Catherine Kern, Cécile Bize, Gaëlle Vincent, Elsa Hernandez, Sandrine Vinat, Rémi Laville
2019, 25th IFSCC conference
Skin aging is a complex and multifactorial process wherein senescent cells accumulate in skin. One of the most specific markers of senescence is the senescence-associated β-galactosidase (SA-β-gal). Furthermore, senescent cells produce and secrete various bioactive molecules named SASP (Senescence-Associated Secretory Phenotype) or SMS (Senescence Messaging Secretome), of which one of the most prominent is interleukin-6 (IL-6). SMS from senescent cells trigger premature senescence in surrounding cells. This senescence-induced bystander effect or contagious aging contributes to the increasing frequency of senescent cells with age and to the impact senescent cells have upon their environment. Inspired by the chemical communication mechanism of Sea Hares, an Asparagopsis armata extract (AArE) was eco-designed to maximize its content in Mycosporine-like Amino Acids (MAA), a key component of Sea Hare intraspecific alarm cue. For this purpose, a mixture of 1,3-propanediol (PDO) and water 40:60 was chosen to enhance the content of MAA and the auto-preservation capacity of the extract.
Our aim was to investigate the effect of AArE and a concentrated fraction of MAA (MAAf) on senescence-induced bystander effect in vitro and thus if AArE could contribute to healthy aging in vivo. An innovative in vitro model was developed to mimic contagious aging by collecting SMS-enriched conditioned medium (CM) from senescent primary human fibroblasts obtained from repeated cell divisions and using it to stress young fibroblasts. Contagious aging and SMS effect were studied by quantifying IL-6 secretion as representative of SMS and SA-β-gal as marker of senescence in CM-stressed young fibroblasts. CM induced a significant increase in IL-6 secretion and SA-β-gal activity by 362% and 218% respectively in young fibroblasts. AArE 0.1% and MAAf 50 µg/mL (equivalent concentration as found in AArE 0.1%) reduced IL-6 secretion by 28% and 29% respectively in CM-exposed fibroblasts. They also reduced the increase of SA-β-gal activity by 67% and 54% respectively. PDO showed no protective effect in this model. Thus, AArE was able to protect young fibroblasts from senescence-induced bystander effect and MAAf largely participated in this effect, making it a biomarker of AArE.
The efficacy of AArE was confirmed in vivo, by evaluating a cosmetic composition containing 2% AArE in 32 Caucasian women presenting first ageing signs (wrinkles on the crow’s foot, on forehead and on underneath eye). Volunteers applied the product on the full face twice a day for 28 days. At D0 and D28, photographies of the front face and each 3⁄4 profile were taken in standard light and D0/D28 paired photographs were scored by the panel on which picture the person looked younger, on which picture the person was less wrinkled and which picture reflected the “after treatment”. Pictures at D28 were promoted by +8% versus D0 on the first question, as well as by +13% on the second one and by +9.4% on the third one. For 85% of the scoring people, criterion “wrinkles and fine lines” was critical. Images of the under eye wrinkles were also acquired at D0 and D28 for instrumental measurement of the eye wrinkles surface, length and volume. A significant decrease of the under eye wrinkles surface by 12.7% was observed, together with a significant decrease of the under eye wrinkles length by 11.5% and a limit significant decrease of the under eye wrinkles volume by 13.6%. Finally, after 4 weeks of AArE formulation application, 77% of the volunteers declared that their feature looked rested, less tired, 68% that their complexion looked more even and 61% that their complexion looked more luminous. This study showed that AArE improved perception on skin which looked younger and less wrinkled, and these results were confirmed by an instrumental evaluation of the under eye wrinkles. Thus, AArE can be proposed as a healthy aging active ingredient, allowing the protection of the skin from contagious aging.
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