In-depth comparison of Anc80L65 and AAV9 retinal targeting and characterization of cross-reactivity to multiple AAV serotypes in humans

Anc80L65 is a synthetic, ancestral adeno-associated virus that has high tropism toward retinal photoreceptors after subretinal injection in mice and non-human primates. We characterized, for the first time, the post-intravitreal cell-specific transduction profile of Anc80L65 compared with AAV9. Here we use Anc80L65 and AAV9 to intravitreally deliver a copy of the gene encoding GFP into WT C57Bl/6J mice. GFP expression was driven by one of two clinically relevant promoters, chicken β actin (CB) or truncated MECP2 (P546). After qualitative assessment of relative GFP expression, we found Anc80L65 and AAV9 to have similar transduction profiles. Through the development of a novel method for quantifying GFP-positive retinal cells, we found Anc80L65 to have higher tropism in Müller glia and AAV9 to have higher tropism in horizontal cells. In addition, we found P546 to promote GFP expression at a more moderate level compared with the high levels seen under the CB promoter. Finally, for the first time, we characterized Anc80L65 cross-reactivity in human sera; 83% of patients with AAV2 pre-existing antibodies were found to be seropositive for Anc80L65. This study demonstrates the expanded therapeutic applications of Anc80L65 to treat retinal disease and provides the first insights to Anc80L65 pre-existing immunity in humans.

Integrated Low-Voltage Compliance and Wide-Dynamic Stimulator Design for Neural Implantable Devices

In this study, a pulse frequency modulation (PFM)-based stimulator is proposed for use in biomedical implantable devices. Conventionally, functional electrical stimulation (FES) techniques have been used to reinforce damaged nerves, such as retina tissue and brain tissue, by injecting a certain amount of charge into tissues. Although several design methods are present for implementing FES devices, an FES stimulator for retinal implants is difficult to realize because of the chip area, which needs to be inserted in a fovea, sized 5 mm x 5 mm, and power limitations to prevent the heat generation that causes tissue damage. In this work, we propose a novel stimulation structure to reduce the compliance voltage during stimulation, which can result in high-speed and low-voltage operation. A new stimulator that is composed of a modified high-speed PFM, a 4-bit counter, a serializer, a digital controller, and a current driver is designed and verified using a DB HiTek standard 0.18 μm process. This proposed stimulator can generate a charge up to 130 nC, consumes an average power of 375 µW during a stimulation period, and occupies a total area of 700 µm × 68 µm.

Long-term observations of macular thickness after subretinal implantation of a photovoltaic prosthesis in patients with atrophic age-related macular degeneration

Objective. Subretinal prostheses electrically stimulate the residual inner retinal neurons to partially restore vision. We investigated the changes in neurosensory macular structures and it is thickness associated with subretinal implantation in geographic atrophy (GA) secondary to age-related macular degeneration (AMD).Approach. Using optical coherence tomography, changes in distance between electrodes and retinal inner nuclear layer (INL) as well as alterations in thickness of retinal layers were measured over time above and near the subretinal chip implanted within the atrophic area. Retinal thickness (RT) was quantified across the implant surface and edges as well as outside the implant zone to compare with the natural macular changes following subretinal surgery, and the natural course of dry AMD.Main results. GA was defined based on complete retinal pigment epithelium and outer retinal atrophy (cRORA). Based on the analysis of three patients with subretinal implantation, we found that the distance between the implant and the target cells was stable over the long-term follow-up. Total RT above the implant decreased on average, by 39 ± 12µm during 3 months post-implantation, but no significant changes were observed after that, up to 36 months of the follow-up. RT also changed near the temporal entry point areas outside the implantation zone following the surgical trauma of retinal detachment. There was no change in the macula cRORA nasal to the implanted zone, where there was no surgical trauma or manipulation.Significance. The surgical delivery of the photovoltaic subretinal implant causes minor RT changes that settle after 3 months, and then remain stable over long-term with no adverse structural or functional effects. Distance between the implant and the INL remains stable up to 36 months of the follow-up.

