Table 1.
Composition of bone ECM.
| Molecular Weight | Function/regulates | Binds To | ||
|---|---|---|---|---|
| Organic (20% of bone mass) | Collagens | |||
| Type I | Range | Structural protein | Itg, TSP, OSN, OSP, BG, DC, BSP | |
| Type X | Range | Present in hypertropic cartilage | ||
| Type III | Range | Col fibril diameter | ||
| Type V | Range | Col fibril diameter | ||
| Adhesion proteins | ||||
| Fibronectin | ~ 400kD | Adhesion | Itg, Col, heparin, | |
| Thrombospondin | ~ 450 kD | Adhesion, bone formation | Ca, HAP, OSN | |
| Vitronectin | ~ 70kD | Adhesion | Itg, Col, heparin, | |
| Osteopontin | ~44-75kD | Adhesion, proliferation, resorption | Itg | |
| Osteonectin | ~35-45kD | HAP deposition, bone formation | Ca, HAP, Col, TSP | |
| Osteocalcin | ~5kD | Osteoclast activity | Ca | |
| Bone Sialoprotein | ~46-75kD | Adhesion, mineralization | Itg, Col | |
| Alkaline Phosphatase | ~80kD | Mineralization | - | |
| Proteoglycans | ||||
| Biglycan | ~270kD | Col fibril diameter | Col | |
| Decorin | ~150kD | Col fibril diameter | Col, TGF-β | |
| Inorganic (70% of bone mass) | Hydroxyapatite | - | Mechanical strength of bone | - |
Itg – Integrins, Col –Collagen, HAP –Hydroxyapatite, Ca –Calcium, TSP –Thrombospondin, OSN – Osteonectin, OSP – Osteopontin, BG – Biglycan, DC–Decorin, BSP – Bone Sialoprotein, TGF-β transforming growth factor- β.