Syndecan 4 facilitates HCV transmission. (A) Different Syndecan cell lines express Syndecan 1-4, on the cell surface determined by flow cytometry. One representative experiment out of 2 is depicted. (B,C) Different Syndecan cell lines were exposed to (B) replicative HCV or (C) pseudotyped HCV (B,C) and transmission by LCs to Huh 7.5 cells was determined. (D) Pseudotyped HCV was pre-incubated with unfractionated heparin (500U) or dalteparin (500U) or tinzaparin (500U) or enoxaparin (500U) and transmission by LCs to Huh 7.5 cells was determined. (E) Syndecan 4 cells were cultured in the presence of PNP-Xyl inhibitor for 72 h and heparan sulfate surface expression was determined by flow cytometry. One representative donor out of 3 is depicted. (F) Syndecan 4 cells were cultured in the presence of PNP-Xyl inhibitor for 72 h, harvested, exposed to pseudotyped HCV and transmission by Syndecan 4 cells to Huh 7.5 cells was determined. Error bars are the mean ± SD of (B) one representative donor measured in quadruplicate. (C) one representative donor out of 3 measured in quadruplicate. (D) n = 5 experiments (medium and HCV) or n = 3 experiments (heparin, dalteparin, tinzaparin, enoxaparin) measured in triplicate or quadruplicate. (F) n = 5 experiments measured in quadruplicate. *p < 0.05, **p < 0.01, ***p < 0.001, by two-tailed, unpaired, parametric, Student t-test. SDC1: Syndecan 1, SDC2: Syndecan 2, SDC3: Syndecan 3, SDC4: Syndecan 4, PNP-Xyl: p-Nitrophenyl-β-d-xylopyranoside, HS: heparan sulfates, FI: fluorescent intensity, RLU: relative light units, HCV: Hepatitis C virus.