Name: quantification of vascular parameters in whole mount retinas of mice with non-proliferative and proliferative retinopathies
Uploaded: 2022-03-12T15:00:00
Description: Watch this Scientific Journal Video about Quantification of Vascular Parameters in Whole Mount Retinas of Mice with Non-Proliferative and Proliferative Retinopathies at JoVE.com

We thank Carlos Mas, Mar&#237;a Pilar Crespo, and Cecilia Sampedro of CEMINCO (Centro de Micro y Nanoscop&#237;a C&#243;rdoba, CONICET-UNC, C&#243;rdoba, Argentina) for assistance in confocal microscopy, to Soledad Mir&#243; and Victoria Blanco for dedicated animal care and Laura Gatica for histological assistance. We also thank to Victor Diaz (Pro-Secretary of Institutional Communication of FCQ) for the video production and edition and Paul Hobson for his critical reading and language revision of the manuscript.
This article was funded by grants from Secretar&#237;a de Ciencia y Tecnolog&#237;a, Universidad Nacional de C&#243;rdoba (SECyT-UNC) Consolidar 2018-2021, Fondo para la Investigaci&#243;n Cient&#237;fica y Tecnol&#243;gica (FONCyT), Proyecto de Investigaci&#243;n en Ciencia y Tecnolog&#237;a (PICT) 2015 N&#176; 1314 (all to M.C.S.).

C57BL/6J mice were handled according to guidelines of the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Experimental procedures were designed and approved by the Institutional Animal Care and Use Committee (CICUAL) of the Faculty of Chemical Sciences, National University of C&#243;rdoba (Res. HCD 1216/18).
1. Preparation of buffer solutions and reagents
<ol>
	<li>Preparation of 1x phosphate buffer saline (PBS): Add 8 g of sodium chloride (NaCl), 0....

