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Biochemistry Final Exam > Chondrocytes and TMJ > Flashcards

Chondrocytes and TMJ Flashcards

1
Q

How do we know that IHH acts back on the earlier stages of chondrocyte differentiation?

A

because its receptor PTC1 is present at earlier stages on earlier cells

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2
Q

Where would you find fibrocartilage in the body?

A
  • pubic symphysis
  • intervertebral discs
  • TMJ
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3
Q

Why is the IHH/PTHrP regulatory loop important in chondrocyte differentiation?

A

because the feedback loop ensures that once cells enter hypertrophy, they produce enough IHH, and then PTHrP, to ensure a continual supply of chondrocytes to replace them

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4
Q

Stickler syndrome and early onset osteoarthritis are both ____ type II collagen mutations.

A

mild

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5
Q

When is type II collagen expressed in the ECM of cartilage?

A

from the mesenchymal cells until the prehypertrophic chondrocyte

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6
Q

Why is aggrecan so important in cartilage?

A

because its negative charge allows it to bind large amounts of water and contribute greatly to the gel-like consistency of cartilage

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7
Q

Which transcription factors turn on later, when chondrocytes become hypertrophic?

A

RUNX2

Osterix (OSX)

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8
Q

Does cartilage have a blood supply?

A

NO - it is avascular

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9
Q

What are some extracellular matrix components of chondrocyte differentiation?

A

COL2A1 (type II)
ACAN (aggrecan)
COL10A1 (type X)

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10
Q

Which syndrome results in short stature, cone-shaped epiphysis in the hands and hips, and premature fusion of the growth plates?

A

acrocapitofemoral dysplasia

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11
Q

Which receptors are expressed in prehypertrophic chondrocytes?

A

PTH1R

FGFR3

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12
Q

What are the classifications of TMJ disorders?

A
  • articular disorders (intrecapsular)

- non-articular disorders (extracapsular)

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13
Q

Hyaline cartilage contains type __ and type __ collagen fibers.

A

II; X

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14
Q

What are 4 important signaling molecules involved in chondrocyte differentiation?

A

IHH
PTHrP
FGFs
VEGF

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15
Q

What are some mutations that can cause chondrodysplasias?

A
  • mutations in transcription factors
  • mutations in signaling molecules and their receptors
  • mutations in cartilage ECM components
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16
Q

What are the 4 main groups of GAGs?

A
  • hyaluronan
  • chondroitin sulfate and dermatan sulfate
  • heparan sulfate and heparin
  • keratan sulfate
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17
Q

There are 23 FGF genes and 4 FGF receptor genes, many of them being expressed in ____.

A

endochondral bone formation

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18
Q

What are the attributes of Jansen’s metaphyseal chondrodysplasia or Eiken syndrome?

A
  • delayed growth plate maturation
  • delayed skeletal maturation
  • short stature
  • malpositioning of teeth
  • hypercalcemia
  • hypophosphatemia
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19
Q

Aggrecan may have a role in regulating what mineral?

A

calcium

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20
Q

In ____, patients present with shortened digits, short stature, and premature fusion of growth plates.

A

brachydactyly type A1

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21
Q

What is the syndrome that results from an inactivating mutation in the PTH1R receptor?

A

Blomstrand Lethal Chondrodysplasia

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22
Q

What acts as a brake on chondrocyte proliferation?

A

FGFR3

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23
Q

What is the major type of fibrillar collagen in cartilage?

A

Type II collagen

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24
Q

What are some features of patients with achondroplasia?

A
  • short limbs
  • short fingers/toes
  • large head/prominent forehead
  • flattened nasal bridge
  • kyphosis or lordosis
  • bowleg/knock knees
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25
Q

Where would you NOT find SOX9 contained in the cells of chondrocyte differentiation?

A

within the hypertrophic chondrocytes (only found in precursors or proliferating chondrocytes)

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26
Q

Mutations in PTHrP, IHH, PTH1R, and FGFR3 result in ____.

A

chondrodysplasias

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27
Q

What does the recruitment of blood vessels to newly forming bone do?

