Biochemistry of the Periodontal Ligament in Health and Disease 2 Flashcards
1
Q
Which cells produce collagenase in HEALTH?
A
Fibroblasts
2
Q
Which cells produce collagenase in DISEASE?
A
polymorphonucleocytes
macrophages
Some bacteria can also secrete collagenase
3
Q
Name the enzyme that breaks down collagen
A
Collagenase
4
Q
What type of enzyme is collagen?
A
It is a matrix metalloprotease (MMP)
It is an Endopeptidase
5
Q
Describe the optimum conditions for collagenase to work at
A
- Neutral pH
- Need Calcium ions
3, Need six ions
6
Q
In what form do cells secrete collagenase in?
A
They secrete it in its inactive precursor form
This needs to be self activated after secretions
7
Q
How is collagenase turned off after it has been activated?
A
By a small peptide called tissue inhibitor of metalloproteases (TIMP)
8
Q
What is TIMP produced by?
A
By the cells that secrete collagenase
9
Q
What does TIMP synthesis regulate?
A
Will regulate collagen degradation within a tissue
10
Q
What link has been suggested between TIMP and periodontal disease?
A
there has been some suggestion that TIMP may be downregulated in certain patients tipping the balance towards periodontal breakdown.
11
Q
What does collagenase do?
A
It cleaves collagen molecules within their length in to three quarter and one quarter length fragments
12
Q
Which enzyme hooks collagenase to break down collagen?
A
gelatinases
13
Q
What do gelatinases do?
A
They take over and degrade the collagen fragments completely.
14
Q
How quickly does collagen turnover occur?
A
In less than an hour
15
Q
Which has the quickest turnover:
Skin
PDL
Gingiva?
A
PDL
16
Q
How much faster is collagen synthesis in PDL compared to subdermal gingiva?
A
2 times
17
Q
How much faster is collagen synthesis in PDL compared to Skin
A
4 times faster
18
Q
How much faster is collagen synthesis in PDL compared to Alveolar bone?
A
6 times fater
19
Q
How much faster is collagen breakdown in PDL compared to the gingiva?
A
5 time faster
20
Q
How much faster is collagen breakdown in PDL compared to skin?
A
15 times faster
21
Q
How much faster is collagen breakdown in PDL compared to alveolar bone
A
6 times faster
22
Q
What is the half life of collagen in the PDL, gingiva and skin
A
PDL: 40 mins
Gingiva: 80 mins
Skin: 360 mins
23
Q
What model can we use to help us understand disease progrssion within the periodontal ligament ?
A
By using sheep
24
Q
What do some sheep suffer from?
A
A condition called broken moth
25
What is broken mouth clinical similar to?
To rapidally progressing periodontitis in men
26
What happens ti sheep suffering from broken mouth?
Their quickly lose their lower teeth
27
What happen to the amount of collagen in sheep suffering from broken mouth?
there was an overall loss of collagen from the gingiva and periodontal ligament with disease
28
Loss of collagen from the gingiva and PDL results in what?
Accounts for the loss of attachment and increased pocket depth
29
What happens to the activity of gelatinase in sheep suffering from broken mouth?
There was an increased activity of the enzymes in the diseased tissue
30
What does increased activity of gelatinase lead to?
greater degradative activity of collagen if gelatinase activity increases
31
What 3 things did scientist look at in sheep with broken mouth disease?
Gelatinase enzyme activity
Collagen levels
GCF was tested
32
What were scientist looking fro when they tested the GCF of disease sheep?
looked for evidence of any collagen fragments that might be present in the sulcus
33
What was the underlying hypothesis scientists were working around when they were looking at sheep with broken mouth disease?
The underlying hypothesis was that if there is increased collagen degradation occurring during episodes of active periodontal disease, then some of those fragments might “wash out” in to the gingival crevice due to the increase fluid outflow that occurs with gingival inflammation.
34
What did southern blotting of the GCF in sheep with broken mouth disease show?
detected fragments of collagen in the crevicular fluid of diseased animals but not in healthy animals.
35
Has a strong correlation between PDL conditions in sheep with broken mouth disease and humans with periodontitis been found?
No a strong correlation has not been found
36
Where is the ground substance found?
