Hematopoietic progenitors polarize in contact with bone marrow stromal cells in response to SDF1

2021 ◽  
Vol 220 (11) ◽  
Author(s):  
Thomas Bessy ◽  
Adrian Candelas ◽  
Benoit Souquet ◽  
Khansa Saadallah ◽  
Alexandre Schaeffer ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stromal Cells ◽  
Contact Site ◽  
Cellular Mechanisms ◽  
Microtubule Network ◽  
Hematopoietic Stem ◽  
Discrete Contact ◽  
Stem And Progenitor Cells ◽  
Potential Impact ◽  
The Impact

The fate of hematopoietic stem and progenitor cells (HSPCs) is regulated by their interaction with stromal cells in the bone marrow. However, the cellular mechanisms regulating HSPC interaction with these cells and their potential impact on HSPC polarity are still poorly understood. Here we evaluated the impact of cell–cell contacts with osteoblasts or endothelial cells on the polarity of HSPC. We found that an HSPC can form a discrete contact site that leads to the extensive polarization of its cytoskeleton architecture. Notably, the centrosome was located in proximity to the contact site. The capacity of HSPCs to polarize in contact with stromal cells of the bone marrow appeared to be specific, as it was not observed in primary lymphoid or myeloid cells or in HSPCs in contact with skin fibroblasts. The receptors ICAM, VCAM, and SDF1 were identified in the polarizing contact. Only SDF1 was independently capable of inducing the polarization of the centrosome–microtubule network.

scholarly journals Hematopoietic progenitors polarize in contact with bone marrow stromal cells by engaging CXCR4 receptors

2020 ◽  
Author(s):  
Thomas Bessy ◽  
Benoit Souquet ◽  
Benoit Vianay ◽  
Alexandre Schaeffer ◽  
Thierry Jaffredo ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stromal Cells ◽  
Bone Matrix ◽  
Cell Types ◽  
Cell Contact ◽  
Bone Marrow Niche ◽  
Cellular Mechanisms ◽  
Microtubule Network ◽  
Hematopoietic Stem ◽  
Cell Cell

AbstractHematopoietic stem and progenitor cells (HSPCs) are located in the bone marrow, where they regulate the permanent production and renewal of all blood-cell types. HSPC proliferation and differentiation is locally regulated by their interaction with cells forming specific microenvironments close to the bone matrix or close to blood vessels. However, the cellular mechanisms underlying HSPC’s interaction with these cells and their potential impact on HSPC polarity is still poorly understood. Here we modelled the bone-marrow niche using microfluidic technologies in a bone-marrow on a chip device, and evaluated long-duration cell-cell contacts between single HSPCs and stromal cells or endothelial cells in a custom-designed microwell cell-culture system. We found that an HSPC can form a discrete contact site that leads to the extensive polarization of their cytoskeleton architectures. As in the case with immune synapses formed by lymphocytes, the centrosome was located in proximity of the cell-cell contact. The entire microtubule network emanated from the centrosome, and the nucleus was confined to the side opposite of the cell-cell contact. The capacity of the HSPC to polarize appeared specific as it was not observed in contact with skin fibroblasts. The receptors ICAM, VCAM and CXCR4 were identified in the polarizing contact, and were all independently capable of inducing morphological polarization. However, only CXCR4 was independently capable of inducing the polarization of the centrosome-microtubule network. Altogether these results revealed a novel mechanism of HSPC polarization associated with its anchorage to specific cells in the bone-marrow, which might be instrumental in the regulation of their fate.

scholarly journals TLR2 and Dectin-1 Signaling in Mouse Hematopoietic Stem and Progenitor Cells Impacts the Ability of the Antigen Presenting Cells They Produce to Activate CD4 T Cells

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1317 ◽  
Author(s):  
Alba Martínez ◽  
Cristina Bono ◽  
Daniel Gozalbo ◽  
Helen S. Goodridge ◽  
M. Luisa Gil ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Proinflammatory Cytokine ◽  
Cytokine Production ◽  
Antigen Presenting Cells ◽  
Proinflammatory Cytokine Production ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells ◽  
Antigen Presenting ◽  
The Impact

