Stem Cell Treatment in Retinal Diseases: Recent Developments

Evaluating the impact of mesenchymal stem cell therapy on visual acuity and retinal nerve fiber layer thickness in optic neuropathy patients: a comprehensive systematic review and meta-analysis

BACKGROUND

Stem cell therapy has emerged as a potential therapeutic avenue for optic neuropathy patients. To assess its safety and efficacy, we conducted a systematic review and meta-analysis, focusing on the latest evidence pertaining to the improvement of visual acuity (VA) through stem cell therapy.

METHODS

We analyzed Each database from its inception until June 2024. PubMed, Scopus, and Google Scholar were systematically searched to identify the included studies. Data were extracted regarding the year of publication, the name of the first author, sample size, VA (Log Mar), and Retinal Nerve Fiber Layer (RNFL) thickness. PRISMA protocol was used as a guide to perform this meta-analysis. STATA 16 was used for statistical analysis.

RESULTS

A total of 66 eyes were examined in seven papers. Based on the meta-analysis, the mean VA (Log MAR) of patients with optic neuropathy improved from 0.90 to 0.65 following stem cell therapy intervention (p-value = 0.001). The thickness of the RNFLs did not demonstrate a significant change (p-value was 0.174).

CONCLUSION

According to this systematic review and meta-analysis, stem cell therapy may improve the visual acuity of patients with optic neuropathy. Aside from the traditional therapy that can be provided to patients with optic neuropathy, stem cell therapy may also be beneficial.

Peptoid-Cross-Linked Hydrogel Stiffness Modulates Human Mesenchymal Stromal Cell Immunoregulatory Potential in the Presence of Interferon-Gamma

Human mesenchymal stromal cell (hMSC) manufacturing requires the production of large numbers of therapeutically potent cells. Licensing with soluble cytokines improves hMSC therapeutic potency by enhancing secretion of immunoactive factors but typically decreases proliferative ability. Soft hydrogels, however, have shown promise for boosting immunomodulatory potential, which may compensate for decreased proliferation. Here, hydrogels are cross-linked with peptoids of different secondary structures to generate substrates of various bulk stiffnesses but fixed network connectivity. Secretions of interleukin 6, monocyte chemoattractive protein-1, macrophage colony-stimulating factor, and vascular endothelial growth factor are shown to depend on hydrogel stiffness in the presence of interferon gamma (IFN-γ) supplementation, with soft substrates further improving secretion. The immunological function of these secreted cytokines is then investigated via coculture of hMSCs seeded on hydrogels with primary peripheral blood mononuclear cells (PBMCs) in the presence and absence of IFN-γ. Cocultures with hMSCs seeded on softer hydrogels show decreased PBMC proliferation with IFN-γ. To probe possible signaling pathways, immunofluorescent studies probe the nuclear factor kappa B pathway and demonstrate that IFN-γ supplementation and softer hydrogel mechanics lead to higher activation of this pathway. Overall, these studies may allow for production of more efficacious therapeutic hMSCs in the presence of IFN-γ.

Multimodal Imaging-Guided Stem Cell Ocular Treatment

Stem cell therapies are gaining traction as promising treatments for a variety of degenerative conditions. Both clinical and preclinical studies of regenerative medicine are hampered by the lack of technologies that can evaluate the migration and behavior of stem cells post-transplantation. This study proposes an innovative method to longitudinally image in vivo human-induced pluripotent stem cells differentiated to retinal pigment epithelium (hiPSC-RPE) cells by multimodal photoacoustic microscopy, optical coherence tomography, and fluorescence imaging powered by ultraminiature chain-like gold nanoparticle cluster (GNC) nanosensors. The GNC exhibits an optical absorption peak in the near-infrared regime, and the 7-8 nm size in diameter after disassembly enables renal excretion and improved safety as well as biocompatibility. In a clinically relevant rabbit model, GNC-labeled hiPSC-RPE cells migrated to RPE degeneration areas and regenerated damaged tissues. The hiPSC-RPE cells' distribution and migration were noninvasively, longitudinally monitored for 6 months with exceptional sensitivity and spatial resolution. This advanced platform for cellular imaging has the potential to enhance regenerative cell-based therapies.

Cell therapy for retinal degenerative disorders: a systematic review and three-level meta-analysis

BACKGROUND

Retinal degenerative disorders (RDDs) cause vision loss by damaging retinal neurons and photoreceptors, affecting individuals of all ages. Cell-based therapy has emerged as an effective approach for the treatment of RDDs with promising results. This meta-analysis aims to comprehensively evaluate the efficacy of cell therapy in treating age-related macular degeneration (AMD), retinitis pigmentosa (RP), and Stargardt macular degeneration (SMD) as the most prevalent RDDs.

METHODS

PubMed, Scopus, Web of Science, and Embase were searched using keywords related to various retinal diseases and cell therapy treatments until November 25th, 2023. The studies' quality was evaluated using the Joanna Briggs Institute's (JBI) checklist for quasi-experimental studies. Visual acuity measured as LogMAR score was used as our main outcome. A three-level random-effect meta-analysis was used to explore the visual acuity in patients who received cell-based therapy. Heterogeneity among the included studies was evaluated using subgroup and sensitivity analyses. Moreover, meta-regression for the type of cells, year of publication, and mean age of participants were performed.

