Chondrocyte

Chondrocyte
Chondrocytes of hyaline cartilage showing organelles, lacunae and matrix.
Latin	chondrocytus
Code	TH H2.00.03.5.00003

Chondrocytes (from Greek chondros 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.^{[citation needed]}

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 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 condrogenic 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.

Gallery

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  Chondrocytes in hyaline cartilage

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  Chondrocyte, stained for calcium, showing nucleus (N) and mitochondria (M)

See also

• Endochondral ossification
• Intramembranous ossification

References

• Dominici M, Hofmann T, Horwitz E (2001). "Bone marrow mesenchymal cells: biological properties and clinical applications". J Biol Regul Homeost Agents 15 (1): 28–37. PMID 11388742. 
• Bianco P, Riminucci M, Gronthos S, Robey P (2001). "Bone marrow stromal stem cells: nature, biology, and potential applications". Stem Cells 19 (3): 180–92. doi:10.1634/stemcells.19-3-180. PMID 11359943. 
• Stem cell information

External links

• BU Histology Learning System: 03317loa
• Chondrocytes at the US National Library of Medicine Medical Subject Headings (MeSH)