101
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Tran KA, Partyka PP, Jin Y, Bouyer J, Fischer I, Galie PA. Vascularization of self-assembled peptide scaffolds for spinal cord injury repair. Acta Biomater 2020; 104:76-84. [PMID: 31904559 DOI: 10.1016/j.actbio.2019.12.033] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Revised: 12/19/2019] [Accepted: 12/30/2019] [Indexed: 01/05/2023]
Abstract
The disruption of the blood-spinal cord barrier (BSCB) following spinal cord injury contributes to inflammation and glial scarring that inhibits axon growth and diminishes the effectiveness of conduits transplanted to the injury site to promote this growth. The purpose of this study is to evaluate whether scaffolds containing microvessels that exhibit BSCB integrity reduce inflammation and scar formation at the injury site and lead to increased axon growth. For these studies, a self-assembling peptide scaffold, RADA-16I, is used due to its established permissiveness to axon growth and ability to support vascularization. Immunocytochemistry and permeability transport assays verify the formation of tight-junction containing microvessels within the scaffold. Peptide scaffolds seeded with different concentrations of microvascular cells are then injected into a spinal contusion injury in rats to evaluate how microvessels affect axon growth and neurovascular interaction. The effect of the vascularized scaffold on inflammation and scar formation is evaluated by quantifying histological sections stained with ED-1 and GFAP, respectively. Our results indicate that the peptide scaffolds containing microvessels reduce inflammation and glial scar formation and increase the density of axons growing into the injury/transplant site. These results demonstrate the potential benefit of scaffold vascularization to treat spinal cord injury. STATEMENT OF SIGNIFICANCE: This study evaluates the benefit of transplanting microvascular cells within a self-assembling peptide scaffold, RADA-16I, that has shown promise for facilitating regeneration in the central nervous system in previous studies. Our results indicate that vasculature featuring tight junctions that give rise to the blood-spinal cord barrier can be formed within the peptide scaffold both in vitro and in a rat model of a subacute contusion spinal cord injury. Histological analysis indicates that the presence of the microvessels encourages axon infiltration into the site of injury and reduces the area of astrocyte activation and inflammation. Overall, these results demonstrate the potential of vascularizing scaffolds for the repair of spinal cord injury.
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102
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Cooper JG, Sicard D, Sharma S, Van Gulden S, McGuire TL, Cajiao MP, Tschumperlin DJ, Kessler JA. Spinal Cord Injury Results in Chronic Mechanical Stiffening. J Neurotrauma 2020; 37:494-506. [PMID: 31516087 PMCID: PMC6978780 DOI: 10.1089/neu.2019.6540] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Gliosis and fibrosis after spinal cord injury (SCI) lead to formation of a scar that is thought to present both molecular and mechanical barriers to neuronal regeneration. The scar consists of a meshwork of reactive glia and deposited, cross-linked, extracellular matrix (ECM) that has long been assumed to present a mechanically "stiff" blockade. However, remarkably little quantitative information is available about the rheological properties of chronically injured spinal tissue. In this study we utilize atomic force microscopy microindentation to provide quantitative evidence of chronic mechanical stiffening after SCI. Using the results of this tissue characterization, we assessed the sensitivity of both mouse and human astrocytes in vitro and determined that they are exquisitely mechanosensitive within the relevant range of substrate stiffness observed in the injured/uninjured spinal cord. We then utilized a novel immune modifying nanoparticle (IMP) treatment as a tool to reveal fibrotic scarring as one of the key drivers of mechanical stiffening after SCI in vivo. We also demonstrate that glial scar-forming astrocytes form a highly aligned, anisotropic network of glial fibers after SCI, and that IMP treatment mitigates this pathological alignment. Taken together, our results identify chronic mechanical stiffening as a critically important aspect of the complex lesion milieu after SCI that must be considered when assessing and developing potential clinical interventions for SCI.
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Affiliation(s)
- John G. Cooper
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Delphine Sicard
- Department of Physiology and Biomedical Engineering, College of Medicine and Science, Mayo Clinic, Rochester, Minnesota
| | - Sripadh Sharma
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Stephanie Van Gulden
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Tammy L. McGuire
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Miguel Pareja Cajiao
- Department of Anesthesiology, College of Medicine and Science, Mayo Clinic, Rochester, Minnesota
| | - Daniel J. Tschumperlin
- Department of Physiology and Biomedical Engineering, College of Medicine and Science, Mayo Clinic, Rochester, Minnesota
| | - John A. Kessler
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
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103
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Nervous Tissue Stiffens Postinjury. Biophys J 2020; 118:276-278. [PMID: 31968236 DOI: 10.1016/j.bpj.2019.09.050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 09/24/2019] [Indexed: 11/20/2022] Open
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104
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Jain D, Mattiassi S, Goh EL, Yim EKF. Extracellular matrix and biomimetic engineering microenvironment for neuronal differentiation. Neural Regen Res 2020; 15:573-585. [PMID: 31638079 PMCID: PMC6975142 DOI: 10.4103/1673-5374.266907] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Extracellular matrix (ECM) influences cell differentiation through its structural and biochemical properties. In nervous system, neuronal behavior is influenced by these ECMs structures which are present in a meshwork, fibrous, or tubular forms encompassing specific molecular compositions. In addition to contact guidance, ECM composition and structures also exert its effect on neuronal differentiation. This short report reviewed the native ECM structure and composition in central nervous system and peripheral nervous system, and their impact on neural regeneration and neuronal differentiation. Using topographies, stem cells have been differentiated to neurons. Further, focussing on engineered biomimicking topographies, we highlighted the role of anisotropic topographies in stem cell differentiation to neurons and its recent temporal application for efficient neuronal differentiation.
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Affiliation(s)
- Deepak Jain
- Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Sabrina Mattiassi
- Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Eyleen L Goh
- Neuroscience Academic Clinical Programme, Duke-NUS Medical School, Singapore
| | - Evelyn K F Yim
- Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada
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105
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Möllmert S, Kharlamova MA, Hoche T, Taubenberger AV, Abuhattum S, Kuscha V, Kurth T, Brand M, Guck J. Zebrafish Spinal Cord Repair Is Accompanied by Transient Tissue Stiffening. Biophys J 2019; 118:448-463. [PMID: 31870536 DOI: 10.1016/j.bpj.2019.10.044] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/17/2019] [Accepted: 10/24/2019] [Indexed: 01/11/2023] Open
Abstract
Severe injury to the mammalian spinal cord results in permanent loss of function due to the formation of a glial-fibrotic scar. Both the chemical composition and the mechanical properties of the scar tissue have been implicated to inhibit neuronal regrowth and functional recovery. By contrast, adult zebrafish are able to repair spinal cord tissue and restore motor function after complete spinal cord transection owing to a complex cellular response that includes axon regrowth and is accompanied by neurogenesis. The mechanical mechanisms contributing to successful spinal cord repair in adult zebrafish are, however, currently unknown. Here, we employ atomic force microscopy-enabled nanoindentation to determine the spatial distributions of apparent elastic moduli of living spinal cord tissue sections obtained from uninjured zebrafish and at distinct time points after complete spinal cord transection. In uninjured specimens, spinal gray matter regions were stiffer than white matter regions. During regeneration after transection, the spinal cord tissues displayed a significant increase of the respective apparent elastic moduli that transiently obliterated the mechanical difference between the two types of matter before returning to baseline values after the completion of repair. Tissue stiffness correlated variably with cell number density, oligodendrocyte interconnectivity, axonal orientation, and vascularization. This work constitutes the first quantitative mapping of the spatiotemporal changes of spinal cord tissue stiffness in regenerating adult zebrafish and provides the tissue mechanical basis for future studies into the role of mechanosensing in spinal cord repair.
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Affiliation(s)
| | | | - Tobias Hoche
- Biotechnology Center, Technische Universität Dresden, Dresden, Germany
| | | | - Shada Abuhattum
- Biotechnology Center, Technische Universität Dresden, Dresden, Germany; JPK Instruments, Berlin, Germany; Max Planck Institut for the Science of Light & Max-Planck Institut für Physik und Medizin, Erlangen, Germany
| | - Veronika Kuscha
- Center for Regenerative Therapies, Technische Universität Dresden, Dresden, Germany
| | - Thomas Kurth
- Center for Regenerative Therapies, Technische Universität Dresden, Dresden, Germany
| | - Michael Brand
- Center for Regenerative Therapies, Technische Universität Dresden, Dresden, Germany
| | - Jochen Guck
- Biotechnology Center, Technische Universität Dresden, Dresden, Germany; Max Planck Institut for the Science of Light & Max-Planck Institut für Physik und Medizin, Erlangen, Germany.
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106
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Pyka-Fościak G, Zemła J, Lis GJ, Litwin JA, Lekka M. Changes in spinal cord stiffness in the course of experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. Arch Biochem Biophys 2019; 680:108221. [PMID: 31816310 DOI: 10.1016/j.abb.2019.108221] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/05/2019] [Accepted: 12/04/2019] [Indexed: 12/13/2022]
Abstract
Experimental autoimmune encephalomyelitis (EAE) is a commonly used mouse model of multiple sclerosis, a chronic inflammatory disease of the central nervous system (CNS) characterized by demyelination leading to brain and spinal cord malfunctions. We postulate that not only biological but also biomechanical properties play an important role in impairements of CNS function. Atomic force microscopy (AFM) was applied to investigate mechanical properties of spinal cords collected from EAE mice in preonset, onset, peak, and chronic disease phases. Biomechanical changes were compared with histopathological alterations observed in the successive phases. The deformability of gray matter did not change, while rigidity of white matter increased during the onset phase, remained at the same level in the peak phase and decreased in the chronic phase. Inflammatory infiltration and laminin content accompanied the tissue rigidity increase, whereas demyelination and axonal damage showed an opposite effect. The increase in white matter rigidity can be regarded as an early signature of EAE.
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Affiliation(s)
- G Pyka-Fościak
- Department of Histology, Jagiellonian University Medical College, Kopernika 7, 31-034, Krakow, Poland.
| | - J Zemła
- Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland
| | - G J Lis
- Department of Histology, Jagiellonian University Medical College, Kopernika 7, 31-034, Krakow, Poland
| | - J A Litwin
- Department of Histology, Jagiellonian University Medical College, Kopernika 7, 31-034, Krakow, Poland
| | - M Lekka
- Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland.
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107
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Wagner K, Girardo S, Goswami R, Rosso G, Ulbricht E, Müller P, Soteriou D, Träber N, Guck J. Colloidal crystals of compliant microgel beads to study cell migration and mechanosensitivity in 3D. SOFT MATTER 2019; 15:9776-9787. [PMID: 31742293 DOI: 10.1039/c9sm01226e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Tissues are defined not only by their biochemical composition, but also by their distinct mechanical properties. It is now widely accepted that cells sense their mechanical environment and respond to it. However, studying the effects of mechanics in in vitro 3D environments is challenging since current 3D hydrogel assays convolve mechanics with gel porosity and adhesion. Here, we present novel colloidal crystals as modular 3D scaffolds where these parameters are principally decoupled by using monodisperse, protein-coated PAAm microgel beads as building blocks, so that variable stiffness regions can be achieved within one 3D colloidal crystal. Characterization of the colloidal crystal and oxygen diffusion simulations suggested the suitability of the scaffold to support cell survival and growth. This was confirmed by live-cell imaging and fibroblast culture over a period of four days. Moreover, we demonstrate unambiguous durotactic fibroblast migration and mechanosensitive neurite outgrowth of dorsal root ganglion neurons in 3D. This modular approach of assembling 3D scaffolds from mechanically and biochemically well-defined building blocks allows the spatial patterning of stiffness decoupled from porosity and adhesion sites in principle and provides a platform to investigate mechanosensitivity in 3D environments approximating tissues in vitro.
