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Graybill PM, Jacobs EJ, Jana A, Agashe A, Nain AS, Davalos RV. Ultra-thin and ultra-porous nanofiber networks as a basement-membrane mimic. LAB ON A CHIP 2023; 23:4565-4578. [PMID: 37772328 PMCID: PMC10623910 DOI: 10.1039/d3lc00304c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Current basement membrane (BM) mimics used for modeling endothelial and epithelial barriers in vitro do not faithfully recapitulate key in vivo physiological properties such as BM thickness, porosity, stiffness, and fibrous composition. Here, we use networks of precisely arranged nanofibers to form ultra-thin (∼3 μm thick) and ultra-porous (∼90%) BM mimics for blood-brain barrier modeling. We show that these nanofiber networks enable close contact between endothelial monolayers and pericytes across the membrane, which are known to regulate barrier tightness. Cytoskeletal staining and transendothelial electrical resistance (TEER) measurements reveal barrier formation on nanofiber membranes integrated within microfluidic devices and transwell inserts. Further, significantly higher TEER values indicate a biological benefit for co-cultures formed on the ultra-thin nanofiber membranes. Our BM mimic overcomes critical technological challenges in forming co-cultures that are in proximity and facilitate cell-cell contact, while still being constrained to their respective sides. We anticipate that our nanofiber networks will find applications in drug discovery, cell migration, and barrier dysfunction studies.
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Affiliation(s)
- Philip M Graybill
- Bioelectromechanical Systems Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, USA.
| | - Edward J Jacobs
- Bioelectromechanical Systems Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, USA.
| | - Aniket Jana
- Spinneret-Based Tunable Engineering Parameters (STEP) Lab, Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA.
| | - Atharva Agashe
- Spinneret-Based Tunable Engineering Parameters (STEP) Lab, Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA.
| | - Amrinder S Nain
- Spinneret-Based Tunable Engineering Parameters (STEP) Lab, Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA.
| | - Rafael V Davalos
- Bioelectromechanical Systems Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, USA.
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Melo P, S Silveira M, Mendes-Pinto I, Relvas JB. MorphoMacro for in vivo and ex vivo quantitative morphometric analysis of microglia. Methods Cell Biol 2023; 174:75-92. [PMID: 36710053 DOI: 10.1016/bs.mcb.2022.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Microglia cells dynamically survey the central nervous system microenvironment and, in response to tissue damage inflicted by radiation therapy, disease or infection, undergo morphological and functional changes that culminate in microglia activation. Cell shape transformation can be assessed descriptively or, alternatively, it can be quantified as a continuous variable for parameters including total cell size as well as protrusion length, ramification and complexity. The purpose of the MorphoMacro method is to quantitatively profile multiple and single microglia cells using the available ImageJ platform. This method outlines the required steps and ImageJ plugins to convert fluorescence and bright-field photomicrographs into representative binary and skeletonized images and to analyze them using the MorphoMacro software plugin for multiparametric and multilevel description of microglia cell morphology in vivo and ex vivo. Overall, the protocol provides a quantitative and comprehensive tool that can be used to identify, stratify, and monitor diverse microglia morphologies in homeostatic, different disease conditions and subsequent therapeutic monitoring.
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Affiliation(s)
- Pedro Melo
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
| | - Mariana S Silveira
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal; Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Inês Mendes-Pinto
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal.
| | - João B Relvas
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal; Departmento de Biomedicina, Faculdade de Medicina, Universidade do Porto, Porto, Portugal.
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Ogaki A, Ikegaya Y, Koyama R. Replacement of Mouse Microglia With Human Induced Pluripotent Stem Cell (hiPSC)-Derived Microglia in Mouse Organotypic Slice Cultures. Front Cell Neurosci 2022; 16:918442. [PMID: 35910250 PMCID: PMC9325970 DOI: 10.3389/fncel.2022.918442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 06/20/2022] [Indexed: 11/24/2022] Open
Abstract
Microglia, the major immune cells in the brain, are reported to differ in gene expression patterns among species. Therefore, it would be preferable in some cases to use human microglia rather than mouse microglia in microglia-targeted disease research. In the past half a decade, researchers have developed in vivo transplantation methods in which human induced pluripotent stem cell-derived microglia (hiPSC-MG) are transplanted into a living mouse brain. However, in vivo transplantation methods are not necessarily accessible to all researchers due to the difficulty of obtaining the materials needed and the transplantation technique itself. In addition, for in vivo systems for microglia-targeted drug screening, it is difficult to control the pharmacokinetics, especially blood-brain barrier permeability. Therefore, in addition to existing in vivo transplantation systems, the development of an ex vivo transplantation system would help to further evaluate the properties of hiPSC-MG. In this study, we aimed to establish a method to efficiently transplant hiPSC-MG into cultured mouse hippocampal slices. We found that approximately 80% of the total microglia in a cultured slice were replaced by hiPSC-derived microglia when innate microglia were pharmacologically removed prior to transplantation. Furthermore, when neuronal death was induced by applying Kainic acid (KA) to slice cultures, transplanted hiPSC-MG changed their morphology and phagocytosed cell debris. Thus, this study provides a method to transplant hiPSC-MG into the mouse hippocampal slice cultures with a high replacement rate. Because the transplanted microglia survived and exerted phagocytic functions, this method will be useful for evaluating the properties of hiPSC-MG ex vivo.
