Proteins involved in focal adhesion signaling pathways are differentially regulated in experimental branch retinal vein occlusion

Integrated Proteomics Analysis of Baseline Protein Expression in Pig Tissues

The availability of an increasingly large amount of public proteomics data sets presents an opportunity for performing combined analyses to generate comprehensive organism-wide protein expression maps across different organisms and biological conditions. Sus scrofa, a domestic pig, is a model organism relevant for food production and for human biomedical research. Here, we reanalyzed 14 public proteomics data sets from the PRIDE database coming from pig tissues to assess baseline (without any biological perturbation) protein abundance in 14 organs, encompassing a total of 20 healthy tissues from 128 samples. The analysis involved the quantification of protein abundance in 599 mass spectrometry runs. We compared protein expression patterns among different pig organs and examined the distribution of proteins across these organs. Then, we studied how protein abundances were compared across different data sets and studied the tissue specificity of the detected proteins. Of particular interest, we conducted a comparative analysis of protein expression between pig and human tissues, revealing a high degree of correlation in protein expression among orthologs, particularly in brain, kidney, heart, and liver samples. We have integrated the protein expression results into the Expression Atlas resource for easy access and visualization of the protein expression data individually or alongside gene expression data.

Proteome Analysis of Bevacizumab Intervention in Experimental Central Retinal Vein Occlusion

Bevacizumab is a frequently used inhibitor of vascular endothelial growth factor (VEGF) in the management of macular edema in central retinal vein occlusion (CRVO). Studying retinal protein changes in bevacizumab intervention may provide insights into mechanisms of action. In nine Danish Landrace pigs, experimental CRVO was induced in both eyes with argon laser. The right eyes received an intravitreal injection of 0.05 mL bevacizumab (n = 9), while the left control eyes received 0.05 mL saline water (NaCl). Retinal samples were collected 15 days after induced CRVO. Label-free quantification nano-liquid chromatography-tandem mass spectrometry identified 59 proteins that were regulated following bevacizumab treatment. Following bevacizumab intervention, altered levels of bevacizumab components, including the Ig gamma-1 chain C region and the Ig kappa chain C region, were observed. Changes in other significantly regulated proteins ranged between 0.58-1.73, including for the NADH-ubiquinone oxidoreductase chain (fold change = 1.73), protein-transport protein Sec24B (fold change = 1.71), glycerol kinase (fold change = 1.61), guanine-nucleotide-binding protein G(T) subunit-gamma-T1 (fold change = 0.67), and prefoldin subunit 6 (fold change = 0.58). A high retinal concentration of bevacizumab was achieved within 15 days. Changes in the additional proteins were limited, suggesting a narrow mechanism of action.

Tear film proteome changes following Tobradex® therapy in anterior blepharitis

PURPOSE

The management of blepharitis continues to challenge clinicians due to the poorly understood aetiology of the condition. We recently identified the family of intracellular plakin proteins as essential driving forces underlying anterior blepharitis. A large-scale protein analysis was used to study if a topical dexamethasone/tobramycin solution could be used to reverse the expression of plakin proteins.

METHODS

Tear film samples from treatment naïve patients with anterior blepharitis (n = 15) were collected with Schirmer filtration paper. A subgroup of the patients (n = 10) received treatment with a dexamethasone/tobramycin 1 + 3 mg/mL ophthalmic suspension (Tobradex® ) for 3 weeks and collection of tear film samples was repeated. The samples were analysed with label-free quantification nano liquid chromatography-tandem mass spectrometry requiring quantification in at least 70% of the samples in each group. Proteins were considered differentially expressed if p < 0.05.