A

blood vessels initiate cartilage destruction and allow bone formation in the center of the developing mass

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28
Q

____ cartilage has primarily type II and type X collagen fibers and is the most abundant type of cartilage found in the body.

A

Hyaline

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29
Q

What amino acid is replaced in a lethal mutation of type II collagen called Achonrogenesis type II or hypochondrogenesis?

A

glycine (replaced by a much bulkier amino acid)

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30
Q

Fusion of the growth plates prematurely is indicative of a mutation in the ___ gene.

A

IHH

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31
Q

Where is hyaline cartilage found in the body?

A
  • growth plates
  • bone precursor in embryo
  • joint articular surfaces
  • costal cartilage
  • nose, ear, trachea, larynx cartilage
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32
Q

Which zone at the epiphyseal growth plate contains swollen chondrocytes that attract capillaries and osteoblasts?

A

Hypertrophic Zone

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33
Q

What type of cartilage has type II collagen along with elastic fibers (elastin)?

A

elastic cartilage

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34
Q

Where would you find RUNX2 and OSX expressed?

A

in prehypertrophic and hypertrophic chondrocytes

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35
Q

What are the enzymes or proteases involved with the hypertrophic chondrocytes?

A

TNSALP

MMP13

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36
Q

What pathway also stimulates periosteal cells at the sides of the bone to form the mineralized bone collar?

A

IHH

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37
Q

What is the principle engine for longitudinal bone growth?

A

the proliferation of columnar chondrocytes in the Proliferation Zone and expansion of chondrocytes in the Hypertrophic Zone

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38
Q

How are most GAGs found? What are they attached to?

A

in the form of a proteoglycan (they are found covalently attached to a protein core)

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39
Q

Which is the major type of collagen expressed in hypertrophic cartilage?

A

Type X collagen

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40
Q

SOX9 inhibits ____, which is why SOX9 must be down-regulated in order to allow chondrocytes to mature.

A

RUNX2

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41
Q

___ stimulates chondrocyte proliferation.

A

IHH

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42
Q

What would happen if IHH signaling was impaired?

A

no replacement of proliferating cells would occur once they enter hypertrophy (premature closing of the growth plate)

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43
Q

What are the 3 articulation surfaces of the TMJ?

A

articular tubercle
mandibular fossa
mandibular head

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44
Q

How many synovial joint cavities does the TMJ have?

A

2

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45
Q

In which type of cartilage are the chondrocytes dispersed among fine, spongy collagen in layered arrays?

A

fibrocartilage

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46
Q

What is SOX9 expressed in?

A

chondroprogenitors and proliferating chondrocytes

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47
Q

What particular growth factor do hypertrophic chondrocytes attract?

A

VEGF

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48
Q

____ diffuses to the ends of bones and acts on early proliferating cells, stimulating them to produce more PTHrP.

A

IHH

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49
Q

_____ of TMJ are intracapsular and can be causes by inflammation, non-inflammatory factors, or disc displacement.

A

Articular disorders

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50
Q

What type of collagen is expressed in hypertrophic chondrocytes?

A

Type X collagen (before hypertrophy they were expressing type II)

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51
Q

____ signaling is a critical regulator of chondrocyte/cartilage proliferation and differentiation.

A

FGF

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52
Q

Impaired IHH and impaired PTHrP signaling lead to what condition?

A

dwarfism

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53
Q

Cartilage has a ____ regenerative capacity and is considered a specialized connective tissue.

A

limited

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54
Q

What might happen if SOX9 was not able to be downregulated?

A

the chondrocytes would not be able to mature since SOX9 inhibits RUNX2

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55
Q

What two pathways are very important in the regulation of longitudinal bone growth?

A

IHH

PTHrP

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56
Q

What gene suppresses IHH?

A

FGFR3

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57
Q

What muscle of the head and neck inserts onto the articular disc of the TMJ?

A

upper head of lateral pterygoid muscle

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58
Q

What type of cartilage typically covers articular joints?

A

hyaline cartilage

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59
Q

GAGs are usually ____ sulfated.

A

highly (= negatively charged)

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60
Q

Achondrogenesis type II/hypochondrogenesis is a ____ type II collagen mutation.

