School of Medicine, School of Medicine, UCDHSCUCDHSCDisease & Defense BlockDisease & Defense BlockFebruary 5February 5thth, 2007, 2007

Cell & Tissue InjuryCell & Tissue Injury

Francisco G. La Rosa, MDAssistant Professor, Department of Pathology

University of Colorado at Denver Health Science Center, Denver, Colorado

Stages in the cellular response to stress and injurious stimuliStages in the cellular response to stress and injurious stimuli

• Human disease occurs because of Human disease occurs because of injury to cells / tissueinjury to cells / tissue

Principle # 1Principle # 1

• Most human disease results from injury to epithelium

Principle # 2Principle # 2

Principle # 3Principle # 3

• Injury to one tissue usually affects the Injury to one tissue usually affects the adjacent or underlying tissue as welladjacent or underlying tissue as well

• Cell injury produces morphologic changes Cell injury produces morphologic changes

Principle # 4Principle # 4

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

Cell InjuryCell Injury

Damage or alteration of one or more cellular Damage or alteration of one or more cellular componentscomponents

1.1. Many types of injury are tissue-specific Many types of injury are tissue-specific because of anatomic relationships and because of anatomic relationships and tissue tropism of chemical and tissue tropism of chemical and infectious agents.infectious agents.

2.2. Cell injury perturbs cell physiology; Cell injury perturbs cell physiology; the cell does not function at full the cell does not function at full capacitycapacity

Consequences of InjuryConsequences of Injury

1.1. No long term effects- - the cell damage is No long term effects- - the cell damage is repaired, the effects of the injury are repaired, the effects of the injury are reversible.reversible.

2.2. The cell “adapts” to the damaging stimulus.The cell “adapts” to the damaging stimulus.

3.3. The cell dies, undergoing necrosis. The The cell dies, undergoing necrosis. The damage is irreversible.damage is irreversible.

Cell Injury Produces:Cell Injury Produces:

1.1. SignsSigns - abnormal physical findings - - abnormal physical findings - ObjectiveObjective

2.2. SymptomsSymptoms - complaints experienced - complaints experienced by the patient - Subjectiveby the patient - Subjective

Basic Types of TissuesBasic Types of Tissues

1.1. EpitheliumEpithelium

2.2. Muscle (skeletal, smooth, cardiac)Muscle (skeletal, smooth, cardiac)

3.3. Nerve (CNS, PNS)Nerve (CNS, PNS)

4.4. Connective (bone, cartilage, soft Connective (bone, cartilage, soft tissue, adventitia, ligaments, blood tissue, adventitia, ligaments, blood and lymph, etc)and lymph, etc)

Epithelium:Epithelium:Arises from each of three germ layersArises from each of three germ layers

1.1. Cells cover external surfaces (skin); line Cells cover external surfaces (skin); line internal closed cavities, secretory glands internal closed cavities, secretory glands and tubes (GI, respiratory, GU tracts) and tubes (GI, respiratory, GU tracts) that communicate with external surfacesthat communicate with external surfaces

2.2. Liver, exocrine pancreas, parotid glands, Liver, exocrine pancreas, parotid glands, thyroid, parathyroid, kidney epitheliumthyroid, parathyroid, kidney epithelium

3.3. Vascular endothelium and mesotheliumVascular endothelium and mesothelium

Adaptation to injuryAdaptation to injury

1. 1. HypertrophyHypertrophy - an increase in the size of the cell - an increase in the size of the cell secondary to an increase in cell function. secondary to an increase in cell function. Increase in the number of mitochondria and ER, Increase in the number of mitochondria and ER, etc.etc. 2. 2. HyperplasiaHyperplasia - an increase in the number of cells - an increase in the number of cells of a tissue in response to a stimulus or injury. of a tissue in response to a stimulus or injury.

3. 3. MetaplasiaMetaplasia - replacement of one type of tissue - replacement of one type of tissue with another in response to an injury.with another in response to an injury.

4. 4. AtrophyAtrophy - decrease in the size and functional - decrease in the size and functional capacity of the cell. capacity of the cell.

Hypertrophy versus Necrosis Hypertrophy versus Necrosis

Physiologic hypertrophy of the uterus during pregnancy.Physiologic hypertrophy of the uterus during pregnancy.A, Gross appearance of a normal uterus (right) and a gravid uterus A, Gross appearance of a normal uterus (right) and a gravid uterus

(removed for postpartum bleeding) (left). B, Small spindle-shaped uterine (removed for postpartum bleeding) (left). B, Small spindle-shaped uterine smooth muscle cells from a normal uterus (left) compared with large smooth muscle cells from a normal uterus (left) compared with large

plump cells in gravid uterus (right).plump cells in gravid uterus (right).

