oligonucleotides

2026-02-05 | Anticodon-edited transfer RNAs (ACE-tRNAs) encoded as therapeutic nonviral minimal DNA vectors.

Nonsense mutations, resulting from a premature termination codon (PTC), make up ∼11% of all genetic lesions causing disease, affecting millions of people worldwide. Nonsense suppressor anticodon-edited transfer RNAs (ACE-tRNAs) have emerged as a therapeutic modality for the rescue of PTCs. Delivery of ACE-tRNAs in vivo has been achieved by adeno-associated viral vector and RNA-lipid nanoparticle; however, due to drawbacks associated with these approaches, DNA delivery remains an attractive approach. DNA-based approaches afford ease of manufacturing at a relatively low cost and exhibit improved therapeutic durability and safety as compared to viral vector- or RNA-based approaches. Due to the small size of human tRNA genes employed as ACE-tRNAs, in principle, DNA vectors <200 base pairs (bp) in size (minivectors) could be utilized for delivery of actively transcribed ACE-tRNAs. Here, we demonstrate that linear DNA ACE-tRNA vectors as small as 200 bp effectively suppress several nonsense mutations in CFTR and REP1, and that ACE-tRNA minivectors, when tested in cell or ex vivo models, display significantly improved bioavailability, reduced innate immune burden, and superior biostability as compared to conventional plasmid DNA vectors.

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2023-07-13 | Lipid nanoparticle-mediated delivery of mRNA into the mouse and human retina and other ocular tissues

Structured Abstract Purpose Lipid nanoparticles (LNPs) show promise in their ability to introduce mRNA to drive protein expression in specific cell types of the mammalian eye. Here, we examined the ability of mRNA encapsulated in lipid nanoparticles (LNPs) with two distinct formulations to drive gene expression in mouse and human retina and other ocular tissues. Methods We introduced mRNA carrying LNPs into two biological systems. Intravitreal injections were tested to deliver LNPs into the mouse eye. Human retinal pigment epithelium (RPE) and retinal explants were used to assess mRNA expression in human tissue. We analyzed specificity of expression using histology, immunofluorescence, and imaging. Results In mice, mRNAs encoding GFP and ciliary neurotrophic factor (CNTF) were specifically expressed by Müller glia and retinal pigment epithelium (RPE). Acute inflammatory changes measured by microglia distribution (Iba-1) or interleukin-6 (IL-6) expression were not observed 6 hours post-injection. Human RPE also expressed high levels of GFP. Human retinal explants expressed GFP in cells with apical and basal processes consistent with Müller glia and in perivascular cells consistent with macrophages. Conclusions We demonstrated the ability to reliably transfect subpopulations of retinal cells in mice eye tissues in vivo and in human ocular tissues. Of significance, intravitreal injections were sufficient to transfect the RPE in mice. To our knowledge we demonstrate delivery of mRNA using LNPs in human ocular tissues for the first time. Translational Relevance Ocular gene-replacement therapies using non-viral vector methods are of interest as alternatives to adeno-associated virus (AAV) vectors. Our studies show that mRNA LNP delivery can be used to transfect retinal cells in both mouse and human tissues without inducing significant inflammation. This promising methodology could be used to transfect retinal cell lines, tissue explants, mice, or potentially as gene-replacement therapy in a clinical setting in the future.

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2023-03-27 | AAV2-Mediated Gene Therapy for Choroideremia: 5-Year Results and Alternate Anti-sense Oligonucleotide Therapy.

To assess the long-term safety and efficacy of AAV2-REP1 in choroideremia (CHM) patients, and to test a potential antisense oligonucleotide therapy for CHM. Extended, prospective phase 1/2 clinical trial and laboratory investigation. Five patients who received a single subfoveal injection of AAV2-REP1 were studied. The long-term safety was evaluated by ophthalmic examination, spectral domain optical coherence tomography, and fundus autofluorescence (FAF) for up to 5 years. Functional and structural changes were determined by different test modalities. Four antisense oligonucleotides (ASOs) were designed to treat the CHM c.1245-521A>G mutation, which was present in 2 patients within this trial. Subject P3 experienced a localized intraretinal immune response that resulted in a significant loss of preserved retinal pigment epithelium (RPE). P4 experienced an exacerbation of peripheral retinoschisis. P2 had a constant ≥15-letter best-corrected visual acuity (BCVA) gain in the treated eye, whereas P5 had ≥15-letter BCVA improvement once in the untreated eye. The preserved FAF areas declined more rapidly in the treated eyes compared to the untreated eyes (P = .043). A customized 25-mer ASO recovered 83.2% to 95.0% of the normal RNA and 57.5% of the normal protein in fibroblasts from 2 trial patients. Intraretinal inflammation triggered by AAV2-REP1 subretinal injection stabilized after 2 years but resulted in permanent damage to the retinal structure. Long-term progression of the disease was seen in both treated and untreated eyes, casting doubt as to the effectiveness of this approach in late-stage CHM. Alternative approaches such as ASO may have a therapeutic effect in a subgroup of CHM patients.