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Affiliation(s)
- Katrin Wagner
- Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
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108
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Dumas JP, Jiang JY, Gates EM, Hoffman BD, Pierce MC, Boustany NN. FRET efficiency measurement in a molecular tension probe with a low-cost frequency-domain fluorescence lifetime imaging microscope. JOURNAL OF BIOMEDICAL OPTICS 2019; 24:1-11. [PMID: 31884745 PMCID: PMC6935677 DOI: 10.1117/1.jbo.24.12.126501] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 11/11/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate the possibility of measuring FRET efficiency with a low-cost frequency-domain fluorescence lifetime imaging microscope (FD-FLIM). The system utilizes single-frequency-modulated excitation, which enables the use of cost-effective laser sources and electronics, simplification of data acquisition and analysis, and a dual-channel detection capability. Following calibration with coumarin 6, we measured the apparent donor lifetime in mTFP1-mVenus FRET standards expressed in living cells. We evaluated the system's sensitivity by differentiating the short and long lifetimes of mTFP1 corresponding to the known standards' high and low FRET efficiency, respectively. Furthermore, we show that the lifetime of the vinculin tension sensor, VinTS, at focal adhesions (2.30 ± 0.16 ns) is significantly (p < 10 - 6) longer than the lifetime of the unloaded TSMod probe (2.02 ± 0.16 ns). The pixel dwell time was 6.8 μs for samples expressing the FRET standards, with signal typically an order of magnitude higher than VinTS. The apparent FRET efficiency (<inline-formula>EFRETapp</inline-formula>) of the standards, calculated from the measured apparent lifetime, was linearly related to their known FRET efficiency by a factor of 0.92 to 0.99 (R2 = 0.98). This relationship serves as a calibration curve to convert apparent FRET to true FRET and circumvent the need to measure multiexponential lifetime decays. This approach yielded a FRET efficiency of 18% to 19.5%, for VinTS, in agreement with published values. Taken together, our results demonstrate a cost-effective, fast, and sensitive FD-FLIM approach with the potential to facilitate applications of FLIM in mechanobiology and FRET-based biosensing.
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Affiliation(s)
- John-Paul Dumas
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
- Thorlabs Inc., Newton, New Jersey, United States
| | | | - Evan M. Gates
- Duke University, Department of Biomedical Engineering, Durham, North Carolina, United States
| | - Brenton D. Hoffman
- Duke University, Department of Biomedical Engineering, Durham, North Carolina, United States
| | - Mark C. Pierce
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
| | - Nada N. Boustany
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
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109
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Jekhmane S, Prachar M, Pugliese R, Fontana F, Medeiros‐Silva J, Gelain F, Weingarth M. Design Parameters of Tissue‐Engineering Scaffolds at the Atomic Scale. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shehrazade Jekhmane
- NMR SpectroscopyBijvoet Center for Biomolecular ResearchDepartment of ChemistryFaculty of ScienceUtrecht University Padualaan 8, 3584 CH Utrecht The Netherlands
| | - Marek Prachar
- NMR SpectroscopyBijvoet Center for Biomolecular ResearchDepartment of ChemistryFaculty of ScienceUtrecht University Padualaan 8, 3584 CH Utrecht The Netherlands
| | - Raffaele Pugliese
- Fondazione IRCCS Casa Sollievo della SofferenzaUnita' di Ingegneria Tissutale Viale Cappuccini 1 71013 San Giovanni Rotondo Italy
| | - Federico Fontana
- Fondazione IRCCS Casa Sollievo della SofferenzaUnita' di Ingegneria Tissutale Viale Cappuccini 1 71013 San Giovanni Rotondo Italy
- ASST Grande Ospedale Metropolitano NiguardaCenter for Nanomedicine and Tissue Engineering Piazza dell'Ospedale Maggiore 3 20162 Milan Italy
| | - João Medeiros‐Silva
- NMR SpectroscopyBijvoet Center for Biomolecular ResearchDepartment of ChemistryFaculty of ScienceUtrecht University Padualaan 8, 3584 CH Utrecht The Netherlands
| | - Fabrizio Gelain
- Fondazione IRCCS Casa Sollievo della SofferenzaUnita' di Ingegneria Tissutale Viale Cappuccini 1 71013 San Giovanni Rotondo Italy
- ASST Grande Ospedale Metropolitano NiguardaCenter for Nanomedicine and Tissue Engineering Piazza dell'Ospedale Maggiore 3 20162 Milan Italy
| | - Markus Weingarth
- NMR SpectroscopyBijvoet Center for Biomolecular ResearchDepartment of ChemistryFaculty of ScienceUtrecht University Padualaan 8, 3584 CH Utrecht The Netherlands
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110
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Guo J, Bertalan G, Meierhofer D, Klein C, Schreyer S, Steiner B, Wang S, Vieira da Silva R, Infante-Duarte C, Koch S, Boehm-Sturm P, Braun J, Sack I. Brain maturation is associated with increasing tissue stiffness and decreasing tissue fluidity. Acta Biomater 2019; 99:433-442. [PMID: 31449927 DOI: 10.1016/j.actbio.2019.08.036] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 08/16/2019] [Accepted: 08/21/2019] [Indexed: 12/21/2022]
Abstract
Biomechanical cues guide proliferation, growth and maturation of neurons. Yet the molecules that shape the brain's biomechanical properties are unidentified and the relationship between neural development and viscoelasticity of brain tissue remains elusive. Here we combined novel in-vivo tomoelastography and ex-vivo proteomics to investigate whether viscoelasticity of the mouse brain correlates with protein alterations within the critical phase of brain maturation. For the first time, high-resolution atlases of viscoelasticity of the mouse brain were generated, revealing that (i) brain stiffness increased alongside progressive accumulation of microtubular structures, myelination, cytoskeleton linkage and cell-matrix attachment, and that (ii) viscosity-related tissue fluidity decreased alongside downregulated actin crosslinking and axonal organization. Taken together, our results show that brain maturation is associated with a shift of brain mechanical properties towards a more solid-rigid behavior consistent with reduced tissue fluidity. This shift appears to be driven by several molecular processes associated with myelination, cytoskeletal crosslinking and axonal organization. STATEMENT OF SIGNIFICANCE: The viscoelastic properties of brain tissue shape the environment in which neurons proliferate, grow, and mature. In the present study, novel tomoelastography was used to spatially map tissue mechanical properties of the in-vivo mouse brain during maturation. In vivo tomoelastography was also combined with ex vivo mass spectrometry proteomic analysis to identify the molecules which shape the biomechanical properties of brain tissue. With the combined technique, we observed that brain maturation is associated with a shift of brain mechanical properties towards a more solid-rigid behavior consistent with reduced tissue fluidity which is driven by multiple molecular processes. We believe that this shift of brain mechanical properties discovered in our study reflects a fundamental biophysical signature of brain maturation.
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111
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Jekhmane S, Prachar M, Pugliese R, Fontana F, Medeiros-Silva J, Gelain F, Weingarth M. Design Parameters of Tissue-Engineering Scaffolds at the Atomic Scale. Angew Chem Int Ed Engl 2019; 58:16943-16951. [PMID: 31573131 PMCID: PMC6899630 DOI: 10.1002/anie.201907880] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 09/03/2019] [Indexed: 01/08/2023]
Abstract
Stem-cell behavior is regulated by the material properties of the surrounding extracellular matrix, which has important implications for the design of tissue-engineering scaffolds. However, our understanding of the material properties of stem-cell scaffolds is limited to nanoscopic-to-macroscopic length scales. Herein, a solid-state NMR approach is presented that provides atomic-scale information on complex stem-cell substrates at near physiological conditions and at natural isotope abundance. Using self-assembled peptidic scaffolds designed for nervous-tissue regeneration, we show at atomic scale how scaffold-assembly degree, mechanics, and homogeneity correlate with favorable stem cell behavior. Integration of solid-state NMR data with molecular dynamics simulations reveals a highly ordered fibrillar structure as the most favorable stem-cell scaffold. This could improve the design of tissue-engineering scaffolds and other self-assembled biomaterials.
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Affiliation(s)
- Shehrazade Jekhmane
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands
| | - Marek Prachar
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands
| | - Raffaele Pugliese
- Fondazione IRCCS Casa Sollievo della Sofferenza, Unita' di Ingegneria Tissutale, Viale Cappuccini 1, 71013, San Giovanni Rotondo, Italy
| | - Federico Fontana
- Fondazione IRCCS Casa Sollievo della Sofferenza, Unita' di Ingegneria Tissutale, Viale Cappuccini 1, 71013, San Giovanni Rotondo, Italy.,ASST Grande Ospedale Metropolitano Niguarda, Center for Nanomedicine and Tissue Engineering, Piazza dell'Ospedale Maggiore 3, 20162, Milan, Italy
| | - João Medeiros-Silva
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands
| | - Fabrizio Gelain
- Fondazione IRCCS Casa Sollievo della Sofferenza, Unita' di Ingegneria Tissutale, Viale Cappuccini 1, 71013, San Giovanni Rotondo, Italy.,ASST Grande Ospedale Metropolitano Niguarda, Center for Nanomedicine and Tissue Engineering, Piazza dell'Ospedale Maggiore 3, 20162, Milan, Italy
| | - Markus Weingarth
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584, CH, Utrecht, The Netherlands
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112
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Schiavone G, Wagner F, Fallegger F, Kang X, Vachicouras N, Barra B, Capogrosso M, Bloch J, Courtine G, Lacour SP. Long-term functionality of a soft electrode array for epidural spinal cord stimulation in a minipig model. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2018:1432-1435. [PMID: 30440661 DOI: 10.1109/embc.2018.8512584] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Long-term biointegration of man-made neural interfaces is influenced by the mechanical properties of the implant materials. Substantial experimental work currently aims at replacing conventional hard implant materials with soft alternatives that can favour a lower immune response. Here we assess the performance of a soft electrode array implanted in the spinal epidural space of a minipig model for a period of 6 months. The electrode array includes platinum-silicone electrode contacts and elastic thin-film gold interconnects embedded in silicone. textbfIn-vivo electrode impedance and voltage transients were monitored over time. Following implantation, epidural stimulation produced muscle-specific evoked potentials and visible muscle contractions. Over time, postoperative and stimulation induced changes in electrode impedance were observed. Such trends provide a basis for future technological improvements aiming at ensuring the stability of soft implantable electrodes for neural interfacing.
