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Micheletti C, Shah FA. Bone hierarchical organization through the lens of materials science: Present opportunities and future challenges. Bone Rep 2024; 22:101783. [PMID: 39100913 PMCID: PMC11295937 DOI: 10.1016/j.bonr.2024.101783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 06/20/2024] [Accepted: 06/22/2024] [Indexed: 08/06/2024] Open
Abstract
Multiscale characterization is essential to better understand the hierarchical architecture of bone and an array of analytical methods contributes to exploring the various structural and compositional aspects. Incorporating X-ray tomography, X-ray scattering, vibrational spectroscopy, and atom probe tomography alongside electron microscopy provides a comprehensive approach, offering insights into the diverse levels of organization within bone. X-ray scattering techniques reveal information about collagen-mineral spatial relationships, while X-ray tomography captures 3D structural details, especially at the microscale. Electron microscopy, such as scanning and transmission electron microscopy, extends resolution to the nanoscale, showcasing intricate features such as collagen fibril organization. Additionally, atom probe tomography achieves sub-nanoscale resolution and high chemical sensitivity, enabling detailed examination of bone composition. Despite various technical challenges, a correlative approach allows for a comprehensive understanding of bone material properties. Real-time investigations through in situ and in operando approaches shed light on the dynamic processes in bone. Recently developed techniques such as liquid, in situ transmission electron microscopy provide insights into calcium phosphate formation and collagen mineralization. Mechanical models developed in the effort to link structure, composition, and function currently remain oversimplified but can be improved. In conclusion, correlative analytical platforms provide a holistic perspective of bone extracellular matrix and are essential for unraveling the intricate interplay between structure and composition within bone.
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Affiliation(s)
- Chiara Micheletti
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Furqan A. Shah
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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2
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Vom Scheidt A, Krug J, Goggin P, Bakker AD, Busse B. 2D vs. 3D Evaluation of Osteocyte Lacunae - Methodological Approaches, Recommended Parameters, and Challenges: A Narrative Review by the European Calcified Tissue Society (ECTS). Curr Osteoporos Rep 2024; 22:396-415. [PMID: 38980532 PMCID: PMC11324773 DOI: 10.1007/s11914-024-00877-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/11/2024] [Indexed: 07/10/2024]
Abstract
PURPOSE OF REVIEW Quantification of the morphology of osteocyte lacunae has become a powerful tool to investigate bone metabolism, pathologies and aging. This review will provide a brief overview of 2D and 3D imaging methods for the determination of lacunar shape, orientation, density, and volume. Deviations between 2D-based and 3D-based lacunar volume estimations are often not sufficiently addressed and may give rise to contradictory findings. Thus, the systematic error arising from 2D-based estimations of lacunar volume will be discussed, and an alternative calculation proposed. Further, standardized morphological parameters and best practices for sampling and segmentation are suggested. RECENT FINDINGS We quantified the errors in reported estimation methods of lacunar volume based on 2D cross-sections, which increase with variations in lacunar orientation and histological cutting plane. The estimations of lacunar volume based on common practice in 2D imaging methods resulted in an underestimation of lacunar volume of up to 85% compared to actual lacunar volume in an artificial dataset. For a representative estimation of lacunar size and morphology based on 2D images, at least 400 lacunae should be assessed per sample.
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Affiliation(s)
- Annika Vom Scheidt
- Division of Macroscopic and Clinical Anatomy, Gottfried Schatz Research Center, Medical University of Graz, Auenbruggerplatz 25, Graz, 8036, Austria.
| | - Johannes Krug
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 55a, 22529, Hamburg, Germany
- Interdisciplinary Competence Center for Interface Research, University Medical Center Hamburg-Eppendorf, Butenfeld 34, 22529, Hamburg, Germany
| | - Patricia Goggin
- Biomedical Imaging Unit, Laboratory and Pathology Block, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK
| | - Astrid Diana Bakker
- Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam Movement Sciences, University of Amsterdam and Vrije Universiteit Amsterdam, Gustav Mahlerlaan, Amsterdam, 3004, 1081 LA, The Netherlands
| | - Björn Busse
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Lottestr. 55a, 22529, Hamburg, Germany
- Interdisciplinary Competence Center for Interface Research, University Medical Center Hamburg-Eppendorf, Butenfeld 34, 22529, Hamburg, Germany
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3
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Schwarcz HP, Nassif N, Kis VK. Curved mineral platelets in bone. Acta Biomater 2024; 183:201-209. [PMID: 38838906 DOI: 10.1016/j.actbio.2024.05.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/24/2024] [Accepted: 05/30/2024] [Indexed: 06/07/2024]
Abstract
Bone is a composite material principally made up of a mineral phase (apatite) and collagen fibrils. The mineral component of bone occurs in the form of polycrystalline platelets 2-6 nm in thickness. These platelets are packed and probably glued together in stacks of two or more, ranging up to >30 platelets. Here we show that most of these stacks are curved flat sheets whose cylindrical axes are oriented parallel to the long axes of collagen fibrils. Consequently, the curvature of the platelets is not detectable in TEM sections cut parallel to the collagen fibril axes. The radius of curvature around these axes ranges from about 25 nm (the average radius of the collagen fibrils) to 100's of nm. The shapes of these curved forms contribute to the compressive strength of bone. STATEMENT OF SIGNIFICANCE: Bone, the material of which bones are made, is mainly composed of a protein, collagen, and the mineral apatite (calcium phosphate). The crystals have long been known to be flat plates about 5 nanometers (nm) thick. Here we show that the crystals are bound together in curved platelets with a radius of curvature between 25 and several hundred nm, which weave between fibrils of collagen. Some platelets wrap tightly around fibrils. The platelets form stacks of from two to up to 30. The crystals in the platelets are all oriented parallel to the cylindrical fibrils even though most crystals are not in contact with collagen. These curved structures provide greater strength to bone.
