An IMAGING-based method to evaluate anti-acne efficacy AT EARLY STAGE

LI Shuting*, ZHOU Zhijun (Amanda) *, LIU Xin (Sean) *, WANG Hequn (Tracy) *, FLAMENT Frédéric**, STEEL Andrew*
* Research and Innovation Department, L’Oréal China，550 Jinyu Road, Pudong, Shanghai, China;
**Research and Innovation Department, L’Oréal,188-200 Rue Paul Hochart, 94550 CHEVILLY-LARUE, France
Key words: acne prone, hyper-keratinization, hair follicle, reflectance confocal microscopy (RCM)

Background
Acne is a common skin condition with a high prevalence, worldwide. Current method to clinically evaluate treatment efficacy for individuals with acne prone skin relies on observing the evolution of the clinical inflammatory and non-inflammatory lesions. However, before the acne lesions emerge, there is no way to define and characterize acne proneness through visualization. Hyper-keratinization of follicle is one of the main pathogenic factors of acne development, which happens underneath skin surface and even at the early stage before clinical lesions form. Reflectance confocal microscopy (RCM) with its nature of having high image contrast from keratin structure, opens a new window onto the in-vivo characterization of follicle and pore health at microstructure level and provide new possibility to provide management plans for acne prone skin at early stage.

Objectives
We aim to explore the structural differences between normal skin and acne prone skin with macroscopically normal appearance, so that to characterize the features of acne prone skin and to build new method to evaluate anti-acne efficacy.

Method
10 volunteers with acne-prone skin and 5 volunteers with less acne-prone skin were recruited and completed this clinical trial. RCM was applied to explore and analyze the features of microstructure of hair follicles on normal-looking skin on lower cheek area of both acne prone skin and less acne prone skin. Volunteers with acne prone skin were asked to use a serum product with peeling ingredients (glycolic acid, salicylic acid, capryloyl salicylic acid) for 4 weeks. Product efficacy on microstructure (hyper-keratinization, shape, and diameter of hair follicle duct etc.) of hair follicle was evaluated after 4-week of application. Correlation among RCM measurement, clinical evaluation, and self-claimed acne history were also analyzed.

Results
This study showed that the size of the follicles in acne-prone skin range (80 to 230 um) is larger than less acne prone (50um to120 um) skin follicle’s size at epidermis level. Acne prone skin also found a higher rate of hyper-keratinized hair follicle (51.39% vs.26.24%), higher rate of thick keratinized border (25.48% vs.11.20%) more irregular shaped hair follicle (25.27% vs.16.00%), and more hair follicles with inner keratin contents (14.09% vs. 6.70%) than less acne prone skin. RCM measurement results also showed a high correlation with clinical signs of inflammatory acnes, PIE (Post-inflammation erythema), PIH (Post-inflammation hyperpigmentation) and self-claimed historical acne frequency. It was also found that after 4-week treatment, the ratio of hyper-keratinized hair follicles reduced 12.25% (p<0.05) and the ratio of thick keratin border decreases 10.51% (p<0.05).

Conclusions
We found by observing micro-structure of hair follicle based on RCM is an efficient and potential new method to characterize acne proneness. It also opens a new direction of clinical assessment focusing on anti-acne and acne-prevention efficacy.