Increased expression level of Dicer in placenta is associated with the early onset of preeclampsia

This is a Letter to the Editor and does not have an abstract.

A subgroup of PE samples was also examined using immunohistochemical methods to determine whether mRNA levels reflected protein expression.
Immunostaining of placental sections indicated that Dicer was expressed in all placental cells (syncytiotrophoblast, cytotrophoblast, endothelial cells, and Hofbauer cells) in both PE and controls.
The participants affected by severe and early onset PE displayed increased staining intensity, predominantly in syncytiotrophoblast and cytotrophoblast cells.The mild PE samples showed moderate staining and in controls, mild staining was observed (Figure 2).The relative staining intensity of different cells was quantified, and severe PE showed increased Dicer expression compared to other experimental groups.In the current study, the expression levels of Dicer gene were evaluated in healthy control and different stages of PE using qRT-PCR and immunohistochemistry methods.As shown in figure 2, expression of Dicer in the transcription level increased in the early onset of PE compared to control samples and other PE stages.Furthermore, the expression of Dicer in the translation state has been evaluated using immunohistochemistry experiment, and its expression was also found to be increased in the early onset of severe PE (Figure 2).
During the normal development of the placenta, many miRNA molecules are expressed in the human placenta which display an essential role in physiological processes including differentiation, proliferation, angiogenesis, migration, invasion, apoptosis, and metabolism of placental cells development, particularly trophoblast cells (6).A previous study reported upregulation of miR-21-5p and miR-155-5p miRNA molecules in preeclamptic pregnancies, especially in severe and late-onset PE subgroups compared to healthy pregnancies (7).In our study, increased expression of Dicer in severe PE may explain the overexpression of miR-21-5p and miR-155-5p miRNAs in PE.Overexpression of miR-210 in PE can suggest it as a promising biomarker for monitoring pregnancy.Overexpression of this molecule displays a negative effect on some cell processes, such as cell migration and trophoblast invasion (8).
Key molecules such as Dicer and Drosha are involved in the process of miRNA biogenesis and maturation.Previous studies have indicated that the knockdown of Dicer induces cell proliferation, apoptosis, angiogenesis inhibition, reduced endothelial cells migration, and loss of miRNA mature sequence (9).Based on a previous study, the expression levels of Drosha, another member of miRNAsprocessing proteins, were found to be reduced in the preeclamptic placentas (10).In contrast, our study indicated upregulation of Dicer in the early onset of severe PE.Since the production of miRNAs is a complex process and various enzymes are involved in it, the overexpression of Dicer in the early onset of severe PE cannot be considered as a predictive biomarker for PE.Therefore, the expression of various proteins involved in miRNA processing as well as the expression levels of different miRNAs should be studied in detail.
The results of this study indicated overexpression of Dicer in the early onset of severe PE.Regarding the importance of miRNA molecules in placental development, the RNase III enzymes such as Dicer which drives miRNA biogenesis should be investigated for their role in PE pathogenesis to shed light on some aspects of this phenomenon.

Figure 1 .
Figure 1.A) Relative expression levels of the Dicer gene in different experimental groups.B) Comparison of Dicer expression levels in the control group with severe early onset and severe late-onset PE.

Figure 2 .
Figure 2. Detection of Dicer expression in the placenta of control and different PE samples using immunohistochemistry experiment.C, E, H, and S correspond to cytotrophoblast, endothelial, Hofbauer, and syncytiotrophoblast cells, respectively.The cells were observed with magnification x400.