Multifocal ERG defects associated with insufficient long-term glycemic control in adolescents with type 1 diabetes

Proteomic analysis of aqueous humor reveals novel regulators of diabetic macular edema

Diabetic macular edema (DME) is the most common cause of blindness in patients with diabetic retinopathy. To investigate the proteomic profiles of the aqueous humor (AH) of individuals with diabetic macular edema (DME), AH samples were collected from patients with non-diabetes mellitus (NDM), DM, nonproliferative diabetic retinopathy (NPDR), and DME. We performed comparative proteomic analyses using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics analyses. We identified 425 proteins in these AH samples, of which 113 showed changes in expression in DME compared with NDM, 95 showed changes in expression in DME vs. DM, and 84 showed changes in expression in DME compared with NPDR. The bioinformatics analysis suggested that DME is closely associated with platelet degranulation, oxidative stress-related pathway, and vascular-related pathways. Upregulation of haptoglobin (HP) and downregulation of fibrillin 1 (FBN1) were validated by ELISA. Receiver operating characteristic (ROC) analysis showed that HP and FBN1 could distinguish DME from NPDR with areas under the curve of 0.987 (p = 0.00608) and 0.791 (p = 0.00629), respectively. The findings provide potential clues for further analysis of the molecular mechanisms and the development of new treatments for DME. HP and FBN1 may be potential key proteins and therapeutic targets in human DME. The proteomics dataset generated has been deposited to the ProteomeXchange/iProX Consortium with Identifier: PXD033404/IPX0004353001.

Contrast sensitivity function under three light conditions in patients with type 1 diabetes mellitus without retinopathy: a cross-sectional, case-control study

PURPOSE

To determine whether patients with type 1 diabetes mellitus (T1DM), without any sign of diabetic retinopathy, have any alteration in Contrast Sensitivity Function (CSF), in relation to patients without this disease, and whether CSF assessment in three different light conditions can be an effective test in the early detection of diabetic retinopathy.

METHODS

A prospective, cross-sectional, case-control study was preformed including 80 patients (40 with T1DM without diabetic retinopathy and 40 controls) between 11 and 47 years old. CSF was assessed at four spatial frequencies (3, 6, 12 and 18 cycles/degree) using the CSV-1000E test, under three light conditions: high (550 lx), medium (200 lx) and low (< 2 lx).

RESULTS

A lower CSF in the T1DM group was found at the three light conditions studied. The most spatial frequency affected was 18 cpd, 0.08 log units (p = 0.048) in high, 0.10 log units (p = 0.010) in medium (p = 0.010) and 0.16 log units (p < 0.001) in low-light conditions in mean CS values. The least spatial frequency affected was 3 cpd (p > 0.05 in all three light conditions).

CONCLUSION

Patients with T1DM, without diabetic retinopathy, presented a loss of CS to sine-wave gratings, with respect to people with the same characteristics without the disease, mainly at medium and high frequencies, and in medium and low-light conditions.

Serum glial fibrillary acidic protein and neurofilament light chain as biomarkers of retinal neurodysfunction in early diabetic retinopathy: results of the EUROCONDOR study

AIMS

Neurodegeneration and glial activation are primary events in the pathogenesis of diabetic retinopathy. Serum glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) are biomarkers of underlying neuroinflammatory and neurodegenerative disease processes. The aim of the present study was to assess the usefulness of these serum biomarkers for the identification and monitoring of retinal neurodysfunction in subjects with type 2 diabetes.

METHODS

A case-control study was designed including 38 patients from the placebo arm of the EUROCONDOR clinical trial: 19 with and 19 without retinal neurodysfunction assessed by multifocal electroretinography. GFAP and NfL were measured by Simoa.

RESULTS

Serum levels of GFAP and NfL directly correlated with age (r = 0.37, p = 0.023 and r = 0.54, p < 0.001, respectively). In addition, a direct correlation between GFAP and NfL was observed (r = 0.495, p = 0.002). Serum levels of GFAP were significantly higher at baseline in those subjects in whom neurodysfunction progressed after the 2 years of follow-up (139.1 ± 52.5 pg/mL vs. 100.2 ± 54.6 pg/mL; p = 0.04).