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Affiliation(s)
- H P Schwarcz
- School of Earth, Environment and Society, McMaster University, Hamilton, Ontario, Canada; School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada.
| | - Nadine Nassif
- CNRS, Sorbonne Université, Collège de France, Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), F-75005 Paris, France
| | - Viktoria Kovacs Kis
- HUN-REN Centre for Energy Research, Konkoly-Thege Miklós u. 29-33, H-1121 Budapest, Hungary; Department of Mineralogy, Eötvös Loránd University, Pázmány Péter sétány 1/c, H-1119 Budapest, Hungary
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4
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Micheletti C, DiCecco LA, Deering J, Chen W, Ervolino da Silva AC, Shah FA, Palmquist A, Okamoto R, Grandfield K. Mesoscale characterization of osseointegration around an additively manufactured genistein-coated implant. Sci Rep 2024; 14:15339. [PMID: 38961115 PMCID: PMC11222380 DOI: 10.1038/s41598-024-66058-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Accepted: 06/26/2024] [Indexed: 07/05/2024] Open
Abstract
Given the hierarchical nature of bone and bone interfaces, osseointegration, namely the formation of a direct bone-implant contact, is best evaluated using a multiscale approach. However, a trade-off exists between field of view and spatial resolution, making it challenging to image large volumes with high resolution. In this study, we combine established electron microscopy techniques to probe bone-implant interfaces at the microscale and nanoscale with plasma focused ion beam-scanning electron microscopy (PFIB-SEM) tomography to evaluate osseointegration at the mesoscale. This characterization workflow is demonstrated for bone response to an additively manufactured Ti-6Al-4V implant which combines engineered porosity to facilitate bone ingrowth and surface functionalization via genistein, a phytoestrogen, to counteract bone loss in osteoporosis. SEM demonstrated new bone formation at the implant site, including in the internal implant pores. At the nanoscale, scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the gradual nature of the bone-implant interface. By leveraging mesoscale analysis with PFIB-SEM tomography that captures large volumes of bone-implant interface with nearly nanoscale resolution, the presence of mineral ellipsoids varying in size and orientation was revealed. In addition, a well-developed lacuno-canalicular network and mineralization fronts directed both towards the implant and away from it were highlighted.
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Affiliation(s)
- Chiara Micheletti
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada.
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
| | - Liza-Anastasia DiCecco
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada
| | - Joseph Deering
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada
| | - Wanqi Chen
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada
| | | | - Furqan A Shah
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Anders Palmquist
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Roberta Okamoto
- Department of Basic Sciences, Araçatuba Dental School, São Paulo State University, Araçatuba, SP, Brazil
- Research Productivity Scholarship (Process: 309408/2020-2), Araçatuba, SP, Brazil
| | - Kathryn Grandfield
- Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada.
- School of Biomedical Engineering, McMaster University, Hamilton, ON, Canada.
- Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, Canada.
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5
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Couoh LR, Bucio L, Ruvalcaba JL, Manoel B, Tang T, Gourrier A, Grandfield K. Tooth acellular extrinsic fibre cementum incremental lines in humans are formed by parallel branched Sharpey's fibres and not by its mineral phase. J Struct Biol 2024; 216:108084. [PMID: 38479547 DOI: 10.1016/j.jsb.2024.108084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 02/28/2024] [Accepted: 03/10/2024] [Indexed: 03/18/2024]
Abstract
In humans, the growth pattern of the acellular extrinsic fibre cementum (AEFC) has been useful to estimate the age-at-death. However, the structural organization behind such a pattern remains poorly understood. In this study tooth cementum from seven individuals from a Mexican modern skeletal series were analyzed with the aim of unveiling the AEFC collagenous and mineral structure using multimodal imaging approaches. The organization of collagen fibres was first determined using: light microscopy, transmission electron microscopy (TEM), electron tomography, and plasma FIB scanning electron microscopy (PFIB-SEM) tomography. The mineral properties were then investigated using: synchrotron small-angle X-ray scattering (SAXS) for T-parameter (correlation length between mineral particles); synchrotron X-ray diffraction (XRD) for L-parameter (mineral crystalline domain size estimation), alignment parameter (crystals preferred orientation) and lattice parameters a and c; as well as synchrotron X-ray fluorescence for spatial distribution of calcium, phosphorus and zinc. Results show that Sharpey's fibres branched out fibres that cover and uncover other collagen bundles forming aligned arched structures that are joined by these same fibres but in a parallel fashion. The parallel fibres are not set as a continuum on the same plane and when they are superimposed project the AEFC incremental lines due to the collagen birefringence. The orientation of the apatite crystallites is subject to the arrangement of the collagen fibres, and the obtained parameter values along with the elemental distribution maps, revealed this mineral tissue as relatively homogeneous. Therefore, no intrinsic characteristics of the mineral phase could be associated with the alternating AEFC incremental pattern.
