Biology subjects

Duwaerts, C. C.

Publications and source records attributed to Duwaerts, C. C..

5 recordsLinked to original sources

bioRxiv2025

iPSC-Derived Hepatocytes from Patients with MASLD Exhibit Early Mitochondrial Dysfunction

Background & AimsA hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD) is a decline in the ability of hepatocyte mitochondria to adapt to excess lipid. This leads to the production of reactive oxygen species (ROS) and the instigation of a vicious cycle of further mitochondrial damage and cellular dysfunction that promotes disease progression. In this study, we investigated whether induced pluripotent stem cells (iPSCs) from MASLD patients exhibit features of mitochondrial dysfunction when differentiated to hepatocyte-like cells (iPSC-Heps). MethodsiPSCs from 10 MASLD patients and 10 healthy control subjects genotyped for the I148M variant of PNPLA3 were differentiated to iPSC-Heps. Mitochondrial mass and function were assessed under basal culture conditions and following short-term exposure to exogenous palmitate. Outcomes included gene expression, mitochondrial oxygen consumption, ROS production and cellular energy status. ResultsiPSC-Heps from MASLD patients spontaneously accrued more lipid than control iPSC-Heps. Mitochondrial content was similar in MASLD and control iPSC-Heps, but MASLD iPSC-Heps displayed significant differences in mitochondrial function including a decrease in oxygen consumption rate when challenged with palmitate. Antioxidant gene expression was increased at baseline in MASLD vs. control iPSC-Heps, and MASLD iPSC-Heps produced more ROS and less ATP than controls after palmitate treatment. Differences persisted even when controlling for PNPLA3 genotype. ConclusionsiPSC-Heps from MASLD patients exhibit mitochondrial alterations characteristic of their diseased origin. The degree of mitochondrial dysfunction seen in MASLD iPSC-Heps is reminiscent of that described clinically in early MASLD, prior to progression to steatohepatitis. Mitochondrial alterations in MASLD iPSC-Heps occur independently of PNPLA3 genotype.

cell biology↗

bioRxiv2022

Targeting Acid Ceramidase Ameliorates Fibrosis in Mouse Models of Nonalcoholic Steatohepatitis

1)Nonalcoholic fatty liver disease (NAFLD) is a common cause of liver disease worldwide, and is characterized by the accumulation of fat in the liver. Nonalcoholic steatohepatitis (NASH), an advanced form of NAFLD, is a leading cause of liver transplantation. Fibrosis is the histologic feature most associated with liver-related morbidity and mortality in patients with NASH, and treatment options remain limited. In previous studies, we discovered that acid ceramidase (aCDase) is a potent antifibrotic target using human hepatic stellate cells (HSCs) and models of hepatic fibrogenesis. Using two dietary mouse models, we demonstrate that depletion of aCDase in HSC reduces fibrosis without worsening metabolic features of NASH, including steatosis, inflammation, and insulin resistance. Consistently, pharmacologic inhibition of aCDase ameliorates fibrosis but does not alter metabolic parameters. The findings suggest that targeting aCDase is a viable therapeutic option to reduce fibrosis in patients with NASH.

systems biology↗

bioRxiv2022

Neonatal hepatic myeloid progenitors expand and propagate liver inflammation in mice

Background and AimsBiliary atresia is a rapidly progressive pediatric inflammatory disease of the liver that leads to cirrhosis and necessitates liver transplantation. The rapid progression from liver injury to fulminant liver failure in children with biliary atresia suggests that factors specific to the perinatal hepatic environment are important for disease propagation. Hematopoietic stem and progenitor cells (HSPCs) serve as central hubs of inflammation and rely on inflammatory signals for their emigration from the liver to the bone marrow in neonatal mice. We hypothesized that HSPCs are critical for the propagation of perinatal liver inflammation (PLI). MethodsNewborn BALB/c mice were injected intraperitoneally with 1.5x106 focus forming units of Rhesus Rotavirus (RRV) to induce PLI or with PBS as control. Livers from RRV- and PBS-injected mice were compared using histology and flow cytometry. To determine the effects of HSPCs on perinatal inflammation, RRV-infected neonatal mice were injected with anti-CD47 and anti-CD117 to deplete HSPCs. ResultsRRV-induced PLI led to a significant increase in the number of common myeloid progenitors (Flt3+ CMPs: PBS=4426{+/-}247.2 vs RRV=9856{+/-}2009, p=0.0316; Flt3- CMPs: PBS=3063{+/-}254.9 vs RRV=9743{+/-}1539, p=0.0012). We corroborated these findings by observing a significant increase in CD34+ hematopoietic progenitors/cm2 in histological sections of RRV-infected livers (PBS=4.977{+/-}2.573 vs RRV=27.09{+/-}12.49, p=0.0075). Elimination of progenitors through antibody-mediated myeloablation rescued animals from PLI and significantly increased survival (RRV+isotype control 55.56% vs RRV+myeloablation 94.12%, Chi-test=0.01). ConclusionsThese data demonstrate that RRV causes expansion of HSPCs and propagates PLI. Targeting of HSPCs may be useful in preventing and treating neonatal inflammatory diseases of the liver like biliary atresia. SYNOPSISHematopoietic progenitors reside in juvenile mouse livers even after the main site of hematopoiesis has shifted to the bone marrow. These progenitors are critical for the pathogenesis of perinatal liver inflammation as myeloablation rescues animals from disease.

