We thank all our collaboration partners of the Immunostroke Consortia (FOR 2879, From immune cells to stroke recovery) for suggestions and discussions. This work was funded by the Deutsche Forschungsgemeinschaft (DFG,German Research Foundation) under Germany&#39;s Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy - ID 390857198) and under the grants LI-2534/6-1, LI-2534/7-1 and LL-112/1-1.

The experiments reported in this video were conducted according to the national guidelines for the use of experimental animals, and the protocols were approved by the German governmental committees (Regierung von Oberbayern, Munich, Germany). The mice used in this study were male C57Bl/6J mice, 10-12 weeks old, and dispatched by Charles River Germany. The animals were housed under controlled temperatures (22 &#176;C &#177; 2 &#176;C), with a 12 h light-dark cycle period and access to pelleted food and water ad libitum.
1. Preparation of the material and instruments
<ol>
	<li>Dissolve Rose Bengal in 0.9% saline solution to reach a final concentration of 10 mg/mL. Connect the heat blanket to keep the operation area warm and maintain the mouse body temperature during anesthesia at 37 &#176;C.</li>
	<li>Prepare scissors, forceps, pieces of cotton, dexpanthenol eye ointment, and suture material. Prepare a syringe with saline solution (without needle) to maintain the operation area hydrated. Prepare the anesthesia gas (100% O2 + isoflurane).</li>
</ol>
2. Preparation of the animal
<ol>
	<li>Inject analgesia 30 min before surgery (4 mg/kg Carprofen and 0.1 mg/kg Buprenorphine).</li>
	<li>Record the mouse body weight to adjust the dose of Rose Bengal to be injected (10 &#181;L/g i.e., 100 &#181;g/g).</li>
	<li>Place the mouse in the induction chamber with an isoflurane flow rate of 4% to anesthetize it until the spontaneous movement of the body and vibrissae stops.</li>
	<li>Transfer the mouse into the stereotactic frame and place it in a prone position with its nose into the anesthesia mask. Fix the animal and maintain the isoflurane concentration at 4% for 1 min. Then reduce and maintain the isoflurane concentration at 2%.</li>
	<li>Gently insert the rectal probe to monitor the temperature throughout the surgical procedures. Set the associated feedback-controlled heating pad to maintain the mouse body temperature at 37 &#176;C.</li>
	<li>Apply dexpanthenol eye ointment to both eyes and clean the skin and surrounding fur with a disinfectant agent.</li>
</ol>
3. Photothrombosis model
<ol>
	<li>Make a 2.0-2.5 cm longitudinal incision and retract to expose the skull. Perform the skull exposure with a single cut to avoid wound complications.</li>
	<li>Remove the periosteum gently with cotton and identify the coronal sutures.</li>
	<li>Put on the protective glasses, switch on the 561 nm laser and mark the bregma +3 mm left.</li>
	<li>Switch off the laser, attach a sticker with a 4 mm diameter hole placed at the marked coordinates mentioned above.</li>
	<li>Inject the mouse with Bengal Rose (10 &#181;L/g), intraperitoneally. Place the laser beam at 4-5 cm from the skull, switch on the 561 nm laser and illuminate the skull for 20 min.</li>
	<li>Apply two drops of 0.9% saline on&#160;the skull to rehydrate, suture the wound, and place the animal in a recovery chamber at 37 &#176;C to recover from anesthesia. After 1 h, return the mice to their cages in a temperature-controlled room.</li>
	<li>Inject analgesia every 12 h for 3 days after surgery (4 mg/kg Carprofen and 0.1 mg/kg Buprenorphine).</li>
</ol>
4. Sham operation
<ol>
	<li>Carry out two different procedures of Sham operations as described in steps 4.1.1 and 4.1.2.
	<ol>
		<li>Perform all the procedures identically to the operation described above. Inject Rose Bengal without switching on the laser. After 20 min under anesthesia, allow the animals to stay in the recovery chamber for 1 h to recover, before being returned to their cages.</li>
		<li>Perform all the procedures identically to the operation described above, switching on the laser. Do not inject Rose Bengal. After 20 min of laser illumination, allow the animals to stay in the recovery chamber for 1 h to recover from anesthesia, before being returned to their cages.</li>
	</ol>
	</li>
</ol>
5. Laser speckle
<ol>
	<li>Connect the heated blanket to keep the operation area warm and maintain the mouse body temperature during anesthesia at 37 &#176;C.</li>
	<li>Place the mouse into the induction chamber with an isoflurane flow rate of 4% to anesthetize it until the spontaneous movement of the body and vibrissae stops and then transfer the mouse into the stereotactic frame.</li>
	<li>Place the mouse in a prone position with its nose into the anesthesia mask. Fix the animal and maintain the isoflurane concentration at 4% for 1 min. T hen reduce and maintain it at 2%.</li>
