Harvard scientists cure deaf mice with gene therapy

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A gene-editing treatment has been developed that has been hailed as a dramatic step towards a cure for children who are born deaf.

Deafness has genetic causes in more than 50 per cent of people – and is largely incurable.

But now a successful test of a treatment which reversed deafness in mice offers hope for human treatments, a hearing loss charity said last night.

The new treatment pioneered by Harvard University researchers used a technique called Crispr CAS-9.

Crispr is a method of modifying DNA in living cells.

Gene-editing treatment has been  been hailed as a step towards a cure for children born deaf

Gene-editing treatment has been been hailed as a step towards a cure for children born deaf

WHAT CAUSES DEAFNESS? 

Many children are born deaf for genetic reasons.

This can be passed down in families even if there appears to be no history of hearing loss.

Deafness can also be caused by complications in pregnancy.

These can include rubella, CMV, toxoplasmosis and herpes.

Medicines, such as ototoxic drugs like aspirin and ibuprofen, can also damage babies’ hearing before birth. 

After birth, certain injections can cause deafness in premature babies.

Severe jaundice and lack of oxygen can also lead to hearing loss.

Meningitis, measles and mumps in childhood can also cause deafness.

It is occasionally the result of head injuries or exposure to loud noise.

Source: Deaf Child Worldwide 

Hope for human treatment 

In mice born with a condition that makes them get progressively more deaf, the technique turned off a deafness-causing variant of a gene called TMC1.

As humans who carry the same gene variant also suffer progressive deafness, it is hoped that the treatment will one day could be used for humans.

The Crispr CAS-9 technique alters DNA by using a virus, enclosed in a blob of liquid, to alter DNA.

The virus was injected into the mice’s cochleas – part of the inner ear which picks up sounds.

This altered the DNA, allowing hair cells that pick up sounds to grow normally.

The researchers, publishing their findings in Nature, found the treatment ‘substantially reduces progressive hearing loss’.

‘Reason for optimism’ 

Ralph Holme, Director of Research at Action on Hearing Loss, said: ‘Inherited- deafness is thought to account for more than half of all childhood deafness and can have a massive impact.

‘There are over 100 different genes that can cause childhood deafness, but we don’t yet have treatments able to modify any of these genes to prevent hearing loss.

‘That’s why the research showing that it is possible, using a specific protein, to silence one of these genes in mice to reduce hearing loss is such a big deal for those who are seeking treatments.

‘The approach could be used to modify other deafness genes, although it is best suited to progressive forms of deafness that develop after birth. Many types of genetic deafness affect the structures within the ear before birth, which create extra challenges in terms of getting any treatment into the ear at the right time.’

A leading hearing researcher, Fyodor Urnov, commenting in Nature said the study was ‘an essential first step towards moving this type of approach nearer the clinic by providing evidence that it is safe and effective in an animal that has a similar genetic mutation and comparable loss to those in humans.’

Dr Urnov said the breakthrough was a ‘reason for optimism’ – although further tests will be needed to be carried out before it is proven to be safe.





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