Local delivery of COMP-angiopoietin 1 accelerates new bone formation in rat calvarial defects

Recombinant COMP‐Ang1, a chimera of angiopoietin‐1 (Ang1) and a short coiled‐coil domain of cartilage oligomeric matrix protein (COMP), is under consideration as a therapeutic agent in bone reconstruction. However, the potential of COMP‐Ang1 to regenerate impaired bone and induce new bone formation has not been completely explored. In this study, male Sprague–Dawley rats underwent calvarial defect surgery and divided into two groups: scaffold treatment alone (control group) and COMP‐Ang1‐impregnated scaffold (COMP‐Ang1 group). According to live micro‐CT and histological analyses, the COMP‐Ang1 group showed greater new bone formation and maturation than did the control both four and eight weeks after surgery. The values of bone volume, bone mineral density, and bone surface were also higher in the COMP‐Ang1 group than in the control at the same weeks after surgery. In addition, the delivery of COMP‐Ang1 facilitated significantly the expression of osteoblast‐specific markers such as runt‐related transcription factor 2 (p