Jae Sook Koh

Skin aging is characterized by decreased collagen synthesis and increased extracellular matrix degradation, leading to wrinkle formation and reduced skin elasticity. This study evaluated the anti-aging potential of hydrolyzed fish skin (HFS) extract through complementary in vitro and clinical investigations. In human dermal fibroblasts, treatment with HFS extract enhanced type I procollagen production and suppressed UVB-induced matrix-degrading enzymes, including matrix metalloproteinase-1 (MMP-1) and elastase, suggesting a mechanism that supports dermal matrix homeostasis. A randomized, double-blind, split-face clinical trial was conducted in 20 female participants over 12 weeks. A formulation containing 0.5% HFS extract was applied to one side of the face, while an identical vehicle control formulation without HFS extract was applied to the contralateral side. Wrinkle parameters were assessed using a three-dimensional imaging system. After 12 weeks, the test group showed significant improvements compared to baseline, with reductions of 12.75% in arithmetic mean roughness (Ra), 12.46% in root mean square roughness (Rq), and 11.32% in maximum wrinkle height (Rmax) (p < 0.05). No adverse events were observed. These findings demonstrate that HFS extract improves wrinkle-related skin parameters, potentially through promoting collagen synthesis while inhibiting matrix degradation. The combined molecular and clinical evidence supports its application as a functional cosmetic ingredient in anti-aging formulations.

Background/Objectives: Ultraviolet radiation (UVR) induces oxidative stress in the skin by generating reactive oxygen species (ROS), which can lead to inflammatory conditions including erythema (a sign of sunburn). This clinical study aims to develop an instrumental evaluation method to determine the minimal erythema dose (MED) for UVR. Methods: Fourteen human subjects aged 27 to 57 years (48.93 ± 8.54) participated in this study. Six subsites were designated on the test skin site of each subject and irradiated with UVR at different doses. The examiner visually assessed erythema, determining the ‘visual MED’. Additionally, the a* value (a chrominance parameter presenting greenness to redness) was measured using a spectrophotometer as an indicator of erythema. The a* values of the UVR-irradiated subsites were compared to the non-irradiated control value, and the differences were referred to as Δa*. The Δa* value of the subsites irradiated with UVR at the ‘visual MED’ was referred to as the Δa*_VMED for each subject. The mean of the Δa*_VMED values of all subjects was chosen as a criterion value for the ‘instrumental MED’. The ‘instrumental MED’ was defined as the lowest dose of UVR that causes an Δa* value equivalent to the criterion value. The ‘visual MED’ and ‘instrumental MED’ values of all subjects were subjected to correlation analysis. Results: The mean of the Δa*_VMED values of all subjects was 1.88 ± 0.8. The means of the ‘visual MED’ and ‘instrumental MED’ values (in J m⁻² unit) of all subjects were 300.14 ± 84.16 and 303.29 ± 77.99, respectively. In Pearson correlation analysis, the ‘instrumental MED’ and ‘visual MED’ values had a very strong positive correlation with each other (r = 0.864, p = 0.000). Conclusions: This study suggests that the instrumental evaluation method of MED based on the spectrophotometric measurement of the a* values can complement or replace the visual evaluation method and that this method will be useful in monitoring skin tolerance to oxidative stress affected by prooxidant factors and defensive factors.

The skin aging process is governed by intrinsic and extrinsic factors causing skin wrinkles, sagging, and loosening. The 1-monoeicosapentaenoin (1-MEST) is a component isolated from Micractinium, a genus of microalgae (Chlorophyta, Trebouxiophyceae). However, the anti-wrinkle effects of 1-MEST are not yet known. This study aimed to evaluate the anti-wrinkle effects of 1-MEST in vitro and in clinical trials. The cytotoxicity of 1-MEST was investigated in vitro using the MTS assay in human epidermal keratinocytes (HEKs). Expression of matrix metalloproteinase (MMP)-1 and MMP-9 was determined by ELISA in HEKs irradiated with UVB after treatment with 1-MEST. A split-face randomized, double-blind, placebo-controlled study was conducted to evaluate the safety and efficacy of 1-MEST. The study evaluated wrinkle parameters and visual assessment, self-efficacy and usability questionnaires, and adverse events. The study showed that the 1-MEST was not cytotoxic in HEKs, suppressed MMP-1 secretion and MMP-9 protein expression in HEKs irradiated with UVB. The wrinkle parameters and mean visual assessment score were significantly decreased in the test group after 12 weeks and differed from the control group. There were no significant differences in efficacy and usability. Adverse effects were also not observed. The 1-MEST showed anti-wrinkle properties to slow down or prevent skin aging.