<ol>
	<li>Kur, J., Newman, E. A., Chan-Ling, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+physiological+mechanisms+underlying+blood+flow+regulation+in+the+retina+and+choroid+in+health+and+disease.">Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease.</a> Progress in Retinal and Eye Research. 31 (5), 377-406 (2012).</li><li>McDougal, D. H., Gamlin, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autonomic+control+of+the+eye.">Autonomic control of the eye.</a> Comprehensive Physiology. 5 (1), 439-473 (2015).</li><li>Selvam, S., Kumar, T., Fruttiger, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+vasculature+development+in+health+and+disease.">Retinal vasculature development in health and disease.</a> Progress in Retinal and Eye Research. 63, 1-19 (2018).</li><li>Wei, 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=Age-related+alterations+in+the+retinal+microvasculature,+microcirculation,+and+microstructure.">Age-related alterations in the retinal microvasculature, microcirculation, and microstructure.</a> Investigative Ophthalmology &amp; Visual Science. 58 (9), 3804-3817 (2017).</li><li>Lavia, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced+vessel+density+in+the+superficial+and+deep+plexuses+in+diabetic+retinopathy+is+associated+with+structural+changes+in+corresponding+retinal+layers.">Reduced vessel density in the superficial and deep plexuses in diabetic retinopathy is associated with structural changes in corresponding retinal layers.</a> PLoS One. 14 (7), 0219164 (2019).</li><li>Rosenblatt, T. 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J., Berglin, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+choroidal+and+retinal+neovascularization.">Animal models of choroidal and retinal neovascularization.</a> Progress in Retinal and Eye Research. 29 (6), 500-519 (2010).</li><li>Han, N., Xu, H., Yu, N., Wu, Y., Yu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MiR-203a-3p+inhibits+retinal+angiogenesis+and+alleviates+proliferative+diabetic+retinopathy+in+oxygen-induced+retinopathy+(OIR)+rat+model+via+targeting+VEGFA+and+HIF-1&#945;.">MiR-203a-3p inhibits retinal angiogenesis and alleviates proliferative diabetic retinopathy in oxygen-induced retinopathy (OIR) rat model via targeting VEGFA and HIF-1&#945;.</a> Clinical and Experimental Pharmacology &amp; Physiology. 47 (1), 85-94 (2020).</li><li>Paz, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolic+syndrome+triggered+by+fructose+diet+impairs+neuronal+function+and+vascular+integrity+in+ApoE-KO+mouse+retinas:+Implications+of+autophagy+deficient+activation.">Metabolic syndrome triggered by fructose diet impairs neuronal function and vascular integrity in ApoE-KO mouse retinas: Implications of autophagy deficient activation.</a> Frontiers in Cell and Developmental Biology. 8, 573987 (2020).</li><li>Connor, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+oxygen-induced+retinopathy+in+the+mouse:+a+model+of+vessel+loss,+vessel+regrowth+and+pathological+angiogenesis.">Quantification of oxygen-induced retinopathy in the mouse: a model of vessel loss, vessel regrowth and pathological angiogenesis.</a> Nature Protocols. 4 (11), 1565-1573 (2009).</li><li>Zarb, 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=Ossified+blood+vessels+in+primary+familial+brain+calcification+elicit+a+neurotoxic+astrocyte+response.">Ossified blood vessels in primary familial brain calcification elicit a neurotoxic astrocyte response.</a> Brain. 142 (4), 885-902 (2019).</li><li>Smith, L. E., 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=Oxygen-induced+retinopathy+in+the+mouse.">Oxygen-induced retinopathy in the mouse.</a> Investigative Ophthalmology &amp; Visual Science. 35 (1), 101-111 (1994).</li><li>Subirada, P. V., 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=Effect+of+autophagy+modulators+on+vascular,+glial,+and+neuronal+alterations+in+the+oxygen-induced+retinopathy+mouse+model.">Effect of autophagy modulators on vascular, glial, and neuronal alterations in the oxygen-induced retinopathy mouse model.</a> Frontiers in Cellular Neuroscience. 13, 279 (2019).</li><li>Lutty, G. A., McLeod, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+hyaloid,+choroidal+and+retinal+vasculatures+in+the+fetal+human+eye.">Development of the hyaloid, choroidal and retinal vasculatures in the fetal human eye.</a> Progress in Retinal and Eye Research. 62, 58-76 (2018).</li><li>Kim, C. B., D'Amore, P. A., Connor, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Revisiting+the+mouse+model+of+oxygen-induced+retinopathy.">Revisiting the mouse model of oxygen-induced retinopathy.</a> Eye and Brain. 8, 67-79 (2016).</li><li>Guaiquil, V. 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=A+murine+model+for+retinopathy+of+prematurity+identifies+endothelial+cell+proliferation+as+a+potential+mechanism+for+plus+disease.">A murine model for retinopathy of prematurity identifies endothelial cell proliferation as a potential mechanism for plus disease.</a> Investigative Ophthalmology &amp; Visual Science. 54 (8), 5294-5302 (2013).</li><li>Mezu-Ndubuisi, O. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+angiography+quantifies+oxygen-induced+retinopathy+vascular+recovery.">In vivo angiography quantifies oxygen-induced retinopathy vascular recovery.</a> Optometry and Vision Science: Official Publication of the American Academy of Optometry. 93 (10), 1268-1279 (2016).</li><li>Scott, A., Powner, M. 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H., Wang, Z., Sun, Y., Chen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+ocular+angiogenesis:+from+development+to+pathologies.">Animal models of ocular angiogenesis: from development to pathologies.</a> FASEB Journal. 31 (11), 4665-4681 (2017).</li><li>Grossniklaus, H. E., Kang, S. J., Berglin, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+choroidal+and+retinal+neovascularization.">Animal models of choroidal and retinal neovascularization.</a> Progress in Retinal and Eye Research. 29 (6), 500-519 (2010).</li><li>Kern, T. S., Antonetti, D. A., Smith, L. E. 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W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contribution+of+microglia+as+passenger+leukocytes+to+the+fate+of+intraocular+neuronal+retinal+grafts.">Contribution of microglia as passenger leukocytes to the fate of intraocular neuronal retinal grafts.</a> Investigative Ophthalmology &amp; Visual Science. 39 (12), 2384-2393 (1998).</li><li>Mazzaferri, J., Larriv&#233;e, B., Cakir, B., Sapieha, P., Costantino, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+machine+learning+approach+for+automated+assessment+of+retinal+vasculature+in+the+oxygen+induced+retinopathy+model.">A machine learning approach for automated assessment of retinal vasculature in the oxygen induced retinopathy model.</a> Scientific Reports. 8 (1), 3916 (2018).</li><li>Milde, F., Lauw, S., Koumoutsakos, P., Iruela-Arispe, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mouse+retina+in+3D:+quantification+of+vascular+growth+and+remodeling.">The mouse retina in 3D: quantification of vascular growth and remodeling.</a> Integrative Biology: Quantitative Biosciences from Nano to Macro (Camb). 5 (12), 1426-1438 (2013).</li><li>Yang, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pericytes+of+indirect+contact+coculture+decrease+integrity+of+inner+blood-retina+barrier+model+in+vitro+by+upgrading+MMP-2/9+activity.">Pericytes of indirect contact coculture decrease integrity of inner blood-retina barrier model in vitro by upgrading MMP-2/9 activity.</a> Disease Markers. 2021, 7124835 (2021).</li><li>Huang, Q., Wang, S., Sorenson, C. 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Animal models of retinopathies are powerful tools for studying vascular development, remodeling, or pathological angiogenesis. The success of these studies in the field relies on the easy access to the tissue that allows to perform a wide variety of techniques, providing data from in vivo and postmortem mice26,27. Moreover, great correlation has been found between in vivo studies and clinical analysis, providing solid traceability and r...