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Affiliation(s)
- Lourdes R Couoh
- Dirección de Antropología Física, Instituto Nacional de Antropología e Historia, Paseo de la Reforma y Gandhi, Chapultepec Polanco 11560, CDMX, México.
| | - Lauro Bucio
- Laboratorio de Cristalofísica y Materiales Naturales, Instituto de Física, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510, CDMX, México
| | - José Luis Ruvalcaba
- Laboratorio Nacional de Ciencias para la Investigación y Conservación del Patrimonio Cultural, Instituto de Física, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510, CDMX, México
| | - Britta Manoel
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs 38000, Grenoble, France; Bruker AXS Advanced X-ray Solutions GmbH, Östliche Rheinbrückenstraße 49 76187, Karlsruhe, Germany
| | - Tengteng Tang
- Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada
| | | | - Kathryn Grandfield
- Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada; School of Biomedical Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada.
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6
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Weiner S, Shahar R. Vertebrate mineralized tissues: A modular structural analysis. Acta Biomater 2024; 179:1-12. [PMID: 38561073 DOI: 10.1016/j.actbio.2024.03.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 03/25/2024] [Accepted: 03/27/2024] [Indexed: 04/04/2024]
Abstract
Vertebrate mineralized tissues, present in bones, teeth and scales, have complex 3D hierarchical structures. As more of these tissues are characterized in 3D using mainly FIB SEM at a resolution that reveals the mineralized collagen fibrils and their organization into collagen fibril bundles, highly complex and diverse structures are being revealed. In this perspective we propose an approach to analyzing these tissues based on the presence of modular structures: material textures, pore shapes and sizes, as well as extents of mineralization. This modular approach is complimentary to the widely used hierarchical approach for describing these mineralized tissues. We present a series of case studies that show how some of the same structural modules can be found in different mineralized tissues, including in bone, dentin and scales. The organizations in 3D of the various structural modules in different tissues may differ. This approach facilitates the framing of basic questions such as: are the spatial relations between modular structures the same or similar in different mineralized tissues? Do tissues with similar sets of modules carry out similar functions or can similar functions be carried out using a different set of modular structures? Do mineralized tissues with similar sets of modules have a common developmental or evolutionary pathway? STATEMENT OF SIGNIFICANCE: 3D organization studies of diverse vertebrate mineralized tissues are revealing detailed, but often confusing details about the material textures, the arrangements of pores and differences in the extent of mineralization within a tissue. The widely used hierarchical scheme for describing such organizations does not adequately provide a basis for comparing these tissues, or addressing issues such as structural components thought to be characteristic of bone, being present in dermal tissues and so on. The classification scheme we present is based on identifying structural components within a tissue that can then be systematically compared to other vertebrate mineralized tissues. We anticipate that this classification approach will provide insights into structure-function relations, as well as the evolution of these tissues.
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Affiliation(s)
- Steve Weiner
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Ron Shahar
- Faculty of Agriculture Food & Environment, Koret School of Veterinary Medicine, Hebrew University Jerusalem, P.O.B. 12, Rehovot 7610001, Israel
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7
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Micheletti C, Shah FA, Palmquist A, Grandfield K. Ultrastructure and Nanoporosity of Human Bone Shown with Correlative On-Axis Electron and Spectroscopic Tomographies. ACS NANO 2023; 17:24710-24724. [PMID: 37846873 PMCID: PMC10753897 DOI: 10.1021/acsnano.3c04633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 10/06/2023] [Indexed: 10/18/2023]
Abstract
Mineralized collagen fibrils are the building block units of bone at the nanoscale. While it is known that collagen fibrils are mineralized both inside their gap zones (intra-fibrillar mineralization) and on their outer surfaces (extra-fibrillar mineralization), a clear visualization of this architecture in three dimensions (3D), combining structural and compositional information over large volumes, but without compromising the resolution, remains challenging. In this study, we demonstrate the use of on-axis Z-contrast electron tomography (ET) with correlative energy-dispersive X-ray spectroscopy (EDX) tomography to examine rod-shaped samples with diameters up to 700 nm prepared from individual osteonal lamellae in the human femur. Our work mainly focuses on two aspects: (i) low-contrast nanosized circular spaces ("holes") observed in sections of bone oriented perpendicular to the long axis of a long bone, and (ii) extra-fibrillar mineral, especially in terms of morphology and spatial relationship with respect to intra-fibrillar mineral and collagen fibrils. From our analyses, it emerges quite clearly that most "holes" are cross-sectional views of collagen fibrils. While this had been postulated before, our 3D reconstructions and reslicing along meaningful two-dimensional (2D) cross-sections provide a direct visual confirmation. Extra-fibrillar mineral appears to be composed of thin plates that are interconnected and span over several collagen fibrils, confirming that mineralization is cross-fibrillar, at least for the extra-fibrillar phase. EDX tomography shows mineral signatures (Ca and P) within the gap zones, but the signal appears weaker than that associated with the extra-fibrillar mineral, pointing toward the existence of dissimilarities between the two types of mineralization.
