Noninvasive Imaging of Retinal Pericytes and Endothelial Cells in Living Human Eyes

Abstract

 

Purpose

 

To image the retinal vascular pericytes and endothelial cells in living human retina using an adaptive optics scanning laser ophthalmoscope (AOSLO).

 

Methods

 

In vivo arteriolar wall imaging was performed on 8 healthy subjects using the Indiana AOSLO (Ferguson et al, 2010). Vessel wall imaging was performed using systematic control of the position of a large confocal aperture (Chui et al, 2012). Peripapillary arteries and arterioles were divided into 4 groups based on their lumen diameters (Gr 1: ≥100µm; Gr 2: 50-99µm; Gr 3: 10-49µm; Gr 4: retinal capillaries).

 

Results

 

The retinal microvasculature and scattering behavior of erythrocytes were clearly visualized in all 8 subjects. On the smaller vessels the pericytes were visualized as distinct cells laying along the lumen of the blood vessel. The smaller vessel pericytes bulged outward from the vessel wall resulting in a wall of irregular thickness. For the larger Gr 1 vessels the pericytes were much flatter and formed the outer corrugated layer of a two (or more) layered vascular wall. While pericytes were readily seen in vessel groups 1, 2, and 3, endothelial cells were only visible in Gr 1 vessels - the largest retinal arteries. Fig 1A shows the fine structure of arteriolar wall in a Gr 1 and Gr 3 vessel. The ratio of pericytes to endothelial cells was approximately 1:1 in the Gr 1 arteries (Fig 1B). Vascular wall components were not identified in the smallest retinal capillaries (Gr 4).

 

Conclusions

 

Our results show that retinal pericytes can be readily resolved in normal subjects for arterioles with a lumen diameter >10µm. Our noninvasive imaging approach allows direct assessment of the cellular structure of the vascular wall in vivo with potential applications in retinal vasculopathies such as diabetic retinopathy.

 

 

Fig1 A) Fine structure of vessel wall in peripapillary arterioles. Asterisks indicate the vessel lumen of a 100µm diameter and 14µm diameter arteriole. The inner and outer vessel wall linings of the larger arteriole are indicated by the white arrows. Pericytes (black arrows) are observed in a precapillary arteriole with a lumen diameter of 14µm. B) Magnified region of the white box on A. Endothelial cells (white arrows) and pericytes (black arrows) are readily seen along the inner and outer vessel wall linings. Note the one to one ratio of endothelial cells and pericytes.

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 499 diabetic retinopathy • 436 blood supply