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biochem exam 5 > Chondrocytes and Cartilage > Flashcards

Chondrocytes and Cartilage Flashcards

1
Q

What are the characteristics of cartilage?

A
  • specalized connective tissue
  • avascular
  • limited regenerative capacity
  • gelatinous ground substance (collagen and elastic protein fibers)
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2
Q

Where is cartilage typically found?

A

found in locations where support, flexibility, resistance to compression are important

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3
Q

What type of bone formation is cartilage important in?

A
  • endochondral (embryonic bone formation)
  • growth plate (longitudinal bone growth)
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4
Q

What are the three major types of cartilage?

A

hyaline
elastic
fibrocartilage

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5
Q

What are the characteristics of hyaline cartilage?

A
  • protein collagen fibers
  • glossy appearance with evenly dispersed chondrocytes
  • supportive ct
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6
Q

What is the most abundant type of cartilage?

A

hyaline cartilage

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7
Q

Where is hyaline cartilage found?

A
  • growth plate
  • joint articular surfaces
  • costal cartilages
  • cartilage in nose, ears, trachea, larynx, smaller respiratory tubes
  • precursor to bone in embryonic skeleton
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8
Q

What are the main types of hyaline cartilage?

A

collagen II and X

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9
Q

What type of cartilage is mainly type II collagen with lots of elastic fibers?

A

elastic cartilage

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10
Q

Where is elastic cartilage located?

A
  • pharyngotympanic (eustachian) tubes
  • epiglottis
  • ear lobes
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11
Q

What type of cartilage is a mixture of fibrous tissue (type 1 collagen) and hyaline cartilage?

A

fibrocartilage

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12
Q

What are the characteristics of fibrocartilage?

A
  • chondrocytes dispersed among fine collagen
  • spongy (good shock absorber)
  • ECM of fibrocartilage contains both type I and type II collagen
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13
Q

Where is fibrocartilage found?

A
  • pubic symphysis
  • intervertebral disk
  • temporomandibular joint (TMJ)
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14
Q

Osteoblasts, chondrocytes, myoblasts, and adipocytes all differentiate from ____________________

A

a common mesenchymal precursor

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15
Q

What are the steps to endochondral bone formation?

A
  1. mesenchymal condensation
  2. differentiation
  3. blood vessels initiate cartilage destruction/bone formation in the center (bone collar)
  4. secondary ossification centers form following vascular invasion
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16
Q

What are the different zones of differentiation in an epiphyseal growth plate?

A

resting zone
proliferative zone
maturing chondrocytes
hypertrophic zone

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17
Q

What are the important transcription factors in chondrocyte differentiation?

A

SOX9
RUNX2
OSX

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18
Q

What are the imporant signaling molecules in chondrocyte differentiation?

A

IHH
PTHrP
FGFs
VEGF

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19
Q

What are the important receptors for signaling molecules in chondrocyte differentiation?

A

PTC1
PTH1R
FGFR3

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20
Q

What are the important ECM components in chondrocyte differentiation?

A

COL2A1
ACAN
COL10A1

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21
Q

What are the important enzymes/proteases for condrocyte differentiation?

A

TNSALP
MMP13

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22
Q

What are the key transcriptional rregulations of cartilage differentiation?

A

SOX9
RUNX2
OSX

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23
Q

What is the master transcription factor that drives differentiation down chondrocyte pathway?

A

SOX9

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24
Q

What are the functions of SOX9?

A
  • expressed in chondroprogenitor/proliferating chondrocytes
  • master transcription factor
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25
Q

_____ must be downregulated to allow chondrocytes to mature

A

SOX9

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26
Q

What happens during chondrocyte hypertrophy?

A
  • chondrocytes swell in size
  • increase in RUNX2 and OSX
  • decrease in SOX9
  • express type X collagen
  • express alkaline phosphatase (promotes mineralization)
  • express MMP13/VEGF (promotes vascular invasion)
  • undergoes apoptosis
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27
Q

What inhibits RUNX2?