The eyes are nourished by two arterio-venous system: the choroidal vasculature, an external vascular network that irrigates retinal pigmented epithelium and photoreceptors; and the neuro-retinal vasculature that irrigate the ganglion cells layer and the inner nuclear layer of the retina1. The retinal vasculature is an organized network of vessels that deliver nutrients and oxygen to the retinal cells and harvest waste products to ensure proper visual signaling transduction. This vasculature has some distinct features, including: the lack of autonomous innervation, the regulation of vascular tone by intrinsic retinal mechanisms and the possession of a complex retinal-blood barrier2. Therefore, retinal vasculature has been the focus of many researchers who have extensively studied not only vasculogenesis during the development, but also the alterations and the pathological angiogenesis that these vessels undergo in diseases3. The most common vascular changes observed in retinopathies are vessel dilatation, neovascularization, loss of vascular arborization and deformation of the retinal main vessels, which makes them more ziggaggy4,5,6. One or more of the described alterations are the earliest signs to be detected by clinicians. Vascular visualization provides a rapid, non-invasive, and inexpensive screening method7. The extensive study of the alterations observed in the vascular tree will determine whether the retinopathy is non-proliferative or proliferative and the further treatment. The non-proliferative retinopathies can manifest themselves with aberrant vascular morphology, decreased vascular density, acellular capillaries, pericytes death, macular edema, among others. In addition, proliferative retinopathies also develop increased vascular permeability, extracellular remodeling, and the formation of vascular tufts toward the vitreous cavity that easily breakdown or induce retinal detachment8.
Once detected, the retinopathy can be monitored through its vascular changes9,10. The progression of the pathology can be followed through the structural changes of the vessels, which clearly define stages of the disease11. The quantification of vascular alterations in these models allowed to correlate vessel changes and neuronal death and to test pharmacological therapies for patients in different phases of the disease.
In light of the above statements, we consider that the recognition and quantification of vascular alterations are fundamental in retinopathies studies. In this work, we will show how to measure different vascular parameters. To do that, we will employ two animal models. One of them is the Oxygen-induced retinopathy mouse model12, which mimics Retinopathy of Prematurity and some aspects of proliferative Diabetic Retinopathy13,14. In this model, we will measure avascular areas, neovascular areas and the dilatation and tortuosity of main vessels. In our laboratory, a Metabolic Syndrome (MetS) mouse model has been developed, which induces a non-proliferative retinopathy15. Here, we will evaluate vascular density and branching.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Aluminuim foil</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Merck</td>
			<td>A4503</td>
			<td>quality</td>
		</tr>
		<tr>
			<td>Calcium chloride dihydrate</td>
			<td>Merck</td>
			<td>C3306</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Biopack</td>
			<td>9632.08</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal Microscope FV1200</td>
			<td>Olympus</td>
			<td>FV1200</td>
			<td>with motorized plate</td>
		</tr>
		<tr>
			<td>Covers</td>
			<td>Paul Marienfeld GmnH &#38; Co.</td>
			<td>111520</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting Microscope</td>
			<td>NIKON</td>
			<td>SMZ645</td>
			<td></td>
		</tr>
		<tr>
			<td>Disodium-hydrogen-phosphate dihydrate</td>
			<td>Merck</td>
			<td>119753</td>
			<td></td>
		</tr>
		<tr>
			<td>200 &#181;L&#160; tube</td>
			<td>Merck</td>
			<td>Z316121</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter paper</td>
			<td>Merck</td>
			<td>WHA5201090</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator shaker GyroMini</td>
			<td>LabNet International</td>
			<td>S0500</td>
			<td></td>
		</tr>
		<tr>
			<td>Isolectin GS-IB4 From Griffonia simplicifolia, Alexa Fluor 488 Conjugate</td>
			<td>Invitrogen</td>
			<td>I21411</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(vinyl alcohol) (Mowiol 4-88)</td>
			<td>Merck</td>
			<td>475904</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Merck</td>
			<td>158127</td>
			<td></td>
		</tr>
		<tr>
			<td>pHmeter</td>
			<td>SANXIN</td>
			<td>PHS-3D-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>Merck</td>
			<td>P9541</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium-dihydrogen phosphate</td>
			<td>Merck</td>
			<td>1,04,873</td>
			<td></td>
		</tr>
		<tr>
			<td>Slides</td>
			<td>Fisher Scientific</td>
			<td>12-550-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Merck</td>
			<td>S3014</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Merck</td>
			<td>S5881</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>Merck</td>
			<td>GE17-1321-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Merck</td>
			<td>X100-1GA</td>
			<td></td>
		</tr>
		<tr>
			<td>Vessel Analysis Fiji software</td>
			<td>Mai Elfarnawany</td>
			<td></td>
			<td>https://imagej.net/Vessel_Analysis</td>
		</tr>
	</tbody>
</table>