RESULTS

Overall, 8345 studies were retrieved by the search, and 39 met the eligibility criteria, out of which 18 studies with a total of 224 eyes were included in the meta-analysis. There were 12 studies conducted on AMD, 7 on SMD, and 2 on RP. Cell therapy for AMD showed significant improvement in LogMAR (p < 0.05). Also, cell therapy decreased the LogMAR score in SMD and RP (p < 0.01 and p < 0.0001, respectively). Across all conditions, no substantial publication bias was detected (p < 0.05).

CONCLUSION

The findings of the study highlight that the application of cell therapy can enhance the visual acuity in AMD, SMD, and RP.

Evaluation of Full-Field Stimulus Threshold Test Results in Retinitis Pigmentosa: Relationship with Full-Field Electroretinography, Multifocal Electroretinography, Optical Coherence Tomography, and Visual Field

Objectives

The full-field stimulus threshold (FST) test was developed to evaluate the efficacy and safety of treatments of hereditary retinal diseases. In this study we performed the FST test in patients with retinitis pigmentosa (RP) and compared the results with findings from other ophthalmological tests.

Materials and Methods

The study included 51 intermediate and advanced RP patients and 21 normal subjects. All patients and controls underwent routine examination and ophthalmological tests including visual field, optical coherence tomography, full-field and multifocal electroretinography (mfERG), and FST tests. During FST testing, the perception thresholds of retina to the white, blue, and red FST were determined in decibels.

Results

The mean age of the patients and the controls were 35.2 and 33.5 years, respectively. For all RP patients, no response was obtained on full-field ERG. All subjects were able to perform reliable FST tests. The mean values of visual acuity and central macular thickness were significantly lower and visual field mean deviation values were significantly higher in the RP group than the controls. When we evaluated the mfERG findings, the mean P1 wave amplitudes in all rings were significantly lower and the mean peak times were significantly longer in RP patients than controls. In comparisons of FST test results, the mean values for white, blue, red and the difference between blue-red thresholds were significantly lower in the RP group than the control group.

Conclusion

The FST test is a fast and a reliable exam which can be done in subjects with poor visual acuity and reduced visual field. The results of this study confirm that the FST test can measure retinal sensitivity in severely affected RP subjects with flat flash ERG.

Beyond Vision: An Overview of Regenerative Medicine and Its Current Applications in Ophthalmological Care

Regenerative medicine (RM) has emerged as a promising and revolutionary solution to address a range of unmet needs in healthcare, including ophthalmology. Moreover, RM takes advantage of the body's innate ability to repair and replace pathologically affected tissues. On the other hand, despite its immense promise, RM faces challenges such as ethical concerns, host-related immune responses, and the need for additional scientific validation, among others. The primary aim of this review is to present a high-level overview of current strategies in the domain of RM (cell therapy, exosomes, scaffolds, in vivo reprogramming, organoids, and interspecies chimerism), centering around the field of ophthalmology. A search conducted on clinicaltrials.gov unveiled a total of at least 209 interventional trials related to RM within the ophthalmological field. Among these trials, there were numerous early-phase studies, including phase I, I/II, II, II/III, and III trials. Many of these studies demonstrate potential in addressing previously challenging and degenerative eye conditions, spanning from posterior segment pathologies like Age-related Macular Degeneration and Retinitis Pigmentosa to anterior structure diseases such as Dry Eye Disease and Limbal Stem Cell Deficiency. Notably, these therapeutic approaches offer tailored solutions specific to the underlying causes of each pathology, thus allowing for the hopeful possibility of bringing forth a treatment for ocular diseases that previously seemed incurable and significantly enhancing patients' quality of life. As advancements in research and technology continue to unfold, future objectives should focus on ensuring the safety and prolonged viability of transplanted cells, devising efficient delivery techniques, etc.

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.

Future regenerative medicine developments and their therapeutic applications

Although the currently available pharmacological assays can cure most pathological disorders, they have limited therapeutic value in relieving certain disorders like myocardial infarct, peripheral vascular disease, amputated limbs, or organ failure (e.g. renal failure). Pilot studies to overcome such problems using regenerative medicine (RM) delivered promising data. Comprehensive investigations of RM in zebrafish or reptilians are necessary for better understanding. However, the precise mechanisms remain poorly understood despite the tremendous amount of data obtained using the zebrafish model investigating the exact mechanisms behind their regenerative capability. Indeed, understanding such mechanisms and their application to humans can save millions of lives from dying due to potentially life-threatening events. Recent studies have launched a revolution in replacing damaged human organs via different approaches in the last few decades. The newly established branch of medicine (known as Regenerative Medicine aims to enhance natural repair mechanisms. This can be done through the application of several advanced broad-spectrum technologies such as organ transplantation, tissue engineering, and application of Scaffolds technology (support vascularization using an extracellular matrix), stem cell therapy, miRNA treatment, development of 3D mini-organs (organoids), and the construction of artificial tissues using nanomedicine and 3D bio-printers. Moreover, in the next few decades, revolutionary approaches in regenerative medicine will be applied based on artificial intelligence and wireless data exchange, soft intelligence biomaterials, nanorobotics, and even living robotics capable of self-repair. The present work presents a comprehensive overview that summarizes the new and future advances in the field of RM.

