We thank M.T. Pardue for advice on the SD&#173;OCT, F. Schaeffel for advice on measurements of refraction and corneal curvature, Mr. Sanshouo for recreating the three-dimensional frame data, M. Miyauchi; K. Tsubota; Y. Tanaka; S. Kondo; C. Shoda; M. Ibuki; Y. Miwa; Y. Hagiwara; A. Ishida; Y. Tomita; Y. Katada; E. Yotsukura; K. Takahashi; and Y. Wang for critical discussions. This work was supported by Grants&#173; in&#173;Aid for Scientific Research (KAKENHI, number 15K10881) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) to TK. This work is also supported by the grant for myopia research from Tsubota Laboratory, Inc. (Tokyo Japan).

All procedures were approved by the Ethics Committee on Animal Research of the Keio University School of Medicine adhered to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research, the Institutional Guidelines on Animal Experimentation at Keio University, and the Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines for the use of animals in research.
1. Assembling the Eyeglasses for Mice
<ol>
	<li>Prepare parts needed for assembling the eyeglasses (Figure 1a). For each mouse, prepare all followings: one head-mounted nylon stick, one higher and one lower titanium frame, two lenses with proper powers according to the purpose of the experiment, one M1.4 size screw with the length of 10 mm, one nut for M1.4 size screw, one plain washer for M1.4 size screw with the thickness of 0.3 mm, and two artificial fingernail tips (Table of Materials). 
	NOTE: Two kinds of frames exist with different heights. For one mouse, one higher frame and one lower frame are used as a set. Higher frames should be put above the lower ones in order to make the vision fields symmetrical. Frames and lenses are specially designed and manufactured by authors&#8217; research group. These are available by contacting the corresponding authors of this article. Other parts can be found in retail tool shops.</li>
	<li>Assemble the frame for the right and left eye separately.
	<ol>
		<li>Arrange the fingernail tip to face the outside direction to achieve the best protective effect. Adjust the angle between the fingernail tip and the frame to be about 130&#176; to avoid masking the mouse vision field (Figure 1b). Adhere the artificial fingernail tips to the frame using cyanoacrylate adhesive. 
		NOTE: Fingernail tips can help to protect the lens from being scratched by the mouse. The direction of the fingernail tips must be opposite because the higher frame and the lower frame are used for the right eye and the left eye, respectively.</li>
		<li>Wait for at least 12 h to let the adhesive dry completely, then use a nail clipper to adjust the shape of the fingernail tips to be about 1 cm &#215; 1 cm by cutting and trimming.</li>
		<li>Adhere the lens to the frame using cyanoacrylate adhesive. Put the lens onto the frame by hand and hold the frame horizontally. Inject the cyanoacrylate adhesive from the edge of the lens and let the adhesive spread by surface tension. 
		NOTE: The adhesive will erode the lens and influence its transparency, so make sure the adhesive only touches the peripheral part of the lens. Use 0 diopter (D) plano lens as control and minus lens to induce myopia. The effect of different powers of minus lenses (&#8211;10 D to &#8211;50 D) has been described elsewhere4. To maximize the myopia inducement, &#8211;30 D lens is recommended for inducing myopia. FDM can also be induced with the same device simply by changing the lens into the cap of 1.5 mL microtube as the diffuser.</li>
	</ol>
	</li>
	<li>Tighten the screw into the nylon stick together with the washer from the flat side of the stick. Prepare the eye glasses and sticks before the experiment respectively and stock for further use (Figure 1c). 
	NOTE: The protocol can be paused here.</li>
</ol>
2. Measurements of the Refraction and AL Baseline.
<ol>
	<li>Apply one drop of mydriatic agent containing 5 mg/mL tropicamide and 5 mg/mL phenylephrine hydrochloride on each side of the eyeball to dilate the pupil. Wait for at least 5 min before general anesthesia. 
	NOTE: Dilate the pupil under general anesthesia will cause reversible cataract which influences the measurement afterwards. Always dilate the pupil before general anesthesia and wait for at least 5 min. One drop (approximately 0.05 mL) of the mydriatic agent is enough for dilating the pupil of the mouse eye, while more agent will do no harm to the following steps.</li>
	<li>Put the mouse under general anesthesia. Grasp the back skin of the mouse softly to keep the mouse from bumping its eye until it is completely anaesthetized. Judge the depth of general anesthesia to be enough if the mouse does not move around when it is put on the table freely. 
	NOTE: A combination of midazolam (40 &#956;g/100 &#956;L), medetomidine (7.5 &#956;g/100 &#956;L) and butorphanol tartrate (50 &#956;g/100 &#956;L) is used here for general anesthesia for mice with a volume of 0.01 mL/g intraperitoneal injection. Generally, less than 5 min are needed for mice to fall asleep. Long time of general anesthesia causes low body temperature and slow heartbeat. To avoid the potential influence of general anesthesia to the measurement, finishing all the measurements within 10 min after the injection of anesthetic is recommended.&#160;The butorphanol provided in the anesthetic cocktail provide approximately 4 hours of analgesia. Proper recipe for general anesthesia may different by institutions.</li>
