Name: a benchtop approach to the location specific blood brain barrier opening using focused ultrasound in a rat model
Uploaded: 2020-06-13T12:30:00
Description: Watch this Scientific Journal Video about A Benchtop Approach to the Location Specific Blood Brain Barrier Opening using Focused Ultrasound in a Rat Model at JoVE.com

This research was supported in part by an NSF EPSCoR Research Infrastructure grant to Clemson University (1632881). In addition, this research was supported in part by the Civitan International Research Center, Birmingham, AL. The authors gratefully acknowledge the use of the services and facilities of the University of Alabama at Birmingham Small Animal Imaging Shared Facility Grant [NIH P30 CA013148]. The authors acknowledge Rajiv Chopra for his support and guidance.

All experimental procedures were done in accordance with UAB Institutional Animal Care and Use Committee (IACUC) guidelines.
1. Focused ultrasound driving equipment setup
<ol>
	<li>Use 50 Ohm coaxial BNC cables to connect (1) the input of the ultrasound transducer to the output of the RF amplifier and (2) the input of the RF amplifier to the output of the function generator.</li>
	<li>Set the function generator mode to a sinusoid burst once per second with a 1% duty cycle.
	<ol>
		<li>For th...

Here we described a benchtop approach to microbubble assisted FUS BBB opening with alternative approaches including, two different transducers and methods for intracranial targeting with and without MRI guidance. Currently, in order to establish MRI-guided FUS BBB opening in the lab, there is the option to purchase excellent ready-to use devices that provide highly standardized and reproducible results with user-friendly interfaces. However, many labs are not prepared for the cost of such instruments. Therefore, the main...

Despite the many discoveries in basic neuroscience, the number of emerging treatments for neurodevelopmental and neurodegenerative disorders remains relatively limited1,2. A deeper understanding of the genes, molecules and cellular circuitry involved in neurological disorders has suggested promising treatments unrealizable in humans with current techniques3. Effective treatments are often limited by the need to be brain penetrable and site-specific4,5,6,7,8. However, existing methods of localized drug delivery to specific brain regions (e.g., delivery via injection or cannula) are invasive and require an opening to be made in the skull9. The invasiveness of this surgery prevents the routine use of localized delivery into the human brain. Additionally, tissue damage and the resulting inflammatory responses are ubiquitous confounds for basic and preclinical studies that rely on intracerebral injection10. The ability to noninvasively deliver agents across the blood brain barrier (BBB) and target them to specific brain regions could have a tremendous impact on treatments for neurological disorders, while simultaneously providing a powerful investigational tool for preclinical research.
One method of targeted transport across the BBB with minimal tissue damage is transcranial focused ultrasound (FUS) together with microbubbles to focally and transiently open the BBB11,12,13,14,15,16. FUS BBB opening has gained recent attention for the treatment of neurodegenerative disorders, stroke and glioma by localizing therapeutics to target brain regions such as neurotrophic factors17,18,19, gene therapies20,21,22, antibodies23, neurotransmitters24, and nanoparticles25,26,27,28,29. With its wide range of applications and its noninvasive nature30,31, FUS BBB opening is an ideal alternative to routine stereotaxic intracranial injections. Furthermore, due to its current use in humans30,32, preclinical investigations using this technique can be considered highly translational. However, FUS BBB opening has yet to be a widely established technique in basic science and preclinical research due to lack of accessibility. Therefore, we provide a detailed protocol for a benchtop approach to FUS BBB opening as a starting point for labs interested in establishing this technique.
These studies were conducted with either a high-power air backed FUS specific ultrasound transducer or a low power damped focused ultrasonic immersion transducer. The transducers were driven by an RF power amplifier designed for reactive loads and a standard benchtop function generator. Details for these items can be found in the Table of Materials.

