Scientists funded by the National Institutes of Health have restored the ability to smell in a mouse model of a human genetic disorder that causes congenital anosmia-the inability to smell from birth. The approach uses gene therapy to regrow cilia, cell structures that are essential for olfactory function.
The study was funded by four parts of NIH: the National Institute on Deafness and Other Communications Disorders (NIDCD), the National Institute on Diabetes and Digestive and Kidney Diseases (NIDDK), the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), and the National Eye Institute (NEI). It was published online in the September 2, 2012, issue of the journal Nature Medicine.
"These results could lead to one of the first therapeutic options for treating people with congenital anosmia," said James F. Battey, Jr., M.D., Ph.D., director of NIDCD. "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."
Olfactory dysfunction can be a symptom of a newly recognized class of genetic disorders, known as ciliopathies, which include diseases as diverse as polycystic kidney disease and retinitis pigmentosa, an inherited, degenerative eye disease that causes severe vision impairment and blindness. The disorders are caused by defects in cilia, antenna-like projections on cells that help them sense their environment. Scientists believe that nearly every cell in the body has the capacity to grow one or more cilia. In the olfactory system, multiple cilia project from olfactory sensory neurons, sensory cells that are found in the olfactory epithelium, tissue high up in the nasal cavity. Receptors that bind odorants are localized on the cilia, which is why a loss of cilia results in a loss in the ability to smell.
The team of researchers, led by Jeffrey R. Martens, Ph.D., at the University of Michigan, Ann Arbor, and Jeremy C. McIntyre, Ph.D., a post-doctoral fellow in Martens' laboratory, worked with a mouse model carrying a mutation in the IFT88 gene. The mutation causes a decrease in the IFT88 protein, which leads to a dramatic reduction in cilia function in several different organ systems, including the olfactory system.