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Abstract
PURPOSE OF REVIEW Growing evidence supports the critical role of transcriptional mechanisms in promoting the spatial and temporal progression of bone healing. In this review, we evaluate and discuss new transcriptional and post-transcriptional regulatory mechanisms of secondary bone repair, along with emerging evidence for epigenetic regulation of fracture healing. RECENT FINDINGS Using the candidate gene approach has identified new roles for several transcription factors in mediating the reactive, reparative, and remodeling phases of fracture repair. Further characterization of the different epigenetic controls of fracture healing and fracture-driven transcriptome changes between young and aged fracture has identified key biological pathways that may yield therapeutic targets. Furthermore, exogenously delivered microRNA to post-transcriptionally control gene expression is quickly becoming an area with great therapeutic potential. Activation of specific transcriptional networks can promote the proper progression of secondary bone healing. Targeting these key factors using small molecules or through microRNA may yield effective therapies to enhance and possibly accelerate fracture healing.
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Affiliation(s)
- Joseph L Roberts
- Department of Orthopaedics, School of Medicine, Emory University, Atlanta, GA, USA
- Nutrition and Health Sciences, Laney Graduate School, Emory University, Atlanta, GA, USA
| | - David N Paglia
- Department of Orthopaedics, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Hicham Drissi
- Department of Orthopaedics, School of Medicine, Emory University, Atlanta, GA, USA.
- Nutrition and Health Sciences, Laney Graduate School, Emory University, Atlanta, GA, USA.
- Atlanta VA Medical Center, 1670 Clairmont Rd, Decatur, GA, 30033, USA.
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152
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Javaheri B, Caetano-Silva SP, Kanakis I, Bou-Gharios G, Pitsillides AA. The Chondro-Osseous Continuum: Is It Possible to Unlock the Potential Assigned Within? Front Bioeng Biotechnol 2018; 6:28. [PMID: 29619368 PMCID: PMC5871702 DOI: 10.3389/fbioe.2018.00028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/08/2018] [Indexed: 01/08/2023] Open
Abstract
Endochondral ossification (EO), by which long bones of the axial skeleton form, is a tightly regulated process involving chondrocyte maturation with successive stages of proliferation, maturation, and hypertrophy, accompanied by cartilage matrix synthesis, calcification, and angiogenesis, followed by osteoblast-mediated ossification. This developmental sequence reappears during fracture repair and in osteoarthritic etiopathology. These similarities suggest that EO, and the cells involved, are of great clinical importance for bone regeneration as it could provide novel targeted approaches to increase specific signaling to promote fracture healing, and if regulated appropriately in the treatment of osteoarthritis. The long-held accepted dogma states that hypertrophic chondrocytes are terminally differentiated and will eventually undergo apoptosis. In this mini review, we will explore recent evidence from experiments that revisit the idea that hypertrophic chondrocytes have pluripotent capacity and may instead transdifferentiate into a specific sub-population of osteoblast cells. There are multiple lines of evidence, including our own, showing that local, selective alterations in cartilage extracellular matrix (ECM) remodeling also indelibly alter bone quality. This would be consistent with the hypothesis that osteoblast behavior in long bones is regulated by a combination of their lineage origins and the epigenetic effects of chondrocyte-derived ECM which they encounter during their recruitment. Further exploration of these processes could help to unlock potential novel targets for bone repair and regeneration and in the treatment of osteoarthritis.
