Stem cells treatments for deafness?

Starting with embryo stem cells (ES cells), US scientists have managed to grow inner ear cells in the laboratory: a development that could mean new treatments for age and damage-related hearing problems. Stem cells present in early embryos are 'master cells', which, under the right conditions, are capable of growing into any type of tissue. Researchers at the Massachusetts Eye and Ear Infirmary in Boston have managed to coax mouse ES cells to grow into sound-detecting hair cells, by exposing them to a cocktail of growth-promoting chemicals. The scientists say their findings, published in the Proceedings of the National Academy of Sciences (PNAS) last week, will further research into cell transplant treatments for deafness.

Hair cells line the inner ear, where they pick up sound waves and convert them into electrical signals, which are then sent to the brain. In mammals, hair cells die off with age, causing gradual hearing loss. The new study shows that it might be possible to replace these lost cells: either by carrying out transplants, or identifying chemical signals that could trigger their re-growth. The researchers, lead by Stefan Heller, transplanted the laboratory-grown hair cells into a chick embryo, and found that they continued to develop as expected. They now want to find out if the cells, which look like normal ear hair cells, also behave like them. Heller says the next step will be to see if the cells can successfully treat hearing loss in mice.

UK expert Matthew Holley stressed that the research wouldn't immediately produce any new treatments: 'I'd say that if you are 65 years old with hearing damage today, it won't arrive in time for you' he told the BBC. However, he said the work could eventually lead to new drugs that can trick adult ear cells into producing new hair cells. 'This research is helping us understand the mechanics involved in producing these cells' he added.

Meanwhile, another US team have produced primitive versions of human organs and tissues in the laboratory, using human embryo stem cells grown on a biodegradable polymer 'scaffold'. The scientists, based at the Massachusetts Institute of Technology in Boston, grew artificial structures that resembled cartilage, liver and nerve tissue by exposing ES cells to several hormones as they grew on the spongy supports. When they transplanted these tissues into mice, the animal's blood vessels began to grow into the 'organs', supplying them with nutrients for further growth. The work 'holds promise for addressing organ shortages' say the authors, who also published their study in PNAS.