1
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Bergs J, Morr AS, Silva RV, Infante-Duarte C, Sack I. The Networking Brain: How Extracellular Matrix, Cellular Networks, and Vasculature Shape the In Vivo Mechanical Properties of the Brain. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2402338. [PMID: 38874205 DOI: 10.1002/advs.202402338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 05/22/2024] [Indexed: 06/15/2024]
Abstract
Mechanically, the brain is characterized by both solid and fluid properties. The resulting unique material behavior fosters proliferation, differentiation, and repair of cellular and vascular networks, and optimally protects them from damaging shear forces. Magnetic resonance elastography (MRE) is a noninvasive imaging technique that maps the mechanical properties of the brain in vivo. MRE studies have shown that abnormal processes such as neuronal degeneration, demyelination, inflammation, and vascular leakage lead to tissue softening. In contrast, neuronal proliferation, cellular network formation, and higher vascular pressure result in brain stiffening. In addition, brain viscosity has been reported to change with normal blood perfusion variability and brain maturation as well as disease conditions such as tumor invasion. In this article, the contributions of the neuronal, glial, extracellular, and vascular networks are discussed to the coarse-grained parameters determined by MRE. This reductionist multi-network model of brain mechanics helps to explain many MRE observations in terms of microanatomical changes and suggests that cerebral viscoelasticity is a suitable imaging marker for brain disease.
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Affiliation(s)
- Judith Bergs
- Department of Radiology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Anna S Morr
- Department of Radiology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Rafaela V Silva
- Experimental and Clinical Research Center, a cooperation between the Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin, Lindenberger Weg 80, 13125, Berlin, Germany
- Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, ECRC Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125, Berlin, Germany
| | - Carmen Infante-Duarte
- Experimental and Clinical Research Center, a cooperation between the Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin, Lindenberger Weg 80, 13125, Berlin, Germany
- Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, ECRC Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany
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2
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Zhang X, van den Hurk EAN, Weickenmeier J. Insights into the Mechanical Characterization of Mouse Brain Tissue Using Microindentation Testing. Curr Protoc 2024; 4:e1011. [PMID: 38648070 DOI: 10.1002/cpz1.1011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Indentation testing is the most common approach to quantify mechanical brain tissue properties. Despite a myriad of studies conducted already, reported stiffness values vary extensively and continue to be subject of study. Moreover, the growing interest in the relationship between the brain's spatially heterogeneous microstructure and local tissue stiffness warrants the development of standardized measurement protocols to enable comparability between studies and assess repeatability of reported data. Here, we present three individual protocols that outline (1) sample preparation of a 1000-µm thick coronal slice, (2) a comprehensive list of experimental parameters associated with the FemtoTools FT-MTA03 Micromechanical Testing System for spherical indentation, and (3) two different approaches to derive the elastic modulus from raw force-displacement data. Lastly, we demonstrate that our protocols deliver a robust experimental framework that enables us to determine the spatially heterogeneous microstructural properties of (mouse) brain tissue. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Mouse brain sample preparation Basic Protocol 2: Indentation testing of mouse brain tissue using the FemtoTools FT-MTA03 Micromechanical Testing and Assembly System Basic Protocol 3: Tissue stiffness identification from force-displacement data.
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Affiliation(s)
- Xuesong Zhang
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey
| | - Eva A N van den Hurk
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
| | - Johannes Weickenmeier
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey
- Center for Neuromechanics, Stevens Institute of Technology, Hoboken, New Jersey
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3
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Chen L, Jiang C, Xu Q, Jin J, A S, Wang X, Li X, Hu Y, Sun H, Lu X, Duan S, Gao Z, Wang W, Wang Y. Biphasic release of betamethasone from an injectable HA hydrogel implant for alleviating lumbar disc herniation induced sciatica. Acta Biomater 2024; 176:173-189. [PMID: 38244658 DOI: 10.1016/j.actbio.2024.01.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 12/17/2023] [Accepted: 01/11/2024] [Indexed: 01/22/2024]
Abstract
Epidural steroid injection (ESI) is a common therapeutic approach for managing sciatica caused by lumbar disc herniation (LDH). However, the short duration of therapeutic efficacy and the need for repeated injections pose challenges in LDH treatment. The development of a controlled delivery system capable of prolonging the effectiveness of ESI and reducing the frequency of injections, is highly significant in LDH clinical practice. In this study, we utilized a thiol-ene click chemistry to create a series of injectable hyaluronic acid (HA) based release systems loaded with diphasic betamethasone, including betamethasone dipropionate (BD) and betamethasone 21-phosphate disodium (BP) (BD/BP@HA). BD/BP@HA hydrogel implants demonstrated biocompatibility and biodegradability to matched neuronal tissues, avoiding artificial compression following injection. The sustained release of betamethasone from BD/BP@HA hydrogels effectively inhibited both acute and chronic neuroinflammation by suppressing the nuclear factor kappa-B (NF-κB) pathway. In a mouse model of LDH, the epidural administration of BD/BP@HA efficiently alleviated LDH-induced sciatica for at least 10 days by inhibiting the activation of macrophages and microglia in dorsal root ganglion and spinal dorsal horn, respectively. The newly developed HA hydrogels represent a valuable platform for achieving sustained drug release. Additionally, we provide a simple paradigm for fabricating BD/BP@HA for epidural injection, demonstrating greater and sustained efficiency in alleviating LDH-induced sciatica compared to traditional ESI and displaying potentials for clinical translation. This system has the potential to revolutionize drug delivery for co-delivery of both soluble and insoluble drugs, thereby making a significant impact in the pharmaceutical industry. STATEMENT OF SIGNIFICANCE: Lumbar disc herniation (LDH) is a common degenerative disorder leading to sciatica and spine surgery. Although epidural steroid injection (ESI) is routinely used to alleviate sciatica, the efficacy is short and repeated injections are required. There remains challenging to prolong the efficacy of ESI. Herein, an injectable hyaluronic acid (HA) hydrogel implant by crosslinking acrylated-modified HA (HA-A) with thiol-modified HA (HA-SH) was designed to achieve a biphasic release of betamethasone. The hydrogel showed biocompatibility and biodegradability to match neuronal tissues. Notably, compared to traditional ESI, the hydrogel better alleviated sciatica in vivo by synergistically inhibiting the neuroinflammation in central and peripheral nervous systems. We anticipate the injectable HA hydrogel implant has the potential for clinical translation in treating LDH-induced sciatica.
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Affiliation(s)
- Lunhao Chen
- Spine Lab, Department of Orthopedic Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Chao Jiang
- Spine Lab, Department of Orthopedic Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Qian Xu
- The Charles Institute of Dermatology, School of Medicine, University College Dublin, Dublin D04V1W8, Ireland; School of Pharmaceutical Science, Wenzhou Medical University, Wenzhou, Zhejiang 325000, China
| | - Jiale Jin
- Spine Lab, Department of Orthopedic Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Sigen A
- School of Medicine, Anhui University of Science and Technology, Huainan, China; The Charles Institute of Dermatology, School of Medicine, University College Dublin, Dublin D04V1W8, Ireland
| | - Xi Wang
- The Charles Institute of Dermatology, School of Medicine, University College Dublin, Dublin D04V1W8, Ireland
| | - Xiaolin Li
- The Charles Institute of Dermatology, School of Medicine, University College Dublin, Dublin D04V1W8, Ireland
| | - Yaling Hu
- Liangzhu Laboratory, Zhejiang University Medical Center, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou 311121, China; NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Pancreatic Diseases, The First Affiliated Hospital, University School of Medicine, Hangzhou 310003, China
| | - Huankun Sun
- Zhejiang Provincial Key Laboratory of Pancreatic Diseases, The First Affiliated Hospital, University School of Medicine, Hangzhou 310003, China
| | - Xuan Lu
- Spine Lab, Department of Orthopedic Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Shumin Duan
- Liangzhu Laboratory, Zhejiang University Medical Center, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou 311121, China; NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University, Hangzhou 310058, China
| | - Zhihua Gao
- Liangzhu Laboratory, Zhejiang University Medical Center, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou 311121, China; NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University, Hangzhou 310058, China.
| | - Wenxin Wang
- Research and Clinical Translation Center of Gene Medicine and Tissue Engineering, School of Public Health, Anhui University of Science and Technology, Huainan, China; School of Medicine, Anhui University of Science and Technology, Huainan, China; The Charles Institute of Dermatology, School of Medicine, University College Dublin, Dublin D04V1W8, Ireland.
| | - Yue Wang
- Spine Lab, Department of Orthopedic Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China.
