Improved calvarial bone repair by hASCs engineered with Cre/loxP‐based baculovirus conferring prolonged BMP‐2 and MiR‐148b co‐expression

Repairing large calvarial bone defects remains a challenging task. Previously, it was discovered that that miR‐148b, when acting in concert with bone morphogenetic protein 2 (BMP‐2), enhanced the osteogenesis of human adipose‐derived stem cells (hASCs) and improved calvarial bone healing in nude mice. However, the molecular target of miR‐148b remained elusive. Here it is revealed that miR‐148b directly targets NOG, whose gene product (noggin) is an antagonist to BMPs and negatively regulates BMP‐induced osteogenic differentiation and bone formation. A new Cre/loxP‐based baculovirus system was employed to drive prolonged BMP‐2 and miR‐148b overexpression in hASCs, wherein the BMP‐2 overexpression induced noggin expression but the concurrent miR‐148b expression downregulated noggin, thus relieving the negative regulatory loop and ameliorating hASC osteogenesis without hindering hASC proliferation or triggering appreciable cytotoxicity. Implantation of the engineered hASCs coexpressing BMP‐2 and miR‐148b into nude mice enabled substantial repair of critical‐size calvarial bone defects (4 mm diameter) at 12 weeks post‐transplantation, filling 83% of the defect area, 75% of bone volume and restoring the bone density to 89% of the original bone density. Such superior healing effects indicate the potential of the Cre/loxP‐based baculovirus‐mediated BMP‐2/miR‐148b expression for calvarial bone repair. Copyright © 2016 John Wiley & Sons, Ltd.