Cellular Pathologypeople.upei.ca/hanna/CELL PATH 4/CellPath-L4WEB-18.pdfRaw egg white (albumin...
Transcript of Cellular Pathologypeople.upei.ca/hanna/CELL PATH 4/CellPath-L4WEB-18.pdfRaw egg white (albumin...
Cellular Pathology
(VPM 152)
Lecture 4 (Web)
Paul Hanna Jan 2018
• describes the range of morphologic changes that follow cell death in living tissue
• the morphologic appearance is due to 2 concurrent processes:
denaturation of proteins (nonproteolytic alteration 2o or 3o structure)
IRREVERSIBLE CELL INJURY
1) Necrosis
enzymatic digestion
autolysis* (self digestion) = endogenous enzymes derived from the lysosomes of the dead cells themselves
heterolysis = lysosomes of immigrant leukocytes
*autolysis also used for changes that occur in all cells after death, ie postmortem autolysis
Raw egg white (albumin protein) is a transparent / clear
viscous liquid Adding heat, acid or alkali will denature (misfold) the proteins which results
in a change of the color to white / opaque & the texture becomes solid
• distinctive morphologic patterns depending on whether enzyme catabolism or
protein denaturation predominates
• morphologic patterns of necrosis include: Coagulation Necrosis
Liquefactive Necrosis
Caseous Necrosis
*Gangrenous Necrosis
*Fat Necrosis
1) Necrosis
• most common manifestation of cell death
• characteristic of hypoxic / ischemic death of cells in all tissues (except brain)
• necrotic cells eventually removed by leukocyte proteolysis & phagocytosis
• on LM, basic outline of the coagulated cell persists at least a few days
(protein denaturation predominates over enzymatic digestion)
a) Coagulation Necrosis
Gross Appearance
• architecture resembles normal tissue, but color and texture are different
• lighter in color- denatured cytoplasmic proteins and decreased blood flow
• usually firm
• necrotic tissue may be swollen or shrunken
• may see a local vascular / inflammatory reaction to necrotic tissue
a) Coagulation Necrosis
Figure 01-18A (McGavin & Zachary). Coagulation
necrosis, infarcts, kidney, cow. A, Note the pale
regions of acute coagulation necrosis surrounded by a red
rim of active hyperemia and inflammation (far left).
Bovine, kidney, renal infarct, cut surface. Note pyramidal
(wedge) shaped area of necrosis with hyperemic border.
Bovine, fetus, liver, multifocal hepatic necrosis.
Bovine herpesvirus 1 (BoHV-1) causes IBR
(infectious bovine rhinotracheitis) in adult cattle
and can also cause abortion when a pregnant
cow is infected. Often see multifocal hepatic
necrosis (necrotizing hepatitis) in the fetus.
Bovine, liver: Multifocal hepatic necrosis (coagulative) due to infection with the bacterium Fusobacterium necrophorum.
The majority of bacterial infections cause liquefactive necrosis due to the marked infiltration of neutrophils with associated
heterolysis; however in this particular bacterial infection there are toxins which result in coagulative necrosis (at least initially).
Bovine, heart, myocardial necrosis (coagulative);
note irregular area of pallor within myocardium.
Microscopic Appearance
• original cell shape & tissue architecture is preserved (ie eosinophilic "shadow“)
• cytoplasm:
increased eosinophilia (H&E stain)
usually hyalinized (homogeneous / glassy)
may be mineralized
a) Coagulation Necrosis
• nucleus:
karyolysis
pyknosis
karyorrhexis
Figure 01-17B (McGavin & Zachary). Pyknosis and karyolysis, renal cortex, chloroform toxicosis, mouse. Some epithelial cells
exhibit hydropic degeneration, whereas others are necrotic. Some necrotic cells exhibit pyknosis (arrow), whereas others have lost
the nucleus or have a very pale nucleus, ie karyolysis (arrowheads)
Figure 01-17C (McGavin & Zachary) Karyorrhexis, lymphocytes, spleen, dog. Spleen of a dog with
parvovirus infection. Lymphocyte nuclei have fragmented because of the infection (arrow). H&E stain.
White muscle disease, skeletal muscle, calf. Note coagulation necrosis of myofibers characterized
by fragmentation and hyalinization; also note extensive mineralization (blue-purple staining)
Path Basis of Vet Disease, 8th ed
Ultrastructural Appearance of Irreversible Injury
Irreversible ischemic injury - renal tubular epithelium
Disrupted cell membranes
Marked mitochondrial swelling with
amorphous densities
Dense pyknotic nucleus
Fig 2-10 (Robbins). C, Proximal tubular cell showing late injury,
expected to be irreversible. Note the markedly swollen
mitochondria containing electron-dense deposits, expected to
contain precipitated calcium and proteins. Higher magnification
micrographs of the cell would show disrupted plasma
membrane and swelling and fragmentation of organelles.
