Polysaccharide hydrogel combined with mesenchymal stem cells promotes the healing of corneal alkali burn in rats

The proliferative effects of stem cells from apical papilla-conditioned medium on rat corneal endothelial cells

The cornea, positioned at the forefront of the eye, refracts the light for focusing images on the retina. Damage to this transparent structure can lead to various visual disorders. The corneal endothelial cells (CECs) are crucial for transparency and homeostasis, but lack the ability to reproduce. Significant damage results in structure destruction and vision impairment. While extensive research has aimed at the restoring the corneal endothelial layer, including endothelial proliferation for functional monolayers remains challenging. Our previous studies confirmed the proliferative activity of stem cells from apical papilla-conditioned medium (SCAP-CM) on the retinal pigmented epithelium as a single cell layer. This study investigates how SCAP-CM influences the proliferation and migration of CECs. Our results introduced Matrigel, as a new matrix component for in vitro culture of CECs. Moreover, 60% of SCAP-CM was able to stimulate CEC proliferation as well as migrate to repair wound healing during 24 h. Confluent CECs also expressed specific markers, ATP1a1, ZO-1 and CD56, indicative of CEC characteristics, aligning with the recapitulation of differentiation when forming a homogenous monolayer at the same level of isolated CECs without in vitro culture. These findings suggested that SCAP-CM administration could be useful for future preclinical and clinical applications.

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.

Unlocking the versatile potential: Adipose-derived mesenchymal stem cells in ocular surface reconstruction and oculoplastics

This review comprehensively explores the versatile potential of mesenchymal stem cells (MSCs) with a specific focus on adipose-derived MSCs. Ophthalmic and oculoplastic surgery, encompassing diverse procedures for ocular and periocular enhancement, demands advanced solutions for tissue restoration, functional and aesthetic refinement, and aging. Investigating immunomodulatory, regenerative, and healing capacities of MSCs, this review underscores the potential use of adipose-derived MSCs as a cost-effective alternative from bench to bedside, addressing common unmet needs in the field of reconstructive and regenerative surgery.

Advancements in Ocular Regenerative Therapies

The use of stem cells (SCs) has emerged as a promising avenue in ophthalmology, offering potential therapeutic solutions for various vision impairments and degenerative eye diseases. SCs possess the unique ability to self-renew and differentiate into specialised cell types, making them valuable tools for repairing damaged tissues and restoring visual function. Stem cell-based therapies hold significant potential for addressing conditions such as age-related macular degeneration (AMD), retinitis pigmentosa (RP), corneal disorders, and optic nerve damage. Therefore, researchers have explored different sources of stem cells, including embryonic stem cells (ESC), induced pluripotent stem cells (iPSCs), and adult stem cells, for ocular tissue regeneration. Preclinical studies and early-phase clinical trials have demonstrated promising outcomes, with some patients experiencing improved vision following stem cell-based interventions. However, several challenges remain, including optimising the differentiation protocols, ensuring transplanted cells' safety and long-term viability, and developing effective delivery methods. The field of stem cell research in ophthalmology witnesses a constant influx of new reports and discoveries. To effectively navigate these tons of information, it becomes crucial to summarise and systematise these findings periodically. In light of recent discoveries, this paper demonstrates the potential applications of stem cells in ophthalmology, focusing on their use in various eye tissues, including the cornea, retina, conjunctiva, iris, trabecular meshwork, lens, ciliary body, sclera, and orbital fat.

Concise Review: Bioengineering of Limbal Stem Cell Niche

The corneal epithelium is composed of nonkeratinized stratified squamous cells and has a significant turnover rate. Limbal integrity is vital to maintain the clarity and avascularity of the cornea as well as regeneration of the corneal epithelium. Limbal epithelial stem cells (LESCs) are located in the basal epithelial layer of the limbus and preserve this homeostasis. Proper functioning of LESCs is dependent on a specific microenvironment, known as the limbal stem cell niche (LSCN). This structure is made up of various cells, an extracellular matrix (ECM), and signaling molecules. Different etiologies may damage the LSCN, leading to limbal stem cell deficiency (LSCD), which is characterized by conjunctivalization of the cornea. In this review, we first summarize the basics of the LSCN and then focus on current and emerging bioengineering strategies for LSCN restoration to combat LSCD.

Enhancement of Cell Behavior by the Polysaccharide Extract of Arthrospira and Potential Biomedical Applications

Arthrospira is one of the most studied cyanobacteria and has been reported with practical applications. Among the substances derived from Arthrospira, polysaccharides have received relatively less attention than phycocyanins, though they have more abundant structural variations and specific properties. Herein, a new Arthrospira-derived sulfated polysaccharide was explored for its potential bioactive functions. The ability of this sulfated polysaccharide to promote the behavior of neural stem cells (NSCs) in three-dimensional hydrogel was examined for the first time. NSCs encapsulated in the sulfated polysaccharide-containing hydrogel showed better proliferation than the control hydrogel as well as a unique cell clustering behavior, i.e., formation of multicellular spherical clusters (40-60 μm). The sulfated polysaccharide, in an appropriate range of concentration (5 mg/mL), also maintained the stemness of NSCs in hydrogel and facilitated their differentiation. In addition, the potentials of the new sulfated polysaccharide as a coating material and as a component for drug carrier were verified. The sulfated polysaccharide-modified substrate exhibited superhydrophilicity (contact angle ~9°) and promoted cell adhesion to the substrate. Composite nanoparticles composed of the sulfated polysaccharide and other differently charged polysaccharides were produced with an average diameter of ~240 nm and estimated drug loading of ~18%. The new Arthrospira-derived sulfated polysaccharide is a promising candidate for cell culture, surface-modification, and drug-delivery applications in the biomedical field.

Applications of mesenchymal stem cells in ocular surface diseases: sources and routes of delivery

INTRODUCTION

Mesenchymal stem cells (MSCs) are novel, promising agents for treating ocular surface disorders. MSCs can be isolated from several tissues and delivered by local or systemic routes. They produce several trophic factors and cytokines, which affect immunomodulatory, transdifferentiating, angiogenic, and pro-survival pathways in their local microenvironment via paracrine secretion. Moreover, they exert their therapeutic effect through a contact-dependent manner.

AREAS COVERED

In this review, we discuss the characteristics, sources, delivery methods, and applications of MSCs in ocular surface disorders. We also explore the potential application of MSCs to inhibit senescence at the ocular surface.