Microbial recognition by pattern recognition receptors (PRRs) expressed on hematopoietic stem and progenitor cells (HSPCs) not only activates myelopoiesis but also programs the function of the monocytes and macrophages they produce. For instance, changes in HSPC programming modify the ability of macrophages derived from them to produce inflammatory cytokines. While HSPCs exposed to a TLR2 agonist give rise to tolerized macrophages (lower proinflammatory cytokine production), HSPCs treated with Dectin-1 ligands produce trained macrophages (higher proinflammatory cytokine production). However, nothing is known about the impact of HSPC exposure to microbes on the function of antigen presenting cells (APCs). In this study we evaluated whether treatment of murine bone marrow HSPCs with a TLR2 or Dectin-1 ligand impacts the antigen presenting capacity of APCs derived from them in vitro. Following activation with microbial ligands or Candida albicans yeasts, APCs derived from TLR2/Dectin-1-programed HSPCs exhibit altered expression of MHCII (signal 1), co-stimulatory molecules (CD40, CD80 and CD86; signal 2) and cytokines (TNF-α, IL-6, IL-12 p40 and IL-2; signal 3). Moreover, APCs derived from TLR2/Dectin-1-programed HSPCs prime enhanced Th1 and Th17 responses, which are important for antifungal defense, in CD4 T cell cocultures. Overall, these results demonstrate for the first time that microbial detection by bone marrow HSPCs can modulate the adaptive immune response by inducing the production of APCs with an altered phenotype.

Mesenchymal Stem and Progenitor Cells In the Mouse Bone Marrow Lack Expression of CD44.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2581-2581
Author(s):  
Hong Qian ◽  
Mikael Sigvardsson
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Hematopoietic Cells ◽  
Hematopoietic Stem ◽  
Colony Forming Unit ◽  
Stem And Progenitor Cells ◽  
Cell Fractions

Abstract Abstract 2581 The bone marrow (BM) microenvironment consists of a heterogeneous population including mesenchymal stem cells and as well as more differentiated cells like osteoblast and adipocytes. These cells are believed to be crucial regulators of hematopoetic cell development, however, so far, their identity and specific functions has not been well defined. We have by using Ebf2 reporter transgenic Tg(Ebf2-Gfp) mice found that CD45−TER119−EBF2+ cells are selectively expressed in non-hematopoietic cells in mouse BM and highly enriched with MSCs whereas the EBF2− stromal cells are very heterogenous (Qian, et al., manuscript, 2010). In the present study, we have subfractionated the EBF2− stromal cells by fluorescent activated cell sorter (FACS) using CD44. On contrary to previous findings on cultured MSCs, we found that the freshly isolated CD45−TER119−EBF2+ MSCs were absent for CD44 whereas around 40% of the CD45−TER119−EBF2− cells express CD44. Colony forming unit-fibroblast (CFU-F) assay revealed that among the CD45−LIN−EBF2− cells, CD44− cells contained generated 20-fold more CFU-Fs (1/140) than the CD44+ cells. The EBF2−CD44− cells could be grown sustainably in vitro while the CD44+ cells could not, suggesting that Cd44− cells represents a more primitive cell population. In agreement with this, global gene expression analysis revealed that the CD44− cells, but not in the CD44+ cells expressed a set of genes including connective tissue growth factor (Ctgf), collagen type I (Col1a1), NOV and Runx2 and Necdin(Ndn) known to mark MSCs (Djouad et al., 2007) (Tanabe et al., 2008). Furthermore, microarray data and Q-PCR analysis from two independent experiments revealed a dramatic downregulation of cell cycle genes including Cdc6, Cdca7,-8 and Ki67, Cdk4-6) and up-regulation of Cdkis such as p57 and p21 in the EBF2−CD44− cells, compared to the CD44+ cells indicating a relatively quiescent state of the CD44− cells ex vivo. This was confirmed by FACS analysis of KI67 staining. Furthermore, our microarray analysis suggested high expression of a set of hematopoietic growth factors and cytokines genes including Angiopoietin like 1, Kit ligand, Cxcl12 and Jag-1 in the EBF2−CD44− stromal cells in comparison with that in the EBF2+ or EBF2−CD44+ cell fractions, indicating a potential role of the EBF2− cells in hematopoiesis. The hematopoiesis supporting activity of the different stromal cell fractions were tested by in vitro hematopoietic stem and progenitor assays- cobblestone area forming cells (CAFC) and colony forming unit in culture (CFU-C). We found an increased numbers of CAFCs and CFU-Cs from hematopoietic stem and progenitor cells (Lineage−SCA1+KIT+) in culture with feeder layer of the EBF2−CD44− cells, compared to that in culture with previously defined EBF2+ MSCs (Qian, et al., manuscript, 2010), confirming a high capacity of the EBF2−CD44− cells to support hematopoietic stem and progenitor cell activities. Since the EBF2+ cells display a much higher CFU-F cloning frequency (1/6) than the CD44−EBF2− cells, this would also indicate that MSCs might not be the most critical regulators of HSC activity. Taken together, we have identified three functionally and molecularly distinct cell populations by using CD44 and transgenic EBF2 expression and provided clear evidence of that primary mesenchymal stem and progenitor cells reside in the CD44− cell fraction in mouse BM. The findings provide new evidence for biological and molecular features of primary stromal cell subsets and important basis for future identification of stage-specific cellular and molecular interaction pathways between hematopoietic cells and their cellular niche components. Disclosures: No relevant conflicts of interest to declare.

