15 Follistatin-Like 3 Protein (FSTL3) is upregulated in preeclampsia

Abstract

Objectives The role of Follistatin-Like 3 Protein (FSTL3), previously shown to be upregulated in preeclamptic placentas, remains unclear. Our aim was to investigate the role of FSTL3 in the pathogenesis of preeclampsia. Methods We first evaluated FSTL3 mRNA expression in preeclamptic and control placentas using real time PCR (PE n = 8, control n = 8). We then performed immunohistochemistry for FSTL3 to evaluate the cell type origin in placental tissue. We measured maternal serum levels of FSTL3 by manual ELISA throughout pregnancy (at 4 time points) in both preeclamptic and control women (PE n = 32, control n = 44).∼To investigate the biological role of FSTL3, we evaluated the role of recombinant FSTL3 in endothelial tube formation assays using human umbilical vein endothelial cells (HUVEC), as well as co-culture studies using an immortalized trophoblast cell line (HTR8 SVneo) and HUVECs. For quantitation, we measured total tube length using ImageJ software. Statistical analysis was performed via unpaired t -test and one-way ANOVA tests, as appropriate. Results FSTL3 mRNA expression was elevated in the placentas of preeclamptic patients (median = 25094.1 ng/mg versus median = 572.9 ng/mg n = 8). Interestingly, FSTL3 protein was localized to the syncytiotrophoblast layer of the placenta and was ∼3 fold elevated in preeclamptic placentas. Maternal serum levels of FSTL3 were elevated in the third trimester samples among preeclamptic patients as compared to healthy controls (median = 25.30 ng/mL versus median = 15.64 ng/mL, p = 0.0004), but not in earlier gestational time periods. We further noted that recombinant FSTL3 protein increased tube formation in both endothelial tube formation assay and trophoblast co-culture studies, in a dose-dependent fashion. Conclusions Our data suggest that placentally derived FSTL3 is a third trimester biomarker of preeclampsia, which could provide diagnostic utility. We propose that this elevation of FSTL3 protein may be a counter-regulatory proangiogenic response by the preeclamptic placenta against the generalized circulating anti-angiogenic state of preeclampsia.