EXPERT OPINION

Therapeutic application of MSCs in ocular surface disorders are currently under investigation. One major research area is corneal epitheliopathies, including chemical or thermal burns, limbal stem cell deficiency, neurotrophic keratopathy, and infectious keratitis. MSCs can promote corneal epithelial repair and prevent visually devastating sequelae of non-healing wounds. However, the optimal dosages and delivery routes have yet to be determined and further clinical trials are needed to address these fundamental questions.

[Granulomatous inflammation of the orbit as a complication of stem cells injection (case study)]

The article present a case report of orbital granulomatous inflammation after a retrobulbar injection of allogenous stem cells. Experimental treatment resulted in an orbital tumor that required surgical excision. Lymphogranulomatous inflammation with a secondary abscess was verified by morphological and immunohistochemical analyses. This case demonstrates the possible dangerous complications of the "off-label" therapy amid the rising popularity of stem cells treatment.

Functional Hydrogel Dressings for Treatment of Burn Wounds

The therapy of burns is a challenging clinical issue. Burns are long-term injuries, and numerous patients suffer from chronic pain. Burn treatment includes management, infection control, wound debridement and escharotomy, dressing coverage, skin transplantation, and the use of skin substitutes. The future of advanced care of burn wounds lies in the development of “active dressings”. Hydrogel dressings have been employed universally to accelerate wound healing based on their unique properties to overcome the limitations of existing treatment methods. This review briefly introduces the advantages of hydrogel dressings and discusses the development of new hydrogel dressings for wound healing along with skin regeneration. Further, the treatment strategies for burns, ranging from external to clinical, are reviewed, and the functional classifications of hydrogel dressings along with their clinical value for burns are discussed.

The Limbal Niche and Regenerative Strategies

The protective function and transparency provided by the corneal epithelium are dependent on and maintained by the regenerative capacity of limbal epithelial stem cells (LESCs). These LESCs are supported by the limbal niche, a specialized microenvironment consisting of cellular and non-cellular components. Disruption of the limbal niche, primarily from injuries or inflammatory processes, can negatively impact the regenerative ability of LESCs. Limbal stem cell deficiency (LSCD) directly hampers the regenerative ability of the corneal epithelium and allows the conjunctival epithelium to invade the cornea, which results in severe visual impairment. Treatment involves restoring the LESC population and functionality; however, few clinically practiced therapies currently exist. This review outlines the current understanding of the limbal niche, its pathology and the emerging approaches targeted at restoring the limbal niche. Most emerging approaches are in developmental phases but show promise for treating LSCD and accelerating corneal regeneration. Specifically, we examine cell-based therapies, bio-active extracellular matrices and soluble factor therapies in considerable depth.

Stem Cell Niche Microenvironment: Review

The cornea comprises a pool of self-regenerating epithelial cells that are crucial to preserving clarity and visibility. Limbal epithelial stem cells (LESCs), which live in a specialized stem cell niche (SCN), are crucial for the survival of the human corneal epithelium. They live at the bottom of the limbal crypts, in a physically enclosed microenvironment with a number of neighboring niche cells. Scientists also simplified features of these diverse microenvironments for more analysis in situ by designing and recreating features of different SCNs. Recent methods for regenerating the corneal epithelium after serious trauma, including burns and allergic assaults, focus mainly on regenerating the LESCs. Mesenchymal stem cells, which can transform into self-renewing and skeletal tissues, hold immense interest for tissue engineering and innovative medicinal exploration. This review summarizes all types of LESCs, identity and location of the human epithelial stem cells (HESCs), reconstruction of LSCN and artificial stem cells for self-renewal.

Application of mesenchymal stem cells in corneal regeneration

Due to delicate its structure, the cornea is susceptible to physical, chemical, and genetic damages. Corneal transplantation is the main treatment for serious corneal damage, but it faces significant challenges, including donor shortages and severe complications. In recent years, cell therapy is suggested as a novel alternative method for corneal regeneration. Regarding the unique characteristics of Mesenchymal stem cells including the potential to differentiate into discrete cell types, secretion of growth factors, mobilization potency, and availability from different sources; special attention has been paid to these cells in corneal engineering. Differentiation of MSCs into specialized corneal cells such as keratocytes, epithelial and endothelial cells is reported. Potential for Treatment of keratitis, reducing inflammation, and inhibition of neovascularization by MSCs, introducing them as novel agents for corneal repairing. In this review, various types of MSCs used to treat corneal injuries as well as their potential for restoring different corneal layers was investigated.

Mesenchymal stem cell-based therapy for burn wound healing

Burns, with their high incidence and mortality rates, have a devastating effect on patients. There are still huge challenges in the management of burns. Mesenchymal stem cells (MSCs), which have multidirectional differentiation potential, have aroused interest in exploring the capacity for treating different intractable diseases due to their strong proliferation, tissue repair, immune tolerance and paracrine abilities, among other features. Currently, several animal studies have shown that MSCs play various roles and have beneficial effects in promoting wound healing, inhibiting burn inflammation and preventing the formation of pathological scars during burn healing process. The substances MSCs secrete can act on peripheral cells and promote burn repair. According to preclinical research, MSC-based treatments can effectively improve burn wound healing and reduce pain. However, due to the small number of patients and the lack of controls, treatment plans and evaluation criteria vary widely, thus limiting the value of these clinical studies. Therefore, to better evaluate the safety and effectiveness of MSC-based burn treatments, standardization of the application scheme and evaluation criteria of MSC therapy in burn treatment is required in the future. In addition, the combination of MSC pretreatment and dressing materials are also conducive to improving the therapeutic effect of MSCs on burns. In this article, we review current animal research and clinical trials based on the use of stem cell therapy for treating burns and discuss the main challenges and coping strategies facing future clinical applications.

Evaluation of Clinical and Histological Outcomes of Adipose-Derived Mesenchymal Stem Cells in a Rabbit Corneal Alkali Burn Model

To assess effects of adipose-derived mesenchymal stem cells (AMSCs) in corneal alkali injuries in an experimental animal model. Twenty white New Zealand rabbits were included in the study. The animal models were randomly divided into 2 groups. Rabbits in the AMSC group (n = 10) received an intrastromal, a subconjunctival injection, and topical instillation of 0.5 ml totally of phosphate-buffered saline (PBS) containing 2 × 10⁶ AMSCs. In the control group (n = 10), rabbits received only 0.5 ml of PBS using the same methods. A masked investigator measured the corneal sensation, anterior chamber Inflammation (ACI), and conjunctival congestion. Additionally, a blind histological and immunohistochemical evaluation was made. In the AMSC group, the central corneal sensation was increased whereas ACI and conjunctival congestion were reduced compared to the control group in the 28 days of follow-up (p < 0.05). A statistically significant difference (p < 0.05) was noted between the two groups as recorded in the above parameters. Histological analysis showed that pathological vascularization was markedly reduced in the AMSC group which was consistent with the absence of factor VIII in the immunohistochemistry sections. There is a trend towards improved clinical outcomes including corneal sensation as well as acceleration in the restoration of normal corneal architecture in corneal alkali burns treated with AMSCs, results that support the need for further research in the field.

