6 research outputs found
In Vitro Model for Hepatotoxicity Studies Based on Primary Human Hepatocyte Cultivation in a Perfused 3D Bioreactor System
Accurate prediction of the potential hepatotoxic nature of new pharmaceuticals
remains highly challenging. Therefore, novel in vitro models with improved
external validity are needed to investigate hepatic metabolism and timely
identify any toxicity of drugs in humans. In this study, we examined the
effects of diclofenac, as a model substance with a known risk of
hepatotoxicity in vivo, in a dynamic multi-compartment bioreactor using
primary human liver cells. Biotransformation pathways of the drug and possible
effects on metabolic activities, morphology and cell transcriptome were
evaluated. Formation rates of diclofenac metabolites were relatively stable
over the application period of seven days in bioreactors exposed to 300 µM
diclofenac (300 µM bioreactors (300 µM BR)), while in bioreactors exposed to
1000 µM diclofenac (1000 µM BR) metabolite concentrations declined
drastically. The biochemical data showed a significant decrease in lactate
production and for the higher dose a significant increase in ammonia
secretion, indicating a dose-dependent effect of diclofenac application. The
microarray analyses performed revealed a stable hepatic phenotype of the cells
over time and the observed transcriptional changes were in line with
functional readouts of the system. In conclusion, the data highlight the
suitability of the bioreactor technology for studying the hepatotoxicity of
drugs in vitro
A widespread family of bacterial cell wall assembly proteins
Teichoic acids and acidic capsular polysaccharides are major anionic cell wall polymers (APs) in many bacteria, with various critical cell functions, including maintenance of cell shape and structural integrity, charge and cation homeostasis, and multiple aspects of pathogenesis. We have identified the widespread LytR–Cps2A–Psr (LCP) protein family, of previously unknown function, as novel enzymes required for AP synthesis. Structural and biochemical analysis of several LCP proteins suggest that they carry out the final step of transferring APs from their lipid-linked precursor to cell wall peptidoglycan (PG). In Bacillus subtilis, LCP proteins are found in association with the MreB cytoskeleton, suggesting that MreB proteins coordinate the insertion of the major polymers, PG and AP, into the cell wall
Effects of Co-Culture Media on Hepatic Differentiation of hiPSC with or without HUVEC Co-Culture
The derivation of hepatocytes from human induced pluripotent stem cells (hiPSC) is of great interest for applications in pharmacological research. However, full maturation of hiPSC-derived hepatocytes has not yet been achieved in vitro. To improve hepatic differentiation, co-cultivation of hiPSC with human umbilical vein endothelial cells (HUVEC) during hepatic differentiation was investigated in this study. In the first step, different culture media variations based on hepatocyte culture medium (HCM) were tested in HUVEC mono-cultures to establish a suitable culture medium for co-culture experiments. Based on the results, two media variants were selected to differentiate hiPSC-derived definitive endodermal (DE) cells into mature hepatocytes with or without HUVEC addition. DE cells differentiated in mono-cultures in the presence of those media variants showed a significant increase (p < 0.05) in secretion of α-fetoprotein and in activities of cytochrome P450 (CYP) isoenzymes CYP2B6 and CYP3A4 as compared with cells differentiated in unmodified HCM used as control. Co-cultivation with HUVEC did not further improve the differentiation outcome. Thus, it can be concluded that the effect of the used medium outweighed the effect of HUVEC co-culture, emphasizing the importance of the culture medium composition for hiPSC differentiation