Research reported in this publication was supported by NIH Grants R01EY018341 and R01EY019250&#160;(C.S.S.), NIH Grant F31EY035156 (A.H.), and P30 EY011373. The funding organization had no role in the design or conduct of this research.

The use of animal subjects in this study was approved by the Institutional Animal Care and Use Committee (IACUC) of Case Western Reserve University.
1. Reagents preparation
<ol>
	<li>Prepare wash buffer medium by supplementing Hank&#39;s balanced salt solution (HBSS), no calcium, no magnesium, no phenol red with 10 mM HEPES buffer solution. Keep solution at 4 &#176;C until use.</li>
	<li>Prepare RPE medium by supplementing Dulbecco&#39;s Modified Eagle&#39;s Medium with 4.5 g/L glucose, 1.25x GlutaMAX Supplement (stock concentration 100x or 200 mM; final concentration of 2.5 mM L-glutamine), with 10% fetal bovine serum, 1% penicillin/streptomycin, and 1x MEM Non-Essential Amino Acids Solution (100x). Before use, pre-warm the media to 37 &#176;C in a water bath.</li>
</ol>
2. Mouse eye extraction
<ol>
	<li>Euthanize the mouse, preferably ranging from 3- to 14-weeks in age, using an IACUC-approved method of euthanasia (cervical dislocation under anesthesia using a Ketamine/xylazine cocktail at 0.1 mL per 20 g of mouse [87.5 mg/kg Ketamine and 12.5 mg/kg Xylazine] was the method used in this study). 
	NOTE: Eyes collected from younger mice will facilitate increased retinal pigment epithelial cell yield over time and extend the capacity for successive passages.</li>
	<li>Lay the mouse flat on its side with the eye oriented upwards.</li>
	<li>Place the index finger and thumb above and below the eye, respectively. Gently apply pressure on the bone structure surrounding the eye to induce protrusion of the eyeball.</li>
	<li>Insert the tip of slightly opened scissors underneath the eye and gently rotate the wrist away from the eye 90&#176; until the eye detaches from the socket. 
	NOTE: Do not close the scissors to cut the eye or the optic nerve, as it will make dissection of the eyecup more difficult.</li>
	<li>Immediately place and roll the eye in 70% ethanol for no more than 5 s before transferring it to a wash buffer medium kept on ice.</li>
	<li>Under a dissecting microscope, transfer one eye at a time to a Petri dish filled with wash buffer and strips of soaked gauze.</li>
	<li>Stabilize the eye by holding the optic nerve with tweezers. Gently make an incision at the level of the ora serrata using a 3.00 mm 45&#176; surgical knife or 0.009&#34; razor blade.</li>
	<li>Using Vannas scissors, gently insert the scissor into the incision and cut around the circumference of the ora serrata until the anterior segment and vitreous can be removed and discarded.</li>
	<li>Gently peel away the retina from the eyecup using tethered forceps, careful not to disturb the RPE layer. 
	NOTE: To make the retina easier to remove, fill a transfer pipette with wash buffer medium and carefully apply it to the edges of the eyecup to gently lift the retina.</li>
	<li>Finally, remove the optic nerve and excess connective tissue from the eyecup using scissors. Be careful not to puncture the eyecup.</li>
</ol>
3. Isolation of primary RPE
<ol>
	<li>Transfer the eyecup to a 1.5 mL microcentrifuge tube containing 1 mL of 0.25% trypsin + 0.02% EDTA. 
	NOTE: Two eyecups can be added to one aliquot of Trypsin-EDTA to increase the yield of culturable RPE.</li>
	<li>Transfer microcentrifuge tubes to a water bath set at 37 &#176;C and incubate for 10 min. Every 2 min, remove the tubes from the water bath and firmly tap the bottom of the tube 40 times onto the countertop.</li>
	<li>After 10 min, gently disrupt the eyecup mechanically using a P1000 or a 2 mL serological pipet by pipetting up and down no more than 3 times. 
	NOTE: Fragmentation of the RPE sheets is essential as large sheets will not adhere properly.</li>
	<li>Neutralize the trypsin immediately by layering the detached RPE sheets, but not the eyecup, onto 0.5 mL of fetal bovine serum (FBS) in a 15 mL conical tube.</li>
	<li>Further, dilute the trypsin by layering 3 mL of RPE media dropwise onto the layers of FBS and RPE sheets.</li>
	<li>Centrifuge the RPE at 340 x g for 3 min.</li>
	<li>Discard the supernatant and resuspend cells in a suitable amount of RPE media for either a 24-well plate (1.9 cm2/well) or a 48-well plate (0.75 cm2/well). 
	NOTE: RPE can be plated onto well plates coated with extracellular matrix proteins, specifically laminin, collagen IV, or fibronectin, to increase adherence11. RPE can also be resuspended in 1 mL of RPE media and layered onto a 40% density separation gradient to further isolate pure RPE cells. Additionally, spinning the plate at 340 x g for 3-5 min may increase cell adhesion13.</li>
	<li>Incubate at 37 &#176;C at 5% CO2.</li>
</ol>
4. Culturing RPE
<ol>
	<li>Do not disrupt the isolated RPE for at least 3 days. After 72 h, gently remove the old medium and replace it with fresh, pre-warmed media.</li>
	<li>Change the medium every 48 h after the first 3 days.</li>
	<li>Once cells reach confluency, passage the cells using 0.25% trypsin + 0.02% EDTA and reduce the FBS in the RPE media to 2%. 
	NOTE: Primary RPE were previously reported to begin de-differentiation after 5-7 passages and will begin to lose their hexagonal shape and pigmentation14.</li>
</ol>