Subconjunctival injection of mesenchymal stem cells for corneal failure due to limbal stem cell deficiency: state of the art

Mesenchymal stem cells (MSCs) have unique and beneficial properties and are currently used to treat a broad variety of diseases. These properties include the potential for differentiation into other cell types, secretion of different trophic factors that promote a regenerative microenvironment, anti-inflammatory actions, selective migration to damaged tissues, and non-immunogenicity. MSCs are effective for the treatment of ocular surface diseases such as dry eye, corneal burns, and limbal stem cell deficiency (LSCD), both in experimental models and in humans. LSCD is a pathological condition in which damage occurs to the limbal epithelial stem cells, or their niche, that are responsible for the continuous regeneration of the corneal epithelium. If LSCD is extensive and/or severe, it usually causes corneal epithelial defects, ulceration, and conjunctival overgrowth of the cornea. These changes can result in neovascularization and corneal opacity, severe inflammation, pain, and visual loss. The effectiveness of MSCs to reduce corneal opacity, neovascularization, and inflammation has been widely studied in different experimental models of LSCD and in some clinical trials; however, the methodological disparity used in the different studies makes it hard to compare outcomes among them. In this regard, the MSC route of administration used to treat LSCD and other ocular surface diseases is an important factor. It should be efficient, minimally invasive, and safe. So far, intravenous and intraperitoneal injections, topical administration, and MSC transplantation using carrier substrata like amniotic membrane (AM), fibrin, or synthetic biopolymers have been the most commonly used administration routes in experimental models. However, systemic administration carries the risk of potential side effects and transplantation requires surgical procedures that could complicate the process. Alternatively, subconjunctival injection is a minimally invasive and straightforward technique frequently used in ophthalmology. It enables performance of local treatments using high cell doses. In this review, we provide an overview of the current status of MSC administration by subconjunctival injection, analyzing the convenience, safety, and efficacy for treatment of corneal failure due to LSCD in different experimental models. We also provide a summary of the clinical trials that have been completed, are in progress, or being planned.

Rapid bioprinting of conjunctival stem cell micro-constructs for subconjunctival ocular injection

Ocular surface diseases including conjunctival disorders are multifactorial progressive conditions that can severely affect vision and quality of life. In recent years, stem cell therapies based on conjunctival stem cells (CjSCs) have become a potential solution for treating ocular surface diseases. However, neither an efficient culture of CjSCs nor the development of a minimally invasive ocular surface CjSC transplantation therapy has been reported. Here, we developed a robust in vitro expansion method for primary rabbit-derived CjSCs and applied digital light processing (DLP)-based bioprinting to produce CjSC-loaded hydrogel micro-constructs for injectable delivery. Expansion medium containing small molecule cocktail generated fast dividing and highly homogenous CjSCs for more than 10 passages in feeder-free culture. Bioprinted hydrogel micro-constructs with tunable mechanical properties enabled the 3D culture of CjSCs while supporting viability, stem cell phenotype, and differentiation potency into conjunctival goblet cells. These hydrogel micro-constructs were well-suited for scalable dynamic suspension culture of CjSCs and were successfully delivered to the bulbar conjunctival epithelium via minimally invasive subconjunctival injection. This work integrates novel cell culture strategies with bioprinting to develop a clinically relevant injectable-delivery approach for CjSCs towards the stem cell therapies for the treatment of ocular surface diseases.

Evaluation of Anti-Inflammatory and Antiapoptotic Effects of Bone Marrow and Adipose-Derived Mesenchymal Stem Cells in Acute Alkaline Corneal Burn

Purpose: The aim of the present study is to comparatively evaluate the anti-inflammatory and antiapoptotic effects of bone marrow and adipose-derived mesenchymal stem cells (MSCs) applied subconjunctivally after alkaline corneal burn. Methods: Thirty-two rats were divided into 4 groups and included in the study (n = 8). While no intervention was made in the control group, a chemical burn was created by applying 4 μL of NaOH soaked in 6 mm filter paper to the right eye of each subject in the other groups under general anesthesia. While only subconjunctival 0.1 mL phosphate-buffered saline (PBS) was injected to in the group 1, 2 × 10⁶ adipose or bone marrow-derived MSC in 0.1 mL PBS was applied subconjunctivally to the subjects in the remaining groups (Group 2 and 3, respectively). Tissue samples were collected for histological analysis on the third day after the burn. Tissue samples were evaluated light microscopically and immunohistochemically stained for interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), caspase-3 (Cas-3), and CD68. Results: The IL-1β and TNF-α staining scores and the number of CD68- and Cas-3-positive stained cells were significantly lower in the groups given bone marrow and adipose-derived MSC compared to the alkaline burn group (P < 0.0001, for all parameters). Epithelial IL-1β and TNF-α staining scores were significantly lower in the bone marrow-derived MSC group compared to the adipose-derived MSC group (P < 0.0001, for all parameters). Conclusions: The presented study shows that both bone-marrow and adipose-derived MSCs support wound healing in the corneal tissue and strongly suppress the inflammation occured in the tissue.

Subconjunctival injection of tumor necrosis factor-α pre-stimulated bone marrow-derived mesenchymal stem cells enhances anti-inflammation and anti-fibrosis in ocular alkali burns

PURPOSE

To investigate the therapeutic effect of subconjunctival injection of tumor necrosis factor-α (TNF-α) pre-stimulated bone marrow-derived mesenchymal stem cells (BMMSCs) on ocular alkali burns in a rat model.

METHODS

After applying a 6 mm filter paper soaking in 1 N NaOH on the cornea of rats, the suspension of TNF-α pre-stimulated BMMSCs, BMMSCs and PBS were given subconjunctivally and respectively. Corneal epithelial defect, corneal opacity, inflammation as well as PTGS2 and TSG-6 expression on day 7 and fibrosis on day 14 were compared.

