Although hair follicles affected by hair loss contain the same concentration of melanocytes as normal follicles, they are smaller in size, and the overall number of melanocytes in the bulb is reduced. However, no differences have been observed in the distribution or pattern of melanin expression between normal follicles and those affected by hair loss.
The only difference is that in dermal papilla cell cultures from hair loss follicles, there is reduced secretion of Stem Cell Factor (SCF), which plays a key role in melanocyte development. This suggests that the mechanism behind pigment reduction in androgenetic alopecia involves androgen binding to receptors in the dermal papilla, inhibiting SCF gene expression and melanin synthesis by dermal papilla cells throughout the anagen phase, resulting in decreased pigment production by melanocytes in the bulb.
Overall, these findings indicate that modulators of SCF/c-Kit signaling—or yet unidentified regulators of c-Kit-negative melanocyte stem cells—could offer future therapeutic options for altering hair pigmentation with clinical implications in androgen-dependent hair disorders, including hirsutism and androgenetic alopecia, as well as aesthetic concerns related to graying.
Changes in human skin are among the earliest visible signs of aging, and hair follicles age like any other organ. The lifespan of normal scalp hair follicles shortens with age, accompanied by a decline in hair “quality.” When visible changes in hair appearance occur in an elderly individual without hair loss, this is referred to as senile alopecia, characterized by clinical thinning and a reduction in hair count. Paradoxically, this condition is associated with an increased proportion of thicker hairs.
Hair graying is directly linked to chronological aging and typically begins gradually in Caucasians from the mid-30s onwards. Premature graying, occurring before ages 20–25, has been associated with osteopenia and a potential increased risk of cardiovascular disease. Graying results from a decrease in active melanocytes in the hair bulb, alongside morphological and mechanical differences between gray/white and normally pigmented hairs. Interestingly, loss of pigmentation positively affects hair metabolism, leading to a significant increase in growth rate, and an increase in the diameter of white hairs has also been reported.
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