Project description:A comparative single cell transcriptional analysis of murine CXCL12-abundant reticular stromal cells isolated from ablated and control bone marrow
Project description:Hematopoiesis in adult mammals involves cognate interactions between developing hematopoietic cells and bone marrow stromal cell niches. SCF and CXCL12 play key roles in the maintenance of HSC, while early B cell differentiation requires CXCL12 and IL7. In this study, we characterized mouse BM stromal cells expressing IL7 by performing a transcriptomic analysis. We found that SCF, CXCL12 and IL7 were co-expressed by a unique peri-sinusoidal stromal cell subset.
Project description:Fate decisions of haematopoietic stem cells (HSCs) to self-renew or differentiate in response to various demands are finely tuned by specialized microenvironments called “niches” in the bone marrow. Recent studies suggest that arterioles and sinusoids accompanied with distinct stromal cells marked by nerve/glial antigen 2 (NG2) and leptin receptor (LepR), compose distinct niches regulating quiescence and proliferation of HSCs, respectively. However, it remains unknown how the distinct niche cells differentially regulate the HSC functions. Here we show that effects of cytokines regulating HSC functions are dependent on the producing cell sources. Deletion of chemokine C-X-C motif ligand 12 (CXCL12) in NG2-cre targeted cells, which exclusively overlap with Nestin-GFP (Nes-GFP)+ stromal cells associated with arterioles and sinusoids, resulted in a robust reductions of HSCs in the bone marrow and massive mobilization. Deletion of CXCL12 from arteriolar NG2+ vascular smooth muscle cells caused a significant decrease of HSCs and altered HSC location in the marrow, while CXCL12 depletion from sinusoidal LepR+ cells did not reduce HSC numbers in the bone marrow. By contrast, deletion of stem cell factor (SCF) in LepR+ cells led to significant reductions in HSC numbers whereas SCF deletion in arteriolar NG2+ cells showed no effect on HSC numbers in the marrow. These results uncover the distinct contributions of cytokines derived from perivascular cells in separate vascular niches for HSC maintenance and mobilization. We sought to obtain comprehensive understanding of differences between peri-arteriolar and peri-sinusoidal niche cells by the present RNA-seq analysis.
Project description:Cell cycle quiescence is a critical feature contributing to haematopoietic stem cell (HSC) maintenance. Although various candidate stromal cells have been identified as potential HSC niches, the spatial localization of quiescent HSC in the bone marrow (BM) remains unclear. Here, using a novel approach that combines whole-mount confocal immunofluorescence imaging technique and computational modelling to analyse significant tridimensional associations among vascular structures, stromal cells and HSCs, we show that quiescent HSCs associate specifically with small arterioles that are preferentially found in endosteal BM. These arterioles are ensheathed exclusively by rare Nestin-GFP-peri/NG2+ pericytes, distinct from sinusoid-associated Nestin-GFP-retic/LepR+ cells. The present RNA-seq study sought to obtain a comprehensive understanding of the differences between the two distinct HSC cellular niches. mRNA profiles of sorted Nestin-GFP-peri and -GFP-retic bone marrow stromal cells were generated from pooled mice in triplicate by Illumina HiSeq 2000 sequencing.