	<li>Gently insert the rectal probe to monitor the temperature throughout the surgical procedures. Set the associated feedback-controlled heating pad to maintain the mouse body temperature at 37 &#176;C and apply dexpanthenol eye ointment to both eyes. Clean the skin and the surrounding fur with a disinfectant agent.</li>
	<li>Make a 2.0-2.5 cm longitudinal incision and retract to expose the skull. Perform the skull exposure with a single cut to avoid wound complications.</li>
	<li>Place the sterotactic frame under the laser speckle and adjust the height to obtain a sharp image. Focus the laser speckle perfusion imaging (LSI) camera on the cranial window. Configure the high resolution laser speckle imaging (LSI) camera system as previously described15.</li>
	<li>Acquire data from a 1 cm x 1 cm field of view using a 785 nm wavelength and 80 mW lasers with a frame rate of 21 images/s at a working distance of 1 cm for 1 min.</li>
	<li>After imaging, apply two drops of 0.9% saline to the skull to rehydrate, suture the wound and place the animal in a recovery chamber at 37 &#176;C to recover from anesthesia for 1 h. After 1 h, return the mice to their cages in a temperature-controlled room.</li>
</ol>
6. Neuroscore
NOTE: For the neurological deficit analysis, a modified neurological scale published by Eckenstein et al. in 1997 is used15.
<ol>
	<li>Score the animals for general (Table 1) and focal deficits (Table 2). This composite scale ranges from 0 (no deficits) to 46 (severe impairments).</li>
	<li>Perform the neuroscore at the same time each day and use surgical clothes to keep a neutral smell.</li>
	<li>Habituate the mice for 30 min in the room with an open cage prior to the testing and allow them to observe each item for 30 s.</li>
</ol>
7. Perfusion
<ol>
	<li>Prepare a 20 mL syringe containing PBS-heparin (2 U/mL) and place it 1 m above the bench to facilitate/ensure gravity-driven perfusion.</li>
	<li>Inject intraperitoneally 100 &#181;L of ketamine and xylazine (120/16 mg/kg body weight, respectively). Wait for 5 min and corroborate the cessation of spontaneous body movement and vibrissae.</li>
	<li>Fix the animal in a supine position and disinfect the abdominal body surface with 100% ethanol. Make a 3 cm long incision in the abdomen; cut the diaphragm and the ribs to completely visualize the heart.</li>
	<li>Make a small incision in the right atrium and insert the perfusion cannula into the left ventricle and perfuse with 20 mL PBS-heparin.</li>
	<li>After perfusion, decapitate the animal and remove the brain, freeze it using dry ice and store them at -80 &#176;C until further use.</li>
</ol>
8. Infarct volumetry
<ol>
	<li>Cryosectioning: Cut the brain serially on a cryostat to 20 &#181;m thick sections every 120 &#181;m and mount on slides. Store the slides at -80 &#176;C until further processing.</li>
	<li>Cresyl violet (CV) staining
	<ol>
		<li>To prepare the staining solution, mix 0.5 g of CV acetate in 500 mL of H2O. Stir and heat (60 &#176;C) until the crystals are dissolved. Allow the solution to cool and store it in a dark bottle. Reheat to 60 &#176;C and filter (paper filter) before every use.</li>
		<li>Dry the slides at room temperature for 30 min. Place them in 95% ethanol for 15 min, followed by 70% ethanol for 1 min, and afterwards in 50% ethanol for 1 min.</li>
		<li>Place the slides in distilled water for 2 min, refresh the distilled water, and place the slides in water again for 1 min. Then, place the slides in the pre-heated staining solution for 10 min at 60 &#176;C. Wash the slides twice in distilled water for 1 min.</li>
		<li>Place the slides in 95% ethanol for 2 min. Then place them into 100% ethanol for 5 min, refresh the 100% ethanol and place the slides in 100% ethanol again for 2 min. Afterwards, cover the slides with a mounting medium.</li>
		<li>Analysis: Scan the slides and analyze the indirect infarct volume by the Swanson method16 to correct for edema: Ischemic area = (ischemic region)-((ipsilateral hemisphere) - (contralateral hemisphere)).</li>
	</ol>
	</li>
</ol>
9. Tunel staining (in situ apoptosis detection kit)
<ol>
	<li>Dry the slides, post-fix in 4% paraformaldehyde in PBS (ph 7.4) for 10-20 min at RT. Wash in PBS, post-fix in precooled ethanol: acetic acid 2:1 for 5 min at -20 &#176;C.</li>
	<li>Wash in PBS and apply equilibration buffer (10 s to a maximum of 60 min at RT) and apply working strength TdT enzyme (1 h at 37 &#176;C in humidified chamber)</li>
	<li>Apply working strength stop/wash enzyme (10 min at RT), wash in PBS and apply warmed (RT) working strength anti-digoxigenin conjugate (30 min at RT in dark)</li>
	<li>Wash in PBS, incubate with DAPI for 5 min at RT and mount the slides with fluoromount media.</li>
</ol>

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The authors have no competing interests to disclose.

