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Delsmann MM, Peichl J, Yorgan TA, Beil FT, Amling M, Demay MB, Rolvien T. Prevention of Hypomineralization In Auditory Ossicles of Vitamin D Receptor (Vdr) Deficient Mice. Front Endocrinol (Lausanne) 2022; 13:901265. [PMID: 35733772 PMCID: PMC9207527 DOI: 10.3389/fendo.2022.901265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 04/21/2022] [Indexed: 11/20/2022] Open
Abstract
Intact mineralization of the auditory ossicles - the smallest bones in the body - is essential for sound transmission in the middle ear, while ossicular hypomineralization is associated with conductive hearing loss. Here, we performed a high-resolution analysis of the ossicles in vitamin D receptor deficient mice (Vdr-/- ), which are characterized by hypocalcemia and skeletal mineralization defects, and investigated whether local hypomineralization can be prevented by feeding a calcium-rich rescue diet (Vdr-/- res ). In Vdr-/- mice fed a regular diet (Vdr-/- reg ), quantitative backscattered electron imaging (qBEI) revealed an increased void volume (porosity, p<0.0001) along with lower mean calcium content (CaMean, p=0.0008) and higher heterogeneity of mineralization (CaWidth, p=0.003) compared to WT mice. Furthermore, a higher osteoid volume per bone volume (OV/BV; p=0.0002) and a higher osteocyte lacunar area (Lc.Ar; p=0.01) were found in histomorphometric analysis in Vdr-/- reg mice. In Vdr-/- res mice, full rescue of OV/BV and Lc.Ar (both p>0.05 vs. WT) and partial rescue of porosity and CaWidth (p=0.02 and p=0.04 vs. WT) were observed. Compared with Hyp mice, a model of X-linked hypophosphatemic rickets, Vdr-/- reg mice showed a lower osteoid volume in the ossicles (p=0.0002), but similar values in the lumbar spine. These results are consistent with later postnatal impairment of mineral homeostasis in Vdr-/- mice than in Hyp mice, underscoring the importance of intact mineral homeostasis for ossicle mineralization during development. In conclusion, we revealed a distinct phenotype of hypomineralization in the auditory ossicles of Vdr-/- mice that can be partially prevented by a rescue diet. Since a positive effect of a calcium-rich diet on ossicular mineralization was demonstrated, our results open new treatment strategies for conductive hearing loss. Future studies should investigate the impact of improved ossicular mineralization on hearing function.
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Affiliation(s)
- Maximilian M. Delsmann
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Jonathan Peichl
- Department of Otorhinolaryngology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Timur A. Yorgan
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Frank Timo Beil
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Marie B. Demay
- Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Tim Rolvien
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- *Correspondence: Tim Rolvien,
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2
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Ni X, Li X, Zhang Q, Liu C, Gong Y, Wang O, Li M, Xing X, Jiang Y, Xia W. Clinical Characteristics and Bone Features of Autosomal Recessive Hypophosphatemic Rickets Type 1 in Three Chinese Families: Report of Five Chinese Cases and Review of the Literature. Calcif Tissue Int 2020; 107:636-648. [PMID: 32920683 DOI: 10.1007/s00223-020-00755-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 09/02/2020] [Indexed: 12/15/2022]
Abstract
Autosomal recessive hypophosphatemic rickets type 1 (ARHR1) was reported to be caused by homozygous mutation of dentin matrix protein 1 (DMP1). To date, very few cases have been reported. Here, we summarized clinical, laboratory and imaging findings of ARHR1 patients in our hospital. Literature review was performed to analyze genotype-phenotype correlation. Five Chinese patients from three unrelated pedigrees presented with lower extremity deformity and short stature. Hypophosphatemia, elevated alkaline phosphatase, high intact fibroblast growth factor 23 and sclerostin were found. X-ray uncovered coexistence of osteomalacia and osteosclerosis. Although areal bone mineral density (aBMD) of axial bone measured by dual-energy X-ray absorptiometry was relatively high in all patients, volumetric BMD (vBMD) and microstructure of one adult patient's peripheral bone detected by HR-pQCT were damaged. Mutation analyses of DMP1 revealed three homozygous mutations including two novel mutations, c.54 + 1G > C and c.94C > A (p.E32X), and a reported mutation c.184-1G > A. Genotype-phenotype correlation analysis including 30 cases (25 from literature review and 5 from our study) revealed that patients harboring mutations affecting C-terminal fragment of DMP1 presented with shorter stature (Z score of height = - 3.4 ± 1.6 vs - 1.0 ± 1.6, p = 0.001) and lower serum phosphate level (0.70 ± 0.15 vs 0.84 ± 0.16, p = 0.03) than those harboring mutations only affecting N-terminal fragment. In summary, we reported five Chinese ARHR1 patients and identified two novel DMP1 mutations. High aBMD and local osteosclerosis in axial bone with low vBMD and damaged microstructure in peripheral bone were featured. Genotype-phenotype correlation analysis confirmed the important role of C-terminal fragment of DMP1.
