Search Results (123)

Corneal blindness remains a major cause of visual impairment worldwide and may result from trauma, infectious keratitis, degenerative disorders, endothelial dysfunction, and limbal stem cell deficiency (LSCD). Although corneal transplantation remains the standard treatment for advanced disease, its effectiveness is limited by donor tissue shortage, immune-mediated rejection, postoperative complications, and progressive graft failure. These limitations have accelerated interest in regenerative approaches aimed at restoring native corneal structure and function. Induced pluripotent stem cells (iPSCs) have emerged as a promising platform for corneal regeneration because of their pluripotency, self-renewal capacity, and potential for autologous or immune-compatible therapy. Recent advances in differentiation protocols have enabled the generation of corneal epithelial-like cells, stromal keratocyte-like cells, and corneal endothelial-like cells from iPSCs. Preclinical studies have demonstrated encouraging improvements in corneal transparency, epithelial restoration, fibrosis reduction, and endothelial function, while early clinical investigations, particularly in LSCD, have reported favorable short-term safety and functional outcomes. However, major translational barriers remain, including tumorigenicity, immunogenicity, genomic instability, manufacturing complexity, scalability, and long-term safety concerns. Stromal regeneration also remains comparatively underdeveloped relative to epithelial and endothelial applications. This review summarizes current differentiation strategies, biological mechanisms, preclinical and early clinical evidence, and the principal translational challenges associated with iPSC-based corneal regeneration. Overall, iPSC-derived corneal therapies demonstrate considerable regenerative potential, although further standardization, long-term safety evaluation, and multicenter clinical validation remain necessary before widespread clinical adoption. Full article

DNA oxidation damage and its repair are essential for maintaining genomic integrity in the human limbal epithelium, which harbors corneal epithelial stem cells. This study investigated the distribution of the DNA base oxidation 8-oxoguanine (8-oxoG) and the base excision repair (BER) enzymes 8-oxoguanine DNA glycosylase (OGG1) and apurinic/apyrimidinic endonuclease 1 (APE1) in non-cultured and eye-bank organ-cultured human limbal epithelia. Immunohistochemistry was used to assess the localization and staining intensity of 8-oxoG, OGG1, and APE1, evaluated semi-quantitatively and by image analysis. In situ hybridization was performed to detect the distribution of OGG1 and APE1 gene expression in organ-cultured tissue. In non-cultured limbal epithelia, nuclear 8-oxoG staining was more frequently observed in superficial epithelial layers, whereas nuclear OGG1 and APE1 staining predominated in basal layers. In organ-cultured epithelia, a higher proportion of superficial nuclei exhibited 8-oxoG staining, while the basal predominance of OGG1 was reduced and that of APE1 was preserved. Transcripts of OGG1 and APE1 were detected in basal- as well as in suprabasal layers of organ-cultured epithelia. These findings demonstrate the presence of DNA base oxidation and BER-related enzymes in basal and suprabasal human limbal epithelial cells during storage of corneal tissue under commonly used eye-bank organ-cultured conditions prior to transplantation. Full article

Nervous system and corneal disorders are major causes of permanent disability worldwide, largely due to the limited regenerative capacity of ectoderm-derived tissues. Therefore, the development of accessible and ethically acceptable cell-based therapies promoting the repair and regeneration of these tissues is of considerable translational importance. In this study, we aimed to comparatively evaluate the ectodermal differentiation potential of human adipose-derived stem cells (ADSCs) and human amniotic epithelial cells (hAECs) in vitro, with hAECs serving as a reference cell population with established ectodermal plasticity. Primary ADSCs and hAECs were characterized phenotypically using flow cytometry and functional differentiation assays. Cells were subjected to a directed ectodermal differentiation protocol and assessed via morphological analysis, immunostaining for ectoderm-associated proteins, and RT-qPCR analysis of lineage-specific genes. ADSCs exhibited morphological changes following differentiation, including a more epithelial-like phenotype and an increased nucleus-to-cytoplasm ratio. Immunostaining revealed the induction of nestin and OTX2 expression after differentiation, which was particularly pronounced in ADSCs. Gene expression analysis demonstrated statistically significant upregulation of the ectoderm-related genes EN2, SOX1, and PAX6 exclusively in hAECs. Results suggest that in ADSCs the differentiation process was only partially activated. In conclusion, our findings further support the suitability of hAECs as a reference cell line for studies investigating ectodermal differentiation protocols, while also demonstrating that ADSCs exhibit a limited but detectable capacity for acquiring ectoderm-specific characteristics under defined in vitro culture conditions. Full article