Ocular Manifestations in Patients with Sensorineural Hearing Loss

Identification of ocular manifestations in patients with sensorineural hearing loss (SNHL) can have a large impact on the outcome and treatment of pediatric patients. Due to the common co-incidence of ocular manifestations and SNHL in children, both ophthalmologic and hearing loss screening and routine examinations must be conducted to minimize adverse outcomes and worsening of pathology. Early evaluation and diagnosis is imperative for intervention and further development of the patient. Co-incidence requires a thorough evaluation that includes a comprehensive history, examination, and diagnostic testing. In this article, a literature review was conducted to analyze the presentations of various diseases and syndromes, such as Alport Syndrome, Waardenburg Syndrome, Norrie Disease, Usher Disease, Stickler Syndrome, Marfan Syndrome, Congenital Rubella, and Hereditary Optic Neuropathies. We divided the various ocular pathologies into anterior and posterior segment presentations and associated systemic findings for better understanding. Additionally, this review aims to include an update on the management of patients with both ocular and hearing loss manifestations.

Mesenchymal Stem Cell Studies in the Goat Model for Biomedical Research—A Review of the Scientific Literature

Simple Summary

This review article aims to compile the works published in the scientific literature, over the last two decades, that use the goat as an animal model in preclinical studies using stem cells, alone or associated with biomaterials, for the treatment of injury or disease in divers organ systems. These preclinical studies are performed prior to human clinical trials for the implementation of new medical or surgical therapies in clinical practice. Thus, it appears that, in the area of tissue engineering and regenerative medicine, the caprine model is particularly used in studies using stem cells in the musculoskeletal system but, although in a more limited way, also in the field of dermatology, ophthalmology, dentistry, pneumology, cardiology, and urology. It appears that the goat represents a particularly useful animal model for studies related to the locomotor system because of its size, and also because they have a more active behavior than sheep, being more similar to the human species in this aspect. Additionally, the goat knee anatomy and the thickness of the cartilage that covers this joint are closer to that of humans than that of other large animal models commonly used in orthopedic research.

Abstract

Mesenchymal stem cells (MSCs) are multipotent cells, defined by their ability to self-renew, while maintaining the capacity to differentiate into different cellular lineages, presumably from their own germinal layer. MSCs therapy is based on its anti-inflammatory, immunomodulatory, and regenerative potential. Firstly, they can differentiate into the target cell type, allowing them to regenerate the damaged area. Secondly, they have a great immunomodulatory capacity through paracrine effects (by secreting several cytokines and growth factors to adjacent cells) and by cell-to-cell contact, leading to vascularization, cellular proliferation in wounded tissues, and reducing inflammation. Currently, MSCs are being widely investigated for numerous tissue engineering and regenerative medicine applications. Appropriate animal models are crucial for the development and evaluation of regenerative medicine-based treatments and eventual treatments for debilitating diseases with the hope of application in upcoming human clinical trials. Here, we summarize the latest research focused on studying the biological and therapeutic potential of MSCs in the goat model, namely in the fields of orthopedics, dermatology, ophthalmology, dentistry, pneumology, cardiology, and urology fields.

Utilization of Modified Induced Pluripotent Stem Cells as the Advance Therapy of Glaucoma: A Systematic Review

Glaucoma is an optic neuropathy disease that causes cupping of the optic disc and decreased visual field. Glaucoma is still the second leading cause of blindness globally, with a worldwide prevalence of more than 76 million people in 2020. However, no therapy can cure glaucoma completely, especially when optic nerve damage has occurred. Available treatments only play a role in keeping the intraocular pressure stable This research aims to determine the potential use of modified stem cell therapy to treat intraocular damage in glaucoma cases. Literature research was conducted by involving seven online databases, namely Pubmed, ScienceDirect^®, Proquest, EBSCOhost^®, SAGE^®, Clinicalkey^®, and Scopus, published between 2010–2020 with the keywords stem cells; therapy; glaucoma; optic nerve. Six articles were selected, and out of the six articles, all writings were experimental research. The entire literature states that modified stem cell therapy has the potential as a therapeutic option in treating intraocular damage in patients with glaucoma. Based on the systematic literature review that has been carried out, it is known that stem cell therapy has the potential to be a therapeutic option in treating glaucoma cases. Much more research is needed to assess the effectiveness of modified stem cell therapy in managing intraocular damage due to glaucoma.

Human-induced pluripotent stem cells-derived retinal pigmented epithelium, a new horizon for cells-based therapies for age-related macular degeneration

Retinal pigment epithelium (RPE) degeneration is the hallmark of age-related macular degeneration (AMD). AMD, as one of the most common causes of irreversible visual impairment worldwide, remains in need of an appropriate approach to restore retinal function. Wet AMD, which is characterized by neovascular formation, can be stabilized by currently available therapies, including laser photocoagulation, photodynamic therapy, and intraocular injections of anti-VEFG (anti-vascular endothelial growth factor) therapy or a combination of these modalities. Unlike wet AMD, there is no effective therapy for progressive dry (non-neovascular) AMD. However, stem cell-based therapies, a part of regenerative medicine, have shown promising results for retinal degenerative diseases such as AMD. The goal of RPE cell therapy is to return the normal structure and function of the retina by re-establishing its interaction with photoreceptors, which is essential to vision. Considering the limited source of naturally occurring RPE cells, recent progress in stem cell research has allowed the generation of RPE cells from human pluripotent cells, both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSC). Since iPSCs face neither ethical arguments nor significant immunological considerations when compared to ESCs, they open a new horizon for cell therapy of AMD. The current study aims to discuss AMD, review the protocols for making human iPSCs-derived RPEs, and summarize recent developments in the field of iPSC-derived RPEs cell therapy.

