Early changes in diabetic retinopathy: capillary loss and blood-retina barrier permeability in relation to metabolic control

Frontiers in diabetic retinal disease

Diabetic retinal disease (DRD) remains a leading cause of vision loss and blindness globally. Although treatments can be effective when given at vision-threatening stages of DRD, there is a lack of knowledge about the earliest mechanisms leading to the development of clinically evident DRD. Recent advances in retinal imaging methods for patients with diabetes allow a more precise and granular characterization of the different stages of DRD than is provided by the classic Diabetic Retinopathy Severity Scale based on fundus photographs. In addition, recent clinical studies have yielded more information on how to adjust blood glucose levels, lipid levels and blood pressure to minimize the risk of DRD. Given the incomplete success of current therapies, there is a critical need for better understanding of the mechanisms underlying DRD and novel treatment targets that address the entire neurovascular retina. Moreover, the causes for interindividual variability in the development of DRD in patients with similar glycemic history and other metabolic factors are not yet clarified either. Finally, greater focus on patients' experience with visual disabilities and treatment effects should be addressed in research in this field.

Characterization of Hyperreflective Dots by Structural and Angiographic Optical Coherence Tomography in Patients with Diabetic Retinopathy and Healthy Subjects

Hyperreflective dots are a common but highly variable feature of optical coherence tomography (OCT) scans of the retina. We studied the spatial characteristics and perfusion of hyperreflective dots using both structural and angiographic OCT B-scans of the macula in 16 eyes in 8 healthy subjects and 8 patients with diabetic retinopathy without macular edema. Hyperreflective dots were manually graded in a 1000 µm parafoveal area by number, diameter, location and perfusion status and traced through adjacent B-scans at 11 µm intervals to determine their length. Thereby, this study defined a procedure to identify granular and elongated hyperreflective elements and differentiate between presumably perfused and occluded capillaries. The latter were only found in the diabetic patients. This classification can potentially be automated to non-invasively identify capillary non-perfusion in vivo.

The relationship between perifoveal capillary ring alterations and visual acuity in diabetic retinopathy

Background/Aim. The relationship between the foveal avascular zone (FAV) and visual acuity (VA) in retinal dis-eases remains a matter of discussion. The aim of this study was to determine the impact of diabetic macular ischemia (DMI) on VA through the analysis of the perifoveal capillary network in various stages of diabetic retinopathy - DR (non-proliferative diabetic retinopathy ? NPDR and proliferative diabetic retinopathy ? PDR). Methods. Qualitative and quantitative analysis of 143 angiograms of patients with different stages of DR was performed. The degree of macular ischemia was assessed by the analysis of 2 parameters: perifoveal capillary ring, ie, the FAZ outline irregularity, and capillary loss. Finally, a comparison was made between the degree of macular ischemia with the best-corrected VA, depending on macular thickness. Results. In the eyes with mild and moderate NPDR, without significant macular thickening, no statistically significant decrease in VA caused by macular ischemia was noticed (p = 0.81). Opposite, in a subgroup with severe NPDR and PDR, without significant macular thickening, a statistically significant difference was presented among eyes with moderate and severe macular ischemia compared to eyes with lower grades of macular ischemia (p = 0.021 and p = 0.018, respectively). In the eyes with moderate NPDR and mild macular ischemia, the increase in macular thickness resulted in a statistically insignificant decrease in VA compared to eyes with a normal macular thickness (p = 0.088). However, in the eyes with severe NPDR, every pathological increase in macular thickness caused a statistically significant decrease in VA, regardless of the degree of macular ischemia (p = 0.018?0.040). A similar relationship was also found in the eyes with PDR (p = 0.017?0.042). In the eyes with a statistically significant decrease in VA, most of the examined eyes (98%) had the FAZ outline irregularity in the nasal perifoveal subfield. Conclusion. In the absence of significant macular thickening, the destruction of one-half of the perifoveal capillary network, or greater, is associated with reduced VA. The location of macular ischemic changes in the nasal parts of the perifoveal capillary ring plays a crucial role in its effects on visual function.

Spatial distribution of diabetic capillary non-perfusion

OBJECTIVE

To evaluate the distribution of capillary non-perfusion (CNP) in superficial and deep capillary plexuses (SCP and DCP) in eyes with diabetic retinopathy (DR).

METHODS

In this retrospective case series, macular optical coherence tomography angiography (OCTA) images were obtained from eyes with DR without diabetic macular edema (DME). The area of CNP in SCP and DCP was delineated using an automated approach after excluding the foveal avascular zone (FAZ) and major retinal vessels. The distribution and spatial correlation of the CNP in each layer were analyzed.

RESULTS

Forty-three eyes of 27 patients with DR with a mean age of 59.10 ± 9.05 years were included. The mean CNP area in SCP was statistically significantly higher than DCP (0.722 ± 0.437 mm² vs. 0.184 ± 0.145 mm² , respectively, p < .001). There was a statistically significant association between mean BCVA (0.28 ± 0.21 logMAR) and CNP area in DCP (p = .01). After automated subtraction of CNP areas in DCP from SCP, 25.43 ± 15.05% of CNP areas in the DCP had co-localized CNP areas in SCP. The CNP percentage was statistically significantly different between the concentric rings on foveal center, both in SCP and in DCP (both p < .001) showing a decreasing trend from the outer ring toward the center.

CONCLUSION

In DR, SCP is more ischemic than DCP. This is in contrast to the previously described oxygenation-dependent ischemic cascade following acute retinal vascular occlusions. This study provides further insight into the retinal ischemia in DR.

Effects of intravitreal conbercept before panretinal photocoagulation on lipid exudates in diabetic macular documented by optical coherence tomography

AIM

To evaluate the effects of intravitreal conbercept (IVC) as adjunctive treatments before panretinal photocoagulation (PRP) to decrease hyperreflective dots (HRDs) in Chinese proliferative diabetic retinopathy (PDR) patients.

METHODS

Fifty-nine enrolled patients were categorized into 2 groups: single dose IVC (0.5 mg/0.05 mL) 1wk before PRP (Plus group) or PRP only (PRP group). Six months later, we measured the best corrected visual acuity (BCVA), central macula thickness (CMT) by optical coherence tomography and counted the number of HRDs in different retina layers.

RESULTS

The average CMT significantly decreased in Plus group but increased in PRP group. The average BCVA in the Plus group was also significantly better than that in the PRP group. Total HRDs decreased in the Plus group but increased in PRP group significantly. IVC pre-treatment has beneficial effects on reducing HRDs forming in the inner retina layer while the PRP alone increased the HRDs in the outer retina layer.

CONCLUSION

IVC is a promising adjunctive treatment to PRP in the treatment of PDR. Single dose IVC one week before PRP is suggested to improve retina blood-retina barrier, decrease lipid exudate and inhibit HRDs development in PDR.

Distances From Capillaries to Arterioles or Venules Measured Using OCTA and AOSLO

Purpose

To investigate distances from retinal capillaries to arterioles or venules noninvasively.