Neuropeptide Y Is Critical for Bone Marrow Stromal Cells and Hematopoietic Recovery Following Injury

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 173-173
Author(s):  
Pratibha Singh ◽  
Louis M. Pelus
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Stromal Cells ◽  
Nerve Fibers ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Hematopoietic Recovery ◽  
Donor Cells ◽  
Cd34 Cells ◽  
Stem And Progenitor Cells

Abstract Bone marrow suppression is the most common limiting side-effect of conventional cancer chemo/radio therapy and is the primary cause of morbidity/mortality after accidental exposure to a high dose of ionizing radiation. The mechanisms mediating radiation-induced hematopoietic stem and stromal cell dysfunction however are not well understood. Radiation therapy causes substantial sensory neuropathy in patients. Recent studies reveal that bone marrow cells are highly innervated by sympathetic nerve fibers and that chemotherapy induced nerve-damage can impair hematopoietic regeneration, suggesting a contribution of nerve fibers in the regulation of hematopoietic stem cell and stromal cell activities. Whether irradiation- mediated nerve injury is a crucial lesion that causes deficits in hematopoietic recovery is not known. We recently discovered that differential signaling from the neuropeptide Y (NPY) receptors on bone marrow endothelial cells regulates vascular permeability and stem cell egress. NPY is an important neurotransmitter of the sympathetic nervous system and the principal adreno-medullary hormone. In this study, we found that NPY is important for reconstitution of the bone marrow niche and hematopoietic regeneration following sublethal irradiation (650 cGy). The levels of NPY were significantly reduced in bone marrow of irradiated mice suggesting damage to nerve fibers. Treatment of wild-type mice with full length NPY (1µg/mouse/day) for 3 consecutive days after irradiation markedly reduced the loss of mesenchymal stem cells (CD45-Ter119-CD31-Nestin+PDGFR+CD51+), endothelial cells (CD45-Ter119-CD31+VE-cadherin+) and hematopoietic stem and progenitor cells (SLAM LSK and LSK) in the bone marrow and promoted faster hematopoietic recovery. In addition, pharmacological NPY treatment prevented irradiation mediated nerve fiber damage. In contrast, in NPY knockout mice, regeneration of CD45neg stromal cells, SLAM LSK and LSK cells after irradiation was significantly reduced compared to wild-type controls. This reduced hematopoietic recovery in NPY deficient mice following irradiation was associated with increased apoptosis/necrosis of stromal cells and hematopoietic stem and progenitor cells. We also examined whether NPY played an intrinsic or extrinsic role in stem cell homing. Wild-type or NPY deficient BM cells were transplanted into wild-type or NPY knockout recipients. Strikingly, the homing of wild-type donor cells into NPY deficient recipients or NPY knockout donor cells into wild-type recipients were both reduced. To explore whether NPY regulates human stem cells, we treated human cord blood CD34+ cells ex vivo with NPY for 3 days and evaluated cell expansion. Long-term culture assays demonstrated that NPY treatment enhanced the clonal expansion of CD34+ cells. In conclusion, our studies suggests that NPY plays both an intrinsic and extrinsic role in hematopoiesis and that NPY-mediated protection of the sympathetic nervous system within the bone marrow can facilitate stem cell niche regeneration and enhance regenerative hematopoiesis following irradiation/injury. Disclosures No relevant conflicts of interest to declare.

