Direct rAAV SOX9 administration for durable articular cartilage repair with delayed terminal differentiation and hypertrophy in vivo
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Direct gene transfer strategies are of promising value to treat articular cartilage defects. Here, we tested the ability of a recombinant adeno-associated virus (rAAV) SOX9 vector to enhance the repair of cartilage lesions in vivo. The candidate construct was provided to osteochondral defects in rabbit knee joints vis-à-vis control (lacZ) vector treatment and to cells relevant of the repair tissue (mesenchymal stem cells, chondrocytes). Efficient, long-term transgene expression was noted within the lesions (up to 16 weeks) and in cells in vitro (21 days). Administration of the SOX9 vector was capable of stimulating the biological activities in vitro and over time in vivo. SOX9 treatment in vivo was well tolerated, leading to improved cartilage repair processes with enhanced production of major matrix components. Remarkably, application of rAAV SOX9 delayed premature terminal differentiation and hypertrophy in the newly formed cartilage, possible due to contrasting effects of SOX9 on RUNX2 and β-catenin osteogenic expression in this area. Most strikingly, SOX9 treatment improved the reconstitution of the subchondral bone in the defects, possibly due to an increase in RUNX2 expression in this location. These findings show the potential of direct rAAV gene delivery as an efficient tool to treat cartilage lesions.
KeywordsArticular cartilage defects Rabbits Gene transfer rAAV SOX9
This study was supported by the German Research Society (DFG CU 55/1-1,/1-2,/1-3) and the German Osteoarthritis Foundation (Deutsche Arthrose-Hilfe). The authors declare no competing financial or other interests. We thank R. J. Samulski (The Gene Therapy Center, University of North Carolina, Chapel Hill, NC) and X. Xiao (The Gene Therapy Center, University of Pittsburgh, Pittsburgh, PA, USA) for providing genomic AAV-2 plasmid clones and the 293 cell line and G. Scherer (Institute for Human Genetics and Anthropology, Albert-Ludwig University, Freiburg, Germany) for the human SOX9 cDNA. We are also thankful to T. Thurn and G. Schmitt (Center of Experimental Orthopaedics, Homburg/Saar, Germany) for technical assistance and to D. Zurakowski (Children’s Hospital, Orthopaedic Surgery and Biostatistics, Harvard Medical School, Boston, MA, USA), M. D. Menger (Institute for Experimental Surgery, Homburg/Saar, Germany), D. Kohn (Department of Orthopaedic Surgery, Homburg/Saar, Germany), and A. Pinzano (CNRS, UMR 7561, Vandoeuvre-lès-Nancy, France) for helpful discussions.
Conflict of interest
The authors declare no conflict of interest.
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