RESULTS

TNF-α pre-stimulated BMMSCs group had a more predominate effect on promoting corneal epithelial repairing, decreasing corneal opacity, reducing inflammatory cells and CD68 + macrophages on day 7 and suppressing fibrosis on day 14 compared to BMMSCs group. Besides, it had significant increased expressions of PTGS2 and TSG-6 in vitro. Pre-treated with Indomethacin revealed a reverse effect on above-mentioned changes.

CONCLUSION

Subconjunctival injection of TNF-α pre-stimulated BMMSCs enhanced anti-inflammatory and anti-fibrotic effect in ocular alkali burns, which was possibly though up regulation of PTGS2 and TSG-6 expression.

Potential of mesenchymal stem cells as topical immunomodulatory cell therapies for ocular surface inflammatory disorders

Ocular surface inflammatory disorders (OSIDs) are a group of highly prevalent, heterogeneous diseases that display a variety of aetiologies and symptoms and are risk factors for serious complications, including ocular and cornea impairment. Corneal inflammation is a common factor of all OSIDs, regardless of their cause or symptoms. Current medications include over‐the‐counter lubricating eye drops, corticosteroids, and ciclosporin, which either do not treat the corneal inflammation or have been associated with multiple side effects leading to alternative treatments being sought. Regenerative medicine cell therapies, particularly mesenchymal stem cells (MSCs), have shown great promise for immunosuppression and disease amelioration across multiple tissues, including the cornea. However, for successful development and clinical translation of MSC therapy for OSIDs, significant problems must be addressed. This review aims to highlight considerations, including whether the source of MSC isolation impacts the efficacy and safety of the therapy, in addition to assessing the feasibility of MSC topical application to the cornea and ocular surface through analysis of potential scaffolds and cell carriers for application to the eye. The literature contains limited data assessing MSCs incorporated into scaffolds for corneal administration, thus here we highlight the necessity of further investigations to truly exploit the potential of an MSC‐based cell therapy for the treatment of OSIDs.

Evaluation of His6-Metal Assemblies as a Drug Delivery Vehicle in the Treatment of Anterior Segment Disease Using a Corneal Inflammation Model

Keratitis is a common ophthalmological disease and also a common cause of blindness (second only to cataracts). This disease is routinely treated by topical administration of dexamethasone sodium phosphate (Dexp). However, due to the presence of anatomical and physiological barriers, frequent administration is needed, often resulting in poor patient compliance and diverse side effects. In this work, Dexp was in situ encapsulated into a His₆-metal assembly (HmA) to generate Dexp@HmA, which was utilized in the ocular delivery of Dexp. The physicochemical properties of HmA and Dexp@HmA particles were characterized in detail using various techniques such as dynamic light scattering (DLS), scanning electron microscopy (SEM), and UV-vis spectroscopy. Compared to commercial Eudragi and reported PLGA nanoparticles, HmA showed higher encapsulation efficiency (EE%) and higher loading capacity (LC wt %) of Dexp. Dexp@HmA displayed pH-dependent release; after 33 days at pH 5.8, 6.5, and 7.2, 100%, 65%, and 42% of Dexp, respectively, had been released. In addition, HmA and Dexp@HmA showed low cytotoxicity to macrophages and to all common ocular cell types tested. The effect of Dexp@HmA on corneal inflammation was evaluated using in vitro and in vivo models. Our results demonstrate that Dexp@HmA is much superior to free Dexp in both in vitro and in vivo models. These positive results suggest that HmA may represent a promising candidate nanocarrier for the treatment of various diseases of the anterior segment of the eye.

Recent developments in regenerative ophthalmology

Regenerative medicine (RM) is one of the most promising disciplines for advancements in modern medicine, and regenerative ophthalmology (RO) is one of the most active fields of regenerative medicine. This review aims to provide an overview of regenerative ophthalmology, including the range of tools and materials being used, and to describe its application in ophthalmologic subspecialties, with the exception of surgical implantation of artificial tissues or organs (e.g., contact lens, artificial cornea, intraocular lens, artificial retina, and bionic eyes) due to space limitations. In addition, current challenges and limitations of regenerative ophthalmology are discussed and future directions are highlighted.

A Systematic Review of Emerging Therapeutic Strategies in the Management of Chemical Injuries of the Ocular Surface

OBJECTIVES

To evaluate recent in vivo studies on emerging therapies for managing corneal epithelial injuries.

METHODS

The search was conducted on PubMed for articles published between January 2015 and September 2019 and in English language.

RESULTS

Thirty studies were identified for evaluation, including those on mesenchymal stem cells, amniotic membrane-derived therapies, endogenous peptides and their inhibitors, as well as hydrogel therapies. Intermediate to strong levels of evidence are presented regarding the use of these strategies on chemically injured cornea, including their effects on healing of corneal epithelial defect, anti-inflammatory properties, prevention of corneal neovascularization, as well as restoration of anatomy and functions of the anterior eye, although clinical trials are needed to determine the safety and efficacy of these strategies on humans.

CONCLUSION

Recent advances and understanding in various novel therapeutic methods for corneal epithelial chemical injuries should provide potential alternatives to current standard treatment regimens and help reduce risks of complications, hence improve patient outcomes.

MSCs helped reduce scarring in the cornea after fungal infection when combined with anti-fungal treatment

Background

Fungal Keratitis (FK) is an infective keratopathy with extremely high blindness rate. The damaging effect of this disease is not only the destruction of corneal tissue during fungal infection, but also the cornea scar formed during the healing period after infection control, which can also seriously affect a patient’s vision. The purpose of the study was to observe the effect of umbilical cord mesenchymal stem cells (uMSCs) on corneal scar formation in FK.

Methods

The FK mouse model was made according to a previously reported method. Natamycin eye drops were used for antifungal treatment 24 h after modeling. There are four groups involved in the study, including control group, FK group, vehicle^inj FK group and uMSCs^inj FK group. Mice in uMSCs^inj FK group received repeated subconjunctival injections of uMSCs for 3 times at the 1d, 4d and 7d after FK modeling. At 14d, 21d and 28d after trauma, clinical observation, histological examination, second harmonic generation and molecular assays were performed.

Results

The uMSCs topical administration reduced corneal scar formation area and corneal opacity, accompanying with decreased corneal thickness and inflammatory cell infiltration, following down-regulated fibrotic-related factors α-SMA, TGFβ1, CTGF, and COLI and finally inhibited phosphorylation of TGFβ1/Smad2 signaling pathway during FK corneal fibrosis.

Conclusion

The results confirmed that uMSCs can improve corneal opacity during the scar formation stage of FK, and exert anti-inflammatory and anti-fibrotic effects.

