abstract
The increasing incidence of physiologic/pathologic conditions that impair the otherwise routine healing of endochondral bone fractures and the occurrence of severe bone injuries necessitate novel approaches to enhance clinically challenging bone fracture repair. To promote the healing of nonunion fractures, we tested an approach that used two small molecules to sequentially enhance cartilage development and conversion to the bone in the callus of a murine femoral segmental defect nonunion model of bone injury. Systemic injections of smoothened agonist 21k (SAG21k) were used to stimulate chondrogenesis through the activation of the sonic hedgehog (SHH) pathway early in bone repair, while injections of the prolyl hydroxylase domain (PHD)2 inhibitor, IOX2, were used to stimulate hypoxia signaling-mediated endochondral bone formation. The expression of SHH pathway genes and Phd2 target genes was increased in chondrocyte cell lines in response to SAG21k and IOX2 treatment, respectively. The segmental defect responded to sequential systemic administration of these small molecules with increased chondrocyte expression of PTCH1, GLI1, and SOX9 in response to SAG and increased expression of hypoxia-induced factor-1α and vascular endothelial growth factor-A in the defect tissues in response to IOX2. At 6 weeks postsurgery, the combined SAG-IOX2 therapy produced increased bone formation in the defect with the bony union over the injury. Clinical significance: This therapeutic approach was successful in promoting cartilage and bone formation within a critical-size segmental defect and established the utility of a sequential small molecule therapy for the enhancement of fracture callus development in clinically challenging bone injuries.
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Affiliation(s)
- Charles H. Rundle
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
- Department of Medicine, Loma Linda University, Loma Linda, California, USA
| | - Gustavo A. Gomez
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
| | - Sheila Pourteymoor
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
- Department of Medicine, Loma Linda University, Loma Linda, California, USA
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Kesavan C, Gomez GA, Pourteymoor S, Mohan S. Development of an Animal Model for Traumatic Brain Injury Augmentation of Heterotopic Ossification in Response to Local Injury. Biomedicines 2023; 11:943. [PMID: 36979922 PMCID: PMC10046150 DOI: 10.3390/biomedicines11030943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/09/2023] [Accepted: 03/13/2023] [Indexed: 03/22/2023] Open
Abstract
Heterotopic ossification (HO) is the abnormal growth of bone in soft connective tissues that occurs as a frequent complication in individuals with traumatic brain injury (TBI) and in rare genetic disorders. Therefore, understanding the mechanisms behind ectopic bone formation in response to TBI is likely to have a significant impact on identification of novel therapeutic targets for HO treatment. In this study, we induced repetitive mild TBI (mTBI) using a weight drop model in mice and then stimulated HO formation via a local injury to the Achilles tendon or fibula. The amount of ectopic bone, as evaluated by micro-CT analyses, was increased by four-fold in the injured leg of mTBI mice compared to control mice. However, there was no evidence of HO formation in the uninjured leg of mTBI mice. Since tissue injury leads to the activation of hypoxia signaling, which is known to promote endochondral ossification, we evaluated the effect of IOX2, a chemical inhibitor of PHD2 and a known inducer of hypoxia signaling on HO development in response to fibular injury. IOX2 treatment increased HO volume by five-fold compared to vehicle. Since pericytes located in the endothelium of microvascular capillaries are known to function as multipotent tissue-resident progenitors, we determined if activation of hypoxia signaling promotes pericyte recruitment at the injury site. We found that markers of pericytes, NG2 and PDGFRβ, were abundantly expressed at the site of injury in IOX2 treated mice. Treatment of pericytes with IOX2 for 72 h stimulated expression of targets of hypoxia signaling (Vegf and Epo), as well as markers of chondrocyte differentiation (Col2α1 and Col10α1). Furthermore, serum collected from TBI mice was more effective in promoting the proliferation and differentiation of pericytes than control mouse serum. In conclusion, our data show that the hypoxic state at the injury site in soft tissues of TBI mice provides an environment leading to increased accumulation and activation of pericytes to form endochondral bone.
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Affiliation(s)
- Chandrasekhar Kesavan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
- Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
| | - Gustavo A. Gomez
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Sheila Pourteymoor
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA 92357, USA
- Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
- Orthopedic Surgery, Loma Linda University, Loma Linda, CA 92354, USA
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Negri AL. Role of prolyl hydroxylase/HIF-1 signaling in vascular calcification. Clin Kidney J 2022; 16:205-209. [PMID: 36755843 PMCID: PMC9900523 DOI: 10.1093/ckj/sfac224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Indexed: 11/13/2022] Open
Abstract
Morbidity and mortality of chronic kidney disease (CKD) patients are largely associated with vascular calcification, an actively regulated process in which vascular smooth muscle cells (VSMCs) change into cells similar to osteocytes/chondrocytes, known as trans-differentiation. Cellular and systemic response to low oxygen (hypoxia) is regulated by the prolyl hydroxylase/hypoxia-inducible factor (HIF)-1 pathway. Recent studies highlighted that hypoxia-mediated activation of HIF-1 induces trans-differentiation of VSMCs into bone-forming type through an increase in osteo-/chondrogenic genes. Inhibition of the HIF-1 pathway abolished osteochondrogenic differentiation of VSMCs. Hypoxia strongly enhanced elevated phosphate-induced VSMC osteogenic trans-differentiation and calcification. HIF-1 was shown to be essential for phosphate enhanced VSMC calcification. O2-dependent degradation HIF-1 is triggered by the prolyl hydroxylase domain proteins (PHD). Prolyl hydroxylase inhibitors, daprodustat and roxadustat, increase high phosphate-induced VC in VSMCs, stabilizing HIF-1α and activating the HIF-1 pathway in these cells. Whether the use of these PHD inhibitors to treat anemia in CKD patients will favor the development and progression of vascular calcification remains to be explored.