Characterization and Morphological Dynamics of Cultured Primary Murine RPE

<ol><li>Strauss, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+retinal+pigment+epithelium+in+visual+function%5BTitle%5D)+AND+%22Physiol+Rev%22%5BJournal%5D)">The retinal pigment epithelium in visual function.</a> Physiol Rev. 85 (3), 845-881 (2005).</li>
<li>Lakkaraju, A., et al. The cell biology of the retinal pigment epithelium. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aLakkaraju%2C+A+%22Prog+Retin+Eye+Res%22">Prog Retin Eye Res</a>. 100846, (2020).</li>
<li>Lambros, M. L., Plafker, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Oxidative+stress+and+the+Nrf2+anti-oxidant+transcription+factor+in+age-related+macular+degeneration%5BTitle%5D)+AND+%22Adv+Exp+Med+Biol%22%5BJournal%5D)">Oxidative stress and the Nrf2 anti-oxidant transcription factor in age-related macular degeneration.</a> Adv Exp Med Biol. 854, 67-72 (2016).</li>
<li>Ferrari, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Retinitis+pigmentosa%3A+genes+and+disease+mechanisms%5BTitle%5D)+AND+%22Curr+Genomics%22%5BJournal%5D)">Retinitis pigmentosa: genes and disease mechanisms.</a> Curr Genomics. 12 (4), 238-249 (2011).</li>
<li>Xia, T., Rizzolo, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+diabetic+retinopathy+on+the+barrier+functions+of+the+retinal+pigment+epithelium%5BTitle%5D)+AND+%22Vision+Res%22%5BJournal%5D)">Effects of diabetic retinopathy on the barrier functions of the retinal pigment epithelium.</a> Vision Res. 139, 72-81 (2017).</li>
<li>Edwards, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Culture+of+rat+retinal+pigment+epithelium%5BTitle%5D)+AND+%22In+Vitro%22%5BJournal%5D)">Culture of rat retinal pigment epithelium.</a> In Vitro. 13 (5), 301-304 (1977).</li>
<li>Mayerson, P. L., Hall, M. O., Clark, V., Abrams, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+improved+method+for+isolation+and+culture+of+rat+retinal+pigment+epithelial+cells%5BTitle%5D)+AND+%22Invest+Ophthalmol+Vis+Sci%22%5BJournal%5D)">An improved method for isolation and culture of rat retinal pigment epithelial cells.</a> Invest Ophthalmol Vis Sci. 26 (11), 1599-1609 (1985).</li>
<li>Chang, C. W., Roque, R. S., Defoe, D. M., Caldwell, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+improved+method+for+isolation+and+culture+of+pigment+epithelial+cells+from+rat+retina%5BTitle%5D)+AND+%22Curr+Eye+Res%22%5BJournal%5D)">An improved method for isolation and culture of pigment epithelial cells from rat retina.</a> Curr Eye Res. 10 (11), 1081-1086 (1991).</li>
<li>Wang, N., Koutz, C. A., Anderson, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+method+for+the+isolation+of+retinal+pigment+epithelial+cells+from+adult+rats%5BTitle%5D)+AND+%22Invest+Ophthalmol+Vis+Sci%22%5BJournal%5D)">A method for the isolation of retinal pigment epithelial cells from adult rats.</a> Invest Ophthalmol Vis Sci. 34 (1), 101-107 (1993).</li>