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Affiliation(s)
- Chiara Micheletti
- Department
of Materials Science and Engineering, McMaster
University, Hamilton L8S 4L7, Ontario, Canada
- Department
of Biomaterials, Sahlgrenska Academy, University
of Gothenburg, Göteborg 40530, Sweden
| | - Furqan A. Shah
- Department
of Biomaterials, Sahlgrenska Academy, University
of Gothenburg, Göteborg 40530, Sweden
| | - Anders Palmquist
- Department
of Biomaterials, Sahlgrenska Academy, University
of Gothenburg, Göteborg 40530, Sweden
| | - Kathryn Grandfield
- Department
of Materials Science and Engineering, McMaster
University, Hamilton L8S 4L7, Ontario, Canada
- School
of Biomedical Engineering, McMaster University, Hamilton L8S 4L7, Ontario, Canada
- Brockhouse
Institute for Materials Research, McMaster
University, Hamilton L8S 4L7, Ontario, Canada
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8
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Ibrahim J, Rechav K, Boaretto E, Weiner S. Three dimensional structures of the inner and outer pig petrous bone using FIB-SEM: Implications for development and ancient DNA preservation. J Struct Biol 2023; 215:107998. [PMID: 37422275 DOI: 10.1016/j.jsb.2023.107998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 07/03/2023] [Accepted: 07/05/2023] [Indexed: 07/10/2023]
Abstract
We report on the 3D ultrastructure of the mineralized petrous bone of mature pig using focused ion beam - scanning electron microscopy (FIB-SEM). We divide the petrous bone into two zones based on the degree of mineralization; one zone close to the otic chamber has higher mineral density than the second zone further away from the otic chamber. The hypermineralization of the petrous bone results in the collagen D-banding being poorly revealed in the lower mineral density zone (LMD), and absent in the high mineral density zone (HMD). We therefore could not use D-banding to decipher the 3D structure of the collagen assembly. Instead we exploited the anisotropy option in the Dragonfly image processing software to visualize the less mineralized collagen fibrils and/or nanopores that surround the more mineralized zones known as tesselles. This approach therefore indirectly tracks the orientations of the collagen fibrils in the matrix itself. We show that the HMD bone has a structure similar to that of woven bone, and the LMD is composed of lamellar bone with a plywood-like structural motif. This agrees with the fact that the bone close to the otic chamber is fetal bone and is not remodeled. The lamellar structure of the bone further away from the otic chamber is consistent with modeling/remodeling. The absence of the less mineralized collagen fibrils and nanopores resulting from the confluence of the mineral tesselles may contribute to shielding DNA during diagenesis. We show that anisotropy evaluation of the less mineralized collagen fibrils could be a useful tool to analyze bone ultrastructures and in particular the directionality of collagen fibril bundles that make up the bone matrix.
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Affiliation(s)
- Jamal Ibrahim
- Scientific Archaeology Unit, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Katya Rechav
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Elisabetta Boaretto
- Scientific Archaeology Unit, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Steve Weiner
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel.
