Table 1.
Types of collagens that may be present in articular cartilage.
| Collagen | Chains | Genes | Clasification | % * | Distribution in Articular Cartilage | Distribution in the Human Body |
|---|---|---|---|---|---|---|
| Type I | [α1(I)]2α2(I) | COL1A1 COL1A2 | Fibrill-forming collagen | 0% | Fibrocartilage | Bone, skin, cornea, and many interstitial connective tissues with the exception of hyaline cartilage, brain and vitreous body. |
| Type II | [α1(II)]3 | COL2A1 | Fibrill-forming collagen | 90–95% | ECM of all zones | Cartilage, vitreous, and intervertebral disc. |
| Type III | [α1(III)]3 | COL3A1 | Fibrill-forming collagen | n/a | n/a | Bloods vessels, uterus, bowel, skin, tendon, ligament, cartilage, periodontal ligament, and synovial membranes. |
| Type IV | [α1(IV)]2α2(IV) α3(IV)α4(IV)α5(IV) [α5(IV)]2α6(IV) |
COL4A1 COL4A2 COL4A3 COL4A4 COL4A5 COL4A6 | Network-forming collagen | n/a | PCM | Skin, basement membranes, lung, kidney, cochlea eye, smooth muscle, oesophagus, and cartilage. |
| Type V | α1(V)2α2(V) | COL5A1 COL5A2 | Fibrill-forming collagen | n/a | PCM | Adipose tissue, skeletal muscle, cartilage, pancreatic islets, skin, placenta, and lung. |
| Type VI | α1(VI)α2(V)α3(V) α1(VI)α2(V)α4(V) α1(VI)α2(V)α5(V) α1(VI)α2(V)α6(V) |
COL6A1 COL6A2 COL6A3 COL6A4 COL6A5 COL6A6 | Beaded filament collagen | 1–2% | PCM | Skin, cornea, blood vessels, heart, lung, adipose tissue, nervous, pancreas, bone, cartilage, and muscle. |
| Type IX | α1(IX)α2(IX)α3(IX) | COL9A1 COL9A2 COL9A3 | FACIT | 1–5% | ECM of all zones and growth plate in adults | Cartilages, eye vitreum, avian cornea, ear, and intervertebral disc. |
| Type X | [α1(X)]3 | COL10A1 | Network-forming collagen | 1% | Calcified zone and hypertrophic cartilage | Hypertrophic cartilage and the calcified zone. |
| Type XI | α1(XI)α2(XI)α3(XI) | COL11A1 COL11A2 COL2A1 | Fibrill-forming collagen | 1–5% | ECM of all zones and PCM | Cartilage, tendons, trabecular bone, testis, trachea, skeletal muscle, placenta, ovarian, lung, and brain. |
*: percentage of collagen in healthy articular cartilage; ECM: extracellular matrix; PCM: pericellular matrix; FACIT: fibril-associated collagens with interrupted triple helices. n/a: no studies have been found to support it.