Organoid-derived C-Kit+/SSEA4- human retinal progenitor cells promote a protective retinal microenvironment during transplantation in rodents

Mesenchymal stem cell-derived small extracellular vesicles enhance the therapeutic effect of retinal progenitor cells in retinal degenerative disease rats

JOURNAL/nrgr/04.03/01300535-202602000-00050/figure1/v/2025-05-05T160104Z/r/image-tiff Our previous study demonstrated that combined transplantation of bone marrow mesenchymal stem cells and retinal progenitor cells in rats has therapeutic effects on retinal degeneration that are superior to transplantation of retinal progenitor cells alone. Bone marrow mesenchymal stem cells regulate and interact with various cells in the retinal microenvironment by secreting neurotrophic factors and extracellular vesicles. Small extracellular vesicles derived from bone marrow mesenchymal stem cells, which offer low immunogenicity, minimal tumorigenic risk, and ease of transportation, have been utilized in the treatment of various neurological diseases. These vesicles exhibit various activities, including anti-inflammatory actions, promotion of tissue repair, and immune regulation. Therefore, novel strategies using human retinal progenitor cells combined with bone marrow mesenchymal stem cell-derived small extracellular vesicles may represent an innovation in stem cell therapy for retinal degeneration. In this study, we developed such an approach utilizing retinal progenitor cells combined with bone marrow mesenchymal stem cell-derived small extracellular vesicles to treat retinal degeneration in Royal College of Surgeons rats, a genetic model of retinal degeneration. Our findings revealed that the combination of bone marrow mesenchymal stem cell-derived small extracellular vesicles and retinal progenitor cells significantly improved visual function in these rats. The addition of bone marrow mesenchymal stem cell-derived small extracellular vesicles as adjuvants to stem cell transplantation with retinal progenitor cells enhanced the survival, migration, and differentiation of the exogenous retinal progenitor cells. Concurrently, these small extracellular vesicles inhibited the activation of regional microglia, promoted the migration of transplanted retinal progenitor cells to the inner nuclear layer of the retina, and facilitated their differentiation into photoreceptors and bipolar cells. These findings suggest that bone marrow mesenchymal stem cell-derived small extracellular vesicles potentiate the therapeutic efficacy of retinal progenitor cells in retinal degeneration by promoting their survival and differentiation.

Revealing the neurodevelopmental toxicity of face mask-derived microplastics to humans based on neural organoids

The massive use of face masks during and after the COVID-19 pandemic has raised global concerns about environmental issues. Microplastics released from face masks pose great threats to ecosystems and human health. However, the potentially hazardous effects of face mask-derived microplastics (FMMs) on humans remain poorly understood. Using neural organoid models aims to reveal the toxicity of FMMs to human early neural development. Retinal organoids derived from human embryonic stem cells were exposed to FMMs for 21 days during early retinogenesis. FMMs were internalized by retinal organoids. Exposure to FMMs disrupted the growth and development of retinal organoids in dose- and time-dependent manners, as evidenced by abnormal morphologies. Aberrant cell events, such as cell proliferation, apoptosis, and differentiation contributed to the disarrangement of the neural retina. Transcriptome data proved that the neurotoxicity of FMMs was closely related to disordered neurogenesis, anatomical structure morphogenesis, and axon guidance. Co-exposure to triphenyl phosphate (a common organophosphate flame retardant) and FMMs exhibited more pronounced neurotoxicity than FMM exposure alone. These findings are expected to uncover the potential threats of FMMs to human neurodevelopment and emphasize the importance of optimizing the management and safe disposal of used face masks.

Single-cell RNA sequencing in the study of human retinal organoids

Single-cell RNA sequencing (scRNA-seq) has transformed the study of retinal development and diseases by enabling a detailed analysis of cellular diversity within retinal organoids (ROs). ROs generated from pluripotent stem cells mimic the essential characteristics of the human retina and provide a valuable in vitro model for investigating retinal development, cell interactions, and disease mechanisms. This review summarizes the application of scRNA-seq on RO research, emphasizing its capacity to identify distinct cell populations, uncover developmental trajectories, and reveal the molecular signatures of retinal diseases. scRNA-seq provides new insights into retinal neurogenesis, cellular diversity, and the pathophysiology of retinal degenerative diseases. This technology has enabled the identification of novel biomarkers and potential therapeutic targets. Integrating scRNA-seq with other technologies, such as spatial transcriptomics and CRISPR-based screening, can further deepen our understanding of retinal biology and improve treatment strategies.

Mesenchymal stem cells derived from hPSC via neural crest attenuate chemotherapy-induced premature ovarian insufficiency by ameliorating apoptosis and oxidative stress in granulosa cells

BACKGROUND

Premature ovarian insufficiency (POI) poses a significant threat to female reproductive health and currently lacks effective interventions. Recent studies highlight the promising potential of human pluripotent stem cell-derived mesenchymal stem cells (hPSC-MSC) in regenerative medicine. However, research on hPSC-MSC-based treatments for POI remains limited, particularly in the characterization of the intermediate differentiation stages from hPSC to MSC. This study presents an accelerated differentiation protocol for generating hPSC-MSC via neural crest cells (NCC) and evaluates their therapeutic potential in chemotherapy-induced POI.

METHODS

We modified a canonical small molecule-mediated protocol for hPSC-NCC-MSC differentiation. Systematic characterization of differentiated-cells was performed using qPCR, immunofluorescence, cell viability assays, flow cytometry and trilineage differentiation. In vivo, hPSC-NCC-MSC were transplanted into chemotherapy-induced POI SD rat models, and parameters such as body weight, ovarian weight, estrous cycle, hormone levels, follicle count, and mating were assessed. Granulosa cells (GC) apoptosis was analyzed using TUNEL assay and immunohistochemistry. In vitro, their effects on apoptosis inhibition and oxidative stress alleviation were investigated in a cultured GC cell line. Additionally, comparisons between umbilical cord MSC (UC-MSC) and hPSC-NCC-MSC in chemotherapy-induced POI was conducted.

RESULTS

Our optimized protocol, combining CHIR99021 and SB431542, efficiently induced NCC from both human embryonic stem cells (hESC) and human induced pluripotent stem cells (hiPSC). The programmed hPSC-NCC-MSC, characterized by specific NCC markers (P75, HNK1, SOX10, and AP2α), exhibited typical MSC morphology, trilineage differentiation potential, favorable cell viability, and prominent anti-senescence properties. Among these, NCC differentiated from H1-hESCs (H1-NCC) demonstrated the highest induction efficiency (72.45%), and H1-NCC-derived MSC (H1-NCC-MSC) displayed superior proliferation and anti-senescence properties compared to UC-MSC. Besides, H1-NCC-MSC exhibited therapeutic efficacy comparable to UC-MSC in both in vivo and in vitro models of chemotherapy-induced POI, potentially through mechanisms involving reduced GC apoptosis, alleviated oxidative stress, and improved mitochondrial function.

CONCLUSIONS

Our findings propose a modified hPSC-NCC-MSC differentiation protocol, offering an inexhaustible and stable source for regenerative therapies. Furthermore, we provide the first experimental evidence that hPSC-NCC-MSC have therapeutic potential comparable to UC-MSC in restoring chemotherapy-induced POI. The underlying mechanisms are likely associated with paracrine-mediated effects on GC apoptosis, oxidative stress, and mitochondrial dysfunction.

Animal models for the evaluation of retinal stem cell therapies

Retinal degeneration (RD) diseases leading to severe vision loss can affect photoreceptors (PRs) that are responsible for phototransduction, or retinal pigmented epithelium (RPE) providing support for PRs. Human pluripotent stem cell (hPSC)-based therapies are a potential approach for restoration of retinal structure in patients with currently incurable RD diseases. Currently, there are two targeted hPSC therapeutics: PR rescue and PR replacement. PR rescue involves the transplantation of RPE or other neural progenitors into the subretinal space to slow down or prevent further RD. RPE transplantation plays a critical role in preserving photoreceptors by providing trophic support and maintaining retinal integrity, particularly in diseases like age-related macular degeneration (AMD). Advances in RPE transplantation methods, such as polarized monolayer cultures and scaffold-based approaches, have shown promise in enhancing graft survival and integration. However, limitations include inconsistent integration, variable neurotrophic factor secretion, and immune rejection risks in non-autologous transplants. In PR replacement, stem cell-derived photoreceptor-like cells or photoreceptor progenitors (PRP) obtained are transplanted into the eye. While PRPs are commonly obtained from retinal organoids (ROs), alternative sources, such as early differentiation stages or direct differentiation protocols, are also utilized to enhance the efficiency and scalability of PRP generation. Challenges include achieving proper integration, forming outer segments, rosette formation, and avoiding immune rejection or tumorigenicity. Various animal models that simulate human RD diseases are being used for establishing surgical feasibility, graft survival and visual functional recovery but fail to replicate clinical immune challenges. Rodent models lack macula-like structures and have limited reliability in detecting subtle functional changes, while larger animal models pose ethical, logistical, and financial challenges. Immunocompromised models have been developed for minimizing xenograft issues. Visual functional testing for efficacy includes optokinetic testing (OKN), electroretinography (ERG), and electrophysiological recordings from the retina and brain. These tests often fail to capture the complexity of human visual recovery, highlighting the need for advanced models and improved functional testing techniques. This review aims to aggregate current knowledge about approaches to stem cell transplantation, requirements of animal models chosen for validating vision benefits of transplantation studies, advantages of using specific disease models and their limitations. While promising strides have been made, addressing these limitations remains essential for translating stem cell-based therapies into clinical success.