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113
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Chighizola M, Dini T, Lenardi C, Milani P, Podestà A, Schulte C. Mechanotransduction in neuronal cell development and functioning. Biophys Rev 2019; 11:701-720. [PMID: 31617079 PMCID: PMC6815321 DOI: 10.1007/s12551-019-00587-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 08/29/2019] [Indexed: 12/21/2022] Open
Abstract
Although many details remain still elusive, it became increasingly evident in recent years that mechanosensing of microenvironmental biophysical cues and subsequent mechanotransduction are strongly involved in the regulation of neuronal cell development and functioning. This review gives an overview about the current understanding of brain and neuronal cell mechanobiology and how it impacts on neurogenesis, neuronal migration, differentiation, and maturation. We will focus particularly on the events in the cell/microenvironment interface and the decisive extracellular matrix (ECM) parameters (i.e. rigidity and nanometric spatial organisation of adhesion sites) that modulate integrin adhesion complex-based mechanosensing and mechanotransductive signalling. It will also be outlined how biomaterial approaches mimicking essential ECM features help to understand these processes and how they can be used to control and guide neuronal cell behaviour by providing appropriate biophysical cues. In addition, principal biophysical methods will be highlighted that have been crucial for the study of neuronal mechanobiology.
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Affiliation(s)
- Matteo Chighizola
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Tania Dini
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Cristina Lenardi
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Paolo Milani
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Alessandro Podestà
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Carsten Schulte
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy.
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114
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Aregueta-Robles UA, Martens PJ, Poole-Warren LA, Green RA. Tissue engineered hydrogels supporting 3D neural networks. Acta Biomater 2019; 95:269-284. [PMID: 30500450 DOI: 10.1016/j.actbio.2018.11.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 11/08/2018] [Accepted: 11/26/2018] [Indexed: 01/07/2023]
Abstract
Promoting nerve regeneration requires engineering cellular carriers to physically and biochemically support neuronal growth into a long lasting functional tissue. This study systematically evaluated the capacity of a biosynthetic poly(vinyl alcohol) (PVA) hydrogel to support growth and differentiation of co-encapsulated neurons and glia. A significant challenge is to understand the role of the dynamic degradable hydrogel mechanical properties on expression of relevant cellular morphologies and function. It was hypothesised that a carrier with mechanical properties akin to neural tissue will provide glia with conditions to thrive, and that glia in turn will support neuronal survival and development. PVA co-polymerised with biological macromolecules sericin and gelatin (PVA-SG) and with tailored nerve tissue-like mechanical properties were used to encapsulate Schwann cells (SCs) alone and subsequently a co-culture of SCs and neural-like PC12s. SCs were encapsulated within two PVA-SG gel variants with initial compressive moduli of 16 kPa and 2 kPa, spanning a range of reported mechanical properties for neural tissues. Both hydrogels were shown to support cell viability and expression of extracellular matrix proteins, however, SCs grown within the PVA-SG with a higher initial modulus were observed to present with greater physiologically relevant morphologies and increased expression of extracellular matrix proteins. The higher modulus PVA-SG was subsequently shown to support development of neuronal networks when SCs were co-encapsulated with PC12s. The lower modulus hydrogel was unable to support effective development of neural networks. This study demonstrates the critical link between hydrogel properties and glial cell phenotype on development of functional neural tissues. STATEMENT OF SIGNIFICANCE: Hydrogels as platforms for tissue regeneration must provide encapsulated cellular progenitors with physical and biochemical cues for initial survival and to support ongoing tissue formation as the artificial network degrades. While most research focuses on tailoring scaffold properties to suit neurons, this work aims to support glia SCs as the key cellular component that physically and biochemically supports the neuronal network. The challenge is to modify hydrogel properties to support growth and development of multiple cell types into a neuronal network. Given SCs ability to respond to substrate mechanical properties, the significance of this work lies in understanding the relationship between dynamic hydrogel mechanical properties and glia SCs development as the element that enables formation of mature, differentiated neural networks.
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Affiliation(s)
| | - Penny J Martens
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
| | - Laura A Poole-Warren
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
| | - Rylie A Green
- Department of Bioengineering, Imperial College London, London, UK
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115
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Rosso G, Guck J. Mechanical changes of peripheral nerve tissue microenvironment and their structural basis during development. APL Bioeng 2019; 3:036107. [PMID: 31893255 PMCID: PMC6932855 DOI: 10.1063/1.5108867] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 09/05/2019] [Indexed: 12/15/2022] Open
Abstract
Peripheral nerves are constantly exposed to mechanical stresses associated with body growth and limb movements. Although some aspects of these nerves' biomechanical properties are known, the link between nerve biomechanics and tissue microstructures during development is poorly understood. Here, we used atomic force microscopy to comprehensively investigate the elastic modulus of living peripheral nerve tissue cross sections ex vivo at distinct stages of development and correlated these elastic moduli with various cellular and extracellular aspects of the underlying histological microstructure. We found that local nerve tissue stiffness is spatially heterogeneous and evolves biphasically during maturation. Furthermore, we found the intracellular microtubule network and the extracellular matrix collagens type I and type IV as major contributors to the nerves' biomechanical properties, but surprisingly not cellular density and myelin content as previously shown for the central nervous system. Overall, these findings characterize the mechanical microenvironment that surrounds Schwann cells and neurons and will further our understanding of their mechanosensing mechanisms during nerve development. These data also provide the design of artificial nerve scaffolds to promote biomedical nerve regeneration therapies by considering mechanical properties that better reflect the nerve microenvironment.
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116
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Bradbury EJ, Burnside ER. Moving beyond the glial scar for spinal cord repair. Nat Commun 2019; 10:3879. [PMID: 31462640 PMCID: PMC6713740 DOI: 10.1038/s41467-019-11707-7] [Citation(s) in RCA: 388] [Impact Index Per Article: 77.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 07/25/2019] [Indexed: 02/08/2023] Open
Abstract
Traumatic spinal cord injury results in severe and irreversible loss of function. The injury triggers a complex cascade of inflammatory and pathological processes, culminating in formation of a scar. While traditionally referred to as a glial scar, the spinal injury scar in fact comprises multiple cellular and extracellular components. This multidimensional nature should be considered when aiming to understand the role of scarring in limiting tissue repair and recovery. In this Review we discuss recent advances in understanding the composition and phenotypic characteristics of the spinal injury scar, the oversimplification of defining the scar in binary terms as good or bad, and the development of therapeutic approaches to target scar components to enable improved functional outcome after spinal cord injury.
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Affiliation(s)
- Elizabeth J Bradbury
- King's College London, Regeneration Group, The Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), Guy's Campus, London Bridge, London, SE1 1UL, UK.
| | - Emily R Burnside
- King's College London, Regeneration Group, The Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), Guy's Campus, London Bridge, London, SE1 1UL, UK
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117
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Simsek AN, Braeutigam A, Koch MD, Shaevitz JW, Huang Y, Gompper G, Sabass B. Substrate-rigidity dependent migration of an idealized twitching bacterium. SOFT MATTER 2019; 15:6224-6236. [PMID: 31334524 DOI: 10.1039/c9sm00541b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mechanical properties of the extracellular matrix are important determinants of cellular migration in diverse processes, such as immune response, wound healing, and cancer metastasis. Moreover, recent studies indicate that even bacterial surface colonization can depend on the mechanics of the substrate. Here, we focus on physical mechanisms that can give rise to substrate-rigidity dependent migration. We study a "twitcher", a cell driven by extension-retraction cycles, to idealize bacteria and perhaps eukaryotic cells that employ a slip-stick mode of motion. The twitcher is asymmetric and always pulls itself forward at its front. Analytical calculations show that the migration speed of a twitcher depends non-linearly on substrate rigidity. For soft substrates, deformations do not lead to build-up of significant force and the migration speed is therefore determined by stochastic adhesion unbinding. For rigid substrates, forced adhesion rupture determines the migration speed. Depending on the force-sensitivity of front and rear adhesions, forced bond rupture implies an increase or a decrease of the migration speed. A requirement for the occurrence of rigidity-dependent stick-slip migration is a "sticky" substrate, with binding rates being an order of magnitude larger than unbinding rates in absence of force. Computer simulations show that small stall forces of the driving machinery lead to a reduced movement on high rigidities, regardless of force-sensitivities of bonds. The simulations also confirm the occurrence of rigidity-dependent migration speed in a generic model for slip-stick migration of cells on a sticky substrate.
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Affiliation(s)
- Ahmet Nihat Simsek
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Andrea Braeutigam
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Matthias D Koch
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, NJ 08544, USA
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, NJ 08544, USA
| | - Yunfei Huang
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Benedikt Sabass
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
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118
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Unal DB, Caliari SR, Lampe KJ. Engineering biomaterial microenvironments to promote myelination in the central nervous system. Brain Res Bull 2019; 152:159-174. [PMID: 31306690 DOI: 10.1016/j.brainresbull.2019.07.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 06/09/2019] [Accepted: 07/08/2019] [Indexed: 01/01/2023]
Abstract
Promoting remyelination and/or minimizing demyelination are key therapeutic strategies under investigation for diseases and injuries like multiple sclerosis (MS), spinal cord injury, stroke, and virus-induced encephalopathy. Myelination is essential for efficacious neuronal signaling. This myelination process is originated by oligodendrocyte progenitor cells (OPCs) in the central nervous system (CNS). Resident OPCs are capable of both proliferation and differentiation, and also migration to demyelinated injury sites. OPCs can then engage with these unmyelinated or demyelinated axons and differentiate into myelin-forming oligodendrocytes (OLs). However this process is frequently incomplete and often does not occur at all. Biomaterial strategies can now be used to guide OPC and OL development with the goal of regenerating healthy myelin sheaths in formerly damaged CNS tissue. Growth and neurotrophic factors delivered from such materials can promote proliferation of OPCs or differentiation into OLs. While cell transplantation techniques have been used to replace damaged cells in wound sites, they have also resulted in poor transplant cell viability, uncontrollable differentiation, and poor integration into the host. Biomaterial scaffolds made from extracellular matrix (ECM) mimics that are naturally or synthetically derived can improve transplanted cell survival, support both transplanted and endogenous cell populations, and direct their fate. In particular, stiffness and degradability of these scaffolds are two parameters that can influence the fate of OPCs and OLs. The future outlook for biomaterials research includes 3D in vitro models of myelination / remyelination / demyelination to better mimic and study these processes. These models should provide simple relationships of myelination to microenvironmental biophysical and biochemical properties to inform improved therapeutic approaches.
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Affiliation(s)
- Deniz B Unal
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, United States
| | - Steven R Caliari
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, United States; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22903, United States
| | - Kyle J Lampe
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, United States.