Targeting Ocular Drug Delivery: An Examination of Local Anatomy and Current Approaches

Ocular drug delivery remains the focus of much modern research. Primary routes of administration include the surface, the intravitreal space, the subretinal space, and the subconjunctival space, each with its own series of unique challenges, limitations, and advantages. Each of these approaches requires careful consideration of the local anatomy, physical barriers, and key cells as well as the interface between the anatomy and the drug or drug system being delivered. While least invasive, the topical route poses a challenge with the many physical barriers that prevent drug penetration into the eye; while injection into the intravitreal, subretinal, and subconjunctival spaces are direct and targeted but limited due to the many internal clearance mechanisms and potential for damage to the eye. Polymeric-based, sustained-release drug delivery systems have been identified as a potential solution to many of these challenges; however, the design and successful implementation of a sustained-release system that is well-tolerated, bioactive, biocompatible, and degradable remains, in many cases, only in the early stages. The drugs and biomaterials in question also require special attention as small chemical changes could result in vastly different outcomes. This paper explores the anatomy and key cells of these four primary drug delivery routes as well as the interface between drug and drug delivery systems and the anatomy, reviewing the recent developments and current state of research in each area. Finally, this paper also examines the frequently used drugs and biomaterials found in ocular drug delivery and summarizes the primary interactions observed.

First Case of Subretinal Ocular Angiostrongyliasis Associated with Retinal Detachment in the United States

Angiostrongylus cantonensis, commonly known as the rat lungworm, is mostly found in Asia, the Pacific Basin, and the Caribbean, but is also endemic in Hawai'i, especially on the Island of Hawai'i. Ocular angiostrongyliasis is an uncommon but previously reported complication associated with permanent vision loss. This is the first reported case of ocular angiostrongyliasis involving the retina or posterior segment of the eye in the US. A 24-year-old male from Chicago visited the Island of Hawai'i, where he worked on a farm and ate a vegetarian diet. When he returned to Chicago, he became sick and was hospitalized for eosinophilic meningitis. One month later, he developed a retinal detachment which required surgical repair involving a pars plana vitrectomy. During the reattachment of the retina during surgery, a live motile was identified nematode in the subretinal space. An endolaser probe immobilized and killed the nematode, and it was subsequently extracted through the sclerotomy. Thermal scars around all retinal holes including the retinotomy site were made to stabilize the retina, and perfluoropropane gas was injected to achieve temporary tamponade. Thereafter, the patient's cerebrospinal fluid returned positive for angiostrongylus cantonensis antibodies. During extended follow-up, the patient eventually lost all vision in the affected eye due to recurrent retinal detachment. This case of ocular angiostrongyliasis demonstrates the importance of obtaining travel history from endemic areas, knowing the risk of developing eosinophilic meningitis, and understanding the risk of permanent vision loss in cases involving the retina.

Transplantation Efficacy of Human Ciliary Epithelium Cells from Fetal Eye and Lin-ve Stem Cells from Umbilical Cord Blood in the Murine Retinal Degeneration Model of Laser Injury

A number of degenerative conditions affecting the neural retina including age-related macular degeneration have no successful treatment, resulting in partial or complete vision loss. There are a number of stem cell replacement strategies for recovery of retinal damage using cells from variable sources. However, literature is still deficit in the comparison of efficacy of types of stem cells. The purpose of the study was to compare the therapeutic efficacy of undifferentiated cells, i.e., lineage negative stem cells (Lin-ve SC) with differentiated neurosphere derived from ciliary epithelium (CE) cells on retinal markers associated with laser-induced retinal injury. Laser-induced photocoagulation was carried out to disrupt Bruch’s membrane and retinal pigmented epithelium in C57BL/6 mouse model. Lineage negative cells were isolated from human umbilical cord blood, whereas neurospheres were derived from CE of post-aborted human eyeballs. The cells were then transplanted into subretinal space to study their effect on injury. Markers of neurotropic factors, retina, apoptosis, and proliferation were analyzed after injury and transplantation. mRNA expression was also analyzed by real-time polymerase chain reaction at 1 week, and 3-month immunohistochemistry was evaluated at 1-week time point. CE cell transplantation showed enhanced differentiation of rods and retinal glial cells. However, Lin-ve cells exerted paracrine-dependent modulation of neurotrophic factors, which is possibly mediated by antiapoptotic and proliferative effects. In conclusion, CE transplantation showed superior regenerative outcome in comparison to Lin-ve SC for rescue of artificially injured rodent retinal cells. It is imperative that this source for transplantation may be extensively studied in various doses and additional retinal degeneration models for prospective clinical applications.

