[Comparative study on infection rate of different adeno-associated virus for knee joint cartilage in mice]

To explore infection rate of different adeno-associated virus (AAV) on knee joint cartilage in mice and to find a good gene editing tool for mice chondrocytes of knee joint.

Forty-five 4-week-old SPF C57BL/6 weighed(14.3±0.2) g were selected. According to different injections(6 μl) for right knee joint, mice were divided into 9 different groups, 5 mice in each group. The groups were such as following:control group (normal saline), Vigene 2 group (AAV2 from vigene biosciences, titer for 1×10¹³ vg/ml), Vigene 5 group (AAV5 from vigene biosciences, titer for 1×10¹³ vg/ml), Vigene 6 group (AAV6 from vigene biosciences, titer for 1×10¹³ vg/ml), Vigene 7 group (AAV7 from vigene biosciences, titer for 1×10¹³ vg/ml), Vigene 8 group (AAV8 from vigene biosciences, titer for 1×10¹³ vg/ml), Vigene 9 group (AAV9 from vigene biosciences, titer for 1×10¹³ vg/ml), Hanbio DJ group(AAV2-DJ from Hanbio, titer for 1×10¹² vg/ml), Hanbio 5 group (AAV5 from Hanbio, titer for 1×10¹² vg/ml). All AAVs were over-expressed green fluorescent protein(GFP). Knee joint specimens were taken and observed injury of cartilage under stereomicroscope at 30 days after injection, then 10 μm thick frozen sections were prepared. Distribution of green fluorescent protein of meniscus and cartilage of knee joint was observed under fluorescence microscope.

Stereomicroscope observation indicated that no obvious lesion was observed in knee joint cartilage of mice after intra-articular injection of AAV. According to frozen sections of knee joints, strong green fluorescence was observed in knee joint cartilage in all AAV experimental groups. Compared with other groups, significantly stronger green fluorescence were observed both in AAV2 and AAV7 groups, whose average fluorescence density was 0.077±0.020 and 0.061±0.022. There were significant differences between two groups and other groups.

AAV could infect chondrocyte of knee joint in vivo by injecting into knee joint cavity. Higher infection efficiency of AAV2 and AAV7 on knee joint cartilage were observed. Local injection of AAV into knee joint cavity could be used as an effective tool for gene editing of knee joint chondrocyte.