1. School of Medicine, UCDHSC Disease & Defense Block February 5 th, 2007 Cell & Tissue Injury Francisco G. La Rosa, MD Assistant Professor, Department of Pathology University of Colorado at Denver Health Science Center, Denver, Colorado

2. Stages in the cellular response to stress and injurious stimuli

3. Human disease occurs because of injury to cells / tissueHuman disease occurs because of injury to cells / tissue Principle # 1

4. Most human disease results from injury to epithelium Principle # 2

5. Principle # 3 Injury to one tissue usually affects the adjacent or underlying tissue as wellInjury to one tissue usually affects the adjacent or underlying tissue as well

6. Cell injury produces morphologic changesCell injury produces morphologic changes Principle # 4

7. Pathologists classify and diagnose disease based upon the morphologic change induced by cell & tissue injury

8. Visual changes in the cell or tissue morphology is seen under microscopy when cells are stained.

11. Cell Injury Damage or alteration of one or more cellular components 1.Many types of injury are tissue-specific because of anatomic relationships and tissue tropism of chemical and infectious agents. 2.Cell injury perturbs cell physiology; the cell does not function at full capacity

12. Consequences of Injury 1.No long term effects- - the cell damage is repaired, the effects of the injury are reversible. 2.The cell “adapts” to the damaging stimulus. 3.The cell dies, undergoing necrosis. The damage is irreversible.

14. Cell Injury Produces: 1.Signs - abnormal physical findings - Objective 2.Symptoms - complaints experienced by the patient - Subjective

17. Basic Types of Tissues 1.Epithelium 2.Muscle (skeletal, smooth, cardiac) 3.Nerve (CNS, PNS) 4.Connective (bone, cartilage, soft tissue, adventitia, ligaments, blood and lymph, etc)

18. Epithelium: Arises from each of three germ layers 1.Cells cover external surfaces (skin); line internal closed cavities, secretory glands and tubes (GI, respiratory, GU tracts) that communicate with external surfaces 2.Liver, exocrine pancreas, parotid glands, thyroid, parathyroid, kidney epithelium 3.Vascular endothelium and mesothelium

19. Adaptation to injury 1. Hypertrophy - an increase in the size of the cell secondary to an increase in cell function. Increase in the number of mitochondria and ER, etc. 2. Hyperplasia - an increase in the number of cells of a tissue in response to a stimulus or injury. 3. Metaplasia - replacement of one type of tissue with another in response to an injury. 4. Atrophy - decrease in the size and functional capacity of the cell.

20. Hypertrophy versus Necrosis

24. Physiologic hypertrophy of the uterus during pregnancy. A, Gross appearance of a normal uterus (right) and a gravid uterus (removed for postpartum bleeding) (left). B, Small spindle-shaped uterine smooth muscle cells from a normal uterus (left) compared with large plump cells in gravid uterus (right).

26. Changes in the expression of selected genes and proteins during myocardial hypertrophy.

27. Diagram of columnar to squamous metaplasia. Metaplasia

28. Metaplasia

29. Cell Atrophy, Causes 1.Loss of blood supply or innervations 2.Loss of endocrine factors (ex. TSH) 3.Decrease in the workload 4.Aging, chronic illness

30. A, Atrophy of the brain in an 82-year-old male with atherosclerotic disease. Note that loss of brain substance narrows the gyri and widens the sulci. B, Normal brain of a 36-year-old male.

32. Outcomes from cell injury depend upon: 1.Type of injury 2.Severity of the injury 3.Duration of the injury 4.Type of cell being injured- Some cell types sustain injury better than others; some tissues (e.g. liver) have a capacity to regenerate

34. Reversible Cell Injury 1.Cell swelling – usually accompanies all types of injury. Results from an increase in water permeability. Reverses once membrane function is restored 2.Increase in extracellular metabolite -- Because of a biochemical derangement. i.e.: Increase in extracellular glycogen in diabetes

35. Reversible Cell Injury … 3.Fatty change in liver. Vacuoles of fat accumulate within the liver cell following many types of injury: alcohol intoxication, chronic illness, diabetes mellitus, etc. This may be due to: An increase in entry of free fatty acidsAn increase in entry of free fatty acids An increase in synthesis of free fatty acidsAn increase in synthesis of free fatty acids A decrease in fatty acid oxidationA decrease in fatty acid oxidation

