Project description:Hematopoietic stem cells (HSCs) primarily reside in the bone marrow where signals generated by stromal cells regulate their self-renewal, proliferation, and trafficking. Endosteal osteoblasts and perivascular stromal cells including endothelial cells3, CXCL12-abundant reticular (CAR) cells, leptin-receptor positive stromal cells, and nestin-GFP positive mesenchymal progenitors have all been implicated in HSC maintenance. However, it is unclear if specific hematopoietic progenitor cell (HPC) subsets reside in distinct niches defined by the surrounding stromal cells and the regulatory molecules they produce. CXCL12 (stromal-derived factor-1, SDF-1) regulates both HSCs and lymphoid progenitors and is expressed by all of these stromal cell populations. Here, we selectively deleted Cxcl12 from candidate niche stromal cell populations and characterized the effect on HPCs. Deletion of Cxcl12 from mineralizing osteoblasts has no effect on HSCs or lymphoid progenitors. Deletion of Cxcl12 from osterix-expressing stromal cells, which includes CAR cells and osteoblasts, results in constitutive HPC mobilization and a loss of B lymphoid progenitors, but HSC function is normal. Cxcl12 deletion in endothelial cells results in a modest loss of long-term repopulating activity. Strikingly, deletion of Cxcl12 in nestin-negative mesenchymal progenitors using Prx1-Cre is associated with a marked loss of HSCs, long-term repopulating activity, HSC quiescence, and common lymphoid progenitors. These data suggest that osterix-expressing stromal cells comprise a distinct niche that supports B lymphoid progenitors and retains HPC in the bone marrow, while expression of CXCL12 from stromal cells in the perivascular region, including endothelial cells and mesenchymal progenitors, support HSCs. Total of three samples of two groups analyzed. Replica samples of CXCL12-abundant reticular (CAR) cells from two CXCL12-GFP knock-in mice and a combined sample of PDGFRa+ Sca+ CD45- lineage- cells from three Prx1-Cre Rosa26Ai9/+ Cxcl12gfp/+ mice were used and analyzed.
Project description:In order to assess the descendants of hypertrophic chondrocytes, we utilized Collagen10-Cre;Rosa26-tdTomato mouse bone marrow harvested at 2 months of age by centrifugation and light Collagenase II digestion. After sequencing and downstream analysis using Seurat, we observed clusters of cells with gene profiles matching classically defined skeletal stem and progenitor cells as well as CXCL12 abundant reticular (CAR) cells. These cells appear to be upstream of both osteoblasts and adipocytes. We conclude that hypertrophic chondrocytes dedifferentiate to this progentior stage before further differentiation.
Project description:A comparative single cell transcriptional analysis of murine CXCL12-abundant reticular stromal cells isolated from ablated and control bone marrow
Project description:In mouse bone marrow, mesenchymal stem cells (MSC) has the potential to form osteocytes, adipocytes and cartilage. In the process of osteogenesis, MSCs differenetiate into stromal cells, such as CAR cells. Osteoblast is responsible for the formation of osteocytes and osteoblasts may be differentiated from a subset of CAR cells. Dmp1-Cre targeted CAR cells are thought to enrich for a osteoblast progenitor population. We used microarrays to detail the gene expression profiles among Dmp1-Cre targeted and non-targeted CAR cells. Gene expression diffferences were compared to support the hypothesis that Dmp1-Cre targeted CAR cells may be enriched for osteoblast progenitors. Dmp1-Cre targeted and non-targeted CAR cells were FACS sorted from three mice. RNA were extracted from these sorted cells and processed for microarray using Affymetrix mogene 1.0 ST chip. Cells from one mouse represent one sample
Project description:Crosstalk between mesenchymal stromal cells (MSCs) and hematopoietic stem and cells (HSCs) is essential for hematopoietic homeostasis and lineage output. Ebf1-deficient MSCs have reduced mesenchymal lineage potential. Ebf1 deletion in Cxcl12-abundant reticular (CAR) cells and PDGFRα+Sca1+CD45-CD31-Lin- (PαS) cells in the bone marrow decreased the numbers of HSPCs and myeloid cells. EBF1 in the bone marrow niche regulates a transcriptional program that determines the functional interactions with HSCs and the long-term balance between the myeloid and lymphoid cell fates.
Project description:G-CSF treatment targets CXCL12-abundant reticular (CAR) cells to suppress their production of a number of B trophic factors, including CXCL12, IL-6, IL-7, IGF-1, and Flt3 ligand.
Project description:In mouse bone marrow, mesenchymal stem cells (MSC) has the potential to form osteocytes, adipocytes and cartilage. In the process of osteogenesis, MSCs differenetiate into stromal cells, such as CAR cells. Osteoblast is responsible for the formation of osteocytes and osteoblasts may be differentiated from a subset of CAR cells. Dmp1-Cre targeted CAR cells are thought to enrich for a osteoblast progenitor population. We used microarrays to detail the gene expression profiles among Dmp1-Cre targeted and non-targeted CAR cells. Gene expression diffferences were compared to support the hypothesis that Dmp1-Cre targeted CAR cells may be enriched for osteoblast progenitors.
Project description:Hematopoietic stem cells (HSCs) primarily reside in the bone marrow where signals generated by stromal cells regulate their self-renewal, proliferation, and trafficking. Endosteal osteoblasts and perivascular stromal cells including endothelial cells3, CXCL12-abundant reticular (CAR) cells, leptin-receptor positive stromal cells, and nestin-GFP positive mesenchymal progenitors have all been implicated in HSC maintenance. However, it is unclear if specific hematopoietic progenitor cell (HPC) subsets reside in distinct niches defined by the surrounding stromal cells and the regulatory molecules they produce. CXCL12 (stromal-derived factor-1, SDF-1) regulates both HSCs and lymphoid progenitors and is expressed by all of these stromal cell populations. Here, we selectively deleted Cxcl12 from candidate niche stromal cell populations and characterized the effect on HPCs. Deletion of Cxcl12 from mineralizing osteoblasts has no effect on HSCs or lymphoid progenitors. Deletion of Cxcl12 from osterix-expressing stromal cells, which includes CAR cells and osteoblasts, results in constitutive HPC mobilization and a loss of B lymphoid progenitors, but HSC function is normal. Cxcl12 deletion in endothelial cells results in a modest loss of long-term repopulating activity. Strikingly, deletion of Cxcl12 in nestin-negative mesenchymal progenitors using Prx1-Cre is associated with a marked loss of HSCs, long-term repopulating activity, HSC quiescence, and common lymphoid progenitors. These data suggest that osterix-expressing stromal cells comprise a distinct niche that supports B lymphoid progenitors and retains HPC in the bone marrow, while expression of CXCL12 from stromal cells in the perivascular region, including endothelial cells and mesenchymal progenitors, support HSCs.