The presented protocol describes the experimental stroke model of photothrombosis by illuminating the intact skull with a 561 nm laser, with a previous intraperitoneal injection of Rose Bengal. Until recently, the use of this model has been low but is steadily increasing.
Mortality during stroke induction in this model is absent. The overall mortality of less than 5% arises during operation due to anesthesiological complications or sacrifice after meeting the exclusion criteria. To warrant the...

Ischemic stroke remains a principal cause of death and acquired adult disability in developed countries in the 21st century accounting for approximately 2.7 million deaths in 2017 worldwide1. Even with the immense efforts of the scientific community, few treatments are available. Furthermore, with such high exclusion criteria, these already limited options are not accessible to many patients, resulting in an urgent need for novel treatments to improve functional recovery after stroke.
Considering the incapability of in vitro models to replicate the complex interactions of the brain, animal models are essential for preclinical stroke research. Mice are the most frequently used animal model in the stroke research field. The majority of these mouse models aim to induce infarctions by blocking the blood flow within the middle cerebral artery (MCA) since the majority of human stroke lesions are located in the MCA territory2. Although these models better recapitulate human stroke lesions, they involve convulated surgeries with high infarct volume variability.
Since Rosenblum and El-Sabban&#39;s proposal of the photothrombotic model in 19773, and later the application of this model to rats Watson et al.4, it has become widely used in ischemic stroke research5,6. The photothrombotic stroke model induces a local and defined cortical infarct as a result of the photoactivation of a light-sensitive dye previously injected into the blood flow. This causes local thrombosis of the vessels in the areas exposed to light. Briefly, upon exposure to light from the injected photosensitive dye, localized oxidative injury of the endothelial cell membrane is induced, leading to platelet aggregation and thrombus formation, followed by local disruption of cerebral blood flow7.
The principal advantage of this technique resides in its simplicity of execution and the possibility to direct the lesion to the desired region. Unlike other experimental stroke models, minor surgical expertise is needed to perform the photothrombotic stroke model as the lesion is induced through illumination of the intact skull. Moreover, the well-delimited borders (Figure 2A and Figure 5B) and the flexibility to induce the lesion to a specific brain region can facilitate the study of cellular responses within the ischemic or intact cortical area8. For these reasons, this approach is suitable for the study of cellular and molecular mechanisms of cortical plasticity.
Over the past few decades, the growing concern regarding the lack of reproducibility between research groups has been coined the so-called replication crisis9. After the coordination of the first preclinical randomized controlled multicenter trial study in 201510, a proposed tool to improve preclinical research11,12,13, it was confirmed that one cause for failing reproducibility between preclinical studies from independent laboratories was the lack of sufficient standardization of experimental stroke models and outcome parameters14. Accordingly, when the ImmunoStroke consortium was established (https://immunostroke.de/), a collaboration which aims to understand brain-immune interactions underlying the mechanistic principles of stroke recovery, the standardization of all the experimental stroke models among each research group was essential.
Described here is the standardized procedure for the induction of the photothrombotic model as used in the above-mentioned research consortium. Briefly, an animal underwent anesthetics, received a Rose Bengal injection (10 &#181;L/g) intraperitonally, and the intact skull, 3 mm left from bregma, was immediately illuminated by a 561 nm laser for 20 min (Figure 1). Additionally, a related histological and behavioral method to analyze the stroke outcome in this model is reported. All methods are based on standard operating procedures developed and used in the laboratory.

