Name: dissection of human retina and rpe-choroid for proteomic analysis
Uploaded: 2017-11-12T14:00:00.000+00:00
Duration: 6 min 54 s
Description: Watch this Scientific Journal Video about Dissection of Human Retina and RPE-Choroid for Proteomic Analysis at JoVE.com

VBM is supported by NIH grants [K08EY020530, R01EY024665, R01EY025225, R01EY024698 and R21AG050437], Doris Duke Charitable Foundation Grant #: 2013103, and Research to Prevent Blindness (RPB), New York, NY. MT and GV are supported by NIH grant T32GM007337.

This study was approved by the University of Iowa&#39;s Institutional Review Board and adheres to the tenets set forth in the Declaration of Helsinki.
1. Foveal and Macular Biopsy Punch
<ol>
	<li>Open and butterfly the human eye, such that it consists of 4 separate flaps of tissue, as described in a previous publication.5</li>
	<li>Beginning with a butterflied human eye placed in a Petri dish, center a 4-mm punch biopsy tool over the fovea, press down, and roll gently until an incision is made around the fovea.</li>
	<li>Next, generate an incision around the macula by centering and pressing down an 8-mm skin punch biopsy tool within the arcades of the macula, applying gentle pressure and rolling. This will produce a second, outer ring of tissue surrounding the first.</li>
</ol>
2. Peripheral Retinal Biopsy Punch
<ol>
	<li>Use the 4-mm skin punch biopsy tool to make a series of punches in the peripheral retina, just outside the arcade. Here, make two punches for each quadrant flap. 
	NOTE: After all the punches are made, the eye will have two concentric punches in the center, representing the fovea and macula, and two punches at the base of each flap-totaling 8 punches in the peripheral retina.</li>
</ol>
3. Fovea and Macula Biopsy Collection
<ol>
	<li>As the tissue is now ready for collection, collect all tissue biopsies in separate microfuge tubes and freeze using liquid nitrogen for downstream processing. Store all samples at -80 &#176;C until utilization.</li>
	<li>Use a curved 0.12 Colibri forceps to grab the edges of the translucent tissue of the retinal fovea. To collect, elevate and separate the foveal tissue from the underlying RPE-choroid.</li>
	<li>Similarly, use the 0.12 Colibri forceps to grasp the outer ring of the translucent macula tissue. If the tissue is still attached to underlying or adjacent tissue, use a pair of Westcott scissors to carefully trim the edge, capturing just the retinal component and dissecting away any optic nerve tissue included in the punch.</li>
</ol>
4. Peripheral Retina Collection
<ol>
	<li>Use the curved 0.12 Colibri forceps to gently separate the peripheral retinal tissue discs from the underlying RPE-choroid and place within individual microfuge tubes.</li>
	<li>In the case of residual vitreous gel, use the forceps to lift and separate the gel away as much as possible before collection of the retinal tissue. Once the retina has been removed, the pigmented RPE-choroid remains below.</li>
</ol>
5. Foveal and Macula RPE-Choroid Collection
<ol>
	<li>Use the 0.12 Colibri forceps to grasp the edges of the dark RPE-choroid tissue that lies beneath the area of the removed fovea. Carefully separate this tissue from the sclera and collect.</li>
	<li>Using the same forceps, grasp the edges of the outer ring of dark RPE-choroid tissue underlying the removed macular area. Carefully separate this tissue from the sclera by grasping the edges at different points around the ring and lightly pulling. Eventually, the ring of RPE-choroid tissue will be dislodged and may be collected. 
	NOTE: Secondary forceps in the opposite hand can be helpful in manipulating the RPE-choroid tissue during removal. Like the retinal tissue, Wescott scissors can be used to assist in removing any tissue that was not fully incised using the punch tool.</li>
</ol>
6. Peripheral Retina RPE-Choroid Collection
<ol>
	<li>Use the 0.12 Colibri forceps to peel away the RPE-choroid in the 8 peripheral punch areas.</li>
	<li>As previously, place the RPE-choroid tissue in microfuge tubes and freeze using liquid nitrogen for downstream processing. Keep all samples at -80 &#176;C until utilization.</li>
</ol>
7. Scissor Dissection
NOTE: If the punch biopsy blade is dull or the punch biopsy tool is not pushed hard enough, there may not be a clean-cut surrounding the tissue.
<ol>
	<li>In these cases, pull the tissue away as much as possible, and then use Westcott scissors to trim and separate.</li>
</ol>

