['According to previous studies, sulodexide suppresses intravascular inflammation when used in patients with chronic venous disease (CVD). In the current study, we tested the effect of prolonged in vitro exposure of human venous endothelial cells to the serum from patients with CVD, examining the function of these cells and how it is modified when these cells are simultaneously exposed to sulodexide.', 'Human umbilical venous cells (HUVEC) were cultured in standard medium (control), in medium supplemented with 5% serum pooled from CVD patients (CVD-serum) or in medium from CVD patients who were treated with sulodexide (CVD-serum-SUL). The synthesis of interleukin-6 (IL-6), monocyte chemoattractant protein -1(MCP-1) and soluble intercellular adhesion molecule - 1 (s-ICAM-1) were studied at the beginning of incubation and were measured after 9 and 15 days of exposure to the studied media. The concentration of IL-6 after cell stimulation by interleukin -1 (IL-1) was also measured. In a subsequent part of the experiment, the effect of the studied sera on the in vitro replicative ageing of HUVEC was evaluated. A total of 15 passages of the cell culture were performed and both the PDT (population doubling time) and the cell hypertrophy were assessed.', 'The concentrations of Il-6, MCP-1, and ICAM-1 gradually increased in the supernatants containing 5% CVD serum compared with the control medium. In the supernatants obtained after cell incubation with serum from sulodexide treated patients, the increase in concentrations of IL-6, MCP-1 and ICAM-1 was significantly less than the control. Release of IL-6 after stimulation with IL-1 (100 pg/mL) was the highest in the CVD-serum group: 3540±670 pg/105 cells vs. 1850±540 pg/105 cells in the control (P<0.01 vs. CVD-serum) and 2320 ±430 pg/105 cells in CVD-serum-SUL (P<0.02 vs. CVD-serum). PDT was significantly longer in the cells incubated with CVD serum compared with the control group, and PDT was reduced when serum from sulodexide treated patients was used. The cells became senescent in the presence of CVD serum, but the cells obtained from patients at the end of 8 weeks of treatment with sulodexide showed a much weaker inflammatory phenotype than the CVD group.'] Does sulodexide reduce the inflammatory reaction and senescence of endothelial cells in conditions involving chronic venous disease?