quantification of vascular parameters in whole mount retinas of mice with non-proliferative and proliferative retinopathies

Retinopathies are a heterogeneous group of diseases that affect the neurosensory tissue of the eye. They are characterized by neurodegeneration, gliosis&#160;and a progressive change in vascular function and structure. Although the onset of the retinopathies is characterized by subtle disturbances in visual perception, the modifications in the vascular plexus are the first signs detected by clinicians. The absence or presence of neovascularization determines whether the retinopathy is classified as either non-proliferative (NPDR) or proliferative (PDR). In this sense, several animal models tried to mimic specific vascular features of each stage to determine the underlying mechanisms involved in endothelium alterations, neuronal death and other events taking place in the retina. In this article, we will provide a complete description of the procedures required for the measurement of retinal vascular parameters in adults and early birth mice at postnatal day (P)17. We will detail the protocols to carry out retinal vascular staining with Isolectin GSA-IB4 in whole mounts for later microscopic visualization. Key steps for image processing with Image J Fiji software are also provided, therefore, the readers will be able to measure vessel density, diameter and tortuosity, vascular branching, as well as avascular and neovascular areas. These tools are highly helpful to evaluate and quantify vascular alterations in both non-proliferative and proliferative retinopathies.

As described in the protocol section, from a single fluorescent staining assay you can obtain the vascular morphology and evaluate several parameters of interest quantitatively. The search of a specific alteration will depend on the type of retinopathy studied. In this article, avascular and neovascular areas, tortuosity, and dilatation were evaluated in a mouse model of proliferative retinopathy, whereas the vascular branching and density were analyzed in a MetS mouse model, which induces a non-proliferative retinopathy...

Watch this Scientific Journal Video about Quantification of Vascular Parameters in Whole Mount Retinas of Mice with Non-Proliferative and Proliferative Retinopathies at JoVE.com

Quantification of Vascular Parameters in Whole Mount Retinas of Mice with Non-Proliferative and Proliferative Retinopathies

This article describes a well-established and reproducible lectin stain assay for the whole mount retinal preparations and the protocols required for the quantitative measurement of vascular parameters frequently altered in proliferative and non-proliferative retinopathies.

Retinopathies are a heterogeneous group of diseases that affect the neurosensory tissue of the eye. They are characterized by neurodegeneration, ...