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McCarthy CM, McKevitt KL, Connolly SA, Andersson I, Leahy FC, Egan S, Moloney MA, Kavanagh EG, Peirce C, Cunnane EM, McGourty KD, Walsh MT, Mulvihill JJE. Microindentation of fresh soft biological tissue: A rapid tissue sectioning and mounting protocol. PLoS One 2024; 19:e0297618. [PMID: 38422111 PMCID: PMC10903917 DOI: 10.1371/journal.pone.0297618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 01/03/2024] [Indexed: 03/02/2024] Open
Abstract
Microindentation of fresh biological tissues is necessary for the creation of 3D biomimetic models that accurately represent the native extracellular matrix microenvironment. However, tissue must first be precisely sectioned into slices. Challenges exist in the preparation of fresh tissue slices, as they can tear easily and must be processed rapidly in order to mitigate tissue degradation. In this study, we propose an optimised mounting condition for microindentation and demonstrate that embedding tissue in a mixture of 2.5% agarose and 1.5% gelatin is the most favourable method of tissue slice mounting for microindentation. This protocol allows for rapid processing of fresh biological tissue and is applicable to a variety of tissue types.
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Affiliation(s)
- Clíona M. McCarthy
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
| | - Kevin L. McKevitt
- Department of Vascular & Endovascular Surgery, University Hospital Limerick, Limerick, Ireland
| | - Sinéad A. Connolly
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
| | - Isabel Andersson
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
| | - Fiona C. Leahy
- Department of Vascular & Endovascular Surgery, University Hospital Limerick, Limerick, Ireland
| | - Siobhan Egan
- Department of Colorectal Surgery, University Hospital Limerick, Limerick, Ireland
| | - Michael A. Moloney
- Department of Vascular & Endovascular Surgery, University Hospital Limerick, Limerick, Ireland
| | - Eamon G. Kavanagh
- Department of Vascular & Endovascular Surgery, University Hospital Limerick, Limerick, Ireland
| | - Colin Peirce
- Department of Colorectal Surgery, University Hospital Limerick, Limerick, Ireland
| | - Eoghan M. Cunnane
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
- Health Research Institute, University of Limerick, Limerick, Ireland
| | - Kieran D. McGourty
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
- School of Chemical Sciences, University of Limerick, Limerick, Ireland
| | - Michael T. Walsh
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
- Health Research Institute, University of Limerick, Limerick, Ireland
| | - John J. E. Mulvihill
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland
- School of Engineering, University of Limerick, Limerick, Ireland
- Health Research Institute, University of Limerick, Limerick, Ireland
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5
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Nakamura F. The Role of Mechanotransduction in Contact Inhibition of Locomotion and Proliferation. Int J Mol Sci 2024; 25:2135. [PMID: 38396812 PMCID: PMC10889191 DOI: 10.3390/ijms25042135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/30/2024] [Accepted: 02/01/2024] [Indexed: 02/25/2024] Open
Abstract
Contact inhibition (CI) represents a crucial tumor-suppressive mechanism responsible for controlling the unbridled growth of cells, thus preventing the formation of cancerous tissues. CI can be further categorized into two distinct yet interrelated components: CI of locomotion (CIL) and CI of proliferation (CIP). These two components of CI have historically been viewed as separate processes, but emerging research suggests that they may be regulated by both distinct and shared pathways. Specifically, recent studies have indicated that both CIP and CIL utilize mechanotransduction pathways, a process that involves cells sensing and responding to mechanical forces. This review article describes the role of mechanotransduction in CI, shedding light on how mechanical forces regulate CIL and CIP. Emphasis is placed on filamin A (FLNA)-mediated mechanotransduction, elucidating how FLNA senses mechanical forces and translates them into crucial biochemical signals that regulate cell locomotion and proliferation. In addition to FLNA, trans-acting factors (TAFs), which are proteins or regulatory RNAs capable of directly or indirectly binding to specific DNA sequences in distant genes to regulate gene expression, emerge as sensitive players in both the mechanotransduction and signaling pathways of CI. This article presents methods for identifying these TAF proteins and profiling the associated changes in chromatin structure, offering valuable insights into CI and other biological functions mediated by mechanotransduction. Finally, it addresses unanswered research questions in these fields and delineates their possible future directions.
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Affiliation(s)
- Fumihiko Nakamura
- School of Pharmaceutical Science and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
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6
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Pillai EK, Franze K. Mechanics in the nervous system: From development to disease. Neuron 2024; 112:342-361. [PMID: 37967561 DOI: 10.1016/j.neuron.2023.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 09/29/2023] [Accepted: 10/04/2023] [Indexed: 11/17/2023]
Abstract
Physical forces are ubiquitous in biological processes across scales and diverse contexts. This review highlights the significance of mechanical forces in nervous system development, homeostasis, and disease. We provide an overview of mechanical signals present in the nervous system and delve into mechanotransduction mechanisms translating these mechanical cues into biochemical signals. During development, mechanical cues regulate a plethora of processes, including cell proliferation, differentiation, migration, network formation, and cortex folding. Forces then continue exerting their influence on physiological processes, such as neuronal activity, glial cell function, and the interplay between these different cell types. Notably, changes in tissue mechanics manifest in neurodegenerative diseases and brain tumors, potentially offering new diagnostic and therapeutic target opportunities. Understanding the role of cellular forces and tissue mechanics in nervous system physiology and pathology adds a new facet to neurobiology, shedding new light on many processes that remain incompletely understood.
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Affiliation(s)
- Eva K Pillai
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK; Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany; Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany.
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK; Institute of Medical Physics and Microtissue Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestraße 91, 91052 Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, Kussmaulallee 1, 91054 Erlangen, Germany.
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7
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Li Y, Zhang Q, Zhao J, Wang Z, Zong X, Yang L, Zhang C, Zhao H. Mechanical behavior and microstructure of porcine brain tissues under pulsed electric fields. Biomech Model Mechanobiol 2024; 23:241-254. [PMID: 37861916 DOI: 10.1007/s10237-023-01771-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 08/29/2023] [Indexed: 10/21/2023]
Abstract
Pulsed electric fields are extensively utilized in clinical treatments, such as subthalamic deep brain stimulation, where electric field loading is in direct contact with brain tissue. However, the alterations in brain tissue's mechanical properties and microstructure due to changes in electric field parameters have not received adequate attention. In this study, the mechanical properties and microstructure of the brain tissue under pulsed electric fields were focused on. Herein, a custom indentation device was equipped with a module for electric field loading. Parameters such as pulse amplitude and frequency were adjusted. The results demonstrated that following an indentation process lasting 5 s and reaching a depth of 1000 μm, and a relaxation process of 175 s, the average shear modulus of brain tissue was reduced, and viscosity decreased. At the same amplitude, high-frequency pulsed electric fields had a smaller effect on brain tissue than low-frequency ones. Furthermore, pulsed electric fields induced cell polarization and reduced the proteoglycan concentration in brain tissue. As pulse frequency increased, cell polarization diminished, and proteoglycan concentration decreased significantly. High-frequency pulsed electric fields applied to brain tissue were found to reduce impedance fluctuation amplitude. This study revealed the effect of pulsed electric fields on the mechanical properties and microstructure of ex vivo brain tissue, providing essential information to promote the advancement of brain tissue electrotherapy in clinical settings.
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Affiliation(s)
- Yiqiang Li
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
| | - Qixun Zhang
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Chongqing Research Institute, Jilin University, Chongqing, 401100, People's Republic of China
| | - Jiucheng Zhao
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
| | - Zhaoxin Wang
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
| | - Xiangyu Zong
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
| | - Li Yang
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, 130062, People's Republic of China
| | - Chi Zhang
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China.
