Human aqueous humor exosomes

Isolation and Characterization of Exosomes from Ocular Samples

Exosomes are microsize vesicles secreted by nearly all cells to the extracellular space. The vesicles transport cell signaling and communicate with other cells. Ultracentrifugation is the standard method to isolate exosomes from culture media or body fluid. Without ultracentrifuge, exosomes can be precipitated by polyethylene glycol or separated by size exclusion chromatography. After isolation, nanoparticle tracking analysis can help to estimate the size and concentration of exosome samples. Transmission electron microscopy can directly show the size and morphology of exosomes. Moreover, the sample should be characterized by the expression of several exosome biomarker proteins. Exosomal contents such as proteins and miRNAs could be profiled using appropriate technologies.

Unraveling the nexus of oxidative stress, ocular diseases, and small extracellular vesicles to identify novel glaucoma biomarkers through in-depth proteomics

Chronic ocular pathologies such as cataracts and glaucoma are emerging as an important problem for public health due to the changes in lifestyle and longevity. These age-related ocular diseases are largely mediated by oxidative stress. Small extracellular vesicles (sEVs) are involved in cell-to-cell communication and transport. There is an increasing interest about the function of small extracellular vesicles (sEVs) in the eye. However, the proteome content and characterization of sEVs released by ocular cells under pathological conditions are not yet well known. Here, we aimed to analyze the protein profile of sEVs and the intracellular protein content from two ocular cell lines (lens epithelial cells and retinal ganglion cells) exposed to oxidative stress to identify altered proteins that could serve as potential diagnostic biomarkers. The protein content was analyzed by quantitative mass spectrometry-based proteomics. Validation was performed by WB and ELISA using cell extracts and aqueous humor from cataract and glaucoma patients. After data analysis, 176 and 7 dysregulated proteins with an expression ratio≥1.5 were identified in lens epithelial cells' protein extract and sEVs, respectively, upon oxidative stress induction. In retinal ganglion cells, oxidative stress induction resulted in the dysregulation of 1033 proteins in cell extracts and 9 proteins in sEVs. In addition, by WB and ELISA, the dysregulation of proteins was mostly confirmed in aqueous humor samples from cataract or glaucoma patients in comparison to ICL individuals, with RAD23B showing high glaucoma diagnostic ability. Importantly, this work expands the knowledge of the proteome characterization of cataracts and glaucoma and provides new potential diagnostic glaucoma biomarkers.

Advances in Exosome-Based Therapies for the Repair of Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are the term used to describe injuries that occur to the nerve fibers of the peripheral nervous system (PNS). Such injuries may be caused by trauma, infection, or aberrant immunological response. Although the peripheral nervous system has a limited capacity for self-repair, in cases of severe damage, this process is either interrupted entirely or is only partially completed. The evaluation of variables that promote the repair of peripheral nerves has consistently been a focal point. Exosomes are a subtype of extracellular vesicles that originate from cellular sources and possess abundant proteins, lipids, and nucleic acids, play a critical role in facilitating intercellular communication. Due to their modifiable composition, they possess exceptional capabilities as carriers for therapeutic compounds, including but not limited to mRNAs or microRNAs. Exosome-based therapies have gained significant attention in the treatment of several nervous system diseases due to their advantageous properties, such as low toxicity, high stability, and limited immune system activation. The objective of this review article is to provide an overview of exosome-based treatments that have been developed in recent years for a range of PNIs, including nerve trauma, diabetic neuropathy, amyotrophic lateral sclerosis (ALS), glaucoma, and Guillain-Barre syndrome (GBS). It was concluded that exosomes could provide favorable results in the improvement of peripheral PNIs by facilitating the transfer of regenerative factors. The development of bioengineered exosome therapy for PNIs should be given more attention to enhance the efficacy of exosome treatment for PNIs.

Parallel Analysis of Exosomes and Cytokines in Aqueous Humor Samples to Evaluate Biomarkers for Glaucoma

Recent emerging studies have demonstrated numerous critical roles of exosomes in cell-to-cell signaling. We investigated exosomes in the aqueous humor of glaucoma patients and controls and compared their characteristics with other biomarkers such as cytokines. Glaucoma patients exhibited higher exosome particle counts and smaller sizes compared to controls. Higher exosome density was correlated with more severe visual field loss. Conversely, concentrations of aqueous humor cytokines, particularly PD-L1, were primarily associated with intraocular pressure, and none of the cytokines showed a significant association with visual field damage. This may reflect the characteristics of exosomes, which are advantageous for crossing various biological barriers. Exosomes may contain more information about glaucoma functional damage occurring in the retina or optic nerve head. This highlights the potential importance of exosomes as signaling mediators distinct from other existing molecules.

Comparative Single Vesicle Analysis of Aqueous Humor Extracellular Vesicles before and after Radiation in Uveal Melanoma Eyes

Small extracellular vesicles (sEVs) have been shown to promote tumorigenesis, treatment resistance, and metastasis in multiple cancer types; however, sEVs in the aqueous humor (AH) of uveal melanoma (UM) patients have never previously been profiled. In this study, we used single particle analysis to characterize sEV subpopulations in the AH of UM patients by quantifying their size, concentration, and phenotypes based on cell surface markers, specifically the tetraspanin co-expression patterns of CD9, CD63, and CD81. sEVs were analyzed from paired pre- and post-treatment (brachytherapy, a form of radiation) AH samples collected from 19 UM patients. In post-brachytherapy samples, two subpopulations, CD63/81+ and CD9/63/81+ sEVs, were significantly increased. These trends existed even when stratified by tumor location and GEP class 1 and class 2 (albeit not significant for GEP class 2). In this initial report of single vesicle profiling of sEVs in the AH of UM patients, we demonstrated that sEVs can be detected in the AH. We further identified two subpopulations that were increased post-brachytherapy, which may suggest radiation-induced release of these particles, potentially from tumor cells. Further study of the cargo carried by these sEV subpopulations may uncover important biomarkers and insights into tumorigenesis for UM.

Identification of circular RNA-Dcaf6 as a therapeutic target for optic nerve crush-induced RGC degeneration

The death of retinal ganglion cells (RGCs) can cause irreversible injury in visual function. Clarifying the mechanism of RGC degeneration is critical for the development of therapeutic strategies. Circular RNAs (circRNAs) are important regulators in many biological and pathological processes. Herein, we performed circRNA microarrays to identify dysregulated circRNAs following optic nerve crush (ONC). The results showed that 221 circRNAs were differentially expressed between ONC retinas and normal retinas. Notably, the levels of circular RNA-Dcaf6 (cDcaf6) expression in aqueous humor of glaucoma patients were higher than that in cataract patients. cDcaf6 silencing could reduce oxidative stress-induced RGC apoptosis in vitro and alleviate retinal neurodegeneration in vivo as shown by increased neuronal nuclei antigen (NeuN, neuronal bodies) and beta-III-tubulin (TUBB3, neuronal filaments) staining and reduced glial fibrillary acidic protein (GFAP, activated glial cells) and vimentin (activated glial cells) staining. Collectively, this study identifies a promising target for treating retinal neurodegeneration.