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Affiliation(s)
- Xiaolin Ni
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Xiang Li
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Qi Zhang
- Laboratory Department, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Chang Liu
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Yiyi Gong
- Central Research Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Ou Wang
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Mei Li
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Xiaoping Xing
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Yan Jiang
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China.
| | - Weibo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology, National Commission of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China.
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Abstract
PURPOSE OF REVIEW Multiple dietary components have the potential to positively affect bone mineral density in early life and reduce loss of bone mass with aging. In addition, regular weight-bearing physical activity has a strong positive effect on bone through activation of osteocyte signaling. We will explore possible synergistic effects of dietary components and mechanical stimuli for bone health by identifying dietary components that have the potential to alter the response of osteocytes to mechanical loading. RECENT FINDINGS Several (sub)cellular aspects of osteocytes determine their signaling towards osteoblasts and osteoclasts in response to mechanical stimuli, such as the osteocyte cytoskeleton, estrogen receptor α, the vitamin D receptor, and the architecture of the lacunocanalicular system. Potential modulators of these features include 1,25-dihydroxy vitamin D3, several forms of vitamin K, and the phytoestrogen genistein. Multiple dietary components potentially affect osteocyte function and therefore may have a synergistic effect on bone health when combined with a regime of physical activity.
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Affiliation(s)
- Hubertine M E Willems
- Department of Preventive Dentistry, Academic Center for Dentistry Amsterdam, Vrije Universiteit Amsterdam and University of Amsterdam, Amsterdam, The Netherlands
| | | | | | - Jenneke Klein-Nulend
- Department of Oral Cell Biology, Academic Center for Dentistry Amsterdam, Vrije Universiteit Amsterdam and University of Amsterdam, Amsterdam Movement Sciences, Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands
| | - Astrid D Bakker
- Department of Oral Cell Biology, Academic Center for Dentistry Amsterdam, Vrije Universiteit Amsterdam and University of Amsterdam, Amsterdam Movement Sciences, Gustav Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands.
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Yorgan TA, Heckt T, Rendenbach C, Helmis C, Seitz S, Streichert T, Amling M, Schinke T. Immediate effects of retinoic acid on gene expression in primary murine osteoblasts. J Bone Miner Metab 2016; 34:161-70. [PMID: 25956707 DOI: 10.1007/s00774-015-0666-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 02/16/2015] [Indexed: 10/23/2022]
Abstract
Consistent with clinical observations demonstrating that hypervitaminosis A is associated with increased skeletal fracture risk, we have previously found that dietary retinol deprivation partially corrects the bone mineralization defects in a mouse model of X-linked hypophosphatemic rickets. That retinol-dependent signaling pathways impact the skeleton is further supported by various findings demonstrating a negative influence of retinoic acid (RA) on bone-forming osteoblasts. We hypothesized that RA would directly regulate the expression of specific target genes in osteoblasts, and we aimed to identify these by genome-wide expression analyses. Here we show that high dietary retinol intake in mice causes low bone mass associated with increased osteoclastogenesis and decreased osteoblastogenesis, but intact bone matrix mineralization. We additionally found that short-term treatment of primary osteoblasts with RA causes a rapid induction of specific genes involved in either retinol-dependent signaling (i.e. Rara, Crabp2) or skeletal remodeling (i.e. Twist2, Tnfsf11). In contrast, neither expression of established osteoblast differentiation markers nor the proliferation rate was immediately affected by RA administration. Collectively, our data suggest that the negative effects of vitamin A on skeletal integrity are explainable by an immediate influence of RA signaling on specific genes in osteoblasts that in turn influence bone remodeling.
