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.

The skin is composed of three layers including the epidermis, dermis, and hypodermis, each of which play a specific role in the skin. 1 Interestingly, the dermis provides all the biomechanical properties of the skin such as elasticity and firmness, and imparts resilience through its specific composition and organization. It is a highly vascularized tissue, mainly composed of fibroblasts capable of synthesizing structural proteins such as collagens, 2 which are the most abundant. The two main types of collagen synthesized in the dermis are type I and type III collagen, 3 both of which are composed of three polypeptide chains organized in a triple helix which is involved in mechanic resistance of tissues against traction. 4 In the upper dermis, also known as the papillary dermis, collagen fibers are arranged perpendicularly to the epidermis, intertwined with thinner vertical elastic fibers named oxytalan and elaunin fibers having few elastic properties due to a low amount of elastin. 5 In contrast, collagen fibers from the underlying reticular dermis are larger and arranged

Background During aging, human skin is facing hyperpigmentation disorders: senile lentigo (chronobiologic aging) leads to loss of melanogenesis' control while solar lentigo (UV exposure) promotes an increase of oxidized proteins, melanogenesis, and lipofuscin. Aims Stromal‐cell‐derived‐factor‐1 (SDF‐1) was identified as key regulator of hyperpigmentation and its expression is reduced in senescent fibroblasts, highlighting this protein as new target for skin hyperpigmentation. Materials We developed two skin explant models mimicking of senile and solar lentigo, based on H2O2 systemic treatment and UV irradiation, respectively. We evaluated Himanthalia elongata extract (HEX) on these models after 5 days of treatment and analyzed SDF‐1 expression and skin pigmentation. For solar lentigo, we also analyzed oxidized proteins and lipofuscin accumulation. Finally, we evaluated HEX in vivo on nearly 100 multi ethnicities' volunteers. Results SDF‐1 expression decreased in senile lentigo model, associated with hyperpigmentation. HEX application restored SDF‐1 expression, leading to skin pigmentation decrease. For solar lentigo, we showed an impact of UVs on SDF‐1 expression linked to hyperpigmentation, while the application of HEX restored SDF‐1 expression and reduced skin pigmentation. On same model, HEX reduced oxidized proteins quantity and lipofuscin which increased after UV exposure. Clinically, HEX reduced dark spot pigmentation on Caucasian volunteers' hands and on Asian and African volunteers' face after 28 days. Discussion We have developed ex vivo models mimetic of senile and solar lentigo and showed for a very first time that SDF‐1 can be also a key regulator for UV‐induced hyperpigmentation. Conclusion Our ex vivo and clinical studies highlighted the power of HEX with strong reduction of dark spots regardless of volunteers' ethnicities.

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