Pathology of extracellular matrix and connective tissue

Dr. Radina IvanovaDr. Radina Ivanova

Associate Professor of PathologyAssociate Professor of PathologyMedical University of SofiaMedical University of Sofia

Pathology of extracellular matrix and connective tissue

Abnormal accumulations in the extracellular matrix – types.

Disorders in the metabolism and structure of the collagen.

Disorders in the content of the proteoglycans.

Fibrinoid change in the extracellular matrix. Hyaline change in the extracellular matrix.

Pathology of extracellular matrix and connective tissue

Amyloid deposition in the extracellular matrix. Types of amyloidosis.

Generalized systemic amyloidosis. Localized amyloidosis. Special staining

methods. Tincture properties of the amyloid. Morphology of amyloid deposition. Deposition of calcium in the extracellular

matrix. Deposition of urates in the extracellular

matrix.

Extracellular matrix

It consists of: the interstitial matrix between cells basement membranes underlying epithelia and

surrounding vessels The ECM serves several important functions:

It provides mechanical support to tissues (collagens and elastin)

It acts as a substrate for cell growth and the formation of tissue microenvironments

It regulates cell proliferation and differentiation proteoglycans bind growth factors and display them at high

concentration, and fibronectin and laminin stimulate cells via cellular integrin receptors

An intact ECM is required for tissue regeneration if the ECM is damaged, repair can only be accomplished by

scar formation.

Extracellular matrix 3 basic components of ECM

fibrous structural proteins such as collagens and elastins, which confer tensile strength and recoil

fibrillar and nonfibrillar BM - nonfibrillar collagen type

IV water-hydrated gels such as

proteoglycans and hyaluronan, which permit lubrication

glycosaminoglycans (dermatan sulfate and heparan sulfate)

adhesive glycoproteins that connect the matrix elements to one another and to cells

fibronectin Laminin Integrins

Abnormal accumulations in the extracellular matrix - types.

Disorders in the metabolism and structure of the collagen.

Disorders in the metabolism and structure of the elastins.

Disorders in the content of the proteoglycans Abnormal accumulations in the ECM

Proteins Fibrinod Hyalin Amyloid

Inorganic substances Ca Urates

Disorders in the metabolism and structure of the collagen

Increased collagen synthesis (fibrosis)

Abnormal structure of collagen Abnormal collagenolysis

Increased collagen synthesis

= Fibrosis (sclerosis) Fibroblasts, myofibroblasts,

smooth mucle cells Van Gieson – collagen - red

activity of lysyl-oxidase Types

Substitutive Heart - cicatrix post MI Liver cirrhosis – chronic

hepatitis Intestitial

Pulmo – in chronic left-sided heart failure (induratio fusca pulmonis)

Abnormal structure of collagen

Genetic defects in collagen structure Marfan’s syndrome Ehlers-Danlos syndrome

Marfan’s syndrome Autosomal dominant disorder of connective tissues, the

basic biochemical abnormality affects fibrillin 1. Which is the major component of microfibrils found in the

extracellular matrix, component of elastins Mutations in the FBN1 gene, which maps to chromosome

15q21. Morphology

Skeleton Arachnodactyly, hyperextensibility of joints, spinal deformities,

such as kyphoscoliosis, deformed chest Eyes

bilateral dislocation or subluxation cardiovascular system

aneurysmal dilation and aortic dissection Regurgitation of mitral valve, congestive heart failure

Ehlers-Danlos syndromes

There are six variants of Ehlers-Danlos syndromes, all caused by defects in collagen synthesis or assembly

30 distinct types of collagen, and all of them have characteristic tissue distributions and are the products of different genes

the clinical heterogeneity of EDS can be explained by mutations in different collagen genes

Deficiency of the enzyme lysyl hydroxylase Deficient synthesis of type III collagen resulting from mutations

affecting the COL3A1 gene conversion of procollagen type I to collagen, resulting from a

mutation in two type I collagen genes (COL1A1 and COL1A2) Clinical features are:

fragile, hyperextensible skin vulnerable to trauma hypermobile joints rupture of internal organs like colon, cornea, and large

arteries Wound healing is poor

Abnormal collagenolysis

activity of collagenlytic enzymes Collagenasess

activity of anticollagenases 1- antitrypsin, 1- anticollagenase

1- antitrypsin defficiency an autosomal recessive disorder

marked by abnormally low serum levels of this protease inhibitor

synthesized predominantly by hepatocytes

The AAT gene, chromosome 14, very polymorphic, and at least 75

forms have been identified PiZZ genotype) have circulating AAT

levels that are only 10% of normal levels

marked cholestasis with hepatocyte necrosis in newborns, to childhood cirrhosis, or to a chronic inflammatory hepatitis