<ol>
	<li>Chirco, K. R., Sohn, E. H., Stone, E. M., Tucker, B. A., Mullins, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+molecular+changes+in+the+aging+choroid:+implications+for+age-related+macular+degeneration.">Structural and molecular changes in the aging choroid: implications for age-related macular degeneration.</a> Eye (Lond). , (2016).</li><li>Zhang, P., 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=Defining+the+proteome+of+human+iris,+ciliary+body,+retinal+pigment+epithelium,+and+choroid.">Defining the proteome of human iris, ciliary body, retinal pigment epithelium, and choroid.</a> Proteomics. 16 (7), 1146-1153 (2016).</li><li>Funke, S., 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=Glaucoma+related+Proteomic+Alterations+in+Human+Retina+Samples.">Glaucoma related Proteomic Alterations in Human Retina Samples.</a> Sci Rep. 6, 29759 (2016).</li><li>Decanini, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+retinal+pigment+epithelium+proteome+changes+in+early+diabetes.">Human retinal pigment epithelium proteome changes in early diabetes.</a> Diabetologia. 51 (6), 1051-1061 (2008).</li><li>Skeie, J. M., Mahajan, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissection+of+human+vitreous+body+elements+for+proteomic+analysis.">Dissection of human vitreous body elements for proteomic analysis.</a> J Vis Exp. (47), (2011).</li><li>Skeie, J. M., Mahajan, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+landscape+of+the+human+choroid-retinal+pigment+epithelial+complex.">Proteomic landscape of the human choroid-retinal pigment epithelial complex.</a> JAMA Ophthalmol. 132 (11), 1271-1281 (2014).</li><li>Skeie, J. M., Tsang, S. H., Mahajan, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evisceration+of+mouse+vitreous+and+retina+for+proteomic+analyses.">Evisceration of mouse vitreous and retina for proteomic analyses.</a> J Vis Exp. (50), (2011).</li><li>Skeie, J. 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=Proteomic+analysis+of+vitreous+biopsy+techniques.">Proteomic analysis of vitreous biopsy techniques.</a> Retina. 32 (10), 2141-2149 (2012).</li><li>Skeie, J. M., Mahajan, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+interactions+in+the+mouse+vitreous-retina+complex.">Proteomic interactions in the mouse vitreous-retina complex.</a> PLoS One. 8 (11), e82140 (2013).</li><li>Mahajan, V. B., Skeie, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+vitreous+proteomics.">Translational vitreous proteomics.</a> Proteomics Clin Appl. 8 (3-4), 204-208 (2014).</li><li>Skeie, J. M., Roybal, C. N., Mahajan, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+insight+into+the+molecular+function+of+the+vitreous.">Proteomic insight into the molecular function of the vitreous.</a> PLoS One. 10 (5), e0127567 (2015).</li><li>Velez, G., 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=Precision+Medicine:+Personalized+Proteomics+for+the+Diagnosis+and+Treatment+of+Idiopathic+Inflammatory+Disease.">Precision Medicine: Personalized Proteomics for the Diagnosis and Treatment of Idiopathic Inflammatory Disease.</a> JAMA Ophthalmol. 134 (4), 444-448 (2016).</li><li>Velez, G., 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=Proteomic+analysis+of+elevated+intraocular+pressure+with+retinal+detachment.">Proteomic analysis of elevated intraocular pressure with retinal detachment.</a> Am J Ophthalmol Case Rep. 5, 107-110 (2017).</li><li>Skeie, J. 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=A+biorepository+for+ophthalmic+surgical+specimens.">A biorepository for ophthalmic surgical specimens.</a> Proteomics Clin Appl. 8 (3-4), 209-217 (2014).</li><li>Ferrer, I., 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=Brain+protein+preservation+largely+depends+on+the+postmortem+storage+temperature:+implications+for+study+of+proteins+in+human+neurologic+diseases+and+management+of+brain+banks:+a+BrainNet+Europe+Study.">Brain protein preservation largely depends on the postmortem storage temperature: implications for study of proteins in human neurologic diseases and management of brain banks: a BrainNet Europe Study.</a> J Neuropathol Exp Neurol. 66 (1), 35-46 (2007).</li><li>Ahmed, M. M., Gardiner, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preserving+protein+profiles+in+tissue+samples:+differing+outcomes+with+and+without+heat+stabilization.">Preserving protein profiles in tissue samples: differing outcomes with and without heat stabilization.</a> J Neurosci Methods. 196 (1), 99-106 (2011).</li><li>Kanshin, E., Tyers, M., Thibault, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sample+Collection+Method+Bias+Effects+in+Quantitative+Phosphoproteomics.">Sample Collection Method Bias Effects in Quantitative Phosphoproteomics.</a> J Proteome Res. 14 (7), 2998-3004 (2015).</li><li>Crecelius, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+quantitative+post-mortem+changes+in+the+gray+matter+of+the+human+frontal+cortex+proteome+by+2-D+DIGE.">Assessing quantitative post-mortem changes in the gray matter of the human frontal cortex proteome by 2-D DIGE.</a> Proteomics. 8 (6), 1276-1291 (2008).</li><li>Oka, T., Tagawa, K., Ito, H., Okazawa, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+changes+of+the+phosphoproteome+in+postmortem+mouse+brains.">Dynamic changes of the phosphoproteome in postmortem mouse brains.</a> PLoS One. 6 (6), e21405 (2011).</li><li>Nagy, 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=Effects+of+postmortem+interval+on+biomolecule+integrity+in+the+brain.">Effects of postmortem interval on biomolecule integrity in the brain.</a> J Neuropathol Exp Neurol. 74 (5), 459-469 (2015).</li><li>Mukherjee, S., 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=Proteomic+analysis+of+frozen+tissue+samples+using+laser+capture+microdissection.">Proteomic analysis of frozen tissue samples using laser capture microdissection.</a> Methods Mol Biol. 1002, 71-83 (2013).</li></ol>

