Browsing by Author "Swiderska-Syn, Marzena"

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    Liver regeneration requires Yap1-TGFβ-dependent epithelial-mesenchymal transition in hepatocytes.
    (Journal of hepatology, 2018-05-11) Oh, Seh-Hoon; Swiderska-Syn, Marzena; Jewell, Mark L; Premont, Richard T; Diehl, Anna Mae
    Chronic failure of mechanisms that promote effective regeneration of dead hepatocytes causes replacement of functional hepatic parenchyma with fibrous scar and ultimately results in cirrhosis. Therefore, defining and optimizing mechanisms that orchestrate effective regeneration might prevent cirrhosis. We hypothesized that effective regeneration of injured livers requires hepatocytes to evade the growth inhibitory actions of TGF-β since TGF-β signaling inhibits mature hepatocyte growth but drives cirrhosis pathogenesis. Approach Wild type mice underwent partial hepatectomy (PH); TGF-β expression and signaling were evaluated in intact tissue and primary hepatocytes before, during, and after the period of maximal hepatocyte proliferation that occurs from 24-72h after PH. To determine the role of Yap1 in regulating TGF-β signaling in hepatocytes, studies were repeated after selectively deleting Yap1 from hepatocytes of Yap1flox/flox mice.TGF-β expression and hepatocyte nuclear accumulation of pSmad2 and Yap1 increased in parallel with hepatocyte proliferative activity after PH. Proliferative hepatocytes also upregulated Snai1, a pSmad2 target gene that promotes epithelial-to-mesenchymal transition (EMT), suppressed epithelial genes, induced myofibroblast markers, and produced collagen 1α1. Deleting Yap1 from hepatocytes blocked their nuclear accumulation of pSmad2 and EMT-like response, as well as their proliferation.Interactions between the TGF-β and Hippo-Yap signaling pathways stimulate hepatocytes to undergo an EMT-like response that is necessary for them to grow in a TGF-β-enriched microenvironment and regenerate injured livers.The adult liver has an extraordinary ability to regenerate after injury despite the accumulation of scar-forming factors that normally block the proliferation and reduce the survival of residual liver cells. We discovered that liver cells manage to escape these growth-inhibitory influences by transiently becoming more like fibroblasts themselves, and showed that they do this by reactivating programs that are known to drive tissue growth during fetal development and in many cancers. Understanding how the liver is able to control programs that are involved in scarring and cancer may help develop new treatments for cirrhosis and liver cancer.
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    Loss of pericyte smoothened activity in mice with genetic deficiency of leptin.
    (BMC Cell Biol, 2017-04-20) Xie, Guanhua; Swiderska-Syn, Marzena; Jewell, Mark L; Machado, Mariana Verdelho; Michelotti, Gregory A; Premont, Richard T; Diehl, Anna Mae
    BACKGROUND: Obesity is associated with multiple diseases, but it is unclear how obesity promotes progressive tissue damage. Recovery from injury requires repair, an energy-expensive process that is coupled to energy availability at the cellular level. The satiety factor, leptin, is a key component of the sensor that matches cellular energy utilization to available energy supplies. Leptin deficiency signals energy depletion, whereas activating the Hedgehog pathway drives energy-consuming activities. Tissue repair is impaired in mice that are obese due to genetic leptin deficiency. Tissue repair is also blocked and obesity enhanced by inhibiting Hedgehog activity. We evaluated the hypothesis that loss of leptin silences Hedgehog signaling in pericytes, multipotent leptin-target cells that regulate a variety of responses that are often defective in obesity, including tissue repair and adipocyte differentiation. RESULTS: We found that pericytes from liver and white adipose tissue require leptin to maintain expression of the Hedgehog co-receptor, Smoothened, which controls the activities of Hedgehog-regulated Gli transcription factors that orchestrate gene expression programs that dictate pericyte fate. Smoothened suppression prevents liver pericytes from being reprogrammed into myofibroblasts, but stimulates adipose-derived pericytes to become white adipocytes. Progressive Hedgehog pathway decay promotes senescence in leptin-deficient liver pericytes, which, in turn, generate paracrine signals that cause neighboring hepatocytes to become fatty and less proliferative, enhancing vulnerability to liver damage. CONCLUSIONS: Leptin-responsive pericytes evaluate energy availability to inform tissue construction by modulating Hedgehog pathway activity and thus, are at the root of progressive obesity-related tissue pathology. Leptin deficiency inhibits Hedgehog signaling in pericytes to trigger a pericytopathy that promotes both adiposity and obesity-related tissue damage.
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    Markers of Tissue Repair and Cellular Aging Are Increased in the Liver Tissue of Patients With HIV Infection Regardless of Presence of HCV Coinfection.
