Gene therapy has been used to give mice born without a sense of smell the ability to sniff their surroundings, an international team of researchers say.The mice had a genetic disease which affected microscopic hairs in their body - called cilia - which can detect chemicals in the air.Researchers hope their findings will lead to treatments for diseased cilia, which can cause blindness, deafness and kidney disease in people.The study is in Nature Medicine.Microscopic cilia stick out from many cells in the body. A range of genetic disorders called ciliopathies result in damaged cilia which can be fatal or severely debilitating. One symptom can be a lifetime without a sense of smell, called congenital anosmia.Gene therapyA groups of researchers, lead by the University of Michigan, looked at mice with a mutation in their Ift88 gene, which meant they struggled to produce cilia and could not smell.The group created a virus which was capable of infecting cells with a working version of the Ift88 gene. This was injected into the nose on three consecutive days. This was able to restore the cilia and a sense of smell.Prof Philip Beales from University College London was involved in the study. He told the BBC: "It is a proof of concept that has shown we can get that gene back into these cells, produce the right protein, produce cilia and function as expected.He said the mice were then able to use their sense of smell to seek out food. However, it is hoped a similar approach could be used for other symptoms of the disorders.Dr James Battey, director of the US National Institute on Deafness and Other Communications Disorders which part funded the research 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."