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9
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Buss DJ, Rechav K, Reznikov N, McKee MD. Mineral tessellation in mouse enthesis fibrocartilage, Achilles tendon, and Hyp calcifying enthesopathy: A shared 3D mineralization pattern. Bone 2023:116818. [PMID: 37295663 DOI: 10.1016/j.bone.2023.116818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/17/2023] [Accepted: 06/01/2023] [Indexed: 06/12/2023]
Abstract
The hallmark of enthesis architecture is the 3D compositional and structural gradient encompassing four tissue zones - tendon/ligament, uncalcified fibrocartilage, calcified fibrocartilage and bone. This functional gradient accommodates the large stiffness differential between calcified bone and uncalcified tendon/ligament. Here we analyze in 3D the organization of the mouse Achilles enthesis and mineralizing Achilles tendon in comparison to lamellar bone. We use correlative, multiscale high-resolution volume imaging methods including μCT with submicrometer resolution and FIB-SEM tomography (both with deep learning-based image segmentation), and TEM and SEM imaging, to describe ultrastructural features of physiologic, age-related and aberrant mineral patterning. We applied these approaches to murine wildtype (WT) Achilles enthesis tissues to describe in normal calcifying fibrocartilage a crossfibrillar mineral tessellation pattern similar to that observed in lamellar bone, but with greater variance in mineral tesselle morphology and size. We also examined Achilles enthesis structure in Hyp mice, a murine model for the inherited osteomalacic disease X-linked hypophosphatemia (XLH) with calcifying enthesopathy. In Achilles enthesis fibrocartilage of Hyp mice, we show defective crossfibrillar mineral tessellation similar to that which occurs in Hyp lamellar bone. At the cellular level in fibrocartilage, unlike in bone where enlarged osteocyte mineral lacunae are found as peri-osteocytic lesions, mineral lacunar volumes for fibrochondrocytes did not differ between WT and Hyp mice. While both WT and Hyp aged mice demonstrate Achilles tendon midsubstance ectopic mineralization, a consistently defective mineralization pattern was observed in Hyp mice. Strong immunostaining for osteopontin was observed at all mineralization sites examined in both WT and Hyp mice. Taken together, this new 3D ultrastructural information describes details of common mineralization trajectories for enthesis, tendon and bone, which in Hyp/XLH are defective.
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Affiliation(s)
- Daniel J Buss
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Katya Rechav
- Electron Microscopy Unit, Weizmann Institute of Science, Rehovot, Israel
| | - Natalie Reznikov
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Department of Bioengineering, Faculty of Engineering, McGill University, Montreal, Quebec, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Marc D McKee
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada.
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10
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Martynowycz MW, Shiriaeva A, Clabbers MTB, Nicolas WJ, Weaver SJ, Hattne J, Gonen T. A robust approach for MicroED sample preparation of lipidic cubic phase embedded membrane protein crystals. Nat Commun 2023; 14:1086. [PMID: 36841804 PMCID: PMC9968316 DOI: 10.1038/s41467-023-36733-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 02/15/2023] [Indexed: 02/26/2023] Open
Abstract
Crystallizing G protein-coupled receptors (GPCRs) in lipidic cubic phase (LCP) often yields crystals suited for the cryogenic electron microscopy (cryoEM) method microcrystal electron diffraction (MicroED). However, sample preparation is challenging. Embedded crystals cannot be targeted topologically. Here, we use an integrated fluorescence light microscope (iFLM) inside of a focused ion beam and scanning electron microscope (FIB-SEM) to identify fluorescently labeled GPCR crystals. Crystals are targeted using the iFLM and LCP is milled using a plasma focused ion beam (pFIB). The optimal ion source for preparing biological lamellae is identified using standard crystals of proteinase K. Lamellae prepared using either argon or xenon produced the highest quality data and structures. MicroED data are collected from the milled lamellae and the structures are determined. This study outlines a robust approach to identify and mill membrane protein crystals for MicroED and demonstrates plasma ion-beam milling is a powerful tool for preparing biological lamellae.
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Affiliation(s)
- Michael W Martynowycz
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA.,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - Anna Shiriaeva
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA.,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - Max T B Clabbers
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA.,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - William J Nicolas
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA.,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - Sara J Weaver
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA.,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - Johan Hattne
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA.,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - Tamir Gonen
- Howard Hughes Medical Institute, University of California, Los Angeles, CA, 90095, USA. .,Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA. .,Department of Physiology, University of California, Los Angeles, CA, 90095, USA.
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11
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Sato M, Shah FA. Contributions of Resin Cast Etching to Visualising the Osteocyte Lacuno-Canalicular Network Architecture in Bone Biology and Tissue Engineering. Calcif Tissue Int 2023; 112:525-542. [PMID: 36611094 PMCID: PMC10106349 DOI: 10.1007/s00223-022-01058-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 12/21/2022] [Indexed: 01/09/2023]
Abstract
Recent years have witnessed an evolution of imaging technologies towards sophisticated approaches for visualising cells within their natural environment(s) and for investigating their interactions with other cells, with adjacent anatomical structures, and with implanted biomaterials. Resin cast etching (RCE) is an uncomplicated technique involving sequential acid etching and alkali digestion of resin embedded bone to observe the osteocyte lacuno-canalicular network using scanning electron microscopy. This review summarises the applicability of RCE to bone and the bone-implant interface. Quantitative parameters such as osteocyte size, osteocyte density, and number of canaliculi per osteocyte, and qualitative metrics including osteocyte shape, disturbances in the arrangement of osteocytes and canaliculi, and physical communication between osteocytes and implant surfaces can be investigated. Ageing, osteoporosis, long-term immobilisation, spinal cord injury, osteoarthritis, irradiation, and chronic kidney disease have been shown to impact osteocyte lacuno-canalicular network morphology. In addition to titanium, calcium phosphates, and bioactive glass, observation of direct connectivity between osteocytes and cobalt chromium provides new insights into the osseointegration potential of materials conventionally viewed as non-osseointegrating. Other applications include in vivo and in vitro testing of polymer-based tissue engineering scaffolds and tissue-engineered ossicles, validation of ectopic osteochondral defect models, ex vivo organ culture of whole bones, and observing the effects of gene dysfunction/deletion on the osteocyte lacuno-canalicular network. Without additional contrast staining, any resin embedded specimen (including clinical biopsies) can be used for RCE. The multitude of applications described here attest to the versatility of RCE for routine use within correlative analytical workflows, particularly in biomaterials science.