CONCLUSIONS

GFAP could be a useful serum biomarker for retinal neurodysfunction. Monitoring retinal neurodysfunction using blood samples would be of benefit in clinical decision-making. However, further research is needed to validate this result as well as to establish the best cutoff values.

Contrast Sensitivity Assessment in Early Diagnosis of Diabetic Retinopathy: A Systematic Review

INTRODUCTION

The purpose of this systematic review was to study whether contrast sensitivity assessment in people with diabetes could be a reliable test in early detection of diabetic retinopathy. A systematic search based on population, intervention, comparison, and outcome strategy was performed.

METHODS

PubMed, Scopus, and Web of Science were searched for English articles of human patients with type 1 and type 2 diabetes and contrast sensitivity measurements as domain studied.

RESULTS

Twentyone comparative cross-sectional studies were included. All of them showed significant loss of contrast sensitivity in people with diabetes and diabetic retinopathy regarding control patients of the same age, regardless of the method used. However, those without diabetic retinopathy, involve a loss of contrast sensitivity, although not always significant.

CONCLUSION

Changes in contrast sensitivity suggest that there is damage to the retina prior to the vascular ones and that they could be detected by this test.

Clinical electroretinography in diabetic retinopathy: a review

The electroretinogram (ERG) is a noninvasive, objective technique to evaluate retinal function that has become increasingly important in the study of diabetic retinopathy. We summarize the principles and rationale of the ERG, present findings from recent clinical studies that have used the full-field ERG, multifocal ERG, and pattern ERG to evaluate neural dysfunction in patients with diabetes, and weigh the strengths and limitations of the technique as it applies to clinical studies and management of patients with diabetic retinopathy. Taken together, ERG studies have provided convincing evidence for dysfunction of the neural retina in patients with diabetes, including those who have no clinically-apparent retinal vascular abnormalities. Recent full-field ERG findings have pointed to the intriguing possibility that photoreceptor function is abnormal in early-stage disease. Pattern ERG data, in conjunction with recently developed photopic negative response analyses, indicate inner retina dysfunction. In addition, multifocal ERG studies have shown spatially localized neural abnormalities that can predict the location of future microaneurysms. Given the insights provided by the ERG, it is likely to play a growing role in understanding the natural history of neural dysfunction in diabetes, as well as providing an attractive outcome measure for future clinical trials that target neural preservation in diabetic retinopathy.

AMPLITUDE LOSS OF THE HIGH-FREQUENCY FLICKER ELECTRORETINOGRAM IN EARLY DIABETIC RETINOPATHY

PURPOSE

To evaluate retinal dysfunction in diabetic patients who have mild or no nonproliferative diabetic retinopathy (DR) using the high-frequency flicker electroretinogram.

METHODS

Light-adapted flicker electroretinograms were recorded from 15 diabetic patients who have no clinically apparent retinopathy, 15 diabetic patients who have mild nonproliferative DR, and 15 nondiabetic, age-equivalent controls. Electroretinograms were elicited by full-field flicker at 2 temporal frequencies, 31.25 and 62.5 Hz, and were recorded using conventional techniques. Amplitude and timing of the flicker responses were compared among the groups and correlated with clinical characteristics including age, acuity, disease duration, and HbA1c.

RESULTS

The 31.25-Hz flicker amplitude was slightly, but nonsignificantly, smaller for subjects with no DR and mild nonproliferative DR , compared with the control group (both t < 1.38, P > 0.31); small, nonsignificant response delays for both patient groups were also observed (both t < 1.57, P > 0.12). By contrast, there were significant amplitude reductions for the 62.5-Hz flicker stimulus: mean amplitude was reduced by 32% for subjects with no DR and by 41% for subjects with mild nonproliferative DR (both t > 2.92 and P < 0.01). Response timing at 62.5 Hz did not differ significantly from control for either group (both t < 1.2 and P > 0.39). Electroretinogram amplitude and timing were not correlated significantly with clinical characteristics.

CONCLUSION

The 62.5-Hz flicker electroretinogram is useful for evaluating retinal dysfunction in diabetic patients who have mild or no DR because this response can be significantly reduced. Attenuation of the high-frequency flicker electroretinogram, which is primarily generated by bipolar cells, suggests a relatively early retinal site of neural dysfunction.

