Human Hair Graying Revisited: Principles, Misconceptions, and Key Research Frontiers.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic models and expert opinion without new human data
PubMed 38099887 · doi:10.1016/j.jid.2023.09.276
What was done
This is a narrative review synthesizing current evidence, mechanistic pathways, and clinical observations regarding human hair graying (canities), hair follicle pigmentary unit dynamics, and potential repigmentation pathways.
What was found
The abstract reports no numerical data or effect estimates. It details that hair graying is driven by cumulative oxidative and DNA damage, excessive mTORC1 activity, melanocyte senescence, and reduced MITF- and tyrosinase-mediated melanogenesis. Phenotypic graying and repigmentation occur exclusively during anagen, and hair graying remains reversible until bulge melanocyte stem cells are fully exhausted.
Why it matters
It consolidates current models of human hair follicle aging, highlighting that early graying is biologically reversible and mapping molecular pathways for potential human antigraying interventions.
Limits
This is a narrative review presenting no new primary empirical data or quantitative meta-analysis. The abstract explicitly cautions that concepts derived from mouse models cannot be directly translated to human hair pigmentation.