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Affiliation(s)
- Timur A Yorgan
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Timo Heckt
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Carsten Rendenbach
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Christina Helmis
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Sebastian Seitz
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Thomas Streichert
- Department of Clinical Chemistry, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany.
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Jeschke A, Bonitz M, Simon M, Peters S, Baum W, Schett G, Ruether W, Niemeier A, Schinke T, Amling M. Deficiency of Thrombospondin-4 in Mice Does Not Affect Skeletal Growth or Bone Mass Acquisition, but Causes a Transient Reduction of Articular Cartilage Thickness. PLoS One 2015; 10:e0144272. [PMID: 26629997 PMCID: PMC4667928 DOI: 10.1371/journal.pone.0144272] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 11/16/2015] [Indexed: 12/22/2022] Open
Abstract
Although articular cartilage degeneration represents a major public health problem, the underlying molecular mechanisms are still poorly characterized. We have previously utilized genome-wide expression analysis to identify specific markers of porcine articular cartilage, one of them being Thrombospondin-4 (Thbs4). In the present study we analyzed Thbs4 expression in mice, thereby confirming its predominant expression in articular cartilage, but also identifying expression in other tissues, including bone. To study the role of Thbs4 in skeletal development and integrity we took advantage of a Thbs4-deficient mouse model that was analyzed by undecalcified bone histology. We found that Thbs4-deficient mice do not display phenotypic differences towards wildtype littermates in terms of skeletal growth or bone mass acquisition. Since Thbs4 has previously been found over-expressed in bones of Phex-deficient Hyp mice, we additionally generated Thbs4-deficient Hyp mice, but failed to detect phenotypic differences towards Hyp littermates. With respect to articular cartilage we found that Thbs4-deficient mice display transient thinning of articular cartilage, suggesting a protective role of Thbs4 for joint integrity. Gene expression analysis using porcine primary cells revealed that Thbs4 is not expressed by synovial fibroblasts and that it represents the only member of the Thbs gene family with specific expression in articular, but not in growth plate chondrocytes. In an attempt to identify specific molecular effects of Thbs4 we treated porcine articular chondrocytes with human THBS4 in the absence or presence of conditioned medium from porcine synovial fibroblasts. Here we did not observe a significant influence of THBS4 on proliferation, metabolic activity, apoptosis or gene expression, suggesting that it does not act as a signaling molecule. Taken together, our data demonstrate that Thbs4 is highly expressed in articular chondrocytes, where its presence in the extracellular matrix is required for articular cartilage integrity.
