Involvement of Heparanase in early pregnancy losses

Background: Heparanase cloned from and abundant in the placenta is implicated in cell invasion, tumor angiogenesis and metastasis. Recently, we demonstrated that heparanase is involved in the regulation of the hemostatic system. Heparanase was found to up-regulate tissue factor (TF) expression (Nadir et al., JTH, 2006) and interact with tissue factor pathway inhibitor (TFPI) on the cell surface, leading to dissociation of TFPI from the cell membrane resulting in increased cell surface coagulation activity (Nadir et al., TH, 2008). Herein, we investigated the role of heparanase in the placenta, focusing on its effect on TF, TFPI, TFPI-2, and vascular endothelial growth factor (VEGF)-A.

Methods: Twenty formalin embedded placenta samples of abortions (weeks 6-10) were studied applying real time RT-PCR and immunostaining. Ten cases were miscarriages of women with thrombophilia and recurrent fetal losses, and ten control cases were pregnancy terminations. JAR (human choriocarcinoma trophoblasts) cells were transfected with full-length heparanase cDNA or incubated with active (50+8 kDa) recombinant heparanase and the effects on TF, TFPI, TFPI-2 and VEGF-A were examined using real time RT-PCR and immunoblotting.

Results: Sections obtained from miscarriages revealed increased (2-3-folds) levels of heparanase, VEGF-A and TFPI-2 compared to placentas from controls in maternal as well as in fetal placenta elements. JAR cells overexpressing heparanase or incubated with exogenous recombinant 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 levels. Accumulation of TFPI and TFPI-2 in the cell culture medium was increased 4-6-folds, exceeding the observed induction of TFPI and TFPI-2 gene transcription.

Conclusions: These results indicate a regulatory effect of heparanase on TFPI and TFPI-2 in trophoblasts, suggesting a potential involvement of heparanase in early miscarriages.