Defective Angiogenesis and Intraretinal Bleeding in Mouse Models With Disrupted Inner Retinal Lamination

Associated factors of diabetic retinopathy in type 1 and 2 diabetes in Limpopo province in South Africa

Background

Diabetic retinopathy (DR) is the major cause of vision impairment or blindness in individuals who have diabetes. It has accounted for 2.6% of all cases of blindness, and 1.9% of all cases of vision impairments globally. There is a lack of data on the prevalence of diabetic retinopathy and its associated factors amongst diabetic rural populations. Hence, the current study aimed to determine factors associated with diabetic retinopathy (DR) among diabetes mellitus (DM) patients undergoing diabetic therapy.

Methods

The study was cross-sectional in design and the participants were selected using convenient sampling. STATA version 15 software was used for data analysis. Chi-square was used to compare proportions. Logistic regression was used to determine the relationship between DR and associated risk factors.

Results

The prevalence of DR was 35.3%, of which 32% were mild and 3.4% were moderate non-proliferative DR (NPDR). Females were more unemployed than males (32.1% versus 16.8%, p=0.0058). Males were found to drink alcohol (21.8% versus 1.9%, p<0.001) and smoke cigarettes (4% versus 0.3%, p=0.0034) more than females. Being aged ≥ 55 years (OR: 2.7, 95% CI: 1.6-4.4), with matric qualification (OR: 0.6; 95% CI: 0.4-1.0); employed (OR: 1.4, 95% CI: 1.2-1.6); having high systolic blood pressure (OR=1.4, 95%CI=1.1-1.7) were the independent determinants of DR.

Conclusions

The prevalence of diabetic retinopathy was 34%. DR was determined by high systolic blood pressure, old age, and employment. Although not statistically significant, gender, hyperglycemic state, poor glycemic control, smoking, and increased body mass index (BMI) were associated with increased risk of developing DR.

Microglia in retinal angiogenesis and diabetic retinopathy

Diabetic retinopathy has a high probability of causing visual impairment or blindness throughout the disease progression and is characterized by the growth of new blood vessels in the retina at an advanced, proliferative stage. Microglia are a resident immune population in the central nervous system, known to play a crucial role in regulating retinal angiogenesis in both physiological and pathological conditions, including diabetic retinopathy. Physiologically, they are located close to blood vessels and are essential for forming new blood vessels (neovascularization). In diabetic retinopathy, microglia become widely activated, showing a distinct polarization phenotype that leads to their accumulation around neovascular tufts. These activated microglia induce pathogenic angiogenesis through the secretion of various angiogenic factors and by regulating the status of endothelial cells. Interestingly, some subtypes of microglia simultaneously promote the regression of neovascularization tufts and normal angiogenesis in neovascularization lesions. Modulating the state of microglial activation to ameliorate neovascularization thus appears as a promising potential therapeutic approach for managing diabetic retinopathy.

Role of DSCAM in the Development of Neural Control of Movement and Locomotion

Locomotion results in an alternance of flexor and extensor muscles between left and right limbs generated by motoneurons that are controlled by the spinal interneuronal circuit. This spinal locomotor circuit is modulated by sensory afferents, which relay proprioceptive and cutaneous inputs that inform the spatial position of limbs in space and potential contacts with our environment respectively, but also by supraspinal descending commands of the brain that allow us to navigate in complex environments, avoid obstacles, chase prey, or flee predators. Although signaling pathways are important in the establishment and maintenance of motor circuits, the role of DSCAM, a cell adherence molecule associated with Down syndrome, has only recently been investigated in the context of motor control and locomotion in the rodent. DSCAM is known to be involved in lamination and delamination, synaptic targeting, axonal guidance, dendritic and cell tiling, axonal fasciculation and branching, programmed cell death, and synaptogenesis, all of which can impact the establishment of motor circuits during development, but also their maintenance through adulthood. We discuss herein how DSCAM is important for proper motor coordination, especially for breathing and locomotion.

Reduced mTORC1-signaling in retinal ganglion cells leads to vascular retinopathy

BACKGROUND

The coordinated wiring of neurons, glia and endothelial cells into neurovascular units is critical for central nervous system development. This is best exemplified in the mammalian retina where interneurons, astrocytes and retinal ganglion cells sculpt their vascular environment to meet the metabolic demands of visual function. Identifying the molecular networks that underlie neurovascular unit formation is an important step towards a deeper understanding of nervous system development and function.

RESULTS

Here, we report that cell-to-cell mTORC1-signaling is essential for neurovascular unit formation during mouse retinal development. Using a conditional knockout approach we demonstrate that reduced mTORC1 activity in asymmetrically positioned retinal ganglion cells induces a delay in postnatal vascular network formation in addition to the production of rudimentary and tortuous vessel networks in adult animals. The severity of this vascular phenotype is directly correlated to the degree of mTORC1 down regulation within the neighboring retinal ganglion cell population.

CONCLUSIONS

This study establishes a cell nonautonomous role for mTORC1-signaling during retinal development. These findings contribute to our current understanding of neurovascular unit formation and demonstrate how ganglion cells actively sculpt their local environment to ensure that the retina is perfused with an appropriate supply of oxygen and nutrients.

