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Rooney AM, McNeill TJ, Ross FP, Bostrom MPG, van der Meulen MCH. PTH Treatment Increases Cortical Bone Mass More in Response to Compression than Tension in Mice. J Bone Miner Res 2023; 38:59-69. [PMID: 36281491 DOI: 10.1002/jbmr.4728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 10/08/2022] [Accepted: 10/19/2022] [Indexed: 01/10/2023]
Abstract
Parathyroid hormone (PTH) is an anabolic osteoporosis treatment that increases bone mass and reduces fracture risk. Clinically, the effects of PTH are site-specific, increasing bone mass more at the spine than the hip and not increasing bone mass at the radius. Differences in local loading environment between the spine, hip, and radius may help explain the variation in efficacy, as PTH and mechanical loading have been shown to synergistically increase bone mass. We hypothesized that differences in loading mode might further explain these variations. Owing to the curvature of the mouse tibia, cyclic compression of the hindlimb causes bending at the tibial midshaft, placing the anterior surface under tension and the posterior surface under compression. We investigated the combination of PTH treatment and tibial loading in an osteoblast-specific estrogen receptor-alpha knockout mouse model of low bone mass (pOC-ERαKO) and their littermate controls (LCs) and analyzed bone morphology in the tensile, compressive, and neutral regions of the tibial midshaft. We also hypothesized that pretreating wild-type C57Bl/6J (WT) mice with PTH prior to mechanical loading would enhance the synergistic anabolic effects. Compression was more anabolic than tension, and PTH enhanced the effect of loading, particularly under compression. PTH pretreatment maintained the synergistic anabolic effect for longer durations than concurrent treatment and loading alone. Together these data provide insights into more effective physical therapy and exercise regimens for patients receiving PTH treatment. © 2022 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Amanda M Rooney
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA
| | - Tyler J McNeill
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA
| | | | | | - Marjolein C H van der Meulen
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA
- Research Division, Hospital for Special Surgery, New York, New York, USA
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2
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Kalyanaraman H, China SP, Cabriales JA, Moininazeri J, Casteel DE, Garcia JJ, Wong VW, Chen A, Sah RL, Boss GR, Pilz RB. Protein Kinase G2 Is Essential for Skeletal Homeostasis and Adaptation to Mechanical Loading in Male but Not Female Mice. J Bone Miner Res 2023; 38:171-185. [PMID: 36371651 PMCID: PMC9825661 DOI: 10.1002/jbmr.4746] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 11/04/2022] [Accepted: 11/10/2022] [Indexed: 11/14/2022]
Abstract
We previously showed that the NO/cGMP/protein kinase G (PKG) signaling pathway positively regulates osteoblast proliferation, differentiation, and survival in vitro, and that cGMP-elevating agents have bone-anabolic effects in mice. Here, we generated mice with an osteoblast-specific (OB) knockout (KO) of type 2 PKG (gene name Prkg2) using a Col1a1(2.3 kb)-Cre driver. Compared to wild type (WT) littermates, 8-week-old male OB Prkg2-KO mice had fewer osteoblasts, reduced bone formation rates, and lower trabecular and cortical bone volumes. Female OB Prkg2-KO littermates showed no bone abnormalities, despite the same degree of PKG2 deficiency in bone. Expression of osteoblast differentiation- and Wnt/β-catenin-related genes was lower in primary osteoblasts and bones of male KO but not female KO mice compared to WT littermates. Osteoclast parameters were unaffected in both sexes. Since PKG2 is part of a mechano-sensitive complex in osteoblast membranes, we examined its role during mechanical loading. Cyclical compression of the tibia increased cortical thickness and induced mechanosensitive and Wnt/β-catenin-related genes to a similar extent in male and female WT mice and female OB Prkg2-KO mice, but loading had a minimal effect in male KO mice. We conclude that PKG2 drives bone acquisition and adaptation to mechanical loading via the Wnt/β-catenin pathway in male mice. The striking sexual dimorphism of OB Prkg2-KO mice suggests that current U.S. Food and Drug Administration-approved cGMP-elevating agents may represent novel effective treatment options for male osteoporosis. © 2022 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Hema Kalyanaraman
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
- These two authors contributed equally to the work
| | - Shyamsundar Pal China
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
- These two authors contributed equally to the work
| | - Justin A. Cabriales
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jafar Moininazeri
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Darren E. Casteel