<li>Sakagami, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+rapid+method+for+isolation+of+retinal+pigment+epithelial+cells+from+rat+eyeballs%5BTitle%5D)+AND+%22Ophthalmic+Res%22%5BJournal%5D)">A rapid method for isolation of retinal pigment epithelial cells from rat eyeballs.</a> Ophthalmic Res. 27 (5), 262-267 (1995).</li>
<li>Heller, J. P., Kwok, J. C., Vecino, E., Martin, K. R., Fawcett, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+method+for+the+isolation+and+culture+of+adult+rat+retinal+pigment+epithelial+%28RPE%29+cells+to+study+retinal+diseases%5BTitle%5D)+AND+%22Front+Cell+Neurosci%22%5BJournal%5D)">A method for the isolation and culture of adult rat retinal pigment epithelial (RPE) cells to study retinal diseases.</a> Front Cell Neurosci. 9, 449(2015).</li>
<li>Shen, J., He, J., Wang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Isolation+and+culture+of+primary+mouse+retinal+pigment+epithelial+%28RPE%29+cells+with+Rho-Kinase+and+TGFbetaR-1%2FALK5+inhibitor%5BTitle%5D)+AND+%22Med+Sci+Monit%22%5BJournal%5D)">Isolation and culture of primary mouse retinal pigment epithelial (RPE) cells with Rho-Kinase and TGFbetaR-1/ALK5 inhibitor.</a> Med Sci Monit. 23, 6132-6136 (2017).</li>
<li>Hood, E. M. S., Curcio, C., Lipinski, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Isolation%2C+culture%2C+and+cryosectioning+of+primary+porcine+retinal+pigment+epithelium+on+transwell+cell+culture+inserts%5BTitle%5D)+AND+%22STAR+Protoc%22%5BJournal%5D)">Isolation, culture, and cryosectioning of primary porcine retinal pigment epithelium on transwell cell culture inserts.</a> STAR Protoc. 3 (4), 101758(2022).</li>
<li>Naylor, A., Hopkins, A., Hudson, N., Campbell, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tight+Junctions+of+the+outer+blood+retina+barrier%5BTitle%5D)+AND+%22Int+J+Mol+Sci%22%5BJournal%5D)">Tight Junctions of the outer blood retina barrier.</a> Int J Mol Sci. 21 (1), 211(2019).</li>
<li>Ban, B., Rizzolo, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+culture+model+of+development+reveals+multiple+properties+of+RPE+tight+junctions%5BTitle%5D)+AND+%22Mol+Vis%22%5BJournal%5D)">A culture model of development reveals multiple properties of RPE tight junctions.</a> Mol Vis. 3, 18(1997).</li>
<li>Fernandez-Godino, R., Garland, D. L., Pierce, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Isolation%2C+culture+and+characterization+of+primary+mouse+RPE+cells%5BTitle%5D)+AND+%22Nat+Protoc%22%5BJournal%5D)">Isolation, culture and characterization of primary mouse RPE cells.</a> Nat Protoc. 11 (7), 1206-1218 (2016).</li>
<li>Yang, S., Zhou, J., Dengwen, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Functions+and+diseases+of+the+retinal+pigment+epithelium%5BTitle%5D)+AND+%22Front+Pharmacol%22%5BJournal%5D)">Functions and diseases of the retinal pigment epithelium.</a> Front Pharmacol. 12, 727870(2021).</li>
</ol>