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			<td>561 nm wavelenght laser</td>
			<td>Solna</td>
			<td>Cobolt HS-03</td>
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			<td>Acetic Acid</td>
			<td>Sigma Life Science</td>
			<td>695092</td>
			<td></td>
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			<td>Anesthesia system for isoflurane</td>
			<td>Drager</td>
			<td></td>
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			<td>ApopTag Peroxidase In Situ Apoptosis Detection Kit</td>
			<td>Millipore</td>
			<td>S7100</td>
			<td></td>
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			<td>Bepanthen pomade</td>
			<td>Bayer</td>
			<td>1578681</td>
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			<td>C57Bl/6J mice</td>
			<td>Charles River</td>
			<td>000664</td>
			<td></td>
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			<td>Collimeter</td>
			<td>Thorlabs</td>
			<td>F240APC-A</td>
			<td></td>
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			<td>Cotons</td>
			<td>NOBA Verbondmitel Danz</td>
			<td>974116</td>
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			<td>Cresyl violet</td>
			<td>Sigma Life Science</td>
			<td>C5042-10G</td>
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			<td>Cryostat</td>
			<td>Thermo Scientific CryoStarNX70</td>
			<td></td>
			<td></td>
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			<td>Ethanol 70%</td>
			<td>CLN Chemikalien Laborbedorf</td>
			<td>521005</td>
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			<td>Ethanol 96%</td>
			<td>CLN Chemikalien Laborbedorf</td>
			<td>522078</td>
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			<td>Ethanol 99%</td>
			<td>CLN Chemikalien Laborbedorf</td>
			<td>ETO-5000-99-1</td>
			<td></td>
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			<td>Filter paper</td>
			<td>Macherey-Nagel</td>
			<td>432018</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine Scissors</td>
			<td>FST</td>
			<td>15000-00</td>
			<td></td>
		</tr>
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			<td>Forceps</td>
			<td>FST</td>
			<td>11616-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating blanket</td>
			<td>FHC DC Temperature Controller</td>
			<td>&#160;40-90-8D</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Abbot</td>
			<td>B506</td>
			<td></td>
		</tr>
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			<td>Isopentane</td>
			<td>Fluka</td>
			<td>59070</td>
			<td></td>
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			<td>Ketamine</td>
			<td>Inresa Arzneimittel GmbH</td>
			<td></td>
			<td></td>
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			<td>Laser Speckle</td>
			<td>Perimed</td>
			<td>PeriCam PSI HR</td>
			<td></td>
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			<td>Mayor Scissors</td>
			<td>FST</td>
			<td>1410-15</td>
			<td></td>
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			<td>Phosphate Buffered Saline PH: 7.4</td>
			<td>Apotheke Innestadt Uni Munchen</td>
			<td>P32799</td>
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			<td>Protective glasses</td>
			<td>Laser 2000</td>
			<td>NIR-ZS2-38</td>
			<td></td>
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		<tr>
			<td>Rose Bengal</td>
			<td>Sigma Aldrich</td>
			<td>198250-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Roti-Histokit mounting medium</td>
			<td>Roth</td>
			<td>6638.1</td>
			<td></td>
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			<td>Saline solution</td>
			<td>Braun</td>
			<td>131321</td>
			<td></td>
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			<td>Stereomikroskop</td>
			<td>Zeiss</td>
			<td>Stemi DV4</td>
			<td></td>
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			<td>Stereotactic frame</td>
			<td>Stoelting</td>
			<td>51500U</td>
			<td></td>
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		<tr>
			<td>Superfrost Plus Slides</td>
			<td>Thermo Scientific</td>
			<td>J1800AMNZ</td>
			<td></td>
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		<tr>
			<td>Xylacine</td>
			<td>Albrecht</td>
			<td></td>
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modeling stroke in mice: focal cortical lesions by photothrombosis

Stroke is a leading cause of death and acquired adult disability in developed countries. Despite extensive investigation for novel therapeutic strategies, there remain limited therapeutic options for stroke patients. Therefore, more research is needed for pathophysiological pathways such as post-stroke inflammation, angiogenesis, neuronal plasticity, and regeneration. Given the inability of in vitro models to reproduce the complexity of the brain, experimental stroke models are essential for the analysis and subsequent evaluation of novel drug targets for these mechanisms. In addition, detailed standardized models for all procedures are urgently needed to overcome the so-called replication crisis. As an effort within the ImmunoStroke research consortium, a standardized photothrombotic mouse model using an intraperitoneal injection of Rose Bengal and the illumination of the intact skull with a 561 nm laser is described. This model allows the performance of stroke in mice with allocation to any cortical region of the brain without invasive surgery; thus, enabling the study of stroke in various areas of the brain. In this video, the surgical methods of stroke induction in the photothrombotic model along with&#160;histological analysis are demonstrated.

The model described here is a photothrombotic stroke model by Rose Bengal injection and intact skull illumination for 20 min, at a constant 561 nm wavelength and 25 mW output power at the fiber. Although the complete photothrombotic surgery lasts 30 min, the animal is kept under low anesthesia and the brain damage is moderate. Approximately 10 min after transfer to their cages, all the animals were awake, freely moving in the cage, and interacting with littermates.
Infarct volumetry was perfor...

