What happens to our cells when we age?
Senescence describes the process of cell ageing, with the number of these ageing cells increasing as we get older.
These cells can no longer repair and replenish damaged body parts in the same way as when we’re young, so older people suffer from poor wound healing because their cells don’t divide as often as young cells.
They accumulate damage to the blueprint of the cell – the DNA – which can lead to changes in expression of our crucial genes.
How does ageing impact our eyes?
You may notice lower tear production and difficulties adjusting to changing light levels. The proteins in the lens also begin to change, which can lead to cataracts or longsightedness, meaning you may need reading glasses after 40. In dry AMD, there is a failure to recycle worn out molecules, which can lead to deposits called drusen.
Over time, this failure to recycle waste products can lead to cell death and vision loss. In wet AMD, new blood vessels grow and leak across the back of the eye.
This can disrupt the layers of the macula and stop light reaching the photoreceptors to be interpreted as our vision. Over time the vessels and fluid may stop the photoreceptors from getting nutrients and lead to photoreceptors dying.
How can this research impact AMD treatments?
At the back of your eye is a layer of cells called the retinal pigment epithelium (RPE). In AMD, these RPE cells can become senescent. Scientists are exploring ways to treat AMD by targeting these cells.
This includes replacing damaged RPE cells using induced pluripotent stem cells. These are adult cells reprogrammed into stem cells and a ‘patch’ made from the new cells placed into the eye.
Researchers are also looking to delay senescence by protecting telomeres, the ends of chromosomes that shorten as we age.
A drug called TA65 has shown promise in a small clinical trial in maintaining telomere length and improving vision. As well as delaying senescence, teams want to remove senescent cells to restore normal retinal structure.
Drugs have been tested in mice with encouraging results and these treatments are now being tested in humans for related eye diseases.
Scientists are also trying to block inflammatory pathways using new drugs to reduce damage and cell death in late-stage dry AMD. These new strategies offer hope for better AMD treatments, though many are still experimental.