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Affiliation(s)
- Behzad Javaheri
- Skeletal Biology Group, Comparative Biomedical Sciences, The Royal Veterinary College, London, United Kingdom
| | - Soraia P Caetano-Silva
- Skeletal Biology Group, Comparative Biomedical Sciences, The Royal Veterinary College, London, United Kingdom
| | - Ioannis Kanakis
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - George Bou-Gharios
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Andrew A Pitsillides
- Skeletal Biology Group, Comparative Biomedical Sciences, The Royal Veterinary College, London, United Kingdom
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153
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Sielatycki JA, Saito M, Yuasa M, Moore‐Lotridge SN, Uppuganti S, Colazo JM, Hysong AA, Robinette JP, Okawa A, Yoshii T, Schwartz HS, Nyman JS, Schoenecker JG. Autologous chondrocyte grafting promotes bone formation in the posterolateral spine. JOR Spine 2018; 1:e1001. [PMID: 31463433 PMCID: PMC6686810 DOI: 10.1002/jsp2.1001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 01/23/2018] [Accepted: 01/25/2018] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND CONTEXT Pseudarthrosis following spinal fusion remains problematic despite modern surgical and grafting techniques. In surgical spinal fusion, new bone forms via intramembranous and endochondral ossification, with endochondral ossification occurring in the hypoxic zones of the fusion bed. During bone development and fracture healing, the key cellular mediator of endochondral ossification is the hypertrophic chondrocyte given its ability to function in hypoxia and induce neovascularization and ossification. We therefore hypothesize that hypertrophic chondrocytes may be an effective bone graft alternative. PURPOSE Spinal fusion procedures have increased substantially; yet 5% to 35% of all spinal fusions may result in pseudoarthrosis. Pseudoarthrosis may occur because of implant failure, infection, or biological failure, among other reasons. Advances in surgical techniques and bone grafting have improved fusion; however pseudarthrosis rates remain unacceptably high. Thus, the goal of this study is to investigate hypertrophic chondrocytes as a potential biological graft alternative. METHODS Using a validated murine fracture model, hypertrophic chondrocytes were harvested from fracture calluses and transplanted into the posterolateral spines of identical mice. New bone formation was assessed by X-ray, microcomputed tomography (μCT), and in vivo fluorescent imaging. Results were compared against a standard iliac crest bone graft and a sham surgery control group. Funding for this work was provided by the Department of Orthopaedics and Rehabilitation, the OREF (Grant #16-150), and The Caitlin Lovejoy Fund. RESULTS Radiography, μCT, and in vivo fluorescent imaging demonstrated that hypertrophic chondrocytes promoted bone formation at rates equivalent to iliac crest autograft. Additionally, μCT analysis demonstrated similar fusion rates in a subset of mice from the iliac crest and hypertrophic chondrocyte groups. CONCLUSIONS This proof-of-concept study indicates that hypertrophic chondrocytes can promote bone formation comparable to iliac crest bone graft. These findings provide the foundation for future studies to investigate the potential therapeutic use of hypertrophic chondrocytes in spinal fusion.
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Affiliation(s)
- J. Alex Sielatycki
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
| | - Masanori Saito
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
- Department of Orthopaedic SurgeryTokyo Medical and Dental UniversityTokyoJapan
| | - Masato Yuasa
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
- Department of Orthopaedic SurgeryTokyo Medical and Dental UniversityTokyoJapan
| | - Stephanie N. Moore‐Lotridge
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
- Department of PharmacologyVanderbilt UniversityNashvilleTennessee
| | - Sasidhar Uppuganti
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
| | - Juan M. Colazo
- Vanderbilt University School of MedicineNashvilleTennessee
| | | | | | - Atsushi Okawa
- Department of Orthopaedic SurgeryTokyo Medical and Dental UniversityTokyoJapan
| | - Toshitaka Yoshii
- Department of Orthopaedic SurgeryTokyo Medical and Dental UniversityTokyoJapan
| | - Herbert S. Schwartz
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
| | - Jeffry S. Nyman
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
- Department of Biomedical EngineeringVanderbilt UniversityNashvilleTennessee
