1. Necrosis and apoptosis
Dr. Maha Arafah
Assistant Professor
Department of Pathology
King Khalid University Hospital and King Saud University
Sunday, Oct 10, 2010
10:00 to 11:00 am
Cell injury L2

2. Objectives Define necrosis and apoptosis
List the different conditions associated with apoptosis, its morphology and its mechanism
List the different types of necrosis, examples of each and its features
Know the difference between apoptosis and necrosis

3. Objectives Define necrosis and apoptosis
List the different conditions associated with apoptosis, its morphology and its mechanism
List the different types of necrosis, examples of each and its features
Know the difference between apoptosis and necrosis

4. Cell Death Death of cells occurs in two ways:
Necrosis--changes produced by enzymatic digestion ofcells after irreversible injury
Apoptosis--vital process that helps eliminate unwanted cells--an internally programmed series of events effected by dedicated gene products
Autolysis
Autolysis is the death of individual cells and tissues after the death of the whole organism.
The cells are degraded by the post-mortem release of digestive enzymes from the cytoplasmic lysosomes.

5. Objectives Define necrosis and apoptosis
List the different conditions associated with apoptosis, its morphology and its mechanism
List the different types of necrosis, examples of each and its features
Know the difference between apoptosis and necrosis

6. Apoptosis Vital process. Programmed cell death.
Can occurs in physiological or pathological conditions.

7. Physiologic process to die
Apoptosis
Physiologic process to die
This process helps to eliminate unwanted cells by an internally programmed series of events effected by dedicated gene products. It serves several vital functions and is seen under various settings.
Remember: apoptosis require energy to die

8. Apoptosis A. Physiologic
SEEN IN THE FOLLOWING CONDITIONS:
A. Physiologic
During development for removal of excess cells during embryogenesis
To maintain cell population in tissues with high turnover of cells, such as skin, bowels.
To eliminate immune cells after cytokine depletion, and autoreactive T-cells in developing thymus.
Hormone-dependent involution - Endometrium, ovary, breasts etc.

9. Apoptosis B. Pathologic To remove damaged cells by virus
Atrophy (virtually never accompanied by necrosis).
To eliminate cells after DNA damage by radiation, cytotoxic agents etc.
Cell death in tumors.

10. Morphology of Apoptosis
Shrinkage of cells
Condensation of nuclear chromatin peripherally under nuclear membrane
Formation of apoptotic bodies by fragmentation of the cells and nuclei. The fragments remain membrane- bound and contain cell organelles with or without nuclear fragments.
Phagocytosis of apoptotic  bodies by adjacent healthy cells or phagocytes.
Unlike necrosis, apoptosis is not accompanied by inflammatory reaction

12. Apoptosis: liver cells are dying individually from injury by viral hepatitis.

13. Liver biopsy - viral hepatitis: acidophilic body (councilman body)
(apoptosis, i.e., induced, or programmed, individual cell death).
Vacuolar change is reversible.

14. Skin, apoptotic Keratinocyte

15. MECHANISMS OF APOPTOSIS
1. Chromatin condensation is mediated by calcium- sensitive endonuclease leading to internucleosomal DNA fragmentation. 2. Alteration in cell volume (shrinkage) due to action of transglutaminase. 3. Phagocytosis of apoptotic bodies is mediated by receptors on the macrophages. 4. Apoptosis is dependent on gene activation and new protein synthesis, e.g. bcl-2, c-myc oncogene and p53.

17. Apoptosis summary

18. Apoptosis regulating genes

19. Genes that regulate apoptosis:
Oncogene Bcl-2
Bcl-2 overexpression prevents apoptosis
Antagonized by cell death (ced) genes & others (bax,bad)
Localized to mitochondria, nuclear envelope and ER
Bcl-2 overexpression is found in follicular lymphoma.
Tumor suppressor gene p-53
Will cause cells with DNA damage (eg amplified myc) to go apoptosis
Induce bax expression
Reversed by overexpression of bcl-2

20. Objectives Define necrosis and apoptosis
List the different conditions associated with apoptosis, its morphology and its mechanism
List the different types of necrosis, examples of each and its features
Know the difference between apoptosis and necrosis

21. Necrosis
Necrosis is defined as the morphological changes that result from cell death within living tissues.
In necrosis, death of a large number of cells in one area occurs.
These changes occur because of digestion and denaturation of cellular proteins.

