*3.9. Cells and Culture Conditions*

The H9c2 cell line, derived from embryonic rat hearts (ATCC; Manassas, VA, USA), and primary fibroblasts from a patient affected by early-onset Parkinson's disease (PD) and from one healthy subject, obtained by explants from a skin punch biopsy after informed consent [40,41], were grown in high-glucose Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% (*v*/*v*) fetal bovine serum (FBS), 1% (*v*/*v*) L-glutamine, and 1% (*v*/*v*) penicillin/streptomycin at 37 ◦C in a humidified atmosphere of 5% CO2. For the treatment conditions, cells were seeded in 96-well plates and grown for 24 h. After that, the media was removed, and the cells were cultured at 37 ◦C in culture plates for 24, 48, and 72 h in fresh media containing different concentrations of red onion samples.
