Corneal Regeneration Research Articles

Investigation of healing strategies in a rat corneal opacity model with polychromatic light and stem cells injection

Corneal opacities are a major cause of vision loss worldwide. However, the current therapies are suboptimal to manage the corneal wound healing process. Therefore, there is an obvious need to develop new treatment strategies that are efficient in promoting wound healing in patients with severe corneal disorders. In this study, we investigated and compared the efficacy of adipose-derived mesenchymal stem cells (ADMSCs) and photobiomodulation (PBM) with polychromatic light in the NIR (600–1200 nm) alone and in combination, on corneal opacity, inflammatory response, and tissue architecture in a rat corneal opacity model created by mechanical injury. All animals were divided into four groups randomly following the injury: injury only (no treatment), ADMSCs treatment, PBM treatment and combined (ADMSCs+PBM) treatment (n = 12 eyes per group). At the 10th and 30th day following injury, corneal opacity formation, neovascularization, and corneal thickness were assessed. On the 30th day the harvested corneas were analyzed by transmission electron microscopy (TEM), histological evaluation, immunohistochemical (IHC) staining and real-time polymerase chain reaction (RT-PCR). On day 30, the corneal opacity score, neovascularization grade, and corneal thickness in all treatment groups were significantly lower in comparison with the untreated injured corneas. The TEM imaging and H&E staining together clearly revealed a significant enhancement in corneal regeneration with improved corneal microenvironment and reduced vascularization in the combined administration of PBM and ADMSCs compared to treatment of PBM and ADMSCs alone. In addition, the IHC staining, and RT-PCR analysis supported our hypothesis that combining ADMSCs therapy with PBM alleviated the inflammatory response, and significantly decreased scar formation compared to either ADMSCs or PBM alone during the corneal wound healing.

Multiscale characterization of electrospun non-wovens for corneal regeneration: Impact of microstructure on mechanical, optical and biological properties

The multiscale approach in designing substrates for regenerative medicine endows them with beneficial properties determining their performance in the body. Substrates for corneal regeneration should reveal the proper transparency, mechanical properties and microstructure to maintain the functionality of the regenerated tissue. In our study, series of non-wovens with different fibres orientation (random (R), aligned (A)), topography (shish-kebab (KK), core-shell (CS)) and thickness were fabricated via electrospinning. The samples were assessed for mechanical (static tensile test) and optical properties (spectroscopy UV–Vis). The research evaluated the impact of different microstructures on the viability and morphology of three cell lines (Hs 680, HaCaT and RAW 264.7). The results showed how the fibres arrangement influenced mechanical behaviour of the non-wovens. The randomly oriented fibres were more elongated (up to 50 mm) and had a lower maximum tensile force (up to 0.46 N). In turn, the aligned fibres were characterized by lower elongation (up to 19 mm) and higher force (up to 1.45 N). The conducted transparency tests showed the relation between thickness (of the non-woven and fibres) and morphology of the substrate and light transmission. To simulate the in vivo conditions, prior to the light transmission studies, samples were immersed in water. All the samples exhibited high transparency after immersion in water (>80%). The impact of various morphologies was observed in the in vitro studies. All the samples proved high cells viability. Moreover, the substrate morphology had a significant impact on the orientation and arrangement of the fibroblast cytoskeleton. The aligned fibres were oriented in exactly the same direction. The conducted research proved that, by altering the non-wovens microstructure, the properties can be adjusted so as to induce the desirable cellular reaction. This indicates the high potential of electrospun fibres in terms of modulating the corneal cell behaviour in response to the implanted substrate.

Dopamine Receptor 1 Treatment Promotes Epithelial Repair of Corneal Injury by Inhibiting NOD-Like Receptor Protein 3-Associated Inflammation.