Evaluation of neuroprotective and immunomodulatory properties of mesenchymal stem cells in an ex vivo retinal explant model

BACKGROUND

Glaucoma is a blinding degenerative neuropathy in which the death of retinal ganglion cells (RGCs) causes progressive loss of visual field and eventually vision. Neuroinflammation appears to be a key event in the progression and spread of this disease. Thus, microglial immunomodulation represents a promising therapeutic approach in which mesenchymal stem cells (MSCs) might play a crucial role. Their neuroprotective and regenerative potentials have already raised hope in animal models. Yet no definitive treatment has been developed, and some safety concerns have been reported in human trials. In the present study, we investigated the neuroprotective and immunomodulatory properties as well as the safety of MSCs in an ex vivo neuroretina explant model.

METHODS

Labeled rat bone marrow MSCs were placed in coculture with rat retinal explants after optic nerve axotomy. We analyzed the neuroprotective effect of MSCs on RGC survival by immunofluorescence using RBPMS, Brn3a, and NeuN markers. Gliosis and retinal microglial activation were measured by using GFAP, CD68, and ITGAM mRNA quantification and GFAP, CD68, and Iba1 immunofluorescence stainings. We also analyzed the mRNA expression of both 'M1' or classically activated state inflammatory cytokines (TNFα, IL1β, and IL6), and 'M2' or alternatively activated state microglial markers (Arginase 1, IL10, CD163, and TNFAIP6).

RESULTS

The number of RGCs was significantly higher in retinal explants cultured with MSCs compared to the control group at Day 7 following the optic nerve axotomy. Retinal explants cultured with MSCs showed a decrease in mRNA markers of gliosis and microglial activations, and immunostainings revealed that GFAP, Iba1, and CD68 were limited to the inner layers of the retina compared to controls in which microglial activation was observed throughout the retina. In addition, MSCs inhibited the M1 phenotype of the microglia. However, edema of the explants was observed in presence of MSCs, with an increase in fibronectin labeling at the surface of the explant corresponding to an epiretinal membrane-like phenotype.

CONCLUSION

Using an ex vivo neuroretina model, we demonstrated a neuroprotective and immunomodulatory effect of MSCs on RGCs. Unfortunately, the presence of MSCs also led to explant edema and epiretinal membrane formation, as described in human trials. Using the MSC secretome might offer the beneficial effects of MSCs without their potential adverse effects, through paracrine signaling.

Features of Local Expression of Genes of Immune Response Cytokines and Trophic and Vasoregulatory Factors in Modeling of Retinal Pigment Epithelium Atrophy

Local expression of genes encoding IL-1β, IL-18, MCP-1/CCL2, PEDF, VEGF-A, and ZO-1 in the retina-retinal pigment epithelium-chorioidea tissue complex was studied in healthy rabbits and animals with simulated retinal pigment epithelium atrophy. Retinal pigment epithelium atrophy was modeled by single subretinal injection of 0.01 ml 0.9% NaCl (group 1; n=17) or 0.01 ml solution containing angiogenesis inhibitor bevacizumab in a dose of 0.025 mg (group 2; n=18). The gene expression was evaluated by reverse transcription PCR. In 27.7% cases, atrophic changes in the fundus were accompanied by a significant increase of IL-1β gene expression and in more than 50% cases by an increase in VEGF-A and MCP-1/CCL2 mRNA levels. These factors contribute to an increase in the permeability of the blood-retina barrier and abolition of the immune privilege of the posterior eye segment, which should be taken into account when testing invasive approaches, in particular, for approbation of various options of replacement therapy with retinal pigment epithelium stem cells and development and use of neuroprotectors and drugs of targeted action.

Stem cell transplantation as a progressing treatment for retinitis pigmentosa

Retinal degenerative diseases such as retinitis pigmentosa (RP) are of the major causes of vision loss in developed countries. Despite the unclear pathophysiology, treatment methods have been investigated vastly in the past decades. This review article mainly discusses the advances in application of stem cell and progenitor transplantation for retinitis pigmentosa. Stem cell sources such as mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells, neural stem cells, retinal progenitor cells, and olfactory ensheathing cells are discussed separately in addition to a brief description of two approaches for treatment of early-stage RP, including gene therapy and nutritional therapy.

PRPH2 mutation update: In silico assessment of 245 reported and 7 novel variants in patients with retinal disease

Mutations in PRPH2, encoding peripherin-2, are associated with the development of a wide variety of inherited retinal diseases (IRDs). To determine the causality of the many PRPH2 variants that have been discovered over the last decades, we surveyed all published PRPH2 variants up to July 2020, describing 720 index patients that in total carried 245 unique variants. In addition, we identified seven novel PRPH2 variants in eight additional index patients. The pathogenicity of all variants was determined using the ACMG guidelines. With this, 107 variants were classified as pathogenic, 92 as likely pathogenic, one as benign, and two as likely benign. The remaining 50 variants were classified as variants of uncertain significance. Interestingly, of the total 252 PRPH2 variants, more than half (n = 137) were missense variants. All variants were uploaded into the Leiden Open source Variation and ClinVar databases. Our study underscores the need for experimental assays for variants of unknown significance to improve pathogenicity classification, which would allow us to better understand genotype-phenotype correlations, and in the long-term, hopefully also support the development of therapeutic strategies for patients with PRPH2-associated IRD.

