Gene activated tissue grafts for sustained bone morphogenetic protein-2 delivery and bone engineering: is muscle with fascia superior to muscle and fat?

Background Previously, we have presented an expedited strategy for sustained delivery of BMP-2 to bone lesions based on the implantation of gene activated fat and muscle fragments. The aim of the present in vitro experiments was to evaluate the potential of muscle with fascia as a BMP-2 delivering osteo-regenerative implant in comparison to fat tissue and muscle alone. Methods Subcutaneous fat, muscle and muscle with fascia were harvested from Fischer 344 rats. The tissues were cut into small pieces and cultured for up to 90 days after direct transduction with adenoviral BMP-2 or GFP vectors. Different vector doses were applied and proliferation, long-term BMP-2 production, as well as osteogenic differentiation of the three different tissues were investigated in vitro. Results Muscle with fascia produced the largest amounts of BMP-2. Expression of the transgene was detected for up to 90 days. Proliferation was reduced with increased vector doses. Muscle with fascia showed a higher potential for osteogenic differentiation than fat but it was not improved as compared to muscle alone. A dose of 4x108 plaque forming units of the adenoviral BMP-2 vector appeared to be the optimal dose for transduction of muscle with fascia. Discussion Since muscle with fascia produced higher amounts of BMP-2 as compared to muscle alone or fat tissue grafts, showing a high potential for osteogenic differentiation, it might represent an improved osteo-regenerative implant facilitating endogenous repair. Future studies should investigate the effect of muscle with fascia transduced with 4x108 plaque forming units on bone healing in vivo.