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Fernandes Da Costa C, Attik N, Gauthier R. Influence of intramedullary pressure on Lacuno-Canalicular fluid flow: A systematic review. Acta Biomater 2024; 178:41-49. [PMID: 38484832 DOI: 10.1016/j.actbio.2024.03.003] [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: 10/26/2023] [Revised: 03/01/2024] [Accepted: 03/06/2024] [Indexed: 03/24/2024]
Abstract
While most of current models investigating bone remodelling are based on matrix deformation, intramedullary pressure also plays a role. Bone remodelling is orchestrated by the Lacuno-Canalicular Network (LCN) fluid-flow. The aim of this review was hence to assess the influence of intramedullary pressure on the fluid circulation within the LCN. Three databases (Science Direct, Web of Science, and PubMed) were used. The first phase of the search returned 731 articles, of which 9 respected the inclusion/exclusion criteria and were included. These studies confirm the association between intramedullary pressure and fluid dynamics in the LCN. Among the included studies, 7 experimental studies using animal models and 2 numerical models were found. The studies were then ranked according to the nature of the applied loading, either axial compression or direct cyclic intramedullary pressure. The current review revealed that there is an influence of intramedullary pressure on LCN fluid dynamics and that this influence depends on the magnitude and the frequency of the applied pressure. Two studies confirmed that the influence was effective even without bone matrix deformation. While intramedullary pressure is closely associated with LCN fluid, there is a severe lack of studies on this topic. STATEMENT OF SIGNIFICANCE: Since the 1990's, numerical models developed to investigate fluid flow in bone submicrometric porous network are based on the flow induced by matrix deformation. Bone fluid flow is known to be involved in cells stimulation and hence directly influences bone remodeling. Different studies have shown that intramedullary pressure is also associated with bone mechanosensitive adaptation. This pressure is developed in bone due to blood circulation and is increased during loading or muscle stimulation. The current article reviews the studies investigating the influence of this pressure on bone porous fluid flow. They show that fluid flow is involved by this pressure even without bone matrix deformation. The current review article highlights the severe lack of studies about this mechanism.
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Affiliation(s)
- Cassandra Fernandes Da Costa
- UMR CNRS 5615, Laboratoire des Multimatériaux et Interfaces, Université de Lyon, Université Claude Bernard Lyon 1, Lyon 69372 CEDEX 08, France; CNRS, INSA Lyon, MATEIS, UMR5510, Université de Lyon, Université Claude Bernard Lyon 1, 7 avenue Jean Capelle, Villeurbanne CEDEX 69621, France
| | - Nina Attik
- UMR CNRS 5615, Laboratoire des Multimatériaux et Interfaces, Université de Lyon, Université Claude Bernard Lyon 1, Lyon 69372 CEDEX 08, France; Faculté d'Odontologie, Université de Lyon, Université Claude Bernard Lyon 1, Lyon 69372 CEDEX 08, France.
| | - Remy Gauthier
- CNRS, INSA Lyon, MATEIS, UMR5510, Université de Lyon, Université Claude Bernard Lyon 1, 7 avenue Jean Capelle, Villeurbanne CEDEX 69621, France.
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Bolger MW, Tekkey T, Kohn DH. Peripheral canalicular branching is decreased in streptozotocin-induced diabetes and correlates with decreased whole-bone ultimate load and perilacunar elastic work. JBMR Plus 2024; 8:ziad017. [PMID: 38505218 PMCID: PMC10945723 DOI: 10.1093/jbmrpl/ziad017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 12/01/2023] [Accepted: 12/06/2023] [Indexed: 03/21/2024] Open
Abstract
Osteocytes, the most abundant cell type in bone, play a crucial role in mechanosensation and signaling for bone formation and resorption. These cells reside within a complex lacuno-canalicular network (OLCN). Osteocyte signaling is reduced under diabetic conditions, and both type 1 and type 2 diabetes lead to reduced bone turnover, perturbed bone composition, and increased fracture risk. We hypothesized that this reduced bone turnover, and altered bone composition with diabetes is associated with reduced OLCN architecture and connectivity. This study aimed to elucidate: (1) the sequence of OLCN changes with diabetes related to bone turnover and (2) whether changes to the OLCN are associated with tissue composition and mechanical properties. Twelve- to fourteen-week-old male C57BL/6 mice were administered streptozotocin at 50 mg/kg for 5 consecutive days to induce hyperglycemia, sacrificed at baseline (BL), or after being diabetic for 3 (D3) and 7 (D7) wk with age-matched (C3, C7) controls (n = 10-12 per group). Mineralized femoral sections were infiltrated with rhodamine, imaged with confocal microscopy, then the OLCN morphology and topology were characterized and correlated against bone histomorphometry, as well as local and whole-bone mechanics and composition. D7 mice exhibited a lower number of peripheral branches relative to C7. The total number of canalicular intersections (nodes) was lower in D3 and D7 relative to BL (P < 0.05 for all), and a reduced bone formation rate (BFR) was observed at D7 vs C7. The number of nodes explained only 15% of BFR, but 45% of Ct.BV/TV, and 31% of ultimate load. The number of branches explained 30% and 22% of the elastic work at the perilacunar and intracortical region, respectively. Collectively, the reduction in OLCN architecture and association of OLCN measures with bone turnover, mechanics, and composition highlights the relevance of the osteocyte and the OLCN and a potential therapeutic target for treating diabetic skeletal fragility.
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Affiliation(s)
- Morgan W Bolger
- Department of Biomedical Engineering, College of Engineering, University of Michigan, Ann Arbor, MI 48109, United States
| | - Tara Tekkey
- Department of Chemistry, College of Literature, Science and the Arts, University of Michigan, Ann Arbor, MI 48109, United States
| | - David H Kohn
- Department of Biomedical Engineering, College of Engineering, University of Michigan, Ann Arbor, MI 48109, United States
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, United States
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3
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Meslier QA, DiMauro N, Somanchi P, Nano S, Shefelbine SJ. Manipulating load-induced fluid flow in vivo to promote bone adaptation. Bone 2022; 165:116547. [PMID: 36113842 DOI: 10.1016/j.bone.2022.116547] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 09/01/2022] [Accepted: 09/12/2022] [Indexed: 11/02/2022]
Abstract
Mechanical stimulation is critical to maintaining bone mass and strength. Strain has been commonly thought of as the mechanical stimulus driving bone adaptation. However, numerous studies have hypothesized that fluid flow in the lacunar-canalicular system plays a role in mechanoadaptation. The role of fluid flow compared to strain magnitude on bone remodeling has yet to be characterized. This study aimed to determine the contribution of fluid flow velocity compared to strain on bone adaptation. We used finite element modeling to design in vivo experiments, manipulating strain and fluid flow contributions. Using a uniaxial compression tibia model in mice, we demonstrated that high fluid flow velocity results in significant bone adaptation even under low strain magnitude. In contrast, high strain magnitude paired with low fluid velocity does not trigger a bone response. These findings support previous hypotheses stating that fluid flow is the principal mechanical stimulus driving bone adaptation. Moreover, they give new insights regarding bone adaptative response and provide new pathways toward treatment against age-related mechanosensitivity loss in bone.
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Affiliation(s)
- Quentin A Meslier
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Nicole DiMauro
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Priya Somanchi
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Sarah Nano
- Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Sandra J Shefelbine
- Department of Bioengineering, Northeastern University, Boston, MA, USA; Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA.