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119
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Ayad NME, Kaushik S, Weaver VM. Tissue mechanics, an important regulator of development and disease. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180215. [PMID: 31431174 DOI: 10.1098/rstb.2018.0215] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A growing body of work describes how physical forces in and around cells affect their growth, proliferation, migration, function and differentiation into specialized types. How cells receive and respond biochemically to mechanical signals is a process termed mechanotransduction. Disease may arise if a disruption occurs within this mechanism of sensing and interpreting mechanics. Cancer, cardiovascular diseases and developmental defects, such as during the process of neural tube formation, are linked to changes in cell and tissue mechanics. A breakdown in normal tissue and cellular forces activates mechanosignalling pathways that affect their function and can promote disease progression. The recent advent of high-resolution techniques enables quantitative measurements of mechanical properties of the cell and its extracellular matrix, providing insight into how mechanotransduction is regulated. In this review, we will address the standard methods and new technologies available to properly measure mechanical properties, highlighting the challenges and limitations of probing different length-scales. We will focus on the unique environment present throughout the development and maintenance of the central nervous system and discuss cases where disease, such as brain cancer, arises in response to changes in the mechanical properties of the microenvironment that disrupt homeostasis. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.
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Affiliation(s)
- Nadia M E Ayad
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA, USA
| | - Shelly Kaushik
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Valerie M Weaver
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.,Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA, USA.,UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, USA.,Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA.,Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
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120
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Gill NK, Ly C, Kim PH, Saunders CA, Fong LG, Young SG, Luxton GWG, Rowat AC. DYT1 Dystonia Patient-Derived Fibroblasts Have Increased Deformability and Susceptibility to Damage by Mechanical Forces. Front Cell Dev Biol 2019; 7:103. [PMID: 31294022 PMCID: PMC6606767 DOI: 10.3389/fcell.2019.00103] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 05/27/2019] [Indexed: 12/24/2022] Open
Abstract
DYT1 dystonia is a neurological movement disorder that is caused by a loss-of-function mutation in the DYT1/TOR1A gene, which encodes torsinA, a conserved luminal ATPases-associated with various cellular activities (AAA+) protein. TorsinA is required for the assembly of functional linker of nucleoskeleton and cytoskeleton (LINC) complexes, and consequently the mechanical integration of the nucleus and the cytoskeleton. Despite the potential implications of altered mechanobiology in dystonia pathogenesis, the role of torsinA in regulating cellular mechanical phenotype, or mechanotype, in DYT1 dystonia remains unknown. Here, we define the deformability of mouse fibroblasts lacking functional torsinA as well as human fibroblasts isolated from DYT1 dystonia patients. We find that the deletion of torsinA or the expression of torsinA containing the DYT1 dystonia-causing ΔE302/303 (ΔE) mutation results in more deformable cells. We observe a similar increased deformability of mouse fibroblasts that lack lamina-associated polypeptide 1 (LAP1), which interacts with and stimulates the ATPase activity of torsinA in vitro, as well as with the absence of the LINC complex proteins, Sad1/UNC-84 1 (SUN1) and SUN2, lamin A/C, or lamin B1. Consistent with these findings, we also determine that DYT1 dystonia patient-derived fibroblasts are more compliant than fibroblasts isolated from unafflicted individuals. DYT1 dystonia patient-derived fibroblasts also exhibit increased nuclear strain and decreased viability following mechanical stretch. Taken together, our results establish the foundation for future mechanistic studies of the role of cellular mechanotype and LINC-dependent nuclear-cytoskeletal coupling in regulating cell survival following exposure to mechanical stresses.
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Affiliation(s)
- Navjot Kaur Gill
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, United States
| | - Chau Ly
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, United States.,Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States
| | - Paul H Kim
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Cosmo A Saunders
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, United States
| | - Loren G Fong
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Stephen G Young
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States.,Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA, United States.,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
| | - G W Gant Luxton
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, United States.,Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States
| | - Amy C Rowat
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, United States
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121
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Microtubule Polymerization and Cross-Link Dynamics Explain Axonal Stiffness and Damage. Biophys J 2019; 114:201-212. [PMID: 29320687 DOI: 10.1016/j.bpj.2017.11.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/27/2017] [Accepted: 11/10/2017] [Indexed: 01/02/2023] Open
Abstract
Axonal damage is a critical indicator for traumatic effects of physical impact to the brain. However, the precise mechanisms of axonal damage are still unclear. Here, we establish a mechanistic and highly dynamic model of the axon to explore the evolution of damage in response to physical forces. Our axon model consists of a bundle of dynamically polymerizing and depolymerizing microtubules connected by dynamically detaching and reattaching cross-links. Although the probability of cross-link attachment depends exclusively on thermal fluctuations, the probability of detachment increases in the presence of physical forces. We systematically probe the landscape of axonal stretch and stretch rate and characterize the overall axonal force, stiffness, and damage as a direct result of the interplay between microtubule and cross-link dynamics. Our simulations reveal that slow loading is dominated by cross-link dynamics, a net reduction of cross-links, and a gradual accumulation of damage, whereas fast loading is dominated by cross-link deformations, a rapid increase in stretch, and an immediate risk of rupture. Microtubule polymerization and depolymerization decrease the overall axonal stiffness, but do not affect the evolution of damage at timescales relevant to axonal failure. Our study explains different failure mechanisms in the axon as emergent properties of microtubule polymerization, cross-link dynamics, and physical forces. We anticipate that our model will provide insight into causal relations by which molecular mechanisms determine the timeline and severity of axon damage after a physical impact to the brain.
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122
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Yildirimer L, Zhang Q, Kuang S, Cheung CWJ, Chu KA, He Y, Yang M, Zhao X. Engineering three-dimensional microenvironments towards
in vitro
disease models of the central nervous system. Biofabrication 2019; 11:032003. [DOI: 10.1088/1758-5090/ab17aa] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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123
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A mechanoelectrical coupling model of neurons under stretching. J Mech Behav Biomed Mater 2019; 93:213-221. [DOI: 10.1016/j.jmbbm.2019.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 02/04/2019] [Accepted: 02/04/2019] [Indexed: 12/20/2022]
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124
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Song Y, Li D, Farrelly O, Miles L, Li F, Kim SE, Lo TY, Wang F, Li T, Thompson-Peer KL, Gong J, Murthy SE, Coste B, Yakubovich N, Patapoutian A, Xiang Y, Rompolas P, Jan LY, Jan YN. The Mechanosensitive Ion Channel Piezo Inhibits Axon Regeneration. Neuron 2019; 102:373-389.e6. [PMID: 30819546 PMCID: PMC6487666 DOI: 10.1016/j.neuron.2019.01.050] [Citation(s) in RCA: 126] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 11/27/2018] [Accepted: 01/23/2019] [Indexed: 01/09/2023]
Abstract
Neurons exhibit a limited ability of repair. Given that mechanical forces affect neuronal outgrowth, it is important to investigate whether mechanosensitive ion channels may regulate axon regeneration. Here, we show that DmPiezo, a Ca2+-permeable non-selective cation channel, functions as an intrinsic inhibitor for axon regeneration in Drosophila. DmPiezo activation during axon regeneration induces local Ca2+ transients at the growth cone, leading to activation of nitric oxide synthase and the downstream cGMP kinase Foraging or PKG to restrict axon regrowth. Loss of DmPiezo enhances axon regeneration of sensory neurons in the peripheral and CNS. Conditional knockout of its mammalian homolog Piezo1 in vivo accelerates regeneration, while its pharmacological activation in vitro modestly reduces regeneration, suggesting the role of Piezo in inhibiting regeneration may be evolutionarily conserved. These findings provide a precedent for the involvement of mechanosensitive channels in axon regeneration and add a potential target for modulating nervous system repair.
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Affiliation(s)
- Yuanquan Song
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Dan Li
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA,These authors contributed equally
| | - Olivia Farrelly
- Department of Dermatology, University of Pennsylvania, Philadelphia, PA 19104, USA,These authors contributed equally
| | - Leann Miles
- The Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA,These authors contributed equally
| | - Feng Li
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sung Eun Kim
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Tsz Y. Lo
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Fei Wang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Tun Li
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Katherine L. Thompson-Peer
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jiaxin Gong
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Swetha E. Murthy
- Department of Neuroscience, The Scripps Research Institute, Howard Hughes Medical Institute, La Jolla, CA 92037, USA
| | - Bertrand Coste
- Department of Neuroscience, The Scripps Research Institute, Howard Hughes Medical Institute, La Jolla, CA 92037, USA,Present address: Aix Marseille Université, CNRS, LNC-UMR 7291, 13344 Marseille, France
| | - Nikita Yakubovich
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Ardem Patapoutian
- Department of Neuroscience, The Scripps Research Institute, Howard Hughes Medical Institute, La Jolla, CA 92037, USA
| | - Yang Xiang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Panteleimon Rompolas
- Department of Dermatology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lily Yeh Jan
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Yuh Nung Jan
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
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125
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Baranes K, Hibsh D, Cohen S, Yamin T, Efroni S, Sharoni A, Shefi O. Comparing Transcriptome Profiles of Neurons Interfacing Adjacent Cells and Nanopatterned Substrates Reveals Fundamental Neuronal Interactions. NANO LETTERS 2019; 19:1451-1459. [PMID: 30704243 DOI: 10.1021/acs.nanolett.8b03879] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Developing neuronal axons are directed by chemical and physical signals toward a myriad of target cells. According to current dogma, the resulting network architecture is critically shaped by electrical interconnections, the synapses; however, key mechanisms translating neuronal interactions into neuronal growth behavior during network formation are still unresolved. To elucidate these mechanisms, we examined neurons interfacing nanopatterned substrates and compared them to natural interneuron interactions. We grew similar neuronal populations under three connectivity conditions, (1) the neurons are isolated, (2) the neurons are interconnected, and (3) the neurons are connected only to artificial substrates, then quantitatively compared both the cell morphologies and the transcriptome-expression profiles. Our analysis shows that whereas axon-guidance signaling pathways in isolated neurons are predominant, in isolated neurons interfacing nanotopography, these pathways are downregulated, similar to the interconnected neurons. Moreover, in nanotopography, interfacing neuron genes related to synaptogenesis and synaptic regulation are highly expressed, that is, again resembling the behavior of interconnected neurons. These molecular findings demonstrate that interactions with nanotopographies, although not leading to electrical coupling, play a comparable functional role in two major routes, neuronal guidance and network formation, with high relevance to the design of regenerative interfaces.
