Hair follicle and fibre testing

This preclinical category covers biological models of the follicle and relevant assessments of fibre structure. Living follicle responses and the properties of an already formed hair shaft are different questions and require different methods.

Follicular growth and signalling

Isolated follicle culture or suitable cell models can examine growth-associated responses, anagen maintenance and transitions toward catagen. Enzyme assays can assess 5α-reductase activity and DHT formation, but they do not establish that a topical ingredient reverses androgen-related hair loss. Growth-factor expression is also not proof of prolonged anagen without an appropriate functional model.

Protein, pigment and cell endpoints

• Hair-keratin expression in suitable follicular cells
• Protein damage or protection in relevant fibre preparations
• Follicular responses relevant to unwanted-hair research
• Hair-bulb melanocyte activity relevant to greying mechanisms
• Stem-cell-associated markers or colony-forming behaviour

Marker expression alone does not demonstrate stem-cell activation, reversal of greying or selective reduction of unwanted hair. Shaft-protection findings should identify the stressor and measured property rather than imply biological repair of non-living fibre.

Connect mechanisms to further evidence

Reports should identify the model, concentration, exposure and viability controls. Laboratory results can guide later hair or scalp studies, but hair-growth, hair-loss and hormone-related statements may affect product classification and need market-specific review and appropriate human evidence.