Clinical Presentation and Demographic Distribution of Retinitis Pigmentosa in India and Implications for Potential Treatments: Electronic Medical Records Driven Big Data Analytics: Report I

AimTo describe the clinical presentation and demographic distribution of retinitis pigmentosa in patients presenting to a multi-tier ophthalmology hospital network in India and implications for potential treatments.DesignCross-sectional hospital-based study.MethodsThis study included 2,541,810 patients presenting between March 2012 and October 2020. Patients with a clinical diagnosis of retinitis pigmentosa in at least one eye were included as cases. The data were collected using an electronic medical record system.ResultsOverall, 15,062 (0.59%) new patients were diagnosed with retinitis pigmentosa and were included for analysis. The median age was 35 (IQR: 21-49) years and adult age (84.56%) presented more often. The most common presenting age group was between 21 and 30 years (20%). Majority of patients were male (61.68%) and had bilateral (96.39%) affliction. There was a family history in a tenth of the patients (10.46%) and a history of consanguinity in a minority (5.53%). The majority of the eyes had mild or no central visual acuity impairment of <20/70 (34.25%) followed by blindness <20/400 to 20/1200 (21.26%). The predominant retinal signs included disc pallor (76.43%), attenuated arterioles (82.61%) and bony spicule pigmentation (90.15%), and almost all had retinal pigmentary changes. A minority of the eyes underwent a surgical procedure (4.96%).ConclusionRetinitis pigmentosa is commonly bilateral and predominantly affects males. Most patients present in the third decade of life with severe visual acuity impairment. More than half of the eyes from our study are potential candidates for newer therapies. These results have implications for upcoming treatment choices and planning.

Potential therapeutic applications of mesenchymal stem cells for the treatment of eye diseases

Stem cell-based treatments have been extensively explored in the last few decades to develop therapeutic strategies aimed at providing effective alternatives for those human pathologies in which surgical or pharmacological therapies produce limited effects. Among stem cells of different sources, mesenchymal stem cells (MSCs) offer several advantages, such as the absence of ethical concerns, easy harvesting, low immunogenicity and reduced tumorigenesis risks. Other than a multipotent differentiation ability, MSCs can release extracellular vesicles conveying proteins, mRNA and microRNA. Thanks to these properties, new therapeutic approaches have been designed for the treatment of various pathologies, including ocular diseases. In this review, the use of different MSCs and different administration strategies are described for the treatment of diabetic retinopathy, glaucoma, and retinitis pigmentosa. In a large number of investigations, positive results have been obtained by in vitro experiments and by MSC administration in animal models. Most authors agree that beneficial effects are likely related to MSC paracrine activity. Based on these considerations, many clinical trials have already been carried out. Overall, although some adverse effects have been described, promising outcomes are reported. It can be assumed that in the near future, safer and more effective protocols will be developed for more numerous clinical applications to improve the quality of life of patients affected by eye diseases.

First Year Results of Suprachoroidal Adipose Tissue Derived Mesenchymal Stem Cell Implantation in Degenerative Macular Diseases

Background and Objectives

This study shows the clinical data of 1-year follow-up of 8 patients with degenerative macular diseases who received suprachoroidal adipose tissue derived mesenchymal stem cell (ADMSC) implantation.

Methods and Results

This prospective, single-center, phase 1/2 study enrolled 8 eyes of 8 patients with degenerative macular diseases of various reasons who underwent suprachoroidal implantation of ADMSCs. All patients had severe visual field defects and severe visual loss. All patients had defective multifocal electroretinography (mf ERG). The worse eye of the patient was selected for the operation. Patients were evaluated on the first day, first month, sixth month and at 1 year postoperatively. Best corrected visual acuity (BCVA), anterior segment and fundus examination, color photography, optical coherence tomography (OCT) and visual field (VF) examination were carried out at each visit. Fundus fluorescein angiography (FFA) and mfERG recordings were performed at the end of the sixth months. All 8 patients completed the 1 year follow-up. None of them had any systemic or ocular complications. Seven of the patients experienced visual acuity improvement, visual field improvement and improvement in the mfERG recordings. We found choroidal thickening in OCT of the four treated eyes.

Conclusions

Even though the sample size is small, stem cell treatment with suprachoroidal implantation of ADMSCs seems to be safe and the improvements were encouraging. To optimize the cell delivery technique and to evaluate the effects of this therapy on visual acuity and the quality of life of these patients, future studies with larger number of cases will be necessary.

Clinical Application of Human Induced Pluripotent Stem Cell-Derived Organoids as an Alternative to Organ Transplantation

Transplantation is essential and crucial for individuals suffering from end-stage organ failure diseases. However, there are still many challenges regarding these procedures, such as high rates of organ rejection, shortage of organ donors, and long waiting lines. Thus, investments and efforts to develop laboratory-grown organs have increased over the past years, and with the recent progress in regenerative medicine, growing organs in vitro might be a reality within the next decades. One of the many different strategies to address this issue relies on organoid technology, a miniaturized and simplified version of an organ. Here, we address recent progress on organoid research, focusing on transplantation of intestine, retina, kidney, liver, pancreas, brain, lung, and heart organoids. Also, we discuss the main outcomes after organoid transplantation, common challenges faced by these promising regenerative medicine approaches, and future perspectives on the field.