Potential therapeutic application of mesenchymal stem cells in ophthalmology

At present a wide variety of methods have been proposed to treat eye disorders, drug therapies are most commonly used. It should be noted that effective treatment modalities especially for degeneration of the retina and optic nerve are lacking. In the last few years stem cell transplantation has been proposed as an alternative method. The opportunities that stem cells provide within clinical use are almost unlimited. These cells are presently applied to treat various traumatic and degenerative disorders due to their unique biologic properties. Stem cells have high proliferative capabilities and are a self-maintained population of cells capable of differentiating into different cell types. Thus, they are represent a very primary stage of a cell lineage. Their ability to differentiate into different pathways provides animals with great plasticity in the renewal of somatic cells in postnatal ontogenesis. Pre-clinical and clinical ophthalmology studies where mesenchymal stem cells are applied and various methods of their administration are discussed herein. In addition the safety and efficacy of using bone marrow- and adipose tissue-derived mesenchymal stem cells have been discussed.

The Wound Healing Effect of Doxycycline after Corneal Alkali Burn in Rats

Purpose

To evaluate the wound healing effect of doxycycline and its underlying mechanisms in a rat model of corneal alkali burn.

Methods

Male SD rats were administered 1.0 N NaOH in the right cornea for 25 seconds and randomly divided into the doxycycline group and the control group, with 84 rats in each group. 1.0 g·L⁻¹ doxycycline eye drops (doxycycline group) or vehicle (control group) was topically instilled onto the rat cornea after chemical injury. Three days, 7 days, and 14 days after alkali burn, microscopy was used to observe corneal wound healing by fluorescein staining and the degree of corneal opacity. The expression of transforming growth factor-beta 1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) was detected by RT-PCR and ELISA, alpha-smooth muscle actin (a-SMA) levels were measured by immunofluorescent staining, and Western blot assays for TGF-β1, a-SMA, and nuclear factor-kappa B (NF-κB) were also performed.

Results

Corneal wound healing and corneal opacity scores were better in the doxycycline group than in the control group. Three, 7, and 14 days after corneal alkali burn, a significant increase in TGF-β1 was observed in corneas from the control group, compared with the corneas from the doxycycline group (P < 0.05). The corneal levels of MMP-9 in the doxycycline group were lower than those in the control group 3 days and 7 days after alkali burn (P < 0.05). In addition, doxycycline inhibited α-SMA expression and suppressed NF-κB expression.

Conclusion

Doxycycline treatment promoted corneal healing and reduced corneal opacity in SD rats. Doxycycline protected the cornea from alkali burn injury by reducing TGF-β1, MMP-9, NF-κB, and α-SMA expression.

MSCs inhibits the angiogenesis of HUVECs through the miR-211/Prox1 pathway

The aim of this study was to investigate the effect of mesenchymal stem cells (MSCs) on the angiogenesis of human umbilical vein endothelial cells (HUVECs). MSCs were subconjunctival injected into rat corneal alkali burn models. Their impacts on the degree of corneal neovascularization (CNV) and corneal opacity were evaluated at 3, 6, 9 and 12 days after injection. An in vitro experiment of MSCs affecting HUVECs angiogenesis was performed and evaluated using the tube formation assay. The results showed that both CNV and corneal opacity were decreased in rats after MSCs injection. In HUVECs, angiogenesis of cells was inhibited by miR-211 overexpression. miR-211 negatively regulated Prox1 expression. Knockdown of miR-211 blocked the decrease of Prox1 expression induced by MSCs and the inhibitory effect of MSCs on the angiogenesis of HUVECs. The critical role of miR-211 in MSCs inhibition of corneal angiogenesis was confirmed in rat experiments. We concluded that MSCs inhibited the angiogenesis of HUVEC through miR-211 mediating the down-regulation of Prox1.

Mesenchymal stromal cells for ocular surface repair

INTRODUCTION

Cornea is a transparent, robust tissue that comprises highly organized cells. Disruption of this specialized tissue can lead to scarring and subsequent blindness, making corneal damage a considerable challenge worldwide. At present, the available medical treatments are unable to address the wide range of corneal diseases. Mesenchymal stem cells (MSCs) have increasingly been investigated for their regenerative effect on ocular surface injury due to their unique ability for growth factor production, anti-inflammatory activity, immunomodulatory capacity and differentiation into multiple cell lineages.

AREAS COVERED

Within this review, we explore the pathogenesis of corneal disorders in response to injury and disease, and the potential for MSCs to modulate this process as a treatment. Through the review of over 25 animal studies, we investigate the common mechanisms of action by which MSCs have their effect and discuss their potential for treating and/or preventing corneal deterioration

EXPERT OPINION

Depending on the environmental cues, MSCs can exert a potent effect on corneal wound healing through reducing opacity and vascularization, whilst promoting re-epithelialization. Whilst their mechanism is multifactorial, it seems clear that the anti-inflammatory/immunomodulatory factors they produce in response to damage are key to their control of cellular milieu and improving healing outcomes.

MMP-9 Downregulation with Lipid Nanoparticles for Inhibiting Corneal Neovascularization by Gene Silencing

Gene silencing targeting proangiogenic factors have been shown to be a useful strategy in the treatment of corneal neovascularization (CNV). Among interference RNA (RNAi) molecules, short-hairpin RNA (shRNA) is a plasmid-coded RNA able to down-regulate the expression of the desired gene. It is continuously produced in the host cell, inducing a durable gene silencing effect. The aim of this work was to develop a solid lipid nanoparticle (SLN)-based shRNA delivery system to downregulate metalloproteinase 9 (MMP-9), a proangiogenic factor, in corneal cells for the treatment of CNV associated with inflammation. The nanovectors were prepared using a solvent emulsification-evaporation technique, and after physicochemical evaluation, they were evaluated in different culture cell models. Transfection efficacy, cell internalization, cell viability, the effect on MMP-9 expression, and cell migration were evaluated in human corneal epithelial cells (HCE-2). The inhibition of tube formation using human umbilical vein endothelial cells (HUVEC) was also assayed. The non-viral vectors based on SLN were able to downregulate the MMP-9 expression in HCE-2 cells via gene silencing, and, consequently, to inhibit cell migration and tube formation. These results demonstrate the potential of lipid nanoparticles as gene delivery systems for the treatment of CNV-associated inflammation by RNAi technology.