Exosomes and their miRNA/protein profile in keratoconus-derived corneal stromal cells

Keratoconus (KC) is a corneal thinning disorder and a leading cause of corneal transplantation worldwide. Exosomes are small, secreted extracellular vesicles (30-150 nm) that mediate cellular communication via their protein, lipid, and nucleic acid content. We aimed to characterize the exosomes secreted by primary corneal fibroblasts from subjects with or without KC. Using human keratoconus stromal fibroblast cells (HKC, n = 4) and healthy stromal fibroblasts (HCF, n = 4), we collected and isolated exosomes using serial ultracentrifugation. Using nanoparticle tracking analysis (NTA) with ZetaView®, we compared the size and concentration of isolated exosomes. Different exosomal markers were identified and quantified using a transmission electron microscope (TEM) (CD81) and Western blot (CD9 and CD63). Exosomal miRNA profiles were determined by qRT-PCR using Exiqon Human panel I miRNA assays of 368 pre-selected miRNAs. Proteomic profiles were determined using a label-free spectral counting method with mass spectrometry. Differential expression analysis for miRNAs and proteins was done using student's t-test with a significance cutoff of p-value ≤0.05. We successfully characterized exosomes isolated from HCFs using several complementary techniques. We found no significant differences in the size, quantity, or morphology between exosomes secreted by HCFs with or without KC. Expression of CD81 was confirmed by immuno-EM, and expression of CD63 and CD9 with western blots in all exosome samples. We detected the expression of 72-144 miRNAs (threshold cycle Ct < 36) in all exosome samples. In HKC-derived exosome samples, miR-328-3p, miR-532-5p, miR-345-5p, and miR-424-5p showed unique expression, while let-7c-5p and miR-665 have increased expression. Protein profiling identified 157 proteins in at least half of the exosome samples, with 38 known exosomal proteins. We identified 12 up- and 2 down-regulated proteins in HKC-derived exosomes. The proteins are involved in membrane-bounded vesicles, cytoskeletal, calcium binding, and nucleotide binding. These proteins are predicted to be regulated by NRF2, miR-205, and TGF-β1, which are involved in KC pathogenesis. We successfully characterized the HKC-derived exosomes and profiled their miRNA and protein contents, suggesting their potential role in KC development. Further studies are necessary to determine if and how these exosomes with differential protein/miRNA profiles contribute to the pathogenesis of KC.

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.

Comparison of the extracellular vesicle proteome between glaucoma and non-glaucoma trabecular meshwork cells

Introduction

Extracellular matrix (ECM) materials accumulate in the trabecular meshwork (TM) tissue of patients with glaucoma, which is associated with a decrease in aqueous humor outflow and therefore an increase in intraocular pressure. To explore a potential mechanism for ECM regulation in the TM, we purified extracellular vesicles (EVs) from conditioned media of differentiated TM cells in culture isolated from non-glaucomatous and glaucomatous human donor eyes.

Methods

EVs were purified using the double cushion ultracentrifugation gradient method. Fractions containing EV markers CD9 and TSG101 were analyzed using nanoparticle tracking analysis to determine their size and concentration. We then determined their proteomic cargo by mass spectrometry and compared protein profiles of EVs between normal and glaucomatous TM cells using PANTHER. Key protein components from EV preparations were validated with Western blotting.

Results

Results showed changes in the percentage of ECM proteins associated with EVs from glaucomatous TM cells compared to non-glaucomatous TM cells (5.7% vs 13.1% respectively). Correspondingly, we found that two ECM-related cargo proteins found across all samples, fibronectin and EDIL3 were significantly less abundant in glaucomatous EVs (<0.3 fold change across all groups) compared to non-glaucomatous EVs.

Discussion

Overall, these data establish that ECM materials are prominent proteomic cargo in EVs from TM cells, and their binding to EVs is diminished in glaucoma.

Selective drug delivery to the retinal cells: Biological barriers and avenues

Retinal drug delivery is a challenging, but important task, because most retinal diseases are still without any proper therapy. Drug delivery to the retina is hampered by the anatomical and physiological barriers resulting in minimal bioavailability after topical ocular and systemic administrations. Intravitreal injections are current method-of-choice in retinal delivery, but these injections show short duration of action for small molecules and low target bioavailability for many protein, gene based drugs and nanomedicines. State-of-art delivery systems are based on prolonged retention, controlled drug release and physical features (e.g. size and charge). However, drug delivery to the retina is not cell-specific and these approaches do not facilitate intracellular delivery of modern biological drugs (e.g. intracellular proteins, RNA based medicines, gene editing). In this focused review we highlight biological factors and mechanisms that form the basis for the selective retinal drug delivery systems in the future. Therefore, we are presenting current knowledge related to retinal membrane transporters, receptors and targeting ligands in relation to nanomedicines, conjugates, extracellular vesicles, and melanin binding. These issues are discussed in the light of retinal structure and cell types as well as future prospects in the field. Unlike in some other fields of targeted drug delivery (e.g. cancer research), selective delivery technologies have been rarely studied, even though cell targeted delivery may be even more feasible after local administration into the eye.

Glaucomatous aqueous humor vesicles are smaller and differ in composition compared to controls

Cells communicate with each other using vesicles of varying sizes, including a specific repertoire known as exosomes. We isolated aqueous humor (AH)-derived vesicles using two different methods: ultracentrifugation and an exosome isolation kit. We confirmed a unique vesicle size distribution in the AH derived from control and primary open-angle glaucoma (POAG) patients using various techniques, including Nanotracker, dynamic light scattering, atomic force imaging, and electron microscopy. Bonafide vesicle and/or exosome markers were present by dot blot in both control and POAG AH-derived vesicles. Marker levels differed between POAG and control samples, while non-vesicle negative markers were absent in both. Quantitative labeled (iTRAQ) proteomics showed a reduced presence of a specific protein, STT3B, in POAG compared to controls, which was further confirmed using dot blot, Western blot, and ELISA assays. Along the lines of previous findings with AH profiles, we found vast differences in the total phospholipid composition of AH vesicles in POAG compared to controls. Electron microscopy further showed that the addition of mixed phospholipids alters the average size of vesicles in POAG. We found that the cumulative particle size of type I collagen decreased in the presence of Cathepsin D, which normal AH vesicles were able to protect against, but POAG AH vesicles did not. AH alone had no effect on collagen particles. We observed a protective effect on collagen particles with an increase in artificial vesicle sizes, consistent with the protective effects observed with larger control AH vesicles but not with the smaller-sized POAG AH vesicles. Our experiments suggest that AH vesicles in the control group provide greater protection for collagen beams compared to POAG, and their increased vesicle sizes are likely contributing factors to this protection.

Exosomal miR-184 in the aqueous humor of patients with central serous chorioretinopathy: a potential diagnostic and prognostic biomarker

BACKGROUND

Central serous chorioretinopathy (CSC) is the fourth most prevalent retinal disease leading to age-related macular degeneration (AMD) and retinal atrophy. However, CSC's pathogenesis and therapeutic target need to be better understood.

RESULTS

We investigated exosomal microRNA in the aqueous humor of CSC patients using next-generation sequencing (NGS) to identify potential biomarkers associated with CSC pathogenesis. Bioinformatic evaluations and NGS were performed on exosomal miRNAs obtained from AH samples of 62 eyes (42 CSC and 20 controls). For subgroup analysis, patients were divided into treatment responders (CSC-R, 17 eyes) and non-responders (CSC-NR, 25 eyes). To validate the functions of miRNA in CECs, primary cultured-human choroidal endothelial cells (hCEC) of the donor eyes were utilized for in vitro assays. NGS detected 376 miRNAs. Our results showed that patients with CSC had 12 significantly upregulated and 17 downregulated miRNAs compared to controls. miR-184 was significantly upregulated in CSC-R and CSC-NR patients compared to controls and higher in CSC-NR than CSC-R. In vitro assays using primary cultured-human choroidal endothelial cells (hCEC) demonstrated that miR-184 suppressed the proliferation and migration of hCECs. STC2 was identified as a strong candidate for the posttranscriptional down-regulated target gene of miR-184.

CONCLUSION

Our findings suggest that exosomal miR-184 may serve as a biomarker reflecting the angiostatic capacity of CEC in patients with CSC.

