US researchers have received approval to test whether cord blood stem cells could be used to reverse hearing loss in children.
The phase I clinical trial, the first cord blood trial to be given the go-ahead by the US Food and Drug Administration (FDA), will determine the safety of the treatment. The team from the Children's Memorial Hermann Hospital in Houston will recruit ten children, aged six weeks to 18 months, who developed hearing loss after birth.
In 2008 a European team used human cord blood stem cells to reverse a kind of hearing loss - called sensorineural hearing loss - in mice. Dr Samer Fakhri, the principal investigator for the clinical trial, told the Winnipeg Free Press that these animal studies had been successful; after only two months the mice's 'inner ear organization and structure were basically restored'.
The majority of sensorineural hearing loss in humans is due to damaged hair cells in part of the inner ear called the cochlea. They are responsible for picking up and transferring signals to the brain to interpret.
It is not known how the stem cells repaired the damaged tissue in the mice - it could be that they regenerate these hair cells or that they initiate the body's own repair mechanisms.
'Currently, the only treatment options for sensorineural hearing loss are hearing aids or cochlear implants. We hope that this study will open avenues to additional treatment options for hearing loss in children', said Dr Fakhri.
The therapy will use stem cells taken from the patients' own cord blood, which has been banked at birth. At the start of the study the patients will have a brain scan, as well as blood, hearing and speech tests. Follow-up will be over the course of a year, with tests at one, six and twelve months post-treatment and a brain scan at six months.
It is stressed that the trial is primarily to assess the safety of injecting the stem cells into the children, and other researchers are treating the trial with care.
'We're a long way from looking at the possible therapeutic value of this in terms of restoring some sort of hearing', Dr Robert Harrison, a director of the Hearing Foundation of Canada, told the Winnipeg Free Press. 'It's a very theoretical concept, and in my opinion it's not going to happen soon'.
The study is being funded by the Cord Blood Registry and will take place at separate medical institutions in Texas and Georgia.
'If both of them can reproduce the same results then I would say it has some validity to it', Dr Stephen Epstein, an otolaryngologist in Maryland who is not involved in the study, told the AFP. 'This is certainly a welcome, acceptable experiment, but it should be looked at with caution and time will tell'.