scholarly journals Characterization of the Hematopoietic Supporting Activity of Osteoblasts Derived from Bone Marrow Mesenchymal Stromal Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4358-4358
Author(s):  
Manal Alsheikh ◽  
Roya Pasha ◽  
Nicolas Pineault
Keyword(s):  
Bone Marrow ◽  
Osteogenic Differentiation ◽  
Mesenchymal Stromal Cells ◽  
Stromal Cells ◽  
Conflicts Of Interest ◽  
Soluble Factors ◽  
Hematopoietic Stem ◽  
Cd34 Cells ◽  
The Impact ◽  
Myeloid Progenitors

Abstract Osteoblasts (OST) found within the endosteal niche are important regulators of Hematopoietic Stem and Progenitor Cells (HSPC) under steady state and during hematopoietic reconstitution. OST are derived from mesenchymal stromal cells (MSC) following osteogenic differentiation. MSC and OST secrete a wide array of soluble factors that sustain hematopoiesis. Recently, we showed that media conditioned with OST derived from MSC (referred as M-OST) after 6 days of osteogenic differentiation were superior to MSC conditioned media (CM) for the expansion of cord blood (CB) progenitors, and CB cells expanded with M-OST CM supported a more robust engraftment of platelets in NSG mice after transplantation. These findings raised the possibility that M-OST could be superior to MSC for the ex vivoexpansion HSPC. In this study, we set out to test the hypothesis that the growth modulatory activity of M-OST would vary as a function of their maturation status. The objectives were to first monitor the impact of M-OST differentiation and maturation status on the expression of soluble factors that promote HSPC expansion and in second, to investigate the capacity of M-OST CMs prepared from M-OST at distinct stages of differentiation to support the expansion and differentiation of HSPCs in culture. M-OST at distinct stages of differentiation were derived by culturing bone marrow MSC in osteogenic medium for various length of time (3 to 21 days). All CB CD34+ enriched (92±7% purity) cell cultures were done with serum free media conditioned or not with MSC or M-OST and supplemented with cytokines SCF, TPO and FL. We first confirmed the progressive differentiation and maturation of M-OST as a function of osteogenic culture length, which was evident by the induction of the osteogenic transcription factors Osterix, Msx2 and Runx2 mRNAs, the gradual increase in osteopontin and alkaline phosphatase positive cells and quantitative increases in calcium deposit. Next, we investigated the expression in MSC and M-OSTs of genes known to collaborate for the expansion of HSPCs by Q-PCR. Transcript copy numbers for IGFBP-2 increased swiftly during osteogenic differentiation, peaking at day-3 (˃100-fold vs MSC, n=2) and returning below MSC level by day-21. In contrast, ANGPTL members (ANGPTL-1, -2, -3 and -5) remained superior in M-OSTs throughout osteogenic differentiation with expression levels peaking around day 6 (n=2). Next, we tested the capacity of media conditioned with primitive (day-3, -6), semi-mature (day-10, -14) and mature M-OST (day-21) to support the growth of CB cells. All M-OST CMs increased (p˂0.03) the growth of total nucleated cells (TNC) after 6 days of culture compared to non-conditioned medium used as control (mean 2.0-fold, n=4). Moreover, there was a positive correlation between cell growth and M-OST maturation status though differences between the different M-OST CMs tested were not significant. The capacity of M-OST CMs to increase (mean 2-fold, n=4) the expansion of CD34+ cells was also shared by all M-OST CMs (p˂0.05), as supported by significant increases with immature day-3 (mean ± SD of 18 ± 6, p˂0.02) and mature day-21 M-OST CMs (14 ± 5, p˂0.05) vs. control (8 ± 3, n=4). Conversely, expansions of TNC and CD34+ cells in MSC CM cultures were in-between that of control and M-OST CMs cultures. Interestingly, M-OST CMs also modulated the expansion of the HSPC compartment. Indeed, while the expansion of multipotent progenitors defined as CD34+CD45RA+ was promoted in control culture (ratio of 4.5 for CD34+CD45RA+/CD34+CD45RA- cells), M-OST CMs supported greater expansion of the more primitive CD34+CD45RA- HSPC subpopulation reducing the ratio to 3.3±0.4 for M-OST cultures (cumulative mean of 10 cultures, n=2). Moreover, the expansions of CD34+CD38- cells and of the long term HSC-enriched subpopulation (CD34+CD38-CD45RA-Thy1+) in M-OST CM cultures were respectively 2.7- and 2.8-fold greater than those measured in control cultures (n=2-4). Finally, the impact of M-OST CMs on the expansion of myeloid progenitors was investigated using a colony forming assay; expansion of myeloid progenitors were superior in all M-OST CM cultures (1.6±0.2 fold, n=2). In conclusion, our results demonstrate that M-OST rapidly acquire the expression of growth factors known to promote HSPC expansion. Moreover, the capacity of M-OST CMs to support the expansion of HSPCs appears to be a property shared by M-OST at various stages of maturation. Disclosures No relevant conflicts of interest to declare.