A

SOX9

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28
Q

What increases in expression during chondrocyte hypertrophy?

A

RUNX2 and OSX

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29
Q

What decreases in expression during chondrocyte hypertrophy?

A

SOX9

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30
Q

What is expressed in prehypertrophic and hypertrophic chondrocytes?

A

RUNX2 and OSX

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31
Q

What are the key regulators of chondrogenesis?

A

IHH
PTHrP

32
Q

How does IHH and PTRrP work?

A

signal through their receptors to regulate chondrocyte prolieration/differentiation and determine length of the proliferating columns of chondrocytes

33
Q

_________ axis is very important in regulating bone longitudinal bone growth

A

IHH/PTHrP

34
Q

What are the steps of IHH/PTHrP regualtory loop controling chondrocyte differentiation kinetics?

A
  1. PTHrP is produced by early proliferative chondrocytes (EPC) near ends of bone/growth plate
  2. acts on PTH1P receptor in late proliferating chondrocytes
  3. when chondrocytes are far away from growth plate they synthesize IHH
  4. IHH stimulates chondrocyte proliferation
  5. IHH diffuses to ends of bones and stimulates EPC to produce more PTHrP
  6. IHH induces periosteal cells to form bone collar
35
Q

What does the PTHrP do?

A

keeps chondrocytes proliferating (prevents hypertrophy)

36
Q

What does IHH do?

A

stimulates chondrocyte proliferation and induces bone collar formation

37
Q

What fibroblast grown factor signal is very important in proliferating chondrocytes for regulation?

A

FGFR3

38
Q

What growth factor suppresses IHH?

A

FGFR3

39
Q

What type of signaling is a critical regulator of chondrocyte proliferation?

A

FGF signaling

40
Q

What are the key ECM proteins in cartilage?

A

Type II collagen
Aggrecan
Type X collagen

41
Q

What is the major fibrillar collagen in cartilage, vitreous humor, and inner ear?

A

type II collagen

42
Q

What gene encodes for type II collagen?

A

COL2A1

43
Q

What is the major collagen expressed in hypertrophic cartilage?

A

type X collagen

44
Q

What gene encodes for type X collagen?

A

COL10A1

45
Q

What are the characteristics of GAGs (glycosaminoglycans)?

A
  • unbranched polysaccharide chains composed of repeating disacccharide units
  • highly sulfated (negatively charged)
46
Q

What are the 4 main groups of GAGs?

A

hyaluronan
chondroitin sulfate and dermatan sulfate
heparan sulfate and heparin
keratan sulfate

47
Q

Most GAGs are found covalently attached to a protein core in the form of _________________________

A

proteoglycans

48
Q

What are the two major proteoglycans of skeletal tissue?

A

aggrecan
versican

49
Q

What is the major proteoglycan in cartilage?

A

aggrecan

50
Q

What GAGs does the aggrecan core protein have?

A

keratan sulphate
chondroitin sulfate

51
Q

_________ assembles with hyaluronan to form huge aggregates

A

aggrecan

52
Q

What are the characteristics of aggrecan/hyaluronan assemblies?

A
  • bind high amounts of water (negatie charge)
  • may regulate calcification
53
Q

What happens when there are mutations in genes involved with cartilage differentiation and function?

A

chondrodysplasias (hereditary skeletal disorders)

54
Q

What are chondrodysplasias?

A

hereditary skeletal disorders characterized by abnormal growth plate function leading to skeletal deformities/growth defects

55
Q

What syndrome is caused by heterozygous loss of function mutation in SOX9?

A

Camplomelic Dysplasia

56
Q

What are the characteristics of camplomelic dysplasia?

A
  • mutation in SOX9 (haploinsufficiency)
  • autosomal dominant
  • affects development of skeleton/reproductive system
  • life threatening in neonatal period
57
Q

What symptoms are associated with camplomelic dysplasia?