There are no relevant financial or nonfinancial disclosures.

In this article, we have outlined a simplified protocol for the isolation and culture of murine retinal pigment epithelium. RPE cells isolated from the eyes of adult mice expressed an RPE-specific marker, RPE65, and an intercellular junction marker, ZO-1. Additionally, the cultured cells developed into pigmented, hexagonal sheets in culture.
Several methods for isolation of RPE in rodents have been published previously6,7,<s...

The retinal pigment epithelium (RPE) is a specialized cell monolayer lining the Bruch&#39;s membrane located between photoreceptors and the choroid1. RPE cells play a critical role in the proper function of the retina. RPE cells transport glucose and vitamin A to photoreceptors, promote vision by re-isomerization of all-trans retinal into 11-cis retinal and maintain outer segments of photoreceptor through phagocytosis of shed outer segments, remove water from the subretinal space, form the outer blood-retinal barrier through the presence of tight junctions and secrete neurotropic growth factors (such as Pigment Epithelium Derived Factor, and Basic Fibroblast Growth Factor) that support photoreceptors2. Dysfunction of RPE cells is involved in the pathogenesis of various retinopathies, including age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy3,4,5. In vitro studies using RPE cells are critical to improving our understanding of the pathogenesis of these diseases. Primary RPE cells are much preferred for these studies since RPE cell lines, while readily available, lack key characteristics of primary RPE cells.
Whereas various species have been utilized as sources of primary RPE cells, mice have the advantage of using genetic modifications to help understand the pathogenesis of retinopathies. Previously described protocols to isolate RPE cells from rodents either require the use of neonatal animals, are lengthy, require technical skill, or are not suitable for culture6,7,8,9,10,11,12. We describe a simple and fast method to isolate RPE cells from adult mice that yield highly pure cultures of these cells.

<table><tbody><tr><td>0.009 RD Single-Edge Blades</td><td>Personna</td><td>941202</td><td></td></tr><tr><td>Dulbecco&#039;s Modified Eagle&#039;s Medium (DMEM)</td><td>Corning</td><td>10-013-CV</td><td>with 4.5 g/L glucose, L-glutamine, sodium pyruvate</td></tr><tr><td>Fetal bovine serum</td><td>Corning</td><td>35010CV</td><td></td></tr><tr><td>GlutaMAX, 100x</td><td>Gibco</td><td>35050061</td><td></td></tr><tr><td>Hank&#039;s Balanced Salt Solution</td><td>Gibco</td><td>14175095</td><td>no Calcium, no magnesium, no phenol red</td></tr><tr><td>HEPES Buffer Solution (1M)</td><td>Gibco</td><td>15630106</td><td></td></tr><tr><td>MEM Non-Essential Amino Acids, 100x</td><td>Gibco</td><td>11140050</td><td></td></tr><tr><td>Micro-Unitome Knife</td><td>BVI Beaver</td><td>377546</td><td></td></tr><tr><td>Penicillin-Streptomycin Solution, 100x</td><td>Corning</td><td>30-002-CI</td><td></td></tr><tr><td>Polystyrene Microplates</td><td>Falcon</td><td>08-772-1</td><td>24-well or 48-well</td></tr><tr><td>Regular Fetal Bovine Serum</td><td>Corning</td><td>35-010-CV</td><td></td></tr><tr><td>Trypsin-EDTA (0.25%)</td><td>Gibco</td><td>25200056</td><td>with phenol red</td></tr><tr><td>Vannas scissors</td><td>Fine Science Tools</td><td>10091-12</td><td></td></tr></tbody></table>

a simplified method for isolation and culture of retinal pigment epithelial cells from adult mice