	<li>Measure the refraction of the mouse eye using an infrared photorefractor4,9,14. Adjust the direction of one of the mouse eyes to keep the first Purkinje image in the center of the pupil and measure the refraction along the optical axis. After the measurement, measure the opposite eye with the same procedures (Figure 2a). 
	NOTE: The value measured for the refraction is strongly influenced by the position of the mouse eye along the optic axis. Ensure the first Purkinje image is aligned within &#177;3 degrees from the center of the pupil. The workbench of the spectral domain optical coherence tomography (SD-OCT) system may be used for fine tuning of the direction of pupil in refraction measurements4.</li>
	<li>Measure the AL of the mouse eye using a SD-OCT system4,15,16. Define the AL as the distance from the corneal vertex to the brightest boundary near the optical nerve (Figure 2b). 
	NOTE: Similar with the measurement of the refraction, the AL is strongly influenced by the direction of the mouse eye. The corneal vertex can be confirmed by the point-like reflection on the surface of the cornea. The boundary of the retina side will be very hazy at the point of optical nerve. Adjust the direction a little to let the boundary be clear enough for measuring but not too far from the optical nerve.</li>
</ol>
3. Fixation of the Frame onto the Mouse Cranium.
<ol>
	<li>Apply one drop of 0.1% purified sodium hyaluronate eye drop to prevent dryness on each eye. 
	NOTE: Eye drop on the eye surface will influence the values of refraction and axial length measurements. Do not use the eye drop after the anesthesia until all the measurements are done.</li>
	<li>Put the chin of the anesthetized mouse onto a slope made of clay or anything can be used as a pillow to make the upfront plane of the cranium be horizontal.</li>
	<li>Sterilize the hair and scalp between ears and eyes using cotton swab with 70% ethanol.</li>
	<li>Cut the skin between ears and eyes to expose the skull for about 0.8 cm2 using surgical scissors and tweezers. Use dental etching liquid and cotton swab to remove the periosteum. Sterilize the surgical scissors and tweezers with 70% ethanol before the surgery of each mouse. 
	NOTE: Clipping the hair and wearing sterile gloves may be required.&#160; Check the provisions of relevant animal care committee before this procedure.&#160;In most cases, the dental etching liquid can be found as one of the attachments in the self-cure dental adhesive system. If the dental etching liquid is not available, use 70% ethanol instead.</li>
	<li>Assemble a set of frames without lens to help fix the stick onto the right position. Put the frames onto the mouse head. Carefully adjust the position of the frames to make sure both eyes are in the middle of the empty frame.</li>
	<li>Use a self-cure dental adhesive system to attach the stick onto the mouse head. Be careful not to let the liquid of the adhere system flow into the mouse eye. 
	NOTE: The method for using the self-cure dental adhesive system is different between products. Refer to the instruction carefully. 
	CAUTION: Some of the reagents in the dental adhesive system may be toxic.</li>
	<li>Wait for about 5 min and take off the frame and the nut carefully without changing the position of the stick (Figure 3a).</li>
	<li>Inject 0.75 mg/kg atipamezole hydrochloride intraperitoneally to help the mouse to recovery from the anesthesia more quickly. Put the mouse into an individual cage until fully recovered. Do not leave the mouse unattended until it has regained sufficient consciousness to maintain sternal recumbency. The protocol can be paused here.</li>
</ol>
4. Initiation of the Myopia Induction and the Maintenance Afterwards
<ol>
	<li>Wait for at least 24 h after the surgery to let the mouse recover from anesthesia completely. Grasp the stick and put on the frames with lenses. The inducement begins at this time point (Figure 3b). 
	NOTE: To minimize the discomfort during the recovery from anesthesia and give enough time for the dental adhesive system to coagulate, it is highly recommended to put on the frame after the mice fully recovered from anesthesia. The resin cement of the adhesive system will fully cover the cut of the scalp. Therefore, no specific post-surgical treatment is needed for preventing infection and ameliorating post-surgical pain. Right after the first time of putting on the frame, mice will be over conscious to the existence of the lens and scratch it a lot. The gross behavior will be back to normal after a few hours.&#160;The mice with lenses can be kept with the same density to the normal mice.</li>
	<li>Remove the frame and clean the lenses and fingernail tips with cotton swabs at least twice a week to maintain the transparency of the lens. 
	NOTE: It is not necessary to put the mouse under anesthesia for removing and putting on the frame.&#160;Provide a support for the mice to sit on, rather than having them hang while working with them could reduce distress.
	<ol>
		<li>If an interim measurement is necessary, put the mouse under anesthesia and measure the mouse as previously described. The inducement can be continued after the mouse recovering from the anesthesia.</li>
	</ol>
	</li>
	<li>Clean the cage at least twice a week. 
	NOTE: This help to maintain lens clarity. Putting a net between the mouse and the cage bottom to filtrate the food scraps may also be helpful.</li>
	<li>Monitor the body weight and gross behavior. Compare them with the same age untouched mice during the whole experimental process. 
	NOTE: Except for some scratching behaviors, no significant change including the body weight is found between experiment mice with untreated mice.</li>
</ol>

