Lecture 5: Tissues under load 3

Question 1

what is osteopenia?

Answer 1

when osteoclast activity starts to outpace osteoblast activity, and bone mineral density reduces

Question 2

at what point does osteopenia develop into osteoperosis?

Answer 2

when bone mineral density reduces further and can effect normal function with increased fracture risk

Question 3

what are the risks osteopenia and osteoporosis present?

Answer 3

• brittle bones so increased risk of fracture
• lower bone strength due to decreased mineral density so worse ability to withstand mechanical load

Question 4

what influences the onset of osteopenia/osteoporosis?

Answer 4

• age
• sedentary lifestyle

Question 5

what does osteoporosis look like in spongy bone

Answer 5

• thinning of trabeculae
• loss in connectivity of bone network

Question 6

why do older people often hunch over?

Answer 6

because of osteoporosis causing wedge/compression fractures in the vertebrae

Question 7

what are the risk factors that contribute to osteoporosis

Answer 7

• aging
• females
• menopause (less estrogen to maintain bone density)
• family history
• low body weight
• smoking and alcohol
• low calcium and vitamin D
• sedentary lifestyle

Question 8

what is the most common treatment for osteoporosis?

Answer 8

Bisphosphonates which reduce osteoclast activity
- hormone replacement therapy also works - increases osteoblast activity

possible vitamin D therapy

Question 9

how does testosterone have an impact on osteoporosis?

Answer 9

less of it still means less bone maintenance, but not as big of an impact as estrogen

Question 10

what is the most critical thing to cartilage health?

Answer 10

mechanical loading

Question 11

what is articular cartilage?

Answer 11

a specialized form of hyaline cartilage found at the synovial joints which is stronger to manage mechanical loads.

Question 12

true or false: articular cartilage is aneural and avascular

Answer 12

true

Question 13

what does limited vascularity mean for articular cartilage?

Answer 13

limited to no ability to repair

Question 14

what are the major components of articular cartilage ECM?

Answer 14

collagen type II, water and aggrecan
- only 5% chondrocytes, but up to 85% water

Question 15

what are the features of articular cartilage?

Answer 15

• glassy like surface
• acts as a protective cushion for underlying bone
• has to transition from gel like tissue to hard, ossified bone, with an intermediate of articular cartilage

Question 16

what are the zones in articular cartilage?

Answer 16

• superficial
• middle
• deep
• calcified intermediate zone
• subchondral bone

Question 17

what are the features of the superficial zone?

Answer 17

collagen fibres are aligned parallel to the joint space to resist shear and distribute weight across the surface

Question 18

how are the collagen fibres arranged in the middle zone and why?

Answer 18

at 90 degree angles to each other to resist compressive loads from different directions

Question 19

how are the collagen fibres arranged in the deep zone and why?

Answer 19

at a 90 degree angle to the subchondral bone, as they plug into the bone

Question 20

hypothetically, if a mechanical load was on a joint for long enough and all the water had dissipated, what would stop the tissue from flattening?

Answer 20

the negative charges between proteoglycans

Question 21

true or false: when water enters the cartilage when it is unloaded, it fills the layers evenly

Answer 21

false, it fills the top layer first

Question 22

where in the knee is osteoarthritis the worst?

Answer 22

in the medial aspect

Question 23

what is osteoarthritis?

Answer 23

degenerative joint disease
the reduction of articular cartilage at a joint, but also effects ligaments, bone, and muscle.

Question 24

what are osteophytes?

Answer 24

painful bone spurs that abnormally grow in a joint that is effected by osteoarthritis

Question 25

how does osteoarthritis lead to a loss of proteoglycans?

Answer 25

- top collagen layer reduces in size - inflammation occurs and signals for increased metalloproteases and aggrecanases - proteoglycan breakdown

Question 26

in osteoarthritis, the ECM is worn down both ___________ and ____________

Answer 26

mechanically and chemically

Question 27

can osteoarthritis be cured?

Answer 27

no, but it can be managed by: - exercise - weight management - education - non-steroidal anti-inflammatory drugs

Question 28

why do we need tissue engineering of bone?

Answer 28

when the gaps of a break dont line up

Question 29

what is post-traumatic osteoarthritis?

Answer 29

an injury or instability in a joint causes inflammation, which brings about aggrecanases and metalloproteases and causing softening of articular cartilage

Question 30

what is the normal osteoarthritis type?

Answer 30

primary osteoarthritis

Question 31

what is the first sign of osteoarthritis in the joint?

Answer 31

reduction of/damage to the superficial cartilage layer

Question 32

what are the two types of tissue engineering?

Answer 32

tissue replacement (restores mechanical funtion) and cell replacement (restores biochemical function)

Question 33

what are the three cell sources for tissue engineering?

Answer 33

- autologous (self tissue) - allogenic (same species) - xenogenic (different species)

Question 34

what are the requirements of a scaffold

Answer 34

- must be biodegradable and/or biocompatable - provides support for the initial growth phase e.g allow cells to attach - can apply mechanical loads - allow nutrient and waste delivery

Question 35

can scaffolds be 3D printed?

Answer 35

yes

Question 36

why can't we tissue engineer articular cartilage?

Answer 36

- we cannot engineer tissue to withstand mechanical loads yet