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

Diagram of columnar to squamous metaplasia.Diagram of columnar to squamous metaplasia.

MetaplasiaMetaplasia

MetaplasiaMetaplasia

Cell Atrophy, CausesCell Atrophy, Causes

1.1. Loss of blood supply or innervationsLoss of blood supply or innervations

2.2. Loss of endocrine factors (ex. TSH)Loss of endocrine factors (ex. TSH)

3.3. Decrease in the workloadDecrease in the workload

4.4. Aging, chronic illnessAging, chronic illness

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

B, Normal brain of a 36-year-old male. B, Normal brain of a 36-year-old male.

Outcomes from cell injury depend upon:Outcomes from cell injury depend upon:

1.1. Type of injuryType of injury

2.2. Severity of the injurySeverity of the injury

3.3. Duration of the injuryDuration of the injury

4.4. Type of cell being injured- Some cell Type of cell being injured- Some cell types sustain injury better than others; types sustain injury better than others; some tissues (e.g. liver) have a some tissues (e.g. liver) have a capacity to regeneratecapacity to regenerate

Reversible Cell InjuryReversible Cell Injury

1.1. Cell swelling – usually accompanies all Cell swelling – usually accompanies all types of injury. Results from an increase types of injury. Results from an increase in water permeability. Reverses once in water permeability. Reverses once membrane function is restoredmembrane function is restored

2.2. Increase in extracellular metabolite -- Increase in extracellular metabolite -- Because of a biochemical derangement. Because of a biochemical derangement. i.e.: Increase in extracellular glycogen in i.e.: Increase in extracellular glycogen in diabetesdiabetes

Reversible Cell Injury …Reversible Cell Injury …

3.3. Fatty change in liver. Vacuoles of fat Fatty change in liver. Vacuoles of fat accumulate within the liver cell following accumulate within the liver cell following many types of injury: alcohol intoxication, many types of injury: alcohol intoxication, chronic illness, diabetes mellitus, etc.chronic illness, diabetes mellitus, etc.

This may be due to: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

Vulnerable Sites of the CellVulnerable Sites of the Cell

1.1. Cell membranesCell membranes

2.2. MitochondriaMitochondria

3.3. Endoplasmic reticulumEndoplasmic reticulum

4.4. NucleusNucleus

Cell MembranesCell Membranes why so easily injured?why so easily injured?

1.1. Membrane is in contact with the external Membrane is in contact with the external environment:environment: - sustains “trauma” - sustains “trauma” - extracellular oxidants, proteases, etc. - extracellular oxidants, proteases, etc.

2.2. Requires a constant supply of ATP for Requires a constant supply of ATP for normal function (ion pumps)normal function (ion pumps)

3.3. Lipid molecules in the membrane are Lipid molecules in the membrane are easily oxidized and support oxidative easily oxidized and support oxidative chain reaction called lipid peroxidationchain reaction called lipid peroxidation

Cell MembraneCell MembraneInjuryInjury

Epithelial cell proximal kidney tubuleEpithelial cell proximal kidney tubule

A.A. NormalNormalB.B. Reversible ischemic changesReversible ischemic changesC.C. Irreversible ischemic changesIrreversible ischemic changes

Mitochondrial dysfunction in cell injury.Mitochondrial dysfunction in cell injury.

Mitochondrial InjuryMitochondrial Injury

Endoplasmic Reticulum InjuryEndoplasmic Reticulum Injury

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

Cell DeathCell Death

• ApoptosisApoptosis

• NecrosisNecrosis

ApoptosisApoptosis

Agarose gel electrophoresis of Agarose gel electrophoresis of DNA extracted from culture cellsDNA extracted from culture cells

A. ControlA. Control

B. Exposed to heatB. Exposed to heat

C. Massive necrosisC. Massive necrosis

Morphology of NecrosisMorphology of Necrosis

PyknosisPyknosis

• Shrunken nucleus with dark stainingShrunken nucleus with dark staining

• Seen in a necrotic (dead) cellSeen in a necrotic (dead) cell

KaryorrhexisKaryorrhexis

• Fragmentation of pyknotic nucleusFragmentation of pyknotic nucleus

KaryolysisKaryolysis

• Extensive hydrolysis of pyknotic nucleus Extensive hydrolysis of pyknotic nucleus with loss of stainingwith loss of staining

• Represents breakdown of the denatured Represents breakdown of the denatured chromatinchromatin

Karyolysis

Coagulative NecrosisCoagulative Necrosis

• Dead cells remain as ghost-like remnants Dead cells remain as ghost-like remnants of their former selfof their former self

• Classically seen in an MIClassically seen in an MI

Liquefactive NecrosisLiquefactive Necrosis

• The dead cell undergoes extensive The dead cell undergoes extensive autolysis, caused by the release of autolysis, caused by the release of lysosomal hydrolases (proteinases, lysosomal hydrolases (proteinases, DNases, RNases, lipases, etc.)DNases, RNases, lipases, etc.)