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Qin Q, Liu Y, Yang Z, Aimaijiang M, Ma R, Yang Y, Zhang Y, Zhou Y. Hypoxia-Inducible Factors Signaling in Osteogenesis and Skeletal Repair. Int J Mol Sci 2022; 23:ijms231911201. [PMID: 36232501 PMCID: PMC9569554 DOI: 10.3390/ijms231911201] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/10/2022] [Accepted: 09/14/2022] [Indexed: 11/23/2022] Open
Abstract
Sufficient oxygen is required to maintain normal cellular and physiological function, such as a creature’s development, breeding, and homeostasis. Lately, some researchers have reported that both pathological hypoxia and environmental hypoxia might affect bone health. Adaptation to hypoxia is a pivotal cellular event in normal cell development and differentiation and in pathological settings such as ischemia. As central mediators of homeostasis, hypoxia-inducible transcription factors (HIFs) can allow cells to survive in a low-oxygen environment and are essential for the regulation of osteogenesis and skeletal repair. From this perspective, we summarized the role of HIF-1 and HIF-2 in signaling pathways implicated in bone development and skeletal repair and outlined the molecular mechanism of regulation of downstream growth factors and protein molecules such as VEGF, EPO, and so on. All of these present an opportunity for developing therapies for bone regeneration.
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Wolf D, Muralidharan A, Mohan S. Role of prolyl hydroxylase domain proteins in bone metabolism. Osteoporos Sarcopenia 2022; 8:1-10. [PMID: 35415275 PMCID: PMC8987327 DOI: 10.1016/j.afos.2022.03.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 01/12/2022] [Accepted: 03/04/2022] [Indexed: 11/03/2022] Open
Abstract
Cellular metabolism requires dissolved oxygen gas. Because evolutionary refinements have constrained mammalian dissolved oxygen levels, intracellular oxygen sensors are vital for optimizing the bioenergetic and biosynthetic use of dissolved oxygen. Prolyl hydroxylase domain (PHD) homologs 1-3 (PHD1/2/3) are molecular oxygen dependent non-heme dioxygenases whose enzymatic activity is regulated by the concentration of dissolved oxygen. PHD oxygen dependency has evolved into an important intracellular oxygen sensor. The most well studied mechanism of PHD oxygen-sensing is its regulation of the hypoxia-inducible factor (HIF) hypoxia signaling pathway. Heterodimeric HIF transcription factor activity is regulated post-translationally by selective PHD proline hydroxylation of its HIF1α subunit, accelerating HIF1α ubiquitination and proteasomal degradation, preventing HIF heterodimer assembly, nuclear accumulation, and activation of its target oxygen homeostasis genes. Phd2 has been shown to be the key isoform responsible for HIF1α subunit regulation in many cell types and accordingly disruption of the Phd2 gene results in embryonic lethality. In bone cells Phd2 is expressed in high abundance and tightly regulated. Conditional disruption of the Phd1, Phd2 and/or Phd3 gene in various bone cell types using different Cre drivers reveals a major role for PHD2 in skeletal growth and development. In this review, we will summarize the state of current knowledge on the role and mechanism of action of PHD2 as oxygen sensor in regulating bone metabolism.