immunology↗

bioRxiv2020

Hepatocyte-specific deletion of XBP1 sensitizes mice to liver injury through hyperactivation of IRE1α

X-box binding protein-1 (XBP1) is a transcription factor that plays a central role in controlling cellular responses to endoplasmic reticulum (ER) stress. Under stress conditions, the transcriptionally active form of XBP1 is generated by unique splicing of Xbp1 mRNA by the ER-resident protein inositol-requiring enzyme-1 (IRE1). Genetic deletion of XBP1 has multiple consequences: some resulting from the loss of the transcription factor per se, and others related to compensatory upstream activation of IRE1. The objective of the current study was to investigate the effects of XBP1 deletion in adult mouse liver and determine to what extent they are direct or indirect. XBP1 was deleted specifically from hepatocytes in adult Xbp1fl/fl mice using AAV8-Transthyretin-Cre (Xbp1{Delta}hep). Xbp1{Delta}hep mice exhibited no liver disease at baseline, but developed acute biochemical and histologic liver injury in response to a dietary challenge with fructose for 4 wk. Fructose-mediated liver injury in Xbp1{Delta}hep mice coincided with heightened IRE1 activity, as demonstrated by cJun phosphorylation and regulated IRE1 -dependent RNA decay (RIDD). Activation of eIF2 was also evident, with associated up-regulation of the pro-apoptotic molecules CHOP, BIM and PUMA. To determine whether the adverse consequences of liver-specific XBP1 deletion were due to XBP1 loss or heightened IRE1 activity, we repeated a fructose challenge in mice with liver-specific deletion of both XBP1 and IRE1 (Xbp1{Delta}hep;IRE1{Delta}hep). Xbp1{Delta}hep;IRE1{Delta}hep mice were protected from fructose-mediated liver injury and failed to exhibit any of the signs of ER stress seen in mice lacking XBP1 alone. The protective effect of IRE1 deletion persisted even with long-term exposure to fructose. Xbp1{Delta}hep mice developed liver fibrosis at 16 wk, but Xbp1{Delta}hep;IRE1{Delta}hep mice did not. Overall, the results indicate that the deleterious effects of hepatocyte-specific XBP1 deletion are due primarily to hyperactivation of IRE1. They support further exploration of IRE1 as a contributor to acute and chronic liver diseases.

cell biology↗

bioRxiv2020

iPSC-derived hepatocytes from patients with nonalcoholic fatty liver disease display a disease-specific gene expression profile

Nonalcoholic fatty liver disease (NAFLD) is one of the leading causes of liver disease worldwide.1 Animal models are widely used to investigate the mechanisms of fatty liver disease, but they do not faithfully represent NAFLD in humans.2 Thus, there is strong interest in studying NAFLD pathogenesis directly in humans whenever possible. One strategy that is gaining momentum is to utilize iPSC-derived hepatocytes from individual human subjects in complex cell/organ platforms with the goal of reproducing a NAFLD-like state in vitro.3-6 Our group has taken a different approach, positing that iPSC-Heps from a population of NAFLD patients would provide independent insight into the human disease. In this study we generated iPSCs and iPSC-Heps from a well-defined cohort of NAFLD patients. Our objective was to determine whether as a group, in the absence of any metabolic challenge, they exhibit common disease-specific signatures that are distinct from healthy controls.Competing Interest StatementThis work was funded by research grants from the California Institute for Regenerative Medicine (IT1-06563), AbbVie, Inc. and NIH: R21 DK118380 (JJM), UG3 DK120004 (HW) and K08 DK098270 (ANM). Additional support was provided by core facilities within the UCSF Liver Center (P30 DK026743).View Full Text

pathology↗