A

lethal

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61
Q

Of the IHH/PTHrP signaling-pathway associated syndromes, which are loss-of-function mutations?

A
  • Blomstrand Lethal Chondrodysplasia
  • brachydactyly type E2
  • brachydactyly type A1
  • acrocapitofemoral dysplasia
62
Q

What happens when a patient is affected by autosomal recessive spondyloepimetaphyseal dysplasia, with aggrecan being affected?

A

these patients are very, very short (about 2 feet tall)

63
Q

____, a transcriptional regulator, is working with the proliferative cells in cartilage differentiation: the mesenchymal cells, chondrocytes, and flat columnar chondrocytes.

A

SOX9

64
Q

____ and ____ are transcription regulators associating with prehypertrophic chondrocytes, hypertrophic chondrocytes, and terminal hypertrophic chondrocytes.

A

RUNX2; OSX (Osterix)

65
Q

In which type of bone formation is there the production of a cartilage template?

A

endochondral bone formation

66
Q

What hereditary skeletal disorders are characterized by abnormal growth plate function leading to skeletal deformities and growth defects?

A

the chondrodysplasias

67
Q

What is the structure called that mineralizes on the outside to essentially provide the outermost scaffold for endochondral bone formation?

A

periosteal bone collar

68
Q

What are some unique characteristics of the TMJ?

A
  • TMJ enclosed in a fibrous capsule
  • thick ligaments surround it
  • split synovium
  • 3 articulation surfaces that do not touch
69
Q

Does cartilage have a role in embryonic bone formation?

A

YES - endochondral bone formation (AKA the one with the precursor)

70
Q

What is TNSALP?

A

tissue non-specific alkaline phosphatase

71
Q

As chondrocytes move away from the growth plate, they become less and less exposed to PTHrP, which allows them to do what?

A

when they are no longer stimulated by PTHrP they stop proliferating and become prehypertrophic, which causes them to synthesize IHH

72
Q

Achondroplasia is a ___-of-function mutation involving the FGFR3 signaling pathway.

A

gain

73
Q

Mutations in Type II or Type X collagen, as well as aggrecan can result in ____.

A

chondrodysplasias

74
Q

____ is a disease where the growth plate prematurely closes, the skeleton matures too quickly, bone density is increased, and joints fuse.

A

Blomstrand Lethal Chondrodysplasia

75
Q

What condition(s) results from an inactivating mutation in IHH?

A

Brachydactyly type A1

Acrocapitofemoral dysplasia

76
Q

What are the 3 transcription factors important in chondrocyte differentiation?

A

SOX9
RUNX2
Osterix (OSX)

77
Q

What type of structures are formed following vascular invasion of bone in endochondral bone formation?

A

secondary ossification centers called growth plates

78
Q

When is ACAN (aggrecan) expressed in the ECM of cartilage?

A

from the chondrocyte until the prehypertrophic chondrocyte

79
Q

What is the master transcription factor/regulator of chondrocyte differentiation?

A

SOX9 (SRY-box 9)

80
Q

Coordinated actions of ___ and ___ signaling through their receptors PTC1 and PTH1R regulate chondrocyte proliferation and differentiation determining the length of the columns of chondrocytes.

A

IHH; PTHrP

81
Q

Schmid-type (spondylo)metaphyseal chondrodysplasia is caused by mutations in the ____ collagen gene.

A

COL10A1

82
Q

What is the most common TMJ arthropathy?

A

disc displacement

83
Q

Spondyloepiphyseal dysplasia is causes by a mutation in the ____ collagen gene.

A

COL2A1

84
Q

Which receptors are expressed in chondrocytes and flat columnar chondrocytes?

A

PTC1

FGFR3

85
Q

What receptor is expressed in chondrocytes, flat columnar chondrocytes, and prehypertrophic chondrocytes?

A

FGFR3

86
Q

___ and ___ are important regulators of hypertrophy.

A

RUNX2; OSX

87
Q

What is the first sugar residue of a GAG?