Umbilical cord-derived mesenchymal stem cell implantation in patients with optic atrophy

BACKGROUND

Optic nerve cells can be irreversibly damaged by common various causes. Unfortunately optic nerve and retinal ganglion cells have no regenerative capacity and undergo apoptosis in case of damage. In this study, our aim is to investigate the safety and efficacy of suprachoroidal umbilical cord-derived MSCs (UC-MSCs) implantation in patients with optic atrophy.

METHODS

This study enrolled 29 eyes of 23 patients with optic atrophy who were followed in the ophthalmology department of our hospital. BCVA, anterior segment, fundus examination, color photography, and optical coherence tomography (OCT) were carried out at each visit. Fundus fluorescein angiography and visual field examination were performed at the end of the first, third, sixth months, and 1 year follow-up.

RESULTS

After suprachoroidal UC-MSCs implantation there were statistically significant improvements in BCVA and VF results during 12 months follow-up (p < 0.05). When we evaluate the results of VF tests, the mean deviation (MD) value at baseline was -26.11 ± 8.36 (range -14.18 to -34.41). At the end of the first year it improved to -25.01 ± 8.73 (range -12.56 to -34.41) which was statistically significant (p < 0.05). When we evaluate the mean RNFL thickness measurements at baseline and at 12 month follow-up the results were 81.8 ± 24.9 μm and 76.6 ± 22.6 μm, respectively. There was not a significant difference between the mean values (p > 0.05).

CONCLUSION

Stem cell treatment with suprachoroidal implantation of UCMSCs seems to be safe and effective in the treatment for optic nerve diseases that currently have no curative treatment options.

Antioxidant and Biological Properties of Mesenchymal Cells Used for Therapy in Retinitis Pigmentosa

Both tissue repair and regeneration are a priority in regenerative medicine. Retinitis pigmentosa (RP), a complex retinal disease characterized by the progressive loss of impaired photoreceptors, is currently lacking effective therapies: this represents one of the greatest challenges in the field of ophthalmological research. Although this inherited retinal dystrophy is still an incurable genetic disease, the oxidative damage is an important pathogenetic element that may represent a viable target of therapy. In this review, we summarize the current neuroscientific evidence regarding the effectiveness of cell therapies in RP, especially those based on mesenchymal cells, and we focus on their therapeutic action: limitation of both oxidative stress and apoptotic processes triggered by the disease and promotion of cell survival. Cell therapy could therefore represent a feasible therapeutic option in RP.

Umbilical cord derived mesenchymal stem cell implantation in retinitis pigmentosa: a 6-month follow-up results of a phase 3 trial

AIM

To investigate the efficacy and the safety of umbilical cord derived mesenchymal stem cell (UC-MSC) implantation in patients with retinitis pigmentosa (RP).

METHODS

This prospective, single-center, phase 3 clinical study enrolled 124 eyes of 82 RP patients. The patients received 5 million UC-MSCs to the suprachoroidal area with a surgical procedure. Patients were evaluated on the 1^st day, 1^st, and 6^th months postoperatively. Best corrected visual acuity (BCVA), anterior segment and fundus examinations, color photography, optical coherence tomography (OCT), and visual field (VF) tests were carried out at each visit. Fundus fluorescein angiography (FFA) and multifocal electroretinography (mfERG) recordings were performed at the end of the 6^th month. Ocular and systemic adverse events of the surgical procedure were also noted.

RESULTS

All of the 82 patients completed the 6-month follow-up period. None of them had any serious systemic or ocular complications. There were statistically significant improvements in BCVA and VF during the study (all P<0.05). The amplitudes of the P1 waves in the central areas showed significant improvements in mfERG recordings. There were also significant increases in implicit times of P1 waves in the central areas.

CONCLUSION

Suprachoroidal administration of UC-MSCs has beneficial effect on BCVA, VF, and mfERG measurements during the 6-month follow-up period. Cell mediated therapy based on the secretion of growth factors (GFs) seems to be an effective and safe option for degenerative retinal diseases.

Reprogramming of Differentiated Mammalian and Human Retinal Pigment Epithelium: Current Achievements and Prospects

Abstract

Impairment of the homeostatic and functional integrity of the retina and retinal pigment epithelium (RPE) is the main cause of some degenerative diseases of the human eye, which are accompanied by loss of eyesight. Despite the significant progress made over the past decades in the development of new methods for treatment for this pathology, there are still several complications when using surgical methods for correction of eyesight and so far insurmountable limitations in the applications of modern approaches, such as gene therapy and genetic engineering. One of the promising approaches to the treatment of degenerative diseases of the retina may be an approach based on the application of regenerative capacities of its endogenous cells with high plasticity, in particular, of RPE cells and Müller glia. Currently, vertebrate RPE cells are of great interest as a source of new photoreceptors and other neurons in the degrading retina in vivo. In this regard, the possibilities of their direct reprogramming by genetic, epigenetic, and chemical methods and their combination are being investigated. This review focuses on research in gene-directed reprogramming of vertebrate RPE cells into retinal neurons, with detailed analysis of the genes used as the main reprogramming factors, comparative analysis, and extrapolation of experimental data from animals to humans. Also, this review covers studies on the application of alternative approaches to gene-directed reprogramming, such as chemical-mediated reprogramming with the use of cocktails of therapeutic low-molecular-weight compounds and microRNAs. In general, the research results indicate the complexity of the process for direct reprogramming of human RPE cells into retinal neurons. However, taking into account the results of direct reprogramming of vertebrate cells and the accessibility of human RPE cells for various vectors that deliver a variety of molecules to cells, such as transcription factors, chimeric endonucleases, recombinant proteins, and low-weight molecular compounds, the most optimal combination of factors for the successful conversion of human RPE cells to retinal neurons can be suggested.