RESULTS

Following Tobradex® intervention, 27 proteins were upregulated while 61 proteins were downregulated. Regulated proteins after Tobradex® treatment were involved in intermediate filament cytoskeleton organization including downregulation of the plakin proteins envoplakin, epiplakin and periplakin. Plectin, a protein of the plakin family, remained unchanged after Tobradex® therapy. Tobradex® treatment resulted in the regulation of proteins involved in translation including a cluster of downregulated ribosomal proteins. Tobradex® intervention was associated with the regulation of proteins involved in fructose metabolism and glycolytic processes including fructose-1.6-bisphosphatase 1, fructose-bisphosphate aldolases A and B, pyruvate kinase PKM and transketolase. Ig lambda chain V-I region, prominin-1, and protein Niban were upregulated after Tobradex® treatment.

CONCLUSIONS

Tobradex treatment reversed the expression of plakin proteins in anterior blepharitis. Topical solutions which inhibit the expression of plakin proteins may have the potential to restore the ocular surface integrity in anterior blepharitis and should be explored further.

Meibomian Gland Dysfunction Is Associated with Low Levels of Immunoglobulin Chains and Cystatin-SN

Meibomian gland dysfunction (MGD) is a highly prevalent condition and the most common cause of evaporative dry eye disease. Studying the proteome of MGD can result in important advances in the management of the condition. Here, we collected tear film samples from treatment naïve patients with MGD (n = 10) and age-matched controls (n = 11) with Schirmer filtration paper. The samples were analyzed with label-free quantification nano liquid chromatography-tandem mass spectrometry. The proteins were considered differentially expressed if p < 0.05. A total of 88 proteins were significantly regulated. The largest change was observed in cystatin-SN, which was downregulated in MGD and correlated negatively with tear meniscus height. The downregulation of cystatin-SN was confirmed with targeted mass spectrometry by single reaction monitoring (SRM). Eighteen immunoglobulin components involved in B cell activation, phagocytosis, and complement activation were downregulated in MGD including Ig alpha-1 chain C region, immunoglobulin J chain, immunoglobulin heavy variable 3-15, and Ig mu chain C region. The changes in cystatin-SN and immunoglobulin chains are likely to result from the inflammatory changes related to tear film evaporation, and future studies may assess their association with the meibum quality.

Macular Edema in Central Retinal Vein Occlusion Correlates With Aqueous Fibrinogen Alpha Chain

Purpose

The global protein profile of the aqueous humor has been found to correlate with the severity of retinal vascular disease. Studying the aqueous humor in central retinal vein occlusion (CRVO) with proteomic techniques may bring insights to the molecular mechanisms underlying the condition.

Methods

Aqueous humor samples from treatment naïve patients with CRVO complicated by macular edema (n = 28) and age-matched controls (n = 20) were analyzed by label-free quantification liquid chromatography - tandem mass spectrometry. Best corrected visual acuity (BCVA) was measured as logMAR, and the severity of macular edema was evaluated as central retinal thickness (CRT) with optical coherence tomography. Control samples were obtained prior to cataract surgery. Significantly changed proteins were identified by a permutation-based calculation with a false discovery rate of 0.05.

Results

A total of 177 proteins were differentially expressed in CRVO. Regulated proteins were involved in complement activation, innate immune response, blood coagulation, and cell adhesion. Upregulated proteins that correlated with BCVA and CRT included fibrinogen alpha, beta, and gamma chains, fibronectin, Ig lambda-6 chain C region, Ig alpha-1 chain C region, and complement C7. Downregulated proteins that correlated negatively with BCVA, and CRT, included procollagen C-endopeptidase enhancer 1, clusterin, opticin, reelin, fibrillin-1, and cadherin-2. Monocyte differentiation antigen CD14 and lipopolysaccharide-binding protein were increased in CRVO.

Conclusions

Fibrinogen chains, fibronectin, and immunoglobulin components correlated with BCVA and CRT, suggesting a multifactorial response. Protective anti-angiogenic proteins, including procollagen C-endopeptidase enhancer 1, clusterin, and opticin, were downregulated in CRVO and correlated negatively with BCVA and CRT.