Retinal pigment epithelial cells (RPE) are critical for the proper function of the retina. RPE dysfunction is involved in the pathogenesis of important retinal diseases, such as age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy. We present a streamlined approach for the isolation of RPE from murine adult eyes. In contrast to previously reported methods, this approach enables the isolation and culture of highly pure RPE from adult mice. This simple and fast method does not require extensive technical skill and is achievable with basic scientific tools and reagents. Primary RPE are isolated from C57BL/6 background mice aged 3- to 14-weeks by enucleation of the eye followed by the removal of the anterior segment. Enzymatic trypsinization and centrifugation are used to dissociate and isolate the RPE from the eyecup. In conclusion, this approach offers a quick and effective protocol for the utilization of RPE in the study of retinal function and disease.

The described protocol has been used on C57BL/6 background mice. Gender does not appear to change the ability to culture RPE. Mice under 6 weeks yield limited RPE sheets in comparison to older mice, and more eyes may be needed to reach optimal confluency. Following isolation, RPE cells take roughly 3 days to stabilize and attach to the cell culture plate. Approximately 24 h after isolation, round, pigmented cells that appear anucleate have begun to settle but have not fully adhered to the plate (Figu...

Author Spotlight: Efficient Isolation of Primary Retinal Pigment Epithelial Cells from Adult Mice for Retinopathy Research

Retinal pigment epithelium (RPE) acts as a crucial barrier between the choroid and retina, promoting the health and function of retinal cell types, such as photoreceptors. Herein, we describe a simple and effective protocol for isolating and culturing adult murine RPE.

A Simplified Method for Isolation and Culture of Retinal Pigment Epithelial Cells from Adult Mice

Retinal pigment epithelial cells (RPE) are critical for the proper function of the retina. RPE dysfunction is involved in the pathogenesis of important ...

a-simplified-method-for-isolation-culture-retinal-pigment-epithelial

Research

JoVE Journal

Neuroscience

1.1K Views.  Case Western Reserve University. Retinale pigmentepitheelcellen of RPE bevinden zich tussen fotoreceptoren en het vaatvlies. Disfunctie van RPE is belangrijk bij de pathogenese van ziekten, zoals leeftijdsgebonden maculaire degeneratie, diabetische retinopathie en retinitis pigmentosa. Het gebruik van primaire RPE is de sleutel tot studies om het begrip van hoe ziekte zich ontwikkelt te verbeteren.Hoewel verschillende soorten zijn gebruikt als bron van primaire RPE, hebben muizen het ...

Video: Auteur in de schijnwerpers: efficiënte isolatie van primaire retinale pigmentepitheelcellen van volwassen muizen voor onderzoek naar retinopathie

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

Isolation of Primary Murine Retinal Ganglion Cells (RGCs) by Flow Cytometry

Neurodegenerative diseases often have a devastating impact on those affected. Retinal ganglion cell (RGC) loss is implicated in an array of diseases, including diabetic retinopathy and glaucoma, in addition to normal aging. Despite their importance, RGCs have been extremely difficult to study until now due in part to the fact that they comprise only a small percentage of the wide variety of cells in the retina. In addition, current isolation methods use intracellular markers to identify RGCs, which produce non-viable cells. These techniques also involve lengthy isolation protocols, so there is a lack of practical, standardized, and dependable methods to obtain and isolate RGCs. This work describes an efficient, comprehensive, and reliable method to isolate primary RGCs from mice retinae using a protocol based on both positive and negative selection criteria. The presented methods allow for the future study of RGCs, with the goal of better understanding the major decline in visual acuity that results from the loss of functional RGCs in neurodegenerative diseases.

