Thermosensitive Hydrogel Based on PEO–PPO–PEO Poloxamers for a Controlled In Situ Release of Recombinant Adeno‐Associated Viral Vectors for Effective Gene Therapy of Cartilage Defects

Abstract

Advanced biomaterial‐guided delivery of gene vectors is an emerging and highly attractive therapeutic solution for targeted articular cartilage repair, allowing for a controlled and minimally invasive delivery of gene vectors in a spatiotemporally precise manner, reducing intra‐articular vector spread and possible loss of the therapeutic gene product. As far as it is known, the very first successful in vivo application of such a biomaterial‐guided delivery of a potent gene vector in an orthotopic large animal model of cartilage damage is reported here. In detail, an injectable and thermosensitive hydrogel based on poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO)–PEO poloxamers, capable of controlled release of a therapeutic recombinant adeno‐associated virus (rAAV) vector overexpressing the chondrogenic sox9 transcription factor in full‐thickness chondral defects, is applied in a clinically relevant minipig model in vivo. These comprehensive analyses of the entire osteochondral unit with multiple standardized evaluation methods indicate that rAAV‐FLAG‐hsox9/PEO–PPO–PEO hydrogel‐augmented microfracture significantly improves cartilage repair with a collagen fiber orientation more similar to the normal cartilage and protects the subchondral bone plate from early bone loss.

Materials promoting viral gene delivery

“…Controlled release of the therapeutic SOX9 from the poloxamer gel improved repair of full-thickness chondral defects. 238 To further enhance adhesiveness of poloxamer 407 for local viral delivery to organ surfaces, it was blended with >1% polycarbophil, a polyacrylic acid cross-linked with divinyl glycol. Addition of polycarbophil changed the sol-gel transition temperature and led to higher adhesiveness due to numerous carboxylic groups, which can easily form bonds with surrounding molecules.…”

Enhanced Chondrogenic Differentiation Activities in Human Bone Marrow Aspirates via sox9 Overexpression Mediated by pNaSS-Grafted PCL Film-Guided rAAV Gene Transfer

“…Scaffold-assisted gene therapy is a powerful tool to durably and safely enhance the processes of cartilage repair [10][11][12] via single-step, controlled delivery of clinically adapted rAAV gene transfer vectors [25][26][27][28][29][30][31][32][33]. In the current work, we tested the ability of mechanically stable, biocompatible PCL scaffolds functionalized with a bioactive pNaSS molecule to transfer rAAV vectors coding for the cartilage-specific SOX9 transcription factor to human bone marrow aspirates as a means to generate more efficient, non-invasive systems to treat focal cartilage lesions compared with a less stable scaffold-free vector application lacking scaffolding benefits for the cell targets [42] or with complex, indirect transplantation of rAAV-modified aspirates via such materials [43].…”

“…As a matter of fact, a number of studies reported the potential of applying rAAV for experimental cartilage research via hydrogel systems (alginate, fibrin, poloxamers/poloxamines, self-assembling peptides, polypseudorotaxanes) [25][26][27][28][29][30][31][32][33] while there is still little information on the potential benefits of solid, mechanically more stable biomaterials that may provide scaffolding and stability to the target cells [34] for rAAV-mediated gene transfer. In this regard, we recently provided evidence that biocompatible solid polyester poly(ε-caprolactone) (PCL) [35], an aliphatic polyester approved by the FDA [36,37], further grafted with poly(sodium styrene sulfonate) (pNaSS) to activate reparative cellular responses [38] is capable of supporting the delivery of reporter rAAV gene vectors to effectively modify human bone marrow aspirates [39].…”

Scaffold-Mediated Gene Delivery for Osteochondral Repair

“…Next, the apparent absence of an immune response in all defects (lack of expression of CD3 for T-lymphocytes, of CD11b for activated macrophages, and of human leukocyte antigen isotype DR alpha—HLA-DRα—for class II major histocompatibility complex—MHC—antigens) supported the use of such PEO-PPO-PEO poloxamers to protect rAAV-mediated gene transfer from neutralization by antibodies directed against the AAV capsid. Although not directly applied to an osteochondral defect model, this study showed by a comprehensive analyses of the entire osteochondral unit that rAAV-FLAG-h sox9 /PEO-PPO-PEO hydrogel-augmented microfracture significantly improves osteochondral repair [ 151 ].…”