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Julian J. Garcia
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Van W. Wong
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Albert Chen
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Robert L. Sah
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Gerry R. Boss
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Renate B. Pilz
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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3
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Wolff LI, Houben A, Fabritius C, Angus-Hill M, Basler K, Hartmann C. Only the Co-Transcriptional Activity of β-Catenin Is Required for the Local Regulatory Effects in Hypertrophic Chondrocytes on Developmental Bone Modeling. J Bone Miner Res 2021; 36:2039-2052. [PMID: 34155688 DOI: 10.1002/jbmr.4396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 06/02/2021] [Accepted: 06/16/2021] [Indexed: 12/13/2022]
Abstract
In hypertrophic chondrocytes, β-catenin has two roles. First, it locally suppresses the differentiation of osteoclasts at the chondro-osseous junction by maintaining the pro-osteoclastic factor receptor activator of NF-κB ligand (RANKL) at low levels. Second, it promotes the differentiation of osteoblast-precursors from chondrocytes. Yet, β-catenin is a dual-function protein, which can either participate in cell-cell adherens junctions or serve as a transcriptional co-activator in canonical Wnt signaling interacting with T-cell factor/lymphoid enhancer-binding factor (TCF/LEF) transcription factors. Hence, whenever studying tissue-specific requirements of β-catenin using a conventional conditional knockout approach, the functional mechanisms underlying the defects in the conditional mutants remain ambiguous. To decipher mechanistically which of the two molecular functions of β-catenin is required in hypertrophic chondrocytes, we used different approaches. We analyzed the long bones of newborn mice carrying either the null-alleles of Lef1 or Tcf7, or mice in which Tcf7l2 was conditionally deleted in the hypertrophic chondrocytes, as well as double mutants for Lef1 and Tcf7l2, and Tcf7 and Tcf7l2. Furthermore, we analyzed Ctnnb1 mutant newborns expressing a signaling-defective allele that retains the cell adhesion function in hypertrophic chondrocytes. None of the analyzed Tcf/Lef single or double mutants recapitulated the previously published phenotype upon loss of β-catenin in hypertrophic chondrocytes. However, using this particular Ctnnb1 allele, maintaining cell adhesion function, we show that it is the co-transcriptional activity of β-catenin, which is required in hypertrophic chondrocytes to suppress osteoclastogenesis and to promote chondrocyte-derived osteoblast differentiation. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Lena I Wolff
- Institute of Musculoskeletal Medicine, Department of Bone and Skeletal Research, Medical Faculty of the Westphalian Wilhelms University, Münster, Germany
| | - Astrid Houben
- Institute of Musculoskeletal Medicine, Department of Bone and Skeletal Research, Medical Faculty of the Westphalian Wilhelms University, Münster, Germany
| | - Christine Fabritius
- Institute of Musculoskeletal Medicine, Department of Bone and Skeletal Research, Medical Faculty of the Westphalian Wilhelms University, Münster, Germany
| | | | - Konrad Basler
- Department of Molecular Life Science, University of Zurich, Zurich, Switzerland
| | - Christine Hartmann
- Institute of Musculoskeletal Medicine, Department of Bone and Skeletal Research, Medical Faculty of the Westphalian Wilhelms University, Münster, Germany
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4
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Wei Z, Li S, Tao X, Zhu G, Sun Z, Wei Z, Jiao Q, Zhang H, Chen L, Li B, Zhang Z, Yue H. Mutations in Profilin 1 Cause Early-Onset Paget's Disease of Bone With Giant Cell Tumors. J Bone Miner Res 2021; 36:1088-1103. [PMID: 33599011 PMCID: PMC8251538 DOI: 10.1002/jbmr.4275] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 02/02/2021] [Accepted: 02/14/2021] [Indexed: 12/24/2022]
Abstract
Paget's disease of bone (PDB) is a late-onset chronic progressive bone disease characterized by abnormal activation of osteoclasts that results in bone pain, deformities, and fractures. PDB is very rare in Asia. A subset of PDB patients have early onset and can develop malignant giant cell tumors (GCTs) of the bone (PDB/GCTs), which arise within Paget bone lesions; the result is a significantly higher mortality rate. SQSTM1, TNFRSF11A, OPG, VCP, and HNRNPA2B1 have been identified as pathogenic genes of PDB, and ZNF687 is the only confirmed gene to date known to cause PDB/GCT. However, the molecular mechanism underlying PDB/GCT has not been fully elucidated. Here, we investigate an extended Chinese pedigree with eight individuals affected by early-onset and polyostotic PDB, two of whom developed GCTs. We identified a heterozygous 4-bp deletion in the Profilin 1 (PFN1) gene (c.318_321delTGAC) by genetic linkage analysis and exome sequencing for the family. Sanger sequencing revealed another heterozygous 1-bp deletion in PFN1 (c.324_324delG) in a sporadic early-onset PDB/GCT patient, further proving its causative role. Interestingly, a heterozygous missense mutation of PFN1 (c.335 T > C) was identified in another PDB/GCT family, revealing that not only deletion but also missense mutations in PFN1 can cause PDB/GCT. Furthermore, we established a Pfn1-mutated mouse model (C57BL/6J mice) and successfully obtained Pagetic phenotypes in heterozygous mice, verifying loss of function of PFN1 as the cause of PDB/GCT development. In conclusion, our findings reveal mutations in PFN1 as the pathological mechanism in PDB/GCT, and we successfully established Pfn1-mutated mice as a suitable animal model for studying PDB-associated pathological mechanisms. The identification of PFN1 mutations has great diagnostic value for identifying PDB individuals predisposed toward developing GCTs. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Zhe Wei
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Shanshan Li
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Xiaohui Tao
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Guoying Zhu
- Department of Radiation Health, Institute of Radiation Medicine, Fudan University, Shanghai, China
| | - Zhenkui Sun
- Department of Nuclear Medicine, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Zhanying Wei
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Qiong Jiao
- Department of Pathology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Huizhen Zhang
- Department of Pathology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Lin Chen
- Department of Wound Repair and Rehabilitation Medicine, State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Army Medical University, Chongqing, China
| | - Baojie Li
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.,Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Shanghai Jiao Tong University, Ministry of Education, Shanghai, China
| | - Zhenlin Zhang
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
| | - Hua Yue
- Shanghai Clinical Research Center of Bone Disease, Department of Osteoporosis and Bone Diseases, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China
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5
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Lee JM, Kim MJ, Lee SJ, Kim BG, Choi JY, Lee SM, Ham HJ, Koh JM, Jeon JH, Lee IK. PDK2 Deficiency Prevents Ovariectomy-Induced Bone Loss in Mice by Regulating the RANKL-NFATc1 Pathway During Osteoclastogenesis. J Bone Miner Res 2021; 36:553-566. [PMID: 33125772 DOI: 10.1002/jbmr.4202] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 10/08/2020] [Accepted: 10/17/2020] [Indexed: 12/17/2022]
Abstract
Estrogen deficiency leads to osteoporosis as a result of an imbalance in bone remodeling due to greater bone resorption. Estrogen deficiency increases the osteoclastic resorption of bone, and many of the FDA-approved therapies for osteoporosis are antiresorptive drugs that mainly act by reducing osteoclast activity. The mitochondrial enzyme pyruvate dehydrogenase kinase (PDK) is a critical regulator of aerobic glycolysis that exerts its effects by phosphorylating the pyruvate dehydrogenase complex (PDC), which is responsible for oxidative phosphorylation. In the present study, we found that during osteoclast differentiation, PDK2 expression increased more than that of the other PDK isoenzymes. Bone loss was delayed and the number of osteoclasts was lower in ovariectomized (OVX) Pdk2-/- mice than in OVX wild-type mice. The differentiation of osteoclasts was suppressed in Pdk2-/- bone marrow-derived monocyte/macrophage lineage cells, which was associated with lower phosphorylation of cAMP response element-binding protein (CREB) and c-FOS, and a consequent reduction in NFATc1 transcription. Administration of AZD7545, a specific inhibitor of PDK2, prevented the OVX-induced bone loss and reduced the phosphorylation of CREB and c-FOS, and the protein expression of NFATc1, in osteoclasts. Collectively, these results indicate that the inhibition of PDK2 prevents osteoporosis in estrogen-deficient mice by reducing aberrant osteoclast activation, probably via inhibition of the RANKL-CREB-cFOS-NFATc1 pathway. These findings imply that PDK2 inhibitors might be repurposed for the therapy of estrogen deficiency-induced osteoporosis. © 2020 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Ji-Min Lee
- Department of Biomedical Science, Graduate School, Kyungpook National University, Daegu, Republic of Korea.,BK21 plus KNU Biomedical Convergence Programs, Department of Biomedical Science, Kyungpook National University Daegu, Republic of Korea
| | - Min-Ji Kim
- Department of Internal Medicine, School of Medicine, Kyungpook National University, Kyungpook National University Hospital, Daegu, Republic of Korea
| | - Sun Joo Lee
