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      Regenerating hair cells – a new approach?

      Once hair cells in the human ear are damaged they do not regrow, so once they’re gone, they’re gone for good. However, new research at Harvard University has suggested that it could potentially be possible to induce regeneration in damaged hair cells in the cochlea. Tracey Pollard, from our Biomedical Research team, tells us more about this research.

      By: Tracey Pollard | 16 June 2015

      Could we regrow hair cells?

      Attempts to regrow lost hair cells in the cochlea to restore hearing are focussed on two main areas – developing stem cell therapies that can be implanted into the inner ear to replace the missing cells, or developing therapies that will induce the inner ear itself to regrow the missing cells using the body’s normal regeneration processes. Unlike other species, such as birds or amphibians, inner ear hair cells in mammals don’t regrow when they’re damaged, so once they’re gone, they’re gone for good. The reasons for this are unknown, but it might be due to the more intricate arrangement of cells in the mammalian cochlea.

      In birds and amphibians, new hair cells are generated from supporting cells, a layer of cells within the inner ear which surround the hair cells, and ‘support’ them. However, in mammals, these supporting cells appear to lose their capacity to proliferate and turn into other cell types (like hair cells) before birth. However, recent research from the laboratory of Albert Edge, at Harvard University, has found that this is not necessarily the case.

      Mammalian supporting cells turn into hair cells in the laboratory

      In 2012, the group published research showing that supporting cells could be grown in culture in the laboratory, and that they formed structures called ‘neurospheres’, made up of dividing cells, some of which then turned into hair cells. The source of these new hair cells was a subset of the supporting cells in which a gene called Lgr5 was activated. The Lgr5 gene produces a protein receptor on the surface of cells which interacts with particular proteins on the surface of other cells known as R-spondins. When Lgr5 and an R-spondin interact, a signalling reaction ensues involving a gene called Wnt, and this signalling leads the supporting cells to proliferate and turn into hair cells.

      Lgr5 is also known to be produced by cells which can regenerate in other areas in the body, such as the intestine, and is used to identify adult stem cells. It is possible therefore, that in the cochlea, Lgr5 similarly identifies a population of cells with regenerative potential, even if they don’t necessarily use it. Not all cochlear supporting cells produce Lgr5 and it is only those that do that can turn into new hair cells.

      However, whilst this happens in tissue culture dishes in the lab, there was no indication that it really happens in the cochlea until new research, published this month by the same group, suggested otherwise.

      Growth of new hair cells after cochlear damage in mice

      Using gentamicin, an ototoxic antibiotic which damages hair cells, the group developed a model of hair cell damage in the newborn mouse cochlea. High doses of gentamicin caused significant levels of hair cell death, but surprisingly, the researchers observed a low level of spontaneous hair cell regeneration in response to this damage. They showed that these new hair cells were derived from the supporting cells which produce Lgr5 as described above.

      In addition, this group had previously shown that blocking another cell-to-cell signalling process (called Notch signalling) promoted hair cell regeneration after noise damage in adult mice and partially restored their hearing. However, they were unable to determine where the new hair cells were coming from. Inhibiting this same process in their new model of hair cell damage had a similar effect, and the group were also able to show that this hair cell regeneration was controlled by the Lgr5/Wnt signalling mentioned previously. This indicated that the Lgr5-producing supporting cells described above are indeed the source of new hair cells in the cochlea.

      Now that the cells in the cochlea that can produce new hair cells after damage have been identified, and as we learn more about the molecular processes that control a cell’s destiny, it may be possible to develop therapies that can target these cells and processes to induce regeneration of hair cells in the cochlea and one day, restore hearing.

      Find out more

      This research was published online last month in the journal Stem Cell Reports and you can read the article here.

      Visit the biomedical research section of our website for more information on our biomedical research programme and to find out how you can support our research.

      Recent Posts

      The cuticular plate: the foundations of hearing

      Tiny sensory cells in the inner ear, called hair cells, are vital for our hearing. One particular part of the hair cell, the cuticular plate, has recently been the focus of research by a team at the University of Virginia School of Medicine. The structure was found to play an important role in hearing and it was discovered that defects in it may lead to hearing loss.

      By: Dr Marta Narkiewicz
      15 April 2019

      Identifying antibiotics that are less toxic to the ear

      We funded a consortium of researchers from universities and industry to identify antibiotics, which are less toxic to the ear, but that are still effective in fighting life-threatening bacterial infections. The results have now been published in the journal Scientific Reports. Our Translational Research Manager, Dr Carina Santos, tells us more about their work.

      By: Dr Carina Santos
      15 April 2019

      Stress-relieving products to make life easier

      To mark Stress Awareness Month, we’ve selected our top stress-relieving products for people with deafness, tinnitus and hearing loss. We’ve a practical solution for every situation, to reduce anxiety and give you, or a loved one, a renewed zest for life.

      By: Sally Bromham
      14 April 2019

      Kick starting new research

      Our Flexi grant helps researchers kick start new lines of research. We’re awarding funding to three new projects that could lead to new diagnostic tools, a gene therapy for a specific type of inherited deafness and pave the way for clinical trials of treatments to prevent hearing loss caused by the anti-cancer drug cisplatin. Our Executive Director of Research, Dr Ralph Holme, tells us more.

      By: Dr Ralph Holme
      11 April 2019

      Recent Posts

      The cuticular plate: the foundations of hearing

      Tiny sensory cells in the inner ear, called hair cells, are vital for our hearing. One particular part of the hair cell, the cuticular plate, has recently been the focus of research by a team at the University of Virginia School of Medicine. The structure was found to play an important role in hearing and it was discovered that defects in it may lead to hearing loss.

      By: Dr Marta Narkiewicz
      15 April 2019

      Identifying antibiotics that are less toxic to the ear

      We funded a consortium of researchers from universities and industry to identify antibiotics, which are less toxic to the ear, but that are still effective in fighting life-threatening bacterial infections. The results have now been published in the journal Scientific Reports. Our Translational Research Manager, Dr Carina Santos, tells us more about their work.

      By: Dr Carina Santos
      15 April 2019

      Stress-relieving products to make life easier

      To mark Stress Awareness Month, we’ve selected our top stress-relieving products for people with deafness, tinnitus and hearing loss. We’ve a practical solution for every situation, to reduce anxiety and give you, or a loved one, a renewed zest for life.

      By: Sally Bromham
      14 April 2019

      Kick starting new research

      Our Flexi grant helps researchers kick start new lines of research. We’re awarding funding to three new projects that could lead to new diagnostic tools, a gene therapy for a specific type of inherited deafness and pave the way for clinical trials of treatments to prevent hearing loss caused by the anti-cancer drug cisplatin. Our Executive Director of Research, Dr Ralph Holme, tells us more.

      By: Dr Ralph Holme
      11 April 2019

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      We campaign for changes that make life better for people who are confronting deafness, tinnitus and hearing loss.

      Our ears are our organs of hearing and balance. They have three parts: the outer, middle and inner ear.