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.