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Cheng YT, Lett KM, Xu C, Schaffer CB. Three-photon excited fluorescence microscopy enables imaging of blood flow, neural structure and inflammatory response deep into mouse spinal cord in vivo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.04.588110. [PMID: 38617307 PMCID: PMC11014502 DOI: 10.1101/2024.04.04.588110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Nonlinear optical microscopy enables non-invasive imaging in scattering samples with cellular resolution. The spinal cord connects the brain with the periphery and governs fundamental behaviors such as locomotion and somatosensation. Because of dense myelination on the dorsal surface, imaging to the spinal grey matter is challenging, even with two-photon microscopy. Here we show that three-photon excited fluorescence (3PEF) microscopy enables multicolor imaging at depths of up to ~550 μm into the mouse spinal cord, in vivo. We quantified blood flow across vessel types along the spinal vascular network. We then followed the response of neurites and microglia after occlusion of a surface venule, where we observed depth-dependent structural changes in neurites and interactions of perivascular microglia with vessel branches upstream from the clot. This work establishes that 3PEF imaging enables studies of functional dynamics and cell type interactions in the top 550 μm of the murine spinal cord, in vivo.
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Affiliation(s)
- Yu-Ting Cheng
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, USA
| | - Kawasi M. Lett
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Chris Xu
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Chris B. Schaffer
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
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Orem BC, Rajaee A, Stirling DP. IP 3R-mediated intra-axonal Ca 2+ release contributes to secondary axonal degeneration following contusive spinal cord injury. Neurobiol Dis 2020; 146:105123. [PMID: 33011333 DOI: 10.1016/j.nbd.2020.105123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/15/2020] [Accepted: 09/28/2020] [Indexed: 01/11/2023] Open
Abstract
Secondary axonal loss contributes to the persistent functional disability following trauma. Consequently, preserving axons following spinal cord injury (SCI) is a major therapeutic goal to improve neurological outcome; however, the complex molecular mechanisms that mediate secondary axonal degeneration remain unclear. We previously showed that IP3R-mediated Ca2+ release contributes to axonal dieback and axonal loss following an ex vivo laser-induced SCI. Nevertheless, targeting IP3R in a clinically relevant in vivo model of SCI and determining its contribution to secondary axonal degeneration has yet to be explored. Here we used intravital two-photon excitation microscopy to assess the role of IP3R in secondary axonal degeneration in real-time after a contusive-SCI in vivo. To visualize Ca2+ changes specifically in spinal axons over time, adult 6-8 week-old triple transgenic Avil-Cre:Ai9:Ai95 (sensory neuron-specific expression of tdTomato and the genetic calcium indicator GCaMP6f) mice were subjected to a mild (30 kdyn) T12 contusive-SCI and received delayed treatment with the IP3R blocker 2-APB (100 μM, intrathecal delivery at 3, and 24 h following injury) or vehicle control. To determine the IP3R subtype involved, we knocked-down IP3R3 using capped phosphodiester oligonucleotides. Delayed treatment with 2-APB significantly reduced axonal spheroids, increased axonal survival, and reduced intra-axonal Ca2+ accumulation within dorsal column axons at 24 h following SCI in vivo. Additionally, knockdown of IP3R3 yielded increased axon survival 24 h post-SCI. These results suggest that IP3R-mediated Ca2+ release contributes to secondary axonal degeneration in vivo following SCI.
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Affiliation(s)
- Ben C Orem
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - Arezoo Rajaee
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Departments of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - David P Stirling
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Departments of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Microbiology and Immunology, University of Louisville, School of Medicine, Louisville, KY 40202, USA.
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Rajaee A, Geisen ME, Sellers AK, Stirling DP. Repeat intravital imaging of the murine spinal cord reveals degenerative and reparative responses of spinal axons in real-time following a contusive SCI. Exp Neurol 2020; 327:113258. [PMID: 32105708 DOI: 10.1016/j.expneurol.2020.113258] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 02/06/2020] [Accepted: 02/22/2020] [Indexed: 12/18/2022]
Abstract
Spinal cord injury (SCI) induces a secondary degenerative response that causes the loss of spared axons and worsens neurological outcome. The complex molecular mechanisms that mediate secondary axonal degeneration remain poorly understood. To further our understanding of secondary axonal degeneration following SCI, we assessed the spatiotemporal dynamics of axonal spheroid and terminal bulb formation following a contusive SCI in real-time in vivo. Adult 6-8 week old Thy1YFP transgenic mice underwent a T12 laminectomy for acute imaging sessions or were implanted with a custom spinal cord imaging chamber for chronic imaging of the spinal cord. Two-photon excitation time-lapse microscopy was performed prior to a mild contusion SCI (30 kilodyne, IH Impactor) and at 1-4 h and 1-14 days post-SCI. We quantified the number of axonal spheroids, their size and distribution, the number of endbulbs, and axonal survival from 1 h to 14 days post-SCI. Our data reveal that the majority of axons underwent swelling and axonal spheroid formation acutely after SCI resulting in the loss of ~70% of axons by 1 day after injury. In agreement, the number of axonal spheroids rapidly increased at 1 h after SCI and remained significantly elevated up to 14 days after SCI. Furthermore, the distribution of axonal spheroids spread mediolaterally over time indicative of delayed secondary degenerative processes. In contrast, axonal endbulbs were relatively sparse and their numbers peaked at 1 day after injury. Intriguingly, axonal survival significantly increased at 7 and 14 days compared to 3 days after SCI revealing a potential endogenous axonal repair process that mirrors the known spontaneous functional recovery after SCI. In support, ~43% of tracked axonal spheroids resolved over the course of observation revealing their dynamic nature. Furthermore, axonal spheroids and endbulbs accumulated mitochondria and excessive tubulin polyglutamylation suggestive of disrupted axonal transport as a shared mechanism. Collectively, this study provides important insight into both degenerative and recoverable responses of axons following contusive SCI in real-time. Understanding how axons spontaneously recover after SCI will be an important avenue for future SCI research and may help guide future clinical trials.
