Gene expression analysis of Apolipoproteins: APOD, APOE and APOL1. Quantification of (a, b) apolipoprotein D (APOD), (c, d) apolipoprotein E (APOE) and (e, f) apolipoprotein L1 (APOL1) 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 < 0.0001; *p < 0.03; Control 10% FCS: 10% LPDS, -FCS ratio/siNK 10% FCS: 10% LPDS, −FCS ratio: +++p < 0.0004; ++p < 0.003; +p < 0.04; PXE 10% FCS: 10% LPDS, −FCS ratio/siABCC6 10% FCS: 10% LPDS, -FCS ratio: ###p < 0.0001; ##p < 0.005; #p < 0.05.