<ol>
	<li>Dolgin, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+myopia+boom.">The myopia boom.</a> Nature. 519 (7543), 276-278 (2015).</li><li>Ohno-Matsui, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathologic+Myopia.">Pathologic Myopia.</a> Asia-Pacific Journal of Ophthalmology (Philadelphia, Pa). 5 (6), 415-423 (2016).</li><li>Morgan, I. G., Ashby, R. S., Nickla, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Form+deprivation+and+lens-induced+myopia:+are+they+different.">Form deprivation and lens-induced myopia: are they different.</a> Ophthalmic &amp; Physiological Optics. 33 (3), 355-361 (2013).</li><li>Jiang, X., 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+highly+efficient+murine+model+of+experimental+myopia.">A highly efficient murine model of experimental myopia.</a> Scientific Reports. 8 (1), 2026 (2018).</li><li>Torii, H., 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=Violet+Light+Exposure+Can+Be+a+Preventive+Strategy+Against+Myopia+Progression.">Violet Light Exposure Can Be a Preventive Strategy Against Myopia Progression.</a> EBioMedicine. 15, 210-219 (2017).</li><li>Smith, E. L., 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=Effects+of+Long-Wavelength+Lighting+on+Refractive+Development+in+Infant+Rhesus+Monkeys.">Effects of Long-Wavelength Lighting on Refractive Development in Infant Rhesus Monkeys.</a> Investigative Ophthalmology &amp; Visual Science. 56 (11), 6490-6500 (2015).</li><li>Gawne, T. J., Siegwart, J. T., Ward, A. H., Norton, T. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+wavelength+composition+and+temporal+modulation+of+ambient+lighting+strongly+affect+refractive+development+in+young+tree+shrews.">The wavelength composition and temporal modulation of ambient lighting strongly affect refractive development in young tree shrews.</a> Experimental Eye Research. 155, 75-84 (2017).</li><li>Wu, Y., 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=Early+quantitative+profiling+of+differential+retinal+protein+expression+in+lens-induced+myopia+in+guinea+pig+using+fluorescence+difference+two-dimensional+gel+electrophoresis.">Early quantitative profiling of differential retinal protein expression in lens-induced myopia in guinea pig using fluorescence difference two-dimensional gel electrophoresis.</a> Molecular Medicine Reports. , (2018).</li><li>Schaeffel, F., Burkhardt, E., Howland, H. C., Williams, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+refractive+state+and+deprivation+myopia+in+two+strains+of+mice.">Measurement of refractive state and deprivation myopia in two strains of mice.</a> Optometry and Vision Science. 81 (2), 99-110 (2004).</li><li>Tkatchenko, T. V., Shen, Y., Tkatchenko, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+experimental+myopia+has+features+of+primate+myopia.">Mouse experimental myopia has features of primate myopia.</a> Investigative Ophthalmology &amp; Visual Science. 51 (3), 1297-1303 (2010).</li><li>Faulkner, A. E., Kim, M. K., Iuvone, P. M., Pardue, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Head-mounted+goggles+for+murine+form+deprivation+myopia.">Head-mounted goggles for murine form deprivation myopia.</a> Journal of Neuroscience Methods. 161 (1), 96-100 (2007).</li><li>Gu, Y., 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+Head-Mounted+Spectacle+Frame+for+the+Study+of+Mouse+Lens-Induced+Myopia.">A Head-Mounted Spectacle Frame for the Study of Mouse Lens-Induced Myopia.</a> Journal of Ophthalmology. 2016, 8497278 (2016).</li><li>Siegwart, J. T., Norton, T. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Goggles+for+controlling+the+visual+environment+of+small+animals.">Goggles for controlling the visual environment of small animals.</a> Laboratory Animal Science. 44 (3), 292-294 (1994).</li><li>Tkatchenko, T. V., Tkatchenko, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ketamine-xylazine+anesthesia+causes+hyperopic+refractive+shift+in+mice.">Ketamine-xylazine anesthesia causes hyperopic refractive shift in mice.</a> Journal of Neuroscience Methods. 193 (1), 67-71 (2010).</li><li>Chou, T. H., 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=Postnatal+elongation+of+eye+size+in+DBA/2J+mice+compared+with+C57BL/6J+mice:+in+vivo+analysis+with+whole-eye+OCT.">Postnatal elongation of eye size in DBA/2J mice compared with C57BL/6J mice: in vivo analysis with whole-eye OCT.</a> Investigative Ophthalmology &amp; Visual Science. 52 (6), 3604-3612 (2011).</li><li>Park, H., 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=Assessment+of+axial+length+measurements+in+mouse+eyes.">Assessment of axial length measurements in mouse eyes.</a> Optometry and Vision Science. 89 (3), 296-303 (2012).</li></ol>

