Adeno-associated viruses (AAVs) have emerged as powerful tools for delivering genes to various cell types, including pancreatic endocrine cells. AAV serotype 8 (AAV8) is the primary AAV vector employed for transducing pancreatic cells for transgene expression. We aimed to address whether alternative serotypes, namely AAV2, AAV6, and AAV9, commonly used for gene transfer, can transduce pancreatic cells efficiently 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). Heparin and neuraminidase were screened to understand the interaction between the foregoing AAV types and the cells for optimal transduction. AAV2 outperformed AAV9 in transducing pancreatic cells (βTC cells, MOI 5,000, AAV2: 73% GFP+; AAV9: 8%), while AAV6 induced cytotoxicity. Both AAV2 and AAV9 displayed slightly higher tropism for α-cells than for β-cells (αTC1-6 cells, MOI 5,000, AAV2: 98%; AAV9: 39%), 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 the pancreatic cells (3T3 cells, MOI 5,000, AAV2: 10%; AAV9: 2%). Incubation of AAV2 with heparin before transduction failed to induce transgene expression in β-cells (p<10-4, n=4), pointing to HSPGs as primary interaction sites with pancreatic cells. Treating β-cells with neuraminidase before exposure to AAV9 did not significantly improve the transduction efficiency (MOI 500, p=0.525, n=4). These findings expand the serotypes for AAVs available to deliver transgenes to pancreatic endocrine cells in vitro and will contribute to designing efficacious gene therapy strategies for pancreas pathologies. The National Science Foundation (NSF; CBET-1951104, CBET-2015849, CBET-2326510) has provided funding support.
