Ageing: there’s much more to it than losing your hair (cells)

As we grow older, we’re more likely to lose our hearing – so we’re funding research to tell us why. Carina Santos, from our Biomedical Research team, tells us more.

Scientific advancements in the last few decades may have helped us live longer, but science is still not capable of stopping the train that is the ageing process. Like all systems in our body, our auditory system ages as we grow older and we gradually lose our hearing. More than 40% of people in the UK aged over 50 have hearing loss and this number rises to 71% in people over 70 – which shows that ageing is a major contributor to hearing loss.

How does ageing lead to hearing loss?

To be able to hear well, we need good communication between our ears and our brain. Hair cells, located in the inner ear, convert sound waves into electrical signals. These signals are then transmitted to the brain by auditory nerve cells. Damage to the hair cells, auditory nerve cells that connect the ear to the brain or brain lead to hearing loss. For a long time, researchers have thought that the main cause of age-related hearing loss was the loss of, or damage to, hair cells. However, recent studies have shown that there’s much more to it than this. We now know that losing hair cells is not the only cause of age-related hearing loss. Damage to the auditory nerve, and disruption of the connections between the hair cells and the auditory nerve cells, can also lead to hearing loss – and, in fact, may be the first step on that path.

This year, we’ve partnered with the Dunhill Medical Trust to invest together in research into age-related hearing loss. Our Pauline Ashley Fellowship scheme supports the career development of the UK’s most talented new investigators towards becoming independent scientists, and helps increase the number of researchers working in hearing research. We’ve awarded one of our co-funded Pauline Ashley Fellowships to Dr Katie Smith, a skilled young researcher from the Ear Institute at University College London. Katie will investigate the processes involved in age-related hearing loss, focusing on the auditory nerve cells. 

Auditory nerve cells and ageing

The auditory nerve cells that connect the ear to the brain are wrapped by glial cells (or glia), which form an insulating layer around the nerve fibres. This insulating layer is interspersed with short gaps that form highly organised regions called microdomains. The structure and organisation of these microdomains is essential for the auditory nerve to transmit fast and precise electrical sound signals from the ear to the brain. Previous studies have shown that assaults to the ear (such as loud noises), can alter the organisation of these microdomains and lead to hearing loss.

Katie’s project has two main aims. First, she will look at how microdomains form. She will study auditory nerve cells in mice, to determine when individual proteins first appear within different regions of the microdomains as they form. She will use a number of techniques, including high-resolution microscopy,  and measure electrical signals along the nerve cells, to study how the glial cells influence the development of microdomains. She will also study how the glial cells themselves change – in terms of both structure and what they do – as the nerve forms and matures.

Secondly, Katie will look at the microdomains in great detail during the ageing process, to determine how they change over time. As part of this, she will find out whether specific protein components are lost that could contribute to age-related hearing loss, and if this happens before the disruption of communication between the ear and the brain.

Understanding how the microdomains form in auditory nerve cells is the first step towards developing treatments that can restore a healthy organisation and structure of the microdomains – and, ultimately, restore hearing loss that’s due to getting older.

Why is this work important?

Age-related hearing loss can – and does – affect any one of us. Understanding the sequence of events in the ear and the brain (as well as in the nerve cells that connect the two), as we age, is crucial if we want to develop new ways of preventing the progressive loss of our hearing. Unlike birds, which can regenerate their hearing after it’s damaged, we have to depend on medical treatments to preserve or restore our hearing. By investing in research projects – and the scientists who are behind them – now, we hope that this will bring significant advances in the development of treatments for hearing loss and tinnitus.

  • It seems to me research has been going on 50 years or more and still cannot reverse cochlear hair decline, and despite in 1995 the RNID posted 'A cure for hearing loss via cochlear hair regeneration, will be found in 5 years (Official)'  A few years after a gerbil and a few rats had some success, but they still haven't done trials on people, and that takes another 10 years.... we are still waiting... Is too much funding being spent on maintaining hearing loss, instead of addressing it? Far better ALL AOHL funding was dedicated to the 'cure'.  genetics  (Again an AOHL), blurb,'means we can reverse the decline but, using stem cells would be like using a scattergun with unknown random effects (we don't want ears growing on our bum etc), because it cannot be targetted'.  Is there ANY realistic hope that hearing loss CAN be reversed?  Or is this just a  never-ending sop to a cure with no real belief it can ever happen?  Neither a HA or a CI is a cure.