Publications by authors named "Mandeep S Singh"

Photoreceptor transplantation is a potential therapeutic strategy for degenerative retinal diseases. Studies on mechanisms contributing to retinal regeneration and vision repair identified cellular components transfer (CCT) as playing a role, in addition to somatic augmentation (referred to as "cell replacement" in this paper). In CCT, donor photoreceptors shuttle proteins, RNA, and mitochondria to host photoreceptors through intercellular connections.

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The transplantation of human organoid-derived retinal cells is being studied as a potentially viable strategy to treat vision loss due to retinal degeneration. Experiments in animal models have demonstrated the feasibility of organoid-derived photoreceptor transplantation in various recipient contexts. In some cases, vision repair has been shown.

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Aim: Retinal cell therapy modalities, in the category of advanced therapy medicinal products (ATMPs), are being developed to target several retinal diseases. Testing in large animal models (LAMs) is a crucial step in translating retinal ATMPs into clinical practice. However, challenges including budgetary and infrastructure constraints can hinder LAM research design and execution.

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  • - The study aimed to analyze how often and why patients with inherited retinal diseases (IRDs) undergo eye surgeries, using a retrospective cohort design at Johns Hopkins Genetic Eye Disease Center.
  • - Out of 736 subjects, about 31.3% had eye surgeries, with cataract extraction being the most prevalent procedure, especially common among those with retinitis pigmentosa (RP).
  • - The research found differences in the frequency and timing of surgeries based on the specific type of IRD, suggesting that these factors may influence surgical needs in affected patients.
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  • The study looked at how well artificial intelligence (AI) can find tiny spots (called flecks) in people with Stargardt disease, a condition that affects vision.
  • Researchers used special images from 170 eyes of 85 patients, training the AI to recognize these flecks and comparing its results to what humans found.
  • The AI was good at spotting more flecks and was sensitive in detection, but it also made more mistakes by identifying spots that weren't actually flecks; further improvements are needed to make it more accurate for future research.
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Transplantation of photoreceptor cells and retinal pigment epithelial (RPE) cells provide a potential therapy for retinal degeneration diseases. Subretinal transplantation of therapeutic donor cells into mouse recipients is challenging due to the limited surgical space allowed by the small volume of the mouse eye. We developed a trans-scleral surgical transplantation platform with direct transpupillary vision guidance to facilitate the subretinal delivery of exogenous cells in mouse recipients.

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Purpose: Proliferative vitreoretinopathy (PVR) is the most common cause of failure of surgically repaired rhegmatogenous retinal detachment (RRD). Chemically induced and cell injection PVR models do not fully simulate the clinical characteristics of PVR in the post-RRD context. There is an unmet need for translational models in which to study mechanisms and treatments specific to RRD-PVR.

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Objective: To cluster the diverse phenotypic features of Stargardt disease (STGD) using unsupervised clustering of multimodal retinal structure and function data.

Design: Retrospective cross-sectional study.

Subjects: Eyes of subjects with STGD and fundus autofluorescence (FAF), OCT, electroretinography (ERG), and microperimetry (MP) data available within 1 year of the baseline evaluation.

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Purpose: Proliferative vitreoretinopathy (PVR) is the most common cause of failure of retinal reattachment surgery, and the molecular changes leading to this aberrant wound healing process are currently unknown. Our ultimate goal is to study PVR pathogenesis by employing single-cell transcriptomics to dissect cellular heterogeneity.

Design: Here we aimed to compare single-cell RNA sequencing (scRNA-seq)  and single-nucleus RNA-sequencing (snRNA-seq) of retinal PVR samples in the rabbit model.

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Background: Cystoid macular lesions (CML) in inherited retinal diseases (IRDs) can contribute to vision impairment. Studying the morphologic range and outlier presentations of CML may inform clinical associations, mechanistic research, and trial design. Thus, we aim to describe the distribution of optical coherence tomography (OCT) parameters in IRD cases with CML and identify phenotype-genotype associations in very large cystoid macular lesions (VLCML).

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  • Human retinal organoid transplantation shows promise for treating degenerative retinal diseases, but how transplanted cells survive and develop is not well understood.
  • Researchers transplanted retinal organoid cells into mice lacking photoreceptors and found that transplanted human cells, identified as astrocytes and neural precursors, migrated throughout the recipient retina unlike those in cultured organoids.
  • The study indicates that the host retina environment enhances the maturation of photoreceptors and supports the survival of atypical migratory cell types, which could have important implications for future cell-based therapies for retinal diseases.
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Objective: Primary proliferative vitreoretinopathy (PVR) is established as an important cause of the failed repair of a fresh retinal detachment (RD) and the consequent need for secondary repair. However, the burden of multiple repairs beyond the initial failure has not been studied in detail. We aimed to determine the association between primary PVR and the occurrence of tertiary, quaternary, and quinary RD repairs, using a nationwide database.

