title: Transgenic Expression of Osteoactivin/gpnmb Enhances Bone Formation In Vivo and Osteoprogenitor Differentiation Ex Vivo.
abstract: Initial identification of osteoactivin (OA)/glycoprotein non-melanoma clone B (gpnmb) was demonstrated in an osteopetrotic rat model, where OA expression was increased threefold in mutant bones, compared to normal. OA mRNA and protein expression increase during active bone regeneration post-fracture, and primary rat osteoblasts show increased OA expression during differentiation in vitro. To further examine OA/gpnmb as an osteoinductive agent, we characterized the skeletal phenotype of transgenic mouse overexpressing OA/gpnmb under the CMV-promoter (OA-Tg). Western blot analysis showed increased OA/gpnmb in OA-Tg osteoblasts, compared to wild-type (WT). In OA-Tg mouse femurs versus WT littermates, micro-CT analysis showed increased trabecular bone volume and thickness, and cortical bone thickness; histomorphometry showed increased osteoblast numbers, bone formation and mineral apposition rates in OA-Tg mice; and biomechanical testing showed higher peak moment and stiffness. Given that OA/gpnmb is also over-expressed in osteoclasts in OA-Tg mice, we evaluated bone resorption by ELISA and histomorphometry, and observed decreased serum CTX-1 and RANK-L, and decreased osteoclast numbers in OA-Tg, compared to WT mice, indicating decreased bone remodeling in OA-Tg mice. The proliferation rate of OA-Tg osteoblasts in vitro was higher, compared to WT, as was alkaline phosphatase staining and activity, the latter indicating enhanced differentiation of OA-Tg osteoprogenitors. Quantitative RT-PCR analysis showed increased TGF-β1 and TGF-β receptors I and II expression in OA-Tg osteoblasts, compared to WT. Together, these data suggest that OA overexpression has an osteoinductive effect on bone mass in vivo and stimulates osteoprogenitor differentiation ex vivo.
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania.
authors.forename: Nagat
authors.initials: N
authors.lastname: Frara
authors.affiliation: Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Samir M
authors.initials: SM
authors.lastname: Abdelmagid
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, Ohio.|School of Biomedical Sciences, Kent State University, Kent, Ohio.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Sondag
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, Ohio.|School of Biomedical Sciences, Kent State University, Kent, Ohio.
authors.forename: Fouad M
authors.initials: FM
authors.lastname: Moussa
authors.affiliation: Department of Kinesiology, California State University, East Bay, Hayward, California.
authors.forename: Vanessa R
authors.initials: VR
authors.lastname: Yingling
authors.affiliation: School of Theoretical and Applied Science (TAS), Ramapo College of New Jersey, Mahwah, New Jersey.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Owen
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Popoff
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania.
authors.forename: Mary F
authors.initials: MF
authors.lastname: Barbe
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, Ohio.|School of Biomedical Sciences, Kent State University, Kent, Ohio.
authors.forename: Fayez F
authors.initials: FF
authors.lastname: Safadi
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology; D016723:Bone Remodeling / Q000235:genetics / Q000502:physiology*; D001862:Bone Resorption / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology*; D010010:Osteoclasts / Q000166:cytology*; D010012:Osteogenesis / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D005136:Eye Proteins; C445671:Gpnmb protein, mouse; D008562:Membrane Glycoproteins; D018125:Receptors, Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625843:Tgfbr1 protein, rat