Direct Intravital Imaging of the Bone Marrow and Splenic Hematopoietic Niches in Individual Mice to Define the Early Engraftment Kinetics Following HSC-Transplant

Abstract Hematopoietic stem cells (HSCs) give rise to and maintain the entire hematopoietic system for the life of an organism. This remarkable feat has established HSC transplant as an indispensable tool for treating a variety of hematological disorders. Yet the initial steps of homing, engraftment, and clonal expansion, which lead to eventual long-term hematopoietic recovery after HSC transplant, remain incompletely characterized. Given the determinative effect that early HSC activity has on transplant outcomes, a more complete understanding of initial engraftment dynamics is imperative for bettering HSC therapies. Preliminary studies aimed at functional characterization of classic HSC and hematopoietic stem and progenitor cell (HSPC) populations-namely the CD150 +CD48 -Sca-1 +c-Kit +Lin - (SLAM SKL) and Sca-1 +c-Kit +Lin - (SKL) populations, respectively-revealed that these populations exhibit disparate early engraftment dynamics. Using previously developed intravital imaging techniques, we were able to partially characterize early HSC and HSPC engraftment dynamics in mice competitively transplanted with GFP + SLAM SKL and DsRed + SKL cells. The SKL population was found to primarily engraft in the bone marrow, completely recapitulating engraftment behavior of transplanted whole bone marrow. In contrast, the more purified SLAM SKL population engrafted poorly in the marrow space and instead preferentially engrafted in the spleen, where it produced the majority of donor-derived blood at early stages (7 days) after competitive transplant into lethally irradiated mice. However, by 14 days post-transplant, SLAM SKL-derived cells migrated from the spleen to repopulate the majority of bone marrow space. These results reflect the dynamic nature of hematopoietic recovery in a myeloablative model and highlight the need for in vivo imaging techniques to fully understand hematopoietic reconstitution by the SLAM SKL population. In order to further dissect the interactive processes of bone marrow hematopoiesis and splenic extramedullary hematopoiesis, we have developed a novel, multi-organ intravital imaging technique that allows for simultaneous analysis of defined hematopoietic compartments in a single animal. Our multimodal imaging approach combines direct visualization of fluorescently labeled hematopoietic cells in the spleen via our recently developed spleen window, with concomitant observation of hematopoietic cells in tibia marrow environment. Our spleen window is a specially engineered biocompatible ring with an affixed coverslip to allow for direct, non-invasive microscopic visualization of labeled hematopoietic cells in the spleen. The spleen window can be installed with the tibia window in an individual mouse. Multimodal mice can be visualized repeatedly over a minimum of 7 days post-HSC transplant to follow individual cell behaviors within the living recipient. Preliminary results from competitive repopulation assays utilizing our multimodal imaging approach suggest that the SLAM SKL population is an active one that confers rapid hematopoietic recovery in lethally irradiated recipients primarily from extramedullary hematopoiesis in the spleen (CFU-S). The results of ongoing work characterizing the active use of the splenic and marrow niches will be presented. Disclosures Cogle: Celgene: Membership on an entity's Board of Directors or advisory committees; Aptevo therapeutics: Research Funding.

Download Full-text

Multimodal imaging reveals structural and functional heterogeneity in different bone marrow compartments: functional implications on hematopoietic stem cells

Blood ◽

10.1182/blood-2012-11-467498 ◽

2013 ◽

Vol 122 (10) ◽

pp. 1730-1740 ◽

Cited By ~ 61

Author(s):

Francois Lassailly ◽

Katie Foster ◽

Lourdes Lopez-Onieva ◽

Erin Currie ◽

Dominique Bonnet

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Comparative Analysis ◽

Hematopoietic Stem Cells ◽

Multimodal Imaging ◽

Intravital Imaging ◽

Functional Heterogeneity ◽

Hematopoietic Stem ◽

Key Points ◽

Functional Implications

Key Points Comparative analysis of epiphyses, diaphyses, and calvaria in terms of homeostatic HSC content, homing, and early reconstitution is described. Noninvasive intravital imaging of intact bones and assessment of BVF, BRA, and hypoxia are reported.

