The Melanocyte originated from embryonic development (specifically the Neural Crest) and is located throughout the body where pigment can be seen such as the hair, skin and eyes. As a skin treatment therapist specialising in corneotherapy, I am briefly going to discuss epidermal pigmentation in two parts. Located on the Basal Layer of the epidermis, the melanocyte is adjacent to 10 keratinocytes (cuboidal cells) and can make contact with up to 30-36 different keratinocytes by releasing melanosomes (pigment granules) via their long branching extensions (dendrites) to be received by the keratinocytes for cellular protection against UV radiation.
When melanosomes are being manufactured inside the Golgi Apparatus of the melanocyte, the pigment granules are completely colourless until immediate contact with the keratinocytes PAR-2 Receptor takes place. Melanosomes are programmed to settle on top of the nucleus of the keratinocyte to protect the individual’s genetic material from the sun; think of these pigment molecules as a fundamental sunhat. The keratinocyte will continue its programmed journey of differentiation towards the Stratum Corneum until it will finally desquamate as a corneocyte; taking the pigment granules along with it.
Melanin begins formation when there is direct UV radiation exposure; whether direct skin-to-skin contact or through the retina of the eye, the melanocyte is programmed to make the pigment carrying melanosome to protect and defend the body. If the melanocyte has received too much sun exposure, this will result in DNA damage to not only the melanocyte, but also to the keratinocyte cell membrane and result in the overproduction or underproduction (depending on the level of cellular damage) of pigment granules to the surrounding keratinocytes. Remember, the melanocyte has access to 30-36 different keratinocytes and the ratio of melanosomes towards these cells can be altered and result in pigmentation disorders.
Damage to the melanocyte cell membrane causes the dendrites to become less flexible and viable; compromising the melanosome transfer from melanocyte to keratinocyte and this can result in pigmentation. It’s important to understand the melanocyte is a cell that does NOT desquamate which makes it very difficult to treat.
Please note, if the keratinocyte mother cell (stem cell) becomes impregnated with melanosomes, that individual is going to have to live with the damage. Melanosomes can also filter down into the Dermal/Epidermal Junction (connective tissue) and overtime, can become visible on the skin as this junction contains many intricate channels for pigment granules to accumulate. Cellular damage (ageing process/UV radiation) causes the Dermal/Epidermal Junction to collapse and the pigment granules are released into the dermal matrix; resulting in dermal pigmentation.
The melanocyte has an excellent memory and if its programmed manufacturing of melanosomes becomes compromised in anyway, the individual has to live with the damage. There are modalities available to treat this condition, however, the minute your skin or eyes has direct UV radiation exposure, BANG! All of your hard work to inhibit the formation of pigment becomes undone and as skin treatment therapists say in this industry, prevention is always better than cure.
Written by Kai Atkinson (Practicing Corneotherapist)