Watch this Scientific Journal Video about Modeling Stroke in Mice: Focal Cortical Lesions by Photothrombosis at JoVE.com

Modeling Stroke in Mice: Focal Cortical Lesions by Photothrombosis

Described here is the photothrombotic stroke model, where a stroke is produced through the intact skull by inducing permanent microvascular occlusion using laser illumination after administration of a photosensitive dye.

Stroke is a leading cause of death and acquired adult disability in developed countries. Despite extensive investigation for novel therapeutic strategies, ...

modeling-stroke-in-mice-focal-cortical-lesions-by-photothrombosis

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Neuroscience

5.9K Views.  LMU Munich. Described here is the photothrombotic stroke model, where a stroke is produced through the intact skull by inducing permanent microvascular occlusion using laser illumination after administration of a photosensitive dye.

Video: Modeling Stroke in Mice: Focal Cortical Lesions by Photothrombosis

Focal Cerebral Ischemia Model by Endovascular Suture Occlusion of the Middle Cerebral Artery in the Rat

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable clinical state; in the development of animal models of focal ischemia, however, achieving reproducibility of experimentally induced infarct volume is essential. The rat is a widely used animal model for stroke due to its relatively low animal husbandry costs and to the similarity of its cranial circulation to that of humans2,3. In humans, the middle cerebral artery (MCA) is most commonly affected in stroke syndromes and multiple methods of MCA occlusion (MCAO) have been described to mimic this clinical syndrome in animal models. Because recanalization commonly occurs following an acute stroke in the human, reperfusion after a period of occlusion has been included in many of these models. In this video, we demonstrate the transient endovascular suture MCAO model in the spontaneously hypertensive rat (SHR). A filament with a silicon tip coating is placed intraluminally at the MCA origin for 60 minutes, followed by reperfusion. Note that the optimal occlusion period may vary in other rat strains, such as Wistar or Sprague-Dawley. Several behavioral indicators of stroke in the rat are shown. Focal ischemia is confirmed using T2-weighted magnetic resonance images and by staining brain sections with 2,3,5-triphenyltetrazolium chloride (TTC) 24 hours after MCAO.

Surgical induction of ischemic brain damage in the rat is a widely used model for stroke research. Here we demonstrate the induction of focal cerebral ischemia by occlusion of the middle cerebral artery. Visualization of the resulting infarct by histological staining and magnetic resonance imaging is also shown.

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable ...

Measurement of Total Calcium in Neurons by Electron Probe X-ray Microanalysis

In this article the tools, techniques, and instruments appropriate for quantitative measurements of intracellular elemental content using the technique known as electron probe microanalysis (EPMA) are described. Intramitochondrial calcium is a particular focus because of the critical role that mitochondrial calcium overload plays in neurodegenerative diseases. The method is based on the analysis of X-rays generated in an electron microscope (EM) by interaction of an electron beam with the specimen. In order to maintain the native distribution of diffusible elements in electron microscopy specimens, EPMA requires &#34;cryofixation&#34; of tissue followed by the preparation of ultrathin cryosections. Rapid freezing of cultured cells or organotypic slice cultures is carried out by plunge freezing in liquid ethane or by slam freezing against a cold metal block, respectively. Cryosections nominally 80 nm thick are cut dry with a diamond knife at ca. -160 &#176;C, mounted on carbon/pioloform-coated copper grids, and cryotransferred into a cryo-EM using a specialized cryospecimen holder. After visual survey and location mapping at &#8804;-160 &#176;C and low electron dose, frozen-hydrated cryosections are freeze-dried at -100 &#176;C for ~30 min. Organelle-level images of dried cryosections are recorded, also at low dose, by means of a slow-scan CCD camera and subcellular regions of interest selected for analysis. X-rays emitted from ROIs by a stationary, focused, high-intensity electron probe are collected by an energy-dispersive X-ray (EDX) spectrometer, processed by associated electronics, and presented as an X-ray spectrum, that is, a plot of X-ray intensity vs. energy. Additional software facilitates: 1) identification of elemental components by their &#34;characteristic&#34; peak energies and fingerprint; and 2) quantitative analysis by extraction of peak areas/background. This paper concludes with two examples that illustrate typical EPMA applications, one in which mitochondrial calcium analysis provided critical insight into mechanisms of excitotoxic injury and another that revealed the basis of ischemia resistance.

This paper describes the application of cryoanalytical electron microscopy to the quantitative measurement of total calcium content and distribution at subcellular resolution in physiologically defined biological specimens.