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Affiliation(s)
- David Wolf
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA, 92357, USA
| | - Aruljothi Muralidharan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA, 92357, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA, 92357, USA
- Department of Medicine, Loma Linda University, Loma Linda, CA, 92354, USA
- Department Biochemistry and Orthopedic Surgery, Loma Linda University, Loma Linda, CA, 92354, USA
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Edwards DF, Miller CJ, Quintana‐Martinez A, Wright CS, Prideaux M, Atkins GJ, Thompson WR, Clinkenbeard EL. Differential Iron Requirements for Osteoblast and Adipocyte Differentiation. JBMR Plus 2021; 5:e10529. [PMID: 34532614 PMCID: PMC8441506 DOI: 10.1002/jbm4.10529] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 05/24/2021] [Accepted: 06/27/2021] [Indexed: 12/17/2022] Open
Abstract
Bone marrow mesenchymal progenitor cells are precursors for various cell types including osteoblasts, adipocytes, and chondrocytes. The external environment and signals act to direct the pathway of differentiation. Importantly, situations such as aging and chronic kidney disease display alterations in the balance of osteoblast and adipocyte differentiation, adversely affecting bone integrity. Iron deficiency, which can often occur during aging and chronic kidney disease, is associated with reduced bone density. The purpose of this study was to assess the effects of iron deficiency on the capacity of progenitor cell differentiation pathways. Mouse and human progenitor cells, differentiated under standard osteoblast and adipocyte protocols in the presence of the iron chelator deferoxamine (DFO), were used. Under osteogenic conditions, 5μM DFO significantly impaired expression of critical osteoblast genes, including osteocalcin, type 1 collagen, and dentin matrix protein 1. This led to a reduction in alkaline phosphatase activity and impaired mineralization. Despite prolonged exposure to chronic iron deficiency, cells retained viability as well as normal hypoxic responses with significant increases in transferrin receptor and protein accumulation of hypoxia inducible factor 1α. Similar concentrations of DFO were used when cells were maintained in adipogenic conditions. In contrast to osteoblast differentiation, DFO modestly suppressed adipocyte gene expression of peroxisome-proliferating activated receptor gamma, lipoprotein lipase, and adiponectin at earlier time points with normalization at later stages. Lipid accumulation was also similar in all conditions. These data suggest the critical importance of iron in osteoblast differentiation, and as long as the external stimuli are present, iron deficiency does not impede adipogenesis. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Daniel F. Edwards
- Department of Medical and Molecular GeneticsSchool of Medicine, Indiana UniversityIndianapolisINUSA
| | - Christopher J. Miller
- Department of Medical and Molecular GeneticsSchool of Medicine, Indiana UniversityIndianapolisINUSA
| | - Arelis Quintana‐Martinez
- Department of Medical and Molecular GeneticsSchool of Medicine, Indiana UniversityIndianapolisINUSA
| | - Christian S. Wright
- Department of Physical TherapySchool of Health & Human Sciences, Indiana UniversityIndianapolisINUSA
| | - Matthew Prideaux
- Indiana Center for Musculoskeletal HealthIndiana UniversityIndianapolisINUSA
| | - Gerald J. Atkins
- Centre for Orthopaedic & Trauma ResearchUniversity of AdelaideAdelaideSouth AustraliaAustralia
| | - William R. Thompson
- Department of Physical TherapySchool of Health & Human Sciences, Indiana UniversityIndianapolisINUSA
| | - Erica L. Clinkenbeard
- Department of Medical and Molecular GeneticsSchool of Medicine, Indiana UniversityIndianapolisINUSA
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Prolyl Hydroxylase Domain-Containing Protein 3 Gene Expression in Chondrocytes Is Not Essential for Bone Development in Mice. Cells 2021; 10:cells10092200. [PMID: 34571849 PMCID: PMC8470734 DOI: 10.3390/cells10092200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/16/2021] [Accepted: 08/20/2021] [Indexed: 01/28/2023] Open
Abstract
We previously showed that conditional disruption of the Phd2 gene in chondrocytes led to a massive increase in long bone trabecular bone mass. Loss of Phd2 gene expression or inhibition of PHD2 activity by a specific inhibitor resulted in a several-fold compensatory increase in Phd3 expression in chondrocytes. To determine if expression of PHD3 plays a role in endochondral bone formation, we conditionally disrupted the Phd3 gene in chondrocytes by crossing Phd3 floxed (Phd3flox/flox) mice with Col2α1-Cre mice. Loss of Phd3 expression in the chondrocytes of Cre+; Phd3flox/flox conditional knockout (cKO) mice was confirmed by real time PCR. At 16 weeks of age, neither body weight nor body length was significantly different in the Phd3 cKO mice compared to Cre−; Phd3flox/flox wild-type (WT) mice. Areal BMD measurements of total body as well as femur, tibia, and lumbar skeletal sites were not significantly different between the cKO and WT mice at 16 weeks of age. Micro-CT measurements revealed significant gender differences in the trabecular bone volume adjusted for tissue volume at the secondary spongiosa of the femur and the tibia for both genotypes, but no genotype difference was found for any of the trabecular bone measurements of either the femur or the tibia. Trabecular bone volume of distal femur epiphysis was not different between cKO and WT mice. Histology analyses revealed Phd3 cKO mice exhibited a comparable chondrocyte differentiation and proliferation, as evidenced by no changes in cartilage thickness and area in the cKO mice as compared to WT littermates. Consistent with the in vivo data, lentiviral shRNA-mediated knockdown of Phd3 expression in chondrocytes did not affect the expression of markers of chondrocyte differentiation (Col2, Col10, Acan, Sox9). Our study found that Phd2 but not Phd3 expressed in chondrocytes regulates endochondral bone formation, and the compensatory increase in Phd3 expression in the chondrocytes of Phd2 cKO mice is not the cause for increased trabecular bone mass in Phd2 cKO mice.
