Osteochondral tissue regeneration through polymeric delivery of DNA encoding for the SOX trio and RUNX2

Abstract

Native osteochondral repair is often inadequate due to the inherent properties of the tissue and current clinical repair strategies can result in healing with a limited lifespan and donor site morbidity. This work investigates the use of polymeric gene therapy to address this problem by delivering DNA encoding for transcription factors complexed with the branched poly(ethylenimine)-hyaluronic acid (bPEI-HA) delivery vector via a porous oligo[poly(ethylene glycol) fumarate] (OPF) hydrogel scaffold. To evaluate the potential of this approach, a bilayered scaffold mimicking native osteochondral tissue organization was loaded with DNA/bPEI-HA complexes. Next, bilayered implants either unloaded or loaded in a spatial fashion with bPEI-HA and DNA encoding for either Runt-related transcription factor 2 (RUNX2) or SRY (sex determining region Y)-box 5, 6, and 9 (the SOX trio), to generate bone and cartilage tissues respectively, were fabricated and implanted in a rat osteochondral defect. At 6 weeks post-implantation, micro-computed tomography (micro-CT) analysis and histological scoring were performed on the explants to evaluate the quality and quantity of tissue repair in each group. The incorporation of DNA encoding for RUNX2 in the bone layer of these scaffolds significantly increased bone growth. Additionally, a spatially loaded combination of RUNX2 and SOX trio DNA loading significantly improved healing relative to empty hydrogels or either factor alone. Finally, the results of this study suggest that subchondral bone formation is necessary for correct cartilage healing.

Gene therapy for chondral and osteochondral regeneration: is the future now?

“…They can deliver large genes and are easy to produce on a large scale. In addition, polymeric gene therapy is employed to delivery genes without transfecting cells, by complexing the plasmid with (a) a branched poly(ethylenimine)-hyaluronic acid (bPEI-HA) delivery vector, via a porous oligo-[poly(ethylene glycol) fumarate] hydrogel scaffold; (b) type I collagen gels, or (c) collagen-glycosaminoglycan scaffold in vivo by electrotransfer [12,[22][23][24].…”

“…Such genes are insulin-like growth factor 1 (IGF-1) [15-18, 20, 23, 25], transforming growth factor β (TGF-β) [14,26,27], bone morphogenetic proteins (BMPs) [20,22] and fibroblast growth factor 2 (FGF-2) [16,18,21]. Other genes belong to the transcription factors family, SRY-related HMG box (SOX) [24], the anti-inflammatory cytokine Interleukin 10 (IL10) [12] and cartilage oligomeric matrix protein (COMP), a ECM component [19] (Table 1). …”

“…Adenovirus is used to transfer GF genes (TGF-β, FGF-2, IGF-1, BMPs and Growth and differentiation factor 5, GDF-5) into cells [8,20,25,[40][41][42][43][44][45][46][47][48][49]. Genes, in encapsuled viral [24] vector, can be injected directly in vivo [50,51] or through decalcified cortical bone matrix (DCBM) as scaffold that contains the viral particles [52]. Indian hedgehog homolog (iHH) and SOXs genes employ adenovirus for transport into MSCs both in vitro [53,54] and in vivo [55,56].…”

“…The co-infection of SOX9 and TGF-β potentiates chondrogenesis of MSCs in vitro, in comparison to their separate use [64]. The trioco-transduction of SOXs (SOX-5, -6 and -9) increases osteochondral defect and OA healing in vivo and chondrogenesis of MSCs in vitro [73], and their combination with RUNX2 gene further improves osteochondral defect regeneration [24].…”

“…The cell vehicles, with and without scaffolds, are MSCs of different origin [14, 17, 26, 27, 40-42, 46, 54, 55, 59, 61, 71-75, 77, 82], chondrocytes [16,21,44,59,61,62,70,83] and, to a lesser extent, fibroblasts [18,56]. In fewer cases vectors are implanted into scaffolds without cells as vehicles: the plasmid vector is supported by a collagen I sponge or complexed with bPEI-HA via a porous oligo[poly(ethylene glycol) fumarate] hydrogel scaffold [22,24] and adenoviral vector by DCBM [51] (Table 1).…”