Aberrant survival of uterine natural killer subsets in uterus transplant recipients

Abstract

Abstract Uterine natural killer cells (uNKs) are critical mediators of pregnancy success, but how aberrancies in uNK survival or differentiation underpin pregnancy complications is unknown. To improve our understanding of normal and abnormal uNK biology, we studied 1) uNKs in uterus transplant (UTx) recipients at high risk for pregnancy complications and 2) uNK survival after exposure to pharmacologic immunosuppression in vitro. To address the first question, we analyzed uNKs isolated from endometrial biopsies of healthy controls (n=3) or UTx recipients (n=5) using scRNA-seq. In healthy controls, CD103-expressing uNK3 cells were the dominant uNK subset (30% of all uNK cells). In contrast, uNK1 cells were the most frequent (30%) in the majority of UTx recipients. This dominance of uNK1 cells in UTx recipients did not appear to arise only from loss of uNK3 cells, as the uNK1 transcriptional signature was abnormally upregulated in immature proliferating uNKs. Next, we used multiparameter flow cytometry to study single-cell suspensions of whole endometrium from deceased organ donors (n=4) that were cultured for one week with or without the calcineurin inhibitor FK506. Although FK506 significantly impaired the survival of CD103+ uNK3 cells in vitro, there was no evidence of uNK1 enhancement. Instead, FK506 appeared to selectively deplete CD39+ cells – a marker currently used to identify human decidual NK1 cells. Altogether, these results demonstrate that the distribution of uNK subsets is often altered in UTx recipients, and that FK506 can impact the survival of specific uNK subsets. Identification of the additional factors which impact uNK differentiation and survival will be necessary to understand the genesis of pregnancy complications. Supported by NIH/NIAID (R01 AI 145905) University of Pennsylvania Institute for Immunology