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Changes in interstitial fluid flow, mass transport and the bone cell response in microgravity and normogravity. Bone Res 2022; 10:65. [PMID: 36411278 PMCID: PMC9678891 DOI: 10.1038/s41413-022-00234-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 08/17/2022] [Accepted: 08/29/2022] [Indexed: 11/22/2022] Open
Abstract
In recent years, our scientific interest in spaceflight has grown exponentially and resulted in a thriving area of research, with hundreds of astronauts spending months of their time in space. A recent shift toward pursuing territories farther afield, aiming at near-Earth asteroids, the Moon, and Mars combined with the anticipated availability of commercial flights to space in the near future, warrants continued understanding of the human physiological processes and response mechanisms when in this extreme environment. Acute skeletal loss, more severe than any bone loss seen on Earth, has significant implications for deep space exploration, and it remains elusive as to why there is such a magnitude of difference between bone loss on Earth and loss in microgravity. The removal of gravity eliminates a critical primary mechano-stimulus, and when combined with exposure to both galactic and solar cosmic radiation, healthy human tissue function can be negatively affected. An additional effect found in microgravity, and one with limited insight, involves changes in dynamic fluid flow. Fluids provide the most fundamental way to transport chemical and biochemical elements within our bodies and apply an essential mechano-stimulus to cells. Furthermore, the cell cytoplasm is not a simple liquid, and fluid transport phenomena together with viscoelastic deformation of the cytoskeleton play key roles in cell function. In microgravity, flow behavior changes drastically, and the impact on cells within the porous system of bone and the influence of an expanding level of adiposity are not well understood. This review explores the role of interstitial fluid motion and solute transport in porous bone under two different conditions: normogravity and microgravity.
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Allison H, O'Sullivan L, McNamara L. Temporal changes in cortical microporosity during estrogen deficiency associated with perilacunar resorption and osteocyte apoptosis: A pilot study. Bone Rep 2022; 16:101590. [PMID: 35663377 PMCID: PMC9156983 DOI: 10.1016/j.bonr.2022.101590] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 05/13/2022] [Accepted: 05/14/2022] [Indexed: 02/07/2023] Open
Abstract
Osteocytes can actively regulate bone microporosity, through either perilacunar resorption or micropetrosis following apoptosis. Osteocyte apoptosis is more prevalent in estrogen deficiency and changes in the lacunar-canalicular network of osteocytes have been reported. Temporal changes in bone mineralisation and osteocytes cellular strains occur, which might be associated with osteocyte-driven microporosity changes, although time dependant changes in bone microporosity are not yet fully understood. In this pilot study we conducted micro-CT analysis, backscatter electron imaging and histological analysis of femoral cortical bone form an ovariectomized rat model of osteoporosis to investigate whether estrogen deficiency causes temporal changes in lacunar and vascular porosity. We also assessed MMP14 expression, lacunar occupancy and mineral infilling, as indicators of perilacunar resorption and micropetrosis. We report temporal changes in cortical microporosity in estrogen deficiency. Specifically, canalicular and vascular porosity initially increased (4 weeks post-OVX), coinciding with the period of rapid bone loss, whereas in the longer term (14 weeks post-OVX) lacunar and canalicular diameter decreased. Interestingly, these changes coincided with an increased prevalence of empty lacunae and osteocyte lacunae were observed to be more circular with a mineralised border around the lacunar space. In addition we report an increase in MMP14+ osteocytes, which also suggests active matrix degradation by these cells. Together these results provide an insight into the temporal changes in cortical microporosity during estrogen deficiency and suggest the likelihood of occurrence of both perilacunar resorption and osteocyte apoptosis leading to micropetrosis. We propose that microporosity changes arise due to processes driven by distinct populations of osteocytes, which are either actively resorbing their matrix or have undergone apoptosis and are infilling lacunae by micropetrosis.
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Key Words
- BMDD, Bone mineral density distribution
- BSEM
- BSEM, Backscattered scanning electron microscopy
- BV, Bone volume
- Dm, Diameter
- Estrogen deficiency
- Lacunar
- Lc, Lacunar
- MMP, Matrix metalloproteases
- Micro-CT, Micro computed tomography
- Microporosity
- OVX, Ovariectomized
- PLR, Perilacunar resorption
- Sp, spacing
- TRAP, Tartrate-resistant acid phosphatase
- TV, Total volume
- Tb, Trabecular
- Th, Thickness
- V Ca, Vascular canal
- Vascular canals
- micro-CT
- με, Microstrain (ε ×10−6)
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Affiliation(s)
- H. Allison
- Mechanobiology and Medical Devices Research Group (MMDRG), Centre for Biomechanics Research (BioMEC), Biomedical Engineering, College of Science and Engineering, National University of Ireland Galway, Ireland
| | - L.M. O'Sullivan
- Mechanobiology and Medical Devices Research Group (MMDRG), Centre for Biomechanics Research (BioMEC), Biomedical Engineering, College of Science and Engineering, National University of Ireland Galway, Ireland
| | - L.M. McNamara
- Mechanobiology and Medical Devices Research Group (MMDRG), Centre for Biomechanics Research (BioMEC), Biomedical Engineering, College of Science and Engineering, National University of Ireland Galway, Ireland
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Murshid SA. Bone permeability and mechanotransduction: Some current insights into the function of the lacunar-canalicular network. Tissue Cell 2022; 75:101730. [PMID: 35032785 DOI: 10.1016/j.tice.2022.101730] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/05/2022] [Accepted: 01/06/2022] [Indexed: 10/19/2022]
Abstract
Lacunar-canalicular (LC) permeability involves the passage of fluids, nutrients, oxygen, ions, and signalling molecules through bone tissue, facilitating the maintenance of bone vitality and function and responses to various physiological conditions and diseases. LC permeability and fluid flow-shear stress/drag force play important roles in mechanotransduction in bone tissue by inducing mechanical stimuli in osteocytes, modulating cellular functions, and determining bone adaptation. Alterations in LC structure may therefore influence the fluid flow pattern through the LC network, thereby affecting the ability of osteocytes to sense and translate mechanical signals and possibly contributing to bone remodelling. Several bone-health conditions are associated with changes in LC structure and function and may affect mechanotransduction and responses, although the mechanisms underlying these associations are still not fully understood. In this review, recent studies of LC networks, their formation and transfer mechanical stimuli, and changes in structure, functional permeability, and mechanotransduction that result from age, pathology, and mechanical loading are discussed. Additionally, applications of vibration and low-intensity pulsed ultrasound in bone healthcare and regeneration fields are also presented.
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Affiliation(s)
- Sakhr Ahmed Murshid
- Institute for Globally Distributed Open Research and Education (IGDORE); Ilmajoki Health Public Dental Clinics, Social and Health Care Services in Jalasjärvi, Ilmajoki, Kurikka, Finland.
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Sun Y, Wan B, Wang R, Zhang B, Luo P, Wang D, Nie JJ, Chen D, Wu X. Mechanical Stimulation on Mesenchymal Stem Cells and Surrounding Microenvironments in Bone Regeneration: Regulations and Applications. Front Cell Dev Biol 2022; 10:808303. [PMID: 35127684 PMCID: PMC8815029 DOI: 10.3389/fcell.2022.808303] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 01/03/2022] [Indexed: 01/15/2023] Open
Abstract
Treatment of bone defects remains a challenge in the clinic. Artificial bone grafts are the most promising alternative to autologous bone grafting. However, one of the limiting factors of artificial bone grafts is the limited means of regulating stem cell differentiation during bone regeneration. As a weight-bearing organ, bone is in a continuous mechanical environment. External mechanical force, a type of biophysical stimulation, plays an essential role in bone regeneration. It is generally accepted that osteocytes are mechanosensitive cells in bone. However, recent studies have shown that mesenchymal stem cells (MSCs) can also respond to mechanical signals. This article reviews the mechanotransduction mechanisms of MSCs, the regulation of mechanical stimulation on microenvironments surrounding MSCs by modulating the immune response, angiogenesis and osteogenesis, and the application of mechanical stimulation of MSCs in bone regeneration. The review provides a deep and extensive understanding of mechanical stimulation mechanisms, and prospects feasible designs of biomaterials for bone regeneration and the potential clinical applications of mechanical stimulation.