Download Full-text

Platelet-Derived Microparticels Stimulate Proliferation of Colony-Forming Unit Granulocyte-Macrophage of Umbilical Cord Blood Hematopoietic Stem Cells.

Blood ◽

10.1182/blood.v106.11.4191.4191 ◽

2005 ◽

Vol 106 (11) ◽

pp. 4191-4191

Author(s):

Bao-An Chen ◽

Fei Fei ◽

Cheng-Yin Huang ◽

Cui-Ping Li ◽

Xiao-Ping Pei ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Cord Blood ◽

Adhesion Molecules ◽

Umbilical Cord ◽

Umbilical Cord Blood ◽

Hematopoietic Cells ◽

Control Group ◽

Hematopoietic Stem ◽

Hematopoietic Recovery

Abstract Umbilical Cord blood has become an important source of hematopoietic stem-progenitor cells for transplantation, however hematopoietic recovery after transplantation with umbilical cord blood is slower than with bone marrow or mobilized peripheral blood. Adhesion molecules on hematopoietic cells are involved in hematopoietic cells’ homing, which is considered the most important step of hematological recovery. Some articles indicated that expressions of adhesion molecules on CD34+ cells could predict the time to hematopoietic recovery after transplantation with bone marrow and peripheral blood of many adhesion molecules (such as CD62, CXCR4) are significantly lower on umbilical cord blood than on bone marrow. It is a possible reason for the difficulty in hematopoietic recovery after umbilical cord blood transplant. Platelet -derived microparticles (PMPs) are submicroscopic (<1 μm) membrane vesicles released from platelet if they are stimulated with agonists such as thrombin, collagen, or calcium ionophore A23187 or if exposed to high-stress shear forces. PMPs express several platelet-endothelium attachment receptors on their surface, for example, glycoprotein IIb/IIIa (CD41), Ib and IaIIa, and P-selectin (CD62P) and several other platelet relevant receptors such as CXCR4 and PAR-1. Some articles indicate that PMPs can affect the function of hematopoietic stem cells by increasing the adhesion of hematopoietic cells to fibrinogen, which suggests that PMP-transferred CD41 antigen plays an important role in this process. PMPs can also increase the survival of human hematopoietic cells including human CD34+ clonogenic progenitors. In our research, we observe the function of PMP to affect the cloning efficiency of colony-forming unit granulocyte-macrophage (CFU-GM). We adopt different concentrations of Thrombin (2U/ml, 1.5U/ml, 1.0U/ml and 0.5U/ml) to activate the platelet and acquire PMPs. Then PMPs were evaluated by using flow cytometry. Based on the result that stimulation of platelets by Thrombin (1U/ml) can acquire the best efficiency of PMPs, we used this concentration in all subsequent experiments. Umbilical cord mononuclear cells (MNCs) were obtained from healthy donors and isolate the MNCs by Ficoll-Hypaque density gradient centrifugation. Briefly, MNCs incubated with or without PMPs cultured in 2.7% methylcellulose. CFU-GM growth was stimulated with 30% umbilical cord serum, rhIL-3 and rh GM-CSF. Cultures were incubated at 37°C in a fully humidified atmosphere supplemented with 5% CO2. Colonies were counted under an inverted microscope after 7 or 10 days. The research was divided into four groups: 1. control group; 2. PMPs(10μg/ml); 3. PMPs(50μg/ml); 4. PMPs(100μg/ml). The colony formation was enhanced with PMPs and is dependently stimulated with PMPs. The number of colonies in the group of PMPs(100μg/ml) is more than that of other groups. The number of colonies in control group, PMPs(10μg/ml), PMPs(50μg/ml) and PMPs(100μg/ml) are 57.4±3.2, 65.6±5.6, 77.1±1.7 and 87.8±5.0 per 1×105 respectively. These increases in different groups were statistically significant when compared with control group(p<0.05). To sum up, PMPs can affect the cloning efficiency of CFU-GM of umbilical cord hematopoietic stem cells and the efficiencies are depended on the concentration of PMPs.

