This work was supported by the Ocular Genomics Institute at Massachusetts Eye and Ear.

The guidelines of the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research were followed.
NOTE: This method has been proven successful with mice of different genetic backgrounds, including C57BL/6J, B10.D2-Hco H2d H2-T18c/oSnJ, and albino mice, at various ages. Preferably use 8 to 12-week-old mice to obtain RPE cells. RPE cells from older mice proliferate less in culture and younger mice have fewer and smaller cells, which requires pooling eyes from different animals to have viable cultures.
1. Preparation of reagents and the membrane inserts
<ol>
	<li>Prepare the following reagents.
	<ol>
		<li>Prepare HBSS-H&#8722; (HBSS without calcium, without magnesium buffer + 10 mM HEPES): Add 1 mL of 1 M HEPES to 99 mL of HBSS- (without Ca/Mg) buffer. Store at 4 &#176;C up to 1 month.</li>
		<li>Prepare HBSS-H+ (HBSS with calcium, with magnesium buffer + 10 mM HEPES): Add 1 mL of 1 M HEPES to 99 mL of HBSS+ (with Ca/Mg) buffer. Store at 4 &#176;C up to 1 month.</li>
		<li>Prepare hyaluronidase solution (1 mg/mL): Add 10 mg of hyaluronidase to 10 mL of HBSS-H&#8722; and filter it with a 0.4 &#181;m sterile syringe filter using a 10 mL syringe. Prepare fresh before use and leave it at room temperature (RT; 20-25 &#176;C).</li>
		<li>Prepare FBS solution: Mix 20% FBS with HBSS-H+. Add 2 mL of FBS to 8 mL of HBSS-H+. Prepare fresh before use.</li>
		<li>Prepare RPE medium: N1 Medium Supplement 1/100 (v/v), glutamine 1/100 (v/v), penicillin-streptomycin 1/100 (v/v) and nonessential amino acid solution 1/100 (v/v), hydrocortisone (20 &#181;g/L), taurine (250 mg/L) and triiodo-thyronin (0.013 &#181;g/L) in alpha MEM + 5% FBS or without FBS1,23,24. If desired, FBS may be heat-inactivated; no differences have been observed. Prepare fresh for RPE isolation. For cell culture maintenance, store at 4 &#176;C up to 1 month.</li>
		<li>Prepare trypsin-EDTA: Prepare small single-use aliquots (~8 mL) of fresh trypsin-EDTA (0.25%) and freeze them at -20 &#7506;C. Thaw them at RT before each use. Avoid freeze-thaw cycles.</li>
	</ol>
	</li>
	<li>Prepare the membrane inserts (e.g., Transwell inserts).
	<ol>
		<li>Equilibrate the 6.5-mm membrane inserts with RPE medium for at least 30 min at 37 &#176;C, in a 5% CO2-aerated incubator. Use one membrane insert to seed RPE cells from two mouse eyes.</li>
		<li>After incubation, replace the medium of the lower compartment with 700 &#181;L of PBS.</li>
		<li>Remove the medium from the top compartment and coat the membrane insert with 100 &#181;L of 10 &#181;g/mL mouse laminin (in PBS) for at least 2 h at RT (shorter incubations may lead to poor attachment of the cells to the insert).</li>
		<li>Coat an extra membrane insert to use as a blank for TER measurements.</li>
	</ol>
	</li>
</ol>
2. Dissection and enucleation of the mouse eyes
<ol>
	<li>Euthanize the mice by CO2 asphyxiation by placing them in a CO2 chamber and slowly releasing CO2 at a fill rate of 30-70% of the chamber volume per minute.</li>
	<li>Place the angled, serrated tips of micro-forceps on each side of the mouse eye and gently press to proptose the eyeball (enucleation).</li>
	<li>Close the forceps placed around the eyeball. Then, pull gently while moving forward and backward to detach the whole eye with the optic nerve from the ocular muscles, ensuring that no connective tissue remains attached to the sclera.</li>
	<li>Rinse the enucleated eyeball in 70% ethanol before placing them into one well of a six-well plate with 3 mL of HBSS-H&#8722; on ice.</li>
	<li>Repeat steps 2.2 to 2.4 to remove the second eye of the mouse. Proceed with the next steps within 30 min. 
	NOTE: It is recommended enucleating/dissecting only two eyes at a time until some experience is acquired.</li>
</ol>
3. Collection of the RPE
NOTE: Perform the following steps under sterile conditions in a laminar flow hood. To avoid extended incubations on ice, which can result in RPE cell death, do not collect more than two eyes at a time.
<ol>
	<li>Use a dissecting stereomicroscope, Dumont #5 forceps, and angled scissors to carefully clean away all the connective tissue, blood and muscles remaining attached to the eyeball without making any cuts in the sclera. Change the 3 mL of HBSS-H&#8722; buffer regularly, as needed, to keep the eye fresh and clean, and avoid the contamination of the RPE cultures.</li>
	<li>Use the optic nerve as a handle to hold the eyeball and make a hole in the center of the cornea with a sharp carbon-steel #11 blade.</li>
	<li>Use Dumont #5 scissors to make three incisions in the cornea through the aforementioned hole, ensuring that there is sufficient space to remove the lens.</li>
	<li>Hold the optic nerve and apply slight pressure to the ora serrata with the base of the angled scissors until the lens comes completely out. Leave the iris epithelium in place to prevent the detachment of the neural retina and RPE during incubation. Place the eye in HBSS-H-buffer.</li>
	<li>Repeat Steps 3.1-3.4 to dissect the second eye.</li>
	<li>Incubate the eyes without lenses in hyaluronidase solution in a 12-well plate at 37 &#176;C for 45 min in a 5% CO2-aerated incubator (1.5 mL/well) to detach the neural retina from the RPE.</li>
