Alternative methods for the study of infrared radiation effects on human skin
Author: Samara Eberlin
Published at: November 02, 2016
29th IFSCC Congress (International Federation of Societies of Cosmetic Chemists), Orlando, 30 outubro a 02 novembro, 2016.
Pinheiro ALTA, Facchini G, Clerici SP, Eberlin S, Pinheiro AS, Eberlin S.
For a long time, it was believed that skin photoaging was exclusively attributed to ultraviolet radiation, but lately infrared radiation A (IRA) has attracted interest from the scientific community for inducing similar skin structural changes to those observed by prolonged exposure to ultraviolet radiation. With the advent of the 3Rs policy (Replace, Reduce and Refine), the applied research to the cosmetic market on the understanding of this photoaging provided by IRA was restricted to in vitro and clinical testing. The evaluation of the biological mechanisms using skin biopsies obtained from human volunteers as a test system is a model for understanding the damage triggered by an aggressing agent. However, this procedure can be considered invasive as an ordinary research tool. In this sense, an alternative to fill this gap between in vitro and clinical is the use of skin fragments from elective plastic surgery (ex vivo study).
The objective of this study was to correlate the effects of IRA radiation in biopsies, ex vivo skin fragments, and human fibroblasts cultured, through the quantification of MMP-1, TIMP-1, and GADD45a mediators. Biopsies of human skin, as well as the human skin fragments originating from elective plastic surgery, were obtained after approval of the ethics committee and voluntary consent. Together with cultured human fibroblasts (HFF-1), these test systems were incubated for 48 hours at 37°C in a humidified atmosphere with 5% CO2. Afterward, they were exposed to a dose of 360 J/cm2 infrared-A radiation using Hydrosun 750 and HBM1 devices (Hydrosun Medizintechnik GmbH, Müllheim, Germany). After irradiation, test systems were incubated with fresh culture medium and maintained for 24 hours to collect the culture supernatant and quantification of MMP-1, TIMP-1, and GADD45a by enzyme-linked immunosorbent assay.
The results demonstrated that in the three models used, IRA radiation induced an increase in MMP-1 and did not alter the values of this protease inhibitor (TIMP-1). A similar effect can be observed with the GADD45a protein, as radiation was able to inhibit the synthesis of this cellular stress sensor in the biopsies, ex vivo fragments, and in cell culture. Therefore, due to the positive correlation of results between the three models studied, it may be suggested that an alternative approach to human biopsies is the use of an ex vivo model, as it is characterized as a plausible and sustainable tool to address the differences between the knowledge generated from in vitro and clinical experiments.