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Sha Y, Cai W, Mohanad Khalid A, Chi Q, Wang J, Sun T, Wang C. Pretreatment with mechano growth factor E peptide attenuates osteoarthritis through improving cell proliferation and extracellular matrix synthesis in chondrocytes under severe hypoxia. Int Immunopharmacol 2021; 97:107628. [PMID: 34015701 DOI: 10.1016/j.intimp.2021.107628] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 03/28/2021] [Accepted: 03/29/2021] [Indexed: 10/21/2022]
Abstract
Osteoarthritis (OA) is characterized by pain and declining gait function associated with degeneration of cartilage. A severe hypoxic environment occurs due to tissue injury in the joint cavity and may aggravate the development of OA. In this study, the effects of severe hypoxia and treatment with mechano growth factor (MGF) E peptide on metabolism of the extracellular matrix (ECM) during the progression of OA were determined. The results showed that cell viability, cell proliferation, and type II collagen expression in chondrocytes were significantly inhibited by cobalt chloride (CoCl2)-simulated severe hypoxia, whereas cell apoptosis and expression levels of hypoxia inducible factor 1 alpha, type I collagen, and matrix metalloproteinases 1/13 were clearly induced. Pretreatment with MGF E peptide reduced the abovementioned adverse effects induced by CoCl2-simulated severe hypoxia in chondrocytes. Pretreatment also upregulated the proliferation of chondrocytes under severe hypoxia through the PI3K-Akt and MEK-ERK1/2 signaling pathways. In a rat model of monosodium iodoacetate (MIA)-induced OA. MIA treatment induced tissue necrosis and cartilage degeneration, and histological score was significantly decreased. The levels of type II collagen and aggrecan were reduced after MIA treatment for 4 or 6 weeks, and abnormal distribution of ECM occurred in the inner epicondyle after 6 weeks. MGF E peptide also reduced the progression of MIA-induced OA by retarding cartilage degeneration, upregulating type II collagen synthesis, and improving ECM distribution after 4 or 6 weeks. Our findings suggest that MGF attenuates the progression of OA, and thus may be applied for the treatment of OA in the clinic.
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Affiliation(s)
- Yongqiang Sha
- Center for Precision Medicine, School of Medicine and School of Biomedical Sciences, Huaqiao University, Xiamen, Fujian 361021, PR China.
| | - Wenjie Cai
- Departments of Radiation Oncology, First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou, Fujian 362000, PR China
| | - Alani Mohanad Khalid
- Department of Microbiology, College of Medicine, Tikrit University, Tikrīt, Sallahaldin 009642, Iraq
| | - Qingjia Chi
- Department of Mechanics and Engineering Structure, Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics, Wuhan University of Technology, Wuhan, Hubei 430070, PR China
| | - Jing Wang
- Center for Precision Medicine, School of Medicine and School of Biomedical Sciences, Huaqiao University, Xiamen, Fujian 361021, PR China
| | - Tao Sun
- Center for Precision Medicine, School of Medicine and School of Biomedical Sciences, Huaqiao University, Xiamen, Fujian 361021, PR China
| | - Chunli Wang
- National Innovation and Attracting Talents "111" base, Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400030, PR China.
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Partial deficiency of HIF-1α in chondrocytes effected bone repair of mandibular condylar neck. Arch Oral Biol 2020; 122:105023. [PMID: 33348208 DOI: 10.1016/j.archoralbio.2020.105023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/16/2020] [Accepted: 12/02/2020] [Indexed: 11/22/2022]
Abstract
OBJECTIVES This study aimed to explore the expression of hypoxia-inducible factor 1α (HIF-1α) in chondrocytes with the healing process after unilateral mandibular condylar neck osteotomy and to verify its effect on bone repair. METHODS Models of mandibular condylar neck osteotomy were established in mice. Transgenic mice with heterozygous deficiency in HIF-1α gene in chondrocytes were used. Radiographic evaluation, quantitative reverse transcription polymerase chain reaction and histomorphometric analyses were used to compare the difference in capacities of chondrogenesis, vasifaction, osteogenesis, and bone resorption. RESULTS HIF-1α was expressed in the chondrocytes of calluses. Decreased expression of HIF-1α in chondrocytes promoted the proliferation of chondrocytes and upregulated the expression of apoptosis markers. However, the density and thickness of newly formed trabecula in transgenic mice were reduced on post-osteotomy day 28, and some expression of angiogenic, osteogenic, and osteoclastogenic markers was impaired. CONCLUSIONS These results demonstrated the importance of HIF-1α to chondrocytes and bone repair during the healing process after osteotomy of the mandibular condylar neck. Decreased HIF-1α promoted the chondrocyte proliferation, and effected endochondral ossification.
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Bajwa NM, Kesavan C, Mohan S. Long-term Consequences of Traumatic Brain Injury in Bone Metabolism. Front Neurol 2018; 9:115. [PMID: 29556212 PMCID: PMC5845384 DOI: 10.3389/fneur.2018.00115] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 02/15/2018] [Indexed: 12/14/2022] Open
Abstract
Traumatic brain injury (TBI) leads to long-term cognitive, behavioral, affective deficits, and increase neurodegenerative diseases. It is only in recent years that there is growing awareness that TBI even in its milder form poses long-term health consequences to not only the brain but to other organ systems. Also, the concept that hormonal signals and neural circuits that originate in the hypothalamus play key roles in regulating skeletal system is gaining recognition based on recent mouse genetic studies. Accordingly, many TBI patients have also presented with hormonal dysfunction, increased skeletal fragility, and increased risk of skeletal diseases. Research from animal models suggests that TBI may exacerbate the activation and inactivation of molecular pathways leading to changes in both osteogenesis and bone destruction. TBI has also been found to induce the formation of heterotopic ossification and increased callus formation at sites of muscle or fracture injury through increased vascularization and activation of systemic factors. Recent studies also suggest that the disruption of endocrine factors and neuropeptides caused by TBI may induce adverse skeletal effects. This review will discuss the long-term consequences of TBI on the skeletal system and TBI-induced signaling pathways that contribute to the formation of ectopic bone, altered fracture healing, and reduced bone mass.
