How do connections in the retina re-wire after damage to the light-sensors?

Overview

The eye works a bit like a digital camera. In a camera, light passes through the lens and lands on millions of sensors that turn light energy into an electrical charge.  The sensors are connected to circuitry in a computer chip that converts their electrical charges into a picture. If the chip is broken, the camera won’t work, even if the sensors are ok.

Inside the eye, the light-sensitive part of the eye is the retina. It contain cells, called photoreceptors that act as light-sensors. They connect to nerve cells in a complex wiring circuit that means different features can be processed at once, e.g. colour and contrast. If the photoreceptors are working but the circuitry is damaged, messages from the photoreceptors can’t get through to the brain (which is where the image we see is put together). This leads to blindness.

Many researchers have been working on ways to replace photoreceptors, e.g. by transplanting stem cells, when photoreceptors stop working or die due to a genetic fault or because they have been damaged by inflammation or injury. The problem is that only a few of the transplanted cells actually connect with the remaining circuitry in the retina. One reason is that the wiring changes when photoreceptors are damaged and nerve cells that were connected to the lost photoreceptors can die too.

In this project the teams is investigating how changes to the wiring of the retina might be stopped or reversed, so that replacement stem cells that are transplanted to the retina have a better chance of connecting with the remaining retinal circuitry.  They are using human cells for their investigations so that the results can be translated more directly to patient care.