The design of the mouse eyeglass has been applied for a patent (Application no. 2017&#173;41349).

To make sure the eyeglasses to be fixed stably on the mouse head, several steps in this protocol need to be paid great attention. The periosteum must be removed completely before using the dental adhesive system. The blood on the skull also need to be cleaned up with care. While a little fine tuning is acceptable right after the application of the adhesive, do not move the stick frequently before the adhesive system dry up. Follow the instruction of the adhesive system carefully, especially the ratio of each component of...

The prevalence of myopia has increased dramatically recently, while the mechanism of its onset and progression are still largely unknow1. The most characteristic phenotype of myopia is the elongation of axial length (AL), which increases risk for retinal complications or even blindness2. To better understand the pathogenesis of myopia and develop effective treatments, robust myopic animal models and stable phenotype evaluation are necessary.
Briefly, two methods exist for inducing myopic states in animals: form-deprivation myopia (FDM) and lens-induced myopia (LIM)3. The former places diffusers in front of the eye or sutures the eyelid to obscure the image, which influences the normal development of the eyeball, resulting in a myopia phenotype. The latter places minus lenses in front of the eye to move the focal point behind the retina. The retina detects the shift of the focus and elongates the eyeball to realign the retina and focal point. For FDM, after the eyelid is closed or the diffuser has been fixed in front of the eye, almost no further maintenance is needed. For LIM, the lens needs to be taken off for cleaning in order to keep it transparent. Thus, FDM is relatively easy to be induced technically. However, the mechanisms of FDM and LIM are different, and which method mimics the myopia in human better is still under debate3. One of the strengths of LIM is the stronger phenotype compared with FDM, at least in the case of mice4.
Animals that have been used for inducing myopia include chicks5, monkeys6, tree shrews7, guinea pigs8, and mice4. Considering the possibility of genetic manipulation, abundant available antibodies, and low cost for breeding, mice could have been the first choice as the animal model of myopia. However, compared with other larger animals, fixing lenses or diffusers in front of the mouse eye is relatively difficult especially for young mice such as right after weaning. For the experiments that need topical drug administration or multiple interim eye measurements, it is also necessary for the frame to be removable. Another challenge is the small morphological change of mouse eyeball, which needs sophisticated technics and devices to evaluate. To date, different inducing and measuring protocols used in different research teams make it hard to compare and repeat the results across laboratories. A standard protocol with details is needed.
Previous works described multiple methods to fix lenses or diffusers in front of the mouse eye, such as gluing9, stitching10 and head-mounted goggle frame11,12. We combined the exist head-mounted goggle technics11,12,13 with our newly designed frame to develop an ameliorated protocol for inducing robust and efficient experimental myopia in mice. The protocol can be applied to young mice soon after weaning at postnatal day 21 (p21). We also optimized the processes for stable and precise evaluation of phenotypes including the refraction and AL. We hope this standardized protocol can help to make myopic mice a more easily accessible model for myopia research.