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China.
| | - Hongwei Zhao
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China.
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, People's Republic of China.
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8
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Carnicer-Lombarte A, Barone DG, Wronowski F, Malliaras GG, Fawcett JW, Franze K. Regenerative capacity of neural tissue scales with changes in tissue mechanics post injury. Biomaterials 2023; 303:122393. [PMID: 37977006 DOI: 10.1016/j.biomaterials.2023.122393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 10/23/2023] [Accepted: 11/05/2023] [Indexed: 11/19/2023]
Abstract
Spinal cord injuries have devastating consequences for humans, as mammalian neurons of the central nervous system (CNS) cannot regenerate. In the peripheral nervous system (PNS), however, neurons may regenerate to restore lost function following injury. While mammalian CNS tissue softens after injury, how PNS tissue mechanics changes in response to mechanical trauma is currently poorly understood. Here we characterised mechanical rat nerve tissue properties before and after in vivo crush and transection injuries using atomic force microscopy-based indentation measurements. Unlike CNS tissue, PNS tissue significantly stiffened after both types of tissue damage. This nerve tissue stiffening strongly correlated with an increase in collagen I levels. Schwann cells, which crucially support PNS regeneration, became more motile and proliferative on stiffer substrates in vitro, suggesting that changes in tissue stiffness may play a key role in facilitating or impeding nervous system regeneration.
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Affiliation(s)
- Alejandro Carnicer-Lombarte
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0PY, UK; Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, CB2 3DY, UK; Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK.
| | - Damiano G Barone
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0PY, UK
| | - Filip Wronowski
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
| | - George G Malliaras
- Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, UK
| | - James W Fawcett
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0PY, UK; Centre for Reconstructive Neuroscience, Institute for Experimental Medicine CAS, Prague, Czech Republic
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, CB2 3DY, UK; Institute of Medical Physics and Micro-Tissue Engineering, Friedrich-Alexander Universität Erlangen-Nürnberg, 91052, Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, 91054, Erlangen, Germany.
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9
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Roth JG, Huang MS, Navarro RS, Akram JT, LeSavage BL, Heilshorn SC. Tunable hydrogel viscoelasticity modulates human neural maturation. SCIENCE ADVANCES 2023; 9:eadh8313. [PMID: 37862423 PMCID: PMC10588948 DOI: 10.1126/sciadv.adh8313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 09/15/2023] [Indexed: 10/22/2023]
Abstract
Human-induced pluripotent stem cells (hiPSCs) have emerged as a promising in vitro model system for studying neurodevelopment. However, current models remain limited in their ability to incorporate tunable biomechanical signaling cues imparted by the extracellular matrix (ECM). The native brain ECM is viscoelastic and stress-relaxing, exhibiting a time-dependent response to an applied force. To recapitulate the remodelability of the neural ECM, we developed a family of protein-engineered hydrogels that exhibit tunable stress relaxation rates. hiPSC-derived neural progenitor cells (NPCs) encapsulated within these gels underwent relaxation rate-dependent maturation. Specifically, NPCs within hydrogels with faster stress relaxation rates extended longer, more complex neuritic projections, exhibited decreased metabolic activity, and expressed higher levels of genes associated with neural maturation. By inhibiting actin polymerization, we observed decreased neuritic projections and a concomitant decrease in neural maturation gene expression. Together, these results suggest that microenvironmental viscoelasticity is sufficient to bias human NPC maturation.
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Affiliation(s)
- Julien G. Roth
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, USA
- Complex in Vitro Systems, Safety Assessment, Genentech Inc., South San Francisco, CA, USA
| | - Michelle S. Huang
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
| | - Renato S. Navarro
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Jason T. Akram
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Bauer L. LeSavage
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Sarah C. Heilshorn
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
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10
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Zhang X, Weickenmeier J. Brain Stiffness Follows Cuprizone-Induced Variations in Local Myelin Content. Acta Biomater 2023; 170:507-518. [PMID: 37660962 DOI: 10.1016/j.actbio.2023.08.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 08/08/2023] [Accepted: 08/17/2023] [Indexed: 09/05/2023]
Abstract
Brain maturation and neurological diseases are intricately linked to microstructural changes that inherently affect the brain's mechanical behavior. Animal models are frequently used to explore relative brain stiffness changes as a function of underlying microstructure. Here, we are using the cuprizone mouse model to study indentation-derived stiffness changes resulting from acute and chronic demyelination during a 15-week observation period. We focus on the corpus callosum, cingulum, and cortex which undergo different degrees of de- and remyelination and, therefore, result in region-specific stiffness changes. Mean stiffness of the corpus callosum starts at 1.1 ± 0.3 kPa in untreated mice, then cuprizone treatment causes stiffness to drop to 0.6 ± 0.1 kPa by week 3, temporarily increase to 0.9 ± 0.3 kPa by week 6, and ultimately stabilize around 0.7 ± 0.1 kPa by week 9 for the rest of the observation period. The cingulum starts at 3.2 ± 0.9 kPa, then drops to 1.6 ± 0.4 kPa by week 3, and then gradually stabilizes around 1.4 ± 0.3 kPa by week 9. Cortical stiffness exhibits less stiffness variations overall; it starts at 4.2 ± 1.3 kPa, drops to 2.4 ± 0.6 kPa by week 3, and stabilizes around 2.7 ± 0.9 kPa by week 6. We also assess the impact of tissue fixation on indentation-based mechanical tissue characterization. On the one hand, fixation drastically increases untreated mean tissue stiffness by a factor of 3.3 for the corpus callosum, 2.9 for the cingulum, and 3.6 for the cortex; on the other hand, fixation influences interregional stiffness ratios during demyelination, thus suggesting that fixation affects individual brain tissues differently. Lastly, we determine the spatial correlation between stiffness measurements and myelin density and observe a region-specific proportionality between myelin content and tissue stiffness. STATEMENT OF SIGNIFICANCE: Despite extensive work, the relationship between microstructure and mechanical behavior in the brain remains mostly unknown. Additionally, the existing variation of measurement results reported in literature requires in depth investigation of the impact of individual cell and protein populations on tissue stiffness and interregional stiffness ratios. Here, we used microindentation measurements to show that brain stiffness changes with myelin density in the cuprizone-based demyelination mouse model. Moreover, we explored the impact of tissue fixation prior to mechanical characterization because of conflicting results reported in literature. We observe that fixation has a distinctly different impact on our three regions of interest, thus causing region-specific tissue stiffening and, more importantly, changing interregional stiffness ratios.
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Affiliation(s)
- Xuesong Zhang
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 United States
| | - Johannes Weickenmeier
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 United States.
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11
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Morrison O, Destrade M, Tripathi BB. An atlas of the heterogeneous viscoelastic brain with local power-law attenuation synthesised using Prony-series. Acta Biomater 2023; 169:66-87. [PMID: 37507033 DOI: 10.1016/j.actbio.2023.07.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 07/16/2023] [Accepted: 07/24/2023] [Indexed: 07/30/2023]
Abstract
This review addresses the acute need to acknowledge the mechanical heterogeneity of brain matter and to accurately calibrate its local viscoelastic material properties accordingly. Specifically, it is important to compile the existing and disparate literature on attenuation power-laws and dispersion to make progress in wave physics of brain matter, a field of research that has the potential to explain the mechanisms at play in diffuse axonal injury and mild traumatic brain injury in general. Currently, viscous effects in the brain are modelled using Prony-series, i.e., a sum of decaying exponentials at different relaxation times. Here we collect and synthesise the Prony-series coefficients appearing in the literature for twelve regions: brainstem, basal ganglia, cerebellum, corona radiata, corpus callosum, cortex, dentate gyrus, hippocampus, thalamus, grey matter, white matter, homogeneous brain, and for eight different mammals: pig, rat, human, mouse, cow, sheep, monkey and dog. Using this data, we compute the fractional-exponent attenuation power-laws for different tissues of the brain, the corresponding dispersion laws resulting from causality, and the averaged Prony-series coefficients. STATEMENT OF SIGNIFICANCE: Traumatic brain injuries are considered a silent epidemic and finite element methods (FEMs) are used in modelling brain deformation, requiring access to viscoelastic properties of brain. To the best of our knowledge, this work presents 1) the first multi-frequency viscoelastic atlas of the heterogeneous brain, 2) the first review focusing on viscoelastic modelling in both FEMs and experimental works, 3) the first attempt to conglomerate the disparate existing literature on the viscoelastic modelling of the brain and 4) the largest collection of viscoelastic parameters for the brain (212 different Prony-series spanning 12 different tissues and 8 different animal surrogates). Furthermore, this work presents the first brain atlas of attenuation power-laws essential for modelling shear waves in brain.