• Seen classically in the spleen and Seen classically in the spleen and brain following infarctionbrain following infarction

Liquefactive NecrosisLiquefactive Necrosis

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

Caseous Necrosis Caseous Necrosis (caseum - cheesy)(caseum - cheesy)

• Resembles cottage cheeseResembles cottage cheese

• Soft, friable, whitish-greySoft, friable, whitish-grey

• Present within infected tissuesPresent within infected tissues

• Seen in Tuberculosis Seen in Tuberculosis ((Mycobacterium tuberculosisMycobacterium tuberculosis))

Caseous NecrosisCaseous Necrosis

Caseous NecrosisCaseous Necrosis

Fat NecrosisFat Necrosis

•Leakage of lipases from dead cells attack Leakage of lipases from dead cells attack triglycerides in surrounding fat tissue and triglycerides in surrounding fat tissue and generate free fatty acids and calcium generate free fatty acids and calcium soapssoaps

•These soaps have a chalky-white These soaps have a chalky-white appearanceappearance

•Seen in the pancreas following acute Seen in the pancreas following acute inflammationinflammation

Causes of Cell and Causes of Cell and Tissue InjuryTissue Injury

Causes of Cell and Tissue InjuryCauses of Cell and Tissue Injury

1.1. Physical agentsPhysical agents

2.2. Chemicals and drugsChemicals and drugs

3.3. Infectious pathogensInfectious pathogens

4.4. Immunologic reactionsImmunologic reactions

5.5. Genetic mutationsGenetic mutations

6.6. Nutritional imbalancesNutritional imbalances

Causes of Cell and Tissue Injury Causes of Cell and Tissue Injury ……

7.7. Hypoxia and Ischemia-Hypoxia and Ischemia-cell injury resulting from inadequate cell injury resulting from inadequate levels of oxygen.levels of oxygen.

Causes:Causes:A. Inadequate blood supplyA. Inadequate blood supplyB. Lung diseaseB. Lung diseaseC. Heart failureC. Heart failureD. ShockD. Shock

Hypoxia and Ischemia-Hypoxia and Ischemia- Why So Important?Why So Important?

All cells in the body require a All cells in the body require a continuous supply of oxygen in order continuous supply of oxygen in order to produce ATP via oxidative to produce ATP via oxidative phosphorylation in mitochondria.phosphorylation in mitochondria.

ATP is absolutely critical for life.ATP is absolutely critical for life.

Susceptibility of specific cells Susceptibility of specific cells to ischemic injuryto ischemic injury

• Neurons: Neurons: 3 to 5 min.3 to 5 min.

• Cardiac myocytes, hepatocytes, renal Cardiac myocytes, hepatocytes, renal epithelium: epithelium: 30 min. to 2 hr.30 min. to 2 hr.

• Cells of soft tissue, skin, skeletal Cells of soft tissue, skin, skeletal muscle: muscle: many hoursmany hours

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

Hypoxic InjuryHypoxic InjuryReversible ChangesReversible Changes

1.1. Decrease in extracellular ATP levelsDecrease in extracellular ATP levels

2.2. Decrease in the Na pump: cell swellingDecrease in the Na pump: cell swelling

3.3. Increase in glycolysis, with a decrease Increase in glycolysis, with a decrease in intracellular pHin intracellular pH

4.4. Decrease in protein synthesisDecrease in protein synthesis

1.1. Activation of lysosomal enzymes: Activation of lysosomal enzymes: lysosomal enzymes are active at low lysosomal enzymes are active at low pH, ca. pH 4-5pH, ca. pH 4-5

2.2. Degradation of DNA and proteinDegradation of DNA and protein

3.3. Influx of CaInflux of Ca++++, which activates many , which activates many lipases and proteaseslipases and proteases

Hypoxic InjuryHypoxic InjuryIrreversible ChangesIrreversible Changes

ProblemProblemIschemia ReperfusionIschemia Reperfusion

Oxygen free radicals produce severe Oxygen free radicals produce severe injury to cellular membranes, injury to cellular membranes, proteins, RNA and DNA.proteins, RNA and DNA.

