Current Trends and Future Perspective of Mesenchymal Stem Cells and Exosomes in Corneal Diseases. Int J Mol Sci. 2019;20. [PMID: 31212734 PMCID: PMC6627168 DOI: 10.3390/ijms20122853]

Crosstalk among miR-29, α-SMA, and TGFβ1/β3 in melatonin-induced exosome (Mel-prExo) treated human limbal mesenchymal stem cells (hLMSCs): An insight into scarless healing of the cornea

Inflammatory mediators that infiltrate the corneal stroma after corneal infections, trauma or refractive surgery can trigger the transformation of corneal keratocytes into myofibroblasts, resulting in highly irregular collagen deposition and subsequently corneal scarring. Mesenchymal stem cells (MSCs) can be used as therapeutic agents to regenerate corneal and conjunctival tissue damage, regulate inflammation, and reduce the development of limbal stem cell failure. The use of MSC-derived exosomes as a cell-free therapeutic vector is a novel therapeutic approach. This study aimed to assess the effect of exosomes obtained from melatonin (Mel)-treated human limbal mesenchymal stem cells (hLMSCs) on naïve hLMSCs and to determine their influence on the antifibrotic and pro-regenerative pathways involved in corneal scarring. hLMSCs were treated with varying concentrations of Mel, followed by isolation and characterization of the procured exosomes (Mel-prExos). These exosomes were added to the cell culture media of naïve hLMSCs to examine their antifibrotic and pro-regenerative effects. The expression of miR-155, miR-29, TGFβ1, TGFβ3, PPARγ, and α-SMA miRNAs and genes were compared between Mel-treated hLMSCs and Mel-prExo-treated hLMSCs by using real-time PCR. We found that at 1 μM Mel and in the presence of Mel-prExos, TGFβ1 was expressed 0.001-fold, while TGFβ3 was expressed 0.6-fold. miR-29 expression was increased 38-fold in the control-Exo group compared to that in the control group. Changes in TGFβ1/β3 and α-SMA expression are associated with miR-29 and miR-155. This approach could prove beneficial for ocular surface tissue engineering applications.

Neurotrophic keratopathy: General features and new therapies

Neurotrophic keratopathy is an uncommon degenerative corneal disorder characterized by compromised corneal sensory innervation resulting in the formation of epithelial defects and nonhealing corneal ulcers. Various treatment modalities are available to stabilize disease progression, improve patient well-being, and prevent vision loss. For eligible patients, medical and surgical reinnervation have emerged as pioneering therapies, holding promise for better management. We present a comprehensive review of the disorder, providing an update relevant to ophthalmologists on pathogenesis, diagnosis, treatment options, and novel therapies targeting pathophysiological pathways.

Compounding engineered mesenchymal stem cell-derived exosomes: A potential rescue strategy for retinal degeneration

The prevalence of retinal degenerative diseases, including age-related macular degeneration and retinitis pigmentosa, has been increasing globally and is linked to the aging population and improved life expectancy. These diseases are characterized by chronic, progressive neuronal damage or depletion of the photoreceptor cells in the retina, and limited effective treatment options are currently available. Mesenchymal stem cell-derived exosomes (MSC-EXOs) containing cytokines, growth factors, lipids, mRNA, and miRNA, which act as mediators of intercellular communication transferring bioactive molecules to recipient cells, offer an appealing, non-cellular nanotherapeutic approach for retinal degenerative diseases. However, treatment specificity is compromised due to their high heterogeneity in size, content, functional effects, and parental cellular source. To improve this, engineered MSC-EXOs with increased drug-loading capacity, targeting ability, and resistance to bodily degradation and elimination have been developed. This review summarizes the recent advances in miRNAs of MSC-EXOs as a treatment for retinal degeneration, discussing the strategies and methods for engineering therapeutic MSC-EXOs. Notably, to address the single functional role of engineered MSC-EXOs, we propose a novel concept called "Compound Engineered MSC-EXOs (Co-E-MSC-EXOs)" along with its derived potential therapeutic approaches. The advantages and challenges of employing Co-E-MSC-EXOs for retinal degeneration in clinical applications, as well as the strategies and issues related to them, are also highlighted.

Exosomal microRNAs as potential biomarkers and therapeutic targets in corneal diseases

Exosomes are a subtype of extracellular vesicle (EV) that are released and found in almost all body fluids. Exosomes consist of and carry a variety of bioactive molecules, including genetic information in the form of microRNAs (miRNAs). miRNA, a type of small non-coding RNA, plays a key role in regulating genes by suppressing their translation. miRNAs are often disrupted in the pathophysiology of different conditions, including eye disease. The stability and easy detectability of exosomal miRNAs in body fluids make them promising biomarkers for the diagnosis of different diseases. Additionally, due to the natural delivery capabilities of exosomes, they can be modified to transport therapeutic miRNAs to specific recipient cells. Most exosome research has primarily focused on cancer, so there is limited research highlighting the importance of exosomes in ocular biology, particularly in cornea-associated pathologies. This review provides an overview of the existing evidence regarding the primary functions of exosomal miRNAs and their potential role in diagnostic and therapeutic applications in the human cornea.

Research progress on hydrogel-based drug therapy in melanoma immunotherapy

Melanoma is one of the most aggressive skin tumors, and conventional treatment modalities are not effective in treating advanced melanoma. Although immunotherapy is an effective treatment for melanoma, it has disadvantages, such as a poor response rate and serious systemic immune-related toxic side effects. The main solution to this problem is the use of biological materials such as hydrogels to reduce these side effects and amplify the immune killing effect against tumor cells. Hydrogels have great advantages as local slow-release drug carriers, including the ability to deliver antitumor drugs directly to the tumor site, enhance the local drug concentration in tumor tissue, reduce systemic drug distribution and exhibit good degradability. Despite these advantages, there has been limited research on the application of hydrogels in melanoma treatment. Therefore, this article provides a comprehensive review of the potential application of hydrogels in melanoma immunotherapy. Hydrogels can serve as carriers for sustained drug delivery, enabling the targeted and localized delivery of drugs with minimal systemic side effects. This approach has the potential to improve the efficacy of immunotherapy for melanoma. Thus, the use of hydrogels as drug delivery vehicles for melanoma immunotherapy has great potential and warrants further exploration. [BMB Reports 2024; 57(2): 71-78].