scholarly journals Intrinsic Type 1 Interferon (IFN1) Profile of Uncultured Human Bone Marrow CD45lowCD271+ Multipotential Stromal Cells (BM-MSCs): The Impact of Donor Age, Culture Expansion and IFNα and IFNβ Stimulation

Biomedicines ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 214
Author(s):  
Payal Ganguly ◽  
Agata Burska ◽  
Charlotte Davis ◽  
Jehan J. El-Jawhari ◽  
Peter V. Giannoudis ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Stromal Cells ◽  
Gene Expression Signature ◽  
Proliferative Potential ◽  
Donor Age ◽  
Hematopoietic Stem ◽  
Type 1 Interferon ◽  
The Impact

Skeletal aging is associated with reduced proliferative potential of bone marrow (BM) multipotential stromal cells (MSCs). Recent data suggest the involvement of type 1 interferon (IFN1) signalling in hematopoietic stem cell (HSC) senescence. Considering that BM-HSCs and BM-MSCs share the same BM niche, we investigated IFN1 expression profile in human BM-MSCs in relation to donor age, culture-expansion and IFN1 (α and β) stimulation. Fluorescence-activated cell sorting was used to purify uncultured BM-MSCs from younger (19–41, n = 6) and older (59–89, n = 6) donors based on the CD45lowCD271+ phenotype, and hematopoietic-lineage cells (BM-HLCs, CD45+CD271−) were used as controls. Gene expression was analysed using integrated circuits arrays in sorted fractions as well as cultured/stimulated BM-MSCs and Y201/Y202 immortalised cell lines. IFN1 stimulation led to BM-MSC growth arrest and upregulation of many IFN1-stimulated genes (ISGs), with IFNβ demonstrating stronger effects. Uncultured MSCs were characterised by a moderate-level ISG expression similar to Y201 cells. Age-related changes in ISG expression were negligible in BM-MSCs compared to BM-HLCs, and intracellular reactive oxygen species (ROS) levels in BM-MSCs did not significantly correlate with donor age. Antiaging genes Klotho and SIRT6 correlated with more ISGs in BM-MSCs than in BM-HLCs. In patients with osteoarthritis (OA), BM-MSCs expressed considerably lower levels of several ISGs, indicating that their IFN1 signature is affected in a pathological condition. In summary, BM-MSCs possess homeostatic IFN1 gene expression signature in health, which is sensitive to in vitro culture and external IFN1 stimulation. IFN signalling may facilitate in vivo BM-MSC responses to DNA damage and combating senescence and aberrant immune activation.