To elucidate the influence of dopamine receptor 1 (DRD1) on the proliferation of mouse corneal epithelial cells (MCECs) under inflammatory conditions. In vitro, immortalized MCECs (iMCECs) were treated with IL-1β, with and without pcDNA3.1_DRD1. Primary MCECs (pMCECs) were exposed to IL-1β, with and without DRD1 agonist (A68930). Cell proliferation was quantified using the Cell Counting Kit-8 (CCK-8) assay and immunofluorescence staining for Ki-67 and p63. Expression levels of NOD-like receptor protein 3 (NLRP3), IL-1β, and IL-6 were assessed. To establish a corneal injury model in mice, a 2-mm superficial keratectomy was performed. Either 0.1% A68930 or PBS was topically administered three times daily to the injured eyes for up to 5days post-injury. Immunofluorescence analysis was employed to evaluate the expression of Ki-67, p63, and CD45 in mouse corneas. Western blotting and real-time quantitative PCR were utilized for quantitative analysis of DRD1, NLRP3, IL-1β, and IL-6 in mouse corneas. Corneal epithelial regeneration was monitored through fluorescein sodium staining for a duration of up to 5days following the injury. Overexpression of DRD1 and A68930 promoted MCEC proliferation and suppressed the expression of NLRP3, IL-1β, and IL-6 in vitro. Topical application of the 0.1% A68930 following mechanical corneal injury in mice led to increased Ki-67 and p63 expression compared to PBS treatment. Furthermore, topical administration of the 0.1% A68930 reduced the expression of CD45, NLRP3, IL-1β, and IL-6. Analysis with fluorescein sodium indicated accelerated corneal epithelial regeneration in the 0.1% A68930 treatment group. DRD1 treatment counteracts NLRP3-associated inflammation and facilitates epithelial repair of corneal injury.

Evaluation of the Possible Influence of Povidone Iodine (PVI) Solution and Polyhexanide (PHMB) on Wound Healing in Corneal Epithelial Regeneration.

This study investigates the possible toxic effects of the preoperative antiseptic substances povidone iodine (PVI) and polyhexanide (PHMB; Serasept® 2) on wound healing in ophthalmology. To assess this impact, human telomerase-immortalized corneal epithelial (hTCEpi) cells and human telomerase-immortalized conjunctival epithelial (hCjE) cells were exposed to 1% and 5% PVI or 0.04% PHMB for different periods to evaluate the cytotoxicity of these two antiseptics. Furthermore, the toxicity of these antiseptics was investigated in a human tissue-specific corneal epithelial construct and porcine eye culture model. The results reveal the high cytotoxicity of PVI and PHMB in the hTCEpi and hCjE in monolayer cell culture models, independent of the incubation time and concentration of these substances. However, after hTCEpi cell differentiation into a tissue-specific corneal epithelial construct, contact with these antiseptics for the relevant preoperative time did not alter cPARP1 or Ki67 expression. Furthermore, the wound-healing process in the porcine cornea was not significantly influenced after incubation with these antiseptics. In summary, corneal and conjunctival epithelial cell lines are very sensitive to PVI and PHMB, whereas no significant alterations were found in intact tissue-specific corneal epithelial constructs or porcine corneas. Therefore, we could not identify PVI and PHMB as reasons for postoperative eye irritation.

Advances in tissue engineering and 3D bioprinting for corneal regeneration

Blindness resulting from corneal damage affects millions of people worldwide. The scarcity of corneal donors adds a layer of complexity to patient treatment. Consequently, exploring artificial cornea substitutes has become imperative in the realm of clinical research. Scientific advancements have ushered in a plethora of innovative solutions, including keratoprostheses or decellularized cornea scaffolds. The development of three-dimensional (3D) printing has further expanded the horizons of research in this field, delving into the feasibility of bioprinted corneas and yielding numerous promising outcomes. However, the manufacturing of corneal products via 3D printing poses a substantial challenge, demanding a meticulous selection of materials and techniques to ensure the transparency and preservation of the optical and mechanical properties of the artificial cornea. In the review, we present the artificial cornea substitutes. Additionally, we aim to provide a concise overview of the 3D printing techniques and materials applicable to corneal bioprinting.

