Scientists a step closer to reversing hearing loss

Hearing and balance disorders may one day be a thing of the past with a new study revealing that damaged cells in the inner ear can be instructed to regenerate.

More than one in six Australians experience some form of hearing loss during their lives and GPs report a growing incidence of patients presenting with vertigo and balance problems. Both conditions are caused by the same problem – a lack of or damage to a group of cells in the inner ear known as ‘hair cells’.

These cells act like receivers, absorbing sound vibrations entering the ear and converting them to an electrical signal to be sent to the brain for processing.

They also form part of the inner ear’s vestibular system, a series of fluid-filled sacs that detect gravity and motion.

Over a lifetime, the delicate hair cells can be damaged and destroyed – mostly by exposure to loud noise. Without these cells, problems with hearing and maintaining balance can emerge as the brain isn’t receiving the information it needs. Crucially, these cells are non-regenerative, so once they’re gone, they’re gone forever. Or at least that has been the case.

Read: The four types of hearing loss explained

But what if we could get these cells to regenerate? New research published in the journal Developmental Cell suggests we may be able to do just that.

The research uncovered a previously unknown natural barrier to our inner ear regenerating sensory cells. It seems that early on in life an ability to regenerate these cells exists through a process known as ‘transdifferentiation’, but soon after birth this ability is lost through a gradual loss of the DNA molecules that mediate it.

The inner ear contains two major types of sensory cells: the previously mentioned hair cells and what are known as ‘supporting cells’ that play important structural and functional roles within the ear by passing genetic instructions to the hair cells.

“In supporting cells, the hundreds of genes that instruct transdifferentiation into hair cells are normally turned off,” the study says.

“To turn genes on and off, the body relies on activating and repressing molecules that decorate the proteins known as ‘histones’.

“The histone proteins wrap the DNA into each cell nucleus, controlling which genes are turned ‘on’ by being loosely wrapped and accessible, and which are turned ‘off’ by being tightly wrapped and inaccessible. In this way, epigenetic modifications regulate gene activity and control the emergent properties of the genome.”

Read: Five things to know about vertigo

In short, the ability for the hair cells to regenerate is there, but has been shut off by tightly wrapped proteins. The research suggests that by targeting these proteins it may be possible to get the regeneration process running again.

“Our study raises the possibility of using therapeutic drugs, gene editing or other strategies to make epigenetic modifications that tap into the latent regenerative capacity of inner ear cells as a way to restore hearing,” study co-author Professor Neil Segil told Science Daily.

“Permanent hearing loss affects more than 60 per cent of the population that reaches retirement age.”

The researchers found that using drugs that suppress these proteins can preserve the innate ability to regenerate cells in lab mice.

“Similar epigenetic modifications may also prove useful in other non-regenerating tissues, such as the retina, kidney, lung and heart,” Prof. Segil said.

Read: Drug can stop hearing loss: study

The results could open up breakthrough methods of treating hearing loss, with the possibility of reversing previously permanent deafness or lowered hearing levels.

“Overcoming this barrier may be a first step in returning inner ear cells to a newborn-like state that’s primed for regeneration,” Science Daily reported.

“The study suggests new gene engineering approaches that could be used to channel some of the same regenerative capability present in embryonic inner ear cells.”

Can you envisage a day when hearing loss may be repaired by the body? Let us know your thoughts in the comments section below.

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Written by Brad Lockyer



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