The influence of SARS-CoV-2 spike protein exposure on retinal development in the human retinal organoids

BACKGROUND

Pregnant women are considered a high-risk population for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as the virus can infect the placenta and embryos. Recently, SARS-CoV-2 has been widely reported to cause retinal pathological changes and to infect the embryonic retina. The infection of host cells by SARS-CoV-2 is primarily mediated through spike (S) protein, which also plays a crucial role in the pathogenesis of SARS-CoV-2. However, it remains poorly understood how the S protein of SARS-CoV-2 affects retinal development, and the underlying mechanism has not yet been clarified.

METHODS

We used human embryonic stem cell-derived retinal organoids (hEROs) as a model to study the effect of S protein exposure at different stages of retinal development. hEROs were treated with 2 μg/mL of S protein on days 90 and 280. Immunofluorescence staining, RNA sequencing, and RT-PCR were performed to assess the influence of S protein exposure on retinal development at both early and late stages.

RESULTS

The results showed that ACE2 and TMPRSS2, the receptors facilitating SARS-CoV-2 entry into host cells, were expressed in hEROs. Exposure to the S protein induced an inflammatory response in both the early and late stages of retinal development in the hEROs. Additionally, RNA sequencing indicated that early exposure of the S protein to hEROs affected nuclear components and lipid metabolism, while late-stages exposure resulted in changes to cell membrane components and the extracellular matrix.

CONCLUSION

This work highlights the differential effects of SARS-CoV-2 S protein exposure on retinal development at both early and late stages, providing insights into the cellular and molecular mechanisms underlying SARS-CoV-2-induced developmental impairments in the human retina.

Identification and characterization of human retinal stem cells capable of retinal regeneration

Human retinal stem cells hold great promise in regenerative medicine, yet their existence and characteristics remain elusive. Here, we performed single-cell multiomics and spatial transcriptomics of human fetal retinas and uncovered a cell subpopulation, human neural retinal stem-like cells (hNRSCs), distinct from retinal pigment epithelium stem-like cells and traditional retinal progenitor cells. We found that these hNRSCs reside in the peripheral retina in the ciliary marginal zone, exhibiting substantial self-renewal and differentiation potential. We conducted single-cell and spatial transcriptomic analyses of human retinal organoids (hROs) and revealed that hROs contain a population of hNRSCs with similar transcriptional profiles and developmental trajectories to hNRSCs in the fetal retina potentially capable of regenerating all retinal cells. Furthermore, we identified crucial transcription factors, such as MECOM, governing hNRSC commitment to neural retinogenesis and regulating repair processes in hROs. hRO-derived hNRSCs transplanted into the rd10 mouse model of retinitis pigmentosa differentiated and were integrated into the retina, alleviated retinal degeneration, and improved visual function. Overall, our work identifies and characterizes a distinct category of retinal stem cells from human retinas, underscoring their regenerative potential and promise for transplantation therapy.

Immune-responsive gene 1/itaconate pathway inhibits microglia activation to alleviate traumatic optic neuropathy in mice

Retinal inflammatory microenvironment caused by microglia over-activation is deemed to be crucial pathological changes that lead to the massive death of retinal ganglion cells (RGCs) after traumatic optic neuropathy (TON), which then results in visual impairment and even blindness. Therefore, exploring effective targets to suppress microglia activation is a promising therapeutic strategy for TON. In the present work, we determined the roles of immune-responsive gene 1 (IRG1)/itaconate pathway on retinal microglia activation and neuroinflammation after TON, through endogenously manipulating Irg1 expression and exogenously supplementing itaconate derivatives, we evaluated its effects on RGCs survival, retinal structural damage and visual function after TON. Finally, we identified the downstream mechanism by which the Irg1/itaconate pathway regulates microglia through transcriptome analysis. We found that specifically overexpression of Irg1 in retinal microglia significantly inhibited microglia activation and alleviated neuroinflammation after TON, thereby promoting RGCs survival and improving visual function. While knockdown of Irg1 caused microglia over-activation and exacerbated neuroinflammation, thus aggravating RGCs damage and deteriorating visual function after TON. Further in vivo and in vitro experiments confirmed that itaconate derivatives significantly inhibited microglia activation and alleviated neuroinflammation, hence alleviated RGCs damage and visual impairment. Finally, transcriptome analysis indicated that complement and coagulation cascades pathway might be the crucial downstream mechanism of the Irg1/itaconate pathway. Our study identifies the Irg1/itaconate pathway as a prospective target for treating TON.

Influences of lead-based perovskite nanoparticles exposure on early development of human retina

BACKGROUND

Lead-based perovskite nanoparticles (Pb-PNPs) are widely utilized in the photovoltaic industry. However, due to their poor stability and high water solubility, lead often gets released into the environment, which can negatively impact the development of the central nervous system (CNS). As an extension of the CNS, the effects and mechanisms of Pb-PNPs on human retinal development have remained elusive.

OBJECTIVES

We aimed to investigate the effects of Pb-PNPs on human retinal development.

METHODS

Human embryonic stem cell-derived three-dimensional floating retinal organoids (hEROs) were established to simulate early retinal development. Using immunofluorescence staining, biological-transmission electron microscopy analysis, inductively coupled plasma-mass spectrometry, two-dimensional element distribution detection, and RNA sequencing, we evaluated and compared the toxicity of CsPbBr3 nanoparticles (a representative substance of Pb-PNPs) and Pb(AC)2 and investigated the toxicity-reducing effects of SiO2 encapsulation.

RESULTS

Our findings revealed that CsPbBr3 nanoparticles exposure resulted in a concentration-dependent decrease in the area and thickness of the neural retina in hEROs. Additionally, CsPbBr3 nanoparticles exposure hindered cell proliferation and promoted cell apoptosis while suppressing the retinal ganglion cell differentiation, an alteration that further led to the disruption of retinal structure. By contrast, CsPbBr3 nanoparticles exposure to hEROs was slightly less toxic than Pb(AC)2. Mechanistically, CsPbBr3 nanoparticles exposure activated endoplasmic reticulum stress, which promoted apoptosis by up-regulating Caspase-3 and inhibited retinal ganglion cell development by down-regulating Pax6. Interestingly, after coating CsPbBr3 nanoparticles with silica, it exhibited lower toxicities to hEROs by alleviating endoplasmic reticulum stress.

CONCLUSION

Overall, our study provides evidence of Pb-PNPs-induced developmental toxicity in the human retina, explores the potential mechanisms of CsPbBr3 nanoparticles' developmental toxicity, and suggests a feasible strategy to reduce toxicity.

Progress in photoreceptor replacement therapy for retinal degenerative diseases

Retinal degenerative diseases encompass a diverse range of eye conditions that result in blindness, many due to photoreceptor dysfunction and loss. Regrettably, current clinical treatments are frequently not overly effective. However, photoreceptor transplantation shows promise as a potential therapy for late-stage retinal degenerative diseases. This article will review the various donor cell sources for this transplantation, as well as the mechanisms and factors that impact donor cell integration and material transfer, donor cell maturation, and other auxiliary methods that can be combined with photoreceptor transplantation to treat these degenerative retinal diseases.

Cellular component transfer between photoreceptor cells of the retina

Photoreceptor transplantation is a potential therapeutic strategy for degenerative retinal diseases. Studies on mechanisms contributing to retinal regeneration and vision repair identified cellular components transfer (CCT) as playing a role, in addition to somatic augmentation (referred to as "cell replacement" in this paper). In CCT, donor photoreceptors shuttle proteins, RNA, and mitochondria to host photoreceptors through intercellular connections. The discovery of CCT in the transplantation context triggered a re-interpretation of prior transplantation studies that generally did not include specific CCT assays and thereby broadly emphasized the cell replacement model, reflecting the prevailing understanding of retinal transplantation biology at that time. In addition to clarifying our understanding of photoreceptor biology, CCT has raised the possibility of developing treatments to replenish molecular deficiencies in diseased photoreceptor cells. As the CCT field evolves, investigators have used diverse terminology, and implemented different CCT assays following transplantation in animal models. The non-standardized terminology of CCT and absent minimal assay standards for detection can hinder communication between investigators and comparison between studies. In this review, we discuss the current understanding of CCT, provide an overview of transplantation and regeneration studies in small and large animals, and propose terminology and a minimal assay standard for CCT. Further research on CCT may eventually provide new avenues to treat a range of hereditary and acquired retinopathies while illuminating mechanisms of cell-cell interaction in the retina.

