MiR-204-5p promoted maternally expressed gene 3 (MEG3) through SP1-mediated DNMT1 pathway in trophoblast cells in recurrent miscarriage.

Background: Recurrent miscarriage (RM) affects 1-2% of couples. Maternally expressed gene 3 (MEG3) is aberrantly expressed in RM patients.

Objective: To investigate a novel regulatory mechanism, we examined the miR-204-5p/Specificity protein 1 (SP1)/DNA methyltransferase 1 (DNMT1)/MEG3 axis in the trophoblast cell line HTR-8/SVneo.

Methods: Human trophoblast cell line HTR-8/SVneo was used and cells were transfected with siRNA targeting SP1, miR-204-5p mimics, pcDNA3.1-DNMT1, or their negative controls (NCs). The methylation inhibitor, 5-azadC, was used to treat the cells transfected with pcDNA3.1-SP1. The reverse transcription quantitative polymerase chain reaction (RT-qPCR) method was used to examine the relative RNA levels of SP1, DNMT1 and MEG3. Western blot assay was performed to measure the protein levels of SP1 and DNMT1. The dual-luciferase reporter gene assay was used to validate the miR-204-5p bindings to SP1. Functional assays were utilized to assess cell apoptosis, colony formation, migration, and invasion.

Results: SP1 knockdown inhibited DNMT1 and increased MEG3 expression. The expression of MEG3 was enhanced by methylation inhibition through 5-azadC, but SP1 upregulation reversed this effect. SP1 knockdown increased apoptosis and decreased migration and invasion, which was reversed by DNMT1 overexpression. SP1 was targeted and inhibited by miR-204-5p. miR-204-5p also inhibited DNMT1, and enhanced the expression of MEG3. miR-204-5p inhibited cell proliferation, migration and invasion, and promoted apoptosis. Overexpression of SP1 partially reversed these effects by activating DNMT1 and inhibiting MEG3.

Conclusions: miR-204-5p promoted MEG3 expression in trophoblast cells via SP1-mediated DNMT1 inhibition, leading to reduced cell migration, proliferation and invasion, as well as increased apoptosis. This study reveals a novel regulatory axis in trophoblast cells, providing insights into potential regulatory mechanisms in RM.