<table>
	<tbody>
		<tr>
			<td>screw</td>
			<td>NBK</td>
			<td>SNZS-M1.4-10</td>
			<td></td>
		</tr>
		<tr>
			<td>washer</td>
			<td>MonotaRO</td>
			<td>42166397</td>
			<td></td>
		</tr>
		<tr>
			<td>nut</td>
			<td>MonotaRO</td>
			<td>42214243</td>
			<td></td>
		</tr>
		<tr>
			<td>stick</td>
			<td>DMM Make</td>
			<td>none</td>
			<td>designed by authers and output by the 3D printer rented from DMM Make.</td>
		</tr>
		<tr>
			<td>frame</td>
			<td>DMM Make</td>
			<td>none</td>
			<td>designed by authers and output by the 3D printer rented from DMM Make.</td>
		</tr>
		<tr>
			<td>lenses</td>
			<td>RAINBOW CONTACT LENS</td>
			<td>none</td>
			<td>customized for mice use by the company</td>
		</tr>
		<tr>
			<td>cyanoacrylate glue</td>
			<td>OK MODEL</td>
			<td>MP 20g</td>
			<td></td>
		</tr>
		<tr>
			<td>dental adhesive resin cement</td>
			<td>SUN MEDICAL</td>
			<td>super bond</td>
			<td>contains the etching liquid used for removing the periosteum of the mouse skull</td>
		</tr>
		<tr>
			<td>infrared photorefractor</td>
			<td>Steinbeis Transfer Center</td>
			<td>none</td>
			<td>designed and offered by Dr. Frank Schaeffel from university of T&#252;bingen</td>
		</tr>
		<tr>
			<td>Spectral domain OCT</td>
			<td>Leica</td>
			<td>R4310</td>
			<td></td>
		</tr>
		<tr>
			<td>Tropicamide, Penylephrine Hydrochloride solution</td>
			<td>Santen</td>
			<td>Mydrin-P</td>
			<td></td>
		</tr>
		<tr>
			<td>midazolam</td>
			<td>Sandoz K.K.</td>
			<td>SANDOZ</td>
			<td>components for the anesthetic</td>
		</tr>
		<tr>
			<td>medetomidine&#160;</td>
			<td>Orion Corporation</td>
			<td>Domitor</td>
			<td>components for the anesthetic</td>
		</tr>
		<tr>
			<td>butorphanol tartrate&#160;</td>
			<td>Meiji Seika Pharma</td>
			<td>Vetorphale</td>
			<td>components for the anesthetic</td>
		</tr>
		<tr>
			<td>0.1 % purified sodium hyaluronate</td>
			<td>Santen</td>
			<td>Hyalein</td>
			<td></td>
		</tr>
		<tr>
			<td>atipamezole hydrochloride</td>
			<td>Zenoaq</td>
			<td>antisedan</td>
			<td></td>
		</tr>
	</tbody>
</table>

inducement and evaluation of a murine model of experimental myopia

Murine model of myopia can be a powerful tool for myopia research because of the comparatively easy genetic manipulation. One way to induce myopia in animals is to put clear minus lenses in front of eyes for weeks (lens-induced myopia, LIM). However, extant protocols for inducement and evaluation vary from laboratory to laboratory. Here, we described a highly practical and reproducible method to induce LIM in mice using newly designed eyeglasses. The method fixes the lens stably in front of the mouse eye while allows the lens to be taken off for cleaning or topical drug administration. The phenotype is robust and efficient, and the variance is small. The method described here can be applied to mice right after weaning which extends the possible duration for experiments. We also gave technical advises for achieving reproducible results in refraction and axial length measurements. We hope the step-by-step protocol described here and the detailed article can help researchers perform myopia experiments with myopia more smoothly and make the data comparable across laboratories.

At first, check if all the necessary parts are prepared (Figure 1a). An example of a piece of assembled eyeglasses is shown in Figure 1b. Except for the main body of the frames and the nut, all other parts are disposable for each mouse. A set of completed eyeglasses is shown in Figure 1c. Change the angle between the two frames to fit the mouse with different ages.
<p class="jove_content" fo:keep...

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Inducement and Evaluation of a Murine Model of Experimental Myopia

In this protocol, we describe the full process of experimental myopia inducement in mice using newly designed eyeglasses and the technic needed for achieving stable and reproducible results in ocular parameter measurements.

Murine model of myopia can be a powerful tool for myopia research because of the comparatively easy genetic manipulation. One way to induce myopia in ...

inducement-and-evaluation-of-a-murine-model-of-experimental-myopia

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9.7K Views.  Keio University School of Medicine. In this protocol, we describe the full process of experimental myopia inducement in mice using newly designed eyeglasses and the technic needed for achieving stable and reproducible results in ocular parameter measurements.

Video: Inducement and Evaluation of a Murine Model of Experimental Myopia

Hyponeophagia: A Measure of Anxiety in the Mouse

Before the present day, when fast-acting and potent rodenticides such as alpha-chloralose were not yet in use, the work of pest controllers was often hampered by a phenomenon known as "bait shyness". Mice and rats cannot vomit, due to the tightness of the cardiac sphincter of the stomach, so to overcome the problem of potential food toxicity they have evolved a strategy of first ingesting only very small amounts of novel substances. The amounts ingested then gradually increase until the animal has determined whether the substance is safe and nutritious. So the old rat-catchers would first put a palatable substance such as oatmeal, which was to be the vehicle for the toxin, in the infested area. Only when large amounts were being readily consumed would they then add the poison, in amounts calculated not to affect the taste of the vehicle. The poisoned bait, which the animals were now readily eating in large amounts, would then swiftly perform its function.
Bait shyness is now used in the behavioural laboratory as a way of measuring anxiety. A highly palatable but novel substance, such as sweet corn, nuts or sweetened condensed milk, is offered to the mice (or rats) in a novel situation, such as a new cage. The latency to consume a defined amount of the new food is then measured.
Robert M.J. Deacon can be reach at <a href="mailto:robert.deacon@psy.ox.ac.uk">robert.deacon@psy.ox.ac.uk</a>

