Stromal-derived factor-1 and inflammatory cytokines in retinal vein occlusion

Cytokine Levels in Experimental Branch Retinal Vein Occlusion Treated With Either Bevacizumab or Triamcinolone Acetonide

Purpose

To compare gene expression changes following branch retinal vein occlusion (BRVO) in the pig with and without bevacizumab (BEV) and triamcinolone acetonide (TA).

Methods

Photothrombotic BRVOs were created in both eyes of four groups of nine pigs (2, 6, 10, and 20 days). In each group, six pigs received intravitreal injections of BEV in one eye and TA in the fellow eye, with three pigs serving as untreated BRVO controls. Three untreated pigs served as healthy controls. Expression of mRNA of vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), dystrophin (DMD), potassium inwardly rectifying channel subfamily J member 10 protein (Kir4.1, KCNJ10), aquaporin-4 (AQP4), stromal cell-derived factor-1α (CXCL12), interleukin-6 (IL6), interleukin-8 (IL8), monocyte chemoattractant protein-1 (CCL2), intercellular adhesion molecule 1 (ICAM1), and heat shock factor 1 (HSF1) were analyzed by quantitative reverse-transcription polymerase chain reaction. Retinal VEGF protein levels were characterized by immunohistochemistry.

Results

In untreated eyes, BRVO significantly increased expression of GFAP, IL8, CCL2, ICAM1, HSF1, and AQP4. Expression of VEGF, KCNJ10, and CXCL12 was significantly reduced by 6 days post-BRVO, with expression recovering to healthy control levels by day 20. Treatment with BEV or TA significantly increased VEGF, DMD, and IL6 expression compared with untreated BRVO eyes and suppressed BRVO-induced CCL2 and AQP4 upregulation, as well as recovery of KCNJ10 expression, at 10 to 20 days post-BRVO.

Conclusions

Inflammation and cellular osmohomeostasis rather than VEGF suppression appear to play important roles in BRVO-induced retinal neurodegeneration, enhanced in both BEV- and TA-treated retinas.

Translational Relevance

Inner retinal neurodegeneration seen in this acute model of BRVO appears to be mediated by inflammation and alterations in osmohomeostasis rather than VEGF inhibition, which may have implications for more specific treatment modalities in the acute phase of BRVO.

PON1, APOE and SDF-1 Gene Polymorphisms and Risk of Retinal Vein Occlusion: A Case-Control Study

Numerous studies have tried to evaluate the potential role of thrombophilia-related genes in retinal vein occlusion (RVO); however, there is limited research on genes related to different pathophysiological mechanisms involved in RVO. In view of the strong contribution of oxidative stress and inflammation to the pathogenesis of RVO, the purpose of the present study was to investigate the association of inflammation- and oxidative-stress-related polymorphisms from three different genes [apolipoprotein E (APOE), paraoxonase 1 (PON1) and stromal cell-derived factor 1 (SDF-1)] and the risk of RVO in a Greek population. Participants in this case-control study were 50 RVO patients (RVO group) and 50 healthy volunteers (control group). Blood samples were collected on EDTA tubes and genomic DNA was extracted. Genotyping of rs854560 (L55M) and rs662 (Q192R) for the PON1 gene, rs429358 and rs7412 for the APOE gene and rs1801157 [SDF1-3'G(801)A] for SDF-1 gene was performed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Multiple genetic models (codominant, dominant, recessive, overdominant and log-additive) and haplotype analyses were performed using the SNPStats web tool to assess the correlation between the genetic polymorphisms and the risk of RVO. Binary logistic regression analysis was used for the association analysis between APOE gene variants and RVO. Given the multifactorial nature of the disease, our statistical analysis was adjusted for the most important systemic risk factors (age, hypertension and diabetes mellitus). The dominant genetic model for the PON1 Q192R single nucleotide polymorphism (SNP) of the association analysis revealed that there was a statistically significant difference between the RVO group and the control group. Specifically, after adjusting for age and hypertension, the PON1 192 R allele (QR + RR) was found to be associated with a statistically significantly higher risk of RVO compared to the QQ genotype (OR = 2.51; 95% CI = 1.02-6.14, p = 0.04). The statistically significant results were maintained after including diabetes in the multivariate model in addition to age and hypertension (OR = 2.83; 95% CI = 1.01-7.97, p = 0.042). No statistically significant association was revealed between the other studied polymorphisms and the risk of RVO. Haplotype analysis for PON1 SNPs, L55M and Q192R, revealed no statistically significant correlation. In conclusion, PON1 192 R allele carriers (QR + RR) were associated with a statistically significantly increased risk of RVO compared to the QQ homozygotes. These findings suggest that the R allele of the PON1 Q192R is likely to play a role as a risk factor for retinal vein occlusion.

