Primary fibroblast lines were generated as described by Carter et al.26 Briefly, 5 mm skin biopsies were obtained under aseptic conditions and were shortly stored in DMEM/F-12, GlutaMAX (Life Technologies) supplemented with 10% FBS and 1% penicillin/streptomycin at 4°C until being processed. After the epidermal layer was removed, the biopsy samples were dissected into small pieces which were then immobilized under a glass coverslip for 24 hr (37°C, 5% CO2). Fresh medium was added the following day and renewed every 2–3 days. At ∼70% confluence, the cultures were passed through a cell strainer to remove pieces of tissue and finally seeded in T25 flasks.