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Affiliation(s)
- Mari Sato
- Oral Biochemistry and Molecular Biology, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Furqan A Shah
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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Shah FA, Jolic M, Micheletti C, Omar O, Norlindh B, Emanuelsson L, Engqvist H, Engstrand T, Palmquist A, Thomsen P. Bone without borders - Monetite-based calcium phosphate guides bone formation beyond the skeletal envelope. Bioact Mater 2023; 19:103-114. [PMID: 35441115 PMCID: PMC9005875 DOI: 10.1016/j.bioactmat.2022.03.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 03/02/2022] [Accepted: 03/07/2022] [Indexed: 12/18/2022] Open
Abstract
Calcium phosphates (CaP) represent an important class of osteoconductive and osteoinductive biomaterials. As proof-of-concept, we show how a multi-component CaP formulation (monetite, beta-tricalcium phosphate, and calcium pyrophosphate) guides osteogenesis beyond the physiological envelope. In a sheep model, hollow dome-shaped constructs were placed directly over the occipital bone. At 12 months, large amounts of bone (∼75%) occupy the hollow space with strong evidence of ongoing remodelling. Features of both compact bone (osteonal/osteon-like arrangements) and spongy bone (trabeculae separated by marrow cavities) reveal insights into function/need-driven microstructural adaptation. Pores within the CaP also contain both woven bone and vascularised lamellar bone. Osteoclasts actively contribute to CaP degradation/removal. Of the constituent phases, only calcium pyrophosphate persists within osseous (cutting cones) and non-osseous (macrophages) sites. From a translational perspective, this multi-component CaP opens up exciting new avenues for osteotomy-free and minimally-invasive repair of large bone defects and augmentation of the dental alveolar ridge.
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Affiliation(s)
- Furqan A. Shah
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Martina Jolic
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Chiara Micheletti
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada
| | - Omar Omar
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Birgitta Norlindh
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lena Emanuelsson
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Håkan Engqvist
- Department of Engineering Sciences, Applied Materials Science Section, Uppsala University, Uppsala, Sweden
| | - Thomas Engstrand
- Department of Reconstructive Plastic Surgery, Karolinska University Hospital, Stockholm, Sweden
| | - Anders Palmquist
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Peter Thomsen
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Grandfield K, Micheletti C, Deering J, Arcuri G, Tang T, Langelier B. Atom Probe Tomography for Biomaterials and Biomineralization. Acta Biomater 2022; 148:44-60. [DOI: 10.1016/j.actbio.2022.06.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/18/2022] [Accepted: 06/06/2022] [Indexed: 01/27/2023]
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Tang T, Landis W, Raguin E, Werner P, Bertinetti L, Dean M, Wagermaier W, Fratzl P. A 3D Network of Nanochannels for Possible Ion and Molecule Transit in Mineralizing Bone and Cartilage. ADVANCED NANOBIOMED RESEARCH 2022. [DOI: 10.1002/anbr.202100162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Tengteng Tang
- Department of Biomaterials Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany
| | - William Landis
- Department of Preventive and Restorative Dental Sciences University of California at San Francisco 707 Parnassus Avenue San Francisco CA 94143 USA
| | - Emeline Raguin
- Department of Biomaterials Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany
| | - Peter Werner
- Department of Biomaterials Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany
| | - Luca Bertinetti
- Center for Molecular Bioengineering TU Dresden Tatzberg 41 01307 Dresden Germany
| | - Mason Dean
- Department of Infectious Diseases and Public Health City University of Hong Kong 31 To Yuen Street, Tat Chee Avenue Kowloon Hong Kong
| | - Wolfgang Wagermaier
- Department of Biomaterials Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany
| | - Peter Fratzl
- Department of Biomaterials Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany
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Micheletti C, Hurley A, Gourrier A, Palmquist A, Tang T, Shah FA, Grandfield K. Bone mineral organization at the mesoscale: A review of mineral ellipsoids in bone and at bone interfaces. Acta Biomater 2022; 142:1-13. [PMID: 35202855 DOI: 10.1016/j.actbio.2022.02.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 01/14/2022] [Accepted: 02/17/2022] [Indexed: 01/13/2023]
Abstract