Ocular surface inflammation is a major disruptor of corneal epithelial homeostasis and a key driver of limbal stem cell deficiency (LSCD). Limbal stem cells (LSCs), residing within the specialized limbal niche, maintain corneal transparency through continuous epithelial renewal and by preventing conjunctival encroachment onto the corneal surface. Chronic or severe inflammatory insults—stemming from systemic autoimmune disorders, ocular surface diseases, infections, trauma, or environmental stressors—can damage both LSCs and their microenvironment, ultimately leading to limbal insufficiency. This review synthesizes current insights into the mechanisms by which inflammation impairs LSC survival, including cytokine-mediated cytotoxicity, oxidative stress, immune cell infiltration, and disruption of essential signaling pathways such as Wnt, Notch, and BMP. The distinction between LSC depletion and LSC dysfunction is highlighted, as residual stem cells may persist even in clinically advanced disease and can regenerate the corneal surface once the inflammatory milieu is corrected. Clinical manifestations, staging systems, and diagnostic markers—including p63α, ABCG2, and additional emerging molecular indicators—are summarized to support accurate assessment of LSCD severity. Current therapeutic strategies, ranging from anti-inflammatory medical management to surgical approaches such as SLET, CLET, and allogeneic transplantation, are reviewed alongside evolving regenerative and cell-based therapies. By integrating mechanistic understanding with clinical implications, this review underscores the critical interplay between inflammation and limbal niche failure and emphasizes the importance of early recognition and targeted intervention to preserve or restore LSC function. Full article

Purpose: Preclinical studies report low-intensity ultraviolet C (UVC) light to be safe and effective in treating murine bacterial keratitis, however, limbal impacts of UVC have yet to be investigated directly. This study evaluated the depth and density of UVC-induced DNA damage in the porcine and human limbus following UVC exposures of varying supratherapeutic dose. Methods: The corneoscleral junction (limbus) of full-thickness porcine corneas was exposed to supratherapeutic doses of UVC light (265 nm, 1.93 mW/cm²) for 5, 10, 15, 30, or 60 min (exposure groups) or remained unexposed for the same durations (control groups), with a sample size of 6 per group. In parallel, human corneal tissue was exposed to UVC for 1 or 5 min and processed identically. Following exposure, all tissues were frozen, dissected, and analysed using immunohistochemistry to detect cyclobutane pyrimidine dimers (CPDs) as markers of DNA damage. CPD distribution, depth, and density were subsequently evaluated. Results: CPDs were localised predominantly in the superficial corneal epithelial layers, irrespective of the UVC dose. The mean ± SD thickness of the corneal epithelium in the UVC-exposed groups was 38.9 ± 18.9 µm, and the average depth of CPD formation was 13.3 ± 8.43 µm. The proportions of cells affected by CPDs within the corneal epithelium (mean ± SD) were 47.8 ± 25.6%, 58.5 ± 16.2%, 39.9 ± 26.4%, 41.3 ± 27.3%, and 38.9 ± 28.3% for exposure durations of 5, 10, 15, 30, and 60 min, respectively (p > 0.05). Human cornea showed similarly limited penetration, with no difference in CPD proportions between the 1 and 5 min UVC exposures (p = 0.70). Conclusions: UVC-induced DNA damage in both species was confined to the superficial cellular layers of the cornea, with no detectable damage observed in deeper tissues, including those where limbal stem cells reside, even after supratherapeutic doses of up to one hour of exposure. Full article

