Cell Injury, Cell Death and Adaptations - PDF

CELL INJURY, CELL DEATH AND ADAPTATIONS 3 Manar A. AbdelMageed, DVM, PhD  INTRACELLULAR AND EXTRACELLULAR ACCUMULATIONS ENDOGENOUS INTRACELLULAR EXOGENOUS EXTRACELLULAR W...

CELL INJURY, CELL DEATH AND ADAPTATIONS 3 Manar A. AbdelMageed, DVM, PhD  INTRACELLULAR AND EXTRACELLULAR ACCUMULATIONS ENDOGENOUS INTRACELLULAR EXOGENOUS EXTRACELLULAR Water Protein Lipid Carbohydrate Mineral Pigment  FATTY CHANGE Aka: STEATOSIS - LIPIDOSIS Is a biochemical and morphological change characterized by accumulation of neutral fat (triglycerides) within parenchymal cells (liver – kidney – heart – skeletal muscles) Most common is hepatic steatosis (primary Neutral fat (TG) organ of fat metabolism) Intracellular accumulation – Reversible Phospholipid  FATTY CHANGE CAUSES AND PATHOGENESIS Imbalance between fatty acids intake, catabolism and secretion from the liver. 1. Excessive delivery of free fatty acids (FFAs) from fat stores or diet. 2. Decreased oxidation or use of FFAs. 3. Impaired synthesis of apoprotein. 4. Impaired combination of protein and triglycerides to form lipoproteins. 5. Impaired release of lipoproteins from hepatocytes.  FATTY CHANGE CAUSES AND PATHOGENESIS Imbalance between fatty acids intake, catabolism and secretion from the liver. In summary steatosis happens due to: 1. Increased uptake by the cell 2. Decreased catabolism by the cell 3. Decreased secretion by the cell  FATTY CHANGE Macroscopic picture: Liver is enlarged, yellow in color, with rounded borders and tense capsule. On cross section, greasy texture. Will float in formalin (or water). Horse, liver. Hepatic lipidosis  FATTY CHANGE The liver floats in formalin The liver is diffusely pale yellow with rounded edges.  FATTY CHANGE Macroscopic picture: Heart has a characteristic Tabby-cat or Tigeroid appearance. Yellow streaks alternating with the normal brown muscle fibers.  FATTY CHANGE Microscopically: 1. The hepatocytes are vacuolated. The vacuoles are different in size but have sharp discrete borders (microsteatosis) 2. These vacuoles may coalesce to form large vacuoles (macrosteatosis) displacing the nuclei of the hepatic cells to the periphery giving the characteristic signet-ring appearance where the cell resembles adipocytes. FATTY CHANGE  FATTY CHANGE H&E Special stains of neutral fat Sudan III Sudan IV Oil red O Osmic acid  FATTY CHANGE Feline fatty liver syndrome Anorexia (esp. obese cats) Mobilization of fat stores Lipid processing overwhelmed Fatty liver Pregnancy toxemia/ketosis (cattle – sheep and goat) Late pregnancy – early lactation in over- conditioned animals Feed intake inadequate to meet nutritional demand Fat stores are mobilized Fatty Liver  OTHER FORMS OF LIPID ACCUMULATIONS Fatty infiltration: Is an increase in the number and/or volume of adipocytes in the interstitium of an organ or tissue (e.g: cardiac and skeletal ms.). Obesity Atrophied tissues (such as skeletal ms, thymus and thyroid gland) What is the difference between fatty change (steatosis) and fatty Overall pale muscle with pale streaks from collagen and fat infiltration infiltration, denervation atrophy, equine motor neuron disease, horse. Equine motor neuron disease muscle (right) compared Fatty change à intracellular accumulation of neutral fat with normal muscle (left). Fatty infiltration à extracellular deposition of adipocytes  INTRACELLULAR AND EXTRACELLULAR ACCUMULATIONS ENDOGENOUS INTRACELLULAR EXOGENOUS EXTRACELLULAR Water Protein Lipid Carbohydrate Mineral Pigment  ACCUMULATION OF GLYCOGEN Intracellular excessive accumulation of Glycogen In the liver in cases of Hyperadrenocorticism Glycogen storage disease Congenital absence of glucose 6- phosphatase which is necessary for the breakdown of glycogen into glucose Macroscopically: Swollen and pale brown liver Microscopically : Intracellular vacuoles less sharply defined than the lipid vacuoles in steatosis.  ACCUMULATION OF GLYCOGEN Intracellular excessive accumulation of Glycogen In the liver in cases of Hyperadrenocorticism Glycogen storage disease Congenital absence of glucose 6- phosphatase which is necessary for the breakdown of glycogen into glucose Macroscopically: Swollen and pale brown liver Microscopically : Intracellular vacuoles less sharply defined than the lipid vacuoles in steatosis.  