How stem cells become different taste receptors

Scientists from the Monell Chemical Senses Center, Philadelphia, USA, conducted a study that reveals the mechanism of renewal of taste receptors with the help of stem cells. The results of the work, published on June 21, 2017 in Scientific Reports, can be used to treat taste disorders and even to fine tune taste perception to stimulate healthy eating.

The unique ability of taste buds is their ability to update every 10-14 days. A new study by American scientists makes it possible to understand how stem cells form mature taste receptor cells that that detect either bitter, sweet, salty, sour, or umami (taste of sodium glutamate, or, more generally, taste of amino acids).

“We still have many open questions about how the sense of taste works. Some of these newly-discovered genes may help us better understand how a taste cell detects a given taste quality,” – said Monell Center molecular neurobiologist Peihua Jiang, PhD, the study’s senior author.

“Who knows, someday we may be able to use this knowledge to generate fewer bitter cells in a bitter-sensitive person to help that person enjoy healthy bitter-tasting vegetables.”

Taste cells are located in clusters called taste buds, which in turn are found in papillae the raised bumps visible on the tongue’s surface. Two different types of specialized taste cells contain chemoreceptors and intracellular molecular mechanisms of taste perception. It is considered that the third type of cells appears to serve as a supporting cell.

In 2013, Jiang was able to identify stem cells (progenitor cells, SCs) that gives rise to these three types of taste receptor cells. In further experiments, he helped to place these taste stem cells in a culture dish and prompt their differentiation into various types of mature taste cells, forming a taste bud in a dish scientifically known as “taste organoids”

In this paper, Jiang and his colleagues studied the taste organoids at different stages of growth to identify which genes are included at each stage of the formation of taste cells. Using a powerful technique of RNA sequencing (RNA-Seq), a group of scientists determined a virtually complete set of genes, including those not previously identified, that determine the development of taste cells.

Studies revealed that during the differentiation of stem cells, these genes influence what kind of taste will ultimately perceive the receptor: salty, sweet, sour, bitter, or umami.

Other experiments conducted have revealed molecular signals that guide the taste stem cells in one way or another. Using pharmacological approaches, researchers identified so-called signal proteins in the SCs that control their division and differentiation into certain types of cells.

These experiments demonstrated the important roles of several signaling pathways, including those whose role in the formation of gustatory sensations has not been known to date.

“By better understanding how our taste cells detect and translate information about the chemical constituents of our food, we may be able to confirm how humans detect poorly-understood qualities such as fat or calcium, or even identify entirely new tastes,” – said study co-author Robert Margolskee.

Dr. Jiang notes that the results of the study may have treatment implications for patients who lose their sense of taste following radiation for head and neck cancers.

“Understanding how taste cells grow may help us develop novel strategies to help patients with taste disorders,” – he said.

In further research, scientists want to identify the functions of the newly-discovered taste genes. It is also planned to study the mechanisms of molecular signaling, which determines the differentiation of stem cells and determines the function of taste receptors.