22. Morphology of necrosis:
Cellular swelling or rupture
Denaturation  and coagulation of cytoplasmic proteins
Breakdown of cell organelles
Breakdown of nuclear DNA

23. The results of cell death can include:
Cessation of function of a tissue or organ.
Release of cellular enzymes, these can sometimes be detected in the blood and used as markers of the extent or timing of damage to a particular organ, e.g. cardiac enzyme after myocardial infarction.
Initiation of the inflammatory response (vital reaction).

24. Patterns of Necrosis: In Tissues or Organs
As a result of cell death the tissues or organs display one of these six macroscopic changes:
Coagulative necrosis
Liquifactive necrosis
Caseous necrosis
Fat necrosis
Gangrenous necrosis
Fibrinoid necrosis

25. Patterns of Necrosis In Tissues or Organs
Coagulative necrosis:
Denaturation of intracellular protein leads to the pale firm nature of the tissues affected. The cells show the microscopic features of cell death but the general architecture of the tissue and cell ghosts remain discernible for a short time.
The outline of the dead cells are maintained and the tissue is somewhat firm.
Example: kidney and heart injury caused by ischaemia.

26. Removal of the dead tissue leaves behind a scar
Coagulative necrosis
Kidney: ischemia and infarction
(loss of blood supply and resultant
tissue anoxia).
Removal of the dead tissue leaves behind a scar

27. Infarcts (vascular distribution) are wedge-shaped
Coagulative necrosis: is due to loss of blood supply
Infarcts (vascular distribution) are wedge-shaped
with a base on the organ capsule.
Spleen

28. Necrosis of the liver induced by herpesvirus.
Herpesvirus invades liver cell nuclei producing nuclear ('ground glass') mildly basophilic inclusions.

29. Changes in the cytoplasm and the nucleus
Coagulative Necrosis
Changes in the cytoplasm and the nucleus  
Karyorrhexis
Karyolysis 
Pyknosis

30. Acute renal tubular necrosis (ischemia) :
increased eosinophilia and pyknosis in necrotic cells
Normal
Necrotic

31. Coagulative necrosis:
Remember: True coagulation necrosis involves groups of cells, and is almost always accompanied, by acute inflammation (infiltrate)

32. Patterns of Necrosis In Tissues or Organs
2. Liquefactive necrosis:
The dead cells undergo disintegration and affected tissue is liquefied.
This results from release of hydrolytic lysosomal enzymes and leads to an accumulation of semi- fluid tissue.
Example:
cerebral infarction.
Abscess

33. Cerebral infarction - this will liquefy eventualy

34. Liquefactive necrosis in brain leads to resolution with cystic spaces.

35. Liquefactive necrosis in the brain: in a patient suffered a "stroke"

36. Liquefactive necrosis of the brain: macrophages cleaning
up the necrotic cellular debris
Removal of the dead tissue leaves behind a cavity

37. … a mess - so many cells have died - the tissue is not recognizable
… a mess - so many cells have died - the tissue is not recognizable. Nuclei have become pyknotic (shrunken and dark), undergone karorrhexis (fragmentation) and karyolysis(dissolution)
Necrotic myocardium

38. Removal of the dead tissue leaves behind a cavity or scar
Liquefactive necrosis: two lung abscesses
Removal of the dead tissue leaves behind a cavity or scar

39. Removal of the dead tissue leaves behind a scar
Localized liquefactive necrosis liver abscess
Removal of the dead tissue leaves behind a scar

40. Patterns of Necrosis In Tissues or Organs
3. Caseous necrosis:
A form of coagulative necrosis but appear cheese-like.
The creamy white appearance of the dead tissue is probably a result of the accumulation of partly digested waxy lipid cell wall components of the TB organisms. The tissue architecture is completely destroyed.
Example:
tuberculosis lesions
fungal infections
Coccidioidomycosis
blastomycosis
histoplasmosis

41. Caseous necrosis in a hilar pulmonary lymp node infected with tuberculosis.

42. Caseous necrosis:
confluent cheesy tan granulomas in the lung in a patient with tuberculosis

43. Caseous necrosis: confluent cheesy tan granulomas in the lung in a patient with tuberculosis.
This is characteristic of a poorly -understood subtype of immune injury, seen in certain granulomatous diseases (tuberculosis and certain fungal infections (coccidioidomycosis, blastomycosis and histoplasmosis)
The macrophage-derived protein tumor-necrosis factor alpha ("cachectin") is the principal toxin that causes cells to undergo caseous necrosis