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Affiliation(s)
- Koby Baranes
- Faculty of Engineering , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
| | - Dror Hibsh
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Faculty of Life Sciences , Bar-Ilan University , Ramat-Gan 5290002 , Israel
| | - Sharon Cohen
- Faculty of Engineering , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Gonda Multidisciplinary Brain Research Center , Bar-Ilan University , Ramat-Gan 5290002 , Israel
| | - Tony Yamin
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Department of Physics , Bar-Ilan University , Ramat-Gan 5290002 , Israel
| | - Sol Efroni
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Faculty of Life Sciences , Bar-Ilan University , Ramat-Gan 5290002 , Israel
| | - Amos Sharoni
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Department of Physics , Bar-Ilan University , Ramat-Gan 5290002 , Israel
| | - Orit Shefi
- Faculty of Engineering , Bar-Ilan University , Ramat-Gan 5290002 , Israel
- Bar-Ilan Institute of Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 5290002 , Israel
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126
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How Forces Fold the Cerebral Cortex. J Neurosci 2019; 38:767-775. [PMID: 29367287 DOI: 10.1523/jneurosci.1105-17.2017] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 11/15/2017] [Accepted: 11/20/2017] [Indexed: 12/31/2022] Open
Abstract
Improved understanding of the factors that govern folding of the cerebral cortex is desirable for many reasons. The existence of consistent patterns in folding within and between species suggests a fundamental role in brain function. Abnormal folding patterns found in individuals affected by a diverse array of neurodevelopmental disorders underline the clinical relevance of understanding the folding process. Recent experimental and computational efforts to elucidate the biomechanical forces involved in cerebral cortical folding have converged on a consistent approach. Brain growth is modeled with two components: an expanding outer zone, destined to become the cerebral cortex, is mechanically coupled to an inner zone, destined to become white matter, that grows at a slower rate, perhaps in response to stress induced by expansion from the outer layer. This framework is consistent with experimentally observed internal forces in developing brains, and with observations of the folding process in physical models. In addition, computational simulations based on this foundation can produce folding patterns that recapitulate the characteristics of folding patterns found in gyroencephalic brains. This perspective establishes the importance of mechanical forces in our current understanding of how brains fold, and identifies realistic ranges for specific parameters in biophysical models of developing brain tissue. However, further refinement of this approach is needed. An understanding of mechanical forces that arise during brain development and their cellular-level origins is necessary to interpret the consequences of abnormal brain folding and its role in functional deficits as well as neurodevelopmental disease.Dual Perspectives Companion Paper: How Cells Fold the Cerebral Cortex, by Víctor Borrell.
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127
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Acute and chronic demyelinated CNS lesions exhibit opposite elastic properties. Sci Rep 2019; 9:999. [PMID: 30700777 PMCID: PMC6354022 DOI: 10.1038/s41598-018-37745-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 12/07/2018] [Indexed: 01/07/2023] Open
Abstract
Increased deposition of extracellular matrix (ECM) is a known inhibitor of axonal regrowth and remyelination. Recent in vitro studies have demonstrated that oligodendrocyte differentiation is impacted by the physical properties of the ECM. However, characterization of the mechanical properties of the healthy and injured CNS myelin is challenging, and has largely relied on non-invasive, low-resolution methods. To address this, we have employed atomic force microscopy to perform micro-indentation measurements of demyelinated tissue at cellular scale. Analysis of mouse and human demyelinated brains indicate that acute demyelination results in decreased tissue stiffness that recovers with remyelination; while chronic demyelination is characterized by increased tissue stiffness, which correlates with augmented ECM deposition. Thus, changes in the mechanical properties of the acutely (softer) or chronically (stiffer) demyelinated brain might contribute to differences in their regenerative capacity. Our findings are relevant to the optimization of cell-based therapies aimed at promoting CNS regeneration and remyelination.
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128
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Qian L, Sun Y, Tong Q, Tian J, Ren Z, Zhao H. Indentation response in porcine brain under electric fields. SOFT MATTER 2019; 15:623-632. [PMID: 30608501 DOI: 10.1039/c8sm01272e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Electric fields in the environment can have profound effects on brain function and behavior. In clinical practice, some noninvasive/microinvasive therapies with electrical fields such as transcranial electrical stimulation (tES), deep brain stimulation (DBS), and electroconvulsive therapy (ECT) have emerged as powerful tools for the treatment of neuropsychiatric disorders and neuromodulation. Nonetheless, currently, most studies focus on the mechanisms and effects of therapies and do not to address the mechanical properties of brain tissue under electric fields. Thus, the mechanical behavior of brain tissue, which plays an important role in modulating both brain form and brain function, should be given attention. The present study addresses this paucity by presenting, for the first time, the mechanical properties of brain tissue under various intensities of direct current electric field (0, 2, 5, 10, 20, and 50 V) using a custom-designed indentation device. Prior to brain indentation, validation tests were performed in different hydrogels to ensure that there was no interference in the electric fields from the indentation device. Subsequently, the load trace data obtained from the indentation-relaxation tests was fitted to both linear elastic and viscoelastic models to characterize the sensitivity of the mechanical behavior of the brain tissue to the electric fields. The brain tissue was found to be softened at a higher electric field level and less viscous, and substantially responded more quickly with an increase in electric field. The explanations for the above behaviors were further discussed based on the analysis of the resistance and thermal responses during the testing process. Understanding the effect of electric fields on brain tissue at the mechanical level can provide a better understanding of the mechanisms of some therapies, which may be beneficial to guide therapy protocols.
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Affiliation(s)
- Long Qian
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130025, China.
| | - Yifan Sun
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130025, China.
| | - Qian Tong
- Department of Cardiology, The First Hospital of Jilin University, Changchun 130021, China.
| | - Jiyu Tian
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130025, China.
| | - Zhuang Ren
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130025, China.
| | - Hongwei Zhao
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130025, China.
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129
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Cell-matrix tension contributes to hypoxia in astrocyte-seeded viscoelastic hydrogels composed of collagen and hyaluronan. Exp Cell Res 2019; 376:49-57. [PMID: 30658092 DOI: 10.1016/j.yexcr.2019.01.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/08/2019] [Accepted: 01/14/2019] [Indexed: 11/22/2022]
Abstract
Astrocyte activation is crucial for wound contraction and glial scar formation following central nervous system injury, but the mechanism by which activation leads to astrocyte contractility and matrix reorganization in the central nervous system (CNS) is unknown. Current means to measure cell traction forces within three-dimensional scaffolds are limited to analyzing individual or small groups of cells, within extracellular matrices, whereas gap junctions and other cell-cell adhesions connect astrocytes to form a functional syncytium within the glial scar. Here, we measure the viscoelastic properties of cell-seeded hydrogels to yield insight into the collective contractility of astrocytes as they exert tension on the surrounding matrix and change its bulk mechanical properties. Our results indicate that incorporation of the CNS matrix component hyaluronan into a collagen hydrogel increases expression of the intermediate filament protein GFAP and results in a higher shear storage modulus of the cell/matrix composite, establishing the correlation between astrocyte activation and increased cell contractility. The effects of thrombin and blebbistatin, known mediators of actomyosin-mediated contraction, verify that cell-matrix tension dictates the hydrogel mechanical properties. Viability assays indicate that increased cell traction exacerbates cell death at the center of the scaffold, and message level analysis reveals that cells in the hyaluronan-containing matrix have a ~ 3-fold increase in HIF-1α gene expression. Overall, these findings suggest that astrocyte activation not only increases cell traction, but may also contribute to hypoxia near sites of central nervous system injury.
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130
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Fouquet C, Trembleau A. Preparation and Manipulation of Olfactory Epithelium Explant Cultures for Measurement of the Mechanical Tension of Individual Axons Using the Biomembrane Force Probe. Bio Protoc 2019; 9:e3213. [PMID: 31131294 DOI: 10.21769/bioprotoc.3213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In this paper, we describe a protocol allowing measurement of the mechanical tension of individual axons grown ex vivo from neural tissue explants. This protocol was developed with primary cultures of olfactory epithelium explants from embryonic (E13.5) mice. It includes a detailed description of explant dissection and culture, as well as the main steps of the procedure for axon tension measurement using the previously established Biomembrane Force Probe.
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Affiliation(s)
- Coralie Fouquet
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris Seine, Laboratoire Neuroscience Paris Seine, F-75005 Paris, France
| | - Alain Trembleau
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris Seine, Laboratoire Neuroscience Paris Seine, F-75005 Paris, France
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131
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Miller KE, Suter DM. An Integrated Cytoskeletal Model of Neurite Outgrowth. Front Cell Neurosci 2018; 12:447. [PMID: 30534055 PMCID: PMC6275320 DOI: 10.3389/fncel.2018.00447] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 11/07/2018] [Indexed: 12/27/2022] Open
Abstract
Neurite outgrowth underlies the wiring of the nervous system during development and regeneration. Despite a significant body of research, the underlying cytoskeletal mechanics of growth and guidance are not fully understood, and the relative contributions of individual cytoskeletal processes to neurite growth are controversial. Here, we review the structural organization and biophysical properties of neurons to make a semi-quantitative comparison of the relative contributions of different processes to neurite growth. From this, we develop the idea that neurons are active fluids, which generate strong contractile forces in the growth cone and weaker contractile forces along the axon. As a result of subcellular gradients in forces and material properties, actin flows rapidly rearward in the growth cone periphery, and microtubules flow forward in bulk along the axon. With this framework, an integrated model of neurite outgrowth is proposed that hopefully will guide new approaches to stimulate neuronal growth.
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Affiliation(s)
- Kyle E Miller
- Department of Integrative Biology, Michigan State University, East Lansing, MI, United States
| | - Daniel M Suter
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States.,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN, United States.,Bindley Bioscience Center, Purdue University, West Lafayette, IN, United States.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, United States
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132
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Schulte C, Lamanna J, Moro AS, Piazzoni C, Borghi F, Chighizola M, Ortoleva S, Racchetti G, Lenardi C, Podestà A, Malgaroli A, Milani P. Neuronal Cells Confinement by Micropatterned Cluster-Assembled Dots with Mechanotransductive Nanotopography. ACS Biomater Sci Eng 2018; 4:4062-4075. [DOI: 10.1021/acsbiomaterials.8b00916] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Carsten Schulte
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Jacopo Lamanna
- Center for Behavioral Neuroscience and Communication (BNC), Università Vita-Salute San Raffaele and Neurobiology of Learning Unit, Division of Neuroscience, Scientific
Institute San Raffaele, Milano, Italy
| | - Andrea Stefano Moro
- Center for Behavioral Neuroscience and Communication (BNC), Università Vita-Salute San Raffaele and Neurobiology of Learning Unit, Division of Neuroscience, Scientific
Institute San Raffaele, Milano, Italy
| | - Claudio Piazzoni
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Francesca Borghi
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Matteo Chighizola
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Serena Ortoleva
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Gabriella Racchetti
- Center for Behavioral Neuroscience and Communication (BNC), Università Vita-Salute San Raffaele and Neurobiology of Learning Unit, Division of Neuroscience, Scientific
Institute San Raffaele, Milano, Italy
| | - Cristina Lenardi
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Alessandro Podestà
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
| | - Antonio Malgaroli
- Center for Behavioral Neuroscience and Communication (BNC), Università Vita-Salute San Raffaele and Neurobiology of Learning Unit, Division of Neuroscience, Scientific
Institute San Raffaele, Milano, Italy
| | - Paolo Milani
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (CIMaINa) and Department of Physics, Università degli Studi di Milano, Milano, Italy
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133
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Qing B, Canovic EP, Mijailovic AS, Jagielska A, Whitfield MJ, Lowe AL, Kelly EH, Turner D, Sahin M, Van Vliet K. PROBING MECHANICAL PROPERTIES OF BRAIN IN A TUBEROUS SCLEROSIS MODEL OF AUTISM. J Biomech Eng 2018; 141:2709743. [PMID: 30347048 DOI: 10.1115/1.4040945] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Indexed: 01/03/2023]
Abstract
Causes of Autism Spectrum Disorders (ASD) are understood poorly, making diagnosis and treatment challenging. While many studies have investigated the biochemical and genetic aspects of ASD, whether and how mechanical characteristics of the autistic brain can modulate neuronal connectivity and cognition in ASD are unknown. Previously, it has been shown that ASD brains are characterized by abnormal white matter and disorganized neuronal connectivity; we hypothesized that these significant cellular-level structural changes may translate to changes in the mechanical properties of the autistic brain or regions therein. Here, we focused on tuberous sclerosis complex (TSC), a genetic disorder with a high penetrance of ASD. We investigated mechanical differences between murine brains obtained from control and TSC cohorts at various deformation length- and time-scales. At the microscale, we conducted creep-compliance and stress relaxation experiments using atomic force microscope-enabled indentation. At the mesoscale, we conducted impact indentation using a pendulum-based instrumented indenter to extract mechanical energy dissipation metrics. At the macroscale, we used oscillatory shear rheology to quantify the frequency-dependent shear moduli. Despite significant changes in the cellular organization of TSC brain tissue, we found no corresponding changes in the quantified mechanical properties at every length- and time-scale explored. This investigation of the mechanical characteristics of the brain has broadened our understanding of causes and markers of TSC/ASD, while raising questions about whether any mechanical differences can be detected in other animal models of ASD or other disease models that also feature abnormal brain structure.