<table border="0" cellpadding="0" cellspacing="0" style="width:1437px;" width="1437">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Bubble shaker</td>
			<td style="width:240px;">Lantheus Medical Imaging</td>
			<td style="width:197px;">VMIX</td>
			<td style="width:729px;">VIALMIX, actiation device used to activate Definity microbubbles</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Catheter plug/ Injection cap</td>
			<td>SAI infusion technologies</td>
			<td>Part Number: IC</td>
			<td style="width:729px;">Catheter plug/ Injection cap</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Evans blue dye</td>
			<td style="width:240px;">Sigma</td>
			<td style="width:197px;">E2129-10G</td>
			<td style="width:729px;">Evans blue dye</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Function generator</td>
			<td style="width:240px;">Tektronix</td>
			<td style="width:197px;">AFG3022B</td>
			<td>Dual channel, 250MS/s, 25MHz</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FUS transducer, 1.1MHz</td>
			<td style="width:240px;">FUS Instruments</td>
			<td>TX-110</td>
			<td>1 MHz MRI-compatible spherically focused ultrasound transducer with a hydrophone</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Heating pad for Mice and Rats</td>
			<td style="width:240px;">Kent Scientific</td>
			<td style="width:197px;">PS-03</td>
			<td>Heating pad- PhysioSuite for Mice and Rats</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Infusion pump</td>
			<td style="width:240px;">KD Scientific</td>
			<td style="width:197px;">780100</td>
			<td>KDS 100 Legacy Single Syringe Infusion Pump</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Kapton tape</td>
			<td style="width:240px;">Gizmo Dorks</td>
			<td>https://www.amazon.com/dp/B01N1GGKRC/ 
			ref=cm_sw_em_r_mt_dp_U_GbR7Db56HKD91</td>
			<td>Gizmo Dorks Kapton Tape (Polyimide) for 3D Printers and Printing, 8 x 8 inches, 10 Sheets per Pack</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Low power immersion transducer, 1MHz</td>
			<td style="width:240px;">Olympus</td>
			<td>V303-SU</td>
			<td>Immersion Transducer, 1 MHz, 0.50 in. Element Diameter, Standard Case Style, Straight UHF Connector, F=0.80IN PTF</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Magnet sets</td>
			<td style="width:240px;">WINOMO</td>
			<td>https://www.amazon.com/dp/B01DJZQJBG/ 
			ref=cm_sw_em_r_mt_dp_U_JYQ7DbM32E5QC</td>
			<td>WINOMO 15mm Sew In Magnetic Bag Clasps for Sewing Scrapbooking - 10 Sets</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RF amplifier</td>
			<td style="width:240px;">E&#38;I</td>
			<td style="width:197px;">A075</td>
			<td>75W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Tail vein catheter</td>
			<td style="width:240px;">BD</td>
			<td>382512/ Fisher Item: NC1228513</td>
			<td>24g BD Insyte Autoguard shielded IV catheters (non-winged)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Ultrasound contrast microbubbles</td>
			<td>Lantheus Medical Imaging</td>
			<td style="width:197px;">DE4, DE16</td>
			<td>DEFINITY (Perflutren Lipid Microsphere)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Ultrasound gel</td>
			<td style="width:240px;">Aquasonic</td>
			<td>https://www.amazon.com/dp/B07FPQDM4F/ 
			ref=cm_sw_em_r_mt_dp_U_D6Q7Db3J9QP7P</td>
			<td>Ultrasound Gel Aquasonic 100 Transmission 1 Liter Squeeze Bottle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Winged infusion sets, 22ga.</td>
			<td style="width:240px;">Fisher Healthcare</td>
			<td>22-258087</td>
			<td>Terumo Surflo Winged Infusion Sets</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">motor controller software</td>
			<td style="width:240px;">N/A</td>
			<td>N/A</td>
			<td style="width:729px;">custom software written in LabView for controlling the Velmex motor controller</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">runtime environment for the motor controller software</td>
			<td style="width:240px;">National Instruments</td>
			<td>LabView runtime engine version 2017 or better</td>
			<td>https://www.ni.com/en-us/support/downloads/software-products/download.labview.html</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">3 axis Linear stage actuator (XYZ positioner)</td>
			<td style="width:240px;">Velmex</td>
			<td style="width:197px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">bolts</td>
