We thank Dr. Miguel Sena-Esteves at the University of Massachusetts Chan Medical School for gifting the AAV(PHP.eB)-Syn1-EGFP virus, and Debra Cameron at the University of Massachusetts Chan Medical School for drawing the mice skull sketch. We also thank current and past members of the Bosco, Schafer and Henninger labs for their suggestions and support. This work was funded by the Department of Defense (W81XWH202071/PRARP) to DAB, DS, and NH.

<ol>
	<li>Bowman, K., Matney, C., Berwick, D. 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C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+first+NINDS/NIBIB+consensus+meeting+to+define+neuropathological+criteria+for+the+diagnosis+of+chronic+traumatic+encephalopathy.">The first NINDS/NIBIB consensus meeting to define neuropathological criteria for the diagnosis of chronic traumatic encephalopathy.</a> Acta Neuropathologica. 131 (1), 75-86 (2016).</li><li>Henninger, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attenuated+traumatic+axonal+injury+and+improved+functional+outcome+after+traumatic+brain+injury+in+mice+lacking+Sarm1.">Attenuated traumatic axonal injury and improved functional outcome after traumatic brain injury in mice lacking Sarm1.</a> Brain. 139, 1094-1105 (2016).</li><li>Bouley, J., Chung, D. Y., Ayata, C., Brown, R. 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T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+in+vivo+imaging+of+experience-dependent+synaptic+plasticity+in+adult+cortex.">Long-term in vivo imaging of experience-dependent synaptic plasticity in adult cortex.</a> Nature. 420 (6917), 788-794 (2002).</li><li>Mostany, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+synaptic+dynamics+during+normal+brain+aging.">Altered synaptic dynamics during normal brain aging.</a> The Journal of Neuroscience. 33 (9), 4094-4104 (2013).</li><li>Yang, Q., Vazquez, A. L., Cui, X. 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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+closed+head+injury+model+induced+by+a+weight-drop+device.">Mouse closed head injury model induced by a weight-drop device.</a> Nature Protocols. 4 (9), 1328-1337 (2009).</li><li>Sun, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+two-photon+imaging+of+anesthesia-specific+alterations+in+microglial+surveillance+and+photodamage-directed+motility+in+mouse+cortex.">In vivo two-photon imaging of anesthesia-specific alterations in microglial surveillance and photodamage-directed motility in mouse cortex.</a> Frontiers in Neuroscience. 13, 421 (2019).</li><li>Li, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Through-Intact-Skull+(TIS)+chronic+window+technique+for+cortical+structure+and+function+observation+in+mice.">A Through-Intact-Skull (TIS) chronic window technique for cortical structure and function observation in mice.</a> eLight. 2 (1), 1-18 (2022).</li><li>Paveliev, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acute+brain+trauma+in+mice+followed+by+longitudinal+two-photon+imaging.">Acute brain trauma in mice followed by longitudinal two-photon imaging.</a> Journal of Visualized Experiments. 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No conflicts of interest are declared.

In this study, AAV injection, TBI administration, and a headpost with cranial window implantation were combined for longitudinal imaging analysis of EGFP-labeled neurons within the mouse brain cortex (layers IV and V) to observe the effects of TBI on cortical neurons. This study notes that the TBI site chosen here, above the hippocampus, provides a relatively flat and broad surface for implantation of the cranial window. Conversely, the skull is relatively narrow anterior to this site, and therefore it is difficult to en...