No conflicts of interest declared.

After tissue collection, sample handling and treatment are crucial considerations14. Preservation in liquid nitrogen is preferred over chemical fixation, as the latter may result in damage to protein structure, which could skew downstream analysis. Additionally, liquid nitrogen preservation is preferred to methods which do not involve freezing of samples. Notably, Ferrer et al. showed significant differences in protein levels between brain samples preserved at 4 &#176;C or room temperature, compared to those stored at 0 &#176;C15. Further, it is important to be careful when processing samples, as specific chemical and physical treatment before freezing has the potential to alter protein levels and post-translational modifications16,17. This point emphasizes the importance of considering the intended downstream analysis of samples. Separately, post-mortem timing of tissue harvesting is another factor that can affect levels and stability of specific proteins. Degradation can occur to the sample proteome depending on time post-mortem and storage temperature18,19,20. Moreover, controlling for time post-mortem degradation, such as by use of internal controls between disease tissue and healthy tissue, is crucial. If the timing factor is ignored, degradation could skew results. As a general rule, the sooner the tissue is analyzed post-mortem, the less risk for degradation to alter study results.
Several procedural modifications can be made to this protocol to better suit a specific research question. One modification is that different size skin punch biopsy tools may be used to collect different amounts of tissue samples. Less or more tissue may be required for downstream proteomic processing depending on quantity or stability of specific proteins of interest. Moreover, the size of the tissue punch biopsy can determine how grossly the specific regions of the retina or RPE-choroid will be sampled. For example, if specific, fine regions of pathologic tissue are required, smaller skin punch biopsy tools may be needed. Furthermore, if a section is so fine that it drops below the capabilities of punch biopsy tools, microdissection may be required21. Additionally, the use of visual aids, such as a dissecting scope or magnifying glass, may aid the tissue collection process-particularly in cases of smaller globe sizes, such as with infantile ocular tissue.
Finally, it is important to note that while this technique groups the RPE and choroid tissues as a single complex, these tissues remain molecularly and functionally distinct. Indeed, the proteomes differ markedly between these two tissues. However, despite these differences, the RPE and choroid remain anatomically, functionally, and clinically linked2,6,7. Thus any downstream proteomic analysis of the RPE-choroid complex should bear in mind this key distinction.
This manuscript demonstrates a straightforward, reliable, low-overhead approach to sample collection for proteomic analysis of fovea, macula, and peripheral retina and RPE-choroid tissue in human eyes. At the discretion of the investigator, modifications can be made to either the collection process or tissue handling, pre-collection and post-collection, depending on the intended downstream proteomic analysis.