A
  • Hypoplasia of skeletal elements
  • Bowing of limbs
  • Shortened limbs/dislocated hips
  • Underdeveloped shoulder blades
  • 11 pairs of ribs instead of 12
  • Clubfoot
  • Ambiguous genitalia
  • Craniofacial abnormalities
58
Q

What happens when PTHrP signaling is impaired?

A

late proliferating chondrocytes enter hypertrophy too soon (growth retardation)

59
Q

What happens when IHH signaling?

A

no replacement of proliferating cells once they have gone into hypertrophy (growth retardation)

60
Q

What disorders are from inactivating mutations in PTHrP?

A

brachydactyly type E2

61
Q

What disorders are from inactivating mutations in IHH?

A

Brachydactyly type A1
Acrocapitofemoral Dysplasia

62
Q

What disorders are from mutations in PTH1R (receptor)?

A
  • Blomstrand Lethal chondrodysplasia
  • Jansen’s metaphyseal chondrodysplasia (Eiken syndrome)
63
Q

Disorders from point mutations in FGFR3 in humans that result in gain of function mutation are called…

A

Achondroplasia

64
Q

What is the most common form of short limbed dwarfism?

A

Achondroplasia

65
Q

What are the characteristics of achondroplasia?

A
  • FGFR3 activated via mutation
  • autosomal dominant
  • 80% are sporadic mutation
  • homozygotes = severe disease (stillborn or die shortly after)
66
Q

What are the features of achondroplasia?

A
  • Short stature w/ disproportionately short limbs (trunk relatively normal)
  • Short fingers/toes
  • Large head/prominent forehead
  • Small midface/flattened nasal bridge
  • Spinal kyphosis (convex curvature) or lordosis (concave curvature)
  • Varus (bowleg) or valgus (knock knee) deformities
67
Q

What are examples of lethal type II collagen mutations?

A

achondrogenesis type II/hypochondrgenesis

68
Q

What are examples of severe type II collagen mutations?

A
  • spondyloepiphyseal dysplasia (SED)
  • sponyloepimetaphyseal dyplasia congenita
  • Marshall syndrome
69
Q

What are examples of mild type II collagen mutations?

A
  • stickler syndrome
  • early onset osteoarthritis
70
Q

What are the characteristics of anchondrogenesis type II/hypochondrogenesis?

A

-die perinatally or in first weeks of life
-short, barrel-shaped trunk
-very short extremities
-large head, soft cranium
-flat face
-underossification of the vertebral bodies
and pelvis
-hypercellular epiphyseal cartilage
-poorly organized or absent growth plate
-diminished extracellular matrix
-thick, irregular collagen fibrils

71
Q

What mutations are involved in achondrogenesis type II/hypochondrogenesis?

A
  • ten mutations are known in ACGII-HCG
  • all involve replacement of glycine by a bulkier amino acid in the triple helical region of the alpha1(II) chain
72
Q

What gene is mutated in spondyloepiphyseal dysplasia?

A

COL2A1 gene

73
Q

What are the characteristics of spondyloepiphyseal dysplasia?

A
  • Autosomal dominant
  • Short stature from birth (2– 4.5ft)
  • Kyphoscoliosis (curved spine) / vertebral defects (e.g. flattened vertebrae)
  • Short trunk, neck, limbs
  • Hands/feet less affected
  • Hip deformities/clubfoot
74
Q

What gene is mutated in schmid-type metaphyseal chondrodysplasia?

A

COL10A1 gene

75
Q

What are the characteristics of schmid-type metaphyseal chondrodysplasia?

A
  • short stature
  • bowing of the long bones
  • widening/irregularity of growth plates
76
Q

What are the two types of spondyloephiphyseal dysplasia (SED)?

A
  1. Autosomal recessive Spondyloepimetaphyseal Dysplasia, Aggrecan Type
  2. Autosomal dominant Spondyloephiphyseal Dysplasia (SED) type Kimberley (milder)

biochem exam 5 (12 decks)

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