ACCUMULATION OF GLYCOGEN Intracellular excessive accumulation of Glycogen Special stain of glycogen and what color does it stain glycogen Periodic acid- Schiff (PAS) stains glycogen red Hemotoxylin and eosin (H&E) stain Periodic acid- Schiff (PAS) stain showing showing enlarged and distended increased glycogen content (red) in the hepatocytes with clear cytoplasm cytoplasm of hepatocytes.  INTRACELLULAR AND EXTRACELLULAR ACCUMULATIONS ENDOGENOUS INTRACELLULAR EXOGENOUS EXTRACELLULAR Water Protein Lipid Carbohydrate Mineral Pigment  ACCUMULATION OF PROTEIN Proteins are eosinophilic The term hyaline is used to describe a homogeneous, eosinophilic, and translucent (glassy) appearance to a cellular or extracellular substance. Intracellular accumulations of Extracellular accumulations of proteins proteins are described in different physiologic and pathologic conditions including: Hyaline cast Hyaline membranes (ARDS) Hyaline droplets (kidney - intestine) Amyloid Russell bodies (plasma cells) Gout (Uric acids!)  ACCUMULATION OF PROTEIN Hyaline droplets (Reabsorption droplets in the renal proximal tubules) In cases of glomerular diseases à protein leakage from the glomeruli à reabsorbed into vesicles in the cytoplasm à appear as pink hyaline material inside the proximal renal tubular epithelium Reversible à if the proteinuria diminished à the protein droplet are metabolized and disappear. Hyaline droplets are also seen in the intestinal epithelium of neonates ingesting colostrum.  ACCUMULATION OF PROTEIN Hyaline droplets (Reabsorption droplets in the renal proximal tubules) In cases of glomerular diseases à protein leakage from the glomeruli à reabsorbed into vesicles in the cytoplasm à appear as pink hyaline material inside the proximal renal tubular epithelium Reversible à if the proteinuria diminished à the protein droplet are metabolized and disappear. Hyaline droplets are also seen in the intestinal epithelium of neonates ingesting colostrum.  ACCUMULATION OF PROTEIN Russell bodies (Mott cells) In plasma cells actively synthesizing immunoglobulins Endoplasmic reticulum (ER) is hugely distended with homogenously eosinophilic inclusions (immunoglobulin-containing protein) Seen in autoimmune diseases and plasma cell disorders.  ACCUMULATION OF PROTEIN Proteins are eosinophilic The term hyaline is used to describe a homogeneous, eosinophilic, and translucent (glassy) appearance to a cellular or extracellular substance. Intracellular accumulations of Extracellular accumulations of proteins proteins are described in different physiologic and pathologic conditions including: Hyaline cast Hyaline membranes (ARDS) Hyaline droplets (kidney - intestine) Amyloid Russell bodies (plasma cells) Gout (Uric acids!)  ACCUMULATION OF PROTEIN Hyaline cast In cases of glomerular diseases à protein (albumin) leakage from the glomeruli à exceeds the tubular epithelial ability of reabsorption à forms a cast in the tubular lumen.  ACCUMULATION OF PROTEIN Hyaline membranes Hyalinized alveolar walls Diffuse alveolar damage ( Acute respiratory distress syndrome) as in COVID Alveolar hyaline membranes consist of fibrin-rich edema fluid mixed with the remnants of necrotic epithelial cells  AMYLOIDOSIS Amyloid = starch like Kidney section stained with lugol’s iodine followed by diluted sulfuric acid à purple dots at amyloid depositions Rudolf Virchow (1821-1902)  AMYLOIDOSIS Amyloidosis is a protein misfolding disorder characterized by extracellular deposition of an insoluble non- functional fibrillar protein in affected tissues. Biochemically, these proteins are rich in β-pleated sheet conformation. β-pleated sheet Misfolded proteins conformation are normally renders the degraded protein less soluble In Amyloidosis à the protein is misfolded or only partially folded and it’s not degraded due to some faulty genes or other mechanism.  