Malignant tumors notably decrease life expectancy. Despite advances in cancer diagnosis and treatment, the mechanisms underlying tumorigenesis, progression and drug resistance have not been fully elucidated. An emerging method to study tumors is tumor organoids, which are a three‑dimensional miniature structure. These retain the patient‑specific tumor heterogeneity while demonstrating the histological, genetic and molecular features of original tumors. Compared with conventional cancer cell lines and animal models, patient‑derived tumor organoids are more advanced at physiological and clinical levels. Their synergistic combination with other technologies, such as organ‑on‑a‑chip, 3D‑bioprinting, tissue‑engineered cell scaffolds and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‑associated protein 9, may overcome limitations of the conventional 3D organoid culture and result in the development of more appropriate model systems that preserve the complex tumor stroma, inter‑organ and intra‑organ communications. The present review summarizes the evolution of tumor organoids and their combination with advanced technologies, as well as the application of tumor organoids in basic and clinical research.

To objectively assess the long-term corneal epithelial recovery after autologous simple limbal epithelial transplantation (SLET) for ocular chemical burn (OCB)-induced unilateral limbal stem cell deficiency (LSCD).

Prospective, fellow-eye controlled, cross-sectional imaging and diagnostic study.

The study included 47 patients, who were 5 to 12 years postautologous SLET done for OCB-induced unilateral LSCD.

The donor and recipient eyes of all patients were assessed at a single follow-up visit with slit-lamp biomicroscopy (SLB), in vivo confocal microscopy (IVCM), impression cytology (IC), anterior segment optical coherence tomography (ASOCT), and Scheimpflug imaging (SI). The objective parameters that were assessed were corneal epithelial phenotype (CEP), thickness (CET), reflectivity (CER), and densitometry (CED). Median values with inter-quartile ranges were assessed for all parameters and analyzed using non-parametric tests.

The primary outcome measure was successful restoration of normal CEP on SLB, IVCM, and IC. Secondary outcome measures were comparison of CET and CER on ASOCT, and CED on SI between the eyes with successful and failed CEP restoration, and donor eyes.

The study analyzed 94 eyes of 47 patients, with a median follow-up of 5.75 years post-SLET. Successful restoration of CEP on SLB, IVCM, and IC was observed in 32 (68%) recipient eyes, while failure was seen in 15 (32%) eyes. The CEP was normal in all 47 (100%) donor eyes. The median CET was similar in healthy donor eyes, eyes with successful CEP restoration (55.9 microns, 50.3-59.2 vs. 57.8, 49.9-63.1; P = .47) and eyes with failure (57.7 microns, 50.9-66.2; P ≥ .59). Although, the median CER (100.72, 89.9-111.2 vs. 121.6, 109.7-139.8; P = .001) and CED (14.7, 13.4-17.1 vs. 26.5, 20.1-30.2; P = .02) values were significantly lower in eyes with successful CEP restoration as compared to eyes with failure, they were still significantly greater than corresponding values in the healthy donor eyes for CER (90.33, 84.9-96.9; P = .02), and CED (13.5, 11.4-15.1; P = .03), respectively.

Long-term 5-12 year successful restoration of the corneal epithelial phenotype was seen in two-thirds of eyes postautologous SLET. While corneal epithelial reflectivity, and densitometry were relatively better in eyes with successful outcomes, corneal epithelial thickness was similar in all eyes.

Limbal stem cells (LSCs) are essential for corneal epithelial regeneration and ocular surface homeostasis. Dysfunction of LSCs results in LSC deficiency (LSCD), a leading cause of global blindness. Although ex vivo expansion and autologous transplantation of LSCs have demonstrated promising clinical outcomes, no Food and Drug Administration-approved therapies for LSCD are available in the United States. To address this gap, we developed a novel 2-step process for isolating and expanding LSCs on human amniotic membrane under good manufacturing practice conditions, using a xenobiotic-free, serum-free, and antibiotic-free environment.

Autologous limbal biopsies were used to generate cultivated autologous limbal epithelial cell (CALEC) constructs, ensuring rigorous safety and efficacy measures. Furthermore, we compared the success rates of good manufacturing practice-manufactured cultivated limbal epithelial transplantation (CLET) products with those of CALEC.

Among 16 limbal biopsies harvested from 15 participants, 14 resulted in successful manufacturing of CALEC grafts. Phase I clinical trial demonstrated preliminary feasibility and no safety concerns. In the phase II trial, 92% of grafts showed partial or complete success at 18 months, with no safety issues. The success rate of CALEC grafts was comparable to currently available CLET products.

The findings underscore the safety and efficacy of CALEC transplantation as a promising therapeutic strategy for LSCD. The current review focuses on the manufacturing, quality control, and clinical performance of CALEC constructs in phase I/II trials for unilateral LSCD, paving the way for future trials in advancing LSC-based regenerative therapies in the United States.

Stem cell therapy in regenerative medicine has a scope for treating ocular diseases. Stem cell therapy aims to repair damaged tissue and restore vision. The present review focuses on the advancements in stem cell therapies for ocular disorders, their mechanism of action, and clinical applications while addressing some outstanding challenges. Stem cells that include embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), and retinal progenitor cells have regenerative potential for ocular repair. They differentiate into specialized ocular cell types, conduct neuroprotection, and modulate immune responses. It is emphasized in preclinical and clinical studies that stem cell therapy can treat corneal disorders such as limbal stem cell deficiency, retinal diseases like dry age macular degeneration and retinitis pigmentosa, and diabetic retinopathy. Various studies suggested that stem cells have considerable scope in glaucoma treatment by supporting retinal ganglion cell survival and optic nerve regeneration. Advanced approaches such as gene editing, organoid generation, and artificial intelligence enhance these therapies. Effective delivery to target areas, engraftment, orientation, and long-term survival of transplanted cells need optimization. Issues such as immune rejection and tumorigenicity must be addressed. This approach is further hindered by regulatory issues and overly complicated approval processes and trials. Ethical issues related to sourcing embryonic stem cells and patient consent complicate the issue. The cost of manufacturing stem cells and their accessibility are other factors posing potential barriers to widespread application. These regulatory, ethical, and economic issues must be tackled if stem cell treatments are to be made safe, accessible, and effective. Future studies will include refining therapeutic protocols, scaling manufacturing processes, and overcoming socio-economic barriers, eventually improving clinical outcomes.