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Affiliation(s)
- Nikita M Bajwa
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA, United States
| | - Chandrasekhar Kesavan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA, United States.,Department of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, CA, United States.,Department of Medicine, Loma Linda University, Loma Linda, CA, United States.,Department of Orthopedic Surgery, Loma Linda University, Loma Linda, CA, United States
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Bajwa NM, Sanchez CP, Lindsey RC, Watt H, Mohan S. Cortical and trabecular bone are equally affected in rats with renal failure and secondary hyperparathyroidism. BMC Nephrol 2018; 19:24. [PMID: 29394885 PMCID: PMC5796449 DOI: 10.1186/s12882-018-0822-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 01/21/2018] [Indexed: 12/31/2022] Open
Abstract
Background Changes in mineral metabolism and bone structure develop early in the course of chronic kidney disease and at end-stage are associated with increased risk of fragility fractures. The disruption of phosphorus homeostasis leads to secondary hyperparathyroidism, a common complication of chronic kidney disease. However, the molecular pathways by which high phosphorus influences bone metabolism in the early stages of the disease are not completely understood. We investigated the effects of a high phosphorus diet on bone and mineral metabolism using a 5/6 nephrectomy model of chronic kidney disease. Methods Four-week old rats were randomly assigned into groups: 1) Control with standard diet, 2) Nephrectomy with standard rodent diet, and 3) Nephrectomy with high phosphorus diet. Rats underwent in vivo imaging at baseline, day 14, and day 28, followed by ex vivo imaging. Results Cortical bone density at the femoral mid-diaphysis was reduced in nephrectomy-control and nephrectomy-high phosphorus compared to control rats. In contrast, trabecular bone mass was reduced at both the lumbar vertebrae and the femoral secondary spongiosa in nephrectomy-high phosphorus but not in nephrectomy-control. Reduced trabecular bone volume adjusted for tissue volume was caused by changes in trabecular number and separation at day 35. Histomorphometry revealed increased bone resorption in tibial secondary spongiosa in nephrectomy-control. High phosphorus diet-induced changes in bone microstructure were accompanied by increased serum parathyroid hormone and fibroblast growth factor 23 levels. Conclusion Our study demonstrates that changes in mineral metabolism and hormonal dysfunction contribute to trabecular and cortical bone changes in this model of early chronic kidney disease.
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Affiliation(s)
- Nikita M Bajwa
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA, 92357, USA
| | - Cheryl P Sanchez
- Department of Pediatrics, Loma Linda University, Loma Linda, CA, 92354, USA
| | - Richard C Lindsey
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA, 92357, USA
| | - Heather Watt
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA, 92357, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA, 92357, USA. .,Department of Medicine, Loma Linda University, Loma Linda, CA, 92354, USA. .,Department of Orthopedic Surgery, Loma Linda University, Loma Linda, CA, 92354, USA.
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15
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Kaplan JM, Sharma N, Dikdan S. Hypoxia-Inducible Factor and Its Role in the Management of Anemia in Chronic Kidney Disease. Int J Mol Sci 2018; 19:ijms19020389. [PMID: 29382128 PMCID: PMC5855611 DOI: 10.3390/ijms19020389] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 01/04/2018] [Accepted: 01/08/2018] [Indexed: 12/25/2022] Open
Abstract
Hypoxia-inducible factor (HIF) plays a crucial role in the response to hypoxia at the cellular, tissue, and organism level. New agents under development to pharmacologically manipulate HIF may provide new and exciting possibilities in the treatment of anemia of chronic kidney disease (CKD) as well as in multiple other disease states involving ischemia-reperfusion injury. This article provides an overview of recent studies describing current standards of care for patients with anemia in CKD and associated clinical issues, and those supporting the clinical potential for targeting HIF stabilization with HIF prolyl-hydroxylase inhibitors (HIF-PHI) in these patients. Additionally, articles reporting the clinical potential for HIF-PHIs in 'other' putative therapeutic areas, the tissue and intracellular distribution of HIF- and prolyl-hydroxylase domain (PHD) isoforms, and HIF isoforms targeted by the different PHDs, were identified. There is increasing uncertainty regarding the optimal treatment for anemia of CKD with poorer outcomes associated with treatment to higher hemoglobin targets, and the increasing use of iron and consequent risk of iron imbalance. Attainment and maintenance of more physiologic erythropoietin levels associated with HIF stabilization may improve the management of patients resistant to treatment with erythropoiesis-stimulating agents and improve outcomes at higher hemoglobin targets.
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Affiliation(s)
- Joshua M Kaplan
- Division of Nephrology and Hypertension, Rutgers-New Jersey Medical School, University Hospital, 185 South Orange Avenue, I512, Newark, NJ 07103, USA.
| | - Neeraj Sharma
- Division of Nephrology and Hypertension, Rutgers-New Jersey Medical School, University Hospital, 185 South Orange Avenue, I512, Newark, NJ 07103, USA.
| | - Sean Dikdan
- Division of Nephrology and Hypertension, Rutgers-New Jersey Medical School, University Hospital, 185 South Orange Avenue, I512, Newark, NJ 07103, USA.
