Investigation of Liver Steatogenic Effects of Cosmetic Compounds Using a Human Skin Stem Cell-Derived Hepatic Cell Model

Details

Supervisors

Tamara VANHAECKE

Faculty

Faculté de pharmacie et des sciences biomédicales

Degree label

Master [120] en sciences biomédicales, à finalité spécialisée: toxicologie

Abstract

The increasing number and variety of synthetic chemicals, including those used in cosmetics products, has led to their immense exposure to humans. A risk assessment process needs to be performed by the responsible bodies to ensure human safety. Traditionally, these safety assessments are done on animals, and this is still the case for most types of compounds, except cosmetics. Indeed, in 2013, the European Commission declared an animal testing ban for cosmetic products and their ingredients. Consequently, developing alternatives to in vivo animal testing methods based on mechanistic approaches and integrating in vitro, in silico and in chemico assays has become an important field of research, especially addressing complex endpoints, e.g., systemic organ toxicity. These alternative methods to animal testing are called new approach methodologies (NAMs). Previous research from the host lab based on publicly available in vivo laboratory animal data has shown that the liver is a frequent target organ after repeated exposure to certain cosmetic ingredients leading to liver toxicity. The in vivo indications of liver toxicity point to a specific type of hepatotoxicity known as steatosis or fatty liver, characterized by fat accumulation in hepatocytes. Investigating toxicant-associated fatty liver disease (TAFLD) upon repeated exposure to cosmetic ingredients is tackled by this study. We aim to detect in vitro potential steatogenic compounds using an innovative human-based stem cell model. Hereto, adult human skin stem cells are isolated and differentiated in vitro towards hepatocyte-like cells using a protocol mimicking the in vivo liver embryogenesis. Subsequently, the cells are exposed to different non-cytotoxic concentrations of the selected cosmetic ingredients. At various time points, samples are taken, and the effects of the compounds on the lipid metabolism signaling pathway are assessed through fluorostaining, RT-qPCR, and flow cytometric analyses. The investigation of Na-VPA (Sodium Valproate) as a steatosis-inducing compound on hSKP-HPC (Human skin-derived precursors-hepatic progenitor cells) confirmed that this cell model is fit for the study. Our test compound, Triclosan, revealed to be implicated in lipid accumulation at both 24- and 72- hours exposure at respectively 1µg/ml, 2µg/ml, and 5µg/ml for 24 hours and at 3µg/ml for 72 hours. Basic Red 51, another test compound showed no lipid accumulation at the two exposure regimens. The data from RT-qPCR demonstrated how the genes counteract with each other resulting in no lipid accumulation. No conclusions could be made for Hydroxypropyl p-phenylenediamine and its dihydrochloride salt since more assays needs to be done.