Methods

An adaptive optics scanning laser ophthalmoscope (AOSLO) and optical coherence tomography angiography (OCTA) imager acquired detailed maps of retinal vasculature. Using OCTA, we quantified the distance from the edge of an arteriole or venule to the middle of the nearest capillaries (periarteriole or perivenule capillary-free zones, respectively) within the superficial vascular plexus of 20 young healthy subjects with normal axial lengths. These distances were compared to AOSLO images for three subjects. We tested the relation between the peripheral capillary-free zones and FAZ horizontal, vertical, effective diameters, and asymmetry indices in the deep vascular plexus. We examined enlargement with OCTA of capillary-free zones in a type 2 diabetic patient.

Results

The periarteriole capillary-free zone (67.2 ± 25.3 μm) was readily visible and larger than the perivenule capillary-free zone (42.7 ± 14.4 μm), F_{(1, 998)} = 771, P < 0.0001. The distance from foveal center (P = 0.003) and diameter (P = 0.048) were predictive of perivenule capillary-free zone values. OCTA and AOSLO corresponded for arterioles. FAZ effective diameter was positively associated with asymmetry indices, r = 0.49, P = 0.028, but not peripheral capillary-free zones, although focal enlargements were found in a diabetic patient.

Conclusions

For normal retinas, periarteriole and perivenule capillary-free zones are readily visible with OCTA and AOSLO. Periarteriole capillary-free zones were larger, consistent with arterioles carrying oxygen rich blood that diffuses to support the retina.

Enlargement of the foveal avascular zone detected by optical coherence tomography angiography in diabetic children without diabetic retinopathy

PURPOSE

Evaluation of foveal avascular zone (FAZ) in children with diabetes (DM) using OCTA.

METHODS

We examined 112 diabetic children without DR aged 6-18 years and 30 age-matched controls using Topcon OCT Angiography and measured FAZ in superficial (SCP) and deep capillary plexus (DCP). The study group was divided into three subgroups depending on DM duration group 1: < 5 years (n = 40), group 2: 5-10 years (n = 42), group 3: > 10 years (n = 30).

RESULTS

The mean DCP FAZ increased with DM duration from 502.2 μm² (SD 137.8) in group 1 to 523.9 μm² (SD 159.2) in group 2 and 539.7 μm² (SD 189.1) in group 3. Control group differed significantly from group 1 (p = 0.0120), group 2 (p = 0.0019) and group 3 (p = 0.0011). The mean DCP to SCP FAZ surface ratio was 1.88 (SD 0.68) in the study vs 1.58 (SD 0.48) in the control group (p = 0.0232). The DCP and SCP FAZ surface difference was 217.6 μm² (SD 100.8 μm²) in diabetics vs. 124.2 μm² (SD 72.8 μm²) in controls (p < 0.0001). In the control group, it was significantly smaller than in group 1 (p < 0.006), group 2 (p < 0.0001) and group 3 (p < 0.0001).

CONCLUSIONS

Changes can be detected in FAZ of diabetic children before DR development which can be vital for screening.

An Overview of Our Current Understanding of Diabetic Macular Ischemia (DMI)

Diabetic macular ischemia (DMI) is a troublesome complication of diabetes mellitus. The pathogenesis, progression, consequences, and treatment options for this disease are still poorly understood. However, it is believed that this complication is associated with several risk factors like poor glycemic control and high blood pressure. Two factors have been identified in the pathogenesis of the disease that play pivotal roles in disease development and progression. One of these factors includes extensive damage to the microvasculature of the retina. This includes narrowing of the vascular lumen and extensive damage to the endothelial cells, pericytes and the extracellular matrix. The second factor includes extensive damage to the neurosensory layer of the retina. DMI is always associated with other complications of diabetic retinopathy like retinal edema, so it is very difficult to find an isolated case of DMI. Moreover, the condition is also very rare making it very difficult to study and diagnose. However, a number of diagnostic tests like optical coherence tomography (OCT), fluorescence angiography (FA), and perimetry can be used as tools for the early detection of DMI. Since this disease damages the retina, loss of vision is an inevitable consequence that can progressively worsen over time. Also, DMI has been implicated as a risk factor for retinal edema and progressive diabetic retinopathy. Until now, no defined treatment protocol has been devised. The only available treatments focus on the management of risk factors (hyperglycemia and hypertension). Still, many aspects of DMI remain poorly studied and understood. This review paper aims to add to our current understanding of diabetic macular ischemia (DMI).

Parafoveal Nonperfusion Analysis in Diabetic Retinopathy Using Optical Coherence Tomography Angiography

Purpose

To describe a new technique for mapping parafoveal intercapillary areas (PICAs) using optical coherence tomography angiography (OCTA), and demonstrate its utility for quantifying parafoveal nonperfusion in diabetic retinopathy (DR).

Methods

Nineteen controls, 15 diabetics with no retinopathy (noDR), 15 with nonproliferative diabetic retinopathy (NPDR), and 15 with proliferative diabetic retinopathy (PDR) were imaged with 10 macular OCTA scans. PICAs were automatically delineated on the averaged superficial OCTA images. Following creation of an eccentricity-specific reference database from the controls, all PICAs greater than 2 SD above the reference means for PICA area and minor axis length were identified as nonperfused areas. Regions of interest (ROI) at 300 μm and 1000 μm from the foveal avascular zone (FAZ) margin were analyzed. Percent nonperfused area was defined as summed nonperfused areas divided by ROI area. Values were compared using Kruskal-Wallis and post-hoc Mann-Whitney U tests.

Results

Median values for total percent nonperfused area at the 300-μm ROI were 2.09, 2.44, 18.08, and 27.55 in the control, noDR, NPDR, and PDR groups, respectively. Median values at the 1000-μm ROI were 3.10, 3.31, 13.42, and 23.00. While there were no significant differences between the control and noDR groups, significant differences were observed between all other groups at both ROIs.

Conclusions

Percent nonperfused area can quantify parafoveal nonperfusion in DR and can be calculated through automatic delineation of PICAs in an eccentricity-specific manner using a standard deviation mapping approach.

Translational Relevance

Percent nonperfused area shows promise as a metric to measure disease severity in diabetic retinopathy.

Intraretinal changes in idiopathic versus diabetic epiretinal membranes after macular peeling

Introduction

Epiretinal traction is not responsible only for epiretinal but also intraretinal changes. This study aims to describe structural and vascular intraretinal changes after macular peeling in idiopathic (iERM) vs diabetic ERM (dERM).

Methods

We conducted a prospective interventional study on forty-two eyes, 23 with iERMs and 19 with dERMs, undergoing ERM-ILM peeling. We performed SD-OCT preoperatively, 1 and 6 months postoperatively to assess central macular thickness (CMT), intraretinal cysts (IC) and/or continuous ectopic inner foveal layers (CEIFL), superficial and deep capillary free zone (CFZ) area on OCT-A. Glial fibrillary acidic protein (GFAP), as a Müller cells marker, was detected immunohistochemically on ILM specimens, to assess Müller cells iatrogenic damage.