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Affiliation(s)
- Yuyang Sun
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
| | - Ben Wan
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
- Department of Oral and Maxillofacial Surgery/Pathology, Amsterdam UMC and Academic Center for Dentistry Amsterdam (ACTA), Vrije Universiteit Amsterdam (VU), Amsterdam Movement Science (AMS), Amsterdam, Netherlands
| | - Renxian Wang
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
| | - Bowen Zhang
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
| | - Peng Luo
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
| | - Diaodiao Wang
- Department of Joint Surgery, Peking University Ninth School of Clinical Medicine, Beijing Shijitan Hospital, Capital Medical University, Beijing, China
| | - Jing-Jun Nie
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
- *Correspondence: Jing-Jun Nie, ; Dafu Chen,
| | - Dafu Chen
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
- *Correspondence: Jing-Jun Nie, ; Dafu Chen,
| | - Xinbao Wu
- Laboratory of Bone Tissue Engineering, Beijing Laboratory of Biomedical Materials, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Beijing, China
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Abstract
PURPOSE OF REVIEW Postmenopausal osteoporosis reduces circulating estrogen levels, which leads to osteoclast resorption, bone loss, and fracture. This review addresses emerging evidence that osteoporosis is not simply a disease of bone loss but that mechanosensitive osteocytes that regulate both osteoclasts and osteoblasts are also impacted by estrogen deficiency. RECENT FINDINGS At the onset of estrogen deficiency, the osteocyte mechanical environment is altered, which coincides with temporal changes in bone tissue composition. The osteocyte microenvironment is also altered, apoptosis is more prevalent, and hypermineralization occurs. The mechanobiological responses of osteocytes are impaired under estrogen deficiency, which exacerbates osteocyte paracrine regulation of osteoclasts. Recent research reveals changes in osteocytes during estrogen deficiency that may play a critical role in the etiology of the disease. A paradigm change for osteoporosis therapy requires an advanced understanding of such changes to establish the efficacy of osteocyte-targeted therapies to inhibit resorption and secondary mineralization.
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Affiliation(s)
- Laoise M McNamara
- Mechanobiology and Medical Device Research Group, Biomedical Engineering, College of Science and Engineering, National University of Ireland, Galway, Ireland.
- Centre for Research in Medical Devices (CÚRAM), National University of Ireland, Galway, Ireland.
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Aguirre JI, Castillo EJ, Kimmel DB. Biologic and pathologic aspects of osteocytes in the setting of medication-related osteonecrosis of the jaw (MRONJ). Bone 2021; 153:116168. [PMID: 34487892 PMCID: PMC8478908 DOI: 10.1016/j.bone.2021.116168] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 08/02/2021] [Accepted: 08/31/2021] [Indexed: 02/08/2023]
Abstract
Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe, debilitating condition affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). Oral risk factors associated with the development of MRONJ include tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection). In bone tissues, osteocytes play a bidirectional role in which they not only act as the "receiver" of systemic signals from blood vessels, such as hormones and drugs, or local signals from the mineralized matrix as it is deformed, but they also play a critical role as "transmitter" of signals to the cells that execute bone modeling and remodeling (osteoclasts, osteoblasts and lining cells). When the survival capacity of osteocytes is overwhelmed, they can die. Osteocyte death has been associated with several pathological conditions. Whereas the causes and mechanisms of osteocyte death have been studied in conditions like osteonecrosis of the femoral head (ONFH), few studies of the causes and mechanisms of osteocyte death have been done in MRONJ. The three forms of cell death that affect most of the different cells in the body (apoptosis, autophagy, and necrosis) have been recognized in osteocytes. Notably, necroptosis, a form of regulated cell death with "a necrotic cell death phenotype," has also been identified as a form of cell death in osteocytes under certain pathologic conditions. Improving the understanding of osteocyte death in MRONJ may be critical for preventing disease and developing treatment approaches. In this review, we intend to provide insight into the biology of osteocytes, cell death, in general, and osteocyte death, in particular, and discuss hypothetical mechanisms involved in osteocyte death associated with MRONJ.
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Affiliation(s)
- J I Aguirre
- Department of Physiological Sciences, University of Florida (UF), Gainesville, FL, United States of America.
| | - E J Castillo
- Department of Physiological Sciences, University of Florida (UF), Gainesville, FL, United States of America.
| | - D B Kimmel
- Department of Physiological Sciences, University of Florida (UF), Gainesville, FL, United States of America
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10
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Lewis KJ, Cabahug-Zuckerman P, Boorman-Padgett JF, Basta-Pljakic J, Louie J, Stephen S, Spray DC, Thi MM, Seref-Ferlengez Z, Majeska RJ, Weinbaum S, Schaffler MB. Estrogen depletion on In vivo osteocyte calcium signaling responses to mechanical loading. Bone 2021; 152:116072. [PMID: 34171514 PMCID: PMC8316427 DOI: 10.1016/j.bone.2021.116072] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 06/15/2021] [Accepted: 06/20/2021] [Indexed: 11/27/2022]
Abstract
Microstructural adaptation of bone in response to mechanical stimuli is diminished with estrogen deprivation. Here we tested in vivo whether ovariectomy (OVX) alters the acute response of osteocytes, the principal mechanosensory cells of bone, to mechanical loading in mice. We also used super resolution microscopy (Structured Illumination microscopy or SIM) in conjunction with immunohistochemistry to assess changes in the number and organization of "osteocyte mechanosomes" - complexes of Panx1 channels, P2X7 receptors and CaV3 voltage-gated Ca2+ channels clustered around αvβ3 integrin foci on osteocyte processes. Third metatarsals bones of mice expressing an osteocyte-targeted genetically encoded Ca2+ indicator (DMP1-GCaMP3) were cyclically loaded in vivo to strains from 250 to 3000 με and osteocyte intracellular Ca2+ signaling responses were assessed in mid-diaphyses using multiphoton microscopy. The number of Ca2+ signaling osteocytes in control mice increase monotonically with applied strain magnitude for the physiological range of strains. The relationship between the number of Ca2+ signaling osteocytes and loading was unchanged at 2 days post-OVX. However, it was altered markedly at 28 days post-OVX. At loads up to 1000 με, there was a dramatic reduction in number of responding (i.e. Ca2+ signaling) osteocytes; however, at higher strains the numbers of Ca2+ signaling osteocytes were similar to control mice. OVX significantly altered the abundance, make-up and organization of osteocyte mechanosome complexes on dendritic processes. Numbers of αvβ3 foci also staining with either Panx 1, P2X7R or CaV3 declined by nearly half after OVX, pointing to a loss of osteocyte mechanosomes on the dendritic processes with estrogen depletion. At the same time, the areas of the remaining foci that stained for αvβ3 and channel proteins increased significantly, a redistribution of mechanosome components suggesting a potential compensatory response. These results demonstrate that the deleterious effects of estrogen depletion on skeletal mechanical adaptation appear at the level of mechanosensation; osteocytes lose the ability to sense small (physiological) mechanical stimuli. This decline may result at least partly from changes in the structure and organization of osteocyte mechanosomes, which contribute to the distinctive sensitivity of osteocytes (particularly their dendritic processes) to mechanical stimulation.
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Affiliation(s)
- Karl J Lewis
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Pamela Cabahug-Zuckerman
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - James F Boorman-Padgett
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Jelena Basta-Pljakic
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Joyce Louie
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Samuel Stephen
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Mia M Thi
- Orthopaedic Surgery, Albert Einstein College of Medicine, Bronx, NY, United States of America; Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Zeynep Seref-Ferlengez
- Orthopaedic Surgery, Albert Einstein College of Medicine, Bronx, NY, United States of America
| | - Robert J Majeska
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Sheldon Weinbaum
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America
| | - Mitchell B Schaffler
- Department of Biomedical Engineering, The City College of New York, New York, NY, United States of America.