Normal human epithelial cell (Scanning EM).
Epithelial cell 24 hours after exposure to sulfur mustard (SEM).
Note loss of microvilli and perforations / invaginations of the
plasma membrane. http://www.nal.usda.gov/awic/newsletters/v8n3/graphics/8n3afg1c.gif
Irreversible Injury
• after cell death:
- cell parts continue to be digested by lysosomal acid hydrolases
- leakage of cellular enzymes into ECF (eg muscle CK, liver ALT)
- influx of ions (eg Ca2+) and macromolecules from the ECF
- cells debris removed by phagocytosis or broken into fatty acid residues
Irreversible Injury Irreversible Injury
• when enzymatic digestion of necrotic cells predominates
• many bacterial infections; neutrophils contain potent hydrolases
• in hypoxic damage of the CNS
Gross appearance
• affected tissue is liquefied, ie soft to viscous to fluid mass
• in inflammation, the liquid is often mostly dead WBC’s (pus)
Microscopic appearance
• may see degenerate neutrophils and/or amorphous necrotic material
b) Liquefactive Necrosis
Porcine, abscess in ventral neck / shoulder area.
Escape of purulent exudate (pus) when the abscess
is lanced.
Note, suppurative (= purulent) exudate is a common
type of liquefactive necrosis.
Porcine, kidney, suppurative pyelonephritis, note
purulent exudate (again an example of liquefactive
necrosis).
Cytology of an aspirate from abscess / suppurative
exudate. The predominate cell type is neutrophils
and there are fewer scattered macrophages.
Figure 01-20A (McGavin & Zachary). Liquefactive necrosis. Acute polioencephalomalacia, brain, goat. A thiamine deficiency has
resulted in polioencephalomalacia (ie polio = grey, encephalo = brain and malacia = necrosis). This is liquefaction necrosis with
varying degrees of tissue separation (arrows). Scale bar = 2 cm. Note: this same lesion can result from either ischemia, lead
poisoning or “salt” poisoning.
• typical seen with specific bacterial diseases, eg TB, caseous lymphadenitis
• infections in birds, since heterophils lack myeloperoxidase
Gross appearance
• grey-white, dry, friable to pasty (caseous = cheese like)
Microscopic appearance
• dead cells persist as amorphous, coarsely granular, eosinophilic debris
• retain cellular outline (coagulative) caseous complete dissolution (liquefactive)
c) Caseous Necrosis
Ovine, submandibular lymph node, with “caseous
lymphadenitis” an infectious disease caused by
infection with the bacteria Corynebacterium
pseudotuberculosis;
note the type of necrosis in this exudate is caseous
(not quite liquefactive, but more broken down than
coagulation necrosis, ie it would be a thick pasty
texture, if you could cut / feel it)
Equine, lung tissue, pyogranulomatous
pneumonia due to Rhodococcus equi;
note caseous exudate (arrows).
Figure 01-19. Tuberculosis, lymph node,
transverse section, ox. A, The lymph has been
replaced by a caseating granuloma. Note the
caseous necrosis characterized by a pale yellow,
crumbly exudate. B, Granulomatous inflammation in
caseous necrosis. Cell walls are disrupted and tissue
architecture is lost. Mineralization (not seen here) is
common in this type of necrosis. H&E stain.
• definition = necrosis (usually ischemic) of extremities, eg digits, ear tips
• dry gangrene = coagulation necrosis of an extremity
• wet gangrene = when the coagulative necrosis of dry gangrene is modified
by liquefactive action of saprophytic / putrefactive bacteria
d) Gangrenous Necrosis
Frostbite of the hand in a person (above). Cat with sloughing
of ear tips and paws following dry gangrene due to frostbite.
Calf, gangrenous necrosis of distal limbs due to
ischemia; this ischemia could result from frostbite or
sepsis or a mycotoxin such as ergot.
Bovine, calf, gangrenous necrosis / dry gangrene with
sloughing of distal limbs, ergot poisoning
Bovine, mammary gland, wet gangrene;
tissue starting to slough.
Fig 1-21A (McGavin & Zachary), Moist gangrene,
udder, sheep. The surrounding tissue is well
vascularized, which contributes to the wet and bloody
nature of the lesion. Often saprophytic bacteria and
clostridia contaminate areas of necrosis.
Bovine, lung, “gangrenous” pneumonia following aspiration of rumen content. [Although historically called “gangrenous”
pneumonia, it is probably better called necrotizing pneumonia as a morphologic Dx or aspiration pneumonia as an etiologic Dx]
• distinguished by its location within body fat stores
• etiology: inflammation (eg pancreatitis), Vit E deficiency, trauma, idiopathic
e) Fat Necrosis
Canine, recurrent pancreatic necrosis (“pancreatitis”) with mesenteric fat necrosis
Canine, recurrent pancreatic necrosis
(“pancreatitis”) with omental fat necrosis.
