Cartilage tissue composition Flashcards
What cells make up the cartilage?
Only one cell type is found in cartilage
Chondrocyes
Where are chondrocytes derived from?
Mesenchymal cells
Same precursors as osteoblasts - differentiation depends on transcription factors stimulated
Sox9 = chondrocyte Col1 = osteoblasts
Role of chondrocytes
Secrete matrix into pericellular space
Limited proliferative capacity
What do chondrocytes express?
SOX9
Aggrecan
Collagen type II
How are chondrocytes found in the ECM?
Reside as spherical cells
Embedded into cartilage ECM within chondrons
What are chondrons?
Clusters of isogenic groups
What are the three mechanisms by which chondrocytes increase cartilage size and mass?
Appositional growth
Interstitial growth
Undergo hypertrophy
What is appositional growth?
Increase in width
ECM deposition on existing matrix
What is interstitial growth?
Increase in length
Cell divisinon and ECM secretion
What are common cartilage ECM molecules?
Collagen type II
Proteoglycans
Glucosaminoglycans
Glycoproteins
Common proteoglycan found in cartilage ECM?
Aggrecan
Describe the structure of Aggrecan
Mass of 3 x 10^6 Da
Made of over 100 GAG chains
GAG chains on protein core form Aggrecan
Many aggrecan molecules connect to a larger protein Hyaluronan core-> forms large aggregates
Function of Aggrecan
Water-retaining ability
Large stable 3D structure
Properties of Aggrecan are main cause of the hydrated gel properties of articular cartilage
Common GAG found in cartilage?
Hyaluronan aka Hyaluronic acid
Structure of Hyaluronan
Regular repeating sequence of 25 000 disaccharide units
Simplest of the GAGs