- Center for Bone BiologyVanderbilt University Medical CenterNashvilleTennessee
- Department of Veterans AffairsTennessee Valley Health Care SystemNashvilleTennessee
| | - Jonathan G. Schoenecker
- Department of Orthopaedics and RehabilitationVanderbilt University Medical CenterNashvilleTennessee
- Department of PharmacologyVanderbilt UniversityNashvilleTennessee
- Department of Pathology, Microbiology, and ImmunologyVanderbilt University Medical CenterNashvilleTennessee
- Department of PediatricsVanderbilt University Medical CenterNashvilleTennessee
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154
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Kennedy RC, Marmor M, Marcucio R, Hunt CA. Simulation enabled search for explanatory mechanisms of the fracture healing process. PLoS Comput Biol 2018; 14:e1005980. [PMID: 29394245 PMCID: PMC5812655 DOI: 10.1371/journal.pcbi.1005980] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 02/14/2018] [Accepted: 01/11/2018] [Indexed: 12/25/2022] Open
Abstract
A significant portion of bone fractures fail to heal properly, increasing healthcare costs. Advances in fracture management have slowed because translation barriers have limited generation of mechanism-based explanations for the healing process. When uncertainties are numerous, analogical modeling can be an effective strategy for developing plausible explanations of complex phenomena. We demonstrate the feasibility of engineering analogical models in software to facilitate discovery of biomimetic explanations for how fracture healing may progress. Concrete analogical models—Callus Analogs—were created using the MASON simulation toolkit. We designated a Target Region initial state within a characteristic tissue section of mouse tibia fracture at day-7 and posited a corresponding day-10 Target Region final state. The goal was to discover a coarse-grain analog mechanism that would enable the discretized initial state to transform itself into the corresponding Target Region final state, thereby providing an alternative way to study the healing process. One of nine quasi-autonomous Tissue Unit types is assigned to each grid space, which maps to an 80×80 μm region of the tissue section. All Tissue Units have an opportunity each time step to act based on individualized logic, probabilities, and information about adjacent neighbors. Action causes transition from one Tissue Unit type to another, and simulation through several thousand time steps generates a coarse-grain analog—a theory—of the healing process. We prespecified a minimum measure of success: simulated and actual Target Region states achieve ≥ 70% Similarity. We used an iterative refinement protocol to explore many combinations of Tissue Unit logic and action constraints. Workflows progressed through four stages of analog mechanisms. Similarities of 73–90% were achieved for Mechanisms 2–4. The range of Upper-Level similarities increased to 83–94% when we allowed for uncertainty about two Tissue Unit designations. We have demonstrated how Callus Analog experiments provide domain experts with a fresh medium and tools for thinking about and understanding the fracture healing process. Translation barriers have limited the generation of mechanism-based explanations of fracture healing processes. Those barriers help explain why, to date, biological therapeutics have had only a minor impact on fracture management. Alternative approaches are needed, and we present one that is intended to help develop incrementally better mechanism-based explanations of fracture healing phenomena. We created virtual Callus Analogs to simulate how the histologic appearance of a mouse fracture callus may transition from day-7 to day-10. Callus Analogs use software-based model mechanisms, and simulation experiments enable challenging and improving those model mechanisms. During execution, model mechanism operation provides a coarse-grain explanation (a theory) of a four-day portion of the healing process. Simulated day-10 callus histologic images achieved 73–94% Similarity to a corresponding day-10 fracture callus image, thus demonstrating feasibility. Simulated healing provides an alternative perspective on the actual healing process and an alternative way of thinking about plausible fracture healing mechanisms. Our working hypothesis is that the approach can be extended to cover more of the healing process while making features of simulated and actual fracture healing increasingly analogous. The methods presented are intended to be extensible to other research areas that use histologic analysis to investigate and explain tissue level phenomena.
