PP035. Genome-wide expression profile of first and second trimester human uterine natural killer cells.

Introduction: Uterine Natural Killer (uNK) cells are key regulators of the placental bed during early placental development and account for 40% of decidual cells. uNK cells have been suggested to play a role in pregnancy complications including maternal placental syndromes, such as preeclampsia. Furthermore uNK cells are involved in angiogenesis, immunomodulation, trophoblast invasion and spiral artery remodeling. These temporal processes are essential for normal placentation and may suggest a time dependent role for uNK cells.

Objective: To determine uNK cell phenotypic changes during early human placental development.

Methods: uNK cells were isolated from first (7-8 wks, n=6) and second trimester decidual tissue (13-14wks, n=6) by enzymatic digestion and flow sorting, based on uNK cell specific surface marker expression (CD56(high)CD16-CD3-). Total RNA was isolated and subjected to genome-wide gene expression profiling. Expression patterns were validated by quantitative rt-PCR.

Results: Using purified uNK cells we identified 140 transcripts that are differentially expressed between the first and second trimester of pregnancy. Many of these transcripts cluster into promising novel and established NK cell functional characteristics.

Conclusion: The uNK cell phenotype changes over the course of early pregnancy. We propose that these phenotypic changes of NK cells may be dictated by the "uterine niche" to promote the orderly and precisely timed process of placentation.