Quantitative Proteomics Analysis of Vitreous Humor from Diabetic Retinopathy Patients

Update in the molecular mechanism and biomarkers of diabetic retinopathy

Diabetic retinopathy (DR) is a serious complication of diabetes caused by long-term hyperglycemia that leads to microvascular and neuronal damage in the retina. The molecular mechanisms of DR involve oxidative stress, inflammatory responses, neurodegenerative changes, and vascular dysfunction triggered by hyperglycemia. Oxidative stress activates multiple metabolic pathways, such as the polyol, hexosamine, and protein kinase C (PKC) pathways, resulting in the production of, which in turn promote the formation of advanced glycation end products (AGEs). These pathways exacerbate vascular endothelial damage and the release of inflammatory factors, activating inflammatory signaling pathways such as the NF-κB pathway, leading to retinal cell damage and apoptosis. Additionally, DR involves neurodegenerative changes, including the activation of glial cells, neuronal dysfunction, and cell death. Research on the multiomics molecular markers of DR has revealed complex mechanisms at the genetic, epigenetic, and transcriptional levels. Genome-wide association studies (GWASs) have identified multiple genetic loci associated with DR that are involved in metabolic and inflammatory pathways. Noncoding RNAs, such as miRNAs, circRNAs, and lncRNAs, participate in the development of DR by regulating gene expression. Proteomic, metabolomic and lipidomic analyses have revealed specific proteins, metabolites and lipid changes associated with DR, providing potential biomarkers for the early diagnosis and treatment of this disease. This review provides a comprehensive perspective for understanding the molecular network of DR and facilitates the exploration of innovative therapeutic approaches.

Stage-dependent proteomic alterations in aqueous humor of diabetic retinopathy patients based on data-independent acquisition and parallel reaction monitoring

BACKGROUND

Diabetic retinopathy (DR), a microvascular complication of diabetes mellitus (DM), represents the predominant cause of preventable vision loss in working-age populations globally. While the pathophysiological mechanisms underlying DR progression remain incompletely understood, our study employs comprehensive proteomic profiling of aqueous humor (AH) to identify stage-specific biomarkers and therapeutic targets in type 2 diabetes mellitus (T2DM) patients across DR progression.

METHODS

Utilizing data-independent acquisition (DIA) mass spectrometry, we quantified AH proteomes in a discovery cohort comprising 24 subjects: 18 T2DM patients stratified by DR severity [6 non-DR, 6 non-proliferative DR (NPDR), 6 proliferative DR (PDR)] and 6 cataract controls without diabetes (non-DM). Validation cohort analysis (including 10 AH samples in each group) was performed using parallel reaction monitoring (PRM) strategy for verification of target proteins. Comprehensive bioinformatics analyses included gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, protein-protein interaction (PPI) network construction, receiver operating characteristic (ROC) curve analysis, and ConnectivityMap (Cmap)-based drug prediction.

RESULTS

Proteomic profiling identified 739 quantifiable AH proteins (62% extracellular) with clear separation among the four clinical stages in the discovery cohort. GSEA uncovered altered expression of proteins mainly related to complement and coagulation cascades, folate metabolism, and the selenium micronutrient network in patients with DR. WGCNA-derived protein modules yielded 83 PRM-validated targets, including 5 hub proteins differentiating NPDR from non-DR and 33 hub proteins showed significant upregulation in PDR versus NPDR comparison. Clinical correlation analysis identified F2, FGG, FGB, RBP4, AMBP, VTN, C8A, CPB2, and C2 associated with clinical traits. C6, FAM3C, SPP1, and JCHAIN levels were altered post-anti-VEGF treatment. Pharmacological prediction identified potential therapeutic compounds, including perindopril, triciribine, and XAV-939 for NPDR, and topiramate, triciribine, and vecuronium for PDR.

CONCLUSION

This study established a comprehensive AH proteomic signature of DR progression, offering insights into the pathogenesis of DR and highlighting potential biomarkers and novel therapeutic targets.

Proteomic Analysis of Aqueous Humor Identified Clinically Relevant Molecular Targets for Neovascular Complications in Diabetic Retinopathy

Diabetic retinopathy (DR) is a leading cause of blindness in adults under 40 in the developed world, with a significant proportion progressing to vision-threatening stages such as proliferative diabetic retinopathy (PDR) and neovascular glaucoma (NVG). This study aims to explore the molecular mechanisms underlying the progression from nonproliferative DR to PDR and NVG, focusing on identifying potential biomarkers and therapeutic targets. Utilizing discovery-based proteomics, specifically label-free quantification and tandem mass tag, we analyzed aqueous humor (AH) proteins obtained during cataract surgery or anterior chamber paracentesis from patients with nonproliferative DR, PDR, and NVG. Validation of marker candidates for each disease state was conducted using triple quadrupole-MS for targeted protein quantification. Our proteomic analysis identified 2255 proteins, and gene ontology analysis and functional annotation highlighted key biological processes implicated in DR, such as lens development, immune responses, and lipid metabolism. Validation of potential biomarkers identified 20 proteins with significant concentration changes, including several candidates with diagnostic utility based on ROC curve analysis. Further investigation into clinical relevance revealed that crystallin gamma-S is strongly associated with cataract severity, highlighting its role as a potential marker for ocular complications in DR. Importantly, we identified that the pathological factors driving DR progression have a much greater impact than age, a previously known variable, in shaping the proteomic landscape of AH. Additionally, proteins associated with macular degeneration (CA1, CA2, and HBA1) were uncovered, providing new insights into overlapping mechanisms between DR and other retinal diseases. Finally, proteins linked to panretinal photocoagulation treatment, including APOB and CST6, were identified, suggesting their involvement in the therapeutic response and post-treatment adaptation. These findings underscore the potential of AH proteomics in uncovering predictive biomarkers and elucidating the molecular pathogenesis of DR and its complications.

A case-control prospective study to unravel zinc alpha 2 glycoprotein role in the pathophysiology of diabetic retinopathy

BACKGROUND AND OBJECTIVES

Diabetic retinopathy (DR) is a leading neurovascular complication affecting the working age group worldwide. Zinc alpha-2-glycoprotein (ZAG) is indeed an important adipokine, and it has been found to play a role in various metabolic conditions, including diabetes, metabolic syndrome and responses to lifestyle changes. In this study, we have assessed the levels of ZAG in the aqueous and vitreous humour of DR cases as a marker for the disease. It's a case-control prospective study wherein 65 Proliferative Diabetic Retinopathy (PDR) patients in the age group of 50-60 years with type 2 diabetes mellitus and with no other ocular complications were included. The PDR cases were classified with Tractional Retinal Detachment (TRD) and Fibrovascular Proliferation (FVP). 15 Macular hole (MH) patients in the age group of 60-70 years with no history of diabetes were included as disease control subjects. The groups were evaluated for demographic variables, biochemical parameters, vitreous ZAG levels and biomarkers. Data between the groups were compared statistically.

RESULTS

A significant increase in ZAG protein levels was observed in both vitreous humour and aqueous humour of PDR cases compared to MH control. A positive correlation was observed between ZAG and various biomarkers like adiponectin, leptin, galectin-3, Vascular endothelial growth factor (VEGF), pentraxin-3 (PTX3) and tumour necrosis factor-alpha (TNF- alpha). Unconditional logistic regression analysis was conducted, and ZAG had 20.167 odds ratio (95% CI 3.927-103.576, P = 0.001).

CONCLUSION

The present study shows that ZAG is increased in the vitreous and aqueous humour of the PDR cases compared to the macular hole. It was also correlated with the already reported biomarkers. It could be a risk factor for the disease based on the odds ratio.

Advances in molecular epidemiology of diabetic retinopathy: from genomics to gut microbiomics

Diabetic retinopathy (DR) remains a prevalent complication of diabetes mellitus and a leading cause of blindness worldwide. The growing global diabetic population underscores the urgency to deepen our understanding of DR pathogenesis and develop effective prevention strategies. This review synthesizes recent advancements in molecular epidemiology, spanning genomics, epigenomics, transcriptomics, proteomics, metabolomics, and gut microbiomics, elucidating genetic underpinnings, epigenetic modifications, transcriptional alterations, protein biomarkers, metabolic disruptions, and gut microbiota dysbiosis associated with DR. Highlighted are key findings from genome-wide association studies (GWAS), Mendelian randomization (MR) studies, candidate gene association studies, and advancements in epigenetic mechanisms, revealing intricate disease pathways and potential therapeutic targets. Additionally, insights into altered metabolic profiles and gut microbiota compositions in DR underscore their emerging roles in disease progression and complications. Challenges and future directions in molecular epidemiological research are discussed to accelerate the translation of these findings into clinical applications for personalized DR management. The integration of multi-omics research findings may provide novel perspectives for facilitating rapid and accurate disease diagnosis, enabling dynamic disease monitoring, and advancing targeted therapeutic strategies.

Liquid Biopsy for Proliferative Diabetic Retinopathy: Single-Cell Transcriptomics of Human Vitreous Reveals Inflammatory T-Cell Signature

Purpose

Current therapies for proliferative diabetic retinopathy (PDR) do not specifically target VEGF-independent, cell-type-specific processes that lead to vision loss, such as inflammatory pathways. This study aimed to identify targetable cell types and corresponding signaling pathways by elucidating the single-cell landscape of the vitreous of patients with PDR.

