Role of Adenoviral Mediated Expression of BMP-2 in Tissue Engineering

Objective: Bone tissue engineering (BTE) is evolving as a promising alternative to autologous bone grafts in the treatment of critical sized bone defects. Bone marrow mesenchymal stem cells (BMSC) in a supportive scaffold , and osteoinductive growth factors can facilitate bone regeneration. The release of osteoinductive factors and the mode of delivery at the defect site are crucial for the biological effects. Recombinant growth factors have short half- life , leading to rapid diffusion and non -availability at the defect site and requires high doses. To combat these limitations, gene transfer employing viral vectors is an emerging new technique for sustained delivery of growth factors . The objective of this study is to examine usefulness of BMSC engineered to express growth factor via adenoviral transfection as a means of growth factor delivery system in BTE.

Methods: Adenoviral vector expressing BMP-2 (AdBMP2) was constructed and BMSC were successfully infected and seeded into 3D copolymer scaffold Poly (L- lactide)-co-º-caprolactone {Poly (LLA-co-CL)}. In vitro Osteogenic effect of BMP-2 expression was analysed by using PCR array, ALP staining and Alizarin red staining. Furthermore, to evaluate in vivo osteogenic effect of AdBMP-2 , 3D copolymer {Poly (LLA-co-CL)} scaffolds loaded with BMP-2 expressing BMSC were implanted subcutaneously using NODSCID mouse –model.

Results: BMP-2 overexpression was verified in BMSC grown in copolymer scaffolds by quantitative RT-PCR (qRT-PCR) and ELISA at 3 and 14 days. PCR array showed that genes associated with osteogenesis including ALP, were upregulated both at 3 and 14 days. Moreover, enhanced ALP activity was verified by ALP staining in BMSC overexpressing BMP-2. Alizarin red staining showed increased calcium deposition.

Conclusion: Adenoviral mediated expression of BMP-2 in bone marrow mesenchymal  stem  cells grown in 3D copolymer scaffold {Poly(LLA-co-CL)} enhanced osteogenesis by promoting the expression of osteogenic markers and can be a promising approach in bone tissue engineering.