Current Advances in Corneal Stromal Stem Cell Biology and Therapeutic Applications

Corneal stromal stem cells (CSSCs) are of particular interest in regenerative ophthalmology, offering a new therapeutic target for corneal injuries and diseases. This review provides a comprehensive examination of CSSCs, exploring their anatomy, functions, and role in maintaining corneal integrity. Molecular markers, wound healing mechanisms, and potential therapeutic applications are discussed. Global corneal blindness, especially in more resource-limited regions, underscores the need for innovative solutions. Challenges posed by corneal defects, emphasizing the urgent need for advanced therapeutic interventions, are discussed. The review places a spotlight on exosome therapy as a potential therapy. CSSC-derived exosomes exhibit significant potential for modulating inflammation, promoting tissue repair, and addressing corneal transparency. Additionally, the rejuvenation potential of CSSCs through epigenetic reprogramming adds to the evolving regenerative landscape. The imperative for clinical trials and human studies to seamlessly integrate these strategies into practice is emphasized. This points towards a future where CSSC-based therapies, particularly leveraging exosomes, play a central role in diversifying ophthalmic regenerative medicine.

Co- and Triaxial Electrospinning for Stem Cell-based Bone Regeneration

Bone tissue is composed of organic minerals and cells. It has the capacity to heal for certain minor damages, but when the bone defects surpass the critical threshold, they need fixing. Bone regeneration through natural and synthetic biodegradable materials requires various steps, such as manufacturing methods and materials selection. A successful biodegradable bone graft should have a high surface area/ volume ratio, strength, and a biocompatible, porous structure capable of promoting cell adhesion, proliferation, and differentiation. Considering these requirements, the electrospinning technique is promising for creating functional nano-sized scaffolds. The multi-axial methods, such as coaxial and triaxial electrospinning, are the most popular techniques to produce double or tri-layered scaffolds, respectively. Recently, stem cell culture on scaffolds and the application of osteogenic differentiation protocols on these scaffolds have opened new possibilities in the field of biomaterials research. This review discusses an overview of the progress in coaxial and triaxial technology through biodegradable composite bone materials. The review also carefully elaborates the osteogenic differentiation using stem cells and their performance with nano-sized scaffolds.

Gingival mesenchymal stem cell therapy, immune cells, and immunoinflammatory application

MSC-based therapeutic strategies have proven to be incredibly effective. Robust self-renewal, multilineage differentiation, and potential for tissue regeneration and disease treatments are all features of MSCs isolated from oral tissue. Human exfoliated deciduous teeth, dental follicles, dental pulp, apical papilla SCs, and alveolar bone are the primary sources of oral MSC production. The early immunoinflammatory response is the first stage of the healing process. Oral MSCs can interact with various cells, such as immune cells, revealing potential immunomodulatory regulators. They also have strong differentiation and regeneration potential. Therefore, a ground-breaking strategy would be to research novel immunomodulatory approaches for treating disease and tissue regeneration that depend on the immunomodulatory activities of oral MSCs during tissue regeneration.

New dawn for keratoconus treatment: potential strategies for corneal stromal regeneration

Keratoconus is a progressive, ectatic and blinding disorder of the cornea, characterized by thinning of corneal stroma. As a highly prevalent among adolescents, keratoconus has been a leading indication for corneal transplantation worldwide. However, the severe shortage of donor corneas is a global issue, and the traditional corneal transplantation surgeries may superinduce multiple complications, necessitating efforts to develop more effective strategies for keratoconus treatment. In this review, we summarized several strategies to promote corneal stromal regeneration or improve corneal stromal thickness, including cell-based therapies, biosynthetic alternatives for inducing corneal regeneration, minimally invasive intrastromal implantation and bioengineered tissues for implantation. These strategies provided more accessible but safer alternatives from various perspectives for keratoconus treatment, paving the way for arresting the keratoconus progression in its earlier stage. For the treatments of corneal ectatic diseases beyond keratoconus, these approaches will provide important references and widen the therapy options in a donor tissue-independent manner.

The Application of MicroRNAs in Glaucoma Research: A Bibliometric and Visualized Analysis

Glaucoma is similar to a neurodegenerative disorder and leads to global irreversible loss of vision. Despite extensive research, the pathophysiological mechanisms of glaucoma remain unclear, and no complete cure has yet been identified for glaucoma. Recent studies have shown that microRNAs can serve as diagnostic biomarkers or therapeutic targets for glaucoma; however, there are few bibliometric studies that focus on using microRNAs in glaucoma research. Here, we have adopted a bibliometric analysis in the field of microRNAs in glaucoma research to manifest the current tendencies and research hotspots and to present a visual map of the past and emerging tendencies in this field. In this study, we retrieved publications in the Web of Science database that centered on this field between 2007 and 2022. Next, we used VOSviewer, CiteSpace, Scimago Graphica, and Microsoft Excel to present visual representations of a co-occurrence analysis, co-citation analysis, tendencies, hotspots, and the contributions of authors, institutions, journals, and countries/regions. The United States was the main contributor. Investigative Ophthalmology and Visual Science has published the most articles in this field. Over the past 15 years, there has been exponential growth in the number of publications and citations in this field across various countries, organizations, and authors. Thus, this study illustrates the current trends, hotspots, and emerging frontiers and provides new insight and guidance for searching for new diagnostic biomarkers and clinical trials for glaucoma in the future. Furthermore, international collaborations can also be used to broaden and deepen the field of microRNAs in glaucoma research.

Intrastromal versus subconjunctival injection of mesenchymal stem/stromal cells for promoting corneal repair

PURPOSE

Different approaches to delivery of mesenchymal stem/stromal cells (MSCs) for ameliorating corneal injuries have been investigated. This study was aimed to compare the efficacy of intrastromal and subconjunctival injection of human bone marrow-derived MSCs (hBM-MSCs) in a corneal epithelial injury model.

METHODS

Twenty-four C57BL/6J mice underwent total corneal and limbal epithelial debridement. Then, the mice were divided into three different groups: (1) intrastromal hBM-MSCs injection, (2) subconjunctival hBM-MSCs injection, and (3) injection of frozen medium as a control. Mice were monitored by slit lamp and underwent anterior segment optical coherence tomography (ASOCT). Following euthanasia, the corneas were further evaluated by histology and immunostaining.

RESULTS

hBM-MSC injection successfully healed epithelial defects regardless of the delivery route (P < 0.001). However, intrastromal injection was superior to subconjunctival injection in reducing defect area (P = 0.001). Intrastromal injection of hBM-MSCs also significantly reduced corneal opacity and neovascularization and improved ASOCT parameters compared to subconjunctival injection or no treatment (P < 0.001, P = 0.003, and P < 0.001, respectively). Although both of the treatment groups were positive for CK12 and had reduced levels of MUC5AC compared to the control, CK12 staining was stronger in the intrastromal group compared to the subconjunctival group. Also, persistency of MSCs was confirmed by in vivo (up to 2 weeks) and in vitro assessments (up to 4 weeks).