Microglia in retinal diseases: From pathogenesis towards therapeutic strategies

Microglia, a widely dispersed cohort of immune cells in the retina, are intricately involved in a diverse range of pivotal biological processes, including inflammation, vascular development, complement activation, antigen presentation, and phagocytosis. Within the retinal milieu, microglia are crucial for the clearance of dead cells and cellular debris, release of anti-inflammatory agents, and orchestration of vascular network remodeling to maintain homeostasis. In addition, microglia are key mediators of neuroinflammation. Triggered by oxidative stress, elevated intraocular pressure, genetic anomalies, and immune dysregulation, microglia release numerous inflammatory cytokines, contributing to the pathogenesis of various retinal disorders. Recent studies on the ontogeny and broad functions of microglia in the retina have elucidated their characteristics during retinal development, homeostasis, and disease. Furthermore, therapeutic strategies that target microglia and their effector cytokines have been developed and shown positive results for some retinal diseases. Therefore, we systematically review the microglial ontogeny in the retina, elucidate their dual roles in retinal homeostasis and disease pathogenesis, and demonstrate microglia-based targeted therapeutic strategies for retinal diseases.

Cell-cell interactions between transplanted retinal organoid cells and recipient tissues

The transplantation of human organoid-derived retinal cells is being studied as a potentially viable strategy to treat vision loss due to retinal degeneration. Experiments in animal models have demonstrated the feasibility of organoid-derived photoreceptor transplantation in various recipient contexts. In some cases, vision repair has been shown. However, recipient-donor cell-cell interactions are incompletely understood. This review briefly summarizes these interactions, categorizing them as synaptic structure formation, cellular component transfer, glial activation, immune cell infiltration, and cellular migration. Each of these interactions may affect the survival and functionality of the donor cells and, ultimately, their efficacy as a treatment substrate. Additionally, recipient characteristics, such as the cytoarchitecture of the retina and immune status, may also impact the type and frequency of cell-cell interactions. Despite the procedural challenges associated with culturing human retinal organoids and the technical difficulties in transplanting donor cells into the delicate recipient retina, transplantation of retinal organoid-derived cells is a promising tool for degenerative retinal disease treatment.

Inhibiting NLRP3 Inflammasome Activation to Alleviate Retinal Inflammation and Protect the Optic Nerve of OPTN(E50K)Mice

OPTN (E50K) mutation is one of the significant pathogenic mutations in normal tension glaucoma (NTG). The molecular mechanism of NTG optic nerve injury is complex and diverse; its key mechanism is still unclear. The NLR family pyrin domain containing (NLRP3) inflammasome plays an essential role in the occurrence and development of inflammation. There is no report on whether NLRP3 inflammasome activation plays a crucial role in NTG optic nerve injury. Here, we explored the role of retinal inflammatory cascade reaction triggered by NLRP3 inflammasome activation in OPTN (E50K) mutated NTG optic nerve injury. This research may provide innovative strategies for effectively treating NTG optic nerve injury caused by OPTN (E50K) mutation. The R28 cell was constructed by AAV2 transfection, named GFP-R28, WT-R28, and E50K-R28 groups. Western blot, qPCR, and immunofluorescence were performed to measure the expression levels of the neurotrophic factors, the senescence indicators, the NLRP3-related indicators, the expression of the glial cell markers, and the inflammatory cytokines. Further, observe the changes in the above indicators in the WT-R28 and E50K-R28 groups after treatment with MCC950. Next, we compared the expression of neurotrophic factors and senescence indicators, NLRP3-related indicators, glial cell markers, and inflammatory factors between young and old WT and OPTN (E50K) mice. We examined the visual function of mice on days 1, 4 and 7. Furthermore, we observed the retinal morphology and the expression of neurotrophic factors and senescence indicators, NLRP3-related indicators, glial cell markers, and inflammatory factors between all groups were measured. We found that OPTN (E50K) mutations lead to NLRP3 inflammasome activation. The OPTN (E50K) mutant groups showed an inflammatory cascade, including glial cell activation and release of proinflammatory factors, leading to retinal structural and functional impairment in mice.MCC950 effectively inhibited the activation of the NLRP3 inflammasome and alleviated the retinal inflammatory cascade caused by the OPTN (E50K) mutation, ultimately improving visual function and retinal damage in mice. OPTN (E50K) mutation induces the activation of the NLRP3 inflammasome, which leads to a retinal inflammatory cascade. MCC950 can inhibit the activation of the NLRP3 inflammasome and retinal inflammatory cascade, improving visual function in OPTN (E50K) mutation mice.

Subretinal microglia support donor photoreceptor survival in rd1 mice

PURPOSE

To investigate the potential relationship between subretinal microglia and transplanted donor photoreceptors.

METHODS

Photoreceptor precursors were transplanted into wild-type mice and rd1 mice by trans-scleral injection. Immunohistochemistry was employed to detect microglia and macrophages. PlX5622 feed was used to achieve microglia depletion and microglia repopulation. RNA-seq and qPCR were utilized to evaluate gene expression. Confocal microscopy was used to observe the interaction between microglia and donor photoreceptors.

RESULTS

Donor photoreceptors survived in rd1 mice but not in wild-type mice after trans-scleral injection. The microglial cells closely interacted with donor cells. While donor cells failed to survive in rd1 mice after microglia depletion, they could survive following microglia repopulation. The RNA-seq analysis showed a pro-neurodevelopmental effect of sub-retinal microglia/RPE tissue in rd1 mice.

CONCLUSIONS

Subretinal microglia supported donor photoreceptor survival in rd1 mice.

Exosomes derived from IFNγ-stimulated mesenchymal stem cells protect photoreceptors in RCS rats by restoring immune homeostasis through tsRNAs

BACKGROUND

Retinitis pigmentosa is a neurodegenerative disease with major pathologies of photoreceptor apoptosis and immune imbalance. Mesenchymal stem cells (MSCs) have been approved for clinical application for treating various immune-related or neurodegenerative diseases. The objective of this research was to investigate the mechanisms underlying the safeguarding effects of MSC-derived exosomes in a retinal degenerative disease model.

METHODS

Interferon gamma-stimulated exosomes (IFNγ-Exos) secreted from MSCs were isolated, purified, and injected into the vitreous body of RCS rats on postnatal day (P) 21. Morphological and functional changes in the retina were examined at P28, P35, P42, and P49 in Royal College of Surgeons (RCS) rats. The mechanism was explored using high-throughput sequencing technology and confirmed in vitro.

RESULTS

Treatment with IFNγ-Exo produced better protective effects on photoreceptors and improved visual function in RCS rats. IFNγ-Exo significantly suppressed the activated microglia and inhibited the inflammatory responses in the retina of RCS rats, which was also confirmed in the lipopolysaccharide-activated microglia cell line BV2. Furthermore, through tRNA-derived small RNA (tsRNA) sequencing, we found that IFNγ-Exos from MSCs contained higher levels of Other-1_17-tRNA-Phe-GAA-1-M3, Other-6_23-tRNA-Lys-TTT-3, and TRF-57:75-GLN-CGG-2-m2 than native exosomes, which mainly regulated inflammatory and immune-related pathways, including the mTOR signaling pathway and EGFR tyrosine kinase inhibitor resistance.

CONCLUSIONS

IFNγ stimulation enhanced the neuroprotective effects of MSC-derived exosomes on photoreceptors of the degenerative retina, which may be mediated by immune regulatory tsRNAs acting on microglia. In conclusion, IFNγ-Exo is a promising nanotherapeutic agent for the treatment of retinitis pigmentosa.

Organoids and organoid extracellular vesicles-based disease treatment strategies

Organoids are "mini-organs" that self-organize and differentiate from stem cells under in vitro 3D culture conditions, mimicking the spatial structure and function of tissues in vivo. Extracellular vesicles (EVs) are nanoscale phospholipid bilayer vesicles secreted by living cells, rich in bioactive molecules, with excellent biocompatibility and low immunogenicity. Compared to EVs, organoid-derived EVs (OEVs) exhibit higher yield and enhanced biological functions. Organoids possess stem cell characteristics, and OEVs are capable of delivering active substances, making both highly promising for medical applications. In this review, we provide an overview of the fundamental biological principles of organoids and OEVs, and discuss their current applications in disease treatment. We then focus on the differences between OEVs and traditional EVs. Subsequently, we present methods for the engineering modification of OEVs. Finally, we critically summarize the advantages and challenges of organoids and OEVs. In conclusion, we believe that a deeper understanding of organoids and OEVs will provide innovative solutions to complex diseases.