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Precise and reliable cell-specific gene delivery remains technically challenging. Here we report a splicing-based approach for controlling gene expression whereby separate translational reading frames are coupled to the inclusion or exclusion of mutated, frameshifting cell-specific alternative exons. Candidate exons are identified by analyzing thousands of publicly available RNA sequencing datasets and filtering by cell specificity, conservation, and local intron length.

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Background: The efficiency of clinical trials for retinitis pigmentosa (RP) treatment is limited by the screening burden and lack of reliable surrogate markers for functional end points. Automated methods to determine visual acuity (VA) may help address these challenges. We aimed to determine if VA could be estimated using confocal scanning laser ophthalmoscopy (cSLO) imaging and deep learning (DL).

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Purpose: Cataract surgery is commonly performed to improve vision in patients with retinitis pigmentosa (RP). However, the risk of postoperative cystoid macular edema (CME) in RP remains unclear. Here, we leveraged a large multiyear claims database to estimate the risk of CME after cataract surgery in patients with and without RP.

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We assessed genotype-phenotype correlations among the visual, auditory, and olfactory phenotypes of 127 participants with Usher syndrome (USH2) (n =80) or nonsyndromic autosomal recessive retinitis pigmentosa (ARRP) (n = 47) due to USH2A variants, using clinical data and molecular diagnostics from the Rate of Progression in USH2A Related Retinal Degeneration (RUSH2A) study. USH2A truncating alleles were associated with USH2 and had a dose-dependent effect on hearing loss severity with no effect on visual loss severity within the USH2 subgroup. A group of missense alleles in an interfibronectin domain appeared to be hypomorphic in ARRP.

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  • This study investigates the patterns of preserved peripheral visual field (pVF) in patients with retinitis pigmentosa (RP), a condition that leads to vision loss, to better understand potential therapeutic targets.
  • Researchers created a computational tool to map the spatial distribution of retained pVF using data from 152 subjects, segmented by disease duration, and found that preservation is typically located in specific areas of the retina.
  • The study concludes that some retinal cells in the superonasal region may be more resilient to degeneration, suggesting that further research on these cells could help develop new treatments for RP.
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Late-stage retinal degenerative disease involving photoreceptor loss can be treated by optogenetic therapy, cell transplantation and retinal prostheses. These approaches aim to restore light sensitivity to the retina as well as visual perception by integrating neuronal responses for transmission to the cortex. In age-related macular degeneration, some cell-based therapies also aim to restore photoreceptor-supporting tissue to prevent complete photoreceptor loss.

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Purpose: Cell-based therapy development for geographic atrophy (GA) in age-related macular degeneration (AMD) is hampered by the paucity of models of localized photoreceptor and retinal pigment epithelium (RPE) degeneration. We aimed to characterize the structural and functional deficits in a laser-induced nonhuman primate model, including an analysis of the choroid.

Methods: Macular laser photocoagulation was applied in four macaques.

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Pluripotent stem cells (PSCs), which include human embryonic stem cells (hESCs) and induced pluripotent stem cell (iPSC), have been used to study development of disease processes, and as potential therapies in multiple organ systems. In recent years, there has been increasing interest in the use of PSC-based transplantation to treat disorders of the retina in which retinal cells have been functionally damaged or lost through degeneration. The retina, which consists of neuronal tissue, provides an excellent system to test the therapeutic utility of PSC-based transplantation due to its accessibility and the availability of high-resolution imaging technology to evaluate effects.

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  • The study aims to improve cone photoreceptor transplantation for macular diseases by creating a donor mouse model with a cone-rich retina featuring a cone-specific EGFP reporter.
  • The researchers developed OPN1LW-EGFP/NRL mice and characterized their retinas using imaging techniques; they also measured the retinal function through electroretinography (ERG).
  • Results indicated that the OPN1LW-EGFP/NRL retinas had improved cone photoreceptor expression, with greater survival rates in retinal sheet grafts compared to cell suspensions three months after transplantation.
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  • Researchers studied how problems with tiny blood vessels (choriocapillaris) in the eye might be linked to vision loss in people with a type of eye disease called retinitis pigmentosa (RP).
  • They looked at different eyes from people with severe RP, mild RP, and healthy controls using special imaging technology to see the blood vessel flow and measure the thickness of the outer part of the retina.
  • The results showed that those with severe RP had less blood flow in those tiny vessels and thinner retinas compared to healthy eyes, suggesting a relationship between blood flow issues and vision damage in RP.
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: Stargardt disease (SD) is the most common juvenile macular degeneration and a leading cause of uncorrectable childhood blindness. The progressive and incurable nature of this chronic condition entails a long-term financial burden on affected individuals. The economic costs of SD have not been characterized in detail, so we aimed to estimate the direct healthcare cost of SD.

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