Results

The CEIFLs were significantly more common in iERMs (12 (52.2%) in iERMs vs 2 (10.5%) in dERMs, p = 0.004), whereas ICs in dERMs (6 (26.1%) in iERMs vs 17 (89.5%) in dERMs, p<0.001). Median preoperative and postoperative BCVA was 20/50 [20/40-20/66] and 20/33 [20/25-20/40] in iERMs and 20/100 [20/66-20/200] and 20/50 [20/50-20/66] in dERMs, respectively. Median preoperative and postoperative CMT was 423 [370–488] and 364 [329–382] μm in iERM group and 465 [447–503] and 378 [359–433] μm in dERM group, respectively. The BCVA improvement and reduction of CMT thickness were significant in both groups (p<0.001). The presence of CEIFL was associated with lower BCVA in iERMs. Deep CFZ network significantly increased only in dERMs, passing from 0.34 [0.29–0.42] mm² preoperatively to 0.56 [0.46–0.6] mm² at 6-month follow-up (p<0.001). The GFAP expression was significantly higher in dERMs (p = 0.001).

Conclusion

The intraretinal changes are different in iERMs and dERMs, as increased expression of CEIFLs in iERMs vs ICs in dERMs. The CEIFLs are associated with worse anatomical and functional outcomes in iERMs, whereas GFAP espression in peeled ILMs is higher in dERMs.

Early microvascular retinal changes in optical coherence tomography angiography in patients with type 1 diabetes mellitus

PURPOSE

Diabetic retinopathy (DR) can lead to significant vision loss and blindness and has a particularly high prevalence in patients with type 1 diabetes (DM1). In this study, we investigate quantitative differences in optical coherence tomography angiography (OCTA) data between DM1 patients with no or mild signs of retinopathy and non-diabetic subjects.

METHODS

Optical coherence tomography angiography (OCTA) imaging was performed on DM1 patients with no or mild nonproliferative diabetic retinopathy and healthy, age-matched controls. Parafoveal vessel density and foveal avascular zone (FAZ) area in the deep capillary plexus (DCP) and superficial capillary plexus (SCP) were calculated with automated quantification software and compared between patient cohorts.

RESULTS

A significant decrease in parafoveal vessel density was seen in the DCP of DM1 patients compared to non-diabetic controls (57.0 ± 3.3% versus 60.7 ± 2.4%, p < 0.001). There was no significant difference in SCP parafoveal vessel density, DCP FAZ area, or SCP FAZ area between cohorts.

CONCLUSION

M1 patients with no or mild signs of retinopathy have reduced parafoveal vessel density in the DCP on OCTA when compared to non-diabetic controls. These OCTA findings suggest that parafoveal capillary nonperfusion is an early process in DM1-related retinal changes and occurs initially at the level of the DCP. Further investigation is needed to understand the prognostic role of these vascular changes.

Foveal avascular zone area and parafoveal vessel density measurements in different stages of diabetic retinopathy by optical coherence tomography angiography

AIM

To investigate foveal avascular zone (FAZ) and parafoveal vessel densities (PRVD) by means of optical coherence tomography angiography (OCTA) in diabetic patients with or without diabetic retinopathy (DR) and to assess the reproducibility of FAZ and PRVD measurements.

METHODS

Sixty diabetic patients (60 eyes) with different stage of DR (graded according to the International Clinical Severity Scale for DR) and 20 healthy subjects underwent FAZ area and PRVD measurements using OCTA by two experienced examiners. FAZ area in all patients was also assessed using fluorescein angiography (FA).

RESULTS

In subject with proliferative DR and with moderate-severe non proliferative DR, FAZ area was significantly increased compared to healthy controls (P=0.025 and P=0.050 respectively measured with OCTA and P=0.025 and P=0.048 respectively measured with FA). OCTA showed significantly less inter-observer variability compared to FA. Concordance correlation coefficient (CCC) for FAZ area measurements was 0.829 (95%CI: 0.736-0.891) P<0.001 with FA and 1.000 (95%CI: 0.999-1.000) P<0.001 with OCTA. CCC was 0.834 (95%CI: 0.746-0.893) P<0.001 and 0.890 (95%CI: 0.828-0.930) P<0.001 for parafoveal superficial and deep vessel density measurements, respectively.

CONCLUSION

OCTA shows progressive increase of FAZ area and reduction of PRVD in both superficial and deep plexus at increasing DR severity. FAZ area and PRVD measurements using OCTA are highly reproducible.

Optical coherence tomography angiography analysis of retinal vascular plexuses and choriocapillaris in patients with type 1 diabetes without diabetic retinopathy

AIMS

To analyze retinal vascular plexuses and choriocapillaris by optical coherence tomography angiography (OCT-A) and retinal nerve fiber layer and ganglion cell layer (GCL) by structural optical coherence tomography (OCT) in patients with type 1 diabetes mellitus (T1DM) without diabetic retinopathy (DR).

METHODS

A total of 25 eyes of 25 consecutive T1DM patients without signs of DR were prospectively recruited and compared to 25 healthy subjects (control eyes). All patients underwent OCT-A (CIRRUS HD-OCT model 5000, Carl Zeiss Meditec, Dublin, CA) and structural OCT. Qualitative and quantitative analyses with vessel density were performed on OCT-A images in the superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris for all patients.

RESULTS

By means of OCT-A, a rarefaction of the perifoveal capillary network in SCP was detected in 7 out of 25 eyes. No significant difference was found in FAZ area of both SCP and DCP comparing diabetic and control groups. By analyzing the DCP, diabetic eyes revealed a significant decreased vessel density compared to control eyes [0.464 ± 0.016 and 0.477 ± 0.014, respectively (p = 0.005)]. Instead, no significant difference was found in the vessel density of all-retina plexus, SCP and choriocapillaris. By RFNL and GCL thickness analysis, no significant differences were disclosed between diabetics and healthy subjects.

CONCLUSIONS

We demonstrated the ability of OCT-A to disclose early vascular alterations in patients with T1DM diagnosed as without any signs of DR on the basis of fundus biomicroscopy. Our results also suggest that microvascular changes could precede detectable damage of diabetic neuroretinopathy.

Parafoveal OCT Angiography Features in Diabetic Patients without Clinical Diabetic Retinopathy: A Qualitative and Quantitative Analysis

Purpose

To evaluate the capacity of OCT angiography (OCTA) for detecting infraclinical lesions in parafoveal capillaries in diabetic patients without diabetic retinopathy (DR).

Methods

This prospective observational cross-sectional case-control study analyzed the superficial and deep capillary plexuses (SCP and DCP) on macular OCTA scans (3 × 3 mm) centered on the fovea. We compared 22 diabetic patients (34 eyes included) without DR diagnosis on color fundus photographs, with 22 age- and gender-matched nondiabetic controls (40 eyes included). Qualitative analysis concerned morphological ischemic capillary alterations. Quantitative analysis measured foveal avascular zone (FAZ) size, parafoveal capillary density, and enlargement coefficient of FAZ between SCP and DCP.

Results

Neither the qualitative nor quantitative parameters were significantly different between both groups. No microaneurysms or venous tortuosity was observed in any of the analyzed images. On the SCP, the mean FAZ area was 0.322 ± 0.125 mm² in diabetic patients and 0.285 ± 0.150 mm² in controls, P = 0.31. On the DCP, the mean FAZ area was 0.444 ± 0.153 mm² in cases and 0.398 ± 0.138 mm² in controls, P = 0.20.