Cell Therapy in a Mouse Model of Immune-Mediated Bone Marrow Failure.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1689-1689
Author(s):  
Jichun Chen ◽  
Neal S. Young
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Progenitor Cells ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Adherent Cells ◽  
Hematopoietic Stem ◽  
Cell Counts ◽  
Immune Mediated ◽  
Stem And Progenitor Cells

Abstract Immune-mediated bone marrow (BM) failure has been modeled in the mouse by infusion of lymph node cells from allogeneic C57BL/6 (B6) donors into major or minor histocompatibility antigen-mismatched recipients (Chen et al., Blood 2004; Bloom et al., Exp Hematol 2004, Chen et al., J Immunol 2007). Co-infusion of limited numbers of CD4+CD25+ regulatory T lymphocytes (Tregs) can alleviate clinical manifestations by suppressing the expansion of pathogenic T cells (Chen et al., J Immunol 2007). In the current study, we investigated the effectiveness of Tregs and suppressor cells contained in BM stroma in this fatal disease. Infusion of fewer than 3 × 103 Tregs to each recipient mouse had only a minor effect in preserving BM cells and did not prevent pancytopenia. Fifteen-50 × 103 thymic Tregs was moderately protective: blood WBC, RBC, platelet and BM cell counts at three weeks after cell infusion were 197%, 116%, 155% and 158% of those of control animals that did not receive Treg infusion; 5–10 × 103 B6 splenic Tregs produced the largest effect as WBC, RBC, platelet and BM cell counts were 275%, 143%, 276%, and 198% of controls. Overall, Treg therapy was helpful but its effectiveness was limited and variable among individual recipients as no antigen-specific Tregs can be identified for the treatment of BM failure. Learned about the immunosuppressive effects of mesenchymal stem cells (MSCs), we went on to test the effectiveness of stromal cells as another therapeutic modality for BM failure, since stromal cells contain MSCs. These cells were derived from B6 BM by culture in α-modified Eagle medium at 33°C with 5% CO2 for two weeks. After separating the non-adherent cells, we detached the adherent stromal cells and infused them into TBI + B6 LN-infused C.B10 mice. Injection of 106 stromal cells at the time of LN cell infusion effectively preserved WBCs (3.09 ± 0.51 vs 0.61 ± 0.18), RBCs (8.72 ± 0.14 vs 3.52 ± 0.46), platelets (924 ± 93 vs 147 ± 25) and BM cells (186.6 ± 8.7 vs 52.7 ± 7.8) when compared to LN-cell-infused mice without stromal cell addition. Delayed stromal cell injection at day 9 after LN cell infusion had only a mild effect on the preservation of RBCs (147%), platelets (276%) and BM cells (223%) and no effect on WBCs (64%), and infusion of non-adherent cells from the same stromal cell culture had no therapeutic effect. Stromal cell-infused mice had higher proportion of FoxP3+CD4+ cells in the peripheral blood (59.7 ± 10.7% vs 29.8 ± 5.4%) and more Lin−CD117+CD34− hematopoietic stem and progenitor cells in the BM (591 ± 95 vs 60 ± 43, thousand) in comparison to LN cell infused mice without stromal cell treatment. Mitigation of pathogenic T cells, including both CD4 and CD8 T lymphocytes, is the potential mechanism for the effectiveness of Treg and stromal cell therapies that helped to protect hematopoietic stem and progenitor cells in the BM of affected animals. Figure Figure

Bone Marrow Derived Mesenchymal Cells Secrete Granulopoietic Cytokines upon Danger Signaling

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4115-4115
Author(s):  
Stefan Wirths ◽  
Stefanie Bugl ◽  
Markus P. Radsak ◽  
Melanie Märklin ◽  
Martin R. Müller ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Steady State ◽  
Progenitor Cells ◽  
Stromal Cells ◽  
Feedback Loop ◽  
Hematopoietic Stem ◽  
Gm Csf ◽  
Caspase 1 ◽  
Stem And Progenitor Cells ◽  
Myd88 Signaling