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Affiliation(s)
- Bo Qing
- Department of Biological Engineering, MIT, Cambridge, MA, USA
| | | | | | - Anna Jagielska
- Department of Materials Science and Engineering, MIT, Cambridge, MA, USA
| | | | - Alexis L Lowe
- Department of Neuroscience, Wellesley College, Wellesley, MA, USA
| | - Elyza H Kelly
- The F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Daria Turner
- The F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Mustafa Sahin
- The F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Krystyn Van Vliet
- Department of Biological Engineering, MIT, Cambridge, MA, USA; Department of Materials Science and Engineering, MIT, Cambridge, MA, USA
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134
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Nötzel M, Rosso G, Möllmert S, Seifert A, Schlüßler R, Kim K, Hermann A, Guck J. Axonal Transport, Phase-Separated Compartments, and Neuron Mechanics - A New Approach to Investigate Neurodegenerative Diseases. Front Cell Neurosci 2018; 12:358. [PMID: 30356682 PMCID: PMC6189317 DOI: 10.3389/fncel.2018.00358] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 09/24/2018] [Indexed: 01/07/2023] Open
Abstract
Many molecular and cellular pathogenic mechanisms of neurodegenerative diseases have been revealed. However, it is unclear what role a putatively impaired neuronal transport with respect to altered mechanical properties of neurons play in the initiation and progression of such diseases. The biochemical aspects of intracellular axonal transport, which is important for molecular movements through the cytoplasm, e.g., mitochondrial movement, has already been studied. Interestingly, transport deficiencies are associated with the emergence of the affliction and potentially linked to disease transmission. Transport along the axon depends on the normal function of the neuronal cytoskeleton, which is also a major contributor to neuronal mechanical properties. By contrast, little attention has been paid to the mechanical properties of neurons and axons impaired by neurodegeneration, and of membraneless, phase-separated organelles such as stress granules (SGs) within neurons. Mechanical changes may indicate cytoskeleton reorganization and function, and thus give information about the transport and other system impairment. Nowadays, several techniques to investigate cellular mechanical properties are available. In this review, we discuss how select biophysical methods to probe material properties could contribute to the general understanding of mechanisms underlying neurodegenerative diseases.
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Affiliation(s)
- Martin Nötzel
- Biotechnology Center, Dresden University of Technology, Dresden, Germany
| | - Gonzalo Rosso
- Biotechnology Center, Dresden University of Technology, Dresden, Germany
| | - Stephanie Möllmert
- Biotechnology Center, Dresden University of Technology, Dresden, Germany
| | - Anne Seifert
- Department of Neurology, Technische Universität Dresden, Dresden, Germany
- Center for Regenerative Therapies (CRTD), Technische Universität Dresden, Dresden, Germany
- German Center for Neurodegenerative Diseases, Dresden, Germany
| | - Raimund Schlüßler
- Biotechnology Center, Dresden University of Technology, Dresden, Germany
| | - Kyoohyun Kim
- Biotechnology Center, Dresden University of Technology, Dresden, Germany
| | - Andreas Hermann
- Department of Neurology, Technische Universität Dresden, Dresden, Germany
- Center for Regenerative Therapies (CRTD), Technische Universität Dresden, Dresden, Germany
- German Center for Neurodegenerative Diseases, Dresden, Germany
| | - Jochen Guck
- Biotechnology Center, Dresden University of Technology, Dresden, Germany
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135
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Mapping heterogeneity of cellular mechanics by multi-harmonic atomic force microscopy. Nat Protoc 2018; 13:2200-2216. [DOI: 10.1038/s41596-018-0031-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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136
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Kuhl E. Mechanical Cues in Spinal Cord Injury. Biophys J 2018; 115:751-753. [PMID: 30119835 DOI: 10.1016/j.bpj.2018.04.052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 04/10/2018] [Indexed: 11/25/2022] Open
Affiliation(s)
- Ellen Kuhl
- Departments of Mechanical Engineering and Bioengineering, Stanford University, Stanford, California.
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137
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Mechanical Mapping of Spinal Cord Growth and Repair in Living Zebrafish Larvae by Brillouin Imaging. Biophys J 2018; 115:911-923. [PMID: 30122291 PMCID: PMC6127462 DOI: 10.1016/j.bpj.2018.07.027] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 07/03/2018] [Accepted: 07/25/2018] [Indexed: 12/21/2022] Open
Abstract
The mechanical properties of biological tissues are increasingly recognized as important factors in developmental and pathological processes. Most existing mechanical measurement techniques either necessitate destruction of the tissue for access or provide insufficient spatial resolution. Here, we show for the first time to our knowledge a systematic application of confocal Brillouin microscopy to quantitatively map the mechanical properties of spinal cord tissues during biologically relevant processes in a contact-free and nondestructive manner. Living zebrafish larvae were mechanically imaged in all anatomical planes during development and after spinal cord injury. These experiments revealed that Brillouin microscopy is capable of detecting the mechanical properties of distinct anatomical structures without interfering with the animal’s natural development. The Brillouin shift within the spinal cord remained comparable during development and transiently decreased during the repair processes after spinal cord transection. By taking into account the refractive index distribution, we explicitly determined the apparent longitudinal modulus and viscosity of different larval zebrafish tissues. Importantly, mechanical properties differed between tissues in situ and in excised slices. The presented work constitutes the first step toward an in vivo assessment of spinal cord tissue mechanics during regeneration, provides a methodical basis to identify key determinants of mechanical tissue properties, and allows us to test their relative importance in combination with biochemical and genetic factors during developmental and regenerative processes.
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138
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Orr MB, Gensel JC. Spinal Cord Injury Scarring and Inflammation: Therapies Targeting Glial and Inflammatory Responses. Neurotherapeutics 2018; 15:541-553. [PMID: 29717413 PMCID: PMC6095779 DOI: 10.1007/s13311-018-0631-6] [Citation(s) in RCA: 350] [Impact Index Per Article: 58.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Deficits in neuronal function are a hallmark of spinal cord injury (SCI) and therapeutic efforts are often focused on central nervous system (CNS) axon regeneration. However, secondary injury responses by astrocytes, microglia, pericytes, endothelial cells, Schwann cells, fibroblasts, meningeal cells, and other glia not only potentiate SCI damage but also facilitate endogenous repair. Due to their profound impact on the progression of SCI, glial cells and modification of the glial scar are focuses of SCI therapeutic research. Within and around the glial scar, cells deposit extracellular matrix (ECM) proteins that affect axon growth such as chondroitin sulfate proteoglycans (CSPGs), laminin, collagen, and fibronectin. This dense deposition of material, i.e., the fibrotic scar, is another barrier to endogenous repair and is a target of SCI therapies. Infiltrating neutrophils and monocytes are recruited to the injury site through glial chemokine and cytokine release and subsequent upregulation of chemotactic cellular adhesion molecules and selectins on endothelial cells. These peripheral immune cells, along with endogenous microglia, drive a robust inflammatory response to injury with heterogeneous reparative and pathological properties and are targeted for therapeutic modification. Here, we review the role of glial and inflammatory cells after SCI and the therapeutic strategies that aim to replace, dampen, or alter their activity to modulate SCI scarring and inflammation and improve injury outcomes.
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Affiliation(s)
- Michael B Orr
- Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky College of Medicine, 741 S. Limestone, B463 BBSRB, Lexington, Kentucky, 40536, USA
| | - John C Gensel
- Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky College of Medicine, 741 S. Limestone, B463 BBSRB, Lexington, Kentucky, 40536, USA.
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139
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Nanoscale mechanics of brain abscess: An atomic force microscopy study. Micron 2018; 113:34-40. [PMID: 29957562 DOI: 10.1016/j.micron.2018.06.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 06/19/2018] [Accepted: 06/19/2018] [Indexed: 12/11/2022]
Abstract
Mechanical stimuli are a fundamental player in the pathophysiology of the brain influencing its physiological development and contributing to the onset and progression of many diseases. In some pathological states, the involvement of mechanical and physical stimuli might be extremely subtle; in others, it is more evident and particularly relevant. Among the latter pathologies, one of the most serious life-threatening condition is the brain abscess (BA), a focal infection localized in the brain parenchyma, which causes large brain mechanical deformations, giving rise to a wide range of neurological impairments. In this paper, we present the first nano-mechanical characterization of surgically removed human brain abscess tissues by means of atomic force microscopy (AFM) in the spectroscopy mode. Consistently with previous histological findings, we modeled the brain abscess as a multilayered structure, composed of three main layers: the cerebritis layer, the collagen capsule, and the internal inflammatory border. We probed the viscoelastic behavior of each layer separately through the measure of the apparent Young's modulus (E), that gives information about the sample stiffness, and the AFM hysteresis (H), that estimates the contribution of viscous and dissipative forces. Our experimental findings provide a full mechanical characterization of the abscess, showing an average E of (94 ± 5) kPa and H of 0.37 ± 0.01 for the cerebritis layer, an average E = (1.04 ± 0.05) MPa and H = 0.10 ± 0.01 for the collagen capsule and an average E = (9.8 ± 0.4) kPa and H = 0.57 ± 0.01 for the internal border. The results here presented have the potential to contribute to the development of novel surgical instruments dedicated to the treatment of the pathology and to stimulate the implementation of novel constitutive mechanical models for the estimation of brain compression and damage during BA progression.
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140
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Gangatharan G, Schneider-Maunoury S, Breau MA. Role of mechanical cues in shaping neuronal morphology and connectivity. Biol Cell 2018; 110:125-136. [PMID: 29698566 DOI: 10.1111/boc.201800003] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 04/09/2018] [Indexed: 02/06/2023]
Abstract
Neuronal circuits, the functional building blocks of the nervous system, assemble during development through a series of dynamic processes including the migration of neurons to their final position, the growth and navigation of axons and their synaptic connection with target cells. While the role of chemical cues in guiding neuronal migration and axonal development has been extensively analysed, the contribution of mechanical inputs, such as forces and stiffness, has received far less attention. In this article, we review the in vitro and more recent in vivo studies supporting the notion that mechanical signals are critical for multiple aspects of neuronal circuit assembly, from the emergence of axons to the formation of functional synapses. By combining live imaging approaches with tools designed to measure and manipulate the mechanical environment of neurons, the emerging field of neuromechanics will add a new paradigm in our understanding of neuronal development and potentially inspire novel regenerative therapies.
