Liver Injury 2x PDF

Morphologic Patterns of Hepatic Injury and Cirrhosis: Regeneration / Fibrogenesis Prof. Dr. Çiğdem (Ataizi) ÇELİKEL HEPATOCELLULAR INJURY REVERSIBLE IRREVERSIBLE  REVERSIBLE INJURY ❑ Balooning Degeneration ❑ Mallory-Denk Bodies ❑ Steatosis Balooning Degeneration ATP ↓ ↑ intra...

Morphologic Patterns of Hepatic Injury and Cirrhosis: Regeneration / Fibrogenesis Prof. Dr. Çiğdem (Ataizi) ÇELİKEL HEPATOCELLULAR INJURY REVERSIBLE IRREVERSIBLE  REVERSIBLE INJURY ❑ Balooning Degeneration ❑ Mallory-Denk Bodies ❑ Steatosis Balooning Degeneration ATP ↓ ↑ intracellular Ca+ membrane volume control derangement reversible hepatocellular injury Mallory-Denk Bodies ▪ Cytoskeletal keratin changes type I(K8) > II(K18) ▪ TNF α –R binding apoptosis neutrophil chemotaxis reversible hepatocellular injury ▪ Alcoholic Liver Disease (ALD) ▪ NAFLD Macrosteatosis ▪ Viral Hepatitis -HCV(genotype 3), HBV, HDV ▪ Drug ▪ insulin-unrelated metabolic and endocrine diseases (Wilson, galactosemia, tyrosinemia) ▪ lipoprotein metabolism defects ▪ starving, total parenteral nutrition reversible hepatocellular injury  Microsteatosis ▪ Alcoholic Foamy Degeneration ▪ Pregnancy associated acute fatty liver ▪ Reye Syndrome ▪ Drug and toxin (valproat, anti- retroviral) ▪ Acute iron toxicity ▪ HELLP syndrome ▪ Metabolic Diseases (Wolman, cholesterol ester, urea cycle and fatty acid metabolism defects) mitocondrial β oxidation defects (genetic or acquired) HEPATOCELLULAR INJURY REVERSIBLE IRREVERSIBLE ❑ Apoptosis ❑ Necrosis  CELL DEATH ❑ NECROSIS ❑ APOPTOSIS ▪ pathologic death ▪ programmed cell death ▪ metabolic degredation ▪ specific stimuli leading to degredation cascade necrosis apoptosis ❑ APOPTOSIS sufficient MITOCHONDRIA programmed cell death ❑ NECROSIS intracellular ATP oncotic necrosis, oncosis insufficient internal external ❖ Necroptosis / membrane membrane Aponecrosis cell death Programmed Cell Death chromatin condensation (pyknosis) chromatin fregmantation (karyorrhexis) Kupffer cell phagocytosis apoptosis acidophilic/apoptotic bodies, Councilman bodies  EXTRINSIC Pathway ▪ stimulation of death receptors ▪ Decrease of dependence receptor – threshold level INTRINSIC Pathway apoptosis EXTRINSIC Pathway ▪ stimulation of death receptors and caspases will lead to pyknosis and pyriaxis in the nuclei. So what we see is apoptosis. Now, intrinsic pathway mainly affects mitochondria. INTRINSIC Pathway Cell Death apoptosis cytotoxic T lymphocytes ligand, cytokine ‘natural killer’ cells TNFα FasL TRAIL Cell Surface Death Receptors TNF-R1 Fas TRAIL-R membrane stabilization «initiator» caspases 8, 10 «executioner» caspases 3, 6, 7 DNAse activation chromatin degradation apoptosis extrinsic pathway  Fas Hepatocyte Cholangiocyte Kupffer cells Endothelial cells cytotoxic-T Stellate cells lymphocyte NK- cells Fas / FasL HBV, HCV Acute liver NAFLD insufficiency Fas Fas L Alcoholic hepatitis Drug Fulminant Toxic hepatitis T-cell apoptosis Zekri AR. Characterization of chronic HCV-induced apoptosis. IL-1β Comp Hepatol 2011 Jul 23;10(1):4. chronicity apoptosis extrinsic pathway TNFR-1 / TNF-α HBV, HCV NAFLD Alcoholic hepatitis Fulminant hepatitis cellular inhibitör of apoptosis prt NF-κB transkripsiyon IL-8, IL-6 anti-apoptotic apoptosis necroptosis inflammation cell survival apoptosis extrinsic pathway TRAIL-R / TRAIL In which cells do we see trail receptor? ▪ infected hepatocyte ▪ bile acid containing hepatocyte All death receptors, including trail FAS ▪ neoplastic cell and TNF Alpha can be seen in normal necrosis. False. ❖ Normal hepatocyte ineffective apoptosis extrinsic pathway intrinsic extrinsic intrinsic pathway Mitochondrial function defect Endoplasmic reticulum stress mitochondrial external membrane permiabilization apoptosis smac/DIABLO cytochrome C inducing factor (AİF) caspase dependent apoptosis  Mitochondrial regulation of cell death. EXTRINSIC APOPTOSİS INTRINSIC APOPTOSİS NECROPTOSİS Galluzzi L et al. Circulation Research 2012;111:1198-1207.  When we see apoptosis in the liver, it means that there is an acute injury or ongoing chronic injury. So there is continuous damage to the hepatocytes. Either it's an acute problem or a chronic disease with acute exacerbations. Acute Injury Ongoing Chronic Injury apoptosis  You see massive apoptosis usually in acute problems, mainly due to either ischemic conditions or there is hypo perfusion to the liver. or there is a toxic damage either related to drugs and toxins massive apoptosis ❑normal development of liver - physiologic ❑inflamatory liver diseases (viral, autoimmune, ALD, NAFLD, drug) → cytotoxicT cells ❑chronic cholestatic diseases – bile salts, direct toxic effect → intrinsic / extrinsic apoptosis  Trigger inflammatory and fibrotic response ❑Apoptotic cells secrete ATP and UDP → macrophage and HSC membrane receptor stimulation ❑HSC →TGFβ profibrogenic cytokine release How does HSC cause apoptosis APOPTOSIS inflammation fibrogenesis chronisity (viral) infected / injured cell degredation HEPATOCELLULAR INJURY REVERSIBLE IRREVERSIBLE ❑ Apoptosis ❑ Necrosis  ATP ↓↓ NECROSIS osmotic regulation derangement (Ca-ATPase, oncotic necrosis Na-K ATPase) oncosis intracellular Ca+ ↑↑↑ ‘mitochondrial permeability transition pore’ ATP ↓↓↓↓ balloning karyolysis cell death ❑ischemic- hypoxic injury ❑oxidative stress leading to reactive oxygen species formation necrosis REPAIR AFTER INJURY REGENERATION FIBROGENESIS REGENERATION ❑ MATURE LIVER CELL proliferation ❑ STEM CELL/ PROGENITOR CELL proliferation and differantiation NORMAL CELL CYCLE Hepatocyte (survival time : 200-300 days) Santral ven Lobül “streaming liver” Duncan AW et al. Gastroenterol 2009;137:466–481.  Mature hepatocyte proliferation Any hyperperfusion states will affect pericentral areas due to the blood flow from the portal area towards the central area. This is one reason. And the second reason is that the hepatocytes that are located in the pericentral zone are old and cannot compensate the Partial hepatectomy Acute liver injury ▪ Hepatocyte ▪ Cholangiocyte Alison MR, et al. J Pathol 2009; 217: 282–298. ▪ Endothelial cell ▪ Mesenchymal cell regeneration  cell cycle arrest Alison MR, et al. J Pathol 2009; 217: 282–298. So I mentioned that hepatocytes are in G0 phase, stable state, but they can enter to the cell cycle with a stimuli. This stimuli comes from Kupfer cells. I mentioned that apoptotic cells are engulfed by Kupfer cells. And when they engulf Kupfer cells, 42:17 Cooper cells will trigger hepatocytes, go through the cell cycle, and regenerate. And this is the main mechanism. And what are the cytokines that are involved here? The two important ones are