Accessome
”To make the deaf hear and to make the blind see”
This widely-used quote derived from a bible verse has been famously used to describe a miracle, something impossible to achieve by an ordinary person. Now, we can directly link it to man-made progress, because science has managed to achieve one of the two goals, perfecting a technique that might prove to be more effective than the current treatments regarding deafness. This milestone has another important achievement of this century at its base: gene editing.
Types of Hearing Loss and Deafness
There are many causes for hearing loss, but the word ”deaf” acts as an umbrella term for all. In order to better understand the procedure developed to restore the ability to comprehend sound, we need to go over the basics: Deafness at birth or Congenital deafness refers to the cases where a child is born with the inability to hear. Congenital deafness is often caused by genetic factors, meaning the child has a genetic mutation that affects their hearing.
Genetic deafness can be: Syndromic, where the gene variation causes a collection of related symptoms.
Non-Syndromic, where the gene variation is only known to cause deafness.
Congenital deafness can be inherited, although the majority of children with genetic deafness do not have any deaf members of their family.
Acquired Deafness is the occurrence of hearing loss later in life, due to a variety of factors ranging from infections and injuries to medical treatments. It is categorized by occurrence or the issues related to the deficiency: Sudden Sensorineural Hearing Loss appears instantly or develops over the course of a few days.
Conductive Hearing Loss is linked with blockage or issues in the outer or middle ear. Sound may be blocked by earwax or a foreign object located in the ear canal, the middle ear space may be impacted with fluid, infection or a bone abnormality or the eardrum may have been injured. Ear infection residues such as cholesteatomas can also be a factor.
Mixed Hearing Loss is the term for when both categories of hearing loss play a part.
How Does the Procedure Work?
Before diving in to the details, we first need to know what the main player of this treatment is. According to Hearing Research, gene therapy is a technique by which exogenous genetic material is introduced into target cells to treat or prevent diseases caused by genetic mutations. In this case, the edited genetic material is introduced in the form of a liquid trough the cochlea aqueduct, a previously ”unexplored” passage in to the bone-structure. The genetic material in question is an adeno-associated virus(a single stranded genome belonging to the parvovirus family that usually doesn’t trigger immune responses) injected in the cisterna magna, a large reservoir of cerebrospinal fluid found at the base of the skull. The gene therapy delivered expresses a protein called vesicular glutamate transporter-3, which enables the hair cells to transmit signals and rescue hearing in the subjects, in this case adult mice.
As a small fun fact, this channels connection to the glymphatic system makes it a candidate to a new way to deliver drugs into the brain, a major challenge in developing drugs for neurological disorders.
Conclusion
It seems as if, slowly but steadily, many of the disabilities and diseases that marked our history as humans are being removed trough techniques far beyond our imagination. This new procedure is one of them.
Restabilizing sound-transmitting hair cells in the ear has long been regarded as an impossible goal, but now, when technologies like gene editing allow us to play with the very core of our individualism, nothing is beyond reach. This discovery puts forward a simple, yet interesting question: what will we ”solve” next?