Traumatic brain injury (TBI), which can result from sports injuries, vehicle collisions, and military combat, is a worldwide health concern. TBI can lead to physiological, cognitive, and behavioral deficits, and&#160;lifelong disability or mortality1,2. TBI severity can be classified as mild, moderate, and severe, the vast majority being mild TBI (75%-90%)3. It is increasingly recognized that TBI, particularly repetitive occurrences of TBI, can promote neuronal degeneration and serve as risk factors for several neurodegenerative diseases, including Alzheimer&#39;s disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and chronic traumatic encephalopathy (CTE)4,5,6. However, the molecular mechanisms underlying TBI-induced neurodegeneration remain unclear, and thus represent an active area of study. To gain insight into how neurons respond to and recover from TBI, a method for monitoring fluorescently tagged proteins of interest, specifically within neurons, by longitudinal intravital imaging in mice after TBI is described herein.
To this end, this study shows how to combine a surgical procedure for the administration of closed-skull TBI that is similar to what that has been reported previously7,8, together with a surgical procedure for implantation of a cranial window for downstream intravital imaging, as described by Goldey et al9. Notably, it is not feasible to implant a cranial window first and subsequently perform a TBI in the same region, as the impact of the weight drop that induces the TBI is likely to damage the window and cause irreparable harm to the mouse. Therefore, this protocol was designed to administer the TBI and then implant the cranial window directly over the impact site, all within the same surgical session. An advantage of combining both the TBI and cranial window implantation in a single surgical session is a reduction in the number of times a mouse is subjected to surgery. Further, it allows one to monitor the immediate response (i.e., on the timescale of hours) to TBI, as opposed to implanting the window at a later surgical session (i.e., initial imaging starting on a timescale of days post-TBI). The cranial window and intravital imaging platform also offer advantages over monitoring neuronal proteins by conventional methods such as immunostaining of fixed tissues. For example, fewer mice are required for intravital imaging, as the same mouse can be studied at multiple time points, as opposed to separate cohorts of mice needed for discrete time points. Further, the same neurons can be monitored over time, allowing one to track specific biological or pathological events within the same cell.
As a proof of concept, the neuron-specific expression of enhanced green fluorescent protein (EGFP) under the synapsin promoter is demonstrated here10. This approach can be extended to 1) different brain cell-types by utilizing other cell-type specific promoters, such as myelin basic protein (MBP) promoter for oligodendrocytes and glial fibrillary acidic protein (GFAP) promoter for astrocytes11 , 2) different target proteins of interest by fusing their genes with the EGFP gene, and 3) co-expressing multiple proteins fused to different fluorophores. Here, EGFP is packaged and expressed via adeno-associated virus (AAV) delivery through an intracranial injection. A closed-skull TBI is administered using a weight-drop device, followed by implantation of a cranial window. Visualization of neuronal EGFP is achieved through the cranial window, using two-photon microscopy to detect EGFP fluorescence in vivo. With the two-photon laser, it is possible to penetrate deeper into the cortical tissue with minimal photodamage, allowing for repeated longitudinal imaging of the same cortical regions within an individual mouse for days and up to months12,13,14,15. In sum, this approach of combining a TBI surgery with intravital imaging aims to advance the understanding of the molecular events that contribute to TBI-induced disease pathology16,17.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Adjustable Precision Applicator Brushes</td>
