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Lewis KJ, Cabahug-Zuckerman P, Boorman-Padgett JF, Basta-Pljakic J, Louie J, Stephen S, Spray DC, Thi MM, Seref-Ferlengez Z, Majeska RJ, Weinbaum S, Schaffler MB. Estrogen depletion on In vivo osteocyte calcium signaling responses to mechanical loading. Bone 2021; 152:116072. [PMID: 34171514 PMCID: PMC8316427 DOI: 10.1016/j.bone.2021.116072] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [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: 02/19/2021] [Revised: 06/15/2021] [Accepted: 06/20/2021] [Indexed: 11/27/2022]
Abstract
Microstructural adaptation of bone in response to mechanical stimuli is diminished with estrogen deprivation. Here we tested in vivo whether ovariectomy (OVX) alters the acute response of osteocytes, the principal mechanosensory cells of bone, to mechanical loading in mice. We also used super resolution microscopy (Structured Illumination microscopy or SIM) in conjunction with immunohistochemistry to assess changes in the number and organization of "osteocyte mechanosomes" - complexes of Panx1 channels, P2X7 receptors and CaV3 voltage-gated Ca2+ channels clustered around αvβ3 integrin foci on osteocyte processes. Third metatarsals bones of mice expressing an osteocyte-targeted genetically encoded Ca2+ indicator (DMP1-GCaMP3) were cyclically loaded in vivo to strains from 250 to 3000 με and osteocyte intracellular Ca2+ signaling responses were assessed in mid-diaphyses using multiphoton microscopy. The number of Ca2+ signaling osteocytes in control mice increase monotonically with applied strain magnitude for the physiological range of strains. The relationship between the number of Ca2+ signaling osteocytes and loading was unchanged at 2 days post-OVX. However, it was altered markedly at 28 days post-OVX. At loads up to 1000 με, there was a dramatic reduction in number of responding (i.e. Ca2+ signaling) osteocytes; however, at higher strains the numbers of Ca2+ signaling osteocytes were similar to control mice. OVX significantly altered the abundance, make-up and organization of osteocyte mechanosome complexes on dendritic processes. Numbers of αvβ3 foci also staining with either Panx 1, P2X7R or CaV3 declined by nearly half after OVX, pointing to a loss of osteocyte mechanosomes on the dendritic processes with estrogen depletion. At the same time, the areas of the remaining foci that stained for αvβ3 and channel proteins increased significantly, a redistribution of mechanosome components suggesting a potential compensatory response. These results demonstrate that the deleterious effects of estrogen depletion on skeletal mechanical adaptation appear at the level of mechanosensation; osteocytes lose the ability to sense small (physiological) mechanical stimuli. This decline may result at least partly from changes in the structure and organization of osteocyte mechanosomes, which contribute to the distinctive sensitivity of osteocytes (particularly their dendritic processes) to mechanical stimulation.
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Affiliation(s)
- Karl J Lewis
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Pamela Cabahug-Zuckerman
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - James F Boorman-Padgett
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Jelena Basta-Pljakic
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Joyce Louie
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Samuel Stephen
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Mia M Thi
- Orthopaedic Surgery, Albert Einstein College of Medicine, Bronx, NY, United States of America; Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Zeynep Seref-Ferlengez
- Orthopaedic Surgery, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Robert J Majeska
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Sheldon Weinbaum
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Mitchell B Schaffler
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America.