Design

Case series.

Subjects

Vitreous and peripheral blood obtained from 5 adult patients (6 eyes) undergoing pars plana vitrectomy for vision-threatening PDR.

Methods

Single-cell RNA sequencing (scRNA-seq) was performed on vitreous cells obtained from diluted cassette washings during vitrectomy from 6 eyes and peripheral blood mononuclear cells (PBMCs, n = 5). Droplet-based scRNA-seq was performed using the Chromium 10x platform to obtain single-cell transcriptomes. Differences in tissue compartments were analyzed with gene ontology enrichment of differentially expressed genes and an unbiased ligand-receptor interaction analysis.

Main Outcome Measures

Single-cell transcriptomic profiles of vitreous and peripheral blood.

Results

Transcriptomes from 13 675 surgically harvested vitreous cells and 22 636 PBMCs were included. Clustering revealed 4 cell states consistently across all eyes with representative transcripts for T cells (CD2, CD3D, CD3E, and GZMA), B cells (CD79A, IGHM, MS4A1 (CD20), and HLA-DRA), myeloid cells (LYZ, CST3, AIF1, and IFI30), and neutrophils (BASP1, CXCR2, S100A8, and S100A9). Most vitreous cells were T cells (91.6%), unlike the peripheral blood (46.2%), whereas neutrophils in the vitreous were essentially absent. The full repertoire of adaptive T cells including CD4+, CD8+ and T regulatory cells (Treg) and innate immune system effectors (i.e., natural killer T cells) was present in the vitreous. Pathway analysis also demonstrated activation of CD4+ and CD8+ memory T cells and ligand-receptor interactions unique to the vitreous.

Conclusions

In the first single-cell transcriptomic characterization of human vitreous in a disease state, we show PDR vitreous is primarily composed of T cells, a critical component of adaptive immunity, with activity and proportions distinct from T cells within the peripheral blood, and neutrophils are essentially absent. These results demonstrate the feasibility of liquid vitreous biopsies via collection of otherwise discarded, diluted cassette washings during vitrectomy to gain mechanistic and therapeutic insights into human vitreoretinal disease.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Bioinformatics analysis of immune infiltration in human diabetic retinopathy and identification of immune-related hub genes and their ceRNA networks

Diabetic retinopathy (DR) is the most common microvascular complication in diabetic patients, and recent studies have shown that immune regulatory mechanisms are closely associated with retinal damage in DR. Therefore, this study focused on exploring immune cells and immune-related genes (IRGs) in DR and gaining insight into the ceRNA mechanisms by which IRGs regulate DR progression. Four datasets from human DR model retinal tissues were obtained from the Gene Expression Omnibus (GEO) database. R software was first used to identify differentially expressed mRNAs (DE-mRNAs) in the dataset GSE160306-mRNAs, then the distribution of immune cells in the gene matrix was analyzed by xCell and ImmuCellAI, ImmPort and InnateDB database were used to obtain immune-related hub genes (IRHGs) in the DR, and finally the STRING online tool and Cytoscape to construct the immune-related ceRNA network. The datasets GSE102485, GSE160308 and GSE160306-lncRNAs were used to validate the results of the ceRNA network further. The results of immune cell infiltration analysis showed that macrophages are important immune cells in DR; immune-related gene screening showed that FCGR2B is an IRHG in DR, and 2 immune-related ceRNA networks of IRHG were obtained: DDN-AS1/miR-10a-5p/FCGR2B and LINC01515/miR-10a-5p/FCGR2B. Our study suggests that infiltration of immune cells, especially the immune role of macrophages, is an important component of DR progression; the immune-related hub gene FCGR2B and its ceRNA network may be a key regulatory network for DR progression. The discovery of key immune cells, IRHG and ceRNA networks in this study may provide new prospects for early intervention and targeted treatment of DR.

Identification of Potential Growth-Related Proteins in Chick Vitreous during Emmetropization Using SWATH-MS and Targeted-Based Proteomics (MRMHR)

The vitreous humor (VH) is a transparent gelatin-like substance that occupies two-thirds of the eyeball and undergoes the most significant changes during eye elongation. Quantitative proteomics on the normal growth period in the VH could provide new insights into understanding its progression mechanism in the early stages of myopia. In this study, a data-independent acquisition (SWATH-MS) was combined with targeted LC-ESI-MS/MS to identify and quantify the relative protein changes in the vitreous during the normal growth period (4, 7, 14, 21 and 28 days old) in the chick model. Chicks were raised under normal growing conditions (12/12 h Dark/light cycle) for 28 days, where ocular measurements, including refractive and biometric measurements, were performed on days 4 (baseline), 7, 14, 21 and 28 (n = 6 chicks at each time point). Extracted vitreous proteins from individual animals were digested and pooled into a left eye pool and a right pool at each time point for protein analysis. The vitreous proteome for chicks was generated using an information-dependent acquisition (IDA) method by combining injections from individual time points. Using individual pool samples, SWATH-MS was employed to quantify proteins between each time point. DEPs were subsequently confirmed in separate batches of animals individually on random eyes (n = 4) using MRMHR between day 7 and day 14. Refraction and vitreous chamber depth (VCD) were found to be significantly changed (p < 0.05, n = 6 at each time point) during the period. A comprehensive vitreous protein ion library was built with 1576 non-redundant proteins (22987 distinct peptides) identified at a 1% false discovery rate (FDR). A total of 12 up-regulated and 26 down-regulated proteins were found across all time points compared to day 7 using SWATH-MS. Several DEPs, such as alpha-fetoprotein, the cadherin family group, neurocan, and reelin, involved in structural and growth-related pathways, were validated for the first time using MRMHR under this experimental condition. This study provided the first comprehensive spectral library of the vitreous for chicks during normal growth as well as a list of potential growth-related protein biomarker candidates using SWATH-MS and MRMHR during the emmetropization period.

Diabetic retinopathy from the vitreous proteome perspective: The INSC94Y transgenic pig model study

INSC94Y transgenic pigs represent a model for mutant insulin gene-induced diabetes of youth, with impaired insulin secretion and beta cell loss, leading to elevated fasting blood glucose levels. A key complication of diabetes mellitus is diabetic retinopathy (DR), characterized by hyperglycemia-induced abnormalities in the retina. Adjacent to the retina lies the vitreous, a gelatinous matrix vital for ocular function. It harbors proteins and signaling molecules, offering insights into vitreous biology and ocular health. Moreover, as a reservoir for secreted molecules, the vitreous illuminates molecular processes within intraocular structures, especially under pathological conditions. To uncover the proteomic profile of porcine vitreous and explore its relevance to DR, we employed discovery proteomics to compare vitreous samples from INSC94Y transgenic pigs and wild-type controls. Our analysis identified 1404 proteins, with 266 showing differential abundance in INSC94Y vitreous. Notably, the abundances of ITGB1, COX2, and GRIFIN were significantly elevated in INSC94Y vitreous. Gene Set Enrichment Analysis unveiled heightened MYC and mTORC1 signaling in INSC94Y vitreous, shedding light on its biological significance in diabetes-associated ocular pathophysiology. These findings deepen our understanding of vitreous involvement in DR and provide valuable insights into potential therapeutic targets. Raw data are accessible via ProteomeXchange (PXD038198).

Ocular drug-metabolizing enzymes: focus on esterases

This review describes current knowledge on the expression of ocular phase I and II drug-metabolizing enzymes in the main animal species used in ocular drug development and in humans, with a focus on ocular esterases and their prodrug substrates. The eye possesses a unique metabolic profile, exhibiting a lower and restricted expression of major cytochrome P450s (CYPs) and most transferases apart from glutathione S-transferases (GST) when compared to the liver. In contrast, hydrolytic enzymes are abundant in many ocular tissues. These enzymes have attracted interest because of their role in prodrug activation and drug elimination. A literature survey suggests profound variations in tissue expression levels and activities between different species but also points out significant gaps in knowledge. These uncertainties highlight a need for more detailed characterization of enzymes in individual ocular tissues and across species to aid future translational studies in ophthalmic drug research. Thus, an in-depth analysis of ocular drug metabolism and species differences is crucial for ocular drug development.

Aqueous humor proteomics analyzed by bioinformatics and machine learning in PDR cases versus controls

BACKGROUND

To comprehend the complexities of pathophysiological mechanisms and molecular events that contribute to proliferative diabetic retinopathy (PDR) and evaluate the diagnostic value of aqueous humor (AH) in monitoring the onset of PDR.

METHODS

A cohort containing 16 PDR and 10 cataract patients and another validation cohort containing 8 PDR and 4 cataract patients were studied. AH was collected and subjected to proteomics analyses. Bioinformatics analysis and a machine learning-based pipeline called inference of biomolecular combinations with minimal bias were used to explore the functional relevance, hub proteins, and biomarkers.

RESULTS

Deep profiling of AH proteomes revealed several insights. First, the combination of SIAE, SEMA7A, GNS, and IGKV3D-15 and the combination of ATP6AP1, SPARCL1, and SERPINA7 could serve as surrogate protein biomarkers for monitoring PDR progression. Second, ALB, FN1, ACTB, SERPINA1, C3, and VTN acted as hub proteins in the profiling of AH proteomes. SERPINA1 was the protein with the highest correlation coefficient not only for BCVA but also for the duration of diabetes. Third, "Complement and coagulation cascades" was an important pathway for PDR development.