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Affiliation(s)
- Arezoo Rajaee
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - Mariah E Geisen
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - Alexandra K Sellers
- Department of Bioengineering, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - David P Stirling
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Microbiology and Immunology, University of Louisville, School of Medicine, Louisville, KY 40202, USA.
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Xu Q, Dong X. Calcium imaging approaches in investigation of pain mechanism in the spinal cord. Exp Neurol 2019; 317:129-132. [PMID: 30853387 PMCID: PMC6544469 DOI: 10.1016/j.expneurol.2019.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 02/16/2019] [Accepted: 03/06/2019] [Indexed: 11/28/2022]
Abstract
The continuous advancement of microscopic imaging techniques combined with the discovery and use of more powerful calcium indicators has made calcium imaging technology much more effective and has increased its use in the study of pain circuitry. Using calcium imaging to study spinal pain mechanisms causes less damage to animals compared to electrophysiological techniques and is also able to observe the firing pattern of spinal neurons and the connections between them on a large scale. These advantages allow any changes in spinal cord circuits caused by pain transmission to be observed more effectively. This review will discuss the development of calcium indicators over the past decades as well as the various applications of calcium imaging, from in vitro to in vivo spinal cord experiments, in the study of pain circuits. We will also discuss possible directions for the study of spinal pain circuits in the future.
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Affiliation(s)
- Qian Xu
- The Solomon H. Snyder Department of Neuroscience and the Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience and the Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Cheng YT, Lett KM, Schaffer CB. Surgical preparations, labeling strategies, and optical techniques for cell-resolved, in vivo imaging in the mouse spinal cord. Exp Neurol 2019; 318:192-204. [PMID: 31095935 DOI: 10.1016/j.expneurol.2019.05.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/25/2019] [Accepted: 05/10/2019] [Indexed: 11/16/2022]
Abstract
In vivo optical imaging has enabled detailed studies of cellular dynamics in the brain of rodents in both healthy and diseased states. Such studies were made possible by three advances: surgical preparations that give optical access to the brain; strategies for in vivo labeling of cells with structural and functional fluorescent indicators; and optical imaging techniques that are relatively insensitive to light scattering by tissue. In vivo imaging in the rodent spinal cord has lagged behind than that in the brain, largely due to the anatomy around the spinal cord that complicates the surgical preparation, and to the strong optical scattering of the dorsal white matter that limits the ability to image deep into the spinal cord. Here, we review recent advances in surgical methods, labeling strategies, and optical tools that have enabled in vivo, high-resolution imaging of the dynamic behaviors of cells in the spinal cord in mice. Surgical preparations that enable long-term optical access and robust stabilization of the spinal cord are now available. Labeling strategies that have been used in the spinal cord tend to follow those that have been used in the brain, and some recent advances in genetically-encoded labeling strategies remain to be capitalized on. The optical imaging methods used to date, including two photon excited fluorescence microscopy, are largely limited to imaging the superficial layers of the spinal cord by the optical scattering of the white matter. Finally, we show preliminary data that points to the use of higher-order nonlinear optical processes, such as three photon excited fluorescence, as a means to image deeper into the mouse spinal cord.
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Affiliation(s)
- Yu-Ting Cheng
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA; Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, USA
| | - Kawasi M Lett
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA
| | - Chris B Schaffer
- Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, USA.
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van Grinsven E, Prunier C, Vrisekoop N, Ritsma L. Two-Photon Intravital Microscopy Animal Preparation Protocol to Study Cellular Dynamics in Pathogenesis. Methods Mol Biol 2017; 1563:51-71. [PMID: 28324601 DOI: 10.1007/978-1-4939-6810-7_4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Two-photon intravital microscopy (2P-IVM) is an advanced imaging platform that allows the visualization of dynamic processes at subcellular resolution in vivo. Dynamic processes like cell migration, cell proliferation, cell-cell interactions, and cell signaling have an interactive character and occur in complex environments. Hence, it is of pivotal importance to study these processes in living animals, using for example 2P-IVM. 2P-IVM can be performed on a variety of tissues, from the skin of the animal to internal organs, and a variety of methods can be utilized to perform 2P-IVM on these tissues. Here, we discuss the protocols and considerations for four of those 2P-IVM methods, namely tissue explant imaging, skin imaging, surgical exposure imaging, and multi-day window imaging. We carefully compare and explain in depth how to set up each method. Lastly, in the notes section we mention some alternative solutions for the 2P-IVM methods described. In conclusion, this protocol can be used as a guide towards deciding which 2P-IVM method to use and to enable the setup of this method.
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Affiliation(s)
- Erinke van Grinsven
- Department of Respiratory Medicine, Laboratory of Translational Immunology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Chloé Prunier
- Department of Molecular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
| | - Nienke Vrisekoop
- Department of Respiratory Medicine, Laboratory of Translational Immunology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Laila Ritsma
- Department of Molecular Cell Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands.
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