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Cabahug-Zuckerman P, Liu C, Cai C, Mahaffey I, Norman SC, Cole W, Castillo AB. Site-Specific Load-Induced Expansion of Sca-1 +Prrx1 + and Sca-1 -Prrx1 + Cells in Adult Mouse Long Bone Is Attenuated With Age. JBMR Plus 2019; 3:e10199. [PMID: 31667455 PMCID: PMC6808224 DOI: 10.1002/jbm4.10199] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [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: 11/15/2018] [Revised: 04/22/2019] [Accepted: 04/23/2019] [Indexed: 02/04/2023] Open
Abstract
Aging is associated with significant bone loss and increased fracture risk, which has been attributed to a diminished response to anabolic mechanical loading. In adults, skeletal progenitors proliferate and differentiate into bone‐forming osteoblasts in response to increasing mechanical stimuli, though the effects of aging on this response are not well‐understood. Here we show that both adult and aged mice exhibit load‐induced periosteal bone formation, though the response is significantly attenuated with age. We also show that the acute response of adult bone to loading involves expansion of Sca‐1+Prrx1+ and Sca‐1−Prrx1+ cells in the periosteum. On the endosteal surface, loading enhances proliferation of both these cell populations, though the response is delayed by 2 days relative to the periosteal surface. In contrast to the periosteum and endosteum, the marrow does not exhibit increased proliferation of Sca‐1+Prrx1+ cells, but only of Sca‐1−Prrx1+ cells, underscoring fundamental differences in how the stem cell niche in distinct bone envelopes respond to mechanical stimuli. Notably, the proliferative response to loading is absent in aged bone even though there are similar baseline numbers of Prrx1 + cells in the periosteum and endosteum, suggesting that the proliferative capacity of progenitors is attenuated with age, and proliferation of the Sca‐1+Prrx1+ population is critical for load‐induced periosteal bone formation. These findings provide a basis for the development of novel therapeutics targeting these cell populations to enhance osteogenesis for overcoming age‐related bone loss. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Pamela Cabahug-Zuckerman
- Department of Orthopaedic Surgery NYU Langone Health, New York University New York NY USA.,Department of Biomedical Engineering Tandon School of Engineering, New York University New York NY USA.,Rehabilitation Research and Development Veterans Affairs New York Harbor Healthcare System New York NY USA
| | - Chao Liu
- Department of Orthopaedic Surgery NYU Langone Health, New York University New York NY USA.,Department of Biomedical Engineering Tandon School of Engineering, New York University New York NY USA.,Rehabilitation Research and Development Veterans Affairs New York Harbor Healthcare System New York NY USA
| | - Cinyee Cai
- Department of Orthopaedic Surgery NYU Langone Health, New York University New York NY USA.,Department of Biomedical Engineering Tandon School of Engineering, New York University New York NY USA
| | - Ian Mahaffey
- Rehabilitation Research and Development Veterans Affairs Palo Alto Healthcare System Palo Alto CA USA
| | - Stephanie C Norman
- Rehabilitation Research and Development Veterans Affairs Palo Alto Healthcare System Palo Alto CA USA
| | - Whitney Cole
- Rehabilitation Research and Development Veterans Affairs Palo Alto Healthcare System Palo Alto CA USA
| | - Alesha B Castillo
- Department of Orthopaedic Surgery NYU Langone Health, New York University New York NY USA.,Department of Biomedical Engineering Tandon School of Engineering, New York University New York NY USA.,Rehabilitation Research and Development Veterans Affairs New York Harbor Healthcare System New York NY USA
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Liu C, Cabahug-Zuckerman P, Stubbs C, Pendola M, Cai C, Mann KA, Castillo AB. Mechanical Loading Promotes the Expansion of Primitive Osteoprogenitors and Organizes Matrix and Vascular Morphology in Long Bone Defects. J Bone Miner Res 2019; 34:896-910. [PMID: 30645780 PMCID: PMC8263903 DOI: 10.1002/jbmr.3668] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [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: 05/03/2018] [Revised: 12/17/2018] [Accepted: 01/07/2019] [Indexed: 12/18/2022]
Abstract
