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

Summary

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.

Abstract

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.

Introduction

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 countries^1,2. The pathological process of AMD is associated with "drusen" accumulation between the RPE layer and the underlying Br....

Protocol

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

1. 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.
   1. Isolate primary hRPE cells from human donor eyes aged 50-90 years and culture cells in 24-well plates¹². Cryopreserve the cells at passage 1, thaw as needed and culture passage 2 (P2) cells for 4-5 weeks (

Results

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.......

Discussion

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' 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.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.25% Trypsin-EDTA (1x)	Life Technologies	25200-072
DNAse I	Sigma	DN-25
1xDulbecco’s Phosphate Buffered Saline without Calcium & Magnesium (1xDPBS-CMF)	Corning Cellgro	431219
Sterile Balanced Salt Solution (BSS)	Alcon	00065079550
Sterile eye wash	Moore Medical	75519
Sterile 0.9% saline	Hospira	488810
Proparacaine Hydrochloride Ophthalmic Solution (0.5%)	Akorn	17478026312
Tropicamide Ophthalmic Solution, USP (1%)	Bausch & Lomb	24208058559
Phenylepherine Ophtalmic Solution, USP (10%) stock	Bausch & Lomb	42702010305	This is used to make 2.5% Phenylepherine
Buprenex	Patterson	433502
Dexamethasone	APP Pharmaceuticals	63323051610
100% Ethanol	Thermo Scientific	615090040
70% Ethanol	Ricca Chemical Company	2546.70-5
Sterile GenTeal Lubricant Eye Gel	Novartis	78042947
Sterile Systane Ultra Lubricant Eye Drops	Alcon	00065143105
hRPESC-RPE cells	Not available commercially		Please refer to "Reference #12" for cell isolation and mainteinance.
24-well plates	Corning	3526
Conical tubes (15 ml)	Sarstedt	62554002
Microcentrifuge cap with o-ring	LPS inc	L233126
Capless Microcentrifuge tubes (1.7 ml)	LPS inc	L233041
Centrifuge	Eppendorf	5804R
Sterile alcohol wipe	McKesson	58-204
Sterile cotton tip applicators	McKesson	24-106-2S
Sterile Weck-Cel spears	Beaver-Visitec International	0008680
Sterile surgical drapes	McKesson	25-515
Gauze	McKesson	16-4242
Nanofil syringe (10 ul)	World Precision Instruments	Nanofil
Nanofil beveled 33-gauge needle	World Precision Instruments	NF33BV-2
Insulin syringe needles 31-gauge	Becton Dickinson	328418
Rat toothed forceps	World Precision Instruments	555041FT
Vannas Micro Dissecting Spring Scissors	Roboz	RS-5602
Circulating water T pump	Stryker	TP700
Heating pad	Kent Scientific	TPZ-814
Animal anesthesia system	World Precision Instruments	EZ-7000
Balance	Ohaus	PA1502
Stereo microscope	Zeiss	Stemi 2000
Microscope light source	Schott	ACE series
Bioptigen Envisu Spectral Domain Ophthalmic Imaging System	Bioptigen	R2210
Sterile black marker pen	Viscot Industries	1416S-100
Miniature measuring scale	Ted Pella Inc	13623
Infrared Basking Spot Lamp	EXO-TERRA	PT2144	This is used as a heating lamp for animals during the post-surgical recovery  phase