Laser-Induced Porcine Model of Experimental Retinal Vein Occlusion: An Optimized Reproducible Approach

Retinal vein occlusion (RVO) is a frequent visually disabling condition. The management of RVO continues to challenge clinicians. Macular edema secondary to RVO is often recurrent, and patients typically require intravitreal injections for several years. Understanding molecular mechanisms in RVO is a key element in improving the treatment of the condition. Studying the molecular mechanisms in RVO at the retinal level is possible using animal models of experimental RVO. Most studies of experimental RVO have been sporadic, using only a few animals per experiment. Here, we report on 10 years of experience of the use of argon laser-induced experimental RVO in 108 porcine eyes from 65 animals, including 65 eyes with experimental branch retinal vein occlusion (BRVO) and 43 eyes with experimental central retinal vein occlusion (CRVO). Reproducibility and methods for evaluating and controlling ischemia in experimental RVO are reviewed. Methods for studying protein changes in RVO are discussed in detail, including proteomic analysis, Western blotting, and immunohistochemistry. Experimental RVO has brought significant insights into molecular changes in RVO. Testing intravitreal interventions in experimental RVO may be a significant step in developing personalized therapeutic approaches for patients with RVO.

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.

Tear Proteome Revealed Association of S100A Family Proteins and Mesothelin with Thrombosis in Elderly Patients with Retinal Vein Occlusion

Tear samples collected from patients with central retinal vein occlusion (CRVO; n = 28) and healthy volunteers (n = 29) were analyzed using a proteomic label-free absolute quantitative approach. A large proportion (458 proteins with a frequency > 0.6) of tear proteomes was found to be shared between the study groups. Comparative proteomic analysis revealed 29 proteins (p < 0.05) significantly differed between CRVO patients and the control group. Among them, S100A6 (log (2) FC = 1.11, p < 0.001), S100A8 (log (2) FC = 2.45, p < 0.001), S100A9 (log2 (FC) = 2.08, p < 0.001), and mesothelin ((log2 (FC) = 0.82, p < 0.001) were the most abundantly represented upregulated proteins, and β2-microglobulin was the most downregulated protein (log2 (FC) = −2.13, p < 0.001). The selected up- and downregulated proteins were gathered to customize a map of CRVO-related critical protein interactions with quantitative properties. The customized map (FDR < 0.01) revealed inflammation, impairment of retinal hemostasis, and immune response as the main set of processes associated with CRVO ischemic condition. The semantic analysis displayed the prevalence of core biological processes covering dysregulation of mitochondrial organization and utilization of improperly or topologically incorrect folded proteins as a consequence of oxidative stress, and escalating of the ischemic condition caused by the local retinal hemostasis dysregulation. The most significantly different proteins (S100A6, S100A8, S100A9, MSLN, and β2-microglobulin) were applied for the ROC analysis, and their AUC varied from 0.772 to 0.952, suggesting probable association with the CRVO.

Dexamethasone Intravitreal Implant Is Active at the Molecular Level Eight Weeks after Implantation in Experimental Central Retinal Vein Occlusion

Central retinal vein occlusion (CRVO) is a visually disabling condition resulting from a thrombus in the major outflow vessel of the eye. The inflammatory response in CRVO is effectively treated with a dexamethasone (DEX) intravitreal implant. Uncovering the proteome changes following DEX implant intervention in CRVO may identify key proteins that mediate the beneficial effects of DEX. In six Göttingen minipigs, CRVO was induced in both eyes with an argon laser using a well-established experimental model. The right eyes were treated with a DEX intravitreal implant (Ozurdex, Allergan), while the left control eyes received a sham injection. Eight weeks after DEX intervention, retinal samples were collected and analyzed with tandem mass tag-based mass spectrometry. DEX implant intervention resulted in the upregulation of peptidyl-prolyl cis-trans isomerase FKBP5 (FKBP5) and ubiquilin-4. Immunohistochemistry showed expression of FKBP5 in the nuclei in all cellular layers of the retina. Cell adhesion molecule 3, tumor necrosis factor receptor superfamily member 16, and trans-1,2-dihydrobenzene-1,2-diol dehydrogenase were downregulated following DEX intervention. The upregulation of the corticosteroid-sensitive protein FKBP5 suggests that the implant remained active at the molecular level after eight weeks of treatment. Future studies may investigate if FKBP5 regulates the efficacy and duration of the DEX implant.