CONCLUSIONS

AH proteomics provides stable and accurate biomarkers for early warning and diagnosis of PDR. This study provides a deep understanding of the molecular mechanisms of PDR and a rich resource for optimizing PDR management.

Tandem Mass Tag LC-MS/MS of Aqueous Humor From Individuals With Type 2 Diabetes Without Retinopathy Reveals Early Dysregulation of Synaptic Proteins

Purpose

An early neurodegenerative component of diabetic retinal disease (DRD) that precedes the vascular findings of clinically diagnosed diabetic retinopathy (DR) is increasingly being recognized. However, the relevant molecular mechanisms and biomarkers for early DRD are poorly defined. The purpose of this study was to uncover novel potential mediators of early diabetic retinal neuronal dysfunction through analysis of the aqueous fluid proteome in preclinical DR.

Methods

Aqueous fluid was collected from subjects with type 2 diabetes mellitus (DM) but no clinical DR and from nondiabetic controls undergoing routine cataract surgery. Preoperative spectral-domain optical coherence tomography of the macula was obtained. Tandem mass tag LC-MS/MS was performed to identify proteins differentially present in diabetic and control aqueous fluid, and proteins with >50% change and P < 0.05 were considered significant. Selected results were validated with western blot of human aqueous fluid samples.

Results

We identified decreased levels of proteins implicated in neuronal synapse formation and increased levels of inflammatory proteins in the aqueous fluid from patients with type 2 DM but no DR compared with controls. Of the differentially present synaptic proteins that we identified and confirmed with western blot, the majority have not previously been linked with DRD.

Conclusions

The proteomic profile of aqueous fluid from individuals with type 2 DM but no DR suggests that retinal neuronal dysfunction and inflammation represent very early events in the pathophysiology of DRD. These findings support the concept that diabetic retinal neurodegeneration precedes vascular pathology and reveal novel potential mediators and/or biomarkers warranting further investigation.

Safety and Efficacy of Dexamethasone Intravitreal Implant Given Either First-Line or Second-Line in Diabetic Macular Edema

Diabetic macular edema (DME) is a common sight-threatening complication of diabetic retinopathy (DR) and the leading cause of severe visual impairment among the working-age population. Several therapeutic options are available for the management of DME, including intravitreal corticosteroids. They have been traditionally used as second-line treatment, due to the risk of intraocular pressure increase and cataract-related adverse events. However, attention has recently been focused on the primary or early use of intravitreal corticosteroids, due to growing evidence of the crucial role of inflammation in the pathogenesis of DME. Furthermore, intravitreal steroid implants offer the additional advantage of a longer duration of action compared to anti-vascular endothelial growth factor agents (anti-VEGF). This review aims to summarize the available evidence on the efficacy and safety profile of dexamethasone (DEX) intravitreal implant, with a specific focus on clinical scenarios in which it might be considered or even preferred as first-line treatment option by adequate selection of patients, considering both advantages and possible adverse events. Patients with contraindications to anti-VEGF, DME with high inflammatory OCT biomarkers, pseudophakic patients and phakic patients' candidates to cataract surgery as well as vitrectomized eyes may all benefit from first-line DEX implant. Additionally, DME not responders to anti-VEGF should be considered for a switch to DEX implant and a combination therapy of DEX implant and anti-VEGF could be a valid option in severe and persistent DME.

Development of diabetic macular oedema shows associations with systemic medication - An epidemiological study

PURPOSE

To identify associations between systemic drugs and the incidence of diabetic macular oedema (DME). Of interest was to find beneficial and/or deleterious associations of used drugs.

METHODS

A historic cohort design based on administrative data. Study population consisted of 150 353 individuals with diabetes. Endpoint event was the development of DME (ICD-10 H36.01), censoring events were death or study end December 2017. The follow-up started between 1997 and 2010. The systemic medication consisted of 95 substances. We constructed a nested case-control study design comparing 2630 cases with DME to 13 144 age- and sex-matched controls without DME. Results are reported as odds ratios (ORs) with 95% confidence intervals (CIs) based on conditional logistic regression models.

RESULTS

Incidence rate for DME was 1.80 per 1000 person-years (95% CI 1.73-1.87). In all, we observed a lower incidence rate of DME in females (IRR 0.57; 95% CI 0.52-0.62) compared to males. Exposure to hormone replacement therapy estradiol (OR 0.42; 0.25-0.68), temazepam (0.23; 0.08-0.62) and allopurinol (0.61; 0.43-0.86) were associated with lower risk of DME, while use of insulin or insulin analogue (3.30; 2.99-3.64), sulfonylureas (1.21; 1.05-1.40), diuretic furosemide (1.90; 1.61-2.24), calcium channel blocker amlodipine (1.53; 1.34-1.75), ACE inhibitors ramipril (1.66; 1.46-1.89) and enalapril (1.38; 1.16-1.64) were associated with an increased risk of DME.

CONCLUSIONS

Large-scale studies examining the incidence of DME are lacking. Our findings suggest that associations of systemic medications with the incidence of DME may shed light on the pathogenesis of complex DME, encouraging further studies.

LC/MS Assessment of Glycoform Clearance of A Biotherapeutic MAb in Rabbit Ocular Tissues

Many biotherapeutics such as monoclonal antibodies (mAbs) consist of various glycoforms, which can have different PK properties upon administration to animals and human. As a result, it is necessary to monitor the abundance of glycoforms and limit lot-to-lot variability during the manufacturing process. However, limited information is known about the clearance of mAb glycoforms from ocular space upon intravitreal injection. We present here an assessment of glycoform clearance of a biotherapeutic mAb (IgG1) from rabbit vitreous humor, aqueous humor and retina tissue using LC/MS. The results show that G0, G0F and G1F have similar T1/2, while mannose-5 has a longer T1/2 and is cleared slower in rabbit ocular space, which contradicted with what has been reported in the literature in which Mann5 was cleared faster systematically.

Comparative proteomics of proliferative diabetic retinopathy in people with Type 2 diabetes highlights the role of inflammation, visual transduction, and extracellular matrix pathways

Purpose

To explore the vitreous humor proteome from type 2 diabetes subjects with proliferative diabetic retinopathy (PDR) in the Indian population.

Methods

We performed mass spectrometry-based label-free quantitative analysis of vitreous proteome of PDR (n = 13) and idiopathic macular hole (IMH; control) subjects (n = 14). Nine samples of PDR and 10 samples of IMH were pooled as case and control, respectively, and compared. Four samples each of PDR and IMH were analyzed individually without pooling to validate the results of the pooled analysis. Comparative quantification was performed using Scaffold software which calculated the fold changes of differential expression. Bioinformatics analysis was performed using DAVID and STRING software.

Results

We identified 469 proteins in PDR and 517 proteins in IMH vitreous, with an overlap of 172 proteins. Also, 297 unique proteins were identified in PDR and 345 in IMH. In PDR vitreous, 37 proteins were upregulated (P < 0.05) and 19 proteins were downregulated compared to IMH. Protein distribution analysis clearly demonstrated a separation of protein expression in PDR and IMH. Significantly upregulated proteins included fibrinogen gamma chain, fibrinogen beta chain, and carbonic anhydrase 1 and downregulated proteins included alpha-1-antitrypsin, retinol-binding protein 3, neuroserpin, cystatin C, carboxypeptidase E and cathepsin-D.

Conclusion

Diabetic retinopathy pathogenesis involves proteins which belong to inflammation, visual transduction, and extracellular matrix pathways. Validation-based experiments using enzyme-linked immunosorbent assay (ELISA) or western blotting are needed to establish cause and effect relationships of these proteins to the disease state, to develop them as biomarkers or drug molecules.

Current Innovations in Intraocular Pressure Monitoring Biosensors for Diagnosis and Treatment of Glaucoma-Novel Strategies and Future Perspectives

Biosensors are devices that quantify biologically significant information required for diverse applications, such as disease diagnosis, food safety, drug discovery and detection of environmental pollutants. Recent advancements in microfluidics, nanotechnology and electronics have led to the development of novel implantable and wearable biosensors for the expedient monitoring of diseases such as diabetes, glaucoma and cancer. Glaucoma is an ocular disease which ranks as the second leading cause for loss of vision. It is characterized by the increase in intraocular pressure (IOP) in human eyes, which results in irreversible blindness. Currently, the reduction of IOP is the only treatment used to manage glaucoma. However, the success rate of medicines used to treat glaucoma is quite minimal due to their curbed bioavailability and reduced therapeutic efficacy. The drugs must pass through various barriers to reach the intraocular space, which in turn serves as a major challenge in glaucoma treatment. Rapid progress has been observed in nano-drug delivery systems for the early diagnosis and prompt therapy of ocular diseases. This review gives a deep insight into the current advancements in the field of nanotechnology for detecting and treating glaucoma, as well as for the continuous monitoring of IOP. Various nanotechnology-based achievements, such as nanoparticle/nanofiber-based contact lenses and biosensors that can efficiently monitor IOP for the efficient detection of glaucoma, are also discussed.