			<td>Parkell</td>
			<td>S379</td>
			<td></td>
		</tr>
		<tr>
			<td>BD insulin syringe</td>
			<td>BD</td>
			<td>NDC/HRI#08290-3284-38</td>
			<td>5/16&#34; x 31G</td>
		</tr>
		<tr>
			<td>Betadine</td>
			<td>Purdue</td>
			<td>NDC67618-151-17</td>
			<td>including 7.5% povidone iodine</td>
		</tr>
		<tr>
			<td>Buprenorphine</td>
			<td>PAR Pharmaceutical</td>
			<td>NDC 42023-179-05</td>
			<td></td>
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			<td>Cefazolin</td>
			<td>HIKMA Pharmaceutical</td>
			<td>NDC 0143-9924-90</td>
			<td></td>
		</tr>
		<tr>
			<td>Ceramic Mixing Dish</td>
			<td>Parkell</td>
			<td>SKU: S387</td>
			<td>For dental cement preparation</td>
		</tr>
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			<td>Cotton Tipped Applicators</td>
			<td>ZORO</td>
			<td>catlog #: G9531702</td>
			<td></td>
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			<td>Catalyst</td>
			<td>Parkell</td>
			<td>S371</td>
			<td>full name: &#34;C&#34; Universal TBB Catalyst</td>
		</tr>
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			<td>Dental cement powder</td>
			<td>Parkell</td>
			<td>S396</td>
			<td>Radiopaque L-Powder for C&#38;B Metabond</td>
		</tr>
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			<td>Dental drill</td>
			<td>Foredom</td>
			<td>H.MH-130</td>
			<td></td>
		</tr>
		<tr>
			<td>Dental drill controller</td>
			<td>Foredom</td>
			<td>HP4-310</td>
			<td></td>
		</tr>
		<tr>
			<td>Dexamethasone</td>
			<td>Phoenix</td>
			<td>NDC 57319-519-05</td>
			<td></td>
		</tr>
		<tr>
			<td>EF4 carbide bit</td>
			<td>Microcopy</td>
			<td>Lot# C150113</td>
			<td>Head Dia/Lgth/mm 1.0/4.2</td>
		</tr>
		<tr>
			<td>Ethonal</td>
			<td>Fisher Scientific</td>
			<td>04355223EA</td>
			<td>75%</td>
		</tr>
		<tr>
			<td>FG1/4 carbide bit</td>
			<td>Microcopy</td>
			<td>Lot# C150413</td>
			<td>Head Dia/Lgth/mm 0.5/0.4</td>
		</tr>
		<tr>
			<td>FG4 carbide bit</td>
			<td>Microcopy</td>
			<td>Lot# C150309</td>
			<td>Head Dia/Lgth/mm 1.4/1.1</td>
		</tr>
		<tr>
			<td>Headpost</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Custom-manufactured</td>
		</tr>
		<tr>
			<td>Heating apparatus</td>
			<td>CWE</td>
			<td>TC-1000 Mouse</td>
			<td>equiped with the stereotaxic instrument and be used while operating surgery</td>
		</tr>
		<tr>
			<td>Heating blanket</td>
			<td>CVS pharmacy</td>
			<td>E12107</td>
			<td>extra heating device and be used after surgery</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Pivetal</td>
			<td>NDC 46066-755-03</td>
			<td></td>
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			<td>Isoflurane induction chamber</td>
			<td>Vetequip</td>
			<td>89012-688</td>
			<td>induction chamber for short</td>
		</tr>
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			<td>Isoflurane volatilizing machine</td>
			<td>Vetequip</td>
			<td>911103</td>
			<td></td>
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			<td>Isoflurane volatilizing machine holder</td>
			<td>Vetequip</td>
			<td>901801</td>
			<td></td>
		</tr>
		<tr>
			<td>Leica surgical microscope</td>
			<td>Leica</td>
			<td>LEICA 10450243</td>
			<td></td>
		</tr>
		<tr>
			<td>Lubricant ophthalmic ointment</td>
			<td>Picetal</td>
			<td>NDC 46066-753-55</td>
			<td></td>
		</tr>
		<tr>
			<td>Marker pen</td>
			<td>Delasco</td>
			<td>SMP-BK</td>
			<td></td>
		</tr>
		<tr>
			<td>Meloxicam</td>
			<td>Norbrook</td>
			<td>NDC 55529-040-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Microinjection pump and its controller</td>
			<td>World Precision Instruments</td>
			<td>micro4 and UMP3</td>
			<td></td>
		</tr>