Micelle-solubilized axitinib for ocular administration in anti-neovascularization

The development of new blood vessels is directly related to the occurrence of eye diseases. Anti-angiogenic drugs can theoretically be extended to the treatment of ophthalmic diseases. In this study, axitinib, a class of tyrosine kinase inhibitors, was loaded via the amphiphilic copolymer MPEG-PCL, improving its dispersibility in water. Axitinib-loaded micelles showed low toxicity in concentration gradient assays. Additionally, multiple doses by scratch assay confirmed that axitinib had no significant effect on normal cell migration, and biosafety test results showed good cell compatibility. After we established the corneal neovascularization model after an alkali burn in rats, the anti-angiogenic efficacy was tested, with dexamethasone as a positive control. The results showed that axitinib-loaded micelles had anti-angiogenic effects without obvious tissue toxicity. As a class of targeted tyrosine kinase inhibitors, axitinib can be used in the treatment of ocular neovascular diseases through nanocrystallization.

Emerging Approaches for Ocular Surface Regeneration

Purpose of review

In this manuscript, the recent advancements and novel approaches for regeneration of the ocular surface are summarized.

Recent findings

Following severe injuries, persistent inflammation can alter the rehabilitative capability of the ocular surface environment. Limbal stem cell deficiency (LSCD) is one of the most characterized ocular surface disorders mediated by deficiency and/or dysfunction of the limbal epithelial stem cells (LESCs) located in the limbal niche. Currently, the most advanced approach for revitalizing the ocular surface and limbal niche is based on transplantation of limbal tissues harboring LESCs. Emerging approaches have focused on restoring the ocular surface microenvironment using (1) cell-based therapies including cells with capabilities to support the LESCs and modulate the inflammation, e.g., mesenchymal stem cells (MSCs), (2) bio-active extracellular matrices from decellularized tissues, and/or purified/synthetic molecules to regenerate the microenvironment structure, and (3) soluble cytokine/growth factor cocktails to revive the signaling pathways.

Summary

Ocular surface/limbal environment revitalization provide promising approaches for regeneration of the ocular surface.

Corneal Wound Healing Effects of Mesenchymal Stem Cell Secretome Delivered Within a Viscoelastic Gel Carrier

Severe corneal injuries often result in permanent vision loss and remain a clinical challenge. Human bone marrow-derived mesenchymal stem cells (MSCs) and their secreted factors (secretome) have been studied for their antiscarring, anti-inflammatory, and antiangiogeneic properties. We aimed to deliver lyophilized MSC secretome (MSC-S) within a viscoelastic gel composed of hyaluronic acid (HA) and chondroitin sulfate (CS) as a way to enhance corneal re-epithelialization and reduce complications after mechanical and chemical injuries of the cornea. We hypothesized that delivering MSC-S within HA/CS would have improved wound healing effects compared the with either MSC-S or HA/CS alone. The results showed that a once-daily application of MSC-S in HA/CS enhances epithelial cell proliferation and wound healing after injury to the cornea. It also reduced scar formation, neovascularization, and hemorrhage after alkaline corneal burns. We found that combining MSC-S and HA/CS increased the expression of CD44 receptors colocalized with HA, suggesting that the observed therapeutic effects between the MSC-S and HA/CS are in part mediated by CD44 receptor upregulation and activation by HA. The results from this study demonstrate a reproducible and efficient approach for delivering the MSC-S to the ocular surface for treatment of severe corneal injuries. Stem Cells Translational Medicine 2019;8:478-489.

Strategies for reconstructing the limbal stem cell niche

The epithelial cell layer that covers the surface of the cornea provides a protective barrier while maintaining corneal transparency. The rapid and effective turnover of these epithelial cells depends, in part, on the limbal epithelial stem cells (LESCs) located in a specialized microenvironment known as the limbal niche. Many disorders affecting the regeneration of the corneal epithelium are related to deficiency and/or dysfunction of LESCs and the limbal niche. Current approaches for regenerating the corneal epithelium following significant injuries such as burns and inflammatory attacks are primarily aimed at repopulating the LESCs. This review summarizes and assesses the clinical feasibility and efficacy of current and emerging approaches for reconstruction of the limbal niche. In particular, the application of mesenchymal stem cells along with appropriate biological scaffolds appear to be promising strategies for long-term revitalization of the limbal niche.

Effect of Various Temperatures on Bletillae Rhizoma Polysaccharide Extraction and Physicochemical Properties

Six fractional polysaccharides were prepared by water extraction and alcohol precipitation under controlled temperature from bletillae rhizoma, a traditional Chinese medicine. Based on this, yields of bletillae rhizome polysaccharides (RBPs) were obtained. The extracting temperature impacted the characteristics of the fractional polysaccharides. The fractional polysaccharides were characterized by glucomannan (GM) content, thermal stability, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and x-ray diffraction (XRD). For the analysis, 2.0% w/v dispersions of the six fractional polysaccharides were prepared and their flow behaviors were evaluated using a rotational rheometer. The results showed that increased extraction temperature led to increased GM extraction yields and extraction rate, but GM content was relative stable (over 90%). The average molecular weight (Mw) of fractional polysaccharides obtained at 30, 40, 50, 60, 70, and 80 °C was 3.598 × 104, 4.188 × 104, 8.632 × 104, 8.850 × 104, 2.372 × 105, and 3.081 × 105 g/mol, respectively. SEM revealed that fractional polysaccharides had a porous structure of different sizes and densities. Thermal analysis, FTIR, and XRD results indicated that extraction temperature affects the structure and moisture content of fractional polysaccharides. All results showed that the extraction temperature has an obvious impact on the morphology, molecular weight, and polydispersity of the RBPs. This simple process is a promising method for the preparation of fractional polysaccharides.

Alginate encapsulated multipotent adult progenitor cells promote corneal stromal cell activation via release of soluble factors

To reduce the increasing need for corneal transplantation, attempts are currently aiming to restore corneal clarity, one potent source of cells are multipotent adult progenitor cells (MAPC^®). These cells release a powerful cocktail of paracrine factors that can guide wound healing and tissue regeneration. However, their role in corneal regeneration has been overlooked. Thus, we sought to explore the potential of combining the cytoprotective storage feature of alginate, with MAPC to generate a storable cell-laden gel for corneal wound healing. 72 hours following hypothermic storage, alginate encapsulation was shown to maintain MAPC viability at either 4 or 15°C. Encapsulated MAPC (2 x10⁶ cells/mL) stored at 15°C presented the optimum temperature that allowed for cell recovery. These cells had the ability to reattach to tissue culture plastic whilst exhibiting normal phenotype and this was maintained in serum-free and xenobiotic-free medium. Furthermore, corneal stromal cells presented a significant decrease in scratch-wounds in the presence of alginate encapsulated MAPC compared to a no-cell control (p = 0.018). This study shows that immobilization of MAPC within an alginate hydrogel does not hinder their ability to affect a secondary cell population via soluble factors and that these effects are successfully retained following hypothermic storage.

