Some recent reports have suggested the presence of interactions between skin resident cells, keratinocytes, fibroblasts and melanocytes, in UV-induced skin pigmentation. In this study, we demonstrated the possibility of interactions between keratinocytes and fibroblasts through the IL-1α/KGF/FGF7 axis on the transfer of mature melanosomes into keratinocytes. Furthermore, the presence of interactions between UVA-irradiated fibroblasts and keratinocytes or melanocytes was confirmed regarding the transfer of melanosomes to keratinocytes and the synthesis of tyrosinase in melanocytes. The results of this study indicate the possibility that UV-induced skin pigmentation is achieved by the integrated actions of skin resident cells which are keratinocytes, melanocytes and fibroblasts. In order to propose clues towards regulating that process, we evaluated the potential of a fruit extract of Cerasus sargentii (CS), which is harvested from the Necklace Road located around Mount Iwaki in the Aomori Prefecture. The results show that the CS extract has an excellent potential to prevent UV-induced skin pigmentation by interfering with the interactions between skin resident cells. Thus, this study proposes that CS is a promising new candidate to prevent/improve UV-induced skin pigmentation by interfering with interactions between skin resident cells.

Studies on the changes in facial appearance with age, such as wrinkle formation and skin sagging, have revealed chronological alterations in the physical properties of the deep skin. However, the association of the skin surface with the changes in facial appearance has not been clarified yet, even though the external appearance is related to the surface elements. In this study, we investigated the phenomena occurring on the skin surface in association with the morphological changes on the face by observing the surface area, degree of skin folding, stratum corneum (SC) cell size, and skin motion in half of the face. Our results revealed that the enlargement of the facial surface area with aging and concomitant wrinkle formation are accompanied by changes in the size of SC cells. Additionally, the degree of skin movement during facial expressions exhibited a significant correlation with SC cell size distribution in the older individuals. These observations suggest that the skin surface undergoes morphological modifications by changing the size and distribution of SC cells in relation to the specific motion of each area. Repetitive stretch of the eye corner skin reduced the difference in SC cell size and improved wrinkles. Therefore, skin movement contributes to both the development and improvement of changes in SC cell size distribution. In conclusion, SC cell size and its macroscopic distribution can be considered as a novel and important target for morphological anti-aging, and these findings will help to enhance the application of cosmetics.

In this study, the authors investigated hair colouring by utilising chemical oxidation of biocatechols, which are obtained from organisms and have catechol (o-dihydroxybenzenes) groups such as (+)-catechin (Cat), (-)-epicatechin (EC), _L-3,4-dihydroxyphenylalanine (DOPA), hematoxyline (HX), braziline (BZ), rosmarinic acid (RA), caffeic acid (CA) and chlorogenic acid (ChA). The three types of dyeing methods for the chemically decolourised white human hair were tried as follows: the dyeing by using the solution of the oxidised bio-catechols at 30 °C and pH = 7 (redissolution dyeing), the dyeing by using the oxidation solution of bio-catechol reacting at 30 °C and pH = 10.8 with the introduction of O₂ gas continuously (simultaneous oxidation dyeing) and the oxidation by O₂ at 30 °C and pH = 11.6 after the treatment of hair with the bio-catechol solution at 30 °C (post-oxidation dyeing). The order of the hair dyeability of the methods using Cat as the bio-catechol was found to be post-oxidation>redissolution>simultaneous oxidation dyeing. Moreover, the resulting colour of hair dyed with Cat by post-oxidation dyeing was reddish brown. The results demonstrate that EC, HX and BZ are also available for hair dyeing by using post-oxidation dyeing and the colours of the dyed hair are yellowish brown, deep brown and reddish brown, respectively. It was found that the bio-catechols having a chroman (3,4-dihydro-2H-1-benzopyran) structure with the catechol part work effectively as dye precursors for colouring hair by the post-oxidation dyeing technique.

Fatigue is one of the physiological phenomena felt by living organisms. It is a symptom that includes both physical and mental components. People feel fatigue in daily life, and the accumulation of fatigue can lead to the onset of diseases and accidents. For this reason, understanding fatigue is an important issue. Questionnaire-based monitoring is now being conducted in companies. However, due to the burden on the participants and the management, the monitoring is conducted only once or twice a year, which leads to a practicality problem. To increase the practicality, a simple and highly accurate monitoring technology is desired. Since the relationship between fatigue and skin condition has been reported in many past studies, we thought there was the possibility of constructing a fatigue prediction technique using skin information. In this study, we apply deep learning technology to predict subjective fatigue assessments and physiological fatigue assessments by blood and urine from the morphological information of epidermal stratum corneum cells obtained by tape stripping. As a result, we can predict several fatigue states from stratum corneum images. This study shows the new possibility of using the skin analysis technology developed in cosmetics research for the realization of a healthy society.

