Name: performing subretinal injections in rodents to deliver retinal pigment epithelium cells in suspension
Uploaded: 2015-01-23T13:00:00
Description: Watch this Scientific Journal Video about Performing Subretinal Injections in Rodents to Deliver Retinal Pigment Epithelium Cells in Suspension at JoVE.com

We wish to thank Alison Dorsey for helping to develop the subretinal injection technique. We also acknowledge the National Eye Institute (NEI grants EY11254 and EY021416), California Institute for Regenerative Medicine (CIRM grant TR1-01219), and the Lowy Medical Research Institute (LMRI) for very generous funding for this project.

NOTE: All animals were treated in accordance with the ethical guidelines established by the Scripps Research Institute.
1. Preparation of Materials for the Injection (~20 min)
<ol style="margin-left: 40px;">
	<li>Pre-warm cell dissociation solution (preferably one that is inactivated through dilution, not with serum), sterile PBS, and culture media (Table 1).</li>
	<li>Sterilize the syringe with a blunt needle by disassembling it and boiling the parts in water for 15 min.</l...

In this article we describe a relatively simple method for performing subretinal injections of RPE cells in suspension in rats and mice. The protocol is easy to learn and more experience with the technique will translate in fewer traumas (Figure 3; this represents one of the better injections), especially if a micromanipulator is used (Figure 1A). Any trauma can be monitored in vivo with a cSLO and OCT system (Figure 2) if available. If higher resolution and les...

The sensory retina is organized in functional tiers of neurons, glia, and endothelial cells. Photoreceptors at the back of the retina are activated by light; through phototransduction they convert photons into electrical signals that are refined by interneurons and transmitted to the visual cortex in the brain. Phototransduction cannot occur without the coordinated efforts of Mueller glia and retinal pigment epithelium (RPE) cells. RPE are organized in a monolayer directly behind the photoreceptors and perform multiple and diverse functions integral to photoreceptor function and homeostasis. In fact, RPE and photoreceptors are so co-dependent that they are considered to be one functional unit. Death or dysfunction of RPE results in devastating secondary effects on photoreceptors and is associated with age-related macular degeneration (AMD), the leading cause of blindness in the elderly1,2.
While no cure has been discovered for AMD, several clinical studies have shown that RPE cell replacement may be a promising therapeutic option3-13. With the advent of stem cell technology, it is now possible to generate large numbers of RPE cells in vitro from embryonic and induced pluripotent stem cells (hES and hiPS) that strongly resemble their somatic counterparts functionally and anatomically14-26. Stem cell-derived RPE have also been shown to function in vivo by multiple independent groups, including our own, to significantly slow retinal degeneration in rat and mouse lines with spontaneous retinal degeneration16,18,21,22,25,28,29. This combination of clinical and preclinical supporting evidence is so compelling that several clinical trials to prevent retinal degeneration using stem cell-derived RPE cells are now ongoing30,31. 
RPE can be readily derived from hES and/or hiPS and implanted in the subretinal space of rodents using various derivation and injection techniques32,33. (See Westenskow et al. for a methods paper in multimedia format demonstrating the directed differentiation protocol we employ)34. There are critical remaining questions regarding the safety, survival, and functional capacity of exogenously delivered RPE cells upon implantation, therefore the ability to perform subretinal injections in rodents is a critical skill16,18,21,29,36,37. The delivery of RPE is not trivial, and the field is divided on the most effective injection technique. The protocol we describe here is a simple and effective way to deliver of bolus of RPE cells subretinally, and was used in the first clinical trial for stem cell-derived RPE transplantation31. (The reader may also refer to another JoVE article by Eberle et al. for an alternative depiction of subretinal injections in rodents.38) 
The technique outlined in this manuscript cannot be visualized and trauma is unavoidable (as with any subretinal injection technique). It is performed by making a hole just under the limbus vessels and inserting a blunt needle along a transscleral route to inject a bolus of cells under the diametrically opposed retina. The person doing the injection will feel resistance as the blunt needle touches the retina. The cells may be directly visualized after the injection, however, and the degree of the induced retinal detachment can be determined by labeling the RPE cells with a transient fluorescent marker and detecting them with a confocal scanning ophthalmoscope (cSLO). An optical coherence tomography (OCT) system can also be used to monitor the trauma and easily identify the injection site.