Limbal stem cell (LSC) transplantation is an important treatment for limbal stem cell deficiency (LSCD), but low efficacy in maintaining LSC stemness during in vitro expansion greatly affects its wider application. The primary contributing factors include a low proportion of stem cells and the lack of a stable, supportive microenvironment over prolonged culture. Rabbit corneal tissues preserved under deep cryogenic conditions for more than six months retain viable limbal stem cells (LSCs), and primary LSCs isolated from these tissues exhibit robust stem cell characteristics. It is noteworthy that the NLRP3/Caspase-1/IL-1β signaling axis was activated in corneal epithelial cells, and outer limbal layers preserved for one or two years. Based on these findings, a combined strategy integrating deep cryopreservation with IL-1β induction was established for the processing of limbal tissues. The combined cryogenic and IL-1β preconditioning yielded primary LSCs with maintained p63⁺ cell proportions, a reduction in K3⁺ differentiated cells from approximately 80% to 60%, and a 6.25-fold increase in colony-forming efficiency. In addition, an increased proportion of cells in the G2/M phase and enhanced proliferative capacity were observed. The enriched LSC population also exhibited improved stratified epithelial reconstruction potential. These findings identify an effective strategy for preserving and enriching LSCs from limbal tissue, providing a practical and efficient approach for LSC preparation prior to transplantation. Further in vivo studies will be important to validate the functional performance of these cells in ocular surface reconstruction. Full article

Background: Corneal organoids derived from pluripotent stem cells have emerged as powerful tools for studying corneal development, disease modeling, and regenerative medicine applications. While previous protocols have successfully generated corneal tissue structures, there remains a need for three-dimensional models that recapitulate the complex cellular architecture and diversity of native human cornea. Methods: We developed a modified spontaneous three-dimensional corneal organoid model using human embryonic stem cells (hESCs) through an adapted Self-formed Ectoderm Autonomous Multi-zone (SEAM) protocol. hESCs were cultured as spheroids in ultra-low-binding plates under normoxic conditions and differentiated over 7–8 weeks. Organoids were characterized using immunofluorescence staining for corneal-specific markers and single-cell RNA sequencing to assess cellular composition and gene expression patterns. Results: Approximately 20% of organoids developed transparent regions characteristic of corneal tissue by day 30 of differentiation. Immunofluorescence analysis revealed spatially organized expression of corneal markers, including ZO-1 and E-cadherin in the outermost epithelial layers, P63α-positive putative limbal stem cells at the epithelial–stromal interface, vimentin-positive stromal cells in the interior, and laminin-1 deposition that suggests Bowman’s membrane formation. The organoids expressed cornea-specific keratins (K3, K12, and K15) and the master regulator PAX6 in appropriate cellular compartments. Single-cell RNA sequencing identified 18 distinct cell clusters, including three corneal epithelium subclusters with differential expression of MUC16, KRT12, and ΔNp63α, two stromal populations with distinct inflammatory profiles, and a corneal endothelium cluster. Transcriptomic analysis confirmed expression of key corneal genes, including AQP3, CDH1, multiple keratins, mucins, and extracellular matrix components (HAS2, CD34, CD44, COL8A1, and KERA). Conclusions: This three-dimensional spheroid-based putative corneal organoid model successfully recapitulates the multilayered architecture and cellular diversity of human cornea, including stratified epithelium, putative limbal stem cells, stroma, and endothelium in spatially appropriate arrangements. The model demonstrates molecular signatures consistent with native corneal tissue and provides a valuable platform for studying corneal development, disease mechanisms, and potential therapeutic applications. Future optimization to improve organoid formation efficiency and functional maturation will enhance the utility of this system for both basic research and translational medicine. Full article

Background/Objectives: Anterior segment optical coherence tomography (AS-OCT) and optical coherence tomography angiography (AS-OCTA) have enhanced the evaluation of the cornea, ocular surface, and ocular surface diseases (OSD), offering high-resolution structural and anterior segment vascular imaging. This review summarizes recent advances in these modalities and their clinical applications. Methods: A comprehensive literature search was conducted using PubMed, Web of Science, and Google Scholar with the terms OCT, OCTA, anterior segment, and ocular surface disease. Studies published in the past five years were included, emphasizing more recent developments such as ultra-high-resolution AS-OCT (UHR-AS-OCT) and swept-source AS-OCTA technologies. Results: UHR-AS-OCT provides non-invasive, sub-micron imaging of the cornea and the ocular surface, including tear film morphology and epithelial thickness to correlate with clinical tests such as tear break-up time, and fluorescein staining. Advances in AS-OCTA allow dye-free, depth-resolved imaging of corneal and conjunctival vasculature. These vascular biomarkers have shown promising utility in conditions such as limbal stem cell deficiency, chemical ocular injury, and ocular surface squamous neoplasia. Improvements in image acquisition, motion correction, and segmentation algorithms have enhanced accuracy and repeatability, supporting broader clinical translation. Conclusions: AS-OCT and AS-OCTA have become useful adjunctive imaging tools for the cornea and ocular surface evaluation. Their non-invasive, quantitative, and reproducible metrics may enable earlier diagnosis, objective staging, and longitudinal monitoring of OSD. Integration of OCT-based imaging with artificial intelligence and multimodal data, including tear proteomics and meibography, may optimize personalized treatment for ocular surface disorders. Full article