Mice and rats, due to their innate cautiousness, are initially slow in consuming a novel food, particularly in a novel place. This hyponeophagia can readily be measured in the laboratory, even though laboratory animals are much less anxious than their wild counterparts

Before the present day, when fast-acting and potent rodenticides such as alpha-chloralose were not yet in use, the work of pest controllers was often ...

Isolation and Culture of Neural Crest Cells from Embryonic Murine Neural Tube

The embryonic neural crest (NC) is a multipotent progenitor population that originates at the dorsal aspect of the neural tube, undergoes an epithelial to mesenchymal transition (EMT) and migrates throughout the embryo, giving rise to diverse cell types 1-3. NC also has the unique ability to influence the differentiation and maturation of target organs4-6. When explanted in vitro, NC progenitors undergo self-renewal, migrate and differentiate into a variety of tissue types including neurons, glia, smooth muscle cells, cartilage and bone. 
NC multipotency was first described from explants of the avian neural tube7-9. In vitro isolation of NC cells facilitates the study of NC dynamics including proliferation, migration, and multipotency. Further work in the avian and rat systems demonstrated that explanted NC cells retain their NC potential when transplanted back into the embryo10-13. Because these inherent cellular properties are preserved in explanted NC progenitors, the neural tube explant assay provides an attractive option for studying the NC in vitro. 
To attain a better understanding of the mammalian NC, many methods have been employed to isolate NC populations. NC-derived progenitors can be cultured from post-migratory locations in both the embryo and adult to study the dynamics of post-migratory NC progenitors11,14-20, however isolation of NC progenitors as they emigrate from the neural tube provides optimal preservation of NC cell potential and migratory properties13,21,22. Some protocols employ fluorescence activated cell sorting (FACS) to isolate a NC population enriched for particular progenitors11,13,14,17. However, when starting with early stage embryos, cell numbers adequate for analyses are difficult to obtain with FACS, complicating the isolation of early NC populations from individual embryos. Here, we describe an approach that does not rely on FACS and results in an approximately 96% pure NC population based on a Wnt1-Cre activated lineage reporter23. 
The method presented here is adapted from protocols optimized for the culture of rat NC11,13. The advantages of this protocol compared to previous methods are that 1) the cells are not grown on a feeder layer, 2) FACS is not required to obtain a relatively pure NC population, 3) premigratory NC cells are isolated and 4) results are easily quantified. Furthermore, this protocol can be used for isolation of NC from any mutant mouse model, facilitating the study of NC characteristics with different genetic manipulations. The limitation of this approach is that the NC is removed from the context of the embryo, which is known to influence the survival, migration and differentiation of the NC2,24-28.

Isolation of embryonic neural crest from the neural tube facilitates the use of in vitro methods for studying migration, self-renewal, and multipotency of neural crest.

The embryonic neural crest (NC) is a multipotent progenitor population that originates at the dorsal aspect of the neural tube, undergoes an epithelial to ...

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 ...

Visual Evoked Potential Recording in a Rat Model of Experimental Optic Nerve Demyelination

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to monitor the disease course in the follow-up period. Changes in the VEP parameters closely correlate with pathological damage in the optic nerve. This protocol provides a detailed description about the rodent model of optic nerve microinjection, in which a partial demyelination lesion is produced in the optic nerve. VEP recording techniques are also discussed. Using skull implanted electrodes, we are able to acquire reproducible intra-session and between-session VEP traces. VEPs can be recorded on individual animals over a period of time to assess the functional changes in the optic nerve longitudinally. The optic nerve demyelination model, in conjunction with the VEP recording protocol, provides a tool to investigate the disease processes associated with demyelination and remyelination, and can potentially be employed to evaluate the effects of new remyelinating drugs or neuroprotective therapies.

Focal demyelination is induced in the optic nerve using lysolecithin microinjection. Visual evoked potentials are recorded via skull electrodes implanted over the visual cortex to examine the signal conduction along the visual pathway in vivo. This protocol details the surgical procedures underlying electrode implantation and optic nerve microinjection.

The visual evoked potential (VEP) recording is widely used in clinical practice to assess the severity of optic neuritis in its acute phase, and to ...