Canine, recurrent pancreatic necrosis (“pancreatitis ”) with fat necrosis; note necrosis of
fat (larger arrow) and pancreatic tissues (smaller arrow)– some areas of coagulative type and
other areas with significant enzyme degradation (liquefaction) of necrotic tissue.
• Greek = “falling off”
• death of single cells through activation of genetically programmed “suicide” pathways
• apoptosis indicates selective elimination of cells (either physiologic or pathologic),
while necrosis points to widespread tissue injury (severe pathologic stimuli)
• apoptosis → death of single cells / intact membranes / phagocytosed with no inflam.
necrosis → area of dead cells / damaged membranes / enzyme digest. & 2o inflam.
2) Apoptosis
Figure 17-35 (Molecular Biolology of the Cell, 4th ed) Sculpting the digits in the developing mouse paw by apoptosis (A) The paw in this mouse embryo has
been stained with a dye that specifically labels cells that have undergone apoptosis. The apoptotic cells appear as bright green dots between the developing digits
(arrows). (B) This interdigital cell death eliminates the tissue between the developing digits, as seen one day later, when few, if any, apoptotic cells can be seen.
Incomplete tissue sculpting (ie
incomplete apoptosis) of the
digits results in syndactyly
(from Greek syn = "together" +
dactyly = “digits”)
It can be partial, as in the web
toes (above left) or complete
as seen in the childs hand
(above right) and calves
hooves (below left)
Physiologic causes:
• seen in many physiologic, adaptive and pathologic events:
Cells undergoing normal turnover
- hormone-dependent involution
- cell deletion in proliferating population
2) Apoptosis
Cells undergoing programmed cell death during embryogenesis
Immune System - deletion of autoreactive T cell in thymus
- immune regulation
Specific immune responses – via cytotoxic T cells
Pathologic atrophy of organs after duct obstruction
2) Apoptosis
Pathologic causes:
Misfolded proteins – ER stress
DNA damaged beyond repair – eg radiation, toxins
Specific infectious agents – esp viruses
d) Morphology
Cell shrinkage
- cytoplasm has packed organelles
Chromatin condensation
- dense aggregates of chromatin ± fragmentation
Formation of cytoplasmic blebs / apoptotic bodies
- with intact membranes (± nuclear fragments)
Phagocytosis of apoptotic cells / bodies
- usually by macrophages with no inflammation
2) Apoptosis
• considerable apoptosis may occur in tissues before it is evident on histology
Fig 1-8 (Robbins) Schematic illustration of morphologic changes in cell injury culminating in necrosis or apoptosis. Note: with
necrosis cells swell, lose membrane integrity and incite an inflammatory response VS apoptosis where cells shrink (condense), membranes
remain intact in forming apoptotic bodies and are removed with minimal inflammation.
SEM showing showing cytoplasmic blebbing /
apoptotic body formation.
Figure 3–23 (Junqueira’s Basic Histology) Late apoptosis-formation of apoptotic bodies. TEM of a cell in late apoptosis shows
that during this process the cell’s shape changes radically and large cytoplasmic vesicles (blebs) are formed. These detach from the
cell and often separate one from another, but remain contained within plasma membrane so that no cytoplasmic contents are
released into the extracellular space.
www.skin-science.com
Note, arrows indicate apoptotic epidermal keratinocytes (“sunburn cells”) due to UV-B radiation.
These can be induced within 30 minutes of sun exposure.
Figure 01-33 (McGavin & Zachary). Apoptosis, cytoarchitecture of cells, pancreas, rat. Individual acinar cells are shrunken
and their chromatin condensed and fragmented (arrows). Cytoplasmic blebs are found in adjacent cells. Inflammation is absent.
H&E. (note: blockage of glandular ducts typically results in apoptosis within the gland)
Signaling pathways that initiate apoptosis (“Death Signals”)
• stimulate targets on cell surface or within the cell
Biochemical Mechanisms
Control and integration
• balance of +ve / -ve regulatory molecules determines outcome of the affected cell
Biochemical Mechanisms
Common execution phase
• actual death program accomplished by endonucleases & proteases (esp caspases)
Biochemical Mechanisms
Removal of dead cells
• apoptotic bodies have ligands for phagocytic cells (efficient / no inflammation)
Biochemical Mechanisms
e) Consequences of “too much” or “too little” apoptosis
Disorders associated with defective apoptosis (increased cell survival)
• increased survival of abnormal cells with neoplasia
• increased survival of autoreactive lymphocytes causing autoimmune disorder
Disorders associated with increased apoptosis (excessive cell death)
• increased loss of cells in: neurodegenerative diseases
ischemic injured cells
viral infected cells