		<tr>
			<td>Microliter syringe</td>
			<td>Hamilton</td>
			<td>Hamilton 80014</td>
			<td>1701 RN, 10 &#956;L gauge for syringe and 32 gauge for needle, 2 in, point style 3</td>
		</tr>
		<tr>
			<td>Mosquito forceps</td>
			<td>CAROLINA</td>
			<td>Item #:625314</td>
			<td>Stainless Steel, Curved, 5 in</td>
		</tr>
		<tr>
			<td>Depilatory agent</td>
			<td>McKesson Corporation</td>
			<td>N/A</td>
			<td>Nair Hair Aloe &#38; Lanolin Hair Removal Lotion</td>
		</tr>
		<tr>
			<td>Microscope 1</td>
			<td>Nikon</td>
			<td>SMZ745</td>
			<td>Nikon microscope for cranial window preparation</td>
		</tr>
		<tr>
			<td>Microscope 2</td>
			<td>Zeiss</td>
			<td>LSM 7 MP</td>
			<td>two-photon microscope</td>
		</tr>
		<tr>
			<td>Multiphoton laser</td>
			<td>Coherent</td>
			<td>Chameleon Ultra II, Model: MRU X1, VERDI 18W</td>
			<td>laser for two-photon microscopy</td>
		</tr>
		<tr>
			<td>Non-absorbable surgical suture</td>
			<td>Harvard Apparatus</td>
			<td>catlog# 59-6860</td>
			<td>6-0, with round needle</td>
		</tr>
		<tr>
			<td>Norland Optical Adhesive 81</td>
			<td>Norland Products</td>
			<td>NOA 81</td>
			<td></td>
		</tr>
		<tr>
			<td>No-Snag Needle Holder</td>
			<td>CAROLINA</td>
			<td>Item #: 567912</td>
			<td></td>
		</tr>
		<tr>
			<td>Quick base liquid</td>
			<td>Parkell</td>
			<td>S398</td>
			<td>&#34;B&#34; Quick Base For C&#38;B Metabond</td>
		</tr>
		<tr>
			<td>Regular scissor 1</td>
			<td>Eurostat</td>
			<td>eurostat es5-300</td>
			<td></td>
		</tr>
		<tr>
			<td>Regular scissor 2</td>
			<td>World Precision Instruments</td>
			<td>No. 501759-G</td>
			<td></td>
		</tr>
		<tr>
			<td>Round cover glass 1</td>
			<td>Warner instruments</td>
			<td>CS-5R Cat# 64-0700</td>
			<td>for 5 mm of diameter</td>
		</tr>
		<tr>
			<td>Round cover glass 2</td>
			<td>Warner instruments</td>
			<td>CS-3R Cat# 64-0720</td>
			<td>for 3 mm of diameter</td>
		</tr>
		<tr>
			<td>Rubber rings</td>
			<td>Orings-Online</td>
			<td>Item # OO-014-70-50</td>
			<td>O-Rings</td>
		</tr>
		<tr>
			<td>Saline</td>
			<td>Bioworld</td>
			<td>L19102411PR</td>
			<td></td>
		</tr>
		<tr>
			<td>Spring scissor 1</td>
			<td>World Precision Instruments</td>
			<td>No. 91500-09</td>
			<td>tip straight</td>
		</tr>
		<tr>
			<td>Spring scissor 2</td>
			<td>World Precision Instruments</td>
			<td>No. 91501-09</td>
			<td>tip curved</td>
		</tr>
		<tr>
			<td>Stereotaxic platform</td>
			<td>KOPF</td>
			<td>Model 900LS</td>
			<td></td>
		</tr>
		<tr>
			<td>Super glue</td>
			<td>Henkel</td>
			<td>Item #: 1647358</td>
			<td></td>
		</tr>
		<tr>
			<td>surgical Caliper</td>
			<td>World Precision Instruments</td>
			<td>No. 501200</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical forceps 1</td>
			<td>ELECTRON MICROSCOPY SCIENCES</td>
			<td>Catlog# 0508-5/45-PO</td>
			<td>style 5/45, curved</td>
		</tr>
		<tr>
			<td>Surgical forceps 2</td>
			<td>ELECTRON MICROSCOPY SCIENCES</td>
			<td>catlog# 0103-5-PO</td>
			<td>style 5, straight</td>
		</tr>
		<tr>
			<td>Surgical forceps 3</td>
			<td>ELECTRON MICROSCOPY SCIENCES</td>
			<td>catlog# 72912</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical forceps 4</td>
			<td>ELECTRON MICROSCOPY SCIENCES</td>
			<td>Catlog# 0508-5/45-PO</td>
			<td>style 5/45, curved</td>
		</tr>
		<tr>
			<td>Surgical gauze</td>
			<td>ZORO</td>
			<td>catlog #: G0593801</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical lamp</td>
			<td>Leica</td>
			<td>Leica KL300 LED</td>
			<td></td>
		</tr>
		<tr>
			<td>UV box</td>
			<td>Spectrolinker</td>
			<td>XL-1000</td>
			<td>also called UV crosslinker</td>
		</tr>
		<tr>
			<td>Vaporguard</td>
			<td>Vetequip</td>
			<td>931401</td>
			<td></td>
		</tr>
		<tr>
			<td>Vetbond Tissue Adhesive</td>
			<td>3M Animal Care</td>
			<td>Part Number:014006</td>
			<td></td>
		</tr>
	</tbody>
</table>

