title: Skeletal Mineralization Deficits and Impaired Biogenesis and Function of Chondrocyte-Derived Matrix Vesicles in Phospho1(-/-) and Phospho1/Pi t1 Double-Knockout Mice.
abstract: We have previously shown that ablation of either the Phospho1 or Alpl gene, encoding PHOSPHO1 and tissue-nonspecific alkaline phosphatase (TNAP) respectively, lead to hyperosteoidosis, but that their chondrocyte-derived and osteoblast-derived matrix vesicles (MVs) are able to initiate mineralization. In contrast, the double ablation of Phospho1 and Alpl completely abolish initiation and progression of skeletal mineralization. We argued that MVs initiate mineralization by a dual mechanism: PHOSPHO1-mediated intravesicular generation of inorganic phosphate (Pi ) and phosphate transporter-mediated influx of Pi . To test this hypothesis, we generated mice with col2a1-driven Cre-mediated ablation of Slc20a1, hereafter referred to as Pi t1, alone or in combination with a Phospho1 gene deletion. Pi t1(col2/col2) mice did not show any major phenotypic abnormalities, whereas severe skeletal deformities were observed in the [Phospho1(-/-) ; Pi t1(col2/col2) ] double knockout mice that were more pronounced than those observed in the Phospho1(-/-) mice. Histological analysis of [Phospho1(-/-) ; Pi t1(col2/col2) ] bones showed growth plate abnormalities with a shorter hypertrophic chondrocyte zone and extensive hyperosteoidosis. The [Phospho1(-/-) ; Pi t1(col2/col2) ] skeleton displayed significant decreases in BV/TV%, trabecular number, and bone mineral density, as well as decreased stiffness, decreased strength, and increased postyield deflection compared to Phospho1(-/-) mice. Using atomic force microscopy we found that ∼80% of [Phospho1(-/-) ; Pi t1(col2/col2) ] MVs were devoid of mineral in comparison to ∼50% for the Phospho1(-/-) MVs and ∼25% for the WT and Pi t1(col2/col2) MVs. We also found a significant decrease in the number of MVs produced by both Phospho1(-/-) and [Phospho1(-/-) ; Pi t1(col2/col2) ] chondrocytes. These data support the involvement of phosphate transporter 1, hereafter referred to as Pi T-1, in the initiation of skeletal mineralization and provide compelling evidence that PHOSPHO1 function is involved in MV biogenesis. © 2016 American Society for Bone and Mineral Research.
authors.affiliation: Sanford Children's Health Research Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
authors.forename: Manisha C
authors.initials: MC
authors.lastname: Yadav
authors.affiliation: Department of Experimental Medicine and Surgery, University of Rome Tor Vergata, Rome, Italy.|Inflammatory and Infectious Disease Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
authors.forename: Massimo
authors.initials: M
authors.lastname: Bottini
authors.affiliation: Department of Bioengineering, University of California San Diego, La Jolla, CA, USA.
authors.forename: Esther
authors.initials: E
authors.lastname: Cory
authors.affiliation: Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Kunal
authors.initials: K
authors.lastname: Bhattacharya
authors.affiliation: Sanford Children's Health Research Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
authors.forename: Pia
authors.initials: P
authors.lastname: Kuss
authors.affiliation: Sanford Children's Health Research Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
authors.forename: Sonoko
authors.initials: S
authors.lastname: Narisawa
authors.affiliation: Department of Bioengineering, University of California San Diego, La Jolla, CA, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sah
authors.affiliation: INSERM U791, Centre for Osteoarticular and Dental Tissue Engineering (LIOAD), Nantes, Cedex, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Beck
authors.affiliation: Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Fadeel
authors.affiliation: The Roslin Institute, The University of Edinburgh, Midlothian, Scotland, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Farquharson
authors.affiliation: Sanford Children's Health Research Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Millán
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology*; D002113:Calcification, Physiologic / Q000502:physiology*; D019902:Chondrocytes / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D050611:Sodium-Phosphate Cotransporter Proteins, Type III / Q000235:genetics / Q000378:metabolism*
chemical_list: C493587:Slc20a1 protein, mouse; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; C552022:PHOSPHO1 protein, mouse; D010744:Phosphoric Monoester Hydrolases
keywords: DEVELOPMENT; GENETIC ANIMAL MODELS; GROWTH PLATE; MOLECULAR PATHWAYS