For the treatment of bilateral limbal stem cell deficiency (LSCD), cell therapy with transplantation of cultivated oral mucosa epithelial cells (COMET) is a promising alternative. Although not yet established, current protocols on the cultivation of oral mucosal epithelial cell (OMECs) sheets are based mainly on substrates and xenobiotic additives that may lead to variable outcomes and undesirable immune responses by the patient. The aim of this study was to characterize OMECs cultivated in xenobiotic-free media (XF) seeded on fibrin gel, in comparison to conventional complex (COM) medium. Oral mucosal biopsies were retrieved from 31 donors. After cultivation in COM or XF medium, OMECs were compared based on growth kinetics, morphology, cell size and viability. Using immunofluorescence and gene expression analyses, the degree of stemness, proliferation and differentiation was evaluated in OMEC cultures. Our findings showed that although OMECs showed a similar morphology and viability, and comparable growth kinetics, immunofluorescence revealed the preservation of stemness (p63 + p40 positivity in cells ≤11 μm) and proliferation in both COM and XF. Gene expression analyses showed that keratin (K)13 and K15 expression levels were significantly higher in XF (adj. p < 0.001), but otherwise COM and XF-treated OMECs had comparable transcriptional profiles in a panel of stemness, proliferation and differentiation genes. These results demonstrate the feasibility of culturing OMECs on fibrin gel without xenogeneic additives, while maintaining their undifferentiated state and preserving stemness. In conclusion, both in terms of results and methodology, the procedures presented here are suitable for implementation in clinical practice.

Advances in regenerative medicine, cell therapy, and 3D bioprinting are reshaping the landscape of ocular surgery, offering innovative approaches to address complex conditions affecting the cornea, ocular adnexal structures, and the orbit. These technologies hold the potential to enhance treatment precision, improve functional outcomes, and address limitations in traditional surgical and therapeutic interventions.The cornea, as the eye's primary refractive and protective barrier, is particularly well-suited for regenerative approaches due to its avascular and immune-privileged nature. Cell-based therapies, including limbal stem cell transplantation as well as stromal keratocyte and corneal endothelial cell regeneration, are being investigated for their potential to restore corneal clarity and function in conditions such as limbal stem cell deficiency, keratoconus, and endothelial dysfunction. Simultaneously, 3D bioprinting technologies are enabling the development of biomimetic corneal constructs, potentially addressing the global shortage of donor tissues and facilitating personalized surgical solutions.In oculoplastic and orbital surgery, regenerative strategies and cell therapies are emerging as possible alternatives to conventional approaches for conditions such as eyelid defects, meibomian gland dysfunction, and Graves' orbitopathy. Stem cell-based therapies and bioengineered scaffolds are showing potential in restoring lacrimal glands' function as well as reconstructing complex ocular adnexal and orbital structures. Moreover, 3D-printed orbital implants and scaffolds offer innovative solutions for repairing traumatic, post-tumor resection, and congenital defects, with the potential for improved biocompatibility and precision.Molecular and gene-based therapies, including exosome delivery systems, nanoparticle-based interventions, and gene-editing techniques, are expanding the therapeutic arsenal for ophthalmic disorders. These approaches aim to enhance the efficacy of regenerative treatments by addressing underlying pathophysiological mechanisms of diseases. This chapter provides an overview of these advancements and the challenges of translating laboratory discoveries into effective therapies in clinical practice.

We developed a two-stage manufacturing process utilizing cultivated autologous limbal epithelial cells (CALEC), the first xenobiotic-free, serum-free, antibiotic-free protocol developed in the United States, to treat blindness caused by unilateral limbal stem cell deficiency (LSCD) and conducted a single-center, single-arm, phase I/II clinical trial. Primary outcomes were feasibility (meeting release criteria) and safety (ocular infection, corneal perforation, or graft detachment). Participant eligibility included male or female participants age 18 to <90 years old and ability to provide written informed consent with LSCD. Funding was provided by the National Eye Institute of the National Institutes of Health. CALEC grafts met release criteria in 14 (93%) of 15 participants at conclusion of trial. After first stage manufacturing, intracellular adenosine triphosphate levels correlated with colony forming efficiency (r = 0.65, 95% CI [0.04, 0.89]). One bacterial infection occurred unrelated to treatment, with no other primary safety events. The secondary outcome was to investigate efficacy based on improvement in corneal epithelial surface integrity (complete success) or improvement in corneal vascularization and/or participant symptomatology as measured by OSDI and SANDI (partial success). 86%, 93%, and 92% of grafts resulted in complete or partial success at 3, 12, and 18 months, respectively. Our results provide strong support that CALEC transplantation is safe and feasible and further studies are needed to evaluate therapeutic efficacy. Clinicaltrials.gov registration: NCT02592330.

This study compared the clinical outcomes of allogenic cultured limbal epithelial transplantation (ACLET) and cultivated oral mucosal epithelial transplantation (COMET) in the management of limbal stem cell deficiency (LSCD).

Forty-one COMET procedures in 40 eyes and 69 ACLET procedures in 54 eyes were performed in the Corneoplastic Unit of Queen Victoria Hospital, East Grinstead. Data were examined for demographics, indications, ocular surface stability, absence of epithelial defect, ocular surface inflammation, visual outcomes, and intra- and postoperative complications.

Kaplan-Meier analysis showed that patients in the ACLET group with longer follow-up had a significantly higher graft survival rate (81.7%, n = 56) than the COMET group (60.7%, n = 25) and the difference was statistically significant (p = 0.01). In the COMET group, there was no statistically significant improvement in the visual acuity (VA) while in the ACLET group there was statistically significant improvement in the final VA. Elevated intraocular pressure (IOP) developed in 9 eyes (22.0%) in the COMET group and in 18 eyes (26.1%) in the ACLET group; infection developed in 4 eyes (9.8%) in the COMET group and in 10 eyes (14.5%) in the ACLET group; and perforation or melting happened in 4 eyes (9.8%) in the COMET group and in 1 eye (1.4%) in the ACLET group. Postoperative immunosuppression complications were noted in 9 eyes (13.0%) in the ACLET group. No graft rejection was observed in either group.

Both ACLET and COMET are effective therapeutic procedures for managing advanced and bilateral cases of LSCD. Although COMET has lower graft survival rate than ACLET, it does not mandate systemic immunosuppression therapy to protect against potential graft rejection.

Ocular vision can be hampered by corneal damages, sensibly reducing patients' quality of life and having important social and economic consequences. Ocular surface diseases, which often lead to corneal opacities with visual impairment are the most severe forms of the Limbal Stem Cell Deficiency (LSCD). The present review provides an updated perspective on the available treatments for LSCD, focusing on clinical and biological features, as well as critical points to monitor during clinical translation. Recently developed surgical treatments for LSCD are described, along with their benefits and limitations, with the aim of addressing the issue of correct patient selection. Autologous surgical approaches have been attempted, such as conjunctival limbal autograft (CLAU), simple limbal epithelial transplantation (SLET), and others. Allogeneic limbal stem cell transplantation represents an alternative but carries risk of rejection and requires immunosuppression. Other potential treatments are based on induced pluripotent stem cells (iPSCs), but they require further investigation. The development of advanced therapy medicinal products (ATMPs) such as cultivated limbal epithelial transplantation (CLET), or the use of other epithelia as cultivated oral mucosal epithelial cell transplantation (COMET), has opened additional therapeutic possibilities. Some common critical issues in clinical translation are described, such as patient selection, biopsy procurement, or the use of human/animal derived components, which require rigorous validation to ensure safety and efficacy. Personalized medicine is a promising field for ocular surface restoration, where long-term follow-up studies and standardized criteria are crucial to evaluate the efficacy of these treatments and their cost-effectiveness in providing high-value healthcare.