Human brain organoid: trends, evolution, and remaining challenges

Advanced brain organoids provide promising platforms for deciphering the cellular and molecular processes of human neural development and diseases. Although various studies and reviews have described developments and advancements in brain organoids, few studies have comprehensively summarized and analyzed the global trends in this area of neuroscience. To identify and further facilitate the development of cerebral organoids, we utilized bibliometrics and visualization methods to analyze the global trends and evolution of brain organoids in the last 10 years. First, annual publications, countries/regions, organizations, journals, authors, co-citations, and keywords relating to brain organoids were identified. The hotspots in this field were also systematically identified. Subsequently, current applications for brain organoids in neuroscience, including human neural development, neural disorders, infectious diseases, regenerative medicine, drug discovery, and toxicity assessment studies, are comprehensively discussed. Towards that end, several considerations regarding the current challenges in brain organoid research and future strategies to advance neuroscience will be presented to further promote their application in neurological research.

Organoids: development and applications in disease models, drug discovery, precision medicine, and regenerative medicine

Organoids are miniature, highly accurate representations of organs that capture the structure and unique functions of specific organs. Although the field of organoids has experienced exponential growth, driven by advances in artificial intelligence, gene editing, and bioinstrumentation, a comprehensive and accurate overview of organoid applications remains necessary. This review offers a detailed exploration of the historical origins and characteristics of various organoid types, their applications-including disease modeling, drug toxicity and efficacy assessments, precision medicine, and regenerative medicine-as well as the current challenges and future directions of organoid research. Organoids have proven instrumental in elucidating genetic cell fate in hereditary diseases, infectious diseases, metabolic disorders, and malignancies, as well as in the study of processes such as embryonic development, molecular mechanisms, and host-microbe interactions. Furthermore, the integration of organoid technology with artificial intelligence and microfluidics has significantly advanced large-scale, rapid, and cost-effective drug toxicity and efficacy assessments, thereby propelling progress in precision medicine. Finally, with the advent of high-performance materials, three-dimensional printing technology, and gene editing, organoids are also gaining prominence in the field of regenerative medicine. Our insights and predictions aim to provide valuable guidance to current researchers and to support the continued advancement of this rapidly developing field.

Intraocular Concentration of Stem Cell Factor/c-KIT and Galectin-1 in Retinal Diseases

Purpose

To investigate the intraocular concentration profiles of stem cell factor (SCF)/c-KIT, galectin-1 (GAL-1), and vascular endothelial growth factor (VEGF)-A with regard to retinal disease and treatment response.

Methods

The study group included 13 patients with dry age-related macular degeneration (AMD), 196 with neovascular AMD (nAMD), 21 with diabetic macular edema (DME), 10 with retinal vein occlusion (RVO), and 34 normal subjects with cataracts. Aqueous humor levels of SCF, c-KIT, GAL-1, and VEGF-A were analyzed by immunoassay according to disease group and treatment response.

Results

Increased aqueous levels of SCF, c-KIT, and GAL-1 were observed in eyes with nAMD (2.67 ± 3.66, 296.84 ± 359.56, and 3945.61 ± 5976.2 pg/mL, respectively), DME (1.64 ± 0.89, 238.80 ± 265.54, and 3701.23 ± 4340.54 pg/mL, respectively), and RVO (4.62 ± 8.76, 509.63 ± 647.58, and 9079.60 ± 11909.20 pg/mL, respectively) compared with controls (1.13 ± 0.24, 60.00 ± 0.00, and 613.27 ± 1595.12 pg/mL, respectively). In the eyes of nAMD, the levels of all three cytokines correlated positively with VEGF-A levels. After intravitreal injections of anti-VEGF agents, the levels of GAL-1 and VEGF-A decreased significantly, whereas those of SCF and c-Kit showed no significant change. Eyes of nAMD patients with improved vision after treatment had significantly lower levels of c-KIT, GAL-1, and VEGF-A at baseline.

Conclusions

The intraocular levels of cytokines were significantly elevated in eyes with nAMD, DME, and RVO compared to the controls and they showed different response to anti-VEGF treatment. With this result and their known association with angiogenesis, these cytokines may be potential therapeutic targets for future research.

Towards Stem/Progenitor Cell-Based Therapies for Retinal Degeneration

Retinal degeneration (RD) is a leading cause of blindness worldwide and includes conditions such as retinitis pigmentosa (RP), age-related macular degeneration (AMD), and Stargardt's disease (STGD). These diseases result in the permanent loss of vision due to the progressive and irreversible degeneration of retinal cells, including photoreceptors (PR) and the retinal pigment epithelium (RPE). The adult human retina has limited abilities to regenerate and repair itself, making it challenging to achieve complete self-replenishment and functional repair of retinal cells. Currently, there is no effective clinical treatment for RD. Stem cell therapy, which involves transplanting exogenous stem cells such as retinal progenitor cells (RPCs), embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs), or activating endogenous stem cells like Müller Glia (MG) cells, holds great promise for regenerating and repairing retinal cells in the treatment of RD. Several preclinical and clinical studies have shown the potential of stem cell-based therapies for RD. However, the clinical translation of these therapies for the reconstruction of substantial vision still faces significant challenges. This review provides a comprehensive overview of stem/progenitor cell-based therapy strategies for RD, summarizes recent advances in preclinical studies and clinical trials, and highlights the major challenges in using stem/progenitor cell-based therapies for RD.

Mitochondrial transfer between BMSCs and Müller promotes mitochondrial fusion and suppresses gliosis in degenerative retina

Mitochondrial dysfunction and Müller cells gliosis are significant pathological characteristics of retinal degeneration (RD) and causing blinding. Stem cell therapy is a promising treatment for RD, the recently accepted therapeutic mechanism is cell fusion induced materials transfer. However, whether materials including mitochondrial transfer between grafted stem cells and recipient's cells contribute to suppressing gliosis and mechanism are unclear. In present study, we demonstrated that bone marrow mesenchymal stem cells (BMSCs) transferred mitochondria to Müller cells by cell fusion and tunneling nanotubes. BMSCs-derived mitochondria (BMSCs-mito) were integrated into mitochondrial network of Müller cells, improving mitochondrial function, reducing oxidative stress and gliosis, which protected visual function partially in the degenerative rat retina. RNA sequencing analysis revealed that BMSCs-mito increased mitochondrial DNA (mtDNA) content and facilitated mitochondrial fusion in damaged Müller cells. It suggests that mitochondrial transfer from BMSCs remodels Müller cells metabolism and suppresses gliosis; thus, delaying the degenerative progression of RD.

Small extracellular vesicles of organoid-derived human retinal stem cells remodel Müller cell fate via miRNA: A novel remedy for retinal degeneration

Remodeling retinal Müller glial fate, including gliosis inhibition and pro-reprogramming, represents a crucial avenue for treating degenerative retinal diseases. Stem cell transplantation exerts effects on modulating retinal Müller glial fate. However, the optimized stem cell products and the underlying therapeutic mechanisms need to be investigated. In the present study, we found that retinal progenitor cells from human embryonic stem cell-derived retinal organoids (hERO-RPCs) transferred extracellular vesicles (EVs) into Müller cells following subretinal transplantation into RCS rats. Small EVs from hERO-RPCs (hERO-RPC-sEVs) were collected and were found to delay photoreceptor degeneration and protect retinal function in RCS rats. hERO-RPC-sEVs were taken up by Müller cells both in vivo and in vitro, and inhibited gliosis while promoting early dedifferentiation of Müller cells. We further explored the miRNA profiles of hERO-RPC-sEVs, which suggested a functional signature associated with neuroprotection and development, as well as the regulation of stem cell and glial fate. Mechanistically, hERO-RPC-sEVs might regulate the fate of Müller cells by miRNA-mediated nuclear factor I transcription factors B (NFIB) downregulation. Collectively, our findings offer novel mechanistic insights into stem cell therapy and promote the development of EV-centered therapeutic strategies.

Hyaluronan improves photoreceptor differentiation and maturation in human retinal organoids

Human stem cell-derived organoids enable both disease modeling and serve as a source of cells for transplantation. Human retinal organoids are particularly important as a source of human photoreceptors; however, the long differentiation period required and lack of vascularization in the organoid often results in a necrotic core and death of inner retinal cells before photoreceptors are fully mature. Manipulating the in vitro environment of differentiating retinal organoids through the incorporation of extracellular matrix components could influence retinal development. We investigated the addition of hyaluronan (HA), a component of the interphotoreceptor matrix, as an additive to promote long-term organoid survival and enhance retinal maturation. HA treatment had a significant reduction in the proportion of proliferating (Ki67+) cells and increase in the proportion of photoreceptors (CRX+), suggesting that HA accelerated photoreceptor commitment in vitro. HA significantly upregulated genes specific to photoreceptor maturation and outer segment development. Interestingly, prolonged HA-treatment significantly decreased the length of the brush border layer compared to those in control retinal organoids, where the photoreceptor outer segments reside; however, HA-treated organoids also had more mature outer segments with organized discs structures, as revealed by transmission electron microscopy. The brush border layer length was inversely proportional to the molar mass and viscosity of the hyaluronan added. This is the first study to investigate the role of exogenous HA, viscosity, and polymer molar mass on photoreceptor maturation, emphasizing the importance of material properties on organoid culture. STATEMENT OF SIGNIFICANCE: Retinal organoids are a powerful tool to study retinal development in vitro, though like many other organoid systems, can be highly variable. In this work, Shoichet and colleagues investigated the use of hyaluronan (HA), a native component of the interphotoreceptor matrix, to improve photoreceptor maturation in developing human retinal organoids. HA promoted human photoreceptor differentiation leading to mature outer segments with disc formation and more uniform and healthy retinal organoids. These findings highlight the importance of adding components native to the developing retina to generate more physiologically relevant photoreceptors for cell therapy and in vitro models to drive drug discovery and uncover novel disease mechanisms.

