Heterogeneity of IL-15-expressing mesenchymal stromal cells controls natural killer cell development and immune cell homeostasis

Bone marrow stromal cells have been shown to not only provide bone tissue structure, but guide hematopoiesis and lymphocyte differentiation. The role of Interleukin 15 (IL-15) expression in BM stromal cells and potential implication on immune cell homeostasis remains unknown. Here, we generated an IL15-IRES-EGFP knockin reporter mouse model to define and study IL15-expressing BM stromal cells. Overall design: We profiled non-hematopoietic IL-15 expressing bone and bone marrow stromal cells from IL15-IRES-EGFP reporter mice. We enriched stromal and endothelial cells from eight 7 individual IL15-IRES-EGFP mice at the age of 8-12 weeks by FACS (Aqua Zombie- CD45- Ter119- and CD31- IL15-GFP+ for MSCs and CD31+ IL15-GFP+ for endothelial cells) and profiled them by scRNA-seq (10xGenomics, 3' chemistry)

骨髓基质细胞（bone marrow stromal cells）已被证实不仅可构成骨组织结构，还能调控造血作用与淋巴细胞分化。白细胞介素15（Interleukin 15, IL-15）在骨髓基质细胞中的表达功能，及其对免疫细胞稳态的潜在影响，目前仍未明确。本研究构建了IL15-IRES-EGFP敲入报告小鼠模型，以明确并研究表达IL-15的骨髓基质细胞。
实验整体设计：我们对IL15-IRES-EGFP报告小鼠体内表达IL-15的非造血性骨及骨髓基质细胞开展了转录组谱分析。我们通过荧光激活细胞分选（Fluorescence-Activated Cell Sorting, FACS）从8只8-12周龄的IL15-IRES-EGFP报告小鼠中富集基质细胞与内皮细胞：间充质干细胞（Mesenchymal Stem Cells, MSCs）的分选标记为Aqua Zombie⁻ CD45⁻ Ter119⁻ CD31⁻ IL15-GFP⁺，内皮细胞的分选标记为CD31⁺ IL15-GFP⁺。随后我们采用单细胞RNA测序（single-cell RNA sequencing, scRNA-seq，基于10x Genomics 3'端测序化学法）对上述分选细胞进行了转录组分析。