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Affiliation(s)
- Oisín Morrison
- School of Mathematical and Statistical Sciences, University of Galway, University Road, Galway, Ireland
| | - Michel Destrade
- School of Mathematical and Statistical Sciences, University of Galway, University Road, Galway, Ireland
| | - Bharat B Tripathi
- School of Mathematical and Statistical Sciences, University of Galway, University Road, Galway, Ireland.
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12
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Sáez P, Borau C, Antonovaite N, Franze K. Brain tissue mechanics is governed by microscale relations of the tissue constituents. Biomaterials 2023; 301:122273. [PMID: 37639974 DOI: 10.1016/j.biomaterials.2023.122273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/14/2023] [Accepted: 08/07/2023] [Indexed: 08/31/2023]
Abstract
Local mechanical tissue properties are a critical regulator of cell function in the central nervous system (CNS) during development and disorder. However, we still don't fully understand how the mechanical properties of individual tissue constituents, such as cell nuclei or myelin, determine tissue mechanics. Here we developed a model predicting local tissue mechanics, which induces non-affine deformations of the tissue components. Using the mouse hippocampus and cerebellum as model systems, we show that considering individual tissue components alone, as identified by immunohistochemistry, is not sufficient to reproduce the local mechanical properties of CNS tissue. Our results suggest that brain tissue shows a universal response to applied forces that depends not only on the amount and stiffness of the individual tissue constituents but also on the way how they assemble. Our model may unify current incongruences between the mechanics of soft biological tissues and the underlying constituents and facilitate the design of better biomedical materials and engineered tissues. To this end, we provide a freely-available platform to predict local tissue elasticity upon providing immunohistochemistry images and stiffness values for the constituents of the tissue.
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Affiliation(s)
- P Sáez
- Laboratori de Càlcul Numèric (LaCàN), Universitat Politècnica de Catalunya, Barcelona, Spain; Institute of Mathematics of UPC-BarcelonaTech (IMTech), Barcelona, Spain
| | - C Borau
- Multiscale in Mechanical and Biological Engineering, Aragon Institute of Engineering Research (I3A), Department of Mechanical Engineering, University of Zaragoza, 50018, Zaragoza, Spain
| | - N Antonovaite
- Department of Physics and Astronomy and LaserLab Amsterdam, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, Netherlands
| | - K Franze
- Department of Physiology, Development, and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK; Institute of Medical Physics and Microtissue Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91052, Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, 91054, Erlangen, Germany.
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13
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Hall CM, Lasli S, Serwinski B, Djordjevic B, Sheridan GK, Moeendarbary E. Hippocampus of the APP NL-G-F mouse model of Alzheimer's disease exhibits region-specific tissue softening concomitant with elevated astrogliosis. Front Aging Neurosci 2023; 15:1212212. [PMID: 37547743 PMCID: PMC10398960 DOI: 10.3389/fnagi.2023.1212212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 07/03/2023] [Indexed: 08/08/2023] Open
Abstract
Widespread neurodegeneration, enlargement of cerebral ventricles, and atrophy of cortical and hippocampal brain structures are classic hallmarks of Alzheimer's disease (AD). Prominent macroscopic disturbances to the cytoarchitecture of the AD brain occur alongside changes in the mechanical properties of brain tissue, as reported in recent magnetic resonance elastography (MRE) measurements of human brain mechanics. Whilst MRE has many advantages, a significant shortcoming is its spatial resolution. Higher resolution "cellular scale" assessment of the mechanical alterations to brain regions involved in memory formation, such as the hippocampus, could provide fresh new insight into the etiology of AD. Characterization of brain tissue mechanics at the cellular length scale is the first stepping-stone to understanding how mechanosensitive neurons and glia are impacted by neurodegenerative disease-associated changes in their microenvironment. To provide insight into the microscale mechanics of aging brain tissue, we measured spatiotemporal changes in the mechanical properties of the hippocampus using high resolution atomic force microscopy (AFM) indentation tests on acute brain slices from young and aged wild-type mice and the APPNL-G-F mouse model. Several hippocampal regions in APPNL-G-F mice are significantly softer than age-matched wild-types, notably the dentate granule cell layer and the CA1 pyramidal cell layer. Interestingly, regional softening coincides with an increase in astrocyte reactivity, suggesting that amyloid pathology-mediated alterations to the mechanical properties of brain tissue may impact the function of mechanosensitive astrocytes. Our data also raise questions as to whether aberrant mechanotransduction signaling could impact the susceptibility of neurons to cellular stressors in their microenvironment.
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Affiliation(s)
- Chloe M. Hall
- Department of Mechanical Engineering, University College London, London, United Kingdom
- School of Applied Sciences, University of Brighton, Brighton, United Kingdom
| | - Soufian Lasli
- Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Bianca Serwinski
- Department of Mechanical Engineering, University College London, London, United Kingdom
- 199 Biotechnologies Ltd., London, United Kingdom
- Faculty of Social Sciences, Northeastern University London, London, United Kingdom
| | - Boris Djordjevic
- Department of Mechanical Engineering, University College London, London, United Kingdom
- 199 Biotechnologies Ltd., London, United Kingdom
| | - Graham K. Sheridan
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Emad Moeendarbary
- Department of Mechanical Engineering, University College London, London, United Kingdom
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14
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Janušonis S, Haiman JH, Metzler R, Vojta T. Predicting the distribution of serotonergic axons: a supercomputing simulation of reflected fractional Brownian motion in a 3D-mouse brain model. Front Comput Neurosci 2023; 17:1189853. [PMID: 37265780 PMCID: PMC10231035 DOI: 10.3389/fncom.2023.1189853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 04/24/2023] [Indexed: 06/03/2023] Open
Abstract
The self-organization of the brain matrix of serotonergic axons (fibers) remains an unsolved problem in neuroscience. The regional densities of this matrix have major implications for neuroplasticity, tissue regeneration, and the understanding of mental disorders, but the trajectories of its fibers are strongly stochastic and require novel conceptual and analytical approaches. In a major extension to our previous studies, we used a supercomputing simulation to model around one thousand serotonergic fibers as paths of superdiffusive fractional Brownian motion (FBM), a continuous-time stochastic process. The fibers produced long walks in a complex, three-dimensional shape based on the mouse brain and reflected at the outer (pial) and inner (ventricular) boundaries. The resultant regional densities were compared to the actual fiber densities in the corresponding neuroanatomically-defined regions. The relative densities showed strong qualitative similarities in the forebrain and midbrain, demonstrating the predictive potential of stochastic modeling in this system. The current simulation does not respect tissue heterogeneities but can be further improved with novel models of multifractional FBM. The study demonstrates that serotonergic fiber densities can be strongly influenced by the geometry of the brain, with implications for brain development, plasticity, and evolution.