Association of PON1, APOE and SDF-1 Gene Polymorphisms with Treatment Response to Intravitreal Anti-VEGF Treatment in Patients with Retinal Vein Occlusion

PURPOSE

The purpose of this study was to determine whether specific genetic polymorphisms affect the response to intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment in patients with macular oedema secondary to retinal vein occlusion (RVO).

METHODS

Participants in this prospective study were 50 patients with macular oedema secondary to RVO, who were treated with intravitreal ranibizumab or aflibercept, and were followed-up for 12 months after initiation of treatment. Five single nucleotide polymorphisms (SNPs) from three different genes (APOE, PON1, SDF-1) were examined as potential predictors for treatment response to intravitreal anti-VEGF agents.

RESULTS

Patients with the LL genotype of the PON1 L55M SNP had significantly higher reduction in central subfield thickness (CST) at month 12 after initiation of intravitreal anti-VEGF treatment (101.63 ± 56.80 μm in LL vs. 72.44 ± 39.41 μm in LM vs. 40.25 ± 19.33 μm in MM, p = .026). Patients with the M allele of the PON1 L55M SNP were significantly associated with lower reduction in CST compared to non-carriers (68.29 ± 38.77 μm in LM + MM vs. 101.63 ± 56.80 μm in LL, p = .032).

CONCLUSION

PON1 L55M SNP may serve as a promising genetic biomarker for predicting response to intravitreal anti-VEGF treatment in patients with macular oedema due to RVO.

A Review of Intraocular Biomolecules in Retinal Vein Occlusion: Toward Potential Biomarkers for Companion Diagnostics

Retinal vein occlusion (RVO) is one of the most common retinal vascular diseases. The pathogenesis of RVO is multifactorial and involves a complex interplay among a variety of vascular and inflammatory mediators. Many cytokines, chemokines, growth factors, and cell adhesion molecules have been reported to be implicated. Treatments for RVO are directed at the management of underlying risk factors and vision-threatening complications, including macula edema (ME) and neovascularization. Intravitreal anti-VEGF agents are currently considered as the first-line treatment for ME secondary to RVO (RVO-ME), but a substantial proportion of patients responded insufficiently to anti-VEGF agents. Since RVO-ME refractory to anti-VEGF agents generally responds to corticosteroids and its visual outcome is negatively correlated to disease duration, prediction of treatment response at baseline in RVO-ME may significantly improve both cost-effectiveness and visual prognosis. Several bioactive molecules in the aqueous humor were found to be associated with disease status in RVO. This review aims to present a comprehensive review of intraocular biomolecules reported in RVO, including VEGF, IL-6, IL-8, MCP-1, sICAM-1, IL-12, IL-13, sVEGFR-1, sVEGFR-2, PDGF-AA, etc., highlighting their association with disease severity and/or phenotype, and their potential roles in prognostic prediction and treatment selection. Some of these molecules may serve as biomarkers for aqueous humor-based companion diagnostics for the treatment of RVO in the future.

Changes in Aqueous and Vitreous Inflammatory Cytokine Levels in Retinal Vein Occlusion: A Systematic Review and Meta-analysis

Purpose:

Evidence suggests that inflammatory cytokines not only play a role in the pathogenesis of retinal vein occlusion (RVO) but also may be useful as biomarkers to predict disease severity and response to treatment. We aimed to quantitatively summarize data on inflammatory cytokines associated with RVO.

