Gene therapy offers solution to anosmia

Our sense of smell is one of our most important capabilities as humans. Beyond how we normally define it, smell also plays into our sense of taste and affects our appetite. But what happens when a person suffers from anosmia, the loss of smell, due to a genetic disorder, degenerative disease, or trauma? Can the sense be restored?

Randall Reed, co-director of the Center for Sensory Biology at the Hopkins Institute for Basic Biomedical Sciences, is a co-author on a recent study published in Nature Medicine aimed at answering these questions.

Researchers used gene therapy techniques to test a method of re-establishing a defunct sense of smell. The mice that were used in the experiment had a mutation that halted the synthesis of a protein needed by the cilia of olfactory sensory neurons — smell cells. When cilia are incomplete, the neurons are unable to detect odors and thus results in anosmia.

In the experiment, the scientists chose to alter the common cold viral genes with genes that properly synthesize the proteins needed by the cilia. Infecting the mice with this virus acted as a delivery method of the acceptable gene to the mutated cells.

After this process, Reed and his team tested the mice using smell stimulants and were able to detect corrected chemical signaling among the olfactory sensory neurons. The positive results of the experiment were also detectable in the increased weight of the mice. Their ability to smell the food increased their appetite.

The success of this procedure in mice does not mean that all people who are affected by anosmia will be cured immediately. In humans, the findings are probably only relevant for those that are afflicted by genetic anosmia, not to mention that human gene therapy applications are years away. The authors hope their research will spark interest into fixing anosmia of other causes as well.

The researchers were particularly pleased with their success in using live mice for the therapy. “These studies are the first to use in vivo therapeutic treatment to re-establish cilia in a mammalian ciliopathy. More broadly, our studies indicate that gene therapy is a viable option for cellular and functional rescue of the complex ciliary organelle in established differentiated cells,” the researchers wrote in their journal article.

The rehabilitation of cilia function in olfaction could have even greater research effects. Cilia are essential to many cells other than those that are olfactory, so therapeutic procedures could be applicable for other disorders as well.