A systematic proteomic profiling and pathway analysis of protein biomarkers in diabetic retinopathy with subsequent validation of the IL-6 upstream regulator

Purpose

Diabetic retinopathy (DR) is a leading cause of irreversible blindness worldwide. Identifying risk factors associated with DR development and progression is crucial for improving treatment efficacy. Although proteomic changes in DR have been extensively studied, the results remain equivocal. Hence, this study aims to summarize and identify potential diagnostic or prognostic markers for DR. In addition, the upstream regulator responsible for protein deregulation of this disease was also validated.

Methods

We systematically analyzed the current literature on proteomic profile changes in DR, followed by pathway analysis identification. To validate the protein level changes, ELISA was performed from serum samples collected from 27 patients with DR and 25 healthy controls.

Results

Our analysis revealed that 1 candidate marker (afamin [AFM]) distinguished non-proliferative diabetic retinopathy (NPDR) from type 2 diabetic patients with no diabetic retinopathy/controls, 65 candidate markers distinguished proliferative diabetic retinopathy (PDR) from NPDR, 1 candidate marker (thyroid receptor-interacting protein 11 [TRIP11]) distinguished PDR from PDR-DME/DME, and 3 candidate markers for therapeutic evaluation of PDR. Our results pinpoint that inflammatory response, which IL-6 mainly modulated, is responsible for the changes of proteomic profiles identified in DR. This was also validated by ELISA analysis, indicating that IL-6 could be potentially useful for diagnosing DR.

Conclusion

We report a comprehensive patient-based proteomic approach to identify potential biomarkers for DR diagnosis, prognosis, and treatment evaluation.

Supplementary information

The online version contains supplementary material available at 10.1007/s40200-023-01204-6.

Inflammation: The Link between Neural and Vascular Impairment in the Diabetic Retina and Therapeutic Implications

The etiology of diabetic retinopathy (DR) is complex, multifactorial and compromises all the elements of the retinal neurovascular unit (NVU). This diabetic complication has a chronic low-grade inflammatory component involving multiple inflammatory mediators and adhesion molecules. The diabetic milieu promotes reactive gliosis, pro-inflammatory cytokine production and leukocyte recruitment, which contribute to the disruption of the blood retinal barrier. The understanding and the continuous research of the mechanisms behind the strong inflammatory component of the disease allows the design of new therapeutic strategies to address this unmet medical need. In this context, the aim of this review article is to recapitulate the latest research on the role of inflammation in DR and to discuss the efficacy of currently administered anti-inflammatory treatments and those still under development.

Analysis of protein expression changes in patients with prediabetes using proteomics approaches

RATIONALE

Proteomics and metabolomics are widely used in the study of diabetes, but rarely in prediabetes research. This study aimed to explore the mechanisms of early-onset type 2 diabetes mellitus (T2DM) by analyzing proteomic changes at different stages of glucose metabolism.

METHODS

A total of 40 individuals undergoing routine physical health examinations between December 2016 and April 2017 were enrolled. Subjects were divided into four groups based on fasting blood glucose (FPG) levels: FPG < 5.6 mmol/L (group A); FPG ≥ 5.6 mmol/L and <6.1 mmol/L (group B); FPG ≥ 6.1 mmol/L and <7.0 mmol/L (group C); and FPG ≥ 7.0 mmol/L (group D). Each group had 10 cases. Sera from these 40 subjects were analyzed by label-free quantitative liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). LC/MS/MS with selected reaction monitoring mode was also performed for qualitative and quantitative metabolomics analysis. Differentially expressed proteins were identified. Partial least squares discriminant analysis (PLS-DA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to analyze the differentially expressed metabolites.

RESULTS

A total of 202 differentially expressed proteins were screened and were identified as mainly secreted proteins. Comparing group A with group B, 32 proteins were up-regulated and 18 proteins were down-regulated. Comparing group A with group C, 24 proteins were up-regulated and 24 proteins were down-regulated. Comparing group A with group D, 19 proteins were up-regulated and 17 proteins were down-regulated. The fold change for up-regulated proteins was >1.2, p < 0.05, while the fold change for down-regulated proteins was <-1.2, p < 0.05. PLS-DA and OPLS-DA revealed 113 differentially expressed metabolites. Correlation analysis of differentially expressed metabolites of group A versus group B revealed that among the down-regulated differential proteins, transforming growth factor β-induced protein ig-h3 correlated negatively with metabolite L-saccharin, while among the up-regulated differential proteins, apolipoprotein C-IV correlated negatively with metabolite 3-methyloxindole. Among all differentially expressed proteins, 19 proteins were associated with early initiation of chronic inflammation, including CD14 and CSF-1R, which were newly identified in the early onset of T2DM.

CONCLUSIONS

Many proteins are differentially expressed between prediabetes and after T2DM diagnosis, although the specific mechanism remains unclear. The expression level of CD14 was significantly up-regulated and that of CSF-1R was significantly down-regulated when FPG was ≥5.6 mmol/L, suggesting that CD14 and CSF-1R may be important markers for early-onset T2DM and may serve as new targets for T2DM treatment.

Application of Proteomics Analysis and Animal Models in Optic Nerve Injury Diseases

Optic nerve damage is a common cause of blindness. Optic nerve injury is often accompanied by fundus vascular disease, retinal ganglion cell apoptosis, and changes in retinal thickness. These changes can cause alterations in protein expression within neurons in the retina. Proteomics analysis offers conclusive evidence to decode a biological system. Furthermore, animal models of optic nerve injury made it possible to gain insight into pathological mechanisms, therapeutic targets, and effective treatment of such injuries. Proteomics takes the proteome as the research object and studies protein changes in cells and tissues. At present, a variety of proteomic analysis methods have been widely used in the research of optic nerve injury diseases. This review summarizes the application of proteomic research in optic nerve injury diseases and animal models of optic nerve injury. Additionally, differentially expressed proteins are summarized and analyzed. Various optic nerve injuries, including those associated with different etiologies, are discussed along with their potential therapeutic targets and future directions.

Proteomics profiling of vitreous humor reveals complement and coagulation components, adhesion factors, and neurodegeneration markers as discriminatory biomarkers of vitreoretinal eye diseases

Introduction

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are leading causes of visual impairment and blindness in people aged 50 years or older in middle-income and industrialized countries. Anti-VEGF therapies have improved the management of neovascular AMD (nAMD) and proliferative DR (PDR), no treatment options exist for the highly prevalent dry form of AMD.

Methods

To unravel the biological processes underlying these pathologies and to find new potential biomarkers, a label-free quantitative (LFQ) method was applied to analyze the vitreous proteome in PDR (n=4), AMD (n=4) compared to idiopathic epiretinal membranes (ERM) (n=4).

Results and discussion

Post-hoc tests revealed 96 proteins capable of differentiating among the different groups, whereas 118 proteins were found differentially regulated in PDR compared to ERM and 95 proteins in PDR compared to dry AMD. Pathway analysis indicates that mediators of complement, coagulation cascades and acute phase responses are enriched in PDR vitreous, whilst proteins highly correlated to the extracellular matrix (ECM) organization, platelet degranulation, lysosomal degradation, cell adhesion, and central nervous system development were found underexpressed. According to these results, 35 proteins were selected and monitored by MRM (multiple reaction monitoring) in a larger cohort of patients with ERM (n=21), DR/PDR (n=20), AMD (n=11), and retinal detachment (n=13). Of these, 26 proteins could differentiate between these vitreoretinal diseases. Based on Partial least squares discriminant and multivariate exploratory receiver operating characteristic (ROC) analyses, a panel of 15 discriminatory biomarkers was defined, which includes complement and coagulation components (complement C2 and prothrombin), acute-phase mediators (alpha-1-antichymotrypsin), adhesion molecules (e.g., myocilin, galectin-3-binding protein), ECM components (opticin), and neurodegeneration biomarkers (beta-amyloid, amyloid-like protein 2).

Vitreous Humor: Composition, Characteristics and Implication on Intravitreal Drug Delivery

Purpose: Intravitreal administration of drug molecules is one of the most common routes for treating posterior segment eye diseases. However, the properties of vitreous humour changes with the time. A number of ocular complications such as liquefaction of the vitreous humour, solidification of the vitreous humour in the central vitreous cavity and detachment of the limiting membrane due to the shrinking of vitreous humour are some of the factors that can drastically affect the efficacy of therapeutics delivered via intravitreal route. Although significant research has been conducted for studying the properties of vitreous humour and its changes during the ageing process, there have been limited work to understand the effect of these changes on therapeutic efficacy of intravitreal drug delivery systems. Therefore, in this review we discussed both the coomposition and characteristics of the vitreous humour, and their subsequent influence on intravitreal drug delivery.Methods: Articles were searched on Scopus, PubMed and Web of Science up to March 2022.Results: In this review, we discussed the biological composition and biomechanical properties of vitreous humour, methods to study the properties of vitreous humour and the changes in these properties and their relevance in ocular drug delivery field, with the aim to provide a useful insight into these aspects which can aid the process of development of novel intravitreal drug delivery systems.Conclusions: The composition and characteristics of the vitreous humour, and how these change during natural aging processes, directly influence intravitreal drug delivery. This review therefore highlights the importance of understanding the properties of the vitreous and identifies the need to achieve greater understanding of how changing properties of the vitreous affect the therapeutic efficacy of drugs administered for the treatment of posterior eye diseases.

