title: Pigment epithelium-derived factor restoration increases bone mass and improves bone plasticity in a model of osteogenesis imperfecta type VI via Wnt3a blockade.
abstract: Null mutations in for pigment epithelium-derived factor (PEDF), the protein product of the SERPINF1 gene, are the cause of osteogenesis imperfecta (OI) type VI. The PEDF-knockout (KO) mouse captures crucial elements of the human disease, including diminished bone mineralization and propensity to fracture. Our group and others have demonstrated that PEDF directs human mesenchymal stem cell (hMSC) commitment to the osteoblast lineage and modulates Wnt/β-catenin signaling, a major regulator of bone development; however, the ability of PEDF to restore bone mass in a mouse model of OI type VI has not been determined. In this study, PEDF delivery increased trabecular bone volume/total volume by 52% in 6-mo-old PEDF-KO mice but not in wild-type mice. In young (19-d-old) PEDF-KO mice, PEDF restoration increased bone volume fraction by 35% and enhanced biomechanical parameters of bone plasticity. A Wnt-green fluorescent protein reporter demonstrated dynamic changes in Wnt/β-catenin signaling characterized by early activation and marked suppression during terminal differentiation of hMSCs. Continuous Wnt3a exposure impeded mineralization of hMSCs, whereas the combination of Wnt3a and PEDF potentiated mineralization. Interrogation of the PEDF sequence identified a conserved motif found in other Wnt modulators, such as the dickkopf proteins. Mutation of a single amino acid on a 34-mer PEDF peptide increased mineralization of hMSC cultures compared with the native peptide sequence. These results indicate that PEDF counters Wnt signaling to allow for osteoblast differentiation and provides a mechanistic insight into how the PEDF null state results in OI type VI.-Belinsky, G. S., Sreekumar, B., Andrejecsk, J. W., Saltzman, W. M., Gong, J., Herzog, R. I., Lin, S., Horsley, V., Carpenter, T. O., Chung, C. Pigment epithelium-derived factor restoration increases bone mass and improves bone plasticity in a model of osteogenesis imperfecta type VI via Wnt3a blockade.
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA;
authors.forename: Glenn S
authors.initials: GS
authors.lastname: Belinsky
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA;
authors.forename: Bharath
authors.initials: B
authors.lastname: Sreekumar
authors.affiliation: Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA;
authors.forename: Jillian W
authors.initials: JW
authors.lastname: Andrejecsk
authors.affiliation: Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA;
authors.forename: W Mark
authors.initials: WM
authors.lastname: Saltzman
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA;
authors.forename: Jingjing
authors.initials: J
authors.lastname: Gong
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA;
authors.forename: Raimund I
authors.initials: RI
authors.lastname: Herzog
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut, USA;
authors.forename: Samantha
authors.initials: S
authors.lastname: Lin
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut, USA;
authors.forename: Valerie
authors.initials: V
authors.lastname: Horsley
authors.affiliation: Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA;
authors.forename: Thomas O
authors.initials: TO
authors.lastname: Carpenter
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA; Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA chuhan.chung@yale.edu.
authors.forename: Chuhan
authors.initials: C
authors.lastname: Chung
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000235:genetics / Q000502:physiology*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D049452:Green Fluorescent Proteins; D051379:Mice; D018345:Mice, Knockout; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D010013:Osteogenesis Imperfecta / Q000188:drug therapy* / Q000235:genetics; D015843:Serpins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D060509:Wnt3A Protein / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D005136:Eye Proteins; D049452:Green Fluorescent Proteins; D009414:Nerve Growth Factors; D015843:Serpins; D060509:Wnt3A Protein; D051176:beta Catenin; D000099174:Pigment Epithelium-Derived Factor; C555511:Wnt3a protein, mouse
keywords: PEDF; Wnt signaling; mesenchymal stem cell