Adult stem cells in the eye: Identification, characterisation, and therapeutic application in ocular regeneration - A review.

Adult stem cells, present in various parts of the human body, are undifferentiated cells that can proliferate and differentiate to replace dying cells within tissues. Stem cells have specifically been identified in the cornea, trabecular meshwork, crystalline lens, iris, ciliary body, retina, choroid, sclera, conjunctiva, eyelid, lacrimal gland, and orbital fat. The identification of ocular stem cells broadens the potential therapeutic strategies for untreatable eye diseases. Currently, stem cell transplantation for corneal and conjunctival diseases remains the most common stem cell-based therapy in ocular clinical management. Lens epithelial stem cells have been applied in the treatment of paediatric cataracts. Several early-phase clinical trials for corneal and retinal regeneration using ocular stem cells are also underway. Extensive preclinical studies using ocular stem cells have been conducted, showing encouraging outcomes. Ocular stem cells currently demonstrate great promise in potential treatments of eye diseases. In this review, we focus on the identification, characterisation, and therapeutic application of adult stem cells in the eye.

Inhibition of miR-542-3p augments autophagy to promote diabetic corneal wound healing

BackgroundAutophagy has recently been shown to be critical for protecting peripheral nerve regeneration. This study explored the impact of miR-542-3p on diabetic corneal nerve regeneration and epithelial healing through the regulation of autophagy.MethodsA type 1 diabetes model was established in male mice through streptozotocin administration. Immunofluorescence staining of β-Tubulin III and sodium fluorescein staining were performed to observe corneal nerve fiber density and corneal epithelial healing, respectively. Western blotting, immunofluorescence and transmission electron microscopy were used to determine autophagy levels. Subconjunctival injection of RAPA and 3-MA altered autophagy levels; with them, we evaluated the role of autophagy in diabetic keratopathy. miRNA sequencing and bioinformatics analysis were performed to identify miRNA-mRNA networks with potential autophagy-regulating roles, and miR-542-3p was measured by quantitative real-time polymerase chain reaction (qRT-PCR). miR-542-3p antagomir was injected subconjunctivally to assess the role in diabetic corneal neuropathy.ResultsOur data suggest that autophagy is suppressed in the diabetic corneal nerve and that activation of autophagy promotes diabetic corneal wound healing. We identified a potential autophagy-regulating miRNA-mRNA network in the diabetic trigeminal ganglion, in which miR-542-3p expression was significantly upregulated. Inhibition of miR-542-3p significantly enhanced the level of autophagy in trigeminal ganglion by upregulating ATG4D expression, thereby accelerating diabetic corneal nerve regeneration and epithelial healing.ConclusionsDysregulated autophagy is an important contributor to delayed diabetic corneal injury healing. Inhibiting miR-542-3p promotes diabetic corneal nerve regeneration and epithelial healing through autophagy activation by ATG4D.

A pilot study for decellularizing human and porcine cornea for future use in corneal regeneration

Purpose: To effectively decellularize human and porcine corneas for future use in corneal regeneration by using an already established decellularization technique being efficient in decellularizing blood vessels.Methods: One human and 4 porcine corneas were decellularized by using various washing steps with 3‐[(3‐cholamidopropyl) dimethylammonio]‐1‐propanesulfonate (CHAPS) detergent, Benzonase, Ethylenediaminetetraacetic acid (EDTA), 5% Dextran or 5% D‐Mannitol. The quality of the decellularization process was assessed by quantitative and qualitative measurement of DNA content, glycosaminoglycans (GAGs), immunofluorescent staining for Collagen I, V and keratocan, and Transmission Electron Microscopy (TEM) to observe the structure of the collagen fibrils was used.Results: The decellularization process showed 99,94% and 99,52% DNA content reduction in the human and porcine corneas when using Dextran, respectively, while more DNA remained in the porcine corneas when D‐Mannitol was used. Similar pattern was observed in the preservation of GAGs, with the highest amount being found in the human cornea, and less in the porcine corneas. H&E and Immunofluorescent staining showed no presence of cell nuclei when compared to the control native corneas, while Alcian blue staining qualitatively confirmed the presence of GAGs. Collagen I, V and keratocan were still present in the decellularized corneas when compared to the native ones, while TEM microscopy further confirmed the similar patterns of the collagen fibrils in the decellularized‐, compared to the native‐ corneas.Conclusions: This pilot study showed that our decellularization method is effective in decellularizing human and porcine corneas, with very high amount of DNA being removed from the corneas, while the GAGs were preserved to an acceptable extent, and the structure and pattern of the collagen fibrils maintained.