It is present as the cement around the fibres in all connective tissues, including periodontal ligament
37
What does the ground substance comprise of?
1. Non-collagenous proteins (NCPs)
2. Hyaluronic Acid (GAG)
3. Proteoglycans (PGs)
38
Give an example of a non collagenous protein?
fibronectin which is a glycoprotein
39
What does fibronectin do?
It acts as a linker for cells to their underlying matrix, providing an anchor.
40
What are proteoglycans made up of?
Proteoglycans are made up of a protein core to which is attached a chain(s) of glycosylaminoglycans (GAGs)
41
What are glycosylaminoglycans?
GAGs are carbohydrate heteropolymers, made up of repeating disaccharide sub-units. Each disaccharide sub-unit is comprised of a hexosamine sugar plus a uronic acid residue
42
Are glycosylaminoglycans hydrophilic or hydrophobic?
They are highly HYDROPHILIC and attract and bind many water molecules as part of their extended structure
43
What does each disaccharide sub unit in a glycosylaminoglycans comprise of?
uronic acid residue
| a hexosamine residue (which is subject to modification )
44
What 2 forms can chondroitin sulphate exist in?
chondroitin-6-sulphate
| chondroitin-4-sulphate
45
What is the difference between chondroitin-6-sulphate and chondroitin-4-sulphate?
In chondroitin-6-sulphate the sulphate ion is attached to the 6th carbon
In chondroitin-4-sulphate the sulphate ion is attached to the 4th carbon
46
Which if the 2 forms of chondroitin sulphate is more abundant in hard tissue?
Chondroitin-6-sulphate
47
Which if the 2 forms of chondroitin sulphate is more abundant in the PDL?
Chondroitin-4-sulphate
48
Name the 2 GAGs we need to know
chondroitin sulphate
| dermatan sulphate.
49
What is the difference between chondroitin sulphate and dermatan sulphate?
the form of uronic acid in dermatan sulphate is an epimer called iduronic acid
50
What are proteoglycans?
GAGs that are covalently attached to a protein core
51
What are proteoglycans aggregates?
They are huge aggregated macromolecular structures that arise when proteoglycans have associated non covalently to hyaluronic acid via interactions with small linker proteins
52
What does the number do GAG side chains bound to a single protein core depend on?
depends upon the specific proteoglycan
53
What was the first really well reported proteoglycan structure called?
Aggrecan
54
Where is aggrecan found?
In cartilage
55
Describe what aggrecan is
It is a large, aggregating proteoglycan that looks like a bottle brush structure under the transmission electron microscope
56
What is aggrecan responsible for?
for conferring the stiffness/compressive properties of the tissue due to its ability to bind large amounts of water.
57
What type of proteoglycans do connective tissues contain?
both small (unaggregated) and large (usually aggregated) proteolycans.
58
Name the 2 SMALL proteoglycans found most abundantly in the PDL
mainly two small leucine-rich proteoglycans
| decorin and biglycan
59
What is decorin?
is a small proteoglycan that is rich in dermatan sulphate GAGs
60
Name the BIG proteoglycans found most abundantly in the PDL
Versican
61
What is Versican?
A large proteolglycan that is rich in chondroitin sulphate.
62
Describe the protein cores of small proteoglycans
They contain relatively large amounts of the amino acid leucine
They have a relatively low molecular weight
63
What are small proteoglycans sometimes referred to as?
Small Leucine Rich Proteoglycans (SLRPs)
64
Why are proteoglycans referred to as Small Leucine Rich Proteoglycans (SLRPs)
Because they have a relatively large amounts of the amino acid leucine
65
Do small proteoglycans (SLRPs) aggregate?
They tend not to aggregate
66
How many GAG side chains does decorin have?
1 called dermatan sulphate
67
Where is biglycan more abundant?
In the alveolar bone
68
How many GAG side chains does biglycan have ?
2
| either both chondroitin sulphate or one hondroitin sulphate and the other dermatan sulphate.
69
Describe versicans protein core
Many GAGchains are attached to it
| It is bigger than decorin
70
List the functions of proteoglycans and GAGs in connective tissues
1. Collagen fibril orientation/diameter
2. Control of Mineralisation
3. Generation of the Eruptive Force
71
What do proteoglycans have the ability to bind to?