In retinopathies, vascular alterations are the first sign to be detected by clinicians. They follow the progression of the disease, and they choose a treatment according to these changes. Several animal models have been developed in order to study different stages of the pathology.In this work, we are going to show how to measure different vascular alterations. For that, we are going to employ two animal models. One of these is the Oxygen-Induced Retinopathy mouse model, which reproduces the retinopathy of prematurity and some aspects of the proliferative diabetic retinopathy.Here, we are going to measure avascular areas, neovascular areas, and the dilatation and tortuosity of the arterioles. In our laboratory, a metabolic syndrome mouse model was developed, which induces a nonproliferative retinopathy. Vascular density and branching were evaluated in this work.Upon mice sacrifice, enucleatize with scissors. Fix enucleated eyes with freshly-prepared paraformaldehyde for one hour at room temperature. Under the dissecting microscope, remove the corneas with scissors by cutting along the limbus and dissect the whole retinas.Discard the anterior segment of the eye, and then separate the retina from the RPE-choroid. Place the retinas in 200 microliter tubes. Then block and permeabilize the retinas in 100 microliters of TBS containing 5%bovine serum albumin Triton during six hours at four degrees with gentle agitation in shaker.Then invert the tube to place the retina in the cup and remove the blocking solution with pipette. Add 100 microliter solution containing isolectin. Wrap the tubes with aluminum foil to protect samples from light.Incubate the retinas with lectin solution overnight at four degrees with gentle agitation in shaker. Wash the retinas with 100 microliters of TBS-Triton for 20 minutes with gentle agitation in shaker. Repeat this step three times.Place the retina in a slide and add a drop of PBS. Under dissecting microscope, perform four equally-distant cuts from the edges of the retina towards the optic nerve. To unfold the petals of the retina, use forceps or small pieces of filter paper.Ensure that photoreceptor side is facing down. Remove the remaining PBS off the slide with filter paper. Then add a mounting median and coverslip.Let it dry for one hour at room temperature. Store slides at four degrees protected from light. At the confocal microscope, place the slide in the plate face down.Focus the superior plexus of the retinal vasculature and select an area to start the image acquisition. Set general laser parameters in the software. Set the coordinates in X, Y, and Z axes.Initialize the scanning. Once scanning process finishes, open the image and save it with a preferred extension. In the ImageJ FIJI software, go to the Menu Bar and click File, Open.Select the image to process. In the Bio-Formats Import Option window, select Display OME-XML Metadata and click OK.In the OME Metadata window, search for pixel size information. Copy this data.For image calibration, go to the Menu Bar and select Image Properties. Copy the information and click OK.Assign a preferred lut to the image. To visualize all stack in a single image, go to the Menu Bar and select Image, Stacks, Z Project.In the projection window displayed, select all the stacks where vessels are visualized. In Projection Type, choose Average Intensity and click OK.Go to the Menu Bar, Image, Adjust, Brightness/Contrast. Click Apply and save changes.Copy the parameters selected for brightness and contrast. These must be identical for all images. In the Menu Bar, choose the Wand tool.Select the retinal area that lacks formed vessels. Press T on the keyboard to record the select areas in the ROI Manager. Click Measure in the ROI Manager to obtain the avascular area information.Repeat these steps to measure the total area of the retina. In the Menu Bar, choose the Wand tool. Zoom in the image to better visualize neovessels.Select the neovessels one by one with the Wand tool. Press the T letter on the keyboard to record the selected area in the ROI Manager. Click Measure in the ROI Manager to obtain the area data.In the Menu Bar, select the Straight Line tool. Zoom in the image to better visualize the vessel wall. Perform three transversal lines to the main vessel before the first branch.Press T on the keyboard to record the selected areas in the ROI Manager. Click Measure in the ROI Manager to obtain the distance data. In the Menu Bar, click the Straight Line tool icon with the right button of the mouse and select Segmented Line.Draw a line inside the vessel from the optic nerve until the first vessel ramification, following the vascular shape. Press the T letter on the keyboard to record the selected area in the ROI Manager. In the Menu Bar, select the Straight Line tool.Draw a line from the optic nerve until the first vessel ramification. Press the T letter on the keyboard to record the selected area in the ROI Manager. Click Measure on the ROI Manager to obtain the distances data.With the Oval tool of the Menu Bar, define an area applied equally to all experimental conditions. The selected area must be a concentric circle drawn around the optic nerve. Press the T letter on the keyboard to record the selected area in the ROI Manager.Manually, count the number of primary branches arising from main vessels inside the selection area. Transform the image to 8-bit mode. Go to Plugins in the Menu Bar, select Vessel Analysis, Vascular Density.Define an area with the Square tool of the Menu Bar where you want to measure vessel density. Click OK.The program will display a new window with the information required. In the first experimental example, the Oxygen-Induced Retinopathy mouse model was employed.Intravitreal injections were performed at postnatal day 12 to determine the effectiveness of a drug as an antiangiogenic. Mice injected with vehicle were employed as control. The avascular areas are defined as the zones that lacks retinal blood vessels.From the images acquired, avascular areas can be quantified as the sum of the regions without vessels divided the total area of the retina. Areas with mechanical damage also show absence of vessels. To identify damaged areas, analyze the integrity of neuronal layers with Hoechst stain.Neovessels are small caliber vessels that originate from pre-existing vessels of the superior vascular plexus. We calculated the area occupied by neovessels'tufts by quantifying the neovascular area of the retina occupied by the total area of the retina. As neovessels'shape and size is variable, occasionally, they can look similar to debris and artifacts.To distinguish neovessels, verify that the tuft grows from a mature vessel. For the analysis of the dilatation, we measured the main vessel diameter at three heights before the first branch. Researchers must define a predetermined distance to measure vessel diameter in order to reduce variability among results.Ideally, the furthest point from the optic nerve should be around 300 micrometers. We suggest to perform the analysis, and later, average of at least six animals per condition. Regarding to tortuosity, we measure the distance traveled by the main vessel following its shape, respect to the straight-line distance between the optic nerve and the first branching point.As we can see in the image, there is heterogeneity in the sinuosity of main vessels. To obtain a representative result, not less than six mice per condition must be quantified. The latest parameters, vascular branching and density, were analyzed in a metabolic syndrome model exhibiting non-proliferative retinopathy.For the measurement of vascular branching, we defined the quantification area by drawing a concentric circle, and then we counted, one by one, the primary branches arising from a main central vessel. From the images acquired, the vascular density was quantified as the area occupied by vessels divided by the area of the ROI, which was positioned in different places in each microphotograph. Avoid quantifying areas with mechanical damage.If there are more than two areas with punctures, the retina must be discarded. In summary, in this article, we have shown classical, well-established and reproducible techniques to quantify some of the most relevant parameters taking account in the clinical practice.