- New Drug Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, Republic of Korea
| | - Byung-Gyu Kim
- Center for Genomic Integrity (CGI), Institute for Basic Science (IBS), Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea
| | - Je-Yong Choi
- Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Seung Mi Lee
- Leading-Edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University Hospital, Daegu, Republic of Korea
| | - Hye Jin Ham
- Leading-Edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University Hospital, Daegu, Republic of Korea
| | - Jung-Min Koh
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Jae-Han Jeon
- Leading-Edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University Hospital, Daegu, Republic of Korea.,Department of Internal Medicine, School of Medicine, Kyungpook National University, Kyungpook National University Chilgok Hospital, Daegu, Republic of Korea
| | - In-Kyu Lee
- Department of Biomedical Science, Graduate School, Kyungpook National University, Daegu, Republic of Korea.,Department of Internal Medicine, School of Medicine, Kyungpook National University, Kyungpook National University Hospital, Daegu, Republic of Korea.,Leading-Edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University Hospital, Daegu, Republic of Korea
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6
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Liu H, Xu J, Jiang R. Mkx-Deficient Mice Exhibit Hedgehog Signaling-Dependent Ectopic Ossification in the Achilles Tendons. J Bone Miner Res 2019; 34:557-569. [PMID: 30458056 PMCID: PMC6535142 DOI: 10.1002/jbmr.3630] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 10/25/2018] [Accepted: 11/06/2018] [Indexed: 01/02/2023]
Abstract
Heterotopic ossification is the abnormal formation of mineralized bone in skin, muscle, tendon, or other soft tissues. Tendon ossification often occurs from acute tendon injury or chronic tendon degeneration, for which current treatment relies heavily on surgical removal of the ectopic bony tissues. Unfortunately, surgery creates additional trauma, which often causes recurrence of heterotopic ossification. The molecular mechanisms of heterotopic ossification are not well understood. Previous studies demonstrate that Mkx is a transcription factor crucial for postnatal tendon fibril growth. Here we report that Mkx-/- mutant mice exhibit ectopic ossification in the Achilles tendon within 1 month after birth and the tendon ossification deteriorates with age. Genetic lineage labeling revealed that the tendon ossification in Mkx-/- mice resulted from aberrant differentiation of tendon progenitor cells. Furthermore, tissue-specific inactivation of Mkx in tendon cells postnatally resulted in a similar ossification phenotype, indicating that Mkx plays a key role in tendon tissue homeostasis. Moreover, we show that Hedgehog signaling is ectopically activated at early stages of tendon ossification and that tissue-specific inactivation of Smoothened, which encodes the obligatory transducer of Hedgehog signaling, in the tendon cell lineage prevented or dramatically reduced tendon ossification in Mkx-/- mice. Together, these studies establish a new genetic mouse model of tendon ossification and provide new insight into its pathogenic mechanisms. © 2018 American Society for Bone and Mineral Research.
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Affiliation(s)
- Han Liu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Jingyue Xu
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Rulang Jiang
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.,Shriners Hospitals for Children-Cincinnati, Cincinnati, OH, USA
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7
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Dirkes RK, Ortinau LC, Rector RS, Olver TD, Hinton PS. Insulin-Stimulated Bone Blood Flow and Bone Biomechanical Properties Are Compromised in Obese, Type 2 Diabetic OLETF Rats. JBMR Plus 2017; 1:116-126. [PMID: 30283885 PMCID: PMC6124191 DOI: 10.1002/jbm4.10007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/08/2017] [Accepted: 05/10/2017] [Indexed: 01/20/2023] Open
Abstract
Type 2 diabetes (T2D) increases skeletal fragility and fracture risk; however, the underlying mechanisms remain to be identified. Impaired bone vascular function, in particular insulin‐stimulated vasodilation and blood flow is a potential, yet unexplored mechanism. The purpose of this study was to determine the effects of T2D on femoral biomechanical properties, trabecular microarchitecture, and insulin‐stimulated bone vasodilation by comparison of hyperphagic Otsuka Long‐Evans Tokushima Fatty (OLETF) rats with normoglycemic control OLETF rats. Four‐week old, male OLETF rats were randomized to two groups: type 2 diabetes (O‐T2D) or normoglycemic control (O‐CON). O‐T2D were allowed ad libitum access to a rodent chow diet and O‐CON underwent moderate caloric restriction (30% restriction relative to intake of O‐T2D) to maintain normal body weight (BW) and glycemia until 40 weeks of age. Hyperphagic