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Affiliation(s)
- Girisaran Gangatharan
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France
| | - Sylvie Schneider-Maunoury
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France
| | - Marie Anne Breau
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France.,Sorbonne Université, CNRS UMR 8237, Laboratoire Jean Perrin, Paris, 75005, France
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141
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Evans EB, Brady SW, Tripathi A, Hoffman-Kim D. Schwann cell durotaxis can be guided by physiologically relevant stiffness gradients. Biomater Res 2018; 22:14. [PMID: 29780613 PMCID: PMC5948700 DOI: 10.1186/s40824-018-0124-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 04/13/2018] [Indexed: 12/21/2022] Open
Abstract
Background Successful nerve regeneration depends upon directed migration of morphologically specialized repair state Schwann cells across a nerve defect. Although several groups have studied directed migration of Schwann cells in response to chemical or topographic cues, the current understanding of how the mechanical environment influences migration remains largely understudied and incomplete. Therefore, the focus of this study was to evaluate Schwann cell migration and morphodynamics in the presence of stiffness gradients, which revealed that Schwann cells can follow extracellular gradients of increasing stiffness, in a form of directed migration termed durotaxis. Methods Polyacrylamide substrates were fabricated to mimic the range of stiffness found in peripheral nerve tissue. We assessed Schwann cell response to substrates that were either mechanically uniform or embedded with a shallow or steep stiffness gradient, respectively corresponding to the mechanical niche present during either the fluid phase or subsequent matrix phase of the peripheral nerve regeneration process. We examined cell migration (velocity and directionality) and morphology (elongation, spread area, nuclear aspect ratio, and cell process dynamics). We also characterized the surface morphology of Schwann cells by scanning electron microscopy. Results On laminin-coated polyacrylamide substrates embedded with either a shallow (∼0.04 kPa/mm) or steep (∼0.95 kPa/mm) stiffness gradient, Schwann cells displayed durotaxis, increasing both their speed and directionality along the gradient materials, fabricated with elastic moduli in the range found in peripheral nerve tissue. Uniquely and unlike cell behavior reported in other cell types, the durotactic response of Schwann cells was not dependent upon the slope of the gradient. When we examined whether durotaxis behavior was accompanied by a pro-regenerative Schwann cell phenotype, we observed altered cell morphology, including increases in spread area and the number, elongation, and branching of the cellular processes, on the steep but not the shallow gradient materials. This phenotype emerged within hours of the cells adhering to the materials and was sustained throughout the 24 hour duration of the experiment. Control experiments also showed that unlike most adherent cells, Schwann cells did not alter their morphology in response to uniform substrates of different stiffnesses. Conclusion This study is notable in its report of durotaxis of cells in response to a stiffness gradient slope, which is greater than an order of magnitude less than reported elsewhere in the literature, suggesting Schwann cells are highly sensitive detectors of mechanical heterogeneity. Altogether, this work identifies durotaxis as a new migratory modality in Schwann cells, and further shows that the presence of a steep stiffness gradient can support a pro-regenerative cell morphology. Electronic supplementary material The online version of this article (10.1186/s40824-018-0124-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elisabeth B Evans
- 1Department of Molecular Pharmacology, Physiology, Brown University, Providence, Rhode Island, 02912 USA
| | - Samantha W Brady
- 1Department of Molecular Pharmacology, Physiology, Brown University, Providence, Rhode Island, 02912 USA
| | - Anubhav Tripathi
- 1Department of Molecular Pharmacology, Physiology, Brown University, Providence, Rhode Island, 02912 USA.,2Center for Biomedical Engineering, Brown University, Providence, Rhode Island, 02912 USA
| | - Diane Hoffman-Kim
- 1Department of Molecular Pharmacology, Physiology, Brown University, Providence, Rhode Island, 02912 USA.,2Center for Biomedical Engineering, Brown University, Providence, Rhode Island, 02912 USA.,3Carney Institute for Brain Science, Brown University, Providence, Rhode Island, 02912 USA.,4Center to Advance Predictive Biology, Brown University, Providence, Rhode Island, 02912 USA
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142
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Tanner K. Perspective: The role of mechanobiology in the etiology of brain metastasis. APL Bioeng 2018; 2:031801. [PMID: 31069312 PMCID: PMC6324204 DOI: 10.1063/1.5024394] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 04/18/2018] [Indexed: 12/11/2022] Open
Abstract
Tumor latency and dormancy are obstacles to effective cancer treatment. In brain
metastases, emergence of a lesion can occur at varying intervals from diagnosis
and in some cases following successful treatment of the primary tumor. Genetic
factors that drive brain metastases have been identified, such as those involved
in cell adhesion, signaling, extravasation, and metabolism. From this wealth of
knowledge, vexing questions still remain; why is there a difference in strategy
to facilitate outgrowth and why is there a difference in latency? One missing
link may be the role of tissue biophysics of the brain microenvironment in
infiltrating cells. Here, I discuss the mechanical cues that may influence
disseminated tumor cells in the brain, as a function of age and disease. I
further discuss in vitro and in vivo
preclinical models such as 3D culture systems and zebrafish to study the role of
the mechanical environment in brain metastasis in an effort of providing novel
targeted therapeutics.
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Affiliation(s)
- Kandice Tanner
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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143
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Lawrence BJ, Luciano M, Tew J, Ellenbogen RG, Oshinski JN, Loth F, Culley AP, Martin BA. Cardiac-Related Spinal Cord Tissue Motion at the Foramen Magnum is Increased in Patients with Type I Chiari Malformation and Decreases Postdecompression Surgery. World Neurosurg 2018; 116:e298-e307. [PMID: 29733988 DOI: 10.1016/j.wneu.2018.04.191] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 04/24/2018] [Accepted: 04/25/2018] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Type 1 Chiari malformation (CM-I) is a craniospinal disorder historically defined by cerebellar tonsillar position greater than 3-5 mm below the foramen magnum (FM). This definition has come under question because quantitative measurements of cerebellar herniation do not always correspond with symptom severity. Researchers have proposed several additional radiographic diagnostic criteria based on dynamic motion of fluids and/or tissues. The present study objective was to determine if cardiac-related craniocaudal spinal cord tissue displacement is an accurate indicator of the presence of CM-I and if tissue displacement is altered with decompression. METHODS A cohort of 20 symptomatic patients underwent decompression surgery. Fifteen healthy volunteers were recruited for comparison with the CM-I group. Axial phase-contrast magnetic resonance imaging (PC-MRI) measurements were collected before and after surgery at the FM with cranial-caudal velocity encoding and 20 frames per cardiac cycle with retrospective reconstruction. Spinal cord motion (SCM) at the FM was quantified based on the peak-to-peak integral of average spinal cord velocity. RESULTS Tissue motion for the presurgical group was significantly greater than controls (P = 0.0009). Motion decreased after surgery (P = 0.058) with an effect size of -0.151 mm and a standard error of 0.066 mm. Postoperatively, no statistical difference from controls in bulk displacement at the FM was found (P = 0.200) after post hoc testing using the Tukey adjustment for multiple comparisons. CONCLUSIONS These results support SCM measurement by PC-MRI as a possible noninvasive radiographic diagnostic for CM-I. Dynamic measurement of SCM provides unique diagnostic information about CM-I alongside static quantification of tonsillar position and other intracranial morphometrics.
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Affiliation(s)
- Braden J Lawrence
- School of Medicine, University of Washington, Seattle, Washington, USA; Department of Neurological Surgery, University of Washington, Seattle, Washington, USA; Department of Biological Engineering, University of Idaho, Moscow, Idaho, USA
| | - Mark Luciano
- Department of Neurosurgery, Johns Hopkins University, Baltimore, Maryland, USA
| | - John Tew
- Department of Neurosurgery, University of Cincinnati Neuroscience Institute and University of Cincinnati College of Medicine, and Mayfield Clinic, Cincinnati, Ohio, USA
| | - Richard G Ellenbogen
- Department of Neurological Surgery, University of Washington, Seattle, Washington, USA
| | - John N Oshinski
- Department of Radiology & Imaging Science and Biomedical Engineering, Emory University, Atlanta, Georgia
| | - Francis Loth
- Conquer Chiari Research Center, Department of Mechanical Engineering, University of Akron, Ohio, USA
| | - Amanda P Culley
- Department of Statistical Science, University of Idaho, Moscow, Idaho, USA
| | - Bryn A Martin
- Department of Biological Engineering, University of Idaho, Moscow, Idaho, USA.
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144
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Weickenmeier J, Kurt M, Ozkaya E, de Rooij R, Ovaert TC, Ehman RL, Butts Pauly K, Kuhl E. Brain stiffens post mortem. J Mech Behav Biomed Mater 2018; 84:88-98. [PMID: 29754046 PMCID: PMC6751406 DOI: 10.1016/j.jmbbm.2018.04.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 04/08/2018] [Accepted: 04/10/2018] [Indexed: 12/19/2022]
Abstract
Alterations in brain rheology are increasingly recognized as a diagnostic marker for various neurological conditions. Magnetic resonance elastography now allows us to assess brain rheology repeatably, reproducibly, and non-invasively in vivo. Recent elastography studies suggest that brain stiffness decreases one percent per year during normal aging, and is significantly reduced in Alzheimer’s disease and multiple sclerosis. While existing studies successfully compare brain stiffnesses across different populations, they fail to provide insight into changes within the same brain. Here we characterize rheological alterations in one and the same brain under extreme metabolic changes: alive and dead. Strikingly, the storage and loss moduli of the cerebrum increased by 26% and 60% within only three minutes post mortem and continued to increase by 40% and 103% within 45 minutes. Immediate post mortem stiffening displayed pronounced regional variations; it was largest in the corpus callosum and smallest in the brainstem. We postulate that post mortem stiffening is a manifestation of alterations in polarization, oxidation, perfusion, and metabolism immediately after death. Our results suggest that the stiffness of our brain–unlike any other organ–is a dynamic property that is highly sensitive to the metabolic environment Our findings emphasize the importance of characterizing brain tissue in vivo and question the relevance of ex vivo brain tissue testing as a whole. Knowing the true stiffness of the living brain has important consequences in diagnosing neurological conditions, planning neurosurgical procedures, and modeling the brain’s response to high impact loading.
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Affiliation(s)
- J Weickenmeier
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA; Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA
| | - M Kurt
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA
| | - E Ozkaya
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA
| | - R de Rooij
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
| | - T C Ovaert
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - R L Ehman
- Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA
| | - K Butts Pauly
- Department of Radiology Stanford University Stanford, CA 94305, USA
| | - E Kuhl
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA.
