Placental interferon signaling is involved in chronic intervillositis of unknown etiology

Chronic intervillositis of unknown etiology (CIUE) is a placental inflammatory process associated with pregnancy loss and high recurrence risk. The pathogenesis is unclear but involves aberrant maternal inflammation. This study assesses expression of inflammatory mediators by placenta and intervillus macrophage using digital spatial profiling, which is applicable to formalin fixed paraffin embedded tissue and provides whole transcriptome expression analysis at cellular resolution.

Ethics approval was obtained and all experiments were performed in accordance with applicable guidelines and regulations. Archival tissue from early spontaneous pregnancy loss with high grade CIUE (4 cases) was compared to non-inflamed control normal placenta (4 cases) and granulomatous lymphadenitis as a macrophage inflammation control (4 cases). Differential gene expression between CIUE and relevant controls was assessed using unpaired t-test with Benjamini-Hochberg false discovery correction. Gene Set Enrichment Analysis (GSEA) was used to characterize and compare pathways active in the CIUE and relevant control samples.

Principal component analysis of the gene expression data showed distinct clustering with relatively little intragroup variation in the control tissues whereas the CIUE cases are more variable. Gene expression analysis showed changes in CIUE; however, no genes remained statistically significant after correction for false discovery. GSEA revealed prominent activation of IFN-related signaling pathways in CIUE placenta, particularly IFNγ signaling.

This study demonstrates that CIUE is associated with a specific profile of inflammatory mediators expressed by placenta villi that is dominated by IFN signaling, suggesting that uncontrolled IFNγ signaling may play a primary role in the pathogenetic mechanism underlying CIUE.