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Critical Reviews™ in Eukaryotic Gene Expression

Impact factor: 1.660

ISSN Print: 1045-4403
ISSN Online: 2162-6502

Critical Reviews™ in Eukaryotic Gene Expression

DOI: 10.1615/CritRevEukaryotGeneExpr.v13.i24.180
12 pages

Anti-Osteoactivin Antibody Inhibits Osteoblast Differentiation and Function In Vitro

Abdulhafez A. Selim
Department of Anatomy and Cell Biology, Temple University, School of Medicine, Philadelphia, PA
Samir M. Abdelmagid
Department of Anatomy and Cell Biology, Temple University, School of Medicine, Philadelphia, PA
Reem A. Kanaan
Department of Anatomy and Cell Biology, Temple University, School of Medicine, Philadelphia, PA
Steven L. Smock
Department of Cardiovascular and Metabolic Diseases, Pfizer Global Research and Development - Groton Laboratories, Groton, CT 06340
Thomas A. Owen
Department of Theoretical and Applied Science, Ramapo College of New Jersey, Mahwah, New Jersey; and Department of Cardiovascular and Metabolic Diseases , Pfizer Global Research and Development - Groton Laboratories, Groton, CT 06340, USA
Steven N. Popoff
Department of Anatomy and Cell Biology, and Department of Orthopaedic Surgery and Sport Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
Fayez F. Safadi
Department of Anatomy and Cell Biology, Department of Orthopaedic Surgery and Sport Medicine, Department of Otolaryngology, Temple University School of Medicine, Philadelphia, PA, USA

ABSTRACT

Osteoactivin (OA) is a novel protein identified by mRNA differential display using bone from osteopetrotic versus normal rats. Bioinformatic analysis showed that OA cDNA has an open reading frame of 1716 bp encoding a protein of 572 aa, the first 21 aa constitute a signal peptide. OA sequence analysis also demonstrated 13 putative N-glycosylation sites suggestive of a heavily glycosylated protein. In this study, we localized OA protein in primary osteoblast culture by immunofluorescent staining and Western blot analysis. Primary osteoblast cultures pass through three stages: proliferation from day 1 to 7, matrix formation from day 7 to 14, and matrix mineralization from day 14 to 21. OA protein was detected at all stages examined, with maximal expression at 3 weeks when osteoblasts are terminally differentiated. Using the Chariot transfection reagent as a vehicle to deliver anti-OA antibody into the cells, we demonstrated that anti-OA antibody significantly inhibited osteoblast differentiation markers, including alkaline phosphatase activity, nodule formation, osteocalcin production, and calcium deposition, without affecting cell proliferation or viability. These data suggest that OA is an osteoblast-related protein that plays an important role in the regulation of osteoblast differentiation and function.