Methods:

A systematic search of peer-reviewed English-language articles was performed without year limitation up to August 19, 2019. Studies were included if they provided data on aqueous or vitreous cytokine concentrations in patients with RVO. Data were extracted from 116 studies that encompassed 3242 study eyes with RVO and 1402 control eyes. Effect sizes were generated as standardized mean differences (SMDs) of cytokine concentrations between patients with RVO vs controls.

Results:

Among the 4644 eyes in 116 studies, aqueous and vitreous concentrations (SMD, 95% CI, and P value) of interleukin (IL)-6 (aqueous: 1.23, 0.65 to 1.81, P < .001 vitreous: 0.70, 0.49 to 0.90, P < .001), IL-8 (aqueous: 1.11, 0.73 to 1.49, P < .001; vitreous: 1.19, 0.73 to 1.65, P < .001), monocyte chemoattractant protein 1(aqueous: 1.22, 0.72 to 1.72, P < .001; vitreous 1.42, 0.92 to 1.91, P < .001), vascular endothelial growth factor (VEGF) (aqueous: 1.52, 1.09 to 1.94, P < .001; vitreous: 0.99, 0.78 to 1.21, P < .001) were significantly higher in patients with RVO than in healthy controls. Only aqueous concentrations of IL-10 (0.81, 0.45 to 1.18, P < .001), angiopoietin 4 (1.96, 0.92 to 3.00, P < .001), and platelet-derived growth factor (PDGF)-AA (0.82, 0.35 to 1.30, P < .001) were significantly higher in patients with RVO than in healthy controls. Only the vitreous concentration of soluble intercellular adhesion molecule-1 (sICAM-1) (1.23, 0.83 to 1.63, P < .001) was significantly higher in patients with RVO. No differences, failed sensitivity analyses, or insufficient data were found between patients with RVO and healthy controls for the concentrations of the remaining cytokines.

Conclusions:

Several cytokines in addition to VEGF have the potential to be useful biomarkers and therapeutic targets in RVO.

Comprehensive analysis of vitreous chemokines involved in ischemic retinal vein occlusion

PURPOSE

To investigate vitreous levels of chemokines in eyes with ischemic retinal vein occlusion (RVO).

METHODS

The vitreous humor was collected at the start of 23-gauge pars plana vitrectomy from patients with ischemic RVO and patients with idiopathic preretinal membranes (PRMs) and idiopathic macular holes (IMHs). The levels of 40 different chemokines were measured using magnetic color-bead-based multiplex assay. The chi-square test was performed for clinical variables such as sex, and the Mann-Whitney U test was performed to evaluate the differences in the chemokine levels between the RVO group and the control group.

RESULTS

Vitreous humor was collected from 20 controls and 25 subjects with ischemic RVO. C-C motif ligand 17 (CCL17) was unmeasurable in more than 70% of the samples. The levels of 29 of 39 chemokines were statistically significantly elevated in the RVO group compared with the control group, including CCL21, C-X-C motif ligand (CXCL) 13, CCL27, CCL24, CX3CL1, CXCL6, interferon-gamma (IFN-γ), interleukin (IL) 1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-16, CXCL10, CXCL11, CCL8, CCL7, CCL13, CCL22, macrophage migration inhibitory factor (MIF), CXCL9, CCL3, CCL15, CCL20, CCL19, CCL23, CCL25, and tumor necrosis factor-alpha (TNF-α). Among the 29 elevated chemokines, we found that the levels of three chemokines (IL-8, CXCL9, and TNF-α) showed a more than six-fold increase in the RVO eyes versus controls, and CXCL9 expression showed the greatest change of all tested chemokines.

CONCLUSIONS

Dozens of chemokines were found to be elevated in the vitreous of RVO eyes complicated with vitreous hemorrhage, suggesting that inflammation is severe in the ischemic retina. The knowledge of specific upregulation of chemokines in ischemic RVO could allow more targeted future therapies.

Growth Factors in the Pathogenesis of Retinal Neurodegeneration in Diabetes Mellitus

Neurodegeneration is an initial process in the development of diabetic retinopathy (DR).