Improving transparency and corneal wound healing in rare diseases by promoting corneal nerve regeneration

Corneal nerves play a crucial role in maintaining the integrity of corneal tissue, as well as the proper regulation of tearing and blinking. When activated, corneal nerves release locally several factors, including neuropeptides, that contribute to the trophic maintenance of corneal tissues. So that, the reduction or absence of corneal nerves led to impaired corneal wound healing in addition to a loss of sensory input, resulting in lack of sensitivity and alterations in tearing and blinking rate. Such consequences are seen clinically in several rare diseases where severe nerve deficit is a prominent factor such as in neurotrophic keratopathy, where the cornea spontaneously ulcerates due to its inability to renew the epithelium and to heal epithelial wounds, leading to loss of corneal transparency. An advanced molecular therapy to increase corneal nerve regeneration and support the corneal neurotrophic environment in such ocular rare diseases is proposed.(Supported by RESTORE VISION – 101 080 611, Horizon Europe Framework Programme, European Commission)

Bowman's layer transplantation—A new hope for regaining of correct ocular surface

Aims/Purpose: To present a novel surgical technique of selective Bowman's layer transplantation as well as results of the surgery in patients with neurotrophic corneal ulcers.Methods: 3 eyes from 3 patients with neurotrophic corneal ulcers who underwent corneal grafting with Bowman's layer. Pre‐ and postoperative analyses of the anterior segment of the eye were based on optical coherence tomography and slit lamp assessment.Results: Postoperatively a gradual corneal stroma restoration and fast corneal epithelialisation were noticed.Conclusions: Based on our observations, stiff and firm structure of Bowman's layer is supposed to strengthen corneal surface and maintain its shape. It acts also as an anti‐pathogen and anti‐toxin corneal barrier. Application of this acellular corneal layer transplantation to cover trophic corneal ulcers is an interesting, modern and crucial method of neurotrophic keratitis treatment.Reference1. Hsu HY, Modi D. Etiologies, quantitative hypoesthesia, and clinical outcomes of neurotrophic keratopathy. Eye Contact Lens 2015;41(5):314–7.2. Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol 2014;8:571–9.3. Mantelli F, Mauris J, Argüeso P. The ocular surface epithelial barrier and other mechanisms of mucosal protection: from allergy to infectious diseases. Curr Opin Allergy Clin Immunol. 2013 Oct;13(5): 563–8.4. Wilson SE. Bowman's layer in the cornea‐ structure and function and regeneration. Exp Eye Res 2020 Jun;195:108033.5. Lagali N, Germundsson J, Fagerholm P. The Role of Bowman's Layer in Corneal Regeneration after Phototherapeutic Keratectomy: A Prospective Study Using In Vivo Confocal Microscopy. Invest Ophthalmol Vis Sc. 2009 Sep;50(9):4192–8.

Potential therapeutic effects of peroxisome proliferator-activated receptors on corneal diseases.