44. Pulmonary tuberculosis:tubercle contains amorphous finely granular, caseous ('cheesy') material typical of caseous necrosis.
Removal of the dead tissue leaves behind
a scar

45. Caseous necrosis is characterized by acellular pink areas of necrosis, surrounded by a granulomatous inflammatory process. N

46. Patterns of Necrosis In Tissues or Organs
4. Fat necrosis:
This can result from direct trauma or enzyme released from the diseased pancreas.
Example:
Necrosis of fat by pancreatic enzymes.
Traumatic fat necrosis in breast
Adipocytes rupture and the released fat undergoes lipolysis catalyzed by lipases. Macrophages ingest the oily material and a giant cell inflammatory reaction may follow. Another consequence is the combination of calcium with the released fatty acids.

47. Fat necrosis secondary to acute pancreatitis

48. Fat Necrosis 
Specific to adipose tissue with triglycerides.
With enzymatic destruction(lipases) of cells, fatty  acids are precipitated as calcium soaps.
Grossly- chalky white deposits in the tissue.
Microscopically – amorphous, basohilic /purple deposits at the periphery of necrotic adipocytes. 

49. Patterns of Necrosis In Tissues or Organs
5. Gangrenous necrosis:
This life-threatening condition occurs when coagulative necrosis of tissue is associated with superadded infection by putrefactive bacteria.
These are usually anaerobic gram-positive Clostridia spp. Derived from the gut or soil which thrive in conditions of low oxygen tension.

50. Patterns of Necrosis In Tissues or Organs
5. Gangrenous necrosis:
Gangrenous tissue is foul smelling and black.
The bacteria produce toxins which destroy collagen and enable the infection to spread rapidly. If fermentation occurs, gas gangrene ensues.
Infection can become systemic (i.e. reach the bloodstream, septicaemia).
The commonest clinical situation is gangrene of the lower limb caused by poor blood supply and superimposed bacterial infection. This is a life- threatening emergency and the limb should be amputated.

51. Example: necrosis of distal limbs, usually foot and toes in diabetes.
“Wet" gangrene “ of the lower extremity in patient with diabetes mellitus:
liquefactive component from superimposed infection on
coagulative necrosis from loss of blood supply.

52. Patterns of Necrosis In Tissues or Organs
6. Fibrinoid necrosis:
typically seen in vasculitis and glomerular autoimmune diseases

53. fibrin appear bright red amorphous material
Fibrinoid necrosis:
fibrin appear bright red amorphous material
affect blood vessels and the glomerulus , infiltrated with fibrin
Fibrinoid necrosis of an artery

54. Fibrinoid necrosis: afferent arteriole and part of the glomerulus
are infiltrated with fibrin, (bright red amorphous material)

56. Outcome of necrosis Depending on circumstances:
necrotic tissue may be walled off by scar tissue,
totally converted to scar tissue,
get destroyed (producing a cavity or cyst),
get infected (producing an abscess or "wet gangrene"),
or calcify.
If the supporting tissue framework does not die, and the dead cells are of a type capable of regeneration, you may have complete healing.

57. Objectives Define necrosis and apoptosis
List the different conditions associated with apoptosis, its morphology and its mechanism
List the different types of necrosis, examples of each and its features
Know the difference between apoptosis and necrosis

58. Difference between apoptosis and necrosis
Coagulation Necrosis
Apoptosis
Stimuli
Hypoxia, Toxins
Physiologic and pathologic conditions
Histologic appearance
Cell swelling, coagulation necrosis disruption of organelles
Single cell, chromatin condensation, apoptotic bodies
DNA breakdown
Random and diffuse
internucleosomal
Mechanism
ATP depletion membrane injury
Gene activation, endonucleases, proteases
Tissue reaction
Inflammation
No inflammation, phagocytosis of apoptotic bodies
Energy
Not needed
Needed

59. TAKE HOME MESSAGES:
Apoptosis is a form of programmed cell death which could be physiological or pathological.
Necrosis is a deathof group of cells aecondary to injury. It is associated with inflammatory reaction, (unlike apoptosis).
Necrosis has many types which include Coagulative, liquefaction, gangrenous, caseous and fat necrosis.