Collagen
72
How does decorin interact with collagen?
Decorin is able to interact closely with collagen fibrils and regulate their growth and hence their final fibril diameter within the tissue
73
Where is Dermatan sulphate found?
Mainly in decorin
74
What is Dermatan sulphate associated with in regards to collagen?
It is associated with large collagen fibrils (200 – 300 nm in diameter)
75
What is chondroitin sulphate associated with in regards to collagen?
associated with small fibrils
76
What did Parrys investigations show about collagen fibres?
he found that as the tissue aged and became fully functional, the average size of collagen fibrillar diameters increased from around 50 nm to over 300 nm.
This was associated with a ten fold decrease in the amount of glycosylaminoglycan within the same tissues.
77
According to Parrys investigation what happens to the number of Dermatan sulphate as we age?
It increases with tissue age
| Becomes the most abundant GAG (80% of all tissue GAG present)
78
According to Parrys investigation what happens to the number of Chondroitin sulphate as we age?
Almost all chondroitin was lost in mature tissue, when collagen fibrils were large.
79
What are proteoglycans responsible fro directing with regard to collagen fibrils?
Proteglycans are responsible for directing the orientation of collagen fibres throughout the tissue (important for tissue function)
80
What process do proteoglycans control? (in regards to collagen fibril orientation)
fibrillogenesis
81
How do proteoglycans control fibrillogenesis?
via their ability to bind to
| collagen fibrils.
82
What is a high GAG content associated with?
is associated with unimodal
| distribution of small fibrils
83
In what tissue age is Chondroitin sulphate mainly found?
In foetal tissue
84
What can GAGs inhibition's in skeletal tissue?
GAGS are able to inhibit the nucleation and deposition of the hydroxyapatite crystals that make up the mineral component of skeletal tissues.
85
What determines the extent to which a GAG can interfere/prevent mineralisation?
Depends upon:
the type of GAG
its surrounding environment
what type of proteoglycan it is present in
86
What can some GAGs induce that may affect mineralisation of skeletal tissue?
Some GAGs can induce mineralisation ions and preventing their precipitation and/or their ability to bind to collagen, preventing other proteins nucleating crystals by acting as mask.
87
What may the ability of GAGs being able to inhibit and control mineralisation be related to ?
their high negative charge binding mineral
88
How do GAGs control mineralisation?
GAGs can inhibit deposition of hydroxyapatite crystals in
| soft connective tissues
89
What does the removal of GAGs from the PDL lead to?
leads to deposition of
| hydroxyapatite crystals in and around collagen fibrils
90
Why are proteoglycans and GAGs need for tooth eruption?
GAGs may be responsible, at least in part, for generation
| of the forces required for tooth eruption.
91
What may the ability of proteoglycans and GAGs being able to produce a strong eruptive force be related to?
their highly charged structure and the fact that they are very hydrophilic
92
How does being hydrophilic help proteoglycans and GAGs to produce a strong eruptive force?
They attract water molecules and are potentially capable of generating a significant hydrodynamic force.
93
What is increased tooth eruption associated with?
increased GAG (and therefore increased proteoglycan),
94
What happens to the amount of collagen when someone gets periodontal disease?
It decreases
95
What happens to the total GAG content in the PDL of a sheep with periodontal disease?
It increases
96
What happens to the total Dermatan sulphate content in the PDL of a sheep with periodontal disease?
It decreases
97
What happens to the total Chondroitin sulphate content in the PDL of a sheep with periodontal disease?
It increases
98
What happens to the total decorin content in the PDL of a sheep with periodontal disease?
It decreases
99
What happens to the total Versican content in the PDL of a sheep with periodontal disease?
Increases
100
GAGs that are covalently attached to a protein core are called what?
Proteoglycans
101
Name the structure that forms when proteoglycans associate non covalently to hyaluronic acid via interactions with small linker proteins
proteoglycans aggregates
102
Summarise how the biochemistry of the PDL changes with periodontal disease?
1. Total sulphated GAG content increases
2. Percentage of Dermatan sulphate decreases
3. Decorin decreases
4. Percentage of Chondroitin sulphate increases
5. Versican increases
6. Collagen content decreases
7. Gelatinase activity increases