intravital imaging of fluorescent protein expression in mice with a closed-skull traumatic brain injury and cranial window using a two-photon microscope

The goal of this protocol is to demonstrate how to longitudinally visualize the expression and localization of a protein of interest within specific cell types of an animal's brain, upon exposure to exogenous stimuli. Here, the administration of a closed-skull traumatic brain injury (TBI) and simultaneous implantation of a cranial window for subsequent longitudinal intravital imaging in mice is shown. Mice are intracranially injected with an adeno-associated virus (AAV) expressing enhanced green fluorescent protein (EGFP) under a neuronal specific promoter. After 2 to 4 weeks, the mice are subjected to a repetitive TBI using a weight drop device over the AAV injection location. Within the same surgical session, the mice are implanted with a metal headpost and then a glass cranial window over the TBI impacting site. The expression and cellular localization of EGFP is examined using a two-photon microscope in the same brain region exposed to trauma over the course of months.

As proof of concept for this protocol, viral particles expressing AAV-Syn1-EGFP were injected into the brain cortex of male TDP-43Q331K/Q331K mice (C57BL/6J background)19 at the age of 3 months. It is noted that wild-type C57BL/6J animals can also be used, however this study was carried out in TDP-43Q331K/Q331K mice because the laboratory is focused on neurodegenerative disease research. A TBI surgery was performed 4 weeks after AAV injection. Within the same surgical setting...

Watch this Scientific Journal Video about Intravital Imaging of Fluorescent Protein Expression in Mice with a Closed-Skull Traumatic Brain Injury and Cranial Window Using a Two-Photon Microscope at Jo

Intravital Imaging of Fluorescent Protein Expression in Mice with a Closed-Skull Traumatic Brain Injury and Cranial Window Using a Two-Photon Microscope

This study demonstrates delivery of a repetitive traumatic brain injury to mice and simultaneous implantation of a cranial window for subsequent intravital imaging of a neuron-expressed EGFP using two-photon microscopy.

The goal of this protocol is to demonstrate how to longitudinally visualize the expression and localization of a protein of interest within specific cell ...

intravital-imaging-fluorescent-protein-expression-mice-with-closed

Research

JoVE Journal

Neuroscience

978 Views.  University of Massachusetts Chan Medical School. This study demonstrates delivery of a repetitive traumatic brain injury to mice and simultaneous implantation of a cranial window for subsequent intravital imaging of a neuron-expressed EGFP using two-photon microscopy.

Video: Intravital Imaging of Fluorescent Protein Expression in Mice with a Closed-Skull Traumatic Brain Injury and Cranial Window Using a Two-Photon Microscope

A Thin-skull Window Technique for Chronic Two-photon In vivo Imaging of Murine Microglia in Models of Neuroinflammation

Traditionally in neuroscience, in vivo two photon imaging of the murine central nervous system has either involved the use of open-skull1,2 or thinned-skull 3 preparations. While the open-skull technique is very versatile, it is not optimal for studying microglia because it is invasive and can cause microglial activation. Even though the thinned-skull approach is minimally invasive, the repeated re-thinning of skull required for chronic imaging increases the risks of tissue injury and microglial activation and allows for a limited number of imaging sessions. Here we present a chronic thin-skull window method for monitoring murine microglia in vivo over an extended period of time using two-photon microscopy. We demonstrate how to prepare a stable, accessible, thinned-skull cortical window (TSCW) with an apposed glass coverslip that remains translucent over the course of three weeks of intermittent observation. This TSCW preparation is far more immunologically inert with respect to microglial activation than open craniotomy or repeated skull thinning and allows an arbitrary number of imaging sessions during a time period of weeks. We prepare TSCW in CX3CR1 GFP/+ mice 4 to visualize microglia with enhanced green fluorescent protein to &le;150 &mu;m beneath the pial surface. We also show that this preparation can be used in conjunction with stereotactic brain injections of the HIV-1 neurotoxic protein Tat, adjacent to the TSCW, which is capable of inducing durable microgliosis. Therefore, this method is extremely useful for examining changes in microglial morphology and motility over time in the living brain in models of HIV Associated Neurocognitive Disorder (HAND) and other neurodegenerative diseases with a neuroinflammatory component.

A Thin-skull Window Technique for Chronic Two-photon In vivo Imaging of Murine Microglia in Models of Neuroinflammation

We describe a method for repeatedly visualizing murine microglia and circulating monocytes in vivo over hours, days or weeks using transcranial two-photon microscopy. We demonstrate how to prepare a thinned-skull window that allows intermittent observation of quiescent microglia that can be activated by adjacent stereotactic injection of the HIV-1 regulatory protein Tat.

Traditionally in neuroscience, in vivo two photon imaging of the murine central nervous system has either involved the use of open-skull1,2 or ...