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Affiliation(s)
- Ryan C. Kennedy
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California, United States of America
| | - Meir Marmor
- Department of Orthopaedic Surgery, San Francisco General Hospital Orthopaedic Trauma Institute, University of California, San Francisco, California, United States of America
| | - Ralph Marcucio
- Department of Orthopaedic Surgery, San Francisco General Hospital Orthopaedic Trauma Institute, University of California, San Francisco, California, United States of America
| | - C. Anthony Hunt
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California, United States of America
- * E-mail:
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155
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Youngstrom DW, Senos R, Zondervan RL, Brodeur JD, Lints AR, Young DR, Mitchell TL, Moore ME, Myers MH, Tseng WJ, Loomes KM, Hankenson KD. Intraoperative delivery of the Notch ligand Jagged-1 regenerates appendicular and craniofacial bone defects. NPJ Regen Med 2017; 2:32. [PMID: 29302365 PMCID: PMC5732299 DOI: 10.1038/s41536-017-0037-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 11/07/2017] [Accepted: 11/21/2017] [Indexed: 12/12/2022] Open
Abstract
Each year, 33% of US citizens suffer from a musculoskeletal condition that requires medical intervention, with direct medical costs approaching $1 trillion USD per year. Despite the ubiquity of skeletal dysfunction, there are currently limited safe and efficacious bone growth factors in clinical use. Notch is a cell-cell communication pathway that regulates self-renewal and differentiation within the mesenchymal/osteoblast lineage. The principal Notch ligand in bone, Jagged-1, is a potent osteoinductive protein that positively regulates post-traumatic bone healing in animals. This report describes the temporal regulation of Notch during intramembranous bone formation using marrow ablation as a model system and demonstrates decreased bone formation following disruption of Jagged-1 in mesenchymal progenitor cells. Notch gain-of-function using recombinant Jagged-1 protein on collagen scaffolds promotes healing of craniofacial (calvarial) and appendicular (femoral) surgical defects in both mice and rats. Localized delivery of Jagged-1 promotes bone apposition and defect healing, while avoiding the diffuse bone hypertrophy characteristic of the clinically problematic bone morphogenetic proteins. It is concluded that Jagged-1 is a bone-anabolic agent with therapeutic potential for regenerating traumatic or congenital bone defects.
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Affiliation(s)
- Daniel W Youngstrom
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI USA
| | - Rafael Senos
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI USA
| | - Robert L Zondervan
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI USA.,Department of Physiology, Michigan State University College of Osteopathic Medicine, East Lansing, MI USA
| | - Jack D Brodeur
- Department of Physiology, Michigan State University College of Osteopathic Medicine, East Lansing, MI USA
| | - Austin R Lints
- Department of Physiology, Michigan State University College of Osteopathic Medicine, East Lansing, MI USA
| | - Devin R Young
- Department of Physiology, Michigan State University College of Osteopathic Medicine, East Lansing, MI USA
| | - Troy L Mitchell
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI USA
| | - Megan E Moore
- Department of Physiology, Michigan State University College of Osteopathic Medicine, East Lansing, MI USA
| | - Marc H Myers
- Department of Orthopaedic Surgery, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA USA
| | - Wei-Ju Tseng
- Department of Orthopaedic Surgery, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA USA
| | - Kathleen M Loomes
- Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, Philadelphia, PA USA
| | - Kurt D Hankenson
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI USA.,Department of Orthopaedic Surgery, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA USA
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156
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Stiers PJ, van Gastel N, Moermans K, Stockmans I, Carmeliet G. Regulatory elements driving the expression of skeletal lineage reporters differ during bone development and adulthood. Bone 2017; 105:154-162. [PMID: 28863946 DOI: 10.1016/j.bone.2017.08.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/28/2017] [Accepted: 08/28/2017] [Indexed: 01/06/2023]
Abstract
To improve bone healing or regeneration more insight in the fate and role of the different skeletal cell types is required. Mouse models for fate mapping and lineage tracing of skeletal cells, using stage-specific promoters, have advanced our understanding of bone development, a process that is largely recapitulated during bone repair. However, validation of these models is often only performed during development, whereas proof of the activity and specificity of the used promoters during the bone regenerative process is limited. Here, we show that the regulatory elements of the 6kb collagen type II promoter are not adequate to drive gene expression during bone repair. Similarly, the 2.3kb promoter of collagen type I lacks activity in adult mice, but the 3.2kb promoter is suitable. Furthermore, Cre-mediated fate mapping allows the visualization of progeny, but this label retention may hinder to distinguish these cells from ones with active expression of the marker at later time points. Together, our results show that the lineage-specific regulatory elements driving gene expression during bone development differ from those required later in life and during bone repair, and justify validation of lineage-specific cell tracing and gene silencing strategies during fracture healing and bone regenerative applications.
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Affiliation(s)
- Pieter-Jan Stiers
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Nick van Gastel
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Karen Moermans
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium
| | - Ingrid Stockmans
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium
| | - Geert Carmeliet
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium.