Download Full-text

Zeb2-Defficiency in the Adult Murine Hematopoietic Precursor Cells Leads to Differentiation Defects in Multiple Hematopoietic Lineages and a Myeloproliferative-Like Phenotype

Blood ◽

10.1182/blood.v120.21.1199.1199 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1199-1199

Author(s):

Tamara Riedt ◽

Steven Goossens ◽

Ines Gütgemann ◽

Carmen Carrillo-Garcia ◽

Hichem D Gallala ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Hematopoietic Stem Cells ◽

Hematopoietic Cells ◽

Extramedullary Hematopoiesis ◽

Independent Effect ◽

Self Renewal ◽

Hematopoietic Stem ◽

Reticular Fibers

Abstract Abstract 1199 The life long replenishment of highly specialized blood cells by a small number of hematopoietic cells (HSC) requires a strict regulation between self-renewal and differentiation in the immature compartment of the bone marrow. Perturbation of this equilibrium can result in stem cell loss or hematologic malignancies. This balance is at least in part controlled by a network of transcription factors. Zeb2 is a transcriptional repressor and plays an important role during the embryonic development as a modulator of the epithelial to mesenchymal transition (EMT) as well as tumor progression and metastasis. We have previously identified the essential role of Zeb2 in murine embryonic hematopoiesis, where selective Zeb2 deficiency in the hematopoietic stem cells resulted in early lethality around day 12.5. The aim of this study was to analyze whether Zeb2 plays a specific role in the regulation of homeostasis in the adult hematopoietic system. Using the Mx1-Cre based inducible Zeb2 conditional knock out mouse model we analyzed the impact of Zeb2 loss on adult hematopoietic stem cell function. Upon the induction of Zeb2 deletion we found a significant decrease in most cell lineages of the peripheral blood, except the neutrophil granulocytes. However, the reduction of mature cells in the blood was not accompanied by reduced bone marrow cellularity, as the cellularity was similar between Zeb2Δ/Δ Mx1-Cre (Zeb2 conditional KO) mice and the control animals (Zeb2+/+Mx1-Cre). However, in the bone marrow of the Zeb2Δ/Δ Mx1-Cre animals the granulocytic lineage was dominating, whereas other lineages e.g. red blood cell precursors and B-lymphoid precursors were drastically reduced. Histological sections of the bone marrow cavity revealed megacaryocytes with abnormal morphology reflecting maturation defects and an increased production of reticular fibers in the BM of Zeb2Δ/Δ Mx1-Cre mice. In addition Zeb2Δ/Δ Mx1-Cre mice displayed a two to three fold increase in spleen size compared to control animals due to an extramedullary hematopoiesis. Analysis of the primitive hematopoietic compartment in the bone marrow and spleens revealed that Zeb2 deletion resulted in a pronounced increase in the most immature hematopoietic cells, defined as Lin-Sca1+cKit+CD48-CD150+ population, and perturbation in different lineage restricted progenitor subpopulations. No difference in cell cycling or apoptotic rate in the stem cell enriched bone marrow population (Lin-Sca1+cKit+CD48-CD150+) was detectable between the genotypes. Upon transplantation into lethally irradiated wild type recipients, Zeb2 deficient stem cells demonstrated significantly reduced ability to differentiate into multiple hematopoietic lineages indicating a niche independent effect of Zeb2 in promoting differentiation of hematopoietic stem cells. On the molecular level, gene expression analysis of hematopoietic stem and progenitor cells using microarray approach revealed increased transcripts of downstream targets of Wnt/ß-Catenin signaling, suggesting increased Wnt signaling activity in absence of Zeb2 in the hematopoietic compartment, which at least in part might be responsible for the observed phenotype. These data indicate that Zeb2 is involved in the regulation of the balance between self-renewal and differentiation at multiple stages of hematopoietic cell maturation. Furthermore the lack of Zeb2 in the hematopoietic compartment leads to a phenotype that resembles the features of human myeloproliferative disorders, especially the early stages of primary myelofibrosis with dominant granulopoiesis, production of reticular fibers in the bone marrow, and morphological abnormalities in megacaryocytes, accompanied by extramedullary hematopoiesis. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