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11
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Gatti V, Gelbs MJ, Guerra RB, Gerber MB, Fritton SP. Interstitial fluid velocity is decreased around cortical bone vascular pores and depends on osteocyte position in a rat model of disuse osteoporosis. Biomech Model Mechanobiol 2021; 20:1135-1146. [PMID: 33666792 DOI: 10.1007/s10237-021-01438-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 02/15/2021] [Indexed: 10/22/2022]
Abstract
Muscle paralysis induced with botulinum toxin (Botox) injection increases vascular porosity and reduces osteocyte lacunar density in the tibial cortical bone of skeletally mature rats. These morphological changes potentially affect interstitial fluid flow in the lacunar-canalicular porosity, which is thought to play a role in osteocyte mechanotransduction. The aim of this study was to investigate the effects of disuse-induced morphological changes on interstitial fluid velocity around osteocytes in the bone cortex. Micro-CT images from a previous study that quantified the effects of Botox-induced muscle paralysis on bone microarchitecture in skeletally mature rats were used to create high-resolution, animal-specific finite element models that included the vascular pores and osteocyte lacunae within the tibial metaphysis of Botox-injected (BTX, n = 8) and saline-injected control (CTRL, n = 8) groups. To quantify fluid flow, lacunar and canalicular porosities were modeled as fluid-saturated poroelastic materials, and boundary conditions were applied to simulate physiological loading. This modeling approach allowed a detailed quantification of the fluid flow velocities around osteocytes in a relatively large volume of bone tissue. The analysis demonstrated that interstitial fluid velocity at the vascular pore surfaces was significantly lower in BTX compared to CTRL because of the decreased vascular canal separation. No significant differences in average fluid velocity were observed at the osteocyte lacunae and no correlation was found between the fluid velocity and the lacunar density, which was significantly lower in BTX. Instead, the lacunar fluid velocity was dependent on the osteocyte's specific position in the bone cortex and its proximity to a vascular pore.
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Affiliation(s)
- Vittorio Gatti
- Department of Biomedical Engineering, The City College of New York, New York, NY, USA
| | - Michelle J Gelbs
- Department of Biomedical Engineering, The City College of New York, New York, NY, USA
| | - Rodrigo B Guerra
- Department of Biomedical Engineering, The City College of New York, New York, NY, USA
| | - Michael B Gerber
- Department of Biomedical Engineering, The City College of New York, New York, NY, USA
| | - Susannah P Fritton
- Department of Biomedical Engineering, The City College of New York, New York, NY, USA.
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Carina V, Della Bella E, Costa V, Bellavia D, Veronesi F, Cepollaro S, Fini M, Giavaresi G. Bone's Response to Mechanical Loading in Aging and Osteoporosis: Molecular Mechanisms. Calcif Tissue Int 2020; 107:301-318. [PMID: 32710266 DOI: 10.1007/s00223-020-00724-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/08/2020] [Indexed: 02/07/2023]
Abstract
Mechanotransduction is pivotal in the maintenance of homeostasis in different tissues and involves multiple cell signaling pathways. In bone, mechanical stimuli regulate the balance between bone formation and resorption; osteocytes play a central role in this regulation. Dysfunctions in mechanotransduction signaling or in osteocytes response lead to an imbalance in bone homeostasis. This alteration is very relevant in some conditions such as osteoporosis and aging. Both are characterized by increased bone weakness due to different causes, for example, the increase of osteocyte apoptosis that cause an alteration of fluid space, or the alteration of molecular pathways. There are intertwined yet very different mechanisms involved among the cell-intrinsic effects of aging on bone, the cell-intrinsic and tissue-level effects of estrogen/androgen withdrawal on bone, and the effects of reduced mechanical loading on bone, which are all involved to some degree in how aged bone fails to respond properly to stress/strain compared to younger bone. This review aims at clarifying how the cellular and molecular pathways regulated and induced in bone by mechanical stimulation are altered with aging and in osteoporosis, to highlight new possible targets for antiresorptive or anabolic bone therapeutic approaches.
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Affiliation(s)
- Valeria Carina
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy.
| | | | - Viviana Costa
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy
| | - Daniele Bellavia
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy
| | - Francesca Veronesi
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy
| | - Simona Cepollaro
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy
| | - Milena Fini
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy
| | - Gianluca Giavaresi
- IRCCS Istituto Ortopedico Rizzoli, SC Scienze e Tecnologie Chirurgiche - SS Piattaforma Scienze Omiche per Ortopedia Personalizzata, Via Di Barbiano, 1/10, 40136, Bologna, Italy
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13
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Mann KA, Miller MA, Tatusko ME, Oest ME. Similitude of cement-bone micromechanics in cemented rat and human knee replacement. J Orthop Res 2020; 38:1529-1537. [PMID: 32167182 PMCID: PMC7293949 DOI: 10.1002/jor.24661] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 02/12/2020] [Accepted: 03/06/2020] [Indexed: 02/04/2023]
Abstract
A preclinical rat knee replacement model was recently developed to explore the biological and mechanobiological changes of trabecular resorption for cement-bone interdigitated regions. The goal here was to evaluate the relevance of this model compared with human knee replacement with regards to functional micromechanics. Eight nonsurvival, cemented knee replacement surgeries were performed, the interdigitated gap morphology was quantified, and interface micromotion between cement and bone was measured for 1 to 5 bodyweight loading. Computational fluid dynamics modeling of unit cell geometries with small gaps between trabeculae and cement was used to estimate fluid flow. Gap width (3.6 μm) was substantially smaller compared with cement-bone gaps reported in human knee replacement (11.8 μm). Micromotion at the cement-bone border was also decreased for the rat knee replacement (0.48 μm), compared with human (1.97 μm), for 1 bodyweight loading. However, the micromotion-to-gap width ratio (0.19 and 0.22 for, rat and human), and estimated fluid shear stress (6.47 and 7.13 Pa, for rat and human) were similar. Replicating the fluid dynamic characteristics of cement-bone interdigitated regions in human knee replacements using preclinical models may be important to recapitulate trabecular resorption mechanisms due to proposed supraphysiologic fluid shear stress. Statement of clinical significance: local cement-bone micromotion due to joint loading may contribute to the process of clinical loosening in total joint replacements. This work shows that while micromotion and gap morphology are diminished for the rat knee model compared to human, the motion-to-gap ratio, and corresponding fluid shear stress are of similar magnitudes.