O‐T2D rats had significantly greater BW, body fat, and blood glucose than O‐CON. Total cross‐sectional area (Tt.Ar), cortical area (Ct.Ar), Ct.Ar/Tt.Ar, and polar moment of inertia of the mid‐diaphyseal femur adjusted for BW were greater in O‐T2D rats versus O‐CON. Whole‐bone biomechanical properties of the femur assessed by torsional loading to failure did not differ between O‐T2D and O‐CON, but tissue‐level strength and stiffness adjusted for BW were reduced in O‐T2D relative to O‐CON. Micro–computed tomography (μCT) of the distal epiphysis showed that O‐T2D rats had reduced percent bone volume, trabecular number, and connectivity density, and greater trabecular spacing compared with O‐CON. Basal tibial blood flow assessed by microsphere infusion was similar in O‐T2D and O‐CON, but the blood flow response to insulin stimulation in both the proximal epiphysis and diaphyseal marrow was lesser in O‐T2D compared to O‐CON. In summary, impaired insulin‐stimulated bone blood flow is associated with deleterious changes in bone trabecular microarchitecture and cortical biomechanical properties in T2D, suggesting that vascular dysfunction might play a causal role in diabetic bone fragility. © 2017 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.
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Affiliation(s)
- Rebecca K Dirkes
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA
| | - Laura C Ortinau
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA
| | - R Scott Rector
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA.,Division of Gastroenterology and Hepatology Department of Medicine University of Missouri-Columbia Columbia MO USA.,Research Service Harry S Truman Memorial VA Hospital Columbia MO USA
| | - T Dylan Olver
- Department of Biomedical Sciences University of Missouri-Columbia Columbia MO USA
| | - Pamela S Hinton
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA
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8
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Melville KM, Kelly NH, Surita G, Buchalter DB, Schimenti JC, Main RP, Ross FP, van der Meulen MCH. Effects of Deletion of ERα in Osteoblast-Lineage Cells on Bone Mass and Adaptation to Mechanical Loading Differ in Female and Male Mice. J Bone Miner Res 2015; 30:1468-80. [PMID: 25707500 PMCID: PMC4506717 DOI: 10.1002/jbmr.2488] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 02/17/2015] [Accepted: 02/18/2015] [Indexed: 12/30/2022]
Abstract
Estrogen receptor alpha (ERα) has been implicated in bone's response to mechanical loading in both males and females. ERα in osteoblast lineage cells is important for determining bone mass, but results depend on animal sex and the cellular stage at which ERα is deleted. We demonstrated previously that when ERα is deleted from mature osteoblasts and osteocytes in mixed-background female mice, bone mass and strength are decreased. However, few studies exist examining the skeletal response to loading in bone cell-specific ERαKO mice. Therefore, we crossed ERα floxed (ERα(fl/fl)) and osteocalcin-Cre (OC-Cre) mice to generate animals lacking ERα in mature osteoblasts and osteocytes (pOC-ERαKO) and littermate controls (LC). At 10 weeks of age, the left tibia was loaded in vivo for 2 weeks. We analyzed bone mass through micro-CT, bone formation rate by dynamic histomorphometry, bone strength from mechanical testing, and osteoblast and osteoclast activity by serum chemistry and immunohistochemistry. ERα in mature osteoblasts differentially regulated bone mass in males and females. Compared with LC, female pOC-ERαKO mice had decreased cortical and cancellous bone mass, whereas male pOC-ERαKO mice had equal or greater bone mass than LC. Bone mass results correlated with decreased compressive strength in pOC-ERαKO female L(5) vertebrae and with increased maximum moment in pOC-ERαKO male femora. Female pOC-ERαKO mice responded more to mechanical loading, whereas the response of pOC-ERαKO male animals was similar to their littermate controls.
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Affiliation(s)
- Katherine M Melville
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA.,Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Natalie H Kelly
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA.,Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Gina Surita
- Department of Biological Sciences, Cornell University, Ithaca, NY, USA
| | | | - John C Schimenti
- College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Russell P Main
- College of Veterinary Medicine, Purdue University, West Lafayette, IN, USA.,Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - F Patrick Ross
- Research Division, Hospital for Special Surgery, New York, NY, USA
| | - Marjolein C H van der Meulen
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA.,Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA.,Research Division, Hospital for Special Surgery, New York, NY, USA
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