Conclusion

OCTA did not detect infraclinical qualitative or quantitative differences in parafoveal capillaries of diabetic patients without DR in comparison with nondiabetic controls.

Retinal microvascular alterations related to diabetes assessed by optical coherence tomography angiography: A cross-sectional analysis

Fluorescein angiography has been so far the gold-standard test to assess diabetic macular ischemia (DMI), a cause of irreversible visual impairment in diabetic patients. The aim of this study was to investigate foveal avascular zone (FAZ) and perifoveal microcirculation changes in eyes with nonproliferative diabetic retinopathy (NPDR) using optical coherence tomography angiography (OCTA), a new and noninvasive vascular imaging technique.Cross-sectional study including eyes of diabetic patients with NPDR.All patients underwent medical history, best-corrected visual acuity (BCVA) measurement, slit-lamp and fundus examination, multicolor imaging, SD-OCT, and swept-source OCT. OCTA was performed in order to assess macular superficial and deep capillary plexus, and swept-source OCT was performed to evaluate the central choroidal thickness.Fifty-eight eyes of 35 patients with a mean age of 61.8 years (±12.1) with mean HbA1C level of 7.6% (±1.5) were included in this study. Among them, 19 eyes had mild NPDR, 24 eyes had moderate NPDR, and 15 eyes had severe NPDR. There was a significant progression between NPDR stages for FAZ grade (P < 0.0001), surface (P = 0.0036) and perimeter (P = 0.0001), and for superficial capillary plexus nonperfusion index (NPI) (P = 0.0009). Moreover, a significant correlation was found between NPI and BCVA (P = 0.007).OCT angiography is a useful noninvasive tool to explore early phases of diabetic retinopathy, which are not routinely explore with fluorescein angiography and not precisely enough with color photographs. NPI and foveal avascular zone parameters are correlated with glycated hemoglobin in patients with NPDR. If confirmed by further studies, these results could represent a mean to sensibilize diabetic patients to their disease.

Deep and superficial OCT angiography changes after macular peeling: idiopathic vs diabetic epiretinal membranes

BACKGROUND

To assess changes in deep and superficial perifoveal capillary plexus after macular peeling in idiopathic and diabetic epiretinal membrane (iERM and dERM, respectively).

METHODS

Cross-sectional comparative study. We included 40 eyes from 40 patients affected by iERM (20 eyes) and dERM (20 eyes), as well as 34 eyes from 17 healthy, age-matched patients. Patients received a complete ophthalmic evaluation including axial and en-face scanning spectral-domain analysis, optical coherence tomography angiography, and microperimetry. Split-spectrum amplitude-decorrelation angiography images were obtained to quantify the deep and superficial layers of perifoveal capillary-free zone (CFZ). The main outcome measures were: (i) differences at baseline between deep and superficial CFZ in iERM and dERM vs control, and (ii) changes in deep and superficial CFZ plexus after surgery in iERM vs dERM.

RESULTS

The deep CFZ only significantly increased in dERM at the end of the follow-up period (6 months). No statistically significant differences were found between preoperative and postoperative superficial vascular plexus in iERM or dERM. At the end of the follow-up, statistically significant differences between preoperative and postoperative ganglion cell complex (GCC) average were found only in the iERM group. Best-corrected visual acuity significantly improved after surgery both in the iERM (P = 0.0053) and dERM (P < 0.0001) groups. After 6 months, macular sensitivity increased in the iERM group, but there was no statistically significant change in the dERM group.

CONCLUSIONS

In dERM, the deep CFZ significantly increases after ILM peeling, whereas postoperative angiography changes were not significant in iERM. This could be because the impaired diabetic perifoveal capillary plexus are more sensitive to the iatrogenic damage to Müller cells, induced by peeling.

OSSC1E-K19, a novel phytochemical component of Osteomeles schwerinae, prevents glycated albumin-induced retinal vascular injury in rats

In the pathophysiology of diabetic retinopathy (DR), advanced glycation end products (AGEs) and vascular endothelial growth factor (VEGF) are thought to have important roles. It is known that VEGF causes a breakdown of the blood‑retinal barrier (BRB) and retinal neovascularization; however, how AGEs affect the retina has largely remained elusive. OSSC1E‑K19 is a novel phytochemical component of Osteomeles schwerinae. The objective of the present study was to evaluate the protective effects of OSSC1E‑K19 on retinal vascular injury in AGE‑modified rat serum albumin (AGE-RSA)-induced retinopathy. AGE-RSA-injected rat eyes were used investigate the protective effects of OSSC1E‑K19 on BRB breakdown. Intravitreal injection of OSSC1E-K19 prevented AGE-RSA-induced BRB breakdown and decreased retinal VEGF expression in retinal vessels. In addition, OSSC1E-K19 inhibited the loss of occludin, a significant tight junction protein. These results supported the potential therapeutic utility of OSSC1E-K19 for retinal vascular permeability diseases.

A morphological study of the foveal avascular zone in patients with diabetes mellitus using optical coherence tomography angiography

PURPOSE

To investigate the area and radius of the foveal avascular zone (FAZ) in patients with diabetes mellitus (DM) using optical coherence tomography (OCT) angiography.

METHODS

Sixty-five patients with DM (113 eyes) and 62 healthy controls (85 eyes) were included in the study. All of the participants underwent examination with OCT angiography. The vertical radius (VR), horizontal radius (HR) and area of the FAZ were measured.

RESULTS

The differences in HR, VR and area between the control and DM groups were statistically significant (p = 0.01, 0.00 and 0.00, respectively). There were no statistically significant differences between the control group and the no-diabetic retinopathy (DR) group in HR or VR (p = 0.07 and 0.08, respectively), but there was a statistically significant difference in area (p = 0.04). The size of the FAZ was greater in patients with DR compared to the control group. The differences in HR, VR and area were statistically significant (p = 0.01, 0.00 and 0.00, respectively). In addition, the clinically significant macular oedema (CSME) group also had a larger FAZ area than the non-CSME group (p = 0.02).

CONCLUSIONS

Patients with DM had a larger FAZ, and patients with more severely damaged retinas had a much larger FAZ. OCT angiography is a new convenient and noninvasive method for studying the FAZ. This novel examination will yield considerable amounts of data that cannot be obtained using previous research methods.

Assessment of perfused foveal microvascular density and identification of nonperfused capillaries in healthy and vasculopathic eyes

PURPOSE

To analyze the foveal microvasculature of young healthy eyes and older vasculopathic eyes, imaged using in vivo adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA).

METHODS

AOSLO FA imaging of the superficial retinal microvasculature within an 800-μm radius from the foveal center was performed using simultaneous confocal infrared (IR) reflectance (790 nm) and fluorescence (488 nm) channels. Corresponding IR structural and FA perfusion maps were compared with each other to identify nonperfused capillaries adjacent to the foveal avascular zone. Microvascular densities were calculated from skeletonized FA perfusion maps.

