Changes in macrophage-like cells characterized by en face optical coherence tomography after retinal stroke

The protective effect of anti-VEGF-A/Ang-2 bispecific antibody on retinal vein occlusion model mice

(233/250) Retinal vein occlusion (RVO) causes macular edema and retinal ischemia resulting in visual field and vision loss. A bispecific antibody that blocks VEGF-A and angiopoietin-2 (Ang-2) has been recently launched and applied clinically to treat macular edema, but the role of Ang-2 in the pathogenesis of RVO is still unclear. In this study, we investigated the effects of the anti-VEGF-A/anti-Ang-2 bispecific antibody (BsAb) in a murine RVO model. By using RVO model mice, the expression of Ang-2 gene and protein was examined in the retina through real-time qPCR and Western blotting, respectively. A significant increase in Ang-2 was detected 1 day after occlusion. Immediately after occlusion, control IgG 400 μg/mL, anti-VEGF-A antibody 200 μg/mL, anti-Ang-2 antibody 200 μg/mL, and BsAb 400 μg/mL were intravitreally administered at 2 μL. Visual function was examined using electroretinograms, and apoptosis was examined using TUNEL staining. Interestingly, BsAb partially suppressed the decrease in amplitude of a and b waves compared to control IgG. Anti-Ang-2 antibody and BsAb reduced apoptosis-positive cells 1 day after occlusion. Comprehensive gene expression profiles were also examined using RNA sequencing analysis. RNA sequencing analysis of the retinal tissues showed that BsAb suppressed expression of gene groups associated with inflammatory response and vascular development compared to anti-VEGF-A antibody. Taken together, higher expression of Ang-2 contributes to the pathophysiology of RVO, providing a possible mechanism for the efficacy of BsAb in suppressing retinal dysfunction in RVO.

Vitreoretinal Interface Cells Correlate In Vivo With Uveitis Activity and Decrease With Anti-Inflammatory Treatment

Purpose

To highlight the utility of en face swept-source optical coherence tomography angiography (SS-OCTA) in assessing vitreoretinal interface cells (VRICs) of patients with active uveitis and their dynamics.

Methods

In this prospective, single-center study, 20 eyes from patients with active uveitis were analyzed using six 6 × 6-mm macular scans at three time points: active inflammation (baseline), clinically improving (T1), and resolved inflammation (T2). VRICs were visualized using 3-µm en face OCT slabs on the inner limiting membrane. The variation of VRIC number, density, and size over time was assessed, and VRIC measurements were compared with clinical grading.

Results

At baseline, the VRIC count was significantly higher (552.5 VRICs) than that of the healthy controls (478.2 VRICs), with a density of 15.3 cells/mm2. VRIC number decreased significantly to 394.8 (P = 0.007) at T1, with a density of 10.9 cells/mm2 (P = 0.007). VRIC size reduced from 6.8 µm to 6.3 µm at T1 (P = 0.009) and remained stable at T2 (P = 0.3). Correlation coefficients between inflammatory parameters (anterior chamber cells and National Eye Institute vitreous haze), and VRIC count indicated a positive correlation at baseline (r = 0.53), weakening at T1 (r = 0.36), and becoming negative at T2 (r = -0.24).

Conclusions

En face SS-OCTA revealed increased VRIC number and size in active uveitis, likely due to monocyte recruitment. Post-inflammation control, VRIC number, size, and density significantly decreased, returning to normal despite residual anterior chamber cells or vitreous haze.

Translational Relevance

Visualization of VRICs by in vivo OCT opens up new opportunities for therapeutic targets.

Are intravitreal hyperreflective particles alike in eyes with acute toxoplasma chorioretinitis and non-infectious uveitis?

BACKGROUND

To compare distinctive features of hyperreflective particles observed on spectral-domain optical coherence tomography (OCT) sections in eyes with acute toxoplasma chorioretinitis (TC) and non-infectious uveitis (NIU).

METHODS

Medical records and the spectral-domain OCT images of the patients with TC and NIU were retrospectively reviewed. The TC and NIU groups were compared in terms of age, sex, mean OCT image quality, mean central macular thickness (CMT), presence of intraretinal fluid (IRF), presence of subretinal fluid (SRF), number of hyperreflective particles in the posterior vitreous area and mean particle measurement in the posterior vitreous area.

RESULTS

Non-infectious uveitis group included nine patients (60 %) with Behcet's uveitis, five patients (33.3 %) with idiopathic posterior uveitis or panuveitis, and the remaining patient (6.7 %) with HLA-B27 associated uveitis. Comparison of the mean age, sex distribution, mean OCT image quality, mean CMT, presence of IRF, presence of SRF and the mean number of hyperreflective particles in the posterior vitreous area between the two groups showed no statistically significant differences (p = 0.085, p = 0.051, p = 0.748, p = 0.431, p = 0.109, p = 0.080 and p = 0.152, respectively). However, the mean length of the hyperreflective particles in the posterior vitreous area was 27.22 ± 8.60 μm in the TC group, and 21.91 ± 3.58 μm in the NIU group, with a significant difference between the two groups (p = 0.036).

