Bioactive scaffolding materials and efficient osteoinductive factors are key factors for bone tissue engineering. The present study aimed to mimic the natural bone repair process using an osteoinductive bone morphogenetic protein (BMP)-6-loaded nano-hydroxyapatite (nHA)/gelatin (Gel)/gelatin microsphere (GMS) scaffold pre-seeded with bone marrow mesenchymal stem cells (BMMSCs). BMP-6-loaded GMSs were prepared by cross-linking and BMP-6/nHAG/GMS scaffolds were fabricated by a combination of blending and freeze-drying techniques. Scanning electron microscopy, confocal laser scanning microscopy, and CCK-8 assays were carried out to determine the biocompatibility of the composite scaffolds in vitro. Alkaline phosphatase (ALP) activity was measured to evaluate the osteoinductivity of the composite scaffolds. For in vivo examination, critical-sized calvarial bone defects in Sprague-Dawley rats were randomly implanted with BMMSC/nHAG/GMS and BMMSC/BMP-6/nHAG/GMS scaffolds, and compared with a control group with untreated empty defects. The BMP-6-loaded scaffolds showed cytocompatibility by favoring BMMSC attachment, proliferation, and osteogenic differentiation. In radiological and histological analyses, the BMMSC-seeded scaffolds, especially the BMMSC-seeded BMP-6/nHAG/GMS scaffolds, significantly accelerated new bone formation. It is concluded that the BMP-6/nHAG/GMS scaffold possesses excellent biocompatibility and good osteogenic induction activity in vitro and in vivo, and could be an ideal bioactive substitute for bone tissue engineering.
Keywords: Osteoconductive scaffold; bone marrow mesenchymal stem cells; bone morphogenetic protein-6; bone tissue engineering.