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2022-07-28 | A Novel Hypothesis on Choroideremia-Manifesting Female Carriers: Could CHM In-Frame Variants Exert a Dominant Negative Effect? A Case Report.

Choroideremia is an X-linked recessive condition presenting in males, with progressive degeneration of retinal and choroidal tissues leading to progressive visual loss. Its pathological mechanism is due to alterations in the CHM gene that encodes for REP1, a protein required for prenylation of Rab by the Rab geranylgeranyl transferase (RGGT). Even though female carriers are predicted to be not affected by the disease, a wide phenotypic spectrum ranging from mild to severe cases has been reported in women. The reason why Choroideremia manifests in female carriers remains elusive. While X chromosome inactivation (XCI) skewing has been proposed as a leading putative mechanism, emerging evidence has shown that CHM could variably escape from XCI. We described a family with an initial clinical suspicion of Retinitis Pigmentosa in which a novel CHM pathogenic splicing variant was found by exome sequencing. The variant, initially found in the 63-year-old female presenting with impaired visual acuity and severe retinal degeneration, segregated in the 31-year-old daughter and the 37-year-old son, both presenting with fundus anomalies. mRNA studies revealed a shorter in-frame CHM isoform lacking exon 10. Molecular modeling of the ternary REP1/Rab/RGGT protein complex predicted significant impairing of REP1/Rab binding without alteration of REP1/RGGT interaction. We suggest that, in our female cases, the biallelic expression of CHM may have led to the production of both the mutant and wild type REP1. The mutant isoform, sequestrating RGGT, could reduce its available amount for Rab prenylation, thus exerting a dominant-negative effect. If confirmed with further studies and in large cohorts of female carriers, the here proposed molecular mechanism could help to explain the complexity of manifestation of Choroideremia in females.

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2020-09-19 | A putative frameshift variant in the CHM gene is associated with an unexpected splicing alteration in a choroideremia patient.

Abstract Background Due to the limited availability of mRNA analysis data, the number of exonic variants resulting in splicing impairment is underestimated although aberrant splicing correction is a promising therapeutic option to treat monogenic diseases, including choroideremia (CHM), a rare X‐linked eye disorder arising from sequence alteration of the CHM gene. Herein we report an exonic frameshift variant associated with an mRNA splicing alteration that leads to a CHM hypomorphic allele. Methods Total RNA and genomic DNA were extracted from peripheral blood of a patient affected by a mild form of CHM. The CHM gene was analyzed by PCR‐based methods and Sanger sequencing. Results Besides the known c.1335dup frameshift variant, mRNA analysis revealed a splicing alteration that restored the reading frame of the mutant transcript, likely leading to an aberrant protein with residual activity. Bioinformatic analyses identified novel putative exonic splicing enhancer elements and provided clues that also pre‐mRNA secondary structure should be taken into account when exploring splicing mechanisms. Conclusion A careful molecular characterization of the c.1335dup variant's effect explains the relationship between genotype and phenotype severity in a CHM patient and provides new perspectives for the study of therapeutic strategies based on splicing correction in human diseases.

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gene therapies

2026-08-18 | Perivascular Astrocytic Gliosis Induced by Retinal Gene Therapy.

This retrospective follow-on study reviewed 25 consecutive patients with genetically confirmed choroideremia who were treated with subretinal AAV2-CAG-REP1 in dose-escalation gene therapy clinical trials conducted at Oxford University Hospitals NHS Foundation Trust and the University Eye Hospital Tübingen. Six patients in Oxford received 1010 vector genomes in 100 µL, while a further 19 patients across both centers received 1011 vector genomes in 100 µL. Although the primary safety outcomes of both investigator-led academic studies have previously been reported, retinal imaging changes were observed during follow-up, prompting a more detailed characterization of these findings. Twelve of 25 treated eyes developed imaging features consistent with perivascular astrocytic gliosis during follow-up, representing 48% of the cohort. All affected eyes had received the higher dose, accounting for 12 of 19 eyes treated with 1011 vector genomes. No patients receiving the lower dose (1.0 × 1010 vector genomes) developed this phenotype. The lesions followed the major vascular arcades toward the optic disc, and optical coherence tomography demonstrated inner retinal thickening with a fine, granular hyperreflective texture, without intraretinal cysts. Longitudinal imaging showed no progressive expansion of the involved regions. Clinically, the findings were silent: no patient reported uveitic symptoms, ocular examinations were largely quiet, and no peripheral cellular immune responses were detected in patients with available assays. Perivascular astrocytic gliosis therefore appears to be a common, clinically silent, nonprogressive, and noninflammatory retinal response after subretinal AAV2-CAG-REP1 gene therapy for choroideremia at a dose of 1011 vector genomes, which is generally accepted as the therapeutic human dose for targeting photoreceptors. We hypothesize that local REP1 overexpression in perivascular astrocytes suppresses FOXO3-mediated apoptosis and engages EGFR/STAT3 signaling, driving benign perivascular astrocytic accumulation analogous to retinal astrocytic hamartomas seen in phacomatoses. Gene therapy involving ubiquitous promoters may have unexpected effects, and while benign, may not be predicted.

