Endostatin, a biological active fragment of the extracellular matrix protein collagen XVIII, is known to interfere with cellular motility in the context of pathological angiogenesis. However, the physiological role of endostatin remains largely elusive. Recent evidence suggested that the inhibitor is produced in human decidual cells of early pregnancy, indicating that endostatin could be involved in diverse reproductive processes, such as implantation and/or placental differentiation. To gain more insights into the role of endostatin, we here analyzed its effects on trophoblast motility, proliferation, and signaling using purified primary trophoblasts, first-trimester villous explant cultures, and trophoblastic SGHPL-5 cells. In vitro Transwell assays demonstrated that purified endostatin inhibited both basal and IGF-II-induced migration and invasion as well as outgrowth from villous explant cultures. In contrast, basal and IGF-II-stimulated proliferation was unaffected upon addition of the inhibitor. Analyses of IGF-II-associated downstream signaling events showed that endostatin interfered with activation of various signaling kinases such as ERK1/2, protein kinase B (Akt)/mammalian target of rapamycin/p70 S6 kinase, and focal adhesion kinase. Furthermore, virus-mediated, stable gene silencing of Akt1 in SGHPL-5 cells using a micro-RNA-adapted short hairpin RNA-expressing plasmid revealed that endostatin-mediated inhibition of IGF-II-induced Akt phosphorylation was critically dependent on the expression of the particular isoform. In conclusion, the data suggest that endostatin could be a physiological inhibitor of IGF-II-dependent trophoblast cell motility by suppressing focal adhesion kinase/Akt/mammalian target of rapamycin/p70 S6 kinase signaling.

The objective of our study was to evaluate the correlation of the cervical length at 20–25 weeks of gestation with the incidence of spontaneous preterm delivery in twins in a country with a high incidence of preterm delivery compared to other European countries. Cervical length was measured in 262 consecutive patients. Previous preterm delivery before 34 weeks of gestation, chorionicity, maternal age, body-mass-index, smoking habit and parity were recorded as risk factors for preterm delivery. Women who were symptomatic at 20–25 weeks and who delivered because of other reasons than spontaneous labour and preterm rupture of membranes or at term were excluded. The primary outcome was incidence of preterm birth before 34 weeks. Two hundred and twenty-three patients were analyzed. Thirty-two (14%) delivered before 34 weeks. There was a significant correlation between cervical length of less than 25 mm and spontaneous delivery before 34 weeks (50% vs. 13%,p= .007). In addition, logistic regression analysis found cervical length to be the only significant predictor of spontaneous delivery before 34 weeks (OR 1.084; 95% CI 1.015; 1.159;p= .017). We conclude that the risk of severe preterm delivery in twins is high. Cervical length at mid-gestation was the only predictor of delivery before 34 weeks.

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