27-Hydroxycholesterol Induces Hematopoietic Stem Cell Mobilization and Extramedullary Hematopoiesis Mediated By Estrogen Receptor Alpha

Blood ◽

10.1182/blood.v130.suppl_1.636.636 ◽

2017 ◽

Vol 130 (Suppl_1) ◽

pp. 636-636

Author(s):

Hideyuki Oguro ◽

Jeffrey McDonald ◽

Sean Morrison

Keyword(s):

Bone Marrow ◽

Estrogen Receptor ◽

Steady State ◽

Sex Hormones ◽

Bone Marrow Cells ◽

Hematopoietic Cells ◽

Extramedullary Hematopoiesis ◽

Wild Type ◽

Hematopoietic Stem ◽

Deficient Mice

Abstract In adults, hematopoietic stem cells (HSCs) reside primarily in the bone marrow and their number is tightly regulated under steady state conditions. However, acute demands on the hematopoietic system promote HSC division and mobilization to extramedullary tissues such as the spleen, to increase production of blood cells. While the mechanisms that regulate HSC numbers and residence in the bone marrow under steady-state conditions have been extensively characterized, the mechanisms that activate HSCs in response to acute hematopoietic demands are less well understood. We have previously reported that extramedullary hematopoiesis (EMH) is induced during pregnancy when maternal blood volume expands rapidly. This requires HSC division and mobilization, processes that depend upon estrogen receptor α (ERα) in HSCs. Signaling through this nuclear hormone receptor can be triggered by sex hormones, such as 17β-estradiol (E2), as well as 27-hydroxycholesterol (27HC), which is the first identified endogenous ER ligand other than sex hormones. However, it has been unclear whether 27HC has a physiological role that is effected through ERα signaling in normal mice. Here we show that treatment of mice with E2, which increases during pregnancy, induced HSC division in the bone marrow but did not increase HSC number in the spleen, indicating that E2 treatment does not induce HSC mobilization. In contrast, treatment with the alternative endogenous ERα ligand, 27HC, increased HSC number in the spleen and induced EMH, but not HSC division in the bone marrow, indicating a role in inducing HSC mobilization. The effect of 27HC on HSC mobilization was nullified by deletion of Esr1 (the gene that encodes ERα) in hematopoietic cells using Vav1-icre ; Esr1fl/fl mice, indicating that 27HC-induced HSC mobilization is dependent on ERα. To test whether 27HC acts directly on HSCs, we competitively transplanted Vav1-icre ; Esr1fl/fl donor bone marrow cells along with wild-type competitor bone marrow cells and treated the recipient mice with 27HC four months after the transplantation. 27HC treated mice had significantly lower frequencies of donor-derived (Esr1- deficient) HSCs in the spleen as compared to vehicle-treated mice. This indicates that Esr1- deficient HSCs were at a disadvantage compared to wild-type HSCs in the same mice for mobilization in response to 27HC. ERα thus acts cell-autonomously within HSCs to promote mobilization in response to 27HC. 27HC is generated directly from cholesterol by the sterol hydroxylase, Cyp27a1, and plasma 27HC levels correlate with total cholesterol levels. It has been reported that mice with defects in cholesterol efflux exhibit increased mobilization of hematopoietic stem and progenitor cells (HSPCs) associated with increased serum granulocyte colony-stimulating factor (G-CSF) levels. However, we observed that G-CSF deficiency using Csf3-/- mice did not affect the magnitude of the increase in mobilized HSCs in response to 27HC treatment. Together, 27HC and G-CSF co-treatment additively increased the numbers of colony-forming HSPCs in the blood. Therefore, 27HC and G-CSF likely act through distinct mechanisms. During pregnancy, 27HC levels increased in HSPCs as a result of Cyp27a1. Cyp27a1 -deficient mice had significantly reduced 27HC levels but, under steady-state conditions, Cyp27a1 deficiency did not affect the numbers of HSCs and hematopoietic cells in both bone marrow and spleen. However, during pregnancy, Cyp27a1 -deficient mice had significantly reduced HSC mobilization and EMH, while the increased rate of HSC division and hematopoiesis in the bone marrow was not affected. In contrast, Cyp27a1 deficiency did not affect HSC mobilization and EMH in response to blood loss or G-CSF treatment. Distinct hematopoietic stresses thus induce EMH through different mechanisms. Taken together, these results indicate that two different endogenous ERα ligands, E2 and 27HC, work together to promote EMH during pregnancy, revealing a collaboration of hormone and lipid signaling as well as a physiological function for 27HC in normal mice. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Pediatric MDS and bone marrow failure-associated germline mutations in SAMD9 and SAMD9L impair multiple pathways in primary hematopoietic cells

