A team of researchers from Cologne and Helsinki have discovered a mechanism that helps prevent hair loss.
Hair follicle stem cells, which are essential for the hair to regrow, can prolong their life by switching their metabolic state in response to low oxygen concentration in the tissue.
The team, led by Associate Professor Sara Wickström from the University of Helsinki and Max Planck Institute for the Biology of Ageing and dermatologist Professor Sabine Eming from the University of Cologne, investigated the transcriptional and metabolic profiles of stem cells and their differentiated daughter cells, to ascertain what makes the two populations different.
“Intriguingly, these studies showed that stem cells and daughter cells have distinct metabolic characteristics,” said Dr Christine Kim, co-leading scientist of the study.
“Our analyses further predicted that Rictor, an important but relatively poorly understood molecular component of the metabolic master regulator mTOR pathway, would be involved.”
The mTOR signal transduction regulates processes like growth, energy and oxygen consumption of cells.
In more detailed analyses, the team showed that stem cell depletion was due to the loss of metabolic flexibility.
At the end of each regenerative cycle, during which a new hair is made, the stem cells will return to their specific location and resume a quiescent state.
Dr Xiaolei Ding, the other co-leading scientist, explained: “The key finding of this study is that this so called ‘fate reversibility’ requires a shift from glutamine metabolism and cellular respiration to glycolysis.
“The stem cells reside in an environment with low oxygen availability and thus use glucose rather than glutamine as a carbon source for energy and protein synthesis. This shift is triggered by the low oxygen concentration and Rictor signalling.
“The removal of Rictor impaired the ability of this stem cell fate reversal, triggering slow, age-dependent exhaustion of the stem cells and age-induced hair loss.”
It was observed that mice lacking Rictor had significantly delayed hair follicle regeneration and cycling, which indicated impaired stem cell regulation.
“Interestingly, with ageing, these mice showed hair loss and reduction in stem cell numbers,” added Ding.
In what might be music to the ears of those experiencing hair loss, the researchers said they’d been particularly excited to observe that the application of a glutaminase inhibitor was able to restore stem cell function in the Rictor-deficient mice.