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145
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Mijailovic AS, Qing B, Fortunato D, Van Vliet KJ. Characterizing viscoelastic mechanical properties of highly compliant polymers and biological tissues using impact indentation. Acta Biomater 2018; 71:388-397. [PMID: 29477455 DOI: 10.1016/j.actbio.2018.02.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 01/19/2018] [Accepted: 02/15/2018] [Indexed: 01/24/2023]
Abstract
Precise and accurate measurement of viscoelastic mechanical properties becomes increasingly challenging as sample stiffness decreases to elastic moduli <1 kPa, largely due to difficulties detecting initial contact with the compliant sample surface. This limitation is particularly relevant to characterization of biological soft tissues and compliant gels. Here, we employ impact indentation which, in contrast to shear rheology and conventional indentation, does not require contact detection a priori, and present a novel method to extract viscoelastic moduli and relaxation time constants directly from the impact response. We first validate our approach by using both impact indentation and shear rheology to characterize polydimethylsiloxane (PDMS) elastomers of stiffness ranging from 100 s of Pa to nearly 10 kPa. Assuming a linear viscoelastic constitutive model for the material, we find that the moduli and relaxation times obtained from fitting the impact response agree well with those obtained from fitting the rheological response. Next, we demonstrate our validated method on hydrated, biological soft tissues obtained from porcine brain, murine liver, and murine heart, and report the equilibrium shear moduli, instantaneous shear moduli, and relaxation time constants for each tissue. Together, our findings provide a new and straightforward approach capable of probing local mechanical properties of highly compliant viscoelastic materials with millimeter scale spatial resolution, mitigating complications involving contact detection or sample geometric constraints. STATEMENT OF SIGNIFICANCE Characterization and optimization of mechanical properties can be essential for the proper function of biomaterials in diverse applications. However, precise and accurate measurement of viscoelastic mechanical properties becomes increasingly difficult with increased compliance (particularly for elastic moduli <1 kPa), largely due to challenges detecting initial contact with the compliant sample surface and measuring response at short timescale or high frequency. By contrast, impact indentation has highly accurate contact detection and can be used to measure short timescale (glassy) response. Here, we demonstrate an experimental and analytical method that confers significant advantages over existing approaches to extract spatially resolved viscoelastic moduli and characteristic time constants of biological tissues (e.g., brain and heart) and engineered biomaterials.
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Affiliation(s)
- Aleksandar S Mijailovic
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Bo Qing
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Daniel Fortunato
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Krystyn J Van Vliet
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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146
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Di Lauro M, Benaglia S, Berto M, Bortolotti CA, Zoli M, Biscarini F. Exploiting interfacial phenomena in organic bioelectronics: Conformable devices for bidirectional communication with living systems. Colloids Surf B Biointerfaces 2018; 168:143-147. [PMID: 29588094 DOI: 10.1016/j.colsurfb.2018.03.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 02/09/2018] [Accepted: 03/17/2018] [Indexed: 11/29/2022]
Abstract
A novel fully organic bioelectronic device is presented and validated as electronic transducer and current stimulator for brain implants. The device integrates polymeric electrodes made of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) on paper thin foils, resulting in a high surface-to-volume ratio architecture that exhibits high sensitivity to interfacial ionic transport phenomena. The prototyping technique herein presented yields devices for the bidirectional communication with biological systems whose dimensionality can be controlled according to the desired application. Transduction of ultra-low local-field potentials and delivery of voltage pulse-trains alike those used in deep-brain stimulation are herein assessed, paving the way towards novel theranostic strategies for the treatment of Parkinson's Disease and other severe neurodegenerative and/or traumatic pathologies of the central nervous system.
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Affiliation(s)
- Michele Di Lauro
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Simone Benaglia
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Marcello Berto
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Carlo A Bortolotti
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Michele Zoli
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università di Modena e Reggio Emilia, Via Campi 287, 41125 Modena, Italy
| | - Fabio Biscarini
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 103, 41125 Modena, Italy; Istituto Italiano di Tecnologia - Center for Translational Neurophysiology, Via Fossato di Mortara 17-19, 44121 Ferrara, Italy.
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147
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Makhija E, Jagielska A, Zhu L, Bost AC, Ong W, Chew SY, Shivashankar GV, Van Vliet KJ. Mechanical Strain Alters Cellular and Nuclear Dynamics at Early Stages of Oligodendrocyte Differentiation. Front Cell Neurosci 2018; 12:59. [PMID: 29559894 PMCID: PMC5845683 DOI: 10.3389/fncel.2018.00059] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 02/19/2018] [Indexed: 11/13/2022] Open
Abstract
Mechanical and physical stimuli including material stiffness and topography or applied mechanical strain have been demonstrated to modulate differentiation of glial progenitor and neural stem cells. Recent studies probing such mechanotransduction in oligodendrocytes have focused chiefly on the biomolecular components. However, the cell-level biophysical changes associated with such responses remain largely unknown. Here, we explored mechanotransduction in oligodendrocyte progenitor cells (OPCs) during the first 48 h of differentiation induction by quantifying the biophysical state in terms of nuclear dynamics, cytoskeleton organization, and cell migration. We compared these mechanophenotypic changes in OPCs exposed to both chemical cues (differentiation factors) and mechanical cues (static tensile strain of 10%) with those exposed to only those chemical cues. We observed that mechanical strain significantly hastened the dampening of nuclear fluctuations and decreased OPC migration, consistent with the progression of differentiation. Those biophysical changes were accompanied by increased production of the intracellular microtubule network. These observations provide insights into mechanisms by which mechanical strain of physiological magnitude could promote differentiation of progenitor cells to oligodendrocytes via inducing intracellular biophysical responses over hours to days post induction.
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Affiliation(s)
- Ekta Makhija
- BioSystems and Micromechanics Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore, Singapore
| | - Anna Jagielska
- BioSystems and Micromechanics Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore, Singapore.,Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Lena Zhu
- BioSystems and Micromechanics Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore, Singapore.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Alexander C Bost
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - William Ong
- NTU Institute for Health Technologies (Health Tech NTU), Interdisciplinary Graduate School, Nanyang Technological University, Singapore, Singapore.,School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
| | - Sing Y Chew
- BioSystems and Micromechanics Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore, Singapore.,School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - G V Shivashankar
- BioSystems and Micromechanics Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore, Singapore.,Mechanobiology Institute, Singapore, Singapore.,The FIRC Institute of Molecular Oncology, Milan, Italy
| | - Krystyn J Van Vliet
- BioSystems and Micromechanics Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, CREATE, Singapore, Singapore.,Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States
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148
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Abstract
Understanding the mechanical behavior of human brain is critical to interpret the role of physical stimuli in both normal and pathological processes that occur in CNS tissue, such as development, inflammation, neurodegeneration, aging, and most common brain tumors. Despite clear evidence that mechanical cues influence both normal and transformed brain tissue activity as well as normal and transformed brain cell behavior, little is known about the links between mechanical signals and their biochemical and medical consequences. A multi-level approach from whole organ rheology to single cell mechanics is needed to understand the physical aspects of human brain function and its pathologies. This review summarizes the latest achievements in the field.
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Affiliation(s)
- Katarzyna Pogoda
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, United States.,Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland
| | - Paul A Janmey
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, United States
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149
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Ham TR, Leipzig ND. Biomaterial strategies for limiting the impact of secondary events following spinal cord injury. Biomed Mater 2018; 13:024105. [PMID: 29155409 PMCID: PMC5824690 DOI: 10.1088/1748-605x/aa9bbb] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nature of traumatic spinal cord injury (SCI) often involves limited recovery and long-term quality of life complications. The initial injury sets off a variety of secondary cascades, which result in an expanded lesion area. Ultimately, the native tissue fails to regenerate. As treatments are developed in the laboratory, the management of this secondary cascade is an important first step in achieving recovery of normal function. Current literature identifies four broad targets for intervention: inflammation, oxidative stress, disruption of the blood-spinal cord barrier, and formation of an inhibitory glial scar. Because of the complex and interconnected nature of these events, strategies that combine multiple therapies together show much promise. Specifically, approaches that rely on biomaterials to perform a variety of functions are generating intense research interest. In this review, we examine each target and discuss how biomaterials are currently used to address them. Overall, we show that there are an impressive amount of biomaterials and combinatorial treatments which show good promise for slowing secondary events and improving outcomes. If more emphasis is placed on growing our understanding of how materials can manage secondary events, treatments for SCI can be designed in an increasingly rational manner, ultimately improving their potential for translation to the clinic.
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Affiliation(s)
- Trevor R Ham
- Department of Biomedical Engineering, Auburn Science and Engineering Center 275, West Tower, University of Akron, Akron, OH 44325-3908, United States of America
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150
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Espinosa-Hoyos D, Jagielska A, Homan KA, Du H, Busbee T, Anderson DG, Fang NX, Lewis JA, Van Vliet KJ. Engineered 3D-printed artificial axons. Sci Rep 2018; 8:478. [PMID: 29323240 PMCID: PMC5765144 DOI: 10.1038/s41598-017-18744-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/16/2017] [Indexed: 12/02/2022] Open
Abstract
Myelination is critical for transduction of neuronal signals, neuron survival and normal function of the nervous system. Myelin disorders account for many debilitating neurological diseases such as multiple sclerosis and leukodystrophies. The lack of experimental models and tools to observe and manipulate this process in vitro has constrained progress in understanding and promoting myelination, and ultimately developing effective remyelination therapies. To address this problem, we developed synthetic mimics of neuronal axons, representing key geometric, mechanical, and surface chemistry components of biological axons. These artificial axons exhibit low mechanical stiffness approaching that of a human axon, over unsupported spans that facilitate engagement and wrapping by glial cells, to enable study of myelination in environments reflecting mechanical cues that neurons present in vivo. Our 3D printing approach provides the capacity to vary independently the complex features of the artificial axons that can reflect specific states of development, disease, or injury. Here, we demonstrate that oligodendrocytes' production and wrapping of myelin depend on artificial axon stiffness, diameter, and ligand coating. This biofidelic platform provides direct visualization and quantification of myelin formation and myelinating cells' response to both physical cues and pharmacological agents.
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Affiliation(s)
- Daniela Espinosa-Hoyos
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Biosystems & Micromechanics Interdisciplinary Research Group (BioSyM), Singapore-MIT Alliance in Research & Technology (SMART), Singapore, Singapore
| | - Anna Jagielska
- Biosystems & Micromechanics Interdisciplinary Research Group (BioSyM), Singapore-MIT Alliance in Research & Technology (SMART), Singapore, Singapore
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Kimberly A Homan
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, 02138, USA
- School of Engineering and Applied Sciences, Harvard University, Harvard, MA, 02138, USA
| | - Huifeng Du
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Travis Busbee
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, 02138, USA
- School of Engineering and Applied Sciences, Harvard University, Harvard, MA, 02138, USA
| | - Daniel G Anderson
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Harvard-MIT Division of Health Sciences & Technology, Cambridge, MA, 02139, USA
| | - Nicholas X Fang
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jennifer A Lewis
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, 02138, USA
- School of Engineering and Applied Sciences, Harvard University, Harvard, MA, 02138, USA
| | - Krystyn J Van Vliet
- Biosystems & Micromechanics Interdisciplinary Research Group (BioSyM), Singapore-MIT Alliance in Research & Technology (SMART), Singapore, Singapore.
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
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