Corneal limbal epithelial stem cells (LESCs) play a crucial role in corneal epithelium regeneration. Severe damage to these cells can result in limbal stem cell deficiency (LSCD), characterized by repeated corneal conjunctivalization, leading to corneal turbidity and scar formation. Restoring functional LESCs and their ecological location are essential for treating LSCD. The goal of this review is to provide researchers and clinicians with key insights into LESCs biology and to conclude the current cell-based therapies advancement in LSCD treatments. Therapeutic cell resources mainly include mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), skin keratinocyte stem cells (SKCs), and oral mucosal epithelial cells (OMECs).

This study describes the technique of simple limbal epithelial transplantation (SLET) without amniotic membrane grafting (AMG) in limbal stem cell deficiency (LSCD).

Retrospective, interventional case series of 6 patients who underwent SLET without AMG were included. The procedure followed the standard technique, involving limbal biopsy from the healthy eye, resection of symblephera, and pannus dissection in the affected eye. Following host bed preparation, limbal explants were placed on the bare cornea and secured with fibrin glue. A large-diameter bandage contact lens was applied post surgery. No amniotic membrane was used. Preoperative data, including age, gender, cause of LSCD, best-corrected visual acuity, and previous ocular surgeries, were recorded. Postoperative clinical information, such as the duration of follow-up and recurrence of LSCD, best-corrected visual acuity, and other ocular examination findings, was recorded in an excel sheet.

Preoperatively, 2 patients had total LSCD (secondary to a firecracker injury and excision biopsy for ocular surface squamous neoplasia). 4 patients had partial LSCD (3 chemical injuries, 1 firecracker injury). The mean age of participants was 30.67 ± 15.91 years, with a mean follow-up duration of 9.33 ± 8.04 months. Intraoperatively, all patients exhibited a smooth corneal surface after pannus removal. Postoperatively, all limbal explants remained securely attached, with complete corneal epithelialization achieved within 2 to 3 weeks. The ocular surface remained stable throughout, and no recurrence of LSCD was observed in any patient. No loss of explants was seen.

The present series suggests that AMG may not be a necessary step for performing SLET.

Background: Burns are a global public health issue and a major cause of disability and death around the world. Stem cells, which are the undifferentiated cells with the potential for indefinite proliferation and multilineage differentiation, have the ability to replace injured skin and facilitate the wound repair process through paracrine mechanisms. In light of this, the present study aims to conduct a bibliometric analysis in order to identify research hotspots of stem cell-related burns and assess global research tendencies. Methods: To achieve this objective, we retrieved scientific publications on burns associated with stem cells covering the period from January 1, 1978, to October 13, 2022, from the Web of Science Core Collection (WoSCC). Bibliometric analyses, including production and collaboration analyses between countries, institutions, authors, and journals, as well as keyword and topic analyses, were conducted using the bibliometrix R package, CiteSpace, and VOSviewer. Results: A total of 1648 burns associated with stem cell documents were published and listed on WOSCC. The most contributive country, institution, journal, and author were the United States, LV Prasad Eye Institute, Burns, and Scheffer C.G. Tseng, respectively. More importantly, combined with historical direct citation network, trend topic analysis, keyword co-occurrence network, and substantial literature analysis, we eventually summarized the research hotspots and frontiers on burns associated stem cell reasearch. Conclusion: The present study obtained deep insight into the developing trends and research hotspots on burns associated with stem cells, which arouses growing concerns and implies increasing clinical implications. The mechanism and therapeutics of epidermal stem cells (ESCs) for burn wounds and the mechanism of mesenchymal stem cells (MSCs) and MSC-derived exosomes for burns wounds are two research hotspots in this field.

Approximately 40,000 Australians have received a donor corneal tissue transplant over the last 40 years, with the primary indications being keratoconus, Fuchs' endothelial dystrophy, bullous keratopathy, and failure of a prior corneal transplant. Although corneal cross-linking and rigid contact lenses have emerged as alternative strategies for the management of keratoconus, the demand for donor corneas is increasing in-line with the ageing population in Australia. Moreover, owing to the lack of tissue banking resources in less-developed countries, the global demand for donor corneas exceeds supply by 70-fold. These supply issues, combined with evolving tissue banking and surgical techniques, have led to the emergence of new strategies for the storage, processing and implantation of corneal cells and tissues. Organ culture techniques have been developed that support the storage of donor corneas for up to 30 days, facilitating improvements in tissue supply and surgery scheduling. Bespoke surgical methods have been developed that are tailored to the requirements of specific conditions, allowing reductions in both the volume of tissue required to be transplanted and the size of the necessary surgical incision. Further efficiencies and improvements in patient care may be achieved via exploitation of cell culture technologies as exemplified through use of cultured corneal epithelial cells for the treatment of limbal stem cell deficiency. Promising progress has also been made in developing a cultured corneal endothelial cell therapy for patients with corneal endothelial dysfunction. These evolving strategies are discussed with respect to their potential impact on the clinical presentation and management of patients who have received an implant of donor corneal tissue or cells.

The loss of corneal epithelial stem cells from the limbus at the edge of the cornea has severe consequences for vision, with the pathological manifestations of a limbal stem-cell deficiency (LSCD) difficult to treat. Here, to the best of our knowledge, we report the world's first use of corneal epithelial cell sheets derived from human induced pluripotent stem cells (iPSCs) to treat LSCD.

This non-randomised, single-arm, clinical study involved four eyes of four patients with LSCD at the Department of Ophthalmology, Osaka University Hospital. They comprised a woman aged 44 years with idiopathic LSCD (patient 1), a man aged 66 years with ocular mucous membrane pemphigoid (patient 2), a man aged 72 years with idiopathic LSCD (patient 3), and a woman aged 39 years with toxic epidermal necrosis (patient 4). Allogeneic human iPSC-derived corneal epithelial cell sheets (iCEPSs) were transplanted onto affected eyes. This was done sequentially in two sets of HLA-mismatched surgeries, with patients 1 and 2 receiving low-dose cyclosporin and patients 3 and 4 not. The primary outcome measure was safety, ascertained by adverse events. These were monitored continuously throughout the 52-week follow-up period, and during an additional 1-year safety monitoring period. Secondary outcomes, reflective of efficacy, were also recorded. This study is registered with UMIN, UMIN000036539 and is complete.

Patients were enrolled between June 17, 2019 and Nov 16, 2020. We had 26 adverse events during the 52-week follow-up period (consisting of 18 mild and one moderate event in treated eyes, and seven mild non-ocular events), with nine recorded in the additional 1-year safety monitoring period. No serious adverse events, such as tumourigenesis or clinical rejection, occurred during the whole 2-year observational period. At 52 weeks, secondary measures of efficacy showed that the disease stage had improved, corrected distance visual acuity was enhanced, and corneal opacification had diminished in all treated eyes. Corneal epithelial defects, subjective symptoms, quality-of-life questionnaire scores and corneal neovascularisation mostly improved or were unchanged. Overall, the beneficial efficacy outcomes achieved for patients 1 and 2 were better than those achieved for patients 3 and 4.

iCEPS transplantation for LSCD was found to be safe throughout the study period. A larger clinical trial is planned to further investigate the efficacy of the procedure.