The retina, RPE, and choroid are complex tissues that demonstrate important regional differences in protein expression, physiological function, and pathological susceptibilities1,2. For example, diseases such as Age-Related Macular Degeneration (AMD), retinitis pigmentosa, and central serous retinopathy each demonstrate characteristic localization within the fovea, macula, or retina periphery1,3,4,6. Here, we present a method demonstrating how distinct retinal regions can be independently sampled. The overall goal of this method is to provide a reliable guide for collection of tissue samples from the foveal, macular, and peripheral regions of the human retina and RPE-choroid for proteomic analysis. The rationale for the development and use of this technique is that through proteomic analysis of these specific retinal regions, important molecular insights may be gained into the physiological and pathophysiological functions of these regions.
This approach promises to reveal the proteomic basis for relative regional disease susceptibilities, and to facilitate the identification of new specific therapeutic targets. Indeed, proteomic investigations of the vitreous and its interactions with the retina have provided key insights into the molecular composition and function of healthy and diseased tissue5,7,8,9,10,11,12,13. However, clear comparative proteomic analyses of distinct retinal regions are lacking. The technique will help to support these much-needed studies, providing advantages over other methods by demonstrating a reliable and reproducible tissue collection approach. More so, the approach is very accessible, taking advantage of standard-sized and readily available tissue punch biopsy tools. Our technique emphasizes the appropriate collection and storage of tissues for proteomic processing, making important considerations for protein stability and degradation. Thus, this method is most appropriate for investigators considering downstream molecular analysis of proteomic factors.

<table><tbody><tr><td>4-mm skin punch biopsy tool</td><td>Miltex</td><td>REF 33-34</td><td></td></tr><tr><td>8-mm skin punch biopsy tool</td><td>Miltex</td><td>REF 33-37</td><td></td></tr><tr><td>0.12 Colibri Forceps</td><td>Stephens Instruments</td><td>S5-1145</td><td></td></tr><tr><td>Wescott Scissors</td><td>Sklar Surgical Instruments</td><td>64-3146</td><td></td></tr><tr><td>Microfuge tubes</td><td>Eppendorf</td><td>#022364111</td><td>1.5 mL</td></tr><tr><td>Liquid Nitrogen</td><td>Praxair, Inc.</td><td>7727-37-9 [R]</td><td></td></tr></tbody></table>

dissection of human retina and rpe-choroid for proteomic analysis

The human retina is composed of the sensory neuroretina and the underlying retinal pigmented epithelium (RPE), which is firmly complexed to the vascular choroid layer. Different regions of the retina are anatomically and molecularly distinct, facilitating unique functions and demonstrating differential susceptibility to disease. Proteomic analysis of each of these regions and layers can provide vital insights into the molecular process of many diseases, including Age-Related Macular Degeneration (AMD), diabetes mellitus, and glaucoma. However, separation of retinal regions and layers is essential before quantitative proteomic analysis can be accomplished. Here, we describe a method for dissection and collection of the foveal, macular, and peripheral retinal regions and underlying RPE-choroid complex, involving regional punch biopsies and manual removal of tissue layers from a human eye.One-dimensional SDS-PAGE as well as downstream proteomic analysis, such as liquid chromatography-tandem mass spectrometry (LC-MS/MS), can be used to identify proteins in each dissected retinal layer, revealing molecular biomarkers for retinal disease.