Isolation of Primary Murine Retinal Ganglion Cells RGCs by Flow Cytometry

Millions of people suffer from retinal degenerative diseases that result in irreversible blindness. A common element of many of these diseases is the loss of retinal ganglion cells (RGCs). This detailed protocol describes the isolation of primary murine RGCs by positive and negative selection with flow cytometry.

Neurodegenerative diseases often have a devastating impact on those affected. Retinal ganglion cell (RGC) loss is implicated in an array of diseases, ...

Bioengineering

Isolation of Murine Retinal Endothelial Cells for Next-Generation Sequencing

Recent improvements in next-generation sequencing have advanced researchers&#39; knowledge of molecular and cellular biology, with several studies revealing novel paradigms in vascular biology. Applying these methods to models of vascular development requires the optimization of cell isolation techniques from embryonic and postnatal tissues. Cell yield, viability, and purity all need to be maximal to obtain accurate and reproducible results from next-generation sequencing approaches. The neonatal mouse retinal vascularization model is used by researchers to study mechanisms of vascular development. Researchers have used this model to investigate mechanisms of angiogenesis and arterial-venous fate specification during blood vessel formation and maturation. Applying next-generation sequencing techniques to study the retinal vascular development model requires optimization of a method for the isolation of retinal endothelial cells that maximizes cell yield, viability, and purity. This protocol describes a method for murine retinal tissue isolation, digestion, and purification using fluorescence-activated cell sorting (FACS). The results indicate that the FACS-purified CD31+/CD45- endothelial cell population is highly enriched for endothelial cell gene expression and exhibits no change in viability for 60 min post-FACS. Included are representative results of next-generation sequencing approaches on endothelial cells isolated using this method, including bulk RNA sequencing and single-cell RNA sequencing, demonstrating that this method for retinal endothelial cell isolation is compatible with next-generation sequencing applications. This method of retinal endothelial cell isolation will allow for advanced sequencing techniques to reveal novel mechanisms of vascular development.

This protocol describes a method for the isolation of murine postnatal retinal endothelial cells optimized for cell yield, purity, and viability. These cells are suitable for next-generation sequencing approaches.

Recent improvements in next-generation sequencing have advanced researchers&#39; knowledge of molecular and cellular biology, with several studies ...

Developmental Biology

Isolation of Retinal Stem Cells from the Mouse Eye

The adult mouse retinal stem cell (RSC) is a rare quiescent cell found within the ciliary epithelium (CE) of the mammalian eye1,2,3. The CE is made up of non-pigmented inner and pigmented outer cell layers, and the clonal RSC colonies that arise from a single pigmented cell from the CE are made up of both pigmented and non-pigmented cells which can be differentiated to form all the cell types of the neural retina and the RPE. There is some controversy about whether all the cells within the spheres all contain at least some pigment4; however the cells are still capable of forming the different cell types found within the neural retina1-3. In some species, such as amphibians and fish, their eyes are capable of regeneration after injury5, however; the mammalian eye shows no such regenerative properties. We seek to identify the stem cell in vivo and to understand the mechanisms that keep the mammalian retinal stem cells quiescent6-8, even after injury as well as using them as a potential source of cells to help repair physical or genetic models of eye injury through transplantation9-12. Here we describe how to isolate the ciliary epithelial cells from the mouse eye and grow them in culture in order to form the clonal retinal stem cell spheres. Since there are no known markers of the stem cell in vivo, these spheres are the only known way to prospectively identify the stem cell population within the ciliary epithelium of the eye.

In this video, we will demonstrate how to isolate retinal stem cells from the ciliary epithelium of the mouse eye and grow them in culture to form clonal retinal spheres. The spheres that are isolated possess the cardinal properties of stem cells: self-renewal and multipotentiality.

The adult mouse retinal stem cell (RSC) is a rare quiescent cell found within the ciliary epithelium (CE) of the mammalian eye1,2,3. The CE is made up of ...