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157
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Abstract
PURPOSE OF REVIEW This review summarizes research on the physiological changes that occur with aging and the resulting effects on fracture healing. RECENT FINDINGS Aging affects the inflammatory response during fracture healing through senescence of the immune response and increased systemic pro-inflammatory status. Important cells of the inflammatory response, macrophages, T cells, mesenchymal stem cells, have demonstrated intrinsic age-related changes that could impact fracture healing. Additionally, vascularization and angiogenesis are impaired in fracture healing of the elderly. Finally, osteochondral cells and their progenitors demonstrate decreased activity and quantity within the callus. Age-related changes affect many of the biologic processes involved in fracture healing. However, the contributions of such changes do not fully explain the poorer healing outcomes and increased morbidity reported in elderly patients. Future research should address this gap in understanding in order to provide improved and more directed treatment options for the elderly population.
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Affiliation(s)
- Dan Clark
- Department of Orthopaedic Surgery, University of California at San Francisco, 513 Parnassus Ave., San Francisco, CA, 94143, USA
- Orthopaedic Trauma Institute, Zuckerberg San Francisco General Hospital and Trauma Center, 2550 23rd St, Building 9, San Francisco, CA, 94110, USA
- Department of Oral and Craniofacial Sciences, School of Dentistry, University of California at San Francisco, 513 Parnassus Ave., Rm. S-619A, San Francisco, CA, 94143, USA
| | - Mary Nakamura
- Department of Medicine, University of California at San Francisco, San Francisco, CA, 94143-0451, USA
- Department of Pathology, VA Medical Center, University of California San Francisco & Pathology Service, San Francisco, CA, 94121, USA
| | - Ted Miclau
- Department of Orthopaedic Surgery, University of California at San Francisco, 513 Parnassus Ave., San Francisco, CA, 94143, USA
- Orthopaedic Trauma Institute, Zuckerberg San Francisco General Hospital and Trauma Center, 2550 23rd St, Building 9, San Francisco, CA, 94110, USA
| | - Ralph Marcucio
- Department of Orthopaedic Surgery, University of California at San Francisco, 513 Parnassus Ave., San Francisco, CA, 94143, USA.
- Orthopaedic Trauma Institute, Zuckerberg San Francisco General Hospital and Trauma Center, 2550 23rd St, Building 9, San Francisco, CA, 94110, USA.
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158
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Haffner-Luntzer M, Müller-Graf F, Matthys R, Abaei A, Jonas R, Gebhard F, Rasche V, Ignatius A. In Vivo Evaluation of Fracture Callus Development During Bone Healing in Mice Using an MRI-compatible Osteosynthesis Device for the Mouse Femur. J Vis Exp 2017. [PMID: 29286432 DOI: 10.3791/56679] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Endochondral fracture healing is a complex process involving the development of fibrous, cartilaginous, and osseous tissue in the fracture callus. The amount of the different tissues in the callus provides important information on the fracture healing progress. Available in vivo techniques to longitudinally monitor the callus tissue development in preclinical fracture-healing studies using small animals include digital radiography and µCT imaging. However, both techniques are only able to distinguish between mineralized and non-mineralized tissue. Consequently, it is impossible to discriminate cartilage from fibrous tissue. In contrast, magnetic resonance imaging (MRI) visualizes anatomical structures based on their water content and might therefore be able to noninvasively identify soft tissue and cartilage in the fracture callus. Here, we report the use of an MRI-compatible external fixator for the mouse femur to allow MRI scans during bone regeneration in mice. The experiments demonstrated that the fixator and a custom-made mounting device allow repetitive MRI scans, thus enabling longitudinal analysis of fracture-callus tissue development.