Proteome Analysis of Aflibercept Intervention in Experimental Central Retinal Vein Occlusion

Aflibercept is a frequently used inhibitor of vascular endothelial growth factor (VEGF) in the treatment of macular edema following central retinal vein occlusion (CRVO). Retinal proteome changes following aflibercept intervention in CRVO remain largely unstudied. Studying proteomic changes of aflibercept intervention may generate a better understanding of mechanisms of action and uncover aspects related to the safety profile. In 10 Danish Landrace pigs, CRVO was induced in both eyes with an argon laser. Right eyes were treated with intravitreal aflibercept while left control eyes received isotonic saline water. Retinal samples were collected 15 days after induced CRVO. Proteomic analysis by tandem mass tag-based mass spectrometry identified a total of 21 proteins that were changed in content following aflibercept intervention. In retinas treated with aflibercept, high levels of aflibercept components were reached, including the VEGF receptor-1 and VEGF receptor-2 domains. Fold changes in the additional proteins ranged between 0.70 and 1.19. Aflibercept intervention resulted in a downregulation of pigment epithelium-derived factor (PEDF) (fold change = 0.84) and endoplasmin (fold change = 0.91). The changes were slight and could thereby not be confirmed with less precise immunohistochemistry and Western blotting. Our data suggest that aflibercept had a narrow mechanism of action in the CRVO model. This may be an important observation in cases when macular edema secondary to CRVO is resistant to aflibercept intervention.

Aqueous Fibronectin Correlates With Severity of Macular Edema and Visual Acuity in Patients With Branch Retinal Vein Occlusion: A Proteome Study

Purpose

Large-scale protein analysis may bring important insights into molecular changes following branch retinal vein occlusion (BRVO). Using proteomic techniques this study compared aqueous humor samples from patients with BRVO to age-matched controls.

Methods

Aqueous humor samples from treatment naive patients with BRVO complicated by macular edema (n = 19) and age-matched controls (n = 18) were analyzed with label-free quantification nano liquid chromatography - tandem mass spectrometry (LFQ nLC-MS/MS). The severity of macular edema was measured as central retinal thickness (CRT) with optical coherence tomography. Control samples were obtained prior to cataract surgery. Proteins were filtered by requiring quantification in at least 50% of the samples in each group without imputation of missing values. Significantly changed proteins were identified with a permutation-based calculation with a false discovery rate at 0.05.

Results

In BRVO, 52 proteins were differentially expressed. Regulated proteins were involved in cell adhesion, coagulation, and acute-phase response. Apolipoprotein C-III, complement C3, complement C5, complement factor H, fibronectin, and fibrinogen chains were increased in BRVO and correlated with CRT. Fibronectin also correlated with best corrected visual acuity (BCVA) and vascular endothelial growth factor (VEGF). Monocyte differentiation antigen CD14 (CD14) and lipopolysaccharide-binding protein (LBP) were upregulated in BRVO. Contactin-1 and alpha-enolase were downregulated in BRVO and correlated negatively with CRT.

Conclusions

Multiple proteins, including complement factors, fibrinogen chains, and apolipoprotein C-III, correlated with CRT, indicating a multifactorial response. Fibronectin correlated with BCVA, CRT, and VEGF. Fibronectin may reflect the severity of BRVO. The proinflammatory proteins CD14 and LBP were upregulated in BRVO.

