JOURNAL OF COSMETIC SCIENCE 38 developed under LabView™ language (National Instruments, Austin, TX) allows it to control the whole system. Reconstructed skin (Mimeskin™ BASF Beauty Care Solutions, Lyon, France) was pro- duced from human-cell-cultured keratinocytes and fi broblasts isolated from human skin (30- and 18-year-old women’s breast cells, respectively). Briefl y dermal reconstruction was performed during 28 days with a daily medium change and epidermal reconstruction was performed including a 3 days immersion step and a 14 days air–liquid interface step. Khaya senegalensis bark extract at 0.05% was introduced at each cell medium replacement during the reconstructed skin growth. For each skin sample, residual depth, corresponding to the residual deformation at the end of measuring cycle, was calculated (Figure 4). The smaller the value of residual depth is, the more elastic the skin is. Khaya senegalensis bark extract at 0.05% signifi cantly de- creased the residual depth parameter, demonstrating an improvement of the skin elastic- ity (Figure 5). CLINICAL EVALUATION OF K. SENEGALENSIS BARK EXTRACT The study was a double-blind, placebo-controlled, and randomized study with 25 female volunteers (Fitzpatrick skin type I, II, or III ages 53–65) with self-perceived loss of skin elasticity, crow’s feet wrinkle grade between 3 and 4, and visible pores as graded by a clinical scientist. Figure 4. Non-contact device used for mechanical evaluation and skin deformation curve obtained. Figure 5. Residual depth parameter from reconstructed skins. Signifi cant decrease of the residual depth observed for the skins treated with K. senegalensis bark extract 0.05%. Data are presented as mean values and standard error of the mean from 13 measures. Statistical signifi cance was assessed running Mann–Whitney test, *p 0.05.

COLLAGEN XVIII: A KEY INTERFACIAL COMPONENT 39 Each of the placebo and K. senegalensis bark extract (1%) products was applied to a half- face in a randomized manner and twice a day for 56 days. The effi cacy of K. senegalensis bark extract was evaluated for certain skin parameters associ- ated with aging, e.g., skin elasticity on temple with cutometer, cheek curvature (surface heterogeneity), and skin wrinkles (data not shown) using fringe projection analysis (AEVA technique). Cutometer results: Skin elasticity. Measurements were taken using the Cutometer® SEM 575 (Courage & Khazaka) and immediate elasticity (R7) was calculated as explained in Figure 6. The closer the value of R7 is to 1 (100%), the more elastic the skin is. After only 28 days of treatment, a 9.6% improvement of the immediate elasticity (R7) over placebo was observed (Figure 7). This improvement was confi rmed after 56 days of treatment (11.6% improvement). By stimulating collagen XVIII synthesis in all skin layers, K. senegalensis bark extract dramatically improved skin elasticity. Fringe projection results: Skin cheek curvature. Curvature is a new parameter to identify any feature that has a defi ned curvature without taking into consideration of the depth. This parameter could be related to the visibility of the skin feature. The more detected density of the curvature suggested more visibility of the skin feature. An increase of this param- eter is linked to an increase of skin surface heterogeneity (pores and microrelief). Curva- ture density was detected and analyzed by the Optocat software after image acquisition with the AEVA 3D-HE 3D Imaging System. After 28 and 56 days of treatment by K. senegalensis bark extract, cheek curvature (surface heterogeneity) showed improvement by 22.8% and 38.2%, respectively, compared to the placebo (Figure 8). By stimulating collagen XVIII, K. senegalensis bark extract induced a visible pore reshaping effect (pictures not shown), leading to a signifi cant improvement in skin surface heterogeneity (curvature). CONCLUSION Our results show a decrease of the total amount of collagen XVIII during skin chrono- and photoaging. We demonstrated that collagen XVIII is a relevant structural target for Figure 6. Stress–strain curve of cutometer. R7 (immediate elasticity) is referred as the biological (net) elas- ticity. It is the portion of elasticity compared to the fi nal distension. It is represented by the ratio of “the immediate retraction” to “fi nal distension,” i.e., Ur/Uf.