Hearing loss is often the result of damaged hair cells in the inner ear. Birds have the ability to create new hair cells, but that is an ability that mammals, and therefore humans, do not possess. Researchers are now looking at a way of making stem cells develop into new hair cells, which can possibly re-establish hearing in people.
Dr Marcelo Rivolta at the University of Sheffield has for many years researched stem cells and the possibility of developing them, so that they can become the hair cells that sit in the cochlea in the inner ear, which are essential for hearing. Dr Rivolta identified the specific factors required for stem cells to grow into hair cells. He then tested to see if these cells could be used to repair damaged hair cells. He placed stem cells from humans into mice with destroyed hair cells. The experiments showed that the human cells were incorporated into the tissue and further tests confirmed that the cells were indeed behaving like hair cells.
Will the stem cells function as new hair cells?
The next step in Dr Rivolta's work is to see if it is possible to use these cells in a deaf animal to restore hearing. Once this is proven, the next challenge is extracting the right cells for treatment quickly and with great purity from a large group of cells and to grow these cells efficiently in the laboratory for future treatment.
The researcher hopes to bring the possibility of a stem cell-based therapy for deafness closer to becoming a reality. Dr Rivolta estimates that it will be between 10 and 15 years before such treatment could be made available, but he says the early indications are â€œexcitingâ€.
More re-establishment experimentation
At the University of Michigan, researchers have experimented with the rebuilding of hair cells by introducing the gene MATH1, which is needed by cells to develop into auditory hair cells in for example guinea pigs. Some cells took up the genetic material and started to produce hair cells, and the apical part of these newly formed hair cells had the characteristics of mature hair cells.
What are stem cells?
Stem cells are a class of cell which have the ability to be differentiated into specialised cell types (such as skin, muscle, bone, etc.). Stem cells come from two main sources:
- Embryonic stem cells, which are formed during embryological development and
- Adult stem cells from adult tissue.
Adult stem cells can divide or self-renew indefinitely, enabling them to generate a range of cell types from the originating organ or even regenerate the entire original organ. It is generally thought that adult stem cells are limited in their ability to differentiate based on their tissue of origin, but there is some evidence to suggest that they can differentiate to become other cell types. However, embryonic stem cells are the most potent since they must become every type of cell in the body.
Source: www.rnid.org.uk, www.medicalnewstoday.com, www.bbc.co.uk Audio infos 01/2010
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