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Affiliation(s)
- Skirmantas Janušonis
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Justin H. Haiman
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Ralf Metzler
- Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
- Asia Pacific Center for Theoretical Physics, Pohang, South Korea
| | - Thomas Vojta
- Department of Physics, Missouri University of Science and Technology, Rolla, MO, United States
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15
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Abdolkarimzadeh F, Ashory MR, Ghasemi-Ghalebahman A, Karimi A. A position- and time-dependent pressure profile to model viscoelastic mechanical behavior of the brain tissue due to tumor growth. Comput Methods Biomech Biomed Engin 2023; 26:660-672. [PMID: 35638726 PMCID: PMC9708950 DOI: 10.1080/10255842.2022.2082245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 04/06/2022] [Accepted: 05/23/2022] [Indexed: 11/03/2022]
Abstract
This study proposed a computational framework to calculate the resultant position- and time-dependent pressure profile on the brain tissue due to tumor growth. A finite element (FE) patch of the brain tissue was constructed and an inverse dynamic FE-optimization algorithm was used to calculate its viscoelastic mechanical properties under compressive uniaxial loading. Two patient-specific post-tumor resection FE models were input to the FE-optimization algorithm to calculate the optimized 3rd-order position-dependent and normal distribution time-dependent pressure profile parameters. The optimized viscoelastic material properties, the most suitable simulation time, and the optimized 3rd-order position- and -time-dependent pressure profiles were calculated.
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Affiliation(s)
| | | | | | - Alireza Karimi
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
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16
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Weickenmeier J. Exploring the multiphysics of the brain during development, aging, and in neurological diseases. BRAIN MULTIPHYSICS 2023; 4:100068. [PMID: 37476409 PMCID: PMC10358452 DOI: 10.1016/j.brain.2023.100068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/22/2023] Open
Abstract
The human brain remains an endless source of wonder and represents an intruiging scientific frontier. Multiphysics approaches naturally lend themselves to combine our extensive knowledge about the neurobiology of aging and diseases with mechanics to better capture the multiscale behavior of the brain. Our group uses experimental methods, medical image analysis, and constitutive modeling to develop better disease models with the long-term goal to improve diagnosis, treatment, and ultimately enable prevention of many prevalent age- and disease-related brain changes. In the present perspective, we outline on-going work related to neurodevelopment, aging, and neurodegenerative disease.
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Affiliation(s)
- Johannes Weickenmeier
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, United States of America
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17
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Donnaloja F, Limonta E, Mancosu C, Morandi F, Boeri L, Albani D, Raimondi MT. Unravelling the mechanotransduction pathways in Alzheimer's disease. J Biol Eng 2023; 17:22. [PMID: 36978103 PMCID: PMC10045049 DOI: 10.1186/s13036-023-00336-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 03/02/2023] [Indexed: 03/30/2023] Open
Abstract
Alzheimer's disease (AD) represents one of the most common and debilitating neurodegenerative disorders. By the end of 2040, AD patients might reach 11.2 million in the USA, around 70% higher than 2022, with severe consequences on the society. As now, we still need research to find effective methods to treat AD. Most studies focused on the tau and amyloid hypothesis, but many other factors are likely involved in the pathophysiology of AD. In this review, we summarize scientific evidence dealing with the mechanotransduction players in AD to highlight the most relevant mechano-responsive elements that play a role in AD pathophysiology. We focused on the AD-related role of extracellular matrix (ECM), nuclear lamina, nuclear transport and synaptic activity. The literature supports that ECM alteration causes the lamin A increment in the AD patients, leading to the formation of nuclear blebs and invaginations. Nuclear blebs have consequences on the nuclear pore complexes, impairing nucleo-cytoplasmic transport. This may result in tau hyperphosphorylation and its consequent self-aggregation in tangles, which impairs the neurotransmitters transport. It all exacerbates in synaptic transmission impairment, leading to the characteristic AD patient's memory loss. Here we related for the first time all the evidence associating the mechanotransduction pathway with neurons. In addition, we highlighted the entire pathway influencing neurodegenerative diseases, paving the way for new research perspectives in the context of AD and related pathologies.
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Affiliation(s)
- Francesca Donnaloja
- Politecnico Di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Campus Leonardo, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
| | - Emma Limonta
- Politecnico Di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Campus Leonardo, Piazza Leonardo da Vinci 32, 20133, Milan, Italy
| | - Christian Mancosu
- Politecnico Di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Campus Leonardo, Piazza Leonardo da Vinci 32, 20133, Milan, Italy
| | - Francesco Morandi
- Politecnico Di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Campus Leonardo, Piazza Leonardo da Vinci 32, 20133, Milan, Italy
| | - Lucia Boeri
- Politecnico Di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Campus Leonardo, Piazza Leonardo da Vinci 32, 20133, Milan, Italy
| | - Diego Albani
- Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy
| | - Manuela Teresa Raimondi
- Politecnico Di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Campus Leonardo, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
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18
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Crosslinking of Bovine Gelatin Gels by Genipin Revisited Using Ferrule-Top Micro-Indentation. Gels 2023; 9:gels9020149. [PMID: 36826319 PMCID: PMC9956991 DOI: 10.3390/gels9020149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/07/2023] [Accepted: 02/09/2023] [Indexed: 02/12/2023] Open
Abstract
(1) Background: Gelatin is widely used in food science, bioengineering, and as a sealant. However, for most of those applications, the mechanical properties of gelatin gels need to be improved by means of physical or chemical crosslinking. Among the used chemical agents, genipin allows low cytotoxicity in addition to improved Young's modulus. However, the mechanical properties of gelatin-genipin gels have only been investigated at the macroscale, and there is no knowledge of the influence of the genipin concentration on the surface homogeneity of Young's modulus. (2) Methods: To this aim, the influence of genipin concentration on Young's modulus of gelatin gels was investigated by means of ferrule-top micro-indentation. The data were compared with storage moduli obtained by shear rheology data. (3) Results: Ferrule-top indentation measurements allowed us to show that Young's moduli of gelatin-genipin gels increase up to a plateau value after approximately 12 mg/mL in genipin and 4 h of crosslinking. Young's moduli distribute with high homogeneity over 80 µm × 80 µm surface areas and are consistent with the storage moduli obtained by shear rheology. (4) Conclusions: It has been shown that ferrule-top indentation data fitted with the Hertz model yield Young's moduli of gelatin-genipin gels which are consistent with the storage moduli obtained by characterization at the macroscale using shear rheometry. In addition, Young's moduli are homogenously distributed (with some irregularities at the highest genipin concentrations) and can be increased by two orders of magnitude with respect to the uncrosslinked gel.
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19
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McCarthy CM, Allardyce JM, Hickey SE, Walsh MT, McGourty KD, Mulvihill JJE. Comparison of macroscale and microscale mechanical properties of fresh and fixed-frozen porcine colonic tissue. J Mech Behav Biomed Mater 2023; 138:105599. [PMID: 36462287 DOI: 10.1016/j.jmbbm.2022.105599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/21/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022]
Abstract
Mechanical changes to the microenvironment of the extracellular matrix (ECM) in tissue have been hypothesised to elicit a pathogenic response in the surrounding cells. Hence, 3D scaffolds are a popular method of studying cellular behaviour under conditions that mimic in vivo microenvironment. To create a 3D biomimetic scaffold that captures the in vivo ECM microenvironment a robust mechanical characterisation of the whole ECM at the microscale is necessary. This study examined the multiscale methods of characterising the ECM microenvironment using porcine colon tissue. To facilitate fresh tissue microscale mechanical characterisation, a protocol for sectioning fresh, unfixed, soft biological tissue was developed. Four experiments examined both the microscale and macroscale mechanics of both fresh (Fr) and fixed-frozen (FF) porcine colonic tissue using microindentation for microscale testing and uniaxial compression testing for macroscale testing. The results obtained in this study show a significant difference in elastic modulus between Fr and FF tissue at both the macroscale and microscale. There was an order of magnitude difference between the Fr and FF tissue at the microscale between each of the three layers of the colon tested i.e. the muscularis propria (MP), the submucosa (SM) and the mucosa (M). Macroscale testing cannot capture these regional differences. The findings in this study suggest that the most appropriate method for mechanically characterising the ECM is fresh microscale mechanical microindentation. These methods can be used on a range of biological tissues to create 3D biomimetic scaffolds that are more representative of the in vivo ECM, allowing for a more in-depth characterisation of the disease process.