The Japan Agency for Medical Research and Development, the Ministry of Education, Culture, Sports, Science, and Technology-Japan, and the UK Biotechnology and Biological Sciences Research Council.

This study compared 2-dimensional (monolayer) and 3-dimensional (sandwich) systems for expanding ex vivo limbal epithelial cells on amniotic membrane and evaluated the outcomes after transplantation into rabbits with experimentally induced limbal stem cell deficiency.

Evaluations included markers for progenitor cells, proliferation, apoptosis, and clinical monitoring for up to 63 days. In the monolayer culture, epithelial cells derived from limbal explants were expanded on amniotic membrane as the substrate. In the sandwich culture, the cells were cultured between 2 layers of amniotic membrane. Evaluations included markers for progenitor cells, proliferation, and apoptosis, along with clinical monitoring for up to 63 days.

Sandwich cultures demonstrated increased cellular proliferation and fewer progenitor cells compared with monolayer cultures. In treating limbal stem cell deficiency, the group receiving transplantation from sandwich cultures exhibited reduced neovascularization and decreased corneal ulceration compared with those treated with monolayer cultures, with similar clinical outcomes in corneal opacity. The configuration of the culture system did not affect the presence of apoptotic cells. Corneas treated with sandwich cultures showed a higher presence of progenitor cells compared with the monolayer group, suggesting a potential long-term viability advantage for these transplants.

In conclusion, although the sandwich culture system enhanced cellular proliferation, it also resulted in a decrease in progenitor cells within the cultures. Nevertheless, both systems demonstrated comparable therapeutic efficacy in treating limbal stem cell deficiency, with the sandwich approach potentially offering long-term benefits because of the increased presence of progenitor cells in the transplanted cornea.

Limbal stem cell deficiency (LSCD) is a complex disease of the cornea resulting from dysfunction and/or loss of limbal stem cells (LSCs) and their niche. Most patients with LSCD cannot be treated by conventional corneal transplants because the donor tissue lacks the LSCs necessary for corneal epithelial regeneration. Successful treatment of LSCD depends on effective stem cell transplantation to the ocular surface for replenishment of the LSC reservoir. Thus, stem cell therapies employing carrier substrates for LSCs have been widely explored. Hydrogel biomaterials have many favorable characteristics, including hydrophilicity, flexibility, cytocompatibility, and optical properties suitable for the transplantation of LSCs. Therefore, due to these properties, along with the necessary signals for stem cell proliferation and differentiation, hydrogels are ideal carrier substrates for LSCD treatment. This review summarizes the use of different medical-type hydrogels in LSC transplantation from 2001 to 2024. First, a brief background of LSCD is provided. Then, studies that employed various hydrogel scaffolds as LSC carriers are highlighted to provide a multimodal strategic reference for LSCD treatment. Finally, an analysis of prospective future developments and challenges in the field of hydrogels as LSC carriers for treating LSCD is presented.

The complex network governing self-renewal in epidermal stem cells (EPSCs) is only partially defined. FOXM1 is one of the main players in this network, but the upstream signals regulating its activity remain to be elucidated. In this study, we identify cyclin-dependent kinase 1 (CDK1) as the principal kinase controlling FOXM1 activity in human primary keratinocytes. Mass spectrometry identified CDK1 as a key hub in a stem cell-associated protein network, showing its upregulation and interaction with essential self renewal-related markers. CDK1 phosphorylates FOXM1 at specific residues, stabilizing the protein and enhancing its nuclear localization and transcriptional activity, promoting self-renewal. Additionally, FOXM1 binds to the CDK1 promoter, inducing its expression.We identify the CDK1-FOXM1 feedforward loop as a critical axis sustaining EPSCs during in vitro cultivation. Understanding the upstream regulators of FOXM1 activity offers new insights into the biochemical mechanisms underlying self-renewal and differentiation in human primary keratinocytes.

Treatment of Limbal Stem Cell Deficiency (LSCD), based on autologous transplantation of the patient's stem cells, is one of the few medical stem cell therapies approved by the European Medicines Agency (EMA). It relies on isolating and culturing in vivo Limbal Epithelial Stem Cells (LESC) and then populating them on the fibrin substrate, creating a scaffold for corneal epithelial regeneration. Such a solution is then implanted into the patient's eye. The epithelial cell culture process is specific, and its results strongly depend on the initial cell seeding density. Achieving control of the density and repeatability of the process is a desirable aim and can contribute to the success of the therapy. The study aimed to test bioprinting as a potential technique to increase the control over LESCs seeding on a scaffold and improve process reproducibility. Cells were applied to 0.5 mm thick, flat, transparent fibrin substrates using extrusion bioprinting; the control was the traditional manual application of cells using a pipette. The use of 3D printer enabled uniform coverage of the scaffold surface, and LESCs density in printed lines was close to the targeted value. Moreover, printed cells had higher cell viability than those seeded traditionally (91.1 ± 8.2% vs 82.6 ± 12.8%). The growth rate of the epithelium was higher in bioprinted samples. In both methods, the epithelium had favorable phenotypic features (p63 + and CK14 +). 3D printing constitutes a promising approach in LSCD therapy. It provides favorable conditions for LESCs growth and process reproducibility. Its application may lead to reduced cell requirements, thereby to using fewer cells on lower passages, which will contribute to preserving LESCs proliferative potential.

The eyes are one of the most important sensory organs in the human body. Currently, diseases such as limbal stem cell deficiency, cataract, retinitis pigmentosa and dry eye seriously threaten the quality of people's lives, and the treatment of advanced blinding eye disease and dry eye is ineffective and costly. Thus, new treatment modalities are urgently needed to improve patients' symptoms and suffering. In recent years, stem cell-derived three-dimensional structural organoids have been shown to mimic specific structures and functions similar to those of organs in the human body. Currently, 3D culture systems are used to construct organoids for different ocular growth and development models and ocular disease models to explore their physiological and pathological mechanisms. Eye organoids can also be used as a platform for drug screening. This paper reviews the latest research progress in regard to eye organoids (the cornea, lens, retina, lacrimal gland, and conjunctiva).

To compare the outcomes of simple limbal epithelial transplantation (SLET) with cultivated limbal epithelial transplantation (CLET) for the management of total limbal stem cell deficiency (LSCD) in eyes with unilateral ocular burns.

Randomized controlled trial.

100 patients (100 eyes) with unilateral total LSCD following ocular burns undergoing autologous Limbal Stem Cell Transplantation (LSCT) were enrolled and randomized into SLET and CLET groups. Restoration of an epithelized ocular surface was the primary outcome measure. Occurrences of progressive conjunctivalization and persistent epithelial defects postoperatively were considered surgical failures.