An unusual cause of visual loss: Subfoveal, motile angiostrongyliasis

This is a short report describing the clinical presentation, investigations, treatment and outcome of a patient living in the Jamaican countryside who was diagnosed with a live, motile subfoveal helminth identified as Angiostrongylus cantonensis on optical coherence tomography at the University Hospital of the West Indies Eye Clinic. This is the second documented case in Jamaica. Early recognition of angiostrongyliasis is important as it may manifest as eosinophilic meningitis which can be fatal without prompt treatment.

Age-related macular degeneration masqueraders: From the obvious to the obscure

Age-related macular degeneration (AMD) is one of the leading causes of blindness worldwide with increasing prevalence owing to increased life expectancy. Intravitreal injections of antivascular endothelial growth factor agents are commonly used in exudative AMD and oral antioxidant medication for nonexudative AMD; however, many disorders mimic exudative and nonexudative AMD, and misdiagnosis can seriously affect the management of these patients. We summarize the demographics and clinical and imaging characteristics of each of the conditions that masquerade as AMD. As some of the conditions have features of AMD, a short update on the classical features of AMD is also included.

Human Fetal Pigmented Ciliary Epithelium Stem Cells have Regenerative Capacity in the Murine Retinal Degeneration Model of Laser Injury

BACKGROUND

Retinal degeneration and related eye disorders have limited treatment interventions. Since stem cell therapy has shown promising results, ciliary epithelium (CE) derived stem cells could be a better choice given the fact that cells from eye niche can better integrate with the degenerating retina, rewiring the synaptic damage.

OBJECTIVE

To test the effect of human fetal pigmented ciliary epithelium-derived neurospheres in the mouse model of laser-induced retinal degeneration.

METHODS

C57 male mice were subjected to retinal injury by Laser photocoagulation. Human fetal pigmented ciliary epithelium was obtained from post-aborted human eyeballs and cultured with epidermal growth factor (rhEGF) and fibroblast growth factor (rhFGF). The six day neurospheres were isolated, dissociated and transplanted into the subretinal space of the laser injured mice at the closest proximity to Laser shots. Mice were analyzed for functional vision through electroretinogram (ERG) and sacrificed at 1 week and 12 week time points. Retinal, Neurotropic, Apoptotic and proliferation markers were analysed using real-time polymerase chain reaction (PCR).

RESULTS

The CE neurospheres showed an increase in the expression of candidate genes analyzed in the study at 1 week time point, which sustained for longer time point of 12 weeks.

CONCLUSION

We showed the efficacy of human CE cells in the regeneration of retinal degeneration in murine model for the first time. CE cells need to be explored comprehensively both in disease and degeneration.

A rare case of giant subretinal migration of cysticercosis cyst with extensive epiretinal membrane and subretinal fibrosis

Cysticercosis is caused by cysticercus cellulosae, the larval form of pork tapeworm. In intraocular cysticercosis the cyst enters the subretinal space via the choroid and then gains entry into the vitreous cavity by piercing the retina. It is well established that the cyst can incite extensive intraocular inflammation. Other complications such as epiretinal membrane and cataract have been reported in the literature. Thus far, epiretinal membrane in intraocular cysticercosis has been reported at the site of entry of the cyst into the vitreous cavity. The data on the extent of epiretinal membrane is sparse. We report a rare case of migrating subretinal cysticercosis with extensive epiretinal membrane and subretinal fibrosis.