The cornea is an avascular tissue in the eye that has multiple functions in the eye to maintain clear vision which can significantly impair one's vision when subjected to damage. Peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptor proteins comprising three different peroxisome proliferator-activated receptor (PPAR) isoforms, namely, PPAR alpha (α), PPAR gamma (γ), and PPAR delta (δ), have emerged as potential therapeutic targets for treating corneal diseases. In this review, we summarised the current literature on the therapeutic effects of PPAR agents on corneal diseases. We discussed the role of PPARs in the modulation of corneal wound healing, suppression of corneal inflammation, neovascularisation, fibrosis, stimulation of corneal nerve regeneration, and amelioration of dry eye by inhibiting oxidative stress within the cornea. We also discussed the underlying mechanisms of these therapeutic effects. Future clinical trials are warranted to further attest to the clinical therapeutic efficacy.

Clinical applications of confocal microscopy to corneal innervation

In vivo corneal confocal microscopy (IVCM) is a non‐invasive ophthalmic imaging technique that provides images of the cornea at the cellular level. Despite the uses in ocular surface pathologies, in the last decades IVCM has been used to provide more knowledge in refractive surgery wound healing (LASIK and PRK), dry eye disease, and in some corneal infections (amoebas and filamentous fungi). The observation of the corneal cells, both normal and inflammatory, and the possibility of quantification of the corneal nerve density and quality with manual or automated tools, makes IVCM have a significant potential to improve the diagnosis and prognosis in several systemic and corneal conditions. Neuropathic pain has multiple aetiologies, but a major feature is small fibre dysfunction or damage. IVCM has been utilized to show small nerve fibre loss in patients with diabetic and other neuropathies. IVCM has comparable diagnostic utility to intraepidermal nerve fibre density for diabetic neuropathy, fibromyalgia and amyloid neuropathy and predicts the development of diabetic neuropathy. Moreover, in clinical intervention trials of patients with diabetic and sarcoid neuropathy, corneal nerve regeneration occurs early and precedes an improvement in symptoms and neurophysiology. Corneal nerve fibre loss also occurs and is associated with disease progression in multiple sclerosis, Parkinson's disease, and dementia. Patients with small fibre neuropathy have IVCM nerve changes. In conclusion, IVCM has good diagnostic and prognostic capability and fulfils the criteria as an end point for clinical trials in corneal, and peripheral and central neurodegenerative diseases.

Deciphering cell fates of the human cornea with a multi‐omics meta atlas

The human cornea is a transparent tissue composed of several layers that allow light to enter the eye. Disruption of the function of various cells in different layers can give rise to diseases that affect the transparency of the cornea. Understanding the precise cell fates of the cornea and the underlying molecular mechanisms is pivotal for dissecting the pathology of corneal diseases and exploring treatments and regeneration. Currently, there is a lack of a precise cell fate map for the human cornea. In this study, we constructed a multi‐omics meta‐atlas to define cell fates in the human adult and embryonic cornea, by integrating publicly available datasets. This multi‐omics meta‐atlas is comprised of RNA‐seq data representing genome‐wide gene expression profiles and ATAC‐seq data annotating regulatory genomic regions that control gene expression in single‐cells of the cornea. We identified the key transcription factors and combinations that determine cell fates in the human cornea, with gene regulatory network analyses using the meta‐atlas. Some of these transcription factors are functionally validated. We also applied this meta‐atlas to analyse single cells of the cornea derived from keratoconus patients and showed an expansion of corneal stromal stem cells as a potential disease mechanism. In conclusion, this study provides an extensive reference of cell fates of the human cornea that can be used to dissect disease mechanisms. This meta‐atlas also provides insights for therapeutic discovery and molecular blueprints for corneal regeneration.

ECM-based bioadhesive hydrogel for sutureless repair of deep anterior corneal defects.

