Periodontal Ligament Biochemistry

Question 1

What cells are in the periodontal ligament

Answer 1

Fibroblasts
Cementoblasts
Osteoblasts

Question 2

What fibres and other things make up the periodontal ligament

Answer 2

Nerves and vasculature
Extracellular matrix
Fibres (major is collagen the minor is oxytalan and elastin)
Ground substance

Question 3

How does elastin for and mature?

Answer 3

Oxytalan
Elaunin
Elastin

Elastin protein is deposited in these oxytalan fibres until the mature into elastin

This makes it resemble foetal connective tissue

Question 4

What is elastin made of

Answer 4

10-15 no microfibrils if oxytalan fibre
Microfibrillat component 10%

Amorphous polymeric fore (90%) elastin protein

Question 5

What is collagen made of (structure)

Answer 5

All made of 3 collagen polypeptide (alpha polypeptides)

Question 6

What is the structure of each polypeptide collagen chain

Answer 6

Tripeptide glycine followed by 2 amino acids proline or its hydroxylated form. The third amino acid is alanine

If we looked down the chain we could see the single H side chain faces the middle because there is no steric hinderance here

Every third amino acid proline has its bulky side chain orientated outward this side chain forms H bonds with other things around in the surrounding solution

Question 7

What collagen types form the PDL

Answer 7

Type 1 80%

Type 3 20%

Question 8

What is the importance of hydroxyproline in the collagen structure

Answer 8

Stability in the triple helix through OH group

Question 9

What happens when hydroxilation of proline is absent

Answer 9

Scurvy a connective tissue disease

Question 10

How is proline converted to hydroxyproline

Answer 10

Proline is hydroxilated via a vitamin C dependant enzyme prolyl hydroxalysae. Vitamin C is a reducing agent keeping fe2+ ions mood

Question 11

How is collagen formed (chains assemble)

Answer 11

Alpha chains assemble and are stabilised by S-S bonds at the carboxyl end of the chains then the helix forms spontaneously and the globular end at the N terminus forms

Question 12

What happens to the procollagen when it leaves the cell to the extracellular matrix

Answer 12

The globular ends are cleaved leaving the tropocollagen that can now assemble into fibres

Question 13

What happens in fibrillogenesis

Answer 13

This is the aggregation of tropocollagen to form fibrils intermolecular cross links form

Question 14

How are the fibrils stabilised

Answer 14

Covalent cross links from modified lysine and hydroxylysine residues

Lysyl oxadase converts r groups of LYS and HYL to aldehydes

They are all reducible

Question 15

What are intramolecular allysine cross links

Answer 15

These are formed within the actual tropocollagen molecules

Question 16

What happens to cross linked as collagen ages.

Is this the same in the PDL

Answer 16

More stable non reducible cross links form spontaneously

There are no non reducible cross links in the PDL

Question 17

What is the ration of DHLNL:HLN

Answer 17

1:3

Question 18

Giver and overview of collagen synthesis

Answer 18

Synthesis of alpha chains 
Hydroxylation of PRO&LYS 
Glycosylation og HYL and ASN
Alignment of pro a chains 
Pro-collagen triple helix 

Outside -
Cleavage if terminal ends
Aggregation stagger array
Formation of intermolecular cross links

Question 19

What is the hierarchical structure of collagen type 1

Answer 19

Procollagen 
Tropocollagen 
Microfibrils 
Fibrils 
Fibres 
Fibre bundles

Question 20

How is collagen broken down

Answer 20

Collagenase enzyme (matrix metalloprotiase) produced as an inactive precursor it cleaves collagen to 3/4 and 1/4 parts 
In the PDL phagocytosis by fibroblasts is an significant degradation factor

Question 21

What is the collagen synthesis in the PDL and degradation compared to everything else

Answer 21

6 times alveolar bone and 4 times skin

Degradation is 15 times what it is in the skin and 6 times what it is in alveolar bone

Approx 40 min cycle in PDL

Question 22

What happens to gelatinise activity in sheep with diseased mouths

Answer 22

Greater activity more degradation

Question 23

What does the Western blot of GCF show

Answer 23

Collagen only present in GCF in diseased sheep

Question 24

What comprises ground substance

Answer 24

Non collagenous proteins
Hyaluronic acid
Proteoglycans
Glycoproteins such as fibronectin and these are protiase resistant

Question 25

Proteoglycans in ground substance

Answer 25

Have a protein core and then glycosylaminoglucans (gags)
These are hetropolymers made of repeated disaccharide monomers
GAGs= hexosamine and ironic acid are hydrophilic

Question 26

What is a proteoglycans structure

Answer 26

GAG and core protein to for proteoglycans monomer

Proteoglycans + link protein + hyaluronan monomer = proteoglycans aggregate

Question 27

What proteoglycans are in the PDL

Answer 27

Decorum and biglycan (small)

Versions (large)

D and V sulphate rich

Question 28

Why are proteoglycans needed in ground substance

Answer 28

They control fibrilogenesis via ability to bind collagen
High gag content is associated with unimpdal distribution of small fibrils

Decorin larger fibrils

Proteoglycans also direct orientation of collagen fibrils

Gag in tissue is highest at 2 month

Question 29

What do PGs and GAGs do (2)

Answer 29

Control mineralisation they inhibit mineral deposition

Generates the eruption force

Question 30

What happens to sulphate co centration

Answer 30

Dermatan - decrease 
Chondroitin - increase 
Decorin increases 
Total gag increases collagen content decreases 
Gelatinise activity increase

Question 31

What are the cells of the periodontium

Answer 31

Osteoclasts
Fibroblast
Macrophage
Osteoblasts

Question 32

What’s the secular epethelium

Answer 32

Layer of osteoblasts

Question 33

Where are macrophages found

Answer 33

In the alveolar bone

Question 34

What do fibroblasts do

Answer 34

Degrade and produce collagen in the alveolar bone

Question 35

What’s rankl

Answer 35

This is a protein causing osteoblasts to rise and for osteoclasts
Osteoblasts control osteoclasts formation so production and degradation happens at the same rate

Question 36

How does bone change in reaction loading

Answer 36

Increased bone when increased loading happens

Question 37

What does LPS do

Answer 37

This causes osteoblasts to form Rankl to Christie more osteoclasts and more bone resorption

And on macrophages to for IL 1 which causes osteoblasts to make more osteoclasts

Additionally IL 1 causes fibroblasts to stimulate more IL1 and extracellular collaginases causing net loss off cellular tissue

IL1 causes cathepsin K to increase bone degradation