Elucidating the effects of mechanical stimulation on bone repair is crucial for optimization of the healing process. Specifically, the regulatory role that mechanical loading exerts on the osteogenic stem cell pool and vascular morphology during healing is incompletely understood. Because dynamic loading has been shown to enhance osteogenesis and repair, we hypothesized that loading induces the expansion of the osteoprogenitor cell population within a healing bone defect, leading to an increased presence of osteogenic cells. We further hypothesized that loading during the repair process regulates vascular and collagen matrix morphology and spatial interactions between vessels and osteogenic cells. To address these hypotheses, we used a mechanobiological bone repair model, which produces a consistent and reproducible intramembranous repair response confined in time and space. Bilateral tibial defects were created in adult C57BL/6 mice, which were subjected to axial compressive dynamic loading either during the early cellular invasion phase on postsurgical days (PSDs) 2 to 5 or during the matrix deposition phase on PSD 5 to 8. Confocal and two-photon microscopy was used to generate high-resolution three-dimensional (3D) renderings of longitudinal thick sections of the defect on PSD 10. Endomucin (EMCN)-positive vessels, Paired related homeobox 1 (Prrx1+) stem cell antigen-1 positive (Sca-1+) primitive osteoprogenitors (OPCs), and osterix positive (Osx+) preosteoblasts were visualized and quantified using deep tissue immunohistochemistry. New bone matrix was visualized with second harmonic generation autofluorescence of collagen fibers. We found that mechanical loading during the matrix deposition phase (PSD 5 to 8) increased vessel volume and number, and aligned vessels and collagen fibers to the load-bearing direction of bone. Furthermore, loading led to a significant increase in the proliferation and number of Prrx1+ Sca-1+ primitive OPCs, but not Osx+ preosteoblasts within the defect. Together, these data illustrate the adaptation of both collagen matrix and vascular morphology to better withstand mechanical load during bone repair, and that the mechanoresponsive cell population consists of the primitive osteogenic progenitors. © 2019 American Society for Bone and Mineral Research.
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Affiliation(s)
- Chao Liu
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, NY, USA.,Department of Orthopedic Surgery, School of Medicine, New York University, New York, NY, USA.,Veterans Affairs New York Harbor Healthcare System, New York, NY, USA
| | - Pamela Cabahug-Zuckerman
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, NY, USA.,Department of Orthopedic Surgery, School of Medicine, New York University, New York, NY, USA
| | - Christopher Stubbs
- Department of Mechanical Engineering, New York University, New York, NY, USA
| | - Martin Pendola
- Department of Orthopedic Surgery, School of Medicine, New York University, New York, NY, USA
| | - Cinyee Cai
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, NY, USA
| | - Kenneth A Mann
- Department of Orthopedic Surgery, Upstate Medical University, New York, NY, USA
| | - Alesha B Castillo
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, NY, USA.,Department of Orthopedic Surgery, School of Medicine, New York University, New York, NY, USA.,Veterans Affairs New York Harbor Healthcare System, New York, NY, USA
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Liu C, Carrera R, Flamini V, Kenny L, Cabahug-Zuckerman P, George BM, Hunter D, Liu B, Singh G, Leucht P, Mann KA, Helms JA, Castillo AB. Effects of mechanical loading on cortical defect repair using a novel mechanobiological model of bone healing. Bone 2018; 108:145-155. [PMID: 29305998 PMCID: PMC8262576 DOI: 10.1016/j.bone.2017.12.027] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [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: 04/20/2015] [Revised: 12/20/2017] [Accepted: 12/29/2017] [Indexed: 12/30/2022]
Abstract
Mechanical loading is an important aspect of post-surgical fracture care. The timing of load application relative to the injury event may differentially regulate repair depending on the stage of healing. Here, we used a novel mechanobiological model of cortical defect repair that offers several advantages including its technical simplicity and spatially confined repair program, making effects of both physical and biological interventions more easily assessed. Using this model, we showed that daily loading (5N peak load, 2Hz, 60 cycles, 4 consecutive days) during hematoma consolidation and inflammation disrupted the injury site and activated cartilage formation on the periosteal surface adjacent to the defect. We also showed that daily loading during the matrix deposition phase enhanced both bone and cartilage formation at the defect site, while loading during the remodeling phase resulted in an enlarged woven bone regenerate. All loading regimens resulted in abundant cellular proliferation throughout the regenerate and fibrous tissue formation directly above the defect demonstrating that all phases of cortical defect healing are sensitive to physical stimulation. Stress was concentrated at the edges of the defect during exogenous loading, and finite element (FE)-modeled longitudinal strain (εzz) values along the anterior and posterior borders of the defect (~2200με) was an order of magnitude larger than strain values on the proximal and distal borders (~50-100με). It is concluded that loading during the early stages of repair may impede stabilization of the injury site important for early bone matrix deposition, whereas loading while matrix deposition and remodeling are ongoing may enhance stabilization through the formation of additional cartilage and bone.
