Didier Saint Léger

Androgenic alopecia and stress-induced premature senescence by cumulative ultraviolet light exposure.

Background: Ultraviolet light radiations (UVR) may be responsible for hair cycle synchronization and telogen effluvium in the animal and humans. The effect if any of cumulative UVR on chronic hair shedding and androgenic alopecia (AGA) is largely unknown. Objective: To compare the severity of AGA with the extent of solar elastosis. Method: The present study combining immunohistochemistry and computerized image analysis was undertaken in 140 men with AGA and 50 non-alopecic men. Solar elastosis was identified using the antibody to lysozyme, and collagen was revealed by Sirius red staining. The number and diameter of hair shafts were also assessed. Results: The scalp dermis was significantly thicker in AGA than in unaffected subjects. The difference was mainly due to a severer elastosis in baldness. The earliest signs of solar elastosis preceded hair thinning. When elastosis was thicker than 0.2 mm, a negative exponential correlation was found between hair diameter and severity of solar elastosis. Conclusion: Chronic UVR exposure of the scalp may affect the hair cycle and be one of the exogenous factors influencing negatively the progression of AGA. The induction of stress-induced premature senescence by reactive oxygen species and micro-inflammation might be operative at the level of the follicular stem cells.

Immunohistochemical Patterns in the Interfollicular Caucasian Scalps: Influences of Age, Gender, and Alopecia

Skin ageing and gender influences on the scalp have been seldom studied. We revisited the changes in the interfollicular scalp. The study was performed on a population of 650 volunteers (300 women and 350 men) for over 7 years. Three age groups were selected in both genders, namely, subjects aged 20–35, 50–60, and 60–70 years. The hair status was further considered according to nonalopecic and alopecic patterns and severity (discrete, moderate, and severe). Biopsies from the parietal area were processed for immunohistochemistry. Stromal cells were distinguished according to the presence of vimentin, Factor XIIIa, CD117, and versican. Blood and lymphatic vessels were highlighted by Ulex europaeus agglutinin-1 and human podoplanin immunoreactivities, respectively. Actinic elastosis was identified by the lysozyme coating of elastic fibres. The epidermis was explored using the CD44 variant 3 and Ki67 immunolabellings. Biplot analyses were performed. Immunohistochemistry revealed a prominent gender effect in young adults. Both Factor XIIIa+ dermal dendrocytes and the microvasculature size decreased with scalp ageing. Alopecia changes mimicked stress-induced premature senescence.