Bone Marrow - nonneoplastic

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Bone marrow - nonneoplastic

Normal

Osteoblasts

Reviewers: Dragos Luca, M.D. (see Reviewers page)
Revised: 18 October 2012, last major update September 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Bone forming cell that arises from marrow mesenchymal (stromal) cells, unlike osteoclasts which are of hematopoietic origin
● Along endosteal surface of bony trabeculae or along margins in marrow smears
● Common in children; in adults associated with various diseases and healing biopsy sites
● Synthesize angiopoietin and osteopontin, which inhibit hematopoietic stem cell proliferation (Br J Haematol 2006;134:467, J Clin Invest 2006;116:1195)
● Synthesize and transport collagenous matrix, initiate and regulate mineralization, control removal of bone via osteoclasts
● When active, are plump and present on bone surface; eventually are encased within the collagen they produce and get flattened (and become osteocytes)
● Activity is promoted by physical activity (Wolf’s law of bone adaptation)
● Express parathormone receptors (mediates the activation of osteoclasts) and vitamin D receptor
● Control osteoclast activity via parathyroid hormone (parathormone), PHRP (Parathyroid hormone related protein), IL-1 and TNF alpha
● Digestion of bone by osteoclasts releases cytokines and growth factors for osteoblasts

Diagrams
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Interaction of osteoblasts and hematopoietic stem cells

Key functions and regulation of osteoblasts

Micro description
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● Large (25-50 microns), often oval, with abundant blue-gray cytoplasm and perinuclear hof separated from the nucleus (unlike plasma cells)
● Nucleus is markedly eccentric and round / ovoid with one or more nucleoli

Micro images
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Osteoblasts

Osteoblasts in marrow smear are twice as big as plasma cells, have abundant blue cytoplasm, eccentric nucleus and often single nucleolus

Positive stains
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● Alkaline phosphatase, estrogen receptor, parathyroid hormone and RANKL
● Also CD10, CD44, CD53, CD56, IL-12, IL-18 and IFN-gamma (Biosci Rep 2006;26:39)
● Cells in culture express CD11b, CD13, CD16, CD20, CD23, CD25, CD34, CD44, CD54, CD80, CD86 and HLA-DR (Cell Physiol Biochem 2002;12:359)

Negative stains
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● Cells in culture are negative for CD3, CD14, CD15, CD45 and CD68

Electron microscopy description
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● Resemble fibroblasts due to well-developed rough endoplasmic reticulum and Golgi zone

Electron microscopy images
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Various images

Colorized SEM

Additional references
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● Curr Stem Cell Res Ther 2008;3:131, Acta Reumatol Port 2007;32:103

End of Bone Marrow - nonneoplastic > Normal > Osteoblasts

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