title: Absence of mouse pleiotrophin does not affect bone formation in vivo.
abstract: Pleiotrophin (Ptn) is an extracellular matrix protein that regulates hippocampal synaptic plasticity and learning behavior in vivo. Since the overexpression of Ptn in transgenic mice leads to increased bone formation, we analyzed whether a deficiency in Ptn expression would have a negative effect on bone remodeling. Bones from Ptn-deficient mice and wild-type littermates were analyzed using radiography, muCT imaging and undecalcified histology. Biomechanical stability was determined in a three-point-bending assay. Cellular activities were assessed using dynamic histomorphometry and the determination of urinary collagen degradation products. Skeletons of Ptn-deficient mice have no gross abnormalities, displayed a normal size, and showed no differences in growth plate organization compared to wild-type littermates. There were no obvious differences in bone mass as determined by radiographic and muCT imaging. The absence of a bone remodeling phenotype in Ptn-deficient mice was further confirmed using static histomorphometry and biomechanical testing. Finally, the number, morphology, and function of osteoclasts, osteoblasts, and osteocytes were not altered in Ptn-deficient mice compared to wild-type littermates. The complete skeletal analysis of Ptn-deficient mice presented here demonstrates that the lack of Ptn in mice does not affect bone formation in vivo. Therefore, Ptn does not play a significant role in normal bone physiology.
authors.affiliation: Department of Trauma, Hand, and Reconstructive Surgery, Hamburg University School of Medicine, Hamburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lehmann
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schinke
authors.forename: Arndt F
authors.initials: AF
authors.lastname: Schilling
authors.forename: Philip
authors.initials: P
authors.lastname: Catalá-Lehnen
authors.forename: Matthias
authors.initials: M
authors.lastname: Gebauer
authors.forename: Pia
authors.initials: P
authors.lastname: Pogoda
authors.forename: Louis C
authors.initials: LC
authors.lastname: Gerstenfeld
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Rueger
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Einhorn
authors.forename: Michael
authors.initials: M
authors.lastname: Amling
mesh_terms: D000818:Animals; D015519:Bone Density / Q000235:genetics; D001842:Bone and Bones / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D016207:Cytokines / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010012:Osteogenesis / Q000235:genetics*
chemical_list: D002352:Carrier Proteins; D016207:Cytokines; C066845:pleiotrophin