title: The effects of colony-stimulating factor-1 (CSF-1) on the development of osteoclasts and their expression of tartrate-resistant acid phosphatase (TRAP) in toothless (tl-osteopetrotic) rats.
abstract: The osteopetrotic mutation toothless (tl) in the rat is characterized by a limited number of osteoclasts with reduced amounts and/or activity of tartrate-resistant acid phosphatase (TRAP). Treatment of tl/tl mutants with the cytokine colony-stimulating factor (CSF)-1 increases both osteoclast number and enzyme activity, consistent with a loss-of-function mutation in the CSF-1 gene recently detected in this mutant. We have pursued these observations to demonstrate that there is a dose-dependent increase in osteoclast number, but not to normal levels. Osteoclasts in CSF-1-treated tl/tl mutants are large, have well-developed clear zones and ruffled borders, and secrete TRAP into resorption lacunae. The expression of TRAP mRNA, protein, and enzyme activity per bone appear normal after CSF-1 treatment. However, in contrast to the predominantly apical intracellular distribution in normal osteoclasts, an enrichment of TRAP enzyme activity in osteoclasts of CSF-1-treated tl/tl mutants is observed in the basal part of the cell. Our observations suggest that the CSF-1-treated mutant bones contain an abundance of mature osteoclasts, actively expressing markers for osteoclasts such as TRAP, cathepsin K, and matrix metalloproteinase (MMP)-9. Accumulation of TRAP at the end of the endocytic pathway in mature osteoclasts formed during CSF-1 treatment suggests that the TRAP enzyme has a rapid turnover in these highly active cells and uses a transcytotic pathway.
authors.affiliation: Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, Huddinge University Hospital, 5-141 86 Huddinge, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Norgård
authors.forename: Sandy C
authors.initials: SC
authors.lastname: Marks
authors.forename: Finn P
authors.initials: FP
authors.lastname: Reinholt
authors.forename: Göran
authors.initials: G
authors.lastname: Andersson
mesh_terms: D000135:Acid Phosphatase; D000818:Animals; D030801:Animals, Genetically Modified; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology; D056657:Cathepsin K; D002403:Cathepsins / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004705:Endocytosis; D005269:Femur / Q000473:pathology; D015151:Immunoblotting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007527:Isoenzymes; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D008854:Microscopy, Electron; D009154:Mutation; D010010:Osteoclasts / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011859:Radiography; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071681:Tartrate-Resistant Acid Phosphatase; D013977:Tibia / Q000473:pathology
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D016173:Macrophage Colony-Stimulating Factor; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D002403:Cathepsins; D056657:Cathepsin K; C534133:Ctsk protein, rat; D020780:Matrix Metalloproteinase 9