Evaluation of Bioenergetic Function in Cerebral Vascular Endothelial Cells

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types that comprise the BBB; these cells have a very high-energy demand, which requires optimal mitochondrial function. In the case of disease or injury, the mitochondrial function in these cells can be altered, resulting in disease or&#160;the opening of the BBB. In this manuscript, we introduce a method to measure mitochondrial function in CVE cells by using whole, intact cells and a bioanalyzer. A mito-stress assay is used to challenge the cells that have been perturbed, either physically or chemically, and evaluate their bioenergetic function. Additionally, this method also provides a useful way to screen new therapeutics that have direct effects on mitochondrial function. We have optimized the cell density necessary to yield oxygen consumption rates that allow for the calculation of a variety of mitochondrial parameters, including ATP production, maximal respiration, and spare capacity. We also show the sensitivity of the assay by demonstrating that the introduction of the&#160;microRNA, miR-34a, leads to a pronounced and detectable decrease in mitochondrial activity. While the data shown in this paper is optimized for the bEnd.3 cell line, we have also optimized the protocol for primary CVE cells, further suggesting the utility in preclinical and clinical models.

Endothelial cell mitochondria are critical to maintain blood-brain-barrier integrity. We introduce a protocol to measure bioenergetic function in cerebral vascular endothelial cells.

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types ...

Biodegradable Magnesium Stent Treatment of Saccular Aneurysms in a Rat Model - Introduction of the Surgical Technique

The steady progess in the armamentarium of techniques available for endovascular treatment of intracranial aneurysms requires affordable and reproducable experimental animal models to test novel embolization materials such as stents and flow diverters. The aim of the present project was to design a safe, fast, and standardized surgical technique for stent assisted embolization of saccular aneurysms in a rat animal model.
Saccular aneurysms were created from an arterial graft from the descending aorta.The aneurysms were microsurgically transplanted through end-to-side anastomosis to the infrarenal abdominal aorta of a syngenic male Wistar rat weighing &#62;500 g. Following aneurysm anastomosis, aneurysm embolization was performed using balloon expandable magnesium stents (2.5 mm x 6 mm). The stent system was retrograde introduced from the lower abdominal aorta using a modified Seldinger technique.
Following a pilot series of 6 animals, a total of 67 rats were operated according to established standard operating procedures. Mean surgery time, mean anastomosis time, and mean suturing time of the artery puncture site were 167 &#177; 22 min, 26 &#177; 6 min and 11 &#177; 5 min, respectively. The mortality rate was 6% (n=4). The morbidity rate was 7.5% (n=5), and in-stent thrombosis was found in 4 cases (n=2 early, n=2 late in stent thrombosis).
The results demonstrate the feasibility of standardized stent occlusion of saccular sidewall aneurysms in rats - with low rates of morbidity and mortality. This stent embolization procedure combines the opportunity to study novel concepts of stent or flow diverter based devices as well as the molecular aspects of healing.

Reproducable experimental animal models are needed for the testing of novel embolization materials, which have been designed to treat endovascular occlusion of intracranial aneurysms (IA). The present study aims to develop a safe and standardized surgical technique for stent assisted embolization of saccular aneurysms in a rat animal model.

The steady progess in the armamentarium of techniques available for endovascular treatment of intracranial aneurysms requires affordable and reproducable ...

A Volumetric Method for Quantification of Cerebral Vasospasm in a Murine Model of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a subtype of hemorrhagic stroke. Cerebral vasospasm that occurs in the aftermath of the bleeding is an important factor determining patient outcome and is therefore frequently taken as a study endpoint. However, in small animal studies on SAH, quantification of cerebral vasospasm is a major challenge. Here, an ex vivo method is presented that allows quantification of volumes of entire vessel segments, which can be used as an objective measure to quantify cerebral vasospasm. In a first step, endovascular casting of the cerebral vasculature is performed using a radiopaque casting agent. Then, cross-sectional imaging data are acquired by micro computed tomography. The final step involves 3-dimensional reconstruction of the virtual vascular tree, followed by an algorithm to calculate center lines and volumes of the selected vessel segments. The method resulted in a highly accurate virtual reconstruction of the cerebrovascular tree shown by a diameter-based comparison of anatomical samples with their virtual reconstructions. Compared with vessel diameters alone, the vessel volumes highlight the differences between vasospastic and non-vasospastic vessels shown in a series of SAH and sham-operated mice.

The goal of this article is to present a method that allows a 3-dimensional reconstruction of the cerebrovascular tree in mice after micro computed tomography and determination of volumes of entire vessel segments that can be used to quantify cerebral vasospasm in murine models of subarachnoid hemorrhage.

Subarachnoid hemorrhage (SAH) is a subtype of hemorrhagic stroke. Cerebral vasospasm that occurs in the aftermath of the bleeding is an important factor ...