Background: Skin aging, particularly facial skin, has been actively studied. However, hand skin research is limited.Methods: Aging symptoms of 100 hands of Korean women aged from 20s to 60s were measured by noninvasive and bioengineering methods. Standard grade images were produced.Results: As people got older, skin wrinkles were getting worse and skin tone was uneven with the occurrence of structural flexion. For each symptom, a suitable standard photograph of the skin of the hand was chosen and a new grading scale was made.Conclusions: The new grading scale developed in the present study could be employed in studies to explore aging of hand skin as one of objective indicators.

Objective: In vivo changes in skin barrier function after chemical peeling with alpha hydroxyacids (AHAs) have been previously reported. However, the additional effects of physical treatment with chemical agents on skin barrier function have not been adequately studied. This study measured the degree of acute skin damage and the time required for skin barrier repair using non‐invasive bioengineering methods in vivo with human skin to investigate the additional effect of a 4% AHA chemical jet accelerated at supersonic velocities.Methods: Thirteen female subjects (average age: 29.54 ± 4.86 years) participated in this study. The faces of the subjects were divided into half according to the block randomization design and were then assigned to receive AHA peeling alone or AHA peeling combined with pneumatic pressure on each side of the face. Transepidermal water loss (TEWL), skin colour and skin blood flow were evaluated at baseline and at 30 min, 2, 5 and 7 days after treatment.Results: The TEWL and skin blood flow were significantly increased after 30 min in chemodermabrasion compared with chemical peeling alone (P < 0.05). The TEWL and skin blood flow recovered to baseline after 2 days, and TEWL was significantly decreased at 7 days compared with chemical peeling alone (P < 0.05).Conclusions: Chemodermabrasion can temporarily impair skin barriers, but it is estimated that it can enhance the skin barrier function after 7 days compared to the use of a chemical agent alone. In addition, chemodermabrasion has a more effective impact in the dermis and relatively preserves the skin barrier.

Background: To assess the hair surface condition, scanning electron microscope (SEM) is commonly used and it remains an indispensable hair morphology characterization technique. Yet, the technique is criticized for having subjective viewpoints and limitations in distinguishing the appearance of cuticle layers.Objectives: The aim of this study is to establish an objective classification system and also to subdivide by detailed description of damaged cuticle layers.Methods: Hair samples were collected from female subjects (n = 500) who participated in hair efficacy study and Asian hair bunches (n = 180) that were previously collected. Damage to hair was initiated by chemical, heat stress and ultraviolet irradiation. We suggested the grading criterion on a 12‐point scale and compared with a wide range grading system on a 5‐point scale. We evaluated other hair surface‐related parameters such as hair luster‐ring and combing load to verify the validity and efficacy of our new grading system.Results: The grading criterion on our 12‐point scale revealed an improved discrimination compared to the wide range grading system. Hair surface‐related parameters were significantly improved after hair care product, and these tendencies were likely to be determined to be similarly improved using the 12‐point scale grading system.Conclusion: The 12‐point scale classification system was demonstrated to be a more precise standardization and appropriate evaluation method to investigate the subtle distinction of the hair shaft after hair care product application.

Background/Purpose: Facial cleansing is important to clean and exfoliate the skin while maintaining optimal physiologic function. However, there is insufficient data on the very early stage of skin change after applying soap or cleansing foam. We investigated the recovery kinetics of facial skin physiology during 180 min after exposure to the cleanser.Methods: For the study, 22 Korean female subjects with normal and dry to oily skin type were recruited in this study. Study subjects were required to have face washing done within the 12 hours prior to visiting the research center, with only toner, lotion, or cream applied. The next day, the subjects visited the research center without face washing. We evaluated the skin hydration (Corneometer^® CM 825), sebum (Sebumeter^® SM 815), transepidermal water loss (Tewameter^® TM 300), and pH (Skin‐pH‐Meter^® PH 905) to define recovery kinetics of facial skin physiology during 180 min exposure post‐cleansing.Results: Skin hydration, sebum, and TEWL were significantly decreased at 20 min after washing, as compared to the baseline (P < 0.05). And skin hydration returned at 40 min, and skin sebum and TEWL returned at 120 min after washing. However, skin pH did not show significant differences at all times points.Conclusions: This study indicated that each of the skin parameters was restored at defined time points post‐cleansing. Our result could be a useful reference to set the resting time in the estimation of skin bioengineering parameters.