Cystotomy with or without fibrinogen clot removal for refractory cystoid macular edema secondary to branch retinal vein occlusion

To demonstrate the long-term effect of cystotomy with or without fibrinogen clot removal for treatment-resistant cystoid macular edema (CME) secondary to branch retinal vein occlusion (BRVO). Retrospective clinical study. We retrospectively analyzed medical records of 22 eyes of 22 patients with treatment-resistant CME secondary to BRVO with 12 months observation after cystotomy with or without fibrinogen clot removal. Patients included 11 women and 11 men. The mean ± SD age was 72.7 ± 10.2 years. LogMAR-converted best corrected visual acuity (BCVA) was statistically better at 12 months after surgery (0.30 ± 0.30) than preoperative BCVA (0.39 ± 0.27) (p = 0.01). The central sensitivity of microperimetry (dB) was maintained during follow-up (preoperative sensitivity: 25.4 ± 4.1, postoperative sensitivity at 12 months after the surgery: 25.9 ± 4.2, p = 0.69). Twelve months after surgery, there was a significant improvement in the central retinal thickness (CRT) on optical coherence tomography (OCT) (303.7 ± 80.1) (μm) compared with the preoperative CRT (524.2 ± 114.8) (p < 0.01). In 12 months, CME recurred in 3 of 22 eyes. The preoperative reflectivity in cystoid cavity on OCT was significantly higher in patients with fibrinogen clot removal (n = 5) than in patients without fibrinogen clot removal (n = 17) (p < 0.01). For treatment-resistant CME secondary to BRVO, Cystotomy with or without fibrinogen clot removal may be one of the treatment options.

Aflibercept Intervention in Experimental Branch Retinal Vein Occlusion Results in Upregulation of DnaJ Homolog Subfamily C Member 17

Aflibercept is an inhibitor of vascular endothelial growth factor (VEGF) used to treat macular edema following branch retinal vein occlusion (BRVO). Despite well-documented efficacy, there is limited knowledge about proteome changes following aflibercept intervention in BRVO. Proteome changes may provide insights into mechanisms of action as well as aspects related to safety profile. In seven Danish Landrace pigs, BRVO was induced with a well-established experimental model of argon laser-induced BRVO. BRVO was induced in both eyes. Three days after the induced BRVO, aflibercept was injected intravitreally in the right eyes, while the left eyes received intravitreal isotonic saline water. Retinas were collected 15 days after the induced BRVO and analyzed with label-free quantification liquid chromatography tandem mass spectrometry (LFQ LC-MS/MS). Fourteen proteins were changed in expression following aflibercept intervention in the BRVO model. LFQ LC-MS/MS identified an upregulation of DnaJ homolog subfamily C member 17 (DNAJC17) (fold change = 6.19) and a modest downregulation of isoform 2 of the protein encoded by N-myc downstream regulated gene 2 (NDRG2) (fold change = 0.40). NDRG2 was unchanged by Western blotting. In the additional significantly regulated proteins, only discrete changes were observed (fold changes 0.52–1.59). Our study is the first to report an association between aflibercept intervention and the heat shock protein DNAJC17. Our results indicate that the role of heat shock proteins in the treatment of BRVO should be further explored.

Gene expression profile analysis of the rabbit retinal vein occlusion model

The rabbit retinal vein occlusion (RVO) model is an experimental system that mimics retinal ischemic diseases in humans. The rabbit RVO model is widely used to assess the therapeutic efficacy of various experimental surgical procedures. In the present study, we measured temporal retinal expression of Vegfa, which is known as an ischemic response gene, in rabbit RVO. This analysis revealed that the retinal Vegfa transcriptional response began 7 days after generation of RVO, rather than immediately after induction of ischemia. Next, in order to analyze ischemia-induced changes in gene expression profiles, we performed microarray analysis of day 7 RVO retina versus control retina. The angiogenic regulators Dcn and Mmp1 and pro-inflammatory factors Mmp12 and Cxcl13 were significantly upregulated in RVO retinas. Further, we suggest that epigenetic regulation via the REST/cofactor-complex could contribute to RVO pathology. Among human homologous genes in rabbits, genes associated with hypoxia, angiogenesis, and inflammation were significantly upregulated in RVO retinas. Components of the Tumor necrosis factor-alpha (TNFα) and Nuclear factor-kappa B (NF-κB) pathways, which play regulatory roles in angiogenesis and inflammation, were significantly upregulated in RVO, and the expression levels of downstream factors, such as the transcription factor AP-1 and chemokines, were increased. Further, connectivity map analyses suggested that inhibitors of the NF-κB pathway are potential therapeutic agents for retinal ischemic disease. The present study revealed new insights into the pathology of retinal ischemia using the rabbit RVO model, which accurately recapitulates human disease.

