Maternal CXCR4 deletion results in placental defects and pregnancy loss mediated by immune dysregulation

The pregnant decidua is infiltrated by many immune cells which are thought to originate in the bone marrow (BM) promoting pregnancy. CXCR4 is a key regulator of the development of NK cells and dendritic cells, both of which play an important role in early placental development and immune tolerance at the maternal-fetal interface. However, the role of CXCR4 in pregnancy is not well understood. To generate tamoxifen-inducible CXCR4 knockout mice, we used the Cre/LoxP tamoxifen-inducible system. For animal experiments, Cre+/CXCR4fl/fl mice and their Cre-/CXCR4fl/fl littermates were used. After tamoxifen treatment, we refer to Cre-/CXCR4fl/wt mice as WT (wild type), and Cre+/CXCR4fl/null mice as CXCR4 KO (knockout). For adoptive bone marrow transplant (BMT) experiments, BMT was performed from either WT GFP transgenic male donor mice into WT or CXCR4 KO females, or from CXCR4 KO male donors into CXCR4 KO females as negative control. Collectively, our study found an important role for maternal CXCR4 expression in immune cell function, placental development and pregnancy maintenance. Overall design: Female wild type mice (8-10 weeks old) underwent bone marrow transplantation from GFP-expressing transgenic wild type male donors following 5-fluorouracil-based submyeloablation. After timed mating, uterine implantation sites were collected on E10.5. Implantation sites were dissected to remove embryonic and placental parts. The uterine tissues were finely minced and subjected to enzymatic digestion to obtain single cell suspensions. scRNA-seq was performed using droplet microfluidics (10x Chromium). Libraries were created with Single Cell 3' Library kit V2 according to the manufacturer's protocol, and sequenced on Illumina HISeq 4000 instrument.