Background/Purpose: Many ingredients used in cosmetics evoke a comedogenic response. Rabbit ear model (REM) is a useful method that can replace human in examining materials and products in early developmental stage. However, a number of studies pointed out its disadvantage that it overreacts to comedogenic materials. The purpose of this study was to find the most appropriate region for evaluating comedogenicity in human skin.Methods: Sixty‐six female subjects (age 32.48 ± 10 years; range 20–52 years) with mild to moderate facial acne lesions were included in this study. The whole face, upper chest, and back of volunteers were photographed. Lesion (closed and open comedones) counting, instrumentation of sebum secretion level, and analysis of porphyrin number were performed. The entire study was performed under environmental conditions of specific relative temperature and humidity, controlled and maintained identically for each volunteer.Results: In case of closed comedone, forehead showed a significant correlation with frontal cheek, lateral cheek, chin, and upper back. Meanwhile, significant correlations were observed between frontal cheek and chin as well as lateral cheek and chest. As for open comedone, forehead showed a significant correlation with chin site. A significant correlation was also observed between front cheek and lateral cheek as well as between upper chest and back. Analyzing the correlation between the occurrence of comedones and sebum in each region, a significant correlation between closed comedone and sebum was observed in frontal and lateral cheek. Analyzing the correlation between the occurrence of comedones and porphyrine in each region, a significant correlation between open comedone and porphyrin was observed in chin.Conclusion: When evaluating the comedogenicity of cosmetics ingredients or products, this study recommends using both of the methods of testing on back and directly testing on face according to the characteristics of the materials. In case of mild potent ingredients or products in particular, verification through usability test that the directly test on face will help securing reliability.

Objective: Alpha hydroxy acids (AHA) have been recognized as commonly used therapy for acne. Our studies examined whether an additional effect of physical treatment using chemical peeling combined with negative pressure and compared with AHA treatment only occurs in acne‐prone subjects.Methods: The chemical peeling agent used 4% of an AHA solution (mixture of 1000 mL of carbonated water, 20 mL of glycolic acid and 20 mL of lactic acid). All subjects’ faces were randomly divided into test and control groups. The test group was treated with chemical peeling combined with a physical effect, and the control group applied chemical peeling alone. For the 23 healthy females (average age: 30.17 ± 5.06 year), we measured sebum output level by light transmission, pore area and number by optical image analyser, and comedone counting before treatment and at 1, 2 and 4 weeks after a single treatment.Results: Compared to the before treatment, whiteheads and blackheads were significantly decreased at 1, 2 and 4 weeks in the test group (P < 0.05), but for the control group, whiteheads and blackheads showed a tendency to decrease at 1, 2 and 4 weeks. Also at 1 week, whiteheads and blackheads of the test group significantly decreased compared to the control group (P < 0.05). Pore area and number significantly decreased at 1 week (P < 0.05), and the sebum output level was significantly decreased at 4 weeks (P < 0.05) only in the test group, which did not show any significant group difference for individual parameters.Conclusion: 4% AHA solution combined with a physical effect had rapidly improving effects on whiteheads and blackheads synergistically. Combined physical therapy may have more impact on pore size and seborrhoea.

Background/purpose: Skin aging has been focused the wrinkle on the face than on the body, so most studies have been studied the change in Crow's feet for ages. Only little is known about the age‐dependent changes of wrinkles on body sites. The aim of this study was to establish new grading criteria for severity of wrinkles on knees and to investigate the relationship of wrinkle severity with age‐ and site‐dependent.Methods: The skin on the knee of 38 healthy Korean female volunteers, divided into two groups young and old, were photographed. Standard photograph for body wrinkle was established (grade 0~7), and then visual assessment, skin wrinkle, and skin elasticity were evaluated on Crow's feet and the knee. We examined for any significant differences and the correlation of skin aging parameters with age and two different sites.Results: Skin wrinkle severity with standard photograph and wrinkle parameters (Ra, Rmax, Rz, and Rv) had a significantly positive correlation with age‐dependent on the knee (P < 0.001). Also, skin elastic parameters (R2, R5, R6, R7, and Q1) showed a significant negative correlation with age on the knee (P < 0.001). Skin wrinkle severity with standard photograph was highly correlated with all skin wrinkle parameters and skin elastic parameters (R2, R5, R7, and Q1) on the knee (P < 0.001). In addition, all the skin aging parameters on the knee were significantly correlated with Crow's feet (P < 0.01). Skin aging on the knee had the same tendency as the Crow's feet.Conclusions: This study has shown the new grading criteria of wrinkles on the knee. Skin wrinkle and elasticity on the knee are age‐dependent related and aging on the knee is highly related to Crow's feet. Those parameters are using a quantitative method to evaluate body aging. Also, the knee is considered that it could be a suitable site to evaluate body aging.