Name: development of a refined protocol for trans-scleral subretinal transplantation of human retinal pigment epithelial cells into rat eyes
Uploaded: 2017-08-12T13:00:00
Description: Watch this Scientific Journal Video about Development of a Refined Protocol for Trans-scleral Subretinal Transplantation of Human Retinal Pigment Epithelial Cells into Rat Eyes at JoVE.com

We wish to thank Patty Lederman for her assistance on the surgery and Susan Borden for RPE cell preparation. We also acknowledge NYSTEM C028504 for the funding for this project. Justine D. Miller is supported by NIH grant F32EY025931.

All procedures involving animals have been approved by the Institutional Animal Care and Use Committee (IACUC) at the State University of New York at Albany.
1. Pre-injection Preparation
<ol>
	<li>Preparation of a hRPESC-RPE cell suspension 
	NOTE: All the following steps are performed in sterile tissue culture hood and familiarity with basic sterile technique is required.
	<ol>
		<li>Isolate primary hRPE cells from human donor eyes aged 50-90 years and culture cells in...

<ol>
	<li>De Jong, P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+macular+degeneration.">Age-related macular degeneration.</a> N Engl J Med. 355, 1474-1485 (2006).</li><li>Wong, W. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+prevalence+of+age-related+macular+degeneration+and+disease+burden+projection+for+2020+and+2040:+a+systematic+review+and+meta-analysis.">Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis.</a> Lancet Global Health. 2 (2), e106-e116 (2014).</li><li>Ambati, J., Fowler, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+agerelated+macular+degeneration.">Mechanisms of agerelated macular degeneration.</a> Neuron. 75, 26-39 (2012).</li><li>Abdelsalam, A., Del Priore, L. V., Zarbin, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drusen+in+age-related+macular+degeneration:+Pathogenesis,+natural+course,+and+laser+photocoagulation-induced+regression.">Drusen in age-related macular degeneration: Pathogenesis, natural course, and laser photocoagulation-induced regression.</a> Surv Ophthalmol. 44 (1), 1-29 (1999).</li><li>Jager, R. D., Mieler, W. F., Miller, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+macular+degeneration.">Age-related macular degeneration.</a> N Engl J Med. 358 (24), 2606-2617 (2008).</li><li>Lund, R. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+embryonic+stem+cell-derived+cells+rescue+visual+function+in+dystrophic+RCS+rats.">Human embryonic stem cell-derived cells rescue visual function in dystrophic RCS rats.</a> Cloning Stem Cells. 8 (3), 189-199 (2006).</li><li>Vugler, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+stem+cells+and+retinal+repair.">Embryonic stem cells and retinal repair.</a> Mech Dev. 124 (11-12), 807-829 (2007).</li><li>Schwartz, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+stem+cell+trials+for+macular+degeneration:+a+preliminary+report.">Embryonic stem cell trials for macular degeneration: a preliminary report.</a> Lancet. 379 (9817), 713-720 (2012).</li><li>Schwartz, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+embryonic+stem+cell-derived+retinal+pigment+epithelium+in+patients+with+age-related+macular+degeneration+and+Stargardt's+macular+dystrophy:+follow-up+of+two+open-label+phase+1/2+studies.">Human embryonic stem cell-derived retinal pigment epithelium in patients with age-related macular degeneration and Stargardt's macular dystrophy: follow-up of two open-label phase 1/2 studies.</a> Lancet. 385 (9967), 509-516 (2015).</li><li>Stanzel, B. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+RPE+Stem+Cells+Grown+into+Polarized+RPE+Monolayers+on+a+Polyester+Matrix+Are+Maintained+after+Grafting+into+Rabbit+Subretinal+Space.">Human RPE Stem Cells Grown into Polarized RPE Monolayers on a Polyester Matrix Are Maintained after Grafting into Rabbit Subretinal Space.</a> Stem Cell Reports. 2 (1), 64-77 (2014).</li><li>Blenkinsop, T. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+adult+retinal+pigment+epithelial+stem+cell-derived+RPE+monolayers+exhibit+key+physiological+characteristics+of+native+tissue.">Human adult retinal pigment epithelial stem cell-derived RPE monolayers exhibit key physiological characteristics of native tissue.</a> Invest Ophthalmol Vis Sci. 56 (12), 7085-7099 (2015).</li><li>Salero, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adult+human+RPE+can+be+activated+into+a+multipotent+stem+cell+that+produces+mesenchymal+derivatives.">Adult human RPE can be activated into a multipotent stem cell that produces mesenchymal derivatives.</a> Cell Stem Cell. 10 (1), 88-95 (2012).</li><li>Davis, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+RPE+Stem+Cell-Derived+RPE+Preserves+Photoreceptors+in+the+Royal+College+of+Surgeons+Rat:+Method+for+Quantifying+the+Area+of+Photoreceptor+Sparing.">Human RPE Stem Cell-Derived RPE Preserves Photoreceptors in the Royal College of Surgeons Rat: Method for Quantifying the Area of Photoreceptor Sparing.</a> Journal of Ocular Pharmacology and Therapeutics. 32 (5), 304-309 (2016).</li><li>Westenskow, P. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performing+Subretinal+Injections+in+Rodents+to+Deliver+Retinal+Pigment+Epithelium+Cells+in+Suspension.">Performing Subretinal Injections in Rodents to Deliver Retinal Pigment Epithelium Cells in Suspension.</a> J Vis Exp. (95), e52247 (2015).</li><li>Lopez, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transplanted+Retinal+Pigment+Epithelium+Modifies+the+Retinal+Degeneration+in+the+RCS+Rat.">Transplanted Retinal Pigment Epithelium Modifies the Retinal Degeneration in the RCS Rat.</a> Invest Ophthalmol Vis Sci. 30 (3), 586-588 (1989).</li><li>Eberle, D., Santos-Ferreira, T., Grahl, S., Ader, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subretinal+Transplantation+of+MACS+Purified+Photoreceptor+Precursor+Cells+into+the+Adult+Mouse+Retina.">Subretinal Transplantation of MACS Purified Photoreceptor Precursor Cells into the Adult Mouse Retina.</a> J Vis Exp. (84), e50932 (2014).</li><li>Nair, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Common+Anesthetics+on+Eye+Movement+and+Electroretinogram.">Effects of Common Anesthetics on Eye Movement and Electroretinogram.</a> Doc Ophthalmol. 122 (3), 163-176 (2011).</li><li>McGill, T. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transplantation+of+human+central+nervous+system+stem+cells+-+neuroprotection+in+retinal+degeneration.">Transplantation of human central nervous system stem cells - neuroprotection in retinal degeneration.</a> Eur J Neurosci. 35, 468-477 (2012).</li><li>Al-Hussaini, H., Kam, J. H., Vugler, A., Semo, M., Jeffery, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mature+retinal+pigment+epithelium+cells+are+retained+in+the+cell+cycle+and+proliferate+in+vivo.">Mature retinal pigment epithelium cells are retained in the cell cycle and proliferate in vivo.</a> Mol Vis. 14, 1784-1791 (2008).</li><li>Wang, S., Lu, B., Wood, P., Lund, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grafting+of+ARPE-19+and+Schwann+Cells+to+the+Subretinal+Space+in+RCS+Rats.">Grafting of ARPE-19 and Schwann Cells to the Subretinal Space in RCS Rats.</a> Invest Ophthalmol Vis Sci. 46 (7), 2552-2560 (2005).</li><li>Fabian, R. J., Bond, J. M., Drobeck, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induced+corneal+opacities+in+the+rat.">Induced corneal opacities in the rat.</a> Br J Ophthalmol. 51 (2), 124-129 (1967).</li></ol>

The subretinal injection technique depicted in this article is via the trans-scleral pathway, where the injector needle penetrates the outer layers (sclera-choroid-RPE complex) of the eye wall without harming the neural retina or disturbing the vitreous cavity. An alternative trans-vitreal approach has a potential risk of lens damage leading to cataract, since rodents&#39; lens occupies the majority of the vitreous cavity. Compared to this method, our technique is less risky and causes minimal trauma as the injector need...

