Despite considerable efforts in modeling liver disease in vitro, it remains difficult to recapitulate the pathogenesis of the advanced phases of non‐alcoholic fatty liver disease (NAFLD) with inflammation and fibrosis. Here, a liver‐on‐a‐chip platform with bioengineered multicellular liver microtissues is developed, composed of four major types of liver cells (hepatocytes, endothelial cells, Kupffer cells, and stellate cells) to implement a human hepatic fibrosis model driven by NAFLD: i) lipid accumulation in hepatocytes (steatosis), ii) neovascularization by endothelial cells, iii) inflammation by activated Kupffer cells (steatohepatitis), and iv) extracellular matrix deposition by activated stellate cells (fibrosis). In this model, the presence of stellate cells in the liver‐on‐a‐chip model with fat supplementation showed elevated inflammatory responses and fibrosis marker up‐regulation. Compared to transforming growth factor‐beta‐induced hepatic fibrosis models, this model includes the native pathological and chronological steps of NAFLD which shows i) higher fibrotic phenotypes, ii) increased expression of fibrosis markers, and iii) efficient drug transport and metabolism. Taken together, the proposed platform will enable a better understanding of the mechanisms underlying fibrosis progression in NAFLD as well as the identification of new drugs for the different stages of NAFLD.
Whether the stomach influences the progression of nonalcoholic steatohepatitis (NASH) remains largely unknown. Ghrelin, a 28‐amino acid gastric hormone, is critical for the regulation of energy metabolism and inflammation. We investigated whether ghrelin affects the progression of NASH. NASH was induced with lipopolysaccharide (LPS; 240 μg/kg/day) in male C57BL/6J mice with high‐fat diet (HFD). Ghrelin (11 nmol/kg/day) was administrated by a subcutaneous mini‐pump. Liver steatosis, inflammation, and fibrosis were assessed. Kupffer cells and hepatocytes isolated from wild type, GHSR1a−/−or PPARγ+/−mice were cocultured to determine the cellular and molecular mechanism by which ghrelin ameliorates NASH. A low concentration of LPS activates the Kupffer cells, leading to the development of NASH in mice fed HFD. Ghrelin blocked the progression of NASH induced by LPS via GHSR1a‐mediated attenuation of Kupffer cells M1 polarization. GHSR1a was detected in Kupffer cells isolated from wild‐type mice but not in GHSR1a deficient animals. Upon binding with ghrelin, internalization of GHSR1a occurred. Ghrelin reduced levels of tumor necrosis factor‐α and inducible nitricoxide synthase while increasing Arg1 in Kupffer cells treated with LPS. Ghrelin markedly attenuated the upregulation of lipid accumulation induced by the supernatant of Kupffer cells under both basal and LPS‐treated conditions. Deficiency of PPARγ significantly reduced the effect of LPS on the hepatic steatosis in mice and in cultured hepatocytes. Our studies indicate that the stomach may improve the development of NASH via ghrelin. Ghrelin may serve as a marker and therapeutic target for NASH.
more » « less- NSF-PAR ID:
- 10452681
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Cellular Physiology
- Volume:
- 236
- Issue:
- 7
- ISSN:
- 0021-9541
- Format(s):
- Medium: X Size: p. 5121-5133
- Size(s):
- ["p. 5121-5133"]
- Sponsoring Org:
- National Science Foundation
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Klb) , a co‐receptor for the biological functions of fibroblast growth factor (FGF)15/19 and FGF21. DNA methyltransferases (DNMT) 1 and 3A mediate HFD‐induced methylation at theKlb promoter. Notably, HFD enhances DNMT1 protein stability via a ubiquitination‐mediated mechanism. Liver‐specific deletion ofDnmt1 or3a increasesKlb expression and ameliorates HFD‐induced hepatic steatosis. Single‐nucleus RNA sequencing analysis reveals pathways involved in fatty acid oxidation inDnmt1 ‐deficient hepatocytes. Targeted demethylation at theKlb promoter increasesKlb expression and fatty acid oxidation, resulting in decreased hepatic lipid accumulation. Up‐regulation of methyltransferases by HFD may induce hypermethylation of theKlb promoter and subsequent down‐regulation ofKlb expression, resulting in the development of hepatic steatosis. -
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Graca Almeida-Porada, MD3 1Fetal Research and Therapy Program, Wake Forest Institute for Regenerative Medicine, Winston Salem, NC 2Massachusetts Institute of Technology, Cambridge, MA 3Fetal Research and Therapy Program, Wake Forest Institute For Regenerative Medicine, Winston-Salem, NC Clinical trials employing AAV vectors for hemophilia A have been hindered by unanticipated immunological and/or inflammatory responses in some of the patients. Also, these trials have often yielded lower levels of transgene expression than were expected based upon preclinical studies, highlighting the poor correlation between the transduction efficiency observed in traditional 2D cultures of primary cells in vitro, and that observed in those same cell types in vivo. 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