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Affiliation(s)
- Anke Jeschke
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Martin Bonitz
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Maciej Simon
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
- Department of Orthopedics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Stephanie Peters
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Wolfgang Baum
- Department of Internal Medicine 3 and Institute of Clinical Immunology, University of Erlangen-Nuremberg, Erlangen 91054, Germany
| | - Georg Schett
- Department of Internal Medicine 3 and Institute of Clinical Immunology, University of Erlangen-Nuremberg, Erlangen 91054, Germany
| | - Wolfgang Ruether
- Department of Orthopedics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Andreas Niemeier
- Department of Orthopedics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
- * E-mail:
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Aceto J, Nourizadeh-Lillabadi R, Marée R, Dardenne N, Jeanray N, Wehenkel L, Aleström P, van Loon JJWA, Muller M. Zebrafish Bone and General Physiology Are Differently Affected by Hormones or Changes in Gravity. PLoS One 2015; 10:e0126928. [PMID: 26061167 PMCID: PMC4465622 DOI: 10.1371/journal.pone.0126928] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 04/09/2015] [Indexed: 11/18/2022] Open
Abstract
Teleost fish such as zebrafish (Danio rerio) are increasingly used for physiological, genetic and developmental studies. Our understanding of the physiological consequences of altered gravity in an entire organism is still incomplete. We used altered gravity and drug treatment experiments to evaluate their effects specifically on bone formation and more generally on whole genome gene expression. By combining morphometric tools with an objective scoring system for the state of development for each element in the head skeleton and specific gene expression analysis, we confirmed and characterized in detail the decrease or increase of bone formation caused by a 5 day treatment (from 5dpf to 10 dpf) of, respectively parathyroid hormone (PTH) or vitamin D3 (VitD3). Microarray transcriptome analysis after 24 hours treatment reveals a general effect on physiology upon VitD3 treatment, while PTH causes more specifically developmental effects. Hypergravity (3g from 5dpf to 9 dpf) exposure results in a significantly larger head and a significant increase in bone formation for a subset of the cranial bones. Gene expression analysis after 24 hrs at 3g revealed differential expression of genes involved in the development and function of the skeletal, muscular, nervous, endocrine and cardiovascular systems. Finally, we propose a novel type of experimental approach, the "Reduced Gravity Paradigm", by keeping the developing larvae at 3g hypergravity for the first 5 days before returning them to 1g for one additional day. 5 days exposure to 3g during these early stages also caused increased bone formation, while gene expression analysis revealed a central network of regulatory genes (hes5, sox10, lgals3bp, egr1, edn1, fos, fosb, klf2, gadd45ba and socs3a) whose expression was consistently affected by the transition from hyper- to normal gravity.
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Affiliation(s)
- Jessica Aceto
- Laboratory for Organogenesis and Regeneration, GIGA- Research, University of Liège, B-4000, Liège, Sart-Tilman, Belgium
| | | | - Raphael Marée
- GIGA & Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium
| | - Nadia Dardenne
- Unité de soutien méth. en Biostatistique et Epidémiologie, University of Liège, B23, Sart Tilman, Liège, Belgium
| | - Nathalie Jeanray
- Laboratory for Organogenesis and Regeneration, GIGA- Research, University of Liège, B-4000, Liège, Sart-Tilman, Belgium
| | - Louis Wehenkel
- GIGA & Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium
| | - Peter Aleström
- BasAM, Norwegian University of Life Sciences, Vetbio, 0033 Dep, Oslo, Norway
| | - Jack J. W. A. van Loon
- DESC (Dutch Experiment Support Center), Department of Oral and Maxillofacial Surgery / Oral Pathology, VU University Medical Center & Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands
- ESA-ESTEC, TEC-MMG, NL-2200 AG, Noordwijk, The Netherlands
| | - Marc Muller
- Laboratory for Organogenesis and Regeneration, GIGA- Research, University of Liège, B-4000, Liège, Sart-Tilman, Belgium
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Zou J, Xiong X, Lai B, Sun M, Tu X, Gao X. Glucose metabolic abnormality is associated with defective mineral homeostasis in skeletal disorder mouse model. SCIENCE CHINA-LIFE SCIENCES 2015; 58:359-67. [DOI: 10.1007/s11427-015-4827-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 12/31/2014] [Indexed: 12/17/2022]
