Gene delivery of bone morphogenetic protein-2 plasmid DNA promotes bone formation in a large animal model

Abstract

In the field of bone regeneration, BMP-2 is considered one of the most important growth factors because of its strong osteogenic activity, and is therefore extensively used in clinical practice. However, the short half-life of BMP-2 protein necessitates the use of supraphysiological doses, leading to severe side-effects. This study investigated the efficiency of bone formation at ectopic and orthotopic sites as a result of a low-cost, prolonged presence of BMP-2 in a large animal model. Constructs consisting of alginate hydrogel and BMP-2 cDNA, together acting as a non-viral gene-activated matrix, were combined with goat multipotent stromal cells (gMSCs) and implanted in spinal cassettes or, together with ceramic granules, intramuscularly in goats, both for 16 weeks. Bone formation occurred in all cell-seeded ectopic constructs, but the constructs containing both gMSCs and BMP-2 plasmid DNA showed higher collagen I and bone levels, indicating an osteogenic effect of the BMP-2 plasmid DNA. This was not seen in unseeded constructs, even though transfected, BMP-2-producing cells were detected in all constructs containing plasmid DNA. Orthotopic constructs showed mainly bone formation in the unseeded groups. Besides bone, calcified alginate was present in these groups, acting as a surface for new bone formation. In conclusion, transfection of seeded or resident cells from this DNA delivery system led to stable expression of BMP-2 during 16 weeks, and promoted osteogenic differentiation and subsequent bone formation in cell-seeded constructs at an ectopic location and in cell-free constructs at an orthotopic location in a large animal model.

Sonoporation Increases Therapeutic Efficacy of Inducible and Constitutive BMP2/7 In Vivo Gene Delivery

“…Average bone mineral densities were within the range of ectopic bone mineral densities expected in ectopic bone formation models (Usas et al, 2009;Wijdicks et al, 2009), but lower when compared with BMP9 sonoporative gene transfer (Sheyn et al, 2008). Average bone volumes, determined in this study and in Sheyn et al's (2008) approaches that use biomaterials in conjunction with gene delivery or growth factor delivery (Bessa et al, 2010;Wegman et al, 2012). This is probably because of the template function of biomaterials, which provides a templating environment in contrast to the solution injection approach used in this study.…”

Gene Delivery of TGF-β3 and BMP2 in an MSC-Laden Alginate Hydrogel for Articular Cartilage and Endochondral Bone Tissue Engineering

“…Encapsulation of MSCs in alginate hydrogels has demonstrated potential for both cartilage and bone regeneration in vitro and in vivo [21][22][23][24][25] . Alginate hydrogels have also been used as a 3D gene delivery platform for bone tissue engineering applications [26][27][28][29] , and to support transfected chondrocytes for articular cartilage regeneration 18,19,30 . This hydrogel therefore has broad potential applications in orthopedic medicine if appropriate strategies can be developed to control therapeutic gene delivery and hence cell fate within such constructs.…”

Non-viral gene therapy for bone tissue engineering

“…It is possible that at later timepoints bone could be found, since the alginate calcifies between week 2 and week 6, providing a much more favourable surrounding to deposit bone on for differentiated osteoblasts. In a goat model, in which constructs similar to the ones described here were implanted in the muscle, abundant bone was formed after a longer implantation period 151 . Remarkably, cartilaginous tissue was formed in the human MSC seeded group.…”

“…Besides lipo-or polyplexes, these gels are also often combined with other materials such as synthetic polymers or ceramics for biomechanical and osteopromotive reasons. Although batch variation in some hydrogels might greatly influence transfection efficiencies, the addition of ceramic particles does not 151 .…”