Effect of Arsenic on Mouse Embryonic Stem Cell Gene Expression for Differentiation
Anthony R. Calabro and Frank A. Barile, College of Pharmacy and Health Sciences, Department of Pharmaceutical Sciences
Abstract: Mouse embryonic stem (mES) cells are pluripotent cells derived from the inner cell mass of mouse blastocysts. We examined the effect of arsenic (As; 0.034mmol/l) on tight junction (TJ) and gene expression for differentiation. Gene expression was detected using mRNA purified from confluent monolayers cultured up to 12 days on cell culture inserts, coated with or without extracellular matrix components (collagen Type IV or fibronectin; C-IV, FN, respectively). Concurrently, transmembrane electrical resistance (TMER) was measured as an indicator of tight junction formation. When cells were exposed to As on Day 1, expression of Egfr (epidermal growth factor receptor for differentiated cells) decreased, which was not influenced by ECM substrata. Arsenic on Day 7 however increased Egfr expression when cells were grown on FN or C-IV. Expression of Oct-4 (transcription factor for undifferentiated cells) was reduced in the presence of As on Day 1 or 7, which was not influenced by ECM. After an initial rise without As, TMER declined to near baseline when the metal was introduced on day 7. Furthermore, arsenic exposure early in culture completely suppressed the rise in TMER in culture inserts. The toxicological significance of the results indicates that at low doses, As interferes with cell differentiation, particularly during the early stages. The timing of As exposure and the presence of supporting ECM substrata mitigate the differentiation pattern of mES cells in early culture, possibly mimicking in vivo embryogenesis. The method, using embryonic stem cells, optimizes conditions for screening chemicals in developmental cytotoxicity testing protocols. (Supported in part by International Foundation for Ethical Research, Chicago, IL).