In a discovery that could have important medical implications, scientists claim to have found the cellular origins of smell, sex and self-recognition in a study of mice.
A team of American scientists found that during embryonic development, a set of nasal stem cells give rise to three types of neurons that carry signals making these three vital functions possible.
“These cell types are key for the survival of an organism,” said Anthony-Samuel LaMantia, director of the George Washington Institute for Neuroscience, who led the research at the University of North Carolina, Chapel Hill.
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“You can’t get more essential than that,” LaMantia was quoted as saying by the
The findings, according to the researchers, could aid the study of a host of diseases like autism and schizophrenia, where the sense of smell is altered.
For their research, LaMantia’s team isolated the stem cells from mouse embryos about halfway through their 20-day gestation.
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After 20 hours, cells they took from the sides of the lining of the nasal cavity, called the olfactory epithelium, produced only more of themselves — a key feature of stem cells, LaMantia said.
The researchers found that the nasal stem cells went on to become the three types of nerve cells: olfactory which is responsible for our sense of smell, pheromonal, linked to the ability to sense pheromones, and gonadotropin which is linked to reproduction.
Once formed, gonadotropin releasing hormone neurons, the neurons associated with reproduction, leave the nasal tissue and migrate to the brain’s hypothalamus — a region of the brain that controls many body functions.
These neurons are responsible for the release of two hormones: luteinizing hormone that triggers ovulation in women and testosterone in males, and follicle-stimulating hormone, which regulates puberty and reproductive processes in the body, the scientists said.
While the sex neurons don’t regenerate, the olfactory and pheromonal neurons called vomeronasal receptor neurons are unique in that they can regenerate, they said.
According to the researchers, the results could have important medical implications, particularly for the so-called olfactory receptor neurons — the nerve cells hide out in the nose, detecting chemical signals, which they communicate to the brain via long stems called axons.
“Over the course of a lifetime, it turns out in most parts of the nervous system, the neurons you start with when you are born are the neurons you end up with. If you lose them, you don’t replace them,” LaMantia said. “Except for in the nose.”
There is evidence of the limited addition of new cells aiding in the study of diseases, like autism and schizophrenia, where the sense of smell is altered, he said.
Because these neurons could survive a biopsy, they could potentially be used to study the progression of these diseases. And since some, like autism and schizophrenia, are diagnosed only by observation, olfactory neurons might yield diagnostic tools, the scientist added.
The research was published in the journal Development .