| MadSci Network: Cell Biology |
My short answer to this question is: No or most probably not.
Melanin is a natural pigment that is generated by melanocytes.
Melanocytes were once migratory cells derived from neural crest cells
during embryogenesis.
Some people have areas of absent skin pigmentation because the clonal
ancestor of neural crest cells died before it could migrate to the
specific region of skin where it was programmed to diferentiate into a
melanocyte. The distribution of these areas of absent pigmentation
resembles the "dermatome maps" of spinal cord sensory neurons. This is
because neural crest cells also lead to development of peripheral
nerve cells.
The melanin pigment manufactured by melanocytes remains within
endosomes (vacuoles) in the cytoplasm of these cells. If you were to
inject melanin pigment into the skin you would not be able to control
its distribution as well as the distribution of melanocytes controls
distribution of cytoplasmic pigment. It would take an enormous amount
of small needle pricks to accomplish this. The pain by itself might
prevent someone from doing this. Furthermore, there would be no
certainty that the pigment would stay where it was injected.
Since melanin is a natural material, cells could engulf it and carry it
away, were it deposited in the extracellular matrix. Some cells might
concentrate it in phagocytic vacuoles which would yield dark dots of
pigment surrounded by unpigmented areas. Using existing Tattoo
pigments might be more successful in darkening patches of nonpigmented
skin, but there would be a cost of lots of pain.
While it is not possible at present to cause melanocytes to develop in
areas where they are missing, it may be possible to stimulate existing
melanocytes to make more melanin. This is what happens when people get
a sun tan.
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