			<td style="width:240px;">Velmex</td>
			<td>MB-1</td>
			<td>BiSlide Bolt 1/4-20x3/4&#34; Socket cap screw (10 pack), Qty:3</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">motor controller</td>
			<td style="width:240px;">Velmex</td>
			<td>VXM-3</td>
			<td style="width:729px;">Control,3 axis programmable stepping motor control, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mounting cleats</td>
			<td style="width:240px;">Velmex</td>
			<td>MC-2</td>
			<td>Cleat, 2 hole BiSlide, Qty:6</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mounting cleats</td>
			<td style="width:240px;">Velmex</td>
			<td>MC-2</td>
			<td style="width:729px;">Cleat, 2 hole BiSlide, Qty:2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">usb to serial converter</td>
			<td style="width:240px;">Velmex</td>
			<td>VXM-USB-RS232</td>
			<td style="width:729px;">USB to RS232 Serial Communication Cable 10ft, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">x-axis linear stage</td>
			<td style="width:240px;">Velmex</td>
			<td>MN10-0100-M02-21</td>
			<td style="width:729px;">BiSlide, travel=10 inch, 2 mm/rev, limits, NEMA 23, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">x-axis stepper motor</td>
			<td style="width:240px;">Velmex</td>
			<td>PK266-03A-P1</td>
			<td>Vexta Type 23T2, Single Shaft Stepper Motor, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">y-axis linear stage</td>
			<td style="width:240px;">Velmex</td>
			<td>MN10-0100-M02-21</td>
			<td>BiSlide, travel=10 inch, 2 mm/rev, limits, NEMA 23, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">y-axis stepper motor</td>
			<td style="width:240px;">Velmex</td>
			<td>PK266-03A-P1</td>
			<td style="width:729px;">Vexta Type 23T2, Single Shaft Stepper Motor, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">z-axis damper</td>
			<td style="width:240px;">Velmex</td>
			<td>D6CL-6.3F</td>
			<td style="width:729px;">D6CL Damper for Type 23 Double Shaft Stepper Motor, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">z-axis linear stage</td>
			<td style="width:240px;">Velmex</td>
			<td>MN10-0100-M02-21</td>
			<td style="width:729px;">BiSlide, travel=10 inch, 2 mm/rev, limits, NEMA 23, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">z-axis stepper motor</td>
			<td style="width:240px;">Velmex</td>
			<td>PK266-03B-P2</td>
			<td style="width:729px;">Vexta Type 23T2, Double Shaft Stepper Motor, Qty:1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">3D printable files</td>
			<td style="width:240px;"></td>
			<td style="width:197px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Immersion transducer mount and pointer</td>
			<td></td>
			<td style="width:197px;"></td>
			<td>https://www.tinkercad.com/things/cRgTthGXSRq</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Stereotaxic frame</td>
			<td></td>
			<td style="width:197px;"></td>
			<td>https://www.tinkercad.com/things/ilynoQcdqlH</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Stereotaxic frame holder</td>
			<td></td>
			<td style="width:197px;"></td>
			<td>https://www.tinkercad.com/things/aZNgqhBOHAX</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">9.4T small bore animal MRI</td>
			<td style="width:240px;">Bruker</td>
			<td style="width:197px;">Bruker BioSpec 94/20</td>
			<td>ParaVision version 5.1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">AAV9-hsyn-GFP</td>
			<td style="width:240px;">Addgene</td>
			<td style="width:197px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Cream hair remover</td>
			<td style="width:240px;">Church &#38; Dwight</td>
			<td style="width:197px;"></td>
			<td>Nair cream</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">gadobutrol MRI contrast agent</td>
			<td style="width:240px;">Bayer</td>
			<td style="width:197px;"></td>
			<td>Gadavist (Gadobutrol, 1mM/mL)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Stereotactic frame</td>
			<td style="width:240px;">Stoelting</td>
			<td style="width:197px;">#51500</td>
			<td>not MRI compatible</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">turnkey FUS delivery device</td>
			<td style="width:240px;">FUS Instruments</td>
			<td style="width:197px;">RK-300</td>
			<td style="width:729px;">ready to use MRI compatible FUS for rodents</td>
		</tr>
	</tbody>
</table>

