Involvement of Heparanase in Early Pregnancy Losses

Heparanase activity is implicated in cell invasion, tumor metastasis and angiogenesis. Recently, we have reported that heparanase stimulates tissue factor (TF) expression in endothelial and cancer cells, resulting in elevation of coagulation activity (Nadir et al. JTH, 2006). We also found that heparanase releases tissue factor pathway inhibitor (TFPI) from endothelial and tumor cells, contributing to the local procoagulant balance (Nadir et al. TH, 2008). Heparanase was cloned from and is abundant in the placenta. We investigated the role of heparanase in the placenta, focusing on its effect on TF, TFPI, TFPI-2, and vascular endothelial growth factor-A (VEGF-A). Twenty formalin embedded samples of early pregnancy losses (weeks 5–10) were studied. Ten cases were miscarriages of women with thrombophilia and recurrent fetal losses, and ten control cases were pregnancy terminations. Applying real time RT-PCR and immunostaining for heparanase, TF, TFPI, TFPI-2, and VEGF-A it was found that in fetal losses related to thrombophilia the levels of heparanase, VEGF-A and TFPI-2 were significantly increased (2–3 fold) compared to placentas from controls. Next, JAR (human choriocarcinoma throphoblast) cells were transfected to overexpress the full length (65 kDa) heparanase or incubated with active (50+8 kDa) recombinant heparanase. Immunoblotting and real time RT-PCR showed that throphoblasts overexpressing or incubated with exogenous heparanase exhibited a 2–3 fold increase in TFPI and TFPI-2 in cell lysates both at the protein and mRNA levels, with no detectable effect on VEGF-A and TF. Accumulation of TFPI and TFPI-2 in the cell culture medium was increased 5–6 fold, exceeding the observed induction of TFPI and TFPI-2 gene transcription. Extracellular accumulation of TFPI and TFPI-2 was already evident 60 min following heparanase addition, prior to protein induction, indicating an active release of preformed proteins. These results indicate a regulatory effect of heparanase on TFPI and TFPI-2 in throphoblasts, suggesting a potential involvement in early miscarriages.