PAS stain of liver -red cytoplasmic granules

Disorders in the metabolism and structure of the elastins

Decreased elastogenesis Aging – wrinkles Ectasia of the aorta Senile emphysema

Increased/abnormal elastogenesis=elastosis Senile elastosis –skin Endocardial fibroelastosis

Newborn – left heart ventriculus Aged – right heart ventriculus, carcinoid syndrome

Disorders in the content of the proteoglycans

Impaired proteoglycans’ synthesis Abnormal collagen-proteoglycan

complexes Free proteoglycans accumulate water

tissue swelling mucous appearance Localised

Pretibial myxedema – Bazedow’s disease Generalised

in myxedema (thyroid hypofunction), due to disposal of hondroit-sulfates

Mucoviscidosis

Mucoviscidosis (cystic fibrosis)

Autosomal recessive defect, which leads to lack of a membrane component essential to proper chloride transport across membranes of the mucus-producing exocrine glands and epithelium of respiratory, gastrointestinal tract and pancreas

CFTR, chromosome 7 Viscous secretion in exocrine glands

The disease is named for changes in the pancreas and mucous salivary glands, which have their ducts plugged by viscous mucus, "Cysts" form behind the plugs, and "fibrosis" ensues after years of obstruction.

Clinical features Pancreas and other exocrine glands (bile, duodenum) Pulmo – the bronchial lumens become plugged by super-thick

mucus, there are often lung infections, pneumonias, lung abscesses, bronchiectasis

sweat glands – salty sweat, (chloride is not reabsorbed through the sweat ducts)

Mucoviscidosis pancreatis

Abnormal accumulations in the ECM

Organic substances –mainly proteins Fibrinod Hyalin Amyloid

Inorganic substances Ca Uric acid

Fibrinoid change in ECM

Fibrinoid Morphologic description of non-structured

substance With various chemical composition, mainly plasma

proteins (albumin, globulins, fibrin) Specific staining –positive reaction for fibrin (by Veigert),

yellow – by Van Gieson for fibrosis Concomitant inflammatory reaction

Fibrinoid necrosis In presence of necrotic cells Outcome - cicatrix

Fibrinoid change in ECM Finrinoid in

precipitation of immune complexes Systemic connective

tissue diseases LE, rheumatoid arthritis,

scleroderma and others Localization

skin different organs (ren,

heart, joints) vessels

Rheumatoid arthritis-subcutaneous nodule

- Fibrinoid necrosis and inflammatory reaction

Fibrinoid change in ECM Finrinoid in insudation

of plasma proteins Malignant hypertension

Endothelial cells of small arteriae and arterioles

hyperplastic arteriolosclerosis

Smooth muscle cell hyperplasia and basement membrane duplication

Arterioles have an "onion skin" appearance

Malignant nephrosclerosis

- Fibrinoid necrosis and inflammatory

reaction

Fibrinoid change in ECM

Finrinoid in focal mucosal necrosis Chronic peptic ulcer

Gastric/duodenal Microscopy – 4

zones Debris Fibrinod necrosis Granulation tissue fibrosis

Hyaline change in the ECM

Hyaline Morphologic description of non-

structured substance With various chemical composition,

mainly proteins Hyalos - transparent, “glassy”

Staining –red by Van Gieson for fibrosis No concomitant inflammatory reaction

Hyaline change in the ECMHyalinosis

Connective tissue hyaline

Hyalinization of collagen fibers in fibrosis

Non-structured, without cells, homogenous, “glassy” tissue

Examples Cicatrices, tumors corpus albicans ovarii, glomeruronephritis lien

Corpus albicans ovarii

Hyaline change in the ECMHyalinosis

Vascular hyaline (hyaline arteriolosclerosis)

DM due to nonenzymatic

glycosylation of proteins in the basement membrane and its leak into the vessel wall

Hypertension Increased intraluminal

pressure pushes plasma proteins into the vessel wall.

