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Medicine - Year 1 > Connective tissue diseases - Biochemistry > Flashcards

Connective tissue diseases - Biochemistry Flashcards

1
Q

Describe the role of connective tissues (skin, tendon and cartilage)

A
  • Highly specialised
  • Mechanical support
  • Movement
  • Arena for fighting infection
  • Regulates cell behaviour
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2
Q

Elastic fibres are made of multiple components.

a) What are elastic fibres
b) Name the components
c) List the roles of elastic fibres?

A

a) Long microfibrils between collagen fibre bundles

b)

  • Elastin
  • Fibrillins (1-3)
  • Fibulins
  • Matrix associated glycoproteins (MAGP)

c)

  • Structural role
  • regulatory role (growth factor signalling)
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3
Q

Name 4 defects effecting elastin

A
  1. Cutis laxa
  2. Supravalvular aortic stenosis
  3. 7q11.23 duplication syndrome
  4. Williams syndrome
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4
Q

Name 6 defects in fibrillin-1 (fibrillinopathies)

A
  1. Marfan syndrome
  2. Weill-marchesani syndrome
  3. Acromeliac dysplasia
  4. Stiff skin syndrome
  5. Progeroid syndrome
  6. Congenital contractual arachnodactyly
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5
Q

Proteoglycan is a ‘ground substance’ that is important in connective tissue material properties.

a) Describe their structure
b) Provide 3 examples of their role in connective tissue

A

a) Variable in size and have glycosaminoglycan side chains (GAG)

b)

  1. Hold water in tissue
  2. Confer viscoelastic propertis
  3. Interactions with cells, cytokines, and collagen
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6
Q

Aggrecan is a ‘ground substance’ in connective tissue and forms.

a) Describe their structure
b) Describe their function

A

a) Huge complexes and highly hydrophilic

b)

  • Link protein stabilising binding to hyaluronan (HA)
  • High tugor pressure in tissue - resist compression
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7
Q

What is the main structural component of connective tissues?

A

Collagen fibrils

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8
Q

Describe the structure of collagen fibrils

A
  • Collagen fibril is made up of staggered collagen molecules pack and crosslinked
  • Each collagen molecule is arranged as a triple helix structure
  • The triple helix structure is composed of three alpha chains
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9
Q

Describe the principles of collagen triple helix structure

A
  • Glycine (smallest amino acid) is essential
  • Stabilised by hydrogen bonds
  • Proline and OH-proline provide ridigity and stability
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10
Q

What is collagen synthesis and processing essential for?

A

Stability and structure

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11
Q

Describe the intracellular processing of collagen

A
  1. Post-translational modification (occurs in endoplamic reticulum) - hyrdoxylation and glycosylation
  2. Assembly of three alpha chains (from C terminal)
  3. Disulphide bond formation between alpha chains
  4. Assembly of triple helix is formed
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12
Q

a) Describe the role of vitamin C in collagen and how this can cause scurvy
b) What are the symptoms of scurvy

A

a)

  • Hydroxylation of lysine (and prolines) is dependant on vitami C (ascorbate)
  • Lack of vitamin C (vitamin c deficiency) means you do not hydroxylate collagen. Ths leads to scurvy

b)

  • Bleeding gums
  • Loss of teeth
  • Skin lesions, bruising
  • Poor wound healing
  • Joint pain and weakess
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13
Q

Name 3 diseases that genetic mutations of hyrdoxylase enzymes is associated with

A
  • Osteogenesis Imperfecta
  • Ehlers Danlos
  • Bruck syndrome
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14
Q

How many types of collagen are there?

A

5 - type I, II, II, IV, V

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15
Q

Describe the different types of collagen

A

Type I

  • Approximately 90% of collagen in the body is type I
  • Hydoxyapetite crystal deposits
  • Main components of bone, dermis, tendons and ligaments
  • Utilised in wound healing

Type II

  • Formed in copolymers
  • Main component of cartilage
  • Found in the cornea and vitreous humour

Type III

  • Found in arteries and hollow organs (often in combination with type I)
  • Also known as reticular fibres
  • Skin and blood vessles are rich in type III collagen
  • Forms collagen mixed fibrils with type I

Type IV

  • Forms the basement membrane

Type V

  • Found in cell surfaces, placenta, and hair
  • In the dermis, it helps organise the collagen type I (and Ehler-Danlos syndrome is often associated with mutation in type V collagen)
  • Type V collagen controls initiation of type I collagen fibril assembly (incorrect formation of type V collagen leads to incorrect formation of type I collagen)
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16
Q

Describe type I collagen

A
  • Approximately 90% of collagen in the body is type I
  • Hydoxyapetite crystal deposits
  • Main components of bone, dermis, tendons and ligaments
  • Utilised in wound healing
17
Q

Describe type II collagen

A
  • Formed in copolymers
  • Main component of cartilage
  • Found in the cornea and vitreous humour
18
Q

Describe type III collagen

A
  • Found in arteries and hollow organs (often in combination with type I)
  • Also known as reticular fibres
  • Skin and blood vessles are rich in type III collagen
  • Forms collagen mixed fibrils with type I
19
Q

Describe type IV collagen

A

Forms basement membrane

20
Q

Describe type V collagen

A
  • Found in cell surfaces, placenta, and hair
  • In the dermis, it helps organise the collagen type I (and Ehler-Danlos syndrome is often associated with mutation in type V collagen)
  • Type V collagen controls initiation of type I collagen fibril assembly (incorrect formation of type V collagen leads to incorrect formation of type I collagen)
21
Q

a) What type of collagen is skin mainly comprised of?
b) Describe the fibre structure