Probable Treatment Targets for Diabetic Retinopathy Based on an Integrated Proteomic and Genomic Analysis

Purpose

Using previously approved medications for new indications can expedite the lengthy and expensive drug development process. We describe a bioinformatics pipeline that integrates genomics and proteomics platforms to identify already-approved drugs that might be useful to treat diabetic retinopathy (DR).

Methods

Proteomics analysis of vitreous humor samples from 12 patients undergoing pars plana vitrectomy for DR and a whole genome dataset (UKBiobank TOPMed-imputed) from 1330 individuals with DR and 395,155 controls were analyzed independently to identify biological pathways associated with DR. Common biological pathways shared between both datasets were further analyzed (STRING and REACTOME analyses) to identify target proteins for probable drug modulation. Curated target proteins were subsequently analyzed by the BindingDB database to identify chemical compounds they interact with. Identified chemical compounds were further curated through the Expasy SwissSimilarity database for already-approved drugs that interact with target proteins.

Results

The pathways in each dataset (proteomics and genomics) converged in the upregulation of a previously unknown pathway involved in DR (RUNX2 signaling; constituents MMP-13 and LGALS3), with an emphasis on its role in angiogenesis and blood-retina barrier. Bioinformatics analysis identified U.S. Food and Drug Administration (FDA)-approved medications (raltitrexed, pemetrexed, glyburide, probenecid, clindamycin hydrochloride, and ticagrelor) that, in theory, may modulate this pathway.

Conclusions

The bioinformatics pipeline described here identifies FDA-approved drugs that can be used for new alternative indications. These theoretical candidate drugs should be validated with experimental studies.

Translational Relevance

Our study suggests possible drugs for DR treatment based on an integrated proteomics and genomics pipeline. This approach can potentially expedite the drug discovery process by identifying already-approved drugs that might be used for new indications.

Proliferative diabetic retinopathy and diabetic macular edema are two factors that increase macrophage-like cell density characterized by en face optical coherence tomography

BACKGROUND

Macrophage-like cells (MLCs) located at the ILM were observed in live human retinas using adaptive optics optical coherence tomography (OCT) as well as clinically-used OCT. The study aimed to quantitatively analyzing MLCs at the vitreoretinal interface (VRI) in diabetic retinopathy (DR) using en face OCT and swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

190 DR eyes were included in the study, with 70 proliferative diabetic retinopathy (PDR) eyes and 120 non- proliferative diabetic retinopathy (NPDR) eyes. Sixty-three eyes from normal subjects were included as controls. MLCs were visualized in a 5 μm en face OCT slab above the VRI centered on the fovea. Mann-Whitney U test and Kruskal-Wallis H test were used to compare the OCTA parameters and the MLC parameters among groups. We evaluated the MLC density among groups on binarized images after image processing. We also investigated the relationship between MLC density and other OCT parameters including retina thickness and vessel density (VD).

RESULTS

The MLC density significantly increased in PDR eyes (PDR vs. NPDR, 8.97 (8.40) cells/mm² vs.6.14 (8.78) cells/mm², P = 0.013; PDR vs. normal, 8.97 (8.40) cells/mm²vs. 6.48 (6.71) cells/mm², P = 0.027) and diabetic macular edema (DME) eyes (DME vs. without DME, 8.94 (8.26) vs.6.09 (9.00), P = 0.005). After adjusting for age and gender, MLC density in NPDR eyes negatively correlated to VD of deep capillary plexus (DCP) (P = 0.01).

CONCLUSIONS

SS-OCTA is a non-invasive and simple method for the characterization of MLCs at the VRI. PDR and DME are two factors that increase MLC density. MLC density also correlated with VD.

Diabetic Retinopathy: Soluble and Imaging Ocular Biomarkers

Diabetic retinopathy (DR), the most common microvascular complication of diabetes mellitus, represents the leading cause of acquired blindness in the working-age population. Due to the potential absence of symptoms in the early stages of the disease, the identification of clinical biomarkers can have a crucial role in the early diagnosis of DR as well as for the detection of prognostic factors. In particular, imaging techniques are fundamental tools for screening, diagnosis, classification, monitoring, treatment planning and prognostic assessment in DR. In this context, the identification of ocular and systemic biomarkers is crucial to facilitate the risk stratification of diabetic patients; moreover, reliable biomarkers could provide prognostic information on disease progression as well as assist in predicting a patient's response to therapy. In this context, this review aimed to provide an updated and comprehensive overview of the soluble and anatomical biomarkers associated with DR.

Mass Spectrometry-Based Vitreous Proteomics: Validated Methods and Analysis Pipeline

Retinal diseases like diabetic retinopathy and age-related macular degeneration affect millions of individuals worldwide and often lead to vision loss. Vitreous fluid abuts the retina, is accessible for sampling, and contains many proteins related to retinal disease. Therefore, analysis of vitreous is an important tool for studying retinal disease. Because it is rich in proteins and extracellular vesicles, mass spectrometry-based proteomics is an excellent method for vitreous analysis. Here, we discuss important variables to consider when performing vitreous proteomics via mass spectrometry.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

Essential Role of Multi-Omics Approaches in the Study of Retinal Vascular Diseases

Retinal vascular disease is a highly prevalent vision-threatening ocular disease in the global population; however, its exact mechanism remains unclear. The expansion of omics technologies has revolutionized a new medical research methodology that combines multiple omics data derived from the same patients to generate multi-dimensional and multi-evidence-supported holistic inferences, providing unprecedented opportunities to elucidate the information flow of complex multi-factorial diseases. In this review, we summarize the applications of multi-omics technology to further elucidate the pathogenesis and complex molecular mechanisms underlying retinal vascular diseases. Moreover, we proposed multi-omics-based biomarker and therapeutic strategy discovery methodologies to optimize clinical and basic medicinal research approaches to retinal vascular diseases. Finally, the opportunities, current challenges, and future prospects of multi-omics analyses in retinal vascular disease studies are discussed in detail.

Multitarget Activities of Müller Glial Cells and Low-Density Lipoprotein Receptor-Related Protein 1 in Proliferative Retinopathies

Müller glial cells (MGCs), the main glial component of the retina, play an active role in retinal homeostasis during development and pathological processes. They strongly monitor retinal environment and, in response to retinal imbalance, activate neuroprotective mechanisms mainly characterized by the increase of glial fibrillary acidic protein (GFAP). Under these circumstances, if homeostasis is not reestablished, the retina can be severely injured and GFAP contributes to neuronal degeneration, as they occur in several proliferative retinopathies such as diabetic retinopathy, sickle cell retinopathy and retinopathy of prematurity. In addition, MGCs have an active participation in inflammatory responses releasing proinflammatory mediators and metalloproteinases to the extracellular space and vitreous cavity. MGCs are also involved in the retinal neovascularization and matrix extracellular remodeling during the proliferative stage of retinopathies. Interestingly, low-density lipoprotein receptor-related protein 1 (LRP1) and its ligand α₂-macroglobulin (α₂M) are highly expressed in MGCs and they have been established to participate in multiple cellular and molecular activities with relevance in retinopathies. However, the exact mechanism of regulation of retinal LRP1 in MGCs is still unclear. Thus, the active participation of MGCs and LRP1 in these diseases, strongly supports the potential interest of them for the design of novel therapeutic approaches. In this review, we discuss the role of LRP1 in the multiple MGCs activities involved in the development and progression of proliferative retinopathies, identifying opportunities in the field that beg further research in this topic area.Summary StatementMGCs and LRP1 are active players in injured retinas, participating in key features such as gliosis and neurotoxicity, neovascularization, inflammation, and glucose control homeostasis during the progression of ischemic diseases, such as proliferative retinopathies.

Integrated bioinformatics analysis for novel miRNAs markers and ceRNA network in diabetic retinopathy

In order to seek a more outstanding diagnosis and treatment of diabetic retinopathy (DR), we predicted the miRNA biomarkers of DR and explored the pathological mechanism of DR through bioinformatics analysis.

Method: Based on public omics data and databases, we investigated ncRNA (non-coding RNA) functions based on the ceRNA hypothesis.

Result: Among differentially expressed miRNAs (DE-miRNAs), hsa-miR-1179, -4797-3p and -665 may be diagnosis biomarkers of DR. Functional enrichment analysis revealed differentially expressed mRNAs (DE-mRNAs) enriched in mitochondrial transport, cellular respiration and energy derivation. 18 tissue/organ-specific expressed genes, 10 hub genes and gene cluster modules were identified. The ceRNA networks lncRNA FBXL19-AS1/miR-378f/MRPL39 and lncRNA UBL7-AS1/miR-378f/MRPL39 might be potential RNA regulatory pathways in DR.

Conclusion: Differentially expressed hsa-miR-1179, -4797-3p and -665 can be used as powerful markers for DR diagnosis, and the ceRNA network: lncRNA FBXL19-AS1/UBL7-AS1-miR-378f-MRPL39 may represent an important regulatory role in DR progression.

Hyalocytes in proliferative vitreo-retinal diseases

Introduction

Hyalocytes are sentinel macrophages residing within the posterior vitreous cortex anterior to the retinal inner limiting membrane (ILM). Following anomalous PVD and vitreoschisis, hyalocytes contribute to paucicellular (vitreo-macular traction syndrome, macular holes) and hypercellular (macular pucker, proliferative vitreo-retinopathy, proliferative diabetic vitreo-retinopathy) diseases.

Areas covered

Studies of human tissues employing dark-field, phase, and electron microscopy; immunohistochemistry; and in vivo imaging of human hyalocytes.

