A May 2019 study showed that mice whose sense of smell had been disabled, when given stem cells into their noses, had their olfaction restored.
This was tested first by mice whose sense of smell had been injured, and when the stem cells were introduced into the area, the sense of smell was restored. However, the theory could not be considered fully proven, as there was no way of determining whether the mice’s cells had healed organically or as a result of the stem cells being introduced to the area.
So it was tested again, by genetically engineering mice without the gene necessary to have a sense of smell at all. Again, when certain stem cells were introduced to the nose, they were able to stimulate the production of the cells necessary to gain olfaction, and the theory was proven again.
In this experiment, they only introduced 5-10 μL (that’s between five and ten-millionths of a liter) to the area which, while the mice were lightly anesthetized, the material was able to engraft to the nasal cells, and when the mice were tested 8-10 weeks later, their sense of smell was observed to have returned.
The way they tested for olfaction was by using a controlled environment, scrubbed of other distractions, and even perceptions (by using red lighting and conducting the experiments at night, it was ensured that the mice had no other factors to go off of). The study used a control group, a group of mice that had been given the cells, and a group that hadn’t received any stem cells.
When there was only water in the dish, the mice spent longer exploring the area. When an aversive odorant called isopentylamine, or IPA, that can only be detected through olfactory neurons was introduced to the water dish, the control group and the mice treated with stem cells spent less time exploring their areas, showing that they could, in fact, smell the IPA.
What Does This Study Mean for Humans?
According to the aforementioned study, 12% of the US population have an impaired sense of smell (hyposmia or anosmia) and don’t have many viable treatment options. While there can be a wide variety of causes of this impairment, many of them are permanent.
As of right now, further research and testing will have to be done to know if this can be replicated in humans. But the infinancy of this research is showing promising and versatile use of these cells.
For the full timeline and criteria of the study, view the original study published at the link below.
Study referenced: https://www.cell.com/stem-cell-reports/fulltext/S2213-6711(19)30146-8
Additional articles referenced: https://www.the-scientist.com/news-opinion/stem-cells-delivered-to-the-nose-restore-mices-ability-to-smell-65953