    (Open forum infectious diseases, 2018-07) Naggie, Susanna; Swiderska-Syn, Marzena; Choi, Steve; Lusk, Sam; Lan, Audrey; Ferrari, Guido; Syn, Wing-Kin; Guy, Cynthia D; Diehl, Anna Mae
    Liver disease is a leading cause of HIV-related mortality. Hepatitis C virus (HCV)-related fibrogenesis is accelerated in the setting of HIV coinfection, yet the mechanisms underlying this aggressive pathogenesis are unclear. We identified formalin-fixed paraffin-embedded liver tissue for HIV-infected patients, HCV-infected patients, HIV/HCV-coinfected patients, and controls at Duke University Medical Center. De-identified sections were stained for markers against the wound repair Hedgehog (Hh) pathway, resident T-lymphocytes, and immune activation and cellular aging. HIV infection was independently associated with Hh activation and markers of immune dysregulation in the liver tissue.
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    Pleiotrophin regulates the ductular reaction by controlling the migration of cells in liver progenitor niches.
    (Gut, 2016-04) Michelotti, Gregory A; Tucker, Anikia; Swiderska-Syn, Marzena; Machado, Mariana Verdelho; Choi, Steve S; Kruger, Leandi; Soderblom, Erik; Thompson, J Will; Mayer-Salman, Meredith; Himburg, Heather A; Moylan, Cynthia A; Guy, Cynthia D; Garman, Katherine S; Premont, Richard T; Chute, John P; Diehl, Anna Mae
    OBJECTIVE: The ductular reaction (DR) involves mobilisation of reactive-appearing duct-like cells (RDC) along canals of Hering, and myofibroblastic (MF) differentiation of hepatic stellate cells (HSC) in the space of Disse. Perivascular cells in stem cell niches produce pleiotrophin (PTN) to inactivate the PTN receptor, protein tyrosine phosphatase receptor zeta-1 (PTPRZ1), thereby augmenting phosphoprotein-dependent signalling. We hypothesised that the DR is regulated by PTN/PTPRZ1 signalling. DESIGN: PTN-GFP, PTN-knockout (KO), PTPRZ1-KO, and wild type (WT) mice were examined before and after bile duct ligation (BDL) for PTN, PTPRZ1 and the DR. RDC and HSC from WT, PTN-KO, and PTPRZ1-KO mice were also treated with PTN to determine effects on downstream signaling phosphoproteins, gene expression, growth, and migration. Liver biopsies from patients with DRs were also interrogated. RESULTS: Although quiescent HSC and RDC lines expressed PTN and PTPRZ1 mRNAs, neither PTN nor PTPRZ1 protein was demonstrated in healthy liver. BDL induced PTN in MF-HSC and increased PTPRZ1 in MF-HSC and RDC. In WT mice, BDL triggered a DR characterised by periportal accumulation of collagen, RDC and MF-HSC. All aspects of this DR were increased in PTN-KO mice and suppressed in PTPRZ1-KO mice. In vitro studies revealed PTN-dependent accumulation of phosphoproteins that control cell-cell adhesion and migration, with resultant inhibition of cell migration. PTPRZ1-positive cells were prominent in the DRs of patients with ductal plate defects and adult cholestatic diseases. CONCLUSIONS: PTN, and its receptor, PTPRZ1, regulate the DR to liver injury by controlling the migration of resident cells in adult liver progenitor niches.
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    TWEAK/Fn14 signaling is required for liver regeneration after partial hepatectomy in mice.
    (PLoS One, 2014) Karaca, Gamze; Swiderska-Syn, Marzena; Xie, Guanhua; Syn, Wing-Kin; Krüger, Leandi; Machado, Mariana Verdelho; Garman, Katherine; Choi, Steve S; Michelotti, Gregory A; Burkly, Linda C; Ochoa, Begoña; Diehl, Anna Mae
    BACKGROUND & AIMS: Pro-inflammatory cytokines are important for liver regeneration after partial hepatectomy (PH). Expression of Fibroblast growth factor-inducible 14 (Fn14), the receptor for TNF-like weak inducer of apoptosis (TWEAK), is induced rapidly after PH and remains elevated throughout the period of peak hepatocyte replication. The role of Fn14 in post-PH liver regeneration is uncertain because Fn14 is expressed by liver progenitors and TWEAK-Fn14 interactions stimulate progenitor growth, but replication of mature hepatocytes is thought to drive liver regeneration after PH. METHODS: To clarify the role of TWEAK-Fn14 after PH, we compared post-PH regenerative responses in wild type (WT) mice, Fn14 knockout (KO) mice, TWEAK KO mice, and WT mice treated with anti-TWEAK antibodies. RESULTS: In WT mice, rare Fn14(+) cells localized with other progenitor markers in peri-portal areas before PH. PH rapidly increased proliferation of Fn14(+) cells; hepatocytic cells that expressed Fn14 and other progenitor markers, such as Lgr5, progressively accumulated from 12-8 h post-PH and then declined to baseline by 96 h. When TWEAK/Fn14 signaling was disrupted, progenitor accumulation, induction of pro-regenerative cytokines, hepatocyte and cholangiocyte proliferation, and over-all survival were inhibited, while post-PH liver damage and bilirubin levels were increased. TWEAK stimulated proliferation and increased Lgr5 expression in cultured liver progenitors, but had no effect on either parameter in cultured primary hepatocytes. CONCLUSIONS: TWEAK-FN14 signaling is necessary for the healthy adult liver to regenerate normally after acute partial hepatectomy.