Direct AAV-mediated gene delivery to the temporomandibular joint

Successful intra-temporomandibular joint gene transfer is a prerequisite for gene therapy to induce mandibular condylar growth. This study was carried out to investigate the expression of recombinant adeno-associated virus (rAAV) based vector-mediated enhanced green fluorescence protein (eGFP) in the mandibular condyle. The transduction efficiencies for primary chondrocytes using different hybrids of rAAV vectors were identified by fluorescence microscopy and FACS. Sprague-Dawley rats were injected with either rAAV(2/2)-eGFP construct or saline into both mandibular condyles. The spatial and temporal transgene expression was detected by in situ hybridization, RT-PCR and real-time PCR. Our result showed that rAAVs were capable of infecting rat chondrocytes. rAAV(2/2) was the best serotype to infect chondrocytes in vitro. By in situ hybridization, eGFP expression was clearly detected in the deeper layer of mandibular condyle as early as 7 days after injection. By real-time PCR, the transgene expression reached a peak at 21 days. This study was the first report to explore that rAAV-mediated genes could be transferred to mandibular condyle in vivo. Our results strongly suggest that rAAV(2/2) mediated gene delivery is a promising approach to deliver candidate genes for future regulating mandibular condylar growth.