Role of microRNA 146a on the healing of cornea alkali burn treated with mesenchymal stem cells

The aim of the present study was to investigate the effect of microRNA 146a (miR146a) on promoting the repair of corneal alkali burn with bone marrow mesenchymal stem cells (MSCs). A total of 24 Sprague‑Dawley female rats were divided into a normal group (Control), a normal MSC treatment group (Normal MSCs), an miR146a knockout MSC treatment group (miR146a‑low MSCs) and an miR146a high‑expression MSC treatment group (miR146a‑high MSCs) according to the random number table. Quantitative polymerase chain reaction was used to evaluate the expression levels of miR146a. MTT assay was performed to measure the cell viability of mesenchymal stem cells (MSCs) and apoptosis was measured by flow cytometry. The expression levels of p65 nuclear factor (NF)‑κB, proliferating cell nuclear antigen (PCNA) and Fas proteins were analyzed by western blotting. MSCs were tested for the secretion levels of vascular endothelial growth factor (VEGF), CD45, interferon (IFN)‑γ and interleukin (IL)‑10 by ELISA. The miR146a‑high MSCs improved cell viability of MSCs and inhibited apoptosis of MSCs following alkali burn. miR146a‑high MSCs decreased the expression levels of p65NF‑κB and PCNA, and enhanced the expression level of Fas. Furthermore, miR146a‑high MSCs improved the cornea opacity and enhanced the inhibition of neovascularization in the rats following alkali burn. miR146a‑high MSCs inhibit the expression of VEGF, CD45, IFN‑γ, while enhanced the expression of IL‑10. Therefore, miR146a promotes the repair of corneal alkali burn in rats treated with MSCs.

Olopatadine enhances recovery of alkali-induced corneal injury in rats

AIMS

The alkali-induced corneal injury is an ocular emergency that required an immediate and effective management to preserve the normal corneal functions and transparency. Olopatadine is a fast, topically-effective anti-allergic drug, which exhibited potent anti-inflammatory and anti-angiogenic abilities in different allergic animals' models. Therefore, this study aimed to evaluate the therapeutic effect of olopatadine on alkali-induced corneal injury in rats.

MATERIALS AND METHODS

Corneal alkali injury (CI) induced in the right eyes of an eight-week-old male Wister rats, by application of 3 mm diameter filter-papers, soaked for 10 s in 1 N-NaOH, to the right eyes' corneal centers for 30 s, afterward, the filter paper removed, and the rat right eye rinsed with 20 ml normal saline. For treatment of CI, either 0.2% or 0.77% olopatadine applied topically daily for 14 days, starting immediately after the induction of CI.

KEY FINDINGS

Olopatadine, in the present work, effectively and dose-dependently enhanced the corneal healing after alkali application, with significant reduction of the corneal opacity and neovascularization scores, besides, it suppressed the augmented corneal IL-1β, VEGF, caspase-3 levels, and nuclear NF-κB immunohistochemical expression, meanwhile it abrogated the corneal histopathological changes, induced by alkali application.

SIGNIFICANCE

Olopatadine appears to be a potential treatment option for alkali-induced corneal injury.

Comparison of Two Rabbit Models with Deficiency of Corneal Epithelium and Limbal Stem Cells Established by Different Methods

Limbal stem cell defect model is an important animal model that provides a basis for the study of ocular surface diseases. The rabbit cornea is of moderate size and is widely used in such studies as an experimental animal model. At present, the main modeling methods are alkali burns, and corneal limbus girdling and corneal epithelium doctoring. Each method has its own characteristics. In this study, we observed rabbit models with severe ocular surface defect established by the two methods and changes after amniotic membrane transplantation. In the first, second, third, and fourth week after operation, the clinical manifestations, corneal transparency, and new vessels were observed according to the standard rating scale of ocular surface, compared between the two methods, and then statistically analyzed. In the fourth week after operation, the rabbits were sacrificed and their corneas and corneal limbus were extracted from sclera, embedded by optimum cutting temperature compound, frozen, and sliced for hematoxylin and eosin staining and pathological examination. There were two groups in this study. Group 1 (alkali burns) had more severe complications, such as, conjunctiva, nubecula, new vessel hyperplasia, and so on, compared to group 2 (corneal limbus girdling and corneal epithelium doctoring). In addition, there were striking differences in corneal transparency and new vessels between the two groups (p < 0.05). Corneal transparency in group 1 was lower than in group 2. New vessels in group 1 were less in the first 2 weeks, but obviously increased compared to group 2 in the subsequent weeks. Alkaline burn could be used to study new vessel hyperplasia, while corneal limbus girdling and corneal epithelium doctoring are more suitable for studying stem cell transdifferentiation, interactive roles of stem cells and microenvironment, and so on.

Limbal and corneal epithelial homeostasis

PURPOSE OF REVIEW

The aim of this review is to describe the underlying mechanisms of corneal epithelial homeostasis in addition to illustrating the vital role of the limbal epithelial stem cells (LESCs) and the limbal niche in epithelial regeneration and wound healing.

RECENT FINDINGS

The shedded corneal epithelial cells are constantly replenished by the LESCs which give rise to epithelial cells that proliferate, differentiate, and migrate centripetally. While some recent studies have proposed that epithelial stem cells may also be present in the central cornea, the predominant location for the stem cells is the limbus. The limbal niche is the specialized microenvironment consisting of cells, extracellular matrix, and signaling molecules that are essential for the function of LESCs. Disturbances to limbal niche can result in LESC dysfunction; therefore, limbal stem cell deficiency should also be considered a limbal niche deficiency. Current and in-development therapeutic strategies are aimed at restoring the limbal niche, by medical and/or surgical treatments, administration of trophic factors, and cell based therapies.

SUMMARY

The corneal epithelium is constantly replenished by LESCs that are housed within the limbal niche. The limbal niche is the primary determinant of the LESC function and novel therapeutic approaches should be focused on regeneration of this microenvironment.

Inhibitory effects of S100A4 gene silencing on alkali burn-induced corneal neovascularization: an in vivo study

OBJECTIVE

The purpose of this study is to explore the inhibitory effects of S100A4 gene silencing on alkali burn-induced corneal neovascularization (CNV) in rabbit models.

