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Abstract
The present review acknowledges the tremendous impact of Stephan Perren's strain theory, considered with respect to the earlier contributions of Roux and Pauwels. Then, it provides further insight by examining how the concept of reverse dynamisation extended Perren's theory within a modern context. A key factor of this more contemporary theory is that it introduces variable mechanical conditions at different time points during bone healing, opening the possibility of manipulating biology through mechanics to achieve the desired clinical outcome. The discussion focusses on the current state of the art and the most recent advances made towards optimising and accelerating bone regeneration, by actively controlling the mechanical environment as healing progresses. Reverse dynamisation utilises a very specific mechanical manipulation regimen, with conditions initially flexible to encourage and expedite early callus formation. Once callus has formed, the mechanical conditions are intentionally modified to create a rigid environment under which the soft callus is quickly converted to hard callus, bridging the fracture site and leading to a more rapid union. The relevant literature, principally animal studies, was surveyed to provide ample evidence in support of the effectiveness of reverse dynamisation. By providing a modern perspective on Stephan Perren's strain theory, reverse dynamisation perhaps holds the key to tipping the balance in favour of a more rapid and reliable union when treating acute fractures, osteotomies, non-unions and other circumstances where it is necessary to regenerate bone.
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Affiliation(s)
- V Glatt
- Department of Orthopedic Surgery, University of Texas Health Science Centre San Antonio, 7703 Floyd Curl Drive, MC 7774, San Antonio, TX 78229-3900,
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Liu TY, Bartnikowski M, Wu AC, Veitch M, Sokolowski KA, Millard SM, Pettit AR, Glatt V, Evans CH, Wells JW. Healing of sub-critical femoral osteotomies in mice is unaffected by tacrolimus and deletion of recombination activating gene 1. Eur Cell Mater 2021; 41:345-354. [PMID: 33729540 DOI: 10.22203/ecm.v041a22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Clinical management of delayed healing or non-union of long bone fractures and segmental defects poses a substantial orthopaedic challenge. There are suggestions in the literature that bone healing may be enhanced by inhibiting the activities of T and B lymphocytes, but this remains controversial. To examine this matter in more detail, sub-critical-sized segmental defects were created in the femora of mice and it was assessed whether there might be a benefit from the administration of a Food and Drug Administration (FDA)-approved drug that blocks T cell activation (tacrolimus). Defects were stabilised using an internal plate. In certain groups of animals, 1 mg/kg or 10 mg/kg tacrolimus was delivered locally to the defect site for 3 or 7 d using an implanted osmotic pump with a silicon catheter directing drug delivery into the defect area. Healing was monitored by weekly X-ray and assessed at 12 weeks by mechanical testing, µCT and histology. Radiographic and histological evaluations revealed that 100 % of defects healed well regardless of tacrolimus dosage or duration. A comparison of healed C57BL/6 and Rag1-/- femora by µCT and ex vivo torsion testing showed no differences within mouse strains in terms of bone volume, tissue volume, bone volume/tissue volume ratio, shear modulus, torsional rigidity or torsional stiffness. These data failed to support an important role for tacrolimus in modulating the natural healing of segmental defects under those experimental conditions.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - J W Wells
- The University of Queensland Diamantina Institute, 37 Kent Street, Woolloongabba, QLD 4102,
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Muderis MA, Tetsworth K, Khemka A, Wilmot S, Bosley B, Lord SJ, Glatt V. The Osseointegration Group of Australia Accelerated Protocol (OGAAP-1) for two-stage osseointegrated reconstruction of amputated limbs. Bone Joint J 2017; 98-B:952-60. [PMID: 27365474 DOI: 10.1302/0301-620x.98b7.37547] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [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: 11/11/2015] [Accepted: 02/15/2016] [Indexed: 11/05/2022]
Abstract
AIMS This study describes the Osseointegration Group of Australia's Accelerated Protocol two-stage strategy (OGAAP-1) for the osseointegrated reconstruction of amputated limbs. PATIENTS AND METHODS We report clinical outcomes in 50 unilateral trans-femoral amputees with a mean age of 49.4 years (24 to 73), with a minimum one-year follow-up. Outcome measures included the Questionnaire for persons with a Trans-Femoral Amputation, the health assessment questionnaire Short-Form-36 Health Survey, the Amputation Mobility Predictor scores presented as K-levels, 6 Minute Walk Test and timed up and go tests. Adverse events included soft-tissue problems, infection, fractures and failure of the implant. RESULTS Our results demonstrated statistically significant improvements in all five outcome measures. A total of 27 patients experienced adverse events but at the conclusion of the study, all 50 were walking on osseointegrated prostheses. CONCLUSION These results demonstrate that osseointegrated prostheses are a suitable alternative to socket-fit devices for amputees experiencing socket-related discomfort and that our strategy offers more rapid progress to walking than other similar protocols. Cite this article: Bone Joint J 2016;98-B:952-60.