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8
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Sapir-Koren R, Livshits G. Bone mineralization is regulated by signaling cross talk between molecular factors of local and systemic origin: the role of fibroblast growth factor 23. Biofactors 2014; 40:555-68. [PMID: 25352227 DOI: 10.1002/biof.1186] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 10/06/2014] [Indexed: 01/07/2023]
Abstract
Body phosphate homeostasis is regulated by a hormonal counter-balanced intestine-bone-kidney axis. The major systemic hormones involved in this axis are parathyroid hormone (PTH), 1,25-dihydroxyvitamin-D, and fibroblast growth factor-23 (FGF23). FGF23, produced almost exclusively by the osteocytes, is a phosphaturic hormone that plays a major role in regulation of the bone remodeling process. Remodeling composite components, bone mineralization and resorption cycles create a continuous influx-efflux loop of the inorganic phosphate (Pi) through the skeleton. This "bone Pi loop," which is formed, is controlled by local and systemic factors according to phosphate homeostasis demands. Although FGF23 systemic actions in the kidney, and for the production of PTH and 1,25-dihydroxyvitamin-D are well established, its direct involvement in bone metabolism is currently poorly understood. This review presents the latest available evidence suggesting two aspects of FGF23 bone local activity: (a) Regulation of FGF23 production by both local and systemic factors. The suggested local factors include extracellular levels of Pi and pyrophosphate (PPi), (the Pi/PPi ratio), and another osteocyte-derived protein, sclerostin. In addition, 1,25-dihydroxyvitamin-D, synthesized locally by bone cells, may contribute to regulation of FGF23 production. The systemic control is achieved via PTH and 1,25-dihydroxyvitamin-D endocrine functions. (b) FGF23 acts as a local agent, directly affecting bone mineralization. We support the assumption that under balanced physiological conditions, sclerostin, by para- autocrine signaling, upregulates FGF23 production by the osteocyte. FGF23, in turn, acts as a mineralization inhibitor, by stimulating the generation of the major mineralization antagonist-PPi.
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Affiliation(s)
- Rony Sapir-Koren
- Human Population Biology Research Unit, Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
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Rendenbach C, Yorgan TA, Heckt T, Otto B, Baldauf C, Jeschke A, Streichert T, David JP, Amling M, Schinke T. Effects of extracellular phosphate on gene expression in murine osteoblasts. Calcif Tissue Int 2014; 94:474-83. [PMID: 24366459 DOI: 10.1007/s00223-013-9831-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 12/01/2013] [Indexed: 02/07/2023]
Abstract
That phosphate homeostasis is tightly linked to skeletal mineralization is probably best underscored by the fact that the phosphaturic hormone FGF23 is primarily expressed by terminally differentiated osteoblasts/osteocytes and that increased circulating FGF23 levels are causative for different types of hypophosphatemic rickets. In contrast, FGF23 inactivation results in hyperphosphatemia, and unexpectedly this phenotype is associated with severe osteomalacia in Fgf23-deficient mice. In this context it is interesting that different cell types have been shown to respond to extracellular phosphate, thereby raising the concept that phosphate can act as a signaling molecule. To identify phosphate-responsive genes in primary murine osteoblasts we performed genome wide expression analysis with cells maintained in medium containing either 1 or 4 mM sodium phosphate for 6 h. As confirmed by qRT-PCR, this analysis revealed that several known osteoblast differentiation markers (Bglap, Ibsp, and Phex) were unaffected by raising extracellular phosphate levels. In contrast, we found that the expression of Enpp1 and Ank, two genes encoding inhibitors of matrix mineralization, was induced by extracellular phosphate, while the expression of Sost and Dkk1, two genes encoding inhibitors of bone formation, was negatively regulated. The ability of osteoblasts to respond to extracellular phosphate was dependent on their differentiation state, and shRNA-dependent repression of the phosphate transporter Slc20a1 in MC3T3-E1 cells partially abolished their molecular response to phosphate. Taken together, our results provide further evidence for a role of extracellular phosphate as a signaling molecule and raise the possibility that severe hyperphosphatemia can negatively affect skeletal mineralization.
