Role of trophoblast-derived proteins in the development of pre-eclampsia

Abstract

Pre-eclampsia (PE) is a pregnancy-associated disorder that involves pregnancy-induced maternal hypertension and proteinuria. PE affects approximately 5-7% of pregnant women and despite extensive research the aetiology of this disorder remains unknown. Maternal endothelial cell (EC) dysfunction mediated by excess placenta-derived proteins in maternal plasma is a prominent component to the development of PE. Previous proteomic analysis, conducted by this laboratory, identified four candidate proteins that were increased in the syncytiotrophoblast microparticles (STBM) released from PE placentas compared to gestation matched controls (GMC). The candidate proteins were calreticulin, 14-3-3, Protein Disulfide Isomerase A3 (ERp57) and Valosin-containing protein (VCP). The investigations described in this study were undertaken on these candidate proteins. The overall aim of this study was to provide data from in vitro models that supports a role for trophoblast-derived proteins in the development of PE. The initial aim of this study was to measure the expression of the candidate proteins in the placenta by Western blot; comparing the expression of these proteins in the PE placenta versus GMC. The next aim was to measure the expression of candidate proteins in maternal plasma from normal and PE patients by Western blot. Western blots detected the expression of all four candidate proteins in the placenta, however, expression of the candidate proteins did not change between PE compared with the GMC. Western blots were also used to detect the presence of each protein in PE plasma compared with the GMC. The proteins calreticulin and 14-3-3 were both significantly increased with PE. ERp57 could not be detected in maternal plasma and there was no difference in the presence of VCP in PE maternal plasma compared to the GMC. Calreticulin was studied further. The aim was to measure the presence of calreticulin in plasma from women who at the time the sample was taken showed no clinical signs of PE, but who later develop PE compared to the GMC. Although the difference did not reach significance with the small number of samples available, this study observed an increase in maternal calreticulin concentrations at approximately 16 weeks gestation in women that subsequently develop PE compared with the GMC. The final aims of this study was to assess the effects of exogenous calreticulin at concentrations relevant to normotensive pregnancy (2µg/ml) and to PE (5µg/ml) on the human extravillous trophoblast cell line, HTR8/Svneo and human myometrial microvascular endothelial cells (utMVEC-Myo). Calreticulin, only at the concentration measured in PE plasma, inhibited HTR8/Svneo and stimulated utMVEC-Myo cell migration and reduced utMVEC-Myo cell numbers. Calreticulin at the lower concentration, 2µg/ml, had no effect on HTR8/Svneo or utMVEC-Myo cell function. This study has conducted further work on calreticulin during pregnancy and PE development and identified that the presence of 14-3-3 is increased in plasma with PE. Both these proteins, particularly calreticulin, are factors that may aid in identifying women at risk of developing PE and aid in increasing our knowledge on this pregnancy complication.