An international team of researchers funded in part by NIAMS sought to understand why skin nevi grow long hair. Nevi, which are a type of skin lesion, have an abundance of pigment-producing cells, called melanocytes, that have become aged (or senescent). The team determined that senescent melanocytes within nevi produce large quantities of several signaling molecules. One such molecule, called osteopontin, causes dormant hair stem cells to wake up, which increases hair growth.

The study, which appeared in the journal Nature on June 21, 2023, provides answers as to why nevi are hairy and also uncovers the unexpected growth-promoting potential of senescent cells, which are typically thought to be associated with inhibited tissue growth.