Development of a protocol for maintaining viability while shipping organoid-derived retinal tissue

Retinal organoid technology enables generation of an inexhaustible supply of three-dimensional retinal tissue from human pluripotent stem cells (hPSCs) for regenerative medicine applications. The high similarity of organoid-derived retinal tissue and transplantable human fetal retina provides an opportunity for evaluating and modeling retinal tissue replacement strategies in relevant animal models in the effort to develop a functional retinal patch to restore vision in patients with profound blindness caused by retinal degeneration. Because of the complexity of this very promising approach requiring specialized stem cell and grafting techniques, the tasks of retinal tissue derivation and transplantation are frequently split between geographically distant teams. Delivery of delicate and perishable neural tissue such as retina to the surgical sites requires a reliable shipping protocol and also controlled temperature conditions with damage-reporting mechanisms in place to prevent transplantation of tissue damaged in transit into expensive animal models. We have developed a robust overnight tissue shipping protocol providing reliable temperature control, live monitoring of the shipment conditions and physical location of the package, and damage reporting at the time of delivery. This allows for shipping of viable (transplantation-competent) hPSC-derived retinal tissue over large distances, thus enabling stem cell and surgical teams from different parts of the country to work together and maximize successful engraftment of organoid-derived retinal tissue. Although this protocol was developed for preclinical in vivo studies in animal models, it is potentially translatable for clinical transplantation in the future and will contribute to developing clinical protocols for restoring vision in patients with retinal degeneration.

Optic nerve head retinal artery macroaneurysm: Report of a case

A 61-year-old elderly male, hypertensive patient presented to the retina clinic with sudden drop in vision in the left eye for 6 days. His best-corrected visual acuity at presentation was counting fingers close to face. Fundus examination of the left eye revealed the presence of subretinal and preretinal haemorrhage at the macula along with hypertensive retinopathy changes in both eyes. Fluorescein angiography was done, which showed a retinal artery macroaneurysm at the optic nerve head. Optical coherence tomogram through the optic nerve head also confirmed the presence of retinal artery macroaneurysm. The patient was treated with injection of 0.4 cc of 100% C3F8 to displace the blood off the macula. At final follow-up visit at 2 months post treatment, his vision improved to 6/12, N8. Fundus examination showed a small residual altered blood nasal to the fovea. No treatment was however done to the retinal artery macroaneurysm due to its atypical location and chance of spontaneous involution. In conclusion, retinal artery macroaneurysm at the optic disc is extremely uncommon. Identification of the retinal artery macroaneurysm lesion is more difficult in glaucoma patients due to the large and deep optic cup. Fluorescein angiography remains the main investigative modality to confirm the diagnosis. Spontaneous involution still remains the mainstay of treatment in optic disc retinal artery macroaneurysm.

Protuberant Electrode Structures for Subretinal Electrical Stimulation: Modeling, Fabrication and in vivo Evaluation

Many neural interfaces used for therapeutic applications are based on extracellular electrical stimulation to control cell polarization and thus functional activity. Amongst them, retinal implants have been designed to restore visual perception in blind patients affected by photoreceptor degeneration diseases, such as age-related macular degeneration (AMD) or retinitis pigmentosa (RP). While designing such a neural interface, several aspects must be taken into account, like the stimulation efficiency related to the current distribution within the tissue, the bio-interface optimization to improve resolution and tissue integration, and the material biocompatibility associated with long-term aging. In this study, we investigate the use of original microelectrode geometries for subretinal stimulation. The proposed structures combine the use of 3D wells with protuberant mushroom shaped electrode structures in the bottom, implemented on a flexible substrate that allows the in vivo implantation of the devices. These 3D microelectrode structures were first modeled using finite element analysis. Then, a specific microfabrication process compatible with flexible implants was developed to create the 3D microelectrode structures. These structures were tested in vivo to check the adaptation of the retinal tissue to them. Finally, preliminary in vivo stimulation experiments were performed.