RESULTS

Sixteen healthy adults (26 eyes; mean age 25 years, range, 21-29) and six patients with a retinal vasculopathy (six eyes; mean age 55 years, range, 44-70) were imaged. At least one nonperfused capillary was observed in five of the 16 healthy nonfellow eyes and in four of the six vasculopathic eyes. Compared with healthy eyes, capillary nonperfusion in the vasculopathic eyes was more extensive. Microvascular density of the 16 healthy nonfellow eyes was 42.0 ± 4.2 mm(-1) (range, 33-50 mm(-1)). All six vasculopathic eyes had decreased microvascular densities.

CONCLUSIONS

AOSLO FA provides an in vivo method for estimating foveal microvascular density and reveals occult nonperfused retinal capillaries. Nonperfused capillaries in healthy young adults may represent a normal variation and/or an early sign of pathology. Although limited, the normative data presented here is a step toward developing clinically useful microvascular parameters for ocular and/or systemic diseases.

Emodin-6-O-β-D--glucoside inhibits high-glucose-induced vascular inflammation

Emodin-6-O-β-D-glucoside (EG), a new active compound from Reynoutria japonica, has recently been shown to exert potent anti-inflammatory and barrier protective effects in human umbilical vein endothelial cells (HUVECs) and in mice. Vascular inflammatory process has been suggested to play a key role in initiation and progression of atherosclerosis, a major complication of diabetes mellitus. Thus, we attempted to determine whether EG can suppress the vascular inflammatory process induced by high glucose (HG) in HUVECs and mice. Data showed that HG induced markedly increased vascular permeability, monocyte adhesion, expressions of CAMs, formation of ROS, and activation of NF-κB. Remarkably, all of the above-mentioned vascular inflammatory effects of HG were attenuated by pretreatment with EG. Vascular inflammatory responses induced by HG are critical events underlying development of various diabetic complications; therefore, our results suggest that EG may have significant therapeutic benefits against diabetic complications and atherosclerosis.

Fisetin inhibits high-glucose-induced vascular inflammation in vitro and in vivo

AIM AND OBJECTIVE

Fisetin, an active compound isolated from flowering plants in the family Fabaceae, was reported to have antiviral, neuroprotective, and anti-inflammatory effects. Vascular inflammatory processes have been suggested to play key roles in the initiation and progression of atherosclerosis, a major complication of diabetes mellitus. Thus, we determined the ability of fisetin to suppress vascular inflammatory processes induced by high glucose (HG) in primary human umbilical vein endothelial cells (HUVECs) and mice.

METHODS

The effects of fisetin on HG-induced vascular inflammation were determined by measuring vascular permeability, leukocyte adhesion and migration, cell adhesion molecule (CAM) expression levels, reactive oxygen species (ROS) formation, and nuclear factor (NF)-κB activation.

RESULTS

HG markedly increased vascular permeability, monocyte adhesion, expressions of CAMs, formation of ROS, and activation of NF-κB. Remarkably, all of the observed vascular inflammatory effects induced by HG were inhibited by pretreatment with fisetin.

CONCLUSION

Vascular inflammatory responses induced by HG are critical events underlying the development of diabetic complications; therefore, our results suggest that fisetin possesses significant therapeutic effects against diabetic complications and atherosclerosis.

Predictive factors for the progression of diabetic macular ischemia

PURPOSE

To investigate the predictive factors for diabetic macular ischemia progression through the analysis of fluorescein angiography (FA) parameters.

DESIGN

Retrospective, longitudinal study.

METHODS

Data were collected from 79 eyes of 79 patients with type 2 diabetes mellitus. Macular ischemia severity was assessed using Early Treatment Diabetic Retinopathy Study (ETDRS) protocols and custom software used to quantify the foveal avascular zone (FAZ) area. Patients with ischemia grades "mild," "moderate," or "severe" and at least 2 macula-centered FA images over a minimum of 6 months were included. Main outcome measures were change in macular ischemia grades and FAZ enlargement rate (mm(2)/year).

RESULTS

The median FAZ areas in mild, moderate, and severe ischemia grades at baseline were 0.28, 0.37, and 0.73 mm(2), and significantly increased at the final FA (0.31, 0.41, and 1.23 mm(2)) (P = .001). The median duration of follow-up was 27.5, 31.0, and 24.0 months, and was not significantly different between groups. FAZ enlargement rates were higher in the more advanced ischemia grades--"severe" (0.073 mm(2) [10.4%]/year) compared to "mild" (0.021 mm(2) [7.50%]/year) (P = .02) or "moderate" (0.019 [5.13%] mm(2)/year) (P = .03). A greater ischemia severity grade was predictive for progression (odds ratio [OR] = 2.47, confidence interval [CI] = 1.21-5.05, P = .02). Macular ischemia progression itself was an independent predictive factor for visual acuity loss (OR = 4.60, CI = 1.54-13.7, P = .03).

CONCLUSIONS

The rate of FAZ enlargement ranges from 5%-10% of baseline FAZ area per year in eyes with established ischemia. A greater macular ischemia grade was independently predictive for progression, and diabetic macular ischemia progression itself was predictive of the loss of visual function.

Ethyl pyruvate prevents methyglyoxal-induced retinal vascular injury in rats

Pyruvate is an endogenous antioxidant substance. The aim of this study was to investigate the protective effects of ethyl pyruvate (EP) on retinal vascular injury in diabetic retinopathy. To investigate the protective effect of EP on vascular cell apoptosis and blood-retinal barrier (BRB) breakage, we have used intravitreally methylglyoxal-(MGO-) injected rat eyes. Apoptosis of the retinal vascular cell that was stimulated by the intravitreal injection of MGO was evidently attenuated by the EP treatment. EP exerts inhibitory effect on MGO-induced vascular cell apoptosis by blocking oxidative injury. In addition, EP treatment prevented MGO-induced BRB breakage and the degradation of occludin, an important tight junction protein. These observations suggest that EP acts through an antioxidant mechanism to protect against oxidative stress-induced apoptosis in retinal vessels.

Subclinical capillary changes in non-proliferative diabetic retinopathy

PURPOSE

To establish adaptive optics scanning laser ophthalmoscopy as a method to detect and characterize microscopic signs of diabetic retinopathy in capillaries and cone photoreceptors in the parafovea.

METHODS

Recently, adaptive optics scanning laser ophthalmoscope (AOSLO) has enabled noninvasive assessment of photoreceptors, capillaries, and leukocytes in the retinas of live human subjects. Repeated application of AOSLO imaging along with comparison to fluorescein angiography was used to track individual capillaries near the foveal avascular zone (FAZ) from one eye affected with severe non-proliferative diabetic retinopathy. Fluorescein angiography was used to identify clinical signs of diabetic retinopathy, such as microaneurysms and intraretinal microvascular abnormalities, and corresponding regions were imaged and assessed using the AOSLO. In addition, the structural integrity of photoreceptors and the spatial distribution of leukocytes around the parafoveal capillary network were quantitatively assessed.

RESULTS

Capillaries and cone photoreceptors were visualized using the AOSLO without the use of injected contrast agents. Although the majority of capillaries were stable over a period of 16 months, one capillary at the edge of the FAZ dropped out, leading to a small but significant increase in FAZ size. Longitudinal assessment of the capillaries also showed microaneurysm formation and disappearance as well as the formation of tiny capillary bends similar in appearance to intraretinal microvascular abnormalities. The leukocytes in the capillary network were found to preferentially travel through the same routes in all four visits, suggesting that these channels are robust against small changes to the surrounding capillaries. In this eye, cone photoreceptor spacing was increased in the fovea when compared with normal data but stable across all visits.