Intravital Microscopy of the Mouse Brain Microcirculation using a Closed Cranial Window

This experimental model was designed to assess the mouse pial microcirculation during acute and chronic, physiological and pathophysiological hemodynamic, inflammatory and metabolic conditions, using in vivo fluorescence microscopy. A closed cranial window is placed over the left parieto-occipital cortex of the mice. Local microcirculation is recorded in real time through the window using epi and fluorescence illumination, and measurements of vessels diameters and red blood cell (RBC) velocities are performed. RBC velocity is measured using real-time cross-correlation and/or fluorescent-labeled erythrocytes. Leukocyte and platelet adherence to pial vessels and assessment of perfusion and vascular leakage are made with the help of fluorescence-labeled markers such as Albumin-FITC and anti-CD45-TxR antibodies. Microcirculation can be repeatedly video-recorded over several days. We used for the first time the close window brain intravital microscopy to study the pial microcirculation to follow dynamic changes during the course of Plasmodium berghei ANKA infection in mice and show that expression of CM is associated with microcirculatory dysfunctions characterized by vasoconstriction, profound decrease in blood flow and eventually vascular collapse.

Intravital microscopy to follow temporal and spatial hemodynamic and inflammatory events in the pial microcirculation.

This experimental model was designed to assess the mouse pial microcirculation during acute and chronic, physiological and pathophysiological hemodynamic, ...

Lateral Fluid Percussion: Model of Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes 1,2. Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement 3,4. The resulting hematomas and lacerations cause a vascular response 3,5, and the morphological and functional damage of the white matter leads to diffuse axonal injury 6-8. Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure 9. Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals 10-12, which ultimately result in long-term neurological disabilities 13,14. Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair.
Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration 1. The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue 1,15. Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure 16,17. The weight drop/impact model is characterized by the fall of a rod with a specific mass on the closed skull 18. Among the TBI models, LFP is the most established and commonly used model to evaluate mixed focal and diffuse brain injury 19. It is reproducible and is standardized to allow for the manipulation of injury parameters. LFP recapitulates injuries observed in humans, thus rendering it clinically relevant, and allows for exploration of novel therapeutics for clinical translation 20.
We describe the detailed protocol to perform LFP procedure in mice. The injury inflicted is mild to moderate, with brain regions such as cortex, hippocampus and corpus callosum being most vulnerable. Hippocampal and motor learning tasks are explored following LFP.

Lateral fluid percussion (LFP), an established model of traumatic brain injury in mice, is demonstrated. LFP fulfills three major criteria for animal models: validity, reliability and clinical relevance. The procedure, consisting of surgical craniotomy, fixation of hub followed by induction of injury, resulting in focal and diffuse injuries, is described.

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and ...

Intravital Imaging of Axonal Interactions with Microglia and Macrophages in a Mouse Dorsal Column Crush Injury

Traumatic spinal cord injury causes an inflammatory reaction involving blood-derived macrophages and central nervous system (CNS)-resident microglia. Intra-vital two-photon microscopy enables the study of macrophages and microglia in the spinal cord lesion in the living animal. This can be performed in adult animals with a traumatic injury to the dorsal column. Here, we describe methods for distinguishing macrophages from microglia in the CNS using an irradiation bone marrow chimera to obtain animals in which only macrophages or microglia are labeled with a genetically encoded green fluorescent protein. We also describe a injury model that crushes the dorsal column of the spinal cord, thereby producing a simple, easily accessible, rectangular lesion that is easily visualized in an animal through a laminectomy. Furthermore, we will outline procedures to sequentially image the animals at the anatomical site of injury for the study of cellular interactions during the first few days to weeks after injury.

Two-photon intravital imaging can be used to investigate interactions among different cell types in the spinal cord in their native tissue environment in a bone marrow chimeric animal with a dorsal column traumatic spinal cord crush injury.

Traumatic spinal cord injury causes an inflammatory reaction involving blood-derived macrophages and central nervous system (CNS)-resident microglia. ...

A Method to Inflict Closed Head Traumatic Brain Injury in Drosophila

Traumatic brain injury (TBI) affects millions of people each year, causing impairment of physical, cognitive, and behavioral functions and death. Studies using Drosophila have contributed important breakthroughs in understanding neurological processes. Thus, with the goal of understanding the cellular and molecular basis of TBI pathologies in humans, we developed the High Impact Trauma (HIT) device to inflict closed head TBI in flies. Flies subjected to the HIT device display phenotypes consistent with human TBI such as temporary incapacitation and progressive neurodegeneration. The HIT device uses a spring-based mechanism to propel flies against the wall of a vial, causing mechanical damage to the fly brain. The device is inexpensive and easy to construct, its operation is simple and rapid, and it produces reproducible results. Consequently, the HIT device can be combined with existing experimental tools and techniques for flies to address fundamental questions about TBI that can lead to the development of diagnostics and treatments for TBI. In particular, the HIT device can be used to perform large-scale genetic screens to understand the genetic basis of TBI pathologies.

