Melanocytes function

Melanocytes function.

What are the functions of melanocytes?

The classic melanocytes function is melanin pigment synthesis. The non-classical, non-cutaneous melanocytes
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dispersed across the body carry out a variety of functions depending on their locations. They may retain common lineage signature function of melanin pigment synthesis. The type of melanin pigment (eumelanin or pheomelanin) produced and their relative proportion in the skin decides one's skin color.

Melanocyte precursors cells differentiate and migrate from the neural crest via the mesenchyme into the epidermis and hair follicles. Classical melanocytes are pigment producing cells, which are found in the dermis, epidermis and hair follicles. During development they follow the dorsolateral migratory pathway. Nonclassical melanocytes migrate to several non-cutaneous sites. Interacting continuously with the surrounding tissues, they makeup local populations having different functions. The non-cutaneous sites include eyes, inner ear, brain, leptomeninges and heart.

Classical melanocytes functions

In many species of animals the melanocytes have evolved to provide camouflage from prey and predators. In humans, protection against UV radiation has evolved as one of the primary functions of the pigment producing cells. Skin pigmentation, being the most apparent display of human polymorphic traits, defines ethnicity and race.
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UV radiation causes cellular damage and DNA damage. The cap-like melanin pigment accumulation above the nucleus of the keratinocyte, protects the nucleus from the DNA damage. The antioxidative and redox signaling activity during of the melanogenesis process neutralizes the harmful free radicals in the skin. The hair color is also due to the pigment deposit in the hair shaft. Grey hair appears when the melanocytes in the hair follicle stop producing and depositing melanin.
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The highly reactive quinone intermediates produced during melanogenesis have antibacterial and antifungal properties. The post inflammatory hyperpigmentation by the melanocytes dampens the inflammatory response and suppresses inflammation. They also interact with Langerhans cells and regulate skin immune response.

Nonclassical melanocytes functions

The presence of the melanocytes and melanin is necessary for the proper functioning of inner ear, eyes, heart and brain.

Melanocytes function in eyes

Pigment cells are found in retinal pigment epithelium (RPE) and uveal tract in the eyes.

RPE
RPE melanin is essential for the development of neural retina. RPE cells are thought to produce melanosomes only during the prenatal period. RPE melanin protects the neural retina from reactive oxygen species and macular degeneration. RPE also provides visual acuity.
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Uveal melanocytes
The uvea, the middle layer of eye, is divided into choroid, ciliary body and iris. All the three parts have pigment cells. The pigment cells of the iris impart the eye color to an individual. The pigment in the choroid is believed to protect the cells from oxidative damage by free radicals.

Functions of melanocytes of the inner ear

The pigment producing cells are found in the cochlea and the vestibular organ. The lack of these cells or lack of inner ear melanocyte function can lead to deafness.
Cochlear melanocytes are present within the stria vascularis and the modiolus. They are essential for the proper development and function of cochlea.
The vestibular labyrinth of the inner ear also has pigment cells. It is believed that they may be associated with balance perception.

The melanocytes of the heart

These group of cells are found in the valves and septa of the heart. Cardiac pigment cells, though appear not essential for heart activity, are found to trigger atrial arrhythmia. They may be regulating Ca levels and redox signaling.

Functions of the melanocytes of the brain

These cells are found in the sympathetic cephalic ganglia and leptomeninges. The melanocytes are also found along cerebral capillaries. The ventrolateral surfaces of the medulla oblongata are covered by the pigment cells. Endocrine and redox activity are attributed to these cells. The pigment present is brain-specific neuromelanin.
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Reference:
1.Tsatmali M, Ancans J, Thody AJ. Melanocyte function and its control by melanocortin peptides. J Histochem Cytochem. 2002 Feb;50(2):125-33.
2.Gertrude-E. Costin, Vincent J. Hearing. Human skin pigmentation: melanocytes modulate skin color in response to stress. The FASEB Journal vol. 21 no. 4 976-994.

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Current topic in dynamic skin care: Melanocytes function.