Mean age was 20.2 ± 13.1 years (SLET) and 22.6 ± 14.3 years (CLET) (p = 0.363). Alkali burn was the most common causative factor in both groups and had comparable mean logMAR BCVA at presentation [SLET: 2.33 ± 0.5, CLET: 2.23 ± 1.48 (p = 0.652)]. Median time interval between injury and surgical intervention was 18 months (SLET) and 12 months (CLET) (p = 0.06). 88 % eyes in SLET group maintained a stable ocular surface at 1 year period versus CLET group (86 %) (p = 0.999). Mean logMAR BCVA significantly improved in both groups with SLET having significantly better BCVA versus CLET at 6 months (p = 0.0390), 1 year (p = 0.0001), 2 year (p = 0.0001) and 3 years (p = 0.0001) follow up. Kaplan-Meier survival analysis was statistically insignificant amongst the 2 groups (p = 0.590).

Compared to CLET, SLET is equally efficacious in restoring and maintaining a stable ocular surface in eyes with total LSCD due to ocular burns, with the added advantage of providing superior visual outcomes.

The mammalian cornea is decorated with stem cells bestowed with the life-long task of renewing the epithelium, provided they remain healthy, functional, and in sufficient numbers. If not, a debilitating disease known as limbal stem cell deficiency (LSCD) can develop causing blindness. Decades after the first stem cell (SC) therapy is devised to treat this condition, patients continue to suffer unacceptable failures. During this time, improvements to therapeutics have included identifying better markers to isolate robust SC populations and nurturing them on crudely modified biological or biomaterial scaffolds including human amniotic membrane, fibrin, and contact lenses, prior to their delivery. Researchers are now gathering information about the biomolecular and biomechanical properties of the corneal SC niche to decipher what biological and/or synthetic materials can be incorporated into these carriers. Advances in biomedical engineering including electrospinning and 3D bioprinting with surface functionalization and micropatterning, and self-assembly models, have generated a wealth of biocompatible, biodegradable, integrating scaffolds to choose from, some of which are being tested for their SC delivery capacity in the hope of improving clinical outcomes for patients with LSCD.

The cornea is an ideal testing field for cell therapies. Its highly ordered structure, where specific cell populations are sequestered in different layers, together with its accessibility, has allowed the development of the first stem cell-based therapy approved by the European Medicine Agency. Today, different techniques have been proposed for autologous and allogeneic limbal and non-limbal cell transplantation. Cell replacement has also been attempted in cases of endothelial cell decompensation as it occurs in Fuchs dystrophy: injection of cultivated allogeneic endothelial cells is now in advanced phases of clinical development. Recently, stromal substitutes have been developed with excellent integration capability and transparency. Finally, cell-derived products, such as exosomes obtained from different sources, have been investigated for the treatment of severe corneal diseases with encouraging results. Optimization of the success rate of cell therapies obviously requires high-quality cultured cells/products, but the role of the surrounding microenvironment is equally important to allow engraftment of transplanted cells, to preserve their functions and, ultimately, lead to restoration of tissue integrity and transparency of the cornea.

Ex vivo cultivated oral mucosal epithelial cell transplantation (COMET) was first introduced in Japan in June 2021. This technique is used to treat limbal stem cell deficiency (LSCD). This article provides a detailed description of one of the most critical steps in COMET, which is the harvesting of oral mucosa, along with accompanying videos. The samples harvested using this method were successfully cultured into cell sheets, which were then used in surgical procedures without complications.

To review the published literature on the safety and outcomes of keratolimbal allograft (KLAL) transplantation and living-related conjunctival limbal allograft (lr-CLAL) transplantation for bilateral severe/total limbal stem cell deficiency (LSCD).

Literature searches were last conducted in the PubMed database in February 2023 and were limited to the English language. They yielded 523 citations; 76 were reviewed in full text, and 21 met the inclusion criteria. Two studies were rated level II, and the remaining 19 studies were rated level III. There were no level I studies.

After KLAL surgery, best-corrected visual acuity (BCVA) improved in 42% to 92% of eyes at final follow-up (range, 12-95 months). The BCVA was unchanged in 17% to 39% of eyes and decreased in 8% to 29% of eyes. Two of 14 studies that evaluated the results of KLAL reported a notable decline in visual acuity over time postoperatively. Survival of KLAL was variable, ranging from 21% to 90% at last follow-up (range, 12-95 months) and decreased over time. For patients undergoing lr-CLAL surgery, BCVA improved in 31% to 100% of eyes at final follow-up (range, 16-49 months). Of the 9 studies evaluating lr-CLAL, 4 reported BCVA unchanged in 30% to 39% of patients, and 3 reported a decline in BCVA in 8% to 10% of patients. The survival rate of lr-CLAL ranged from 50% to 100% at final follow-up (range, 16-49 months). The most common complications were postoperative elevation of intraocular pressure, persistent epithelial defects, and acute allograft immune rejections.

Given limited options for patients with bilateral LSCD, both KLAL and lr-CLAL are viable choices that may provide improvement of vision and ocular surface findings. The studies trend toward a lower rejection rate and graft failure with lr-CLAL. However, the level and duration of immunosuppression vary widely between the studies and may impact allograft rejections and long-term graft survival. Complications related to immunosuppression are minimal. Repeat surgery may be needed to maintain a viable ocular surface. Reasonable long-term success can be achieved with both KLAL and lr-CLAL with appropriate systemic immunosuppression.

Proprietary or commercial disclosure may be found after the references.

Findings from this study examining Australian optometrists' insights into ocular stem cell (SC) therapies have capacity to inform continuing professional development (CPD) about these interventions.

This study investigated Australian optometrists' knowledge, views, experiences, and preferred education sources regarding ocular SC therapies.

An online survey was distributed to optometrists via Optometry Australia, Mivision magazine, professional groups, and social media from August 2020 to March 2021. Data were collected on demographics, and SC knowledge, awareness and experience.

Of 81 optometrists who completed the survey, many were metropolitan-based (85%), worked in independent practice (47%), female (56%) and >46 years of age (45%). Approximately one-fifth indicated awareness of ocular SC therapies used in standard practice; one-third had knowledge of SC clinical trials. The most noted SC therapies were for corneal disease in the United States [US] (72%) and Australia (44%). Respondents identified the availability of SC therapies for dry eye disease in Australia and the US (39% and 44% respectively), despite no regulatory-approved treatments for this indication. Clinical trials investigating inherited retinal and corneal diseases in Australia were the most commonly identified (44% and 36%, respectively). Half the respondents felt 'unsure' about the quality of evidence for treating eye conditions using SCs. One-fifth indicated concerns with these therapies; of these, most mentioned efficacy (82%), safety (76%) and/or cost (71%). About one-fifth reported being asked for advice about SCs by patients. Two-thirds felt neutral, uncomfortable, or very uncomfortable providing this advice, due to lack of knowledge or the topic being beyond their expertise. Over half (57%) were unsure if clinical management should change if patients received SC therapies. Respondents were receptive to face-to-face education.

Some optometrists responding to this survey were aware of ocular SC therapies and/or clinical trials. CPD programs may assist with maintaining currency in this evolving field.