Exosome-based crosstalk in glaucoma pathogenesis: a focus on oxidative stress and neuroinflammation

Exosomes are membrane-bound tiny particles that are released by all live cells that contain multiple signal molecules and extensively participate in numerous normal physical activities and pathologies. In glaucoma, the crucial role of exosome-based crosstalk has been primarily revealed in animal models and ex vivo cell studies in the recent decade. In the aqueous drainage system, exosomes derived from non-pigment ciliary epithelium act in an endocrine manner and specifically regulate the function of the trabecular meshwork to cope with persistent oxidative stress challenges. In the retina, a more complicated regulatory network among microglia, retinal neurons, retinal ganglial cells, retinal pigment epithelium, and other immune effector cells by exosomes are responsible for the elaborate modulation of tissue homeostasis under physical state and the widespread propagation of neuroinflammation and its consequent neurodegeneration in glaucoma pathogenesis. Accumulating evidence indicates that exosome-based crosstalk depends on numerous factors, including the specific cargos they carried (particularly micro RNA), concentration, size, and ionization potentials, which largely remain elusive. In this narrative review, we summarize the latest research focus of exosome-based crosstalk in glaucoma pathogenesis, the current research progress of exosome-based therapy for glaucoma and provide in-depth perspectives on its current research gap.

CD63/81 Small Extracellular Vesicles in the Aqueous Humor are Retinoblastoma Associated

Purpose

Although biopsy is contraindicated in retinoblastoma (RB), the aqueous humor (AH) is a robust liquid biopsy source of molecular tumor information, facilitating biomarker discovery. Small extracellular vesicles (sEVs), promising biomarker candidates across multiple cancers, were recently identified in RB AH, but relationships between sEVs and RB clinical features are unknown.

Methods

We analyzed sEVs in 37 AH samples from 18 RB eyes of varying International Intraocular Retinoblastoma Classification (IIRC) groups and explored clinical correlations. Ten samples were collected at diagnosis (DX) and 27 during treatment (Tx). Unprocessed AH underwent Single Particle-Interferometric Reflectance Imaging Sensor (SP-IRIS) analysis for fluorescent particle count and tetraspanin immunophenotyping; counts were subsequentially converted to percentages for analysis.

Results

Comparing DX and Tx samples, a higher percentage of CD63/81+ sEVs was found in DX AH (16.3 ± 11.6% vs. 5.49 ± 3.67% P = 0.0009), with a more homogenous mono-CD63+ sEV population seen in Tx AH (43.5 ± 14.7% vs. 28.8 ± 9.38%, P = 0.0073). Among DX samples, CD63/81+ sEVs were most abundant in group E eyes (n = 2) compared to group D (n = 6) by count (2.75 × 105 ± 3.40 × 105 vs. 5.95 × 103 ± 8.16 × 103, P = 0.0006), and to group A + B (n = 2) by count (2.75 × 105 ± 3.40 × 105 vs. 2.73 × 102 ± 2.59 × 102, P = 0.0096) and percentage (32.1 ± 7.98% vs. 7.79 ± 0.02%, P = 0.0187).

Conclusions

CD63/81+ sEVs enrich AH from RB eyes before treatment and those with more significant tumor burden, suggesting they are tumor-derived. Future research into their cargo may reveal mechanisms of cellular communication via sEVs in RB and novel biomarkers.

Recent advances of exosomes in age-related macular degeneration

Exosomes are 30-150 nm extracellular vesicles that are secreted by almost all types of cells. Exosomes contain a variety of biologically active substances, such as proteins, nucleic acids, and lipids, and are important in the intercellular communication of biological mediators involved in nerve injury and repair, vascular regeneration, immune response, fibrosis formation, and many other pathophysiological processes. Although it has been extensively studied in the field of cancer, the exploration of ocular diseases has only just begun. Here, we discuss the latest developments in exosomes for age-related macular degeneration (AMD), including the pathogenesis of exosomes in age-related macular degeneration, their potential as diagnostic markers, and therapeutic vectors of the disease. Finally, the study of exosomes in age-related macular degeneration is still relatively few, and more detailed basic research and clinical trials are needed to verify its application in treatment and diagnosis, so as to adopt more personalized diagnosis and treatment strategies to stop the progression of age-related macular degeneration.

Knockout of miR-184 in zebrafish leads to ocular abnormalities by elevating p21 levels

miR-184 is one of the most abundant miRNAs expressed in the lens and corneal tissue. Mutations in the seed region of miR-184 are responsible for inherited anterior segment dysgenesis. Animal models recapitulating miR-184-related anterior segment dysgenesis are still lacking, and the molecular basis of ocular abnormalities caused by miR-184 dysfunction has not been well elucidated in vivo. In the present study, we constructed a miR-184-/- zebrafish line by destroying both two dre-mir-184 paralogs with CRISPR-Cas9 technology. Although there were no gross developmental defects, the miR-184-/- zebrafish displayed microphthalmia and cataract phenotypes. Cytoskeletal abnormalities, aggregation of γ-crystallin, and lens fibrosis were induced in miR-184-/- lenses. However, no obvious corneal abnormalities were observed in miR-184-/- zebrafish. Instead of apoptosis, deficiency of miR-184 led to aberrant cell proliferation and a robust increase in p21 levels in zebrafish eyes. Inhibition of p21 by UC2288 compromised the elevation of lens fibrosis markers in miR-184-/- lenses. RNA-seq demonstrated that levels of four transcriptional factors HSF4, Sox9a, CTCF, and Smad6a, all of which could suppress p21 expression, were reduced in miR-184-/- eyes. The predicted zebrafish miR-184 direct target genes (e.g., atp1a3a and nck2a) were identified and verified in miR-184-/- eye tissues. The miR-184-/- zebrafish is the first animal model mimicking miR-184-related anterior segment dysgenesis and could broaden our understanding of the roles of miR-184 in eye development.

Extracellular vesicles: an emerging player in retinal homeostasis

Extracellular vesicles (EVs) encompass secreted membrane vesicles of varied sizes, including exosomes (-30-200 nm) and microvesicles (MVs) that are ∼100-1,000 nm in size. EVs play an important role in autocrine, paracrine, and endocrine signaling and are implicated in myriad human disorders including prominent retinal degenerative diseases, like age related macular degeneration (AMD) and diabetic retinopathy (DR). Studies of EVs in vitro using transformed cell lines, primary cultures, and more recently, induced pluripotent stem cell derived retinal cell type(s) (e.g., retinal pigment epithelium) have provided insights into the composition and function of EVs in the retina. Furthermore, consistent with a causal role of EVs in retinal degenerative diseases, altering EV composition has promoted pro-retinopathy cellular and molecular events in both in vitro and in vivo models. In this review, we summarize the current understanding of the role of EVs in retinal (patho)physiology. Specifically, we will focus on disease-associated EV alterations in specific retinal diseases. Furthermore, we discuss the potential utility of EVs in diagnostic and therapeutic strategies for targeting retinal diseases.

Vascular endothelial cell-derived exosomal miR-1246 facilitates posterior capsule opacification development by targeting GSK-3β in diabetes mellitus

Posterior capsule opacification (PCO) is a serious complication after cataract surgery. Diabetes could increase the occurrence of PCO, but the mechanism is still unclear. The purpose of this study is to investigate the role of small extracellular vesicles (sEVs) derived from diabetic aqueous humor in PCO process. Intraoperatively-derived aqueous humor sEVs from patients with diabetic related cataract (DRC) promoted the epithelial-mesenchymal transition (EMT) and metastasis of human lens epithelial cells (LECs). Via mouse PCO surgical model and DiI labeled fluorescence detection of sEVs, the sEVs derived from vascular endothelium were discovered directly contacting with LECs. Furthermore, we demonstrated that high-glucose-cultured human umbilical vein endothelial cells (HUVEC) -derived sEVs facilitated EMT process of HLE-B3 using co-culture model in vitro. MiRNA-seq data and GEO datasets analysis revealed that miR-1246 was essential in EMT process with diabetes. The miR-1246 was highly expressed in diabetic aqueous humor sEVs and high-glucose-treated vascular-endothelial-cell-derived sEVs. Moreover, miR-1246 promoted the metastasis and EMT process of HLE-B3 cells by directly targeting GSK-3β. Inhibiting miR-1246 could negatively regulated EMT. This finding might serve as a potential therapy for diabetic PCO.