CONCLUSIONS

AOSLO imaging can be used to longitudinally track capillaries, leukocytes, and photoreceptors in diabetic retinopathy. Capillary changes that can be detected include dropout of individual capillaries as well as formation and disappearance of microaneurysms.

Vision, retinal thickness, and foveal avascular zone size after intravitreal bevacizumab for diabetic macular edema

INTRODUCTION

To investigate three monthly intravitreal bevacizumab (IVB) injections effects in chronic diabetic macular edema (DME).

METHODS

A prospective, noncomparative study in which inclusion criteria were; DME with central macular thickness (CMT) of at least 250 μm, and no treatment for diabetic retinopathy (DR) within 4 months before the first injection. All eyes received three monthly 1.25 mg IVB injections. CMT by optical coherence tomography, visual acuity (VA), foveal avascular zone (FAZ) greatest linear dimension (GLD), and area of FAZ by fundus fluorescein angiography were documented initially and 1 month after last injection. Outcomes (P<0.05 were significant) and correlations (r values) were analyzed.

RESULTS

A total of 29 eyes of 29 patients (group 1, 19 female, 10 male), aged 60.7±6.6 years were analyzed. The patients were split into two groups; group 2 included 15 mild-to-moderate nonproliferative DR, and group 3 included 14 more-severe DR. VA gain was significant in all groups (P<0.05). Mean CMT decrease was approximately 46, 36, and 55 μm in groups 1, 2, and 3, respectively (P<0.05 only in group 1). A 0.045-mm2 increase in FAZ area was obtained in group 1 (P<0.05). In group 2, an increase in GLD and area of FAZ was 0.048 mm and 0.058 mm2, respectively (P<0.05), whereas in group 3, FAZ enlargement was nonsignificant. VA and CMT were significantly correlated (r values=0.5-0.6), except for the final VA-final CMT in group 2. FAZ dimensions and other parameters (VA and CMT) were noncorrelated.

CONCLUSION

According to the authors' short-term results, three monthly IVB injections can be used for chronic DME regardless of VA, CMT, or FAZ dimensions, despite the FAZ enlargement encountered, especially in cases with milder DR.

Influence of diabetes on macular thickness measured using optical coherence tomography: the Singapore Indian Eye Study

PURPOSE

To determine the influence of diabetes, diabetic retinopathy (DR), and other factors on macular thickness, measured using optical coherence tomography (OCT), in a population-based sample.

METHODS

Data from the population-based Singapore Indian Eye Study were analyzed. We measured macular thickness using Stratus OCT Fast Macular Thickness scan protocol in 228 participants with diabetes mellitus (including 167 without DR, 44 with mild DR, 17 with moderate or severe DR) and 72 non-diabetic controls without macular oedema or other macular lesions. Analysis was done on right eyes.

RESULTS

The mean age of participants was 60.1 ± 10.1 years, with 53.8% men. Macular thickness measurements did not differ significantly between diabetic participants with no or mild DR and non-diabetic participants. Diabetic participants with moderate or severe DR had greater foveal and temporal outer macula thickness compared with those with no or mild DR (P=0.003). In a multivariate linear regression model, older age (P=0.009), male gender (P=0.005), and lower spherical equivalent (P=0.001) were other factors associated with greater foveal thickness in all participants after controlling for body mass index, glycosylated haemoglobin, total cholesterol, and mean systolic blood pressure.

CONCLUSION

This population-based study showed that diabetic participants with moderate or severe DR had thicker foveal measurements, even in the absence of diabetic macula oedema, than non-diabetic controls. Other factors that influenced macular thickness measurements were age, gender, and spherical equivalent. These data may aid the interpretation of OCT findings in persons with diabetes and DR.

Disruption of the retinal parafoveal capillary network in type 2 diabetes before the onset of diabetic retinopathy

PURPOSE

To establish, using adaptive optics scanning laser ophthalmoscopy (AOSLO), that the retinal parafoveal capillary network is altered before the onset of diabetic retinopathy in adult patients with type 2 diabetes.

METHODS

AOSLO videos were acquired in the parafoveal region of one eye from control subjects and from patients with type 2 diabetes and no retinopathy. Detailed images of the parafoveal capillary network were generated with custom motion contrast enhancement algorithms. The combination of AOSLO images and videos enabled the simultaneous assessment of several features of the parafoveal capillary network. Arteriovenous (AV) channels were identified by finding the least tortuous capillary channels connecting terminal arterioles to postcapillary venules. Measures of capillary dropout and capillary hemodynamics were also quantified.

RESULTS

The average tortuosity of AV channels was 26% higher in patients with type 2 diabetes when compared with controls, even though there were no signs of diabetic retinopathy in any of the eyes that were assessed (P < 0.05). In addition, the metrics of capillary dropout showed small changes (between 3% and 7%), leukocyte speed 14% lower, and pulsatility 25% higher, but none of these differences was statistically significant.

CONCLUSIONS

It is often difficult to find consistent changes in the retinal microvasculature due to large intersubject variability. However, with a novel application of AOSLO imaging, it is possible to visualize parafoveal capillaries and identify AV channels noninvasively. AV channels are disrupted in type 2 diabetes, even before the onset of diabetic retinopathy.

A 5-year follow-up of photocoagulation in diabetic macular edema: the prognostic value of vascular leakage for visual loss

AIM

To study the long-term visual result of photocoagulation of clinically significant macular edema (CSME) in diabetic patients in relation to baseline retinal vascular leakage assessed by vitreous fluorometry.

METHODS

The study enrolled 36 eyes in 27 diabetic patients with CSME at baseline, all subsequently treated by photocoagulation. The diagnosis of CSME and treatment procedure followed the ETDRS criteria. The leakage through the retinal vessels was calculated as the blood-retinal barrier permeability. Five years after initial photocoagulation the patients were reexamined.

RESULTS

The mean visual acuity decreased with 16 letters at follow-up, and in 15 eyes visual loss was substantial, with a decrease of 15 letters or more, corresponding to at least 3 lines. The baseline permeability was significantly higher in eyes with substantial visual loss than in eyes with more stable vision (14.2 nm/sec and 6.3 nm/sec respectively; p = 0.006), the corresponding odds ratio was 16.1 (95% CI: 1.8-146; p = 0.014). The level of retinopathy was significantly correlated to visual loss (Fisher's exact test < 0.02).

CONCLUSION

Visual acuity decreased at follow-up, and a substantial visual loss of 3 or more lines in CSME was associated with higher retinal vascular leakage at baseline with an odds ratio of 16.1. For this relatively small sample, neither diabetes duration, age or HbA(1c) reached statistical significance, indicating that blood-retinal barrier permability is a strong predictor of the visual outcome. The results support the investigation of triamcinolone or VEGF inhibition in patients with severe leakage, and may help to identify patients in need for intravitreal injection.

