Corneal epithelial stem cells for corneal injury

INOS ablation promotes corneal wound healing via activation of Akt signaling

Corneal injury leads to impaired normal structure of the cornea. Improving the wound healing process in epithelial cells significantly contributes to ocular damage treatments. Here, we aimed to investigate the potential mechanisms of nitric oxide (NO) and its mediator, inducible nitric oxide synthase (iNOS), in the process of corneal wound healing. We established a corneal injury model of iNOS-/- mice, and treated human corneal epithelial cell lines (HCE-2) with the iNOS inhibitor L-INL, with or without NO replenishment by supplying sodium nitroferricyanide dihydrate (SNP). Our findings showed that inhibition of NO/iNOS accelerated corneal repair, enhanced uPAR (a receptor protein indicating the migration ability), and improved epithelial cell migration. Furthermore, NO/iNOS ablation activated Akt phosphorylation, reduced neutrophil marker protein MPO expression, and downregulated the transcription of inflammation cytokines CXCL-1, CXCL-2, IL-1β, IL-6, and TNF-α. However, the protective effects of NO/iNOS inhibition are significantly reduced by NO replenishment when treated with SNP. Therefore, we confirmed that inhibiting NO/iNOS improved the corneal wound healing by facilitating epithelial cell migration and reducing inflammatory reactions, which might be related to the activation of the Akt signaling pathway.

The application of a 4D-printed chitosan-based stem cell carrier for the repair of corneal alkali burns

BACKGROUND

Corneal alkali burns can lead to ulceration, perforation, and even corneal blindness due to epithelial defects and extensive cell necrosis, resulting in poor healing outcomes. Previous studies have found that chitosan-based in situ hydrogel loaded with limbal epithelium stem cells (LESCs) has a certain reparative effect on corneal alkali burns. However, the inconsistent pore sizes of the carriers and low cell loading rates have resulted in suboptimal repair outcomes. In this study, 4D bioprinting technology was used to prepare a chitosan-based thermosensitive gel carrier (4D-CTH) with uniform pore size and adjustable shape to improve the transfer capacity of LESCs.

METHODS

Prepare solutions of chitosan acetate, carboxymethyl chitosan, and β-glycerophosphate sodium at specific concentrations, and mix them in certain proportions to create a pore-size uniform scaffold using 4D bioprinting technology. Extract and culture rat LESCs (rLESCs) in vitro, perform immunofluorescence experiments to observe the positivity rate of deltaNp63 cells for cell identification. Conduct a series of experiments to validate the cell compatibility of 4D-CTH, including CCK-8 assay to assess cell toxicity, scratch assay to evaluate the effect of 4D-CTH on rLESCs migration, and Calcein-AM/PI cell staining experiment to examine the impact of 4D-CTH on rLESCs proliferation and morphology. Establish a severe alkali burn model in rat corneas, transplant rLESCs onto the injured cornea using 4D-CTH, periodically observe corneal opacity and neovascularization using a slit lamp, and evaluate epithelial healing by fluorescein sodium staining. Assess the therapeutic effect 4D-CTH-loaded rLESCs on corneal alkali burn through histological evaluation of corneal tissue paraffin sections stained with hematoxylin and eosin, as well as immunofluorescence staining of frozen sections.

RESULTS

Using the 4D-CTH, rLESCs were transferred to the alkali burn wounds of rats. Compared with the traditional treatment group (chitosan in situ hydrogel encapsulating rLESCs), the 4D-CTH-rLESC group had significantly higher repair efficiency of corneal injury, such as lower corneal opacity score (1.2 ± 0.4472 vs 0.4 ± 0.5477, p < 0.05) and neovascularization score (5.5 ± 1.118 vs 2.6 ± 0.9618, p < 0.01), and significantly higher corneal epithelial wound healing rate (72.09 ± 3.568% vs 86.60 ± 5.004%, p < 0.01).