Retinal proteome associated with bradykinin-induced edema

The plasma kallikrein-stimulated generation of bradykinin (BK) has been implicated in diabetic macular edema (DME). This study characterizes the effects of BK on the ultrastructure and proteome of the rat retina. The effects of intravitreal injection of BK on retinal thickness and vascular ultrastructure in Sprague Dawley rats were analyzed and compared with the effects of VEGF using spectral-domain optical coherence tomography. At 24 h post intravitreal injection of BK or saline vehicle retina were harvested and solubilized proteins were analyzed by mass spectrometry-based proteomics. Proteins were identified using X!Tandem and spectral counts were used as a semiquantitative measurement of protein abundance. Proteins identified from retinal extracts were annotated by Gene Ontology (GO) slim terms and compared with a human DME vitreous proteome. Intravitreal injection of BK and VEGF induced transient increases in retinal thickness of 46 μm (24.6%, p = 0.015) and 39 μm (20.3%, p = 0.004), respectively at 24 h, which were resolved to baseline thicknesses at 96 h post injection. BK and VEGF also increased retinal vessel diameters and tortuosity at 24 h post intravitreal injection. Proteomic analyses identified 1757 non-redundant proteins in the rat retina, including 1739 and 1725 proteins from BK- and saline control-injected eyes, respectively. Eighteen proteins, including two proteins associated with intercellular junctions, filamin A and actinin alpha 4, were decreased by at least 50% (p < 0.05) in retina from BK-injected eyes compare with retina from eyes injected with saline. In addition, 32 proteins were increased by > 2-fold (p < 0.05) in retina from BK-injected eyes. Eight proteins, including complement C3, were identified to be increased in both BK-stimulated rat retina and in human DME vitreous. Western blot analysis showed that Complement 3 levels in vitreous from BK-injected eyes in rats and clinical DME samples were increased by 6.6-fold (p = 0.039) and 4.3-fold (p = 0.02), compared with their respective controls. In summary, this study identifies protein changes in rat retina that are associated with BK-induced retinal thickening, including 8 proteins that were previously reported to be increased in the human DME vitreous proteome.

IL-18 and S100A12 Are Upregulated in Experimental Central Retinal Vein Occlusion

Retinal vein occlusion (RVO) is a common retinal vascular disease. RVO may be complicated by pronounced ischemia that often leads to severe loss of visual function. The present work aimed at studying the retinal proteome of RVO complicated by ischemia. In six Danish Landrace pigs RVO was induced with argon laser in the right eye of each animal. As four retinal veins were occluded, the RVO best corresponded to a central retinal vein occlusion (CRVO). Left control eyes received a similar laser treatment without inducing occlusion. RVO and retinal ischemia were verified by angiography. The retinas were collected 15 days after RVO for proteomic analysis. RVO resulted in a downregulation of proteins involved in visual perception, including rhodopsin, transducin alpha chain, and peripherin-2. RVO also caused a downregulation of proteins involved in neurotransmitter transport, including glutamate decarboxylase 1 (GAD1), glutamate decarboxylase 2 (GAD2), and complexins 2⁻4. RVO lead to increased contents of proteins involved in inflammation, including interleukin-18 (IL-18), S100A12, and annexin A1 (ANXA1). Immunohistochemistry revealed a general retinal upregulation of IL-18 and ANXA1 while S100A12 was highly abundant in retinal ganglion cells in RVO. IL-18 and S100A12 are likely to be driving forces in the inflammatory response of RVO complicated by ischemia. Our findings also suggest that RVO results in compromised neurotransmission and a downregulation of proteins involved in visual perception.

