# Exploring UVA1-Induced Metabolic Effects in Different In Vitro, Ex Vivo, and In Vivo Systems

## TL;DR

The study investigates how UVA1 light affects skin metabolism across different experimental models, finding some consistent changes across systems.

## Contribution

The study highlights the importance of using a metabolite-specific approach to select appropriate models for UV-induced metabolic studies.

## Key findings

- Glutamic acid, succinic acid, and threonine show similar metabolic changes across in vitro, ex vivo, and in vivo systems after UVA1 exposure.
- Phenylalanine, citric acid, and pyruvic acid show consistent patterns in in vitro and ex vivo models but not in vivo.
- Metabolic responses to UVA1 vary significantly between experimental systems, emphasizing the need for careful model selection.

## Abstract

Background/Objectives: Studying the role of UV-induced metabolic changes in skin physiology, and especially skin diseases, has gained importance in both medicine and cosmetics. With the development of new technologies, a variety of approaches have been implemented to model these metabolic effects. In this study, we explore the reproducibility of the UVA1-induced metabolic changes observed in different in vitro, ex vivo, and in vivo systems with escalating complexity. Our aim is to elaborate on the role of experimental setups in the reliable representation of in vivo data in other systems. Methods: Metabolic profiles post UVA1 treatment were assessed in skin cell culture, skin explants, and intact skin. For cell culture and explants, the metabolites from the culture medium were assessed via 1D-CPMG NMR. Intact skin samples were collected via microdialysis and the resulting dialysate was measured with GC–TOF-MS. Results: Data show that, despite great metabolic variations between the systems, several metabolites, such as glutamic acid, succinic acid, and threonine, change in a similar manner across multiple systems after UVA1 irradiation, including in vivo settings. Some metabolites, like phenylalanine, citric acid, and pyruvic acid, show similar UVA-mediated metabolic patterns between corresponding in vitro and ex vivo systems, but do not overlap well with in vivo data. Conclusions: Our findings emphasize the need for a metabolite-by-metabolite approach when deciding on the proper experimental system to perform UV irradiation experiments with regard to cutaneous physiology.