CONCLUSION

In summary, the corneas of the 4D-CTH-rLESC treatment group were similar to the normal corneas and had a complete corneal structure. These findings suggested that LESCs encapsulated by 4D-CTH significantly accelerated corneal wound healing after alkali burn and can be considered as a rapid and effective method for treating epithelial defects.

Plasma fibrin membranes loaded with bone marrow mesenchymal stem cells and corneal epithelial cells promote corneal injury healing via attenuating inflammation and fibrosis after corneal burns

The shortage of corneal donors has prompted the development of tissue-engineered corneal grafts as an alternative solution. Currently, amniotic membranes with good biocompatibility are widely used as scaffolds for loading stem cells in the treatment of corneal injury. However, this approach has its limitations. In this study, BMSCs were induced to differentiate into corneal epithelial cells via direct contact co-culture, and platelet-poor plasma was used to prepare fibrin gels, which were compressed to remove excess liquid and then lyophilized to obtain plasma fibrin membranes (PFMs). A tissue-engineered corneal implant with PFMs as a scaffold loaded with BMSCs and corneal epithelial cells was designed and obtained. Scanning electron microscopy showed that PFMs have a uniformly distributed microporous surface that facilitates cell attachment and nutrient transport. The rheological results showed that the freeze-dried and rehydrated PFMs were more rigid than fresh membranes, which makes it easier to use them for transplantation after cell loading. The experimental results of a rat alkali burn cornea injury model showed that PFMs effectively reduced the inflammatory reaction, inhibited fibrosis, and accelerated the healing of corneal wounds. It was also found that some of the BMSCs were successfully implanted into the corneal injury site in rats and differentiated into corneal epithelial cells. These results demonstrate the potential of tissue-engineered corneal implants using BMSCs and corneal epithelial cells and PFMs as scaffolds as a new treatment option for corneal injury.

Two Methods for the Isolation and Cultivation of Porcine Primary Corneal Cells

In ophthalmic research, there is a strong need for in vitro corneal cell models. Here, we describe different protocols for the cultivation of primary corneal cells that were isolated from porcine eyes. This primary cell culture can be used to test new therapeutic options for corneal diseases, such as dry eye disease, traumatic injuries, or corneal infections, and to study limbal epithelial stem cell (LESC) expansion. Two different isolation methods were performed: the outgrowth and the collagenase method. To perform the outgrowth protocol, small explants of the corneal limbus were generated and incubated in culture flasks in an incubator for 4-5 weeks. Regarding the collagenase method, to extract corneal cells, porcine corneas were removed, cut into small pieces, and incubated with collagenase. After incubation and centrifugation, the cells were seeded in 6- or 12-well plates and incubated in an incubator for 2-3 weeks. The differences between corneal cell cultivation with fetal bovine serum (FBS) and without it are also discussed. Therefore, the main advantages of the outgrowth method are that it requires fewer porcine eyes, and it takes less time to be performed compared to the collagenase method. On the other hand, with the collagenase method, mature cells are obtained earlier, at about 2 to 3 weeks.

Exosomes from bone marrow-derived mesenchymal stem cells facilitate corneal wound healing via regulating the p44/42 MAPK pathway

PURPOSE

This study was aimed at exploring the function of Exosomes isolated from bone marrow-derived mesenchymal stem cells (BMSC-Exos) in corneal wound healing and at revealing the underlying mechanisms involving the p44/42 mitogen-activated protein kinase (MAPK) pathway.

METHODS

The isolated BMSC-Exos were identified by transmission electron microscopy, Western blot, and nanoparticle tracking analysis. After coculture with BMSC-Exos, the proliferation and migration of human corneal epithelial cells (HCEs) were evaluated. The protein expression of p-MEK/MEK and p44/42 MAPK was detected by Western blot. A mouse model of alkali-burned cornea was established via NaOH exposure. After injection with BMSC-Exos, the pathological changes and expression of α-SMA (a fibrosis marker) and CD31 (a vascularization marker) in corneal tissues were detected.

