Chondrocyte

Chondrocyte
File:Hypertrophic Zone of Epiphyseal Plate.jpg Light micrograph of hyaline cartilage showing its chondrocytes and organelles, lacunae and matrix.
Details
Latin	chondrocytus
Identifiers
Code	TH H2.00.03.5.00003
TA
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	{{#property:P1402}}
Anatomical terminology [[[d:|edit on Wikidata]]]

Chondrocytes (from Greek χόνδρος, chondros = cartilage + κύτος, 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 the word chondroblast is commonly used to describe an immature chondrocyte, the term is imprecise, since the progenitor of chondrocytes (which are mesenchymal stem cells) can differentiate into various cell types, including osteoblasts.

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

Mesenchymal (mesoderm origin) stem cells (MSC) are undifferentiated, meaning they can differentiate into a variety of generative cells commonly known as osteochondrogenic (or osteogenic, chondrogenic, osteoprogenitor, etc.) cells. When referring to bone, or in this case cartilage, the originally undifferentiated mesenchymal stem cells lose their pluripotency, proliferate and crowd together in a dense aggregate of chondrogenic cells (cartilage) at the location of chondrification. These chondrogenic cells differentiate into so-called chondroblasts, which then synthesize the cartilage extra cellular matrix (ECM), consisting of a ground substance (proteoglycans, glycosaminoglycans for low osmotic potential) and fibers. The chondroblast is now a mature chondrocyte that is usually inactive but can still secrete and degrade the matrix, depending on conditions.

BMP4 and FGF2 have been experimentally shown to increase chondrocyte differentiation.

Chondrocytes undergo terminal differentiation when they become hypertrophic, which happens during endochondral ossification. This last stage is characterized by major phenotypic changes in the cell.

Gallery

• 

  Chondrocytes in hyaline cartilage

• 

  Transmission electron micrograph of a chondrocyte, stained for calcium, showing its nucleus (N) and mitochondria (M).

See also

• Endochondral ossification
• Intramembranous ossification

External links

• Histology image: 03317loa – Histology Learning System at Boston University
• Chondrocytes at the US National Library of Medicine Medical Subject Headings (MeSH)
• Stem cell information