	<li>Place each eye in a new well and incubate it on ice for 30 min with 1.5 mL of cold HBSS-H+ buffer per well to stop the hyaluronidase activity. Do not extend the incubation for longer than 45 min.</li>
	<li>Wash, and place each eye into a 35-mm culture dish with fresh HBSS-H+ buffer and cut the cornea through the original incisions until reaching the the ora serrata&#160;by using 8-cm Vannas scissors. Then, cut below the ora serrata to remove the iris epithelium and cornea.</li>
	<li>Hold the eyecup edge/ora serrata with curved tweezers and, using angled microforceps, pull away the neural retina making sure that the RPE layer is not cut. Then, cut the internal attachment to the optic nerve. If some RPE cells remain attached to the neural retina, extend the incubation time but do not exceed 45 min total.</li>
	<li>Cut the optic nerve and transfer each eyecup to a different 12-well plate containing 1.5 mL of fresh trypsin-EDTA per well. Ensure that the eyecups remain opened and completely submerged in the trypsin. Incubate the eyecups at 37 &#176;C for 45 min in a 5% CO2 incubator.</li>
	<li>Collect each eyecup together with any RPE sheets detached during the trypsin incubation and transfer them into a 12-well plate containing 1.5 mL of FBS solution per well. If RPE sheets remain in the trypsin solution, use a micropipette to transfer them to the well with FBS solution.</li>
</ol>
4. Isolation of primary mouse RPE cells
<ol>
	<li>Hold each eyecup by the optic nerve and shake it face down into the 12-well plate containing 1.5 mL of 20% FBS in HBSS-H+ until the complete detachment of the RPE sheets is achieved.</li>
	<li>Collect any RPE sheets and RPE clusters with a micropipette and place them in a 15-mL tube. Avoid any white pieces of sclera or choroid, which could contaminate the cultures. Pool two eyes from the same mouse in one tube.</li>
	<li>Centrifuge the mixture at 340 x g for 2 min at RT and discard the supernatant.</li>
	<li>Gently resuspend the RPE pellet in 1 mL of trypsin-EDTA (0.25%) and incubate the mixture for 1 min in a water bath at 37 &#176;C to disaggregate the RPE sheets into single cells. After incubation, gently pipet up and down 10x with a micropipette, avoiding bubble formation while pipetting.</li>
	<li>Add 9 mL of freshly prepared RPE medium to dilute and inactivate the trypsin and centrifuge the mixture at 340 x g for 2 min at RT.</li>
	<li>Aspirate the supernatant and carefully resuspend the cell pellet in 150 &#181;L of RPE medium with 5% FBS by using a micropipette, ensuring that cells are homogeneously resuspended and avoiding bubble formation while pipetting.</li>
	<li>Take laminin-coated membrane insert from step 1.2, remove PBS from the bottom chamber and add 700 &#181;L of RPE medium.</li>
	<li>Remove the laminin from the upper chamber of the membrane insert and distribute the RPE cell suspension dropwise and uniformly to the center of the chamber, avoiding bubble formation while pipetting.</li>
	<li>Place the membrane insert in a 5% CO2 incubator at 37 &#176;C and leave undisturbed for at least 24 h.</li>
	<li>After 24 h, check the membrane insert under the microscope to make sure that most RPE cells are attached to the insert and the confluence is at least 50% (Figure 1A). It is critical not to change media during the first 72 h.</li>
</ol>
5. Culture of polarized RPE monolayers
<ol>
	<li>Maintain the isolated RPE cells in culture for at least 72 h before refreshing the RPE medium to allow cell attachment. A cell confluence of 50% or more at seeding is fundamental for the formation of a suitable polarized RPE monolayer.</li>
	<li>Change the culture medium twice a week using fresh and pre-warmed RPE medium (step 1.1.5) after the cells are attached. Serum can be removed from the culture medium after the first 72 h. 
	&#8203;NOTE: After one week in culture, cells should be confluent, hexagonal, bi-nucleated, pigmented and polarized (Figure 1B), with expected cell numbers being around 50,000 cells per 6.5 mm Transwell insert. After two weeks in culture, RPE monolayers comprising of healthy cells are observed. RPE cultures display apical microvilli, basal infoldings, and tight junctions (Figure 1C).</li>
</ol>
6. TER measurement
NOTE: Perform TER measurements of the RPE cells after a minimum of 4 days in culture to ensure a good integrity and polarization of the RPE monolayer.
<ol>
	<li>Clean the electrodes of the voltohmmeter with 70% ethanol and dry them carefully.</li>
	<li>Take the transwells from the incubator and perform TER measurement within 3 min to avoid alterations due to temperature fluctuations. To measure TER, immerse the short electrode of the voltohmmeter in the upper chamber and the long electrode in the bottom chamber of the membrane insert. Avoid contact with the RPE monolayer to prevent cell detachment.</li>
	<li>To calculate TER, deduct the value of the blank (membrane insert coated with laminin without cells) from the sample. Then multiply the obtained value (in ohms) by the surface area of the membrane insert (0.33 cm2 in the case of 6.5-mm membrane insert). The product should be at least 200 &#8486; x cm2 after 72 h in culture. TER values should measure above 400 &#8486; x cm2 after two weeks. Discard RPE cultures with low TER values.</li>
</ol>