36. Vulnerable Sites of the Cell 1.Cell membranes 2.Mitochondria 3.Endoplasmic reticulum 4.Nucleus

38. Cell Membranes why so easily injured? 1.Membrane is in contact with the external environment: - sustains “trauma” - extracellular oxidants, proteases, etc. 2.Requires a constant supply of ATP for normal function (ion pumps) 3.Lipid molecules in the membrane are easily oxidized and support oxidative chain reaction called lipid peroxidation

39. Cell Membrane Injury Epithelial cell proximal kidney tubule A. Normal B. Reversible ischemic changes C. Irreversible ischemic changes

40. Mitochondrial dysfunction in cell injury.

41. Mitochondrial Injury

42. Endoplasmic Reticulum Injury

43. Chaperones, such as heat shock proteins (Hsp), protect unfolded or partially folded protein from degradation and guide proteins into organelles.

44. Cell Death ApoptosisApoptosis NecrosisNecrosis

46. Apoptosis

47. Agarose gel electrophoresis of DNA extracted from culture cells A. Control B. Exposed to heat C. Massive necrosis

48. Morphology of Necrosis

49. Pyknosis Shrunken nucleus with dark stainingShrunken nucleus with dark staining Seen in a necrotic (dead) cellSeen in a necrotic (dead) cell

51. Karyorrhexis Fragmentation of pyknotic nucleusFragmentation of pyknotic nucleus

52. Karyolysis Extensive hydrolysis of pyknotic nucleus with loss of stainingExtensive hydrolysis of pyknotic nucleus with loss of staining Represents breakdown of the denatured chromatinRepresents breakdown of the denatured chromatin

53. Karyolysis

54. Coagulative Necrosis Dead cells remain as ghost-like remnants of their former selfDead cells remain as ghost-like remnants of their former self Classically seen in an MIClassically seen in an MI

58. Liquefactive Necrosis The dead cell undergoes extensive autolysis, caused by the release of lysosomal hydrolases (proteinases, DNases, RNases, lipases, etc.)The dead cell undergoes extensive autolysis, caused by the release of lysosomal hydrolases (proteinases, DNases, RNases, lipases, etc.) Seen classically in the spleen and brain following infarctionSeen classically in the spleen and brain following infarction

59. Liquefactive Necrosis

62. (A) Coagulative vs. (B) Liquefactive Necrosis

63. Caseous Necrosis (caseum - cheesy) Resembles cottage cheeseResembles cottage cheese Soft, friable, whitish-greySoft, friable, whitish-grey Present within infected tissuesPresent within infected tissues Seen in Tuberculosis (Mycobacterium tuberculosis)Seen in Tuberculosis (Mycobacterium tuberculosis)

64. Caseous Necrosis

66. Fat Necrosis Leakage of lipases from dead cells attack triglycerides in surrounding fat tissue and generate free fatty acids and calcium soapsLeakage of lipases from dead cells attack triglycerides in surrounding fat tissue and generate free fatty acids and calcium soaps These soaps have a chalky-white appearanceThese soaps have a chalky-white appearance Seen in the pancreas following acute inflammationSeen in the pancreas following acute inflammation

69. Causes of Cell and Tissue Injury

70. 1.Physical agents 2.Chemicals and drugs 3.Infectious pathogens 4.Immunologic reactions 5.Genetic mutations 6.Nutritional imbalances

71. Causes of Cell and Tissue Injury … 7.Hypoxia and Ischemia- cell injury resulting from inadequate levels of oxygen. Causes: A. Inadequate blood supply B. Lung disease C. Heart failure D. Shock

72. Hypoxia and Ischemia- Why So Important? All cells in the body require a continuous supply of oxygen in order to produce ATP via oxidative phosphorylation in mitochondria. ATP is absolutely critical for life.

