A doxycycline inducible, adenoviral bone morphogenetic protein-2 gene delivery system to bone

Abstract

We report the novel use of a tuneable, non-integrating viral gene delivery system to bone that can be combined with clinically approved biomaterials in an 'off-the-shelf' manner. Specifically, a doxycycline inducible Tet-on adenoviral vector (AdTetBMP-2) in combination with mesenchymal stromal cells (MSCs), fibrin and a biphasic calcium phosphate ceramic (MBCP®) was used to repair large bone defects in nude rats. Bone morphogenetic protein-2 (BMP-2) transgene expression could be effectively tuned by modification of the doxycycline concentration. The effect of adenoviral BMP-2 gene delivery upon bone healing was investigated in vivo in 4 mm critically sized, internally fixated, femoral defects. MSCs were transduced either by direct application of AdTetBMP-2 or by pre-coating MBCP granules with the virus. Radiological assessment scores post-mortem were significantly improved upon delivery of AdTetBMP-2. In AdTetBMP-2 groups, histological analysis revealed significantly more newly formed bone at the defect site compared with controls. Newly formed bone was vascularized and fully integrated with nascent tissue and implanted biomaterial. Improvement in healing outcome was achieved using both methods of vector delivery (direct application vs. pre-coating MCBP). Adenoviral delivery of BMP-2 enhanced bone regeneration achieved by the transplantation of MSCs, fibrin and MBCP in vivo. Importantly, our in vitro and in vivo data suggest that this can be achieved with relatively low (ng/ml) levels of the growth factor. Our model and novel gene delivery system may provide a powerful standardized tool for the optimization of growth factor delivery and release for the healing of large bone defects.

Mouse Embryonic Stem Cells Expressing GDNF Show Enhanced Dopaminergic Differentiation and Promote Behavioral Recovery After Grafting in Parkinsonian Rats

“…This difference in the number of TH + cells has no effect in pharmacological and non-pharmacological tests or neither elevating DA release measured by the HPLC. Our findings suggest that a better strategy to deliver GDNF in grafts should be considered, such as a regulable expression system activated by tetracycline, which proved to be effective in stem cells (Marquardt et al, 2015;Das et al, 2016;Guo et al, 2017;Bara et al, 2018;Ge et al, 2018). final approval of manuscript.…”

Biomimetic delivery of signals for bone tissue engineering

“…The goal of gene therapy is to deliver genes to the bone defect area so that they can regulate the expression of biomolecules (such as proteins) and cell activity to enhance proliferation and/or osteogenic differentiation. Gene transfection is often mediated by either a viral vector 96 , 177 (such as retrovirus, adenovirus, adeno-associated virus, herpesvirus) or a non-viral vector 178 , 179 (such as polycations or liposomes). Viral vectors have shown high gene transfection efficiency; however, associated safety issues, immune response, and side effects are of serious concern and greatly limit the translation of this approach into clinical use.…”

Anabolic Therapies in Osteoporosis and Bone Regeneration

“…Both non-genetic methods, such as conjugating oligoaspartic acid, which has a high affinity for hydroxyapatite in fracture sites and promotes elevated concentrations of the chosen agent within the fracture site, and methods using gene therapy for enhancing local transcription of growth factors have been described [103]. For example, a number of research groups have tried to find alternative methods to modulate the BMP-2 signalling pathway within the fracture site using viral vectors or copolymer-protected gene vectors [104,105]. However, these approaches are purely experimental at this stage and warrant further investigation for their clinical use to promote bone regeneration.…”