Hiroyuki Matsumura and a team from Japan and the Netherlands undertook a study into ageing associated hair loss, while Li Wang and a team in the US examined hair follicle growth, with both being published in the AAAS journal Science, and providing an insight and further understanding.
This is important as understanding fundamental principles of tissue renewal can help develop treatments, and will help scientists understand whether it is intrinsic changes in stem cells or environmental factors that play the more dominant role.
If intrinsic changes are the major factor, the basis for stem cell use to prevent ageing weakens; and if environmental factors play a dominant role, rebuilding stem cell niches or modifying the global body environment will be important, according to Mingxing Lei and Cheng-Ming Chuong, commenting on the research.
Age associated hair loss
Both studies concentrated on hair follicle stem cells (HFSCs), which generate the sacs or follicles that produce hair and keep hair growth going repeatedly over time. Surprisingly, they have even been shown, in mice experiments, to resist ageing.
In the first study, Matsumura and colleagues studied hair follicles in a mouse model of accelerated hair loss to better understand the role HFSCs might play in ageing-associated hair loss.
An analysis of the animals' skin at 18 months, a stage when their hair loss begins, showed that their hair follicles were miniaturized and reduced in number and thickness.
The researchers hypothesized that changes in follicle-generating HFSCs might be to blame, and further studies, including of key genes involved in HFSC maintenance, confirmed their hypothesis.
According to the scientists, accumulating DNA damage in the hair follicle stem cells seems to play a role in driving the changes to them.
One gene found to be especially important to regulating HFSCs was COL17A1, as the stem cells are eliminated in mice engineered to lack this factor.
Hair follicle growth
In the other study Wang and colleagues identified a transcription factor that HFSCs use to initiate hair growth.
During the adult hair cycle, the follicle stem cells periodically go through phases of activation and quiescence to maintain a stem cell population and to produce new hair follicles.
The research team say that by manipulating expression of the Foxc1 gene at different stages of the hair growth cycle they were able to determine that this transcription factor promotes signalling between two key mechanisms that control the dormant phase, Nfatc1 and BMP.
These findings suggest that quiescent HFSCs sense the change of their cellular states and utilise transient gene activation to maintain their identity.
Together, these two studies add volume to the research surrounding hair growth.