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Research

JoVE Journal

Neuroscience

Visualization of the Embryonic Nervous System in Whole-mount Drosophila Embryos

The Drosophila embryo is an attractive model system for investigating the cellular and molecular basis of neuronal development. Here we describe the procedure for the visualization of Drosophila embryonic nervous system using antibodies to neuronal proteins. Since the entire embryonic peripheral nervous and central nervous systems are well characterized at the level of individual cells (Dambly-Chaudi&egrave;re et al., 1986; Bodmer et al., 1987; Bodmer et al., 1989), any aberrations to these systems can be easily identified using antibodies to different neuronal proteins. The developing embryos are collected at certain times to ensure that the embryos are in the proper developmental stages for visualization. After collection, the outer layers of the embryo, the chorion membrane and the vitelline envelope that surrounds the embryo, are removed before fixation. Embryos are then incubated with neuronal antibodies and visualized using fluorescently labeled secondary antibodies. Embryos at stages 12-17 are visualized to access the embryonic nervous system. At stage 12 the CNS germ band starts shortening and by stage 15 the definitive pattern of the commissure has been achieved. By stage 17 the CNS contracts and the PNS is fully developed (Campos-Ortega et al. 1985). Thus changes in the pattern of the PNS and CNS can be easily observed during these developmental stages.

Visualization of the Embryonic Nervous System in Whole-mount Drosophila Embryos

We describe the procedure to prepare staged Drosophila embryos for the visualization of the embryonic nervous system during embryogenesis.

The Drosophila embryo is an attractive model system for investigating the cellular and molecular basis of neuronal development. Here we describe the ...

Dissection of a Mouse Eye for a Whole Mount of the Retinal Pigment Epithelium

The retinal pigment epithelium (RPE) lies at the back of the mammalian eye, just under the neural retina, which contains the photoreceptors (rods and cones). The RPE is a monolayer of pigmented cuboidal cells and associates closely with the neural retina just above it. This association makes the RPE of great interest to researchers studying retinal diseases. The RPE is also the site of an in vivo assay of homology-directed DNA repair, the pun assay. The mouse eye is particularly difficult to dissect due to its small size (about 3.5mm in diameter) and its spherical shape. This article demonstrates in detail a procedure for dissection of the eye resulting in a whole mount of the RPE. In this procedure, we show how to work with, rather than against, the spherical structure of the eye. Briefly, the connective tissue, muscle, and optic nerve are removed from the back of the eye. Then, the cornea and lens are removed. Next, strategic cuts are made that result in significant flattening of the remaining tissue. Finally, the neural retina is gently lifted off, revealing an intact RPE, which is still attached to the underlying choroid and sclera. This whole mount can be used to perform the pun assay or for immunohistochemistry or immunofluorescent assessment of the RPE tissue.

A formal demonstration of the dissection of a mouse eye, resulting in a whole mount of the retinal pigment epithelium.

The retinal pigment epithelium (RPE) lies at the back of the mammalian eye, just under the neural retina, which contains the photoreceptors (rods and ...

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat muscles can offer significant advantage over traditionally used thicker muscles, such as those from the hind limb (e.g. gastrocnemius). Thin muscles allow for comprehensive overview of the entire innervation pattern for a given muscle, which in turn permits identification of selectively vulnerable pools of motor neurons. These muscles also allow analysis of parameters such as motor unit size, axonal branching, and terminal/nodal sprouting. A common obstacle in using such muscles is gaining the technical expertise to dissect them. In this video, we detail the protocol for dissecting the transversus abdominis (TVA) muscle from young mice and performing immunofluorescence to visualize axons and neuromuscular junctions (NMJs). We demonstrate that this technique gives a complete overview of the innervation pattern of the TVA muscle&#160;and can be used to investigate NMJ pathology in a mouse model of the childhood motor neuron disease, spinal muscular atrophy.