Retinal and RPE-choroid tissue can be processed in various ways to suit an individual investigation. After collection, the researcher will possess samples of retinal and RPE-choroid tissue from the foveal region, outer macula, and peripheral retina (Figure 1). Specifically, the foveal region punch will include the fovea, the parafovea, and a small amount of the adjacent perifovea. The macular punch includes the remainder of the perifoveal region as well as a small amount of the adjacent near-peripheral region. Finally, the peripheral punches sample the mid-peripheral and far-peripheral regions. In a representative experiment, tissue samples were trypsin-digested and analyzed using one-dimensional SDS-PAGE to visualize protein content (Figure 2A). The results of this analysis suggest distinct proteins among the different regions of the retina. Analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS)6 properly identified peptides from rhodopsin, a highly abundant and unique retina protein. A representative rhodopsin spectrum obtained from the macular region is shown in Figure 2B. Further analysis of the protein content will provide insights into the molecular functions of the anatomically distinct regions of the retina. In the case that the dissection is not performed carefully, and the retina is not properly separated from the RPE-choroid, differences in protein content between these two tissues will not be discernable.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56203/56203fig1v2.jpg" /> 
Figure 1. Retinal Regions. A representative image of a healthy human retina. Different retinal regions are highlighted by dotted circles, and regions sampled by punch biopsies are indicated by solid circles. The yellow dotted circles represent the foveal region, including the fovea, parafovea, and perifovea (traveling outward from center), while the yellow solid circle represents the 4 mm foveal punch. The blue dotted circle represents the anatomic macular region, while the blue solid circle represents the 8 mm macular punch. Finally, the pink dotted circles represent the near retinal peripheral region (Near P), mid retinal peripheral region (Mid P), and far peripheral region (Far P). The pink solid circles represent the 4 mm peripheral retina punches, which contain the Mid P and Far P regions. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56203/56203fig1v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56203/56203fig2.jpg" /> 
Figure 2. Identification of Retinal Proteins. Peripheral retina, macula, and foveal regions were biopsied and used for proteomic analysis. (A) One-Dimensional SDS-PAGE and silver staining visualized proteins in each retinal region. (B) Retina tissue samples were subject to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The representative spectrum shown is of the rhodopsin protein identified in the macular region. This spectrum represents one of five unique rhodopsin peptides identified in the macula. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56203/56203fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Dissection of Human Retina and RPE-Choroid for Proteomic Analysis at JoVE.com

Dissection of Human Retina and RPE-Choroid for Proteomic Analysis

The human retina is composed of functionally and molecularly distinct regions, including the fovea, macula, and peripheral retina. Here, we describe a method using punch biopsies and manual removal of tissue layers from a human eye to dissect and collect these distinct retinal regions for downstream proteomic analysis.

The human retina is composed of the sensory neuroretina and the underlying retinal pigmented epithelium (RPE), which is firmly complexed to the vascular ...

dissection-of-human-retina-and-rpe-choroid-for-proteomic-analysis

Nanyang Technological University

Research

JoVE Journal

Biochemistry

10.9K Views.  Columbia University. Het menselijke netvlies is samengesteld uit functioneel en moleculair verschillende regio's, met inbegrip van de fovea, macula en perifere retina. Hier beschrijven we een methode met behulp van punch biopsieën en handmatig verwijderen van de lagen weefsel van een menselijk oog te ontleden en deze verschillende retinale regio's voor downstream Proteoom analyse te verzamelen.

Video: Dissection of Human Retina and RPE-Choroid for Proteomic Analysis

Experimental Models for Study of Retinal Pigment Epithelial Physiology and Pathophysiology

We have developed a cell culture procedure that can produce large quantities of confluent monolayers of primary human fetal retinal pigment epithelium (hfRPE) cultures with morphological, physiological and genetic characteristics of native human RPE. These hfRPE cell cultures exhibit heavy pigmentation, and electron microscopy show extensive apical membrane microvilli. The junctional complexes were identified with immunofluorescence labeling of various tight junction proteins. Epithelial polarity and function of these easily reproducible primary cultures closely resemble previously studied mammalian models of native RPE, including human. These results were extended by the development of therapeutic interventions in several animal models of human eye disease. We have focused on strategies for the removal of abnormal fluid accumulation in the retina or subretinal space. The extracellular subretinal space separates the photoreceptor outer segments and the apical membrane of the RPE and is critical for maintenance of retinal attachments and a whole host of RPE/retina interactions.

We provide a reproducible method for culturing confluent monolayers of human fetal retinal pigment epithelial cells (hfRPE) cells that exhibit morphology, physiology, polarity, and protein and gene expression patterns of adult native tissue. This work has been extended to an animal model of several eye diseases.

We have developed a cell culture procedure that can produce large quantities of confluent monolayers of primary human fetal retinal pigment epithelium ...