a benchtop approach to the location specific blood brain barrier opening using focused ultrasound in a rat model

Stereotaxic surgery is the gold standard for localized drug and gene delivery to the rodent brain. This technique has many advantages over systemic delivery including precise localization to a target brain region and reduction of off target side effects. However, stereotaxic surgery is highly invasive which limits its translational efficacy, requires long recovery times, and provides challenges when targeting multiple brain regions. Focused ultrasound (FUS) can be used in combination with circulating microbubbles to transiently open the blood brain barrier (BBB) in millimeter sized regions. This allows intracranial localization of systemically delivered agents that cannot normally cross the BBB. This technique provides a noninvasive alternative to stereotaxic surgery. However, to date this technique has yet to be widely adopted in neuroscience laboratories due to the limited access to equipment and standardized methods. The overall goal of this protocol is to provide a benchtop approach to FUS BBB opening (BBBO) that is affordable and reproducible and can therefore be easily adopted by any laboratory.

Here, we demonstrate that focused ultrasound with microbubbles can induce localized BBB opening using the parameters specified above with both the low-power immersion transducer (Figure 3) and the FUS transducer (Figure 4). First, in early experiments, the low-power immersion transducer was targeted to one brain hemisphere either anterior (Figure 3b) or medial (Figure 3a). Animals were then sacrificed 2...

Watch this Scientific Journal Video about A Benchtop Approach to the Location Specific Blood Brain Barrier Opening using Focused Ultrasound in a Rat Model at JoVE.com

A Benchtop Approach to the Location Specific Blood Brain Barrier Opening using Focused Ultrasound in a Rat Model

Focused ultrasound with microbubble agents can open the blood brain barrier focally and transiently. This technique has been used to deliver a wide range of agents across the blood brain barrier. This article provides a detailed protocol for the localized delivery to the rodent brain with or without MRI guidance.

Stereotaxic surgery is the gold standard for localized drug and gene delivery to the rodent brain. This technique has many advantages over systemic ...

Focused Ultrasound in combination with circulating micro-bubbles can be used to provide temporary millimeter size openings in the blood-brain barrier. This enables non-invasive delivery of systemically circulating agents to target brain regions. To begin, fill the catheter plug with saline and warm the rat's tail with a lamp, taking care not to overheat the animal.Insert a 24 gauge tail vein catheter that will be used to deliver micro-bubbles, Evans blue dye, gadobutrol MRI contrast if using MRI, and the experimental agent of interest. Blood will fill the sheath when the vein is hit. Slowly, remove the inner needle while pushing the sheath further into the vein.Screw the catheter plug into the end of the catheter port, as soon as the port has filled with blood. Carefully wrap lab tape around the catheter and the tail to keep it in place, starting with a small piece at the top and working in the caudal direction. Leave the very end of the catheter plug exposed.Plug the anesthesia line onto the anesthesia connector on the stereotactic frame. Then fix the animal's head into the frame by placing the mouth onto the bite bar, and by guiding the ear bars into both ear canals and tightening the set screws. Move the animal to the MRI bed.Using parameters described in the text manuscript collect coronal and axial T2 weighted images that capture the whole brain as well as the MRI fiducial for coordinate measurements. On the coronal images, find the image in which the fiducial is the largest, indicating the center of the fiducial. Record the distance from the top of the fiducial to the brain region of interest in millimeters, in both the medial-lateral direction and in the dorsal-ventral direction.On the axial images, find the image that shows the very top of the fiducial and record the X and Y coordinates for the center of the fiducial and the X and Y coordinates of the brain region of interest. Calculate the distance from the center of the fiducial to the target brain region in both the rostral-caudal and medial-lateral directions. After gathering the coordinates, collect the pre-scan images.Keeping the animal in this stereotaxic frame, quickly transport it from the MRI bed to the bench top FUS set up. Ensure that the animal remains asleep under the effect of anesthesia. Slide the frame into the frame holder and firmly snap it into place.Use clippers to shave the animal's head, then brush away excess hair and apply hair remover cream to the scalp. Let it sit for three minutes and wipe it away with water and gauze. If using MRI guidance, attach the pointer and move the pointer to the location of the MRI fiducial.Position the pointer at the very top and center of the MRI fiducial then, which is the point from which all distances in the MRI image were calculated. Remove the pointer and move the positioner to the medial-lateral coordinates and the rostral-caudal coordinates. Lick the null position button and raise the positioner up by pressing the up 50 button, to allow for the placement of the water bath and ultrasound gel.Apply ultrasound gel to the animal's scalp and place the water bath over the animal, with the polyimide tape window pressed onto the gel, making sure that there are no air bubbles in the gel. Fill the water bath with degassed water. If using the high power transducer, lower the positioner so that the magnet is just above the water.Attach the transducer to the positioner by carefully lowering the transducer into the water at an angle and connecting the magnets. Lower the positioner to the dorsal-ventral coordinate and turn on the RF power amp. Inject one milliliter per kilogram of 3%Evans blue dye by sticking a needle tip into the catheter plug and injecting.The whole animal should become blue within seconds, indicating the catheter is properly positioned in the tail vein. Allow the dye to circulate for five minutes, then activate the micro-bubbles by shaking them violently with the bubble shaker. Invert this syringe several times to get a uniform distribution of micro-bubbles, then attach and fill the winged infusion set.Position the syringe on the infusion pump and set the infusion pump to deliver 0.2 milliliters at a rate of six milliliters per hour, providing slow infusion of the micro-bubbles over the two minute FUS exposure. Insert the winged needle into the catheter plug. First run the infusion pump, wait three seconds, then start the FUS treatment by pressing the on button and on the function generator.Repeat this twice per region with five minutes in between to allow the micro-bubbles to clear. Press the on button on the function generator again to stop the FUS treatment when the infusion pump stops at two minutes. Wait for five minutes for the micro bubbles to clear, then start the infusion and the second FUS treatment.Immediately after the second FUS treatment, inject gadobutrol contrast and the agent of interest. Total delivered volume of all agents should not exceed five milliliters per kilogram. To confirm BBB opening, place the animal back onto the MRI bed at the exact same location and plug in the anesthesia line.Collect MRI post-scans with the same imaging parameters as the pre-scan images to confirm gadobutrol MRI enhancement in the region of BBB opening. This protocol was used to induce localized blood-brain barrier opening with both the low power immersion transducer and the high power focused ultrasound transducer. First, the low power immersion transducer was targeted to either the anterior or medial brain hemisphere.The animals were sacrificed with or without perfusion, and the BBB opening was visualized via Evans blue dye auto-fluorescence. In later experiments, the FUS transducer was targeted to either the hippocampus or the anterior cingulate cortex. In addition to Evans blue dye, the MRI contrast agent gadobutrol was used to verify the targeted opening of the BBB in VIVO.After the animals were sacrificed, Evans blue dye auto-fluorescence confirmed the opening location. To assess whether this technique could be used for targeted gene delivery, AAV nine expressing green fluorescent protein and gadobutrol contrast were injected immediately after blood brain barrier opening in the hippocampus. The animal was imaged to verify the opening with gadobutrol contrast.Then, gene delivery was confirmed by GFP expression. This protocol offers a bench-top approach to MRI guided Focus Ultrasound mediated blood-brain barrier opening, that can be easily adapted by other laboratories to provide a non-invasive translational alternative to stereotactic surgery.

