Expression Of Hofbauer Cells And Apoptosis-related Proteins In Third Trimester Placentas Of Severe Pre-eclampsia

Hypertensive disorder complicating pregnancy specially breaks out in the course of pregnancy with 9.4% occurrence inland and 7%~12% occurrence abroad. The disease is acute and severe which is the major cause resulting in morbidity and mortality in pregnant women and neonates.So far, there has not existed a clear conclusion about the etiology and pathogenesis of this disease. A lot of reseaches, however, have suggested that immune imbalance and cell apoptosis disorder in placenta may be responsible for this disease.Hofbauer cells (HCs) are a kind of tissue macrophages in placental villous mesenchyma, tightly adjacent to villous trophoblasts and fetal vascular endothelial cells. They are the major cell type present in placental villous mesenchyma. As immunoregulator cells, HCs have the ability of phagocytosis and express a variety of proteins and cytokines. But yet, there have not enough concerns and reseaches about the relation between HCs and this disease.As to placental cell apoptosis, the major view now considers that all the factors regulate the apoptosis process by influencing the ratio between Bax and Bcl-2.So, the aim of this study is to probe the roles of HCs and apoptosis-related proteins in severe pre-eclampsia.Material and Methods:(1) All the subjects were divided into two groups: 1 the pre-eclampsia group (PE,n=30), age ranging from 24 to 32 years, gestational age ranging from 28 to 40 weeks. They were diagnosed according to the diagnostic standard (Obstetrics and Gynecology, the Sixth Edition ); (2) the normotensive group (NT, n=30), age ranging from 22 to 34 years, gestational age ranging from 35 to 40 weeks. All the patients had no other complications of pregnancy and primary hypertension and other vascular disorders. (2) Each specimen no bigger than lcm X lcm X lcm was collected from central placenta (avoiding calcified and necrotic region ) after spontaneous delivery or selective cesearean section. Then they were fixed in neutral formalin and 24h later embedded in paraffin. Sections from each specimen were cut at 4 n m and dried overnight at 37 °C. PV-9000 Polymer Detection System was applied to detect the expressions of HCs> Bcl-2 and Bax in placentas from PE group and NT group. All samples were processed under the same conditions with positive control (provided by Beijing Zhongshan Biotechnology CO.LTD) and negative control (PBS). An average of 10 fields (40X10 multiple) were observed for each specimen using the image analysis system . The average number of HCs and the average optical density of Bcl-2 and Bax of each specimen were calculated and analysed. The ratio of Bax to Bcl-2 was made to represent the balance of placental apoptosis.(3) All the data were processed by SPSS 12.0 software. All values were expressed as means + standard error of mean and differences were compared using Student's Mest .Pearson correlate was made for correlate analysis . Values were considered to be significant at P<0.05.Results(1) There were no statistical differences between PE and NT group in maternal age and gestational age (F>0.05).(2) CD68+ was found in the cytoplasm of the placental villous mesenchyma. HCs(CD68+) were more abundant in PE(22.03±3.23) than that in NT(8.13±2.83)(/><0.01).(3) Anti-apoptotic protein Bcl-2 was expressed in the cytoplasm of syncytiotrophoblasts while pro-apoptotic protein Bax was expressed mainly in the cytoplasm of syncytiotrophoblasts, less in the cytoplasm of cytotrophoblasts andvillous mesenchyma. The average optical density (aOD) of Bcl-2 was smaller in PE(53.71±3.54) than that in NT(65.41±3.59)(i'<0.01). While the aOD of Bax was more larger in PE(41.82±3.54) than that in NT(34.65±2.53) (P<0.01).(4) The ratios of Bax/Bcl-2 were statistically different between PE(0.78±0.02) and NT(0.53±0.01) (P<0.01).(5) In each group, there was positive correlation between the number of HCs and the ratio of Bax/Bcl-2, with r=0.824(PE) and r=0.667(NT) respectively(i><0.01).(6) In each group, there was negative correlation between the aOD of Bcl-2 and the ratio of Bax/Bcl-2, with r= -0.775(PE), r= -0.674(NT) respectively^O.Ol). While the aOD of Bax had positive correlation with the ratio of Bax/Bcl-2, with r=0.791(PE) and r=0.735(NT) respectively(P<0.01).Conclusion(1) In this study, HCs are found to be present in the placental villous mesenchyma. The number of HCs in PE is more abundant than that in NT, suggesting there are much more activated HCs in the third placentas of severe pre-eclampsia.(2) In this study, Bcl-2 and Bax are found to be present mainly in the cytoplasm of syncytiotrophoblasts. In PE, the level of Bcl-2 is obviously lower than that in NT, the level of Bax is much higher than that in NT and the ratio of Bax/Bcl-2 is higher than that in NT, suggesting much more syncytiotrophoblasts are subject to apoptosis in the third trimester of placentas of severe pre-eclampsia.(3) In this study, HCs in two groups have positive correlations with the ratios of Bax/Bcl-2 respectively, suggesting HCs may have the correlations with the apoptosis in syncytiotrophoblasts.(4) In this study, Bcl-2 in two groups have negative correlations with the ratios of Bax/Bcl-2, while Bax in two groups have positive correlations with the ratios, suggesting down-regulation of Bcl-2 and up-regulation of Bax may be mainly responsible for the apoptosis in syncytiotrophoblasts.(5) HCs may have an important role in the pathogenesis of severe pre-eclampsia. By changing the ratio between Bax and Bcl-2 in syncytiotrophoblasts, HCs may be responsible for the overwhelming apoptosis in syncytiotrophoblasts and the followingstructural and functional abnormalities in the third placentas of severe pre-eclampsia.