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</ol>

The authors declare that they have no competing financial interests.

While several methods for mouse RPE cell isolation and culture had been developed before1,13,20,22,26,27, Fernandez-Godino&#39;s method first used membrane inserts allowing the efficient growth of the RPE cells in culture for weeks1,9. Another major change in their protocol1,9 was the use of enzymatic solutions instead of mechanical peeling to dissociate the RPE cells1,13,20,26. The lenses were removed through an incision in the cornea, leaving the iris epithelium intact and preserving the integrity of the retina during the first incubation. The gentle isolation of the RPE cells combined with the use of membrane inserts and specific RPE medium23 results in an improved cell survival, enhancing the formation of a functional confluent monolayer which mimics the physiological conditions of the RPE within days in culture2.&#160;Typically, primary mouse RPE cells cultured with this method display hexagonal morphology, polarization, pigmentation, barrier properties, and proliferation. Moreover, the RPE can be cultured in the absence of serum from day three up to several weeks, which is important to study complement-associated RPE pathologies9.
A limitation of this protocol is that primary mouse RPE cells cultured&#160;on membrane inserts cannot be expanded. Passaging primary mouse RPE cells with enzymatic solutions or culturing them for a long time results in loss of pigmentation, de-differentiation, and decreased TER, thereby losing the properties that resemble in vivo features. The limited amount of RPE cells obtained from one animal obligates to pool samples from different animals for transcriptomic and proteomic analyses, where relatively large amounts of starting material are required. It is not recommended to scale up the RPE cultures by pooling more eyes into a larger membrane insert, as it can result in a higher percentage of cell death and multilayered RPE cultures.
There are some critical steps to the protocol as well. No more than two eyes should be harvested at the same time until some experience is aquired, since a prolonged dissection time results in a higher percentage of cell death. The optic nerve must be cut away only before the incubation with trypsin. It is critical to handle the eyecup without disturbing the RPE cells, but the optic nerve gets digested by trypsin, which leads to impurities in the RPE cultures. Peeling off the ocular muscles must be performed with caution. If the sclera is perforated and the neural retina pops out, the eye must be discarded because the RPE cells will be damaged and will not survive. Minimal pressure should be applied to remove the lenses. It is preferable to perform a larger corneal incision. It is critical that the eyecup is open and completely submerged in trypsin so that all the RPE cells are exposed to the solution. The RPE cells must be collected through gentle shaking of the eyecup, and never by spraying media or peeling them mechanically.

