Oxidative stress in pancreatic alpha and beta cells as a selection criterion for biocompatible biomaterials

The clinical success rate of islet transplantation, namely independence from insulin injections, is limited by factors that lead to graft failure, including inflammation, acute ischemia, acute phase response, and insufficient vascularization. The ischemia and insufficient vascularization both lead to high levels of oxidative stress, which are further aggravated by islet encapsulation, inflammation, and undesirable cell-biomaterial interactions. To identify biomaterials that would not further increase damaging oxidative stress levels and that are also suitable for manufacturing a beta cell encapsulation device, we studied five clinically approved polymers for their effect on oxidative stress and islet (alpha and beta cell) function. We found that 300 poly(ethylene oxide terephthalate) 55/poly(butylene terephthalate) 45 (PEOT/PBT300) was more resistant to breakage and more elastic than other biomaterials, which is important for its immunoprotective function. In addition, it did not induce oxidative stress or reduce viability in the MIN6 beta cell line, and even promoted protective endogenous antioxidant expression over 7 days. Importantly, PEOT/PBT300 is one of the biomaterials we studied that did not interfere with insulin secretion in human islets.Diabetes mellitus: pathophysiological changes and therap

Transcriptomic concentration-response evaluation of valproic acid, cyproconazole, and hexaconazole in the neural embryonic stem cell test (ESTn)

Alternative developmental toxicity assays are urgently needed to reduce animal use in regulatory developmental toxicology. We previously designed an in vitro murine neural embryonic stem cell test (ESTn) as a model for neurodevelopmental toxicity testing (Theunissen et al., 2010). Toxicogenomic approaches have been suggested for incorporation into the ESTn to further increase predictivity and to provide mechanistic insights. Therefore, in this study, using a transcriptomic approach, we investigated the concentration-dependent effects of three known (neuro) developmental toxicants, two triazoles, cyproconazole (CYP) and hexaconazole (HEX), and the anticonvulsant valproic acid (VPA). Compound effects on gene expression during neural differentiation and corresponding regulated gene ontology (GO) terms were identified after 24 h of exposure in relation to morphological changes on day 11 of culture. Concentration-dependent responses on individual gene expression and on biological processes were determined for each compound, providing information on mechanism and concentration-response characteristics. All compounds caused enrichment of the embryonic development process. CYP and VPA but not HEX significantly enriched the neuron development process. Furthermore, specific responses for triazole compounds and VPA were observed within the GO-term sterol metabolic process. The incorporation of transcriptomics in the ESTn was shown to enable detection of effects, which precede morphological changes and provide a more sensitive measure of concentration-dependent effects as compared with classical morphological assessments. Furthermore, mechanistic insight can be instrumental in the extrapolation of effects in the ESTn to human hazard assessment

Transcriptomic concentration-response evaluation of valproic acid, cyproconazole, and hexaconazole in the neural embryonic stem cell test (ESTn)

Alternative developmental toxicity assays are urgently needed to reduce animal use in regulatory developmental toxicology. We previously designed an in vitro murine neural embryonic stem cell test (ESTn) as a model for neurodevelopmental toxicity testing (Theunissen et al., 2010). Toxicogenomic approaches have been suggested for incorporation into the ESTn to further increase predictivity and to provide mechanistic insights. Therefore, in this study, using a transcriptomic approach, we investigated the concentration-dependent effects of three known (neuro) developmental toxicants, two triazoles, cyproconazole (CYP) and hexaconazole (HEX), and the anticonvulsant valproic acid (VPA). Compound effects on gene expression during neural differentiation and corresponding regulated gene ontology (GO) terms were identified after 24 h of exposure in relation to morphological changes on day 11 of culture. Concentration-dependent responses on individual gene expression and on biological processes were determined for each compound, providing information on mechanism and concentration-response characteristics. All compounds caused enrichment of the embryonic development process. CYP and VPA but not HEX significantly enriched the neuron development process. Furthermore, specific responses for triazole compounds and VPA were observed within the GO-term sterol metabolic process. The incorporation of transcriptomics in the ESTn was shown to enable detection of effects, which precede morphological changes and provide a more sensitive measure of concentration-dependent effects as compared with classical morphological assessments. Furthermore, mechanistic insight can be instrumental in the extrapolation of effects in the ESTn to human hazard assessment

A transcriptomics-based in vitro assay for predicting chemical genotoxicity in vivo

The lack of accurate in vitro assays for predicting in vivo toxicity of chemicals together with new legislations demanding replacement and reduction of animal testing has triggered the development of alternative methods. This study aimed at developing a transcriptomics-based in vitro prediction assay for in vivo genotoxicity. Transcriptomics changes induced in the human liver cell line HepG2 by 34 compounds after treatment for 12, 24, and 48h were used for the selection of gene-sets that are capable of discriminating between in vivo genotoxins (GTX) and in vivo nongenotoxins (NGTX). By combining transcriptomics with publicly available results for these chemicals from standard in vitro genotoxicity studies, we developed several prediction models. These models were validated by using an additional set of 28 chemicals. The best prediction was achieved after stratification of chemicals according to results from the Ames bacterial gene mutation assay prior to transcriptomics evaluation after 24h of treatment. A total of 33 genes were selected for discriminating GTX from NGTX for Ames-positive chemicals and 22 for Ames-negative chemicals. Overall, this method resulted in 89% accuracy and 91% specificity, thereby clearly outperforming the standard in vitro test battery. Transcription factor network analysis revealed HNF3a, HNF4a, HNF6, androgen receptor, and SP1 as main factors regulating the expression of classifiers for Ames-positive chemicals. Thus, the classical bacterial gene mutation assay in combination with in vitro transcriptomics in HepG2 is proposed as an upgraded in vitro approach for predicting in vivo genotoxicity of chemicals holding a great promise for reducing animal experimentations on genotoxicity