CONCLUSIONS

Although the injection of hBM-MSC using both intrastromal and subconjunctival methods improve wound healing and reduce neovascularization and opacity, the intrastromal approach is superior in terms of corneal healing.

Keratoconus Diagnosis and Treatment: Recent Advances and Future Directions

Keratoconus is a disorder characterized by progressive corneal thinning and steepening that may result in significant visual impairment secondary to high astigmatism, corneal scarring, or even corneal perforation. Early detection and screening of keratoconus are essential for effective management and treatment. Several screening methods, such as corneal topography and tomography, corneal biomechanics, and genetic testing, are being developed to detect keratoconus at an early stage. Once detected, prevention of progression is the mainstay of keratoconus management. Corneal collagen cross-linking is a minimally invasive treatment option that can slow or halt the progression of keratoconus. Additionally, recent studies have investigated the potential use of copper sulfate eye drops (IVMED-80) and extracellular vesicles to prevent the progression of keratoconus as non-invasive treatment options. For visual rehabilitation, currently available treatments include scleral lenses, intracorneal ring segments, corneal allogenic intrastromal ring segments, and deep anterior lamellar keratoplasty. The safety and efficacy of these emerging treatment options for keratoconus are currently being investigated.

The characteristics and medical applications of antler stem cells

Antlers are the only fully regenerable mammalian appendages whose annual renewal is initiated by antler stem cells (ASCs), defined as a specialized type of mesenchymal stem cells (MSCs) with embryonic stem cell properties. ASCs possess the same biological features as MSCs, including the capacity for self-renewal and multidirectional differentiation, immunomodulatory functions, and the maintenance of stem cell characteristics after multiple passages. Several preclinical studies have shown that ASCs exhibit promising potential in wound healing, bone repair, osteoarthritis, anti-tissue fibrosis, anti-aging, and hair regeneration. Medical applications based on ASCs and ASC-derived molecules provide a new source of stem cells and therapeutic modalities for regenerative medicine. This review begins with a brief description of antler regeneration and the role of ASCs. Then, the properties and advantages of ASCs are described. Finally, medical research advances regarding ASCs are summarized, and the prospects and challenges of ASCs are highlighted.

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

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

Pathological role of inflammation in ocular disease progress and its targeting by mesenchymal stem cells (MSCs) and their exosome; current status and prospect

Because of their unique capacity for differentiation to a diversity of cell lineages and immunosuppressive properties, mesenchymal stem cells (MSC) are being looked at as a potential new treatment option in ophthalmology. The MSCs derived from all tissue sources possess immunomodulatory attributes through cell-to-cell contact and releasing a myriad of immunomodulatory factors (IL-10, TGF-β, growth-related oncogene (GRO), indoleamine 2,3 dioxygenase (IDO), nitric oxide (NO), interleukin 1 receptor antagonist (IL-1Ra), prostaglandin E2 (PGE2)). Such mediators, in turn, alter both the phenotype and action of all immune cells that serve a pathogenic role in the progression of inflammation in eye diseases. Exosomes from MSCs, as natural nano-particles, contain the majority of the bioactive components of parental MSCs and can easily by-pass all biological barriers to reach the target epithelial and immune cells in the eye without interfering with nearby parenchymal cells, thus having no serious side effects. We outlined the most recent research on the molecular mechanisms underlying the therapeutic benefits of MSC and MSC-exosome in the treatment of inflammatory eye diseases in the current article.

Mesenchymal Stem Cells and Exosomes: A Novel Therapeutic Approach for Corneal Diseases

The cornea, with its delicate structure, is vulnerable to damage from physical, chemical, and genetic factors. Corneal transplantation, including penetrating and lamellar keratoplasties, can restore the functions of the cornea in cases of severe damage. However, the process of corneal transplantation presents considerable obstacles, including a shortage of available donors, the risk of severe graft rejection, and potentially life-threatening complications. Over the past few decades, mesenchymal stem cell (MSC) therapy has become a novel alternative approach to corneal regeneration. Numerous studies have demonstrated the potential of MSCs to differentiate into different corneal cell types, such as keratocytes, epithelial cells, and endothelial cells. MSCs are considered a suitable candidate for corneal regeneration because of their promising therapeutic perspective and beneficial properties. MSCs compromise unique immunomodulation, anti-angiogenesis, and anti-inflammatory properties and secrete various growth factors, thus promoting corneal reconstruction. These effects in corneal engineering are mediated by MSCs differentiating into different lineages and paracrine action via exosomes. Early studies have proven the roles of MSC-derived exosomes in corneal regeneration by reducing inflammation, inhibiting neovascularization, and angiogenesis, and by promoting cell proliferation. This review highlights the contribution of MSCs and MSC-derived exosomes, their current usage status to overcome corneal disease, and their potential to restore different corneal layers as novel therapeutic agents. It also discusses feasible future possibilities, applications, challenges, and opportunities for future research in this field.

Extracellular-Vesicle-Based Therapeutics in Neuro-Ophthalmic Disorders

Extracellular vesicles (EVs) have been recognized as promising candidates for developing novel therapeutics for a wide range of pathologies, including ocular disorders, due to their ability to deliver a diverse array of bioactive molecules, including proteins, lipids, and nucleic acids, to recipient cells. Recent studies have shown that EVs derived from various cell types, including mesenchymal stromal cells (MSCs), retinal pigment epithelium cells, and endothelial cells, have therapeutic potential in ocular disorders, such as corneal injury and diabetic retinopathy. EVs exert their effects through various mechanisms, including promoting cell survival, reducing inflammation, and inducing tissue regeneration. Furthermore, EVs have shown promise in promoting nerve regeneration in ocular diseases. In particular, EVs derived from MSCs have been demonstrated to promote axonal regeneration and functional recovery in various animal models of optic nerve injury and glaucoma. EVs contain various neurotrophic factors and cytokines that can enhance neuronal survival and regeneration, promote angiogenesis, and modulate inflammation in the retina and optic nerve. Additionally, in experimental models, the application of EVs as a delivery platform for therapeutic molecules has revealed great promise in the treatment of ocular disorders. However, the clinical translation of EV-based therapies faces several challenges, and further preclinical and clinical studies are needed to fully explore the therapeutic potential of EVs in ocular disorders and to address the challenges for their successful clinical translation. In this review, we will provide an overview of different types of EVs and their cargo, as well as the techniques used for their isolation and characterization. We will then review the preclinical and clinical studies that have explored the role of EVs in the treatment of ocular disorders, highlighting their therapeutic potential and the challenges that need to be addressed for their clinical translation. Finally, we will discuss the future directions of EV-based therapeutics in ocular disorders. Overall, this review aims to provide a comprehensive overview of the current state of the art of EV-based therapeutics in ophthalmic disorders, with a focus on their potential for nerve regeneration in ocular diseases.