Screening for diabetic retinopathy in diabetic patients with a mydriasis-free, full-field flicker electroretinogram recording device

PURPOSE

To investigate the accuracy of the RETeval full-field flicker ERG in the screening of diabetic retinopathy (DR) and vision-threatening diabetic retinopathy (VTDR) and to determine a suitable range of DR diagnostic reference for patients with type 2 diabetes mellitus (T2DM).

METHODS

This was a cross-sectional study involving 172 subjects with T2DM, including 71 subjects without clinically detectable DR (NDR), 25 subjects with mild non-proliferative diabetic retinopathy (NPDR), 24 subjects with moderate NPDR, 27 subjects with severe NPDR and 25 subjects with proliferative diabetic retinopathy (PDR). All the subjects underwent a full-field flicker ERG using the RETeval device (DR assessment protocol), which is a mydriasis-free, full-field electroretinogram (ERG) recording system. The performance of the DR assessment protocol in detecting the DR (including mild NPDR, moderate NPDR, severe NPDR and PDR) and VTDR was analyzed with the receiver operating characteristic (ROC) curve.

RESULTS

For the detection of DR (mild NPDR, moderate NPDR, severe NPDR, PDR), the area under the ROC curve was 0.867 (p < 0.001, 95% CI 0.814-0.920), and the best cutoff value for DR was determined to be 20.75, with a sensitivity of 80.2% and specificity of 81.7%. Meanwhile, for the detection of VTDR, the area under the ROC curve was 0.965 (p < 0.001, 95% CI 0.941-0.989), and the best cutoff value was set to 23.05, with a sensitivity of 94.6% and a specificity of 88.8%.

CONCLUSION

The DR assessment protocol in RETeval device was effective in screening for DR (mild NPDR, moderate NPDR, severe NPDR, PDR) and VTDR in patients with diabetes. It could be helpful in referring and managing patients with T2DM in primary healthcare setting. However, caution should be taken that optimal cutoff value of DR assessment protocol may vary in different ethnic populations.

Retinal Neurodegeneration as an Early Manifestation of Diabetic Eye Disease and Potential Neuroprotective Therapies

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a major cause of visual impairment and blindness throughout the world. Microvascular changes have long been regarded central to disease pathogenesis. In recent years, however, retinal neurodegeneration is increasingly being hypothesized to occur prior to the vascular changes classically associated with DR and contribute to disease pathogenesis.

RECENT FINDINGS

There is growing structural and functional evidence from human and animal studies that suggests retinal neurodegeneration to be an early component of DR. Identification of new therapeutic targets is an ongoing area of research with several different molecules undergoing testing in animal models for their neuroprotective properties and for possible use in humans. Retinal neurodegeneration may play a central role in DR pathogenesis. As new therapies are developed, it will be important to develop criteria for clinically defining retinal neurodegeneration. A standardization of the methods for monitoring neurodegeneration along with more sensitive means of detecting preclinical damage is also needed.

Loss of CD40 attenuates experimental diabetes-induced retinal inflammation but does not protect mice from electroretinogram defects

Chronic low grade inflammation is considered to contribute to the development of experimental diabetic retinopathy (DR). We recently demonstrated that lack of CD40 in mice ameliorates the upregulation of inflammatory molecules in the diabetic retina and prevented capillary degeneration, a hallmark of experimental diabetic retinopathy. Herein, we investigated the contribution of CD40 to diabetes-induced reductions in retinal function via the electroretinogram (ERG) to determine if inflammation plays a role in the development of ERG defects associated with diabetes. We demonstrate that diabetic CD40-/- mice are not protected from reduction to the ERG b-wave despite failing to upregulate inflammatory molecules in the retina. Our data therefore supports the hypothesis that retinal dysfunction found in diabetics occurs independent of the induction of inflammatory processes.