High quantities of glutamate, oxidative stress, induction of the renin-angiotensin system (RAS) and elevated levels of RAGE are crucial elements in the retinal neurodegeneration caused by diabetes mellitus. At least, there is emerging proof to indicate that the equilibrium between the neurotoxic and neuroprotective components will affect the state of the retinal neurons.

Somatostatin (SST), pigment epithelium-derived factor (PEDF), and erythropoietin (Epo) are endogenous neuroprotective peptides that are decreased in the eye of diabetic persons and play an essential role in retinal homeostasis. On the other hand, insulin-like growth factor 1 (IGF-1), and vascular endothelial growth factor (VEGF) are pivotal proteins which participate in the development of new capillaries and finally cause damage to the retinal neurons. During recent years, our knowledge about the function of growth factors in the pathogenesis of retinal neurodegeneration has increased. However, intensive investigations are needed to clarify the basic processes that contribute to retinal neurodegeneration and its association with damage to the capillary blood vessels. The objective of this review article is to show new insights on the role of neurotransmitters and growth factors in the pathogenesis of diabetic retinopathy. The information contained in this manuscript may provide the basis for novel strategies based on the factors of neurodegeneration to diagnose, prevent and treat DR in its earliest phases.

Stromal Cell-Derived Factor 1 Polymorphism in Retinal Vein Occlusion

Background

Stromal cell-derived factor 1 (SDF1) has crucial role in the regulation of angiogenesis and ocular neovascularisation (NV). The purpose of this study was to evaluate the association between SDF1-3’G(801)A polymorphism and NV complications of retinal vein occlusion (RVO).

Methods

130 patients with RVO (median age: 69.0, range 35–93 years; male/female– 58/72; 55 patients had central RVO, 75 patients had branch RVO) were enrolled in this study. In the RVO group, 40 (30.8%) patients were diagnosed with NV complications of RVO and 90 (69.2%) patients without NVs. The median follow up period was 40.3 months (range: 18–57 months). The SDF1-3’G(801)A polymorphism was detected by PCR-RFLP. Allelic prevalence was related to reference values obtained in the control group consisted of 125 randomly selected, age and gender matched, unrelated volunteers (median age: 68.0, range 36–95 years; male/female– 53/72). Statistical analysis of the allele and genotype differences between groups (RVO patients vs controls; RVO patients with NV vs RVO patients without NV) was determined by chi-squared test. P value of <0.05 was considered statistically significant.

Results

Hardy-Weinberg criteria was fulfilled in all groups. The SDF1-3’G(801)A allele and genotype frequencies of RVO patients were similar to controls (SDF1-3’A allele: 22.3% vs 20.8%; SDF1-3’(801)AA: 5.4% vs 4.8%, SDF1-3’(801)GG: 60.8% vs 63.2%). The frequency of SDF1-3’(801)AA and SDF1-3’(801)GA genotypes, as well as the SDF1-3’(801)A allele frequency were higher in RVO patients with NV versus in patients without NV complication (SDF1-3’(801)AA+AG genotypes: 57.5% vs 31.1%, p = 0.008; SDF1-3’(801)A allele: 35.0% vs 16.7%, p = 0.002) or versus controls (SDF1-3’(801)AA+AG genotypes 57.5% vs 36.8%, p = 0.021; SDF1-3’(801)A allele: 35.0% vs 20.8% p = 0.01). Carrying of SDF1-3’(801)A allele increased the risk of neovascularisation complications of RVO by 2.69 (OR, 95% CI = 1.47–4.93).

Conclusion

These findings suggest that carrying SDF1-3’(801)A allele plays a role in the development of neovascular complications in retinal vein occlusion.

Comparison of Choroidal Thickness Changes following Intravitreal Dexamethasone, Ranibizumab, and Triamcinolone in Eyes with Retinal Vein Occlusion

Purpose

To evaluate short-term choroidal thickness changes following intravitreal dexamethasone implant (DEX), ranibizumab (RAN), and triamcinolone acetonide (TA) in eyes with retinal vein occlusion (RVO) and macular edema (ME).