Autoimmune ocular surface diseases represent a complex group of disorders in which systemic immune dysregulation triggers chronic inflammation, epithelial dysfunction, and progressive tissue fibrosis. Systemic lupus erythematosus, primary Sjögren’s syndrome, and ocular cicatricial pemphigoid are the principal entities linking systemic autoimmunity to ocular surface pathology. These conditions share convergent mechanisms—including dysregulated cytokine signaling (IFN-I, IL-6, and IL-17), complement activation, and epithelial–mesenchymal transition—culminating in tear film instability and visual impairment. Recent advances in molecular immunology and omics profiling have elucidated disease-specific pathways and identified actionable therapeutic targets. Conventional immunosuppressants such as corticosteroids and cyclosporine remain fundamental, yet emerging biologics targeting BAFF, IFNAR, and JAK/STAT signaling—alongside regenerative strategies employing mesenchymal and induced pluripotent stem cells—are transforming disease management. Parallel innovations in amniotic membrane transplantation, keratoprosthesis, and bioengineered corneal scaffolds integrate structural reconstruction with immune modulation. Furthermore, the convergence of multi-omics analytics, artificial intelligence-assisted diagnostics, and microbiome-based immunomodulation heralds a new era of precision ophthalmology. This review synthesizes current molecular insights, clinical observations, and translational advances that collectively redefine autoimmune ocular surface diseases—from chronic inflammatory disorders into a targetable, regenerative, and potentially reversible spectrum of conditions. Full article

PAX6 haploinsufficiency-related congenital aniridia is frequently associated with ocular surface disease, including meibomian gland dysfunction (MGD), dry eye, limbal stem cell deficiency (LSCD), aniridia-associated keratopathy (AAK), and inflammation. This study measured ocular surface temperature (OST) at the corneal center and four paracentral points (2 mm from center) in patients with congenital aniridia and examined factors influencing OST. Forty-five eyes from 26 aniridia patients (55.6% female; 26.29 ± 17.78 years) with PAX6 pathogenic variants and 47 eyes from 25 controls (68.1% female; 24.81 ± 4.73 years; p = 0.1639) were included. Body temperature, OSDI, and OST (TG-1000) were recorded; clinical assessment evaluated MGD, LSCD, AAK, iris malformation, epithelial defects, Salzmann nodules, glaucoma and previous ocular surgery. Body temperature and OSDI did not differ in aniridia and controls (p ≥ 0.606). LSCD was mainly Grade 2 (46.7%) or Grade 4 (40.0%), and AAK Grade 1 (33.3%) or Grade 2 (31.1%). MGD affected 51.1%, Salzmann nodules 22.2%, epithelial defects 2.2%, glaucoma 60.0%, and previous ocular surgery 35.5%. Superior OST was higher in aniridia (34.98 ± 0.55 °C vs. 34.75 ± 0.47 °C; p = 0.012). Exploratory univariate analyses identified that higher AAK grade correlated with lower inferior OST (p = 0.030), iris malformation with reduced central/paracentral OST (p ≤ 0.029), and Salzmann nodules with lower OST overall (p ≤ 0.011). However, in a multivariate model, age, Salzmann nodular degeneration, and prior ocular surgery emerged as key determinants of OST. OST may serve as a noninvasive biomarker in congenital aniridia. Full article

