Saturday 22 November 2003
Osteoprogenitor cells are pluripotent mesenchymal stem cells that are located in the vicinity of all bony surfaces.
When appropriately stimulated by growth factors such as bone morphogenic proteins, which are members of the TGF-β superfamily, they undergo cell division and produce offspring that differentiate into osteoblasts.
The process of osteoblastic differentiation is initiated and governed by the transcription factor core binding factor a1, which activates osteoblast-specific gene expression.
The generation of osteoblasts from osteoprogenitor cells is vital to growth, remodeling, and repair of bone throughout life.
Osteoblasts and surface lining cells are located on the surface of bone and synthesize, transport, and arrange the many proteins of matrix detailed later. They also initiate the process of mineralization.
Recently, the hormone leptin and low-density lipoprotein receptor-related protein 5 have been shown to play an important role in determining osteoblastic activity, and they may represent evidence of central nervous system and cell-autonomous control of bone mass, respectively.
Metabolically active osteoblasts have a life span of approximately 3 months and then either undergo apoptosis, become surrounded by matrix and transform into osteocytes, or become quiescent, flattened, bone surface-lining cells.