Identification of a portal vessel-associated fetal liver hematopoietic stem cell niche
ABSTRACT: Whereas the cellular basis of the hematopoietic stem cell (HSC) niche in the bone marrow has been characterized, the nature of the fetal liver (FL) niche is not yet elucidated. We show that Nestin+NG2+ pericytes associate with portal vessels, forming a niche promoting HSC expansion. Nestin+NG2+ cells and HSCs scale during development with the fractal branching patterns of portal vessels, tributaries of the umbilical vein. After closure of the umbilical inlet at birth, portal vessels undergo a transition from Neuropilin-1+Ephrin-B2+ artery to EphB4+ vein phenotype, associated with a loss of peri-portal Nestin+NG2+ cells and emigration of HSCs away from portal vessels. These data support a model in which HSCs are titrated against a peri-portal vascular niche with a fractal-like organization enabled by placental circulation. Characterization of the transcriptome of fetal liver and adult bone marrow niche using RNA-seq
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. Overall design: mRNA profiles of sorted LepR-cre/Tomato+, NG2-cre/Tomato+, Myh11-creER/Tomato+, and CD31+ bone marrow stromal cells were generated by illumina HiSeq2500.
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.
Project description:Hematopoietic stem cells (HSCs) inhabit distinct microenvironments within the adult bone marrow (BM) that govern the delicate balance between HSC quiescence, self-renewal, and differentiation. It has been suggested that quiescent HSCs localize adjacent to BM arteriole endothelial cells in a significant and non-random distribution. This data suggests that the arteriole BM vascular niche may be the primary HSC niche. Because the BM arteriole niche is composed of tightly-associated pericytes, including smooth muscle actin+, LepR+, Nestin+, NG2+, and nonmyelinating Schwann cells, we sought to begin to uncouple the arteriole BM EC niche by examining its capacity to support the maintenance and expansion of HSCs ex vivo and in vivo. We developed a method to isolate and culture BM arteriole endothelial cells in serum-/growth factor-free conditions, allowing for a non-biased approach to examining their instructive function. Utilizing our protocol, we demonstrate that BM endothelial cells, but not BM stromal cells, have the capacity to expand long-term repopulating, multi-lineage HSCs in lieu of complex serum and cytokine supplementation. In addition, transplantation of arteriole endothelial cells promoted rapid hematopoietic recovery and protected HSCs following an LD50 dose of myeloablative irradiation. These data demonstrate that arteriole-derived BM endothelial cells are endowed with the necessary signals to support the self-renewal and regenerative capacity of LT-HSCs and that transplantation of arteriole BM endothelial cells could be used as a therapeutic means to decrease pancytopenias associated with myeloablative treatments to treat a wide array of disease states. Transcriptome sequencing of bone marrow endothelial cells and bone marrow stroma, in vitro and in vivo, with and without HSC co-culture.
Project description:Myeloproliferative neoplasms (MPNs) are diseases caused by mutations in the haematopoietic stem cell (HSC) compartment. Most MPN patients have a common acquired mutation of Janus kinase 2 (JAK2) gene in HSCs that renders this kinase constitutively active, leading to uncontrolled cell expansion. The bone marrow (BM) microenvironment might contribute to the clinical outcomes of this common event. We previously showed that BM nestin+ mesenchymal stem cells (MSCs) innervated by sympathetic nerve fibres regulate normal HSCs. Here we demonstrate that abrogation of this regulatory circuit is essential for MPN pathogenesis. Sympathetic nerve fibres, supporting Schwann cells and nestin+ MSCs are consistently reduced in the BM of MPN patients and mice expressing the human JAK2V617F mutation in HSCs. Unexpectedly, MSC reduction is not due to differentiation but is caused by BM neural damage and Schwann cell death triggered by interleukin-1b produced by mutant HSCs. In turn, in vivo depletion of nestin+ cells or their production of CXCL12 expanded mutant HSCs and accelerated MPN progression. In contrast, administration of neuroprotective or sympathomimetic drugs prevented mutant HSC expansion. Treatment with b3-adrenergic agonists that restored the sympathetic regulation of nestin+ MSCs prevented the loss of these cells and blocked MPN progression by indirectly reducing leukaemic stem cells. Our results demonstrate that mutant HSC-driven niche damage critically contributes to disease manifestation in MPN and identify niche-forming MSCs and their neural regulation as promising therapeutic targets. CD45- CD31- Ter119- GFP+ cells were sorted from the BM of Nes-gfp;Mx1-cre;JAK2-V617F mice and control littermates 6 weeks after pIpC treatment and were subjected to RNA sequencing. Each sample was pooled from 3 animals of the same genotype.