73. Susceptibility of specific cells to ischemic injury Neurons: 3 to 5 min.Neurons: 3 to 5 min. Cardiac myocytes, hepatocytes, renal epithelium: 30 min. to 2 hr.Cardiac myocytes, hepatocytes, renal epithelium: 30 min. to 2 hr. Cells of soft tissue, skin, skeletal muscle: many hoursCells of soft tissue, skin, skeletal muscle: many hours

74. Functional and morphologic consequences of decreased intracellular ATP during cell injury.

75. Hypoxic Injury Reversible Changes 1.Decrease in extracellular ATP levels 2.Decrease in the Na pump: cell swelling 3.Increase in glycolysis, with a decrease in intracellular pH 4.Decrease in protein synthesis

76. 1.Activation of lysosomal enzymes: lysosomal enzymes are active at low pH, ca. pH 4-5 2.Degradation of DNA and protein 3.Influx of Ca ++, which activates many lipases and proteases Hypoxic Injury Irreversible Changes

78. Problem Ischemia Reperfusion Oxygen free radicals produce severe injury to cellular membranes, proteins, RNA and DNA.

79. Hypoxic cells are exposed to damage from oxygen radicals

80. 1.Hypoxic patients are given high levels of oxygen. This oxygen is toxic to the cells lining the alveolar spaces in the lung because the high [0 2 ] produces oxygen radicals

81. 2.Hypoxic tissues are often infiltrated with PMNs, which have enzymes & myleoperoxidases producing activated oxygen Hypoxic cells are exposed to damage from oxygen radicals

83. 3.Hypoxic tissues are often reperfused once the blood supply is restored. Xanthine oxidase, produced from proteolysis during hypoxia, generates free radicals when the 0 2 is brought back to normal levels. Hypoxic cells are exposed to damage from oxygen radicals

85. 0 2 - + 0 2 - + 2H + H 2 0 2 + 0 2 SOD GOOD / BAD REACTION

86. BAD REACTIONS 1. 2. 3. H 2 0 2 H. + 0H. (very reactive) FE ++ + H 2 0 2 FE +++ + 0H. + 0H - H 2 0 2 + 0 2 - 0H. + 0H - + 0 2 FENTON REACTION HABER-WEISS REACTION

87. GOOD REACTIONS 1. 2. GLUTATHIONE PEROXIDASE 2 H 2 0 2 0 2 + 2H 2 0 2 0H. + 2 GSH2 H 2 0 + GSSG H 2 0 2 + 2 GSH 2 H 2 0 + GSSG

89. BURNS

90. Burns, Outcomes Depend upon: 1.Total surface area burned 2.Depth of burn injury- partial vs full thickness 3.Whether lungs were injured 4.Whether treatment was prompt

96. Complications 1.Neurogenic shock, fluid loss 2.Infection-Pseudomonas, Staph 3.Hypermetabolic state 4.Anemia

98. Exertional Heat Stroke 1.Hot, dry skin 2.Usually lactic acidosis 3.May lead to ATN, DIC, multi organ failure

99. Classic Heat Stroke 1.Hot, dry skin 2.No lactic acidosis, but respiratory alkalosis 3.May lead to hypotension, coma, ATN, DIC very uncommon

100. Hypothermic Injury 1.May lead to coma, death. Metabolism in brain is inadequate. 2.Freezing of cells. This causes local concentrations of salt to markedly increase. 3.Poor perfusion of tissues- vasoconstriction, increased viscosity of blood.

101. The toes were involved in a frostbite injury. This is an example of "dry" gangrene in which there is mainly coagulative necrosis from the anoxic injury.

104. Electrical Injury Death from lightening occurs from heat production, disruption of neural, cardiac nerve transmission, cell damage from electroporation of salts across cell membranesDeath from lightening occurs from heat production, disruption of neural, cardiac nerve transmission, cell damage from electroporation of salts across cell membranes Death can occur from household levels of AC current, esp. if the skin is wet, or from respiratory arrest from tetany of chest musclesDeath can occur from household levels of AC current, esp. if the skin is wet, or from respiratory arrest from tetany of chest muscles

105. Summary All human disease occur because of cell/tissue injuryAll human disease occur because of cell/tissue injury Membranes-outer and mitochondrial are key targetsMembranes-outer and mitochondrial are key targets Many early steps are reversibleMany early steps are reversible Cell death follows going beyond a point of no return -drop in pH, rise in Ca 2+Cell death follows going beyond a point of no return -drop in pH, rise in Ca 2+