Neuroscience

Dissection of Human Vitreous Body Elements for Proteomic Analysis

The vitreous is an optically clear, collagenous extracellular matrix that fills the inside of the eye and overlies the retina. 1,2 Abnormal interactions between vitreous substructures and the retina underlie several vitreoretinal diseases, including retinal tear and detachment, macular pucker, macular hole, age-related macular degeneration, vitreomacular traction, proliferative vitreoretinopathy, proliferative diabetic retinopathy, and inherited vitreoretinopathies. 1,2 The molecular composition of the vitreous substructures is not known. Since the vitreous body is transparent with limited surgical access, it has been difficult to study its substructures at the molecular level. We developed a method to separate and preserve these tissues for proteomic and biochemical analysis. The dissection technique in this experimental video shows how to isolate vitreous base, anterior hyaloid, vitreous core, and vitreous cortex from postmortem human eyes. One-dimensional SDS-PAGE analyses of each vitreous component showed that our dissection technique resulted in four unique protein profiles corresponding to each substructure of the human vitreous body. Identification of differentially compartmentalized proteins will reveal candidate molecules underlying various vitreoretinal diseases.

This video shows an effective technique for differentiating and dissecting the various semi-transparent structures of the human vitreous body in post mortem eyes.

The vitreous is an optically clear, collagenous extracellular matrix that fills the inside of the eye and overlies the retina. 1,2 Abnormal interactions ...

Medicine

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 ...

Single-cell Profiling of Developing and Mature Retinal Neurons

Highly specialized, but exceedingly small populations of cells play important roles in many tissues. The identification of cell-type specific markers and gene expression programs for extremely rare cell subsets has been a challenge using standard whole-tissue approaches. Gene expression profiling of individual cells allows for unprecedented access to cell types that comprise only a small percentage of the total tissue1-7. In addition, this technique can be used to examine the gene expression programs that are transiently expressed in small numbers of cells during dynamic developmental transitions8.
This issue of cellular diversity arises repeatedly in the central nervous system (CNS) where neuronal connections can occur between quite diverse cells9. The exact number of distinct cell types is not precisely known, but it has been estimated that there may be as many as 1000 different types in the cortex itself10. The function(s) of complex neural circuits may rely on some of the rare neuronal types and the genes they express. By identifying new markers and helping to molecularly classify different neurons, the single-cell approach is particularly useful in the analysis of cell types in the nervous system. It may also help to elucidate mechanisms of neural development by identifying differentially expressed genes and gene pathways during early stages of neuronal progenitor development.
As a simple, easily accessed tissue with considerable neuronal diversity, the vertebrate retina is an excellent model system for studying the processes of cellular development, neuronal differentiation and neuronal diversification. However, as in other parts of the CNS, this cellular diversity can present a problem for determining the genetic pathways that drive retinal progenitors to adopt a specific cell fate, especially given that rod photoreceptors make up the majority of the total retinal cell population11. Here we report a method for the identification of the transcripts expressed in single retinal cells (Figure 1). The single-cell profiling technique allows for the assessment of the amount of heterogeneity present within different cellular populations of the retina2,4,5,12. In addition, this method has revealed a host of new candidate genes that may play role(s) in the cell fate decision-making processes that occur in subsets of retinal progenitor cells8. With some simple adjustments to the protocol, this technique can be utilized for many different tissues and cell types.

A method for the isolation of single retinal cells and subsequent amplification of their cDNAs is described. Single-cell transcriptomics reveals the degree of cellular heterogeneity present in a tissue and uncovers new marker genes for rare cell populations. The accompanying protocol can be adjusted to suit many different cell types.

Highly specialized, but exceedingly small populations of cells play important roles in many tissues. The identification of cell-type specific markers and ...

The Gateway to the Brain: Dissecting the Primate Eye

The visual system in humans is considered the gateway to the world and plays a principal role in the plethora of sensory, perceptual and cognitive processes. It is therefore not surprising that quality of vision is tied to quality of life . Despite widespread clinical and basic research surrounding the causes of visual disorders, many forms of visual impairments, such as retinitis pigmentosa and macular degeneration, lack effective treatments. Non-human primates have the closest general features of eye development to that of humans. Not only do they have a similar vascular anatomy, but amongst other mammals, primates have the unique characteristic of having a region in the temporal retina specialized for high visual acuity, the fovea1. Here we describe a general technique for dissecting the primate retina to provide tissue for retinal histology, immunohistochemistry, laser capture microdissection, as well as light and electron microscopy. With the extended use of the non-human primate as a translational model, our hope is that improved understanding of the retina will provide insights into effective approaches towards attenuating or reversing the negative impact of visual disorders on the quality of life of affected individuals.

