Whether you are in your late 20s or your early 50s, gray hair is something we will experience as we gradually age.
Melanocytes produce pigment during hair growth and pass it to hair progenitor cells at the base of the hair follicle. These cells later change into the various components of the growing hair.
When our hair grows, pigments are constantly being bonded, which results in our unique hair color. The cells responsible for this process are the pigment-producing melanocytes at the base of the hair follicle.
The follicle produces hair at a rate of around 1 centimeter monthly for several years in normal hair growth.
But all the cells in our body become progressively damaged during our lifetime, and these melanocytes are lost in due course. When all the melanocytes are lost in a particular hair follicle, the next hair that grows will be gray or white.
The biology of hair growth is rather intricate, with a multitude of specialized cells involved in hair follicle structure and function.
What controls pigmentation?
Humans possess two different types of pigment. Eumelanin, which is responsible for black and brown colors, and pheomelanin which is responsible for orange and yellow.
Genes determine the mixture of pigments that each individual produces, which is why hair color is normally similar within families.
The particular mechanisms that control pigmentation are not yet certain, but recent research points to link between several cells in the hair follicle.
Hair progenitor cells release a protein called stem cell factor, which is a requirement for the production of pigment by melanocytes. In mouse studies, the researchers indicated that hair colour is lost if this protein is absent.
The hair follicle undergoes dramatic structural changes and enters a rest period once the hair stops growin,. During this process, melanocytes die naturally.
However, melanocyte stem cells in the hair follicle normally produce a new set of melanocytes at the start of the next hair growth cycle.
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Once the new hair starts to grow, these melanocytes ensure that pigmentation is available. But when the melanocytes are damaged or absent, the hair that is produced lacks color and can look gray or white.
Hair growth after damage
According to research, human hair follicles that produce gray or white hair have higher levels of cellular damage caused by free radicals. In these follicles, melanocytes and melanocyte stem cells are absent.
When the DNA of melanocyte stem cells in the hair follicle of mice were damaged, it resulted in permanent cell damage. These stem cells were then not able to reproduce.
Without the pool of stem cells, the next round of hair growth continues without melanocytes, causing gray hair to appear.