It has been known that advanced glycation end-products (AGEs) produced via the Maillard reaction accumulate in elderly and photoaged skin. In addition, it has been reported that skin accumulating AGEs shows a decrease of skin elasticity and an impairment of barrier function, and results in the acceleration of the process of skin aging. Recently, since some reports have suggested that the accumulation of AGEs in the epidermis is involved in melanogenesis, it has been believed that suppressing AGE accumulation in keratinocytes is an effective approach to prevent the appearance of pigment spots. In this study, we firstly investigated impacts of AGE accumulation in keratinocytes on the appearance of pigment spots focusing on phagocytosis and decomposition of melanosomes (MSs). Secondly, we evaluated the suppressing effect of a derivative of ascorbic acid, 3-O-glyceryl-2-O-hexyl ascorbate (VC-HG), against pigmentation through the inhibition of AGE accumulation in keratinocytes. As a result, it was found that AGE accumulation in keratinocytes enhanced phagocytosis of MSs and reduced activities of cathepsins, which are involved in the decomposition of MSs phagocyted into keratinocytes. On the other hand, VC-HG suppressed the production of AGEs in keratinocytes initiated by glyoxal using carboxymethyl lysine (CML), and improved the situations of keratinocytes on enhancement of MS-phagocytosis and reduction of activities of cathepsins. Taken together, it was concluded that VC-HG has a potential to prevent pigmentation by suppressing the production of AGEs in keratinocytes.

The purpose of this study was to find a cosmetic ingredient that suppresses the growth of Staphylococcus aureus and promotes the growth of Staphylococcus epidermidis, and to confirm the effect of the cosmetic ingredient on human skin and the change in skin microbiome. By co- culturing S. aureus and S. epidermidis, we found Rice lees Extract including Molasses (REM) had the effect of inhibiting the growth of S. aureus. In the human in vivo study, the abundant ratio of S. aureus was significantly reduced in the REM group after 4 weeks, but not in the placebo group. Flaking degree, which was determined by using the ratio of the stratum corneum cells on the skin surface collected in tape stripping to the entire visual field, significantly increased in the REM group but did not change in the placebo group. The multilayer rate decreased in both groups, which was thought to be due to the lotion rather than REM. In a questionnaire conducted after the end of the study, 6 of 10 subjects in the REM group and 2 of 11 in the placebo group responded that their skin became smoother. REM was effective to improve skin smoothness and stratum corneum uniformity and decrease S. aureus abundance. Therefore, it can be useful for cosmetics that recover skin roughness or disorder.

Epidermal thinning refers to the thinning of the entire epidermis with age. It is thought that a decline in the epidermal stem cells leads to epidermal thinning with age, but the mechanism has not been elucidated yet. To elucidate the mechanism of epidermal thinning with age, we focused on epidermal stem cells and their environment. Epidermal stem cells are maintained near the basement membrane, and the oxygen concentration of their environment is lower than the normal oxygen concentration. It is known that a transcription factor called hypoxia inducible factor-1α (HIF-1α) is active in cells in a low oxygen environment. Comparison of the transcriptional activity of HIF-1α by culture of normal human epidermal keratinocytes (NHEKs) in normoxia and hypoxia confirmed that cells cultivated in hypoxia had high HIF-1α transcription activity. Moreover, it was also confirmed that the expression level of melanoma- associated chondroitin sulfate proteoglycan (MCSP), a stem cell marker, was high in hypoxia. Next, we performed a similar test with neonatal-derived and aged-derived epidermal cells, and we confirmed that the HIF-1α transcriptional activity and MCSP synthesis rate were reduced. Based on this, we inferred that HIF-1α transcriptional activity decreases with age and that epidermal stem cells tend to differentiate, the supply of epidermal cells decreases, and the epidermis thins with age. Furthermore, we found that red clover flower extract promotes HIF-1α transcriptional activity and the MCSP synthesis rate. We also analyzed the mechanism by which red clover flower extract promotes HIF-1α transcriptional activity, and we confirmed that the mechanism of HIF-1α was different from that of cobalt chloride, which has a transcriptional activation effect. Moreover, a cream containing red clover flower extract improved the epidermis thickness of the skin within 2 months and increased the stratum corneum water content.

Friction characteristics of foundations are important in designing formulations because they affect the application and finishing. In this study, the friction of 16 different foundations applied on artificial skin was evaluated using a sinusoidal motion friction evaluation system. The obtained friction parameters were subjected to principal component analysis. The obtained principal component Z included the static friction coefficient μ_s, the dynamic friction coefficientt μ_k and the delay time δ. All these factors were involved in the characterization of the friction dynamics of the foundations. Furthermore, cluster analysis was performed on Z and these foundations can be classified into three groups in terms of friction dynamics. These results are useful for understanding the phenomena during the application of foundations.