Abstract Granulopoietic homeostasis is regulated at steady-state to supply sufficient numbers of pooled and circulating neutrophils to maintain barrier function against commensal flora. In addition, upon pathogenic microbial challenge, an increased formation of neutrophils is induced, termed ‘emergency granulopoiesis’. Antibody-mediated reduction of neutrophil numbers in steady-state induces a feedback loop leading to an increase of bone marrow granulopoiesis with expansion of hematopoetic stem and progenitor cells. This feedback loop was demonstrated to depend on TLR4 and TRIF, but not MyD88 signaling (Bugl et al. Blood 2013). In contrast, emergency granulopoiesis was shown to be dependent on MyD88 signaling in endothelial cells (Boettcher et al. Blood 2014). Bone marrow mesenchymal stromal cells (MSC) are niche-forming cells, harboring and regulating hematopoiesis. Upon steady-state neutropenia an increase of niche size was observed. Here we investigated, whether niche-forming MSC act as sensors of pathogen-associated molecular patterns (PAMPs) and induce granulopoietic cytokines to stimulate expansion of adjacent hematopoietic stem and progenitor cells. MSC of C57BL/6 and TLR4-KO mice were cultured in vitro and treated with LPS for 24 hours. Cells were harvested and qRT-PCR for G-CSF, TLR4, MyD88, TRIF, GM-CSF, IL-1β, IL-18 and Casp-1 was performed After treatment with LPS, RNA of granulopoietic cytokines G-CSF and GM-CSF were massively up regulated in MSC of WT mice. Upstream regulating, inflammasome components IL-1ß and caspase-1 RNA levels increased as well, with little changes in IL-18, TLR4, MyD88 and TRIF. Unexpectedly, TLR4-KO MSC up regulated transcription of IL-1β and G-CSF upon LPS stimulation as well, and caspase-1 was found to be strongly up-regulated in unstimulated TLR4-KO compared to WT MSC. In summary, bone marrow stromal cells are found to be PAMP-sensing and secrete cytokines that regulate granulopoiesis. TLR4-independent sensing of LPS by MSC might correspond to the alternative noncanonical inflammasome pathway recently described (Kayagaki et al. Science 2013). Disclosures No relevant conflicts of interest to declare.

scholarly journals Acute exercise mobilizes hematopoietic stem and progenitor cells and alters the mesenchymal stromal cell secretome

2016 ◽  
Vol 120 (6) ◽  
pp. 624-632 ◽  
Author(s):  
Russell Emmons ◽  
Grace M. Niemiro ◽  
Olatomide Owolabi ◽  
Michael De Lisio
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Progenitor Cells ◽  
Stromal Cells ◽  
Acute Exercise ◽  
Marrow Cell ◽  
Exercise Bout ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells

Transplantation of hematopoietic stem and progenitor cells (HSPC), collected from peripheral blood, is the primary treatment for many hematological malignancies; however, variable collection efficacy with current protocols merits further examination into factors responsible for HSPC mobilization. HSPCs primarily reside within the bone marrow and are regulated by mesenchymal stromal cells (MSC). Exercise potently and transiently mobilizes HSPCs from the bone marrow into peripheral circulation. Thus the purpose of the present study was to evaluate potential factors in the bone marrow responsible for HSPC mobilization, investigate potential sites of HSPC homing, and assess changes in bone marrow cell populations following exercise. An acute exercise bout increased circulating HSPCs at 15 min (88%, P < 0.001) that returned to baseline at 60 min. Gene expression for HSPC homing factors (CXCL12, vascular endothelial growth factor-a, and angiopoietin-1) were increased at 15 min in skeletal muscle and HSPC content was increased in the spleen 48 h postexercise (45%, P < 0.01). Acute exercise did not alter HSPCs or MSCs quantity in the bone marrow; however, proliferation of HSPCs (40%, P < 0.001), multipotent progenitors (40%, P < 0.001), short-term hematopoietic stem cells (61%, P < 0.001), long-term hematopoietic stem cells (55%, P = 0.002), and MSCs (20%, P = 0.01) increased postexercise. Acute exercise increased the content of the mobilization agent granulocyte-colony stimulating factor, as well as stem cell factor, interleukin-3, and thrombopoeitin in conditioned media collected from bone marrow stromal cells 15 min postexercise. These findings suggest that the MSC secretome is responsible for HSPC mobilization and proliferation; concurrently, HSPCs are homing to extramedullary sites following exercise.

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