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Experimental repetitive mild traumatic brain injury induces deficits in trabecular bone microarchitecture and strength in mice. Bone Res 2017; 5:17042. [PMID: 29263937 PMCID: PMC5735530 DOI: 10.1038/boneres.2017.42] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/30/2017] [Accepted: 07/04/2017] [Indexed: 01/21/2023] Open
Abstract
To evaluate the long-term consequence of repetitive mild traumatic brain injury (mTBI) on bone, mTBI was induced in 10-week-old female C57BL/6J mice using a weight drop model, once per day for 4 consecutive days at different drop heights (0.5, 1 and 1.5 m) and the skeletal phenotype was evaluated at different time points after the impact. In vivo micro-CT (μ-CT) analysis of the tibial metaphysis at 2, 8 and 12 weeks after the impact revealed a 5%-32% reduction in trabecular bone mass. Histomorphometric analyses showed a reduced bone formation rate in the secondary spongiosa of 1.5 m impacted mice at 12 weeks post impact. Apparent modulus (bone strength), was reduced by 30% (P<0.05) at the proximal tibial metaphysis in the 1.5 m drop height group at 2 and 8 weeks post impact. Ex vivo μ-CT analysis of the fifth lumbar vertebra revealed a significant reduction in trabecular bone mass at 12 weeks of age in all three drop height groups. Serum levels of osteocalcin were decreased by 22%, 15%, and 19% in the 0.5, 1.0 and 1.5 m drop height groups, respectively, at 2 weeks post impact. Serum IGF-I levels were reduced by 18%-32% in mTBI mice compared to contro1 mice at 2 weeks post impact. Serum osteocalcin and IGF-I levels correlated with trabecular BV/TV (r2 =0.14 and 0.16, P<0.05). In conclusion, repetitive mTBI exerts significant negative effects on the trabecular bone microarchitecture and bone mechanical properties by influencing osteoblast function via reduced endocrine IGF-I actions.
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Hulley PA, Bishop T, Vernet A, Schneider JE, Edwards JR, Athanasou NA, Knowles HJ. Hypoxia-inducible factor 1-alpha does not regulate osteoclastogenesis but enhances bone resorption activity via prolyl-4-hydroxylase 2. J Pathol 2017; 242:322-333. [PMID: 28418093 PMCID: PMC5518186 DOI: 10.1002/path.4906] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 02/27/2017] [Accepted: 04/03/2017] [Indexed: 12/12/2022]
Abstract
Osteogenic-angiogenic coupling is promoted by the hypoxia-inducible factor 1-alpha (HIF-1α) transcription factor, provoking interest in HIF activation as a therapeutic strategy to improve osteoblast mineralization and treat pathological osteolysis. However, HIF also enhances the bone-resorbing activity of mature osteoclasts. It is therefore essential to determine the full effect(s) of HIF on both the formation and the bone-resorbing function of osteoclasts in order to understand how they might respond to such a strategy. Expression of HIF-1α mRNA and protein increased during osteoclast differentiation from CD14+ monocytic precursors, additionally inducing expression of the HIF-regulated glycolytic enzymes. However, HIF-1α siRNA only moderately affected osteoclast differentiation, accelerating fusion of precursor cells. HIF induction by inhibition of the regulatory prolyl-4-hydroxylase (PHD) enzymes reduced osteoclastogenesis, but was confirmed to enhance bone resorption by mature osteoclasts. Phd2+/- murine osteoclasts also exhibited enhanced bone resorption, associated with increased expression of resorption-associated Acp5, in comparison with wild-type cells from littermate controls. Phd3-/- bone marrow precursors displayed accelerated early fusion, mirroring results with HIF-1α siRNA. In vivo, Phd2+/- and Phd3-/- mice exhibited reduced trabecular bone mass, associated with reduced mineralization by Phd2+/- osteoblasts. These data indicate that HIF predominantly functions as a regulator of osteoclast-mediated bone resorption, with little effect on osteoclast differentiation. Inhibition of HIF might therefore represent an alternative strategy to treat diseases characterized by pathological levels of osteolysis. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Philippa A Hulley
- Nuffield Department of Orthopaedics Rheumatology & Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Tammie Bishop
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Aude Vernet
- BHF Experimental MR Unit, University of Oxford, Oxford, UK
| | | | - James R Edwards
- Nuffield Department of Orthopaedics Rheumatology & Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Nick A Athanasou
- Nuffield Department of Orthopaedics Rheumatology & Musculoskeletal Sciences, Nuffield Orthopaedic Centre, University of Oxford, Oxford, UK
| | - Helen J Knowles
- Nuffield Department of Orthopaedics Rheumatology & Musculoskeletal Sciences, University of Oxford, Oxford, UK
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18
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Cheng S, Pourteymoor S, Alarcon C, Mohan S. Conditional Deletion of the Phd2 Gene in Articular Chondrocytes Accelerates Differentiation and Reduces Articular Cartilage Thickness. Sci Rep 2017; 7:45408. [PMID: 28349987 PMCID: PMC5368651 DOI: 10.1038/srep45408] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 02/23/2017] [Indexed: 12/16/2022] Open
Abstract
Based on our findings that PHD2 is a negative regulator of chondrocyte differentiation and that hypoxia signaling is implicated in the pathogenesis of osteoarthritis, we investigated the consequence of disruption of the Phd2 gene in chondrocytes on the articular cartilage phenotype in mice. Immunohistochemistry detected high expression of PHD2 in the superficial zone (SZ), while PHD3 and HIF-1α (target of PHD2) are mainly expressed in the middle-deep zone (MDZ). Conditional deletion of the Phd2 gene (cKO) in chondrocytes accelerated the transition of progenitors to hypertrophic (differentiating) chondrocytes as revealed by reduced SZ thickness, and increased MDZ thickness, as well as increased chondrocyte hypertrophy. Immunohistochemistry further revealed decreased levels of progenitor markers but increased levels of hypertrophy markers in the articular cartilage of the cKO mice. Treatment of primary articular chondrocytes, in vitro, with IOX2, a specific inhibitor of PHD2, promoted articular chondrocyte differentiation. Knockdown of Hif-1α expression in primary articular chondrocytes using lentiviral vectors containing Hif-1α shRNA resulted in reduced expression levels of Vegf, Glut1, Pgk1, and Col10 compared to control shRNA. We conclude that Phd2 is a key regulator of articular cartilage development that acts by inhibiting the differentiation of articular cartilage progenitors via modulating HIF-1α signaling.