In this article the tools, techniques, and instruments appropriate for quantitative measurements of intracellular elemental content using the technique ...

Modeling Astrocytoma Pathogenesis In Vitro and In Vivo Using Cortical Astrocytes or Neural Stem Cells from Conditional, Genetically Engineered Mice

Current astrocytoma models are limited in their ability to define the roles of oncogenic mutations in specific brain cell types during disease pathogenesis and their utility for preclinical drug development. In order to design a better model system for these applications, phenotypically wild-type cortical astrocytes and neural stem cells (NSC) from conditional, genetically engineered mice (GEM) that harbor various combinations of floxed oncogenic alleles were harvested and grown in culture. Genetic recombination was induced in vitro using adenoviral Cre-mediated recombination, resulting in expression of mutated oncogenes and deletion of tumor suppressor genes. The phenotypic consequences of these mutations were defined by measuring proliferation, transformation, and drug response in vitro. Orthotopic allograft models, whereby transformed cells are stereotactically injected into the brains of immune-competent, syngeneic littermates, were developed to define the role of oncogenic mutations and cell type on tumorigenesis in vivo. Unlike most established human glioblastoma cell line xenografts, injection of transformed GEM-derived cortical astrocytes into the brains of immune-competent littermates produced astrocytomas, including the most aggressive subtype, glioblastoma, that recapitulated the histopathological hallmarks of human astrocytomas, including diffuse invasion of normal brain parenchyma. Bioluminescence imaging of orthotopic allografts from transformed astrocytes engineered to express luciferase was utilized to monitor in vivo tumor growth over time. Thus, astrocytoma models using astrocytes and NSC harvested from GEM with conditional oncogenic alleles provide an integrated system to study the genetics and cell biology of astrocytoma pathogenesis in vitro and in vivo and may be useful in preclinical drug development for these devastating diseases.

Modeling Astrocytoma Pathogenesis In Vitro and In Vivo Using Cortical Astrocytes or Neural Stem Cells from Conditional, Genetically Engineered Mice

Phenotypically wild-type astrocytes and neural stem cells harvested from mice engineered with floxed, conditional oncogenic alleles and transformed via viral Cre-mediated recombination can be used to model astrocytoma pathogenesis in vitro and in vivo by orthotopic injection of transformed cells into brains of syngeneic, immune-competent littermates.

Current astrocytoma models are limited in their ability to define the roles of oncogenic mutations in specific brain cell types during disease ...

Experimental Demyelination and Remyelination of Murine Spinal Cord by Focal Injection of Lysolecithin

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system characterized by plaque formation containing lost oligodendrocytes, myelin, axons, and neurons. Remyelination is an endogenous repair mechanism whereby new myelin is produced subsequent to proliferation, recruitment, and differentiation of oligodendrocyte precursor cells into myelin-forming oligodendrocytes, and is necessary to protect axons from further damage. Currently, all therapeutics for the treatment of multiple sclerosis target the aberrant immune component of the disease, which reduce inflammatory relapses but do not prevent progression to irreversible neurological decline. It is therefore imperative that remyelination-promoting strategies be developed which may delay disease progression and perhaps reverse neurological symptoms. Several animal models of demyelination exist, including experimental autoimmune encephalomyelitis and curprizone; however, there are limitations in their use for studying remyelination. A more robust approach is the focal injection of toxins into the central nervous system, including the detergent lysolecithin into the spinal cord white matter of rodents. In this protocol, we demonstrate that the surgical procedure involved in injecting lysolecithin into the ventral white matter of mice is fast, cost-effective, and requires no additional materials than those commercially available. This procedure is important not only for studying the normal events involved in the remyelination process, but also as a pre-clinical tool for screening candidate remyelination-promoting therapeutics.

Demyelinating diseases can be modeled in animals by focal application of lysolecithin into the CNS. A single injection of lysolecithin into mouse spinal cord produces a lesion that spontaneously repairs over time. The goal is to study factors involved in de- and remyelination, and to test agents for enhancing repair.

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system characterized by plaque formation containing lost ...