Human Vascular Endothelial Growth Factor A165 Expression Induces the Mouse Model of Neovascular Age-Related Macular Degeneration

Vascular endothelial growth factor (VEGF) expression induces age-related macular degeneration (AMD), which is a common vision-threatening disease due to choroidal neovascularization and a fibrovascular membrane. We describe a mouse model of neovascular AMD with the local expression of human VEGF-A₁₆₅ in the eye. We use a transgenic mouse in which human VEGF-A₁₆₅ has been silenced with the loxP-STOP fragment. The choroidal neovascularization and human VEGF-A₁₆₅ expression in the mouse are induced by subretinal adenoviral Cre gene delivery. Cre gene transfer is compared with adenoviral LacZ gene transfer control. We characterize the AMD phenotype and changes in the vasculature by using fluorescein angiography, optical coherence tomography, and immunohistochemistry. At early time points, mice exhibit increases in retinal thickness (348 ± 114 µm vs. 231 ± 32 µm) and choroidal neovascularization area (12000 ± 15174 µm² vs. 2169 ± 3495 µm²) compared with the control. At later time points, choroidal neovascularization develops into subretinal fibrovascular membrane. Human VEGF-A₁₆₅ expression lasts several weeks. In conclusion, the retinas display vascular abnormalities consistent with choroidal neovascularization. Together with immunohistochemical findings, these changes resemble clinical AMD-like ocular pathologies. We conclude that this mouse model of Cre-induced choroidal neovascularization is useful for mimicking the pathogenesis of AMD, studying the effects of human VEGF-A₁₆₅ in the retina, and evaluating anti-VEGF treatments for choroidal neovascularization.

Nonclinical Safety Evaluation of scAAV8-RLBP1 for Treatment of RLBP1 Retinitis Pigmentosa

Retinitis pigmentosa is a form of retinal degeneration usually caused by genetic mutations affecting key functional proteins. We have previously demonstrated efficacy in a mouse model of RLBP1 deficiency with a self-complementary AAV8 vector carrying the gene for human RLBP1 under control of a short RLBP1 promoter (CPK850).¹ In this article, we describe the nonclinical safety profile of this construct as well as updated efficacy data in the intended clinical formulation. In Rlbp1^−/− mice dosed at a range of CPK850 levels, a minimum efficacious dose of 3 × 10⁷ vg in a volume of 1 μL was observed. For safety assessment in these and Rlbp1^+/+ mice, optical coherence tomography (OCT) and histopathological analysis indicated retinal thinning that appeared to be dose-dependent for both Rlbp1 genotypes, with no qualitative difference noted between Rlbp1^+/+ and Rlbp1^−/− mice. In a non-human primate study, RLBP1 mRNA expression was detected and dose dependent intraocular inflammation and retinal thinning were observed. Inflammation resolved slowly over time and did not appear to be exacerbated in the presence of anti-AAV8 antibodies. Biodistribution was evaluated in rats and satellite animals in the non-human primate study. The vector was largely detected in ocular tissues and low levels in the optic nerve, superior colliculus, and lateral geniculate nucleus, with limited distribution outside of these tissues. These data suggest that an initial subretinal dose of ∼3 × 10⁷ vg/μL CPK850 can safely be used in clinical trials.

Subretinal delivery of erythropoietin alleviates the N-methyl-N-nitrosourea-induced photoreceptor degeneration and visual functional impairments: an in vivo and ex vivo study

Retinitis pigmentosa (RP) is a heterogeneous group hereditary retinal disease that is characterized by photoreceptor degeneration. The present study sought to explore the therapeutic effects of erythropoietin (EPO) on the N-methyl-N-nitrosourea (MNU)-induced photoreceptor degeneration. The MNU-administered mouse or normal control received a subretinal injection of EPO (at the dose of 10U). Twenty-four hours after EPO injection, the retinal EPO levels of experimental animals were quantified. Subsequently, the experimental animals were subjected to optokinetic tests, ERG examination, SD-OCT examination, histology assessment, and immunohistochemistry evaluation. The retinal superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and expression levels of several apoptotic factors were also quantified. The subretinal injection of EPO up-regulated the retinal EPO level in the retinas of MNU-administered mice. The optokinetic tests and ERG examination suggested the visual functional impairments in MNU-administered mice were ameliorated after EPO treatment. The SD-OCT and histological examination suggested the morphological devastations in MNU-administered mice were alleviated after EPO treatment. The cone photoreceptors in MNU-administered mice were protected from the MNU-induced detrimental effects. Moreover, the EPO treatment rectified the apoptotic abnormalities in MNU-administered mice, and enhanced the expression level of Foxo3, a critical mediator of autophagy. The EPO treatment also mitigated the MDA concentration and enhanced the retinal SOD activity, thereby counteracting the retinal oxidative stress in MNU administered mice. In ophthalmological practice, the subretinal delivery of EPO is a feasible therapeutic strategy to alleviate photoreceptor degeneration. These findings would enrich our pharmacological knowledge about EPO and shed light on the development of an effective therapy against RP.