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Affiliation(s)
| | - Fabian Müller-Graf
- Institute of Orthopedic Research and Biomechanics, University Medical Center Ulm; Department of Traumatology, Hand-, Plastic-, and Reconstructive Surgery, University Medical Center Ulm
| | | | - Alireza Abaei
- Core Facility Small Animal MRI, University Medical Center Ulm
| | - René Jonas
- Institute of Orthopedic Research and Biomechanics, University Medical Center Ulm
| | - Florian Gebhard
- Department of Traumatology, Hand-, Plastic-, and Reconstructive Surgery, University Medical Center Ulm
| | - Volker Rasche
- Core Facility Small Animal MRI, University Medical Center Ulm
| | - Anita Ignatius
- Institute of Orthopedic Research and Biomechanics, University Medical Center Ulm
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159
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De La Vega RE, De Padilla CL, Trujillo M, Quirk N, Porter RM, Evans CH, Ferreira E. Contribution of Implanted, Genetically Modified Muscle Progenitor Cells Expressing BMP-2 to New Bone Formation in a Rat Osseous Defect. Mol Ther 2017; 26:208-218. [PMID: 29107477 DOI: 10.1016/j.ymthe.2017.10.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 10/01/2017] [Accepted: 10/01/2017] [Indexed: 01/20/2023] Open
Abstract
Because muscle contains osteoprogenitor cells and has a propensity to form bone, we have explored its utility in healing large osseous defects. Healing is achieved by the insertion of muscle fragments transduced with adenovirus encoding BMP-2 (Ad.BMP-2). However, it is not known whether the genetically modified muscle contributes osteoprogenitor cells to healing defects or merely serves as a local source of BMP-2. This question is part of the larger debate on the fate of progenitor cells introduced into sites of tissue damage to promote regeneration. To address this issue, we harvested fragments of muscle from rats constitutively expressing GFP, transduced them with Ad.BMP-2, and implanted them into femoral defects in wild-type rats under various conditions. GFP+ cells persisted within defects for the entire 8 weeks of the experiments. In the absence of bone formation, these cells presented as fibroblasts. When bone was formed, GFP+ cells were present as osteoblasts and osteocytes and also among the lining cells of new blood vessels. The genetically modified muscle thus contributed progenitor cells as well as BMP-2 to the healing defect, a property of great significance in light of the extensive damage to soft tissue and consequent loss of endogenous progenitors in problematic fractures.
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Affiliation(s)
- Rodolfo E De La Vega
- Rehabilitation Medicine Research Center, Mayo Clinic, Rochester, MN 55905, USA; Center for Advanced Orthopaedic Studies, BIDMC, Boston, MA 02215, USA
| | | | - Miguel Trujillo
- Rehabilitation Medicine Research Center, Mayo Clinic, Rochester, MN 55905, USA
| | - Nicholas Quirk
- Rehabilitation Medicine Research Center, Mayo Clinic, Rochester, MN 55905, USA
| | - Ryan M Porter
- Center for Advanced Orthopaedic Studies, BIDMC, Boston, MA 02215, USA
| | - Christopher H Evans
- Rehabilitation Medicine Research Center, Mayo Clinic, Rochester, MN 55905, USA; Center for Advanced Orthopaedic Studies, BIDMC, Boston, MA 02215, USA; Collaborative Research Center, AO Foundation, Davos, Switzerland.
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160
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Rashid H, Chen H, Hassan Q, Javed A. Dwarfism in homozygous Agc1 CreERT mice is associated with decreased expression of aggrecan. Genesis 2017; 55. [PMID: 28921880 DOI: 10.1002/dvg.23070] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/29/2017] [Accepted: 09/14/2017] [Indexed: 12/19/2022]
Abstract
Aggrecan (Acan), a large proteoglycan is abundantly expressed in cartilage tissue. Disruption of Acan gene causes dwarfism and perinatal lethality of homozygous mice. Because of sustained expression of Acan in the growth plate and articular cartilage, AgcCre model has been developed for the regulated ablation of target gene in chondrocytes. In this model, the IRES-CreERT-Neo-pgk transgene is knocked-in the 3'UTR of the Acan gene. We consistently noticed variable weight and size among the AgcCre littermates, prompting us to examine the cause of this phenotype. Wild-type, Cre-heterozygous (Agc+/Cre ), and Cre-homozygous (AgcCre/Cre ) littermates were indistinguishable at birth. However, by 1-month, AgcCre/Cre mice showed a significant reduction in body weight (18-27%) and body length (19-22%). Low body weight and dwarfism was sustained through adulthood and occurred in both genders. Compared with wild-type and Agc+/Cre littermates, long bones and vertebrae were shorter in AgcCre/Cre mice. Histological analysis of AgcCre/Cre mice revealed a significant reduction in the length of the growth plate and the thickness of articular cartilage. The amount of proteoglycan deposited in the cartilage of AgcCre/Cre mice was nearly half of the WT littermates. Analysis of gene expression indicates impaired differentiation of chondrocyte in hyaline cartilage of AgcCre/Cre mice. Notably, both Acan mRNA and protein was reduced by 50% in AgcCre/Cre mice. A strong correlation was noted between the level of Acan mRNA and the body length. Importantly, Agc+/Cre mice showed no overt skeletal phenotype. Thus to avoid misinterpretation of data, only the Agc+/Cre mice should be used for conditional deletion of a target gene in the cartilage tissue.
