Molecular Structure and Functions of Collagen
Marcel E. Nimni in Collagen, 1988
In regions subjected to compression, connective tissue cells take on the form recognized as that of the osteoblast and secrete an organic intercellular matrix (osteoid) which later becomes calcified and forms bone, a tissue adapted to withstand compression. The intercellular matrix surrounding the osteoblasts contains mostly collagen. Mineralization along these collagen fibers occurs quickly in such an environment and tissue quickly takes on the form of bone. The osteoblast locked in by mineral is identified morphologically as an osteocyte. When the compressive forces change their direction, as occurs following paralysis, orthodontic manipulations, or prolonged bed rest, connective-tissue cells identified as osteoclasts resorb the bone while osteoblasts in the field of compression form new bone.
Actions of Dopamine on the Skin and the Skeleton
Nira Ben-Jonathan in Dopamine, 2020
Bone is a metabolically active tissue composed of several cell types, including osteoblasts, osteocytes, and osteoclasts. Osteoblasts are involved in the creation and mineralization of bone tissue while osteocytes are mostly inactive, and are in contact with other cells in the bone through gap junctions. Osteoclasts are responsible for the breakdown of bone by the process of bone resorption. Osteoblasts and osteocytes are derived from osteoprogenitor cells. They are connective tissue cells found at the surface of bone, which can be stimulated to proliferate and differentiate. Osteoclasts are large, multinucleate cells formed through the fusion of precursor cells. They are derived from a monocyte stem-cell lineage and similar to macrophages have phagocytic properties. As discussed in Chapter 9, the bone marrow contains hematopoietic stem cells which give rise to white blood cells, red blood cells and platelets.
Biochemistry of Exercise Training: Effects on Bone
Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse in The Routledge Handbook on Biochemistry of Exercise, 2020
Osteoblasts partly originate from the stroma located in the bone marrow adjacent to the endosteum or in the periosteum. Bone is produced as layers (lamellae) of calcified material surrounding blood vessels. Throughout matrix formation, some osteoblasts are left behind and become embedded in the new matrix within cavities called lacunae. These trapped osteoblasts convert into mature bone cells called osteocytes and are nourished by long, slender, cytoplasmic processes that extend from the cells to the blood vessels in canals called canaliculi. These cells can then receive and transmit mechanical signals to other bone cells (neighbouring osteocytes, surface osteoblasts, or lining cells). Osteocytes account for more than 90% of adult bone cells, live the longest (up to 25 years), and as mechanosensitive cells, play an important role in the maintenance of bone mass and structure (28, 127). Both osteoblasts and osteocytes play an active role in mineral homeostasis by helping to release calcium from bone into the blood, which regulates the concentration of calcium in body fluids. The osteocyte lifespan depends on the rate of bone turnover (90).
Alveolar bone remodeling after tooth extraction in irradiated mandible: An experimental study with canine model
Published in Ultrastructural Pathology, 2018
Venni Heinonen, Timo J. Ruotsalainen, Lauri Paavola, Jopi J. Mikkonen, Pekka Asikainen, Arto P. Koistinen, Arja M. Kullaa
Bone remodeling process is performed by osteoclasts (bone resorbing cells) and osteoblasts (bone forming cells) at the bone surface. Osteocytes, most abundant bone cells, are believed to be responsible for the bone remodeling.10 Osteocytes react to dynamic and/or static loading such as gravity or exercise, and they are the most common cell type found in bone matrix, comprising more than 90% of all bone cells in mature bone. Osteocytes are derived from osteoblasts that are trapped under the mineralized bone matrix, and form a cellular network, called as lacunar-canalicular network (LCN), which allows communication between neighboring osteocytes, osteoblasts, and bone lining cells. Long dendritic processes of the osteocytes convey signals to the neighboring osteocytes and the cells of the bone surface.11 With this network, osteocytes control bone metabolism, and bone homeostasis (breakdown and formation of bone) by producing bone formation and/or resorption proteins.11,12
Simulation study on the effect of resistance exercise on the hydrodynamic microenvironment of osteocytes in microgravity
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Hai-Ying Liu, Chao-Hui Zhao, Hao Zhang, Wei Wang, Qing-Jian Liu
Bone is typically comprised of dense bone, cancellous bone, and tissue fluid. The osteon is the basic structural and physiological unit of dense bone, and it also has the highest bone density in the human skeletal system (Liu et al. 2020; Larcher and Scheiner 2021). The central tubular area of the osteon is called the Haversian canal, which contains arterial and venous capillaries that permit the transport of nutrients and metabolic waste needed for cell metabolism. The multi-layer circumferential lamellae around the Haversian canal consist of a complicated lacunar-canalicular system (LCS). The osteocytes are located in bone lacunae, and the adjacent osteocytes form a complex spatial mechanical signal transduction network through synaptic connections in the canaliculi. The LCS is an important channel for material exchange between osteocytes and capillaries in the Haversian canal (Kwon et al. 2010). The deformation of the bone matrix under loading can induce liquid flow in the LCS, and the mechanical signals produced by the liquid flow are perceived and responded to by osteocytes, thus regulating the activity of osteoblasts and osteoclasts to adjust bone mineral density to adapt to the current mechanical environment (Tovar et al. 2004).
Multi-scale numerical simulation on mechano-transduction of osteocytes in different gravity fields
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Chaohui Zhao, Haiying Liu, Congbiao Tian, Chunqiu Zhang, Wei Wang
Osteocytes ‘communicate’ with cells on the bone surface and other surrounding osteocytes through osteocyte processes. The tethering elements (TES) are arranged in a double helix along the axial direction of the canaliculi; one end of the TES is connected to the cross filament by transmembrane molecules and fixed to the cell membrane, and the other end is anchored to the inner wall of the canaliculus (You et al. 2004). The resistance to the pericellular matrix (PCM) induced by the flow of tissue fluid in the lacuna-canalicular system (LCS) can make TES ‘perceive’ higher mechanical stimulation. As a result, TES can effectively convey mechanical signals to the surface of the osteocyte process, and the surrounding area of physical connection between the osteocyte process and the TES can produce higher strain. TES can increase the initial strain by several orders of magnitude as a force transfer element in the stress and strain amplification mechanism (You et al. 2004). The strain amplification mechanism can compensate for the strain difference between osteocytes and bone tissue (Han et al. 2004; Wang et al. 2007).
Related Knowledge Centers
- Dmp1
- Gap Junction
- Hydroxyapatite
- Lacuna
- Mesenchyme
- Osteolysis
- Osteoclast
- Osteoblast
- Cell
- Bone Canaliculus