Gene expression profiling in a mouse model of retinal vein occlusion induced by laser treatment reveals a predominant inflammatory and tissue damage response

Purpose

Retinal vein occlusion (RVO) has been investigated in several laser-induced animal models using pigs, rabbits and rats. However, laser-induced RVO has been rarely reported in mice, despite the impressive number of available mutants, ease of handling and cost effectiveness. The aim of this study was to further assess the feasibility of a RVO mouse model for gene expression analysis and its possible use to investigate effects of hypoxia.

Methods

C57Bl/6J mice were injected with eosin Y for photo-sensitization. Subsequently, large retinal veins were laser-treated in one eye to induce vascular occlusion. Contralateral control eyes received non-occlusive retinal laser treatment sparing large vessels. The animals were followed for up to eight days and assessed by funduscopy, angiography, hypoxyprobe staining, histopathology and gene expression analysis by qPCR and RNA sequencing (RNAseq). Another group of mice was left untreated and studied at a single time point to determine baseline characteristics.

Results

Laser-induced RVO persisted in half of the treated veins for three days, and in a third of the veins for the whole observation period of 8 days. Funduscopy revealed large areas of retinal swelling in all laser-treated eyes, irrespective of vascular targeting or occlusion status. Damage of the outer retina, retinal pigment epithelium (RPE), and even choroid and sclera at the laser site was observed in histological sections. Genes associated with inflammation or cell damage were highly up-regulated in all laser-treated eyes as detected by RNAseq and qPCR. Retinal hypoxia was observed by hypoxyprobe staining in all RVO eyes for up to 5 days with a maximal extension at days 2 and 3, but no significant RVO-dependent changes in gene expression were detected for angiogenesis- or hypoxia-related genes.

Conclusion

The laser-induced RVO mouse model is characterized by a predominant general inflammatory and tissue damage response, which may obscure distinct hypoxia- and angiogenesis-related effects. A non-occlusive laser treatment control is essential to allow for proper data interpretation and should be mandatory in animal studies of laser-induced RVO to dissect laser-induced tissue damage from vascular occlusion effects.

Dexamethasone intravitreal implant downregulates PDGFR-α and upregulates caveolin-1 in experimental branch retinal vein occlusion

A dexamethasone (DEX) intravitreal implant (OZURDEX) provides an effective treatment of inflammation secondary to branch retinal vein occlusion (BRVO). Retinal proteome changes which mediate the beneficial effects of the implant remain poorly understood. To study retinal proteome changes in BRVO following an intervention with a DEX implant this study combined an experimental model of BRVO with proteomic techniques. In eight Danish Landrace pigs experimental BRVO was induced in both eyes using argon laser. After inducing BRVO a DEX implant was injected into the right eye of each animal while the left control eye was given an identical injection without an implant. Fifteen days after BRVO and DEX implant intervention the retinas were excised and analyzed with tandem mass tag based mass spectrometry. A total of 26 significantly changed proteins were identified. DEX intervention reduced the retinal levels of platelet-derived growth factor receptor-α (PDGFR-α) and vascular endothelial growth factor receptor 2 (VEGFR-2). DEX treatment resulted in increased levels of caveolin-1, peptidyl-prolyl cis-trans isomerase FKBP5 and transgelin. Changes in PDGFR-α and caveolin-1 were confirmed with immunohistochemistry. In BRVO treated with the DEX implant a strong reaction for caveolin-1 was observed in the innermost retinal layers. DEX implant intervention may inhibit PDGF signaling by decreasing the retinal level of PDGFR-α while an increased content of caveolin-1 may help maintain the integrity of the blood-retinal barrier.