Methods

In this prospective study, 35 eyes of 35 patients with RVO and ME who were treated with intravitreal injections of DEX, RAN, and TA were included. Choroidal thickness was measured using semiautomated segmentation of enhanced depth imaging with optical coherence tomography at fovea and parafoveal areas. Changes in choroidal thickness following treatment were compared statistically.

Results

Choroidal thickness decreased following DEX, RAN, and TA treatments (all p>0.05). In the DEX group, at the first month nasal 1,500 µm (N11,500) and at the third month subfoveal (SF3) and nasal 500 µm (N3500) choroidal thickness revealed a significant reduction compared to RAN and TA groups (all p<0.05). In the TA group, choroidal thickness showed a significant reduction only at nasal 1,500 µm (N31,500) at the third month (p<0.05).

Conclusions

Choroidal thickness was decreased in all 3 groups. The DEX and TA groups showed a significant reduction at some areas. Ranibizumab had the smallest effect on choroidal thickness after 3 months among all groups.

Early results of dexamethasone implant, ranibizumab, and triamcinolone in macular edema due to branch retinal vein occlusion

PURPOSE

To compare the short-term results of the efficacy and safety of dexamethasone intravitreal implant (DEX), ranibizumab (RAN), and intravitreal triamcinolone acetonide (IVTA) in macular edema secondary to branch retinal vein occlusion (BRVO).

METHODS

One eye each of 32 patients who were treated with intravitreal injections for macular edema secondary to BRVO was studied. This retrospective study included 3 groups. The patients received DEX in group 1 (n = 11), RAN in group 2 (n = 11), and IVTA in group 3 (n = 10). Data were collected before and after the injections at the first and third months. Best-corrected visual acuity (BCVA), central macular thickness (CMT), and intraocular pressure (IOP) were analyzed statistically.

RESULTS

The median duration of the follow-up was 3.0 months in overall groups. The BCVA increased significantly in all groups (p = 0.018, p = 0.034, p = 0.014, respectively). The CMT increased significantly in groups 1 and 3 (p = 0.02, p&lt;0.001, respectively), but not in group 2 (p = 0.14). The IOP increased significantly in groups 1 and 3 (p = 0.05, p&lt;0.001, respectively). Antiglaucomatous treatment was required only in group 3. Cataract developed in 2 patients (20%) in group 3 and surgery was required.

CONCLUSIONS

Although RAN was the safest among the 3 agents, DEX and IVTA reduced CMT more than RAN, while significant improvement was achieved in BCVA in all groups. All 3 agents can be effectively used in the treatment of macular edema due to BRVO.

Twelve-month experience with Ozurdex for the treatment of macular edema associated with retinal vein occlusion

PURPOSE

To evaluate the efficacy and safety of a dexamethasone implant (Ozurdex) alone or in combination with bevacizumab.

METHODS

Sixty-four eyes were prospectively investigated. Group 1 (22 central retinal vein occlusion (CRVO) and 16 branch retinal vein occlusion (BRVO)) was treated with Ozurdex alone, and group 2 (14 CRVO and 12 BRVO) was treated with three consecutive bevacizumab injections followed by Ozurdex. Recurrences were treated with Ozurdex only. Patients were seen preoperatively and thereafter in monthly intervals. The primary end point was best-corrected visual acuity (BCVA) at 12 months.

RESULTS

In group 1, BCVA improved by 6.6 (±1.7) letters in CRVO and 7.8 (±2.9) in BRVO patients, and in group 2 by 9.8 (±1.0) vs 9.4 (±2.1) letters. A significant difference was only seen between CRVO patients in group 1 and 2 at 12 months (P<0.05). Recurrence after the first Ozurdex injection occurred after 3.8 (CRVO) and 3.5 months (BRVO) in group 1, vs 3.2 and 3.7 months in group 2. Elevated intraocular pressure (>5 mm Hg) was measured in approximately 40% cataract progression requiring surgery in about 50% of eyes after three Ozurdex injections.