AMYLOIDOSIS Amyloidosis can be classified biochemically according to the identity of the precursor peptide into: AL (Amyloid light chain) protein: The precursor is immunoglobulin light chain produced by abnormal plasma cells. This is considered primary amyloidosis and can be localized or systemic. Seen in plasma cell disorders and neoplastic transformation e.g: multiple myeloma and B cell lymphoma  AMYLOIDOSIS Amyloidosis can be classified biochemically according to the identity of the precursor peptide into: AA (Amyloid associated) protein: The precursor is serum amyloid associated (SAA) protein; an acute phase protein produced by the liver in response to inflammatory stimuli. This is considered secondary amyloidosis (secondary to prolonged production of SAA in chronic inflammation) and is usually systemic/ generalized with the most affected organs being the kidneys, liver, and the white pulps of the spleen.  AMYLOIDOSIS Amyloidosis can be classified biochemically according to the identity of the precursor peptide into: A𝞫 (Amyloid beta) protein: The precursor is a much larger transmembrane glycoprotein called amyloid precursor protein (APP) Seen in the in the cerebral cortex of aged dogs with canine cognitive disorder and in human beings with Alzheimer’s disease.  AMYLOIDOSIS Amyloidosis can be classified biochemically according to the identity of the precursor peptide into: Amyloid light chain Amyloid Associated protein Amyloid beta (AL) (AA) protein (A𝞫) precursor immunoglobulin light serum amyloid associated (SAA) large trans-membrane chain produced by protein; an acute phase protein glycoprotein called abnormal plasma cells. produced by the liver in response amyloid precursor to inflammatory stimuli. protein (APP) Cause Primary in plasma cell Secondary to chronic canine cognitive disorders inflammatory diseases disorders similar to Alzheimer’s. Distribution Localized or systemic Systemic (mainly liver, kidneys, Localized spleen)  AMYLOIDOSIS Macroscopically: Amyloid appears as yellow, waxy, coalescing nodular or amorphous deposits. If stained with iodine à red-brown deposits. If diluted sulfuric acid is subsequently added à purple dots. Right half of the kidney was treated with Lugol’s iodine to demonstrate the amyloidotic glomeruli, resulting in red discoloration of the cortex and pinpoint brown deposits  AMYLOIDOSIS Sago spleen Bacon spleen Focal amyloidosis Splenic follicles (white pulp) Diffuse amyloidosis (White pulp and red pulp)  AMYLOIDOSIS Sago spleen Bacon spleen Focal amyloidosis Splenic follicles (white pulp) Diffuse amyloidosis (White pulp and red pulp) Focal amyloidosis (sago spleen) à Amyloid Types of deposited in white pulp only amyloidosis in the Diffuse amyloidosis (bacon spleen) à Amyloid spleen deposited in white pulp and red pulp  AMYLOIDOSIS Microscopically: 1. Extracellular deposition of homogeneous to fibrillar, pale eosinophilic substance. 2. Mostly in the subendothelial loose connective tissues such as in the space of Disse along the sinusoids in liver and the glomerular tufts in kidneys 3. Pressure atrophy of the surrounding parenchyma 4. Stained orange red with Congo-red stain 5. Congo-red stained sections under polarized light à apple-green birefringence 6. Potassium permanganate pretreatment diminishes the congophilia and the apple-green birefringence of AA proteins and not the AL proteins  AMYLOIDOSIS Kidney à amyloid deposited H&E stain mainly in glomerular tufts  AMYLOIDOSIS Orange-red Under polarized light à apple green Congo-red birefringence  AMYLOIDOSIS Amyloidosis, Liver, H&E Amyloidosis, Liver, Congo red Liver à amyloid deposited mainly in Space of Disse (loose connective tissue below the sinusoids)  ACCUMULATION OF PROTEIN Proteins are eosinophilic The term hyaline is used to describe a homogeneous, eosinophilic, and translucent (glassy) appearance to a cellular or extracellular substance. Intracellular accumulations of Extracellular accumulations of proteins proteins are described in different physiologic and pathologic conditions including: Hyaline cast Hyaline membranes (ARDS) Hyaline droplets (kidney - intestine) Amyloid Russell bodies (plasma cells) Gout (Uric acids!)  GOUT Gout is deposition of uric acid crystals (mostly as sodium urates) in tissues. Occurs in birds, reptiles and primates. Not in domestic animals. There are two forms of gout: Articular gout: Common in humans and rare in birds and reptiles Visceral gout: Common in birds. Uric acid is the end-product of purine metabolism.  