Wound-Healing Effects of Mesenchymal Stromal Cell Secretome in the Cornea and the Role of Exosomes

Mesenchymal stromal/stem cells (MSCs) and their secreted factors have been shown to have immunomodulatory and regenerative effects. In this study, we investigated human bone-marrow-derived MSC secretome (MSC-S) for the treatment of corneal epithelial wounds. Specifically, we evaluated the role of MSC extracellular vesicles (EV)/exosomes in mediating the wound-healing effects of the MSC-S. In vitro studies using human corneal epithelial cells showed that MSC-CM increased cell proliferation in HCEC and HCLE cells, while EV-depleted MSC-CM showed lower cell proliferation in both cell lines compared to the MSC-CM group. In vitro and in vivo experiments revealed that 1X MSC-S consistently promoted wound healing more effectively than 0.5X MSC-S, and MSC-CM promoted wound healing in a dose-dependent manner, while exosome deprivation delayed wound healing. We further evaluated the incubation period of MSC-CM on corneal wound healing and showed that MSC-S collected for 72 h is more effective than MSC-S collected for 48 h. Finally, we evaluated the stability of MSC-S under different storage conditions and found that after one cycle of freeze-thawing, MSC-S is stable at 4 °C for up to 4 weeks. Collectively, we identified the following: (i) MSC-EV/Exo as the active ingredient in MSC-S that mediates the wound-healing effects in the corneal epithelium, providing a measure to optimize its dosing for a potential clinical product; (ii) Treatment with EV/Exo-containing MSC-S resulted in an improved corneal barrier and decreased corneal haze/edema relative to EV/Exo-depleted MSC-S; (iii) The stability of MSC-CM for up to 4 weeks showed that the regular storage condition did not significantly impact its stability and therapeutic functions.

Single-Cell RNA sequencing highlights the regulatory role of T cell marker genes Ctla4, Ccl5 and Tcf7 in corneal allograft rejection of mouse model

BACKGROUND

A mouse corneal allograft model was induced and single-cell RNA sequencing (scRNA-seq) data of corneal tissues and T cells were analyzed to reveal a T cell-mediated mechanism for corneal allograft rejection in mice.

METHODS

Corneal tissue samples from a mouse model of corneal allograft were collected for scRNA-seq analysis, followed by quality control, dimensionality reduction, cluster analysis and enrichment analysis. A large number of highly variable genes were identified in mice with corneal allograft. Significant difference existed in immune T cells, especially in CD4 + T cells.

RESULTS

It was found that T cell marker genes Ctla4, Ccl5, Tcf7, Lgals1, and Itgb1 may play key roles in the corneal allograft rejection. Mice with allograft rejection showed a significant increase in the proportion of CD4 + T cells in the corneal tissues. Besides, Ccl5 and Tcf7 expression was increased in mice with allograft rejection and positively linked to the proportion of CD4 + T cells. Whereas, Ctla4 expression was downregulated and negatively associated with the proportion of CD4 + T cells.

CONCLUSION

Collectively, Ctla4, Ccl5 and Tcf7 may participate in the rejection of corneal allograft in mice by affecting CD4 + T cell activation.

Application of Convergent Science and Technology toward Ocular Disease Treatment

Eyes are one of the main critical organs of the body that provide our brain with the most information about the surrounding environment. Disturbance in the activity of this informational organ, resulting from different ocular diseases, could affect the quality of life, so finding appropriate methods for treating ocular disease has attracted lots of attention. This is especially due to the ineffectiveness of the conventional therapeutic method to deliver drugs into the interior parts of the eye, and the also presence of barriers such as tear film, blood-ocular, and blood-retina barriers. Recently, some novel techniques, such as different types of contact lenses, micro and nanoneedles and in situ gels, have been introduced which can overcome the previously mentioned barriers. These novel techniques could enhance the bioavailability of therapeutic components inside the eyes, deliver them to the posterior side of the eyes, release them in a controlled manner, and reduce the side effects of previous methods (such as eye drops). Accordingly, this review paper aims to summarize some of the evidence on the effectiveness of these new techniques for treating ocular disease, their preclinical and clinical progression, current limitations, and future perspectives.

Adipose Mesenchymal Stromal Cell-Derived Exosomes Carrying MiR-122-5p Antagonize the Inhibitory Effect of Dihydrotestosterone on Hair Follicles by Targeting the TGF-β1/SMAD3 Signaling Pathway

Androgenic alopecia (AGA) is the most common type of hair loss, where local high concentrations of dihydrotestosterone (DHT) in the scalp cause progressive shrinkage of the hair follicles, eventually contributing to hair loss. Due to the limitations of existing methods to treat AGA, the use of multi-origin mesenchymal stromal cell-derived exosomes has been proposed. However, the functions and mechanisms of action of exosomes secreted by adipose mesenchymal stromal cells (ADSCs-Exos) in AGA are still unclear. Using Cell Counting Kit-8 (CCK8) analysis, immunofluorescence staining, scratch assays, and Western blotting, it was found that ADSC-Exos contributed to the proliferation, migration, and differentiation of dermal papilla cells (DPCs) and up-regulated the expression of cyclin, β-catenin, versican, and BMP2. ADSC-Exos also mitigated the inhibitory effects of DHT on DPCs and down-regulated transforming growth factor-beta1 (TGF-β1) and its downstream genes. Moreover, high-throughput miRNA sequencing and bioinformatics analysis identified 225 genes that were co-expressed in ADSC-Exos; of these, miR-122-5p was highly enriched and was found by luciferase assays to target SMAD3. ADSC-Exos carrying miR-122-5p antagonized DHT inhibition of hair follicles, up-regulated the expression of β-catenin and versican in vivo and in vitro, restored hair bulb size and dermal thickness, and promoted the normal growth of hair follicles. So, ADSC-Exos enhanced the regeneration of hair follicles in AGA through the action of miR-122-5p and the inhibition of the TGF-β/SMAD3 axis. These results suggest a novel treatment option for the treatment of AGA.