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Affiliation(s)
- M Al Muderis
- The Australian School of Advanced Medicine, Macquarie University, Suite 303 Level 3, 2 Technology Place, North Ryde, NSW, 2109, Australia
| | - K Tetsworth
- Royal Brisbane Hospital, Level 7, Ned Hanlon Building Butterfield Street, Herston, Brisbane, QLD, 4029, Australia
| | - A Khemka
- University of Notre Dame Australia, 160 Oxford Street, Sydney, NSW, 2010, Australia
| | - S Wilmot
- Norwest Private Hospital, Suite G3, 9 Norbrik Drive, Bella Vista, NSW, 2153, Australia
| | - B Bosley
- Norwest Private Hospital, Suite G3, 9 Norbrik Drive, Bella Vista, NSW, 2153, Australia
| | - S J Lord
- University of Notre Dame Australia, 160 Oxford Street, Sydney, NSW, 2010, Australia
| | - V Glatt
- Institute of Health and Biomedical Innovation at Queensland University of Technology, 60 Musk Avenue, Kevin Grove, Brisbane, 4059, Australia
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Hohmann E, Glatt V, Tetsworth K. Orthopaedic research activity in South Africa measured by publication rates in the 15 highest impact journals related to population size and gross domestic product. SA orthop j 2016. [DOI: 10.17159/2309-8309/2016/v15n4a3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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Liu F, Ferreira E, Porter R, Glatt V, Schinhan M, Shen Z, Randolph M, Kirker-Head C, Wehling C, Vrahas M, Evans C, Wells J, Wells JW. Rapid and reliable healing of critical size bone defects with genetically modified sheep muscle. Eur Cell Mater 2015; 30:118-30; discussion 130-1. [PMID: 26388615 PMCID: PMC4625846 DOI: 10.22203/ecm.v030a09] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [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] [Indexed: 01/31/2023] Open
Abstract
Large segmental defects in bone fail to heal and remain a clinical problem. Muscle is highly osteogenic, and preliminary data suggest that autologous muscle tissue expressing bone morphogenetic protein-2 (BMP-2) efficiently heals critical size defects in rats. Translation into possible human clinical trials requires, inter alia, demonstration of efficacy in a large animal, such as the sheep. Scale-up is fraught with numerous biological, anatomical, mechanical and structural variables, which cannot be addressed systematically because of cost and other practical issues. For this reason, we developed a translational model enabling us to isolate the biological question of whether sheep muscle, transduced with adenovirus expressing BMP-2, could heal critical size defects in vivo. Initial experiments in athymic rats noted strong healing in only about one-third of animals because of unexpected immune responses to sheep antigens. For this reason, subsequent experiments were performed with Fischer rats under transient immunosuppression. Such experiments confirmed remarkably rapid and reliable healing of the defects in all rats, with bridging by 2 weeks and remodelling as early as 3-4 weeks, despite BMP-2 production only in nanogram quantities and persisting for only 1-3 weeks. By 8 weeks the healed defects contained well-organised new bone with advanced neo-cortication and abundant marrow. Bone mineral content and mechanical strength were close to normal values. These data demonstrate the utility of this model when adapting this technology for bone healing in sheep, as a prelude to human clinical trials.
