Role of miR-221/222 and its target genes in the pathogenesis of intrahepatic cholestasis of pregnancy

Abstract:

Objective：To investigate the difference in the expression of microRNA（miR）-221/222 and its target gene in the placenta between normal pregnant women and pregnant women with intrahepatic cholestasis of pregnancy（ICP）， the effect of miR-221/222 on the expression of target gene according to a cell experiment，and the role of miR-221/222 in the pathogenesis of ICP. Methods：A total of 40 placenta samples were collected from normal pregnant women and pregnant women with ICP，all of whom underwent cesarean section in The Second Affiliated Hospital of Chongqing Medical University from September 2015 to March 2016，with 20 samples from each group. miRNA was extracted and qRT-PCR was used to measure the expression of miR-221/222 in the placenta. Apical sodium-dependent bile acid transporter（ASBT），also known as SLC10A2，was predicted to be the target gene of miR-221/222，and Western blot was used to measure the expression of ASBT in the placenta from normal pregnant women and pregnant women with ICP. Normal HTR-8 cells were transfected with miR-221/222 mimic wrapped with Lipofectaine 2000；qRT-PCR was used to measure the expression of miR-221/222，and Western blot was used to measure the expression of ASBT protein after transfection. Results：After correction with the internal control U6，the expression of miR-221 in the ICP and normal placenta was 1.066±0.044 and 0.053±0.009，respectively，and the expression of miR-222 in the ICP and normal placenta was 13.724±4.355 and 0.833±0.189，respectively，suggesting that miR-221/222 was significantly upregulated in the ICP placenta（P <0.05）. The ICP group had significantly lower expression of SLC10A2 than the normal group（0.328±0.102 vs. 0.604±0.119，P=0.000）. After correction with the internal control ACTIN，the expression of ASBT was 0.338±0.064 in the miR-221 transfection group and 0.583±0.040 in the control group；the expression of ASBT was 0.371±0.024 in the miR-222 transfection group and 0.624±0.031 in the control group，suggesting that the transfection group had significantly lower expression of ASBT than the control group. Conclusion：There is an increase in the expression of miR-221/222 in the ICP placenta and a reduction in the expression of its predicted target gene ASBT. The cell experiment shows a reduction in the expression of ASBT in the miR-221/222 transfection group. There may be a negative regulation between them， which affects the reabsorption of bile acid in the intestinal tract and its transport in the liver among pregnant women， thus leading to ICP.