Bone Turnover Flashcards
Inflammatory mediators
Cytokines
Cytokines
A group of proteins and peptides that are used to allow one cell to communicate with anither
Redundancy of cytokines system
Most functions of cytokines can be performed by many different cytokines
Pleiotropism of cytokine system
A single cytokine has many different functional effects on many different cell types or even on the same cell
Hormone mediators of osteoclast differentiation and activity
1,25 dihydroxyvitamin D
Parathyroid hormone
Oestrogen
Leptin
Paracrine/autocrine mediators of osteoclast differentiation and activity
Prostaglandins
Interleukin-1
Interleukin-6
Tumour necrosis factor TNF
Osteoprotegerin OPG (or osteoclastogenesis inhibitory factor OCIF)
Member of the tumour necrosis factor receptor superfamily
Inhibits the differentiation of myeloid precursors into osteoclasts
Decreases resorption by osteoclasts in vitro and in vivo
Derivation of osteoblasts
Mesenchymal stem cells
Effect of OPG
Inhibits osteoclast formation, function and syrvival
RANK ligand
Stimulates osteoclast formation, function and survival
What does RANK stand for
Receptor activator of nuclear factor K
How does osteoprotegerin work
Binding to RANK-ligand, thus blocking the RANK-RANK ligand interaction between osteoblasts/stromal cells and osteoclast precursor
Coupling
Bone formation occurs at sites of previous bone resorption
Balance - bone remodelling
Amount of bone removed by osteoclasts should be replaced by osteoblastic activity
Derivation of osteoclasts
Haematopoietic stem cells