Struggle to smell the roses Gene therapy offers new hope after restoring sense in mice
Scientists restored sense of smell to mice bred to have human genetic disorderHas potential to help patients with dementia, which has been linked to loss of smell
08:52 GMT, 3 September 2012
People born without a sense of smell could enjoy their first aromas, after a scientific breakthrough.
Researchers managed to reverse the problem in mice bred to have the human genetic disorder called congenital anosmia.
They may be able to adapt the procedure to reverse loss of smell caused by ageing or disease.
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The technique regrows parts of cells known as cilia that are essential for olfactory function, according to a study published online in Mature Medicine.
Dr James Battey, director of the National Institute on Deafness and Other Communications Disorders (NIDCD) in the US, said: 'These results could lead to one of the first therapeutic options for treating people with congenital anosmia.
'They also set the stage for therapeutic approaches to treating diseases that involve cilia dysfunction in other organ systems, many of which can be fatal if left untreated.'
Cilia protrude from the surface of cells. Sensory defects, including blindness, and loss of hearing or smell may accompany these disorders.
Olfactory dysfunction can be a symptom of a newly recognised class of genetic disorders, known as ciliopathies which range from kidney to eye disease.
The disorders are caused by the antenna-like 'cilia' projections on cells that help them sense their environment.
Dr Jeffrey Martens, of the University of Michigan, and colleagues and colleagues found a mutation in on a protein called IFT88 is associated with human cilio conditions.
Mice deficient in this protein have shortened and malformed cilia on neurons within the nose and are unable to perceive odours.
But delivery of a virus expressing IFT88 into the nose of these mutant mice rescued cilia defects and the mice responded to odourous molecules.
The researchers also found the treatment restores suckling and feeding behaviours that are controlled by olfactory function in these mice. The study could raise hopes of reversing loss of smell caused by ageing or disease.
Impairment in the sense of smell is associated with Alzheimer's disease, Parkinson's disease, schizophrenia and even normal ageing.
Smell is one of our oldest senses, and the one most closely linked to memory. It is probably related to simple chemo-sensation exhibited by some of the very first uni-cellular creatures on this planet.
The olfactory bulb, a structure in the brain that receives nerve signals from the nose, has direct connections to other parts of the brain such as the amygdala, which controls memory, and the prefrontal cortex, which is involved in processing thoughts.
The researchers plan to continue their work by developing another mouse model to look at the impact on olfactory function and the potential for restoring function when the IFT88 gene is completely missing, rather than just mutated.
Future studies could begin to plot a way to bring this therapeutic tactic to human study volunteers, which could eventually restore the sense of smell, and a better quality of life, to people who are born with anosmia.
Further research could also advance the treatments for other ciliopathies, as these findings show that gene therapy is a viable option for the functional rescue of cilia in established, already differentiated cells.