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LOCO2 > Pathogenesis Of OA > Flashcards

Pathogenesis Of OA Flashcards

1
Q

What type of cartilage is articulate cartilage

A

Hyaline

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2
Q

What provides articulate cartilage with nutrients and hydration

A

Synovial fluid

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3
Q

What merges the deeper layer of articulate cartilage with sub chi drawl bone

A

Calcified cartilage layer
Tidemark

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4
Q

What decides the properties of articulate cartilage

A

ECM composition

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5
Q

Layers of articulate cartilage

A

Superficial zone
Middle zone
Deep zone
Calcified zone
Subchondral zone
Cancellous bone

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6
Q

What layers of articulate cartilage are made up of dead chondrocytes

A

Calcified and subchondral zones

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7
Q

What triggers calcification of chondrocytes at the tide mark of articulate cartilage

A

pH change

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8
Q

How does chondrocyte size, shape, and number vary between the superficial, middle, and deep zones of articulate cartilage

A

Superficial - flatter, smaller, greater density
Middle - rounder, larger, sparser
Deep - stacked

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9
Q

What are chondrocytes found in

A

Lacunae

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10
Q

Why do chondrocytes have low numbers of mitochondria

A

Low oxygen consumption

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11
Q

Why do deep chondrocytes have prominent endoplasmic reticulum and Golgi apparatus

A

Protein synthesis
Sulphation of mucopolysaccharides

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12
Q

What is the main type of collagen in cartilage ECM

A

Type II

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13
Q

What cells make cartilage ECM

A

Chondroblasts

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14
Q

Structure of cartilage ECM

A

Network of collagen fibrils with pockets containing proteoglycan complexes and chondrocytes

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15
Q

Why does cartilage rely on diffusion of nutrients and metabolites

A

No blood or lymphatic vessels (or nerves)

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16
Q

Main 4 types of collagen in cartilage

A

II IX X XI

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17
Q

Is collagen X more common in superficial or deep cartilage

A

Deep calcified

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18
Q

How does collagen fibre orientation differ between superficial, intermediate, and deep cartilage

A

Superficial - parallel with surface - highest strength + allows gliding
Intermediate - oblique lattice - allows compression
Deep - perpendicular to surface - follows chondrocyte stacks and protect from compression

19
Q

What is the main proteoglycan in cartilage

A

Aggrecan

20
Q

Components of aggrecan

A

Core protein
GAG side chains

21
Q

What molecule type are keratin sulphate and chondroitin sulphate

A

GAG

22
Q

What do aggrecan complexes bind to

A

Central hylauronic acid filament

23
Q

Features of osteoarthritic joint

A

Fibrosis
Synovitis
Cartilage failure
Hylauronic acid depolymerised
Osteophytes
Subchondral cysts
Vascular engorgement

24
Q

OA risk genes

A

GDF5
FRZB
DIO2
COL2A1
Vit D receptor
Oestrogen receptor
IL-1R1
PTGS2/PLA2G4A

25
Q

OA pathophysiology

A

Chondrocytes damaged -> emergency signal release -> inflammation -> further damage to cartilage, bone, etc

26
Q

Inflammation of the synovial membrane

A

Synovitis

27
Q

How does Synovitis affect OA

A

Further inflammatory damage
Pain
Loss of function

28
Q

How does loss of HMGB2 increase OA

A

Causes superficial zone cell death, loss of progenitor cells, reduced ECM component synthesis

29
Q

HMGB2 role

A

Wraps around histones in chondrocytes to protect from damage
Supports chondrocyte survival
Regulates differentiation of superficial zone cells

30
Q

Where is HMGB2 expressed

A

Superficial zone chondrocytes

31
Q

3 phases of articulate cartilage degeneration in OA

A

Fibrillation
Erosion and cracking
Eburnation

32
Q

Eburnation

A

Exposed bone becomes polished

33
Q

Microscopic changes in cartilage in OA

A

Chondrocyte necrosis
Isogenic clusters - Focal clumps of chondrocytes from incr proliferation
Change from hyaline to fibro - C2 becomes C1
Duplicated tide mark
Thinner art cart
Thickened calcified cart

34
Q

How does proteoglycan staining appear in OA

A

Patchy

35
Q

How does increased local proliferation of chondrocytes in OA affect chondrocyte arrangement

A

Isogenic clusters instead of stacks

36
Q

Chondromalacia

A

Cartilage softens

37
Q

What causes chondromalacia in OA

A

Art cart thickens and swells but loss of proteoglycans make it less compressible -> water moves in and out faster-> enzymes released from stressed chondrocytes and synovial membrane cells (MMPs ADAMTs collagenases MAC) -> collagen network breaks down

38
Q

What does chondromalacia progress to

A

Fibrillation

39
Q

Main characteristic changes to art cart in early OA

A

Loss of superficial zone
Changes to ECM
Cell cluster emerge

40
Q

Main characteristics of art cart in late stage OA

A

Continued ECM loss
Chondrocyte hypertrophy

41
Q

Effects of OA on exposed Subchondral bone

A

Micro fractures
Increased osteoblast activity
Subchondral sclerosis
Focal pressure necrosis
Subarticular cycts
Vascular engorgement
Bone marrow oedema

42
Q

What causes subarticular cycts

A

Increased osteoclast activity to repair focal pressure necrosis

43
Q

What causes Subchondral sclerosis

A

Increased osteoblast activity

44
Q

Is damage to Subchondral bone equal over the bone surface

A

No

LOCO2 (26 decks)

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