Abnormal α-Synuclein Aggregates Cause Synaptic- and Microcircuit-Specific Deficits in the Retinal Rod Pathway

α-Synuclein (α-Syn) is a key determinator of Parkinson disease (PD) pathology, but synapse and microcircuit pathologies in the retina underlying visual dysfunction are poorly understood. Herein, histochemical and ultrastructural analyses and ophthalmologic measurements in old transgenic M83 PD model (mice aged 16 to 18 months) indicated that abnormal α-Syn aggregation in the outer plexiform layer (OPL) was associated with degeneration in the C-terminal binding protein 2 (CtBP2)+ ribbon synapses of photoreceptor terminals and protein kinase C alpha (PKCα)+ rod bipolar cell terminals, whereas α-Syn aggregates in the inner retina correlated with the reduction and degeneration of tyrosine hydroxylase- and parvalbumin-positive amacrine cells. Phosphorylated Ser129 α-synuclein expression was strikingly restricted in the OPL, with the most severe degenerations in the entire retina, including mitochondrial degeneration and loss of ribbon synapses in 16- to 18-month-old mice. These synapse- and microcircuit-specific deficits of the rod pathway at the CtBP2+ rod terminals and PKCα+ rod bipolar and amacrine cells were associated with attenuated a- and b-wave amplitudes and oscillatory potentials on the electroretinogram. They were also associated with the impairment of visual functions, including reduced contrast sensitivity and impairment of the middle range of spatial frequencies. Collectively, these findings demonstrate that α-Syn aggregates cause the synapse- and microcircuit-specific deficits of the rod pathway and the most severe damage to the OPL, providing the retinal synaptic and microcircuit basis for visual dysfunctions in PD.

Stem cell factor protects against chronic ischemic retinal injury by modulating on neurovascular unit

Retinal ischemia is a significant factor in various vision-threatening diseases, but effective treatments are currently lacking. This study explores the potential of stem cell factor (SCF) in regulating the neurovascular unit as a therapeutic intervention for retinal ischemic diseases. A chronic retinal ischemia model was established in Brown Norway rats using bilateral common carotid artery occlusion (BCCAO). Subsequent SCF treatment resulted in a remarkable recovery of retinal function, as indicated by electroretinogram, light/dark transition test, and optokinetic head tracking test results. Histological examination demonstrated a significant increase in the number of retinal neurons and an overall thickening of the retina. Immunofluorescence confirmed these findings and further demonstrated that SCF treatment regulated retinal remodeling. Notably, SCF treatment ameliorated the disrupted expression of synaptic markers in the control group's BCCAO rats and suppressed the activation of Müller cells and microglia. Retinal whole-mount analysis revealed a significant improvement in the abnormalities in retinal vasculature following SCF treatment. Transcriptome sequencing analysis revealed that SCF-induced transcriptome changes were closely linked to the Wnt7 pathway. Key members of the Wnt7 pathway, exhibited significant upregulation following SCF treatment. These results underscore the protective role of SCF in the neurovascular unit of retinal ischemia rats by modulating the Wnt7 pathway. SCF administration emerges as a promising therapeutic strategy for retinal ischemia-related diseases, offering potential avenues for future clinical interventions.

Transpupillary-Guided Trans-Scleral Transplantation of Subretinal Grafts in a Retinal Degeneration Mouse Model

Transplantation of photoreceptor cells and retinal pigment epithelial (RPE) cells provide a potential therapy for retinal degeneration diseases. Subretinal transplantation of therapeutic donor cells into mouse recipients is challenging due to the limited surgical space allowed by the small volume of the mouse eye. We developed a trans-scleral surgical transplantation platform with direct transpupillary vision guidance to facilitate the subretinal delivery of exogenous cells in mouse recipients. The platform was tested using retinal cell suspensions and three-dimensional retinal sheets collected from rod-rich Rho::EGFP mice and cone-rich OPN1LW-EGFP;NRL-/- mice, respectively. Live/dead assay showed low cell mortality for both forms of donor cells. Retinal grafts were successfully delivered into the subretinal space of a mouse model of retinal degeneration, Rd1/NS, with minimum surgical complications as detected by multimodal confocal scanning laser ophthalmoscope (cSLO) imaging. Two months post-transplantation, histological staining demonstrated evidence of advanced maturation of the retinal grafts into 'adult' rods and cones (by robust Rho::EGFP, S-opsin, and OPN1LW:EGFP expression, respectively) in the subretinal space. Here, we provide a surgical platform that can enable highly accurate subretinal delivery with a low rate of complications in mouse recipients. This technique offers precision and relative ease of skill acquisition. Furthermore, the technique could be used not only for studies of subretinal cell transplantation but also for other intraocular therapeutic studies including gene therapies.

Sstr2 Defines the Cone Differentiation-Competent Late-Stage Retinal Progenitor Cells in the Developing Mouse Retina

Cone cell death is a characteristic shared by various retinal degenerative disorders, such as cone-rod dystrophy, Stargardt disease, achromatopsia, and retinitis pigmentosa. This leads to conditions like color blindness and permanently impaired visual acuity. Stem cell therapy focused on photoreceptor replacement holds promise for addressing these conditions. However, identifying surface markers that aid in enriching retinal progenitor cells (RPCs) capable of differentiating into cones remains a complex task. In this study, we employed single-cell RNA sequencing to scrutinize the transcriptome of developing retinas in C57BL/6J mice. This revealed the distinctive expression of somatostatin receptor 2 (Sstr2), a surface protein, in late-stage RPCs exhibiting the potential for photoreceptor differentiation. In vivo lineage tracing experiments verified that Sstr2+ cells within the late embryonic retina gave rise to cones, amacrine and horizontal cells during the developmental process. Furthermore, Sstr2+ cells that were isolated from the late embryonic mouse retina displayed RPC markers and exhibited the capability to differentiate into cones in vitro. Upon subretinal transplantation into both wild-type and retinal degeneration 10 (rd10) mice, Sstr2+ cells survived and expressed cone-specific markers. This study underscores the ability of Sstr2 to enrich late-stage RPCs primed for cone differentiation to a large extent. It proposes the utility of Sstr2 as a biomarker for RPCs capable of generating cones for transplantation purposes.

Human organoids-on-chips for biomedical research and applications

Human organoids-on-chips (OrgOCs) are the synergism of human organoids (HOs) technology and microfluidic organs-on-chips (OOCs). OOCs can mimic extrinsic characteristics of organs, such as environmental clues of living tissue, while HOs are more amenable to biological analysis and genetic manipulation. By spatial cooperation, OrgOCs served as 3D organotypic living models allowing them to recapitulate critical tissue-specific properties and forecast human responses and outcomes. It represents a giant leap forward from the regular 2D cell monolayers and animal models in the improved human ecological niche modeling. In recent years, OrgOCs have offered potential promises for clinical studies and advanced the preclinical-to-clinical translation in medical and industrial fields. In this review, we highlight the cutting-edge achievements in OrgOCs, introduce the key features of OrgOCs architectures, and share the revolutionary applications in basic biology, disease modeling, preclinical assay and precision medicine. Furthermore, we discuss how to combine a wide range of disciplines with OrgOCs and accelerate translational applications, as well as the challenges and opportunities of OrgOCs in biomedical research and applications.

Extracellular vesicles from organoid-derived human retinal progenitor cells prevent lipid overload-induced retinal pigment epithelium injury by regulating fatty acid metabolism

Retinal degeneration (RD), a group of diseases leading to irreversible vision loss, is characterised by retinal pigment epithelium (RPE) or retinal neuron damage and loss. With fewer risks of immune rejection and tumorigenesis, stem cell-secreted extracellular vesicles (EVs) offer a new cell-free therapeutic paradigm for RD, which remains to be investigated. Human retinal organoid-derived retinal progenitor cells (hERO-RPCs) are an easily accessible and advanced cell source for RD treatment. However, hERO-RPCs-derived EVs require further characterisation. Here, we compared the characteristics of EVs from hERO-RPCs (hRPC-EVs) with those of human embryonic stem cell (hESC)-derived EVs (hESC-EVs) as controls. Based on in-depth proteomic analysis, we revealed remarkable differences between hRPC-EVs and hESC-EVs. A comparison between EVs and their respective cells of origin demonstrated that the protein loading of hRPC-EVs was more selective than that of hESC-EVs. In particular, hESC-EVs were enriched with proteins related to angiogenesis and cell cycle, whereas hRPC-EVs were enriched with proteins associated with immune modulation and retinal development. More importantly, compared with that of hESC-EVs, hRPC-EVs exhibited a lower correlation with cell proliferation and a unique capacity to regulate lipid metabolism. It was further confirmed that hRPC-EVs potentially eliminated lipid deposits, inhibited lipotoxicity and oxidative stress, and enhanced phagocytosis and survival of oleic acid-treated ARPE-19 cells. Mechanistically, hRPC-EVs are integrated into the mitochondrial network of oleic acid-treated ARPE-19 cells, and increased the level of mitochondrial fatty acid β-oxidation-related proteins. Thus, organoid-derived hRPC-EVs represent a promising source of cell-free therapy for RD, especially for blinding diseases related to abnormal lipid metabolism in RPE cells.