The non-human primate is an important translational species for our understanding of development and aging. The anatomical organization of the primate retina may provide important insights into normal and pathological conditions in humans.

The visual system in humans is considered the  gateway  to the world and plays a principal role in the plethora of sensory, perceptual and cognitive ...

Biology

A Protocol to Evaluate and Quantify Retinal Pigmented Epithelium Pathologies in Mouse Models of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a debilitating retinal disorder in aging populations. It is widely believed that dysfunction of the retinal pigmented epithelium (RPE) is a key pathobiological event in AMD. To understand the mechanisms that lead to RPE dysfunction, mouse models can be utilized by researchers. It has been established by previous studies that mice can develop RPE pathologies, some of which are observed in the eyes of individuals diagnosed with AMD. Here, we describe a phenotyping protocol to assess RPE pathologies in mice. This protocol includes the preparation and evaluation of retinal cross-sections using light microscopy and transmission electron microscopy, as well as that of RPE flat mounts by confocal microscopy. We detail the common types of murine RPE pathologies observed by these techniques and ways to quantify them through unbiased methods for statistical testing. As proof of concept, we use this RPE phenotyping protocol to quantify the RPE pathologies observed in mice overexpressing transmembrane protein 135 (Tmem135) and aged wild-type C57BL/6J mice. The main goal of this protocol is to present standard RPE phenotyping methods with unbiased quantitative assessments for scientists using mouse models of AMD.

Mouse models can be useful tools for investigating the biology of the retinal pigmented epithelium (RPE). It has been established that mice can develop an array of RPE pathologies. Here, we describe a phenotyping protocol to elucidate and quantify RPE pathologies in mice using light, transmission electron, and confocal microscopy.

Age-related macular degeneration (AMD) is a debilitating retinal disorder in aging populations. It is widely believed that dysfunction of the retinal ...

Genetics

Microdissection of Zebrafish Embryonic Eye Tissues

Zebrafish is a popular animal model for research on eye development because of its rapid ex utero development and good fecundity. By 3 days post fertilization (dpf), the larvae will show the first visual response. Many genes have been identified to control a proper eye development, but we are far from a complete understanding of the underlying genetic architecture. Whole genome gene expression profiling is a useful tool to elucidate genetic regulatory network for eye development. However, the small size of the embryonic eye in zebrafish makes it challenging to obtain intact and pure eye tissues for expression analysis. For example, the anterior-posterior length of the eye between day 2 and 3 is only approximately 200-300 &mu;m, while the diameter of the lens is less 100 &mu;m. Also, the retinal pigment epithelium (RPE) underlying the retina is just a single-layer epithelium. While gene expression profiles can be obtained from the whole embryo, they do not accurately represent the expression of these tissues. Therefore pure tissue must be obtained for a successful gene expression profiling of eye development. To address this issue, we have developed an approach to microdissect intact retina and retina with RPE attached from 1-3 dpf, which cover major stages of eye morphogenesis. All procedures can be done with fine forceps and general laboratory supplies under standard stereomicroscopes. For retinal dissection, the single-layer RPE is removed and peeled off by brushing action and the preferential adherence of the RPE remnants to the surface of the culture plate for dissection. For RPE-attached retinal dissection, the adherence of RPE to the dissection plate is removed before the dissection so that the RPE can be completely preserved with the retina. A careful lifting action of this tissue can efficiently separate the presumptive choroid and sclera. The lens can be removed in both cases by a chemically etched tungsten needle. In short, our approach can obtain intact eye tissues and has been successfully utilized to study tissue-specific expression profiles of zebrafish retina1, 2 and retinal pigment epithelium3.

This article describes an approach to microdissect zebrafish retinas with and without retinal pigment epithelium attached, from one to three days postfertilization embryos.

Zebrafish is a popular animal model for research on eye development because of its rapid ex utero development and good fecundity. By 3 days post ...