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			<td height="20" style="height:20px;width:419px;">Name of Material/ Equipment (A-Z)</td>
			<td style="width:145px;">Company</td>
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			<td style="width:167px;">Comments/Description</td>
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			<td height="20" style="height:20px;">2-Mercaptoethanol (55 mM)</td>
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			<td>21985-023</td>
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			<td height="20" style="height:20px;">Cell Scapers</td>
			<td>VWR</td>
			<td>89260-222</td>
			<td>Case x 1</td>
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			<td height="20" style="height:20px;">CellTracker Green CMFDA</td>
			<td>Molecular Probes</td>
			<td>C34552</td>
			<td>50 ug x 20</td>
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			<td height="20" style="height:20px;">DPBS, no calcium, no magnesium</td>
			<td>Gibco</td>
			<td>14190-144</td>
			<td>500 mL x 1&#160;</td>
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			<td height="20" style="height:20px;">Fast Green</td>
			<td>Sigma-Aldrich</td>
			<td>F7258</td>
			<td>25 g x 1&#160;</td>
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			<td height="20" style="height:20px;">Genteal Geldrops Moderate to Severe Lubricant Eye Drops&#160;</td>
			<td>Walmart</td>
			<td>4060941</td>
			<td>25 mL x 1</td>
		</tr>
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			<td height="20" style="height:20px;">Hamilton Model 62 RN SYR</td>
			<td>Hamilton</td>
			<td>87942</td>
			<td>Syringe x 1&#160;</td>
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			<td height="21" style="height:21px;width:419px;">Hamilton Needle 33 gauge, 0.5&#34;, point 3 (304 stainless steel)</td>
			<td style="width:145px;">Hamilton</td>
			<td style="width:119px;">7803-05</td>
			<td>Needles x 6</td>
		</tr>
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			<td height="20" style="height:20px;">Knockout DMEM</td>
			<td>Gibco</td>
			<td>10829-018</td>
			<td>500 mL x 1&#160;</td>
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			<td height="20" style="height:20px;">KnockOut Serum Replacement</td>
			<td>Gibco</td>
			<td>10828-028</td>
			<td>500 mL x 1&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">L-Glutamine 200 mM</td>
			<td>Gibco</td>
			<td>25030-081</td>
			<td>100 mL x 1</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:419px;">Magnetic Stand</td>
			<td style="width:145px;">Leica Biosystems</td>
			<td style="width:119px;">39430216</td>
			<td>Stand x 1</td>
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		<tr height="20">
			<td height="20" style="height:20px;">MEM Non-Essential Amino Acids Solution 100X&#160;</td>
			<td>Gibco</td>
			<td>11140-050</td>
			<td>100 mL x 1</td>
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			<td height="20" style="height:20px;width:419px;">Micromanipulator</td>
			<td style="width:145px;">Leica Biosystems</td>
			<td style="width:119px;">3943001</td>
			<td>Manipulator x 1</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin-Streptomycin (10,000 U/mL)</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>100 mL x 1</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Slip Tip Syringes without Needles BD&#160; (3 mL)&#160;&#160;</td>
			<td>VWR</td>
			<td>BD309656</td>
			<td>Pack x 1</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Specialty-Use Needles BD&#160; (30 gauge, 1&#34;)</td>
			<td>VWR</td>
			<td>BD305128</td>
			<td>Box x 1</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">TrypLE Express Enzyme (1X), no phenol red</td>
			<td>Gibco</td>
			<td>12604013</td>
			<td>100 mL x 1</td>
		</tr>
	</tbody>
</table>

performing subretinal injections in rodents to deliver retinal pigment epithelium cells in suspension

The conversion of light into electrical impulses occurs in the outer retina and is accomplished largely by rod and cone photoreceptors and retinal pigment epithelium (RPE) cells. RPE provide critical support for photoreceptors and death or dysfunction of RPE cells is characteristic of age-related macular degeneration (AMD), the leading cause of permanent vision loss in people age 55 and older. While no cure for AMD has been identified, implantation of healthy RPE in diseased eyes may prove to be an effective treatment, and large numbers of RPE cells can be readily generated from pluripotent stem cells. Several interesting questions regarding the safety and efficacy of RPE cell delivery can still be examined in animal models, and well-accepted protocols used to inject RPE have been developed. The technique described here has been used by multiple groups in various studies and involves first creating a hole in the eye with a sharp needle. Then a syringe with a blunt needle loaded with cells is inserted through the hole and passed through the vitreous until it gently touches the RPE. Using this injection method, which is relatively simple and requires minimal equipment, we achieve consistent and efficient integration of stem cell-derived RPE cells in between the host RPE that prevents significant amount of photoreceptor degeneration in animal models. While not part of the actual protocol, we also describe how to determine the extent of the trauma induced by the injection, and how to verify that the cells were injected into the subretinal space using in vivo imaging modalities. Finally, the use of this protocol is not limited to RPE cells; it may be used to inject any compound or cell into the subretinal space.

We can deliver a suspension of RPE cells into the subretinal space of rodents quickly and consistently using the technique described in this manuscript. While not required, traumas can be greatly minimized using the setup shown with a micromanipulator in Figure 1A&#38;B. Hold the rodent as shown in Figure 1C for temporary proptosis. The steps are the same if performed with the micromanipulator or by hand; these are depicted in the cartoon in Figure 1D. When performed cle...

Watch this Scientific Journal Video about Performing Subretinal Injections in Rodents to Deliver Retinal Pigment Epithelium Cells in Suspension at JoVE.com

Performing Subretinal Injections in Rodents to Deliver Retinal Pigment Epithelium Cells in Suspension

Here we present a community accepted protocol in multimedia format for subretinally injecting a bolus of RPE cells in rats and mice. This approach can be used for determining rescue potentials, safety profiles, and survival capacities of grafted RPE cells upon implantation in animal models of retinal degeneration.

The conversion of light into electrical impulses occurs in the outer retina and is accomplished largely by rod and cone photoreceptors and retinal pigment ...

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