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Affiliation(s)
- Shaohong Cheng
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Sheila Pourteymoor
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Catrina Alarcon
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA.,Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
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Cheng S, Aghajanian P, Pourteymoor S, Alarcon C, Mohan S. Prolyl Hydroxylase Domain-Containing Protein 2 (Phd2) Regulates Chondrocyte Differentiation and Secondary Ossification in Mice. Sci Rep 2016; 6:35748. [PMID: 27775044 PMCID: PMC5075779 DOI: 10.1038/srep35748] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 09/30/2016] [Indexed: 12/25/2022] Open
Abstract
Endochondral ossification plays an important role in the formation of the primary ossification centers (POCs) and secondary ossification centers (SOCs) of mammalian long bones. However, the molecular mechanisms that regulate POC and SOC formation are different. We recently demonstrated that Prolyl Hydroxylase Domain-containing Protein 2 (Phd2) is a key mediator of vitamin C effects on bone. We investigated the role of Phd2 on endochondral ossification of the epiphyses by conditionally deleting the Phd2 gene in osteoblasts and chondrocytes. We found that the deletion of Phd2 in osteoblasts did not cause changes in bone parameters in the proximal tibial epiphyses in 5 week old mice. In contrast, deletion of Phd2 in chondrocytes resulted in increased bone mass and bone formation rate (normalized to tissue volume) in long bone epiphyses, indicating that Phd2 expressed in chondrocytes, but not osteoblasts, negatively regulates secondary ossification of epiphyses. Phd2 deletion in chondrocytes elevated mRNA expression of hypoxia-inducible factor (HIF) signaling molecules including Hif-1α, Hif-2α, Vegfa, Vegfb, and Epo, as well as markers for chondrocyte hypertrophy and mineralization such as Col10, osterix, alkaline phosphatase, and bone sialoprotein. These data suggest that Phd2 expressed in chondrocytes inhibits endochondral ossification at the epiphysis by suppressing HIF signaling pathways.
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Affiliation(s)
- Shaohong Cheng
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Patrick Aghajanian
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Sheila Pourteymoor
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Catrina Alarcon
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, Veterans Affairs Loma Linda Healthcare System, 11201 Benton Street, Loma Linda, CA 92357, USA
- Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA
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Zeng C, Goodluck H, Qin X, Liu B, Mohan S, Xing W. Leucine-rich repeat kinase-1 regulates osteoclast function by modulating RAC1/Cdc42 Small GTPase phosphorylation and activation. Am J Physiol Endocrinol Metab 2016; 311:E772-E780. [PMID: 27600824 PMCID: PMC5241559 DOI: 10.1152/ajpendo.00189.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 08/26/2016] [Indexed: 11/24/2022]
Abstract
Leucine-rich repeat kinase-1 (Lrrk1) consists of ankyrin repeats (ANK), leucine-rich repeats (LRR), a GTPase-like domain of Roc (ROC), a COR domain, a serine/threonine kinase domain (KD), and WD40 repeats (WD40). Previous studies have revealed that knockout (KO) of Lrrk1 in mice causes severe osteopetrosis, and a human mutation of Lrrk1 leads to osteosclerotic metaphysial dysplasia. The molecular mechanism by which Lrrk1 regulates osteoclast function is unknown. In this study, we generated a series of Lrrk1 mutants and evaluated their ability to rescue defective bone resorption in Lrrk1-deficient osteoclasts by use of pit formation assays. Overexpression of Lrrk1 or LRR-truncated Lrrk1, but not ANK-truncated Lrrk1, WD40-truncated Lrrk1, Lrrk1-KD, or K651A mutant Lrrk1, rescued bone resorption function of Lrrk1 KO osteoclasts. We next examined whether RAC1/Cdc42 small GTPases are direct substrates of Lrrk1 in osteoclasts. Western blot and pull-down assays revealed that Lrrk1 deficiency in osteoclasts resulted in reduced phosphorylation and activation of RAC1/Cdc42. In vitro kinase assays confirmed that recombinant Lrrk1 phosphorylated RAC1-GST protein, and immunoprecipitation showed that the interaction of Lrrk1 with RAC1 occurred within 10 min after RANKL treatment. Overexpression of constitutively active Q61L RAC1 partially rescued the resorptive function of Lrrk1-deficient osteoclasts. Furthermore, lack of Lrrk1 in osteoclasts led to reduced autophosphorylation of p21 protein-activated kinase-1 at Ser144, catalyzed by RAC1/Cdc42 binding and activation. Our data indicate that Lrrk1 regulates osteoclast function by directly modulating phosphorylation and activation of small GTPase RAC1/Cdc42 and that its function depends on ANK, ROC, WD40, and kinase domains.