Salivary Exosomes in Health and Disease: Future Prospects in the Eye

Exosomes are a group of vesicles that package and transport DNA, RNA, proteins, and lipids to recipient cells. They can be derived from blood, saliva, urine, and/or other biological tissues. Their impact on several diseases, such as neurodegenerative, autoimmune, and ocular diseases, have been reported, but not fully unraveled. The exosomes that are derived from saliva are less studied, but offer significant advantages over exosomes from other sources, due to their accessibility and ease of collection. Thus, their role in the pathophysiology of diseases is largely unknown. In the context of ocular diseases, salivary exosomes have been under-utilized, thus creating an enormous gap in the literature. The current review discusses the state of exosomes research on systemic and ocular diseases and highlights the role and potential of salivary exosomes as future ocular therapeutic vehicles.

Proteomic characterization of aqueous humor in corneal endothelial decompensation after penetrating keratoplasty

Corneal endothelial decompensation (CED) is the major cause of the long-term graft failure, but the underlying mechanisms remain unclear. The purpose of this study was to characterize the proteomic profile in CED aqueous humor (AH) after penetrating keratoplasty (PKP). We collected AH samples (n = 6/group) from CED patients underwent PKP and cataract patients, respectively. The label-free quantitative proteomic analysis was performed to identify the differentially-expressed proteins (DEPs). The biological functions of DEPs were evaluated using Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genome (KEGG) analysis. The protein-protein interaction (PPI) network construction was employed to distinguish the hub proteins of DEPs, and the selected proteins were validated by parallel reaction monitoring (PRM). The human peripheral blood mononuclear cells (PBMCs) were adopted to investigate the effect of biglycan (BGN) on inflammatory response, and the subsequent outcomes of inflammation on human corneal endothelial cells (HCECs). A total of 174 DEPs were identified in CED AH of patients underwent PKP, including 102 up-regulated proteins and 72 down-regulated proteins. Bioinformatics analysis revealed the significant enrichment of cytokine-mediated signaling pathway and extracellular matrix (ECM) organization in the up-regulated proteins, as well as the alterations of cellular components, including the increase of collagen and complement component C1 complex, and reduction in extracellular exosomes. A hub protein cluster of 15 proteins was determined by Molecular Complex Detection (MCODE), including FN1, BGN, COMP, COL11A1, COLA3A1, and COL1A1. Moreover, BGN promoted pro-inflammatory cytokine (such as TNF-α, IL-1β and IL-6) production in PBMCs through NF-κB signaling pathway, which subsequently resulted in HCECs death. These findings provided a systemic protein profile of AH in CED patients after corneal transplantation, with the alterations implicated in cytokine-mediated signaling, ECM, complement system, and exsomes. The identified proteins and signaling pathways probably paved the novel insight into understanding the pathogenesis of the disease.

Extracellular Vesicles as reconfigurable therapeutics for eye diseases: Promises and hurdles

A large number of people worldwide suffer from visual impairment. However, most available therapies rely on impeding the development of a particular eye disorder. Therefore, there is an increasing demand for effective alternative treatments, specifically regenerative therapies. Extracellular vesicles, including exosomes, ectosomes, or microvesicles, are released by cells and play a potential role in regeneration. Following an introduction to EV biogenesis and isolation methods, this integrative review provides an overview of our current knowledge about EVs as a communication paradigm in the eye. Then, we focused on the therapeutic applications of EVs derived from conditioned medium, biological fluid, or tissue and highlighted some recent developments in strategies to boost the innate therapeutic potential of EVs by loading various kinds of drugs or being engineered at the level of producing cells or EVs. Challenges faced in the development of safe and effective translation of EV-based therapy into clinical settings for eye diseases are also discussed to pave the road toward reaching feasible regenerative therapies required for eye-related complications.

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.

Phenotypic and functional characterization of aqueous humor derived extracellular vesicles

Extracellular vesicles (EVs) are double membrane vesicles, abundant in all biological fluids. However, the characterization of EVs in aqueous humor (AH) is still limited. The aim of the present work was to characterize EVs isolated from AH (AH-EVs) in terms of surface markers of cellular origin and functional properties. We obtained AHs from patients with cataract undergoing surgical phacoemulsification and insertion of intraocular lenses (n = 10). Nanoparticle tracking analysis, electron microscopy, super resolution microscopy and bead-based cytofluorimetry were used to characterize EVs from AH. Subsequently, we investigated the effects of AH-EVs on viability, proliferation and wound healing of human immortalized keratinocyte (HaCaT) cells in vitro in comparison with the effect of mesenchymal stromal cell-EVs (MSC-EVs). AH-EVs had a mean size of around 100 nm and expressed the classical tetraspanins (CD9, CD63 and CD81). Super resolution microscopy revealed co-expression of CD9, CD63 and CD81. Moreover, cytofluorimetric analysis highlighted the expression of mesenchymal, stem, epithelial and endothelial markers. In the in vitro wound healing assay on HaCaT cells, AH-EVs induced a significantly faster wound repair, comparable to the effects of MSC-EVs, and promoted HaCaT cell viability and proliferation. We provide evidence, herein, of the possible AH-EV origin from stromal cells, limbal epithelial/stem cells, ciliary epithelium and corneal endothelium. In addition, we showed their in vitro proliferative and regenerative capacities.

Profiling the miRNA from Exosomes of Non-Pigmented Ciliary Epithelium-Derived Identifies Key Gene Targets Relevant to Primary Open-Angle Glaucoma

Oxidative stress (OS) on tissues is a major pathological insult leading to elevated intraocular pressure (IOP) and primary open-angle glaucoma (POAG). Aqueous humor (AH) produced by the non-pigmentary ciliary epithelium (NPCE) drains out via the trabecular meshwork (TM) outflow pathway in the anterior chamber. The exosomes are major constituents of AH, and exosomes can modulate the signaling events, as well as the responses of their target TM tissue. Despite the presence of molecular mechanisms to negate OS, oxidative damage directly, as well as indirectly, influences TM health, AH drainage, and IOP. We proposed that the expression of microRNA (miRNAs) carried by exosomes in the AH can be affected by OS, and this can modulate the pathways in target cells. To assess this, we subjected NPCE to acute and chronic OS (A-OS and C-OS), enriched miRNAs, performed miRNA microarray chip analyses, and miRNA-based gene targeting pathway prediction analysis. We found that various miRNA families, including miR27, miR199, miR23, miR130b, and miR200, changed significantly. Based on pathway prediction analysis, we found that these miRNAs can regulate the genes including Nrf2, Keap1, GSK3B, and serine/threonine-protein phosphatase2A (PP2A). We propose that OS on the NPCE exosomal miRNA cargo can modulate the functionality of the TM tissue.

Where Microneedle Meets Biomarkers: Futuristic Application for Diagnosing and Monitoring Localized External Organ Diseases

Extracellular tissue fluids are interesting biomatrices that have recently attracted scientists' interest. Many significant biomarkers for localized external organ diseases have been isolated from this biofluid. In the diagnostic and disease monitoring context, measuring biochemical entities from the fluids surrounding the diseased tissues may give more important clinical value than measuring them at a systemic level. Despite all these facts, pushing tissue fluid-based diagnosis and monitoring forward to clinical settings faces one major problem: its accessibility. Most extracellular tissue fluid, such as interstitial fluid (ISF), is abundant but hard to collect, and the currently available technologies are invasive and expensive. This is where novel microneedle technology can help tackle this significant obstacle. The ability of microneedle technology to minimally invasively access tissue fluid-containing biomarkers will enable ISF and other tissue fluid utilization in the clinical diagnosis and monitoring of localized diseases. This review attempts to present the current pursuit of the application of microneedle systems as a diagnostic and monitoring platform, along with the recent progress of biomarker detection in diagnosing and monitoring localized external organ diseases. Then, the potential use of various microneedles in future clinical diagnostics and monitoring of localized diseases is discussed by presenting the currently studied cases.