Human Stem Cells for Ophthalmology: Recent Advances in Diagnostic Image Analysis and Computational Modelling

Purpose of Review

To explore the advances and future research directions in image analysis and computational modelling of human stem cells (hSCs) for ophthalmological applications.

Recent Findings

hSCs hold great potential in ocular regenerative medicine due to their application in cell-based therapies and in disease modelling and drug discovery using state-of-the-art 2D and 3D organoid models. However, a deeper characterisation of their complex, multi-scale properties is required to optimise their translation to clinical practice. Image analysis combined with computational modelling is a powerful tool to explore mechanisms of hSC behaviour and aid clinical diagnosis and therapy.

Summary

Many computational models draw on a variety of techniques, often blending continuum and discrete approaches, and have been used to describe cell differentiation and self-organisation. Machine learning tools are having a significant impact in model development and improving image classification processes for clinical diagnosis and treatment and will be the focus of much future research.

Organoids transplantation attenuates intestinal ischemia/reperfusion injury in mice through L-Malic acid-mediated M2 macrophage polarization

Intestinal organoid transplantation is a promising therapy for the treatment of mucosal injury. However, how the transplanted organoids regulate the immune microenvironment of recipient mice and their role in treating intestinal ischemia-reperfusion (I/R) injury remains unclear. Here, we establish a method for transplanting intestinal organoids into intestinal I/R mice. We find that transplantation improve mouse survival, promote self-renewal of intestinal stem cells and regulate the immune microenvironment after intestinal I/R, depending on the enhanced ability of macrophages polarized to an anti-inflammatory M2 phenotype. Specifically, we report that L-Malic acid (MA) is highly expressed and enriched in the organoids-derived conditioned medium and cecal contents of transplanted mice, demonstrating that organoids secrete MA during engraftment. Both in vivo and in vitro experiments demonstrate that MA induces M2 macrophage polarization and restores interleukin-10 levels in a SOCS2-dependent manner. This study provides a therapeutic strategy for intestinal I/R injury.

Influence of hypoxia on retinal progenitor and ganglion cells in human induced pluripotent stem cell-derived retinal organoids

AIM

To observe the effect of low oxygen concentration on the neural retina in human induced pluripotent stem cell (hiPSC)-derived retinal organoids (ROs).

METHODS

The hiPSC and a three-dimensional culture method were used for the experiments. Generated embryoid bodies (EBs) were randomly and equally divided into hypoxic and normoxic groups. Photographs of the EBs were taken on days 38, 45, and 52, and the corresponding volume of EBs was calculated. Simultaneously, samples were collected at these three timepoints, followed by fixation, sectioning, and immunofluorescence.

RESULTS

The proportion of Ki67-positive proliferating cells increased steadily on day 38; this proliferation-promoting effect tended to increase tissue density rather than tissue volume. On days 45 and 52, the two groups had relatively similar ratios of Ki67-positive cells. Further immunofluorescence analysis showed that the ratio of SOX2-positive cells significantly increased within the neural retina on day 52 (P<0.05). In contrast, the percentage of PAX6- and CHX10-positive cells significantly decreased following hypoxia treatment at all three timepoints (P<0.01), except for CHX10 at day 45 (P>0.05). Moreover, the proportion of PAX6-/TUJ1+ cells within the neural retinas increased considerably (P<0.01, <0.05, <0.05 respectively).

CONCLUSION

Low oxygen promotes stemness and proliferation of neural retinas, suggesting that hypoxic conditions can enlarge the retinal progenitor cell pool in hiPSC-derived ROs.

GMP-grade human neural progenitors delivered subretinally protect vision in rat model of retinal degeneration and survive in minipigs

BACKGROUND

Stem cell products are increasingly entering early stage clinical trials for treating retinal degeneration. The field is learning from experience about comparability of cells proposed for preclinical and clinical use. Without this, preclinical data supporting translation to a clinical study might not adequately reflect the performance of subsequent clinical-grade cells in patients.

METHODS

Research-grade human neural progenitor cells (hNPC) and clinical-grade hNPC (termed CNS10-NPC) were injected into the subretinal space of the Royal College of Surgeons (RCS) rat, a rodent model of retinal degeneration such as retinitis pigmentosa. An investigational new drug (IND)-enabling study with CNS10-NPC was performed in the same rodent model. Finally, surgical methodology for subretinal cell delivery in the clinic was optimized in a large animal model with Yucatan minipigs.

RESULTS

Both research-grade hNPC and clinical-grade hNPC can survive and provide functional and morphological protection in a dose-dependent fashion in RCS rats and the optimal cell dose was defined and used in IND-enabling studies. Grafted CNS10-NPC migrated from the injection site without differentiation into retinal cell phenotypes. Additionally, CNS10-NPC showed long-term survival, safety and efficacy in a good laboratory practice (GLP) toxicity and tumorigenicity study, with no observed cell overgrowth even at the maximum deliverable dose. Finally, using a large animal model with the Yucatan minipig, which has an eye size comparable to the human, we optimized the surgical methodology for subretinal cell delivery in the clinic.

CONCLUSIONS

These extensive studies supported an approved IND and the translation of CNS10-NPC to an ongoing Phase 1/2a clinical trial (NCT04284293) for the treatment of retinitis pigmentosa.

MMP9-Responsive Graphene Oxide Quantum Dot-Based Nano-in-Micro Drug Delivery System for Combinatorial Therapy of Choroidal Neovascularization

Age-related macular degeneration (AMD), especially wet AMD with choroidal neovascularization (CNV), commonly causes blindness in older patients and disruption of the choroid followed by second-wave injuries, including chronic inflammation, oxidative stress, and excessive matrix metalloproteinase 9 (MMP9) expression. Increased macrophage infiltrate in parallel with microglial activation and MMP9 overexpression on CNV lesions is shown to contribute to the inflammatory process and then enhance pathological ocular angiogenesis. Graphene oxide quantum dots (GOQDs), as natural antioxidants, exert anti-inflammatory effects and minocycline is a specific macrophage/microglial inhibitor that can suppress both macrophage/microglial activation and MMP9 activity. Herein, an MMP9-responsive GOQD-based minocycline-loaded nano-in-micro drug delivery system (C18PGM) is developed by chemically bonding GOQDs to an octadecyl-modified peptide sequence (C18-GVFHQTVS, C18P) that can be specifically cleaved by MMP9. Using a laser-induced CNV mouse model, the prepared C18PGM shows significant MMP9 inhibitory activity and anti-inflammatory action followed by antiangiogenic effects. Moreover, C18PGM combined with antivascular endothelial growth factor antibody bevacizumab markedly increases the antiangiogenesis effect by interfering with the "inflammation-MMP9-angiogenesis" cascade. The prepared C18PGM shows a good safety profile and no obvious ophthalmic or systemic side effects. The results taken together suggest that C18PGM is an effective and novel strategy for combinatorial therapy of CNV.

A controllable perfusion microfluidic chip for facilitating the development of retinal ganglion cells in human retinal organoids

Retinal organoids (ROs) derived from human pluripotent stem cells (hPSCs) have become a promising model in vitro to recapitulate human retinal development, which can be further employed to explore the mechanisms of retinal diseases. However, the current culture systems for ROs lack physiologically relevant microenvironments, such as controllable mechano-physiological cues and dynamic feedback between cells and the extracellular matrix (ECM), which limits the accurate control of RO development. Therefore, we designed a controllable perfusion microfluidic chip (CPMC) with the advantages of precisely controlling fluidic shear stress (FSS) and oxygen concentration distribution in a human embryonic stem cell (hESC)-derived RO culture system. We found that ROs cultured under this system allow for expanding the retinal progenitor cell (RPC) pool, orchestrating the retinal ganglion cell (RGC) specification, and axon growth without disturbing the spatial and temporal patterning events at the early stage of RO development. Furthermore, RNA sequencing data revealed that the activation of voltage-gated ion channels and the increased expression of ECM components synergistically improve the growth of ROs and facilitate the differentiation of RGCs. This study elaborates on the advantages of the designed CPMC to promote RO growth and provide a controllable and reliable platform for the efficient maturity of RGCs in the ROs, promising applications in modeling RGC-related disorders, drug screening, and cell transplantation.