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2026-07-23 | mRNA delivery to the retina restores REP1 function in choroideremia.

Inherited retinal diseases (IRDs) represent a major cause of blindness, yet current viral vector-based gene therapies are limited by high cost, restricted cargo capacity, and safety concerns related to immunogenicity. We explore here retinal delivery of non-viral, in-vitro-transcribed mRNA using lipid nanoparticles (LNPs) as a safe, cost-effective gene augmentation strategy for choroideremia (CHM). CHM is an X-linked IRD caused by loss-of-function mutations in CHM that encodes Rab escort protein-1 (REP1), which is essential for Rab GTPases prenylation and intracellular trafficking. We demonstrate that subretinal delivery of human CHM-mRNA (hCHM-mRNA) efficiently targets the retinal pigment epithelium (RPE) and choroid, achieving expression that is detectable up to 15 days post-injection, with lower and transient inflammatory response compared to AAV2 vectors. Furthermore, hCHM-mRNA delivery in vitro to human induced pluripotent stem cell (hiPSC)-derived RPE cells from a CHM patient and in vivo via subretinal injection in the Chm ± mouse model successfully restored REP1 levels and reversed Rab prenylation defect. Concordantly, Chm ± treated with hCHM-mRNA showed functional rescue of retinal activity measured by electroretinography 24 h post-injection. Overall, these results provide a strong proof-of-concept for LNP-mediated mRNA technology in the retina, supporting the development of scalable, non-viral gene approaches for IRDs, including CHM.

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2026-05-06 | Independent Degeneration of Photoreceptors and Retinal Pigment Epithelium: Multimodal Imaging Evidence From Choroideremia Carriers.

To characterize retinal structural alterations and elucidate underlying pathogenesis in female carriers of choroideremia (CHM) using multimodal imaging. This single-center retrospective study analyzed 100 eyes of 50 genetically confirmed female CHM carriers. Clinical evaluation comprised genotype, age, visual acuity, color fundus photography, fundus autofluorescence (FAF), infrared reflectance, and optical coherence tomography (OCT). Retinal lesions were identified and classified using point-to-point co-localization analysis across modalities. The mean age of carriers was 39.6 ± 17.8 years (range 3.2-80.3 years). All eyes exhibited varying degrees of retinal abnormalities. Most common findings included yellowish changes on color photographs, mottled areas of hyper- and hypo-autofluorescence on FAF, and isolated interdigitation zone (IZ) loss on OCT. Chorioretinal atrophy beyond the peripapillary region, indicating a severe phenotype, was observed in 18% of eyes. Five characteristic degenerative lesions were identified: Type A, isolated IZ loss; Type B, hyper-autofluorescent spots corresponding to presumed photoreceptor loss; Type C, drusen-like deposits; Type D, degeneration of the retinal pigment epithelium (RPE) and RPE-photoreceptor interface; and Type E, outer retinal degeneration. Type B lesions suggest that photoreceptor loss may precede RPE loss at specific loci. Type A lesions were the earliest abnormality, significantly associated with milder phenotypes, indicating the RPE-photoreceptor interface is the initial site of pathology. In contrast, Type D and E lesions were associated with severe phenotypes. Identified hyper-autofluorescence lesions corresponding to presumed photoreceptor loss indicate independent degeneration of photoreceptors and RPE. These findings suggest that future therapeutic approaches should concurrently target both cellular components.

