Abstract
One of the most visible signs of hair ageing is greying of the hair, also known as canities. This hair disorder is mainly caused by oxidative stress. In preliminary work, we designed various models mimicking the impact of oxidative stress on hair pigmentation, showing an accumulation of reactive oxygen species (ROS) production and a decrease in the presence of melanocytes and melanoblasts, resulting in a decrease in hair pigmentation. A proteomic study on skin scalp explants was performed to identify the dysregulated biological pathways related to canities. We developed a smart active ingredient which has been tested on these biological pathways. We demonstrated that these negative effects were rectified in the presence of the ingredient, showing a reduction of ROS, protection of melanocyte reservoirs and reactivation of hair pigmentation. Finally, a clinical study was carried out on a panel of 44 male volunteers with grey hair. After 4 months, we evidenced a reduction in the proportion of grey hair and in the number of grey hairs/cm2 relative to Day 0. In conclusion, we clearly evidenced that oxidative stress is a key factor in triggering a cascade of events leading to a loss of hair pigmentation. We developed this active ingredient which is capable of restoring all the disrupted mechanisms and of providing hair repigmentation within only 4 months.
Highlights
IntroductionThese melanocyte precursors are undifferentiated amelanotic cells and are not melanogenically active but express the GP100 protein and so are positive for NKI/beteb staining [2,4]
In the category of renewal, we introduced hair cycle-related genes and genes involved in apoptosis and autophagy
The oxidative stress showed a clear effect on melanogenesis by down-regulating the expression of various genes directly linked to this synthesis (MITF, TYR, DKK1, EDN1) and genes encoding for melanogenesis-related functions, such as melanosome formation and transfer (CTNS, HPS5, MLANA, MLPH, MYO5A, SLC24A5)
Summary
These melanocyte precursors are undifferentiated amelanotic cells and are not melanogenically active but express the GP100 protein and so are positive for NKI/beteb staining [2,4] They migrate downward along the outer root sheath (ORS) to populate the hair bulb around the dermal papilla (DP) [3,5]. The follicular active melanocytes are larger, with longer dendrites than epidermal melanocytes They have a more extensive Golgi apparatus and rough endoplasmic reticulum and produce larger melanosomes which are transferred to the precortical keratinocytes of hair shafts [2]. At this stage of the hair cycle (anagen IV), the expression of anti-oxidant proteins is at its highest in order to neutralise the reactive oxygen species (ROS) produced during melanogenesis [2]
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