Microscopy protein deposits in the

vessel wall, which occludes the lumen

Hyalinosis arteriolarum renis

Amyloid deposition in the ECM

Amyloid Abnormal protein substance, which deposits among

the cells in various tissues and organs (amyloidosis) Microscopy – eosinophilic amorphous deposits, similar

to hyaline But with special stainings

R. Virchov - the term amyloid (amyloss = starch) Tincture properties of the amyloid similar to the starch Cut organ is painted with iodine (red-brown) and

sulfuric acid (dark blue) amyloid binds a wide variety of proteoglycans and

glycosaminoglycans and the presence of abundant charged sugar groups give the deposits staining characteristics that were thought to resemble starch

Amyloid deposition in the ECMSpecial staining methods. Metilviolet and cresylviolet

– red staining (metachromasia)

Congo red – red staining under light microscopy

Congo red - apple-green birefringence under polarized light

Tioflavin S – yellow-green fluorescence

Immuhohistochemistry

Pathogenesis of amyloid deposition

Amyloidosis is a disorder of protein misfolding Abnormal folding of normal or mutant proteins

Amyloid is not a structurally homogeneous protein, although it always has the same morphologic appearance

more than 20 (at last count, 23) different proteins can aggregate and form fibrils with the appearance of amyloid

all amyloid deposits are composed of nonbranching fibrils, 7.5 to 10 nm in diameter, each formed of β-sheet polypeptide chains that are wound together

Main types of amyloid proteins Amyloid light chain (AL)

Derived from light chains (e.g., Bence Jones protein) Amyloid-associated (AA)

Derived from serum associated amyloid (SAA), an acute phase reactant

β-Amyloid (Aβ) Derived from amyloid precursor protein (protein

product of chromosome 21) Endocrine amyloid (AE)

Pathogenesis of amyloid deposition

The deposition of these proteins may result from:

excessive production of proteins that are prone to misfolding and aggregation

mutations that produce proteins that cannot fold properly and tend to aggregate

defective or incomplete proteolytic degradation of extracellular proteins

Types of amyloidosis Amyloidosis is a condition associated with a number of inherited and

inflammatory disorders in which extracellular deposits of fibrillar proteins are responsible for tissue damage and functional compromise.

Generalized Systemic Primary amyloidosis (AL amyloid disposition, associated with multiple myelomas) Secondary (reactive) - AA amyloid, associated with chronic inflammation (e.g.,

rheumatoid arthritis, tuberculosis) Hereditary (autosomal recessive disorder involving AA amyloid (e.g., familial

Mediterranean fever) Localized (confined to a single organ, e.g., brain)

Generalized systemic amyloidosis

Primary amyloidosis AL amyloid disposition Associated with immunocyte dyscrasias- multiple myeloma

(30% of cases), some B-cell lymphomas Secondary (reactive)

AA amyloid Associated with chronic inflammation -rheumatoid arthritis,

tuberculosis Similar tissue involvement in both primary and secondary

types Renm liver, heart, GIT

Hereditary Autosomal recessive disorder involving AA amyloid (e.g.,

familial Mediterranean fever) in individuals of Armenian, Sephardic Jewish, and Arabic origins a febrile disorder characterized by attacks of fever

accompanied by inflammation of serosal surfaces, including peritoneum, pleura, and synovial membrane.

Localized amyloidosis Amyloid nodules

AL protein Nodular deposits of amyloid + plasma cells in pulmo, skin,

tongue Alzheimer's disease

Aβ Endocrine Amyloid

certain endocrine tumors, such as medullary carcinoma of the thyroid gland, islet tumors of the pancreas, pheochromocytomas, and undifferentiated carcinomas of the stomach

in the islets of Langerhans – DM type 2 diabetes Amyloid of Aging

Senile systemic amyloidosis in elderly patients (usually in their 70s and 80s

With dominant involvement and related dysfunction of the heart

Senile cerebral

Morphology of amyloid deposition

Histologically, the amyloid deposition is always extracellular it begins between cells, often closely

adjacent to basement membranes

WHERE? BLOOD VESSEL WALLS, at first KIDNEY SPLEEN LIVER HEART

Amyloidosis of the kidney Grossly

may appear unchanged it may be abnormally large, pale,

gray, and firm; in long-standing cases, the kidney

may be reduced in size. Microscopically amyloid deposits

are found in: in the glomeruli

diffuse or nodular thickenings of the basement membranes of the capillary loops

total obliteration of the vascular tuft in the interstitial peritubular tissue

frequently associated with the appearance of amorphous pink casts within the tubular lumens

in the walls of the blood vessels of all sizes

often causing marked vascular narrowing.

Amyloidosis of the kidney HE, MV

Amyloidosis of the spleen Grossly

often causes moderate or even marked enlargement (200-800 gm)

firm in consistency, and cut surfaces reveal pale gray, waxy deposits.