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2025-12-14 | Nanocarrier-Mediated Gene Delivery for Treatment of Inherited Retinal Disorders

Adeno-associated virus (AAV) is now a clinically approved delivery vehicle for inherited retinal disorders, but its fixed packaging capacity, pre-existing population seroprevalence, and re-dosing limitations leave a meaningful gap for genes too large to package and for patients who cannot safely receive a second viral injection. This article synthesizes the literature on nanocarrier-mediated gene delivery to the retina as a complementary response to that gap, tracing the field from the AAV benchmark set by voretigene neparvovec and choroideremia gene therapy through the non-viral nanocarrier chemistries -- compacted DNA nanoparticles, glycol chitosan condensates, and PAMAM dendrimers -- that have been developed specifically for photoreceptor and retinal pigment epithelial delivery, the quantitative physical barriers the vitreous imposes on any intravitreally delivered particle, and the newer dual-AAV and AAV-delivered CRISPR-Cas9 architectures that address the same large-cargo and precision-editing problems from a different direction. Read together, the evidence supports compacted DNA nanoparticles as the most thoroughly characterized non-viral retinal platform to date, with faster onset than AAV, a favorable local safety profile, and biodistribution confined to the treated eye, while leaving transduction-efficiency parity with AAV, large-animal and human validation, and repeat-dosing safety data as an open preclinical agenda before any non-viral retinal nanocarrier can plausibly reach a first-in-human trial.

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2025-10-07 | One down but many more to go: the state of gene therapy for inherited retinal disease.

Gene therapy has ushered in a new era for the treatment of inherited retinal diseases (IRDs). The approval of voretigene neparvovec-rzyl (Luxturna) for RPE65-associated retinal dystrophy marked a pivotal milestone, establishing proof-of-concept that gene addition can restore visual function in IRDs. However, the success of Luxturna is tempered by the reality that it applies to a narrow subset of IRDs, and that no other IRD gene therapy has thus far received regulatory approval. This review outlines the current landscape of IRD gene therapy, including trials for several forms of IRD including achromatopsia, choroideremia, Leber congenital amaurosis, X-linked retinitis pigmentosa, and X-linked retinoschisis. We highlight the central challenges facing the field: narrow gene- or variant-specific indications, vector limitations, and reliance on suboptimal clinical trial endpoints. The review also discusses emerging strategies - including dual AAV and split-intein vectors, non-viral delivery platforms, and precision gene editing technologies such as CRISPR, base editing, and prime editing. These innovations promise to expand therapeutic reach. Finally, we emphasize the need for improved regulatory frameworks and ethical considerations for gene-based therapies for IRD. The field now stands at a critical juncture, where the lessons of Luxturna can inform a more scalable, inclusive, and transformative future.

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small molecules

2025-05-27 | Advancing Therapeutic Strategies for Nonsense-Related Diseases: From Small Molecules to Nucleic Acid-Based Innovations.

Nonsense mutations in gene coding regions introduce an in-frame premature termination codon (PTC) in the mRNA transcript, resulting in the early termination of translation and the production of a truncated, nonfunctional protein. The absence of protein expression and the consequent loss of essential cellular functions are responsible for the severe phenotypes in the so-called genetic nonsense-related diseases (NRDs), such as cystic fibrosis, hemophilia, Duchenne muscular dystrophy, Fabry disease, Choroideremia, Usher syndrome, Shwachman-Diamond syndrome, and even certain types of cancer. Nonsense mutations pose a significant challenge in the treatment of NRDs, as a specific approach directly addressing this genetic defect is currently unavailable. Developing new therapeutic strategies for nonsense suppression is a crucial goal of precision medicine. This review describes some of the most promising therapeutic approaches and emerging strategies for treating NRDs. It considered both the use of small molecules to interfere with molecular mechanisms related to nonsense mutations, such as translational readthrough-inducing drugs (TRIDs) or inhibitors of the nonsense-mediated decay (NMD) pathway, and also innovative approaches involving nucleic acids, such as gene editing, anticodon engineered-tRNA (ACE-tRNA), or mRNA-based therapy. Future research should focus on refining these approaches and exploring integrated and personalized treatments to enhance therapeutic outcomes and ensure continuous improvement in the quality of care.

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2025-05-06 | Lytic photoreceptor cell death caused by Rab escort protein deficiency in Drosophila.

Choroideremia (CHM) is a rare X-linked recessive form of inherited retinal degeneration caused by the deficiency of the Rab escort protein 1 (REP1)-encoding CHM gene. REP1 is essential for the post-translational prenylation of the key players in intracellular membrane trafficking, the Rab GTPases. In this study, we aimed to analyze the mechanisms of retinal degeneration caused by Rep deficiency using the Drosophila retina as a model system. Rab GTPases lost their membrane association ability and diffused into the cytoplasm, and the accumulation of unprenylated Rab6 and Rab7 was observed in Rep-deficient photoreceptors. Notably, Rep-deficient photoreceptors underwent progressive cell death via cell swelling and rupture rather than apoptosis. These findings provide new insight to seek a therapeutic approach to CHM. Impact statement Choroideremia is an inherited retinal degeneration caused by a deficiency of Rab escort protein 1 (Rep-1). We used the Drosophila retina as a model to study the mechanism of retinal degeneration in Rep-deficiency and found that Rep-deficient photoreceptors undergo progressive cell death via cell swelling and rupture rather than apoptosis.