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Affiliation(s)
- C Rendenbach
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, 20246, Hamburg, Germany
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10
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Abstract
PURPOSE OF REVIEW The wealth of data regarding fibroblast growth factor-23 (FGF23) and Klotho in chronic kidney disease (CKD) has risen exponentially over the past decade. This review is an attempt to summarize pivotal aspects of previous research, provide an update of recent findings and define important areas for future investigation. RECENT FINDINGS The phosphaturic hormone FGF23 increases dramatically as renal function declines. Identification of contributing stimuli to the rise in FGF23 is fundamental and recent evidence suggest a multifactorial cause which entails perturbed osteocyte function and renal mechanisms such as Klotho deficiency and, somewhat paradoxically, systemic Klotho excess. Circulating FGF23 predicts adverse outcomes, particularly cardiovascular disease, in CKD as well as in the general population. The concept of FGF23 merely as a biomarker and regulator of mineral metabolism is currently challenged by data linking FGF23 to pathological processes such as cardiac hypertrophy. Conversely, tissue level of the FGF23 coreceptor Klotho declines in early CKD and this deficiency is linked to accelerated ageing, cellular senescence, vascular calcification, oxidative stress and renal fibrosis. At present, methodological difficulties limit the utility of soluble Klotho measurements. Animal proof-of-concept studies have demonstrated beneficial effects of Klotho delivery in CKD, whereas anti-FGF23 therapy using neutralizing antibodies improved biochemical and bone parameters at the expense of increased vascular calcification and mortality. SUMMARY Pathological alterations of FGF23-Klotho in CKD are implicated as clinical biomarkers and may provide novel therapeutic strategies to alleviate the cardiovascular risk and slow CKD progression.
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11
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Lind T, Sundqvist A, Hu L, Pejler G, Andersson G, Jacobson A, Melhus H. Vitamin a is a negative regulator of osteoblast mineralization. PLoS One 2013; 8:e82388. [PMID: 24340023 PMCID: PMC3858291 DOI: 10.1371/journal.pone.0082388] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 10/26/2013] [Indexed: 12/30/2022] Open
Abstract
An excessive intake of vitamin A has been associated with an increased risk of fractures in humans. In animals, a high vitamin A intake leads to a reduction of long bone diameter and spontaneous fractures. Studies in rodents indicate that the bone thinning is due to increased periosteal bone resorption and reduced radial growth. Whether the latter is a consequence of direct effects on bone or indirect effects on appetite and general growth is unknown. In this study we therefore used pair-feeding and dynamic histomorphometry to investigate the direct effect of a high intake of vitamin A on bone formation in rats. Although there were no differences in body weight or femur length compared to controls, there was an approximately halved bone formation and mineral apposition rate at the femur diaphysis of rats fed vitamin A. To try to clarify the mechanism(s) behind this reduction, we treated primary human osteoblasts and a murine preosteoblastic cell line (MC3T3-E1) with the active metabolite of vitamin A; retinoic acid (RA), a retinoic acid receptor (RAR) antagonist (AGN194310), and a Cyp26 inhibitor (R115866) which blocks endogenous RA catabolism. We found that RA, via RARs, suppressed in vitro mineralization. This was independent of a negative effect on osteoblast proliferation. Alkaline phosphatase and bone gamma carboxyglutamate protein (Bglap, Osteocalcin) were drastically reduced in RA treated cells and RA also reduced the protein levels of Runx2 and Osterix, key transcription factors for progression to a mature osteoblast. Normal osteoblast differentiation involved up regulation of Cyp26b1, the major enzyme responsible for RA degradation, suggesting that a drop in RA signaling is required for osteogenesis analogous to what has been found for chondrogenesis. In addition, RA decreased Phex, an osteoblast/osteocyte protein necessary for mineralization. Taken together, our data indicate that vitamin A is a negative regulator of osteoblast mineralization.
