Reduced ANXA5 mRNA and protein expression in pregnancies complicated by preeclampsia

The placental anticoagulant protein Annexin A5 (ANXA5) is a multifunctional protein that is highly expressed on the apical surfaces of syncytiotrophoblasts, and plays an important role in haemostatic regulations, maintaining blood fluidity of the placenta. The aim of this study was to investigate the expression of ANXA5 in pregnancies complicated by preeclampsia (PE).

Placental tissue samples were collected from 23 pregnancies with PE and 34 normal pregnancies. ANXA5 mRNA levels were measured by quantitative Real-Time PCR (qPCR), while ANXA5 protein expression was measured by Western Blot (WB) and immunohistochemistry.

ANXA5 mRNA expression in PE samples was lower than 1% of its expression in normal samples (mean ± SD: 0.002 ± 0.004 vs. 0.55 ± 0.38, p < 0.001), while ANXA5 protein levels in PE samples were approximately at 65% of the average normal expression (mean ± SD: 0.53 ± 0.30 vs. 0.81 ± 0.25, p=0.001). Immunohistochemical analysis also verified the above results, since PE placentas tended to have low labelling indexes (LIs), in contrast to controls which demonstrated high LIs (p=0.020). Statistical analysis of the WB data revealed that ANXA5 protein expression was increased in PE smokers vs. PE non-smokers (mean ± SD: 0.64 ± 0.23 vs. 0.41 ± 0.33, p=0.027).

These results suggest that ANXA5 downregulation could be part of the pathophysiology of PE and the possible impairment in coagulation processes, which are seen in pregnancies that demonstrate PE. Further studies may investigate whether ANXA5 could be used as a biomarker for the early detection of PE and for the prediction of its severity.