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2023-08-30 | Oxidative and Endoplasmic Reticulum Stress Represent Novel Therapeutic Targets for Choroideremia

Choroideremia (CHM) is a rare X-linked chorioretinal dystrophy, affecting the photoreceptors, retinal pigment epithelium (RPE) and choroid, with no approved therapy. CHM is caused by mutations in the CHM gene, which encodes the ubiquitously expressed Rab escort protein 1 (REP1). REP1 is involved in prenylation, a post-translational modification of Rab proteins, and plays an essential role in intracellular trafficking. In this study, we examined oxidative and endoplasmic reticulum (ER) stress pathways in chmru848 zebrafish and CHMY42X patient fibroblasts, and screened a number of neuroprotectants for their ability to reduce stress. The expression of the oxidative stress markers txn, cat and sod3a, and the ER stress markers bip, atf4 and atf6, were dysregulated in chmru848 fish. The expression of SOD2 was also reduced in CHMY42X fibroblasts, along with reduced BIP and increased CHOP expression. The lack of REP1 is associated with defects in vesicular trafficking, photoreceptor outer segment phagocytosis and melanosome transport, leading to increased levels of stress within the retina and RPE. Drugs targeting oxidative and ER stress pathways represent novel therapeutic avenues.

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2022-02-14 | REP1 deficiency causes systemic dysfunction of lipid metabolism and oxidative stress in choroideremia.

Choroideremia (CHM) is an X-linked recessive chorioretinal dystrophy caused by mutations in CHM, encoding for Rab escort protein 1 (REP1). Loss of functional REP1 leads to the accumulation of unprenylated Rab proteins and defective intracellular protein trafficking, the putative cause for photoreceptor, retinal pigment epithelium (RPE), and choroidal degeneration. CHM is ubiquitously expressed, but adequate prenylation is considered to be achieved, outside the retina, through the isoform REP2. Recently, the possibility of systemic features in CHM has been debated; therefore, in this study, whole metabolomic analysis of plasma samples from 25 CHM patients versus age- and sex-matched controls was performed. Results showed plasma alterations in oxidative stress-related metabolites, coupled with alterations in tryptophan metabolism, leading to significantly raised serotonin levels. Lipid metabolism was disrupted with decreased branched fatty acids and acylcarnitines, suggestive of dysfunctional lipid oxidation, as well as imbalances of several sphingolipids and glycerophospholipids. Targeted lipidomics of the chmru848 zebrafish provided further evidence for dysfunction, with the use of fenofibrate over simvastatin circumventing the prenylation pathway to improve the lipid profile and increase survival. This study provides strong evidence for systemic manifestations of CHM and proposes potentially novel pathomechanisms and targets for therapeutic consideration.

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2020-07-14 | Immunomodulatory Effects of Hydroxychloroquine and Chloroquine in Viral Infections and Their Potential Application in Retinal Gene Therapy

Effective treatment of retinal diseases with adeno-associated virus (AAV)-mediated gene therapy is highly dependent on the proportion of successfully transduced cells. However, due to inflammatory reactions at high vector doses, adjunctive treatment may be necessary to enhance the therapeutic outcome. Hydroxychloroquine and chloroquine are anti-malarial drugs that have been successfully used in the treatment of autoimmune diseases. Evidence suggests that at high concentrations, hydroxychloroquine and chloroquine can impact viral infection and replication by increasing endosomal and lysosomal pH. This effect has led to investigations into the potential benefits of these drugs in the treatment of viral infections, including human immunodeficiency virus and severe acute respiratory syndrome coronavirus-2. However, at lower concentrations, hydroxychloroquine and chloroquine appear to exert immunomodulatory effects by inhibiting nucleic acid sensors, including toll-like receptor 9 and cyclic GMP-AMP synthase. This dose-dependent effect on their mechanism of action supports observations of increased viral infections associated with lower drug doses. In this review, we explore the immunomodulatory activity of hydroxychloroquine and chloroquine, their impact on viral infections, and their potential to improve the efficacy and safety of retinal gene therapy by reducing AAV-induced immune responses. The safety and practicalities of delivering hydroxychloroquine into the retina will also be discussed.

