Cellular Pathology Outline 1. Necrosis 2. Apoptosis 3. Pathologic calcification 4. Cellular aging Reading Assignment: Robbins pp. 15 - 23; 42 - 48

Necrosis Mechanism Robbins Fig. 1-3

Necrosis Cellular Morphology 1. Nuclear changes - Pyknosis (shrinking) - Karyorrhexis (fragmentation) - Karyolysis (dissolution) 2. Mitochondrial changes - Dense bodies 3. Cytoplasmic changes - Increased eosinophilia

Necrosis Pyknosis & Karyolysis - Micro Pyknosis is the condensation or darkening of nuclei, and is reversible.

Necrosis Pyknosis - EM EM appearance.

Necrosis Karyorrhexis - EM Karyorhexis is the dissolution of the nucleus by DNAse and RNAse. It is irreversible.

Necrosis Karyolysis - EM Karyolysis is the further degradation of DNA and RNA, as the nucleus disappears under the light microscope. It is irreversible.

Necrosis Mitochondrial Dense Bodies - EM Dense (calcium) deposits in the mitochondria are characteristic of cell death at the EM level.

Cytoplasmic Eosinophilia - Micro Necrosis Cytoplasmic Eosinophilia - Micro Robbins Fig. 1-12

Necrosis Histologic Types 1. Coagulative 2. Liquefactive 3. Fat 4. Caseous 5. Fibrinoid

Coagulative Necrosis Characteristics 1. Organs - Heart and kidney 2. Histology - Preservation of cell outlines - Loss of nuclei

Coagulative Necrosis Heart - Gross Hemorrhage – the earliest gross sign of acute myocardial infarction.

Coagulative Necrosis Heart - Micro Robbins Fig. 1-12

Coagulative Necrosis Coronary Artery - Gross Thrombus in a coronary artery.

Atheroma Coronary Artery - Micro Coronary artery 50% occluded by a “soft” atherosclerotic plaque. These are the most dangerous kind.

Thrombotic Atheroma Coronary Artery - Micro Thrombosis of a coronary artery.

Coagulative Necrosis Kidney - Gross Note wedge-shaped “pale” infarct. The underlying microscopic structure is preserved, at least for a short time, until repair (scarring) takes place.

Coagulative Necrosis Kidney - Micro Note preservation of structure.

Coagulative Necrosis Foot - Gross Gangrene of the foot – amputation specimen from surgical pathology.

Liquefactive Necrosis Characteristics 1. Organs - Brain (ischemic injury) - Pyogenic (pus forming) infection of any organ 2. Histology - Loss of cell outlines - Loss of nuclei - Neutrophil infiltration (if pyogenic)

Liquefactive Necrosis Lung - Gross Note the expansion of the upper lobe, due to lobar pneumnonia (Polymorphonuclear cells within the alveolar spaces. Note also that a portion of the lung has dissolved (liquifactive necrosis), forming an abscess. (A space formed within an organ, due to a collection of pus – liquifactive necrosis).

Liquefactive necrosis Lung - Gross Numerous microabscesses are seen in this lung. These are usually seen with virulent organisms, like Staphylococcus aureus.

Liquefactive necrosis Lung - Micro Lung, abscess with collection of pus and bacteria (blue material at upper left).

Fat Necrosis Characteristics 1. Organs - Adipose tissue (Pancreas, mesentery, breast) 2. Histology - Shadowy outlines of fat cells - Loss of nuclei - Basophilic calcium deposits (dystrophic calcification)

Fat Necrosis Pancreas - Gross Calcium soaps in the pancreas, gross.

Fat Necrosis Pancreas - Micro The outline of the dead fat cells can often be seen (top of picture). The calcium soaps stain blue with standard H&E stains (bottom of picture).

