Chondrocyte

Chondrocytes (from Greek chondros cartilage + kytos cell) are the only cells found in 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 osteoblasts. The organization of chondrocytes within cartilage differs depending upon the type of cartilage and where in the tissue they are found.

Differentiation
From least- to terminally-differentiated, the chondrocytic lineage is:
 * 1) Colony-forming unit-fibroblast (CFU-F)
 * 2) Mesenchymal stem cell / marrow stromal cell (MSC)
 * 3) Chondrocyte
 * 4) Hypertrophic chondrocyte

When referring to bone or cartilage, mesenchymal stem cells (MSC) are commonly known as osteochondrogenic (or osteogenic, chondrogenic, osteoprogenitor, etc.) cells since a single MSC has shown the ability to differentiate into chondrocytes or osteoblasts, depending on the medium. In vivo, differentiation of an MSC in a vascularized area (such as bone) yields an osteoblast, whereas differentiation of an MSC in a non-vascularized area (such as cartilage) yields a chondrocyte. Chondrocytes undergo terminal differentiation when they become hypertrophic during endochondral ossification. This last stage is characterized by major phenotypic changes in the cell.