RESULTS

BMSC-Exos enhanced the proliferation and migration of HCEs in a dose-dependent manner. The p44/42 MAPK pathway was activated by the treatment of BMSC-Exos, and its blocking using U0126 partially abrogated the effects of BMSC-Exos on promoting the proliferation and migration of HCEs. In vivo, the injection of BMSC-Exos facilitated the remission of the pathological changes (inflammation) and weakened the upregulation of α-SMA (fibrosis) and CD31 (vascularization) in corneal tissues of mice with alkali-burn injury.

CONCLUSION

BMSC-Exos promoted the proliferation and migration of HCEs via activating the p44/42 MAPK pathway in vitro and also inhibited alkali burn-induced inflammation, fibrosis, and vascularization in corneal tissues in vivo. BMSC-Exos may be promising resources for promoting corneal wound healing.

Ritanserin, a potent serotonin 2A receptor antagonist, represses MEK/ERK signalling pathway to restore PAX6 production and function in aniridia-like cellular model

Aniridia is a panocular inherited rare eye disease linked to heterozygous mutations on the PAX6 gene, which fail to properly produce sufficient protein essential for normal eye development and function. Most of the patients suffer from aniridia-related keratopathy, a progressive opacification of the cornea. There is no effective treatment for this blinding disease. Here we screen for small compounds and identified Ritanserin, a serotonin 2A receptor antagonist, that can rescue PAX6 haploinsufficiency of mutant limbal cells, defective cell migration and PAX6-target gene expression. We further demonstrated that Ritanserin activates PAX6 production through the selective inactivation of the MEK/ERK signaling pathway. Our data strongly suggest that repurposing this therapeutic molecule could be effective in preventing or treating existing blindness by restoring corneal transparency.

Generation of a Biomimetic Substitute of the Corneal Limbus Using Decellularized Scaffolds

Patients with severe limbal damage and limbal stem cell deficiency are a therapeutic challenge. We evaluated four decellularization protocols applied to the full-thickness and half-thickness porcine limbus, and we used two cell types to recellularize the decellularized limbi. The results demonstrated that all protocols achieved efficient decellularization. However, the method that best preserved the transparency and composition of the limbus extracellular matrix was the use of 0.1% SDS applied to the half-thickness limbus. Recellularization with the limbal epithelial cell line SIRC and human adipose-derived mesenchymal stem cells (hADSCs) was able to generate a stratified epithelium able to express the limbal markers p63, pancytokeratin, and crystallin Z from day 7 in the case of SIRC and after 14-21 days of induction when hADSCs were used. Laminin and collagen IV expression was detected at the basal lamina of both cell types at days 14 and 21 of follow-up. Compared with control native limbi, tissues recellularized with SIRC showed adequate picrosirius red and alcian blue staining intensity, whereas limbi containing hADSCs showed normal collagen staining intensity. These preliminary results suggested that the limbal substitutes generated in this work share important similarities with the native limbus and could be potentially useful in the future.

Stem cell therapy in ocular pathologies in the past 20 years

Stem cell therapies are successfully used in various fields of medicine. This new approach of research is also expanding in ophthalmology. Huge investments, resources and important clinical trials have been performed in stem cell research and in potential therapies. In recent years, great strides have been made in genetic research, which permitted and enhanced the differentiation of stem cells. Moreover, the possibility of exploiting stem cells from other districts (such as adipose, dental pulp, bone marrow stem cells, etc.) for the treatment of ophthalmic diseases, renders this topic fascinating. Furthermore, great strides have been made in biomedical engineering, which have proposed new materials and three-dimensional structures useful for cell therapy of the eye. The encouraging results obtained on clinical trials conducted on animals have given a significant boost in the creation of study protocols also in humans. Results are limited to date, but clinical trials continue to evolve. Our attention is centered on the literature reported over the past 20 years, considering animal (the most represented in literature) and human clinical trials, which are limiting. The aim of our review is to present a brief overview of the main types of treatments based on stem cells in the field of ophthalmic pathologies.