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Affiliation(s)
- Chao Liu
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, USA; Department of Orthopaedic Surgery, New York University Langone Health, NYU Langone Orthopedic Hospital, NY, USA; Department of Veterans Affairs New York Harbor Healthcare System, New York, NY, USA
| | - Robert Carrera
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Vittoria Flamini
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, USA
| | - Lena Kenny
- Department of Orthopaedic Surgery, New York University Langone Health, NYU Langone Orthopedic Hospital, NY, USA
| | - Pamela Cabahug-Zuckerman
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, USA; Department of Orthopaedic Surgery, New York University Langone Health, NYU Langone Orthopedic Hospital, NY, USA; Department of Veterans Affairs New York Harbor Healthcare System, New York, NY, USA
| | - Benson M George
- Department of Surgery, Division of Plastic Surgery, Stanford University, Stanford, CA, USA
| | - Daniel Hunter
- Department of Surgery, Division of Plastic Surgery, Stanford University, Stanford, CA, USA
| | - Bo Liu
- Department of Surgery, Division of Plastic Surgery, Stanford University, Stanford, CA, USA
| | - Gurpreet Singh
- Department of Surgery, Division of Plastic Surgery, Stanford University, Stanford, CA, USA
| | - Philipp Leucht
- Department of Orthopaedic Surgery, New York University Langone Health, NYU Langone Orthopedic Hospital, NY, USA; Department of Cell Biology, New York University, New York, NY, USA
| | - Kenneth A Mann
- Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Jill A Helms
- Department of Surgery, Division of Plastic Surgery, Stanford University, Stanford, CA, USA
| | - Alesha B Castillo
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, USA; Department of Orthopaedic Surgery, New York University Langone Health, NYU Langone Orthopedic Hospital, NY, USA; Department of Veterans Affairs New York Harbor Healthcare System, New York, NY, USA.
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Cabahug-Zuckerman P, Stout RF, Majeska RJ, Thi MM, Spray DC, Weinbaum S, Schaffler MB. Potential role for a specialized β 3 integrin-based structure on osteocyte processes in bone mechanosensation. J Orthop Res 2018; 36:642-652. [PMID: 29087614 PMCID: PMC5839970 DOI: 10.1002/jor.23792] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [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: 05/31/2017] [Accepted: 10/21/2017] [Indexed: 02/04/2023]
Abstract
Osteocyte processes are an order of magnitude more sensitive to mechanical loading than their cell bodies. The mechanisms underlying this remarkable mechanosensitivity are not clear, but may be related to the infrequent αV β3 integrin sites where the osteocyte cell processes attach to canalicular walls. These sites develop dramatically elevated strains during load-induced fluid flow in the lacunar-canalicular system and were recently shown to be primary sites for osteocyte-like MLO-Y4 cell mechanotransduction. These αV β3 integrin sites lack typical integrin transduction mechanisms. Rather, stimulation at these sites alters Ca2+ signaling, ATP release and membrane potential. In the current studies, we tested the hypothesis that in authentic osteocytes in situ, key membrane proteins implicated in osteocyte mechanotransduction are preferentially localized at or near to β3 integrin-foci. We analyzed these spatial relationships in mouse bone osteocytes using immunohistochemistry combined with Structured Illumination Super Resolution Microscopy, a method that permits structural resolution at near electron microscopy levels in tissue sections. We discovered that the purinergic channel pannexin1, the ATP-gated purinergic receptor P2 × 7R and the low voltage transiently opened T-type calcium channel CaV3.2-1 all reside in close proximity to β3 integrin attachment foci on osteocyte processes, suggesting a specialized mechanotransduction complex at these sites. We further confirmed this observation on isolated osteocytes in culture using STochasitc Optical Resonance Microscopy. These findings identify a possible structural basis for the unique mechanosensation and transduction capabilities of the osteocyte process. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:642-652, 2018.
