Why does gray hair appear?

 What are melanocytes?

Skin and hair pigmentation is synthesized in the melanocytes. Melanocytes are the cells in charge of melanin production, the pigment that gives the color to the hair, eyes and skin.

During embryo development, the melanoblasts, the precursory cells of melanocytes, migrate from the neural cristae to the skin, to the follicles and the eye.

Melanocytes and melanin production can be regulated independently, and that’s why there is people with dark skin and blond hair, and the contrary.

There are different types of melanosomes (intracellular vesicles where the melanin is synthesized and storage)

• Pheomelanosome: Small and synthesize yellow and red melanin.

• Eumelanosome: Bigger and produce brown and black pigment.

The distribution of these melanocytes is uniform in every individual, but the degree of density, number of melanosomes and the size is variable.

In dark skin individuals, melanosomes are bigger than in light skin people.

How melanin is synthesized?
In melanin synthesis the precursor molecule is the tyrosine. After several reactions involving different forms of the tyrosinase enzyme, tyrosine is transformed into dopaquinone.

From dopaquinone it can go into two different metabolic routes:

• In the first route, dopaquinone is transformed into cysteinildope involving the aminoacid cystein. After a second transformation and polymeration, the cysteinildope becomes pheomelanin.

• In the other route, dopaquinone transforms into dopachrome, and after some reactions it becomes eumelanin (brown).

Eumelanin becomes black after a polymerization mediated by peroxidase. The scale in colors from brown to black depends on the degree of polymerization of eumelanin. If the polymerization is complete it becomes black.

There are 3 enzymes [tyrosinase and tyrosinase related proteins 1 and 2 (TRP1 and TRP2)] involved in melanogenesis, but only tyrosinase is absolutely necessary to melanin synthesis, due to its key activity in the process.


Why do we have different hair colors?

Differences in the color of the hair and skin depend on the different quantities of eumelanin and pheomelanin.


Why does gray hair comes up?

Over time, melanocytes lose their function and then they disappear. When they die, no melanin is synthesized and the color of the hair is lost.

Together with melanocytes the enzyme tyrosinase is lost.

Is there any method to delay gray hair appearance?

Scientists have found a fruit-derived drug that slows down the depigmentation process, reactivating melanocytes.


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