Aging of melanocytes.

Choroidal melanocytes of the eyes of postnatal animals are classified as postmitotic terminally differentiated cells. They have specific granules, the melanosomes, which undergo changes qualitatively and quantitatively correlated to the animal's increasing age. Epidermal melanocytes, which normally divide only on demand or by stimulation, are classified as intermittent mitotic cells. During their development, lentigines and nevi of the skin show progressive ultrastructural and cytochemical changes similar to those in the choroidal cells, and thus may be considered as aging populations of skin melanocytes. These facts have led to the conclusion that choroidal melanocytes may be used advantageously as a model for studying changes in cells from maturation to senescence.