Expert opinion

Hyalocytes are important in early pathophysiology, stimulating cell migration and proliferation, as well as subsequent membrane contraction and vitreo-retinal traction. Targeting hyalocytes early could mitigate advanced disease. Ultimately, eliminating the role of vitreous and hyalocytes may prevent proliferative vitreo-retinal diseases entirely.

Molecules related to diabetic retinopathy in the vitreous and involved pathways

Diabetic retinopathy (DR) is one of the most common complications of diabetes and major cause of blindness among people over 50 years old. Current studies showed that the vascular endothelial growth factor (VEGF) played a central role in the pathogenesis of DR, and application of anti-VEGF has been widely acknowledged in treatment of DR targeting retinal neovascularization. However, anti-VEGF therapy has several limitations such as drug resistance. It is essential to develop new drugs for future clinical practice. The vitreous takes up 80% of the whole globe volume and is in direct contact with the retina, making it possible to explore the pathogenesis of DR by studying related factors in the vitreous. This article reviewed recent studies on DR-related factors in the vitreous, elaborating the VEGF upstream hypoxia-inducible factor (HIF) pathway and downstream pathways phosphatidylinositol diphosphate (PIP2), phosphoinositide-3-kinase (PI3K), and mitogen-activated protein kinase (MAPK) pathways. Moreover, factors other than VEGF contributing to the pathogenesis of DR in the vitreous were also summarized, which included factors in four major systems, kallikrein-kinin system such as bradykinin, plasma kallikrein, and coagulation factor XII, oxidative stress system such as lipid peroxide, and superoxide dismutase, inflammation-related factors such as interleukin-1β/6/13/37, and interferon-γ, matrix metalloproteinase (MMP) system such as MMP-9/14. Additionally, we also introduced other DR-related factors such as adiponectin, certain specific amino acids, non-coding RNA and renin (pro) receptor in separate studies.

Gene Biomarkers Related to Th17 Cells in Macular Edema of Diabetic Retinopathy: Cutting-Edge Comprehensive Bioinformatics Analysis and In Vivo Validation

Background

Previous studies have shown that T-helper 17 (Th17) cell-related cytokines are significantly increased in the vitreous of proliferative diabetic retinopathy (PDR), suggesting that Th17 cells play an important role in the inflammatory response of diabetic retinopathy (DR), but its cell infiltration and gene correlation in the retina of DR, especially in diabetic macular edema (DME), have not been studied.

Methods

The dataset GSE160306 was downloaded from the Gene Expression Omnibus (GEO) database, which contains 9 NPDR samples and 10 DME samples. ImmuCellAI algorithm was used to estimate the abundance of Th17 cells in 24 kinds of infiltrating immune cells. The differentially expressed Th17 related genes (DETh17RGs) between NPDR and DME were documented by difference analysis and correlation analysis. Through aggregate analyses such as gene ontology (GO) and Kyoto Encyclopedia of Gene and Genome (KEGG) pathway enrichment analysis, a protein-protein interaction (PPI) network was constructed to analyze the potential function of DETh17RGs. CytoHubba plug-in algorithm, Lasso regression analysis and support vector machine recursive feature elimination (SVM-RFE) were implemented to comprehensively identify Hub DETh17RGs. The expression archetypes of Hub DETh17RGs were further verified in several other independent datasets related to DR. The Th17RG score was defined as the genetic characterization of six Hub DETh17RGs using the GSVA sample score method, which was used to distinguish early and advanced diabetic nephropathy (DN) as well as normal and diabetic nephropathy. Finally, real-time quantitative PCR (qPCR) was implemented to verify the transcription levels of Hub DETh17RGs in the STZ-induced DR model mice (C57BL/6J).

Results

238 DETh17RGs were identified, of which 212 genes were positively correlated while only 26 genes were negatively correlated. Six genes (CD44, CDC42, TIMP1, BMP7, RHOC, FLT1) were identified as Hub DETh17RGs. Because DR and DN have a strong correlation in clinical practice, the verification of multiple independent datasets related to DR and DN proved that Hub DETh17RGs can not only distinguish PDR patients from normal people, but also distinguish DN patients from normal people. It can also identify the initial and advanced stages of the two diseases (NPDR vs DME, Early DN vs Advanced DN). Except for CDC42 and TIMP1, the qPCR transcription levels and trends of other Hub DETh17RGs in STZ-induced DR model mice were consistent with the human transcriptome level in this study.

Conclusion

This study will improve our understanding of Th17 cell-related molecular mechanisms in the progression of DME. At the same time, it also provides an updated basis for the molecular mechanism of Th17 cell crosstalk in the eye and kidney in diabetes.

Risk of glaucoma after vitreoretinal surgery - Findings from a population-based cohort study

PURPOSE

To investigate the association between different types of vitrectomy and risk of different types of glaucoma and to determine the effect of systemic medication and diabetes status on this risk.

METHODS

A population-based nested case-control study included individuals of age ≥ 18 years who had undergone single vitrectomy, vitrectomy with retinal procedure, or combined phaco-vitrectomy between 2001 and 2010. End of follow-up was 2017. Odds ratio (OR) for the development of glaucoma after different types of vitrectomy and 95% confidence interval (CI) were based on conditional logistic regression models. For every glaucoma case, five controls were matched by age, sex, start of follow-up year, and hospital district.

RESULTS

The cohort (n = 37 687), of which 52.8% was female, consisted of 6552 individuals diagnosed with glaucoma and 31 135 controls matched by age, sex, and hospital district. Vitrectomy was performed on 103 eyes in the glaucoma group and 158 eyes in the control group. As regards the risk of any glaucoma, the risk was lowest in eyes that underwent combined phaco-vitrectomy (OR: 2.7, 95% CI: 1.8-4.1), followed by single vitrectomy (OR: 3.15, 95% CI: 2.1-4.8), and highest in eyes that underwent vitrectomy with retinal procedure (OR: 4.5, 95% CI: 2.7-7.4). Diabetes had no effect (OR: 0.96, 95% CI: 0.92-1.01), but 5-year systemic statin use slightly decreased glaucoma risk (OR: 0.86, 95% CI: 0.77-0.97).

CONCLUSIONS

Vitreoretinal surgery was associated with an increased glaucoma risk; the risk being related to the complexity of vitrectomy. Long-term systemic statin therapy may decrease glaucoma risk, while diabetes had no association.

Proteome changes associated with the VEGFR pathway and immune system in diabetic macular edema patients at different diabetic retinopathy stages

PURPOSE

Diabetic macular edema (DME) is a major cause of vision loss in all stages of diabetic retinopathy (DR). However, there is limited recognition of aqueous humor (AH) proteome profiles of DME patients at different DR stages. In this study, we aimed to investigate the AH proteome changes between DME patients at the nonproliferative diabetic retinopathy (NPDR) stage and those at the proliferative diabetic retinopathy (PDR) stage.

METHODS

A label-free data-independent acquisition based liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis was performed to profile the abundances of AH proteins in 73 eyes from DME patients at different DR stages. Enzyme-linked immunosorbent assay (ELISA) was used to confirm the proteomics results with AH samples from non-diabetic patients and DME patients at the NPDR or PDR stage.

RESULTS

LC-MS/MS results showed significantly changed expression of 308 proteins between DME patients in the NPDR and PDR groups. Compared to the NPDR group, the proteins relatively up-regulated in the PDR group are involved in the immune system and/or negative regulation of the cell cycle, while proteins relatively down-regulated in the PDR group are associated with the vascular endothelial growth factor receptor (VEGFR) pathway and/or metabolism. ELISA results further verified the proteomic result of down-regulated expression of the immune-associated protein cystatin C (CST3) in the PDR group compared to that in the NPDR and non-diabetic groups.

CONCLUSIONS

In this study, we reported for the first time the decreased abundances of AH proteins associated with the VEGFR pathway and both down- and up-regulated expression of AH proteins associated with the immune system in the PDR group compared to that in the NPDR group. Furthermore, we found negative correlations of immune-associated protein, CST3 concentration in AH with DR severity and central retinal thickness, suggesting CST3 as a promising target independent of the VEGFR pathway in DME-involved DR treatment.

Systemic and vitreous biomarkers - new insights in diabetic retinopathy

PURPOSE

Diabetic retinopathy (DR) is a microvascular inflammatory and neurodegenerative disease. The purpose of this study was to analyze the relationship between DR severity and the levels of potential biomarkers in the serum and/or vitreous.

METHODS

A prospective, consecutive, controlled, observational study was performed between June 2018 and January 2020. Blood and vitreous samples were collected on the day of vitrectomy in patients without diabetes and in patients with diabetes with epiretinal membrane, macular edema, and indication for vitrectomy.

RESULTS

Transthyretin (TTR) was the only blood biomarker with levels statistically higher in patients with diabetes (p = 0.037). However, no correlation with DR severity was observed. Erythropoietin (EPO) was the only blood biomarker whose levels were associated with DR severity (p = 0.036). In vitreous samples, levels of EPO (p = 0.011), interleukin (IL)-6 (p < 0.001), IL-8 (p < 0.001), IL-17 (p = 0.022), monokine induced by interferon-γ (MIG) (p < 0.001), and interferon gamma-induced protein 10 (IP-10) (p = 0.005) were significantly higher in patients with diabetes. Additionally, in vitreous, IL-6, IL-8, MIG, and IPL-10 levels were also higher in more severe DR cases (p < 0.05).

