Cytotoxicity and inhibitory effects of low-concentration triclosan on adipogenic differentiation of human mesenchymal stem cells ☆ Li-Wu Guo a, 1 , Qiangen Wu b, 1 , Bridgett Green a , Greg Nolen a , Leming Shi c , Jessica LoSurdo d , Helen Deng e , Steven Bauer d , Jia-Long Fang b, ⁎, Baitang Ning a, ⁎⁎ a Division of Personalized Nutrition and Medicine, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA b Division of Biochemical Toxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA c Division of Systems Biology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA d Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA e Arkansas Department of Health, Little Rock, AR 72205, USA abstract article info Article history: Received 14 February 2012 Revised 18 April 2012 Accepted 19 April 2012 Available online 1 May 2012 Keywords: Adipocyte differentiation Human mesenchymal stem cell Triclosan Cytotoxicity Humans at all ages are continually exposed to triclosan (TCS), a widely used antimicrobial agent that can be found in many daily hygiene products, such as toothpastes and shampoos; however, the toxicological and biological effects of TCS in the human body after long-term and low-concentration exposure are far from being well understood. In the current study, we investigated the effects of TCS on the differentiation of human mesenchymal stem cells (hMSCs) by measuring the cytotoxicity, morphological changes, lipid accu- mulation, and the expression of adipocyte differentiation biomarkers during 21-day adipogenesis. Significant cytotoxicity was observed in un-induced hMSCs treated with high-concentration TCS (≥5.0 μM TCS), but not with low-concentration treatments (≤2.5 μM TCS). TCS inhibited adipocyte differentiation of hMSCs in a concentration-dependent manner in the 0.156 to 2.5 μM range as indicated by morphological changes with Oil Red O staining, which is an index of lipid accumulation. The inhibitory effect was confirmed by a decrease in gene expression of specific adipocyte differentiation biomarkers including adipocyte protein 2, lipoprotein lipase, and adiponectin. Our study demonstrates that TCS inhibits adipocyte differentiation of hMSCs under concentrations that are not cytotoxic and in the range observed in human blood. Published by Elsevier Inc. Introduction Triclosan (TCS) has been used for more than 40 years in the United States as an antimicrobial agent in personal care products, household items, medical devices, and clinical settings (Jones et al., 2000). The general population is exposed to TCS through dermal contact with daily hygiene products and the consumption of food and drinking water containing TCS. In addition, workers may be exposed to TCS in the manufacturing environment by dermal contact and inhalation (Fang et al., 2010). Allmyr et al. (2006) tested human plasma, breast milk, and urine collected from mothers using TCS-containing and TCS-free personal care products. This study showed that TCS-containing products were the dominant, but not exclusive, source of systemic exposure to TCS. It was reported that TCS was found in three out of five human breast milk samples randomly collected in the Stockholm area in Sweden, although this study only had a small sample size (n=5) (Adolfsson-Erici et al., 2002). In the United States, TCS was detected in human milk (100 to 2100 μg/kg lipid) in 51 out of 62 sam- ples from the Breast Milk Banks in California and Texas (Dayan, 2007). TCS was also detected in human blood plasma samples from Sweden (Sandborgh-Englund et al., 2006) and Australia (Allmyr et al., 2008, 2009). It has been reported that the maximum exposure of babies via breast milk is approximately 7.4 μg per kg body weight per day and that TCS in breast milk presents minimal risk to babies at this level of exposure (Dayan, 2007). Several studies have shown that the blood levels of total TCS in humans following use in either mouth rinses or dentifrices vary from 1.4 nM to 1.4 μM(Bagley and Lin, 2000; DeSalva et al., 1989; Sandborgh-Englund et al., 2006). After absorption, the major fraction of TCS is excreted in urine within 24 h. However, total urinary excretion of TCS varied among indivi- duals, with 24% to 83% of the oral dose being excreted during the first 4 days after exposure (Sandborgh-Englund et al., 2006). In bacteria, sub-lethal concentrations of TCS inhibit enoyl-reductase, a type II fatty acid synthase (FAS) enoyl-reductase (FabI) that is Toxicology and Applied Pharmacology 262 (2012) 117–123 ☆ The views presented in this article do not necessarily reflect those of the U.S. Food and Drug Administration. ⁎ Correspondence to: J.-L. Fang, National Center for Toxicological Research, 3900 NCTR Road, HFT110, Jefferson, AR 72079, USA. Fax: +1 870 543 7136. ⁎⁎ Correspondence to: B. Ning, National Center for Toxicological Research, 3900 NCTR Road, HFT100, Jefferson, AR 72079, USA. Fax: +1 870 543 7773. E-mail addresses: jia-long.fang@fda.hhs.gov (J.-L. Fang), baitang.ning@fda.hhs.gov (B. Ning). 1 These authors contributed equally to the work. 0041-008X/$ – see front matter. Published by Elsevier Inc. doi:10.1016/j.taap.2012.04.024 Contents lists available at SciVerse ScienceDirect Toxicology and Applied Pharmacology journal homepage: www.elsevier.com/locate/ytaap