interleukin 6 and tumor necrosis factor alpha. Now first, the 42:48 The Kuffer cells, when they engulf an apoptotic cell or necrotic cell, secretes TNF-alpha. TNF-alpha auto-stimulates Kuffer cells, and afterj this auto-stimulation, interleukin-6 is secreted from the Kuffer cells, 43:12 And this interleukin-6 will bind to a receptor over the surface of the hepatocyte and will trigger the hepatocytes here to enter to the cell cycle. order for the hepatocyte to enter to the cell cycle, it must be normal. Injured hepatocyte cannot enter to the cell cycle. So this is why we see 44:03 regeneration of the liver in acute injuries by mature hepatocytes. This is not true for chronic injuries. In chronic injuries, the regeneration is by proliferation and differentiation of progenitor cells and stem cells. Because the cells in chronic diseases. ▪ Telomere shortening Experimental ▪ hepatocyte proliferation inhibition ▪ Chronic inflammation (chemical carcinogenesis) ▪ Growth factors ▪ hepatotoxin ▪ Reactive oxygen Chronic Liver Injury Massive liver necrosis Potantial Stem Cell Hepatic Progenitor Cell Proliferation and Differentiation Alison MR, et al. J Pathol 2009; 217: 282–298. Stem Cell / Progenitor Cell Embryonic stem cell → mature hepatocyte / cholangiocyte Stem Cell / Progenitor Cell Embryonic stem cell → mature hepatocyte / cholangiocyte ❑ Extrahepatic cell → transdedifferantiation  transit cell (peribiliary hepatocyte) oval cell intraductal cholangiocyte peribiliary (null) cell Liver Stem Cell Nishe Liver Stem Cell Nishe ❑ Oval cell – Now I mentioned that Kupfer cell secretes (Hering canal) interleukin-6 and interleukin-6 binds to a hepatocyte and the ❑ intraductal cholangiocyte hepatocyte in G0 phase enters the cell cycle. But in chronic disease, when the Kupfer cell secretes interleukin-6, if the cell is ❑ Peribiliary “null” cell injured and cannot regenerate, 05:21 then this cell will stimulate progenitor cells. So the progenitor cell stimulation is ❑ Transit cell by abnormal or injured hepatocyte. So hepatocyte, Peribiliary when it's interlocking six vines to the cell surface, hepatocyte says that I cannot regenerate, so it gives a signal to the progenitor cell Kuwahara R. The Hepatic Stem Cell Niche. Hepatology 2008;47:1994-2002.  hepatocyte remodeling chronic injury ‘streaming liver’ progenitor absent cell FIBROSIS present INACTIVE ACTIVE Biliary c-kit (+) proliferation CK 7, CK 19 EPCAM regenerative CD 133 glutamine nodules NCAM sentase Stem Cell / Progenitor Cell proliferation and differentiation REPAIR AFTER INJURY REGENERATION collagen accumulates within the liver and it interferes with the normal lobular arrangement and hepatocytes cannot remodel the liver when there is fibrosis in the background. FIBROGENESIS  Dynamic Process… HEPATIC FIBROGENESIS EXTRACELLULAR MATRIX INCREASE/CHANGE MICROVASCULAR REARRANGEMENT PARENCHYMAL CHANGE NORMAL LIVER ECM < %3 Type I, III collagen ▪ Portal tracts ▪ Perivenular ▪ Disse space Type IV collagen ▪ Disse space Extracellular Matrix (ECM)  laminin heparane sulphate fibronectin condroitin sulphate Fibrillary Non-fibrillary fibrillin syndecan I, III, V IV, VI tenascin decorin structural proteo- ▪ hyaluronan collagen elastin glycoprt. glycan protein glycoconjugate glycosaminoglycan Extracellular Matrix ▪ increase in density build up ▪ profile change ▪ microstructural structure change destruction ▪ change in distribution Excess Collagen Formation: Fibrogenesis leads to an overall increase in collagen deposition within the liver. The type of collagen changes: less common collagen types increase, altering the usual collagen profile. Changes in Extracellular Matrix (ECM): The ECM composition changes alongside the collagen, contributing to fibrosis. Normally confined to specific regions, collagen is now abnormally distributed. Abnormal Distribution of Collagen: Collagen is found in areas where it is typically absent, such as: ◦ Septa Formation: New fibrous bands connect: ▪ Two portal areas. ▪ Two central areas. ▪ A central area to a portal area. These septa disrupt the liver's normal architecture. Lobular and Sinusoidal Accumulation: Within lobules (functional units of the liver), collagen builds up between hepatocytes, specifically within the sinusoids. Aggregates of collagen appear in abnormal patterns. Functional Implications: These structural changes impede normal liver function, including blood flow and hepatocyte activity, contributing to liver dysfunction seen in fibrosis. FIBROTIC LIVER Type I, III collagen ▪ Lobular ▪ Sinusoidal ▪ Septa Extracellular Matrix Increase and Change FIBROTIC LIVER Type I, III collagen ▪ Lobular ▪ Sinusoidal ▪ Septa  epithelial- hepatocyte mesenchymal bone marrow transition (EMT) cell Metalloproteinase (MMP) ▪ Hepatic ▪ hepatocyte ▪ fibrocyte stellate ▪ cholangiocyte ▪ mesenchymal cell ▪ endothelial cell ▪ fibroblast cell Metalloproteinase inhibitors (TIMP) Extracellular Matrix Build-up and Destruction  autoimmune viral viral active stellate cell alcohol ASH inflammation apoptosis obesity extracellular matrix NAFLD reactive O2 species hepatic metabolic stellate cell drug/ (HSC) cholestase toxin MYOFIBROBLAST  I proliferation HSC chemotaxis N J stimulation Parenchymal U R PDGF Y retinoid loss HSC Active HSH PDGF activation MNC chemotaxis MCP-2 contractility increased fibrogenesis matrix degredation MYOFIBROBLAST  I proliferation HSC chemotaxis N J stimulation Parenchymal U R PDGF Y retinoid loss HSC Active HSH PDGF activation MNC chemotaxis reversion R E MCP-2 S O L contractility U S apoptosis I O N increased fibrogenesis matrix degredation MYOFIBROBLAST  fibroblasts in portal areas, in periductal areas and in the pericentral autoimmune viral viral active stellate cell alcohol ASH inflammation apoptosis obesity extracellular matrix NAFLD reactive O2 species hepatic metabolic stellate cell drug/ (HSC) cholestase toxin fibroblast ▪ portal ▪ periductal ▪ perivascular Fibrillin 1 MYOFIBROBLAST Elastin  only hepatic stem cells have capacity to initiate fibrogenesis false autoimmune viral viral active stellate cell alcohol ASH inflammation apoptosis obesity extracellular matrix NAFLD reactive O2 species hepatic metabolic stellate cell drug/ (HSC) cholestase toxin epithelial-mesenchymal cholangiocyte transition (EMT) hepatocyte bone marrow MYOFIBROBLAST cell fibrocyte mesenchymal cell monocyte  Fibrogenesis Pattern - Patogenesis NECROINFLAMMATION HEMODYNAMIC CHANGES  Chronic Biliary Diseases fibroblast portal periductal  Chronic Hepatitis (viral, autoimmune) Hepatic Stellate Cell Bridging Portal Fibroblasts Fibrosis  ALD, NAFLD Congestive Venopathy Sinusoidal - HSC Perisantral Fibroblast