The cornea is the outermost layer of the eye and plays an essential role in our visual system. Limbal epithelial stem cells (LESCs), which are localized to a highly regulated limbal niche, are the master conductors of corneal epithelial regeneration. Damage to LESCs and their niche may result in limbal stem cell deficiency (LSCD), a disease confused ophthalmologists so many years and can lead to corneal conjunctivalization, neovascularization, and even blindness. How to restore the LESCs function is the hot topic for ocular scientists and clinicians around the world. This review introduced LESCs and the niche microenvironment, outlined various techniques for isolating and culturing LESCs used in LSCD research, presented common diseases that cause LSCD, and provided a comprehensive overview of both the diagnosis and multiple treatments for LSCD from basic research to clinical therapies, especially the emerging cell therapies based on various stem cell sources. In addition, we also innovatively concluded the latest strategies in recent years, including exogenous drugs, tissue engineering, nanotechnology, exosome and gene therapy, as well as the ongoing clinical trials for treating LSCD in recent five years. Finally, we highlighted challenges from bench to bedside in LSCD and discussed cutting-edge areas in LSCD therapeutic research. We hope that this review could pave the way for future research and translation on treating LSCD, a crucial step in the field of ocular health.

Organoid technology has been developed rapidly in the past decade, which involves the exploration of the mechanism of development, regeneration and various diseases, and intersects among multiple disciplines. Thousands of literature on 3D-culture or organoids have been published in the research areas of cell biology tissue engineering, nanoscience, oncology and so on, resulting in it being challenging for researchers to timely summarize these studies. Bibliometric statistics is a helpful way to help researchers clarify the above issues efficiently and manage the whole landscape systematically. In our study, all original articles on organoids were included in the Web of Science database from January 2009 to May 2024, and related information was collected and analyzed using Excel software, "bibliometrix" packages of the R software, VOSviewer and CiteSpace. As results, a total of 6222 papers were included to classify the status quo of the organoids and predict future research areas. Our findings highlight a growing trend in publications related to organoids, with the United States and Netherlands leading in this field. The University of California System, Harvard University, Utrecht University and Utrecht University Medical Center have emerged as pivotal contributors and the key authors in the field include Clevers, H, Beekman, JM and Spence JR. Our results also revealed that the research hotspots and trends of organoids mainly focused on clinical treatment, drug screening, and the application of materials and technologies such as "hydrogel" and "microfluidic technology" in organoids. Next, we had an in-depth interpretation of the development process of organoid research area, including the emergence of technology, the translation from bench to bedsides, the profiles of the most widely studied types of organoids, the application of materials and technologies, and the emerging organoid-immune co-cultures trends. Furthermore, we also discussed the pitfalls, challenges and prospects of organoid technology. In conclusion, this study provides readers straightforward and convenient access to the organoid research field.

Epidermal stem cells (EPSCs) are essential for maintaining skin homeostasis and ensuring a proper wound healing. During in vitro cultivations, EPSCs give rise to transient amplifying progenitors and differentiated cells, finally forming a stratified epithelium that can be grafted onto patients. Epithelial grafts have been used in clinics to cure burned patients or patients affected by genetic diseases. The long-term success of these advanced therapies relies on the presence of a correct amount of EPSCs that guarantees long-term epithelial regeneration. For this reason, a deeper understanding of self-renewal and differentiation is fundamental to fostering their clinical applications.The coordination between energetic metabolism (e.g., glycolysis, tricarboxylic acid cycle, oxidative phosphorylation, and amino acid synthesis pathways), molecular signalling pathways (e.g., p63, YAP, FOXM1, AMPK/mTOR), and epigenetic modifications controls fundamental biological processes as proliferation, self-renewal, and differentiation. This review explores how these signalling and metabolic pathways are interconnected in the epithelial cells, highlighting the distinct metabolic demands and regulatory mechanisms involved in skin physiology.

To assess various potential factors on human limbal epithelial cell (LEC) outgrowth in vitro using corneal donor tissue following long-term storage (organ culture) and a stepwise linear regression algorithm.

Of 215 donors, 304 corneoscleral rings were used for our experiments. For digestion of the limbal tissue and isolation of the limbal epithelial cells, the tissue pieces were incubated with 4.0 mg/mL collagenase A at 37 °C with 95% relative humidity and a 5% CO2 atmosphere overnight. Thereafter, limbal epithelial cells were separated from limbal keratocytes using a 20-µm CellTricks filter. The separated human LECs were cultured in keratinocyte serum-free medium medium, 1% penicillin/streptomycin (P/S), 0.02% epidermal growth factor (EGF), and 0.3% bovine pituitary extract (BPE). The potential effect of donor age (covariate), postmortem time (covariate), medium time (covariate), size of the used corneoscleral ring (360°, 270°180°, 120°, 90°, less than 90°) (covariate), endothelial cell density (ECD) (covariate), gender (factor), number of culture medium changes during organ culture (factor), and origin of the donor (donating institution and storing institution, factor) on the limbal epithelial cell outgrowth was analyzed with a stepwise linear regression algorithm.

The rate of successful human LEC outgrowth was 37.5%. From the stepwise linear regression algorithm, we found out that the relevant influencing parameters on the LEC growth were intercept (p < 0.001), donor age (p = 0.002), number of culture medium changes during organ culture (p < 0.001), total medium time (p = 0.181), and size of the used corneoscleral ring (p = 0.007), as well as medium time × size of the corneoscleral ring (p = 0.007).

The success of LEC outgrowth increases with lower donor age, lower number of organ culture medium changes during storage, shorter medium time in organ culture, and smaller corneoscleral ring size. Our stepwise linear regression algorithm may help us in optimizing LEC cultures in vitro.

Currently, in vitro cultured corneal epithelial transplantation is effective in treating limbal stem cell dysfunction (LSCD). Selecting carriers is crucial for constructing the corneal epithelium through tissue engineering. In this study, the traditional amniotic membrane (AM) was modified, and mesenchymal stem cells (MSCs) were inoculated into the ultra-thin amniotic membrane (UAM) stroma to construct a novel UAM-MSC tissue-engineered corneal epithelial carrier, that could effectively simulate the limbal stem cells (LSCs) microenvironment. The structure of different carriers cultured tissue-engineered corneal epithelium and the managed rabbit LSCD model corneas were observed through hematoxylin-eosin staining. Cell phenotypes were evaluated through fluorescence staining, Western blotting, and RT-qPCR. Additionally, cell junction genes and expression markers related to anti-neovascularization were evaluated using RT-qPCR. Corneal epithelium cell junctions were observed via an electron microscope. The tissue-engineered corneal epithelium culture medium was analyzed through mass spectrometry. Tissue-engineered corneal epithelial cells expanded by LSCs on UAM-MSCs had good transparency. Simultaneously, progenitor cell (K14, PNCA, p63) and corneal epithelial (PAX6) gene expression in tissue-engineered corneal epithelium constructed using UAM-MSCs was higher than that in corneal epithelial cells amplified by UAM and de-epithelialized amniotic membrane. Electron microscopy revealed that corneal epithelial cells grafted with UAM-MSCs were closely connected. In conclusion, the UAM-MSCs vector we constructed could better simulate the limbal microenvironment; the cultured tissue-engineered corneal epithelium had better transparency, anti-neovascularization properties, closer intercellular connections, and closer resemblance to the natural corneal epithelial tissue phenotype.