Hypoxic cells are exposed to Hypoxic cells are exposed to damage from oxygen radicalsdamage from oxygen radicals

Hypoxic cells are exposed to Hypoxic cells are exposed to damage from oxygen radicalsdamage from oxygen radicals

1.1. Hypoxic patients are given high Hypoxic patients are given high levels of oxygen. This oxygen is levels of oxygen. This oxygen is toxic to the cells lining the alveolar toxic to the cells lining the alveolar spaces in the lung because the spaces in the lung because the high high [[0022]] produces oxygen radicals produces oxygen radicals

2.2. Hypoxic tissues are often infiltrated Hypoxic tissues are often infiltrated with PMNs, which have enzymes & with PMNs, which have enzymes & myleoperoxidases producing myleoperoxidases producing activated oxygenactivated oxygen

Hypoxic cells are exposed to Hypoxic cells are exposed to damage from oxygen radicalsdamage from oxygen radicals

3.3. Hypoxic tissues are often reperfused Hypoxic tissues are often reperfused once the blood supply is restored. once the blood supply is restored. Xanthine oxidase, produced from Xanthine oxidase, produced from proteolysis during hypoxia, generates proteolysis during hypoxia, generates free radicals when the 0free radicals when the 022 is brought is brought

back to normal levels.back to normal levels.

Hypoxic cells are exposed to Hypoxic cells are exposed to damage from oxygen radicalsdamage from oxygen radicals

0022-- + 0 + 022

-- + 2H + 2H++ HH220022 + 0 + 022

SODSOD

GOOD / BAD REACTIONGOOD / BAD REACTION

BAD REACTIONSBAD REACTIONS

1.

2.

3.

HH220022 H H.. + 0H + 0H.. (very reactive)(very reactive)

FEFE++++ + H + H220022 FE FE ++++++ + 0H + 0H.. + +

0H0H--

HH220022 + 0 + 022-- 0H 0H.. + 0H + 0H-- + 0 + 022

FENTON REACTIONFENTON REACTION

HABER-WEISS REACTIONHABER-WEISS REACTION

GOOD REACTIONSGOOD REACTIONS

1.

2.

GLUTATHIONE PEROXIDASEGLUTATHIONE PEROXIDASE

2 H202 02 + 2H20

2 0H. + 2 GSH 2 H20 + GSSGH202 + 2 GSH 2 H20 + GSSG

BURNSBURNS

Burns, OutcomesBurns, Outcomes

Depend upon:Depend upon:

1.1. Total surface area burnedTotal surface area burned

2.2. Depth of burn injury- partial vs Depth of burn injury- partial vs full thicknessfull thickness

3.3. Whether lungs were injuredWhether lungs were injured

4.4. Whether treatment was promptWhether treatment was prompt

ComplicationsComplications

1.1. Neurogenic shock, fluid lossNeurogenic shock, fluid loss

2.2. Infection-Pseudomonas, StaphInfection-Pseudomonas, Staph

3.3. Hypermetabolic stateHypermetabolic state

4.4. AnemiaAnemia

Exertional Heat StrokeExertional Heat Stroke

1.1. Hot, dry skinHot, dry skin

2.2. Usually lactic acidosisUsually lactic acidosis

3.3. May lead to ATN, DIC, multi organ May lead to ATN, DIC, multi organ failurefailure

Classic Heat StrokeClassic Heat Stroke

1.1. Hot, dry skinHot, dry skin

2.2. No lactic acidosis, but respiratory No lactic acidosis, but respiratory alkalosisalkalosis

3.3. May lead to hypotension, coma, ATN, May lead to hypotension, coma, ATN, DIC very uncommonDIC very uncommon

Hypothermic InjuryHypothermic Injury

1.1. May lead to coma, death. Metabolism May lead to coma, death. Metabolism in brain is inadequate.in brain is inadequate.

2.2. Freezing of cells. This causes local Freezing of cells. This causes local concentrations of salt to markedly concentrations of salt to markedly increase.increase.

3.3. Poor perfusion of tissues-Poor perfusion of tissues-vasoconstriction, increased vasoconstriction, increased viscosity of blood.viscosity of blood.

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

Electrical InjuryElectrical Injury

• Death from lightening occurs from heat Death from lightening occurs from heat production, disruption of neural, cardiac production, disruption of neural, cardiac nerve transmission, cell damage from nerve transmission, cell damage from electroporation of salts across cell electroporation of salts across cell membranesmembranes

• Death can occur from household levels of AC Death can occur from household levels of AC current, esp. if the skin is wet, or from current, esp. if the skin is wet, or from respiratory arrest from tetany of chest respiratory arrest from tetany of chest musclesmuscles

SummarySummary• All human disease occur because of All human disease occur because of

cell/tissue injurycell/tissue injury

• Membranes-outer and mitochondrial are Membranes-outer and mitochondrial are key targetskey targets

• Many early steps are reversibleMany early steps are reversible

• Cell death follows going beyond a point Cell death follows going beyond a point of no return -drop in pH, rise in Caof no return -drop in pH, rise in Ca2+2+