CONCLUSIONS

Among the studied biomarkers, vitreous IL-6, IL-8, MIG, and IP-10 were the ones whose levels had the strongest coherent relationship with DR severity prediction and, thus, have the best potential post-vitrectomy prognostic value.

Vitreous Humor Proteome: Targeting Oxidative Stress, Inflammation, and Neurodegeneration in Vitreoretinal Diseases

Oxidative stress is defined as an unbalance between pro-oxidants and antioxidants, as evidenced by an increase in reactive oxygen and reactive nitrogen species production over time. It is important in the pathophysiology of retinal disorders such as diabetic retinopathy, age-related macular degeneration, retinal detachment, and proliferative vitreoretinopathy, which are the focus of this article. Although the human organism's defense mechanisms correct autoxidation caused by endogenous or exogenous factors, this may be insufficient, causing an imbalance in favor of excessive ROS production or a weakening of the endogenous antioxidant system, resulting in molecular and cellular damage. Furthermore, modern lifestyles and environmental factors contribute to increased chemical exposure and stress induction, resulting in oxidative stress. In this review, we discuss the current information about oxidative stress and the vitreous proteome with a special focus on vitreoretinal diseases. Additionally, we explore therapies using antioxidants in an attempt to rescue the body from oxidation, restore balance, and maximize healthy body function, as well as new investigational therapies that have shown significant therapeutic potential in preclinical studies and clinical trial outcomes, along with their goals and strategic approaches to combat oxidative stress.

Recent developments of neuroprotective agents for degenerative retinal disorders

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons, which are caused by a group of retinal diseases affecting various age groups, and increasingly prevalent in the elderly. Age-related macular degeneration, diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders, posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics. Whilst pathoetiologies vary, if left untreated, loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment. Irrespective of underlined etiology, loss of neurons and supporting cells including retinal pigment epithelium, microvascular endothelium, and glia, converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation. This review overviews recent developments of potential neuroprotectants including neuropeptides, exosomes, mitochondrial-derived peptides, complement inhibitors, senolytics, autophagy enhancers and antioxidants either still experimentally or in clinical trials. Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.

Proteomic changes of aqueous humor in proliferative diabetic retinopathy patients treated with different intravitreal anti-VEGF agents

Anti-VEGF-based treatment have been regularly used in recent years in proliferative diabetic retinopathy (PDR) patients. However, some of these patients fail to respond effectively to anti-VEGF. Given that VEGF is not the sole factor influencing PDR pathogenesis and that different anti-VEGF pharmaceuticals are likely to differentially impact these underlying pathophysiological processes, we performed a prospective analysis of the protein profiles of the aqueous humor (AH) in PDR patients before and after treatment with three intravitreal anti-VEGF drugs (ranibizumab, aflibercept, and conbercept) to assess and compare the short-term impacts of these agents. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic methods were used to evaluate the AH protein profiles of PDR patients using paired pre- and 7 days post-anti-VEGF treatment samples (ranibizumab [IVR]: n = 10; conbercept [IVC]: n = 10; aflibercept [IVA]: n = 5). Gene ontology (GO) annotation, KEGG pathway analyses, and protein-protein interaction (PPI) networks were then used to explore the functional relevance of proteins that were differentially expressed between groups. Here, a total of 874 proteins from 25 patients (50 AH samples) were identified in the three patient groups. Different and common clusters of regulated proteins for each group were identified. We identified RARRES1, ALDH3A1, and RBP4 as being specifically regulated following treatment with all three tested anti-VEGF agents. We further found that VEGFR1, VEGFR2, APOM, hornerin, and HSP90B1 were differentially expressed in different anti-VEGF agent groups. In summary, we discovered that ALDH3A1 was a previously unreported protein that was related to angiogenesis and was differentially expressed in the three anti-VEGF treatment groups, suggesting that it may be a new target for PDR therapy. The described proteomic changes in the AH of PDR patients treated with different anti-VEGF agents provide novel targets which may explain the heterogeneity of anti-VEGF treatment responses in these patients, providing a robust foundation for future studies of PDR pathogenesis.

A validated analysis pipeline for mass spectrometry-based vitreous proteomics: new insights into proliferative diabetic retinopathy

Background

Vitreous is an accessible, information-rich biofluid that has recently been studied as a source of retinal disease-related proteins and pathways. However, the number of samples required to confidently identify perturbed pathways remains unknown. In order to confidently identify these pathways, power analysis must be performed to determine the number of samples required, and sample preparation and analysis must be rigorously defined.

Methods

Control (n = 27) and proliferative diabetic retinopathy (n = 23) vitreous samples were treated as biologically distinct individuals or pooled together and aliquoted into technical replicates. Quantitative mass spectrometry with tandem mass tag labeling was used to identify proteins in individual or pooled control samples to determine technical and biological variability. To determine effect size and perform power analysis, control and proliferative diabetic retinopathy samples were analyzed across four 10-plexes. Pooled samples were used to normalize the data across plexes and generate a single data matrix for downstream analysis.

Results

The total number of unique proteins identified was 1152 in experiment 1, 989 of which were measured in all samples. In experiment 2, 1191 proteins were identified, 727 of which were measured across all samples in all plexes. Data are available via ProteomeXchange with identifier PXD025986. Spearman correlations of protein abundance estimations revealed minimal technical (0.99–1.00) and biological (0.94–0.98) variability. Each plex contained two unique pooled samples: one for normalizing across each 10-plex, and one to internally validate the normalization algorithm. Spearman correlation of the validation pool following normalization was 0.86–0.90. Principal component analysis revealed stratification of samples by disease and not by plex. Subsequent differential expression and pathway analyses demonstrated significant activation of metabolic pathways and inhibition of neuroprotective pathways in proliferative diabetic retinopathy samples relative to controls.

Conclusions

This study demonstrates a feasible, rigorous, and scalable method that can be applied to future proteomic studies of vitreous and identifies previously unrecognized metabolic pathways that advance understanding of diabetic retinopathy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-021-09328-8.

Proliferative diabetic retinopathy transcriptomes reveal angiogenesis, anti-angiogenic therapy escape mechanisms, fibrosis and lymphatic involvement

Proliferative diabetic retinopathy (PDR) is a sight-threatening diabetic complication in urgent need of new therapies. In this study we identify potential molecular mechanisms and target candidates in the pathogenesis of PDR fibrovascular tissue formation. We performed mRNA sequencing of RNA isolated from eleven excised fibrovascular membranes of type 1 diabetic PDR patients and two non-diabetic patients with rhegmatogenous retinal detachment with proliferative vitreoretinopathy. We determined differentially expressed genes between these groups and performed pathway and gene ontology term enrichment analyses to identify potential underlying mechanisms, pathways, and regulators. Multiple pro-angiogenic processes, including VEGFA-dependent and -independent pathways, as well as processes related to lymphatic development, epithelial to mesenchymal transition (EMT), wound healing, inflammation, fibrosis, and extracellular matrix (ECM) composition, were overrepresented in PDR. Overrepresentation of different angiogenic processes may help to explain the transient nature of the benefits that many patients receive from current intravitreal anti-angiogenic therapies, highlighting the importance of combinatorial treatments. Enrichment of genes and pathways related to lymphatic development indicates that targeting lymphatic involvement in PDR progression could have therapeutic relevance. Together with overrepresentation of EMT and fibrosis as well as differential ECM composition, these findings demonstrate the complexity of PDR fibrovascular tissue formation and provide avenues for the development of novel treatments.

Integrating SWATH-MS proteomics and transcriptome analysis to preliminarily identify three DEGs as biomarkers for proliferative diabetic retinopathy

PURPOSE

We intended to preliminarily find differentially expressed proteins that play crucial roles in proliferative diabetic retinopathy (PDR), and lay the foundation for subsequent further research on the mechanism.

EXPERIMENTAL DESIGN

Here, we developed a new strategy integrated the sequential windowed acquisition of all theoretical fragment ion (SWATH) mass spectra (MS) with multi-dataset joint analysis to screen for the PDR plasma biomarker. The annotation of the given gene list was performed with ClueGO function analysis. Additionally, the protein-protein interaction relationship was also revealed by the STRING database.

RESULTS

In SWATH-MS assays, we identified 23 upregulated and 13 downregulated proteins in PDR plasma. In the mRNA database analysis, 375 genes were identified as differentially expressed genes in GSE102485. Only three genes (FCGR3A, DPEP2, and ADGRF5) were characterized as upregulated in both the dataset and the SWATH-MS list. The area under the ROC curve (AUC) of FCGR3A, DPEP2, and ADGRF5 in distinguishing PDR from others was 0.739, 0.770, and 0.739.

CONCLUSIONS AND CLINICAL RELEVANCE

We provide a novel strategy for biomarker screening and identified plasma FCGR3A, DPEP2, and ADGRF5 as potential biomarkers for patients with PDR. Identifying the key molecules of the disease is essential for the development of new therapeutic molecules and new uses of existing drugs.

Proteomics of Vitreous Humor Reveals PPARA, RXR, and LXR Are Possible Upstream Regulators of Proliferative Diabetic Retinopathy

Purpose: To investigate the key regulators of the disease by comparing the abundance of vitreous proteins between the patients with proliferative diabetic retinopathy (PDR) and the controls with idiopathic epiretinal membrane (iERM).

