Effects of the Levonorgestrel-containing Intrauterine Device, Copper Intrauterine Device, and Levonorgestrel-Containing Oral Contraceptive on the Endometrial and Cervical Transcriptomes Offer Insights into Mechanisms of Action of Intrauterine Devices

The contraceptive effectiveness of intrauterine devices has been attributed in part to effects of a foreign body reaction on the endometrium. We performed this study to identify compare the effects on the endometrial transcriptome of intrauterine devices and combined oral contraceptives, to better understand their mechanisms of action. We collected endometrial and cervical biopsies from women using the levonorgestrel-intrauterine device, copper intrauterine device or levonorgestrel-containing combined oral contraceptives, and from women not using contraceptives (control group). Transcriptional profiling was performed with Affymetrix arrays, Principal Component Analysis and the bioconductor package limma. Pathway analysis was performed using EnrichR and Reactome 2016. In endometrial samples from copper intrauterine device users (n=13), there were no genes with statistically significant differential expression compared to controls (n=11), whereas in levonorgestrel-intrauterine device users (n=11), 2509 genes were significantly dysregulated and mapped onto several immune and inflammatory pathways. In combined oral contraceptive users (n=12), 133 genes were significantly dysregulated and mapped predominantly onto pathways involving regulation of metal ions. Both levonorgestrel-intrauterine device and combined oral contraceptive use were associated with significant downregulation of members of the metallothionein gene family. In cervical samples, none of the groups showed statistically significant differential gene expression compared to controls. In conclusion, hormonal and copper intrauterine devices differ significantly in their effects on the endometrial transcriptome, with endometrium from copper intrauterine device users being indistinguishable from luteal phase endometrium. These results suggest that the contraceptive mechanisms of intrauterine devices are unlikely to rely on a common pathway involving a foreign body reaction in the endometrium. Cross-sectional study using cervical and endometrial samples from 4 groups of women: controls not on hormonal or intrauterine contraceptives (n=12), copper intrauterine device users (cuIUD, n=14), combined oral contraceptive users (COC, n=14), and levonorgestrel-intrauterine device users (LNG-IUD, n=12),