Dissection of the Transversus Abdominis Muscle for Whole-mount Neuromuscular Junction Analysis

In this video we demonstrate a protocol for dissection of the transversus abdominis muscle of the mouse and use immunofluorescence and microscopy to visualize neuromuscular junctions.

Analysis of neuromuscular junction morphology can give important insight into the physiological status of a given motor neuron. Analysis of thin flat ...

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this information to the brain. As such, determining how olfactory information is transferred to the brain, modifying both perception and behavior, merits investigation. Interestingly, there is emerging evidence that cellular transduction and transcriptional factors are involved in the diversification of olfactory receptor neuron. Here we provide a robust whole mount immunological labeling method to assay in vivo olfactory receptor neuron organization. Using this method, we identified all olfactory receptor neurons with anti-ELAV antibody, a known pan-neural marker and Or49a-mCD8::GFP, an olfactory receptor neuron specifically expressed in Nba neuron using anti-GFP antibody.

Whole Mount Immunolabeling of Olfactory Receptor Neurons in the Drosophila Antenna

Herein we describe the process of whole mount immunostaining of Drosophila antennae, which enables us to better understand the molecular mechanisms involved in the diversification of olfactory receptor neurons (ORN)s.

Odorant molecules bind to their target receptors in a precise and coordinated manner. Each receptor recognizes a specific signal and relays this ...

Whole-mount Imaging of Mouse Embryo Sensory Axon Projections

The visualization of full-length neuronal projections in embryos is essential to gain an understanding of how mammalian neuronal networks develop. Here we describe a method to label in situ a subset of dorsal root ganglion (DRG) axon projections to assess their phenotypic characteristics using several genetically manipulated mouse lines. The TrkA-positive neurons are nociceptor neurons, dedicated to the transmission of pain signals. We utilize a TrkAtaulacZ mouse line to label the trajectories of all TrkA-positive peripheral axons in the intact mouse embryo. We further breed the TrkAtaulacZ line onto a Bax null background, which essentially abolishes neuronal apoptosis, in order to assess growth-related questions independently of possible effects of genetic manipulations on neuronal survival. Subsequently, genetically modified mice of interest are bred with the TrkAtaulacZ/Bax null line and are then ready for study using the techniques described herein. This presentation includes detailed information on mouse breeding plans, genotyping at the time of dissection, tissue preparation, staining and clearing to allow for visualization of full-length axonal trajectories in whole-mount preparation.

We present here an optimized protocol to genotype, stain and prepare fetal mice for the imaging of peripheral nociceptor axon projections in the whole animal, as an effective method to assess sensory axon growth phenotypes in developing genetically engineered mice.

The visualization of full-length neuronal projections in embryos is essential to gain an understanding of how mammalian neuronal networks develop. Here we ...

Whole Mount Labeling of Cilia in the Main Olfactory System of Mice

The mouse olfactory system comprises 6-10 million olfactory sensory neurons in the epithelium lining the nasal cavity. Olfactory neurons extend a single dendrite to the surface of the epithelium, ending in a structure called dendritic knob. Cilia emanate from this knob into the mucus covering the epithelial surface. The proteins of the olfactory signal transduction cascade are mainly localized in the ciliary membrane, being in direct contact with volatile substances in the environment. For a detailed understanding of olfactory signal transduction, one important aspect is the exact morphological analysis of signaling protein distribution. Using light microscopical approaches in conventional cryosections, protein localization in olfactory cilia is difficult to determine due to the density of ciliary structures. To overcome this problem, we optimized an approach for whole mount labeling of cilia, leading to improved visualization of their morphology and the distribution of signaling proteins. We demonstrate the power of this approach by comparing whole mount and conventional cryosection labeling of Kirrel2. This axon-guidance adhesion molecule is known to localize in a subset of sensory neurons and their axons in an activity-dependent manner. Whole mount cilia labeling revealed an additional and novel picture of the localization of this protein.

Cilia of olfactory sensory neurons contain proteins of the signal transduction cascade, but a detailed spatial analysis of their distribution is difficult in cryosections. We describe here an optimized approach for whole mount labeling and en face visualization of ciliary proteins.

The mouse olfactory system comprises 6-10 million olfactory sensory neurons in the epithelium lining the nasal cavity. Olfactory neurons extend a single ...

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

Ex vivo ERG can be used to record electrical activity of retinal cells directly from isolated intact retinas of animals or humans. We demonstrate here how common in vivo ERG systems can be adapted for ex vivo ERG recordings in order to dissect the electrical activity of retinal cells.

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise ...