A Method to Inflict Closed Head Traumatic Brain Injury in Drosophila

Here we describe a method to inflict closed head traumatic brain injury (TBI) in Drosophila. This method provides a gateway to investigate the cellular and molecular mechanisms that underlie TBI pathologies using the vast array of experimental tools and techniques available for flies.

Traumatic brain injury (TBI) affects millions of people each year, causing impairment of physical, cognitive, and behavioral functions and death. Studies ...

Two-photon Calcium Imaging in Neuronal Dendrites in Brain Slices

Calcium (Ca2+) imaging is a powerful tool to investigate the spatiotemporal dynamics of intracellular Ca2+ signals in neuronal dendrites. Ca2+ fluctuations can occur through a variety of membrane and intracellular mechanisms and play a crucial role in the induction of synaptic plasticity and regulation of dendritic excitability. Hence, the ability to record different types of Ca2+ signals in dendritic branches is valuable for groups studying how dendrites integrate information. The advent of two-photon microscopy has made such studies significantly easier by solving the problems inherent to imaging in live tissue, such as light scattering and photodamage. Moreover, through combination of conventional electrophysiological techniques with two-photon Ca2+ imaging, it is possible to investigate local Ca2+ fluctuations in neuronal dendrites in parallel with recordings of synaptic activity in soma. Here, we describe how to use this method to study the dynamics of local Ca2+ transients (CaTs) in dendrites of GABAergic inhibitory interneurons. The method can be also applied to studying dendritic Ca2+ signaling in different neuronal types in acute brain slices.

We present a method combining whole-cell patch-clamp recordings and two-photon imaging to record Ca2+ transients in neuronal dendrites in acute brain slices.

Calcium (Ca2+) imaging is a powerful tool to investigate the spatiotemporal dynamics of intracellular Ca2+ signals in neuronal dendrites. Ca2+ ...

A Novel In Vitro Model of Blast Traumatic Brain Injury

Traumatic brain injury is a leading cause of death and disability in military and civilian populations. Blast traumatic brain injury results from the detonation of explosive devices, however, the mechanisms that underlie the brain damage resulting from blast overpressure exposure are not entirely understood and are believed to be unique to this type of brain injury. Preclinical models are crucial tools that contribute to better understand blast-induced brain injury. A novel in vitro blast TBI model was developed using an open-ended shock tube to simulate real-life open-field blast waves modelled by the Friedlander waveform. C57BL/6N mouse organotypic hippocampal slice cultures were exposed to single shock waves and the development of injury was characterized up to 72 h using propidium iodide, a well-established fluorescent marker of cell damage that only penetrates cells with compromised cellular membranes. Propidium iodide fluorescence was significantly higher in the slices exposed to a blast wave when compared with sham slices throughout the duration of the protocol. The brain tissue injury is very reproducible and proportional to the peak overpressure of the shock wave applied.

A Novel In Vitro Model of Blast Traumatic Brain Injury

This paper describes a novel model of primary blast traumatic brain injury. A compressed-air driven shock tube is used to expose in vitro mouse hippocampal slice cultures to a single shock wave. This is a simple and rapid protocol generating a reproducible brain tissue injury with a high throughput.

Traumatic brain injury is a leading cause of death and disability in military and civilian populations. Blast traumatic brain injury results from the ...

Effects of Blast-induced Neurotrauma on Pressurized Rodent Middle Cerebral Arteries

Though there have been studies on the histopathological and behavioral effects of blast exposure, fewer have been dedicated to blast&#39;s cerebral vascular effects. Impact (i.e., non-blast) traumatic brain injury (TBI) is known to decrease pressure autoregulation in the cerebral vasculature in both humans and experimental animals. The hypothesis that blast-induced traumatic brain injury (bTBI), like impact TBI, results in impaired cerebral vascular reactivity was tested by measuring myogenic dilatory responses to reduced intravascular pressure in rodent middle cerebral arterial (MCA) segments from rats subjected to mild bTBI using an Advanced Blast Simulator (ABS) shock tube. Adult, male Sprague-Dawley rats were anesthetized, intubated, ventilated and prepared for Sham bTBI (identical manipulation and anesthesia except for blast injury) or mild bTBI. Rats were randomly assigned to receive Sham bTBI or mild bTBI followed by sacrifice 30 or 60 min post-injury. Immediately after bTBI, righting reflex (RR) suppression times were assessed, euthanasia at the time points post-injury was completed, the brain was harvested and the individual MCA segments were collected, mounted and pressurized. As the intraluminal pressure perfused through the arterial segments was reduced in 20 mmHg increments from 100 to 20 mmHg, MCA diameters were measured and recorded. With decreasing intraluminal pressure, MCA diameters steadily increased significantly above baseline in the Sham bTBI groups while MCA dilator responses were significantly reduced (p &#60; 0.05) in both bTBI groups as evidenced by the impaired, smaller MCA diameters recorded for the bTBI groups. In addition, RR suppression in the bTBI groups was significantly (p &#60; 0.05) higher than in the Sham bTBI groups. MCA&#39;s collected from the Sham bTBI groups exhibited typical vasodilatory properties to decreases in intraluminal pressure while MCA&#39;s collected following bTBI exhibited significantly impaired myogenic vasodilatory responses to reduced pressure that persisted for at least 60 min after bTBI.