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Affiliation(s)
- F. Liu
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
| | - E. Ferreira
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
| | - R.M. Porter
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
| | - V. Glatt
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
| | - M. Schinhan
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Department of Orthopaedic Surgery, University of Vienna Medical School, Vienna, Austria
| | - Z. Shen
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
| | - M.A. Randolph
- Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - C.A. Kirker-Head
- Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA, USA
| | - C. Wehling
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Ludwig Maximilan University Medical School, Munich, Germany
| | - M.S. Vrahas
- Collaborative Research Centre: AO Foundation, Davos, Switzerland
,Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - C.H. Evans
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
,Address for correspondence: Dr Chris Evans, Rehabilitation Medicine Research Center, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA, Telephone Number: 1-507-255-0099,
| | - J.W. Wells
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
,Collaborative Research Centre: AO Foundation, Davos, Switzerland
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Glatt V, Evans CH, Matthys R. Design, characterisation and in vivo testing of a new, adjustable stiffness, external fixator for the rat femur. Eur Cell Mater 2012; 23:289-98; discussion 299. [PMID: 22522283 DOI: 10.22203/ecm.v023a22] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Very little is known about the influence of the mechanical environment on the healing of large segmental defects. This partly reflects the lack of standardised, well characterised technologies to enable such studies. Here we report the design, construction and characterisation of a novel external fixator for use in conjunction with rat femoral defects. This device not only imposes a predetermined axial stiffness on the lesion, but also enables the stiffness to be changed during the healing process. The main frame of the fixator consists of polyethylethylketone with titanium alloy mounting pins. The stiffness of the fixator is determined by interchangeable connection elements of different thicknesses. Fixators were shown to stabilise 5 mm femoral defects in rats in vivo for at least 8 weeks during unrestricted cage activity. No distortion or infections, including pin infections, were noted. The healing process was simulated in vitro by inserting into a 5 mm femoral defect, materials whose Young's moduli approximated those of the different tissues present in regenerating bone. These studies confirmed that, although the external fixator is the major determinant of axial stiffness during the early phase of healing, the regenerate within the lesion subsequently dominates this property. There is much clinical interest in altering the mechanics of the defect to enhance bone healing. Our data suggest that, if alteration of the mechanical environment is to be used to modulate the healing of large segmental defects, this needs to be performed before the tissue properties become dominant.
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Affiliation(s)
- V Glatt
- Center for Advanced Orthopaedic Studies, Harvard Medical School, Boston, MA,
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Wulsten D, Glatt V, Ellinghaus A, Schmidt-Bleek K, Petersen A, Schell H, Lienau J, Sebald W, Plöger F, Seemann P, Duda GN, Duda GN. Time kinetics of bone defect healing in response to BMP-2 and GDF-5 characterised by in vivo biomechanics. Eur Cell Mater 2011; 21:177-92. [PMID: 21312163 DOI: 10.22203/ecm.v021a14] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
This study reports that treatment of osseous defects with different growth factors initiates distinct rates of repair. We developed a new method for monitoring the progression of repair, based upon measuring the in vivo mechanical properties of healing bone. Two different members of the bone morphogenetic protein (BMP) family were chosen to initiate defect healing: BMP-2 to induce osteogenesis, and growth-and-differentiation factor (GDF)-5 to induce chondrogenesis. To evaluate bone healing, BMPs were implanted into stabilised 5 mm bone defects in rat femurs and compared to controls. During the first two weeks, in vivo biomechanical measurements showed similar values regardless of the treatment used. However, 2 weeks after surgery, the rhBMP-2 group had a substantial increase in stiffness, which was supported by the imaging modalities. Although the rhGDF-5 group showed comparable mechanical properties at 6 weeks as the rhBMP-2 group, the temporal development of regenerating tissues appeared different with rhGDF-5, resulting in a smaller callus and delayed tissue mineralisation. Moreover, histology showed the presence of cartilage in the rhGDF-5 group whereas the rhBMP-2 group had no cartilaginous tissue. Therefore, this study shows that rhBMP-2 and rhGDF-5 treated defects, under the same conditions, use distinct rates of bone healing as shown by the tissue mechanical properties. Furthermore, results showed that in vivo biomechanical method is capable of detecting differences in healing rate by means of change in callus stiffness due to tissue mineralisation.