Functional and Structural Findings of Neurodegeneration in Early Stages of Diabetic Retinopathy: Cross-sectional Analyses of Baseline Data of the EUROCONDOR Project

This cross-sectional study evaluated the relationship between 1) functional and structural measurements of neurodegeneration in the initial stages of diabetic retinopathy (DR) and 2) the presence of neurodegeneration and early microvascular impairment. We analyzed baseline data of 449 patients with type 2 diabetes enrolled in the European Consortium for the Early Treatment of Diabetic Retinopathy (EUROCONDOR) study (NCT01726075). Functional studies by multifocal electroretinography (mfERG) evaluated neurodysfunction, and structural measurements using spectral domain optical coherence tomography (SD-OCT) evaluated neurodegeneration. The mfERG P1 amplitude was more sensitive than the P1 implicit time and was lower in patients with Early Treatment of Diabetic Retinopathy Study (ETDRS) level 20-35 than in patients with ETDRS level <20 (P = 0.005). In 58% of patients, mfERG abnormalities were present in the absence of visible retinopathy. Correspondence between SD-OCT thinning and mfERG abnormalities was shown in 67% of the eyes with ETDRS <20 and in 83% of the eyes with ETDRS level 20-35. Notably, 32% of patients with ETDRS 20-35 presented no abnormalities in mfERG or SD-OCT. We conclude that there is a link between mfERG and SD-OCT measurements that increases with the presence of microvascular impairment. However, a significant proportion of patients in our particular study population (ETDRS ≤35) had normal ganglion cell-inner plexiform layer thickness and normal mfERG findings. We raise the hypothesis that neurodegeneration may play a role in the pathogenesis of DR in many but not in all patients with type 2 diabetes.

Neuroprotection as a Therapeutic Target for Diabetic Retinopathy

Diabetic retinopathy (DR) is a multifactorial progressive disease of the retina and a leading cause of vision loss. DR has long been regarded as a vascular disorder, although neuronal death and visual impairment appear before vascular lesions, suggesting an important role played by neurodegeneration in DR and the appropriateness of neuroprotective strategies. Upregulation of vascular endothelial growth factor (VEGF), the main target of current therapies, is likely to be one of the first responses to retinal hyperglycemic stress and VEGF may represent an important survival factor in early phases of DR. Of central importance for clinical trials is the detection of retinal neurodegeneration in the clinical setting, and spectral domain optical coherence tomography seems the most indicated technique. Many substances have been tested in animal studies for their neuroprotective properties and for possible use in humans. Perhaps, the most intriguing perspective is the use of endogenous neuroprotective substances or nutraceuticals. Together, the data point to the central role of neurodegeneration in the pathogenesis of DR and indicate neuroprotection as an effective strategy for treating this disease. However, clinical trials to determine not only the effectiveness and safety but also the compliance of a noninvasive route of drug administration are needed.

Role of Electrophysiology in the Early Diagnosis and Follow-Up of Diabetic Retinopathy

Retinopathy is a severe and common complication of diabetes, representing a leading cause of blindness among working-age people in developed countries. It is estimated that the number of people with diabetic retinopathy (DR) will increase from 126.6 million in 2011 to 191 million by 2030. The pathology seems to be characterized not only by the involvement of retinal microvessels but also by a real neuropathy of central nervous system, similar to what happens to the peripheral nerves, particularly affected by diabetes. The neurophysiological techniques help to assess retinal and nervous (optic tract) function. Electroretinography (ERG) and visual evoked potentials (VEP) allow a more detailed study of the visual function and of the possible effects that diabetes can have on the visual function. These techniques have an important role both in the clinic and in research: the central nervous system, in fact, has received much less attention than the peripheral one in the study of the complications of diabetes. These techniques are safe, repeatable, quick, and objective. In addition, both the ERG (especially the oscillatory potentials and the flicker-ERG) and VEP have proved to be successful tools for the early diagnosis of the disease and, potentially, for the ophthalmologic follow-up of diabetic patients.

