Gray hair is a natural part of aging for most people, but scientists have long been trying to uncover the underlying mechanisms behind hair color fading with age. Now, a recent study published in Nature has shed light on why hair color fades and how it may be possible to reverse the process. The study focused on the stem cells responsible for hair and melanin production. Hair color is determined by melanocytes, which produce melanin that gives hair its color. Stem cells in hair follicles coordinate the growth of new hair, and melanocyte stem cells produce melanocytes. When the regenerative properties of melanocyte stem cells begin failing, hair appears to turn gray.
The study found that melanocyte stem cells can get stuck in the hair bulge, where they are no longer able to mature into melanocytes and generate hair color. As a result, there may be fewer melanocyte stem cells available in the hair germ, leading to graying hair. Researchers used 3D imaging to track the movement of melanocyte stem cells in mouse hairs and discovered that the activity of these cells was much more dynamic than previously thought. Interestingly, the stem cells located in the bulge region can generate daughter melanocyte stem cells that either mature into pigment-producing melanocytes or travel up towards the bulge region to continue their journey as stem cells.
The study's findings suggest that the type of environment that stem cells are exposed to in the hair germ vs. the bulge region may trigger this reversal. The hair germ is the primary site for growth, enabling molecular signaling to create just the right environment for melanocyte stem cells to grow into mature cells. If one of these cells finds itself in the hair bulge before this process can be completed, it no longer has the resources to continue down this path. Rather than dying, these cells simply go back to their initial stem cell state.
While environmental and lifestyle factors also influence aging, people who report gray hairs earlier in life may have fewer melanocyte stem cells to begin with. The study's findings offer hope for reversing gray hair, but more research is needed to develop effective treatments. Overall, the study provides valuable insights into the complex processes that underlie hair growth and aging, and offers potential avenues for future research.