I am trying to introduce a gene into primary astrocytes isolated from the cortex of p1 mouse pups. I can introduce this gene into other cell types, and other genes into these primary astrocytes. I have tried using retrovirus and lentivirus, and at best, 5% of cells express the gene. Transfection efficiency is also poor, and expression does not last long enough to complete my experiments. Does anyone have any ideas on how to get this gene into (more of) my cells?