When Selecting an Adeno‐associated Viral Vector Serotype, Cell Monolayer Transduction Efficiency Does Not Accurately Predict Tissue Transduction Efficiency in Equine Synovial Tissues

Abstract

Low transduction efficiency of synovial tissues is a key concern in osteoarthritis gene therapy approaches. To determine the most efficient gene transfer strategy for effective in‐situ treatment of articular tissues, eight adeno‐associated viral vector (AAV) serotypes were assessed in monolayer‐cultured equine synovial cells and synovial tissue explants. Of the eight serotypes tested at 1x102 genome copies (GC) per cell, AAV2/2 produced the highest transduction efficiency in monolayer‐cultured cells followed by vector AAV2/5. When GC per cell was increased 10‐fold, again vector AAV2/2 produced the highest transduction efficiency followed by vector AAV2/5. However, when the same candidate vectors were used to transduce freshly‐collected synovial tissue explants, the hierarchy in transduction efficiency had changed. At approximately 3x102 GC per cell, vector AAV2/6.2 now produced the highest transduction efficiency followed by vector AAV2/5. When the GC per cell was increased 10‐fold, again vector AAV2/6.2 produced the highest transduction efficiency followed by vector AAV2/5. We conclude that vector AAV2/6.2 appears to be a superior vector for transduction of fibrous synovial joint tissues and that cell monolayer transduction efficiency does not accurately predict tissue transduction efficiency. Research support was provided by Brushwood Stables.