Cellular signaling and potential new treatment targets in diabetic retinopathy

Dysfunction and death of microvascular cells and imbalance between the production and the degradation of extracellular matrix (ECM) proteins are a characteristic feature of diabetic retinopathy (DR). Glucose-induced biochemical alterations in the vascular endothelial cells may activate a cascade of signaling pathways leading to increased production of ECM proteins and cellular dysfunction/death. Chronic diabetes leads to the activation of a number of signaling proteins including protein kinase C, protein kinase B, and mitogen-activated protein kinases. These signaling cascades are activated in response to hyperglycemia-induced oxidative stress, polyol pathway, and advanced glycation end product formation among others. The aberrant signaling pathways ultimately lead to activation of transcription factors such as nuclear factor-κB and activating protein-1. The activity of these transcription factors is also regulated by epigenetic mechanisms through transcriptional coactivator p300. These complex signaling pathways may be involved in glucose-induced alterations of endothelial cell phenotype leading to the production of increased ECM proteins and vasoactive effector molecules causing functional and structural changes in the microvasculature. Understanding of such mechanistic pathways will help to develop future adjuvant therapies for diabetic retinopathy.

Role of angiotensin II in retinal leukostasis in the diabetic rat

To study if the endogenous renin-angiotensin system affects diabetic retinal leukostasis, rats with streptozotocin-induced diabetes were treated with an ACE inhibitor (ramipril), an angiotensin II AT(1) receptor antagonist (losartan) and the Ca channel blocker, (nifedipine). In the diabetic rats, these drug treatments reduced systolic blood pressure by approximately 16 mmHg but did not change blood glucose. After 2 weeks, the rats were examined for retinal leukostasis in vivo with a scanning laser ophthalmoscope (SLO). Retinal leukostasis, which was defined as no movement of arrested leukocytes over 2 min, was markedly higher in diabetic rats than normal controls (P<0.01). Leukostasis was significantly decreased by ramipril and losartan (P<0.01 vs. untreated diabetic rats) but was still higher than normal. Retinal leukostasis after nifedipine treatment was not significantly different than in untreated diabetic rats. The same trend was observed when leukostasis was analyzed on retinal flat mounts with concanavalin A and CD45 immunofluorescence; ramipril and losartan treatment, however, decreased leukostasis to values no different than controls. Retinal leukostasis was lowered by nifedipine (P<0.05, untreated diabetes vs. nifedipine-treated) but was still higher than in normal, ramipril-, or losartan-treated rats. Assays of gene expression of retinal intercellular adhesion molecule (ICAM-1) by semi-quantitative RT-PCR indicated that ICAM-1 mRNA was increased in diabetic rats but was decreased markedly by treatment with losartan or ramipril, and modestly by nifedipine. In summary, suppressing the activity of the endogenous renin-angiotensin system markedly decreases, perhaps even normalizes, the retinal leukostasis that accompanies type I diabetes in rats. These effects seem to be partly independent of blood pressure and to be associated with a decrease in ICAM-1 gene expression. Angiotensin II may, thus, mediate retinal leukostasis in early diabetes.

Semi-automated detection of the foveal avascular zone in fluorescein angiograms in diabetes mellitus

BACKGROUND

The foveal avascular zone (FAZ) is known to enlarge in diabetic retinopathy. In a preliminary study, the authors applied a region growing algorithm to fluorescein angiograms to detect the FAZ in a semi-automated fashion.

METHODS

The FAZ in 44 fluorescein angiograms of 44 eyes of 41 patients with diabetic retinopathy underwent manual outlining, then analysis with the region growing function of the ENVI image analysis software. The same algorithm was applied after median filtering of the images.

RESULTS

Correlation coefficient was 0.98 between the first two authors, 0.89 between the first author and semi-automated detection before median filtering and 0.91 after median filtering. Average surface areas however, were smaller with semi-automated detection (1951 pixels before and 2226 pixels after median filtering) than with manual detection (3032 pixels).

CONCLUSIONS

Semi-automated detection of the FAZ is possible, but refinements need to be made in angiogram quality and/or image pretreatment to improve results.

Metabolic factors and the foveal avascular zone of the retina in diabetes mellitus

AIM

To study the foveal avascular zone (FAZ) of the central retina in diabetic patients with retinopathy having undergone metabolic evaluation.

METHODS

One hundred and ten digital fluorescein angiograms were chosen from our digital image bank after cross matching diabetic patient lists of the ophthalmology and endocrinology departments of our institution. The patients had undergone day visits with systemic, biological and ophthalmologic evaluation, including digital fluorescein angiography.

RESULTS

Sex ratio was M 62/F 48. Average age was 52.4 years (+/- 13.8) with 44 type 1 diabetics and 66 type 2. Retinopathy was present in all patients (54 background (BDR), 30 pre-proliferative (PPDR), 26 proliferative (PDR)). Age was positively correlated with FAZ grade (47.3 years +/- 13.2 for normal FAZ, 53.8 years +/- 13.7 for abnormal FAZ, P=0.03). Lipid profile showed a protective tendency of the Apo A1 fraction of cholesterol on macular vascularization (1.7 gr./l in normal FAZ patients vs 1.43 gr./l in abnormal FAZ patients, P=0.004). Body mass index was negatively correlated with macular ischemia (28.11 if FAZ not severely altered, 25.97 if FAZ severely altered, P=0.03).

CONCLUSIONS

We found possible relations between BMI and Apo A 1 cholesterol and macular vascularization which may warrant further investigation.

Foveal avascular zone in diabetic retinopathy: quantitative vs qualitative assessment

PURPOSE

To describe the relations between foveal avascular zone (FAZ) size and outline in patients presenting diabetic retinopathy.

METHODS

110 high-quality fluorescein angiograms from 110 diabetics were chosen from our digital retinal image databank. Patients with significant media opacities, macular scars, macular hard exsudates, high ametropia, and associated macular pathology were excluded. Both FAZ perimeter and surface area were measured with image analysis software. FAZ outline was graded according to ETDRS report Number 11 (from 0=normal to 4=capillary outline completely destroyed). Data were compared to that of 31 healthy controls. FAZ surface in diabetics was compared to that of controls and FAZ surface was compared to FAZ grade, FAZ perimeter and retinopathy stage in diabetics. Quantitative variables were compared using the U-test of Mann-Whitney or Kruskal-Wallis test and correlations between quantitative variables were estimated with the Spearmann coefficient.

RESULTS

All patients presented diabetic retinopathy (54 BDR, 30 PPDR, 26 PDR). FAZ size was larger in diabetics than controls (P<0.001). In diabetics, FAZ size increased with FAZ grade (P<or=0.006 except between grades 1 and 2=NS) and with retinopathy stage (P<or=0.024). As retinopathy advanced, there was a higher proportion of altered FAZ outlines (P=0.003).

CONCLUSIONS

This study confirms capillary alteration to be the cause of increase in FAZ size in diabetics and presents an alternative evaluation method of the FAZ to FAZ size measurement. No qualitative studies using the ETDRS FAZ grading scale have been performed to our knowledge.