Lateral Chronic Cranial Window Preparation Enables In Vivo Observation Following Distal Middle Cerebral Artery Occlusion in Mice

Focal cerebral ischemia (i.e., ischemic stroke) may cause major brain injury, leading to a severe loss of neuronal function and consequently to a host of motor and cognitive disabilities. Its high prevalence poses a serious health burden, as stroke is among the principal causes of long-term disability and death worldwide1. Recovery of neuronal function is, in most cases, only partial. So far, treatment options are very limited, in particular due to the narrow time window for thrombolysis2,3. Determining methods to accelerate recovery from stroke remains a prime medical goal; however, this has been hampered by insufficient mechanistic insights into the recovery process. Experimental stroke researchers frequently employ rodent models of focal cerebral ischemia. Beyond the acute phase, stroke research is increasingly focused on the sub-acute and chronic phase following cerebral ischemia. Most stroke researchers apply permanent or transient occlusion of the MCA in mice or rats. In patients, occlusions of the MCA are among the most frequent causes of ischemic stroke4. Besides proximal occlusion of the MCA using the filament model, surgical occlusion of the distal MCA is probably the most frequently used model in experimental stroke research5. Occlusion of a distal (to the branching of the lenticulo-striate arteries) MCA branch typically spares the striatum and primarily affects the neocortex. Vessel occlusion can be permanent or transient. High reproducibility of lesion volume and very low mortality rates with respect to the long-term outcome are the main advantages of this model. Here, we demonstrate how to perform a chronic cranial window (CW) preparation lateral to the sagittal sinus, and afterwards how to surgically induce a distal stroke underneath the window using a craniotomy approach. This approach can be applied for sequential imaging of acute and chronic changes following ischemia via epi-illuminating, confocal laser scanning, and two-photon intravital microscopy.

Lateral Chronic Cranial Window Preparation Enables In Vivo Observation Following Distal Middle Cerebral Artery Occlusion in Mice

Surgical occlusion of a distal middle cerebral artery branch (MCAo) is a frequently used model in experimental stroke research. This manuscript describes the basic technique of permanent MCAo, combined with the insertion of a lateral cranial window, which offers the opportunity for longitudinal intravital microscopy in mice.

Focal cerebral ischemia (i.e., ischemic stroke) may cause major brain injury, leading to a severe loss of neuronal function and consequently to a host of ...

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging methods exist for examining the brain tissue of live newborn mammals. Herein we summarize a protocol for imaging individual cortical neurons in living neonatal mice. This protocol includes the following two methodologies: (1) the Supernova system for sparse and bright labeling of cortical neurons in the developing brain, and (2) a surgical procedure for the fragile neonatal skull. This protocol allows the observation of temporal changes of individual cortical neurites during neonatal stages with a high signal-to-noise ratio. Labeled cell-specific gene silencing and knockout can also be achieved by combining the Supernova with RNA interference and CRISPR/Cas9 gene editing systems. This protocol can, thus, be used for analyzing the developmental dynamics of cortical neurons, molecular mechanisms that control the neuronal dynamics, and changes in neuronal dynamics in disease models.

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

We present an in vivo two-photon imaging protocol for imaging the cerebral cortex of neonatal mice. This method is suitable for analyzing the developmental dynamics of cortical neurons, the molecular mechanisms that control the neuronal dynamics, and the changes in neuronal dynamics in disease models.

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging ...

Modeling Stroke in Mice: Transient Middle Cerebral Artery Occlusion via the External Carotid Artery

Stroke is the third most common cause of mortality and the leading cause of acquired adult disability in developed countries. To date, therapeutic options are limited to a small proportion of stroke patients within the first hours after stroke. Novel therapeutic strategies are being extensively investigated, especially to prolong the therapeutic time window. These current investigations include the study of important pathophysiological pathways after stroke, such as post-stroke inflammation, angiogenesis, neuronal plasticity, and regeneration. Over the last decade, there has been increasing concern about the poor reproducibility of experimental results and scientific findings among independent research groups. To overcome the so-called &#8220;replication crisis&#8221;, detailed standardized models for all procedures are urgently needed. As an effort within the &#8220;ImmunoStroke&#8221; research consortium (https://immunostroke.de/), a standardized mouse model of transient middle cerebral artery occlusion (MCAo) is proposed. This model allows the complete restoration of the blood flow upon removal of the filament, simulating the therapeutic or spontaneous clot lysis that occurs in a large proportion of human strokes. The surgical procedure of this &#8220;filament&#8221; stroke model and tools for its functional analysis are demonstrated in the accompanying video.

Different models of middle cerebral artery occlusion (MCAo) are used in experimental stroke research. Here, an experimental stroke model of transient MCAo via the external carotid artery (ECA) is described, which aims to mimic human stroke, in which the cerebrovascular thrombus is removed due to spontaneous clot lysis or therapy.

Stroke is the third most common cause of mortality and the leading cause of acquired adult disability in developed countries. To date, therapeutic options ...