a-benchtop-approach-to-location-specific-blood-brain-barrier-opening

Research

JoVE Journal

Neuroscience

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

Stereotaxic Surgery for Excitotoxic Lesion of Specific Brain Areas in the Adult Rat

Many behavioral functions in mammals, including rodents and humans, are mediated principally by discrete brain regions. A common method for discerning the function of various brain regions for behavior or other experimental outcomes is to implement a localized ablation of function. In humans, patient populations with localized brain lesions are often studied for deficits, in hopes of revealing the underlying function of the damaged area. In rodents, one can experimentally induce lesions of specific brain regions.
Lesion can be accomplished in several ways. Electrolytic lesions can cause localized damage but will damage a variety of cell types as well as traversing fibers from other brain regions that happen to be near the lesion site. Inducible genetic techniques using cell-type specific promoters may also enable site-specific targeting. These techniques are complex and not always practical depending on the target brain area. Excitotoxic lesion using stereotaxic surgery, by contrast, is one of the most reliable and practical methods of lesioning excitatory neurons without damaging local glial cells or traversing fibers.
Here, we present a protocol for stereotaxic infusion of the excitotoxin, N-methyl-D-aspartate (NMDA), into the basolateral amygdala complex. Using anatomical indications, we apply stereotaxic coordinates to determine the location of our target brain region and lower an injection needle in place just above the target. We then infuse our excitotoxin into the brain, resulting in excitotoxic death of nearby neurons. While our experimental subject of choice is a rat, the same methods can be applied to other mammals, with the appropriate adjustments in equipment and coordinates.
This method can be used on a variety of brain regions, including the basolateral amygdala1-6, other amygdala nuclei6, 7, hippocampus8, entorhinal cortex9 and prefrontal cortex10. It can also be used to infuse biological compounds such as viral vectors1, 11. The basic stereotaxic technique could also be adapted for implantation of more permanent osmotic pumps, allowing more prolonged exposure to a compound of interest.

Targeted ablation of specific brain region(s) by infusion of an excitotoxin using stereotaxic coordinates is described. This technique could also be adapted for infusion of other chemicals into the rat brain.