Research progress of exosomes in pathogenesis, diagnosis, and treatment of ocular diseases

Exosomes are natural extracellular vesicles with a diameter of 30-150 nm, which exist in biological fluids and contain biomolecules related to the parent cell, such as proteins, nucleic acids, lipids, etc. It has a wide range of biological functions, and participates in the regulation of important physiological and pathological activities of the body. It can be used as a biomarker for early diagnosis of ocular diseases, a potential therapeutic target, a targeted drug carrier, and has a high potential for clinical application. In this paper, we summarized the genesis mechanism, biological functions, research and application progress of exosomes, focused on the engineering strategy of exosomes, and summarized the advantages and disadvantages of common engineering exosome preparation methods. Systematically combed the role of exosomes in corneal diseases, glaucoma, and retinal diseases, to provide a reference for further understanding of the role of exosomes in the pathogenesis, diagnosis, and treatment of ocular diseases. Finally, we further summarized the opportunities and challenges of exosomes for precision medicine. The extension of exosome research to the field of ophthalmology will help advance current diagnostic and therapeutic methods. Tiny exosomes have huge potential.

Investigation of the Protective Effect of Extracellular Vesicle miR-124 on Retinal Ganglion Cells Using a Photolabile Paper-Based Chip

Purpose

Photolabile paper-based chips were developed to isolate extracellular vesicles (EVs) from small-volume samples (less than 30 µL), such as vitreous humor. Putative neuroprotective effects of EVs' microRNAs were investigated by using the paper chip and a rodent model with nonarteritic anterior ischemic optic neuropathy (rNAION).

Methods

rNAION was established using laser-induced photoactivation of rose bengal administered intravenously. On days 0, 0.25, 1, 3, and 7 after rNAION induction, CD63-positive EV microRNAs (CD63+-EV miRNAs) in vitreous humor samples were enriched using the paper chip and assessed using microarray and quantitative RT-PCR analyses. The viability and visual function of retinal ganglion cells (RGCs) were further assessed by measuring photopic flash visual evoked potentials (FVEPs).

Results

We identified 38 different variations of CD63+-EV miRNAs with more than twofold altered expressions. Among them, M1-related miRNA, mR-31a-5p, and M2-related miRNA, miR-125a-5p, miR-182, miR-181a-5p, and miR-124-3, were capable of coordinating anti-inflammatory reactions during rNAION because of their capacity to activate macrophages. In particular, miR-124, having the most dramatic alteration of gene expression, was synthesized and injected intravitreally. Compared to controls, rats that received miR-124 had shown increased RGC survivability and improved visual function.

Conclusions

Our research team has developed a paper-based chip capable of capturing EVs that can be released after UV exposure. The quantity and quality of EV-miRNAs extracted are adequate for microarray and quantitative RT-PCR analyses. Animal studies suggest that miR-124 may play a neuroprotective role in the natural recovery of rNAION and holds the potential to be a novel treatment option.

Extracellular vesicles in the retina - putative roles in physiology and disease

The retina encompasses a network of neurons, glia and epithelial and vascular endothelia cells, all coordinating visual function. Traditionally, molecular information exchange in this tissue was thought to be orchestrated by synapses and gap junctions. Recent findings have revealed that many cell types are able to package and share molecular information via extracellular vesicles (EVs) and the technological advancements in visualisation and tracking of these delicate nanostructures has shown that the role of EVs in cell communication is pleiotropic. EVs are released under physiological conditions by many cells but they are also released during various disease stages, potentially reflecting the health status of the cells in their cargo. Little is known about the physiological role of EV release in the retina. However, administration of exogenous EVs in vivo after injury suggest a neurotrophic role, whilst photoreceptor transplantation in early stages of retina degeneration, EVs may facilitate interactions between photoreceptors and Müller glia cells. In this review, we consider some of the proposed roles for EVs in retinal physiology and discuss current evidence regarding their potential impact on ocular therapies via gene or cell replacement strategies and direct intraocular administration in the diseased eye.

Extracellular vesicles of human diabetic retinopathy retinal tissue and urine of diabetic retinopathy patients are enriched for the junction plakoglo bin protein

Introduction

Diabetic Retinopathy (DR) is a potentially blinding retinal disorder that develops through the pathogenesis of diabetes. The lack of disease predictors implies a poor prognosis with frequent irreversible retinal damage and vision loss. Extracellular Vesicles (EVs) present a novel opportunity for pre-symptomatic disease diagnosis and prognosis, both severely limited in DR. All biological fluids contain EVs, which are currently being studied as disease biomarkers. EV proteins derived from urine have emerged as potential noninvasive biomarkers.

Methods

In this study, we isolated EVs from DR retinal tissue explants and from DR patients' urine, and characterized the vesicles, finding differences in particle number and size. Next, we performed proteomic analysis on human explanted DR retinal tissue conditioned media, DR retinal EVs and DR urinary EVs and compared to normal human retinal tissue, retinal EVs, and urinary EVs, respectively.

Results

Our system biology analysis of DR tissue and EV expression profiles revealed biological pathways related to cell-to-cell junctions, vesicle biology, and degranulation processes. Junction Plakoglobin (JUP), detected in DR tissue-derived EVs and DR urinary EVs, but not in controls, was revealed to be a central node in many identified pathogenic pathways. Proteomic results were validated by western blot. Urinary EVs obtained from healthy donors and diabetic patient without DR did not contain JUP.

Conclusion

The absence of JUP in healthy urinary EVs provide the basis for development of a novel Diabetic Retinopathy biomarker, potentially facilitating diagnosis.

Extracellular Vesicles as Biomarkers and Therapeutics for Inflammatory Eye Diseases

Extracellular vesicles (EVs) are a group of cell-derived membrane vesicles of varying sizes that can be secreted by most cells. Depending on the type of cell they are derived from, EVs may contain a variety of cargo including proteins, lipids, miRNA, and DNA. Functionally, EVs play important roles in physiological and pathological processes through intercellular communication. While there has already been significant literature on the involvement of EVs in neurological and cardiovascular disease as well as cancer, recent evidence suggests that EVs may also play a role in mediating inflammatory eye diseases. This paper summarizes current advancements in ocular EV research as well as new ways by which EVs may be utilized as novel biomarkers of or therapeutics for inflammatory eye diseases.

α-Synuclein modulates fibronectin expression in the trabecular meshwork independent of TGFβ2

α-Synuclein (α-Syn) is implicated in Parkinson's disease (PD), a neuromotor disorder with prominent visual symptoms. The underlying cause of motor dysfunction has been studied extensively, and is attributed to the death of dopaminergic neurons mediated in part by intracellular aggregation of α-Syn. The cause of visual symptoms, however, is less clear. Neuroretinal degeneration due to the presence of aggregated α-Syn has been reported, but the evidence is controversial. Other symptoms including those arising from primary open angle glaucoma (POAG) are believed to be the side-effects of medications prescribed for PD. Here, we explored the alternative hypothesis that dysfunction of α-Syn in the anterior eye alters the interaction between the actin cytoskeleton of trabecular meshwork (TM) cells with the extracellular matrix (ECM), impairing their ability to respond to physiological changes in intraocular pressure (IOP). A similar dysfunction in neurons is responsible for impaired neuritogenesis, a characteristic feature of PD. Using cadaveric human and bovine TM tissue and primary human TM cells as models, we report two main observations: 1) α-Syn is expressed in human and bovine TM cells, and significant amounts of monomeric and oligomeric α-Syn are present in the AH, and 2) primary human TM cells and human and bovine TM tissue endocytose extracellular recombinant monomeric and oligomeric α-Syn via the prion protein (PrP^C), and upregulate fibronectin (FN) and α-smooth muscle actin (α-SMA), fibrogenic proteins implicated in POAG. Transforming growth factor β2 (TGFβ2), a fibrogenic cytokine implicated in ∼50% cases of POAG, is also increased, and so is RhoA-associated coiled-coil-containing protein kinase 1 (ROCK-1). However, silencing of α-Syn in primary human TM cells reduces FN, α-SMA, and ROCK-1 in the absence or presence of over-expressed active TGFβ2, suggesting modulation of FN and ROCK-1 independent of, or upstream of TGFβ2. These observations suggest that extracellular α-Syn modulates ECM proteins in the TM independently or via PrP^C by activating the RhoA-ROCK pathway. These observations reveal a novel function of α-Syn in the anterior eye, and offer new therapeutic options.