Extracellular vesicles as a new horizon in the diagnosis and treatment of inflammatory eye diseases: A narrative review of the literature

Extracellular vesicles include exosomes, microvesicles, and apoptotic bodies. Their cargos contain a diverse variety of lipids, proteins, and nucleic acids that are involved in both normal physiology and pathology of the ocular system. Thus, studying extracellular vesicles may lead to a more comprehensive understanding of the pathogenesis, diagnosis, and even potential treatments for various diseases. The roles of extracellular vesicles in inflammatory eye disorders have been widely investigated in recent years. The term “inflammatory eye diseases” refers to a variety of eye conditions such as inflammation-related diseases, degenerative conditions with remarkable inflammatory components, neuropathy, and tumors. This study presents an overview of extracellular vesicles’ and exosomes’ pathogenic, diagnostic, and therapeutic values in inflammatory eye diseases, as well as existing and potential challenges.

Human corneal stromal stem cells express anti-fibrotic microRNA-29a and 381-5p - A robust cell selection tool for stem cell therapy of corneal scarring

INTRODUCTION

Corneal blindness due to scarring is treated with corneal transplantation. However, a global problem is the donor material shortage. Preclinical and clinical studies have shown that cell-based therapy using corneal stromal stem cells (CSSCs) suppresses corneal scarring, potentially mediated by specific microRNAs transported in extracellular vesicles (EVs). However, not every CSSC batch from donors achieves similar anti-scarring effects.

OBJECTIVES

To examine miRNA profiles in EVs from human CSSCs showing "healing" versus "non-healing" effects on corneal scarring and to design a tool to select CSSCs with strong healing potency for clinical applications.

METHODS

Small RNAs from CSSC-EVs were extracted for Nanostring nCounter Human miRNA v3 assay. MicroRNAs expressed > 20 folds in "healing" EVs (P < 0.05) were subject to enriched gene ontology (GO) term analysis. MiRNA groups with predictive regulation on inflammatory and fibrotic signalling were studied by mimic transfection to (1) mouse macrophages (RAW264.7) for M1 phenotype assay; (2) human corneal keratocytes for cytokine-induced fibrosis, and (3) human CSSCs for corneal scar prevention in vivo. The expression of miR-29a was screened in additional CSSC batches and the anti-scarring effect of cells was validated in mouse corneal wounds.

RESULTS

Twenty-one miRNAs were significantly expressed in "healing" CSSC-EVs and 9 miRNA groups were predicted to associate with inflammatory and fibrotic responses, and tissue regeneration (P <10-6). Overexpression of miR-29a and 381-5p significantly prevented M1 phenotype transition in RAW264.7 cells after lipopolysaccharide treatment, suppressed transforming growth factor β1-induced fibrosis marker expression in keratocytes, and reduced scarring after corneal injury. High miR-29a expression in EV fractions distinguished human CSSCs with strong healing potency, which inhibited corneal scarring in vivo.

CONCLUSION

We characterized the anti-inflammatory and fibrotic roles of miR-29a and 381-5p in CSSCs, contributing to scar prevention. MiR-29a expression in EVs distinguished CSSCs with anti-scarring quality, identifying good quality cells for a scarless corneal healing.

Embryonic stem cell extracellular vesicles reverse the senescence of retinal pigment epithelial cells by the p38MAPK pathway

Retinal pigment epithelial (RPE) cellular senescence is regarded as an initiator for age-related macular degeneration (AMD). We previously demonstrated that by the coculture way, embryonic stem cells (ESCs) can reverse the senescence of RPE cells, but xenograft cells can cause a plethora of adverse effects. Extracellular vesicles (EVs) derived from ESCs can act as messengers to mediate nearby cell activities and have the same potential as ESCs to reverse RPE senescence. Furthermore, ESC-EVs have achieved preliminary efficacy while treating many age-related diseases. The present study aimed to test the effect of ESC-EVs on the replicative senescence model of RPE cells as well as its mechanism. The results showed that ESC-EVs enhanced the proliferative ability and cell cycle transition of senescent RPE cells, whereas reduced the senescence-associated galactosidase (SA-β-gal) staining rate, as well as the levels of mitochondrial membrane potential (MMP) and reactive oxygen species (ROS). Moreover, classical markers of cellular senescence p21^WAF1/CIP1 (p21) and p16^INK4a (p16) were downregulated. The bioinformatic analysis and further study showed that the inhibition of the p38MAPK pathway by ESC-EVs played a pivotal role in RPE cellular senescence-reversing effect, which was ameliorated or even abolished when dehydrocorydaline were administrated simultaneously, demonstrating that ESC-EVs can effectively reverse RPE cellular senesence by inhibiting the p38MAPK pathway, thus highlights the potential of ESC-derived EVs as biomaterials for preventative and protective therapy in AMD.

Research Progress of Bioinspired Nanostructured Systems for the Treatment of Ocular Disorders

How to enhance the bioavailability and prolong the residence time of drugs in the eye present the major barriers to traditional eye delivery. Nanotechnology has been widely used in ocular drug delivery systems because of its advantages of minimizing adverse reactions, decreasing the frequency of administration, prolonging the release time, and improving the bioavailability of the drug in the eye. As natural product-based nanostructured systems, bioinspired nanostructured systems have presented as less toxic, easy to prepare, and cost-effective and have potential application value in the field of nanotechnology. A systematic classification of bioinspired nanostructured systems based on their inspiration source and formulation and their brief applications in disease are presented here. A review of recent research progress of the bioinspired nanostructured systems for the treatment of the anterior and posterior segment of ocular disorders is then presented in detail. Finally, current challenges and future directions with regard to manufacturing bioinspired nanomaterials are provided.

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.

[Corneal regeneration: is there a place for tissues of perinatal origin?]

The article reviews the main properties of the cornea and the mechanisms of its physiological regeneration and repair in response to damage and describes the most promising methods of treatment aimed at stimulating limbal stem cells and based on the use of native tissues of perinatal origin, umbilical cord mesenchymal stromal cells, and cell-free therapeutic products.

Mechanical stimulation on a microfluidic device to highly enhance small extracellular vesicle secretion of mesenchymal stem cells

Small extracellular vesicles (sEVs) are recognized as promising detection biomarkers and attractive delivery vehicles, showing great potential in diagnosis and treatment of diseases. However, the applications of sEVs are usually restricted by their poor secretion amount from donor cells under routine cell culture conditions, which is especially true for mesenchymal stem cells (MSCs) due to their limited expansion and early senescence. Here, a microfluidic device is proposed for boosting sEV secretion from MSCs derived from human fetal bone marrow (BM-MSCs). As the cells rapidly pass through a microfluidic channel with a series of narrow squeezing ridges, mechanical stimulation permeabilizes the cell membrane, thus promoting them to secrete more sEVs into extracellular space. In this study, the microfluidic device demonstrates that mechanical-squeezing effect could increase the secretion amount of sEVs from the BM-MSCs by approximately 4-fold, while maintaining cellular growth state of the stem cells. Further, the secreted sEVs are efficiently taken up by immortalized human corneal epithelial cells and accelerate corneal epithelial wound healing in vitro, indicating that this technique wound not affect the functionality of sEVs and demonstrating the application potentials of this technique.

