title: Angiopoietin-1 peptide QHREDGS promotes osteoblast differentiation, bone matrix deposition and mineralization on biomedical materials.
abstract: Bone loss occurs as a consequence of a variety of diseases as well as from traumatic injuries, and often requires therapeutic intervention. Strategies for repairing and replacing damaged and/or lost bone tissue include the use of biomaterials and medical implant devices with and without osteoinductive coatings. The soluble growth factor angiopoietin-1 (Ang-1) has been found to promote cell adhesion and survival in a range of cell types including cardiac myocytes, endothelial cells and fibroblasts through an integrin-dependent mechanism. Furthermore, the short sequence QHREDGS has been identified as the integrin-binding sequence of Ang-1 and as a synthetic peptide has been found to possess similar integrin-dependent effects as Ang-1 in the aforementioned cell types. Integrins have been implicated in osteoblast differentiation and bone mineralization, processes critical to bone regeneration. By binding integrins on the osteoblast surface, QHREDGS could promote cell survival and adhesion, as well as conceivably osteoblast differentiation and bone mineralization. Here we immobilized QHREDGS onto polyacrylate (PA)-coated titanium (Ti) plates and polyethylene glycol (PEG) hydrogels. The osteoblast differentiation marker, alkaline phosphatase, peaked in activity 4-12 days earlier on the QHREDGS-immobilized PA-coated Ti plates than on the unimmobilized, DGQESHR (scrambled)- and RGDS-immobilized surfaces. Significantly more bone matrix was deposited on the QHREDGS-immobilized Ti surface than on the other surfaces as determined by atomic force microscopy. The QHREDGS-immobilized hydrogels also had a significantly higher mineral-to-matrix (M/M) ratio determined by Fourier transform infrared spectroscopy. Alizarin Red S and von Kossa staining and quantification, and environmental scanning electron microscopy showed that while both the QHREDGS- and RGDS-immobilized surfaces had extensive mineralization relative to the unimmobilized and DGQESHR-immobilized surfaces, the mineralization was more considerable on the QHREDGS-immobilized surface, both with and without the induction of osteoblast differentiation. Finally, treatment of cell monolayers with soluble QHREDGS was demonstrated to upregulate osteogenic gene expression. Taken together, these results demonstrate that the QHREDGS peptide is osteoinductive, inducing osteoblast differentiation, bone matrix deposition and mineralization.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, M5S 3G9 Canada.
authors.forename: Nicole
authors.initials: N
authors.lastname: Feric
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Calvin C H
authors.initials: CC
authors.lastname: Cheng
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada ; Institute for Optical Sciences, University of Toronto, Toronto, Ontario M5S 1A7, Canada.
authors.forename: M Cynthia
authors.initials: MC
authors.lastname: Goh
authors.affiliation: Covalon Technologies Ltd., Mississauga, Ontario L4Z 3E6, Canada.
authors.forename: Vyacheslav
authors.initials: V
authors.lastname: Dudnyk
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada.
authors.forename: Val
authors.initials: V
authors.lastname: Di Tizio
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, M5S 3G9 Canada ; Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S 3E5, Canada.
authors.forename: Milica
authors.initials: M
authors.lastname: Radisic