On the other end of the line: Extracellular vesicle-mediated communication in glaucoma

In the last decade, extracellular vesicles (EVs) have emerged as a promising field of research due to their ability to participate in cell-to-cell communication via the transfer of their very diverse and complex cargo. The latter reflects the nature and physiological state of the cell of origin and, as such, EVs may not only play a pivotal role in the cellular events that culminate into disease, but also hold great potential as drug delivery vehicles and biomarkers. Yet, their role in glaucoma, the leading cause of irreversible blindness worldwide, has not been fully studied. Here, we provide an overview of the different EV subtypes along with their biogenesis and content. We elaborate on how EVs released by different cell types can exert a specific function in the context of glaucoma. Finally, we discuss how these EVs provide opportunities to be used as biomarkers for diagnosis and monitoring of disease.

Role of extracellular vesicles in mitochondrial eye diseases

Extracellular vesicles (EVs) are small packages that are released by almost all types of cells. While the role of EVs in pathogenesis of certain diseases such as cancer is well established, EVs role in ocular health and disease is still at early stages of investigation. Given the significant role of EVs in pathological development and progression of diseases such as cancer, EVs present a similar opportunity for investigation in ocular pathophysiology. Studies have shown the presence of EVs in fluids from the ocular environment have close links with ocular health and disease. Hence, the cargo carried in EVs from ocular fluids can be used for monitoring disease phenotypes or therapeutic outcomes in eye-related disorders. Furthermore, in recent times EVs have increasingly gained attention as therapeutics and drug-delivery vehicles for treatment of eye diseases. There is a close relationship between EVs and mitochondria functioning with mitochondria dysfunction leading to a significant number of ophthalmic disorders. This review discusses the current knowledge of EVs in visual systems with a special focus on eye diseases resulting from dysfunctional mitochondria.

Cellular Interplay Through Extracellular Vesicle miR-184 Alleviates Corneal Endothelium Degeneration

OBJECTIVE

The objective of the study was to reveal the presence of cellular interplay through extracellular vesicle (EV) microRNAs (miRs), to dampen the vicious cycle to degenerate human corneal endothelium (HCE) tissues.

DESIGN

Prospective, comparative, observational study.

METHODS

The miR levels in neonate-derived corneal tissues, in the aqueous humor (AqH) of bullous keratoplasty and cataract patients, as well as in the culture supernatant (CS) and EV of cultured human corneal endothelial cells (hCECs), were determined using 3D-Gene human miR chips and then validated using the real-time polymerase chain reaction. The extracellularly released miRs were profiled after the forced downregulation of cellular miR-34a, either by an miR-34a inhibitor or exposure to H₂O₂. The senescence-associated secretory phenotypes and mitochondrial membrane potential (MMP) were assessed to determine the functional features of the released miRs.

MAIN OUTCOME MEASURES

Identification of functional miRs attenuating HCE degeneration.

RESULTS

The miRs in AqH were classified into 2 groups: expression in 1 group was significantly reduced in neonate-derived tissues, whereas that in the other group remained almost constant, independent of aging. The miR-34a and -29 families were typical in the former group, whereas miR-184 and -24-3p were typical in the latter. Additionally, a larger amount of the latter miRs was detected in AqH compared with those of the former miRs. There was also a greater abundance of miR-184 and -24-3p in hCECs, EV, and CS in fully mature CD44^-/dull hCEC, leading to sufficient clinical tissue regenerative capacity in cell injection therapy. The repression of cellular miR-34a, either due to miR-34a inhibitors or exposure to oxidative stress, unexpectedly resulted in the elevated release of miR-184 and -24-3p. Secretions of VEGF, interleukin 6, monocyte chemotactic protein-1, and MMP were all repressed in both mature CD44^-/dull and degenerated CD44⁺⁺⁺ hCEC, transfected with an miR-184 mimic.

CONCLUSIONS

The elevated release of miR-184 into AqH may constitute cellular interplay that prevents the aggravation of HCE degeneration induced by oxidative stress, thereby sustaining tissue homeostasis in HCE.

Small Nucleolar RNAs in Pseudoexfoliation Glaucoma

Small nucleolar RNAs (snoRNAs) are small non-coding regulatory RNAs that have been investigated extensively in recent years. However, the relationship between snoRNA and glaucoma is still unknown. This study aims to analyze the levels of snoRNA expression in the aqueous humor (AH) of patients with pseudoexfoliation glaucoma (PEXG) compared to a control group and identify hypothetical snoRNA-dependent mechanisms contributing to PEXG. The AH was obtained from eighteen Caucasian patients, comprising nine PEXG and nine age-matched control patients. RNA was isolated, and a microarray system was used to determine the snoRNA expression profiles. Functional and enrichment analyses were performed. We identified seven snoRNAs, SNORD73B, SNORD58A, SNORD56, SNORA77, SNORA72, SNORA64, and SNORA32, in the AH of the PEXG and control group patients. Five snoRNAs showed statistically significantly lower expression in the PEXG group, and two snoRNAs had statistically significantly higher expression in the PEXG group compared to the control group. In addition, we identified two factors-CACNB3 for SNORA64 and TMEM63C for SNORA32, similar to PEX-related genes (CACNA1A and TMEM136). The enrichment analysis for four genes targeted by snoRNAs revealed possible mechanisms associated with glaucoma and/or PEX, but the direct role of snoRNAs in these biological processes was not proven.

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.

Quantitative analysis of exosomes in the aqueous humor of Korean patients with pseudoexfoliation glaucoma

We aimed to quantitatively analyze the exosome and its cargo in individual aqueous humor (AH) samples from pseudoexfoliation (PEX) glaucoma patients compared to controls using a novel detection platform. We investigated the size distribution and measured the quantitative exosome particle counts in each AH sample. AH (80–120 µL) was obtained during cataract surgery or glaucoma filtering surgery from 12 Korean subjects (six with PEX glaucoma and six age-matched controls). The mean size of the exosomes was 58.9 ± 18.5 nm measured by a tangential flow filtration system using single-particle interferometric reflectance imaging sensor. Exosome particle count in each CD 63, CD 81, and CD9 spot was significantly greater in PEX glaucoma than in controls in total, CD 63, CD9, syntenin, and scattering(all p < 0.003). The CD63 spot showed a particle count of 8319.1 ± 797.7 in PEX glaucoma patients and 4786.8 ± 1302.1 in controls (p = 1.88E−11). Individual fluorescent capture spot images also revealed denser exosome particles in PEX patients than in controls. Syntenin, indicating exosomal origin, was detected in all AH samples. Exosomes differentially detected in AH suggest the possible role of exosomes in the pathogenesis of PEX glaucoma.

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.

Advances in exosome therapies in ophthalmology-From bench to clinical trial

During the last decade, the fields of advanced and personalized therapeutics have been constantly evolving, utilizing novel techniques such as gene editing and RNA therapeutic approaches. However, the method of delivery and tissue specificity remain the main hurdles of these approaches. Exosomes are natural carriers of functional small RNAs and proteins, representing an area of increasing interest in the field of drug delivery. It has been demonstrated that the exosome cargo, especially miRNAs, is at least partially responsible for the therapeutic effects of exosomes. Exosomes deliver their luminal content to the recipient cells and can be used as vesicles for the therapeutic delivery of RNAs and proteins. Synthetic therapeutic drugs can also be encapsulated into exosomes as they have a hydrophilic core, which makes them suitable to carry water-soluble drugs. In addition, engineered exosomes can display a variety of surface molecules, such as peptides, to target specific cells in tissues. The exosome properties present an added advantage to the targeted delivery of therapeutics, leading to increased efficacy and minimizing the adverse side effects. Furthermore, exosomes are natural nanoparticles found in all cell types and as a result, they do not elicit an immune response when administered. Exosomes have also demonstrated decreased long-term accumulation in tissues and organs and thus carry a low risk of systemic toxicity. This review aims to discuss all the advances in exosome therapies in ophthalmology and to give insight into the challenges that would need to be overcome before exosome therapies can be translated into clinical practice.