The potential for mitochondrial therapeutics in the treatment of primary open-angle glaucoma: a review

Glaucoma, an age-related neurodegenerative disease, is characterized by the death of retinal ganglion cells (RGCs) and the corresponding loss of visual fields. This disease is the leading cause of irreversible blindness worldwide, making early diagnosis and effective treatment paramount. The pathophysiology of primary open-angle glaucoma (POAG), the most common form of the disease, remains poorly understood. Current available treatments, which target elevated intraocular pressure (IOP), are not effective at slowing disease progression in approximately 30% of patients. There is a great need to identify and study treatment options that target other disease mechanisms and aid in neuroprotection for POAG. Increasingly, the role of mitochondrial injury in the development of POAG has become an emphasized area of research interest. Disruption in the function of mitochondria has been linked to problems with neurodevelopment and systemic diseases. Recent studies have shown an association between RGC death and damage to the cells' mitochondria. In particular, oxidative stress and disrupted oxidative phosphorylation dynamics have been linked to increased susceptibility of RGC mitochondria to secondary mechanical injury. Several mitochondria-targeted treatments for POAG have been suggested, including physical exercise, diet and nutrition, antioxidant supplementation, stem cell therapy, hypoxia exposure, gene therapy, mitochondrial transplantation, and light therapy. Studies have shown that mitochondrial therapeutics may have the potential to slow the progression of POAG by protecting against mitochondrial decline associated with age, genetic susceptibility, and other pathology. Further, these therapeutics may potentially target already present neuronal damage and symptom manifestations. In this review, the authors outline potential mitochondria-targeted treatment strategies and discuss their utility for use in POAG.

Microneedle/CD-MOF-mediated transdural controlled release of methylprednisolone sodium succinate after spinal cord injury

A new method of transdural delivering drugs to the spinal cord has been developed, involving the use of microneedles (MNs) and a β-cyclodextrin metal-organic framework (CD-MOF). This epidural microneedle array, dubbed MNs@CD-MOF@MPSS, can be utilized to deliver methylprednisolone sodium succinate (MPSS) to the site of spinal cord injury (SCI) in a controlled manner. MNs allows to generate micropores in the dura for direct drug delivery to the spinal cord, overcoming tissue barriers and targeting damaged regions. Additionally, the CD-MOF provides a secondary extended release after separating from the MNs. In in vitro study, inward MNs increased cellular absorption of MPSS and then reduced LPS-induced M1 polarization of microglia. And animal studies have shown that this method of drug delivery results in improved BMS scores and a reduction in M1 phenotype microphage and glial scar formation. Furthermore, the downregulation of the NLRP3-positive inflammasome and related pro-inflammatory cytokines was observed. In conclusion, this new drug platform has potential for clinical application in spinal cord diseases and is a valuable composite for minimally transdural controlled drug delivery. STATEMENT OF SIGNIFICANCE: This research presents a new epidural microneedle patch made up of microneedles (MNs) and a β-cyclodextrin metal-organic framework (CD-MOF). The epidural microneedle patch boasts high drug loading capacity, the ability to penetrate the dura, and controlled release. When loaded with methylprednisolone sodium succinate (MPSS), it effectively reduces inflammation and improves neurological function after spinal cord injury. Therefore, it is a novel and promising drug platform for the treatment of spinal cord diseases in a clinical setting.

Application of Human Stem Cell Derived Retinal Organoids in the Exploration of the Mechanisms of Early Retinal Development

The intricate neural circuit of retina extracts salient features of the natural world and forms bioelectric impulse as the origin of vision. The early development of retina is a highly complex and coordinated process in morphogenesis and neurogenesis. Increasing evidence indicates that stem cells derived human retinal organoids (hROs) in vitro faithfully recapitulates the embryonic developmental process of human retina no matter in the transcriptome, cellular biology and histomorphology. The emergence of hROs greatly deepens on the understanding of early development of human retina. Here, we reviewed the events of early retinal development both in animal embryos and hROs studies, which mainly comprises the formation of optic vesicle and optic cup shape, differentiation of retinal ganglion cells (RGCs), photoreceptor cells (PRs) and its supportive retinal pigment epithelium cells (RPE). We also discussed the classic and frontier molecular pathways up to date to decipher the underlying mechanisms of early development of human retina and hROs. Finally, we summarized the application prospect, challenges and cutting-edge techniques of hROs for uncovering the principles and mechanisms of retinal development and related developmental disorder. hROs is a priori selection for studying human retinal development and function and may be a fundamental tool for unlocking the unknown insight into retinal development and disease.

Single-cell transcriptome analysis of xenotransplanted human retinal organoids defines two migratory cell populations of nonretinal origin

Human retinal organoid transplantation could potentially be a treatment for degenerative retinal diseases. How the recipient retina regulates the survival, maturation, and proliferation of transplanted organoid cells is unknown. We transplanted human retinal organoid-derived cells into photoreceptor-deficient mice and conducted histology and single-cell RNA sequencing alongside time-matched cultured retinal organoids. Unexpectedly, we observed human cells that migrated into all recipient retinal layers and traveled long distances. Using an unbiased approach, we identified these cells as astrocytes and brain/spinal cord-like neural precursors that were absent or rare in stage-matched cultured organoids. In contrast, retinal progenitor-derived rods and cones remained in the subretinal space, maturing more rapidly than those in the cultured controls. These data suggest that recipient microenvironment promotes the maturation of transplanted photoreceptors while inducing or facilitating the survival of migratory cell populations that are not normally derived from retinal progenitors. These findings have important implications for potential cell-based treatments of retinal diseases.

Deficient deposition of new myelin impairs adult optic nerve function in a murine model of diabetes

Visual impairment in diabetes is a growing public health concern. Apart from the well-defined diabetic retinopathy, disturbed optic nerve function, which is dependent on the myelin sheath, has recently been recognized as an early feature of visual impairment in diabetes. However, the underlying cellular mechanisms remain unclear. Using a streptozotocin-induced diabetic mouse model, we observed a myelin deficiency along with a disturbed composition of oligodendroglial lineage cells in diabetic optic nerve. We found that new myelin deposition, a continuous process that lasts throughout adulthood, was diminished during pathogenesis. Genetically dampening newly generated myelin by conditionally deleting olig2 in oligodendrocyte precursor cells within this short time window extensively delayed the signal transmission of the adult optic nerve. In addition, clemastine, an antimuscarinic compound that enhances myelination, significantly restored oligodendroglia, and promoted the functional recovery of the optic nerve in diabetic mice. Together, our results point to the role of new myelin deposition in optic neuropathy under diabetic insult and provide a promising therapeutic target for restoring visual function.

Exosome-mediated inhibition of microRNA-449a promotes the amplification of mouse retinal progenitor cells and enhances their transplantation in retinal degeneration mouse models

Inherited and age-related retinal degenerations are the commonest causes of blindness without effective treatments. Retinal progenitor cells (RPCs), which have the multipotency to differentiate into various retinal cell types, are regarded as a promising source of cell transplantation therapy for retinal degenerative diseases. However, the self-limited expansion of RPCs causes difficulty in cell source supply and restrict its clinical treatment. In this work, we found that inhibition of microRNA-449a (miR-449a) in RPCs can promote proliferation and inhibit apoptosis of RPCs, partially through upregulating Notch signaling. Further optimization of transduction miR-449a inhibitor into RPCs by endothelial cell-derived exosomes can promote the survival of RPCs transplanted in vivo and reduce cell apoptosis in retinal degeneration mouse models. In summary, these studies have shown that exosome-miR-449a inhibitor can effectively promote the expansion of RPCs in vitro and enhance transplanted RPCs survival in vivo, which might provide a novel intervention strategy for retinal degenerations in the future.

Repopulated retinal microglia promote Müller glia reprogramming and preserve visual function in retinal degenerative mice

Rationale: Müller glia (MG) play a key role in maintaining homeostasis of the retinal microenvironment. In zebrafish, MG reprogram into retinal progenitors and repair the injured retina, while this MG regenerative capability is suppressed in mammals. It has been revealed that microglia in zebrafish contribute to MG reprogramming, whereas those in mammals are over-activated during retinal injury or degeneration, causing chronic inflammation, acceleration of photoreceptor apoptosis, and gliosis of MG. Therefore, how to modulate the phenotype of microglia to enhance MG reprogramming rather than gliosis is critical. Methods: PLX3397, a colony-stimulating factor 1 receptor inhibitor, was applied to deplete microglia in the retinas of retinal degeneration 10 (rd10) mice, and withdrawal of PLX3397 was used to induce the repopulated microglia (Rep-MiG). The protective roles of the Rep-MiG on the degenerative retina were assessed using a light/dark transition test, and scotopic electroretinogram recordings. Immunofluorescence, western blot, transcriptomic sequencing, and bioinformatics analysis were performed to investigate the effects and mechanisms of microglia on MG reprogramming. Results: Following PLX3397 withdrawal, Rep-MiG replenished the entire retina with a ramified morphology and significantly improved the retinal outer nuclear layer structure, the electroretinography response, and the visual behavior of rd10 mice. Coincidentally, MG were activated, de-differentiated, and showed properties of retina progenitors in a spatial correlation with Rep-MiG. Morphological and transcriptomic analyses revealed Rep-MiG significantly enhanced protease inhibitor activity and suppressed extracellular matrix (ECM) levels during retinal degeneration. Conclusions: It suggested that Rep-MiG with the homeostasis characteristic stimulated the progenitor cell-like properties of MG, probably through regulating ECM remodeling, which protected photoreceptors and improved visual function of rd10 mice. It might be a potential protocol to reprogram MG and delay mammal retinal degeneration.