This protocol, which was originally reported by Fernandez-Godino et al. in 20161, describes a method to efficiently isolate and culture mouse retinal pigment epithelium (RPE) cells, which form a functional and polarized RPE monolayer within one week on Transwell plates. The&#160;RPE&#160;is a monolayer located in the eye between the neural retina and the Bruch&#39;s membrane. This single layer consists of highly polarized and pigmented epithelial cells joined by tight junctions, exhibiting a hexagonal shape that resembles a honeycomb2. Despite this apparent histological simplicity, the RPE performs a wide variety of functions critical to the retina and the normal visual cycle2,3,4. The main functions of the RPE monolayer include light absorption, nourishment and renewal of photoreceptors, removal of metabolic end products, control of the ion homeostasis in the subretinal space and maintenance of the blood-retinal barrier2,3. The RPE also has an important role in local modulation of the immune system in the eye5,6,7,8,9,10,11. Degeneration and/or dysfunction of the RPE are common features shared by many ocular disorders such as retinitis pigmentosa, Leber congenital amaurosis, albinism, diabetic retinopathy, and macular degeneration12,13,14,15. Unfortunately, the availability of human tissues is limited. Given their highly conserved genetic homology with humans, mouse models represent a suitable and useful tool for studying ocular disorders16,17,18,19. Furthermore, the use of cultured primary RPE cells provides advantages such as genetic manipulation and drug testing that can accelerate the development of new therapies for these vision-threatening disorders9,11.
Existing methods available for mouse RPE isolation and culture lack reproducibly and do not recapitulate the RPE features in vivo with enough reliability. Cells tend to lose pigmentation, hexagonal shape and transepithelial electrical resistance (TER) within a few days in culture13, 20. Since establishing these primary RPE cell cultures from mice is a challenging process, this optimized protocol has been created based on other protocols to isolate RPE cells from rat and human eyes21,22,23 to dissect the mouse eyes, collect the RPE and culture the mouse RPE cells in vitro.