A Review: Proteomics in Retinal Artery Occlusion, Retinal Vein Occlusion, Diabetic Retinopathy and Acquired Macular Disorders

Retinal artery occlusion (RAO), retinal vein occlusion (RVO), diabetic retinopathy (DR) and age-related macular degeneration (AMD) are frequent ocular diseases with potentially sight-threatening outcomes. In the present review we discuss major findings of proteomic studies of RAO, RVO, DR and AMD, including an overview of ocular proteome changes associated with anti-vascular endothelial growth factor (VEGF) treatments. Despite the severe outcomes of RAO, the proteome of the disease remains largely unstudied. There is also limited knowledge about the proteome of RVO, but proteomic studies suggest that RVO is associated with remodeling of the extracellular matrix and adhesion processes. Proteomic studies of DR have resulted in the identification of potential therapeutic targets such as carbonic anhydrase-I. Proliferative diabetic retinopathy is the most intensively studied stage of DR. Proteomic studies have established VEGF, pigment epithelium-derived factor (PEDF) and complement components as key factors associated with AMD. The aim of this review is to highlight the major milestones in proteomics in RAO, RVO, DR and AMD. Through large-scale protein analyses, proteomics is bringing new important insights into these complex pathological conditions.

The Pig PeptideAtlas: A resource for systems biology in animal production and biomedicine

Biological research of Sus scrofa, the domestic pig, is of immediate relevance for food production sciences, and for developing pig as a model organism for human biomedical research. Publicly available data repositories play a fundamental role for all biological sciences, and protein data repositories are in particular essential for the successful development of new proteomic methods. Cumulative proteome data repositories, including the PeptideAtlas, provide the means for targeted proteomics, system-wide observations, and cross-species observational studies, but pigs have so far been underrepresented in existing repositories. We here present a significantly improved build of the Pig PeptideAtlas, which includes pig proteome data from 25 tissues and three body fluid types mapped to 7139 canonical proteins. The content of the Pig PeptideAtlas reflects actively ongoing research within the veterinary proteomics domain, and this article demonstrates how the expression of isoform-unique peptides can be observed across distinct tissues and body fluids. The Pig PeptideAtlas is a unique resource for use in animal proteome research, particularly biomarker discovery and for preliminary design of SRM assays, which are equally important for progress in research that supports farm animal production and veterinary health, as for developing pig models with relevance to human health research.

Retinal proteome changes following experimental branch retinal vein occlusion and intervention with ranibizumab

Animal models of experimental branch retinal vein occlusion (BRVO) provide a unique opportunity to study protein changes directly in retinal tissue. Results from these experimental models suggest that experimental BRVO is associated with an upregulation of extracellular matrix remodeling and adhesion signaling processes. To study whether these processes could be blocked by inhibition of VEGF-A, a porcine model of experimental BRVO was combined with proteomic analyses. In six Danish Landrace pigs experimental BRVO was induced with argon laser in both eyes. After 24 h an injection of 0.05 mL ranibizumab was given in the right eyes of the animals while left eyes received an injection of 0.05 mL 9 mg/mL sodium chloride water. Retinas were dissected three days after BRVO and the retinal samples were analyzed with label-free quantification as well as tandem mass tag based proteomics. In retinas treated with ranibizumab five proteins exhibited statistically significant changes in content with both proteomic techniques. These five proteins, which were all decreased in content, included integrin β-1, peroxisomal 3-ketoacyl-CoA thiolase, OCIA domain-containing protein 1, calnexin and 40S ribosomal protein S5. As anti-integrin therapies are under development for inhibition of angiogenesis in retinal diseases it is interesting that inhibition of VEGF-A in itself resulted in a small decrease in the content of integrin β-1. The decreased content of integrin β-1 indicates that extracellular matrix remodeling and adhesion processes associated with BRVO are at least partly reversed through inhibition of VEGF-A.