CONCLUSION

Combined treatment showed slightly better functional outcome for CRVO patients. Increased intraocular pressure and cataract progression was frequent and should be considered when an individual treatment is planned.

Comparison of intravitreal bevacizumab upload followed by a dexamethasone implant versus dexamethasone implant monotherapy for retinal vein occlusion with macular edema

PURPOSE

To compare the efficacy and safety of three intravitreal bevacizumab upload injections followed by a dexamethasone implant versus dexamethasone implant monotherapy in eyes with macular edema due to retinal vein occlusion.

METHODS

Sixty-four eyes of 64 patients were included in this prospective, consecutive, nonrandomized case series: group 1 consisted of 38 patients (22 with central retinal vein occlusion, CRVO, 16 with branch retinal vein occlusion, BRVO) treated using a dexamethasone implant (Ozurdex) alone; group 2 consisted of 26 patients (14 CRVO, 12 BRVO) treated with three consecutive intravitreal bevacizumab injections at monthly intervals followed by a dexamethasone implant. In case of recurrence, both cohorts received further dexamethasone implants. Preoperatively and monthly best corrected visual acuity (BCVA, ETDRS), central retinal thickness (Spectralis-OCT), intraocular pressure, and wide-angle fundus photodocumentation (Optomap) were performed. The primary clinical endpoint was BCVA at 6 months after initiation of therapy. Secondary endpoints were central retinal thickness and safety of the therapy applied.

RESULTS

In group 1, an increase in BCVA of 2.5 (±1.6) letters in the CRVO and of 13.0 (±3.2) letters in BRVO patients was seen after 6 months, in group 2 of 5.9 (±0.4) letters (CRVO) and 3.8 (±2.4) letters (BRVO), which was not statistically significant. When comparing the two treatment groups with respect to the type of vein occlusion, there was a significant advantage for BRVO patients for the dexamethasone implant monotherapy (BRVO patients in group 1, p = 0.005). Central retinal thickness showed a significant reduction after 6 months only in patients of group 1, both for CRVO (p = 0.01) and BRVO (p = 0.003). First recurrence after the first dexamethasone implant injection occurred after 3.8 months (mean) in CRVO and 3.5 months in BRVO patients (group 1), versus 3.2 and 3.7 months, respectively, in group 2. In group 1, 63.6% with CRVO and 50% with BRVO showed an increased intraocular pressure after treatment; in group 2, 57.1% with CRVO and 50.0% with BRVO, respectively.

CONCLUSION

In CRVO, there was no difference between the two treatment strategies investigated. However, in BRVO, dexamethasone implant monotherapy was associated with better functional outcome.

SCORE Study report #11: incidences of neovascular events in eyes with retinal vein occlusion

PURPOSE

To investigate in The Standard Care versus COrticosteroid for REtinal Vein Occlusion (SCORE) Study: (1) incidences of neovascular events and retinal capillary nonperfusion (abbreviated as "nonperfusion"), and their relationship with treatment groups; (2) neovascular incidences by nonperfusion status; and (3) pertinent baseline factors for their potential risk for neovascular events.

DESIGN

Two multicenter, randomized clinical trials, 1 evaluating participants with central retinal vein occlusion (CRVO) and the other evaluating participants with branch retinal vein occlusion (BRVO).

PARTICIPANTS

At 36 months, data were available for 81 participants with CRVO and 128 with BRVO.

INTERVENTION

Standard care (observation or grid photocoagulation) versus 1 or 4 mg intravitreal triamcinolone.

MAIN OUTCOME MEASURES

Neovascularization of the iris (NVI), neovascular glaucoma (NVG), disc or retinal neovascularization (NVD/NVE), preretinal or vitreous hemorrhage (PRH/VH), and nonperfusion.

