1. Lecture 47: Cellular accumulation
Objectives
This lecture provides an understanding of
Intracellular accumulations
Learning outcomes
At the end of the lecture ,student will be able to
List the major categories of substances that accumulate within and outside the cells
Explain the major processes involved in abnormal intracellular and extracellular accumulation
Discuss the causes mechanism and morphology of steatosis (fatty change)
Discuss the causes mechanism and clinical significance of protein accumulation including amyloid
List exogenous and endogenous pigments accumulation in cells and their clinical conditions
Discuss types, mechanism and clinical significance of pathological calcification
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Dr.Bharathi

2. Intracellular Accumulations
Normal constituents:
water
lipids
proteins
carbohydrates
Abnormal constituents:
Endogenous- products of abnormal synthesis or metabolism
Exogenous – minerals, infectious agents
Pigments – endogenous and exogenous
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3. Mechanisms of intracellular accumulation.
(1) Abnormal metabolism, as in fatty change in the liver.
(2) Mutations causing alterations in protein folding and transport, so that defective molecules accumulate intracellularly.
(3) A deficiency of critical enzymes responsible for breaking down certain compounds, causing substrates to accumulate in lysosomes, as in lysosomal storage diseases.
(4) An inability to degrade phagocytosed particles, as in carbon pigment accumulation m
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4. Fatty change (steatosis)
Fatty change refers to an absolute increase in lipids in parenchymal cells
Occurs in specific diseases like atherosclerosis, lipid storage disease, alcoholic liver disease, diphtheria, diabetes, obesity, toxins, protein malnutrition ,Reyes syndrome ect
Fatty ingrowth is a separate asymptomatic process in which lipids accumulate within stromal connective cells ( heart and pancreas commonly)
Mechanisms
Defects in any of the steps of uptake, catabolism, or secretion can lead to lipid accumulation.
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5. MORPHOLOGY
Fatty change is often seen in the liver and heart and histopathologically studied with special stain like “oil red o”
LIVER – Macro: enlarged, heavy, yellow, soft and greasy
Micro: clear vacuoles within the cytoplasm which coalesce to form bigger vacuoles. occasionally contiguous cells rupture to form fatty cysts
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Dr.Bharathi

6. Fatty change is most commonly seen in the liver and the heart
Mild fatty change – no affect
With increasing accumulation, the organ enlarges and appear bright yellow, soft, and greasy.
Micro:
Early stage -small fat vacuoles in the cytoplasm around the nucleus.
In later stages, the vacuoles coalesce to create cleared spaces that displace the nucleus to the cell periphery
Later contiguous cells rupture, and the enclosed fat globules unite to produce so-called fatty cysts.
HEART
Appears in two patterns
Pattern 1 :due to prolonged moderate hypoxia (anemia)– grossly appears as apparent bands of yellowed myocardium alternating with bands of darker red brown uninvolved myocardium (TIGERED EFFECT)
Pattern 2 :due to prolonged severe hypoxia (diptheria) shows uniformly affected myocardium
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Dr.Bharathi

7. Accumulation of cholesterol/cholesterol esters
Cellular cholesterol metabolism is tightly regulated to ensure normal cell membrane synthesis without significant intracellular accumulation. However, phagocytic cells may become overloaded with lipid (triglycerides, cholesterol, and cholesteryl esters) in several different pathologic processes.
Atherosclerosis – Blood vessels
Xanthomas – skin
Inflammation and necrosis –myelin figures
Cholesterolosis – gall bladder
Niemann - Pick disease type C– in many organs
Accumulation manifests histologically as intracellular vacuoles
These macrophages may be filled with minute, membrane-bound vacuoles of lipid, imparting a foamy appearance to their cytoplasm (foam cells).
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Dr.Bharathi

8. Glycogen
Excessive intracellular deposits of glycogen are associated with abnormalities in the metabolism of either glucose or glycogen.
Seen in
In poorly controlled diabetes mellitus, glycogen accumulates in renal tubular epithelium, cardiac myocytes, and β cells of the islets of Langerhans.
Glycogen storage diseases, or glycogenoses.Mc Ardle
Glycogen masses appear as clear vacuoles within the cytoplasm and best seen when stained with Best carmine or the periodic acid schiff (PAS) reaction imparts a rose-to-violet color to the glycogen
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Dr.Bharathi