• Microscopically – 2 patterns of amyloid deposits are found in:

in the splenic folliculi producing tapioca-like granules

on gross examination in the interstitial peritubular tissue

in the splenic sinuses and splenic pulp

forming large, sheetlike deposits "lardaceous spleen"

Amyloidosis of the spleenHE, MV

Amyloidosis of the liver Grossly

may cause massive enlargement (as much as 9000 gm).

the liver is extremely pale, grayish, and waxy

Microscopically amyloid deposits are found in

in the space of Disse they encroach on the adjacent

hepatic parenchyma and sinusoids

The trapped liver cells undergo compression atrophy and are eventually replaced by sheets of amyloid

normal liver function may be preserved even in the setting of severe involvement

Amyloidosis of the heart Grossly

The deposits may not be evident on gross examination,

or they may cause minimal to moderate cardiac enlargement.

There are gray-pink, dewdrop-like subendocardial elevations, particularly evident in the atrial chambers.

Microscopically amyloid deposits are found

throughout the myocardium between myocardial fibers and eventually causing their

pressure atrophy

Amyloidosis of the other organs

The adrenals, thyroid, and pituitary amyloid deposition begins in relation to stromal and

endothelial cells and progressively encroaches on the parenchymal cells.

In the gastrointestinal tract amyloid may be found at all levels, sometimes producing

tumorous masses that must be distinguished from neoplasms.

Nodular depositions in the tongue may produce macroglossia

On the basis of the frequent involvement of the gastrointestinal tract in systemic cases, gingival, intestinal, and rectal biopsies serve in the diagnosis of suspected cases

In patients receiving long-term dialysis deposition of β2-microglobulin amyloid occurs most

commonly in the carpal ligaments of the wrist, resulting in compression of the median nerve (carpal tunnel

syndrome).

Common Types of Amyloidosis and Associated Clinical Findings

Type of Amyloidosis Clinical Findings

Primary andsecondary

Nephrotic syndrome, renal failure (common cause of death)Arrhythmia, heart failureMacroglossia, malabsorptionHepatosplenomegalyCarpal tunnel syndrome

Prognosis

Techniques used to diagnose amyloidosis

Immunoelectrophoresis (to detect light chains) in primary amyloidosis

Tissue biopsy (e.g., adipose, rectum)

subsequent Congo red staining is the most important tool in the diagnosis of amyloidosis

Deposition of calcium in the ECM

Calcification - calcium salts Dystrophic - in dead or dying

tissues Local causes – any type of necrosis

Atherosclerosis, LN (tbc), heart valves

Metasatic – in hypercalcemia Systemic causes

Hyperparathyroidism Renal failure destruction of bone vitamin D-related disorders

affects the interstitial tissues of the vasculature, kidneys, lungs, and gastric mucosa.

Macroscopy fine white granules or clumps

Microscopy intracellular and/or extracellular

basophilic deposits

Deposition of urates in ECM

Gout a disorder caused by the

tissue accumulation of excessive amounts of uric acid

result from overproduction of uric acid, reduced excretion, or both

recurrent episodes of acute arthritis, formation of large crystalline aggregates called tophi, chronic joint deformity

primary (90%) and secondary forms

Morphology of Gout Acute arthritis is characterized by a

dense neutrophilic infiltrate permeating the synovium and synovial fluid.

Long, slender, needle-shaped monosodium urate crystals are frequently found in the cytoplasm of the neutrophils as well as in small clusters in the synovium.

The synovium is edematous and congested, and contains scattered mononuclear inflammatory cells.

Chronic tophaceous arthritis evolves from repetitive precipitation of

urate crystals during acute attacks. The synovium - hyperplastic, fibrotic, and

thickened by inflammatory cells Severe cases - juxta-articular bone erosions.

fibrous or bony ankylosis Tophi

They can appear in the articular cartilage of joints and in the periarticular ligaments, tendons, and soft tissues, including the ear lobes, nasal cartilages, and skin of the fingertips.

Superficial tophi can lead to large ulcerations of the overlying skin.

Gouty nephropathy multiple renal complications associated with

urate deposition medullary tophi, intratubular precipitations, or

free uric acid crystals and renal calculi Secondary complications such as

pyelonephritis can occur, especially when there is urinary obstruction.

Gouty tophus -an aggregate of dissolved urate crystals is surrounded by reactive fibroblasts, mononuclear inflammatory cells, and giant cells