Biology

Long-Term, Serum-Free Cultivation of Organotypic Mouse Retina Explants with Intact Retinal Pigment Epithelium

In ophthalmic research, there is a strong need for in vitro models of the neuroretina. Here, we present a detailed protocol for organotypic culturing of the mouse neuroretina&#160;with intact retinal pigment epithelium (RPE). Depending on the research question, retinas can be isolated from wild-type animals or from disease models, to study, for instance, diabetic retinopathy or hereditary retinal degeneration. Eyes from early postnatal day 2&#8211;9 animals are enucleated under aseptic conditions. They are partially digested in proteinase K to allow for a detachment of the choroid from the RPE. Under the stereoscope, a small incision is made in the cornea creating two edges from where the choroid and sclera can be gently peeled off from the RPE and neuroretina. The lens is then removed, and the eyecup is cut in four points to give it a four-wedged shape resembling a clover leaf. The tissue is finally transferred in a hanging drop into a cell culture insert holding a polycarbonate culturing membrane. The cultures are then maintained in R16 medium, without serum or antibiotics, under entirely defined conditions, with a medium change every second day.
The procedure described enables the isolation of the retina and the preservation of its normal physiological and histotypic context for culturing periods of at least 2 weeks. These features make organotypic retinal explant cultures an excellent model with high predictive value, for studies into retinal development, disease mechanisms, and electrophysiology, while also enabling pharmacological screening.

The protocol describes organotypic explants of mouse neuroretina, cultivated together with its retinal pigment epithelium (RPE), in R16 defined medium, free of serum and antibiotics. This method is relatively simple to perform, less expensive, and time-consuming when compared to in vivo experiments, and can be adapted to numerous experimental applications.

In ophthalmic research, there is a strong need for in vitro models of the neuroretina. Here, we present a detailed protocol for organotypic culturing of ...

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 ...

Primary Cell Cultures from the Mouse Retinal Pigment Epithelium

The retinal pigment epithelium (RPE) is a highly polarized multi-functional epithelium that is located between the neural retina and the choroid of the eye. It is a single sheet of pigmented cells that are hexagonally packed and connected by tight junctions. The main functions of the RPE include absorption of light, phagocytosis of the shed photoreceptor outer segments, spatial buffering of ions, transport of nutrients, ions and water as well as active involvement in the visual cycle. With such important and diverse functions, it is critically important to study the biology of RPE cells. A number of RPE cell lines have been established; however, passaged and immortalized cells are known to quickly lose some of the morphological and physiological characteristics of natural RPE cells. Thus, primary cells are more suitable for studying different aspects of RPE cell biology and function. Mouse primary RPE cell culture is very useful to researchers since mouse models are widely used in biological studies, however collecting RPE cells from mouse is also very challenging due to their small size. Here, we present a protocol for establishing primary mouse RPE cell cultures which includes enucleation and dissection of the eyes and isolation of the RPE sheets to yield the cells for culturing. This method enables efficient cell recovery. The RPE cells obtained from two mice&#160;can reach confluency on one 12 mm polyester membrane insert pre-loaded in culture plate after one week of culture and display some of the original properties of bona fide RPE cells such as hexagonal shape and pigmentation after two weeks of culture.

The retinal pigment epithelium (RPE) is a multi-functional epithelium of the eye. Here we present a protocol to establish primary cell cultures derived from the murine RPE.

The retinal pigment epithelium (RPE) is a highly polarized multi-functional epithelium that is located between the neural retina and the choroid of the ...