Pericentral Fibroblast  Dynamic Process… HEPATIC FIBROGENESIS EXTRACELLULAR MATRIX INCREASE/CHANGE MICROVASKULAR REARRANGEMENT PARENCHYMAL CHANGE Microvascular Vascular Rearrangement Changes Endothelial ❑ Angiogenesis Permiability ❑ Arterial / Venous Shunts Sinusoidal Blood Flow ▪ porto-systemic venous Vascular Thrombosis shunts Obstruction ▪ arteriovenous shunt Hepatic Fibrogenesis Sinusoids in the liver are unique capillaries that lack a basal membrane and have an endothelial lining with pores, facilitating the exchange of nutrients, oxygen, and waste between the blood and hepatocytes. During liver damage, Ito cells in the Disse space produce collagen, which accumulates and obstructs the endothelial pores. This leads to the formation of a basal membrane-like structure, known as capillarization, reducing nutrient and oxygen delivery to hepatocytes and impairing liver function. The collagen buildup also increases sinusoidal pressure, causing vascular thrombosis, obstruction of blood flow, and external compression. High pressure triggers angiogenesis, but blood flow from the portal area cannot enter the sinusoids properly, resulting in shunt formation, such as porto-central shunts and abnormal connections between the portal vein and hepatic artery. These changes contribute to portal hypertension, further exacerbating liver dysfunction and creating abnormal blood flow patterns. Endothelial Permiability ↓↓↓ Endothelial cell pore narrowing Disse space - basal membrane like material accumulation ❑ Type 1 collagen accumulation ❑ hepatocyte / sinusoid passage is decreased capillarization perfusion ↓↓ microvascular rearrangement resistance to blood flow↑↑↑ HSC → myofibroblast → contractility ↑ → SINUSOIDAL RESISTANCE Portal / vascular fibrosis → PRESINUSOIDAL VASCULAR RESISTANCE Perisantral fibrosis → POSTSINUSOIDAL VASCULAR RESISTANCE microvascular rearrangement Vascular Thrombosis / Obliteration cirrohotic patient → portal vein thrombosis (%0.6-1.6) veno-occlusive lesion (% 74) HSC → ADAMS 13 ↓→ vW factor degredation ↓ perfusion ↓↓ ❑ Parenchymal Loss Lesions (PLL) ❑ Nodulation microvascular rearrangement Neoangiogenesis Chronic inflammation → direct hepatocyte, Kupffer cells Fibrosis → HIPOXIA HSC, endothelial cell HIF-1 Portal myofibroblast angiogenic growth factors Arterial / Venous Shunts ❖ New vascular vessels - adhesion molecule expression increases inflammatuar response vascular changes  Arterial / Venous Shunts ❑ portal tract neoangiogenesis porto-systemic shunts PHT ❑ fibrous septa neoangiogenesis porto-santral shunts parenchymal bypass ischemic injury  Dynamic Process… HEPATIC FIBROGENESIS EXTRACELLULAR MATRIX INCREASE/CHANGE MICROVASKULAR REARRANGEMENT PARENCHYMAL CHANGE PARENCHYMAL Loss Lesions Portal/hepatic vein branch or sinusoidal obstruction → focal ischemic injury injured hepatocytes prior to fibrotic septa fibrotik septa Nodulation  Nodulation Regeneration Thickening of hepatocellular plates Pleomorfism Dysplastic changes Large cell Small cell Fibrosis – septation CIRRHOSIS Nodulation +/- regeneration DIFFUSE Vascular rearrangement ▪ arteriovenous shunts ▪ Portosystemic shunts ▪ sinusoidal capillarization Nodulation Micronodular < 3mm Macronodular > 3mm Alcoholic liver disease Viral hepatitis Metabolic disease Autoimmune hepatitis Venous outflow obstruction