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Affiliation(s)
- D Wulsten
- Julius Wolff Institute and Center for Musculoskeletal Surgery, Berlin-Brandenburg Center for Regenerative Therapies, Charité- Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin, Germany
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Evans C, Liu FJ, Glatt V, Hoyland J, Kirker-Head C, Walsh A, Betz O, Wells J, Betz V, Porter R, Saad F, Gerstenfeld L, Einhorn T, Harris M, Vrahas M. Use of genetically modified muscle and fat grafts to repair defects in bone and cartilage. Eur Cell Mater 2009; 18:96-111. [PMID: 20073015 PMCID: PMC4382019 DOI: 10.22203/ecm.v018a09] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [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] [Indexed: 01/31/2023] Open
Abstract
We report a novel technology for the rapid healing of large osseous and chondral defects, based upon the genetic modification of autologous skeletal muscle and fat grafts. These tissues were selected because they not only possess mesenchymal progenitor cells and scaffolding properties, but also can be biopsied, genetically modified and returned to the patient in a single operative session. First generation adenovirus vector carrying cDNA encoding human bone morphogenetic protein-2 (Ad.BMP-2) was used for gene transfer to biopsies of muscle and fat. To assess bone healing, the genetically modified ("gene activated") tissues were implanted into 5mm-long critical size, mid-diaphyseal, stabilized defects in the femora of Fischer rats. Unlike control defects, those receiving gene-activated muscle underwent rapid healing, with evidence of radiologic bridging as early as 10 days after implantation and restoration of full mechanical strength by 8 weeks. Histologic analysis suggests that the grafts rapidly differentiated into cartilage, followed by efficient endochondral ossification. Fluorescence in situ hybridization detection of Y-chromosomes following the transfer of male donor muscle into female rats demonstrated that at least some of the osteoblasts of the healed bone were derived from donor muscle. Gene activated fat also healed critical sized defects, but less quickly than muscle and with more variability. Anti-adenovirus antibodies were not detected. Pilot studies in a rabbit osteochondral defect model demonstrated the promise of this technology for healing cartilage defects. Further development of these methods should provide ways to heal bone and cartilage more expeditiously, and at lower cost, than is presently possible.
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Affiliation(s)
- C.H. Evans
- Center for Molecular Orthopaedics, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA,Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA,Collaborative Research Center, AO Foundation,Address for correspondence Chris Evans, Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, 330, Brookline Avenue RN-115, Boston MA 02215, USA, Telephone Number: +1 617-667-4621, FAX Number: +1 617-667-7175,
| | - F.-J. Liu
- Center for Molecular Orthopaedics, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA,Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - V. Glatt
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - J.A. Hoyland
- Tissue Injury and Repair Research Group, University of Manchester, Manchester, UK
| | - C. Kirker-Head
- Orthopaedic Research Laboratory, Tufts Cummings School of Veterinary Medicine, Grafton, MA, USA
| | - A. Walsh
- Orthopaedic Research Laboratory, Tufts Cummings School of Veterinary Medicine, Grafton, MA, USA
| | - O. Betz
- Center for Molecular Orthopaedics, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - J.W. Wells
- Center for Molecular Orthopaedics, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA,Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - V. Betz
- Center for Molecular Orthopaedics, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA,Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA, USA
| | - R.M. Porter
- Center for Molecular Orthopaedics, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA,Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - F.A. Saad
- Department of Orthopaedic Surgery, Children’s Hospital, Boston, MA, USA
| | - L.C. Gerstenfeld
- Department of Orthopedic Surgery, Boston University Medical Center, Boston, MA, USA
| | - T.A. Einhorn
- Department of Orthopedic Surgery, Boston University Medical Center, Boston, MA, USA
| | - M.B. Harris
- Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Boston, MA, USA
| | - M.S. Vrahas
- Collaborative Research Center, AO Foundation,Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA, USA