Many behavioral functions in mammals, including rodents and humans, are mediated principally by discrete brain regions. A common method for discerning the ...

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

Ischemic stroke leads to vasogenic cerebral edema and subsequent primary brain injury, which is mediated through destruction of the blood-brain barrier (BBB). Rats with induced ischemic stroke were established and used as in vivo models to investigate the functional integrity of the BBB. Spectrophotometric detection of Evans blue (EB) in the brain samples with ischemic injury could provide reliable justification for the research and development of novel therapeutic modalities. This method generates reproducible results, and is applicable in any laboratory without a need for special equipment. Here, we present a visualized and technical guideline on the detection of the extravasation of EB following induction of ischemic stroke in rats.

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

The overall goal of this procedure is to provide a highly reproducible technique for in vivo assessment of the blood-brain barrier disruption in rat models of ischemic stroke.

Ischemic stroke leads to vasogenic cerebral edema and subsequent primary brain injury, which is mediated through destruction of the blood-brain barrier ...

An Alternative Approach to Study Primary Events in Neurodegeneration Using Ex Vivo Rat Brain Slices

Despite&#160;numerous studies that attempt to develop reliable animal models&#160;which reflecting the primary processes underlying neurodegeneration, very few have been widely accepted. Here, we propose&#160;a new procedure&#160;adapted from the well-known ex vivo brain slice technique, which offers a closer in vivo-like scenario than in vitro preparations, for investigating the early events triggering cell degeneration, as observed in Alzheimer&#39;s disease (AD). This variation consists of simple and easily reproducible steps, which enable preservation of the anatomical cytoarchitecture of the selected brain region and its local functionality in a physiological milieu. Different anatomical areas can be obtained from the same brain, providing the opportunity to perform multiple experiments with the treatments in question in a site-, dose-, and time-dependent manner. Potential limitations&#160;which could affect the outcomes related to this methodology are related to the conservation of the tissue, i.e., the maintenance of its anatomical integrity during the slicing and incubation steps and the section thickness, which can influence the biochemical and immunohistochemical analysis. This approach can be employed for different purposes, such as exploring molecular mechanisms involved in physiological or pathological conditions, drug screening, or dose-response assays. Finally, this protocol could also reduce the number of animals employed in behavioral studies. The application reported here has been recently described and tested for the first time on ex vivo rat brain slices containing the basal forebrain (BF), which is one of the cerebral regions primarily affected in AD. Specifically, it has been demonstrated that the administration of a toxic peptide derived from the C-terminus of acetylcholinesterase (AChE) could prompt an AD-like profile, triggering, along the antero-posterior axis of the BF, a differential expression of proteins altered in AD, such as the alpha7 nicotinic receptor (&#945;7-nAChR), phosphorylated Tau (p-Tau), and amyloid beta (A&#946;).

An Alternative Approach to Study Primary Events in Neurodegeneration Using Ex Vivo Rat Brain Slices

We present a method which can&#160;provide further insights into the early events underlying neurodegeneration and based on the established ex-vivo brain technique, combining the advantages of in vivo and in vitro experiments. Moreover, it represents a unique opportunity for direct comparison of treated and untreated group in the same anatomical plane.

Despite&#160;numerous studies that attempt to develop reliable animal models&#160;which reflecting the primary processes underlying neurodegeneration, ...

A Human Blood-Brain Interface Model to Study Barrier Crossings by Pathogens or Medicines and Their Interactions with the Brain

The early screening of nervous system medicines on a pertinent and reliable in cellulo BBB model for their penetration and their interaction with the barrier and the brain parenchyma is still an unmet need. To fill this gap, we designed a 2D in cellulo model, the BBB-Minibrain, by combining a polyester porous membrane culture insert human BBB model with a Minibrain formed by a tri-culture of human brain cells (neurons, astrocytes and microglial cells). The BBB-Minibrain allowed us to test the transport of a neuroprotective drug candidate (e.g., Neurovita), through the BBB, to determine the specific targeting of this molecule to neurons and to show that the neuroprotective property of the drug was preserved after the drug had crossed the BBB. We have also demonstrated that BBB-Minibrain constitutes an interesting model to detect the passage of virus particles across the endothelial cells barrier and to monitor the infection of the Minibrain by neuroinvasive virus particles. The BBB-Minibrain is a reliable system, easy to handle for researcher trained in cell culture technology and predictive of the brain cells phenotypes after treatment or insult. The interest of such in cellulo testing would be twofold: introducing derisking steps early in the drug development on the one hand and reducing the use of animal testing on the other hand.

