U.S. researchers reported on 13th may, 2010 that stem cells can be coaxed into becoming the hair cells which are present deep inside the ears and destroyed in hearing loss. Mouse stem cells are used by scientists to grow specialized ear cells that are crucial to hearing. The team reported in the journal Cell that this experiment was done by using two types of stem cells and it raises the possibility of treating many types of deafness and hearing loss. Scientists of stem cell have formed inner ear sensory cells in the laboratory, laying concrete on the way to a cure for permanent deafness. Also they are hopeful of transforming human cells.
In each ear, human have 30,000 hair cells at the time of birth. The sensitive hair cell turns sound vibrations into nerve signals for the purpose of hearing. Due to excessively loud noise, the cells are lost or damaged and it can lead to permanent hearing loss or tinnitus (ringing in the ears). Hair cells damage may also affect balance and causing symptoms of vertigo and dizziness. A team from Stanford University School of Medicine that led by Professor Stefan Heller succeeded in programming mouse stem cells to develop into immature hair cells.
Hearing loss is a huge problem. 15 percent of Americans between 20 and 69, or 26 million people, have high frequency hearing loss caused by noise, according to the estimation of the National Institute on Deafness and Other Communication Disorders. The hair cells in the middle ear needed for normal hearing can also be damaged by antibiotics and genetic disorders. By a series of complex structures to the ear's inner cochlea which is filled with fluid that ripples, Sounds are carried. Hair cells are covered with bristles called stereocilia "ride the wave" and as these hair cells bend, the channels open and form an electrical signal that can be carried to the brain. Once the damage of these cells occurs, they can not be replaced. It was believed by Oshima's team that these cells could serve several purposes.
Two types of master cells were used by Dr. Kazuo Oshima of Stanford University in California and colleagues to form the mouse hair cells, embryonic stem cells and a similar type of cells called induced pluripotent stem cells, or iPS cells, which are ordinary cells re-programed to act like stem cells. Embryonic stem cells are "mother" cells which have the ability to transform into virtually any kind of tissue in the body. Both types of master cells came from mice and the next step is to attempt the experiment using human cells. These both cells when viewed under an electron microscope were seen to have bundled structures suggestive of the hair-like tufts of "stereocilia" that give the cells their name.View Facts and Mythes about Stem cell research
Prof Heller said, "They really looked like they were more or less taken out of the ear". It is most important to note that tests on the cells showed that they responded to being moved the way hair cells do, by converting mechanical signals into electrical ones. Experts hope that the cells will provide an invaluable research tool for studying the molecular basis of hearing and deafness. Also these cells could be made in large numbers from multiplying stem cells. "This gives us real hope that there might be some kind of therapy for regenerating hair cells. It could take a decade or more, but it’s a possibility," said by US expert David Corey, professor of neurobiology at Harvard University in Boston.
The cells were exposed to special cocktails of chemicals in both cases. These chemicals caused them to go through a range of development phases normally seen in the womb. Prof Heller said, "We looked at how the ear develops in an embryo, at the developmental steps, and mimicked these steps in a culture dish. The research demonstrated that generation of replacement hair cells from pluripotent stem cells is feasible, a finding that justifies the development of stem cell-based treatment strategies for hearing and balance disorders.”
Also, the researchers recommended that these stem-cell therapies could potentially be used to treat age-related hearing loss, or hearing damage caused by sudden or protracted exposure to noise, such as listening to MP3 players at high volume. To be perfected, the test may take a decade or more. But, it is a main step to be able to restore damaged cells.
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