Abstract
Background:
Numerous studies have demonstrated the promising efficacy of granulocyte colony-stimulating factor (G-CSF) in the treatment of couples with unexplained recurrent pregnancy loss (URPL) during early pregnancy. While neutrophils are recognised as the main effectors mediating immunoregulation, their G-CSF-mobilised phenotype and mechanisms regulating maternal-fetal immunity remain unclear.
Methods:
Single-cell RNA sequencing (scRNA-seq) and single-cell T-cell receptor sequencing (scTCR-seq) were conducted to uncover the immune reconstitution dynamics of peripheral blood under G-CSF stimulation. Integrative analysis of transcriptomic-proteomic profiles with functional validation revealed a unique immunomodulatory neutrophil population. Further, we used spatial transcriptomics, flow cytometry and immunohistochemistry to explore the spatial distribution characteristics of this population at the maternal-fetal interface, and validated its therapeutic efficacy in animal models.
Results:
G-CSF-mobilised peripheral blood (G-PB) displayed immune hyporesponsiveness. Unique neutrophils expressing high levels of CD177 and the S100A gene family expanded substantially in response to G-CSF. These neutrophils exhibited a comparatively immature morphology and impaired T-cell responses via contact-dependent arginase 1 release, as well as upregulation of T-cell immune checkpoints. A reduction of CD177+S100Ahi neutrophils was observed in both peripheral blood and decidua of URPL patients relative to healthy pregnant women. Functional validation in abortion-prone murine models confirmed that exogenous supplementation of G-CSF or adoptive transfer of CD177+S100Ahi neutrophils could successfully improve the pregnancy outcomes.
Conclusion:
G-CSF played a crucial regulatory role in improving pregnancy outcomes by selectively expanding CD177⁺S100Ahi neutrophils with polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) properties, providing a solid theoretical foundation for the treatment of patients with URPL using G-CSF.
Key points:
G-CSF induces peripheral blood immune hyporesponsiveness in patients with UPRL. First to characterize G-CSF mobilised CD177+S100Ahi neutrophils displayed PMN-MDSCs properties. Both CD177+S100Ahi-LDNs and CD177+S100Ahi-NDNs induce T cell hyporesponsiveness through coordinated activation of the ARG1/L-Arg metabolic axis and synergistic upregulation of immune checkpoint molecules. CD177+S100Ahi neutrophils are diminished in the peripheral blood and decidua of patients with UPRL.