Functional Evaluation of Olfactory Pathways in Living Xenopus Tadpoles

Xenopus tadpoles offer a unique platform to investigate the function of the nervous system. They provide multiple experimental advantages, such as accessibility to numerous imaging approaches, electrophysiological techniques and behavioral assays. The Xenopus tadpole olfactory system is particularly well suited to investigate the function of synapses established during normal development or reformed after injury. Here, we describe methodologies to evaluate the processing of olfactory information in living Xenopus larvae. We outline a combination of in vivo measurements of presynaptic calcium responses in glomeruli of the olfactory bulb with olfactory-guided behavior assays. Methods can be combined with the transection of olfactory nerves to study the rewiring of synaptic connectivity. Experiments are presented using both wild-type and genetically modified animals expressing GFP reporters in central nervous system cells. Application of the approaches described to genetically modified tadpoles can be useful for unraveling the molecular bases that define vertebrate behavior.

Functional Evaluation of Olfactory Pathways in Living Xenopus Tadpoles

Xenopus tadpoles offer a unique platform to investigate the function of the nervous system in vivo. We describe methodologies to evaluate the processing of olfactory information in living Xenopus larvae in normal rearing conditions or after injury.

Xenopus tadpoles offer a unique platform to investigate the function of the nervous system. They provide multiple experimental advantages, such as ...

Pre-Chiasmatic, Single Injection of Autologous Blood to Induce Experimental Subarachnoid Hemorrhage in a Rat Model

Despite advances in treatment over the last decades, subarachnoid hemorrhage (SAH) continues to carry a high burden of morbidity and mortality, largely afflicting a fairly young population. Several animal models of SAH have been developed to investigate the pathophysiological mechanisms behind SAH and to test pharmacological interventions. The pre-chiasmatic, single injection model in the rat presented in this article is an experimental model of SAH with a predetermined blood volume. Briefly, the animal is anesthetized, intubated, and kept under mechanical ventilation. Temperature is regulated with a heating pad. A catheter is placed in the tail artery, enabling continuous blood pressure measurement as well as blood sampling. The atlantooccipital membrane is incised and a catheter for pressure recording is placed in the cisterna magna to enable intracerebral pressure measurement. This catheter can also be used for intrathecal therapeutic interventions. The rat is placed in a stereotaxic frame, a burr hole is drilled anteriorly to the bregma, and a catheter is inserted through the burr hole and placed just anterior to the optic chiasm. Autologous blood (0.3 mL) is withdrawn from the tail catheter and manually injected. This results in a rise of intracerebral pressure and a decrease of cerebral blood flow. The animal is kept sedated for 30 min and given subcutaneous saline and analgesics. The animal is extubated and returned to its cage. The pre-chiasmatic model has a high reproducibility rate and limited variation between animals due to the pre-determined blood volume. It mimics SAH in humans making it a relevant model for SAH research.

Subarachnoid hemorrhage continues to carry a high burden of mortality and morbidity in man. To facilitate further research into the condition and its pathophysiology, a pre-chiasmatic, single injection model is presented.

Despite advances in treatment over the last decades, subarachnoid hemorrhage (SAH) continues to carry a high burden of morbidity and mortality, largely ...

A Model for Epilepsy of Infectious Etiology using Theiler's Murine Encephalomyelitis Virus

One of the main causes of epilepsy is an infection of the central nervous system (CNS); approximately 8% of patients who survive such an infection develop epilepsy as a consequence, with rates being significantly higher in less economically developed countries. This work provides an overview of modeling epilepsy of infectious etiology and using it as a platform for novel antiseizure compound testing. A protocol of epilepsy induction by non-stereotactic intracerebral injection of Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6 mice is presented, which replicates many of the early and chronic clinical symptoms of viral encephalitis and subsequent epilepsy in human patients. The clinical evaluation of mice during encephalitis to monitor seizure activity and detect the potential antiseizure effects of novel compounds is described. Furthermore, histopathological consequences of viral encephalitis and seizures such as hippocampal damage and neuroinflammation are shown, as well as long-term consequences such as spontaneous epileptic seizures. The TMEV model is one of the first translational, infection-driven, experimental platforms to allow for the investigation of the mechanisms of epilepsy development as a consequence of CNS infection. Thus, it also serves to identify potential therapeutic targets and compounds for patients at risk of developing epilepsy following a CNS infection.

Intracerebral infection with the Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6 mice replicates many of the early and chronic clinical symptoms of viral encephalitis and subsequent epilepsy in human patients. This paper describes the virus infection, symptoms, and histopathology of the TMEV model.

One of the main causes of epilepsy is an infection of the central nervous system (CNS); approximately 8% of patients who survive such an infection develop ...