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14
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Mustafy T, Londono I, Moldovan F, Villemure I. Isolated Cyclic Loading During Adolescence Improves Tibial Bone Microstructure and Strength at Adulthood. JBMR Plus 2020; 4:e10349. [PMID: 32258967 PMCID: PMC7117850 DOI: 10.1002/jbm4.10349] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 01/24/2020] [Accepted: 01/27/2020] [Indexed: 12/21/2022] Open
Abstract
Bone is a unique living tissue, which responds to the mechanical stimuli regularly imposed on it. Adolescence facilitates a favorable condition for the skeleton that enables the exercise to positively influence bone architecture and overall strength. However, it is still dubious for how long the skeletal benefits gained in adolescence is preserved at adulthood. The current study aims to use a rat model to investigate the effects of in vivo low- (LI), medium- (MI), and high- (HI) intensity cyclic loadings applied during puberty on longitudinal bone development, morphometry, and biomechanics during adolescence as well as at adulthood. Forty-two young (4-week-old) male rats were randomized into control, sham, LI, MI, and HI groups. After a 5 day/week for 8 weeks cyclic loading regime applied on the right tibia, loaded rats underwent a subsequent 41-week, normal cage activity period. Right tibias were removed at 52 weeks of age, and a comprehensive assessment was performed using μCT, mechanical testing, and finite element analysis. HI and MI groups exhibited reduced body weight and food intake at the end of the loading period compared with shams, but these effects disappeared afterward. HI cyclic loading increased BMD, bone volume fraction, trabecular thickness, trabecular number, and decreased trabecular spacing after loading. All loading-induced benefits, except BMD, persisted until the end of the normal cage activity period. Moreover, HI loading induced enhanced bone area, periosteal perimeter, and moment of inertia, which remained up to the 52nd week. After the normal cage activity at adulthood, the HI group showed increased ultimate force and stress, stiffness, postyield displacement and energy, and toughness compared with the sham group. Overall, our findings suggest that even though both trabecular and cortical bone drifted through age-related changes during aging, HI cyclic loading performed during adolescence can render lifelong benefits in bone microstructure and biomechanics. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Tanvir Mustafy
- Department of Mechanical EngineeringÉcole Polytechnique of MontréalMontréalQuébecCanada
- Department of PediatricsSainte‐Justine University Hospital CenterMontréalQuébecCanada
| | - Irène Londono
- Department of PediatricsSainte‐Justine University Hospital CenterMontréalQuébecCanada
| | - Florina Moldovan
- Department of PediatricsSainte‐Justine University Hospital CenterMontréalQuébecCanada
- Department of Stomatology, Faculty of DentistryUniversité de MontréalMontréalQuébecCanada
| | - Isabelle Villemure
- Department of Mechanical EngineeringÉcole Polytechnique of MontréalMontréalQuébecCanada
- Department of PediatricsSainte‐Justine University Hospital CenterMontréalQuébecCanada
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15
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Creecy A, Damrath JG, Wallace JM. Control of Bone Matrix Properties by Osteocytes. Front Endocrinol (Lausanne) 2020; 11:578477. [PMID: 33537002 PMCID: PMC7848033 DOI: 10.3389/fendo.2020.578477] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 12/01/2020] [Indexed: 12/13/2022] Open
Abstract
Osteocytes make up 90-95% of the cellular content of bone and form a rich dendritic network with a vastly greater surface area than either osteoblasts or osteoclasts. Osteocytes are well positioned to play a role in bone homeostasis by interacting directly with the matrix; however, the ability for these cells to modify bone matrix remains incompletely understood. With techniques for examining the nano- and microstructure of bone matrix components including hydroxyapatite and type I collagen becoming more widespread, there is great potential to uncover novel roles for the osteocyte in maintaining bone quality. In this review, we begin with an overview of osteocyte biology and the lacunar-canalicular system. Next, we describe recent findings from in vitro models of osteocytes, focusing on the transitions in cellular phenotype as they mature. Finally, we describe historical and current research on matrix alteration by osteocytes in vivo, focusing on the exciting potential for osteocytes to directly form, degrade, and modify the mineral and collagen in their surrounding matrix.
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Affiliation(s)
- Amy Creecy
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States
| | - John G. Damrath
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States
| | - Joseph M. Wallace
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States
- *Correspondence: Joseph M. Wallace,
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16
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Abstract
PURPOSE OF REVIEW In perilacunar/canalicular remodeling (PLR), osteocytes dynamically resorb, and then replace, the organic and mineral components of the pericellular extracellular matrix. Given the enormous surface area of the osteocyte lacuna-canalicular network (LCN), PLR is important for maintaining homeostasis of the skeleton. The goal of this review is to examine the motivations and critical considerations for the analysis of PLR, in both in vitro and in vivo systems. RECENT FINDINGS Morphological approaches alone are insufficient to elucidate the complex mechanisms regulating PLR in the healthy skeleton and in disease. Understanding the role and regulation of PLR will require the incorporation of standardized PLR outcomes as a routine part of skeletal phenotyping, as well as the development of improved molecular and cellular outcomes. Current PLR outcomes assess PLR enzyme expression, the LCN, and bone matrix composition and organization, among others. Here, we discuss current PLR outcomes and how they have been applied to study PLR induction and suppression in vitro and in vivo. Given the role of PLR in skeletal health and disease, integrated analysis of PLR has potential to elucidate new mechanisms by which osteocytes participate in skeletal health and disease.
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Affiliation(s)
- Cristal S Yee
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, San Francisco, CA, 94143, USA
| | - Charles A Schurman
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, San Francisco, CA, 94143, USA
- UC Berkeley/UCSF Graduate Program in Bioengineering, San Francisco, CA, 94143, USA
| | - Carter R White
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, San Francisco, CA, 94143, USA
| | - Tamara Alliston
- Department of Orthopaedic Surgery, University of California, 513 Parnassus Avenue, San Francisco, CA, 94143, USA.
- UC Berkeley/UCSF Graduate Program in Bioengineering, San Francisco, CA, 94143, USA.
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17
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Wittig NK, Laugesen M, Birkbak ME, Bach-Gansmo FL, Pacureanu A, Bruns S, Wendelboe MH, Brüel A, Sørensen HO, Thomsen JS, Birkedal H. Canalicular Junctions in the Osteocyte Lacuno-Canalicular Network of Cortical Bone. ACS NANO 2019; 13:6421-6430. [PMID: 31095362 DOI: 10.1021/acsnano.8b08478] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The osteocyte lacuno-canalicular network (LCN) is essential for bone remodeling because osteocytes regulate cell recruitment. This has been proposed to occur through liquid-flow-induced shear forces in the canaliculi. Models of the LCN have thus far assumed that it contains canaliculi connecting the osteocyte lacunae. However, here, we reveal that enlarged spaces occur at places where several canaliculi cross; we name these spaces canalicular junctions. We characterize them in detail within mice cortical bone using synchrotron nanotomography at two length scales, with 50 and 130 nm voxel size, and show that canalicular junctions occur at a density similar to that of osteocyte lacunae and that canalicular junctions tend to cluster. Through confocal laser scanning microscopy, we show that canalicular junctions are widespread as we have observed them in cortical bone from several species, even though the number density of the canalicular junctions was not universal. Fluid flow simulations of a simple model system with and without a canalicular junction clearly show that liquid mass transport and flow velocities are altered by the presence of canalicular junctions. We suggest that these canalicular junctions may play an important role in osteocyte communication and possibly also in canalicular fluid flow. Therefore, we believe that they constitute an important component in the bone osteocyte network.
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Affiliation(s)
| | | | | | | | | | - Stefan Bruns
- Department of Chemistry, University of Copenhagen , 2100 Copenhagen Ø , Denmark
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18
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Tsourdi E, Jähn K, Rauner M, Busse B, Bonewald LF. Physiological and pathological osteocytic osteolysis. JOURNAL OF MUSCULOSKELETAL & NEURONAL INTERACTIONS 2018; 18:292-303. [PMID: 30179206 PMCID: PMC6146198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Osteocytes, the most abundant bone cell in the adult skeleton, can function as mechanosensors directing osteoblast and osteoclast function in order to maintain optimal load bearing bone in addition to functioning as endocrine cells regulating phosphate metabolism. A controversial function, previously overlooked or denied, has been osteocytes as regulators of calcium metabolism. Early histologists upon observing enlarged osteocyte lacunae in bone sections proposed that mature osteocytes could remove their perilacunar matrix, a term called "osteocytic osteolysis". New insights into this process have occurred during the last decade using novel technology thereby providing a means to identify molecular mechanisms responsible for osteocytic osteolysis. As release of calcium from a mineralized matrix requires a more acidic pH and specialized enzymes, it was proposed that osteocytes may utilize similar molecular mechanisms as osteoclasts to remove mineral. The idea that a cell descended from mesenchymal progenitors (the osteocyte) could function similarly to a cell descended from hematopoietic progenitors (the osteoclast) was challenged as being improbable. Here we review the molecular mechanisms behind this osteocyte function, the role of osteocytic osteolysis in health and disease, and the capacity of the osteocyte to reverse the osteolytic process by replacing the removed matrix, a revived osteoblast function.