Vascular endothelial cadherin and beta-catenin in human fetoplacental vessels of pregnancies complicated by Type 1 diabetes: associations with angiogenesis and perturbed barrier function

AIMS/HYPOTHESIS

Increased angiogenesis of fetoplacental vessels is a feature of pregnancies complicated by Type 1 diabetes mellitus, but the underlying molecular mechanisms are unknown. This investigation tests whether the diabetic maternal environment alters the phenotypic expression of placental vascular endothelial cadherin and beta-catenin, which have been implicated as key molecules in barrier formation and angiogenesis in the endothelium.

METHODS

Term placental microvessels from normal pregnancies (n=8) and from those complicated by Type 1 diabetes (n=8) were perfused with 76-Mr dextran tracers (1 mg/ml) and subjected to immunocytochemistry, immunoblotting and microscopy. Junctional integrity, localisation and phosphorylation were investigated along with total protein levels of vascular endothelial cadherin, beta-catenin and vascular endothelial growth factor. Stereological sampling and estimation tools were used to quantify aspects of angiogenesis and endothelial proliferation.

RESULTS

In the Type 1 diabetic placentae, junctional localisations of vascular endothelial cadherin and beta-catenin altered significantly, with more than 50% of microvessels showing complete loss of immunoreactivity and with no overall loss of total protein. Tracer leakage was associated with these vessels. There was a two- to three-fold increase in vessels showing junctional phospho-tyrosine immunoreactivity and hyperphosphorylated beta-catenin. Vascular endothelial growth factor levels were higher in these placentae. A four-fold increase in endothelial proliferation was observed, along with an increase in total length of capillaries without any change in luminal diameter.

CONCLUSIONS/INTERPRETATION

Molecular perturbations of vascular endothelial cadherin and beta-catenin occur in fetoplacental vessels of pregnancies complicated by Type 1 diabetes. Phosphorylation and loss of these molecules from the adherens junctional domains may be influenced in part by the elevated levels of vascular endothelial growth factor in the placenta. Perturbations of the junctional proteins may explain the observed breach in barrier integrity and may contribute to the mechanisms that drive proliferation and increases in capillary length.

Can a cilio-retinal artery influence diabetic maculopathy?

AIM

To explore the influence of a cilio-retinal artery on diabetic maculopathy.

METHODS

In the county of North Jutland 481 diabetic subjects underwent examination for diabetic retinopathy during the period 1 June 2000 to 30 June 2001. A unilateral cilio-retinal artery was observed in 104 patients among which 29 revealed variation in right and left eye maculopathy. A bilateral cilio-retinal artery was observed in 15 diabetic subjects. The influence of a cilio-retinal artery on diabetic maculopathy was explored in a paired study.

RESULTS

Diabetic maculopathy was found to be more severe in 26 of 29 eyes with a cilio-retinal artery (p<0.01) compared to eyes without it. The number of red dots (p<0.0001) and hard exudates (p=0.0002) were found to be significantly increased in eyes with a cilio-retinal artery, as also the number of eyes with central photocoagulation (p<0.05). In addition, clinically significant macular oedema was found to be significantly increased in eyes with a cilio-retinal artery compared to eyes without it (0.01<p<0.02).

CONCLUSION

In some patients, the presence of a cilio-retinal artery may worsen diabetic maculopathy.

Clinical and angiographic outcomes of diabetic patients after coronary stenting: a comparison of native vessel stent restenosis rates in different diabetic subgroups

The main objectives of this study were to analyze the relationship between stent restenosis and microalbuminuria, which may express not only the glomerular vessels damage but also widespread microvascular dysfunction including coronary arterial disease, and to determine the angiographic and clinical outcomes of different diabetic subgroups after coronary stenting. Identification of the factors that may predict the outcome after coronary stent placement in diabetic patients could assist in deciding different stenting strategies in different diabetic subgroups. Control coronary angiographies were performed in 136 diabetic patients 6 months after coronary stent implantation. Patients were divided into 3 subgroups according to their microalbuminuria status. Clinical and angiographic outcomes and distribution of various risk factors were determined for these subgroups. Blood pressure and serum cholesterol concentrations were higher in the overt diabetic nephropathy group. The mean diseased vessel segment rate was lower in patients without microalbuminuria. Although the mean stent length and size were similar, patients without microalbuminuria had lower restenosis rates (23.9% vs 53.2% [microalbuminuria] and 46.2% [overt diabetic nephropathy] p<0.01). Insulin therapy or gender caused no difference in restenosis rate. Although stent lengths and diameters were not different, patients with microalbuminuria had higher restenosis rates. The authors suggest that microalbuminuria may be an independent risk factor for restenosis in patients with diabetes.

Advanced glycation end products induce blood-retinal barrier dysfunction in normoglycemic rats

Advanced glycation end products (AGEs) have been implicated in the progressive vascular dysfunction which occurs during diabetic retinopathy. In the current study we have examined the role of these adducts in blood-retinal barrier (BRB) breakdown and investigated expression of the vasopermeabilizing agent vascular endothelial growth factor (VEGF) in the retina. When normoglycemic rats were injected with AGE-modified albumin daily for up to 10 days there was widespread leakage of FITC-dextran and serum albumin from the retinal vasculature when compared to control animals treated with nonmodified albumin. Ultrastructural examination of the vasculature revealed areas of attenuation of the retinal vascular endothelium and increased vesicular organelles only in the AGE-exposed rats. Quantitative RT-PCR and in situ hybridization demonstrated a significant increase in retinal VEGF mRNA expression (P < 0.05). These results suggest that AGEs can initiate BRB dysfunction in nondiabetic rats and a concomitant increase in retinal VEGF expression. These findings may have implications for the role of AGEs in the pathogenesis of diabetic retinopathy.

Analysis of the blood-retinal barrier: its relation to clinical and metabolic factors and progression to retinopathy in juvenile diabetics. A 4-year follow-up study

BACKGROUND

The study was carried out to evaluate the correlation between blood-retinal barrier (BRB) permeability and the development of diabetic retinopathy (DR) and to assess the metabolic and clinical factors related to DR over a 4-year period by means of vitreous fluorophotometry (VF).

METHODS

Thirty-five type I diabetics with no retinopathy, age 7-21 years (mean 14.32 +/- 2.1 years) were enrolled in this longitudinal study. Two visits included standard ophthalmological examination, fluorescein angiography and VF were performed, on entry into the study and 4 years later. The following risk factors in DR were analyzed: age, duration of diabetes, blood pressure, cholesterol, triglycerides, fasting blood glucose levels, glycosylated hemoglobin (HbA1c), insulin dose/kg body weight (IDBW), fructosamine and albuminuria. To estimate the BRB permeability we adopted the vitreous penetration ratio transmittance (VPRt) value.

RESULTS

At 4-year follow-up the mean VPRt had significantly increased. During that time 13 patients developed DR and their final mean VPRt was significantly higher than that in non-DR patients. Additionally, the initial mean VPRt was higher but not significantly so, in patients that later developed DR than in non-DR subjects. A constant linear correlation was found between VPRt and duration of diabetes, HbA1c and microalbuminuria.

CONCLUSION

VF is a quantitative method that could measure and predict the breakdown of the BRB before angiographic retinopathy in type I diabetics. The major clinical and metabolic factors related to alterations in the BRB are duration of diabetes, HbA1c and microalbuminuria.