Much debate still revolves around bone architecture, especially at the nano- and microscale. Bone is a remarkable material where high strength and toughness coexist thanks to an optimized composition of mineral and protein and their hierarchical organization across several distinct length scales. At the nanoscale, mineralized collagen fibrils act as building block units. Despite their key role in biological and mechanical functions, the mechanisms of collagen mineralization and the precise arrangement of the organic and inorganic constituents in the fibrils remains not fully elucidated. Advances in three-dimensional (3D) characterization of mineralized bone tissue by focused ion beam-scanning electron microscopy (FIB-SEM) revealed mineral-rich regions geometrically approximated as prolate ellipsoids, much larger than single collagen fibrils. These structures have yet to become prominently recognized, studied, or adopted into biomechanical models of bone. However, they closely resemble the circular to elliptical features previously identified by scanning transmission electron microscopy (STEM) in two-dimensions (2D). Herein, we review the presence of mineral ellipsoids in bone as observed with electron-based imaging techniques in both 2D and 3D with particular focus on different species, anatomical locations, and in proximity to natural and synthetic biomaterial interfaces. This review reveals that mineral ellipsoids are a ubiquitous structure in all the bones and bone-implant interfaces analyzed. This largely overlooked hierarchical level is expected to bring different perspectives to our understanding of bone mineralization and mechanical properties, in turn shedding light on structure-function relationships in bone. STATEMENT OF SIGNIFICANCE: In bone, the hierarchical organization of organic (mainly collagen type I) and inorganic (calcium-phosphate mineral) components across several length scales contributes to a unique combination of strength and toughness. However, aspects related to the collagen-mineral organization and to mineralization mechanisms remain unclear. Here, we review the presence of mineral prolate ellipsoids across a variety of species, anatomical locations, and interfaces, both natural and with synthetic biomaterials. These mineral ellipsoids represent a largely unstudied feature in the organization of bone at the mesoscale, i.e., at a level connecting nano- and microscale. Thorough understanding of their origin, development, and structure can provide valuable insights into bone architecture and mineralization, assisting the treatment of bone diseases and the design of bio-inspired materials.
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Affiliation(s)
- Chiara Micheletti
- Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada; Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg SE-413 46, Sweden
| | - Ariana Hurley
- Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada; Integrated Biomedical Engineering and Health Sciences, McMaster University, Hamilton L8S 4L7, ON, Canada
| | | | - Anders Palmquist
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg SE-413 46, Sweden
| | - Tengteng Tang
- Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada
| | - Furqan A Shah
- Department of Biomaterials, Sahlgrenska Academy, University of Gothenburg, Gothenburg SE-413 46, Sweden
| | - Kathryn Grandfield
- Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada; School of Biomedical Engineering, McMaster University, Hamilton L8S 4L7, ON, Canada.
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Buss DJ, Kröger R, McKee MD, Reznikov N. Hierarchical organization of bone in three dimensions: A twist of twists. J Struct Biol X 2022; 6:100057. [PMID: 35072054 PMCID: PMC8762463 DOI: 10.1016/j.yjsbx.2021.100057] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/15/2022] Open
Abstract
Structural hierarchy of bone - observed across multiple scales and in three dimensions (3D) - is essential to its mechanical performance. While the mineralized extracellular matrix of bone consists predominantly of carbonate-substituted hydroxyapatite, type I collagen fibrils, water, and noncollagenous organic constituents (mainly proteins and small proteoglycans), it is largely the 3D arrangement of these inorganic and organic constituents at each length scale that endow bone with its exceptional mechanical properties. Focusing on recent volumetric imaging studies of bone at each of these scales - from the level of individual mineralized collagen fibrils to that of whole bones - this graphical review builds upon and re-emphasizes the original work of James Bell Pettigrew and D'Arcy Thompson who first described the ubiquity of spiral structure in Nature. Here we illustrate and discuss the omnipresence of twisted, curved, sinusoidal, coiled, spiraling, and braided motifs in bone in at least nine of its twelve hierarchical levels - a visualization undertaking that has not been possible until recently with advances in 3D imaging technologies (previous 2D imaging does not provide this information). From this perspective, we hypothesize that the twisting motif occurring across each hierarchical level of bone is directly linked to enhancement of function, rather than being simply an energetically favorable way to assemble mineralized matrix components. We propose that attentive consideration of twists in bone and the skeleton at different scales will likely develop, and will enhance our understanding of structure-function relationships in bone.
