Overlap Chronic Placental Inflammation Is Associated with a Unique Gene Expression Pattern

Area of Science:

• Reproductive immunology
• Perinatal pathology
• Molecular biology

Background:

• Chronic placental inflammation, involving maternal immune cell infiltration, is associated with poor fetal outcomes like intrauterine growth restriction and preterm birth.
• Existing research often examines individual histological entities (e.g., chronic villitis) separately, potentially missing unique patterns in overlapping inflammatory conditions.

Purpose of the Study:

• To compare gene expression profiles in placental tissue with and without chronic inflammation, specifically focusing on overlapping chronic chorioamnionitis, chronic villitis of unknown etiology, and chronic deciduitis.
• To identify differentially expressed genes and understand the cellular basis of the unique inflammatory infiltrate in these overlapping conditions.

Main Methods:

• RNA expression profiling using Illumina microarrays on formalin-fixed, paraffin-embedded placental tissues.
• Comparison of gene expression between inflamed and non-inflamed placental samples.
• Immunohistochemical assessment to validate protein expression and cellular localization of key genes, particularly IgJ.

Main Results:

• Increased expression of IGJ was the most significant finding in inflamed placental tissue, alongside other genes associated with T follicular helper cells, natural killer cells, and B cells.
• The identified gene expression signature in overlapping inflammation differs from that seen in individual components like chronic villitis, indicating a unique inflammatory profile.
• Immunohistochemistry confirmed that IgJ expression is primarily from plasma cells, specifically IgA-positive plasma cells, in the context of combined chronic deciduitis, chorioamnionitis, and villitis.

Conclusions:

• Overlapping chronic placental inflammation exhibits a distinct molecular signature compared to isolated inflammatory conditions.
• The increased expression of IgJ, driven by IgA-positive plasma cells, is a key feature of this unique inflammatory infiltrate.
• Understanding these specific immune responses is crucial for developing targeted interventions to improve fetal outcomes in pregnancies complicated by chronic placental inflammation.