The cornea is essential for proper ocular function, yet its histological structure varies considerably among animal species. Of particular importance are the palisades of Vogt in the limbal region, as they serve as a niche for limbal epithelial stem cells involved in corneal epithelial regeneration. This study was conducted on 73 eyeballs collected from 18 species of non-human primates originating from the Wrocław Zoological Garden (Poland). Eyeballs were fixed, processed, and embedded in paraffin. Four-micrometer sections were stained with Mayer’s H&E and PAS. Microscopically, the cornea showed either a four-layered pattern (anterior corneal epithelium, corneal stroma, Descemet’s membrane, posterior corneal epithelium) or a five-layered pattern when Bowman’s layer was present. A four-layered cornea occurred in the ring-tailed lemur, gray mouse lemur, Guianan squirrel monkey, Angolan colobus, and L’Hoest’s monkey, while the remaining species showed a five-layered structure with Bowman’s layer. The anterior corneal epithelium varied between species in thickness and number of cell layers (central region: 2–3 to 10–15 layers; 11.81 ± 0.43 µm to 44.23 ± 0.69 µm; peripheral region: 4–5 to 9–11 layers; 8.63 ± 2.57 µm to 42.45 ± 8.61 µm). Bowman’s layer ranged from 1.18 ± 0.01 µm to 3.22 ± 0.05 µm. The corneal stroma thickness differed markedly (237.96 ± 9.64 µm to 1438.29 ± 16.38 µm), as did Descemet’s membrane (4.92 ± 0.20 µm to 43.45 ± 0.49 µm), along with PAS reaction intensity. In the limbus, palisades of Vogt ranged from weakly to clearly developed; well-defined crypt-like structures were observed in the red-bellied lemur, red ruffed lemur, black-and-white ruffed lemur, Guianan squirrel monkey, L’Hoest’s monkey, Celebes crested macaque, and yellow baboon. The limbal epithelium also varied in thickness (5–6 to 15–17 cell layers). These results confirm distinct species-specific differences in corneal and limbal morphology that may reflect ecological conditions and functional adaptation. The presented data provides a comparative reference for veterinary ophthalmology and for studies on corneal epithelial regeneration involving limbal stem cells. Full article

Background/Objectives: Neovascularization, defined as the sprouting of new blood vessels from pre-existing vasculature, is a critical pathological feature in ocular diseases such as pathological myopia and represents a leading cause of corneal vision loss. Vascular endothelial growth factor A (VEGFA) plays a pivotal role in endothelial cell proliferation, migration, survival by anti-apoptotic signaling, and vascular permeability. Dysregulation of VEGFA is closely linked to pathological neovascularization. Exosomes, nanosized phospholipid bilayer vesicles ranging from 30 to 150 nm, have emerged as promising gene delivery vehicles due to their intrinsic low immunogenicity, superior cellular uptake, and enhanced in vivo stability. This study aimed to investigate whether highly purified mesenchymal stem cell (MSC)-derived exosomes loaded with VEGFA siRNA labeled with FAM can effectively suppress pathological corneal neovascularization (CNV) via targeeted cellular transduction and VEGFA inhibition. Furthermore, we examined whether the therapeutic effect involves the modulation of the PI3K–Akt–Caspase-3 signaling axis. Methods: Exosomes purified by chromatography were characterized by electronmicroscopy, standard marker immunoblotting, and nanoparticle tracking analysis. In vitro, we assessed exosome uptake and cytoplasmic release, suppression of VEGFA mRNA/protein, cell viability, and apoptosis. In a mouse CNV model, we evaluated tissue reach and stromal retention after repeated intrastromal injections; anterior segment angiogenic indices; CD31/VEGFA immunofluorescence/immunoblotting; phosphorylated PI3K and Akt; cleaved caspase-3; histology (H&E); and systemic safety (liver, kidney, and spleen). Results: Exosomes were of high quality and showed peak efficacy at 48 h, with decreased VEGFA mRNA/protein, reduced viability, and increased apoptosis in vitro. In vivo, efficient delivery and stromal retention were observed, with accelerated inhibition of neovascularization after Day 14 and maximal effect on Days 17–19. Treatment reduced CD31 and VEGFA, decreased p-PI3K and p-Akt, and increased cleaved caspase-3. Histologically, concurrent reductions in neovascularization, inflammatory cell infiltration, and inflammatory epithelial thickening were observed, alongside a favorable systemic safety profile. Conclusions:VEGFA siRNA-loaded exosomes effectively reduce pathological CNV via a causal sequence of intracellular uptake, cytoplasmic release, targeted inhibition, and phenotypic suppression. Supported by consistent PI3K–Akt inhibition and caspase-3–mediated apoptosis induction, these exosomes represent a promising local gene therapy that can complement existing antibody-based treatments. Full article