Project description:Myeloproliferative neoplasms (MPNs) are diseases caused by mutations in the haematopoietic stem cell (HSC) compartment. Most MPN patients have a common acquired mutation of Janus kinase 2 (JAK2) gene in HSCs that renders this kinase constitutively active, leading to uncontrolled cell expansion. The bone marrow (BM) microenvironment might contribute to the clinical outcomes of this common event. We previously showed that BM nestin+ mesenchymal stem cells (MSCs) innervated by sympathetic nerve fibres regulate normal HSCs. Here we demonstrate that abrogation of this regulatory circuit is essential for MPN pathogenesis. Sympathetic nerve fibres, supporting Schwann cells and nestin+ MSCs are consistently reduced in the BM of MPN patients and mice expressing the human JAK2V617F mutation in HSCs. Unexpectedly, MSC reduction is not due to differentiation but is caused by BM neural damage and Schwann cell death triggered by interleukin-1b produced by mutant HSCs. In turn, in vivo depletion of nestin+ cells or their production of CXCL12 expanded mutant HSCs and accelerated MPN progression. In contrast, administration of neuroprotective or sympathomimetic drugs prevented mutant HSC expansion. Treatment with b3-adrenergic agonists that restored the sympathetic regulation of nestin+ MSCs prevented the loss of these cells and blocked MPN progression by indirectly reducing leukaemic stem cells. Our results demonstrate that mutant HSC-driven niche damage critically contributes to disease manifestation in MPN and identify niche-forming MSCs and their neural regulation as promising therapeutic targets. Total RNA was isolated from BM CD45- CD31- Ter119- Nes-GFP+ cells obtained from Nes-gfp mice 10 weeks after transplantation with Mx1-cre;JAK2-V617F (n=3) or control cells (n=1). RNA was amplified using the NuGen Ovation system and hybridized to the Affymetrix MoGene 1.0 ST array.
Project description:Mouse model with P53f/f;Nf1f/+;Ptenf/+ configuration driven by Nestin-creERT2 and NG2-creERTM induced at 1 month postnatal forms high grade glioma in the brain. Tumors were harvested and total RNA were extracted for gene expression profile. Three tumors were harvested from the Nestin-creERT2 mouse model and 5 tumors were harvested from the NG2-creERTM mouse model with desired genotype when mice show neurological symptomes. Three control brain tissue for each model were harvested at corresponding anatomical position in the control mice. Total RNA were extracted from the tumor tissue and control tissue
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:Mesenchymal stem cells (MSCs) And osteolineage cells contribute to the hematopoietic stem cell (HSC) Niche in the bone marrow of long bones. However, Their developmental relationships remain unclear. Here we demonstrate that different MSC populations in the developing marrow of long bones have distinct functions. Proliferative mesoderm-derived nestin- MSCs participate in fetal skeletogenesis, And lose MSC activity soon after birth. In contrast, Quiescent neural-crest-derived nestin+ Cells in the same bones preserve MSC activity, But do not generate fetal chondrocytes. Instead, They differentiate into HSC-niche-forming MSCs, Helping to establish the HSC niche by secreting Cxcl12. Perineural migration of these cells to the bone marrow requires the ErbB3 receptor. The neonatal Nestin-GFP+ PDGFR- Cell population also contains Schwann-cell precursors, But does not comprise mature Schwann cells. Thus, In the developing bone marrow HSC-niche-forming MSCs share a common origin with sympathetic peripheral neurons and glial cells, And ontogenically distinct MSCs have non-overlapping functions in endochondrogenesis and HSC niche formation. Total RNA was isolated from small numbers of FACS sorted stromal cells, obtained from neonatal Nes-Gfp bone marrow preparations (2 biological replicates). Each independent set of samples was obtained from pooled skeletal elements (long bones and sterna) form multiple littermates.
Project description:Twenty-four male Sprague-Dawley rats were used for this experiment, a partial portal vein ligadure (PVL) was carried out in 12 rats, the other 12 rats were sham-operated. Superior mesenteric artery (SMA) samples were sequentially obtained from 2 rats from the PVL and sham groups at 1, 6, and 24 hours, and 3, 5 and 14 days after portal vein ligation or sham procedure. Each PVL sample was paired with its corresponding sham sample using a dye swap experiment design (technical replicates) resulting in 12 arrays (6 time points x 2 dye swap).