“…Cell pellets were thoroughly washed with 0.9% sterile saline, flash frozen, and stored at −80 • C. Patient-derived fibroblasts were maintained in DMEM supplemented with 10% FBS, ABAM (streptomycin, penicillin G, and amphotericin B), 1X NEAA, and 2 mM of additional Gln. For experiments, 1 million fibroblasts were plated in 100 mm cell culture dishes and incubated for 24 h to allow adherence, then DMEM ± Asn was added, and cells were incubated for an additional 24 h. At the end of the incubation period, media was collected and stored at −80 • C. Cells were harvested by trypsinization, washed with 0.9% saline, flash frozen, and stored at −80 • C. Cell and media samples were prepared and subjected to GC-MS analysis on a Thermo Scientific Single Quadrupole Mass Spectrometer (ISQ) and Gas Chromatograph (Trace 1310), exactly as reported previously [22,[29][30][31].…”