Methods: Vitreous humor (VH) samples were derived from patients with PDR or iERM through the pars plana vitrectomy. The VH proteins were identified by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. MaxQuant software and Metascape were applied to explore the enrichment of differentially expressed proteins in biological processes, cellular components, and molecular functions. Enrichr online tool and Gene Set Enrichment Analysis (GSEA) were performed to detect upstream transcriptional regulators of the highly expressed proteins.

Results: The present study collected 8 vitreous humor samples from 5 PDR eyes and 3 iERM eyes and identified 88 highly expressed proteins in PDR patients. We validated our highly expressed proteome was able to distinguish the PDR patients from the non-PDR patients by using the VH proteomics data from a previous study. The majority of highly expressed proteins were involved in complement and coagulation cascades, regulating exocytosis, and hemostasis. Using the Gene Set Enrichment Analysis (GSEA), we identified that transcription factors (TFs) PPAR-α, RXR, LXR regulate these proteins.

Conclusions: In this study, we identified a highly expressed proteome in VH of PDR patients. The role of the complement and coagulation system, regulating exocytosis, and hemostasis has been of great significance to PDR. Nuclear receptors PPARA, RXR, LXR were possible upstream regulators of disease progression and required further study.

The Vitreous Ecosystem in Diabetic Retinopathy: Insight into the Patho-Mechanisms of Disease

Diabetic retinopathy is one of the leading causes of blindness in the world with the incidence of disease ever-increasing worldwide. The vitreous humor represents an extensive and complex interactive arena for cytokines in the diabetic eye. In recent decades, there has been significant progress in understanding this environment and its implications in disease pathophysiology. In this review, we investigate the vitreous ecosystem in diabetic retinopathy at the molecular level. Areas of concentration include: the current level of knowledge of growth factors, cytokine and chemokine mediators, and lipid-derived metabolites in the vitreous. We discuss the molecular patho-mechanisms of diabetic retinopathy based upon current vitreous research.

Comprehensive Proteomic Profiling of Aqueous Humor Proteins in Proliferative Diabetic Retinopathy

Purpose

Proliferative diabetic retinopathy (PDR) is a serious ocular disease that can lead to retinal microvascular complications in patients with diabetes mellitus. To date, no studies have explored PDR development by analyzing the aqueous humor (AH). Therefore we carried out tandem mass tag (TMT) proteomic quantification to compare AH protein profiles between PDR and non-PDR subjects.

Methods

We enrolled six PDR and six control (senile cataract) subjects. AH samples were collected during surgery and stored at –80°C. Proteins were extracted, trypsin-digested, and labeled with TMTs for mass spectrometric analysis.

Results

We found 191 proteins to be changed with |log₂ (fold change)| ≥1 (P < 0.05 and identification with at least two peptides per protein). Of them, 111 were downregulated, whereas 80 were upregulated in the PDR group. Proteomic bioinformatic analysis indicated that PDR development was related to complement and coagulation cascades, platelet activation, extracellular matrix–receptor interaction, focal adhesion, protein digestion and absorption, human papillomavirus infection, PI3K-Akt signaling pathway, cholesterol metabolism, peroxisome proliferator-activated receptor signaling pathways, fat digestion and absorption, and vitamin digestion and absorption pathways.

Conclusions

Comprehensive proteomic profiling of the AH revealed 191 differentially expressed proteins between the two groups. Most of these proteins belong to secretory pathways, and therefore can be used as biomarkers in clinical testing and basic research.

Translational Relevance

Pathway analysis and a review of the literature enabled us to draw a novel biological map that will support further studies on the underlying mechanisms and therapeutic control of PDR development.

Peroxiredomin-4 ameliorates lipotoxicity-induced oxidative stress and apoptosis in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM), one severe complication in the diabetes, leads to high mortality in the diabetic patients. However, the understanding of molecular mechanisms underlying DCM is far from completion. Herein, we investigated the disease-related differences in the proteomes of DCM based on db/db mice and verified the protective roles of peroxiredoxin-4 (Prdx4) in H9c2 cardiomyocytes treated by palmitic acid (PA). Fasting blood glucose (FBG) and cardiac function was detected in the 6-month-old control and diabetic mice. The hearts were then collected and analyzed by a coupled label-free and mass spectrometry approach. In vivo investigation indicated that body weight and FBG of db/db mice markedly increased, and diabetic heart exhibited obvious cardiac hypertrophy and lipid droplet accumulation, and cardiac dysfunction as is indicated by the increases of left ventricle posterior wall thickness in systole (LVPWd) and diastole (LVPWs), and reduction of fractional shortening (FS). We used proteomic analysis and then detected a grand total of 2636 proteins. 175 differentially expressed proteins (DEPs) were markedly detected in the diabetic heart. Thereinto, Prdx4 was markedly down-regulated in the diabetic heart. In vitro experiments revealed that 250 μM PA significantly inhibited viability of H9c2 cell. PA induced much accumulation of lipid droplet in cardiomyocytes and resulted in an increase of mRNA expressions of lipogenic genes (FASN and SCD1) and cardiac hypertrophic genes. Additionally, protein level of Prdx4 evidently reduced in the PA-treated H9c2 cell. It was further found that shRNA-mediated Prdx4 knockdown exacerbated PA-induced oxidative stress and cardiomyocyte apoptosis, whereas overexpressing Prdx4 in the H9c2 cells noteworthily limited PA-induced ROS generation and cardiomyocytes apoptosis. These data collectively reveal the essential role of abnormal Prdx4 in pathological alteration of DCM, and provide potentially therapeutic target for the prevention of DCM.

Skeletal muscle proteomes reveal downregulation of mitochondrial proteins in transition from prediabetes into type 2 diabetes

Skeletal muscle insulin resistance is a central defect in the pathogenesis of type 2 diabetes (T2D). Here, we analyzed skeletal muscle proteome in 148 vastus lateralis muscle biopsies obtained from men covering all glucose tolerance phenotypes: normal, impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and T2D. Skeletal muscle proteome was analyzed by a sequential window acquisition of all theoretical mass spectra (SWATH-MS) proteomics technique. Our data indicate a downregulation in several proteins involved in mitochondrial electron transport or respiratory chain complex assembly already in IFG and IGT muscles, with most profound decreases observed in T2D. Additional phosphoproteomic analysis reveals altered phosphorylation in several signaling pathways in IFG, IGT, and T2D muscles, including those regulating glucose metabolic processes, and the structure of muscle cells. These data reveal several alterations present in skeletal muscle already in prediabetes and highlight impaired mitochondrial energy metabolism in the trajectory from prediabetes into T2D.

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Skeletal muscle proteome from men with all stages of glucose tolerance was analyzed

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Phosphoproteomics reveal altered phosphorylation in IFG, IGT, and T2D muscles

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OXPHOS proteins are decreased in prediabetic muscles, with most decrease in T2D

Proteomic Analyses of Vitreous in Proliferative Diabetic Retinopathy: Prior Studies and Future Outlook

Vitreous fluid is becoming an increasingly popular medium for the study of retinal disease. Numerous studies have demonstrated that proteomic analysis of the vitreous from patients with proliferative diabetic retinopathy yields valuable molecular information regarding known and novel proteins and pathways involved in this disease. However, there is no standardized methodology for vitreous proteomic studies. Here, we share a suggested protocol for such studies and outline the various experimental and analytic methods that are currently available. We also review prior mass spectrometry-based proteomic studies of the vitreous from patients with proliferative diabetic retinopathy, discuss common pitfalls of these studies, and propose next steps for moving the field forward.

Diabetes Induced Alterations in Murine Vitreous Proteome Are Mitigated by IL-6 Trans-Signaling Inhibition

Purpose

Diabetic retinopathy (DR) is a microvascular complication caused by prolonged hyperglycemia and characterized by leaky retinal vasculature and ischemia-induced angiogenesis. Vitreous humor is a gel-like biofluid in the posterior segment of the eye between the lens and the retina. Disease-related changes are observed in the biochemical constituents of the vitreous, including proteins and macromolecules. Recently, we found that IL-6 trans-signaling plays a significant role in the vascular leakage and retinal pathology associated with DR. Therefore, in this study, comprehensive proteomic profiling of the murine vitreous was performed to identify diabetes-induced alterations and to determine effects of IL-6 trans-signaling inhibition on these changes.

Methods

Vitreous samples from mice were collected by evisceration, and proteomic analyses were performed using liquid chromatography–tandem mass spectrometry (LC-MS/MS).

Results

A total of 154 proteins were identified with high confidence in control mice and were considered to be characteristic of healthy murine vitreous fluid. The levels of 72 vitreous proteins were significantly altered in diabetic mice, including several members of heat shock proteins, 14-3-3 proteins, and tubulins. Alterations in 52 out of 72 proteins in diabetic mice were mitigated by IL-6 trans-signaling inhibition.

Conclusions

Proteomic analysis of murine vitreous fluid performed in this study provides important information about the changes caused by diabetes in the ocular microenvironment. These diabetes-induced alterations in the murine vitreous proteome were mitigated by IL-6 trans-signaling inhibition. These findings further support that IL-6 trans-signaling may be an important therapeutic target for the treatment of DR.