A Revised View on Growth and Remodeling in the Retinal Vasculature

The mouse retina provides an excellent model for studying angiogenesis. Recent advancements in high-throughput microscopy and image analysis provide great tools to visualize and describe the complexity of the retinal vascular architecture in a detailed and comprehensive way. Most developmental studies have focused on only a few parameters mostly in the inner-most layers that do not describe the entirety of the three-dimensional vascular network. Here, we analyzed the entire three-dimensional retinal vascular architecture and its growth and remodeling starting from the age of postnatal day 3 to 4 months in mice. We show plexus specific characteristics of the vasculature in terms of vascular tissue fraction, branching and length of the blood vessels, and distance and distribution between single capillaries. Such detailed knowledge is of particular interest, as it has become apparent that disease-specific mechanisms and treatments affect the retinal vasculature often in a plexus specific way.

Association of Disorganization of Retinal Inner Layers with Ischemic Index and Visual Acuity in Central Retinal Vein Occlusion

Purpose

To determine whether disorganization of retinal inner layers (DRIL) on optical coherence tomography (OCT) is associated with ischemia on ultra-widefield fluorescein angiography (UWFFA) and with visual outcomes in eyes with acute, treatment-naïve central retinal vein occlusion (CRVO).

Design

Retrospective, single-institution, longitudinal cohort study.

Participants

Twenty-five consecutive patients with treatment-naïve CRVO and ≥ 1 year follow-up.

Methods

Two independent masked graders evaluated the extent of DRIL, ellipsoid zone disruption, external limiting membrane disruption, and other OCT parameters at the baseline, 6- month, 12-month, and final visits. Baseline UWFFA images were assessed for ischemic index values and foveal avascular zone (FAZ) enlargement.

Main Outcome Measures

Associations of DRIL with UWFFA findings and clinical outcomes including corrected visual acuity (VA).

Results

The median time to final follow-up was 24 months (range 12.1 - 43.9 months). Median DRIL extent at baseline was 765 µm (range 0 - 1000 µm). Eighteen of 25 eyes (72%) had some degree of DRIL at baseline, and 20 of 25 eyes (80%) had cystoid macular edema (CME). Neither the presence nor extent of DRIL at baseline was associated with presenting VA. In a cross-sectional analysis of each visit, extent of DRIL correlated with worse VA at both the 6-month (ρ = 0.656; p = 0.001) and final (ρ = 0.509; p = 0.016) visits. At final follow-up, DRIL extent was the OCT parameter most strongly correlated with baseline ischemic index (ρ = 0.418; p = 0.047) and baseline enlarged FAZ (p = 0.057) on UWFFA. On multivariate regression analysis, DRIL extent at final follow-up was the only OCT parameter associated with worse VA (p = 0.013) and remained significant when accounting for CME as a potential confounder.

Conclusions

Extent of DRIL was not associated with presenting VA in treatment-naïve eyes with acute CRVO. Following six months of follow-up however, DRIL extent correlated with worse VA and was predictive of worse VA throughout more than 2 years of follow-up. Ischemic features on UWFFA at baseline are predictive of the extent of DRIL development at final follow-up.

Analysis of Retinal Vascular Plexuses and Interplexus Connections

The retina is a highly organized neural tissue consisting of three neural layers and two synaptic layers. Blood vessels that nourish the mouse and human neural retina mirror this organization consisting of three plexus layers, or plexuses, that run parallel within the retina, connected by interplexus vessels to create a closed vascular network. Here, we describe a methodology to describe this organization that can be used to interrogate factors mediating retinal vessel patterning including: coverage of the vascular plexuses, branching and orientation of the interplexus connections, and digital reconstruction of the retinal vasculature to measure vessel length and density. The methodology focuses on the mouse retina, but can easily be adapted to study retinal vessels of other species.

Association of Disorganization of Retinal Inner Layers With Visual Acuity In Eyes With Uveitic Cystoid Macular Edema

PURPOSE

To determine whether disorganization of retinal inner layers (DRIL) assessed by spectral-domain optical coherence tomography (SDOCT) correlates with visual acuity (VA) in eyes with uveitic cystoid macular edema (CME).

DESIGN

Secondary analysis of randomized clinical trial data.

METHODS

Fifty-six eyes of 42 patients with uveitic CME were prospectively imaged as part of the VISUAL-1 trial (Clinicaltrials.gov identifier NCT01138657). Central subfield thickness (CFT), horizontal and vertical extent of DRIL, foveal DRIL (>500 μm DRIL) hyperreflective foci (HRF), average and largest area of intraretinal (IR) cysts, and extent of disruption of external limiting membrane (ELM) and ellipsoid zone (EZ) were determined within the 1-mm central subfield and correlated with VA at baseline and follow-up visits.

RESULTS

Regression analysis adjusted for clustered observations was used to examine the association between OCT morphologic parameters and VA. Across all visits (n = 168), significant associations were found for CFT (0.080 per 100 μm, P < .001), foveal DRIL (0.170, P < .001), horizontal DRIL length (0.055 per 100 μm, P < .001), vertical DRIL extent (0.001, P = .005), total area of IR cysts (0.204 per mm², P < .001), area of largest IR cyst (1.407 per mm², P < .001), presence of HRF (P = .026), and EZ disruption (0.042 per 100 μm, P = .02). ELM disruption did not show a significant association with VA (-0.013 per 100 μm, P = .61).

CONCLUSION

DRIL is a robust and easily obtained surrogate marker of VA in participants with current or resolved uveitic CME. CFT, DRIL, IR cyst area, EZ disruption, and HRF had a strong association with VA.