Intravitreal, Subretinal, and Suprachoroidal Injections: Evolution of Microneedles for Drug Delivery

Even though the very thought of an injection into the eye may be frightening, an estimated 6 million intravitreal (IVT) injections were made in the USA during 2016. With the introduction of new therapeutic agents, this number is expected to increase. In addition, drug products that are injectable in ocular compartments other than the vitreous humor are expected to enter the back of the eye market in the not so distant future. Besides the IVT route, some of the most actively investigated routes of invasive administration to the eye include periocular, subretinal, and suprachoroidal (SC) routes. While clinical efficacy is the driving force behind new injectable drug product development for the eye, safety is also being improved with time. In the case of IVT injections, the procedural guidelines have evolved over the years to improve patient comfort and reduce injection-related injury and infection. Similar advances are anticipated for other routes of administration of injectable products to the eye. In addition to procedural improvements, the design of needles, particularly those with smaller diameters, length, and controlled bevel angles are expected to improve overall safety and acceptance of injected ophthalmic drug products. A key development in this area is the introduction of microneedles of a length less than a millimeter that can target the SC space. In the future, needles with smaller diameters and lengths, potentially approaching nanodimensions, are expected to revolutionize ophthalmic disease management.

Stem cells in clinical trials for treatment of retinal degeneration

INTRODUCTION

After decades of basic science research involving the testing of regenerative strategies in animal models of retinal degenerative diseases, a number of clinical trials are now underway, with additional trials set to begin shortly. These efforts will evaluate the safety and preliminary efficacy of cell-based products in the eyes of patients with a number of retinal conditions, notably including age-related macular degeneration, retinitis pigmentosa and Stargardt's disease.

AREAS COVERED

This review considers the scientific work and early trials with fetal cells and tissues that set the stage for the current clinical investigatory work, as well the trials themselves, specifically those either now completed, underway or close to initiation. The cells of interest include retinal pigment epithelial cells derived from embryonic stem or induced pluripotent stem cells, undifferentiated neural or retinal progenitors or cells from the vascular/bone marrow compartment or umbilical cord tissue.

EXPERT OPINION

Degenerative diseases of the retina represent a popular target for emerging cell-based therapeutics and initial data from early stage clinical trials suggest that short-term safety objectives can be met in at least some cases. The question of efficacy will require additional time and testing to be adequately resolved.

Spontaneous resolution of subfoveal perfluorocarbon

Perfluorocarbon liquids (PFCL) have transformed the surgical approach to complex retinal detachments, but their use can be complicated by subretinal retention. Migration of peripherally located subretinal PFCL towards the fovea is well established, but spontaneous resolution of subfoveal PFCL without surgical evacuation or displacement has rarely been described. We present a case of a large single retained subfoveal PFCL droplet following vitrectomy with membrane peeling, inferior relaxing retinectomy, and silicone oil tamponade that demonstrated spontaneous resolution 3 weeks postoperatively, with subsequent anatomic and visual improvement. No residual subretinal PFCL was noted, and we hypothesize that the PFCL droplet spontaneously extruded through a transient hole created in the thinned retina overlying the droplet, which subsequently closed spontaneously. Further understanding of the mechanisms of PFCL migration and resolution may facilitate improved treatments for this complication.