Stem cells are responsible for our bodies developing into all of the different tissues we have today. Typically, they move in one direction - towards differentiation. However, recent research has uncovered that not only can differentiated cells revert back to stem cells in order to perform repairs, but they are found in an unlikely place: nerve cells of teeth. This could provide a source of stem cells to be used for research or the development of therapies without the need for embryonic sources. The research was led by Igor Adameyko of the Karolinska Institutet in Sweden and the paper was published in Nature.
Inside the center of the tooth is the living part known as the pulp. This region contains blood vessels, nerves from the gums, and cells that contribute to the structure and health of the tooth. If the tooth becomes damaged, these cells get to work making restorative tissues. However, researchers have failed to understand where these stem cells originate. Through mapping of tooth formation in mice, they discovered the nerves are actually the source of the stem cells.
“We have identified a previously unknown type of stem cells that surprisingly enough belong to the nerves of the tooth; these are nerves that would normally be associated with the tooth's extreme sensitivity to pain,” co-author Kaj Fried said in a press release.
It turns out that some glial cells, which are non-neuron cells that support the nervous system, don’t stay in the nerves during embryonic development. Instead, they leave fairly early on in development and become mesenchymal stem cells. The stem cells can then differentiate into osteoblasts that reside in the outer regions of the tooth pulp and create new dentin. The migration of these cells was discovered by using fluorescent markers to track glial cells throughout development.
“The fact that stem cells are available inside the nerves is highly significant, and this is in no way unique for the tooth,” Adameyko added. “Our results indicate that peripheral nerves, which are found basically everywhere, may function as important stem cell reserves. From such reserves, multipotent stem cells can depart from the nerves and contribute to the healing and reformation of tissues in different parts of the body.”
This study is the first indication that nerve cells are able to revert back to stem cell status, which makes it incredibly exciting. This could give researchers an avenue for creating a supply of mesenchymal stem cells for research, provided they identify the chemical signal that induces the glial cells into reversion. Before the team seeks to begin growing and harvesting stem cells, they hope to use alternative methods to verify their current findings.