ALKBH5 Positively Regulates BMP2 to Influence Endometrial Decidualization in Recurrent Spontaneous Abortion

Recurrent spontaneous abortion (RSA) is a distressing disorder affecting numerous women of reproductive age. N6-methyladenosine (m6A) RNA modification is a crucial epigenetic regulator, but its role in RSA remains elusive. ALKBH5 (AlkB homolog 5) is a pivotal m6A demethylase that erases m6A marks to positively regulate target gene expression. This research examines the role of the m6A demethylase ALKBH5 in the decidualization process associated with RSA. Decidual tissues from RSA patients and healthy controls were collected. ALKBH5 was knocked down or overexpressed in primary human endometrial stromal cells (ESCs). Decidualization was induced using medroxyprogesterone acetate and 8-Br-cAMP. Phenotypes were assessed via morphology, qPCR, ELISA (for IGFBP1/PRL), and Western blotting. RNA-seq, MeRIP-qPCR, dual luciferase reporter assay, and bioinformatics were applied to determine targets and mechanisms, and immunohistochemistry was used to assess protein expression in decidual tissues. ALKBH5 was downregulated in RSA decidual tissues but upregulated during in vitro decidualization. ALKBH5 knockdown inhibited the morphological transformation and reduced the expression and secretion of decidual markers IGFBP1 and PRL. RNA-seq and intersection analysis identified BMP2 as a key candidate target. Mechanistically, ALKBH5 knockdown increased m6A methylation on BMP2 mRNA, leading to decreased BMP2 expression. Conversely, ALKBH5 overexpression reduced BMP2 m6A levels and enhanced BMP2 expression, which further potentiated decidualization. Importantly, BMP2 knockdown reversed the pro-decidualization effects of ALKBH5 overexpression. Clinically, a strong positive correlation was observed between ALKBH5 and BMP2 expression levels in both the HC group and the RSA group. Furthermore, the ROC curve results indicate that either ALKBH5 or BMP2 could serve as a better diagnostic factor for patients with RSA. ALKBH5 promotes endometrial decidualization by demethylating BMP2 mRNA and enhancing its expression. The downregulation of the ALKBH5-BMP2 axis contributes to decidualization deficiency and may represent a novel epigenetic mechanism underlying RSA.