PhD student Jesse Gardner-Russell and his supervisor Associate Professor Luis Alarcon-Martinez in the Visual Neurovascular Unit are investigating the role blood flow through microscopic structures in the eye plays in stroke.

The tiny tubes, known as interpericyte tunnelling nanotubes, connect specialised cells in the eye.

They carry messages and proteins, plus share information which helps ensure that the neurons of the retina get enough energy to sustain vision.

When a stroke interrupts blood supply to the eye, these nanotubes rupture. Gardner-Russell’s research aims to find out how to stop this, and if they can be regrown.

Restoring blood flow

Using laser scanning microscopy to image the living retinas of mice, Gardner-Russell demonstrated the impact changing blood flow to how these tubes function.

They found that if blood flow was restored after a 60-minute stroke, the nanotubes were able to regrow after one week.

More severe damage caused by transient stroke, was also able to be prevented.

But permanent loss of blood flow was catastrophic – and led to near total elimination of the nanotubes in the retina.

“How quickly blood flow returns is the critical factor,’’ says Gardner-Russell.

“This is where our research intersects with the way stroke is managed.’’

Retinal energy

The retina is the most energy-consuming tissue in the human body relative to its size.

It must continuously convert light into electrical signals, pass them through complex neuronal circuits, and transmit the resulting information along the optic nerve to the brain.

“A huge amount of energy is required to constantly make this happen, but energy is a finite resource in our body,” Gardner-Russell says.

“Mammals have developed an important mechanism, almost like an electricity grid. The body reallocates energy to where it’s needed in real time. When you flash a light, the retina needs more blood, and nanotubes are what helps coordinate that response.

“After a stroke and these nanotubes rupture, that system is lost.

“Even though there’s still blood flowing it’s no longer getting dynamically allocated so over time, this can contribute to poor visual outcomes because the neurons are slowly starving.

“We hope this research can provide a way to help fix that mechanism after a stroke – and potentially promote better visual recovery.”

This is part of a broader mission within the Visual Neurovascular Research lab, which is investigating how blood is distributed across the retina and what happens when that distribution breaks down.

The work spans conditions including glaucoma, diabetic retinopathy, age-related macular degeneration and ischaemic retinopathy — conditions that together affect over 800,000 Australians and 150 million people worldwide.

The potential applications of nanotube research reaches beyond the eye and has recently been identified in neurons in the brain as well.

“We want to understand what makes them grow, what makes them break and how many you might need,” Gardner-Russell says.

“Initially we thought more would always be better — but we now think it’s about having them in the right places, not just having more.”

Gardner-Russell is committed to finding solutions, particularly after learning a former colleague had suffered a stroke.

Messages from stroke survivors and their families, many reaching out after hearing him speak about his research on the ABC, added further weight.

“It hit home that there are people out there living this and needing this research,” he says. “It gives me extra motivation because it feels I am contributing to something bigger.”

This story was originally published in Creating the future in sight: Annual Review 2025.