Evaluation of transduction efficiency in pancreatic beta and alpha cells utilizing various AAV serotypes

Adeno-associated viruses (AAVs) have emerged as powerful tools for delivering genes to various cell types, including pancreatic endocrine cells. Currently, AAV serotype 8 (AAV8) is the primary AAV vector employed for transducing pancreatic cells for transgene expression. We aimed to determine whether alternative serotypes, specifically AAV2, AAV6, and AAV9, commonly used for gene transfer, can efficiently transduce pancreatic cells in vitro. Murine pancreatic β-cells, α-cells, and fibroblasts were transduced with AAV serotypes 2, 6, and 9 carrying the transgene for enhanced green fluorescent protein (eGFP). To understand further the interaction between the foregoing AAV types and the cells for optimal transduction, the additives heparin and neuraminidase were screened. AAV2 outperformed AAV9 in transducing pancreatic cells, while AAV6 induced cytotoxicity. Recombinant AAV2 was also utilized to deliver a blue-light photoactivatable adenylyl cyclase (bPAC) to β-cells, resulting in the efficient modulation of insulin secretion upon illumination. Both AAV2 and AAV9 displayed slightly higher tropism for α-cells than for β-cells, potentially mirroring differences in the expression of heparan sulfate proteoglycan (HSPG)-processing enzymes. The fraction of GFP-expressing cells at various multiplicities of infection was consistently lower for fibroblasts than for the pancreatic cells. Incubation of AAV2 with heparin before transduction failed to induce transgene expression in β-cells, indicating that HSPGs are the primary interaction sites with pancreatic cells. Treating β-cells with neuraminidase before exposure to AAV9 did not significantly improve the transduction efficiency. These findings expand the repertoire of available serotypes for AAV-mediated delivery of transgenes to pancreatic endocrine cells in vitro and may contribute to designing efficacious gene therapy strategies for pancreas pathologies.