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Affiliation(s)
- Harunur Rashid
- Department of Oral and Maxillofacial Surgery, Institute of Oral Health Research, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama
| | - Haiyan Chen
- Department of Oral and Maxillofacial Surgery, Institute of Oral Health Research, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama
| | - Quamarul Hassan
- Department of Oral and Maxillofacial Surgery, Institute of Oral Health Research, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama
| | - Amjad Javed
- Department of Oral and Maxillofacial Surgery, Institute of Oral Health Research, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama
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161
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He F, Soriano P. Dysregulated PDGFRα signaling alters coronal suture morphogenesis and leads to craniosynostosis through endochondral ossification. Development 2017; 144:4026-4036. [PMID: 28947535 DOI: 10.1242/dev.151068] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 09/15/2017] [Indexed: 01/02/2023]
Abstract
Craniosynostosis is a prevalent human birth defect characterized by premature fusion of calvarial bones. In this study, we show that tight regulation of endogenous PDGFRα activity is required for normal calvarium development in the mouse and that dysregulated PDGFRα activity causes craniosynostosis. Constitutive activation of PDGFRα leads to expansion of cartilage underlying the coronal sutures, which contribute to suture closure through endochondral ossification, in a process regulated in part by PI3K/AKT signaling. Our results thus identify a novel mechanism underlying calvarial development in craniosynostosis.
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Affiliation(s)
- Fenglei He
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.,Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
| | - Philippe Soriano
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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162
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Miclau KR, Brazina SA, Bahney CS, Hankenson KD, Hunt TK, Marcucio RS, Miclau T. Stimulating Fracture Healing in Ischemic Environments: Does Oxygen Direct Stem Cell Fate during Fracture Healing? Front Cell Dev Biol 2017; 5:45. [PMID: 28523266 PMCID: PMC5416746 DOI: 10.3389/fcell.2017.00045] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 04/12/2017] [Indexed: 01/27/2023] Open
Abstract
Bone fractures represent an enormous societal and economic burden as one of the most prevalent causes of disability worldwide. Each year, nearly 15 million people are affected by fractures in the United States alone. Data indicate that the blood supply is critical for fracture healing; as data indicate that concomitant bone and vascular injury are major risk factors for non-union. However, the various role(s) that the vasculature plays remains speculative. Fracture stabilization dictates stem cell fate choices during repair. In stabilized fractures stem cells differentiate directly into osteoblasts and heal the injury by intramembranous ossification. In contrast, in non-stable fractures stem cells differentiate into chondrocytes and the bone heals through endochondral ossification, where a cartilage template transforms into bone as the chondrocytes transform into osteoblasts. One suggested role of the vasculature has been to participate in the stem cell fate decisions due to delivery of oxygen. In stable fractures, the blood vessels are thought to remain intact and promote osteogenesis, while in non-stable fractures, continual disruption of the vasculature creates hypoxia that favors formation of cartilage, which is avascular. However, recent data suggests that non-stable fractures are more vascularized than stable fractures, that oxygen does not appear associated with differentiation of stem cells into chondrocytes and osteoblasts, that cartilage is not hypoxic, and that oxygen, not sustained hypoxia, is required for angiogenesis. These unexpected results, which contrast other published studies, are indicative of the need to better understand the complex, spatio-temporal regulation of vascularization and oxygenation in fracture healing. This work has also revealed that oxygen, along with the promotion of angiogenesis, may be novel adjuvants that can stimulate healing in select patient populations.