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Affiliation(s)
- Thomas Lind
- Department of Medical Sciences, Section of Clinical Pharmacology, Uppsala University, Uppsala, Sweden
| | - Anders Sundqvist
- Department of Medical Sciences, Section of Clinical Pharmacology, Uppsala University, Uppsala, Sweden
| | - Lijuan Hu
- Department of Medical Sciences, Section of Clinical Pharmacology, Uppsala University, Uppsala, Sweden
| | - Gunnar Pejler
- Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Göran Andersson
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, Huddinge, Sweden
| | - Annica Jacobson
- Department of Medical Sciences, Section of Clinical Pharmacology, Uppsala University, Uppsala, Sweden
| | - Håkan Melhus
- Department of Medical Sciences, Section of Clinical Pharmacology, Uppsala University, Uppsala, Sweden
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Yorgan T, Rendenbach C, Jeschke A, Amling M, Cheah KSE, Schinke T. Increased Col10a1 expression is not causative for the phenotype of Phex-deficient Hyp mice. Biochem Biophys Res Commun 2013; 442:209-13. [PMID: 24269824 DOI: 10.1016/j.bbrc.2013.11.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 11/07/2013] [Indexed: 12/25/2022]
Abstract
X-linked hypophosphatemic rickets (XLHR) is a severe disorder of phosphate homeostasis and skeletal mineralization caused by mutations of PHEX, encoding a bone-specific endopeptidase. Phex-deficient Hyp mice have been extensively studied to understand the molecular bases of XLHR, and here it was found that Fgf23, encoding a major phosphaturic hormone, was transcriptionally activated in bone-forming osteoblasts. We and others could additionally show that Col10a1 expression is increased in Hyp osteoblasts and bones, thereby raising the possibility that ectopic production of type X collagen could contribute to the impaired mineralization of the Hyp bone matrix. Here we show that an additional deficiency of the Col10a1 gene does not overtly affect the skeletal phenotype of Hyp mice. More specifically, Col10a1-deficient Hyp mice displayed severe disturbances of skeletal growth, bone mass acquisition and bone matrix mineralization, and they were essentially indistinguishable from Hyp littermates. This was confirmed by non-decalcified histology and bone-specific histomorphometry quantifying all relevant parameters of growth plate maturation, trabecular bone architecture and osteoid accumulation. Taken together, our results show that increased Col10a1 expression in Phex-deficient osteoblasts is not a major cause of the XLHR phenotype, which was an important issue to address based on the previous findings.
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Affiliation(s)
- Timur Yorgan
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
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Larson SR, Chin J, Zhang X, Brown LG, Coleman IM, Lakely B, Tenniswood M, Corey E, Nelson PS, Vessella RL, Morrissey C. Prostate cancer derived prostatic acid phosphatase promotes an osteoblastic response in the bone microenvironment. Clin Exp Metastasis 2013; 31:247-56. [PMID: 24242705 DOI: 10.1007/s10585-013-9625-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 11/11/2013] [Indexed: 01/17/2023]
Abstract
Approximately 90 % of patients who die of prostate cancer (PCa) have bone metastases, often promoting osteoblastic lesions. We observed that 88 % of castration-resistant PCa (CRPC) bone metastases express prostatic acid phosphatase (PAP), a soluble secreted protein expressed by prostate epithelial cells in predominately osteoblastic (n = 18) or osteolytic (n = 15) lesions. Additionally, conditioned media (CM) of an osteoblastic PCa xenograft LuCaP 23.1 contained significant levels of PAP and promoted mineralization in mouse and human calvaria-derived cells (MC3T3-E1 and HCO). To demonstrate that PAP promotes mineralization, we stimulated MC3T3-E1 cells with PAP and observed increased mineralization, which could be blocked with the specific PAP inhibitor, phosphonic acid. Furthermore, the mineralization promoted by LuCaP 23.1 CM was also blocked by phosphonic acid, suggesting PAP is responsible for the mineralization promoting activity of LuCaP 23.1. In addition, gene expression arrays comparing osteoblastic to osteolytic CRPC (n = 14) identified betacellulin (BTC) as a gene upregulated during the osteoblastic response in osteoblasts during new bone formation. Moreover, BTC levels were increased in bone marrow stromal cells in response to LuCaP 23.1 CM in vitro. Because new bone formation does occur in osteoblastic and can occur in osteolytic CRPC bone metastases, we confirmed by immunohistochemistry (n = 36) that BTC was highly expressed in osteoblasts involved in new bone formation occurring in both osteoblastic and osteolytic sites. These studies suggest a role for PAP in promoting the osteoblastic reaction in CRPC bone metastases and identify BTC as a novel downstream protein expressed in osteoblasts during new bone formation.
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Affiliation(s)
- Sandy R Larson
- Genitourinary Cancer Research Laboratory, Department of Urology, University of Washington, Box 356510, Seattle, WA, 98195, USA
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