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cell therapies

2024-06-09 | Development of self-healing hydrogels to support choroidal endothelial cell transplantation for the treatment of early age related macular degeneration

Abstract In retinal diseases such as age-related macular degeneration (AMD) and choroideremia, a key pathophysiologic step is loss of endothelial cells of the choriocapillaris, the dense vascular bed required for maintaining health and function of the retina. As such, repopulation of choroidal vasculature early in the disease process may halt disease progression. Prior studies have shown that injection of donor cells in suspension results in significant cellular efflux and poor cell survival. As such, the goal of this study was to develop a hydrogel system designed to support CEC transplantation. A library of hydrogels was synthesized using laminin (i.e., LN111, LN121, and LN421), carboxy methyl chitosan, and oxidized dextran via reversible Schiff base chemistry. Each of the developed hydrogels was readily injectable into the suprachoroidal space, with excellent gelation, mechanical, and degradation properties. Laminin-based hydrogels were compatible with immortalized CEC survival in vitro, and suprachoroidal injection of LN111 and LN121 containing gels were well-tolerated in an in vivo rat model, whereas LN421 containing gels caused significant chorioretinal inflammation. Hydrogels were detected in the suprachoroidal space of immunosuppressed rats at 1-week post-injection and were completely resorbed by 1-month post-injection. There were significantly more CECs retained in immunosuppressed rats that received cell laden hydrogels than those that received unsupported cell suspensions (i.e., CECs only). These findings pave the way for future CEC replacement studies in animal models of choroidal cell loss toward the development of future therapies. Statement of significance Age related macular degeneration (AMD) is a leading cause of untreatable blindness in the industrial world. A key pathologic step in AMD is loss of the choriocapillaris endothelial cells, which provide vascular support to the overlying retina, including the light-sensing photoreceptors. We believe that choroidal cell replacement early in disease may prevent retinal cell death and subsequent vision loss. In this study, we present a strategy for repopulating the choriocapillaris using choroidal endothelial cell laden hydrogels. Specifically, we demonstrate the synthesis and characterization of 3 different laminin-based hydrogel systems. LN111 and LN121 hydrogels were found to increase retention of choroidal endothelial cells following suprachoroidal transplantation. These findings pave the way for future cell replacement studies in animal models of choroidal cell dropout.

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2023-11-21 | Cell-based Therapies for Corneal and Retinal Disorders.

Maintenance of the visual function is the desired outcome of ophthalmologic therapies. The shortcomings of the current treatment options, like partial recovery, post-operation failure, rigorous post-operative care, complications, etc., which are usually encountered with the conventional treatment options has warranted newer treatment options that may eliminate the root cause of diseases and minimize the side effects. Cell therapies, a class of regenerative medicines, have emerged as cutting-edge treatment option. The corneal and retinal dystrophies during the ocular disorders are the major cause of blindness, worldwide. Corneal disorders are mainly categorized mainly into corneal epithelial, stromal, and endothelial disorders. On the other hand, glaucoma, retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy, Stargardt Disease, choroideremia, Leber congenital amaurosis are then major retinal degenerative disorders. In this manuscript, we have presented a detailed overview of the development of cell-based therapies, using embryonic stem cells, bone marrow stem cells, mesenchymal stem cells, dental pulp stem cells, induced pluripotent stem cells, limbal stem cells, corneal epithelial, stromal and endothelial, embryonic stem cell-derived differentiated cells (like retinal pigment epithelium or RPE), neural progenitor cells, photoreceptor precursors, and bone marrow-derived hematopoietic stem/progenitor cells etc. The manuscript highlights their efficiency, drawbacks and the strategies that have been explored to regain visual function in the preclinical and clinical state associated with them which can be considered for their potential application in the development of treatment.

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2022-10-14 | Glial remodeling and choroidal vascular pathology in eyes from two donors with Choroideremia

Choroideremia (CHM) is a recessive, X-linked disease that affects 1 in 50,000 people worldwide. CHM causes night blindness in teenage years with vision loss progressing over the next two to three decades. While CHM is known to cause progressive loss of retinal pigment epithelial (RPE) cells, photoreceptors and choroidal vessels, little attention has been given to retinal glial changes in eyes with CHM. In addition, while choroidal loss has been observed clinically, no histopathologic assessment of choroidal loss has been done. We investigated glial remodeling and activation as well as choriocapillaris changes and their association with RPE loss in postmortem eyes from two donors with CHM. Eyes were fixed and cryopreserved or the retina and choroid/RPE were processed as flatmounts with a small piece cut for transmission electron microscopy. A dense glial membrane, made up of vimentin and GFAP double-positive cells, occupied the subretinal space in the area of RPE and photoreceptor loss of both eyes. The membranes did not extend into the far periphery, where RPE and photoreceptors were viable. A glial membrane was also found on the vitreoretinal surface. Transmission electron microscopy analysis demonstrated prominence and disorganization of glial cells, which contained exosome-like vesicles. UEA lectin demonstrated complete absence of choriocapillaris in areas with RPE loss while some large choroidal vessels remained viable. In the far periphery, where the RPE monolayer was intact, choriocapillaris appeared normal. The extensive glial remodeling present in eyes with CHM should be taken into account when therapies such as stem cell replacement are considered as it could impede cells entering the retina. This gliosis would also need to be reversed to some extent for Müller cells to perform their normal homeostatic functions in the retina. Future studies investigating donor eyes as well as clinical imaging from carriers or those with earlier stages of CHM will prove valuable in understanding the glial changes, which could affect disease progression if they occur early. This would also provide insights into the progression of disease in the photoreceptor/RPE/choriocapillaris complex, which is crucial for identifying new treatments and finding the windows for treatment.

