Doctors and researchers have had some success in developing artificial substitutes for other senses, such as cochlear implants to help people with hearing loss. But what is the potential for developing an implant to help to support our sense of smell?
We know that the act of smelling involves many different areas of the brain. Olfactory nerve cells transmit odour signals through the nose directly to the brain and the message is relayed to all the different areas that bring together the knowledge, emotions and other triggers that shape our response to any given smell.
Messages are transmitted around the brain by electrical current. The chain reaction is usually started by an input – in this case, the detection of odour molecules. This suggests the potential to stimulate responses so the brain ‘recognises’ a smell using electrical impulses instead - an artificial nose.
As the team observed, current research has focused on what the stimulation does in a healthy olfactory system, and there are many unknowns about what happens in the brain in cases of smell loss. We would also need to consider the fact that any implant requires some kind of surgery, and how invasive that may be.
There are only a few areas of the brain and nervous system where nerve cells can regrow or new cells can develop. The olfactory bulb and the olfactory epithelium are two of them, which means that damage to these areas can repair naturally, and a lost or altered sense of smell is regained.
Unfortunately not all damage can be repaired, and age may slow down or even stop this ability. Research to better understand what may affect the ability of olfactory nerve cells to regenerate, and the importance of other cells in the olfactory epithelium to support this, is very helpful in understanding the prognosis for smell disorders and helping this regrowth to take place.
Researchers are also investigating ways to stimulate nerve cell regeneration, or to introduce new nerve cells in other ways.
One way that the growth of new cells might be stimulated and used as a treatment is with the introduction of stem cells. Stem cells are cells with the potential to develop into many different types of cells, and can be guided to form olfactory nerve cells. Research has looked at whether treating with stem cells – either directly to the nose, or via blood infusions – can stimulate the growth of olfactory nerve cells and supporting cells. More research is needed to understand what benefit this can have for olfactory function, and to ensure the safety of treatment.
Other studies have investigated the potential to transplant olfactory mucosal tissue from the nose into other areas of the olfactory system. This seems to develop the right cell structures, but again more research is required to understand if this results in improved olfactory function.
There is no guarantee that these futuristic-sounding treatments will come to fruition, but every piece of research is helping us to understand the olfactory system better.