Corneal transplantation is the gold standard treatment for corneal-related blindness; however, this strategy faces challenges such as limited donor cornea, graft rejection, suture-related complications, and the need for specialized equipment and advanced surgical skills. Development of tissue adhesives for corneal regeneration is of great clinical value. However, currently available corneal tissue sealants pose challenges, such as lack of safety, biocompatibility, and desired mechanical properties. To meet these requirements simultaneously, a bovine stromal corneal extracellular matrix (dCor) was used to design a bioadhesive photocurable hydrogel based on gelatin methacrylate (GelMA) and polyethylene glycol diacrylate (PEGDA) hydrogels (dCor/Gel-PEG). Integration of dCor into the dual networks of GelMA and PEGDA (Gel-PEG) led to a bioadhesive hydrogel for curing corneal defects, which could be crosslinked by Irgacure 2959 within 5 min ultraviolet irradiation. The viability of corneal stromal stem cells (CSSCs) was improved on the dCor/Gel-PEG hydrogel in comparison to the Gel-PEG hydrogel. The gene expression profile supported the keratocyte differentiation of CSSCs seeded on dCor/Gel-PEG via increased KERA and ALDH, with inhibited myofibroblast transdifferentiation via decreased α-SMA due to the presence of dCor. Interestingly, the dCor/Gel-PEG hydrogel exhibited favorable mechanical performance in terms of elasticity and bioadherence to the host corneal stroma. Ex vivo and in vivo examinations proved the feasibility of this hydrogel for the sutureless reconstruction of deep anterior corneal defects with promising histopathological results.

In vitro Assay to Examine the Function of Tears on Corneal Epithelial Cells.

Tears contain numerous secreted factors, enzymes, and proteins that help in maintaining the homeostatic condition of the eye and also protect it from the external environment. However, alterations to these enzymes and/or proteins during pathologies such as mechanical injury and viral or fungal infections can disrupt the normal ocular homeostasis, further contributing to disease development. Several tear film components have a significant role in curbing disease progression and promoting corneal regeneration. Additionally, several factors related to disease progression are secreted into the tear film, thereby serving as a valuable reservoir of biomarkers. Tears are readily available and can be collected via non-invasive techniques or simply from contact lenses. Tears can thus serve as a valuable and easy source for studying disease-specific biomarkers. Significant advancements have been made in recent years in the field of tear film proteomics, lipidomics, and transcriptomics to allow a better understanding of how tears can be utilized to gain insight into the etiology of diseases. These advancements have enabled us to study the pathophysiology of various disease states using tear samples. However, the mechanisms by which tears help to maintain corneal homeostasis and how they are able to form the first line of defense against pathogens remain poorly understood and warrant detailed in vitro studies. Herein, we have developed an in vitro assay to characterize the functional importance of patient isolated tears and their components on corneal epithelial cells. This novel approach closely mimics real physiological conditions and could help the researchers gain insight into the underlying mechanisms of ocular pathologies and develop new treatments. Key features • This method provides a new technique for analyzing the effect of tear components on human corneal epithelial cells. • The components of the tears that are altered in response to diseases can be used as a biomarker for detecting ocular complications. • This procedure can be further employed as an in vitro model for assessing the efficacy of drugs and discover potential therapeutic interventions.

A microbial infection‐resistant 3D bioprinted material for corneal stroma regeneration