Single vesicle analysis of aqueous humor in pediatric ocular diseases reveals eye specific CD63-dominant subpopulations

Aqueous humor (AH), the clear fluid in front of the eye, maintains the pressure and vitality of ocular tissues. This fluid is accessible via the clear cornea which enables use of AH as a liquid biopsy source of biomarkers for intraocular disease. Extracellular vesicles are detectable in the AH and small extracellular vesicles (sEVs) are present in the AH from adults. However, EVs in AH from pediatric eyes in vivo have never previously been explored. We know very little about the heterogeneity of AH EV populations in ocular disease. Twenty-seven processing-free AH samples from 19 patients across four different pediatric ocular diseases were subjected to Nanoparticle Tracking Analysis (NTA) and Single Particle-Interferometric Reflectance Imaging Sensor (SP-IRIS) analysis. NTA demonstrated the concentration of AH EV/EPs is 3.11 × 109-1.38 × 1010 particles/ml; the majority sized 76.8-103 nm. SP-IRIS revealed distinct patterns of tetraspanin expression of AH sEVs. An enriched mono-CD63+ sEV subpopulation identified in AH indicates this is a potential AH-specific biomarker. In the setting of retinoblastoma there was a more heterogeneous population of sEVs which normalized with treatment. This suggests a potential clinical application of direct measurement of sEV subpopulations in AH samples to monitor successful tumor response to therapy.

Non-Exosomal and Exosome-Derived miRNAs as Promising Biomarkers in Canine Mammary Cancer

Canine mammary cancer (CMC), similar to human breast cancer (HBC) in many aspects, is the most common neoplasm associated with significant mortality in female dogs. Due to the limited therapy options, biomarkers are highly desirable for early clinical diagnosis or cancer progression monitoring. Since the discovery of microRNAs (miRNAs or miRs) as post-transcriptional gene regulators, they have become attractive biomarkers in oncological research. Except for intracellular miRNAs and cell-free miRNAs, exosome-derived miRNAs (exomiRs) have drawn much attention in recent years as biomarkers for cancer detection. Analysis of exosomes represents a non-invasive, pain-free, time- and money-saving alternative to conventional tissue biopsy. The purpose of this review is to provide a summary of miRNAs that come from non-exosomal sources (canine mammary tumor, mammary tumor cell lines or canine blood serum) and from exosomes as promising biomarkers of CMC based on the current literature. As is discussed, some of the miRNAs postulated as diagnostic or prognostic biomarkers in CMC were also altered in HBC (such as miR-21, miR-29b, miR-141, miR-429, miR-200c, miR-497, miR-210, miR-96, miR-18a, miR19b, miR-20b, miR-93, miR-101, miR-105a, miR-130a, miR-200c, miR-340, miR-486), which may be considered as potential disease-specific biomarkers in both CMC and HBC.

Molecular regulation of neuroinflammation in glaucoma: Current knowledge and the ongoing search for new treatment targets

Neuroinflammation relying on the inflammatory responses of glial cells has emerged as an impactful component of the multifactorial etiology of neurodegeneration in glaucoma. It has become increasingly evident that despite early adaptive and reparative features of glial responses, prolonged reactivity of the resident glia, along with the peripheral immune cells, create widespread toxicity to retinal ganglion cell (RGC) axons, somas, and synapses. As much as the synchronized responses of astrocytes and microglia to glaucoma-related stress or neuron injury, their bi-directional interactions are critical to build and amplify neuroinflammation and to dictate the neurodegenerative outcome. Although distinct molecular programs regulate somatic and axonal degeneration in glaucoma, inhibition of neurodegenerative inflammation can provide a broadly beneficial treatment strategy to rescue RGC integrity and function. Since inflammatory toxicity and mitochondrial dysfunction are converging etiological paths that can boost each other and feed into a vicious cycle, anti-inflammatory treatments may also offer a multi-target potential. This review presents an overview of the current knowledge on neuroinflammation in glaucoma with particular emphasis on the cell-intrinsic and cell-extrinsic factors involved in the reciprocal regulation of glial responses, the interdependence between inflammatory and mitochondrial routes of neurodegeneration, and the research aspects inspiring for prospective immunomodulatory treatments. With the advent of powerful technologies, ongoing research on molecular and functional characteristics of glial responses is expected to accumulate more comprehensive and complementary information and to rapidly move the field forward to safe and effective modulation of the glial pro-inflammatory activities, while restoring or augmenting the glial immune-regulatory and neurosupport functions.

Proteomic Profiling of Aqueous Humor Exosomes from Age-related Macular Degeneration Patients

Purpose: The alteration of the exosomal proteins in the aqueous humor (AH) is linked to the development of eye diseases. The goal of this study was to examine the exosomal protein profile of patients with age-related macular degeneration (AMD) to better understand their role in the pathogenesis of AMD. Methods: Exosomes were isolated from the AH of 28 AMD and 25 control eyes. The quality, concentration, and size distribution of exosomes were measured using a nanoparticle tracking analysis system (NTA). Total exosomal proteins from each sample were purified and digested with trypsin for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Results: Based on LC-MS/MS analysis, we got 105 exosomal peptides from AMD and control patients. Gene ontology (GO) analysis in the biology process revealed that exosomal proteins of AMD were enriched in the lipoprotein metabolic process. T-test analysis revealed six exosomal proteins in patients with AMD were significantly different from controls. Comparing the exosomal protein profile of AMD patients who were receiving anti-VEGF therapy, we observed the amount of two proteins decreased with the duration of the anti-VEGF treatment time. Conclusions: In this study, we successfully isolated and purified AH exosomes. Our results provide pioneering findings for the exosomal protein profile in AMD development and under therapy. These unique proteins could be the new targets for drug discovery or biological markers for evaluating therapeutic efficacy.

The emerging role of extracellular vesicles in retinal diseases

As a type of nanosized membranous vesicles secreted by living cells, extracellular vesicles (EVs) mediate intercellular communications with excellent physicochemical stability and biocompatibility. By delivering biologically active molecules including proteins, nucleic acids and lipids, EVs participate in many physiological and pathological processes. Increasing studies have suggested that EVs may be biomarkers for liquid biopsy of retinal diseases due to the ability to transfer through the blood-retinal barrier. EVs also represent a novel cell-free strategy to repair tissue damage in regenerative medicine. Evidence has indicated that EVs can be engineered and modified to enhance their efficacy. In this review, an overview of the characteristics, isolation, and identification of EVs is provided. Moreover, recent advances with EVs in the diagnosis and treatment of retinal diseases and the engineering approaches to elevate their effects are introduced, and opportunities and challenges for clinical application are discussed.

Exosomes, extracellular vesicles and the eye

Exosomes are a subset of extracellular vesicles which accommodate a cargo of bioactive biomolecules that generally includes proteins, nucleic acids, lipids, sugars, and related conjugates depicting the cellular environment and are known to mediate a wide array of biological functions, like cellular communication, cellular differentiation, immunomodulation, neovascularization, and cellular waste management. The exponential implication of exosomes in the pathological development and progression of various disorders including neurodegenerative diseases, cardiovascular diseases, and cancer has offered a tremendous opportunity for exploring their role in ocular conditions. Ocular diseases such as age-related macular disease, glaucoma, infectious endophthalmitis, diabetic retinopathy, autoimmune uveitis etc face various challenges in their early diagnosis and treatments due to contributing factors such as delay in the onset of symptoms, microbial identification, difficulty in obtaining samples for biopsy or being diagnosed as masquerade syndromes. Studies have reported unique exosomal cargos that are involved in successful delivery of miRNA or proteins to recipient cells to express desired expression or exploited as a diagnostic marker for various diseases. Furthermore, engineered exosomes can be used for targeted delivery of therapeutics and exosomes being natural nanoparticles found in all types of cells, host may not elicit an immune response against it. With the rapid advancement of opting personalized therapeutics, extending exosomal research to sight-threatening ocular infections can possibly advance the current diagnostic and therapeutic approaches. This review briefs about the current knowledge of exosomes in visual systems, advancements in exosomal and ophthalmic research, participation of exosomes in the pathogenesis of common ocular diseases, the challenges for exosomal therapies along with the future of this promising domain of research for diseases that fatally threaten billions of people worldwide.