9. Proteins
Protein accumulations are much less common than lipid accumulations;
Intracellular accumulations of proteins appears as rounded, eosinophilic droplets, vacuoles, or aggregates in the cytoplasm
In some disorders, such as certain forms of amyloidosis, abnormal proteins deposit primarily in the extracellular space
Causes
Reabsorption droplets in proximal renal tubules are seen in renal diseases
Synthesis of excessive amounts of normal secretory protein, as occurs in certain plasma cells engaged in active synthesis of immunoglobulin. The ER becomes hugely distended, producing large, homogeneous eosinophilic inclusions called “Russell bodies
Defects in protein folding
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10. Defects in protein folding
Defective intracellular transport and secretion of critical proteins
Examples
α1-antitrypsin deficiency, causing emphysema
In cystic fibrosis - delays dissociation of a chloride channel protein
In familial hypercholesterolemia, mutations in low-density lipoprotein receptors interfere with proper folding of receptor proteins
ER stress induced by unfolded and misfolded proteins. Unfolded or misfolded proteins accumulate in the ER and trigger a number of cellular responses.
Examples - neurodegenerative diseases, including Alzheimer's, Huntington's, Parkinson's diseases and type II diabetes
Aggregation of abnormal proteins - Abnormal or misfolded proteins may deposit in tissues and interfere with normal functions
Example - amyloidosis
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Dr.Bharathi

11. HYALINE CHANGE Non-specific accumulations of proteinaceous material
The term hyaline usually refers to an alteration within cells or in the extracellular space, which gives a homogeneous, glassy, pink appearance in routine H&E histologic sections
Intracellular hyaline deposits - (reabsorption droplets, Russell bodies, Mallory alcoholic hyaline)
Extracellular hyalin - Collagenous fibrous tissue in old scars may appear hyalinized, In long-standing hypertension and diabetes mellitus, the walls of arterioles become hyalinized.
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Dr.Bharathi

12. Pigments Carbon Tattoo
Pigments are colored substances (normal or abnormal) deposited within cells
Exogenous (comes from outside body), or endogenous (synthesized within body)
Exogenous
Carbon
Tattoo
Endogenous
Lipofuscin
Melanin
Haemosiderin
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13. Exogenous Pigments
Carbon – air pollutant of urban life-Inhaled - picked up by macrophages within the alveoli - transported to the regional lymph nodes
Accumulations of this pigment blacken the lungs &lymph nodes. (anthracosis)
In coal miners, the aggregates of carbon dust may induce a fibroblastic reaction and cause a serious lung disease (coal worker's pneumoconiosis )
Tattooing is a form of localized, exogenous pigmentation of the skin
Localized exogenous pigment within dermal macrophages
Permanent, no inflammation
Continuous phagocytosis
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14. Lipofuscin (fuscus = brown)
Insoluble pigment, also known as lipochrome and wear-and-tear or aging pigment.
Lipofuscin is composed of polymers of lipids and phospholipids complexed with protein
Lipofuscin is not injurious to the cell or its functions.
Its importance lies in its being the telltale sign of free radical injury and lipid peroxidation Prominent in the liver and heart ( Brown atrophy) of aging patients or patients with severe malnutrition and cancer cachexia
In tissue sections, it appears as a yellow-brown, finely granular intracytoplasmic, often perinuclear pigment
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Dr.Bharathi

15. Accumulations of endogenous pigments
Melanin
This pigment is formed from tyrosine by the action of tyrosinase
Increased melanin pigmentation is associated with sun tanning and with a wide variety of disease conditions.
Decreased melanin pigmentation is observed in albinism and vitiligo.
Bilirubin
This pigment is a catabolic product of the heme moiety of hemoglobin
Bilirubin accumulates and stains the blood, sclerae, mucosae, and internal organs, producing a yellowish discoloration called jaundice.
Seen in various pathologic conditions
(1)Hemolytic jaundice, (2)Hepatocellular jaundice
(3)Obstructive jaundice
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16. Hemosiderin
This iron-containing pigment consists of aggregates of ferritin. It appears in tissues as golden brown amorphous aggregates and can be positively identified with Prussian blue dye.
It accumulates pathologically in tissues in excess amounts (sometimes massive)
Hemosiderosis
Defined by accumulation of hemosiderin, primarily within tissue macrophages, without associated tissue or organ damage.
Hemochromatosis is more extensive accumulation of hemosiderin, often within parenchymal cells, with accompanying tissue damage, scarring, and organ dys-function. This condition occurs in both hereditary (primary) and secondary forms.
is associated with liver, heart, and pancreatic damage, resulting in liver fibrosis, heart failure, and diabetes mellitus
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Dr.Bharathi

17. Amyloidosis
Fibrillar protein that forms deposits in interstitial tissue, resulting in organ dysfunction
Characteristics
Linear, nonbranching filaments in a β-pleated sheet
Apple green-colored birefringence in polarized light with Congo red Eosinophilic staining with H&E (hematoxylin and eosin) stain
Derived from various proteins
Major types of amyloid proteins
Amyloid light (AL) chain
Derived from light chains (e.g., Bence Jones protein)
Amyloid-associated (AA)
Derived from serum-associated amyloid, an acute phase reactant
β-Amyloid is associated with Alzheimer's disease in Down syndrome.
β-Amyloid (Aβ)
Derived from amyloid precursor protein (protein product of chromosome 21)
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18. (1) AL amyloid disposition
Primary amyloidosis
(1) AL amyloid disposition
(2) Associated with multiple myeloma (30% of cases)
Secondary (reactive)
(1) AA amyloid
(2) Associated with chronic inflammation (e.g., rheumatoid arthritis, tuberculosis)
Localized
a. Confined to a single organ (e.g., brain)
b. Alzheimer's disease
■(1) Aβ AND (2) Most common cause of dementia
Hereditary
Autosomal recessive disorder involving AA amyloid (e.g., familial Mediterranean fever)
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Dr.Bharathi

