Week 125 Osteoarthritis

Question 0

What are mmp’s & adamts?

Answer 0

Matrix metalloproteinases

Aggrecanases

Question 1

What are the key differences between osteoarthritis and rheumatoid arthritis?

Answer 1

OA: < in mechanical forces and stresses applied to articular cartilage
Likely from injury or trauma
Genetic & environmental factors (i.e. obesity)

RA: Deposition of immune complexes in joint space
Influx of inflammatory cells that secrete cytokines –> cartilage
degrades.
This causes inflammatory arthritis.

Question 2

what causes pseudoachondroplasia?

Answer 2

Mutations in comp gene

Question 3

Name 3 small interstitial proteoglycans and list their functions.

Answer 3

Biglycan - binds growth factors on cell surface receptors

Decorin - binds to collagen fibrils –> regulating fibril size (thickness)

Fibromodulin - bonds to collagen fibrils & regulates fibrinogenesis

Question 4

What is GAG? What is important about its structure?

Answer 4

Glycosaminoglycan

• Long -ve charged polysaccharides
• Polyanions –> strong affinity for water. -ve charges on carboxyl & sulphate groups (providing polyanionic properties)

Question 5

List 3 leucine rich proteoglycans.

Answer 5

decorin
biglycan
fibromodulin

Question 6

What is type II collagen used for?

Answer 6

Tensile strength - makes up 94% of articular cartilage

Question 7

What is type VI collagen used for?

Answer 7

Form fine fibrils in lacunae around cells - globular - protects cells.

Question 8

What does type IX collagen do?

Answer 8

This is a fibril associated collagen. It resists shear forces.

Question 9

What does type XI collagen do?

Answer 9

Fibril nucleation –> inside type II fibrils

Question 10

What does F.A.C.I.T mean & why is it important?

Answer 10

Fibril associated collagen with triple helix. It’s important in organising fibrils in the matrix.

Question 11

What do cartilage collagens do?

Answer 11

Form heterotypic fibrils

Provide tensile and sheer properties to cartilage

Question 12

What is the dry weight composition of articular cartilage?

Answer 12

Collagens - 75%
Proteoglycans - 22%
Other proteins - 3%

Question 13

What is the wet weight composition of cartilage?

Answer 13

Water - 70%
Collagens - 20%
Proteoglycans -7%
Cells - 2%
Other proteins - 1%

Question 14

What do collagenases, gelatinases & stromelysins degrade, respectively?

Answer 14

Collagenases - MMP1 and MMP13 - triple helix collagens
Gelatinases - MMP2 & MMP9 - denatured collagens
Stromelysins - MMP3, MMP8, MMP10 - Non collagens, matrix proteins (not aggrecan)

Question 15

What are the regions of articular cartilage & what is their composition?

Answer 15

Cancellous bone
Subchondral bone
Tidemark
Basal Layer
Intermediate
Tangential

Question 16

Total collagen is composed of:

Answer 16

95% Type II collagen
60-80% (weight) = water
10-20% = collagen
10-15% = Proteoglycan