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Affiliation(s)
- Canjun Zeng
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California; Department of Orthopedics, The Third Affiliated Hospital Of Southern Medical University, Guangzhou, China
| | - Helen Goodluck
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California
| | - Xuezhong Qin
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California; Department of Medicine, Loma Linda University, Loma Linda, California
| | - Bo Liu
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California; Department of Orthopedics, The Third Xiangya Hosptial, Central South University, Changsha, Hunan, China
| | - Subburaman Mohan
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California; Department of Medicine, Loma Linda University, Loma Linda, California
| | - Weirong Xing
- Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California; Department of Medicine, Loma Linda University, Loma Linda, California;
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Abstract
The roles of prolyl hydroxylase domain proteins (PHDs) in bone are incompletely understood. Here we deleted the expression of genes encoding PHD1, PHD2, and PHD3 in osteoblasts in mice by breeding the floxed Phd1-3 mice with Col1a1-Cre transgenic mice. Results showed that mice lacking PHD1-3 in osteoblasts (Phd1-3ob-/-) had increased bone mass. Bone parameters such as bone volume/tissue volume (BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th) were increased, while trabecular spacing (Tb.Sp) was decreased in Phd1-3ob-/- relative to wild-type (WT) femurs. In contrast, loss of PHD1-3 in osteoblasts did not alter cortical thickness (Cort.Th). The mineralization apposition rate (MAR) was increased in Phd1-3ob-/- bone compared to that of wild-type (WT) bone, demonstrating an enhancement of osteoblast function. Loss of PHD1-3 increased the number of osteoblast progenitors (CFU-OBs) in bone marrow cultures. Interestingly, deleting Phd1-3 genes in osteoblasts increased osteoclast formation in vitro and in bone.
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Zhu K, Song P, Lai Y, Xiao G. WITHDRAWN: Prolyl hydroxylase domain proteins regulate bone mass through their expression in osteoblasts. GENE REPORTS 2016. [DOI: 10.1016/j.genrep.2016.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Aghajanian P, Hall S, Wongworawat MD, Mohan S. The Roles and Mechanisms of Actions of Vitamin C in Bone: New Developments. J Bone Miner Res 2015; 30:1945-55. [PMID: 26358868 PMCID: PMC4833003 DOI: 10.1002/jbmr.2709] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 09/03/2015] [Accepted: 09/08/2015] [Indexed: 12/25/2022]
Abstract
Vitamin C is an important antioxidant and cofactor that is involved in the regulation of development, function, and maintenance of several cell types in the body. Deficiencies in vitamin C can lead to conditions such as scurvy, which, among other ailments, causes gingivia, bone pain, and impaired wound healing. This review examines the functional importance of vitamin C as it relates to the development and maintenance of bone tissues. Analysis of several epidemiological studies and genetic mouse models regarding the effect of vitamin C shows a positive effect on bone health. Overall, vitamin C exerts a positive effect on trabecular bone formation by influencing expression of bone matrix genes in osteoblasts. Recent studies on the molecular pathway for vitamin C actions that include direct effects of vitamin C on transcriptional regulation of target genes by influencing the activity of transcription factors and by epigenetic modification of key genes involved in skeletal development and maintenance are discussed. With an understanding of mechanisms involved in the uptake and metabolism of vitamin C and knowledge of precise molecular pathways for vitamin C actions in bone cells, it is possible that novel therapeutic strategies can be developed or existing therapies can be modified for the treatment of osteoporotic fractures.
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Affiliation(s)
- Patrick Aghajanian
- Musculoskeletal Disease Center, Jerry L Pettis VA Medical Center, Loma Linda, CA 92357
| | - Susan Hall
- Musculoskeletal Disease Center, Jerry L Pettis VA Medical Center, Loma Linda, CA 92357
- Department of Medicine, Loma Linda University, Loma Linda, CA 92354
| | - Montri D. Wongworawat
- Musculoskeletal Disease Center, Jerry L Pettis VA Medical Center, Loma Linda, CA 92357
- Orthopedic Surgery, Loma Linda University, Loma Linda, CA 92354
| | - Subburaman Mohan
- Musculoskeletal Disease Center, Jerry L Pettis VA Medical Center, Loma Linda, CA 92357
- Department of Medicine, Loma Linda University, Loma Linda, CA 92354
- Orthopedic Surgery, Loma Linda University, Loma Linda, CA 92354
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