A

amino sugar (N-acetylglucoasamine OR N-acetylgalactosamine)

88
Q

What are IHH’s and PTHrP’s receptors?

A

PTC1

PTH1R

89
Q

What two pathways act as key regulators of chondrogenesis?

A

IHH

PTHrP

90
Q

COL2A1, Aggregan, and COL10A1 are all produced in large amounts by ___.

A

chondrocytes

91
Q

What do chondrocytes originate from?

A

mesenchymal progenitors

92
Q

In _____, patients present with shortened digits, short stature, and delayed tooth eruption.

A

brachydactyly type E2

93
Q

How many articulation surfaces does the temporomandibular joint have?

A

3

94
Q

Which zone at the epiphyseal growth plate contains stem cells?

A

Resting Zone

95
Q

What two pathways determine when chondrocytes enter hypertrophy?

A

IHH + PTC1 receptor

PTHrP + PTH1R receptor

96
Q

Which two GAG chains does the aggrecan core protein contain?

A

keratan sulfate

chondroitin sulfate

97
Q

The extracellular matrix of fibrocartilage contains type __ and type __ collagen.

A

I; II

98
Q

What condition results from an inactivating mutation in PTHrP?

A

brachydactyly type E2

99
Q

Is the central part of the TMJ articular disc vascular or avascular?

A

avascular

100
Q

What is the syndrome that results from an activating mutation in the PTH1R receptor?

A

Jansen’s metaphyseal chondrodysplasia OR Eiken syndrome

101
Q

Aggrecan assembles with ____ to form giant aggregates.

A

hyaluronan

102
Q

This is the major proteoglycan in cartilage, since it is produced in such large amounts by proliferating and prehypertrophic chondrocytes.

A

Aggrecan (ACAN)

103
Q

___ are unbranched polysaccharide chains composed of repeating disaccharide units.

A

Glycosaminoglycans (GAGs)

104
Q

What is the gelatinous ground substance of cartilage primarily composed of? What is embedded in the ground substance?

A

proteoglycans; collagen and elastic protein fibers

105
Q

What is the most common form of short-limbed dwarfism?

A

achondroplasia

106
Q

What are the TMJ articular surfaces separated by?

A

an articular disc

107
Q

Where is elastic cartilage found in the body?

A
  • Eustacian (pharyngotympanic) tubes
  • epiglottis
  • ear lobes
108
Q

Decorin, biglycan, fibromodulin, and osteoglycin are all ____.

A

SLRPs (small leucine rich proteoglycans)

109
Q

What happens after the formation of the periosteal bone collar?

A

chondrocytes become hypertrophic

110
Q

What are the primary components of elastic cartilage?

A 
type II collagen fibers
elastic fibers (elastin)
111
Q

What are the two mutations that can happen to the PTH1R receptor and cause loss-of-function or gain-of-function mutations?

A

inactivating mutations

activating mutations

112
Q

Patients with ____ have shortened and disorganized columns of chondrocytes in their growth plates.

A

achondroplasia

113
Q

What allows us to expand our bones from the growth plate?

A

the massive swelling of hypertrophic chondrocytes

114
Q

What are 3 important receptors for signaling molecules in chondrocyte differentiation?

A

PTC1
FGFR3
PTH1R (PTH/PTHrP receptor)

115
Q

____ and ____ are both major proteoglycans of skeletal tissues.

A

Aggrecan; versican

116
Q

Camplomelic dysplasia is causes by a mutation in the _____ regulation of the SOX9 genes.

A

transcriptional

117
Q

Where do we find cartilage in the body?

A

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

118
Q

What happens when the coordinated system of chondrocyte proliferation and hypertrophy is mutated or altered?

A

chondrodysplasias can occur

119
Q

PTHrP acts on the ___ receptor in late proliferation or prehypertrophic chondrocytes to keep them proliferating (but preventing them from becoming hypertrophic).

A

PTH1R

120
Q

____ is a mixture of fibrous tissue (type I collagen) and hyaline cartilage.

A

Fibrocartilage

121
Q

What would happen if PTHrP signaling was impaired?

