COMP-Ang1, a chimeric form of Angiopoietin 1, enhances BMP2-induced osteoblast differentiation and bone formation

• Published in: Bone (New York, N.Y.) Vol. 46; no. 2; pp. 479 - 486
• Main Authors: Jeong, Byung-Chul, Kim, Hyun-Joo, Bae, In-Ho, Lee, Kkot-Nim, Lee, Kwang-Youl, Oh, Won-Mann, Kim, Sun-Hun, Kang, In-Chol, Lee, Shee-Eun, Koh, Gou-Young, Kim, Kyung-Keun, Koh, Jeong-Tae
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-02-2010; Elsevier
• Subjects: Angiogenesis; Angiopoietin-1 - genetics; Angiopoietin-1 - metabolism; Angiopoietin-1 - pharmacology; Animals; Biological and medical sciences; Bone formation; Bone morphogenetic protein; Bone Morphogenetic Protein 2 - pharmacology; Calcification, Physiologic - drug effects; Cell Differentiation - drug effects; Cell Line; COMP-Ang1; Extracellular Matrix - drug effects; Extracellular Matrix - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; Humans; Male; Mice; Mice, Inbred C57BL; Orthopedics; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteogenesis - drug effects; Osteogenesis - genetics; Phosphorylation - drug effects; Receptor, TIE-2 - genetics; Receptor, TIE-2 - metabolism; Recombinant Fusion Proteins - pharmacology; Signal Transduction - drug effects; Tie2; Transcription, Genetic - drug effects; Transcriptional Activation - drug effects; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Angiogenesis; Bone morphogenetic protein; Bone formation; Tie2; COMP-Ang1; Morphology; Osteoblast; Bone
• ISSN: 8756-3282; 1873-2763
• DOI: 10.1016/j.bone.2009.09.019

Abstract Introduction Angiogenesis is closely associated with bone formation, especially endochondral ossification. Angiopoietin 1 (Ang1) is a specific growth factor functioning to generate a stable and matured vasculature through the Tie2 receptor/PI3K/AKT pathway. Recently cartilage oligomeric matrix protein (COMP)-Ang1, an Ang1 variant which is more potent than native Ang1 in phosphorylating Tie2 receptor and AKT, was developed. This study was designed to examine the effects of angiogenic COMP-Ang1 on BMP2-induced osteoblast differentiation and bone formation. Methods Expression of endogenous Ang-1 and its binding receptor Tie 2 mRNA was examined in osteoblast-like cells and primary mouse calvarial cells by RT-PCR analysis, and was also monitored during osteoblast differentiation induced by BMP-2 and/or ascorbic acid and β-glycerophosphate. Effects of COMP-Ang-1 on osteoblast differentiation and mineralization were evaluated by alkaline phosphatase (ALP) activity and osteocalcin (OC) production, and Alizarin red stain. For a molecular mechanism, Western blot and OG2 and 6xOSE promoter assays were done. For in vivo evaluation, adenoviral (Ad) vectors containing COMP-Ang-1 or BMP-2 gene were administered into thigh muscle of mice, and after 2 weeks bone formation was analyzed by micro-computed tomography and histology. Angiogenic event of COMP-Ang1 was confirmed by immunofluorescence analysis with anti-CD31 antibody. Results Expression of Tie2 receptor was significantly increased in the course of osteoblast differentiation. Treatment or overexpression of COMP-Ang1 enhanced BMP2-induced ALP activity, OC production, and mineral deposition in a dose-dependent manner. In addition, COMP-Ang1 synergistically increased OG2 and 6xOSE promoter activities of BMP2, and sustained p38, Smad and AKT phosphorylation of BMP2. Notably, in vivo intramuscular injection of COMP-Ang1 dose-dependently enhanced BMP2-induced ectopic bone formation with increases in CD31 reactivity. Conclusions These results suggest that COMP-Ang1 synergistically enhanced osteoblast differentiation and bone formation through potentiating BMP2 signaling pathways and angiogenesis. Combination of BMP2 and COMP-Ang1 should be clinically useful for therapeutic application to fracture and destructive bone diseases.