Exosomes Released by Corneal Stromal Cells Show Molecular Alterations in Keratoconus Patients and Induce Different Cellular Behavior

Exosomes have been related to various disorders, but their study in relation to ocular pathologies has been limited. In this article, we analyze exosomes produced by corneal stromal cells from healthy individuals and from patients with keratoconus. The proteomic study allowed for the identification of 14 new proteins with altered expression, related to molecules previously associated with the pathology. miRNA analysis detected 16 altered species, including miR-184, responsible for familial severe keratoconus. The prediction of its potential biological targets identified 1121 genes, including some related to this pathology. Exosomes produced by keratoconic cells induced a marked increase in the migration of stromal cells and corneal epithelium, while those produced by healthy cells had no effect on stromal cells. Both types of nanovesicles reduced the proliferation of stromal and corneal cells, but those produced by healthy cells had less effect. Exosomes produced by healthy cells had concentration-dependent effects on the transcription of genes encoding proteoglycans by keratoconus cells, with a relative normalization observed at concentrations of 240 µg/mL. These results show the alteration of stromal exosomes in keratoconus and suggest an influence on the development of the pathology, although the use of healthy exosomes could also have therapeutic potential.

Exosomes as Neurological Nanosized Machines

In the past few decades, nanomedicine research has advanced dramatically. In spite of this, traditional nanomedicine faces major obstacles, such as blood-brain barriers, low concentrations at target sites, and rapid removal from the body. Exosomes as natural extracellular vesicles contain special bioactive molecules for cell-to-cell communications and nervous tissue function, which could overcome the challenges of nanoparticles. Most recently, microRNAs, long noncoding RNA, and circulating RNA of exosomes have been appealing because of their critical effect on the molecular pathway of target cells. In this review, we have summarized the important role of exosomes of noncoding RNAs in the occurrence of brain diseases.

Exosomes in the visual system: New avenues in ocular diseases

Exosomes are a subgroup of membrane-bound extracellular vesicles secreted by all cell types and present virtually in all biological fluids. The composition of exosomes in the same cell type varies in healthy and disease conditions. Hence, exosomes research is a prime focus area for clinical research in cancer and numerous age-related metabolic syndromes. Functions of exosomes include crucial cell-to-cell communication that mediates complex cellular processes, such as antigen presentation, stem cell differentiation, and angiogenesis. However, very few studies reported the presence and role of exosomes in normal physiological and pathological conditions of specialized ocular tissues of the eye and ocular cancers. The eye being a protected sense organ with unique connectivity with the rest of the body through the blood and natural passages, we believe that the role of exosomes in ocular tissues will significantly improve our understanding of ocular diseases and their interactions with the rest of the body. We present a review that highlights the existence and function of exosomes in various ocular tissues, their role in the progression of some of the neoplastic and non-neoplastic conditions of the eyes.

An Ex Vivo Study on Release, Uptake, and miRNA Profile of Exosomes in Rat Lens

Purpose

To identify the ability of releasing and uptaking exosomes in rat lens and characterize the exosomal microRNA profile of lens-derived exosomes.

Methods

The rat lenses were cultured ex vivo and the medium was collected. The exosomes were isolated from medium and measured in size and concentration by nanoflow cytometry (nFCM) and transmission electron microscopy (TEM) and verified with CD63 and TSG101 by Western blot. The miRNAs in exosomes released from lens epithelial cells (LECs) were sequenced. The plasma exosomes labeled by PKH26 were used to verify the exosomes uptake LECs, and their colocalized fluorescence was imaged by confocal microscopy.

Results

LECs released numerous exosomes into the medium through the capsule, which contained abundant miRNAs. The most abundant miRNAs included miR-184, let-7c-5p, let-7a-5p, let-7b-5p, let-7f-5p, miR-125a-5p, miR-204-5p, miR-125b-5p, miR-1b, and miR-23a-3p. The LECs but not the lens fibre cells showed exosome uptake. The LECs uptake more PKH26-labeled exosomes at day 7 than day 3 and day 14.

Conclusions

Our results suggested that LECs can release and uptake exosomes through the capsule. Exosomes may be an important way for the lens to communicate among LECs, aqueous humour, vitreous body, and other ocular tissues.

OUP accepted manuscript

The corneal epithelium serves to protect the underlying cornea from the external environment and is essential for corneal transparency and optimal visual function. Regeneration of this epithelium is dependent on a population of stem cells residing in the basal layer of the limbus, the junction between the cornea and the sclera. The limbus provides the limbal epithelial stem cells (LESCs) with an optimal microenvironment, the limbal niche, which strictly regulates their proliferation and differentiation. Disturbances to the LESCs and/or their niche can lead to the pathologic condition known as limbal stem cell deficiency (LSCD) whereby the corneal epithelium is not generated effectively. This has deleterious effects on the corneal and visual function, due to impaired healing and secondary corneal opacification. In this concise review, we summarize the characteristics of LESCs and their niche, and present the current and future perspectives in the management of LSCD with an emphasis on restoring the function of the limbal niche.

Mesenchymal stem cells are prospective novel off-the-shelf wound management tools

Chronic/non-healing cutaneous wounds pose a debilitating burden on patients and healthcare system. Presently, treatment modalities are rapidly shifting pace from conventional methods to advanced wound care involving cell-based therapies. Mesenchymal stem cells (MSCs) have come across as a prospective option due to its pleiotropic functions viz. non-immunogenicity, multipotency, multi-lineage plasticity and secretion of growth factors, cytokines, microRNAs (miRNA), exosomes, and microvesicles as part of their secretome for assisting wound healing. We outline the therapeutic role played by MSCs and its secretome in suppressing tissue inflammation, causing immunomodulation, aiding angiogenesis and assisting in scar-free wound healing. We further assess the mechanism of action by which MSCs contribute in manifesting tissue repair. The review flows ahead in exploring factors that influence healing behavior including effect of multiple donor sites, donor age and health status, tissue microenvironment, and in vitro expansion capability. Moving ahead, we overview the advancements achieved in extending the lifespan of cells upon implantation, influence of genetic modifications aimed at altering MSC cargo, and evaluating bioengineered matrix-assisted delivery methods toward faster healing in preclinical and clinical models. We also contribute toward highlighting the challenges faced in commercializing cell-based therapies as standard of care treatment regimens. Finally, we strongly advocate and highlight its application as a futuristic technology for revolutionizing tissue regeneration.