Fat Necrosis Saponification Reaction Triglyceride – (fat) R-C-O-CH2 O R-C-O-CH + lipase + Ca++ = (3) RCOO-Ca++ (soap) O R-C-O-CH2 O

Caseous Necrosis Characteristics 1. Organs - Mycobacterial or fungal infection (any organ) 2. Histology - Large granuloma (histiocytes) - Central region amorphous granular debris - Loss of cell outlines - Loss of nuclei

Caseous Necrosis Lung - Gross

Caseous Necrosis Lung - Micro

Fibrinoid Necrosis Characteristics 1. Organs - Blood vessels (acute vasculitis, malignant hypertension) 2. Histology - Increased eosinophilia of vessel wall - Caused by infiltration of plasma proteins - A misnomer (not true necrosis)

Fibrinoid Necrosis Arteriole - Micro Renal glomerulus – influx of fibrin into the afferent arteriole, due, in this case, to malignant hypertension.

Reperfusion Necrosis Characteristics 1. Definition - Cell death occurring after reperfusion of ischemic organs 2. Organs - Heart and brain 3. Mechanism - Acute inflammation - Oxygen free radicals

Reperfusion Necrosis Heart - Micro Infiltration by polymorphs occurs from 10-48 hours post MI.

Apoptosis Robbins Fig. 1-16

Apoptosis Mechanism Robbins Fig. 1-20

Apoptosis Physiologic Processes 1. Embryogenesis 2. Menstruation 3. Menopause 4. Intestinal homeostasis 5. Immune tolerance

Apoptosis Pathologic Processes 1. Acute inflammation 2. Organ atrophy 3. Neoplasia 4. Graft rejection 5. Viral hepatitis

Apoptosis Morphology 1. Cell shrinkage 2. Chromatin peripheralization 3. Isolated cell involvement 4. Absence of inflammation

Apoptosis Chromatin Peripheralization Robbins Fig. 1-17

Apoptosis Light Microscopy Skin Liver Robbins Fig. 1-18

Pathologic Calcification Types 1. Dystrophic calcification - Occurs in nonviable tissue 2. Metastatic calcification - Occurs in viable tissue - Caused by hypercalcemia or hyperphosphatemia

Dystrophic Calcification Examples 1. Necrotic tissue - fat, coagulative, liquefactive, caseous 2. Atherosclerosis - Central necrotic core 3. Damaged or aging heart valves

Dystrophic Calcification Aortic Valve - Gross Robbins Fig. 2-13

Dystrophic Calcification Mechanism Pathologic Microvesicles Robbins Fig. 2-14

Metastatic Calcification Mechanisms 1. Increased PTH secretion - parathyroid tumor - ectopic PTH secretion 2. Bone destruction - tumors - Paget’s disease - immobilization 3. Vitamin D disorders - vitamin D toxicity - sarcoidosis 4. Renal failure - hyperphosphatemia

Metastatic Calcification Anatomic Sites 1. Lungs - respiratory failure 2. Kidneys - nephrocalcinosis, kidney failure 3. Stomach 4. Arteries 5. Pulmonary veins

Metastatic Calcification Lung - Micro Von Kossa Stain

Cellular Aging Mitotic Activity is Limited Robbins Fig. 2-15 Dice JF: Physiol Rev 73: 150, 1993

Cellular Aging Mechanisms 1. Telomere shortening - telomerase 2. Clock gene activation - clk-1 gene in C. elegans 3. Oxygen free radical damage 4. Nonenzymatic protein glycation

Cellular Aging Telomere Elongation TTAGGG Repeat Robbins Fig. 2-16

Cellular Aging Telomere - Telomerase Hypothesis Robbins Fig. 2-17

Cellular Aging Biochemical Changes 1. Increased lipid oxidation 2. Increased glycation end products - protein cross-linking 3. Abnormally folded proteins

Cellular Aging Functional Changes 1. Reduced mitochondrial function - oxidative phosphorylation 2. Reduced protein synthesis 3. Reduced nutrient uptake 4. Reduced DNA repair

Cellular Aging Morphologic Changes 1. Vacuolated mitochondria 2. Decreased endoplasmic reticulum 3. Distorted Golgi apparatus 4. Increased lipofuscin pigment

Cellular Aging Lipofuscin Pigment Cardiac Myocyte - Electron dense granules in lysosomes - Perinuclear location Robbins Fig. 2-11

Cellular Pathology Summary 1. Necrosis - one type of cell death - many histologic subtypes 2. Apoptosis - second type of cell death - physiologic and pathologic causes 3. Pathologic calcification - dystrophic and metastatic 4. Cellular aging - mechanisms and morphology