Here we present a protocol describing the setting of an in cellulo BBB (Blood brain barrier)-Minibrain polyester porous membrane culture insert system in order to evaluate the transport of biomolecules or infectious agents across a human BBB and their physiological impact on the neighboring brain cells.

The early screening of nervous system medicines on a pertinent and reliable in cellulo BBB model for their penetration and their interaction with the ...

A High-Throughput Image-Guided Stereotactic Neuronavigation and Focused Ultrasound System for Blood-Brain Barrier Opening in Rodents

The blood-brain barrier (BBB) has been a major hurdle for the treatment of various brain diseases. Endothelial cells, connected by tight junctions, form a physiological barrier preventing large molecules (&#62;500 Da) from entering the brain tissue. Microbubble-mediated focused ultrasound (FUS) can be used to induce a transient local BBB opening, allowing larger drugs to enter the brain parenchyma.
In addition to large-scale clinical devices for clinical translation, preclinical research for therapy response assessment of drug candidates requires dedicated small animal ultrasound setups for targeted BBB opening. Preferably, these systems allow high-throughput workflows with both high-spatial precision as well as integrated cavitation monitoring, while still being cost effective in both initial investment and running costs.
Here, we present a bioluminescence and X-ray guided stereotactic small animal FUS system that is based on commercially available components and fulfills the aforementioned requirements. A particular emphasis has been placed on a high degree of automation facilitating the challenges typically encountered in high-volume preclinical drug evaluation studies. Examples of these challenges are the need for standardization in order to ensure data reproducibility, reduce intra-group variability, reduce sample size and thus comply with ethical requirements and decrease unnecessary workload. The proposed BBB system has been validated in the scope of BBB opening facilitated drug delivery trials on patient-derived xenograft models of glioblastoma multiforme and diffuse midline glioma.

The blood-brain barrier (BBB) can be temporarily disrupted with microbubble-mediated focused ultrasound (FUS). Here, we describe a step-by-step protocol for high-throughput BBB opening in vivo using a modular FUS system accessible for non-ultrasound experts.

The blood-brain barrier (BBB) has been a major hurdle for the treatment of various brain diseases. Endothelial cells, connected by tight junctions, form a ...

Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples

One of the most common causes of morbidity and mortality worldwide is ischemic stroke. Historically, an animal model used to stimulate ischemic stroke involves middle cerebral artery occlusion (MCAO). Infarct zone, brain edema and blood-brain barrier (BBB) breakdown are measured as parameters that reflect the extent of brain injury after MCAO. A significant limitation to this method is that these measurements are normally obtained in different rat brain samples, leading to ethical and financial burdens due to the large number of rats that need to be euthanized for an appropriate sample size. Here we present a method to accurately assess brain injury following MCAO by measuring infarct zone, brain edema and BBB permeability in the same set of rat brains. This novel technique provides a more efficient way to evaluate the pathophysiology of stroke.

This protocol describes a novel technique of measuring the three most important parameters of ischemic brain injury on the same set of rodent brain samples. Using only one brain sample is highly advantageous in terms of ethical and economic costs.

One of the most common causes of morbidity and mortality worldwide is ischemic stroke. Historically, an animal model used to stimulate ischemic stroke ...

Focused Ultrasound Induced Blood-Brain Barrier Opening for Targeting Brain Structures and Evaluating Chemogenetic Neuromodulation

Acoustically Targeted Chemogenetics (ATAC) allows for the noninvasive control of specific neural circuits. ATAC achieves such control through a combination of focused ultrasound (FUS) induced blood-brain barrier opening (FUS-BBBO), gene delivery with adeno-associated viral (AAV) vectors, and activation of cellular signaling with engineered, chemogenetic, protein receptors and their cognate ligands. With ATAC, it is possible to transduce both large and small brain regions with millimeter precision using a single noninvasive ultrasound application. This transduction can later allow for a long-term, noninvasive, device-free neuromodulation in freely moving animals using a drug. Since FUS-BBBO, AAVs, and chemogenetics have been used in multiple animals, ATAC should also be scalable for the use in other animal species. This paper expands upon a previously published protocol and outlines how to optimize the gene delivery with FUS-BBBO to small brain regions with MRI-guidance but without a need for a complicated MRI-compatible FUS device. The protocol, also, describes the design of mouse targeting and restraint components that can be 3D-printed by any lab and can be easily modified for different species or custom equipment. To aid reproducibility, the protocol describes in detail how the microbubbles, AAVs, and venipuncture were used in ATAC development. Finally, an example data is shown to guide the preliminary investigations of studies utilizing ATAC.