Whole Mount Dissection and Immunofluorescence of the Adult Mouse Cochlea

The organ of Corti, housed in the cochlea of the inner ear, contains mechanosensory hair cells and surrounding supporting cells which are organized in a spiral shape and have a tonotopic gradient for sound detection. The mouse cochlea is approximately 6 mm long and often divided into three turns (apex, middle, and base) for analysis. To investigate cell loss, cell division, or mosaic gene expression, the whole mount or surface preparation of the cochlea is useful. This dissection method allows visualization of all cells within the organ of Corti when combined with immunostaining and confocal microscopy to image cells at different planes in the z-axis. Multiple optical cross-sections can also be obtained from these z-stack images. In addition, the whole mount dissection method can be used for scanning electron microscopy, although a different fixation method is needed. Here, we present a method to isolate the organ of Corti as three intact cochlear turns (apex, middle, and base). This method can be used for mice ranging from one week of age through adulthood and differs from the technique used for neonatal samples where calcification of the cochlea is incomplete. A slightly modified version can be used for dissection of the rat cochlea. We also demonstrate a procedure for immunostaining with fluorescently tagged antibodies.

We present a method to isolate the adult organ of Corti as three intact cochlear turns (apex, middle, and base). We also demonstrate a procedure for immunostaining with fluorescently tagged antibodies. Together these techniques allow the study of hair cells, supporting cells, and other cell types found in the cochlea.

The organ of Corti, housed in the cochlea of the inner ear, contains mechanosensory hair cells and surrounding supporting cells which are organized in a ...

HSV-Mediated Transgene Expression of Chimeric Constructs to Study Behavioral Function of GPCR Heteromers in Mice

The heteromeric receptor complex between 5-HT2A and mGlu2 has been implicated in some of the behavioral phenotypes in mouse models of psychosis1,2. Consequently, investigation of structural details of the interaction between 5-HT2A and mGlu2 affecting schizophrenia-related behaviors represents a powerful translational tool. As previously shown, the head-twitch response (HTR) in mice is elicited by hallucinogenic drugs and this behavioral response is absent in 5-HT2A knockout (KO) mice3,4. Additionally, by conditionally expressing the 5-HT2A receptor only in cortex, it was demonstrated that 5-HT2A receptor-dependent signaling pathways on cortical pyramidal neurons are sufficient to elicit head-twitch behavior in response to hallucinogenic drugs3. Finally, it has been shown that the head-twitch behavioral response induced by the hallucinogens DOI and lysergic acid diethylamide (LSD) is significantly decreased in mGlu2-KO mice5. These findings suggest that mGlu2 is at least in part necessary for the 5-HT2A receptor-dependent psychosis-like behavioral effects induced by LSD-like drugs. However, this does not provide evidence as to whether the 5-HT2A-mGlu2 receptor complex is necessary for this behavioral phenotype. To address this question, herpes simplex virus (HSV) constructs to express either mGlu2 or mGlu2&#916;TM4N (mGlu2/mGlu3 chimeric construct that does not form the 5-HT2A-mGlu2 receptor complex) in the frontal cortex of mGlu2-KO mice were used to examine whether this GPCR heteromeric complex is needed for the behavioral effects induced by LSD-like drugs6.

This article describes how to inject viral vectors into the mouse frontal cortex to test behavioral assays that require GPCR heteromeric formation.

The heteromeric receptor complex between 5-HT2A and mGlu2 has been implicated in some of the behavioral phenotypes in mouse models of psychosis1,2.  ...

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the molecular and cellular basis of higher brain functions. A whole-mount preparation of adult brains with well-preserved morphology is critical for such whole brain-based studies, but can be technically challenging and time-consuming. This protocol describes an easy-to-learn, one-step dissection approach of an adult fly head in less than 10 s, while keeping the intact brain attached to the rest of the body to facilitate subsequent processing steps. The procedure helps remove most of the eye and tracheal tissues normally associated with the brain that can interfere with the later imaging step, and also places less demand on the quality of the dissecting forceps. Additionally, we describe a simple method that allows convenient flipping of the mounted brain samples on a coverslip, which is important for imaging both sides of the brains with similar signal intensity and quality. As an example of the protocol, we present an analysis of dopaminergic (DA) neurons in adult brains of WT (w1118) flies. The high efficacy of the dissection method makes it particularly useful for large-scale adult brain-based studies in Drosophila.

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

The adult Drosophila brain is a valuable system for studying neuronal circuitry, higher brain functions, and complex disorders. An efficient method to dissect whole brain tissue from the small fly head will facilitate brain-based studies. Here we describe a simple, one-step dissection protocol of adult brains with well-preserved morphology.

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the ...