Week 11 - Bone Biology Clinic + extra slides Flashcards
(18 cards)
Where does bone remodeling and repair occur
o Periosteal surface (outer bone layer)
o Endosteal surface (inner layer)
function of osteocytes
act as mechanosensors:
o Detect stress and release signals that regulate osteoblasts & osteoclasts
what happens to bone exposed to increased mechanical stress
o Undergoes strengthening/remodelling.
what happens to bone with decreased stress
o Undergoes resorption (weakened).
more sensitive to parathyroid hormone → more resorption
tooth loss leads to
o Loss of alveolar bone function
o Progressive bone loss in the jaw
what drives bone resorption
- Mechanical stress
- Calcium homeostasis
- Inflammation (pathological) – other
what stimulates osteoclast activity
activated T-lymphocytes
What is perodontitis
- A chronic inflammatory disease of the supporting structures of teeth.
- Progresses from gingivitis.
- Leads to:
o Destruction of connective tissue attachment
o Loss of supporting alveolar bone (hallmark)- the major cause of tooth loss in adults
o Major cause of adult tooth loss
how is inflammation involved in bone loss
- Bacterial infection triggers immune response.
- However it is the inflammatory response that plays a critical role - Inflammation reaches alveolar bone:
o Requires high local concentrations of inflammatory mediators. - Inflammatory mediators stimulate osteoblasts to express:
o RANKL (Receptor Activator of NF-κB Ligand)
o Cytokines from immune response (e.g., ILs, TNF-α) impact RANKL/OPG balance.
o High inflammatory signals → ↑ RANKL → ↑ osteoclast activity → bone loss.
function of OPG
a decoy receptor produced by osteoblasts:
o Binds RANKL, preventing it from binding RANK.
o Inhibits osteoclast formation and induces apoptosis of mature osteoclasts. – prevents excessive activation of osteoclasts
what happens if there’s high OPG
bone deposition
what is osteoporosis
- Most common bone disease in adults – particularly older age groups
- Results from diminished bone matrix because of decreased osteoblastic activity
Could be caused by: - lack of exercise
- Malnutrition
- Hormonal changes – decreased oestrogen
- Aging – decreased protein anabolic functions
what do normal levels of glucocorticoids do
Support osteoblast differentiation.
what do high levels of glucocorticoids lead to
o Inhibit osteoblasts.
o Promote osteoclast activity.
o Suppress OPG and increase RANKL expression.
* Result: Increased bone resorption and risk of osteoporosis (e.g., in Cushing’s disease).
What is the impact of oestrogen
- Promote OPG production.
- Can operates as both osteoblasts and osteoclasts
- Inhibit RANKL and cytokines that recruit osteoclasts.
- Help oppose PTH-induced resorption.
what does postmenopausal estrogen deficiency cause
less OPG, more bone resorption → osteoporosis.
what does * SERMs selective oestrogen receptor modulators (e.g., raloxifene): do
Mimic estrogen in bone, inhibit in breast/uterus.
what detects mechanical stress
osteocytes → promotes adaptive remodelling.
