There could finally be a way of stopping hair from going grey. Thanks to researchers in the US, stem cells that have the unique ability to move between growth compartments in hair follicles were discovered.
As humans grow older, the melanocyte cells in our hair follicles die. This causes a depletion in the pigment resulting in grey hair over time.
To stop this, the team found that as our hair ages, sheds and repeatedly grows back, more of these stem cells become stuck in a compartment called the hair follicle bulge.
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These hairs stay here rather than travel back to their original location in the compartment, where proteins would have helped them regenerate into pigment cells, meaning that the hair keeps its colour.
Led by researchers at the NYU Grossman School of Medicine, the study observed the physically-aged hairs of mice and found that more and more stem cells became stuck after forced ageing, Wales Live reports.
Just as with humans, these cells were found to remain incapable of regenerating or maturing into pigment-producing hairs which keep their colour.
However, the scientists hope the new research may lead to the necessary answers for keeping our hair healthy and with its natural colour into our old age.
The study focused on cells in the skin of mice which can also be found in humans, called 'melanocyte stem cells' or McSCs.
Our hair colour is controlled by whether non-functional but continually multiplying pools of McSCs within hair follicles receive the signal necessary to become mature cells responsible for making the protein pigments responsible for giving hair its colour.
The NYU study found the McSCs are 'plastic' or adaptable, meaning that during normal hair growth, they continually move back and forth on the maturity axis as they move between compartments of the developing hair follicle.
It is inside these compartments that the McSCs are exposed to differing levels of maturity-influencing protein signals.
The research team found that McSCs transform between their most primitive stem cell state at the next stage of their maturation - the transit-amplifying state - and depending on their location.
As our hair ages, sheds and repeatedly grows back, the study found that increasing numbers of McSCs get stuck in the stem cell compartment called the hair follicle bulge.
Once stuck, the McSCs remain in the bulge and fail to mature into the transit-amplifying state and do not travel back to their original location in the germ compartment. It is here that proteins help them to regenerate into pigment cells.
The researchers say McSC adaptability is not present in other self-regenerating stem cells, such as those making up the hair follicle itself, which are known to move in only one direction along an established timeline as they mature.
Transit-amplifying hair follicle cells never revert to their original stem cell state, for example, which helps explain in part why hair can keep growing even while its pigmentation fails.
The study's lead investigator, Dr Qi Sun, a postdoctoral fellow at NYU Langone Health, explained: "Our study adds to our basic understanding of how melanocyte stem cells work to colour hair. The newfound mechanisms raise the possibility that the same fixed-positioning of melanocyte stem cells may exist in humans.
"If so, it presents a potential pathway for reversing or preventing the greying of human hair by helping jammed cells to move again between developing hair follicle compartments."
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