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Affiliation(s)
| | - Randy F. Stout
- Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine
- Department of Neuroscience, Albert Einstein College of Medicine
| | | | - Mia M. Thi
- Department of Orthopaedic Surgery, Albert Einstein College of Medicine
| | - David C. Spray
- Department of Neuroscience, Albert Einstein College of Medicine
| | - Sheldon Weinbaum
- Department of Biomedical Engineering, The City College of New York
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Cabahug-Zuckerman P, Frikha-Benayed D, Majeska RJ, Tuthill A, Yakar S, Judex S, Schaffler MB. Osteocyte Apoptosis Caused by Hindlimb Unloading is Required to Trigger Osteocyte RANKL Production and Subsequent Resorption of Cortical and Trabecular Bone in Mice Femurs. J Bone Miner Res 2016; 31:1356-65. [PMID: 26852281 PMCID: PMC5488280 DOI: 10.1002/jbmr.2807] [Citation(s) in RCA: 119] [Impact Index Per Article: 14.9] [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] [Received: 09/11/2015] [Revised: 02/02/2016] [Accepted: 02/04/2016] [Indexed: 12/20/2022]
Abstract
Osteocyte apoptosis is essential to activate bone remodeling in response to fatigue microdamage and estrogen withdrawal, such that apoptosis inhibition in vivo prevents the onset of osteoclastic resorption. Osteocyte apoptosis has also been spatially linked to bone resorption owing to disuse, but whether apoptosis plays a similar controlling role is unclear. We, therefore, 1) evaluated the spatial and temporal effects of disuse from hindlimb unloading (HLU) on osteocyte apoptosis, receptor activator of NF-κB ligand (RANKL) expression, bone resorption, and loss in mouse femora, and 2) tested whether osteocyte apoptosis was required to activate osteoclastic activity in cortical and trabecular bone by treating animals subjected to HLU with the pan-caspase apoptosis inhibitor, QVD (quinolyl-valyl-O-methylaspartyl-[-2,6-difluorophenoxy]-methylketone). Immunohistochemistry was used to identify apoptotic and RANKL-producing osteocytes in femoral diaphysis and distal trabecular bone, and µCT was used to determine the extent of trabecular bone loss owing to HLU. In both cortical and trabecular bone, 5 days of HLU increased osteocyte apoptosis significantly (3- and 4-fold, respectively, p < 0.05 versus Ctrl). At day 14, the apoptotic osteocyte number in femoral cortices declined to near control levels but remained elevated in trabeculae (3-fold versus Ctrl, p < 0.05). The number of osteocytes producing RANKL in both bone compartments was also significantly increased at day 5 of HLU (>1.5-fold versus Ctrl, p < 0.05) and further increased by day 14. Increases in osteocyte apoptosis and RANKL production preceded increases in bone resorption at both endocortical and trabecular surfaces. QVD completely inhibited not only the HLU-triggered increases in osteocyte apoptosis but also RANKL production and activation of bone resorption at both sites. Finally, µCT studies revealed that apoptosis inhibition completely prevented the trabecular bone loss caused by HLU. Together these data indicate that osteocyte apoptosis plays a central and controlling role in triggering osteocyte RANKL production and the activation of new resorption leading to bone loss in disuse. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
| | - Dorra Frikha-Benayed
- Department of Biomedical Engineering, City College of New York, New York, NY, USA
| | - Robert J Majeska
- Department of Biomedical Engineering, City College of New York, New York, NY, USA
| | - Alyssa Tuthill
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Shoshana Yakar
- Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY, USA
| | - Stefan Judex
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA
| | - Mitchell B Schaffler
- Department of Biomedical Engineering, City College of New York, New York, NY, USA
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