Hair greying is a common part of the aging process for humans and mice, but the causes have remained a mystery. Each hair follicle contains a specialised population of pigment-producing cells known as melanocytes. These cells are renewed by melanocyte stem cells. A recent study has provided new insights into the behavior of these melanocyte stem cells and their role in hair greying. The findings of this research propose a new model for how stem cells are maintained and suggest that controlling McSC movement may offer a new approach for preventing hair greying.

Key Points:

• The melanocyte stem cell system deteriorates earlier than other tissue stem cell populations, causing hair to turn grey.
• Previously, it was believed that melanocyte stem cells were kept in an inactive, undifferentiated state, separate from their specialized offspring.
• The study shows that melanocytes can switch between differentiated and undifferentaiated roles.
• With time the melanocytes become stuck in higher regions of the hair follicle preventing them from contributing to hair pigmentation.

The Study

To better understand the behavior of melanocytess, researchers used live imaging to visualize the position of the melanocytes and single-cell RNA sequencing, a method that analyzes gene expression in individual cells. They discovered that melanocytes are mobile, moving between two areas: hair follicle stem cell compartments and transit-amplifying compartments. In these areas, melanocytess can reversibly enter different levels of specialization, influenced by signals from their local environment. As an individual ages, nonfunctional melanocytess accumulate, which do not help regenerate hair color-producing cells, leading to hair greying.

Implications and Future Research:

This study introduces a new model for maintaining a balance among stem cells, where the ability to revert to a less specialized state is crucial. The results suggest that controlling melanocytes movement could be a new approach for preventing hair greying.

Further research is needed to better understand the specific mechanisms that control melanocytes movement and how they can be adjusted to prevent or reverse hair greying. Such findings could lead to new treatments for age-related hair color loss in humans and potentially other aspects of the aging process.

An understanding of the relationship between these different melanocyte populations may also enable us to better treat melanoma, the most serious form of skin cancer.

Link to study