19. Pathogenesis Techniques used to diagnose amyloidosis
1.Immunoelectrophoresis (to detect light chains) in primary amyloidosis
2.Tissue biopsy (e.g., adipose, rectum
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Dr.Bharathi

20. The hepatosplenomegaly
Clinical Correlation
Amyloidosis may be an unsuspected finding at autopsy in a patient who has no apparent related clinical manifestations,
or it may be responsible for serious clinical dysfunction and even death.
Nonspecific complaints such as weakness, fatigue, and weight loss are the most common initial symptoms.
Later - renal disease, hepatomegaly, splenomegaly, or cardiac abnormalities.
Renal involvement giving rise to severe proteinuria (nephrotic syndrome- renal failure)
The hepatosplenomegaly
Cardiac amyloidosis may manifest as conduction disturbances or as restrictive cardiomyopathy
The diagnosis by specific tests are Biopsy and subsequent Congo red staining
In suspected cases of AL amyloidosis, serum and urinary protein electrophoresis and immunoelectrophoresis should be performed.
Bone marrow aspirate in such cases usually shows plasmacytosis, even if skeletal lesions of multiple myeloma are not present.
The outlook for patients with generalized amyloidosis is poor
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Dr.Bharathi

21. CYTOSKELETAL ABNORMALITIES
Abnormalities of the cytoskeleton underlie a variety of pathologic states.
The cytoskeleton consists of
Microtubules, thin actin filaments , thick myosin filaments ,and various classes of intermediate filaments.
Thin filaments
Cytochalasin B prevents polymerization of actin filaments
Phalloidin, a toxin of the mushroom Amanita phalloides, also binds actin filaments.
Microtubules Defects
Inhibit sperm motility, causing male sterility
immobilize the cilia of respiratory epithelium, leading to bronchiectasis (Kartagener's syndrome)
Drugs such as colchicine used in gout bind to tubulin and prevent the assembly of microtubules & prevents leukocyte migration and phagocytosis
Microtubules form mitotic spindle - Drugs that bind to microtubules (e.g., vinca alkaloids) can act as antitumor agents.
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Dr.Bharathi

22. Intermediate filaments
The intermediate filaments accumulation
Accumulations of keratin filaments –eg. Mallory body, or "alcoholic hyalin," is an eosinophilic intracytoplasmic inclusion in liver cells that is characteristic of alcoholic liver disease.
The neurofibrillary tangle found in the brain in Alzheimer's disease contains microtubule-associated proteins and neurofilaments
Mutations in intermediate filament genes cause multiple human disorders, including myopathies, neurologic diseases, and skin diseases.
The Wiskott-Aldrich syndrome is an inherited disease is due to defects in the links between receptors and cytoskeletal proteins
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Dr.Bharathi

23. PATHOLOGIC CALCIFICATION
Pathologic calcification is abnormal deposition of calcium salts together with smaller amounts of iron, magnesium, and other minerals.
When the deposition occurs in dead or dying tissues, it is called dystrophic calcification; it occurs in the absence of calcium metabolic derangements
In contrast, the deposition of calcium salts in normal tissues is known as metastatic calcification and almost always reflects some derangement in calcium metabolism (hypercalcemia).
Grossly seen as fine white granules or clumps, often felt as gritty deposits. Sometimes converted to radio-opaque stone. Histologically, calcification appears as intracellular and/or extracellular basophilic deposits. In time, heterotopic bone may be formed in the focus of calcification.
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Dr.Bharathi

24. Dystrophic calcification Metastatic calcification:
Deposition of calcium phosphate in necrotic tissue /occurs in dead or dying tissues
Deposition of calcium phosphate in normal tissue
Normal serum calcium and phosphate
Due to increased serum calcium and/or phosphate
1) Causes of hypercalcemia-primary hyperparathyroidism, malignancy-induced hypercalcemia
(2) Causes of hyperphosphatemia-renal failure, primary hypoparathyroidism
Excess phosphate drives calcium into normal tissue
Examples
(1) Calcification in chronic pancreatitis
(2) Calcified atherosclerotic plaque
(3) Periventricular calcification in congenital cytomegalovirus infection
Examples of metastatic calcification
(1) Calcification of renal tubular basement membranes in the collecting ducts (nephrocalcinosis)This can produce nephrogenic diabetes insipidus and renal failure.
(2) Basal ganglia calcification in hypoparathyroidism
4/28/2017
Dr.Bharathi