<table><tbody><tr><td>10 ml BD Luer-Lok tip syringe, disposable</td><td>BD Biosciences</td><td>309604</td><td></td></tr><tr><td>15 ml centrifuge tube</td><td>VWR International</td><td>21008-103</td><td></td></tr><tr><td>50 ml centrifuge tube</td><td>VWR International</td><td>21008-951</td><td></td></tr><tr><td>Alpha Minimum Essential Medium</td><td>Sigma-Aldrich</td><td>M4526-500ML</td><td></td></tr><tr><td>Angled micro forceps</td><td>WPI</td><td>501727</td><td></td></tr><tr><td>Bench-top centrifuge</td><td>any</td><td></td><td></td></tr><tr><td>CO2 incubator</td><td>Thermo</td><td>HERA VIOS 160I CO2 SST TC 120V</td><td></td></tr><tr><td>Dissecting microscope</td><td>Any</td><td></td><td></td></tr><tr><td>Dulbecco&amp;rsquo;s Phospate Buffered Saline no Calcium, no Magnesium</td><td>Gibco</td><td>14190144</td><td></td></tr><tr><td>Dumont #5 45&amp;deg; Medical Biology tweezers, 0.05 x 0.01 mm tip, 11 cm length</td><td>WPI</td><td>14101</td><td></td></tr><tr><td>Ethanol</td><td>Sigma-Aldrich</td><td>E7023-500ML</td><td></td></tr><tr><td>Falcon Easy-Grip Clear Polystyrene Cell Culture Dish, 35mm</td><td>BD Biosciences</td><td>353001</td><td></td></tr><tr><td>Fetal Bovine Serum</td><td>Hyclone</td><td>SH30071.03</td><td>Heat inactivated.</td></tr><tr><td>Hank&amp;rsquo;s Balanced Salt Solution plus Calcium and Magnesium, no Phenol Red</td><td>Life Technologies</td><td>14175095</td><td></td></tr><tr><td>Hank&amp;rsquo;s Balanced Salt Solution plus Calcium and Magnesium, no Phenol Red B6</td><td>Life Technologies</td><td>14025092</td><td></td></tr><tr><td>HEPES 1M</td><td>Gibco</td><td>15630106</td><td></td></tr><tr><td>Hyaluronidase</td><td>Sigma-Aldrich</td><td>H-3506 1G</td><td></td></tr><tr><td>Hydrocortisone</td><td>Sigma-Aldrich</td><td>H-0396</td><td></td></tr><tr><td>Laminar flow hood</td><td>Thermo</td><td>CLASS II A2 4 115V PACKAGECLA</td><td></td></tr><tr><td>Laminin 1mg/ml</td><td>Sigma-Aldrich</td><td>L2020-1 MG</td><td>Dilute in PBS at 37C to 1mg/ml</td></tr><tr><td>McPherson-Vannas Micro Scissors 8 cm long</td><td>WPI</td><td>503216</td><td></td></tr><tr><td>Non-essential amino acids 100X</td><td>Gibco</td><td>11140050</td><td></td></tr><tr><td>N1 Supplement 100X</td><td>Sigma-Aldrich</td><td>N6530-5ML</td><td></td></tr><tr><td>Penicillin-Streptomycin</td><td>Gibco</td><td>15140-148</td><td></td></tr><tr><td>Sterile Bard-Parker Carbon steel surgical blade size 11</td><td>Fisher-Scientific</td><td>08-914B</td><td></td></tr><tr><td>Taurine</td><td>Sigma-Aldrich</td><td>T-0625</td><td></td></tr><tr><td>Tissue culture treated 12-well plates</td><td>Fisher-Scientific</td><td>08-772-29</td><td></td></tr><tr><td>Tissue culture treated 6-well plates</td><td>Fisher-Scientific</td><td>14-832-11</td><td></td></tr><tr><td>Transwell supports 6.5 mm</td><td>Sigma-Aldrich</td><td>CLS3470-48EA</td><td></td></tr><tr><td>Triiodo-thyronin</td><td>Sigma-Aldrich</td><td>T-5516</td><td></td></tr><tr><td>Trypsin-EDTA (0.25%), phenol red</td><td>Gibco</td><td>25200056</td><td></td></tr><tr><td>Tweezer, Dumont #5 Medical Biology 11 cm, curved, stainless steel 0.02 x 0.06 mm Mod tips</td><td>WPI</td><td>500232</td><td></td></tr><tr><td>Vannas Scissors 8cm long, stainless steel</td><td>WPI</td><td>501790</td><td></td></tr><tr><td>Whatman Puradisc 25mm Syringe Filters 0.45&amp;mu;m pore size</td><td>Fisher-Scientific</td><td>6780-2504</td><td></td></tr></tbody></table>