Evisceration of Mouse Vitreous and Retina for Proteomic Analyses

While the mouse retina has emerged as an important genetic model for inherited retinal disease, the mouse vitreous remains to be explored. The vitreous is a highly aqueous extracellular matrix overlying the retina where intraocular as well as extraocular proteins accumulate during disease.1-3 Abnormal interactions between vitreous and retina underlie several diseases such as retinal detachment, proliferative diabetic retinopathy, uveitis, and proliferative vitreoretinopathy.1,4 The relative mouse vitreous volume is significantly smaller than the human vitreous (Figure 1), since the mouse lens occupies nearly 75% of its eye.5 This has made biochemical studies of mouse vitreous challenging. In this video article, we present a technique to dissect and isolate the mouse vitreous from the retina, which will allow use of transgenic mouse models to more clearly define the role of this extracellular matrix in the development of vitreoretinal diseases.

The dissection technique illustrates evisceration of the vitreous, retina, and lens from the mouse eye, separation by centrifugation, and characterization with protein assays.

While the mouse retina has emerged as an important genetic model for inherited retinal disease, the mouse vitreous remains to be explored. The vitreous is ...

Microsurgical Dissection and Tissue Clearing for High Resolution Intact Whole Retina and Vitreous Imaging

Neuronal and vascular structures of the retina in physiologic and pathologic conditions can be better visualized and characterized by using intact whole retina imaging techniques compared to conventional retinal flat mount preparations and sections. However, immunofluorescent imaging of intact whole retina is hindered by the opaque coatings of the eyeball, i.e., sclera, choroid, and retinal pigment epithelium (RPE) and the light scattering properties of retinal layers that prevent full thickness high resolution optical imaging. Chemical bleaching of the pigmented layers and tissue clearing protocols have been described to address these obstacles; however, currently described methods are not suitable for imaging endogenous fluorescent molecules such as green fluorescent protein (GFP) in intact whole retina. Other approaches bypassed this limitation by surgical removal of pigmented layers and the anterior segment of the eyeball allowing intact eye imaging, though the peripheral retina and hyaloid structures were disrupted. Presented here is an intact whole retina and vitreous immunofluorescent imaging protocol that combines surgical dissection of the sclera/choroid/retina pigment epithelium (RPE) layers with a modified tissue clearing method and light sheet fluorescent microscopy (LSFM). The new approach offers an unprecedented view of&#160;unperturbed vascular and neuronal elements of the retina as well as the vitreous and hyaloid vascular system in pathologic conditions.

Presented here is a protocol for intact whole retina imaging in which the outer opaque/pigmented layers of the eyeball are surgically removed, and optical clearing is applied to render retina transparent enabling the visualization of the peripheral retina and hyaloid vasculature in intact retina using light sheet fluorescent microscopy.

Neuronal and vascular structures of the retina in physiologic and pathologic conditions can be better visualized and characterized by using intact whole ...

Two Peeling Methods for the Isolation of Photoreceptor Cell Compartments in the Mouse Retina for Protein Analysis

Rod photoreceptors are highly polarized sensory neurons with distinct compartments. Mouse rods are long (~80 &#181;m) and thin (~2 &#181;m) and are laterally packed in the outermost layer of the retina, the photoreceptor layer, resulting in alignment of analogous subcellular compartments. Traditionally, tangential sectioning of the frozen flat-mounted retina has been used to study the movement and localization of proteins within different rod compartments. However, the high curvature of the rod-dominant mouse retina makes tangential sectioning challenging. Motivated by the study of protein transport between compartments, we developed two peeling methods that reliably isolate the rod outer segment (ROS) and other subcellular compartments for western blots. Our relatively quick and simple techniques deliver enriched and subcellular-specific fractions to quantitatively measure the distribution and redistribution of important photoreceptor proteins in normal rods. Moreover, these isolation techniques can also be easily adapted to isolate and quantitatively investigate the protein composition of other cellular layers within both healthy and degenerating retinae.

This protocol presents two techniques to isolate the subcellular compartments of murine rod photoreceptors for protein analysis. The first method utilizes live retinae and cellulose filter paper to separate rod outer segments, while the second employs lyophilized retinae and adhesive tape to peel away rod inner and outer segment layers.

Rod photoreceptors are highly polarized sensory neurons with distinct compartments. Mouse rods are long (~80 &#181;m) and thin (~2 &#181;m) and are ...

Dissection of Human Retina and RPE-Choroid for Proteomic Analysis

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