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Affiliation(s)
- Elena Tsourdi
- Department of Medicine III, Technische Universität Dresden Medical Center, Dresden, Germany,Center for Healthy Aging, Technische Universität Dresden, Dresden, Germany,Corresponding author: Elena Tsourdi, M.D., Division of Endocrinology, Diabetes and Metabolic Bone Diseases, Department of Medicine III, Technische Universität Dresden Medical Center, Fetscherstrasse 74, 01307 Dresden, Germany E-mail:
| | - Katharina Jähn
- Department for Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Martina Rauner
- Department of Medicine III, Technische Universität Dresden Medical Center, Dresden, Germany,Center for Healthy Aging, Technische Universität Dresden, Dresden, Germany
| | - Björn Busse
- Department for Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Lynda F. Bonewald
- Indiana Center for Musculoskeletal Health, VanNuys Medical Science Building, Indianapolis, USA
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19
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Sharma D, Larriera AI, Palacio-Mancheno PE, Gatti V, Fritton JC, Bromage TG, Cardoso L, Doty SB, Fritton SP. The effects of estrogen deficiency on cortical bone microporosity and mineralization. Bone 2018; 110:1-10. [PMID: 29357314 PMCID: PMC6377161 DOI: 10.1016/j.bone.2018.01.019] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 01/09/2018] [Accepted: 01/15/2018] [Indexed: 12/22/2022]
Abstract
Recent studies have demonstrated matrix-mineral alterations in bone tissue surrounding osteocytes in estrogen-deficient animals. While cortical bone porosity has been shown to be a contributor to the mechanical properties of bone tissue, little analysis has been done to investigate the effects of estrogen deficiency on bone's microporosities, including the vascular and osteocyte lacunar porosities. In this study we examined alterations in cortical bone microporosity, mineralization, and cancellous bone architecture due to estrogen deficiency in the ovariectomized rat model of postmenopausal osteoporosis. Twenty-week-old female Sprague-Dawley rats were subjected to either ovariectomy or sham surgery. Six weeks post-surgery tibiae were analyzed using high-resolution micro-CT, backscattered electron imaging, nanoindentation, and dynamic histomorphometry. Estrogen deficiency caused an increase in cortical bone vascular porosity, with enlarged vascular pores and little change in tissue mineral density in the proximal tibial metaphysis. Measurements of cancellous architecture corresponded to previous studies reporting a decrease in bone volume fraction, an increase in trabecular separation, and a decrease in trabecular number in the proximal tibia due to estrogen deficiency. Nanoindentation results showed no differences in matrix stiffness in osteocyte-rich areas of the proximal tibia of estrogen-deficient rats, and bone labeling and backscattered electron imaging showed no significant changes in mineralization around the vascular pores. The findings demonstrate local surface alterations of vascular pores due to estrogen deficiency. An increase in cortical vascular porosity may diminish bone strength as well as alter bone mechanotransduction via interstitial fluid flow, both of which could contribute to bone fragility during postmenopausal osteoporosis.
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Affiliation(s)
- Divya Sharma
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, United States
| | - Adriana I Larriera
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, United States
| | - Paolo E Palacio-Mancheno
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, United States
| | - Vittorio Gatti
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, United States
| | - J Christopher Fritton
- Department of Orthopaedics, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Timothy G Bromage
- Department of Biomaterials, New York University College of Dentistry, New York, NY 10010, United States
| | - Luis Cardoso
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, United States
| | - Stephen B Doty
- Research Division, Hospital for Special Surgery, New York, NY 10021, United States
| | - Susannah P Fritton
- Department of Biomedical Engineering, The City College of New York, New York, NY 10031, United States.
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20
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Abstract
PURPOSE OF REVIEW Solute transport in the lacunar-canalicular system (LCS) plays important roles in osteocyte metabolism and cell-cell signaling. This review will summarize recent studies that establish pericellular matrix (PCM), discovered inside the LCS, as a crucial regulator of solute transport in bone. RECENT FINDINGS Utilizing confocal imaging and mathematical modeling, recent studies successfully quantified molecular diffusion and convection in the LCS as well as the size-dependent sieving effects of the PCM, leading to the quantification of the effective PCM fiber spacing (10 to 17 nm) in murine adult bones. Perlecan/HSPG2, a large linear proteoglycan, was identified to be an essential PCM component. The PCM-filled LCS is bone's chromatographic column, where fluid/solute transport to and from the osteocytes is regulated. The chemical composition, deposition rate, and turnover rate of the osteocyte PCM should be further defined to better understand osteocyte physiology and bone metabolism.
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Affiliation(s)
- Liyun Wang
- Center for Biomechanical Research, Department of Mechanical Engineering, University of Delaware, 130 Academy Street, Newark, DE, 19716, USA.
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21
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Microstructural changes associated with osteoporosis negatively affect loading-induced fluid flow around osteocytes in cortical bone. J Biomech 2017; 66:127-136. [PMID: 29217091 DOI: 10.1016/j.jbiomech.2017.11.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 11/05/2017] [Accepted: 11/09/2017] [Indexed: 12/21/2022]
Abstract
Loading-induced interstitial fluid flow in the microporosities of bone is critical for osteocyte mechanotransduction and for the maintenance of tissue health, enhancing convective transport in the lacunar-canalicular system. In recent studies, our group has reported alterations of bone's vascular porosity and lacunar-canalicular system microarchitecture in a rat model of postmenopausal osteoporosis. In this work, poroelastic finite element analysis was used to investigate whether these microstructural changes can affect interstitial fluid flow around osteocytes. Animal-specific finite element models were developed combining micro-CT reconstructions of bone microstructure and measures of the poroelastic material properties. These models were used to quantify and compare loading-induced fluid flow in the lacunar-canalicular system of ovariectomized and sham-operated rats. A parametric analysis was also used to quantify the influence of the lacunar-canalicular permeability and vascular porosity on the fluid velocity magnitude. Results show that mechanically-induced interstitial fluid velocity can be significantly reduced in the lacunar-canalicular system of ovariectomized rats. Interestingly, the vascular porosity is shown to have a major influence on interstitial fluid flow, while the lacunar-canalicular permeability influence is limited when larger than 10-20m2. Altogether our results suggest that microstructural changes associated with the osteoporotic condition can negatively affect interstitial fluid flow around osteocytes in the lacunar-canalicular system of cortical bone. This fluid flow reduction could impair mechanosensation of the osteocytic network, possibly playing a role in the initiation and progression of age-related bone loss and postmenopausal osteoporosis.
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22
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Osteocyte calcium signals encode strain magnitude and loading frequency in vivo. Proc Natl Acad Sci U S A 2017; 114:11775-11780. [PMID: 29078317 DOI: 10.1073/pnas.1707863114] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Osteocytes are considered to be the major mechanosensory cells of bone, but how osteocytes in vivo process, perceive, and respond to mechanical loading remains poorly understood. Intracellular calcium (Ca2+) signaling resulting from mechanical stimulation has been widely studied in osteocytes in vitro and in bone explants, but has yet to be examined in vivo. This is achieved herein by using a three-point bending device which is capable of delivering well-defined mechanical loads to metatarsal bones of living mice while simultaneously monitoring the intracellular Ca2+ responses of individual osteocytes by using a genetically encoded fluorescent Ca2+ indicator. Osteocyte responses are imaged by using multiphoton fluorescence microscopy. We investigated the in vivo responses of osteocytes to strains ranging from 250 to 3,000 [Formula: see text] and frequencies from 0.5 to 2 Hz, which are characteristic of physiological conditions reported for bone. At all loading frequencies examined, the number of responding osteocytes increased strongly with applied strain magnitude. However, Ca2+ intensity within responding osteocytes did not change significantly with physiological loading magnitudes. Our studies offer a glimpse into how these critical bone cells respond to mechanical load in vivo, as well as provide a technique to determine how the cells encode magnitude and frequency of loading.