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 has been used to isolate and culture RPE cells from genetically modified mice1. No differences have been observed between mouse strains or gender. The results have helped to understand some important aspects of the mechanism underlying ocular diseases such as age-related macular degeneration, which is the most common cause of vision loss among the elderly9. RPE cells isolated following this protocol were completely attached to the membrane insert 24 hours after seeding and showed the typical RPE size, morphology and pigmentation after 72 h1. After one week, a highly polarized RPE monolayer was formed by hexagonal pigmented RPE cells with two nuclei joined by tight junctions expressing ZO-1 (Figures 1C, 2). Transmission electron micrographs reveal the presence of apical microvilli and basal infoldings (Figure 1C). Polarization of the RPE monolayer was confirmed by TER values with average higher than 200 &#8486; x cm2, which remained stable over time (Figure 2).
Functional validation of this method was performed though phagocytosis assays. Mouse RPE cells were cultured on membrane inserts and fed with FITC-labeled bovine POS. POS engulfment and digestion were demonstrated by fluorescent microscopy (Figure 3).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62228/62228fig1v2.jpg" /> 
Figure 1.&#160;RPE cells at different time-points. (A) 10x brightfield micrographs of RPE cells 24 h post seeding on the membrane inserts, and (B) after one week. (C) Transmission electron micrographs display apical microvilli, basal infoldings, and melanin pigments (black spots) of the RPE cultured on the membrane inserts for two weeks. Scale bars: A, B: 100 &#181;m, C: 2 &#181;m. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62228/62228fig1v2large.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/62228/62228fig2v2.jpg" /> 
Figure 2. TER over time. The transepithelial electrical resistance (TER) of ~60 primary mouse RPE cell cultures on membrane inserts was measured after 0.5 (n=33), 1 (n=58), 1.5 (n=54), and 2 (n=60) weeks. TER reaches over 200 &#937; x cm2 by 72 hours and remains stable for at least two weeks. Data represented as single values with average &#177; SD. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62228/62228fig2v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/62228/62228fig3v2.jpg" /> 
Figure 3.&#160;Phagocytosis assays. 40x fluorescent micrographs of primary mouse RPE cultures fed with FITC-labeled bovine POS (green) for two hours and fixed with methanol25. Smaller fragments correspond to digested POS inside the cytoplasm of the cell. Visualization of tight junctions (red) was facilitated by immunostaining with antibodies anti-ZO1 as previously described1,9. DAPI (blue) was used to stain nuclei. Typical mouse RPE cells with two nuclei can be observed in the center of the image. Scale bar: 50 &#181;m. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62228/62228fig3v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Efficient Dissection and Culture of Primary Mouse Retinal Pigment Epithelial Cells at JoVE.com

Efficient Dissection and Culture of Primary Mouse Retinal Pigment Epithelial Cells

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 ...

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6.2K Views.  Harvard Medical School. 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.

Video: Efficient Dissection and Culture of Primary Mouse Retinal Pigment Epithelial Cells

Vibratome Sectioning Mouse Retina to Prepare Photoreceptor Cultures

The retina is a part of the central nervous system that has organized architecture, with neurons in layers from the photoreceptors, both rods and cones in contact with the retinal pigmented epithelium in the most distant part on the retina considering the direction of light, and the ganglion cells in the most proximal distance. This architecture allows the isolation of the photoreceptor layer by vibratome sectioning. The dissected neural retina of a mouse aged 8 days is flat-embedded in 4% gelatin on top of a slice of 20% gelatin photoreceptor layer facing down. Using a vibratome and a double edged razor blade, the 100 &#181;m thick inner retina is sectioned. This section contains the ganglion cells and the inner layer with notably the bipolar cells. An intermediary section of 15 &#181;m is discarded before 200 &#181;m of the outer retina containing the photoreceptors is recovered. The gelatin is removed by heating at 37 &#176;C. Pieces of outer layer are incubated in 500 &#181;l of Ringer&#39;s solution with 2 units of activated papain for 20 min at 37 &#176;C. The reaction is stopped by adding 500 &#181;l 10% fetal calf serum (FCS) in Dulbecco&#39;s Modified Eagle Medium (DMEM), then 25 units of DNAse I is added before centrifugation at RT, washed several times to remove serum and the cells are resuspended in 500 &#181;l of DMEM and seeded at 1 x 105 cells/cm2. The cells are grown to 5 days in vitro and their viability scored using live/dead assay. The purity of the culture is first determined by microscopic observation during the experiment. The purity is then validated by seeding and fixing cells on a histological slide and analyzing using a rabbit polyclonal anti-SAG, a photoreceptor marker and mouse monoclonal anti-RHO, a rod photoreceptor specific marker. Alternatively, the photoreceptor layer (97% rods) can be used for gene or protein expression analysis and for transplantation.

Neural retina of a mouse aged 8 days is on top of a 4% gelatin block. After isolation of the photoreceptor layer (200 &#181;m) by vibratome, the photoreceptors are seeded after mechanical and enzymatic dissociation for culture. The photoreceptor layer can be used for molecular, biochemical analyses or transplantation.

