Gene expression analysis of cholesterol biosynthesis I: FDPS, GGPS1 and FDFT1. Quantification of (a, b) Farnesyl diphosphate synthase (FDPS), (c, d) Geranylgeranyl diphosphate synthase (GGPS1) and (e, f) Squalene synthase (FDFT1) mRNA expression in human dermal fibroblasts from healthy controls (n = 4; white), PXE patients (n = 4; black), scramble siRNA-negative control (siNK, n = 4; white-striped) and ABCC6-specific siRNA-treated cells (siABCC6, n = 4; black-shaded) grown for 24 h under different cell culture conditions (+10% FCS, +10% LPDS, −FCS). Expression levels are normalized to reference gene expressions (ACTB, GAPDH, β2M). Data are presented in arbitrary units as means with corresponding standard error. Control: PXE ratio/siABCC6: siNK ratio: ***p < 0.0003; **p < 0.003; *p < 0.04; Control 10% FCS: 10% LPDS, −FCS ratio/siNK 10% FCS: 10% LPDS, −FCS ratio: +++p < 0.0006; ++p < 0.003; +p < 0.05; PXE 10% FCS: 10% LPDS, −FCS ratio/siABCC6 10% FCS: 10% LPDS, -FCS ratio: ###p < 0.0007.