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Affiliation(s)
- Clíona M McCarthy
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland; School of Engineering, University of Limerick, Limerick, Ireland
| | - Joanna M Allardyce
- School of Allied Health, University of Limerick, Ireland; Health Research Institute, University of Limerick, Ireland
| | - Séamus E Hickey
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland; School of Chemical Sciences, University of Limerick, Ireland
| | - Michael T Walsh
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland; School of Engineering, University of Limerick, Limerick, Ireland; Health Research Institute, University of Limerick, Ireland
| | - Kieran D McGourty
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland; School of Chemical Sciences, University of Limerick, Ireland; Health Research Institute, University of Limerick, Ireland
| | - John J E Mulvihill
- Biomaterials Cluster, Bernal Institute, University of Limerick, Limerick, Ireland; School of Engineering, University of Limerick, Limerick, Ireland; Health Research Institute, University of Limerick, Ireland.
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20
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Griffiths E, Budday S. Finite element modeling of traumatic brain injury: Areas of future interest. CURRENT OPINION IN BIOMEDICAL ENGINEERING 2022. [DOI: 10.1016/j.cobme.2022.100421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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21
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Murenu E, Gerhardt MJ, Biel M, Michalakis S. More than meets the eye: The role of microglia in healthy and diseased retina. Front Immunol 2022; 13:1006897. [PMID: 36524119 PMCID: PMC9745050 DOI: 10.3389/fimmu.2022.1006897] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 11/11/2022] [Indexed: 11/30/2022] Open
Abstract
Microglia are the main resident immune cells of the nervous system and as such they are involved in multiple roles ranging from tissue homeostasis to response to insults and circuit refinement. While most knowledge about microglia comes from brain studies, some mechanisms have been confirmed for microglia cells in the retina, the light-sensing compartment of the eye responsible for initial processing of visual information. However, several key pieces of this puzzle are still unaccounted for, as the characterization of retinal microglia has long been hindered by the reduced population size within the retina as well as the previous lack of technologies enabling single-cell analyses. Accumulating evidence indicates that the same cell type may harbor a high degree of transcriptional, morphological and functional differences depending on its location within the central nervous system. Thus, studying the roles and signatures adopted specifically by microglia in the retina has become increasingly important. Here, we review the current understanding of retinal microglia cells in physiology and in disease, with particular emphasis on newly discovered mechanisms and future research directions.
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Affiliation(s)
- Elisa Murenu
- Department of Ophthalmology, Klinikum der Ludwig-Maximilians-Universität München, Munich, Germany,*Correspondence: Elisa Murenu, ; ; Stylianos Michalakis,
| | | | - Martin Biel
- Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Stylianos Michalakis
- Department of Ophthalmology, Klinikum der Ludwig-Maximilians-Universität München, Munich, Germany,*Correspondence: Elisa Murenu, ; ; Stylianos Michalakis,
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22
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Morr AS, Nowicki M, Bertalan G, Vieira Silva R, Infante Duarte C, Koch SP, Boehm-Sturm P, Krügel U, Braun J, Steiner B, Käs JA, Fuhs T, Sack I. Mechanical properties of murine hippocampal subregions investigated by atomic force microscopy and in vivo magnetic resonance elastography. Sci Rep 2022; 12:16723. [PMID: 36202964 PMCID: PMC9537158 DOI: 10.1038/s41598-022-21105-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 09/22/2022] [Indexed: 12/02/2022] Open
Abstract
The hippocampus is a very heterogeneous brain structure with different mechanical properties reflecting its functional variety. In particular, adult neurogenesis in rodent hippocampus has been associated with specific viscoelastic properties in vivo and ex vivo. Here, we study the microscopic mechanical properties of hippocampal subregions using ex vivo atomic force microscopy (AFM) in correlation with the expression of GFP in presence of the nestin promoter, providing a marker of neurogenic activity. We further use magnetic resonance elastography (MRE) to investigate whether in vivo mechanical properties reveal similar spatial patterns, however, on a much coarser scale. AFM showed that tissue stiffness increases with increasing distance from the subgranular zone (p = 0.0069), and that stiffness is 39% lower in GFP than non-GFP regions (p = 0.0004). Consistently, MRE showed that dentate gyrus is, on average, softer than Ammon´s horn (shear wave speed = 3.2 ± 0.2 m/s versus 4.4 ± 0.3 m/s, p = 0.01) with another 3.4% decrease towards the subgranular zone (p = 0.0001). The marked reduction in stiffness measured by AFM in areas of high neurogenic activity is consistent with softer MRE values, indicating the sensitivity of macroscopic mechanical properties in vivo to micromechanical structures as formed by the neurogenic niche of the hippocampus.
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Affiliation(s)
- Anna S Morr
- Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Marcin Nowicki
- Institute of Anatomy, University of Leipzig, Leipzig, Germany
| | - Gergely Bertalan
- Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Rafaela Vieira Silva
- Experimental and Clinical Research Center, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) and Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.,Einstein Center for Neurosciences Berlin, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Carmen Infante Duarte
- Experimental and Clinical Research Center, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) and Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Stefan Paul Koch
- Department of Experimental Neurology and Center for Stroke Research, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence and Charité Core Facility 7T Experimental MRIs, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Philipp Boehm-Sturm
- Department of Experimental Neurology and Center for Stroke Research, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence and Charité Core Facility 7T Experimental MRIs, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ute Krügel
- Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Barbara Steiner
- Clinic for Neurology and Experimental Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Josef A Käs
- Section of Soft Matter Physics, Peter Debye Institute for Soft Matter Physics, Faculty of Physics and Geosciences, University of Leipzig, Leipzig, Germany
| | - Thomas Fuhs
- Section of Soft Matter Physics, Peter Debye Institute for Soft Matter Physics, Faculty of Physics and Geosciences, University of Leipzig, Leipzig, Germany
| | - Ingolf Sack
- Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany.
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23
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Reiter R, Zampini MA, Guidetti M, Majumdar S, Royston TJ, Klatt D. Tabletop MR elastography for investigating effects of the freeze-thaw cycle on the mechanical properties of biological tissues. J Mech Behav Biomed Mater 2022; 135:105458. [PMID: 36116341 DOI: 10.1016/j.jmbbm.2022.105458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 08/23/2022] [Accepted: 09/08/2022] [Indexed: 11/26/2022]
Abstract
PURPOSE We aimed at characterizing the effects of the freeze-thaw cycle (FTC) on ex vivo specimens of porcine muscle, liver, kidney, and brain using tabletop magnetic resonance elastography (MRE) combined with rheological modeling. While frozen tissue banks potentially facilitate access to large amounts of well-preserved biospecimens, the impact of the FTC on their viscoelastic properties remains elusive. METHODS In this proof-of-concept study, fresh specimens from porcine lumbar muscle (n = 6), liver (n = 6), kidney (n = 6), and brain (n = 6) were examined before and after the FTC using 0.5T tabletop MRE at 500 Hz, 1000 Hz, 1500 Hz, and 2000 Hz. Seven standard rheological models (Maxwell, Springpot, Voigt, Zener, Jeffrey, fractional Voigt, fractional Zener) were employed to calculate frequency independent viscoelastic parameters. RESULTS The Zener rheological model showed the best fit quality for tissues before and after FTC in the investigated frequency range. Global rheological behavior after the FTC was softer for all tissues. Differences in mechanical parameters between tissues were preserved after the FTC and showed similar trends as before the FTC. Moreover, rheological fit quality improved after the FTC - a result that will be beneficial in investigating frozen tissue bank samples. CONCLUSION Multifrequency tabletop MRE allows rheological characterization of tissue samples before and after the FTC. Our results encourage further biomechanical characterization of frozen tissue bank samples, which may provide valuable information on the diagnostic potential of elastographic methods.