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2019-12-11 | Retinal Prostheses and Artificial Vision.

In outer retinal degenerative diseases such as retinitis pigmentosa, choroideremia, and geographic atrophy, 30% of the ganglion cell layer in the macula remains intact. With subretinal and epiretinal prostheses, these inner retinal cells are stimulated with controlled electrical current by either a microphotodiode placed in the subretinal area or a microelectrode array tacked to the epiretinal region. As the patient learns to interpret the resulting phosphene patterns created in the brain through special rehabilitation exercises, their orientation, mobility, and quality of life increase. Implants that stimulate the lateral geniculate nucleus or visual cortex are currently being studied for diseases in which the ganglion cells and optic nerve are completely destroyed.

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2016-08-16 | Gene and Cell Therapy for Inherited Retinal Dystrophies

Abstract Gene therapy and cell therapy are intersecting fields of biomedical research with the common aim of repairing the direct causes or consequences of genetic diseases by using genes and cells, respectively. Gene therapy is broadly defined as a set of strategies that modify the expression of an individual's genes for therapeutic benefit. It requires the administration of a specific deoxyribonucleic acid (DNA) (or ribonucleic acid (RNA)) into the patient's cells. Cell therapy on the other hand requires administration of a population of intact live cells to a patient whose cells have been lost due to injury or disease. These emerging strategies can also be applied in acquired diseases in order to re‐establish equilibrium and halt disease progression. In some cases, gene and cell therapy may be combined in order to obtain a therapeutic effect. In addition to becoming emerging therapeutics in the clinic, these two fields of research continually generate tools, concepts and techniques for elucidating biological questions across multiple disciplines. Key Concepts The retina lines the back of the eye and comprises six different types of neuronal cells and their underlying retinal pigment epithelium (RPE). Photoreceptors are the light‐sensitive first‐order neurons of the retina which capture the light stimulus and transform it into an electric signal. Human iPSC have the same features of hESC in terms of their differentiation capacity. Gene therapy is the use of genetic material as a drug to treat a chronic condition.

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other

2026-03-31 | REP-1 deficiency induces aberrant mitochondrial metabolic rewiring from glycolysis to lipid oxidation in CHM disease.

Choroideremia (CHM) is a hereditary retinal degenerative disorder characterized by progressive dysfunction of the retinal pigment epithelium (RPE) and photoreceptors with no available therapy. Despite the recognized genetic basis of CHM, the metabolic pathways driving disease progression remain poorly defined. By investigating REP-1 deficiency in CHM disease, our study reveals a previously unrecognized role for REP-1 in regulating GLUT-1 and GLUT-4 membrane trafficking, controlling glucose uptake, and reprograming mitochondrial metabolism toward lipid oxidation. This chronic metabolic shift results in reduced glycolytic flux, elevated oxidative stress, and compromised ATP production, culminating in a progressive retinal dystrophy. Notably, pharmacological restoration of GLUT trafficking via leptin administration re-established glucose uptake and mitochondrial function, rescuing cellular energetics both in vitro and in vivo. These findings establish REP-1 as a key regulator of retinal metabolic homeostasis and suggest that targeting glucose-lipid metabolic rewiring may represent a novel therapeutic strategy for CHM and related retinal dystrophies.

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2025-05-07 | Genetic Analysis of Choroideremia-Related Rab Escort Proteins.

Choroideremia is a rare X-linked recessive retinal disorder characterized by progressive vision loss caused by retinal degeneration resulting from mutations in the CHM gene, which encodes Rab escort protein 1 (REP-1). In humans and mice, the Rab escort protein (REP) family consists of two members, REP-1 and REP-2, with REP-2 hypothesized to compensate for REP-1 deficiency in tissues outside the eye in choroideremia. In this study, we conducted a systematic mutational analysis of the mouse orthologs of REP-1 and REP-2. Blood analyses revealed metabolic abnormalities in the mutant mice deficient for REP-1, resembling the systemic metabolic disturbances observed in individuals with choroideremia, such as altered lipid and hemoglobin metabolism. We also observed an elevation in systemic inflammatory biomarkers in these mutant mice. Interestingly, these systemic abnormalities emerged before retinal degeneration became detectable in REP-1-deficient mice. Transcriptomic analysis of retinas isolated from REP-1 deficient mice revealed enrichment of proinflammatory signaling pathways. These results suggest important similarities between choroideremia and some forms of retinitis pigmentosa. While engineered loss of REP-2 alone caused no detectable phenotypic changes, dual deficiency in REP-1 and REP-2 resulted in lethality under both in vivo and in vitro conditions. Our findings offer novel insights into REPs and deepen our understanding of choroideremia, which may contribute to the development of new treatments for this genetic condition.