This protocol delineates steps necessary for the gene delivery through focused ultrasound blood brain barrier (BBB) opening, evaluation of the resulting gene expression, and measurement of neuromodulation activity of chemogenetic receptors through histological tests.

Acoustically Targeted Chemogenetics (ATAC) allows for the noninvasive control of specific neural circuits. ATAC achieves such control through a ...

Delivery of Antibodies into the Brain Using Focused Scanning Ultrasound

Only a small fraction of therapeutic antibodies targeting brain diseases are taken up by the brain. Focused ultrasound offers a possibility to increase uptake of antibodies and engagement through transient opening of the blood-brain barrier (BBB). In our laboratory, we are developing therapeutic approaches for neurodegenerative diseases in which an antibody in various formats is delivered across the BBB using microbubbles, concomitant with focused ultrasound application through the skull targeting multiple spots, an approach we refer to as scanning ultrasound (SUS). The mechanical effects of microbubbles and ultrasound on blood vessels increases paracellular transport across the BBB by transiently separating tight junctions and enhances vesicle- mediated transcytosis, allowing antibodies and therapeutic agents to effectively cross. Moreover, ultrasound also facilitates the uptake of antibodies from the interstitial brain into brain cells such as neurons where the antibody distributes throughout the cell body and even into neuritic processes. In our studies, fluorescently labeled antibodies are prepared, mixed with in-house prepared lipid-based microbubbles and injected into mice immediately before SUS is applied to the brain. The increased antibody concentration in the brain is then quantified. To account for alterations in normal brain homeostasis, microglial phagocytosis can be used as a cellular marker. The generated data suggest that ultrasound delivery of antibodies is an attractive approach to treat neurodegenerative diseases.

Presented here is a protocol to transiently open the blood-brain barrier (BBB) either focally or throughout a mouse brain to deliver fluorescently-labeled antibodies and activate microglia. Also presented is a method to detect the delivery of antibodies and microglia activation by histology.

Only a small fraction of therapeutic antibodies targeting brain diseases are taken up by the brain. Focused ultrasound offers a possibility to increase ...

A Rat Model of EcoHIV Brain Infection

It has been well studied that the EcoHIV infected mouse model is of significant utility in investigating HIV associated neurological complications. Establishment of the EcoHIV infected rat model for studies of drug abuse and neurocognitive disorders, would be beneficial in the study of neuroHIV and HIV-1 associated neurocognitive disorders (HAND). In the present study, we demonstrate the successful creation of a rat model of active HIV infection using chimeric HIV (EcoHIV). First, the lentiviral construct of EcoHIV was packaged in cultured 293 FT cells for 48 hours. Then, the conditional medium was concentrated and titered. Next, we performed bilateral stereotaxic injections of the EcoHIV-EGFP into F344/N rat brain tissue. One week after infection, EGFP fluorescence signals were detected in the infected brain tissue, indicating that EcoHIV successfully induces an active HIV infection in rats. In addition, immunostaining for the microglial cell marker, Iba1, was performed. The results indicated that microglia were the predominant cell type harboring EcoHIV. Furthermore, EcoHIV rats exhibited alterations in temporal processing, a potential underlying neurobehavioral mechanism of HAND as well as synaptic dysfunction eight weeks after infection. Collectively, the present study extends the EcoHIV model of HIV-1 infection to the rat offering a valuable biological system to study HIV-1 viral reservoirs in the brain as well as HAND and associated comorbidities such as drug abuse.

Here, we present a protocol to establish a new rat model of active HIV infection using chimeric HIV (EcoHIV), which is critical for enhancing our understanding of HIV-1 viral reservoirs in the brain and offering a system to study HIV-associated neurocognitive disorders and associated comorbidities (i.e., drug abuse).

It has been well studied that the EcoHIV infected mouse model is of significant utility in investigating HIV associated neurological complications. ...