Daily Archives: October 26, 2020
An international research group headed by Associate Professor Sara Wickström at the University of Helsinki has identified a mechanism that is likely to prevent hair loss. Hair follicle stem cells, which promote hair growth, can prolong their life by switching their metabolic state. In experiments conducted with mice, a research group active in Helsinki and Cologne, Germany, has demonstrated that a protein called Rictor holds a key role in the process. Ultraviolet radiation and other environmental factors damage our skin and other tissues every day, with the body continuously removing and renewing the damaged tissue. On average, humans shed daily 500 million cells and a quantity of hairs weighing a total of 1.5 grams. The dead material is replaced by specialised stem cells that promote tissue growth. Tissue function is dependent on the activity and health of these stem cells, as impaired activity results in the ageing of the tissues.
Hair follicle stem cells, which promote hair growth, can prolong their life by switching their metabolic state.
“Although the critical role of stem cells in ageing is established, little is known about the mechanisms that regulate the long-term maintenance of these important cells. The hair follicle with its well understood functions and clearly identifiable stem cells was a perfect model system to study this important question,” says Sara Wickström.
At the end of hair follicles’ regenerative cycle, the moment a new hair is created, stem cells return to their specific location and resume a quiescent state. The key finding in the new study is that this return to the stem cell state requires a change in the cells’ metabolic state. They switch from glutamine-based metabolism and cellular respiration to glycolysis,
a shift triggered by signalling induced by a protein called Rictor, in response to the low oxygen concentration in the tissue. Correspondingly, the present study demonstrated that the absence of the Rictor protein impaired the reversibility of the stem cells, initiating a slow exhaustion of the stem cells and hair loss caused by ageing.
The research group created a genetic mouse model to study the function of the Rictor protein, observing that hair follicle regeneration and cycle were significantly delayed in mice lacking the protein. Ageing mice suffering from Rictor deficiency showed a gradual decrease in their stem cell, resulting in loss of hair.
The study was published in the Cell Metabolism journal.