Early retinal pigment epithelium dysfunction is concomitant with hyperglycemia in mouse models of type 1 and type 2 diabetes

In the diabetic retina, cellular changes in the retinal pigment epithelium (RPE) and neurons occur before vision loss or diabetic retinopathy can be identified clinically. The precise etiologies of retinal pathology are poorly defined, and it remains unclear if the onset and progression of cellular dysfunction differ between type 1 and type 2 diabetes. Three mouse models were used to compare the time course of RPE involvement in type 1 and type 2 diabetes. C57BL/6J mice injected with streptozotocin (STZ mice) modeled type 1 diabetes, whereas Lepr(db/db) mice on both BKS and B6.BKS background strains modeled type 2 diabetes. Electroretinogram (ERG)-based techniques were used to measure light-evoked responses of the RPE (direct current-coupled ERG, dc-ERG) and the neural retina (a-wave, b-wave). Following onset of hyperglycemia, a-wave and b-wave amplitudes of STZ mice declined progressively and by equivalent degrees. Components of the dc-ERG were also altered, with the largest reduction seen in the c-wave. Lepr(db/db) mice on the BKS strain (BKS.Lepr) displayed sustained hyperglycemia and a small increase in insulin, whereas Lepr(db/db) mice on the B6.BKS background (B6.BKS.Lepr) were transiently hyperglycemic and displayed severe hyperinsulinemia. BKS.Lepr mice exhibited sustained reductions in the dc-ERG c-wave, fast oscillation, and off response that were not attributable to reduced photoreceptor activity; B6.BKS.Lepr mice displayed transient reductions in the c-wave and fast oscillation that correlated with hyperglycemia and magnitude of photoreceptor activity. In summary, all mouse models displayed altered RPE function concomitant with the onset of hyperglycemia. These results suggest that RPE function is directly reduced by elevated blood glucose levels. That RPE dysfunction was reversible and mitigated in hyperinsulinemic B6.BKS.Lepr mice provides insight into the underlying mechanism.

Neuroretinal dysfunction with intact blood-retinal barrier and absent vasculopathy in type 1 diabetes

It is unknown whether independent neural damage may occur in the pre-/absent vascular diabetic retinopathy (DR). To exclude vasculopathy, it is important to measure the integrity of the blood-retinal barrier (BRB). This cross-sectional study addressed this problem in type 1 diabetic patients with normal ocular fundus and absent breakdown of the BRB (confirmed with vitreous fluorometry). These were compared with a group with disrupted BRB (with normal fundus or initial DR) and normal controls. Multifocal electroretinography and chromatic/achromatic contrast sensitivity were measured in these 42 patients with preserved visual acuity. Amplitudes of neurophysiological responses (multifocal electroretinogram) were decreased in all eccentricity rings in both clinical groups, when compared with controls, with sensitivity >78% for a specificity level of 90%. Implicit time changes were also found in the absence of initial DR. Impaired contrast sensitivity along chromatic axes was also observed, and achromatic thresholds were also different between controls and both clinical groups. The pattern of changes in the group without baseline BRB permeability alterations, as probed by psychophysical and electrophysiological measurements, does thereby confirm independent damage mechanisms. We conclude that retinal neuronal changes can be diagnosed in type 1 diabetes, independently of the breakdown of the BRB and onset of vasculopathy.

Endothelial progenitor cells in diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of visual impairment worldwide. Patients with DR may irreversibly lose sight as a result of the development of diabetic macular edema (DME) and/or proliferative diabetic retinopathy (PDR); retinal blood vessel dysfunction and degeneration plays an essential role in their pathogenesis. Although new treatments have been recently introduced for DME, including intravitreal vascular endothelial growth factor inhibitors (anti-VEGFs) and steroids, a high proportion of patients (~40-50%) do not respond to these therapies. Furthermore, for people with PDR, laser photocoagulation remains a mainstay therapy despite this being an inherently destructive procedure. Endothelial progenitor cells (EPCs) are a low-frequency population of circulating cells known to be recruited to sites of vessel damage and tissue ischemia where they promote vascular healing and re-perfusion. A growing body of evidence suggests that the number and function of EPCs are altered in patients with varying degrees of diabetes duration, metabolic control, and in the presence or absence of DR. Although there are no clear-cut outcomes from these clinical studies, there is mounting evidence that some EPC sub-types may be involved in the pathogenesis of DR and may also serve as biomarkers for disease progression and stratification. Moreover, some EPC sub-types have considerable potential as therapeutic modalities for DME and PDR in the context of cell therapy. This study presents basic clinical concepts of DR and combines this with a general insight on EPCs and their relation to future directions in understanding and treating this important diabetic complication.