Aims/Purpose: To assess whether 3D bioprinted, scaffold‐immobilized antimicrobial peptides (AMPs) derivatives, BMAP27(1–18) and hLF(1–11) can inhibit microbial colonization to obtain infection‐resistant 3D bioprinted hemi‐corneas.Methods: The research followed the tenets of the Declaration of Helsinki. 3D bioprinting was used to produce transparent nanocellulose‐ and alginate‐based 3D constructs. Functionalized 3D bioprinted scaffolds with AMPs were characterized by contact angle and transparency measurements. The antimicrobial and antifungal activity of the peptides in solution were investigated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods against Staphylococcus epidermidis ATCC 35984, S. aureus ATCC 25923, S. epidermidis ATCC 12228, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and Candida albicans ATCC 90028. The antimicrobial activity of the AMP‐modified scaffolds was studied against P. aeruginosa and C. albicans reference strains by colony forming unit (CFU) counts, and their biocompatibility was investigated by measuring the viability of primary human/cadaver‐isolated corneal stromal‐mesenchymal stromal cells (CS‐MSCs).Results: The original and modified peptides showed MIC (MBC) values of 1–4 (2–8) μM and 16 – >128 (32 – >128) μM, respectively, against S. epidermidis ATCC 35984, S. aureus, S. epidermidis ATCC 12228, P. aeruginosa, E. coli and C. albicans, while ncBP‐BMAP27(1–18) and ncBP‐hLF(1–11) values were 1–16 (2–32) μM 4–128 (4 – >128) μM, respectively, against all the pathogens. The modified scaffolds containing the AMPs attached to the scaffolds, demonstrated the ability to kill 20–96% of P. aeruginosa, and between 60–70% of C. albicans. All the 3D bioprinted scaffolds showed no cytotoxicity towards CS‐MSCs.Conclusions: We could successfully combine 3D bioprinting with immobilization of AMPs that show promising antimicrobial activity against two of the most dangerous pathogens to the cornea, while a good cytocompatibility for the CS‐MSCs could be achieved. Optimal bioink composition and cellularization of tissue equivalents are essential in fine‐tuning a method to promote the current 3D bioprinting technique as a future treatment modality for corneal regeneration.

Cationic human defence peptides and cornea HSV‐1 infections: Results of a rabbit study

In this study, we evaluated the potential of LiQD cornea glue supplemented with LL37‐derived peptide GF19, delivered through Silicium nanoparticles (SiNP) to prevent herpes simplex virus type 1 (HSV‐1) infection in a rabbit corneal model. SiNP‐GF19 was synthesized using a hydrophobic core, a hydrophilic shell, and a reactive surface that allowed covalent bonding to the collagen‐like peptides of our developed LiQD Cornea glue. Our results showed that SiNP‐GF19 was able to effectively release GF19 in a sustained manner, with approximately 60% of the peptide being released over 24 h. The remaining 40% of GF19 is trapped in the SiNP and can only be released upon complete degradation of the nanoparticles, which may occur via cellular uptake and enzymatic degradation. This ensures the prolonged release of GF19. The mechanism of action of GF19 against HSV‐1 may involve preventing the binding of the virus to host cells. Previous studies have shown that LL37, from which GF19 is derived, can block HSV‐1 binding to host cells, leading to decreased viral infection. However, in our study, we did not see reduced viral shedding, furthermore, nanoparticles coated with the GF19 peptide or nanoparticles themselves may have an eye irritant effect. Nevertheless, LiQD Cornea supplemented with SiNP‐GF19 or LiQD alone were effective in promoting corneal regeneration and healing. Specifically, it led to the formation of a relatively mature epithelium composed of 2–3 epithelial layers, expressing CK3 in the outermost epithelial layer, compared to the absence of epithelium or a monolayer of unstructured CK3‐negative epithelium in the cyanoacrylate adhesive control group. LiQD Cornea formulation without SiNP‐GF19 also displayed significantly lower α‐SMA staining than the rest of the experimental groups in the implant area, which overexpression is associated with abnormal extracellular matrix deposition and scar formation. In terms of nerve regeneration, all LiQD Cornea formulations showed βIII tubulin expression, indicating immature neuronal microtubule structures. In summary, all three experimental treatment strategies were significantly more effective compared to the cyanoacrylate adhesive control group, significantly smaller scar tissues without ingrown vascular networks were formed, though, only mild antiviral properties of SiNP‐GF19 were observed.

Regenerated Corneal Epithelium Expresses More βIII-Tubulin After Chemical Injuries Compared to Mechanical Injuries.