Background/Objectives: Ocular graft-versus-host disease (oGVHD) is a chronic, immune-mediated complication of allogeneic hematopoietic stem cell transplantation that can progress to corneal ulceration or perforation. These cases are often refractory to standard therapy and present a high risk of graft failure after keratoplasty. We report a case of oGVHD-related corneal perforation successfully managed with a novel amniotic membrane-assisted “envelope” technique during corneal transplantation. Case Report: A 42-year-old man with chronic oGVHD and a full-thickness corneal perforation underwent urgent repair with a lamellar patch graft completely wrapped in cryopreserved amniotic membrane, followed by penetrating keratoplasty (PKP) using an amniotic membrane envelope surrounding the donor lenticule. Results: The amniotic membrane provided a 360° biological barrier that isolated graft antigens from the inflammatory environment while supporting epithelial healing and stromal remodeling. Despite recurrent inflammatory episodes and multiple procedures—including cataract extraction, pars plana vitrectomy, and multilayer amniotic membrane transplantation—the graft remained clear and stable at 12-month follow-up, achieving a best-corrected visual acuity of 20/40. Conclusions: The amniotic membrane envelope technique may represent a valuable adjunct in managing high-risk corneal perforations secondary to oGVHD. By combining immune modulation and regenerative support, this approach can enhance tectonic stability, reduce rejection risk, and promote durable surface recovery, potentially delaying or avoiding keratoprosthesis in refractory cases. Full article

The cornea maintains transparency by preserving immune and (lymph)angiogenic privilege through active suppression of inflammation and vascular invasion, a process centrally regulated by limbal epithelial stem cells (LESCs) located at the corneoscleral junction. Beyond renewing the corneal epithelium, LESCs maintain immune and vascular balance via extracellular matrix interactions and paracrine signalling, exerting predominantly anti-inflammatory and anti-(lymph)angiogenic effects in vivo. Disruption of the limbal niche by trauma, UV exposure, or genetic disorders such as aniridia leads to limbal stem cell deficiency (LSCD), chronic inflammation, loss of corneal avascularity, and vision loss. The identification of ABCB5 as a key LESC marker has clarified functional limbal subsets, highlighting ABCB5⁺ epithelial cells as mediators of repair, remodelling, and immune suppression, and positioning them as promising therapeutic targets for treatments that restore both epithelial integrity and corneal immune privilege. Full article

Background and Objectives: Corneal opacity is the fifth global cause of blindness and moderate-to-severe visual impairment due to scar tissue formation. The purpose of this study is to provide an integrated overview of the current state of corneal engineering strategies focused on the comparison with healthy corneas. It aims to identify engineering strategies that would result in functional corneas, providing real alternatives to donor corneal transplants. Materials and Methods: systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and according to the protocol with the ID: CRD420250654641 at the PROSPERO database. The focus question, prompted by considering the shortage of human corneal grafts, was: what is the performance of bioengineered corneal grafts in experimental animal models when compared with healthy eyes in the restoration of corneal anatomy and function? Results: Incorporating human corneal epithelial cells w/ or w/o human corneal stromal stem cells into a gelatin methacrylate and polyethylene glycol diacrylate matrix emerges as the leading option for epithelial layer regeneration. Human and bovine decellularized corneas, porcine corneal ECM in Gelatin methacrylate, dual layered collagen vitrigel and tissue-engineered human anterior hemi-corneas have shown promise for simultaneous regeneration of the corneal stromal and epithelial layers. Corneal stromal tissue regeneration could be positively impacted by transplantation with grafts derived from aligned self-lifting analogous tissue equivalents and collagen-based hydrogels. Finally, scaffolds of silk fibroin and human purified type I collagen represent promising approaches for corneal endothelial regeneration, though their effectiveness is contingent upon integration with endothelial cells. Conclusions: Collectively, these findings contribute to the growing body of evidence supporting the potential of tissue-engineered corneal substitutes as viable therapeutic options for corneal blindness and vision impairment. Assessing the optical and functional properties of the regenerated cornea should be a cornerstone in all studies aiming to evaluate their clinical effectiveness. Full article