Chondrocyte terminally-differentiate
From least- to terminally-differentiated, the chondrocytic lineage is:
- Colony-forming unit-fibroblast (CFU-F)
- Mesenchymal stem cell / marrow stromal cell (MSC)
- Chondrocyte
- 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
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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