GOUT Articular gout: Common in humans and rare in birds and reptiles. Urates are deposited on the articular surface of joints à Grossly detectable chalky substance called “Tophi” and the affected joints are swollen and inflamed. Microscopically à the urate crystals appear as acicular spaces (crystals) surrounded by inflammatory cells.  GOUT Gout is not reported in domestic animals because they have uricase enzyme (liver) which converts uric acid into allantoin which is then readily excreted in urine.  GOUT Visceral gout: Common in birds. Urates are deposited on the serosal membranes (esp. pericardium) and in the ureters and renal tubules of birds à grayish white chalky deposits Microscopically à the urate crystals appear as acicular spaces (crystals) surrounded by inflammatory cells. Seen in cases of à high protein diet, renal diseases and vit A def.  GOUT Visceral gout: Common in birds. Urate crystals appear as acicular spaces surrounded by neutrophils, macrophages and giant cells  GOUT Visceral gout: Common in birds. Urate crystals appear as acicular spaces surrounded by neutrophils, macrophages and giant cells GOUT  INTRACELLULAR AND EXTRACELLULAR ACCUMULATIONS ENDOGENOUS INTRACELLULAR EXOGENOUS EXTRACELLULAR Water Protein Lipid Carbohydrate Mineral Pigment  PATHOLOGIC CALCIFICATION Pathologic calcification: Is deposition of calcium salts (usually as ca phosphate or calcium carbonate) in soft tissues. (Where calcium is NOT normally deposited) Two main types Dystrophic calcification Metastatic calcification Local calcification General/systemic calcification Calcium metabolism is normal Calcium metabolism disturbance Calcium level in blood is normal Hypercalcemia ( ↑Ca2+ in blood) Tissue is dead Tissue is normal  PATHOLOGIC CALCIFICATION Dystrophic calcification Occur in areas of necrosis Calcium deposition is an expected sequel to cell death. Loss of Co2 tension due to absence of cellular respiration à alkaline medium à favors deposition of calcium  PATHOLOGIC CALCIFICATION Dystrophic calcification examples Skeletal or myocardial necrosis as a result of Vit E or selenium def. in ruminants à White ms. disease. Remember Zenker’s necrosis? Caseated centers of granulomas (e.g: Tuberculoid granuloma – parasitic granuloma) What type of necrosis do you see in T.B  PATHOLOGIC CALCIFICATION Metastatic calcification Disturbance in calcium metabolism ( ↑Ca2+ in blood) Occur in normal tissues, most commonly in acid secreting and excreting organs; where the alkaline pH of the tissue favors deposition of calcium 1. Stomach (Hydrochloric acid) 2. Lungs (Carbonic acid) 3. Kidneys (Hippuric acid)  PATHOLOGIC CALCIFICATION Metastatic calcification Disturbance in calcium metabolism ( ↑Ca2+ in blood) The plasma level of calcium is normally controlled by: 1. Parathyroid hormone (parathyroid gland): causes hypercalcemia through bone resorption. 2. Calcitonin (parafollicular cells of the thyroid glands): causes hypocalcemia by deposition of ca in bone. 3. Vitamin D helps in the absorption of calcium from the intestine. NB: Normal blood calcium is 10 mg/dl.  PATHOLOGIC CALCIFICATION Metastatic calcification Disturbance in calcium metabolism ( ↑Ca2+ in blood) Metastatic calcification is seen in 4 main conditions: 1. Increased secretion of the parathyroid hormone in parathyroid neoplasms. 2. Hypervitaminosis D à ↑ Ca absorption from the intestine. 3. Resorption of bone à ↑ mobilization from bone. 4. Renal failure à ↑ parathyroid hormone secretion.  PATHOLOGIC CALCIFICATION Macroscopically: If calcification is extensive, it appears grossly as chalky white deposits with a brittle or gritty texture or sound when cut with a knife.  PATHOLOGIC CALCIFICATION Microscopically: Calcium salts appear as H&E amorphous basophilic granules when stained with H&E Von Kossa stains Ca salts black Von Kossa  PATHOLOGIC CALCIFICATION Microscopically: Uremic Calcification, Stomach, Dog. A band of calcification is in the middle of the gastric mucosa. The calcium salts are basophilic (stained blue with hematoxylin). H&E stain. The calcium salts are black with the von Kossa  INTRACELLULAR AND EXTRACELLULAR ACCUMULATIONS ENDOGENOUS INTRACELLULAR EXOGENOUS EXTRACELLULAR Water Protein Lipid Carbohydrate Mineral Pigment