Defining the regenerative response following various types of corneal chemical and mechanical injuries is important for understanding the pathophysiology of the injury and evaluating the effectiveness of the therapies. This study characterizes corneal epithelial healing in a murine chemical and mechanical injury model. Four groups of 10 mice each received complete corneolimbal injuries by AlgerBrush, AlgerBrush/thermal, NaOH (0.5 N), or ethanol. Slit-lamp and optical coherence tomography examinations were performed daily for 14days. Corneal opacity (CO) and neovascularization (NV) were evaluated. The origin of the regenerated epithelium was illustrated by anti-cytokeratin 12 (K12) and anti-K13. The height of regenerated corneal epithelium and intraepithelial free nerve endings (FNEs) stained with anti-βIII-tubulin were measured. The amount of fibrosis was measured by anti-α-smooth muscle actin (α-SMA) monoclonal antibody in the different groups. Statistical analysis was performed by ANOVA and t-test. Corneal opacity and neovascularization were markedly higher in the NaOH and AlgerBrush/thermal groups. Molecular studies revealed the following: Regenerated corneal epithelium thickness was less than normal in all groups, the AlgerBrush group had the shortest height of the regenerated epithelium, βIII-tubulin was expressed in the entire height of corneal epithelium in all groups except in the AlgerBrush group, and K12 was replaced by K13 in all groups. Corneal wound healing is more effective following chemical injuries in terms of epithelial thickness. Inflammation may play an important role in the outcome. Inflammation following different injuries may be redirected to be more effective in corneal regeneration and clarity.

Effects of 1,25-Vitamin D3 and 24,25-Vitamin D3 on Corneal Nerve Regeneration in Diabetic Mice.

Corneal nerve homeostasis is essential for the functional integrity of the ocular surface. Vitamin D deficiency (VDD) and vitamin D receptor knockout (VDR KO) have been found to reduce corneal nerve density in diabetic mice. This is the first study to comprehensively examine the influence of vitamin D on nerve regeneration following corneal epithelial injury in diabetic mice. Corneal nerve regeneration was significantly retarded by diabetes, VDR KO, and VDD, and it was accelerated following topical 1,25 Vit D and 24,25 Vit D administration. Furthermore, topical 1,25 Vit D and 24,25 Vit D increased nerve growth factor, glial cell line-derived neurotropic factor, and neurotropin-3 protein expression, and it increased secretion of GDNF protein from human corneal epithelial cells. CD45+ cells and macrophage numbers were significantly decreased, and vitamin D increased CD45+ cell and macrophage recruitment in these wounded diabetic mouse corneas. The accelerated nerve regeneration observed in these corneas following topical 1,25 Vit D and 24,25 Vit D administration may be related to the vitamin D-stimulated expression, secretion of neurotrophic factors, and recruitment of immune cells.

A Versatile Hydrogel with Antibacterial and Sequential Drug-Releasing Capability for the Programmable Healing of Infectious Keratitis.

Hydrogels have attracted tremendous attention as favorable corneal substitutes for treating severe infectious keratitis (IK). However, current hydrogel-based corneal substitutes were majorly designed to promote the single stage of corneal regeneration, which falls short in meeting the clinical management needs of severe IK including the multiple phases of corneal wound healing. Herein, we introduce a versatile hybrid hydrogel (SQPV) composed of silk fibroin and chitosan, which exhibits spatiotemporal properties for drug release. The SQPV is fabricated by incorporating verteporfin-loaded poly(lactic-co-glycolic)-polyethylene glycol-o-nitrobenzene micelles into a hydrogel network, which is formed from methacrylate silk fibroin and glycidyl methacrylate functionalized quaternized chitosan containing polydeoxyribonucleotide. This double network approach results in a material with exceptional anti-inflammatory, antibacterial, and proliferative stimulation and tissue remodeling regulation capabilities. Furthermore, SQPV showcases mechanical strength and transparency akin to those of native cornea. Extensive in vitro and in vivo studies validate SQPV's ability to effectively eliminate residual bacteria, mitigate inflammation, foster regeneration of corneal epithelium and stroma, prevent corneal scarring, and ultimately expedite wound healing. In summary, the SF/CS-based hybrid hydrogel may represent a promising substitute for comprehensive corneal repair and regeneration in severe IK.