The Role of Inflammatory Cytokines in Neovascularization of Chemical Ocular Injury

Aim: Chemical injuries can potentially lead to the necrosis anterior segment of the eye, and cornea in particular. Inflammatory cytokines are the first factors produced after chemical ocular injuries. Inflammation via promoting the angiogenesis factor tries to implement the wound healing mechanism in the epithelial and stromal layer of the cornea. Methods: Narrative review.Results: In our review, we described the patterns of chemical injuries in the cornea and their molecular mechanisms associated with the expression of inflammatory cytokines. Moreover, the effects of inflammation signals on angiogenesis factors and CNV were explained. Conclusion: The contribution of inflammation and angiogenesis causes de novo formation of blood vessels that is known as the corneal neovascularization (CNV). The new vascularity interrupts cornea clarity and visual acuity. Inflammation also depleted the Limbal stem cells (LSCs) in the limbus causing the failure of normal corneal epithelial healing and conjunctivalization of the cornea.

Risk for corneal injury in intensive care unit patients: A cohort study

AIM

To identify the incidence and risk factors for corneal injury amongst critically ill patients.

METHOD

A prospective cohort study with adult patients from one intensive care unit in Northern Brazil. Logistic regression was performed to predict the risk factors associated with corneal injury.

RESULTS

Data from 149 patients revealed 18.8% (28/149) corneal injuries. Factors independently associated with corneal injury were patients with eyeball exposure (OR: 27.31; 95% CI: 3.50-212.78); lagophthalmos (OR: 17.15; 95% CI: 5.78-50.85); chemosis (OR: 7.39; 95% CI: 2.28-23.97), periorbital oedema (OR: 7.99; 95% CI: 2.19-29.13) and hospitalisation >7-days (OR: 11.96; 95% CI: 3.27-43.66) had a significantly higher risk of developing corneal injury in this ICU.

CONCLUSION

Corneal injury was a common complication amongst critically ill patients and was associated with altered physiological function of the eyes such as exposure, lagophthalmos, chemosis and periorbital oedema. This study suggests introduction of a corneal injury prevention protocol for nursing and adding lagophthalmos and chemosis to the NANDA-I Taxonomy, thus contributing to the assessment and monitoring for the risk for corneal injury in critically ill patients.

Recent Approaches for Angiogenesis in Search of Successful Tissue Engineering and Regeneration

Angiogenesis plays a central role in human physiology from reproduction and fetal development to wound healing and tissue repair/regeneration. Clinically relevant therapies are needed for promoting angiogenesis in order to supply oxygen and nutrients after transplantation, thus relieving the symptoms of ischemia. Increase in angiogenesis can lead to the restoration of damaged tissues, thereby leading the way for successful tissue regeneration. Tissue regeneration is a broad field that has shown the convergence of various interdisciplinary fields, wherein living cells in conjugation with biomaterials have been tried and tested on to the human body. Although there is a prevalence of various approaches that hypothesize enhanced tissue regeneration via angiogenesis, none of them have been successful in gaining clinical relevance. Hence, the current review summarizes the recent cell-based and cell free (exosomes, extracellular vesicles, micro-RNAs) therapies, gene and biomaterial-based approaches that have been used for angiogenesis-mediated tissue regeneration and have been applied in treating disease models like ischemic heart, brain stroke, bone defects and corneal defects. This review also puts forward a concise report of the pre-clinical and clinical studies that have been performed so far; thereby presenting the credible impact of the development of biomaterials and their 3D concepts in the field of tissue engineering and regeneration, which would lead to the probable ways for heralding the successful future of angiogenesis-mediated approaches in the greater perspective of tissue engineering and regenerative medicine.