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Bouxsein ML, Devlin MJ, Glatt V, Dhillon H, Pierroz DD, Ferrari SL. Mice lacking beta-adrenergic receptors have increased bone mass but are not protected from deleterious skeletal effects of ovariectomy. Endocrinology 2009; 150:144-52. [PMID: 18801900 PMCID: PMC2630907 DOI: 10.1210/en.2008-0843] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Activation of beta2-adrenergic receptors inhibits osteoblastic bone formation and enhances osteoclastic bone resorption. Whether beta-blockers inhibit ovariectomy-induced bone loss and decrease fracture risk remains controversial. To further explore the role of beta-adrenergic signaling in skeletal acquisition and response to estrogen deficiency, we evaluated mice lacking the three known beta-adrenergic receptors (beta-less). Body weight, percent fat, and bone mineral density were significantly higher in male beta-less than wild-type (WT) mice, more so with increasing age. Consistent with their greater fat mass, serum leptin was significantly higher in beta-less than WT mice. Mid-femoral cross-sectional area and cortical thickness were significantly higher in adult beta-less than WT mice, as were femoral biomechanical properties (+28 to +49%, P < 0.01). Young male beta-less had higher vertebral (1.3-fold) and distal femoral (3.5-fold) trabecular bone volume than WT (P < 0.001 for both) and lower osteoclast surface. With aging, these differences lessened, with histological evidence of increased osteoclast surface and decreased bone formation rate at the distal femur in beta-less vs. WT mice. Serum tartrate-resistance alkaline phosphatase-5B was elevated in beta-less compared with WT mice from 8-16 wk of age (P < 0.01). Ovariectomy inhibited bone mass gain and decreased trabecular bone volume/total volume similarly in beta-less and WT mice. Altogether, these data indicate that absence of beta-adrenergic signaling results in obesity and increased cortical bone mass in males but does not prevent deleterious effects of estrogen deficiency on trabecular bone microarchitecture. Our findings also suggest direct positive effects of weight and/or leptin on bone turnover and cortical bone structure, independent of adrenergic signaling.
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Affiliation(s)
- M L Bouxsein
- Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, Massachusetts 02215, USA.
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Ferrari SL, Pierroz DD, Glatt V, Goddard DS, Bianchi EN, Lin FT, Manen D, Bouxsein ML. Bone response to intermittent parathyroid hormone is altered in mice null for {beta}-Arrestin2. Endocrinology 2005; 146:1854-62. [PMID: 15705780 DOI: 10.1210/en.2004-1282] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Intermittent PTH administration increases bone turnover, resulting in net anabolic effects on bone. These effects are primarily mediated by intracellular cAMP signaling. However, the molecular mechanisms that regulate PTH activity in bone remain incompletely understood. beta-Arrestin2, a G protein-coupled receptor regulatory protein, inhibits PTH-stimulated cAMP accumulation in vitro. Using beta-arrestin2(-/-) (KO) and wild-type (WT) mice, we investigated the response to PTH in primary osteoblasts (POB) and the effects of intermittent PTH administration on bone mass and microarchitecture in vivo. Compared with that in WT mice, PTH-stimulated intracellular cAMP was increased and sustained in KO POB. Intermittent exposure of POB to PTH significantly decreased the ratio of osteoprotegerin (OPG) receptor activator of nuclear factor-kappaB ligand (RANKL) mRNA expression in KO POB, whereas it increased this ratio in WT POB. Total body bone mass and cortical and trabecular bone parameters were 5-10% lower in male KO mice compared with WT, and these differences were magnified upon in vivo administration of intermittent PTH (80 mug/kg.d) for 1 month. Thus, PTH significantly increased total body bone mineral content as well as vertebral trabecular bone volume and thickness in WT, but not KO mice. The anabolic response to PTH in cortical bone was also slightly more pronounced in WT than KO mice. Histomorphometry indicated that PTH prominently stimulated indexes of bone formation in both WT and KO mice, whereas it significantly increased indexes of bone resorption (i.e. osteoclast number and surface) in KO mice only. In conclusion, these results suggest that beta-arrestins may specify the activity of intermittent PTH on the skeleton by limiting PTH-induced osteoclastogenesis.
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Affiliation(s)
- S L Ferrari
- Service of Bone Diseases, World Health Organization Collaborating Center for Osteoporosis Prevention, Department of Rehabilitation and Geriatrics, Geneva University Hospital, 1211 Geneva 14, Switzerland.
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