Visualization of choroidal vasculature in pigmented mouse eyes from experimental models of AMD

A variety of techniques exist to investigate retinal and choroidal vascular changes in experimental mouse models of human ocular diseases. While all have specific advantages, a method for evaluating the choroidal vasculature in pigmented mouse eyes has been more challenging especially for whole mount visualization and morphometric analysis. Here we report a simple, reliable technique involving bleaching pigment prior to immunostaining the vasculature in whole mounts of pigmented mouse choroids. Eyes from healthy adult pigmented C57BL/6J mice were used to establish the methodology. The retina and anterior segment were separated from the choroid. The choroid with retinal pigment epithelial cells (RPE) and sclera was soaked in 1% ethylenediaminetetraacetic acid (EDTA) to remove the RPE. Tissues were fixed in 2% paraformaldehyde (PFA) in phosphate-buffered saline (PBS). Choroids were subjected to melanin bleaching with 10% hydrogen peroxide (H2O2) at 55 °C for 90 min, washed in PBS and then immunostained with anti-podocalyxin antibody to label vascular endothelium followed by Cy3-AffiniPure donkey anti-goat IgG at 4 °C overnight. Images of immunostained bleached choroids were captured using a Zeiss 710 confocal microscope. In addition to control eyes, this method was used to analyze the choroids from subretinal sodium iodate (NaIO3) RPE atrophy and laser-induced choroidal neovascularization (CNV) mouse models. The H2O2 pretreatment effectively bleached the melanin, resulting in a transparent choroid. Immunolabeling with podocalyxin antibody following bleaching provided excellent visualization of choroidal vasculature in the flat perspective. In control choroids, the choriocapillaris (CC) displayed different anatomical patterns in peripapillary (PP), mid peripheral (MP) and far peripheral (FP) choroid. Morphometric analysis of the vascular area (VA) revealed that the CC was most dense in the PP region (87.4 ± 4.3% VA) and least dense in FP (79.9 ± 6.7% VA). CC diameters also varied depending on location from 11.4 ± 1.97 mm in PP to 15.1 ± 3.15 mm in FP. In the NaIO3-injected eyes, CC density was significantly reduced in the RPE atrophic regions (50.7 ± 5.8% VA in PP and 45.8 ± 6.17% VA in MP) compared to the far peripheral non-atrophic regions (82.8 ± 3.8% VA). CC diameters were significantly reduced in atrophic regions (6.35 ± 1.02 mm in PP and 6.5 ± 1.2 mm in MP) compared to non-atrophic regions (14.16 ± 2.12 mm). In the laser-induced CNV model, CNV area was 0.26 ± 0.09 mm2 and luminal diameters of CNV vessels were 4.7 ± 0.9 mm. Immunostaining on bleached choroids with anti-podocalyxin antibody provides a simple and reliable tool for visualizing normal and pathologic choroidal vasculature in pigmented mouse eyes for quantitative morphometric analysis. This method will be beneficial for examining and evaluating the effects of various treatment modalities on the choroidal vasculature in mouse models of ocular diseases such as age-related macular degeneration, and degenerative genetic diseases.

Evaluation of subclinical changes in recently diagnosed pediatric hypertension patients without hypertensive retinopathy: an OCT study

PURPOSE

To investigate subclinical choroidal and retinal changes in recently diagnosed pediatric hypertension (HT) patients.

METHODS

This prospective case-control study consisted of 62 treatment naive HT patients (34 essential HT and 28 renal-induced HT) and 62 control subjects aged 10-16 years. All demographic data and ocular parameters were noted. Macula and choroid measurements were acquired by spectral domain optical coherence tomography (SD-OCT). Choroidal measurements were obtained by taking the mean of the measurements taken from 3 nasal and 3 temporal locations at 500µ intervals (mean nasal, mean temporal) in addition to the subfoveal area.

RESULTS

All choroidal thickness (ChT) values in HT subjects were significantly lower than in the healthy group (p < 0.001 for all). Also, there was no statistically significant difference between central macular thickness (CMT) and mean macular thickness (MMT) between the two groups. Subfoveal ChT, mean ChT, and CMT values were statistically lower in patients with renal-induced HT compared to essential HT subjects (p < 0.001, p = 0.04, p = 0.014, respectively). No significant correlation was observed between choroidal thicknesses and blood pressure values in essential and renal HT groups except weak correlation between mean temporal ChT and systolic blood pressure (SBP) in renal HT group (r =  - 0.464, p ₌ 0.013).

CONCLUSION

This study demonstrated that choroidal thickness decreased even during the subclinical period in treatment naive pediatric HT subjects. In addition, it has been shown that the choroid is more affected in renal-induced HT compared to essential HT group.