Comparative analysis of media effects on human induced pluripotent stem cell-derived cardiomyocytes in proarrhythmia risk assessment.

INTRODUCTION: Cardiotoxicity assessment using human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) forms a key component of the Comprehensive in Vitro Proarrhythmia Assay (CiPA). A potentially impactful factor on iPSC-CM testing is the presence of serum in the experimental media. Generally, serum-free media is used to most accurately reproduce "free" drug concentration. However, caution is needed; drug solubility and cardiomyocyte electrophysiology could be affected by media formulation, potentially impacting interpretation of drug-induced effects. METHODS: Effects of 25 drugs on properties of spontaneous field potentials in iPSC-CMs were assayed using a high-throughput microelectrode array (MEA) in two media formulations: serum-containing and serum-free. Comparative analysis was conducted on rate-corrected field potential duration (FPDc) and prevalence of arrhythmic events. Further MEA experiments were conducted, varying percentages of serum as well as carbon substrate components. Comparative LC-MS/MS analysis was done on two compounds to evaluate drug concentrations. RESULTS: In serum-free media, 9 drugs prolonged FPDc. In serum-containing, 11 drugs prolonged FPDc. Eighteen drugs induced arrhythmias, 8 of these induced arrhythmias at lower concentrations in serum-containing media. At the highest non-arrhythmic concentrations, 13 of 25 drugs exhibited significant differences in FPDc prolongation/shortening between the media. Increasing fractions of serum in media yielded higher FPDc measurements. LC-MS/MS analysis of moxifloxacin and quinidine showed higher concentrations in serum-containing media. DISCUSSION: The present study highlights media formulation as an important consideration for cardiac safety testing with iPSC-CMs. Results described here suggest that media formulation influences both compound availability and baseline electrophysiological properties. Special attention should be paid to media for future iPSC-CM assays.

Phenol degradation and toxicity assessment upon biostimulation to an indigenous Rhizobium Ralstonia taiwanensis.

This study provides a first attempt from a toxicological perspective to put forward, in general terms and explanations, combined toxic interactions and biostimulation strategy upon nutrient medium to Ralstonia taiwanensis for bioremediation. Dose-response analysis clearly revealed that most of the supplemented nutrients tested (except for gluconic acid) synergistically interact with chronic toxicity to phenol, especially at low doses. Acute toxicity based upon adaptation lag is a more appropriate indicator for comparative analysis of toxicity due to similar toxic ranking at almost all effective concentrations. In addition, comparison upon acute and chronic toxicity for various nutrient media also suggests in parallel that acute toxicity is more significant than chronic toxicity possibly as the result of a more sensitive response of adaptation lag to growth in different media. Feasibility of adding extra nutrient substrates (e.g., phenol, gluconic acid, yeast extract, pyruvic acid, acetic acid, and glycerol) to stimulate proliferation of phenol degraders for better phenol degradation performance was also assessed. The results show that using acetic acid as the augmented nutrient source might be the most feasible biostimulation strategy for phenol degradation.