Electroacupuncture altered expression of microRNAs in Stat5 knockout obese mice

BACKGROUND

Increasing evidence shows that miRNAs contribute to the establishment and development of obesity by affecting many biological and pathological processes, such as adipocyte differentiation, hepatic lipid metabolism, insulin resistance, and neurological regulation of obesity. As a clinical intervention approach, acupuncture has been shown to be effective in the treatment of obesity and other metabolic diseases. Our previous whole genome study in central nervous system (CNS)-specific Stat5 knockout (NKO) obese mice found that electroacupuncture (EA) could reduce body weight and promote white browning.

OBJECTIVE

To clarify the effect of EA on miRNAs and understand how it regulates gene expression.

METHODS

Twelve-week-old male Stat5NKO mice with body weight 20% greater than that of Stat5fl/fl (control) mice were divided into a Stat5NKO (model) group and EA-treated Stat5NKO + EA group. A cohort of Stat5fl/fl mice of the same age were included as the control group. EA was administered under isoflurane anesthesia at unilateral ST36 and ST44 daily (left and right sides were treated every other day), 6 times per week for a total of 4 weeks. The miRNA profile was generated and miRNA regulatory networks were analyzed in the Stat5 nestin-cre mice before and after EA treatment. Autophagy-related proteins in adipocytes were detected after over-expression of miR27a.

RESULTS

EA altered abnormal miRNA expression, including miRNA27a expression, and reduced the autophagy-related proteins ATG5 and ATG12.

CONCLUSION

We found that EA could regulate miRNA27a-mediated autophagy-related proteins and promote white fat browning, which may contribute to weight loss. To our knowledge, this is the first report of miRNAs potentially driving the effect of EA on white fat browning through the autophagy process.

The effects of exosomes derived from trabecular meshwork cells on Schlemm's canal endothelial cells

Trabecular meshwork (TM) and Schlemm’s canal (SC) are the main structures within the conventional outflow pathway, and TM cells and SC endothelial (SCE) cells are essential for controlling intraocular pressure. To examine the interaction between TM cells and SCE cells, we investigated whether exosomes contribute to intercellular communication. Additionally, TM cells in glaucoma acquire mesenchymal characteristics in response to transforming growth factor (TGF)-β2 and extracellular matrix proteins such as collagen type 1 (Col-1); these changes result in increased resistance of aqueous outflow. In this study, we stimulated TM cells with TGF-β2 and Col-1 and characterized the exosomal miRNAs (exomiRs) released in response to each stimulus. Isolated exosomes were rich in miRNAs, with downregulated miR-23a-5p and upregulated miR-3942-5p and miR-7515 levels following Col-1 or TGF-β2 stimulation. Next, a miRNA-mRNA network under TGF-β2 stimulation was constructed. There were no connections among the 3 miRNAs and predicted genes under Col-1 stimulation. GO and KEGG analyses revealed that the identified miRNAs were associated with various signaling pathways, including the inflammatory response. Interestingly, SCE cells treated with miR-7515 mimic showed increased VEGFA, VEGFR2, PECAM, and Tie2 expression. Ultrastructures typical of exosomes and positive staining for exosomal markers were observed in human TM cells. Our data showed that TM cells may communicate with SCE cells via exomiRs and that miR-7515 may be important for SCE cell reprogramming.

Isolation of sensory hair cell specific exosomes in human perilymph

Evaluation of hearing loss patients using clinical audiometry has been unable to give a definitive cellular or molecular diagnosis, hampering the development of treatments of sensorineural hearing loss. However, biopsy of inner ear tissue without losing residual hearing function for pathologic diagnosis is extremely challenging. In a clinical setting, perilymph can be accessed, potentially allowing the development of fluid based diagnostic tests. Recent approaches to improving inner ear diagnostics have been focusing on the evaluation of the proteomic or miRNA profiles of perilymph. Inspired by recent characterization and classification of many neurodegenerative diseases using exosomes which not only are produced in locally in diseased tissue but are transported beyond the blood brain barrier, we demonstrate the isolation of human inner ear specific exosomes using a novel ultrasensitive immunomagnetic nano pom-poms capture-release approach. Using perilymph samples harvested from surgical procedures, we were able to isolate exosomes from sensorineural hearing loss patients in only 2-5 μL of perilymph. By isolating sensory hair cell derived exosomes through their expression level of myosin VIIa, we for the first-time sample material from hair cells in the living human inner ear. This work sets up the first demonstration of immunomagnetic capture-release nano pom-pom isolated exosomes for liquid biopsy diagnosis of sensorineural hearing loss. With the ability to isolate exosomes derived from different cell types for molecular characterization, this method also can be developed for analyzing exosomal biomarkers from more accessible patient tissue fluids such as plasma.

Exosomal miR-29b found in aqueous humour mediates calcium signaling in diabetic patients with cataract

AIM

To investigate the role of exosomal miR-29b and Ca²⁺ in regulating the function of human lens epithelial cells (HLECs).

METHODS

Exosomes were isolated from human aqueous humour (AH) by ultracentrifugation, and visualized by nanoparticle tracking and transmission electron microscopy. Exosomal miRNA sequencing was performed to identify differentially expressed miRNAs between diabetes with cataracts (DMC) group and age-related cataracts (ARC) group. TargetScan was used to predict potential target of certain miRNA. The expression of CACNA1C mRNA was determined by quantitative real-time polymerase chain reaction and CACNA1C protein was determined by Western blotting. Concentration of Ca²⁺ in human AH and the culture supernatant of cells were detected by the calcium assay kit. Cell counting kit-8 was used to determine cell viability.

RESULTS

Exosomes were isolated from human AH, which had a typical cup-shaped phenotype and a particle size distribution in accordance with micro extracellular vesicles. Exosomal miRNA sequencing revealed that miR-29b was significantly downregulated in DMC group compared with ARC. Ca²⁺ concentration of human AH in DMC was higher than that in ARC. The culture supernatant of cells transfected with miR-29b inhibitors had a higher concentration of Ca²⁺ than that transfected with miR-29b mimics. miR-29b reduced the viability of HLECs by upregulating CACNA1C expression.

CONCLUSION

Exosomes isolated from human AH contains abundant miRNAs. A significantly expressed miRNA, miR-29b, can affect the concentration of Ca²⁺ and regulate HLEC processes by upregulating CACNA1C.

Multiplex protein analysis for the study of glaucoma

INTRODUCTION

Glaucoma, a leading cause of irreversible blindness in the world, is a chronic neurodegenerative disease of multifactorial origin. Extensive research is ongoing to better understand, prevent, and treat progressive degeneration of retinal ganglion cells in glaucoma. While experimental models of glaucoma and postmortem tissues of human donors are analyzed for pathophysiological comprehension and improved treatment of this blinding disease, clinical samples of intraocular biofluids and blood collected from glaucoma patients are analyzed to identify predictive, diagnostic, and prognostic biomarkers. Multiplexing techniques for protein analysis offer a valuable approach for translational glaucoma research.

AREAS COVERED

This review provides an overview of the increasing applications of multiplex protein analysis for glaucoma research and also highlights current research challenges in the field and expected solutions from emerging technological advances.

EXPERT OPINION

Analytical techniques for multiplex analysis of proteins can help uncover neurodegenerative processes for enhanced treatment of glaucoma and can help identify molecular biomarkers for improved clinical testing and monitoring of this complex disease. This evolving field and continuously growing availability of new technologies are expected to broaden the comprehension of this complex neurodegenerative disease and speed up the progress toward new therapeutics and personalized patient care to prevent blindness from glaucoma.