Influence of serotype, cell type, tissue composition, and time after inoculation on gene expression in recombinant adeno-associated viral vector-transduced equine joint tissues.

The study investigated the effectiveness of different types of gene therapy treatments for osteoarthritis in horses. The researchers found that the success of the treatments varied based on several factors including the type of viral vector used, the type of cell targeted, and the duration of the treatment.

Experimental Design

• The researchers collected cartilage and synovial (joint fluid) tissues from the knees of three thoroughbred horses of varying ages.
• These horses were healthy and had not received any long-term medication treatments, meaning any results could be confidently attributed to the experimental conditions.
• Eight different types of viral vectors (rAAV) were used to experimentally deliver genes into the collected cells and tissues.

Observations and Findings

• The researchers found that certain combinations of variables yielded better gene transfer results than others.
• Six days post-application, the rAAV2/5 and rAAV2/2 serotypes were the most beneficial in cultured cells.
• Cells found in synovial fluid and mesenchymal stromal cells were more easily modified than were chondrocytes (cartilage cells).
• The rAAV2/6.2 serotype showed the highest initial rate of gene expression in both cartilage and synovial tissues, but this lowered after 30 and 60 days.
• After 30 and 60 days, the gene expression of rAAV2/2 and rAAV2/5 surpassed that of rAAV2/6.2 and all other serotypes.

Conclusions

• For both cell and tissue level treatments, the most efficient serotypes were the ones that showed the best transduction (gene transfer) over time.
• The relatively low gene transfer success in cartilage tissue was mirrored in the results from isolated chondrocytes, suggesting that this is due to poor transduction efficiency of these cells, rather than the high density of the surrounding tissue matrix.
• This suggests that for successful gene therapy in horses, treatments need to be designed in a way that addresses these efficiency constraints in chondrocytes, and maintains high levels of gene expression over long periods.