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Affiliation(s)
- Rolf Reiter
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, 830 South Wood Street, Chicago, IL, 60612, United States; Department of Radiology, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Hindenburgdamm 30, 12203, Berlin, Germany; Berlin Institute of Health at Charité - Universitätsmedizin Berlin, BIH Biomedical Innovation Academy, BIH Charité Digital Clinician Scientist Program, Charitéplatz 1, 10117, Berlin, Germany.
| | - Marco A Zampini
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, 830 South Wood Street, Chicago, IL, 60612, United States; MR Solutions Ltd, Ashbourne House, Old Portsmouth Road, Guildford, Surrey, GU3 1LR, United Kingdom.
| | - Martina Guidetti
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, 830 South Wood Street, Chicago, IL, 60612, United States; Department of Orthopedic Surgery, Rush University, 1611 West Harrison Street, Chicago, IL, 60612, United States.
| | - Shreyan Majumdar
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, 830 South Wood Street, Chicago, IL, 60612, United States.
| | - Thomas J Royston
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, 830 South Wood Street, Chicago, IL, 60612, United States.
| | - Dieter Klatt
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, 830 South Wood Street, Chicago, IL, 60612, United States.
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24
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Hoppstädter M, Püllmann D, Seydewitz R, Kuhl E, Böl M. Correlating the microstructural architecture and macrostructural behaviour of the brain. Acta Biomater 2022; 151:379-395. [PMID: 36002124 DOI: 10.1016/j.actbio.2022.08.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 08/02/2022] [Accepted: 08/16/2022] [Indexed: 11/16/2022]
Abstract
The computational simulation of pathological conditions and surgical procedures, for example the removal of cancerous tissue, can contribute crucially to the future of medicine. Especially for brain surgery, these methods can be important, as the ultra-soft tissue controls vital functions of the body. However, the microstructural interactions and their effects on macroscopic material properties remain incompletely understood. Therefore, we investigated the mechanical behaviour of brain tissue under three different deformation modes, axial tension, compression, and semi-confined compression, in different anatomical regions, and for varying axon orientation. In addition, we characterised the underlying microstructure in terms of myelin, cells, glial cells and neuron area fraction, and density. The correlation of these quantities with the material parameters of the anisotropic Ogden model reveals a decrease in shear modulus with increasing myelin area fraction. Strikingly, the tensile shear modulus correlates positively with cell and neuronal area fraction (Spearman's correlation coefficient of rs=0.40 and rs=0.33), whereas the compressive shear modulus decreases with increasing glial cell area (rs=-0.33). Our study finds that tissue non-linearity significantly depends on the myelin area fraction (rs=0.47), cell density (rs=0.41) and glial cell area (rs=0.49). Our results provide an important step towards understanding the micromechanical load transfer that leads to the non-linear macromechanical behaviour of the brain. STATEMENT OF SIGNIFICANCE: Within this article, we investigate the mechanical behaviour of brain tissue under three different deformation modes, in different anatomical regions, and for varying axon orientation. Further, we characterise the underlying microstructure in terms of various constituents. The correlation of these quantities with the material parameters of the anisotropic Ogden model reveals a decrease in shear modulus with increasing myelin area fraction. Strikingly, the tensile shear modulus correlates positively with cell and neuronal area fraction, whereas the compressive shear modulus decreases with increasing glial cell area. Our study finds that tissue non-linearity significantly depends on the myelin area fraction, cell density, and glial cell area. Our results provide an important step towards understanding the micromechanical load transfer that leads to the non-linear macromechanical behaviour of the brain.
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Affiliation(s)
- Mayra Hoppstädter
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany
| | - Denise Püllmann
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany
| | - Robert Seydewitz
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany
| | - Ellen Kuhl
- Departments of Mechanical Engineering and Bioengineering, Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, United States
| | - Markus Böl
- Institute of Mechanics and Adaptronics, Technische Universität Braunschweig, Braunschweig D-38106, Germany.
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25
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Effect of static offsets on the nonlinear dynamic mechanical properties of human brain tissue. J Mech Behav Biomed Mater 2022; 130:105204. [DOI: 10.1016/j.jmbbm.2022.105204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 10/26/2021] [Accepted: 03/25/2022] [Indexed: 11/23/2022]
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26
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Procès A, Luciano M, Kalukula Y, Ris L, Gabriele S. Multiscale Mechanobiology in Brain Physiology and Diseases. Front Cell Dev Biol 2022; 10:823857. [PMID: 35419366 PMCID: PMC8996382 DOI: 10.3389/fcell.2022.823857] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 03/08/2022] [Indexed: 12/11/2022] Open
Abstract
Increasing evidence suggests that mechanics play a critical role in regulating brain function at different scales. Downstream integration of mechanical inputs into biochemical signals and genomic pathways causes observable and measurable effects on brain cell fate and can also lead to important pathological consequences. Despite recent advances, the mechanical forces that influence neuronal processes remain largely unexplored, and how endogenous mechanical forces are detected and transduced by brain cells into biochemical and genetic programs have received less attention. In this review, we described the composition of brain tissues and their pronounced microstructural heterogeneity. We discuss the individual role of neuronal and glial cell mechanics in brain homeostasis and diseases. We highlight how changes in the composition and mechanical properties of the extracellular matrix can modulate brain cell functions and describe key mechanisms of the mechanosensing process. We then consider the contribution of mechanobiology in the emergence of brain diseases by providing a critical review on traumatic brain injury, neurodegenerative diseases, and neuroblastoma. We show that a better understanding of the mechanobiology of brain tissues will require to manipulate the physico-chemical parameters of the cell microenvironment, and to develop three-dimensional models that can recapitulate the complexity and spatial diversity of brain tissues in a reproducible and predictable manner. Collectively, these emerging insights shed new light on the importance of mechanobiology and its implication in brain and nerve diseases.
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Affiliation(s)
- Anthony Procès
- Mechanobiology and Biomaterials group, Interfaces and Complex Fluids Laboratory, Research Institute for Biosciences, University of Mons, Mons, Belgium.,Neurosciences Department, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Marine Luciano
- Mechanobiology and Biomaterials group, Interfaces and Complex Fluids Laboratory, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Yohalie Kalukula
- Mechanobiology and Biomaterials group, Interfaces and Complex Fluids Laboratory, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Laurence Ris
- Neurosciences Department, Research Institute for Biosciences, University of Mons, Mons, Belgium
| | - Sylvain Gabriele
- Mechanobiology and Biomaterials group, Interfaces and Complex Fluids Laboratory, Research Institute for Biosciences, University of Mons, Mons, Belgium
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27
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Zhang C, Zhao H. The effects of electric fields on the mechanical properties and microstructure of ex vivo porcine brain tissues. SOFT MATTER 2022; 18:1498-1509. [PMID: 35099495 DOI: 10.1039/d1sm01401c] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
As a popular tool for regulating the physiological conditions of the brain and treating brain diseases, electrotherapy has become increasingly mature in clinical applications. However, the mechanical properties and microstructure of the brain that change with weak electric fields are often overlooked. Thus, the mechanical behaviors of the brain tissue, which play a critical role in modulating the brain form and brain function, need to be taken into account. Herein, the direct current electric fields were combined with a customized indentation device and simultaneously focused on the changes in the mechanical properties and microstructure of ex vivo porcine brain tissues under electric fields. The experimental results showed that the electric fields reduced the shear modulus and viscosity and increased the relaxation rate of ex vivo porcine brain tissues. Moreover, electric fields polarized the cell bodies and reduced proteoglycan content in the cortex. The TEM observation confirmed that the electric fields deepened the degree of endoplasmic reticulum expansion and decreased the structural integrity of the cell membrane and myelin sheath. This study confirmed the effect of electric fields on ex vivo brain tissues; concurrently, it created comparable space in microscopic structure/compositions and mechanical parameters for future deeper brain experiments under stress-electric field coupling.
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Affiliation(s)
- Chi Zhang
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, P. R. China.
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, P. R. China
| | - Hongwei Zhao
- School of Mechanical & Aerospace Engineering, Jilin University, 5988 Renmin Street, Changchun, 130025, P. R. China.
- Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, P. R. China
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28
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Xue B, Wen X, Kuwar R, Sun D, Zhang N. Age-dependent viscoelastic characterization of rat brain cortex. BRAIN MULTIPHYSICS 2022; 3. [DOI: 10.1016/j.brain.2022.100056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
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29
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Zhang C, Liu C, Zhao H. Mechanical properties of brain tissue based on microstructure. J Mech Behav Biomed Mater 2021; 126:104924. [PMID: 34998069 DOI: 10.1016/j.jmbbm.2021.104924] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 09/04/2021] [Accepted: 10/24/2021] [Indexed: 11/17/2022]
Abstract
Research on the mechanical properties of brain tissue has gradually deepened recently. Two indentation protocols were used here to characterize the mechanical properties of cortical tissues. Further, histological staining was used to explore the correlation between the mechanical properties and microstructure on the basis of the density of cell nuclei and proteoglycan content. No significant difference was observed in transient contact stiffness between the cerebral cortex and cerebellar cortex at the depth interval of 0-600 μm under the cortical surface; however, the average shear modulus of the cerebral cortex was higher than that of the cerebellar cortex. The cerebral cortex responded more quickly to the change in load and released stress more thoroughly than the cerebellar cortex. In addition, the density of cell nuclei was related to both the transient contact stiffness and second time constant of cortical tissues. Proteoglycan content had a more significant impact on the shear modulus, second time constant, and stress relaxation rate of cortical tissues. Exploring mechanical properties thoroughly will provide more detailed mechanical information for future brain chip implantation. Alternatively, linking the mechanical properties of cortical tissues to the microstructure can provide basic data for the design and manufacture of substitute materials for brain tissue.
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Affiliation(s)
- Chi Zhang
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun, 130025, PR China; Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, PR China
| | - Changyi Liu
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun, 130025, PR China; Key Laboratory of Bionic Engineering, Ministry of Education, Jilin University, Changchun, 130025, PR China.
| | - Hongwei Zhao
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun, 130025, PR China; Key Laboratory of CNC Equipment Reliability, Ministry of Education, Jilin University, 5988 Renmin Street, Changchun, 130025, PR China.
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30
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Ryu Y, Iwashita M, Lee W, Uchimura K, Kosodo Y. A Shift in Tissue Stiffness During Hippocampal Maturation Correlates to the Pattern of Neurogenesis and Composition of the Extracellular Matrix. Front Aging Neurosci 2021; 13:709620. [PMID: 34393762 PMCID: PMC8361493 DOI: 10.3389/fnagi.2021.709620] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 07/14/2021] [Indexed: 12/02/2022] Open
Abstract
Aging changes the mechanical properties of brain tissue, such as stiffness. It has been proposed that the maintenance and differentiation of neural stem cells (NSCs) are regulated in accordance with extracellular stiffness. Neurogenesis is observed in restricted niches, including the dentate gyrus (DG) of the hippocampus, throughout mammalian lifetimes. However, profiles of tissue stiffness in the DG in comparison with the activity of NSCs from the neonatal to the matured brain have rarely been addressed so far. Here, we first applied ultrasound-based shear-wave elasticity imaging (SWEI) in living animals to assess shear modulus as in vivo brain stiffness. To complement the assay, atomic force microscopy (AFM) was utilized to determine the Young’s modulus in the hippocampus as region-specific stiffness in the brain slice. The results revealed that stiffness in the granule cell layer (GCL) and the hilus, including the subgranular zone (SGZ), increased during hippocampal maturation. We then quantified NSCs and immature neural cells in the DG with differentiation markers, and verified an overall decrease of NSCs and proliferative/immature neural cells along stages, showing that a specific profile is dependent on the subregion. Subsequently, we evaluated the amount of chondroitin sulfate proteoglycans (CSPGs), the major extracellular matrix (ECM) components in the premature brain by CS-56 immunoreactivity. We observed differential signal levels of CSPGs by hippocampal subregions, which became weaker during maturation. To address the contribution of the ECM in determining tissue stiffness, we manipulated the function of CSPGs by enzymatic digestion or supplementation with chondroitin sulfate, which resulted in an increase or decrease of stiffness in the DG, respectively. Our results illustrate that stiffness in the hippocampus shifts due to the composition of ECM, which may affect postnatal neurogenesis by altering the mechanical environment of the NSC niche.
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Affiliation(s)
- Youngjae Ryu
- Neural Regeneration Lab, Korea Brain Research Institute, Daegu, South Korea
| | - Misato Iwashita
- Neural Regeneration Lab, Korea Brain Research Institute, Daegu, South Korea
| | - Wonyoung Lee
- Neural Regeneration Lab, Korea Brain Research Institute, Daegu, South Korea
| | - Kenji Uchimura
- Unit of Glycobiology Structure and Functions, CNRS-UMR 8576/University of Lille, Lille, France
| | - Yoichi Kosodo
- Neural Regeneration Lab, Korea Brain Research Institute, Daegu, South Korea
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31
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van Wageningen TA, Antonovaite N, Paardekam E, Brevé JJP, Iannuzzi D, van Dam AM. Viscoelastic properties of white and gray matter-derived microglia differentiate upon treatment with lipopolysaccharide but not upon treatment with myelin. J Neuroinflammation 2021; 18:83. [PMID: 33781276 PMCID: PMC8008683 DOI: 10.1186/s12974-021-02134-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/18/2021] [Indexed: 01/16/2023] Open
Abstract
Background The biomechanical properties of the brain have increasingly been shown to relate to brain pathology in neurological diseases, including multiple sclerosis (MS). Inflammation and demyelination in MS induce significant changes in brain stiffness which can be linked to the relative abundance of glial cells in lesions. We hypothesize that the biomechanical, in addition to biochemical, properties of white (WM) and gray matter (GM)-derived microglia may contribute to the differential microglial phenotypes as seen in MS WM and GM lesions. Methods Primary glial cultures from WM or GM of rat adult brains were treated with either lipopolysaccharide (LPS), myelin, or myelin+LPS for 24 h or left untreated as a control. After treatment, microglial cells were indented using dynamic indentation to determine the storage and loss moduli reflecting cell elasticity and cell viscosity, respectively, and subsequently fixed for immunocytochemical analysis. In parallel, gene expression of inflammatory-related genes were measured using semi-quantitative RT-PCR. Finally, phagocytosis of myelin was determined as well as F-actin visualized to study the cytoskeletal changes. Results WM-derived microglia were significantly more elastic and more viscous than microglia derived from GM. This heterogeneity in microglia biomechanical properties was also apparent when treated with LPS when WM-derived microglia decreased cell elasticity and viscosity, and GM-derived microglia increased elasticity and viscosity. The increase in elasticity and viscosity observed in GM-derived microglia was accompanied by an increase in Tnfα mRNA and reorganization of F-actin which was absent in WM-derived microglia. In contrast, when treated with myelin, both WM- and GM-derived microglia phagocytose myelin decrease their elasticity and viscosity. Conclusions In demyelinating conditions, when myelin debris is phagocytized, as in MS lesions, it is likely that the observed differences in WM- versus GM-derived microglia biomechanics are mainly due to a difference in response to inflammation, rather than to the event of demyelination itself. Thus, the differential biomechanical properties of WM and GM microglia may add to their differential biochemical properties which depend on inflammation present in WM and GM lesions of MS patients. Supplementary Information The online version contains supplementary material available at 10.1186/s12974-021-02134-x.
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Affiliation(s)
- Thecla A van Wageningen
- Department of Anatomy & Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081, HZ, Amsterdam, The Netherlands
| | - Nelda Antonovaite
- Department of Physics and Astronomy and LaserLaB, VU Amsterdam, Amsterdam, The Netherlands
| | - Erik Paardekam
- Department of Physics and Astronomy and LaserLaB, VU Amsterdam, Amsterdam, The Netherlands
| | - John J P Brevé
- Department of Anatomy & Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081, HZ, Amsterdam, The Netherlands
| | - Davide Iannuzzi
- Department of Physics and Astronomy and LaserLaB, VU Amsterdam, Amsterdam, The Netherlands
| | - Anne-Marie van Dam
- Department of Anatomy & Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081, HZ, Amsterdam, The Netherlands.
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