Lecture 5: Tissues under load 3 Flashcards
what is osteopenia?
when osteoclast activity starts to outpace osteoblast activity, and bone mineral density reduces
at what point does osteopenia develop into osteoperosis?
when bone mineral density reduces further and can effect normal function with increased fracture risk
what are the risks osteopenia and osteoporosis present?
- brittle bones so increased risk of fracture
- lower bone strength due to decreased mineral density so worse ability to withstand mechanical load
what influences the onset of osteopenia/osteoporosis?
- age
- sedentary lifestyle
what does osteoporosis look like in spongy bone
- thinning of trabeculae
- loss in connectivity of bone network
why do older people often hunch over?
because of osteoporosis causing wedge/compression fractures in the vertebrae
what are the risk factors that contribute to osteoporosis
- aging
- females
- menopause (less estrogen to maintain bone density)
- family history
- low body weight
- smoking and alcohol
- low calcium and vitamin D
- sedentary lifestyle
what is the most common treatment for osteoporosis?
Bisphosphonates which reduce osteoclast activity
- hormone replacement therapy also works - increases osteoblast activity
how does testosterone have an impact on osteoporosis?
less of it still means less bone maintenance, but not as big of an impact as estrogen
what is the most critical thing to cartilage health?
mechanical loading
what is articular cartilage?
a specialized form of hyaline cartilage found at the synovial joints which is stronger to manage mechanical loads.
true or false: articular cartilage is aneural and avascular
true
what does limited vascularity mean for articular cartilage?
limited to no ability to repair
what are the major components of articular cartilage ECM?
collagen type II, water and aggrecan
- only 5% chondrocytes, but up to 85% water
what are the features of articular cartilage?
- 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
what are the zones in articular cartilage?
- superficial
- middle
- deep
- calcified intermediate zone
- subchondral bone
what are the features of the superficial zone?
collagen fibres are aligned parallel to the joint space to resist shear and distribute weight across the surface
how are the collagen fibres arranged in the middle zone and why?
at 90 degree angles to each other to resist compressive loads from different directions
how are the collagen fibres arranged in the deep zone and why?
at a 90 degree angle to the subchondral bone, as they plug into the bone
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?
the negative charges between proteoglycans
true or false: when water enters the cartilage when it is unloaded, it fills the layers evenly
false, it fills the top layer first
where in the knee is osteoarthritis the worst?
in the medial aspect
what is osteoarthritis?
the reduction of articular cartilage at a joint, but also effects ligaments, bone, and muscle.
what are osteophytes?
painful bone spurs that abnormally grow in a joint that is effected by osteoarthritis
how does osteoarthritis lead to a loss of proteoglycans?
- top collagen layer reduces in size
- inflammation occurs and signals for increased metalloproteases and aggrecanases
- proteoglycan breakdown
in osteoarthritis, the ECM is worn down both ___________ and ____________
mechanically and chemically
can osteoarthritis be cured?
no, but it can be managed by:
- exercise
- weight management
- education
- non-steroidal anti-inflammatory drugs
why do we need tissue engineering of bone?
when the gaps of a break dont line up
what is post-traumatic osteoarthritis?
an injury or instability in a joint causes inflammation, which brings about aggrecanases and metalloproteases and causing softening of articular cartilage
what is the normal osteoarthritis type?
primary osteoarthritis
what is the first sign of osteoarthritis in the joint?
reduction of/damage to the superficial cartilage layer
what are the two types of tissue engineering?
tissue replacement (restores mechanical funtion) and cell replacement (restores biochemical function)
what are the three cell sources for tissue engineering?
- autologous (self tissue)
- allogenic (same species)
- xenogenic (different species)
what are the requirements of a scaffold
- 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
can scaffolds be 3D printed?
yes
why can’t we tissue engineer articular cartilage?
- we cannot engineer tissue to withstand mechanical loads yet