Here, we present a protocol to describe methods for ex vivo vascular reactivity determination following a primary blast traumatic brain injury (bTBI) using isolated, pressurized, rodent middle cerebral arterial (MCA) segments. bTBI induction is accomplished using a shock tube, also known as an Advanced Blast Simulator (ABS) device.

Though there have been studies on the histopathological and behavioral effects of blast exposure, fewer have been dedicated to blast&#39;s cerebral ...

Investigating Alterations in Caecum Microbiota After Traumatic Brain Injury in Mice

Increasing evidence shows that the microbiota-gut-brain axis plays an important role in the pathogenesis of brain diseases. Several studies also demonstrate that traumatic brain injuries cause changes to the gut microbiota. However, mechanisms underlying the bidirectional regulation of the brain-gut axis remain unknown. Currently, few models exist for studying the changes in gut microbiota after traumatic brain injury. Therefore, the presented study combines protocols for inducing traumatic brain injury using a lateral fluid percussion device and analysis of caecum samples following injury for investigating alterations in the gut microbiome. Alterations of the gut microbiota composition after traumatic brain injury are determined using 16S-rDNA sequencing. This protocol provides an effective method for studying the relationships between enteric microorganisms and traumatic brain injury.

Presented here is a protocol to induce diffuse traumatic brain injury using a lateral fluid percussion device followed by the collection of the caecum content for gut microbiome analysis.

Increasing evidence shows that the microbiota-gut-brain axis plays an important role in the pathogenesis of brain diseases. Several studies also ...

Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. Despite their importance, technologies for tracking neuromodulatory events with cellular resolution are just beginning to emerge. Neuromodulators, such as dopamine, norepinephrine, acetylcholine, and serotonin, trigger intracellular signaling events via their respective G protein-coupled receptors to modulate neuronal excitability, synaptic communications, and other neuronal functions, thereby regulating information processing in the neuronal network. The above mentioned neuromodulators converge onto the cAMP/protein kinase A (PKA) pathway. Therefore, in vivo PKA imaging with single-cell resolution was developed as a readout for neuromodulatory events in a manner analogous to calcium imaging for neuronal electrical activities. Herein, a method is presented to visualize PKA activity at the level of individual neurons in the cortex of head-fixed behaving mice. To do so, an improved A-kinase activity reporter (AKAR), called tAKAR&#945;, is used, which is based on F&#246;rster resonance energy transfer (FRET). This genetically-encoded PKA sensor is introduced into the motor cortex via in utero electroporation (IUE) of DNA plasmids, or stereotaxic injection of adeno-associated virus (AAV). FRET changes are imaged using two-photon fluorescence lifetime imaging microscopy (2pFLIM), which offers advantages over ratiometric FRET measurements for quantifying FRET signal in light-scattering brain tissue. To study PKA activities during enforced locomotion, tAKAR&#945; is imaged through a chronic cranial window above the cortex of awake, head-fixed mice, which run or rest on a speed-controlled motorized treadmill. This imaging approach will be applicable to many other brain regions to study corresponding behavior-induced PKA activities and to other FLIM-based sensors for in vivo imaging.

A procedure is presented to visualize protein kinase A activities in head-fixed, behaving mice. An improved A-kinase activity reporter, tAKAR&#945;, is expressed in cortical neurons and made accessible for imaging through a cranial window. Two-photon fluorescence lifetime imaging microscopy is used to visualize PKA activities in vivo during enforced locomotion.

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. ...