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23
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Abstract
PURPOSE OF REVIEW This review assembles recent understanding of the profound loss of muscle and bone in spinal cord injury (SCI). It is important to try to understand these changes, and the context in which they occur, because of their impact on the wellbeing of SC-injured individuals, and the urgent need for viable preventative therapies. RECENT FINDINGS Recent research provides new understanding of the effects of age and systemic factors on the response of bone to loading, of relevance to attempts to provide load therapy for bone in SCI. The rapidly growing dataset describing the biochemical crosstalk between bone and muscle, and the cell and molecular biology of myokines signalling to bone and osteokines regulating muscle metabolism and mass, is reviewed. The ways in which this crosstalk may be altered in SCI is summarised. Therapeutic approaches to the catabolic changes in muscle and bone in SCI require a holistic understanding of their unique mechanical and biochemical context.
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Affiliation(s)
- Jillian M Clark
- Discipline of Orthopaedics and Trauma, The University of Adelaide, North Terrace, Adelaide, South Australia, 5000, Australia.
| | - David M Findlay
- Discipline of Orthopaedics and Trauma, The University of Adelaide, North Terrace, Adelaide, South Australia, 5000, Australia
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24
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Abstract
PURPOSE OF REVIEW Over the past decades, osteocytes have emerged as mechano-sensors of bone and master regulators of bone homeostasis. This article summarizes latest research and progress made in understanding osteocyte mechanobiology and critically reviews tools currently available to study these cells. RECENT FINDINGS Whereas increased mechanical forces promote bone formation, decrease loading is always associated with bone loss and skeletal fragility. Recent studies identified cilia, integrins, calcium channels, and G-protein coupled receptors as important sensors of mechanical forces and Ca2+ and cAMP signaling as key effectors. Among transcripts regulated by mechanical forces, sclerostin and RANKL have emerged as potential therapeutic targets for disuse-induced bone loss. In this paper, we review the mechanisms by which osteocytes perceive and transduce mechanical cues and the models available to study mechano-transduction. Future directions of the field are also discussed.
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Affiliation(s)
- Yuhei Uda
- Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, MA, USA
| | - Ehab Azab
- Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, MA, USA
| | - Ningyuan Sun
- Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, MA, USA
| | - Chao Shi
- Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, MA, USA
- Department of Orthopaedics, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710004, Shaanxi Province, People's Republic of China
| | - Paola Divieti Pajevic
- Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, MA, USA.
- , 700 Albany Street, W201C, Boston, MA, 02118, USA.
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25
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Thiel A, Reumann MK, Boskey A, Wischmann J, von Eisenhart-Rothe R, Mayer-Kuckuk P. Osteoblast migration in vertebrate bone. Biol Rev Camb Philos Soc 2017. [PMID: 28631442 DOI: 10.1111/brv.12345] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Bone formation, for example during bone remodelling or fracture repair, requires mature osteoblasts to deposit bone with remarkable spatial precision. As osteoblast precursors derive either from circulation or resident stem cell pools, they and their progeny are required to migrate within the three-dimensional bone space and to navigate to their destination, i.e. to the site of bone formation. An understanding of this process is emerging based on in vitro and in vivo studies of several vertebrate species. Receptors on the osteoblast surface mediate cell adhesion and polarization, which induces osteoblast migration. Osteoblast migration is then facilitated along gradients of chemoattractants. The latter are secreted or released proteolytically by several cell types interacting with osteoblasts, including osteoclasts and vascular endothelial cells. The positions of these cellular sources of chemoattractants in relation to the position of the osteoblasts provide the migrating osteoblasts with tracks to their destination, and osteoblasts possess the means to follow a track marked by multiple chemoattractant gradients. In addition to chemotactic cues, osteoblasts sense other classes of signals and utilize them as landmarks for navigation. The composition of the osseous surface guides adhesion and hence migration efficiency and can also provide steering through haptotaxis. Further, it is likely that signals received from surface interactions modulate chemotaxis. Besides the nature of the surface, mechanical signals such as fluid flow may also serve as navigation signals for osteoblasts. Alterations in osteoblast migration and navigation might play a role in metabolic bone diseases such as osteoporosis.
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Affiliation(s)
- Antonia Thiel
- Bone Cell and Imaging Laboratory, Department of Orthopedics, Klinikum rechts der Isar, Ismaninger Straße 22, Technical University Munich, 81675 München, Germany
| | - Marie K Reumann
- Siegfried Weller Institute, BG Hospital, University of Tübingen, Schnarrenbergstraße 95, 72076 Tübingen, Germany
| | - Adele Boskey
- Mineralized Tissue Laboratory, Research Division, Hospital for Special Surgery, 535 E 70th Street, New York, NY 10021, U.S.A
| | - Johannes Wischmann
- Bone Cell and Imaging Laboratory, Department of Orthopedics, Klinikum rechts der Isar, Ismaninger Straße 22, Technical University Munich, 81675 München, Germany
| | - Rüdiger von Eisenhart-Rothe
- Bone Cell and Imaging Laboratory, Department of Orthopedics, Klinikum rechts der Isar, Ismaninger Straße 22, Technical University Munich, 81675 München, Germany
| | - Philipp Mayer-Kuckuk
- Bone Cell and Imaging Laboratory, Department of Orthopedics, Klinikum rechts der Isar, Ismaninger Straße 22, Technical University Munich, 81675 München, Germany
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Paschalis EP, Gamsjaeger S, Hassler N, Klaushofer K, Burr D. Ovarian hormone depletion affects cortical bone quality differently on different skeletal envelopes. Bone 2017; 95:55-64. [PMID: 27826024 DOI: 10.1016/j.bone.2016.10.029] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 10/17/2016] [Accepted: 10/25/2016] [Indexed: 12/31/2022]
Abstract
The physical properties of bone tissue are determined by the organic and mineral matrix, and are one aspect of bone quality. As such, the properties of mineral and matrix are a major contributor to bone strength, independent of bone mass. Cortical bone quality may differ regionally on the three skeletal envelopes that compose it. Each of these envelopes may be affected differently by ovarian hormone depletion. Identifying how these regions vary in their tissue adaptive response to ovarian hormones can inform our understanding of how tissue quality contributes to overall bone strength in postmenopausal women. We analyzed humeri from monkeys that were either SHAM-operated or ovariectomized. Raman microspectroscopic analysis was performed as a function of tissue age based on the presence of multiple fluorescent double labels, to determine whether bone compositional properties (mineral/matrix ratio, tissue water, glycosaminoglycan, lipid, and pyridinoline contents, and mineral maturity/crystallinity) are similar between periosteal, osteonal, and endosteal surfaces, as well as to determine the effects of ovarian hormone depletion on them. The results indicate that mineral and organic matrix characteristics, and kinetics of mineral and organic matrix modifications as a function of tissue age are different at periosteal vs. osteonal and endosteal surfaces. Ovarian hormone depletion affects the three cortical surfaces (periosteal, osteonal, endosteal) differently. While ovarian hormone depletion does not significantly affect the quality of either the osteoid or the most recently mineralized tissue, it significantly affects the rate of subsequent mineral accumulation, as well as the kinetics of organic matrix modifications, culminating in significant differences within interstitial bone. These results highlight the complexity of the cortical bone compartments, add to existing knowledge on the effects of ovarian hormone depletion on local cortical bone properties, and may contribute to a better understanding of the location specific action of drugs used in the management of postmenopausal osteoporosis.