Efficient Dissection and Culture of Primary Mouse Retinal Pigment Epithelial Cells

Eye disorders affect millions of people worldwide, but the limited availability of human tissues hinders their study. Mouse models are powerful tools to understand the pathophysiology of ocular diseases because of their similarities with human anatomy and physiology. Alterations in the retinal pigment epithelium (RPE), including changes in morphology and function, are common features shared by many ocular disorders. However, successful isolation and culture of primary mouse RPE cells is very challenging. This paper is an updated audiovisual version of the protocol previously published by Fernandez-Godino et al. in 2016 to efficiently isolate and culture primary mouse RPE cells. This method is highly reproducible and results in robust cultures of highly polarized and pigmented RPE monolayers that can be maintained for several weeks on Transwells. This model opens new avenues for the study of the molecular and cellular mechanisms underlying eye diseases. Moreover, it provides a platform to test therapeutic approaches that can be used to treat important eye diseases with unmet medical needs, including inherited retinal disorders and macular degenerations.

This protocol, which was originally reported by Fernandez-Godino et al. in 20161, describes a method to efficiently isolate and culture mouse RPE cells, which form a functional and polarized RPE monolayer within one week on Transwell plates. The procedure takes approximately 3 hours.

Eye disorders affect millions of people worldwide, but the limited availability of human tissues hinders their study. Mouse models are powerful tools to ...

Isolation of Primary Mouse Retinal Pigmented Epithelium Cells

The retinal pigmented epithelium (RPE) layer lies immediately behind the photoreceptors and harbors a complex metabolic system that plays several critical roles in maintaining the photoreceptors' function. Thus, the RPE structure and function are essential to sustain normal vision. This manuscript presents an established protocol for primary mouse RPE cell isolation. RPE isolation is a great tool to investigate the molecular mechanisms underlying RPE pathology in the different mouse models of ocular disorders. Furthermore, RPE isolation can help in comparing primary mouse RPE cells isolated from wild-type and genetically modified mice, as well as testing drugs that can accelerate the development of therapy for visual disorders. The manuscript presents a step-by-step RPE isolation protocol; the entire procedure, from enucleation to seeding, takes approximately 4 hours. The media shouldn't be changed for 5-7 days after seeding, to allow the growth of the isolated cells without disturbance. This process is followed by the characterization of morphology, pigmentation, and specific markers in the cells via immunofluorescence. Cells can be passaged a maximum of three or four times.

This manuscript describes a simplified protocol for the isolation of retinal pigmented epithelium (RPE) cells from mouse eyes in a stepwise manner. The protocol includes the enucleation and dissection of mouse eyes, followed by the isolation, seeding, and culturing of RPE cells.

The retinal pigmented epithelium (RPE) layer lies immediately behind the photoreceptors and harbors a complex metabolic system that plays several critical ...

Isolation of Retinal Pigment Epithelial Cells from Guinea Pig Eyes

This protocol describes the isolation of cells of the retinal pigment epithelium (RPE) from the eyes of young pigmented guinea pigs for potential application in molecular biology studies, including gene expression analyses. In the context of eye growth regulation and myopia, the RPE likely plays a role as a cellular relay for growth modulatory signals, as it is located between the retina and the two walls of the eye, such as the choroid and sclera. While protocols for isolating the RPE have been developed for both chicks and mice, these protocols have proven not to be directly translatable to the guinea pig, which has become an important and widely used mammalian myopia model. In this study, molecular biology tools were used to examine the expression of specific genes to confirm that the samples were free of contamination from the adjacent tissues. The value of this protocol has already been demonstrated in an RNA-Seq study of RPE from young pigmented guinea pigs exposed to myopia-inducing optical defocus. Beyond eye growth regulation, this protocol has other potential applications in studies of retinal diseases, including myopic maculopathy, one of the leading causes of blindness in myopes, in which the RPE has been implicated. The main advantage of this technique is that it is relatively simple and&#160;once perfected, yields high-quality RPE samples suitable for molecular biology studies, including RNA analysis.

We describe a simple and efficient method for isolating cells of the retinal pigment epithelium (RPE) cells from the eyes of young pigmented guinea pigs. This procedure allows for follow-up molecular biology studies on the isolated RPE, including gene expression analyses.

A Simplified Method for Isolation and Culture of Retinal Pigment Epithelial Cells from Adult Mice

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