Current trends in the monitoring and treatment of diabetic retinopathy in young adults

The diagnosis and treatment of diabetic retinopathy (DR) in young adults have significantly improved in recent years. Research methods have widened significantly, for example, by introducing spectral optical tomography of the eye. Invasive diagnostics, for example, fluorescein angiography, are done less frequently. The early introduction of an insulin pump to improve the administration of insulin is likely to delay the development of diabetic retinopathy, which is particularly important for young patients with type 1 diabetes mellitus (T1DM). The first years of diabetes occurring during childhood and youth are the most appropriate to introduce proper therapeutic intervention before any irreversible changes in the eyes appear. The treatment of DR includes increased metabolic control, laserotherapy, pharmacological treatment (antiangiogenic and anti-inflammatory treatment, enzymatic vitreolysis, and intravitreal injections), and surgery. This paper summarizes the up-to-date developments in the diagnostics and treatment of DR. In the literature search, authors used online databases, PubMed, and clinitrials.gov and browsed through individual ophthalmology journals, books, and leading pharmaceutical company websites.

Multifocal electroretinography in diabetic retinopathy and diabetic macular edema

In this review article, we first present a brief overview of the vascular and neural components of diabetic retinopathy. Next, the multifocal electroretinogram (mfERG) technique, which can map neuroretinal function noninvasively, is described. Findings in diabetic retinal disease using the mfERG are reviewed. We then describe the progress that has been made to predict the onset and progression of diabetic retinopathy and edema in specific retinal locations, using quantitative models based on the mfERG. Finally, we consider the implications for the future of these predictive models.

Association between local neuroretinal function and control of adolescent type 1 diabetes

PURPOSE

To evaluate associations between neuroretinal function measured with multifocal electroretinogram (mfERG) and disease variables in adolescents with type 1 diabetes and no retinopathy.

METHODS

Fundus photographs, blood glucose (BG) concentration, HbA1c, and monocular mfERG were performed on 115 adolescent patients (mean age ± SD; 15.7 ± 1.8 years) and 30 controls (18.0 ± 2.8 years). All subjects had best-corrected visual acuity ≥ 20/20. The 45° mfERG stimulus included 103 hexagons, reversing between dark and bright according to a pseudorandom m-sequence. Amplitudes (AMPs) and implicit times (ITs) were derived from local mfERG response waveforms, and Z-scores were calculated. Retinal maps of abnormality frequencies were generated. Differences between controls and patients were evaluated using t-tests. Associations between mfERG and age, duration, and diabetes control were examined using linear regression analysis.

RESULTS

Mean mfERG IT was significantly longer in the patients compared with that in the controls (P = 0.019), but AMP was not different (P > 0.05). In all, 26 eyes (23%) of the patients had abnormal IT and 3 eyes (3%) had abnormal AMP. IT abnormalities were essentially distributed randomly across the retina. There were too few AMP abnormalities to examine their retinal distribution. IT was positively correlated with HbA1c (P < 0.0002) but not correlated with diabetes duration, BG, or age.

CONCLUSIONS

Higher long-term blood glucose concentration is associated with degraded neuroretinal function in adolescents with type 1 diabetes and no retinopathy. Over 20% of these patients have abnormal neuroretinal function. It will be important to determine longitudinally whether the relationship between mfERG IT and diabetes control exists within individual adolescent patients.

Analysis of multifocal electroretinograms from a population with type 1 diabetes using partial least squares reveals spatial and temporal distribution of changes to retinal function

