Nonalcoholic fatty liver disease (NAFLD/steatosis) is a metabolic disease characterized by the incorporation of fat into hepatocytes. In this study, we developed an in vitro model for NAFLD based on hepatocyte-like cells (HLCs) differentiated from human pluripotent stem cells. We induced fat storage in these HLCs and detected major expression changes of metabolism-associated genes, as well as an overall reduction of liver-related microRNAs. We observed an upregulation of the lipid droplet coating protein Perilipin 2 (PLIN2), as well as of numerous genes of the peroxisome proliferator-activated receptor (PPAR) pathway, which constitutes a regulatory hub for metabolic processes. Interference with PLIN2 and PPARα resulted in major alterations in gene expression, especially affecting lipid, glucose, and purine metabolism. Our model recapitulates many metabolic changes that are characteristic for NAFLD. It permits the dissection of disease-promoting molecular pathways and allows us to investigate the influences of distinct genetic backgrounds on disease progression.
Considered a feature of the metabolic syndrome, nonalcoholic fatty liver disease (NAFLD), is associated with insulin resistance, type 2 diabetes, obesity and drug toxicity. Its prevalence is estimated at about 30% in western countries mainly due to sedentary life styles and high fat diets. Genome-wide association studies have identified polymorphisms in several genes, for example, PNPLA3, and TM6SF2 which confer susceptibility to NAFLD. Here, we review recent findings in the NAFLD field with a particular focus on published transcriptomics datasets which we subject to a meta-analysis. We reveal a common gene signature correlating with the progression of the disease from steatosis and steatohepatitis and reveal that lipogenic and cholesterol metabolic pathways are main actors in this signature. We propose the use of disease-in-adish models based on hepatocyte-like cells derived from patient-specific induced pluripotent stem cells (iPSC). These will enable investigations into the contribution of genetic background in the progression from NALFD to non-alcoholic steatohepatitis. Furthermore, an iPSC-based approach should aid in the elucidation of the function of new biomarkers, thus enabling better diagnostic tests and validation of potential drug targets. STEM CELLS 2017;35:89-96
SIGNIFICANCE STATEMENTThe continuously increasing prevalence of nonalcoholic fatty liver disease (NAFLD) estimated at approximately 30% in western countries and the paucity of available publications incorporating epidemiology, genome-wide association studies, epigenetics and meta-analysis of transcriptome data, served as impetus for this review article. We reveal a NAFLD-gene signature which correlates with the progression of the disease from steatosis to non-alcoholic steatohepatitis, fibrosis, cirrhosis, and eventually liver cancer. We also propose the implementation of patientspecific disease models based on induced pluripotent stem cells differentiated into hepatocytes and challenged with oleic acid to enable a better understanding of the molecular mechanisms underlying the etiology of NAFLD.
Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome and its prevalence increases continuously. Here, we reprogrammed fibroblasts of a high grade NAFLD patient with homozygous wildtype PNPLA3 genotype. The induced pluripotent stem cells (iPSCs) were characterized by immunocytochemistry, flow cytometry, embryoid body formation, pluritest, DNA-fingerprinting and karyotype analysis.
Primary fibroblasts from a low grade steatosis patient were reprogrammed by transduction of a combination of two episomal-based plasmids OCT4,SOX2, c-MYC and KLF4. iPSCs were characterized by immunocytochemistry, embryonic body-formation, DNA-fingerprint karyotype analysis and comparative transcriptome analyses with the human embryonic stem cell line H1 revealed a Pearsons correlation of 0.9251.
Primary fibroblasts from a high grade steatosis patient were reprogrammed by transduction of retroviruses OCT4, SOX2, c-MYC and KLF4. IPSCs were characterized by immunocytochemistry, embryoid body-formation, DNA-fingerprint, karyotype analysis and comparative transcriptome analyses with the human embryonic stem cell line H1 revealed a Pearsons correlation coefficient of 0.9287. Resource table.
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