An osteoclast (from the Greek words for "bone" and "broken") is a type of bone cell that removes bone tissue by removing the bone's mineralized matrix. This process is known as bone resorption. Osteoclasts and osteoblasts are instrumental in controlling the amount of bone tissue. Osteoblasts form bone; osteoclasts resorb bone. Osteoclasts are formed by the fusion of cells of the monocyte-macrophage cell line. Osteoclasts are characterized by high expression of tartrate resistant acid phosphatase (TRAP) and cathepsin K.
acid ATPase
constitutes a unique form in the family of 
				tartrate-resistant acid phosphatases and may thus have the 
				potential as a marker for osteoclast ontogeny and function.
				
				PMID: 2533053
Calcitonin (CT) receptor (CTR)
a specific marker of the differentiated 
				osteoclast that is regulated by calcitonin.
				
				PMID: 7664679
a marker of osteoclast heterogeneity in 
				osteopetrotic rodents.
				
				PMID: 2845732
Carboxyterminal Telopeptide of Type 1 Collagen (1CTP)
a marker of osteoclastic bone resorption.
				
				PMID: 9223389
Cathepsin K
a member of the papain superfamily of 
				cysteine proteases and plays a pivotal role in osteoclast-mediated 
				bone resorption.
				
				PMID: 12910475,
				
				PMID: 11277265
a novel cysteine protease previously reported 
				to be restricted in its expression to osteoclasts.
				
				PMID: 9393764
predominantly expressed in osteoclasts and is 
				closely related to cathepsins L.
				
				PMID: 8874809
CKBB (creatine kinase BB)
predominantly found in brain and is not 
				normally detected in the blood.
				
				PMID: 8889843
Creatine kinase-BB in mammalian osteopetrosis 
				is related to osteoclastic number and size, where it probably 
				reflects the differentiation and maturation of inactive bone 
				resorbing cells.
				
				PMID: 10943208
DAMP (acidotrophic amine 
			3-(2,4-dinitroanillino)-3'-amino-N-methyldipropylamine)
A low pH marker for visualization of acidic 
				compartments in cultured osteoclasts.
				
				PMID: 10639743
ED1
The antibody ED1 stains monocytes, 
				macrophages and osteoclast in the bone marrow and in the newly 
				formed fracture callus.
				
				PMID: 15626449
the combined use of TRAP and ED1 can be used 
				to identify OC and their precursors in vivo.
				
				PMID: 12052261
characterizes rat osteoclasts, monocytes, and 
				macrophages.
				
				PMID: 7730591
Kat1-antigen (Kat1-Ag)
a reliable immunological marker for 
				identifying osteoclast precursors of rats: detection of 
				subpopulations among precursors and initiation of 
				osteoclastogenesis.
				
				PMID: 11326749
P1CP (procollagen carboxyterminal propeptide)
an indicator of osteoblastic bone formation.
				
				PMID: 9223389
RANK
a cell surface marker of human osteoclast 
				precursors in peripheral blood, bone marrow, and giant cell 
				tumors of bone.
				
				PMID: 16939392
Tartrate-resistant acid ATPase
a cytochemical marker for osteoclasts.
				
				PMID: 2461980
TRAP (tartrate-resistant acid phosphatase)
an important cytochemical marker of 
				osteoclasts.
				
				PMID: 9102061
a marker of osteoclast function.
				
				PMID: 6809291
TRAcP activity alone is not a reliable marker 
				for osteoclasts in bone marrow cultures.
				
				PMID: 2064844
Vacuolar-Type Proton Pump (E11)
osteoclast differentiation marker.
				
				PMID: 1701138
Vitronectin Receptor (VR, VNR)
fully differentiated osteoclast marker.
				
				PMID: 11448014,
				
				PMID: 1701138
Rat osteoclast precursors in vivo express a 
				vitronectin receptor and a chloride-bicarbonate exchanger.
				
				PMID: 9862219
Other Osteoclast Markers
calcitonin receptor binding is a 
				morphological and functional marker of osteoclasts that can be 
				used in assessing the pathophysiology of disorders of bone 
				remodeling.
				
				PMID: 2845732
histochemical demonstration of TR-AP versus 
				TS-AP on GMA-embedded bone sections by means of a pre-incubation 
				method can be used as an identification marker of (pre)osteoclasts.
				
				PMID: 3745910
Osteoclasts derive from hematopoietic stem 
				cells according to marker, giant lysosomes of beige mice.
				
				PMID: 6112089
Giant lysosomes, a cytoplasmic marker in 
				osteoclasts of beige mice.
				
				PMID: 7391859
Alkaline phosphatase expression during 
				monocyte differentiation. Overlapping markers as a link between 
				monocytic cells, dendritic cells, osteoclasts and osteoblasts.
				
				PMID: 10879691