A

a) Type I collagen
b) Meshwork of fibres

22
Q

a) What type of collagen is tendon/ligaments mainly comprised of?
b) Describe the fibre structure

A

a) Type I collagen
b) Parallel fibres

23
Q

a) What type of collagen is bone mainly comprised of?
b) Describe the fibre structure

A

a) Type I collagen
b) Sheets (lamella)

24
Q

a) What type of collagen is cartilage mainly comprised of?
b) Describe the fibre structure

A

a) Type II collagen
b) Meshwork of type II collagen and aggrecan

25
Q

Describe the structural and biochemical changes in osteoarthritis cartilage

A

Loss of proteoglycan, collagen ‘fibrillation’ and enzymatic degradation

26
Q

List the components of connective tissue

A
  • Fibres - collagen, elastic fibres
  • ‘Ground substance’ - everything except collagen e.g., proteoglycan
  • Matricellular proteins
  • Cells - fibroblasts (skin, tendon, ligament), chondrocytes (cartilage), osteocytes (bone)
27
Q

Describe the structure of the entheseal fibrocartilage

A

Contains aggrecan and type II collagen

28
Q

The enthesis is a common site of tendon pathology as it is a region of stress concentration and site of microdamage and ‘overuse’ injury. Provide 6 examples of disorders/disease due to this

A
  • Tennis elbow
  • Golfers elbow
  • Jumpers knee
  • Osgood-Schlatter’s
  • Sever’s disease
  • Spondyloarthropathies
29
Q

Describe tendinopathy

A
  • A degenerative condition caused by loss of collagen fibril organisation and reduced fibril diameters
  • Changes in collagen content are: increased type II collage and increased turnover
  • Vascular (and nerve) infiltration
  • Failure to repair
30
Q

Osteogenesis imperfecta is a collegenopathy. There are 4 types

a) What type of defect is it mostly caused by?
b) What is the most common mutation?
c) Describe the relationship between the location of mutation on the gene and severity of OI
d) What is the most common form?
e) What is the mildest form?
f) What is the most severe form?

A

a) Mostly caused by defects in type I collagen genes
b) Glycine replaced with a larger amino acid (e.g., cysteine)
c) The further down the mutation is on the gene the more severe the OI is
d) Type I
e) Type I
d) Type II

31
Q

Describe type I osteogenesis imperfecta

A
  • Mildest and most common form
  • Quantative defect (haploinsufficiency)
  • Half the amount of normal type I collagen
32
Q

Describe type II osteogenesis imperfecta (OI)

A
  • Most severe- death in utero
  • Qualitative defect - missense mutation
  • Abnormal type I collagen
33
Q

What is the result of type II collagent defects and why?

A

Leads to developmental abnormalities because type II collagen is found mainly in cartilage (largely affecting the COL2A1)

34
Q

Describe the presentation of type II collagen defects

A
  • Short stature
  • Enlarged joints
  • Spinal curvature
  • Early arthritis
  • Vision and hearing defects
  • Cleft palate
35
Q

What is Ehlers Danlos syndrome (EDS)

A

EDS ia rare autosomal connective tissue disorder that is primarily characterized by skin hyperextensibility, abnormal wound healing/atrophic scars and joint hypermobility

36
Q

Name the 6 types of Ehlers Danlos Syndrome (EDS)

A
  1. Classical (EDS type I/II) - soft extensible skin, bruise, and scar easily, joint and cardiac defects
  2. Benign hypermobility (EDS type III)
  3. Vascular (EDS type IV)
  4. Kyphoscoliosis (EDS type VI)
  5. Arthrochalasia (EDS type VIIa/VIIb)
  6. Dermatosperaxis (EDS type VII)
37
Q

Marfans syndrome causes defects in elastic fibres (fibrillin-1) aka fibrillinopathy. Describe the clinical symptoms of Marfan’s

A
  • Scoliosis
  • Chest deformities
  • Arachnodactyly (long fingers)
  • Tall, thin
  • Joint hypermobility
  • Cranofacial abnormalities
  • Cardiovascular defects
  • Ocular defects - upward lens dislocation
  • Most serious defects from heart valve and aortic defects (aortic aneurysms)
38
Q

Describe the diagnosis of Ehlers danlos syndrome (and other genetic connective tissue conditions e.g., Marfans)

A
  • Detailed clinical and family history
  • Physical examination
  • Skin biopsy and histology - only really helpful for EDS VIIc (Dermatosperaxis type)
  • Biochemical analysis e.g., culture and urine analysis of collagen cross-links
  • Molecular analysis of specific gene(s) e.g., COL3AQ in 95% of vascular type EDS
39
Q

Describe the treatment and mangement of Ehlers Danlos Syndrome and connective tissue disorders

A
  1. Vascular damage is most important complication
  2. Control risk factors:
  • Healthy lifestyle
  • Protection (bandages, splints, padding)
  • Avoidance of contact sports and heavy excercise
  • Supplementation of vitamin C
  1. Drugs
  • Avoid aspirin, NSAIDs - due to effect of platelet and clotting
  • Beta blockers may reduce aortic dilation

Medicine - Year 1 (61 decks)

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