Epidermal stem cells orchestrate epidermal renewal and timely wound repair through a tight regulation of self-renewal, proliferation, and differentiation. In culture, human epidermal stem cells generate a clonal type referred to as holoclone, which give rise to transient amplifying progenitors (meroclone and paraclone-forming cells) eventually generating terminally differentiated cells. Leveraging single-cell transcriptomic data, we explored the FOXM1-dependent biochemical signals controlling self-renewal and differentiation in epidermal stem cells aimed at improving regenerative medicine applications. We report that the expression of H1 linker histone subtypes decrease during serial cultivation. At clonal level we observed that H1B is the most expressed isoform, particularly in epidermal stem cells, as compared to transient amplifying progenitors. Indeed, its expression decreases in primary epithelial culture where stem cells are exhausted due to FOXM1 downregulation. Conversely, H1B expression increases when the stem cells compartment is sustained by enforced FOXM1 expression, both in primary epithelial cultures derived from healthy donors and JEB patient. Moreover, we demonstrated that FOXM1 binds the promotorial region of H1B, hence regulates its expression. We also show that H1B is bound to the promotorial region of differentiation-related genes and negatively regulates their expression in epidermal stem cells. We propose a novel mechanism wherein the H1B acts downstream of FOXM1, contributing to the fine interplay between self-renewal and differentiation in human epidermal stem cells. These findings further define the networks that sustain self-renewal along the previously identified YAP-FOXM1 axis.

Corneal opacity is one of the leading causes of severe vision impairment. Corneal transplantation is the dominant therapy for irreversible corneal blindness. However, there is a worldwide shortage of donor grafts and consequently an urgent demand for alternatives. Three-dimensional (3D) bioprinting is an innovative additive manufacturing technology for high-resolution distribution of bioink to construct human tissues. The technology has shown great promise in the field of bone, cartilage and skin tissue construction. 3D bioprinting allows precise structural construction and functional cell printing, which makes it possible to print personalized full-thickness or lamellar corneal layers. Seed cells play an important role in producing corneal biological functions. And stem cells are potential seed cells for corneal tissue construction. In this review, the basic anatomy and physiology of the natural human cornea and the grafts for keratoplasties are introduced. Then, the applications of 3D bioprinting techniques and bioinks for corneal tissue construction and their interaction with seed cells are reviewed, and both the application and promising future of stem cells in corneal tissue engineering is discussed. Finally, the development trends requirements and challenges of using stem cells as seed cells in corneal graft construction are summarized, and future development directions are suggested.

To highlight the progress and future direction of limbal stem cell (LSC) therapies for the treatment of limbal stem cell deficiency (LSCD).

Direct LSC transplantation have demonstrated good long-term outcomes. Cultivated limbal epithelial transplantation (CLET) has been an alternative to treat severe to total LSCD aiming to improve the safety and efficacy of the LSC transplant. A prospective early-stage uncontrolled clinical trial shows the feasibility and safety of CLET manufactured under xenobiotic free conditions. Other cell sources for repopulating of the corneal epithelium such as mesenchymal stem cells (MSCs) and induced pluripotent stem cells are being investigated. The first clinical trials of using MSCs showed short-term results, but long-term efficacy seems to be disappointing. A better understanding of the niche function and regulation of LSC survival and proliferation will lead to the development of medical therapies to rejuvenate the residual LSCs found in a majority of eyes with LSCD in vivo. Prior efforts have been largely focused on improving LSC transplantation. Additional effort should be placed on improving the accuracy of diagnosis and staging of LSCD, and implementing standardized outcome measures which enable comparison of efficacy of different LSCD treatments for different severity of LSCD. The choice of LSCD treatment will be customized based on the severity of LSCD in the future.

New approaches for managing different stages of LSCD are being developed. This concise review summarizes the progresses in LSC therapies for LSCD, underlying mechanisms, limitations, and future areas of development.

Among the regenerative therapies being put into clinical use, the field of corneal regenerative therapy is one of the most advanced, with several regulatory approved products. This article describes the progress from initial development through to clinical application in the eye field, with a particular focus on therapies for corneal epithelial and endothelial diseases that have already been regulatory approved as regenerative therapy products. The applications of regenerative therapy to the corneal epithelium were attempted and confirmed earlier than other parts of the cornea, following advancements in basic research on corneal epithelial stem cells. Based on these advances, four regenerative therapy products for corneal epithelial disease, each employing distinct cell sources and culture techniques, have been commercialized since the regulatory approval of Holoclar® in Italy as a regenerative therapy product for corneal epithelial disease in 2015. Corneal endothelial regenerative therapy was started by the development of an in vitro method to expand corneal endothelial cells which do not proliferate in adults. The product was approved in Japan as Vyznova® in 2023. The development of regenerative therapies for retinal and ocular surface diseases is actively being pursued, and these therapies use somatic stem cells and pluripotent stem cells (PSCs), especially induced pluripotent stem cells (iPSCs). Accordingly, the eye field is anticipated to play a pioneering role in regenerative therapy development going forward.

This study compared the long-term outcome of different epithelial transplantation techniques to treat limbal stem cell deficiency (LSCD). We conducted a retrospective 15-year comparative systematic cohort study of patients with LSCD who underwent either cultivated limbal epithelial transplantation (CLET), simple limbal epithelial transplantation (SLET), or cultivated oral mucosal epithelial transplantation (COMET). We reviewed the demographic data, etiology, LSCD severity, best-corrected visual acuity, surgical outcomes, and complications. A total of 103 eyes of 94 patients (mean age, 45.0 ± 16.4 years) with LSCD were enrolled. The most common cause of LSCD was chemical injury (42.7 %). The median follow-up time was 75 months. The success rates of CLET, SLET, and COMET were 45.5 %, 77.8 %, and 57.8 %, respectively. The 7-year survival rates after CLET, SLET, and COMET were 50.0 %, 72.2 %, and 53.2 %, respectively. Steven-Johnson syndrome (SJS) had a significantly lower survival rate than other causes (p < 0.001), but SLET had a significantly higher survival rate than CLET (p = 0.018) and COMET (p = 0.047). Visual improvement of more than four Snellen lines was achieved in 53.1 % of successful cases and 28.2 % of failed cases. SJS, Schirmer I test <5 mm, and the presence of postoperative recurrent epithelial defects were significant risk factors for a failed surgery. All epithelial transplantation techniques had favorable long-term surgical outcomes. More than half of the patients achieved a stable ocular surface and visual acuity improvement up to 7 years postoperatively. SLET tends to have a better surgical outcome than CLET and COMET, especially in patients with SJS.