The human retina located at the back of the eye functions as a light sensory tissue and plays a critical role in vision perception. Retinal cell dysfunction or cell death therefore causes vision problems or permanent blindness. Disorders involving degeneration or dysfunction of cells in different layers of the retina are known as degenerative retinal diseases, among which AMD is the most common type and the leading cause of irreversible blindness in the elderly in developed countries1,2. The pathological process of AMD is associated with &#34;drusen&#34; accumulation between the RPE layer and the underlying Bruch&#39;s membrane, which in turn impairs RPE support of photoreceptor physiology, leading to neural retinal atrophy and vision loss3,4,5. Thus far, there is no cure for advanced dry (non-neovascular) AMD. The emergence of stem cell therapy as a new paradigm in regenerative medicine brings the hope of replacing the dysfunctional or dead RPE cells with stem cell-derived healthy cells. Indeed, extensive preclinical studies of transplanting stem cells (e.g., human embryonic stem cell)-derived RPE cells into RPE-degenerative animal models have been performed6,7, some of which have progressed to clinical trials8,9 (NCT01344993, ClinicalTrials.gov). Recently, an alternative source of stem cells resident in the human RPE layer, the human RPE stem cells (hRPESCs), was identified by our lab and is currently being used in preclinical studies of hRPESC derived-RPE cell (hRPESC-RPE) transplantation therapy for AMD10,11,12,13.
The subretinal injection technique is applied in the preclinical studies mentioned above by multiple groups, including our group. There are two general approaches for subretinal injection in animals: trans-vitreal and trans-scleral. The trans-vitreal approach has the advantage of the surgeon being able to directly observe the needle end as it penetrates the anterior eye, crosses the entire vitreal cavity adjacent to the lens, and penetrates the retina at the back to the eye to reach the subretinal space14,15,16. However, it requires disrupting the retina in two locations (anterior and posterior), carries the risk of damaging the lens, and can result in backflow of cells into the vitreous when the needle is retracted. In contrast, the trans-sclera approach, in principle, avoids involvement of the retina and vitreous, and backflow exits the eye. In pigmented rodents, the surgeon can initially observe penetration of the sclera, but after passage into the pigmented choroid, the needle end is no longer visible. Without direct observation, breaching the retina is common and can result in retinal dissection and delivery of cells and/or blood into the vitreous. Moreover, because the eye surface is curved, it is very difficult to know which needle angles and depths are most effective for trans-scleral injections.
In this visualized article, we introduce a trans-scleral subretinal injection method informed by the use of post-surgical evaluations with Optical Coherence Tomography (OCT), which allows a detailed examination of the injection site. Our trans-scleral injection technique utilizes defined locations, angles, and depths for injection needles to produce very low surgical trauma and high reliability. Here, we specifically demonstrate the injection of hRPESC-RPE cells into the subretinal space of the RCS rat, a pre-clinical model of human AMD. With this injection method, we successfully and consistently delivered hRPESC-RPE cells into the subretinal space of RCS rat eyes with a very high success rate. Injection of cells was previously found to result in preservation of RCS photoreceptors at least 2 months after injection13. This procedure is performed under the dissecting microscope and is easy to learn. It requires two people (a surgeon and an assistant) to perform the injection and the average time of injection for each animal is less than 5 minutes. The defined angles and depths for injection needles make it possible for laboratories, where OCT is unavailable, to achieve successful subretinal injection. It allows for highly reproducible subretinal access and can be used not only for cell transplantation, but also for drug delivery and gene therapies.