Spatial-temporal partial least squares (ST-PLS) is a multivariate statistical analysis that has improved the analysis of modern imaging techniques. Multifocal electroretinograms (mfERGs) contain a large amount of data, and averaging and grouping have been used to reduce the amount of data to levels that can be handled using traditional statistical methods. In contrast, using all acquired data points, ST-PLS enables statistically rigorous testing of changes in waveform shape and in the distributed signal related to retinal function. We hypothesise that ST-PLS will improve analysis of the mfERG. Two mfERG protocols, a 103 hexagon clinical protocol and a slow-flash mfERG (sf-mfERG) protocol, were recorded from an adolescent population with type 1 diabetes and an age similar control population. The standard mfERGs were analysed using a template-fitting algorithm and the sf-mfERG using a signal-to-noise measure. The results of these traditional analysis techniques are compared with those of the ST-PLS analysis. Traditional analysis of the mfERG recordings revealed changes between groups for implicit time but not amplitude; however, the spatial location of these changes could not be identified. In contrast, ST-PLS detected significant changes between groups and displayed the spatial location of these changes on the retinal map and the temporal location within the mfERG waveforms. ST-PLS confirmed that changes to diabetic retinal function occur before the onset of clinical pathology. In addition, it revealed two distinct patterns of change depending on whether the multifocal paradigm was optimised to target outer retinal function (photoreceptors) or middle/inner retinal function (collector cells).

Comparison of aqueous humor cytokine and chemokine levels in diabetic patients with and without retinopathy

PURPOSE

To compare the aqueous humor levels of proinflammatory and angiogenic factors of diabetic patients with and without retinopathy.

METHODS

Aqueous humor was collected at the start of cataract surgery from diabetic subjects and non-diabetic controls. The presence and severity of diabetic retinopathy were graded with fundus examination. Levels of 22 different inflammatory and angiogenic cytokines and chemokines were compared.

RESULTS

Aqueous humor samples from 47 diabetic patients (20 without retinopathy, 27 with retinopathy) and 24 non-diabetic controls were included. Interleukin (IL)-2, IL-10, IL-12, interferon-alpha (IFN-α), and tumor necrosis factor (TNF)-α were measurable in significantly fewer diabetic samples, and where measurable, were at lower levels than in non-diabetic controls. IL-6 was measurable in significantly more diabetic samples, and the median levels were significantly higher in the eyes with retinopathy than the eyes without retinopathy and the non-diabetic eyes. The vascular endothelial growth factor (VEGF) level was significantly higher in the diabetic eyes with and without retinopathy compared to the non-diabetic controls. The IL-6 level positively correlated with the monocyte chemotactic protein-1 (CCL2) and interleukin-8 (CXCL8) levels and negatively with the TNF-α level. The VEGF level negatively correlated with the IL-12 and TNF-α levels.

CONCLUSIONS

The aqueous humor cytokine profile of diabetic patients without retinopathy was similar to that of patients with diabetic retinopathy. These cytokines may be useful biomarkers for early detection and prognosis of diabetic retinopathy. Compared to diabetic patients without retinopathy, only the IL-6 and VEGF levels were significantly higher in diabetic patients with retinopathy.

Comparison of aqueous humor cytokine and chemokine levels in diabetic patients with and without retinopathy

Background

Major-histocompatibility-complex class I-related chain A (MICA) antigens are the ligands of NKG2D, which is an activating or coactivating receptor expressed on human NK cells and CD8⁺T cells. We sought to determine whether MICA expression in human corneal epithelium (HCE) could affect the cytotoxicity mediated by NK cells or CD8⁺T cells.

Methods

Cell cultures of HCE were harvested from human donor eyes. Flow cytometric analysis and ELISA was performed to determine the levels of MICA expression on HCE. Then, HCE was transfected with a lentivirus vector expressing MICA and GFP. Flow cytometric analysis, RT-PCR, western blot and ELISA were performed to check the levels of MICA expression. For cytotoxicity testing, allogeneic NK cells and CD8⁺T cells were isolated from peripheral blood mononuclear cells of healthy volunteers by magnetic cell sorting. The cytolytic activity of NK cells and CD8⁺T cells was assessed against MICA-transfected HCE (NK cells: E:T ratio = 3:1; CD8⁺T cells: E:T ratio = 10:1) using the nonradioactive cytotoxicity detection kit lactate deshydrogenase.

Results

Surface expression of MICA on corneal epithelium was identified at a low level. A cell line of stable human MICA-transfected corneal epithelium was successfully established. Heightened expression of MICA on HCE was found to promote the cytotoxicity mediated by NK cells or CD8⁺T cells, which could be blocked by an anti-MICA antibody.

Conclusion

MICA molecules may contribute to cytotoxic responses mediated by activated immune effector cells in corneal epithelium immunity.