COCH (cochlin) expression in the hair follicle microenvironment was identified as a candidate marker associated with higher cortical disulfide bond content and enhanced tensile resistance of the hair shaft, with both disulfide bond content and tensile resistance declining with age.
Hair tensile resistance and cortical disulfide bond content differ significantly between younger (20–40 years) and older (>50 years) healthy volunteers.
A shared gene-expression signature associated with both reduced disulfide bond content and older donor age was identified in human scalp hair follicles.
COCH (cochlin) emerged as a prominent candidate gene associated with higher cortical disulfide bond content and enhanced tensile resistance of the hair shaft.
Immunohistochemical analysis revealed that COCH protein predominantly localizes to the hair matrix and outer root sheath of the hair follicle.
The study establishes an integrative framework connecting follicular gene expression with age-associated changes in hair shaft mechanics.
This research suggests that as people age, their hair undergoes measurable changes at both the molecular and mechanical levels. Specifically, the study found that hair from people over 50 years old tends to have lower levels of disulfide bonds — chemical cross-links within the hair's protein structure — and reduced resistance to being pulled apart (tensile resistance) compared to hair from people aged 20–40. These properties were measured using laser-based spectroscopy and mechanical testing, providing objective data on hair quality changes with age. To understand what drives these changes at the biological level, the researchers analyzed gene activity in hair follicles — the structures in the scalp that produce hair. They identified a group of genes whose activity was linked both to lower disulfide bond content and to older donor age. Among these, a gene called COCH (which produces a protein called cochlin) stood out as being associated with better-preserved disulfide bonds and stronger hair. They also found that the cochlin protein is located in specific regions of the hair follicle — the hair matrix and outer root sheath — that are responsible for building the hair shaft, suggesting cochlin plays a role in determining the chemical composition of hair as it grows. This research matters because it provides a molecular explanation for why hair may become weaker and more fragile with age, and identifies COCH as a potential biological marker of hair quality. This integrative approach — connecting follicle biology to measurable hair properties — could eventually help researchers develop targeted strategies to better understand or address age-related hair deterioration.
Joo H, Jeong G, Shin S, Kim S, Kim D, Ham M, et al.. (2026). COCH Expression in the Hair Follicle Microenvironment Is Associated With Cortical Disulfide Bonding and Tensile Resistance in Aging Hair.. Experimental dermatology. https://doi.org/10.1111/exd.70348