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			<td style="width:231px;">This is used to make 2.5% Phenylepherine</td>
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			<td height="21" style="height:21px;width:259px;">100% Ethanol</td>
			<td style="width:256px;">Thermo Scientific</td>
			<td style="width:119px;">615090040</td>
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			<td height="21" style="height:21px;width:259px;">70% Ethanol</td>
			<td style="width:256px;">Ricca Chemical Company</td>
			<td style="width:119px;">2546.70-5</td>
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			<td height="24" style="height:24px;width:259px;">Sterile GenTeal Lubricant Eye Gel</td>
			<td style="width:256px;">Novartis</td>
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			<td height="42" style="height:42px;width:259px;">Sterile Systane Ultra Lubricant Eye Drops</td>
			<td style="width:256px;">Alcon</td>
			<td style="width:119px;">00065143105</td>
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		<tr height="44">
			<td height="44" style="height:44px;width:259px;">hRPESC-RPE cells</td>
			<td style="width:256px;">Not available commercially</td>
			<td style="width:119px;"></td>
			<td style="width:231px;">Please refer to &#34;Reference #12&#34; for cell isolation and mainteinance.</td>
		</tr>
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			<td height="21" style="height:21px;width:259px;">24-well plates</td>
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			<td height="21" style="height:21px;width:259px;">Conical tubes (15 ml)</td>
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			<td height="21" style="height:21px;width:259px;">Sterile alcohol wipe</td>
			<td style="width:256px;">McKesson</td>
			<td style="width:119px;">58-204</td>
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			<td height="21" style="height:21px;width:259px;">Sterile cotton tip applicators</td>
			<td style="width:256px;">McKesson</td>
			<td style="width:119px;">24-106-2S</td>
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			<td height="21" style="height:21px;width:259px;">Sterile Weck-Cel spears</td>
			<td style="width:256px;">Beaver-Visitec International&#160;</td>
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			<td height="21" style="height:21px;width:259px;">Sterile surgical drapes&#160;</td>
			<td style="width:256px;">McKesson</td>
			<td style="width:119px;">25-515</td>
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			<td height="21" style="height:21px;width:259px;">Gauze</td>
			<td style="width:256px;">McKesson</td>
			<td style="width:119px;">16-4242</td>
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			<td height="21" style="height:21px;width:259px;">Nanofil syringe (10 ul)</td>
			<td style="width:256px;">World Precision Instruments</td>
			<td style="width:119px;">Nanofil</td>
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			<td height="21" style="height:21px;width:259px;">Nanofil beveled 33-gauge needle</td>
			<td style="width:256px;">World Precision Instruments</td>
			<td style="width:119px;">NF33BV-2</td>
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			<td height="21" style="height:21px;width:259px;">Insulin syringe needles 31-gauge</td>
			<td style="width:256px;">Becton Dickinson</td>
			<td style="width:119px;">328418</td>
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			<td height="21" style="height:21px;width:259px;">Animal anesthesia system</td>
			<td style="width:256px;">World Precision Instruments</td>
			<td style="width:119px;">EZ-7000</td>
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			<td height="21" style="height:21px;width:259px;">Balance</td>
			<td style="width:256px;">Ohaus</td>
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			<td height="21" style="height:21px;width:259px;">Stereo microscope</td>
			<td style="width:256px;">Zeiss</td>
			<td style="width:119px;">Stemi 2000</td>
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development of a refined protocol for trans-scleral subretinal transplantation of human retinal pigment epithelial cells into rat eyes

Degenerative retinal diseases such as age-related macular degeneration (AMD) are the leading cause of irreversible vision loss worldwide. AMD is characterized by the degeneration of retinal pigment epithelial (RPE) cells, which are a monolayer of cells functionally supporting and anatomically wrapping around the neural retina. Current pharmacological treatments for the non-neovascular AMD (dry AMD) only slow down the disease progression but cannot restore vision, necessitating studies aimed at identifying novel therapeutic strategies. Replacing the degenerative RPE cells with healthy cells holds promise to treat dry AMD in the future. Extensive preclinical studies of stem cell replacement therapies for AMD involve the transplantation of stem cell-derived RPE cells into the subretinal space of animal models, in which the subretinal injection technique is applied. The approach most frequently used in these preclinical animal studies is through the trans-scleral route, which is made difficult by the lack of direct visualization of the needle end and can often result in retinal damage. An alternative approach through the vitreous allows for direct observation of the needle end position, but it carries a high risk of surgical traumas as more eye tissues are disturbed. We have developed a less risky and reproducible modified trans-scleral injection method that uses defined needle angles and depths to successfully and consistently deliver RPE cells into the rat subretinal space and avoid excessive retinal damage. Cells delivered in this manner have been previously demonstrated to be efficacious in the Royal College of Surgeons (RCS) rat for at least 2 months. This technique can be used not only for cell transplantation but also for delivery of small molecules or gene therapies.

Using the technique described in this article, we consistently delivered hRPESC-RPE cells into the subretinal space of RCS rats by precisely controlling the location, angle, and depth of the injector needle inserting into the tissue (Figure 1B-D). Immediately following transplantation, an OCT examination was performed to observe the injection site and the subretinal bleb created by the transplanted cells. Post-surgical OCT evaluation serves as a screening...

