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Structure and Development of Osteocytes
- Osteocytes have a stellate shape, with a cell body size of 5-20 micrometers in diameter.
- They form an extensive lacunocanalicular network within the bone matrix.
- Osteocytes were present in bones of jawless fish 400 to 250 million years ago.
- Osteoblasts differentiate into osteocytes during bone formation.
- Osteocytes can also be formed from other osteocytes through cell division.
Functions of Osteocytes
- Osteocytes are the most common cell type in bone and play a crucial role in maintaining bone mass.
- They are capable of molecular synthesis and modification.
- Osteocytes contain glutamate transporters that produce nerve growth factors after bone fracture.
- They regulate mineral metabolism, including phosphates.
- Osteocytes are involved in bone remodeling and resorption.
Sclerostin and Osteocytes
- Osteocytes synthesize sclerostin, a protein that inhibits bone formation.
- Sclerostin acts in a paracrine fashion and is inhibited by parathyroid hormone and mechanical loading.
- Only osteocytes express sclerostin.
- Sclerostin antagonizes the activity of BMP, a cytokine that induces bone and cartilage formation.
Pathophysiology of Osteocytes
- Osteocytes play a role in osteonecrosis and diseases like X-linked hypophosphatemia.
- They are affected by mechanical loading and parathyroid hormone.
- Osteocytes regulate mineral metabolism, including phosphates.
- Dysfunction of osteocytes can lead to bone remodeling and resorption.
- Osteocyte cell death is associated with osteoporosis and osteoarthritis.
Osteocyte Research and Additional Information
- Gel-based in vitro 3D models explore the osteocytic potentiality of human CD34+ stem cells.
- Osteocytes shape and processes depend on actin filaments.
- Osteocytes play a role in bone resorption and mineral homeostasis regulation.
- Additional information includes references to scientific papers and studies on osteocytes, differentiation and ultrastructural studies, and the impact of osteocyte apoptosis on bone resorption and skeletal response.
An osteocyte, an oblate shaped type of bone cell with dendritic processes, is the most commonly found cell in mature bone. It can live as long as the organism itself. The adult human body has about 42 billion of them. Osteocytes do not divide and have an average half life of 25 years. They are derived from osteoprogenitor cells, some of which differentiate into active osteoblasts (which may further differentiate to osteocytes). Osteoblasts/osteocytes develop in mesenchyme.
| Osteocyte | |
|---|---|
 Transverse section of a bone | |
 Illustration showing a single osteocyte | |
| Details | |
| Location | Bone |
| Identifiers | |
| Latin | osteocytus |
| MeSH | D010011 |
| TH | H2.00.03.7.00003 |
| FMA | 66779 |
| Anatomical terms of microanatomy | |
In mature bones, osteocytes and their processes reside inside spaces called lacunae (Latin for a pit) and canaliculi, respectively. Osteocytes are simply osteoblasts trapped in the matrix that they secrete. They are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi, which are used for exchange of nutrients and waste through gap junctions.
Although osteocytes have reduced synthetic activity and (like osteoblasts) are not capable of mitotic division, they are actively involved in the routine turnover of bony matrix, through various mechanosensory mechanisms. They destroy bone through a rapid, transient (relative to osteoclasts) mechanism called osteocytic osteolysis. Hydroxyapatite, calcium carbonate and calcium phosphate is deposited around the cell.
