NOTE: Ethics Statement: The protocol for animal handling was approved by the Institutional Animal Care and Use Committee (IACUC) of the University of California, Irvine, protocol #2010-2943.
1. Removal of Spinal Cord
2. Preparation of Spinal Cord for Imaging
3. 2P Imaging of Ventral Spinal Cord
While the explanted spinal cord imaging protocol can be used to visualize any fluorescence within the spinal cord, our representative results demonstrate eGFP-NPC interactions with eYFP-axons. First, we show the embedded ventral spinal cord preparation in Figure 1A. Next, we show the 2P microscope setup and key components in Figure 1B. Figure 2 demonstrates eGFP and eYFP fluorescence in a single z-stack within the ventral spinal cord. Acquisition of consecutive z-stacks can be compiled to produce time-lapse videos to analyze real-time cellular dynamics within the intact tissue. Using a 520 nm single-edge dichroic and a 560 nm single-edge dichroic beam splitter, as noted in the protocol, can separate eGFP and eYFP signal. Individual channels can be pseudocolored green and yellow using imaging software.
Figure 1: Spinal cord and microscope setup. (A) A spinal cord embedded in a 5% agarose gel (left) and mounted on a coverslip following removal of excess agarose (right). (B) An image of the microscope setup with key components labeled. 1. Water bath set at 37 °C. 2. Pre-warmed RPMI-1640. 3. C/L variable-speed tubing Pump. 4. Single inline solution heater. 5. Dipping objective. 6. Digital thermometer. Please click here to view a larger version of this figure.
Figure 2: Example 2P image acquired inside the ventral spinal cord. 3D reconstructions of the ventral side of an uninfected, non-damaged (A) and JHMV-infected, demyelinated (B) spinal cord from a Thy1-eYFP mouse following transplantation with eGFP-labeled NPCs. Fluorescently-labeled axons are pseudocolored yellow and NPCs are pseudocolored green. Image resolution: 512 pixels; image volume: (A) x = 239 µm, y = 259 μm, z = 65 µm constructed using 26 z-stacks spaced 2.5 µm apart and (B) x = 497 µm, y = 389 µm, z = 127.5 µm constructed using 51 z-stacks spaced 2.5 µm apart.
Name of Reagent/ Equipment | Company | Catalog Number | Comments/Description |
Isoflurane, USP | Piramal Critical Care, Inc | N/A | |
Fine scissors | Fine Science Tools | 14060-09 | sharp |
scalpel blade #10 | Fine Science Tools | 10010-00 | |
scalpel handle | Fine Science Tools | 10003-12 | |
Luer rongeurs | Fine Science Tools | 16001-15 | |
Graefe forceps | Fine Science Tools | 11052-10 | |
Vannas scissors | Fine Science Tools | 15615-08 | |
scalpel blade #11 | Fine Science Tools | 10011-00 | |
RPMI-1640 | Gibco | 12-115F | |
agarose, low gelling temperature | Sigma | A9414-25G | |
Parafilm | Fisher Scientific | 13-374-12 | |
Vetbond (tissue adhesive) | 3M | 1469SB | |
22 mm square cover slip | Fisher Scientific | 12-547 | |
25x dipping objective, 1.1 NA | Nikon | CFI Apo LWD 25XW | |
Single inline solution heater | Warner Instruments | 64-0102 | |
520 nm single-edge dichroic beam splitter | Semrock | FF520-Di02-25×36 | Brightline |
560 nm single-edge dichroic beam splitter | Semrock | FF560-FDi01-25×36 | Brightline |
photomultiplier tubes | Hamamatsu | R928 | |
C/L variable-speed tubing pump | Masterflex | 77122-22 | |
digital thermometer | Comar Instruments | 3501 | |
Chameleon Ultra Ti:Sapphire laser | Coherent | N/A | |
Slidebook 6 software | 3i | N/A | |
Imaris 7.7 software | Bitplane | N/A |
Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for live-cell imaging in the murine spinal cord. This technique is uniquely suited to analyze neural precursor cell (NPC) dynamics following transplantation into spinal cords undergoing neuroinflammatory demyelinating disorders. NPCs migrate to sites of axonal damage, proliferate, differentiate into oligodendrocytes, and participate in direct remyelination. NPCs are thereby a promising therapeutic treatment to ameliorate chronic demyelinating diseases. Because transplanted NPCs migrate to the damaged areas on the ventral side of the spinal cord, traditional intravital 2P imaging is impossible, and only information on static interactions was previously available using histochemical staining approaches. Although this method was generated to image transplanted NPCs in the ventral spinal cord, it can be applied to numerous studies of transplanted and endogenous cells throughout the entire spinal cord. In this article, we demonstrate the preparation and imaging of a spinal cord with enhanced yellow fluorescent protein-expressing axons and enhanced green fluorescent protein-expressing transplanted NPCs.
Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for live-cell imaging in the murine spinal cord. This technique is uniquely suited to analyze neural precursor cell (NPC) dynamics following transplantation into spinal cords undergoing neuroinflammatory demyelinating disorders. NPCs migrate to sites of axonal damage, proliferate, differentiate into oligodendrocytes, and participate in direct remyelination. NPCs are thereby a promising therapeutic treatment to ameliorate chronic demyelinating diseases. Because transplanted NPCs migrate to the damaged areas on the ventral side of the spinal cord, traditional intravital 2P imaging is impossible, and only information on static interactions was previously available using histochemical staining approaches. Although this method was generated to image transplanted NPCs in the ventral spinal cord, it can be applied to numerous studies of transplanted and endogenous cells throughout the entire spinal cord. In this article, we demonstrate the preparation and imaging of a spinal cord with enhanced yellow fluorescent protein-expressing axons and enhanced green fluorescent protein-expressing transplanted NPCs.
Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for live-cell imaging in the murine spinal cord. This technique is uniquely suited to analyze neural precursor cell (NPC) dynamics following transplantation into spinal cords undergoing neuroinflammatory demyelinating disorders. NPCs migrate to sites of axonal damage, proliferate, differentiate into oligodendrocytes, and participate in direct remyelination. NPCs are thereby a promising therapeutic treatment to ameliorate chronic demyelinating diseases. Because transplanted NPCs migrate to the damaged areas on the ventral side of the spinal cord, traditional intravital 2P imaging is impossible, and only information on static interactions was previously available using histochemical staining approaches. Although this method was generated to image transplanted NPCs in the ventral spinal cord, it can be applied to numerous studies of transplanted and endogenous cells throughout the entire spinal cord. In this article, we demonstrate the preparation and imaging of a spinal cord with enhanced yellow fluorescent protein-expressing axons and enhanced green fluorescent protein-expressing transplanted NPCs.