CONCLUSION

This pilot study aimed to assess the hyperreflective particles in the posterior vitreous area using spectral-domain OCT images and image processing software. Despite its limitations, such as the small sample size, limited understanding of the nature of hyperreflective particles, and the absence of differentiation between acute and chronic uveitis, our study points out the potential role of the measurement of the hyperreflective particle length located in the posterior vitreous in differentiating the acute infectious versus non-infectious uveitis as the hyperreflective particles tend to be larger in infectious cases.

Description of Macrophage-Like Cells in Active Ocular Toxoplasmosis

Macrophage-like cells (MLC) have a fundamental role in the maintenance of immunosurveillance, response to inflammation and tissue injury in the retina. MLC can be visualized in vivo with conventional en face optical coherence tomography (OCT). The aim of this study is to describe this population of cells in active toxoplasmosis. We present two cases of active toxoplasma retinochoroiditis imaged at 2 time points, where the MLC were threshold after image processing and averaging for removing background and noise. In both patients the MLC collocated with the area of ischemia at the level of the choriocapillaris and retinal vessels.

Macrophage/microglia polarization for the treatment of diabetic retinopathy

Macrophages/microglia are immune system defense and homeostatic cells that develop from bone marrow progenitor cells. According to the different phenotypes and immune responses of macrophages (Th1 and Th2), the two primary categories of polarized macrophages/microglia are those conventionally activated (M1) and alternatively activated (M2). Macrophage/microglial polarization is a key regulating factor in the development of inflammatory disorders, cancers, metabolic disturbances, and neural degeneration. Macrophage/microglial polarization is involved in inflammation, oxidative stress, pathological angiogenesis, and tissue healing processes in ocular diseases, particularly in diabetic retinopathy (DR). The functional phenotypes of macrophages/microglia affect disease progression and prognosis, and thus regulate the polarization or functional phenotype of microglia at different DR stages, which may offer new concepts for individualized therapy of DR. This review summarizes the involvement of macrophage/microglia polarization in physiological situations and in the pathological process of DR, and discusses the promising role of polarization in personalized treatment of DR.

In Vivo Visualization of Macrophage-Like Cells in Patients with Uveitis by Use of En Face Swept Source Optical Coherence Tomography

AIMS

To detect macrophage-like cells (MLCs) in uveitis patients and describe their characteristics compared to healthy subjects by using en face SS-OCTA.

METHODS

Fifteen consecutive patients with "active" uveitis and 11 healthy participants underwent 6 macular scans of 6×6mm using SS-OCTA. The 3μm en face OCT slabs on inner limiting membrane were used to visualize the MLCs.

RESULTS

In healthy subjects there was an average of 478.2±149.7 MLCs with a density of 13.28±4.16 cells/mm2. MLCs were larger in patients with "active" uveitis than in controls (891.18±69.46 µm2 vs.885±77.53 µm2). Patients with "active" anterior uveitis had a significantly reduced count and density of MLCs (172±14.68 and 4.77±0.4 cell/mm2) compared to controls, while patients with posterior uveitis had a statistically increased count (546.1±132.4) and area (909.23+/-54.97 µm2) of MLCs compared to controls.

CONCLUSIONS

MLCs detected with en face SS-OCTA are increased in number and size in active posterior uveitis eyes compared to controls.

Retinal OCT findings in acute central retinal artery occlusion of varying severity at different disease stages - a retrospective, observational study

PURPOSE

To study the optical coherence tomography (OCT) changes in eyes with acute central retinal artery occlusion (CRAO) of different severity and at different disease stages.

METHODS

The study included acute CRAO cases of < 7 days duration, imaged on OCT at various time points. Based on the OCT findings at presentation, cases were classified into three severity groups: mild, moderate, and severe. OCT scans were evaluated and classified into four-time intervals based on symptom duration.

RESULTS

There were 39 eyes from 38 patients with acute CRAO who underwent 96 OCT scans. At presentation, the study had 11, 16, and 12 cases of mild, moderate, and severe CRAO, respectively. Middle retinal layer opacification was more common in mild CRAO cases, which caused inner retinal layer thinning over time. Moderate CRAO cases had total inner retinal layer opacification, which resulted in retinal thinning over time. Prominent middle limiting membrane (p-MLM) sign was seen in mild and moderate CRAO eyes while were not visualised in severe CRAO. This sign gradually faded out over time. Other OCT findings in higher grades of CRAO included inner retinal fluid, neurosensory detachment, internal limiting membrane detachment, hyperreflective foci, and posterior vitreous opacities. Regardless of the CRAO grade, the final end-point seen was inner retinal layer thinning over time.