Watch this Scientific Journal Video about Development of a Refined Protocol for Trans-scleral Subretinal Transplantation of Human Retinal Pigment Epithelial Cells into Rat Eyes at JoVE.com

Development of a Refined Protocol for Trans-scleral Subretinal Transplantation of Human Retinal Pigment Epithelial Cells into Rat Eyes

Subretinal injection has been widely applied in preclinical studies of stem cell replacement therapy for age-related macular degeneration. In this visualized article, we describe a less risky, reproducible and precisely modified subretinal injection technique via the trans-scleral approach to deliver cells into rat eyes.

Degenerative retinal diseases such as age-related macular degeneration (AMD) are the leading cause of irreversible vision loss worldwide. AMD is ...

The overall goal of this video is to introduce a reproducible trans-scleral subretinal injection technique to deliver human retinal pigment epithelial, or RPE cells, into the subretinal space of rodent's eyes with minimal risk of retina damage. This is a accomplished by first making a small incision in the temporal conjunctiva posterior to the limbus to expose the underlying sclera. Then, a beveled 31-gauge insulin needle is used to penetrate the sclera core complex by inserting the needle 500 microns or approximately half of the tip into the tissue with the beveled side facing up to create a pilot hole.Next, a beveled 33-gauge injection needle attached to a syringe is guided into the pilot hole and inserted at a specific angle and depth, the injection hole self seals after the needle is retracted and no stitch or tissue glue is needed. Degenerative retinopathies consist of a wide spectrum of diseases involving different retinal cell types. Worldwide the most common disease, age-related macular degeneration, or AMD, occurs among the elderly and leads to permanent blindness.The pathological changes occurring in AMD involve an initial degeneration of retinal pigmented epithelial cells, or RPE. RPE loss leads to retinal fluororeceptor dysfunction or death. Current pharmacological treatments for early stage AMD are limited to slowing progression or relieving symptoms.This coupled with a limited regenerative potential of the retina means there is no effective treatment to restore vision. The Neural Stem Cell Institute recently identified a population of adult stem cells in the RPE cell population. These cells can be used as a source for stem cell replacement therapy.Currently our institute is running pre-clinical studies to investigate the efficacy and safety of RPE stem cell transplantation therapy in an RPE degenerative rat animal model. In this study, we utilize a trans-scleral, subretinal injection technique to deliver RPE stem cells into the rat eyes, between the retinal and RPE layers. Our method is an easy and reliable means to successful delivery of cells into the subretinal space.You will need the following reagents and equipment. 1%tropicamide and 2.5%phenylephrine, freshly made from 10%phenylephrine, by diluting it in sterile 0.9%saline on the day of surgery, are used to dilate the pupil. Eye wash is used to rinse the eye and keep the unoperated eye moist.An eye lubricant is used to keep the unoperated right eye moist during the surgery. 0.5%proparacaine is used as a local anesthetic. An eye lubricant is used on the operated left eye during the OCT scanning.A minimal amount of material and equipment is needed for this technique. Detailed information of equipment and reagents used in this technique is outlined in the protocol. A 10 microliter syringe is used to inject cells.Before injection, we first assemble the injector and sterilize it with ethanol. Insert a sterile, 33-gauge beveled needle into the syringe and screw tightly to assemble the injector. Flush the injector with 100%ethanol, then 70%ethanol, and then deionized distilled water, sequentially for five to six times each.Mark the injector needle with a sterile black marker pen at a position 600 microns away from the tip of the needle. Put the injector on a micro manipulator for injection use. Human RPE cells are prepared on the day of surgery and kept in ice water mixture.Gently triturate the cell suspension and load the injector with 1.2 microliters, the extra 0.2 microliters is used to compensate for injection backflow, to guarantee a volume of one microliter injection. Replace the injector filled with the cell suspension on the micromanipulator, or have an assistant hold it vertically, as RPE cells tend to sink easily in solutions. Prepare the sterile surgical area by placing a sterile surgery pad with a heating pad underneath on the stage of the dissecting microscope.All procedures involving animal subjects have been approved by the Institutional Animal Care and Use Committee at the State University of New York at Albany. Weight the animal and anesthetize it using the isoflurane vapor delivery system as shown here. Transfer the rat to the surgical area once it's anesthetized, and place it in a nose cone connected