Modeling Neonatal Intraventricular Hemorrhage Through Intraventricular Injection of Hemoglobin

Neonatal intraventricular hemorrhage (IVH) is a common consequence of premature birth and leads to brain injury, posthemorrhagic hydrocephalus (PHH), and lifelong neurological deficits. While PHH can be treated by temporary and permanent cerebrospinal fluid (CSF) diversion procedures (ventricular reservoir and ventriculoperitoneal shunt, respectively), there are no pharmacological strategies to prevent or treat IVH-induced brain injury and hydrocephalus. Animal models are needed to better understand the pathophysiology of IVH and test pharmacological treatments. While there are existing models of neonatal IVH, those that reliably result in hydrocephalus are often limited by the necessity for large-volume injections, which may complicate modeling of the pathology or introduce variability in the clinical phenotype observed.
Recent clinical studies have implicated hemoglobin and ferritin in causing ventricular enlargement after IVH. Here, we develop a straightforward animal model that mimics the clinical phenotype of PHH utilizing small-volume intraventricular injections of the blood breakdown product hemoglobin. In addition to reliably inducing ventricular enlargement and hydrocephalus, this model results in white matter injury, inflammation, and immune cell infiltration in periventricular and white matter regions. This paper describes this clinically relevant, simple method for modeling IVH-PHH in neonatal rats using intraventricular injection and presents methods for quantifying ventricle size post injection.

We present a model of neonatal intraventricular hemorrhage using rat pups that mimics the pathology seen in humans.

Neonatal intraventricular hemorrhage (IVH) is a common consequence of premature birth and leads to brain injury, posthemorrhagic hydrocephalus (PHH), and ...

A Stably Established Two-Point Injection of Lysophosphatidylcholine-Induced Focal Demyelination Model in Mice

Receptor-mediated lysophospholipid signaling contributes to the pathophysiology of diverse neurological diseases, especially multiple sclerosis (MS). Lysophosphatidylcholine (LPC) is an endogenous lysophospholipid associated with inflammation, and it could induce rapid damage with toxicity to myelin lipids, leading to focal demyelination. Here, a detailed protocol is presented for stereotactic two-point LPC injection that could directly cause severe demyelination and replicate the experimental demyelination injury quickly and stably in mice by surgical procedure. Thus, this model is highly relevant to demyelination diseases, especially MS, and it can contribute to the related advancing clinically-relevant research. Also, immunofluorescence and Luxol fast blue staining methods were used to depict the time course of demyelination in the corpus callosum of mice injected with LPC. In addition, the behavioral method was used to evaluate the cognitive function of mice after modeling. Overall, the two-point injection of lysophosphatidylcholine via a stereotaxic frame is a stable and reproducible method to generate a demyelination model in mice for further study.

The present protocol describes a two-point injection of lysophosphatidylcholine via a stereotaxic frame to generate a stable and reproducible demyelination model in mice.

Receptor-mediated lysophospholipid signaling contributes to the pathophysiology of diverse neurological diseases, especially multiple sclerosis (MS). ...

Establishing a Transcranial Middle Cerebral Artery Occlusion Mice Model

A Modified Transcranial Middle Cerebral Artery Occlusion Model to Study Stroke Outcomes in Aged Mice

In experimental stroke research, middle cerebral artery occlusion (MCAO) with an intraluminal filament is widely used to model ischemic stroke in mice. The filament MCAO model typically exhibits a massive cerebral infarction in C57Bl/6 mice that sometimes includes brain tissue in the territory supplied by the posterior cerebral artery, which is largely due to a high incidence of posterior communicating artery atresia. This phenomenon is considered a major contributor to the high mortality rate observed in C57Bl/6 mice during long-term stroke recovery after filament MCAO. Thus, many chronic stroke studies exploit distal MCAO models. However, these models usually produce infarction only in the cortex area, and consequently, the assessment of post-stroke neurologic deficits could be a challenge. This study has established a modified transcranial MCAO model in which the MCA at the trunk is partially occluded either permanently or transiently via a small cranial window. Since the occlusion location is relatively proximal to the origin of the MCA, this model generates brain damage in both the cortex and striatum. Extensive characterization of this model has demonstrated an excellent long-term survival rate, even in aged mice, as well as readily detectable neurologic deficits. Therefore, the MCAO mouse model described here represents a valuable tool for experimental stroke research.

Author Spotlight: Innovative Techniques and Future Directions in Stroke Research 

This protocol demonstrates a unique mouse stroke model with a medium-sized infarct and an excellent survival rate. This model allows preclinical stroke researchers to extend the ischemia duration, use aged mice, and assess long-term functional outcomes.

In experimental stroke research, middle cerebral artery occlusion (MCAO) with an intraluminal filament is widely used to model ischemic stroke in mice. ...