Increased CXCL12 expression in endometrium of women with abnormal uterine bleeding is post-transcriptionally mediated via miR-23b-3p and is associated with decreased expression of the miR-23b-3p/24-3p/27b-3p cluster: a pilot study

Abstract Objective To study CXCL12 and CXCR4 expression in endometrial tissue from both women with and without AUB of endometrial origin and evaluate their relationship with microRNAs. Design Archived endometrial biopsy tissue and in vitro cell culture using the immortalized endometrial stromal cell line, t-HESC. Setting University-based research laboratory Patients Archived endometrial biopsy tissue was obtained from nine women with and without abnormal uterine bleeding all of which were in the secretory stage of their menstrual cycle. Interventions Immunohistochemical localization of CXCL12 and CXCR4 as well as qRT-PCR assessment of mRNA expression. Endometrial stromal cell line, t-HESC transfection with non-targeting, negative control miRNA mimics or miRNA mimics for miR-23b-3p and mRNA assessment miR-23b-3p expression was confirmed by qRT-PCR and impact on CXCL12 expression was evaluated at the protein level by ELISA and mRNA levels by qRT-PCR. Main Outcome Measures CXCL12 and CXCR4 protein expression by immunohistochemistry and mRNA and miRNA levels of CXCL12 and CXCR4 as well as miR-23b-3p, miR-24b-3p and miR-27b-3p, respectively by qRT-PCR. Results CXCL12 and its receptor CXCR4 expression were upregulated in endometrial tissue of women with AUB and the protein level but this up-regulation of expression was only associated with increased CXCR4 mRNA expression. To evaluate if CXCL12 may be post-transcriptionally regulated, we assessed expression of miR-23b-3p, a bonafide post-transcriptional regulator of CXCL12 expression. miR-23b-3p expression was significantly lower in AUB endometrial tissue as were fellow cluster members miR-24-3p and miR-27-3p. Transfection of t-HESC cells with pre-miR-23b-3p mimics significantly reduced levels of CXCL12 secreted protein, but not mRNA levels, suggesting that miR-23b-3p retards protein translation independent of transcript degradation. Conclusion Reduced expression of the miR-23b-3p/24-3p/27b-3p cluster is associated with elevated expression of CXCL12 which may contribute to the pathophysiology of AUB.