Chondrocytes (from Greekchondros cartilage + kytos cell) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans. Although chondroblast is still commonly used to describe an immature chondrocyte, use of the term is discouraged, for it is technically inaccurate since the progenitor of chondrocytes (which are mesenchymal stem cells) can also differentiate into several cell types including osteoblasts. The organization of chondrocytes within cartilage differs depending upon the type of cartilage and where in the tissue they are found.
From least- to terminally-differentiated, the chondrocytic lineage is:
Colony-forming unit-fibroblast (CFU-F)
Mesenchymal stem cell / marrow stromal cell (MSC)
When referring to bone or cartilage, mesenchymal stem cell (mesoderm origin) are undifferentiated meaning they can differentiate into different variance of generative cells (MSC) are commonly known as osteochondrogenic (or osteogenic, chondrogenic, osteoprogenitor, etc.) cell. Undifferentiated mesenchymal stem cell lose their process, proliferate and crowd together in a dense aggregate of chondrogenic cells(cartilage) at the center of chondrification. These chondrogenic cells will then differentiate to chondroblasts which will then to synthesize the cartilage ECM (extra cellular matrix). Which consists of ground substance(proteoglycans, glycosaminoglycans for low osmotic potential) and fibers. The chondroblasts then trap themselves in a small space that is no longer in contact with the newly created matrix called lacunae which contain extracellular fluid. The chondroblast is now a chondrocyte, which is usually inactive but can still secrete and degrade matrix depending on the conditions. The majority of the cartilage that has been built has been synthesized from the chondroblast which are much more inactive at a late age (adult hood) compared to earlier years (pre-pubesence)
BMP4 and FGF2 have been experimentally shown to increase chondrocyte differentiation.
Chondrocytes undergo terminal differentiation when they become hypertrophic during endochondral ossification. This last stage is characterized by major phenotypic changes in the cell.
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