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An osteoclast is a large multinucleated cell and human osteoclasts on bone typically have four nuclei [5] and are 150–200 μm in diameter. When osteoclast-inducing cytokines are used to convert macrophages to osteoclasts, very large cells that may reach 100 μm in diameter occur. These may have dozens of nuclei, and typically express major ...
Many believed osteoclasts and osteoblasts came from the same progenitor cell. Because of this, osteoclasts were thought to be derived from cells in connective tissue. Studies that observed that bone resorption could be restored by bone marrow and spleen transplants helped prove osteoclasts' hematopoietic origin. [3]
Calcitonin lowers blood levels of calcium by inhibiting the resorption of bone by osteoclasts, and its secretion is increased proportionally with the concentration of calcium. [7] Parafollicular cells are also known to secrete in smaller quantities several neuroendocrine peptides such as serotonin, somatostatin or CGRP.
TREM2 is expressed by microglia [30] and osteoclasts, and is involved in development and/or maintenance of brain and bone. [19] In mice, TREM2 is involved in synaptic pruning, a process of shaping neuronal circuitry by microglia- and astrocyte-mediated removal of excessive synapses via phagocytosis.
Osteocytes are cells of mesenchymal origin and originate from osteoblasts that have migrated into and become trapped and surrounded by a bone matrix that they themselves produced. [11] The spaces the cell body of osteocytes occupy within the mineralized collagen type I matrix are known as lacunae , while the osteocyte cell processes occupy ...
As well as susceptibility to breaks and fractures, osteoporosis can lead to other complications. Bone fractures from osteoporosis can lead to disability and an increased risk of death after the injury in elderly people. [29] Osteoporosis can decrease the quality of life, increase disabilities, and increase the financial costs to health care ...
The calcitonin receptor is a G protein-coupled receptor localized to osteoclasts [20] as well kidney and brain cells. It is coupled to a G s α subunit, thus stimulating cAMP production by adenylate cyclase in target cells. It may also affect the ovaries in women and the testes in men. [citation needed]
Osteoclasts are critical for the bone remodeling cycle which is achieved by the building of bone by osteoblasts, reabsorption by osteoclasts, and remodeling by osteoblasts. [10] Osteoclasts precursor cells and mature osteoclast require stimulation of CSF1R for survival.