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2025-01-08 | Oxidative Stress, Inflammation and Altered Glucose Metabolism Contribute to the Retinal Phenotype in the Choroideremia Zebrafish.

Reactive oxygen species (ROS) within the retina play a key role in maintaining function and cell survival. However, excessive ROS can lead to oxidative stress, inducing dysregulation of metabolic and inflammatory pathways. The chmru848 zebrafish models choroideremia (CHM), an X-linked chorioretinal dystrophy, which predominantly affects the photoreceptors, retinal pigment epithelium (RPE), and choroid. In this study, we examined the transcriptomic signature of the chmru848 zebrafish retina to reveal the upregulation of cytokine pathways and glia migration, upregulation of oxidative, ER stress and apoptosis markers, and the dysregulation of glucose metabolism with the downregulation of glycolysis and the upregulation of the oxidative phase of the pentose phosphate pathway. Glucose uptake was impaired in the chmru848 retina using the 2-NBDG glucose uptake assay. Following the overexpression of human PFKM, partial rescue was seen with the preservation of photoreceptors and RPE and increased glucose uptake, but without modifying glycolysis and oxidative stress markers. Therapies targeting glucose metabolism in CHM may represent a potential remedial approach.

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2024-04-03 | Choroideremia presenting as vision loss secondary to choroidal neovascularization.

Choroidal neovascularization (CNV) is a rare complication of choroideremia that occurs secondary to relative atrophy of the retinal pigment epithelium and eventual rupture of Bruch's membrane. The ideal management of CNV in choroideremia is unclear. Case report. A 14-year-old male with no known ocular history presented to the eye emergency department complaining of a central scotoma in the right eye for 4 days. He had no past medical history and family history was unremarkable for known ocular disease. Visual acuity was 20/70 in the right eye and 20/30 in the left eye. Posterior segment exam revealed chorioretinal atrophy extending from the outer macula to the midperiphery in both eyes. There was CNV with associated subretinal hemorrhage in the right eye. Optical coherence tomography demonstrated the presence of CNV with subretinal fluid in the right eye and parafoveal outer retinal atrophy in both eyes. Genetic testing revealed a hemizygous exon 2 deletion on the CHM gene, pathogenic for choroideremia. The patient received a total of 3 injections 4 weeks apart followed by 1 injection 6 weeks later with resolution of the subretinal hemorrhage and reduction in CNV size with improvement in visual acuity to 20/20 at last follow-up exam. Choroidal neovascularization is a rare cause of central vision loss in patients with choroideremia. In this report, we demonstrate a good functional and anatomic response to intravitreal bevacizumab in a 14-year-old patient with undiagnosed choroideremia who presented with CNV-induced central vision loss.

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2021-05-14 | Choroidal neovascularisation in a predicted female choroideraemia carrier treated with intravitreal anti-vascular endothelial growth factor.

To report a case of choroidal neovascularisation and leakage in a myopic female predicted to be a choroideraemia carrier treated with intravitreal anti-vascular endothelial growth factor (anti-VEGF). Case report. A female magazine editor presented with sudden decrease in vision in her right eye, with Snellen visual acuities (VAs) of 1/60 and 3/60 in the right and left eyes respectively. She was diagnosed with choroidal neovascularisation (CNV) formation and subretinal haemorrhage in her right eye. This is on a background of previous presentations, the first of which was 20 years ago for declining left eye vision. She was subsequently found to be a predicted choroideraemia carrier. However, she also has high myopia, and it is unclear whether the predicted choroideraemia carrier status or high myopia is the main underlying cause of her CNV, although we believe that the former is more likely. The first episode of CNV in her right eye was treated successfully with intravitreal anti-VEGF. However, she experienced four further CNV reactivations in her right eye, all of which were treated successfully with anti-VEGF. At her last follow-up visit to date, Snellen VAs were 6/9 and 3/60 in her right and left eye respectively. This is a unique case of CNV formation in a predicted choroideraemia carrier who also has co-existent high myopia. Prompt treatment of CNV activity with anti-VEGF has been efficacious in prevention of subretinal fibrosis and irreversible vision loss and allowed the patient to continue working in her chosen career.

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