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Affiliation(s)
- Daniel J Buss
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, Quebec H3A 0C7, Canada
| | - Roland Kröger
- Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Marc D McKee
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, Quebec H3A 0C7, Canada.,Faculty of Dentistry, McGill University, 3640 University Street, Montreal, Quebec H3A 0C7, Canada
| | - Natalie Reznikov
- Department of Bioengineering, McGill University, 3480 University Street, Montreal, Quebec H3A 0E9, Canada
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Gomes-Ferreira PHS, Micheletti C, Frigério PB, de Souza Batista FR, Monteiro NG, Bim-júnior O, Lisboa-Filho PN, Grandfield K, Okamoto R. PTH 1-34-functionalized bioactive glass improves peri-implant bone repair in orchiectomized rats: Microscale and ultrastructural evaluation. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2022; 134:112688. [DOI: 10.1016/j.msec.2022.112688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 01/20/2022] [Accepted: 01/27/2022] [Indexed: 11/30/2022]
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Abstract
Understanding the properties of bone is of both fundamental and clinical relevance. The basis of bone’s quality and mechanical resilience lies in its nanoscale building blocks (i.e., mineral, collagen, non-collagenous proteins, and water) and their complex interactions across length scales. Although the structure–mechanical property relationship in healthy bone tissue is relatively well characterized, not much is known about the molecular-level origin of impaired mechanics and higher fracture risks in skeletal disorders such as osteoporosis or Paget’s disease. Alterations in the ultrastructure, chemistry, and nano-/micromechanics of bone tissue in such a diverse group of diseased states have only been briefly explored. Recent research is uncovering the effects of several non-collagenous bone matrix proteins, whose deficiencies or mutations are, to some extent, implicated in bone diseases, on bone matrix quality and mechanics. Herein, we review existing studies on ultrastructural imaging—with a focus on electron microscopy—and chemical, mechanical analysis of pathological bone tissues. The nanometric details offered by these reports, from studying knockout mice models to characterizing exact disease phenotypes, can provide key insights into various bone pathologies and facilitate the development of new treatments.
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Mineral tessellation in bone and the stenciling principle for extracellular matrix mineralization. J Struct Biol 2021; 214:107823. [PMID: 34915130 DOI: 10.1016/j.jsb.2021.107823] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 12/02/2021] [Accepted: 12/06/2021] [Indexed: 11/21/2022]
Abstract
We review here the Stenciling Principle for extracellular matrix mineralization that describes a double-negative process (inhibition of inhibitors) that promotes mineralization in bone and other mineralized tissues, whereas the default condition of inhibition alone prevents mineralization elsewhere in soft connective tissues. The stenciling principle acts across multiple levels from the macroscale (skeleton/dentition vs soft connective tissues), to the microscale (for example, entheses, and the tooth attachment complex where the soft periodontal ligament is situated between mineralized tooth cementum and mineralized alveolar bone), and to the mesoscale (mineral tessellation). It relates to both small-molecule (e.g. pyrophosphate) and protein (e.g. osteopontin) inhibitors of mineralization, and promoters (enzymes, e.g. TNAP, PHEX) that degrade the inhibitors to permit and regulate mineralization. In this process, an organizational motif for bone mineral arises that we call crossfibrillar mineral tessellation where mineral formations - called tesselles - geometrically approximate prolate ellipsoids and traverse multiple collagen fibrils (laterally). Tesselle growth is directed by the structural anisotropy of collagen, being spatially restrained in the shorter transverse tesselle dimensions (averaging 1.6 × 0.8 × 0.8 μm, aspect ratio 2, length range 1.5-2.5 μm). Temporo-spatially, the tesselles abut in 3D (close ellipsoid packing) to fill the volume of lamellar bone extracellular matrix. Poorly mineralized interfacial gaps between adjacent tesselles remain discernable even in mature lamellar bone. Tessellation of a same, small basic unit to form larger structural assemblies results in numerous 3D interfaces, allows dissipation of critical stresses, and enables fail-safe cyclic deformations. Incomplete tessellation in osteomalacia/odontomalacia may explain why soft osteomalacic bones buckle and deform under loading.
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Ionic liquid treatment for efficient sample preparation of hydrated bone for scanning electron microscopy. Micron 2021; 153:103192. [PMID: 34896685 DOI: 10.1016/j.micron.2021.103192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 11/20/2022]
Abstract
This study presents a new protocol for preparing bone samples for scanning electron microscopy (SEM) using a room temperature ionic liquid (RTIL) treatment method. RTIL-based solutions can be adopted as an alternative to lengthy and laborious traditional means of preparation for SEM due to their unique low-vapour pressure and conductive properties. Applied to biological samples, RTILs can be used quickly and efficiently to observe hydrated, unfixed structures in typical SEM systems. This first-time feasibility study of the optimization of this protocol for bone was explored through various SEM modalities using two distinct ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMI][BF4]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMI][BF4]), at varying concentrations of 5, 10, and 25 % v/v in aqueous solution through an addition-based method. Based on qualitative observations in the SEM, a 60-second solution addition treatment of 10 % v/v [BMI][BF4] performed the best in imaging hydrated, unfixed bone samples, resulting in minimal charge buildup and no solution pooling on the surface. The treatment was applied effectively to a variety of bone samples, notably flat and polished, as well as highly topographical bone fracture surfaces of both healthy and osteoporotic human bone samples. In comparison to conventionally dehydrated bone, the RTIL treatment better preserved the natural bone structure, resulting in minimal microcracking in observed structures.
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