Exosomes Derived From Mesenchymal Stem Cells Pretreated With Ischemic Rat Heart Extracts Promote Angiogenesis via the Delivery of DMBT1

Mesenchymal stem cell-derived exosomes (MSC-Exos) have been shown to promote angiogenesis. Treating MSCs with ischemic rat brain extracts was sufficient to augment their benefits in stroke. However, no similar analyses of ischemic heart extracts have been performed to date. We aim to determine whether MSC-Exos derived from MSCs pretreated with ischemic rat heart extract were able to promote angiogenesis and to clarify underlying mechanisms. ELISA (enzyme-linked immunosorbent assay) of heart extracts revealed a significant increase of vascular endothelial growth factor (VEGF) at 24 h post-MI (myocardial infarction) modeling, and time-dependent decreases in hypoxia inducible factor-1α (HIF-1α). MTT and wound healing assays revealed human umbilical vein endothelial cells (HUVECs) migration and proliferation increased following MSCE-Exo treatment (exosomes derived from MSC pretreated with ischemic heart extracts of 24 h post-MI) relative to MSCN-Exo treatment (exosomes derived from MSC pretreated with normal heart extracts). Proteomic analyses of MSCE-Exo and MSCN-Exo were conducted to screen for cargo proteins promoting angiogenesis. Result revealed several angiogenesis-related proteins were upregulated in MSCE-Exo, including DMBT1 (deleted in malignant brain tumors 1). When DMBT1 was silenced in MSCs, HUVECs with MSCDMBT1 RNAi-Exo treatment exhibited impaired proliferative and migratory activity and reductions of DMBT1, p-Akt, β-catenin, and VEGF. To explore how ischemic heart extracts took effects, ELISA was conducted showing a significant increase of IL-22 at 24 h post-MI modeling. P-STAT3, IL22RA1, DMBT1, and VEGF proteins were increased in MSCE relative to MSCN, and VEGF and DMBT1 were increased in MSCE-Exos. Together, these suggest that IL-22 upregulation in ischemic heart extracts can increase DMBT1 in MSCs. Exosomes derived from those MSCs deliver DMBT1 to HUVECs, thereby enhancing their migratory and proliferative activity.

Recent Advances in Natural Materials for Corneal Tissue Engineering

Given the incidence of corneal dysfunctions and diseases worldwide and the limited availability of healthy, human donors, investigators are working to generate engineered cellular and acellular therapeutic approaches as alternatives to corneal transplants from human cadavers. These engineered strategies aim to address existing complications with human corneal transplants, including graft rejection, infection, and complications resulting from surgical methodologies. The main goals of these research endeavors are to (1) determine ideal mechanical properties, (2) devise methodologies to improve the efficacy of engineered corneal grafts and cell-based therapies, and (3) optimize transplantation of engineered tissue structures in the eye. Thus, recent innovations have sought to address these challenges through both in vitro and in vivo studies. This review covers recent work aimed at evaluating engineered materials, potential therapeutic cells, and the resulting cell-material interactions that lead to optimal corneal graft properties. Furthermore, we discuss promising strategies in corneal tissue engineering techniques and in vivo studies in animal models.

Effects of Adipose-Derived Stem Cells and Platelet-Rich Plasma Exosomes on The Inductivity of Hair Dermal Papilla Cells

OBJECTIVE

Hair loss is a prevalent medical problem in both men and women. Maintaining the hair inductivity potential of human dermal papilla cells (hDPCs) during cell culture is the main issue in hair follicle morphogenesis and regeneration. The present study was conducted to compare the effects of different concentrations of exosomes derived from human adipose stem cells (hASCs) and platelet-rich plasma (PRP) on the proliferation, migration and expression of alkaline pholphatase (ALP), versican, and smooth muscle alpha-actin (α-SMA) in human DPCs.

MATERIALS AND METHODS

In this experimental study, hDPCs, human hair DPCs and outer root sheet cells (ORSCs) were separated from healthy hair samples. The protocol of exosome isolation from PRP and hASCs comprises serial low speed centrifugation and ultracentrifugation. The effects of different concentrations of exosomes (25, 50, 100 μg/ ml) derived from hASCs and PRP on proliferation (MTS assay), migration (scratch test) and expression of ALP, versican and α-SMA (real time-polymerase chain reaction) in human DPCs were evaluated.

RESULTS

The flow cytometry analysis of specific cytoplasmic markers showed expression of versican (77%) and α-SMA (60.8%) in DPCs and K15 (73.2%) in ORSCs. According to NanoSight Dynamic Light Scattering, we found the majority of ASCs and PRP-exosomes (ASC-Exo and PRP-Exo) to be 30-150 nm in size. For 100 μg/ml of ASCs-Exo, the expressions of ALP, versican and α-SMA proteins increased by a factor of 1.2, 2 and 3, respectively, compared to the control group. The findings of our experiments illustrated that 100 μg/ml of ASCs-Exo compared to the same concentration of PRP-Exo significantly promote DPC proliferation and migration in culture.

CONCLUSION

This study introduced the potential positive effect of ASC-Exo in increasing the proliferation and survival of DPCs, while maintaining their hair inductivity. Thus, ASCs-Exo possibly provide a new effective procedure for treatment of hair loss.

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.

Cardioprotective Roles of Endothelial Progenitor Cell-Derived Exosomes

With the globally increasing prevalence, cardiovascular diseases (CVDs) have become the leading cause of mortality. The transplantation of endothelial progenitor cells (EPCs) holds a great promise due to their potential for vasculogenesis, angiogenesis, and protective cytokine release, whose mechanisms are essential for CVD therapies. In reality, many investigations have attributed the therapeutic effects of EPC transplantation to the secretion of paracrine factors rather than the differentiation function. Of note, previous studies have suggested that EPCs could also release exosomes (diameter range of 30–150 nm), which carry various lipids and proteins and are abundant in microRNAs. The EPC-derived exosomes (EPC-EXs) were reported to act on the heart and blood vessels and were implicated in anti-inflammation, anti-oxidation, anti-apoptosis, the inhibition of endothelial-to-mesenchymal transition (EndMT), and cardiac fibrosis, as well as anti-vascular remodeling and angiogenesis, which were considered as protective effects against CVDs. In this review, we summarize the current knowledge on using EPC-EXs as therapeutic agents and provide a detailed description of their identified mechanisms of action to promote the prognosis of CVDs.

miR-340-5p mediates the therapeutic effect of mesenchymal stem cells on corneal neovascularization

BACKGROUND

Our previous study revealed that mesenchymal stem cells (MSCs) inhibited angiogenesis via miRNA-mediated repression of prospero homeobox 1 (PROX1). This study aimed to verify whether miR-340-5p participates in the therapeutic effect of MSCs on corneal neovascularization (CNV) via repressing PROX1 and epithelial membrane protein 2 (EMP2).