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Affiliation(s)
- Ari Ogaki
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, Japan
- Institute for AI and Beyond, The University of Tokyo, Bunkyo, Japan
- Center for Information and Neural Networks, National Institute of Information and Communications Technology, Suita, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo, Japan
- Institute for AI and Beyond, The University of Tokyo, Bunkyo, Japan
- *Correspondence: Ryuta Koyama
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Andoh M, Koyama R. Assessing Microglial Dynamics by Live Imaging. Front Immunol 2021; 12:617564. [PMID: 33763064 PMCID: PMC7982483 DOI: 10.3389/fimmu.2021.617564] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 02/16/2021] [Indexed: 12/13/2022] Open
Abstract
Microglia are highly dynamic in the brain in terms of their ability to migrate, proliferate, and phagocytose over the course of an individual's life. Real-time imaging is a useful tool to examine how microglial behavior is regulated and how it affects the surrounding environment. However, microglia are sensitive to environmental stimuli, so they possibly change their state during live imaging in vivo, mainly due to surgical damage, and in vitro due to various effects associated with culture conditions. Therefore, it is difficult to perform live imaging without compromising the properties of the microglia under physiological conditions. To overcome this barrier, various experimental conditions have been developed; recently, it has become possible to perform live imaging of so-called surveillant microglia in vivo, ex vivo, and in vitro, although there are various limitations. Now, we can choose in vivo, ex vivo, or in vitro live imaging systems according to the research objective. In this review, we discuss the advantages and disadvantages of each experimental system and outline the physiological significance and molecular mechanisms of microglial behavior that have been elucidated by live imaging.
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Affiliation(s)
- Megumi Andoh
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
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Ogaki A, Araki T, Ishikawa M, Ikegaya Y, Koyama R. A live imaging-friendly slice culture method using collagen membranes. Neuropsychopharmacol Rep 2020; 40:307-313. [PMID: 32757372 PMCID: PMC7722644 DOI: 10.1002/npr2.12128] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/26/2020] [Accepted: 07/01/2020] [Indexed: 12/28/2022] Open
Abstract
Aim Organotypic brain slice culture preserves the geographical position of neurons and neuronal circuits. The slice cultures also maintain both non‐neuronal cell types and the surrounding extracellular matrix. The interface method has been widely used for slice cultures, in which brain slices are placed on semiporous polytetrafluoroethylene (PTFE) membranes. However, a low optical transparency of PTFE membrane makes it difficult to perform live imaging of deep regions of slice cultures using an inverted microscope. To overcome the issue, we evaluated the suitability of using collagen membranes for slice cultures, especially focusing on live imaging of the cellular dynamics of green fluorescent protein (GFP)‐expressing microglia. Methods Entorhinohippocampal slices were cultured on either collagen or PTFE membranes. The influence of membrane type on the ability to observe deep regions of slice cultures was examined by live imaging using an inverted microscope. Results Collagen membranes were thinner and had better optical transparency compared with PTFE membranes. There were no differences in cell viability, density of neurons or microglia. The densify of visible short branches of microglia in live imaging was higher in collagen membranes than PTFE membranes. Conclusion Collagen membranes are suitable for live imaging of cellular dynamics in slice cultures using an inverted microscope. Live imaging of organotypic slice cultures has been a useful method to study cell dynamics. One remaining issue with live imaging of slice cultures is the low transparency of commonly used polytetrafluoroethylene membranes. Here we report that slice culture membranes made of collagen can solve the issue of low transparency, facilitating live imaging of small cellular structures such as microglial processes.
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Affiliation(s)
- Ari Ogaki
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Tasuku Araki
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Masaya Ishikawa
- Isehara Research Laboratory, Technology and Development Division, Kanto Chemical Co., Inc, Suzukawa, Isehara, Kanagawa, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.,Center for Information and Neural Networks, Suita, Osaka, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
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