Differentiation of retinal organoids from human pluripotent stem cells

Human pluripotent stem cells (hPSCs) possess the remarkable ability to differentiate into any cell type of the body, including those of the retina. Through the differentiation of these cells as retinal organoids, it is now possible to model the spatial and temporal development of the human retina using hPSCs, in which retinal progenitor cells produce the entire repertoire of retinal cells, first differentiating into retinal ganglion cells and ending with mature photoreceptors, bipolar cells, and Müller glia. Importantly, retinal organoids self-assemble into laminated structures that recapitulate the layering of the human retina with a retinal ganglion cell layer lining the inner layer and a distinctly separate photoreceptor layer occupying the outer layers. This organoid technology has provided access to human tissue for developmental and disease modeling, as well as translational applications such as high throughput drug screening and cell replacement therapies. However, the differentiation of retinal organoids does require some expertise and multiple strategies produce inconsistent results. Here, we describe in detail a well-established and relatively simple method for the generation of retinal organoids.

Cell-based approaches towards treating age-related macular degeneration

Age-related macular degeneration as one of the most common causes of worldwide vision loss needs a proper approach for treatment. Therein, cell therapy and regenerative medicine can hold a great promise to be an effective approach. Accordingly, some preclinical and clinical studies were conducted to search around the therapeutic influence of stem cells in Age-related macular degeneration models and subjects. Hereupon, the purpose of the current review is to discuss the mechanisms of age-related macular degeneration, appropriate animal models along with suitable dosage and route of stem cell administration for its treatment.

Potential therapeutic application of mesenchymal stem cells in ophthalmology

At present a wide variety of methods have been proposed to treat eye disorders, drug therapies are most commonly used. It should be noted that effective treatment modalities especially for degeneration of the retina and optic nerve are lacking. In the last few years stem cell transplantation has been proposed as an alternative method. The opportunities that stem cells provide within clinical use are almost unlimited. These cells are presently applied to treat various traumatic and degenerative disorders due to their unique biologic properties. Stem cells have high proliferative capabilities and are a self-maintained population of cells capable of differentiating into different cell types. Thus, they are represent a very primary stage of a cell lineage. Their ability to differentiate into different pathways provides animals with great plasticity in the renewal of somatic cells in postnatal ontogenesis. Pre-clinical and clinical ophthalmology studies where mesenchymal stem cells are applied and various methods of their administration are discussed herein. In addition the safety and efficacy of using bone marrow- and adipose tissue-derived mesenchymal stem cells have been discussed.

Suprachoroidal Adipose Tissue-Derived Mesenchymal Stem Cell Implantation in Patients with Dry-Type Age-Related Macular Degeneration and Stargardt's Macular Dystrophy: 6-Month Follow-Up Results of a Phase 2 Study

This prospective clinical case series aimed to investigate the safety and efficacy of suprachoroidal adipose tissue-derived mesenchymal stem cell (ADMSC) implantation in patients with dry-type age-related macular degeneration (AMD) and Stargardt's macular dystrophy (SMD). This study included four patients with advanced-stage dry-type AMD and four patients with SMD who underwent suprachoroidal implantation of ADMSCs. The best-corrected visual acuity (BCVA) in the study was 20/200. The worse eye of the patient was operated on. Patients were evaluated on the first day, first week, and first, third, and sixth months postoperatively. BCVA, anterior segment and fundus examination, color photography, fundus autofluorescence, optical coherence tomography, and visual field examination were carried out at each visit. Fundus fluorescein angiography and multifocal electroretinography (mf-ERG) recordings were performed at the end of the first, third, and sixth months and anytime if necessary during the follow-up. All eight patients completed the sixth month follow-up. None of them had any systemic or ocular complications. All of the eight patients experienced visual acuity improvement, visual field improvement, and improvement in mf-ERG recordings. Stem cell treatment with suprachoroidal implantation of ADMSCs seems to be safe and effective in the treatment of dry-type AMD and SMD.

Astragalus root extract inhibits retinal cell apoptosis and repairs damaged retinal neovascularization in retinopathy of prematurity

Since the functions of Astragalus root extract in retinopathy remain to be unraveled, this study is performed to elucidate whether Astragalus root extract functions in retinal cell apoptosis and angiogenesis in retinopathy of prematurity (ROP). Newborn mice were selected for establishing mice models of oxygen-induced retinopathy (OIR), which were treated with high-, medium- or low-Astragalus root extract. Evans Blue (EB) was perfused to detect the blood retinal barrier. Additionally, the vascular morphology, number of endothelial cell nuclei of neovascularization, proliferation of blood vessels, ultrastructural changes were determined via a series of assays. Moreover, levels of reactive oxygen species (ROS), expression of other factors such as VEGF, PEDF, IGF-1, HIF-1α, Bax, Bcl-2, eNOS, nNOS, and iNOS were detected. Astragalus root extract was found to protect blood-retinal barrier in the OIR model mice through repairing the structure and morphology of retina, inhibiting ROS production, retinal cell apoptosis, as well as improving retinal vascular angiogenesis. Astragalus root extract was also found to decrease VEGF and HIF-1α expression, but enhance PEDF and IGF-1 expression in the OIR model mice, thereby protecting retinas in ROP. This study highlights that Astragalus root extract is able to suppress retinal cell apoptosis and repair damaged retinal neovascularization in ROP, which provides basis for ROP therapy.