RESULTS

The cumulative 36-month incidences for CRVO and BRVO eyes, respectively, were 8.5% and 2.4% for NVI or NVG; 8.8% and 7.6% for NVD/NVE or PRH/VH. There were no differences in incidences of neovascular events or risk of nonperfusion when comparing the 3 treatment groups within diseases. For CRVO at 36 months, 16.6% of eyes with ≥5.5 disc areas of nonperfusion versus 4.0% of eyes with <5.5 disc areas of nonperfusion developed NVG (P = 0.0003); for BRVO at 36 months, 14.6% versus 2.4% developed NVD/NVE (P<0.0001). Similar results were noted for most other neovascular events. Nonperfusion was the only significant baseline factor for neovascularization in BRVO, with the risk of a neovascular event increasing with greater disc areas of nonperfusion, and the highest risk noted at ≥5.5 disc areas.

CONCLUSIONS

In the SCORE Study, triamcinolone treatment was not associated with lower incidences of neovascular events or nonperfusion status compared with observation or grid photocoagulation. Cumulative 36-month incidences for most neovascular events were significantly higher for nonperfused than perfused eyes. Greater baseline disc areas of nonperfusion increased the risk of neovascularization in BRVO but not CRVO eyes, possibly owing to obscuration of retinal capillary details caused by dense hemorrhage at baseline for CRVO eyes. Increased risk of neovascularization was noted below the historical threshold of 10 disc areas of nonperfusion for retinal vein occlusion.

Stromal cell-derived factor-1 is essential for photoreceptor cell protection in retinal detachment

Stromal cell-derived factor-1 (SDF-1) causes chemotaxis of CXCR4-expressing bone marrow-derived cells. SDF-1 is involved in the pathogenesis of various vascular diseases, including those of the eye. However, the role of SDF-1 in neuronal diseases is not completely understood. Here, we show higher SDF-1 levels in the vitreous humor of patients with retinal detachment (RD) compared with normal patients. SDF-1 correlated positively with the duration as well as the extent of RD. Furthermore, SDF-1 correlated significantly with levels of interleukin-6 and interleukin-8, but not with vascular endothelial growth factor. Western blot analysis results showed significant SDF-1 up-regulation in detached rat retinas compared with normal animals. Immunohistochemistry data showed that SDF-1 was co-localized with the glial cells of the detached retina. SDF-1 blockade with a neutralizing antibody increased photoreceptor cell loss and macrophage accumulation in the subretinal space. The retinal precursor cell line R28 expressed CXCR4. SDF-1 rescued serum starvation-induced apoptosis in R28 cells and enhanced their ability to participate in wound closure in a scratch assay. Our results indicate a surprising, protective role for SDF-1 in RD. This effect may be mediated directly or indirectly through other cell types.

Effect of triamcinolone acetonide on vascular endothelial growth factor and occludin levels in branch retinal vein occlusion

PURPOSE

To investigate the molecular mechanism by which triamcinolone acetonide (TA) may reduce edema in a porcine model of branch retinal vein occlusion (BRVO).

DESIGN

Animal study.

METHOD

After baseline ophthalmoscopic examination and fundus photography, a BRVO was created photothrombotically in each eye of 6 pigs, using argon green photocoagulation and intravenous Rose Bengal. Following this, the left eye was injected intravitreally with 4 mg/0.1 ml TA. After 11 weeks, the eyes were re-examined. Fluorescein angiography, in addition to ophthalmoscopy and fundus photography, was performed. Following sacrifice of the animals, the eyes were enucleated and processed. The distribution of vascular endothelial growth factor (VEGF), occludin, and glial fibrillary acidic protein (GFAP) were localized by immunofluorescence cytochemistry on 10 microm frozen retinal sections of TA-treated and untreated eyes.

RESULTS

Retinal VEGF levels were significantly lower in the TA-treated eyes as compared with the untreated eye (P = .002). Conversely occludin levels were significantly higher in the treated eye (P = .026). There was also a significant reduction in GFAP immunoreactivity in the Muller cells of the treated eyes (P = .015) with no statistical significance in the astrocytes (P = .065).

CONCLUSION

Intravitreal TA down regulates VEGF, which may prevent a decrease in occludin and also inhibits an increase in GFAP expression in Muller cells. These events may contribute to a reduction in the blood retinal barrier breakdown that occurs in BRVO and promote resolution of the associated retinal edema.