Vein wall markers of fibrosis, qRT-PCR analysis. Fibrosis is a landmark on chronic venous thrombosis. We analysed the expression of fibrotic markers to investigate the impact of recurrent VT on fibrosis and compared with single VT. TGF-β, elastin, IL-6, MMP2 and MMP9 gene expression were determined using qRT-PCR showing the pro-fibrotic condition of the recurrent VT compared with single VT. Significance: p < 0.05, n = 5–7 per group. Abbreviations: EIM, electrolytic IVC model; IL-6, interleukin-6; LIG, ligation; MMP, matrix metallopeptidase; qRT-PCR, quantitative real-time polymerase chain reaction; TGF- β, transforming growth factor-β; VT, venous thrombosis.