Onion Epithelial Membrane Scaffolds Transfer Corneal Epithelial Layers in Reconstruction Surgery

Plants and their extracts have been used especially in China for more than ten centuries for preventing and treating disease. However, there are only few reports describing their use in animal cell culture and tissue transplantation. In this study, onion epithelial membranes (OEM) is used as scaffolds to support cultures of a variety of cells such as fibroblasts and epithelial cells notably; they maintain the phenotypic characteristics of corneal epithelial cells. This improvement includes preservation of the proliferative potential and stemness of rabbit corneal epithelial cells (RCECs). Such an outcome suggests that this cost-effective technology warrants further evaluation to determine if OEM is a viable candidate for use as scaffolds in corneal epithelial transplantation surgery. To test this possibility, rabbit corneal epithelial cells expanded on OEM are transplanted to treat corneal epithelial defects in limbal stem cell deficient rabbits. This procedure is successful because it shortens the time required for wound healing to restore losses in corneal epithelial integrity, and forms a more compact and stratified epithelium framework than the untreated group. Ultimately, should they be proven to be effective in other relevant animal model systems, their usefulness for treating wounds in a clinical setting warrants consideration.

Application of autologous SOX9+ airway basal cells in patients with bronchiectasis

INTRODUCTION

Bronchiectasis is a common condition and a leading cause of respiratory morbidity and mortality. The treatment method for bronchiectasis is mainly symptomatic treatment or surgery; however, this condition is extremely prone to recurrence.

OBJECTIVES

To preliminarily evaluate the safety and efficacy of applying SOX9⁺ autologous airway basal cells (BCs) in patients with bronchiectasis.

METHODS

SOX9⁺ BCs were isolated from microscale tissue of a grade 3-5 bronchus by bronchoscopic brushing and expanded in vitro for approximately 4 weeks. Subsequently, the autologous SOX9⁺ BCs were transplanted into the diseased bronchus to treat patients with bronchiectasis.

RESULTS

The forced expiratory volume in1 second (FEV1)%, forced vital capacity (FVC)%, total lung capacity (TLC)%, residual volume (RV)% and RV/TLC ratio of predicted value in patients with bronchiectasis were improved at 4, 12, 24 and 48 weeks after cell transplantation, although the differences were not statistically significant (P > .05). Chest CT scans showed that the lesions in the pulmonary segment had not progressed at 4, 12 and 24 weeks after transplantation. No patients died during the follow-up. At 4, 12 and 24 weeks after transplantation, routine blood tests, liver function tests, renal function tests and myocardial enzymatic indexes were normal (P > .05).

CONCLUSION

Transplantation of autologous SOX9⁺ BCs has positive effects and is safe for patients with bronchiectasis.

Recent innovations with drugs in clinical trials for neurotrophic keratitis and refractory corneal ulcers

Introduction: Corneal ulcers normally resolve spontaneously because of the proliferative ability of the corneal epithelium; however, sometimes, epithelial healing is diminished, even when standard treatments are administered. Hence, the treatment of refractory corneal ulcers is challenging and is the subject of ongoing efforts in preclinical and clinical development. Emerging treatment approaches include thymosine β4, CODA001, and topical insulin. Cenegermin eye drops, containing recombinant human nerve growth factor and ReGenerating Agent, a matrix therapy agent, have recently been commercialized for the treatment of moderate to severe neurotrophic keratitis in adults.Areas covered: We describe emerging therapeutic approaches for the management of refractory corneal ulcers and treatments recently introduced to the market. Pubmed and Clinicaltrial.gov databases were first searched including the terms: "corneal ulcer" or "neurotrophic keratopathy" and "treatment." Each treatment was searched in the same databases separately.Expert opinion: Affections of the sensory corneal nerves are the main factor contributing to the pathophysiology of neurotrophic keratopathy; this explains the healing difficulties of this form of ulcer. Cenegermin is a promising therapy acting as a neurotrophic agent for corneal healing. ReGenerating Agent has led to rapid pain relief and corneal healing, but randomized clinical trials are still necessary for further assessment.

Collagen-based materials combined with microRNA for repairing cornea wounds and inhibiting scar formation

AuNP/miR-133b can be released from cornea regeneration materials and entered into stromal cells to inhibit cornea scar formation.