Health Science Reviews

By Ayanda Mandlana

Diabetes not only affects blood sugar, but it also silently destroys vision through a disease
known as diabetic retinopathy. It is the major cause of preventable blindness worldwide and
is expected to affect over 191 million by 2030 [1]. The vision-stealing disease begins with a
leaky blood-retinal barrier (BRB), the eye’s very defence against harmful molecules in the
blood. But how do scientists even study what goes wrong in the diabetic eye?

Then in 1998, a landmark study by Antonetti and colleagues provided this answer.
Experimenting with diabetic rats, the researchers discovered that long-term high blood sugar
induces the formation of a protein called VEGF (vascular endothelial growth factor).
Although VEGF forms new blood vessels, too much of it, as in diabetes, damages the BRB,
making it leaky and inflamed [2]. The leakiness allows toxins to flow into the retina, setting
off the cascade of retinal damage.

Their work demonstrated how VEGF causes tight junction proteins in retinal blood vessels to
collapse, imagine the eye’s security fence suddenly falling apart. This finding paved the way
for the therapies now used in the clinic that block VEGF to preserve vision.

Now, upcoming scientists like us are taking it a step further with ex-vivo rat retinal explants.
We culture retinae and expose them to high-glucose conditions, mimicking diabetes. By
assessing cell viability and BRB structure, we hope to identify early biomarkers for damage
years before vision is compromised.

Vision loss from diabetes is avoidable. Research like this gives us the roadmap.

Reference:

1. Zheng Y, He M, Congdon N. The worldwide epidemic of diabetic retinopathy. Indian J
   Ophthalmol. 2012 Sep-Oct;60(5):428-31. doi: 10.4103/0301-4738.100542. PMID:
   22944754; PMCID: PMC3491270.
2. D A Antonetti, A J Barber, S Khin, E Lieth, J M Tarbell, T W Gardner; Vascular
   permeability in experimental diabetes is associated with reduced endothelial occludin
   content: vascular endothelial growth factor decreases occludin in retinal endothelial
   cells. Penn State Retina Research Group. Diabetes 1 December 1998; 47 (12):
   1953-1959.  https://doi.org/10.2337/diabetes.47.12.1953