METHODS

Sixty-five rabbits were used to establish alkali-induced CNV models. After the operation, rabbits were given daily antibiotic eye drops and an eye ointment to prevent infection. The models were assigned to either an S100A4 siRNA or an empty vector group. Thirty rabbits were selected as the normal control group. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the mRNA expression of S100A4, vascular endothelial growth factor (VEGF), and tumor necrosis factor-α (TNF-α) in corneal tissues. Immunohistochemistry was used to detect the protein expression of VEGF in corneal tissues, and an enzyme-linked immunosorbent (ELISA) assay was used to detect the protein expression of VEGF and TNF-α in the aqueous humor.

RESULTS

The qRT-PCR results showed that S100A4 mRNA expression was lower in the S100A4 siRNA group than in the empty vector group at 1, 3, 7, 14, and 28 days after an alkali burn. When compared with the empty vector group, the expression of VEGF and TNF-α mRNA was downregulated in the S100A4 siRNA group. The immunohistochemistry results revealed that VEGF protein expression was downregulated in the S100A4 siRNA group when compared to the empty vector group at 1, 3, 7, 14, and 28 days after an alkali burn. The ELISA results suggest that VEGF and TNF-α protein expression is downregulated in the S100A4 siRNA group in comparison to the empty vector group at 1, 3, 7, 14, and 28 days after an alkali burn.

CONCLUSIONS

These findings indicate that S100A4 gene silencing can inhibit alkali burn-induced CNV in rabbits.

Effects of exogenous recombinant human bone morphogenic protein-7 on the corneal epithelial mesenchymal transition and fibrosis

AIM

To evaluate the effect of exogenous recombinant human bone morphogenic protein-7 (rhBMP-7) on transforming growth factor-β (TGF-β)-induced epithelial mesenchymal cell transition (EMT) and assessed its antifibrotic effect via topical application.

METHODS

The cytotoxic effect of rhBMP-7 was evaluated and the EMT of human corneal epithelial cells (HECEs) was induced by TGF-β. HECEs were then cultured in the presence of rhBMP-7 and/or hyaluronic acid (HA). EMT markers, fibronectin, E-cadherin, α-smooth muscle actin (α-SMA), and matrix metaloproteinase-9 (MMP-9), were evaluated. The level of corneal fibrosis and the reepithelization rate were evaluated using a rabbit keratectomy model. Expression of α-SMA in keratocytes were quantified following treatment with different concentrations of rhBMP-7.

RESULTS

Treatment with rhBMP-7 attenuated TGF-β-induced EMT in HECEs. It significantly attenuated fibronectin secretion (31.6%; P<0.05), the α-SMA protein level (72.2%; P<0.01), and MMP-9 expression (23.6%, P<0.05) in HECEs compared with cells grown in the presence of TGF-β alone. E-cadherin expression was significantly enhanced (289.7%; P<0.01) in the presence of rhBMP-7. Topical application of rhBMP-7 combined with 0.1% HA significantly reduced the amount of α-SMA⁺ cells by 43.18% (P<0.05) at a concentration of 2.5 µg/mL and by 47.73% (P<0.05) at 25 µg/mL, compared with the control group, without disturbing corneal reepithelization.

CONCLUSION

rhBMP-7 attenuates TGF-β-induced EMT in vitro, and topical application of rhBMP-7 reduces keratocyte myodifferentiation during the early wound healing stages in vivo without hindering reepithelization. Topical rhBMP-7 application as biological eye drops seems to be feasible in diseases involving TGF-β-related corneal fibrosis with corneal reepithelization disorders.

Subconjunctival injectable dendrimer-dexamethasone gel for the treatment of corneal inflammation

Corneal inflammation is often encountered as a key pathological event in many corneal diseases. Current treatments involve topical corticosteroids which require frequent instillations due to rapid tear turnover, causing side-effects such as corneal toxicity and elevated intraocular pressure (IOP). Hence, new interventions that can reduce side effects, dosing frequency, and increase patient compliance can be highly beneficial. In this study, we explore a subconjunctival injectable gel based on G4-PAMAM dendrimer and hyaluronic acid, cross-linked using thiol-ene click chemistry, incorporated with dendrimer dexamethasone (D-Dex) conjugates as a potential strategy for sustained delivery and enhanced bioavailability of corticosteroids. The efficacy of the injectable gel formulation was evaluated in a rat mild alkali burn model. Fluorescently-labelled dendrimers (D-Cy5) incorporated in the gel release D-Cy5 in vivo. The released D-Cy5 selectively targets and localizes within corneal macrophages in inflamed rat cornea but not in healthy controls. This pathology dependent biodistribution was exploited for drug delivery, by incorporating D-Dex in the injectable gel. The attenuation of corneal inflammation by D-Dex gels was assessed using various clinical and biochemical parameters over a 2-week period. Subconjunctival D-Dex gel treatment resulted in favorable clinically-relevant outcomes with reduced central corneal thickness and improved corneal clarity compared to free-Dex and placebo gel controls. The extent of corneal neovascularization was significantly reduced in the D-Dex group. These findings suggest that D-Dex attenuates corneal inflammation more effectively than free-Dex by attenuating macrophage infiltration and pro-inflammatory cytokines expression. A significant elevation in IOP was not observed in the D-Dex group but was observed in the free-Dex group. This novel injectable D-Dex gel may be a potential drug delivery platform for the treatment of many inflammatory ocular surface disorders such as dry eye, auto-immune keratitis and post-surgical complications where frequent steroid administration is required.

The molecular mechanisms of action of PPAR-γ agonists in the treatment of corneal alkali burns (Review)

Corneal alkali burns (CAB) are characterized by injury-induced inflammation, fibrosis and neovascularization (NV), and may lead to blindness. This review evaluates the current knowledge of the molecular mechanisms responsible for CAB. The processes of cytokine production, chemotaxis, inflammatory responses, immune response, cell signal transduction, matrix metalloproteinase production and vascular factors in CAB are discussed. Previous evidence indicates that peroxisome proliferator-activated receptor γ (PPAR-γ) agonists suppress immune responses, inflammation, corneal fibrosis and NV. This review also discusses the role of PPAR-γ as an anti-inflammatory, anti-fibrotic and anti-angiogenic agent in the treatment of CAB, as well as the potential role of PPAR-γ in the pathological process of CAB. There have been numerous studies evaluating the clinical profiles of CAB, and the aim of this systematic review was to summarize the evidence regarding the treatment of CAB with PPAR-γ agonists.