Abstract
Background: The delivery of therapeutic genes in sites of articular cartilage lesions using non-invasive, scaffold-guided gene therapy procedures is a promising approach to stimulate cartilage repair while protecting the cargos from detrimental immune responses, particularly when targeting chondroreparative bone marrow-derived mesenchymal stromal cells in a natural microenvironment like marrow aspirates. Methods: Here, we evaluated the benefits of providing a sequence for the cartilage-specific sex-determining region Y-type high-mobility group box 9 (SOX9) transcription factor to human marrow aspirates via recombinant adeno-associated virus (rAAV) vectors delivered by poly(ε-caprolactone) (PCL) films functionalized via grafting with poly(sodium styrene sulfonate) (pNaSS) to enhance the marrow chondrogenic potential over time. Results: Effective sox9 overexpression was observed in aspirates treated with pNaSS-grafted or ungrafted PCL films coated with the candidate rAAV-FLAG-hsox9 (FLAG-tagged rAAV vector carrying a human sox9 gene sequence) vector for at least 21 days relative to other conditions (pNaSS-grafted and ungrafted PCL films without vector coating). Overexpression of sox9 via rAAV sox9/pNaSS-grafted or ungrafted PCL films led to increased biological and chondrogenic differentiation activities (matrix deposition) in the aspirates while containing premature osteogenesis and hypertrophy without impacting cell proliferation, with more potent effects noted when using pNaSS-grafted films. Conclusions: These findings show the benefits of targeting patients’ bone marrow via PCL film-guided therapeutic rAAV (sox9) delivery as an off-the-shelf system for future strategies to enhance cartilage repair in translational applications.
Highlights
Focal cartilage defects are critical problems in clinical orthopaedics since the adult articular cartilage has a limited ability for full, self-repair as a result of an absence of access to regenerative cells due a lack of vascularization [1,2]
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) to activate reparative cellular responses [38] is capable of supporting the delivery of reporter recombinant adeno-associated virus (rAAV) gene vectors to effectively modify human bone marrow aspirates [39]
The goal of the present study was to further test the ability of pNaSS-grafted PCL films to directly deliver a therapeutic rAAV vector coding for the cartilage-specific sex-determining region Y-type high mobility group box 9 (SOX9) transcription factor [40] in marrow aspirates as a means to trigger the chondroreparative activities in these samples in light of our earlier work showing that rAAV sex-determining region Y-type high-mobility group box 9 (SOX9) can restore the extracellular matrix in human osteoarthritic cartilage [41]
Summary
Focal cartilage defects are critical problems in clinical orthopaedics since the adult articular cartilage has a limited ability for full, self-repair as a result of an absence of access to regenerative cells due a lack of vascularization [1,2]. Application of chondrogenically competent mesenchymal stromal cells (MSCs) [5,6,7] in focal cartilage lesions is an attractive approach to locally enhance the cartilage repair activities in a natural bone marrow environment as afforded when using marrow concentrates [8,9] Still, even with such minimally invasive procedures, the repair tissue in the treated defects remains of poor structural and mechanical quality [8,9], showing that more effective, new treatments are needed for improved healing properties. Conclusions: These findings show the benefits of targeting patients’ bone marrow via PCL film-guided therapeutic rAAV (sox9) delivery as an off-the-shelf system for future strategies to enhance cartilage repair in translational applications.
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