For transduction of primary fibroblasts we use lentiviral vectors that we produce transiently in HEK293T cells. The efficiency by the lentiviral transduction is quite high (usually above 80-90%). For the infection we use a MOI of 5 and supplement the viral supernatant with 8µg/ml Polybrene. After 8-12h the viral particles are removed and the cells analyzed after 48h (earliest timepoint).