Synthesis and inflammatory response of a novel silk fibroin scaffold containing BMP7 adenovirus for bone regeneration

Gene therapy has garnished tremendous awareness for the repair of osseous defects. It exhibits high efficiency gene transfer and osteogenic differentiation potential making it well suitable for the sustained delivery of growth factors to local tissues. In the present study a simplified solution-based in situ biomimetic synthesis method is demonstrated for bone morphogenetic protein 7 (BMP7) adenovirus combined with silk fibroin scaffolds. This scaffold not only provides the three dimensional space for bone ingrowth, but also releases the BMP7 adenovirus which targets its secretion by host cells in vivo. Scaffolds were tested both in vitro for their osteogenic potential as well as in vivo in a critical-size calvarial defect in mice. Scaffolds loaded with bone morphogenetic protein 7 adenovirus (adBMP7) were able to sustain release of adBMP7 for up to 21 days and support cell proliferation and differentiation to bone forming osteoblasts. Calvarial defects treated with scaffolds containing adBMP7 significantly induced new bone formation in vivo. To demonstrate immuno-compatibility with host tissues, IL-2, IL-6 and TNF-α were measured up to 4 weeks post-implantation. Although these scaffolds demonstrated an initial pro-inflammatory response, levels of IL-2, IL-6 and TNF-α returned to baseline control values at either 2 or 4 weeks post-implantation demonstrating long term compatibility for growth factor delivery via gene therapy. The results from the present study indicate the promise of gene delivery scaffold systems for robust, low cost, and high quality bone tissue engineering applications.