The retina is a part of the central nervous system that has organized architecture, with neurons in layers from the photoreceptors, both rods and cones in ...

Neuroscience

Primary Cell Cultures to Study the Regeneration Potential of Murine M&#252;ller Glia after MicroRNA Treatment

M&#252;ller glia (MG) are the predominant glia in the neural retina and can function as a regenerative source for retinal neurons. In lower vertebrates such as fish, MG-driven regeneration occurs naturally; in mammals, however, stimulation with certain factors or genetic/epigenetic manipulation is required. Since MG comprise only 5% of the retinal cell population, there is a need for model systems that allow the study of this cell population exclusively. One of these model systems is primary MG cultures that are reproducible and can be used for a variety of applications, including molecule/factor screening and identification, testing of compounds or factors, cell monitoring, and/or functional tests. This model is used to study the potential of murine MG to convert into retinal neurons after supplementation or inhibition of microRNAs (miRNAs) via transfection of artificial miRNAs or their inhibitors. The use of MG-specific reporter mice in combination with immunofluorescent labeling and single-cell RNA sequencing (scRNA-seq) confirmed that 80%-90% of the cells found in these cultures are MG. Using this model, it was discovered that miRNAs can reprogram MG into retinal progenitor cells (RPCs), which subsequently differentiate into neuronal-like cells. The advantages of this technique are that miRNA candidates can be tested for their efficiency and outcome before their usage in in vivo applications.

M&#252;ller glia primary cultures obtained from mouse retinas represent a very robust and reliable tool to study the glial conversion into retinal progenitor cells after microRNA treatment. Single molecules or combinations can be tested before their subsequent application of in vivo approaches.

M&#252;ller glia (MG) are the predominant glia in the neural retina and can function as a regenerative source for retinal neurons. In lower vertebrates ...

Developmental Biology

Ex Vivo Culture of Primary Human Fallopian Tube Epithelial Cells

Epithelial ovarian cancer is a leading cause of female cancer mortality in the United States. In contrast to other women-specific cancers, like breast and uterine carcinomas, where death rates have fallen in recent years, ovarian cancer cure rates have remained relatively unchanged over the past two decades 1. This is largely due to the lack of appropriate screening tools for detection of early stage disease where surgery and chemotherapy are most effective 2, 3. As a result, most patients present with advanced stage disease and diffuse abdominal involvement. This is further complicated by the fact that ovarian cancer is a heterogeneous disease with multiple histologic subtypes 4, 5. Serous ovarian carcinoma (SOC) is the most common and aggressive subtype and the form most often associated with mutations in the BRCA genes. Current experimental models in this field involve the use of cancer cell lines and mouse models to better understand the initiating genetic events and pathogenesis of disease 6, 7. Recently, the fallopian tube has emerged as a novel site for the origin of SOC, with the fallopian tube (FT) secretory epithelial cell (FTSEC) as the proposed cell of origin 8, 9. There are currently no cell lines or culture systems available to study the FT epithelium or the FTSEC. Here we describe a novel ex vivo culture system where primary human FT epithelial cells are cultured in a manner that preserves their architecture, polarity, immunophenotype, and response to physiologic and genotoxic stressors. This ex vivo model provides a useful tool for the study of SOC, allowing a better understanding of how tumors can arise from this tissue, and the mechanisms involved in tumor initiation and progression.

Ex Vivo Culture of Primary Human Fallopian Tube Epithelial Cells

The fallopian tube (FT) is emerging as an alternative site of origin for serous ovarian carcinoma (SOC). This protocol describes a novel method for the isolation and ex vivo culture of fallopian tube epithelial cells. This system recapitulates the in vivo epithelium and allows the study of SOC pathogenesis.

Epithelial ovarian cancer is a leading cause of female cancer mortality in the United States. In contrast to other women-specific cancers, like breast and ...

Isolation and Culture of Mouse Primary Pancreatic Acinar Cells

This protocol permits rapid isolation (in less than 1 hr) of murine pancreatic acini, making it possible to maintain them in culture for more than one week. More than 20 x 106 acinar cells can be obtained from a single murine pancreas. This protocol offers the possibility to independently process as many as 10 pancreases in parallel. Because it preserves acinar architecture, this model is well suited for studying the physiology of the exocrine pancreas in vitro in contrast to cell lines established from pancreatic tumors, which display many genetic alterations resulting in partial or total loss of their acinar differentiation.