Current Approaches to Low Vision (Re)Habilitation

With increased life expectancy at birth and especially the rising incidence of age-related macular degeneration, low vision (re)habilitation is becoming more important today. Important factors to consider when presenting rehabilitation and treatment options to patients presenting to low vision centers include the diagnosis of the underlying disease, the patient’s age, their existing visual functions (especially distance and near visual acuity), whether visual loss is central or peripheral, whether their disease is progressive or not, the patient’s education level, and their expectations from us. Low vision patients must be guided to the right centers at the appropriate age, with appropriate indications, and with realistic expectations, and the rehabilitation process must be carried out as a multidisciplinary collaboration.

Retinal cell regeneration using tissue engineered polymeric scaffolds

Degenerative retinal diseases, such as age-related macular degeneration (AMD), can lead to permanent sight loss. Although intravitreal anti-vascular endothelial growth factor (VEGF) and steroid injections are effective for the management of early stages of wet and/or neovascular AMD (nAMD), no proven treatments currently exist for dry AMD or for the advanced geographic atrophy of the retina that follows. Tissue engineering (TE) has recently emerged as a promising alternative to repair retinal damaged and restore its functions. Here, we review recent advances in TE, with a particular emphasis on retinal regeneration. We provide an overview of retinal diseases, followed by a comprehensive review of TE techniques, cells, and polymers used in the fabrication of scaffolds for retinal cell regenerations, in particular the retinal pigment epithelium (RPE).

Emerging Drug Therapies for Inherited Retinal Dystrophies

Worldwide, 1 in 2000 people suffer from inherited retinal dystrophies (IRD). Individuals with IRD typically present with progressive vision loss that ultimately results in blindness. Unfortunately, effective treatment options are not widely available due to the genetic and clinical heterogeneity of these diseases. There are multiple gene, cell, and drug-based therapies in various phases of clinical trials for IRD. This mini-review documents current progress made in drug-based clinical trials for treating IRD.

Revolution in Gene Medicine Therapy and Genome Surgery

Recently, there have been revolutions in the development of both gene medicine therapy and genome surgical treatments for inherited disorders. Much of this progress has been centered on hereditary retinal dystrophies, because the eye is an immune-privileged and anatomically ideal target. Gene therapy treatments, already demonstrated to be safe and efficacious in numerous clinical trials, are benefitting from the development of new viral vectors, such as dual and triple adeno-associated virus (AAV) vectors. CRISPR/Cas9, which revolutionized the field of gene editing, is being adapted into more precise "high fidelity" and catalytically dead variants. Newer CRISPR endonucleases, such as CjCas9 and Cas12a, are generating excitement in the field as well. Stem cell therapy has emerged as a promising alternative, allowing human embryo-derived stem cells and induced pluripotent stem cells to be edited precisely in vitro and then reintroduced into the body. This article highlights recent progress made in gene therapy and genome surgery for retinal disorders, and it provides an update on precision medicine Food and Drug Administration (FDA) treatment trials.

Revolution in Gene Medicine Therapy and Genome Surgery

Recently, there have been revolutions in the development of both gene medicine therapy and genome surgical treatments for inherited disorders. Much of this progress has been centered on hereditary retinal dystrophies, because the eye is an immune-privileged and anatomically ideal target. Gene therapy treatments, already demonstrated to be safe and efficacious in numerous clinical trials, are benefitting from the development of new viral vectors, such as dual and triple adeno-associated virus (AAV) vectors. CRISPR/Cas9, which revolutionized the field of gene editing, is being adapted into more precise "high fidelity" and catalytically dead variants. Newer CRISPR endonucleases, such as CjCas9 and Cas12a, are generating excitement in the field as well. Stem cell therapy has emerged as a promising alternative, allowing human embryo-derived stem cells and induced pluripotent stem cells to be edited precisely in vitro and then reintroduced into the body. This article highlights recent progress made in gene therapy and genome surgery for retinal disorders, and it provides an update on precision medicine Food and Drug Administration (FDA) treatment trials.

Acquired Resilience: An Evolved System of Tissue Protection in Mammals

This review brings together observations on the stress-induced regulation of resilience mechanisms in body tissues. It is argued that the stresses that induce tissue resilience in mammals arise from everyday sources: sunlight, food, lack of food, hypoxia and physical stresses. At low levels, these stresses induce an organised protective response in probably all tissues; and, at some higher level, cause tissue destruction. This pattern of response to stress is well known to toxicologists, who have termed it hormesis. The phenotypes of resilience are diverse and reports of stress-induced resilience are to be found in journals of neuroscience, sports medicine, cancer, healthy ageing, dementia, parkinsonism, ophthalmology and more. This diversity makes the proposing of a general concept of induced resilience a significant task, which this review attempts. We suggest that a system of stress-induced tissue resilience has evolved to enhance the survival of animals. By analogy with acquired immunity, we term this system 'acquired resilience'. Evidence is reviewed that acquired resilience, like acquired immunity, fades with age. This fading is, we suggest, a major component of ageing. Understanding of acquired resilience may, we argue, open pathways for the maintenance of good health in the later decades of human life.