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Affiliation(s)
- E P Paschalis
- Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria.
| | - S Gamsjaeger
- Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria
| | - N Hassler
- Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria
| | - K Klaushofer
- Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK and AUVA Trauma Centre Meidling, 1st Medical Department, Hanusch Hospital, Heinrich Collin Str. 30, A-1140 Vienna, Austria
| | - D Burr
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Biomedical Engineering, Indiana University-Purdue University, Indianapolis (IUPUI), Indianapolis, IN 46202, USA
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Prideaux M, Findlay DM, Atkins GJ. Osteocytes: The master cells in bone remodelling. Curr Opin Pharmacol 2016; 28:24-30. [DOI: 10.1016/j.coph.2016.02.003] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 01/14/2016] [Accepted: 02/09/2016] [Indexed: 10/22/2022]
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28
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KAMEO Y, OOTAO Y, ISHIHARA M. Theoretical investigation of the effect of bending loads on the interstitial fluid flow in a poroelastic lamellar trabecula. ACTA ACUST UNITED AC 2016. [DOI: 10.1299/jbse.15-00663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yoshitaka KAMEO
- Department of Biomechanics, Institute for Frontier Medical Sciences, Kyoto University
| | - Yoshihiro OOTAO
- Department of Mechanical Engineering, Graduate School of Engineering, Osaka Prefecture University
| | - Masayuki ISHIHARA
- Department of Mechanical Engineering, Graduate School of Engineering, Osaka Prefecture University
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29
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Ren L, Yang P, Wang Z, Zhang J, Ding C, Shang P. Biomechanical and biophysical environment of bone from the macroscopic to the pericellular and molecular level. J Mech Behav Biomed Mater 2015; 50:104-22. [DOI: 10.1016/j.jmbbm.2015.04.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 04/12/2015] [Accepted: 04/17/2015] [Indexed: 02/06/2023]
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30
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Berman AG, Clauser CA, Wunderlin C, Hammond MA, Wallace JM. Structural and Mechanical Improvements to Bone Are Strain Dependent with Axial Compression of the Tibia in Female C57BL/6 Mice. PLoS One 2015; 10:e0130504. [PMID: 26114891 PMCID: PMC4482632 DOI: 10.1371/journal.pone.0130504] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 05/19/2015] [Indexed: 01/26/2023] Open
Abstract
Strain-induced adaption of bone has been well-studied in an axial loading model of the mouse tibia. However, most outcomes of these studies are restricted to changes in bone architecture and do not explore the mechanical implications of those changes. Herein, we studied both the mechanical and morphological adaptions of bone to three strain levels using a targeted tibial loading mouse model. We hypothesized that loading would increase bone architecture and improve cortical mechanical properties in a dose-dependent fashion. The right tibiae of female C57BL/6 mice (8 week old) were compressively loaded for 2 weeks to a maximum compressive force of 8.8N, 10.6N, or 12.4N (generating periosteal strains on the anteromedial region of the mid-diaphysis of 1700 με, 2050 με, or 2400 με as determined by a strain calibration), while the left limb served as an non-loaded control. Following loading, ex vivo analyses of bone architecture and cortical mechanical integrity were assessed by micro-computed tomography and 4-point bending. Results indicated that loading improved bone architecture in a dose-dependent manner and improved mechanical outcomes at 2050 με. Loading to 2050 με resulted in a strong and compelling formation response in both cortical and cancellous regions. In addition, both structural and tissue level strength and energy dissipation were positively impacted in the diaphysis. Loading to the highest strain level also resulted in rapid and robust formation of bone in both cortical and cancellous regions. However, these improvements came at the cost of a woven bone response in half of the animals. Loading to the lowest strain level had little effect on bone architecture and failed to impact structural- or tissue-level mechanical properties. Potential systemic effects were identified for trabecular bone volume fraction, and in the pre-yield region of the force-displacement and stress-strain curves. Future studies will focus on a moderate load level which was largely beneficial in terms of cortical/cancellous structure and cortical mechanical function.
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Affiliation(s)
- Alycia G Berman
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States of America
| | - Creasy A Clauser
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States of America
| | - Caitlin Wunderlin
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States of America
| | - Max A Hammond
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States of America
| | - Joseph M Wallace
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States of America; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States of America; Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN, United States of America
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31
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Klein-Nulend J, van Oers RFM, Bakker AD, Bacabac RG. Bone cell mechanosensitivity, estrogen deficiency, and osteoporosis. J Biomech 2014; 48:855-65. [PMID: 25582356 DOI: 10.1016/j.jbiomech.2014.12.007] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2014] [Indexed: 11/26/2022]
Abstract
Adaptation of bone to mechanical stresses normally produces a bone architecture that combines a proper resistance against failure with a minimal use of material. This adaptive process is governed by mechanosensitive osteocytes that transduce the mechanical signals into chemical responses, i.e. the osteocytes release signaling molecules, which orchestrate the recruitment and activity of bone forming osteoblasts and/or bone resorbing osteoclasts. Computer models have shown that the maintenance of a mechanically-efficient bone architecture depends on the intensity and spatial distribution of the mechanical stimulus as well as on the osteocyte response. Osteoporosis is a condition characterized by a reduced bone mass and a compromized resistance of bone against mechanical loads, which has led us to hypothesize that mechanotransduction by osteocytes is altered in osteoporosis. One of the major causal factors for osteoporosis is the loss of estrogen, the major hormonal regulator of bone metabolism. Loss of estrogen may increase osteocyte-mediated activation of bone remodeling, resulting in impaired bone mass and architecture. In this review we highlight current insights on how osteocytes perceive mechanical stimuli placed on whole bones. Particular emphasis is placed on the role of estrogen in signaling pathway activation by mechanical stimuli, and on computer simulation in combination with cell biology to unravel biological processes contributing to bone strength.
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Affiliation(s)
- Jenneke Klein-Nulend
- Department of Oral Cell Biology, ACTA-University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
| | - René F M van Oers
- Department of Oral Cell Biology, ACTA-University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands; Department of Dental Materials Science, ACTA-University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - Astrid D Bakker
- Department of Oral Cell Biology, ACTA-University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - Rommel G Bacabac
- Department of Physics, Medical Biophysics Group, University of San Carlos, Cebu City, Philippines
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32
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Farrell K, O'Conor D, Gonzalez M, Androjna C, Midura RJ, Tewari SN, Belovich J. Substrate concentration influences effective radial diffusion coefficient in canine cortical bone. Ann Biomed Eng 2014; 42:2577-88. [PMID: 25234132 DOI: 10.1007/s10439-014-1123-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 09/11/2014] [Indexed: 11/29/2022]
Abstract
Transport of nutrients and waste across osseous tissue is dependent on the dynamic micro and macrostructure of the tissue; however little quantitative data exists examining how this transport occurs across the entire tissue. Here we investigate in vitro radial diffusion across a section of canine tissue, at dimensions of several hundred microns to millimeters, specifically between several osteons connected through a porous microstructure of Volkmann's canals and canaliculi. The effective diffusion coefficient is measured by a "sample immersion" technique presented here, in which the tissue sample was immersed in solution for 18-30 h, image analysis software was used to quantify the solute concentration profile in the tissue, and the data were fit to a mathematical model of diffusion in the tissue. Measurements of the effective diffusivity of sodium fluorescein using this technique were confirmed using a standard two-chamber diffusion system. As the solute concentration increased, the effective diffusivity decreased, ranging from 1.6 × 10(-7) ± 3.2 × 10(-8) cm(2)/s at 0.3 μM to 1.4 × 10(-8) ± 1.9 × 10(-9) cm(2)/s at 300 μM. The results show that there is no significant difference in mean diffusivity obtained using the two measurement techniques on the same sample, 3.3 × 10(-8) ± 3.3 × 10(-9) cm(2)/s (sample immersion), compared to 4.4 × 10(-8) ± 1.1 × 10(-8) cm(2)/s (diffusion chamber).
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Affiliation(s)
- Kurt Farrell
- Department of Chemical and Biomedical Engineering, Cleveland State University, 2121 Euclid Ave, Cleveland, OH, 44141, USA,
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