Initiating Events of Retinopathy in Spontaneously Hypertensive Rats: Microvascular Rarefaction and Functional...

Area of Science:

• Ophthalmology
• Cardiology
• Neuroscience

Background:

• Target organ damage is critical for hypertension risk stratification.
• Early detection of target organ damage is limited by a lack of sensitive assessment tools.
• The retina serves as a model to investigate subclinical neurovascular damage and identify early imaging biomarkers.

Purpose of the Study:

• To investigate subclinical neurovascular damage in the retina of spontaneously hypertensive rats.
• To identify early imaging biomarkers for hypertension-induced target organ damage.
• To assess the utility of optical coherence tomography angiography in detecting early retinal changes.

Main Methods:

• Weekly noninvasive blood pressure and multimodal fundus imaging (OCT, OCTA, electroretinography) were performed on spontaneously hypertensive rats and Wistar-Kyoto controls from 4 to 9 weeks of age.
• Histological analyses and fluorescein fundus angiography were used to validate microvascular changes and blood-retinal barrier integrity.
• Linear mixed-effects modeling was employed to correlate prehypertensive stage with vascular density.

Main Results:

• Spontaneously hypertensive rats showed increased blood pressure from 5 weeks of age.
• At the prehypertensive stage (6 weeks), decreased superficial vascular plexus density and reduced scotopic electroretinography b-wave amplitude were observed.
• These microvascular and functional deficits preceded structural changes on OCT and blood-retinal barrier breakdown.

Conclusions:

• Superficial microvascular rarefaction and inner retinal dysfunction are early pathological events in hypertension.
• Optical coherence tomography angiography-quantified superficial vascular plexus density is a sensitive biomarker for prehypertensive retinal damage.
• This imaging biomarker precedes macrovascular signs of hypertension-induced target organ damage.