CONCLUSION

OCT in CRAO is a useful for determining the severity of retinal ischemia, disease stage, tissue damage mechanism, and final visual outcome. More prospective studies analysing a larger number of cases at fixed time points will be required in the future.

TRIAL REGISTRATION

Trial Registration Number: Not applicable.

Proliferative diabetic retinopathy and diabetic macular edema are two factors that increase macrophage-like cell density characterized by en face optical coherence tomography

BACKGROUND

Macrophage-like cells (MLCs) located at the ILM were observed in live human retinas using adaptive optics optical coherence tomography (OCT) as well as clinically-used OCT. The study aimed to quantitatively analyzing MLCs at the vitreoretinal interface (VRI) in diabetic retinopathy (DR) using en face OCT and swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

190 DR eyes were included in the study, with 70 proliferative diabetic retinopathy (PDR) eyes and 120 non- proliferative diabetic retinopathy (NPDR) eyes. Sixty-three eyes from normal subjects were included as controls. MLCs were visualized in a 5 μm en face OCT slab above the VRI centered on the fovea. Mann-Whitney U test and Kruskal-Wallis H test were used to compare the OCTA parameters and the MLC parameters among groups. We evaluated the MLC density among groups on binarized images after image processing. We also investigated the relationship between MLC density and other OCT parameters including retina thickness and vessel density (VD).

RESULTS

The MLC density significantly increased in PDR eyes (PDR vs. NPDR, 8.97 (8.40) cells/mm² vs.6.14 (8.78) cells/mm², P = 0.013; PDR vs. normal, 8.97 (8.40) cells/mm²vs. 6.48 (6.71) cells/mm², P = 0.027) and diabetic macular edema (DME) eyes (DME vs. without DME, 8.94 (8.26) vs.6.09 (9.00), P = 0.005). After adjusting for age and gender, MLC density in NPDR eyes negatively correlated to VD of deep capillary plexus (DCP) (P = 0.01).

CONCLUSIONS

SS-OCTA is a non-invasive and simple method for the characterization of MLCs at the VRI. PDR and DME are two factors that increase MLC density. MLC density also correlated with VD.

Characteristics of macrophage-like cells in acute nonarteritic anterior ischemic optic neuropathy and the normal fellow eyes on en face optical coherence tomography

Purpose

To quantitatively analyze macrophage-like cells (MLCs) at the vitreoretinal interface (VRI) in acute nonarteritic anterior ischemic optic neuropathy (NAION) using en face swept-source optical coherence tomography (OCT).

Methods

Twenty-five acute NAION eyes and 25 normal fellow eyes from 25 patients were included in the study. MLCs were visualized in a 3 μm 6 mm×6 mm en face OCT slab above the VRI centered on the optic nerve head (ONH). After semiautomatic binarization and quantification, we evaluated the MLC density between the two groups. We also investigated the relationship between MLC density and other OCT parameters, including the increase in peripapillary retinal nerve fiber layer (RNFL) thickness and loss of vessel density (VD) in radical peripapillary capillary (RPC).

Results

The MLC density in the affected eye of the ONH was highly correlated with that in the fellow eye (r=0.612, p=0.001). The MLC density significantly increased in acute NAION eyes (NAION vs. normal, 11.97 ± 6.66 vs. 9.31 ± 6.10 cell/mm², p=0.028). In sectorial analysis, the increase in MLCs was mainly in the superior regions (4.13 ± 7.49 vs. 0.94 ± 5.21 cell/mm², p=0.001). The VD of RPC decreased significantly in the affected eyes (NAION vs. normal, 37.54 ± 5.25 vs. 40.56 ± 4.25, p=0.016), and the loss of RPC was predominantly in the superior sectors and the temporal sectors when compared to the inferior sectors and the nasal sectors, respectively (superior vs. inferior, -3.54 ± 6.71 vs. -0.37 ± 8.07, p=0.004; temporal vs. nasal, -2.69 ± 8.72 vs. -1.22 ± 6.06, p=0.005). The loss of RPC and the increase in MLC density were greater in affected sector corresponding to the visual field (VF) defect.

Conclision

MLCs located above the VRI increased significantly in acute NAION eyes, especially in subregions corresponding to VF defect, which provides clinical evidence supporting that the inflammatory response participates in the pathological process of NAION. The magnitude of the increase in MLCs corresponds to the RPC loss in the quadrant analysis.