February 4, 2013
A Single Type Of Stem Cell Give Rise To Three Types Of Taste Cells
Brett Smith for redOrbit.com - Your Universe Online
As stem cell research progresses, scientists are becoming more and more specialized in studying the types of cells and tissues that they generate.
In pursuing the mechanisms that drive stem cell specialization, scientists at the Monell Chemical Senses Center in Philadelphia have identified certain genetic characteristics of taste stem cells and their location on the tongue, according to their report in the journal Stem Cells.
"Cancer patients who have taste loss following radiation to the head and neck and elderly individuals with diminished taste function are just two populations who could benefit from the ability to activate adult taste stem cells," said study co-author Dr. Robert Margolskee, a molecular neurobiologist at Monell.
Taste stems cells differentiate into three different types of taste cells, all of which are found within the tiny taste buds that dot the tongue. Two types of taste cells, also referred to as gustatory cells, contain chemoreceptors that convey the various kinds of taste, including bitter, sweet, sour and umami. The third type of taste cell performs more of a structural function.
One of the remarkable properties of taste cells is their ability to regenerate. All three kinds of cells last about 10 to 16 days before being shed in favor of their replacements.
Scientists have been working for decades to find out how taste bud cells develop and regularly regenerate. They were uncertain how many cells were involved in the process and where these cells are located.
The researchers initially hypothesized that a clue to identifying taste stem cells could be found in the physiologically similar endocrine cells located in the intestine. The intestinal stem cells are easily stained using a marker known as Lgr5.
When the same stain was used on taste tissues, it showed two different patterns. The first pattern was a strong signal under the raised protrusions at the back of the tongue´s surface known as taste papillae. The second, weaker signal pattern was located immediately underneath taste buds in those same papillae.
In their report, the scientists concluded that the two different levels of expression could mean there are two different populations of cells. They said that the cells with the stronger expression of Lgr5 could be the true taste stem cells, while those with the weaker expression could be those stem cells that are slowly transforming into functional taste cells.
Using lineage-tracing experiments, the Monell scientists were also able to discover that a single type of stem cell gives rise to all three types of taste cells.
"This is just the tip of the iceberg," said senior author Peihua Jiang, a molecular neurobiologist at Monell. "Identification of these cells opens up a whole new area for studying taste cell renewal, and contributes to stem cell biology in general."
According to the research center, future taste stem cell studies will be focused on identifying how the Lgr5-expressing cells differentiate into the different kinds of taste cell types. They said they also plan to grow these cells in culture, for research and clinical use.