In this publication, we describe a rapid and convenient procedure for isolating and culturing primary pancreatic acinar cells from the murine pancreas. This method constitutes a valuable approach to study the physiology of fresh primary normal/untransformed exocrine pancreatic cells.

This protocol permits rapid isolation (in less than 1 hr) of murine pancreatic acini, making it possible to maintain them in culture for more than one ...

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 ...

Characterization and Morphological Dynamics of Cultured Primary 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 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.

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.

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

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 ...

Primary Culture of Porcine Retinal Pigment Epithelial Cells

The retinal pigment epithelium (RPE) is a monolayer of polarized pigmented epithelial cells, located between the choroid and neuroretina in the retina. Multiple functions, including phagocytosis, nutrient/metabolite transportation, vitamin A metabolism, etc., are conducted by the RPE on a daily basis. RPE cells are terminally differentiated epithelial cells with little or no regenerative capacity. Loss of RPE cells results in multiple eye diseases leading to visual impairment, such as age-related macular degeneration. Therefore, the establishment of an in vitro culture model of primary RPE cells, which more closely resembles the RPE in vivo than cell lines, is critical for the characteristic and mechanistic studies of RPE cells. Considering the fact that the source of human eyeballs is limited, we create a protocol to culture primary porcine RPE cells. By using this protocol, RPE cells can be easily dissociated from adult porcine eyeballs. Subsequently, these dissociated cells attach to culture dishes/inserts, proliferate to form a confluent monolayer, and quickly re-establish key features of epithelial tissue in vivo within 2 wks. By qRT-PCR, it is demonstrated that primary porcine RPE cells express multiple signature genes at comparable levels with native RPE tissue, while the expressions of most of these genes are lost/highly reduced in human RPE-like cells, ARPE-19. Moreover, the immunofluorescence staining shows the distribution of tight junction, tissue polarity, and cytoskeleton proteins, as well as the presence of RPE65, an isomerase critical for vitamin A metabolism, in cultured primary cells. Altogether, we have developed an easy-to-follow approach to culture primary porcine RPE cells with high purity and native RPE features, which could serve as a good model to understand RPE physiology, study cell toxicities, and facilitate drug screenings.

Here, an easy-to-follow method to culture primary porcine retinal pigment epithelial cells in vitro is presented.

The retinal pigment epithelium (RPE) is a monolayer of polarized pigmented epithelial cells, located between the choroid and neuroretina in the retina. ...

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 Primary Mouse Retinal Glial M&#252;ller Cells

The primary supporting cell of the retina is the retinal glial M&#252;ller cell. They cover the entire retinal surface and are in close proximity to both the retinal blood vessels and the retinal neurons. Because of their growth, M&#252;ller cells perform several crucial tasks in a healthy retina, including the uptake and recycling of neurotransmitters, retinoic acid compounds, and ions (like potassium K+). In addition to regulating blood flow and maintaining the blood-retinal barrier, they also regulate the metabolism and the supply of nutrients to the retina. An established procedure for isolating primary mouse M&#252;ller cells is presented in this manuscript. To better understand the underlying molecular processes involved in the various mouse models of ocular disorders, M&#252;ller cell isolation is an excellent approach. This manuscript outlines a detailed procedure for M&#252;ller cell isolation from mice. From enucleation to seeding, the entire process lasts about a few hours. For 5-7 days after seeding, the media shouldn&#39;t be changed in order to allow the isolated cells to grow unhindered. Cell characterization using morphology and distinct immunofluorescent markers comes next in the process. Maximum passages for cells are 3-4 times.

This manuscript describes a detailed protocol for isolating retinal glial M&#252;ller cells from mouse eyes. The protocol starts with enucleation and dissection of mouse eyes, followed by isolation, seeding, and culturing of M&#252;ller cells.

The primary supporting cell of the retina is the retinal glial M&#252;ller cell. They cover the entire retinal surface and are in close proximity to both ...

Efficient Dissection and Culture of Primary Mouse Retinal Pigment Epithelial Cells

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