To determine the safety and feasibility of human autologous adipose tissue-derived adult mesenchymal stem cells (ASCs) for ocular surface regeneration in patients with bilateral limbal stem-cell deficiency (LSCD).

A phase IIa clinical trial was designed (https://Clinicaltrials.gov, NCT01808378) with 8 patients, 3 of whom had aniridia, 2 meibomian glands diseases, 2 multiple surgeries and 1 chronic chemical injury. The therapeutic protocol was as follows: 6-mm of central corneal epithelium was removed, 400,000 ASCs were injected into each limboconjunctival quadrant, 400,000 ASCs were suspended over the cornea for 20 min, and finally the cornea was covered with an amniotic membrane patch.

No adverse events were detected after a mean of 86,5 months of follow-up. One year after surgery, 6 of the 8 transplants were scored as successful, five patients had improved uncorrected visual acuity (mean of 12 letters), two patients presented epithelial defects (also present at baseline) and the mean percentage of corneal neovascularization was of 28.75% (36.98%, at baseline). Re-examination 24 months after treatment disclosed preserved efficacy in 4 patients. At the last visit (after a mean of 86,5 months of follow up) epithelial defects were absent in all patients although improvement in all of the variables was only maintained in patient 3 (meibomian glands agenesia).

ASCs are a feasible and conservative therapy for treating bilateral LSCD. The therapeutic effect differs between etiologies and diminishes over time.

Corneal diseases are a major cause of vision loss worldwide. Traditional methods like corneal transplants from donors are effective but face challenges like limited donor availability and the risk of graft rejection. Therefore, new treatment methods are essential. This review examines the growing field of bioprinting and biofabrication in corneal tissue engineering. We begin by discussing various bioprinting methods such as stereolithography, inkjet, and extrusion printing, highlighting their strengths and weaknesses for eye-related uses. We also explore how biological tissues are made suitable for bioprinting through a process called decellularization, which can be achieved using chemical, physical, or biological methods. The review then looks at natural materials, known as bioinks, used in bioprinting. We focus on materials like gelatin, collagen, fibrin, chitin, chitosan, silk fibroin, and alginate, examining their mechanical and biological properties. The importance of hydrogel scaffolds, particularly those based on collagen and other materials, is also discussed in the context of repairing corneal tissue. Another key area we cover is the use of stem cells in corneal regeneration. We pay special attention to limbal epithelial stem cells and mesenchymal stromal cells, highlighting their roles in this process. The review concludes with an overview of the latest advancements in corneal tissue bioprinting, from early techniques to advanced methods of delivering stem cells using bioengineered materials. In summary, this review presents the current state and future potential of bioprinting and biofabrication in creating functional corneal tissues, highlighting new developments and ongoing challenges with a view towards restoring vision.

In the field of biomedical research, organoids represent a remarkable advancement that has the potential to revolutionize our approach to studying human diseases even before clinical trials. Organoids are essentially miniature 3D models of specific organs or tissues, enabling scientists to investigate the causes of diseases, test new drugs, and explore personalized medicine within a controlled laboratory setting. Over the past decade, organoid technology has made substantial progress, allowing researchers to create highly detailed environments that closely mimic the human body. These organoids can be generated from various sources, including pluripotent stem cells, specialized tissue cells, and tumor tissue cells. This versatility enables scientists to replicate a wide range of diseases affecting different organ systems, effectively creating disease replicas in a laboratory dish. This exciting capability has provided us with unprecedented insights into the progression of diseases and how we can develop improved treatments. In this paper, we will provide an overview of the progress made in utilizing organoids as preclinical models, aiding our understanding and providing a more effective approach to addressing various human diseases.

Regenerative medicine is a highly anticipated field with hopes to provide cures for previously uncurable diseases such as spinal cord injuries and retinal blindness. Most regenerative medical products use either autologous or allogeneic stem cells, which may or may not be genetically modified. The introduction of induced-pluripotent stem cells (iPSCs) has fueled research in the field, and several iPSC-derived cells/tissues are currently undergoing clinical trials. The cornea is one of the pioneering areas of regenerative medicine, and already four cell therapy products are approved for clinical use in Japan. There is one other government-approved cell therapy product approved in Europe, but none are approved in the USA at present. The cornea is transparent and avascular, making it unique as a target for stem cell therapy. This review discusses the unique properties of the cornea and ongoing research in the field.

The current study is aimed to present the long-term results of the patients who underwent conjunctivolimbal autograft (CLAU) as the primary operation in unilateral limbal stem cell deficiency and the ocular surface safety of the donor eyes. The patients were followed up for five years or longer.

The records of all patients who underwent CLAU as the primary operation were retrospectively analyzed. Additional ocular surface operations, ocular surface stability, best-corrected visual acuity (BCVA), and ocular surface status of the donor eyes were investigated.

The mean age of the patients at the time of transplantation was 35.07 ± 12.9 (12-60). Twenty-nine eyes of 29 patients were followed up for an average of 97.82 ± 34.45 (60-186) months. Additional ocular surface operation was required in 27.58% (8/29) of the eyes in order to achieve a stable ocular surface. Ocular surface stability was achieved in 82.75% (24/29) of the eyes at the end of the follow-up period. BCVA increased from 1.78 ± 0.82 to 0.91 ± 0.92 logMAR at the last visit (p < 0.001). Corneal ectasia and vascularization developed in one donor eye in the fifth postoperative year.

CLAU tissues provide ocular surface stability with a successful vision result in the long term. CLAU theoretically carries risks including limbal stem cell deficiency in the donor eye. In the long-term follow-up of donor eyes after CLAU, ectasia and limbal stem cell deficiency were observed in one eye.

To describe a novel corneal surgical technique combining Deep Anterior Lamellar Keratoplasty (DALK) with grafting of allogeneic limbus (Limbo-DALK) for the treatment of eyes with corneal stromal pathology and limbal stem cell deficiency (LSCD).

Clinical records of six Limbo-DALKs performed in five patients diagnosed with LSCD and corneal stromal pathology requiring keratoplasty were retrospectively reviewed. All patients were diagnosed with LSCD due to various pathologies including thermal and chemical burns, congenital aniridia or chronic inflammatory ocular surface disease. Parameters analysed included demographics, diagnoses, clinical history, thickness measurements using anterior segment OCT, visual acuity, and epithelial status. Regular follow-up visits were scheduled at 6 weeks as well as 3, 6, 9, and 12 and 18 months postoperatively. Main outcome measures were time to graft epithelialisation and the occurrence of corneal endothelial decompensation.

Two grafts showed complete epithelial closure at 2 days, two at 14 days. In one eye, complete epithelial closure was not achieved after the first Limbo-DALK, but was achieved one month after the second Limbo-DALK. No endothelial decompensation occurred except in one patient with silicone oil associated keratopathy. Endothelial graft rejection was not observed in any of the grafts.

Based on the data from this pilot series, limbo-DALK appears to be a viable surgical approach for eyes with severe LSCD and corneal stromal pathology, suitable for emergency situations (e.g. corneal ulceration with impending corneal perforation), while minimising the risk of corneal endothelial decompensation.