to the isoflurane system to maintain anesthesia.Cover the rat's body with gauze, and pinch the rat's toe to confirm full anesthesia. Apply a drop of eye lubricant on the rat's right eye position the rat onto its right side, with its left eye facing the ceiling for injection, its head towards the surgeon's right hand, and it's back towards the surgeon. Trim away any whiskers that cover the eye.Drip a small amount of eye wash for the temporal side of the left eye, and collect the excess at the nasal side with a cotton applicator to rinse the eye. Dilate the pupil with 1%tropicamide, 2.5%phenylephrine, for a post-injection optical coherence tomography, or OCT exam, by applying one drop of each. Apply a drop of eye wash to keep the eye moist.Apply a drop of Proparacain on the eye and remove the excess with a cotton applicator. Gently massage the skin surrounding the eye four to six times to open the eyelid, so that the eye temporarily and slightly pops out of its socket to allow for an easy access of the injector needle. Use forces to grip the conjunctiva posterior to the limbus, and rotate the eye around to find a better spot for surgery without damaging the ocular muscles.Gently lift the conjunctiva to make a tent, and rotate the eye nasally. Then use scissors to cut the top of the tent off, to make a small opening in the conjunctiva and expose the sclera. Next, use forceps to grip the edge of the conjunctiva opening next to the limbus, and rotate the eye nasally, so that the pupillary axis is at an angle of about 30 degrees relative to the ground.A sterile beveled 31-gauge insulin needle is used to penetrate the sclera core complex with a bevel pointing up and half of the tip, or about 500 microns inserting into the tissue, to create a pilot hole for injection. Carefully withdraw the insulin needle, and a small effusion of blood may be seen. An eye spear can be applied to clear the hole and stop bleeding if necessary.Guide the RPE cell loaded injector needle into the pilot hole at an angle of about 10 to 15 degrees relative to the local surface of the sclera to reach the subretinal space by inserting the needle with a length of 500 microns completely into the tissue and leaving a 100 micro distance between the point on the needle that is covered by the tissue and the point of the black marker on the needle. Tell the assistant to depress the plunger of the syringe, to inject the appropriate volume of cells. Hold the injector in place for 25 to 30 seconds after injection, then slowly retract the injector.The injection hole seals automatically, and a small amount of about 0.2 microliters of backflow is commonly observed. Rinse the injection site with sterile eyewash three times, and collect the excess with a cotton applicator. Apply a drop of lubricant on the operated eye, and transfer the rat to the OCT station, to examine the location of transplanted cells, and the size of the subretinal bleb.Return the rat to the recovery cage under a heat lamp to keep its body temperature once OCT is done. Observe the rat to ensure it comes out of anesthesia, and monitor daily for any signs of distress. Notify the veterinarian immediately if there are concerns.Using our technique, we consistently and successfully delivered human RPE cells into the subretinal space. Immediately following transplantation, we performed OCT examination to observe the injection site and the subretinal bleb created by the transplanted cells. This serves as a good screening tool for evaluating the quality of injections and the degree of retinal damage, or hemorrhage.Bright light reflection around the injection site and a subretinal bleb filled with the cell suspension could be seen under the OCT scanning. There is no bleeding, interocular fluid leakage, or retinal detachment, seen around the injection site or the intravitreal space in a successful injection, demonstrating the minimal trauma caused by injection. The operated rat eyes were nucleated, fixed, and sectioned for immunohistological analysis at seven days after transplantation.The human nuclear marker, Hunu, and the RPE cell marker, OTX2, were used to detect the transplanted cells. A positive stating of both markers showed that the transplanted human RPE cells were located in the subretinal space of the rat eyes. This trans-scleral subretinal injection technique is simple and easy to learn.It causes less surgery trauma and leaves the retina intact by passing the injection needle through the outer layers of the eye wall, without breaking the neural retina. The quantified drops for the pilot needle and injection needle to go in the tissue and the angle used during injection allow for delivery of cells reliably into the subretinal space with much higher accuracy and success rate. With this injection method, we consistently and successfully delivered human RPE stem cell derived RPE cells into the subretinal space of RCS rats.This procedure can be easily repeated by anyone who watches the video.

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