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Affiliation(s)
- Katherine R Miclau
- Department of Orthopaedic Surgery, University of CaliforniaSan Francisco, CA, USA.,Zuckerberg San Francisco General Hospital, Orthopaedic Trauma InstituteSan Francisco, CA, USA.,Harvard CollegeCambridge, MA, USA
| | - Sloane A Brazina
- Department of Orthopaedic Surgery, University of CaliforniaSan Francisco, CA, USA.,Zuckerberg San Francisco General Hospital, Orthopaedic Trauma InstituteSan Francisco, CA, USA
| | - Chelsea S Bahney
- Department of Orthopaedic Surgery, University of CaliforniaSan Francisco, CA, USA.,Zuckerberg San Francisco General Hospital, Orthopaedic Trauma InstituteSan Francisco, CA, USA
| | - Kurt D Hankenson
- Department of Small Animal Clinical Science and Department of Physiology, Michigan State UniversityEast Lansing, MI, USA.,Department of Orthopaedic Surgery, University of PennsylvaniaPhiladelphia, PA, USA
| | - Thomas K Hunt
- Department of Surgery, University of CaliforniaSan Francisco, CA, USA
| | - Ralph S Marcucio
- Department of Orthopaedic Surgery, University of CaliforniaSan Francisco, CA, USA.,Zuckerberg San Francisco General Hospital, Orthopaedic Trauma InstituteSan Francisco, CA, USA
| | - Theodore Miclau
- Department of Orthopaedic Surgery, University of CaliforniaSan Francisco, CA, USA.,Zuckerberg San Francisco General Hospital, Orthopaedic Trauma InstituteSan Francisco, CA, USA
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Quang Le B, Van Blitterswijk C, De Boer J. An Approach to In Vitro Manufacturing of Hypertrophic Cartilage Matrix for Bone Repair. Bioengineering (Basel) 2017; 4:bioengineering4020035. [PMID: 28952514 PMCID: PMC5590482 DOI: 10.3390/bioengineering4020035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/18/2017] [Accepted: 04/18/2017] [Indexed: 12/18/2022] Open
Abstract
Devitalized hypertrophic cartilage matrix (DCM) is an attractive concept for an off-the-shelf bone graft substitute. Upon implantation, DCM can trigger the natural endochondral ossification process, but only when the hypertrophic cartilage matrix has been reconstituted correctly. In vivo hypertrophic differentiation has been reported for multiple cell types but up-scaling and in vivo devitalization remain a big challenge. To this end, we developed a micro tissue-engineered cartilage (MiTEC) model using the chondrogenic cell line ATDC5. Micro-aggregates of ATDC5 cells (approximately 1000 cells per aggregate) were cultured on a 3% agarose mold consisting of 1585 microwells, each measuring 400 µm in diameter. Chondrogenic differentiation was strongly enhanced using media supplemented with combinations of growth factors e.g., insulin, transforming growth factor beta and dexamethasone. Next, mineralization was induced by supplying the culture medium with beta-glycerophosphate, and finally we boosted the secretion of proangiogenic growth factors using the hypoxia mimetic phenanthroline in the final stage of in vivo culture. Then, ATDC5 aggregates were devitalized by freeze/thawing or sodium dodecyl sulfate treatment before co-culturing with human mesenchymal stromal cells (hMSCs). We observed a strong effect on chondrogenic differentiation of hMSCs. Using this MiTEC model, we were able to not only upscale the production of cartilage to a clinically relevant amount but were also able to vary the cartilage matrix composition in different ways, making MiTEC an ideal model to develop DCM as a bone graft substitute.
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Affiliation(s)
- Bach Quang Le
- Department of Tissue Regeneration, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Postbus 217, 7500 AE Enschede, The Netherlands.
| | - Clemens Van Blitterswijk
- Department of Tissue Regeneration, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Postbus 217, 7500 AE Enschede, The Netherlands.
- Department of Complex Tissue Regeneration, MERLN Institute, University of Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
| | - Jan De Boer
- Department of Tissue Regeneration, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Postbus 217, 7500 AE Enschede, The Netherlands.
- Laboratory for Cell Biology-inspired Tissue Engineering, MERLN Institute, University of Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
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