A

the late proliferating or prehypertrophic chondrocytes would enter hypertrophy too soon leading to premature growth plate maturation

122
Q

What are some manifestations of camplomelic dysplasia?

A
  • hypoplasia of skeletal elements
  • bowing
  • underdeveloped shoulder blades
  • clubfoot
  • 11 ribs instead of 12
  • ambiguous genitalia
123
Q

____ of TMJ are extracapsular and may arise from clenching and bruxism.

A

Non-articular disorders

124
Q

What is growth plate cartilage important for?

A

longitudinal bone growth

125
Q

IHH is produced by ___ chondrocytes in chondrocyte differentiation.

A

prehypertrophic

126
Q

What is the movement of the TMJ called when the joint migrates downward to allow the jaw to open?

A

translation

127
Q

What are the 4 zones of differentiation at the epiphyseal growth plate?

A

Resting Zone
Proliferative Zone
Maturing Chondrocytes
Hypertrophic Zone

128
Q

____ is expressed in the proliferating and prehypertrophic chondrocytes and its signaling is very important additional regulatory step that limits chondrocyte proliferation.

A

FGFR3

129
Q

Why do GAGs bind such high amounts of water and create a gel-like matrix?

A

because the highly-sulfated nature of GAGs makes them negatively charged, so they bind water readily

130
Q

What is the layer around the cartilage cells called in endochondral bone formation?

A

perichondrium

131
Q

Spondyloepiphyseal dysplasia, spondyloepimetaphyseal dysplasia congenita, and Marshall syndrome are all _____ type II collagen mutations.

A

severe

132
Q

When is type X collagen expressed in the ECM of cartilage?

A

from the prehypertrophic chondrocyte until the terminal hypertrophic chondrocyte

133
Q

What does the recruitment of blood vessels to bone initiate?

A

brings in osteoclasts that resorb away the extra hypertrophic cartilage and allow osteogenic precursors to build bone

134
Q

Do the articular surfaces of the TMJ contact each other?

A

NO

135
Q

What is the second sugar residue of a GAG?

A

uronic acid (glucuronic OR iduronic)

136
Q

Which type of cartilage has a glossy appearance with evenly dispersed chondrocytes?

A

hyaline cartilage

137
Q

____ is an enzyme present in chondrocyte hypertrophy that promotes mineralization.

A

Alkaline phosphatase

138
Q

What do hypertrophic chondrocytes express that promotes vascular invasion?

A

MMP13

VEGF

139
Q

PTHrP is produced by ____ cells in chondrocyte differentiation.

A

early proliferative

140
Q

Of the IHH/PTHrP signaling pathway-associated syndromes, which are gain-of-function mutations?

A
  • Jansen’s metaphyseal chondrodysplasia

- Eiken syndrome

141
Q

____ is the rare human syndrome caused by SOX9 haploinsufficiency that affects the development of the skeleton and reproductive system.

A

Camplomelic dysplasia

142
Q

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

A

chondrodysplasias result

143
Q

What is happening regarding the activating mutation of FGFR3 gene in achondroplasia?

A

the FGFR3 gene is being activated, even in the absence of a ligand, so FGFR3 is severely restricting the proliferation of chondrocytes

144
Q

What structure separates the two synovial joints of the TMJ?

A

articular disc

145
Q

Are the receptors produced in the same place as the ligands in chondrocyte differentiation?

A

NO - they’re from different places

146
Q

How is FGFR3 signaling normally acting?

A

it limits chondrocyte proliferation

147
Q

What transcriptional regulator is the main driver of the cartilage differentiation/chondrocyte pathway?

A

SOX9

148
Q

___ is produced by early proliferative chondrocytes near the ends of bone at the growth plates.

A

PTHrP

149
Q

What do mesenchymal progenitors eventually produce in their lineage?

A

myocytes
adipocytes
chondrocytes
osteoblasts

150
Q

What type of cartilage covers the articular surfaces of the TMJ?

A

fibrocartilage

151
Q

How many genes encode type II collagen?

A

1 - COL2A1

152
Q

What is thought to be a contributing factor to temporomandibular disorder (TMD)?

A

malocclusion

Biochemistry Final Exam (8 decks)

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