MATERIALS AND METHODS

The rat CNV model was established by corneal alkali burn. The binding relationship between miR-340-5p and 3'-untranslational regions (3'UTRs) of EMP2 and PROX1 was confirmed using dual-luciferase reporter assay. After culturing corneal epithelial cells (CECs) using MSC supernatants, the vascular endothelial growth factor (VEGF) level in CEC supernatants and the CEC viability were detected. The role of miR-340-5p in the therapeutic effect of MSC on CNV was determined via lentivirus-mediated miR-340-5p intervention in vivo.

RESULTS

The expression of miR-340-5p was reduced and EMP2 and PROX1 were increased in CNV corneal tissues. The lentivirus-mediated overexpression of miR-340-5p inhibited the expressions of EMP2 and PROX1. The dual-luciferase reporter assay confirmed that miR-340-5p could bind with the 3'UTRs of EMP2 and PROX1. miR-340-5p was enriched in MSC supernatants and the culture of CECs using MSC supernatants increased the miR-340-5p expression in CECs. After being cultured in miR-340-5p-knocking down MSC supernatants, the expressions of EMP2 and PROX1 were increased, and the VEGF level and CEC viability were restored. The in vivo experiments also indicated that the therapeutic effect of MSCs was mediated by miR-340-5p.

CONCLUSIONS

miR-340-5p mediates the therapeutic effect of MSCs on CNV via binding and repressing the expressions of EMP2 and PROX1.

A Review on Mesenchymal Stem Cells for Treatment of Retinal Diseases

Mesenchymal Stem Cells (MSCs) have been studied extensively for the treatment of several retinal diseases. The therapeutic potential of MSCs lies in its ability to differentiate into multiple lineages and secretome enriched with immunomodulatory, anti-angiogenic and neurotrophic factors. Several studies have reported the role of MSCs in repair and regeneration of the damaged retina where the secreted factors from MSCs prevent retinal degeneration, improve retinal morphology and function. MSCs also donate mitochondria to rescue the function of retinal cells and exosomes secreted by MSCs were found to have anti-apoptotic and anti-inflammatory effects. Based on several promising results obtained from the preclinical studies, several clinical trials were initiated to explore the potential advantages of MSCs for the treatment of retinal diseases. This review summarizes the various properties of MSCs that help to repair and restore the damaged retinal cells and its potential for the treatment of retinal degenerative diseases.

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.

Programmed cell death in stem cell-based therapy: Mechanisms and clinical applications

Stem cell-based therapy raises hopes for a better approach to promoting tissue repair and functional recovery. However, transplanted stem cells show a high death percentage, creating challenges to successful transplantation and prognosis. Thus, it is necessary to investigate the mechanisms underlying stem cell death, such as apoptotic cascade activation, excessive autophagy, inflammatory response, reactive oxygen species, excitotoxicity, and ischemia/hypoxia. Targeting the molecular pathways involved may be an efficient strategy to enhance stem cell viability and maximize transplantation success. Notably, a more complex network of cell death receives more attention than one crucial pathway in determining stem cell fate, highlighting the challenges in exploring mechanisms and therapeutic targets. In this review, we focus on programmed cell death in transplanted stem cells. We also discuss some promising strategies and challenges in promoting survival for further study.

Stem cell therapy in ocular pathologies in the past 20 years

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

Protective effects of citicoline-containing eye drops against UVB-Induced corneal oxidative damage in a rat model

It has been reported that citicoline increases antioxidant activity in some tissues. However, the effect of citicoline on corneal wound-healing has not yet been demonstrated. The aim was to investigate the protective effects of citicoline on ultraviolet B (UVB) radiation-induced corneal oxidative damage in a rat model. Four groups (eight animals each) were investigated: controls; UVB only; UVB/citicoline; and citicoline only. Corneal oxidative damage was induced by exposure to UVB radiation at 560 μW/cm² for five days in the UVB-exposed groups and 1% citicoline eye drops were applied (3xday) for eight days in the two citicoline groups. Corneal surface damage was evaluated by opacity and fluorescein staining. Corneal injury was assessed biochemically by measuring the concentrations of glutathione (GSH) and malondialdehyde (MDA) and the activity of corneal superoxide dismutase (SOD) and catalase. Matrix metalloproteinase (MMP) -2 and -9 and caspase-3 were evaluated by immunofluorescent staining and microscopic examination and by Western blot analysis. Corneal gene expression analysis was performed for vascular endothelial growth factor (VEGF), interleukin-1 beta (IL-1β) and transforming growth factor-beta (TGF-β). UVB radiation caused significant epithelial damage and evident opacity in the cornea, together with a local decrease in SOD, catalase and GSH activity. Corneal MDA concentrations increased with UVB exposure. The UVB/Citicoline group had significantly less corneal damage, greater SOD, catalase and GSH activity, and decreased MDA concentrations compared to the UVB only group (p < 0.05). Expression of TGF-β, IL-1β and VEGF was significantly lower in the citicoline/UVB group compared to the UVB group (p < 0.05). Interestingly, TGF-β expression was lower in the citicoline only group compared with controls. Immunfluorescent staining and Western blot analysis showed increased MMP-2, -9 and caspase-3 in the UVB only group compared with the UVB/citicoline group. It was shown that citicoline treatment may be effective in suppressing oxidative stress and controlling inflammation in UVB corneal injury.

Paving the way towards an effective treatment for multiple sclerosis: advances in cell therapy

Multiple sclerosis (MS) is a leading cause of chronic neurological disability in young to middle-aged adults, affecting ~2.5 million people worldwide. Currently, most therapeutics for MS are systemic immunosuppressive or immunomodulatory drugs, but these drugs are unable to halt or reverse the disease and have the potential to cause serious adverse events. Hence, there is an urgent need for the development of next-generation treatments that, alone or in combination, stop the undesired autoimmune response and contribute to the restoration of homeostasis. This review analyzes current MS treatments as well as different cell-based therapies that have been proposed to restore homeostasis in MS patients (tolerogenic dendritic cells, regulatory T cells, mesenchymal stem cells, and vaccination with T cells). Data collected from preclinical studies performed in the experimental autoimmune encephalomyelitis (EAE) model of MS in animals, in vitro cultures of cells from MS patients and the initial results of phase I/II clinical trials are analyzed to better understand which parameters are relevant for obtaining an efficient cell-based therapy for MS.