http://hdl.handle.net/10379/1240 2017-10-30T00:12:04Z http://hdl.handle.net/10379/4244 Sequestration of rhBMP-2 into Self-Assembled Polyelectrolyte Complexes Promotes Anatomic Localization of New Bone in a Porcine Model of Spinal Reconstructive Surgery. Abbah, Sunny-Akogwu Efficient and therapeutically safe delivery of recombinant human bone morphogenetic protein 2 (rhBMP-2) continues to be a central issue in bone tissue engineering. Recent evidence indicates that layer-by-layer self-assembly of polyelectrolyte complexes (PECs) can be used to recreate synthetic matrix environments that would act as tuneable reservoirs for delicate biomolecules and cells. Although preliminary in vitro as well as small-animal in vivo studies support this premise, translation into clinically relevant bone defect volumes in larger animal models remains unreported. Here we explored the use of native heparin-based PEC, deposited on a hydrated alginate gel template, to load bioactive rhBMP-2 and to facilitate lumbar interbody spinal fusion in pigs. We observed that triple PEC deposits with the highest protein sequestration efficiency and immobilization capacity promoted higher volume of new bone formation when compared with single PEC with low sequestration efficiency and immobilization capacity. This also resulted in a significantly enhanced biomechanical stability of the fused spinal segment when compared with PEC carriers with relatively low protein sequestration and immobilization capacities (p<0.05). Most importantly, PEC carriers showed a more orderly pattern of new bone deposition and superior containment of bone tissue within implant site when compared to collagen sponge carriers. We conclude that this growth factor sequestration platform is effective in the healing of clinically relevant bone defect volume and could overcome some of the safety concerns and limitations currently associated with rhBMP-2 therapy such as excessive heterotopic ossification. Journal article 2014-02-27T00:00:00Z http://hdl.handle.net/10379/4242 Preferential tendon stem cell response to growth factor supplementation. Holladay, Carolyn; Abbah, Sunny-Akogwu Tendon injuries are increasingly prevalent around the world, accounting for more than 100 000 new clinical cases/year in the USA alone. Cell-based therapies have been proposed as a therapeutic strategy, with recent data advocating the use of tendon stem cells (TSCs) as a potential cell source with clinical relevance for tendon regeneration. However, their in vitro expansion is problematic, as they lose their multipotency and change their protein expression profile in culture. Herein, we ventured to assess the influence of insulin-like growth factor 1 (IGF-1), growth and differentiation factor-5 (GDF-5) and transforming growth factor-β1 (TGFβ1) supplementation in TSC culture. IGF-1 preserved multipotency for up to 28 days. Upregulation of decorin and scleraxis expression was observed as compared to freshly isolated cells. GDF-5 treated cells exhibited reduced differentiation along adipogenic and chondrogenic pathways after 28 days, and decorin, scleraxis and collagen type I expression was increased. After 28 days, TGFβ1 supplementation led to increased scleraxis, osteonectin and collagen type II expression. The varied responses to each growth factor may reflect their role in tendon repair, suggesting that: GDF-5 promotes the transition of tendon stem cells towards tenocytes; TGFβ1 induces differentiation along several pathways, including a phenotype indicative of fibrocartilage or calcified tendon, common problems in tendon healing; and IGF-1 promotes proliferation and maintenance of TSC phenotypes, thereby creating a population sufficient to have a beneficial effect Journal article 2014-01-01T00:00:00Z http://hdl.handle.net/10379/4230 Nano-textured self-assembled aligned collagen hydrogels promote directional neurite guidance and overcome inhibition by myelin associated glycoprotein Abu-Rub, Mohammad T.; Zeugolis, Dimitrios I.; McMahon, Siobhan; Pandit, Abhay The development of nerve guidance conduits is constantly evolving as the need arises for therapies for spinal cord injury. In addition to providing a path for regrowing axons to reconnect with their appropriate targets, the structural and biochemical cues provided by these conduits should be permissive for directional neurite outgrowth and be protective against inhibition in the vicinity of the injury site. Here, we adapted the use of iso-electric focusing to drive the alignment of supramolecular fibrils into self-assembled collagen hydrogels ([similar]300 µm diameter), and tested those hydrogels for the ability to direct and enhance the migration of neurites. Structural characterization revealed anisotropic alignment of nanofibrillar aggregates ([similar]20 nm diameter), arranged in micron-scale bundles ([similar]1 to 2 µm diameter) similar to the hierarchical size scales observed in native tissues. Neurite outgrowth extended bidirectionally along the axes of aligned hydrogels. Furthermore, it was shown that, as opposed to poly-D-lysine, neurite outgrowth on aligned hydrogels is not inhibited in the presence of myelin-associated glycoprotein (p > 0.05). These results highlight for the first time a structural and biochemical role for iso-electrically aligned collagen hydrogels in controlling neuronal growth, and indicate that the short-term signaling associated with these hydrogels can be used in adjunct therapy following injury to the spinal cord. Journal article 2011-01-11T00:00:00Z http://hdl.handle.net/10379/4229 Thermosensitive hydrogel for prolonged delivery of lentiviral vector expressing neurotrophin-3 in vitro McMahon, Siobhan; Nikolskaya, Natalia; Ní Choileain, Siobhan; Hennessy, Niamh; O'Brien, Timothy; Rochev, Yury Background The development of tissue engineering scaffolds for gene delivery has the potential to enhance gene transfer efficiency and safety via controlled temporal and spatial delivery. Lentiviral delivery can be carried out using the natural biopolymer thermoresponsive gel, chitosan/b-glycerol phosphate (b-GP) as a carrier.Methods Three chitosan/b-GP scaffolds were prepared with varying concentrations of chitosan and b-GP to obtain a pH and gelation temperature suitable for in situ delivery. A lentiviral vector expressing either green fluorescent protein (Lenti GFP) or neurotrophin-3 (Lenti NT-3) was incorporated into the chitosan/ b-GP scaffolds and also into collagen 0.1% w/v (control). Viral elution medium was removed at various timepoints and added to the culture medium of preseeded HeLa or primary dorsal root ganglia (DRG) cells, respectively. GFP gene expression was quantified using fluorescence-activated cell sorting analysis. The effect of Lenti NT-3 was analyzed by measuring DRG neurite outgrowth.Results Collagen displayed its most significant elution of virus on day 1 and chitosan/b-GP (with a final concentration of 2.17% chitosan) on day 3.Conclusions The system shows promise for the in situ, thermoresponsive delivery of lentiviral vectors providing long-term gene expression for therapeutic factors to treat conditions such as injury to the nervous system. Copyright (C) 2011 John Wiley & Sons, Ltd. Conference paper 2011-11-01T00:00:00Z