Human Retinal Organoids in Therapeutic Discovery: A Review of Applications

Human embryonic stem cells (hESCs)- and induced pluripotent stem cells (hiPSCs)-derived retinal organoids (ROs) are three-dimensional laminar structures that recapitulate the developmental trajectory of the human retina. The ROs provide a fascinating tool for basic science research, eye disease modeling, treatment development, and biobanking for tissue/cell replacement. Here we review the previous studies that paved the way for RO technology, the two most widely accepted, standardized protocols to generate ROs, and the utilization of ROs in medical discovery. This review is conducted from the perspective of basic science research, transplantation for regenerative medicine, disease modeling, and therapeutic development for drug screening and gene therapy. ROs have opened avenues for new technologies such as assembloids, coculture with other organoids, vasculature or immune cells, microfluidic devices (organ-on-chip), extracellular vesicles for drug delivery, biomaterial engineering, advanced imaging techniques, and artificial intelligence (AI). Nevertheless, some shortcomings of ROs currently limit their translation for medical applications and pose a challenge for future research. Despite these limitations, ROs are a powerful tool for functional studies and therapeutic strategies for retinal diseases.

Retinogenesis in a Dish: Bibliometric Analysis and Visualization of Retinal Organoids From 2011 to 2022

Retinal organoid (RO) is the three-dimensional (3D) retinal culture derived from pluripotent or embryonic stem cells which recapitulates organ functions, which was a revolutionary milestone in stem cell technology. The purpose of this study is to explore the hotspots and future directions on ROs, as well as to better understand the fields of greatest research opportunities. Eligible publications related to RO from 2011 to 2022 were acquired from the Web of Science (WoS) Core Collection database. Bibliometric analysis was performed by using software including VOSviewer, CiteSpace, and ArcGIS. A total of 520 articles were included, and the number of annual publications showed a rapid increase with an average rate of 40.86%. The United States published the most articles (241/520, 46.35%) with highest total citation frequencies (5,344). University College London (UK) contributed the largest publication output (40/520, 7.69%) and received highest total citation frequencies. Investigative Ophthalmology & Visual Science was the most productive journal with 129 articles. Majlinda Lako contributed the most research with 32 articles, while Olivier Goureau has the strongest collaboration work. Research could be subdivided into four keyword clusters: "culture and differentiation," "morphogenesis and modeling," "gene therapy," and "transplantation and visual restoration," and evolution of keywords was identified. Last decade has witnessed the huge progress in the field of RO, which is a young and promising research area with extensive and in-depth studies. More attention should be paid to RO-related models and therapies based on specific retinal diseases, especially inherited retinopathies.

A possible connection between reactive oxygen species and the unfolded protein response in lens development: From insight to foresight

The lens is a relatively special and simple organ. It has become an ideal model to study the common developmental characteristics among different organic systems. Lens development is a complex process influenced by numerous factors, including signals from the intracellular and extracellular environment. Reactive oxygen species (ROS) are a group of highly reactive and oxygen-containing molecules that can cause endoplasmic reticulum stress in lens cells. As an adaptive response to ER stress, lens cells initiate the unfolded protein response (UPR) to maintain normal protein synthesis by selectively increasing/decreasing protein synthesis and increasing the degradation of misfolded proteins. Generally, the UPR signaling pathways have been well characterized in the context of many pathological conditions. However, recent studies have also confirmed that all three UPR signaling pathways participate in a variety of developmental processes, including those of the lens. In this review, we first briefly summarize the three stages of lens development and present the basic profiles of ROS and the UPR. We then discuss the interconnections between lens development and these two mechanisms. Additionally, the potential adoption of human pluripotent stem-cell-based lentoids in lens development research is proposed to provide a novel perspective on future developmental studies.

A chiral microenvironment promotes retinal progenitor cell proliferation by activating the Akt and ERK pathways

Retinal progenitor cell (RPC) transplantation has been proposed as a potential strategy for the treatment of retinal degeneration, which is a leading cause of vision loss. However, a major obstacle is the poor proliferation of RPCs. Accumulating evidence suggests that the chiral features of the extracellular microenvironment are closely related to cell proliferation. Inspired by this, L/D-phenylalanine-derived molecules (LP and DP) are employed to construct a biomimetic chiral microenvironment for enhancing RPC proliferation. LP and DP self-assemble into left-handed and right-handed helical fibrous networks, respectively. It is found that DP nanofibrous films show an excellent ability in promoting RPC proliferation via the activation of the Akt and extracellular signal-regulated kinase (ERK) pathways. In addition, both LP and DP nanofibrous films have the advantage of attenuating inflammation, and LP films can maintain the stem potential of RPCs. Thus, the promotion of RPC proliferation using a bioinspired chiral fibrous microenvironment is a promising strategy for RPC-based therapies for retinal degeneration.

Fullerenol protects cornea from ultraviolet B exposure

The eyes are highly susceptible to the oxidative stress induced by ultraviolet B (UVB, wavelength between 280 ∼ 320 nm), which could cause severe damage to the cornea. Fullerenols are effective antioxidants to alleviate UVB-induced injury, while their application for the eyes is still rare. In present study, we investigated the protective performance and mechanism of fullerenols on cornea under UVB radiation in vivo and in vitro. The synthesized fullerenols exhibited broad-spectrum free radical scavenging properties (applicable to both reactive oxygen species (ROS) and reactive nitrogen species (RNS)) and photo-stability. When compared with another widely used antioxidant glutathione (GSH), the administration of fullerenols markedly decreased the injured area, corneal edema, cell death, and increased the cell proliferation in UVB-induced rat cornea. The effects of fullerenols were confirmed in UVB-exposed human corneal epithelial cells (hCECs), where elevated cell viability and proliferation, decreased oxidative free radical production, repaired mitochondrial dysfunction and DNA lesions were observed. RNA sequencing (RNA-Seq) analysis demonstrated that fullerenol alleviated UVB-induced corneal injury through down-regulation of oxidative stress-related genes and up-regulation of proliferation-associated genes. Our results demonstrate the suitability of fullerenols as a potential exogenous treatment in ameliorating UVB-induced cornea damage.

The Prospects for Retinal Organoids in Treatment of Retinal Diseases

Retinal degeneration (RD) is a significant cause of incurable blindness worldwide. Photoreceptors and retinal pigmented epithelium are irreversibly damaged in advanced RD. Functional replacement of photoreceptors and/or retinal pigmented epithelium cells is a promising approach to restoring vision. This paper reviews the current status and explores future prospects of the transplantation therapy provided by pluripotent stem cell-derived retinal organoids (ROs). This review summarizes the status of rodent RD disease models and discusses RO culture and analytical tools to evaluate RO quality and function. Finally, we review and discuss the studies in which RO-derived cells or sheets were transplanted. In conclusion, methods to derive ROs from pluripotent stem cells have significantly improved and become more efficient in recent years. Meanwhile, more novel technologies are applied to characterize and validate RO quality. However, opportunity remains to optimize tissue differentiation protocols and achieve better RO reproducibility. In order to screen high-quality ROs for downstream applications, approaches such as noninvasive and label-free imaging and electrophysiological functional testing are promising and worth further investigation. Lastly, transplanted RO-derived tissues have allowed improvements in visual function in several RD models, showing promises for clinical applications in the future.

Complement C3 deficiency alleviates alkylation-induced retinal degeneration in mice

BACKGROUND

It has been found that the extensive use of anticancer drugs containing DNA-alkylating agents not only target cancer cells but also cause retinal inflammation through toxic intermediates. Complement C3 (C3) is a core component of the complement activation pathway, and dysregulation of the complement pathway is involved in several retinal degenerative diseases. However, whether C3 plays a critical role in alkylation-induced retinal degeneration is unclear.

METHODS

Following treatment with the alkylating agent methyl methane sulfonate (MMS), the C3 mRNA and protein level was measured, DNA damage and photoreceptor cell death were assessed in both wild-type (WT) C57BL/6J and C3 knockout (KO) mice.

RESULTS

We determined that complement pathway is activated following MMS treatment, and C3 knockout (KO) increased the rate of photoreceptor cell survival and preserved visual function. The mRNA levels of nuclear erythroid-related factor 2 (Nrf2) and related genes were higher after MMS application in C3 KO mice.

CONCLUSION

In summary, our study found that C3 KO promotes photoreceptor cell survival and activates the Nrf2 signaling pathway in the context of alkylation-induced retinal degeneration.