Leukemia ◽

10.1038/s41375-021-01212-6 ◽

2021 ◽

Author(s):

Melvin E. Thomas ◽

Sherif Abdelhamed ◽

Ryan Hiltenbrand ◽

Jason R. Schwartz ◽

Sadie Miki Sakurada ◽

...

Keyword(s):

Bone Marrow ◽

Bone Marrow Failure ◽

Transcriptional Profiling ◽

Hematopoietic Cells ◽

Protein Translation ◽

Germline Mutations ◽

Hematopoietic Stem ◽

Monosomy 7 ◽

Cellular Environment ◽

Primary Mouse

AbstractPediatric myelodysplastic syndromes (MDS) are a heterogeneous disease group associated with impaired hematopoiesis, bone marrow hypocellularity, and frequently have deletions involving chromosome 7 (monosomy 7). We and others recently identified heterozygous germline mutations in SAMD9 and SAMD9L in children with monosomy 7 and MDS. We previously demonstrated an antiproliferative effect of these gene products in non-hematopoietic cells, which was exacerbated by their patient-associated mutations. Here, we used a lentiviral overexpression approach to assess the functional impact and underlying cellular processes of wild-type and mutant SAMD9 or SAMD9L in primary mouse or human hematopoietic stem and progenitor cells (HSPC). Using a combination of protein interactome analyses, transcriptional profiling, and functional validation, we show that SAMD9 and SAMD9L are multifunctional proteins that cause profound alterations in cell cycle, cell proliferation, and protein translation in HSPCs. Importantly, our molecular and functional studies also demonstrated that expression of these genes and their mutations leads to a cellular environment that promotes DNA damage repair defects and ultimately apoptosis in hematopoietic cells. This study provides novel functional insights into SAMD9 and SAMD9L and how their mutations can potentially alter hematopoietic function and lead to bone marrow hypocellularity, a hallmark of pediatric MDS.

Download Full-text

Primitive Human Hematopoietic Cells Are Enriched in Cord Blood Compared With Adult Bone Marrow or Mobilized Peripheral Blood as Measured by the Quantitative In Vivo SCID-Repopulating Cell Assay

Blood ◽

10.1182/blood.v89.11.3919 ◽

1997 ◽

Vol 89 (11) ◽

pp. 3919-3924 ◽

Cited By ~ 328

Author(s):

Jean C.Y. Wang ◽

Monica Doedens ◽

John E. Dick

Keyword(s):

Bone Marrow ◽

Cord Blood ◽

Peripheral Blood ◽

Hematopoietic Cells ◽

Allogeneic Transplantation ◽

Functional Assay ◽

Hematopoietic Stem ◽

Mobilized Peripheral Blood

Abstract We have previously reported the development of in vivo functional assays for primitive human hematopoietic cells based on their ability to repopulate the bone marrow (BM) of severe combined immunodeficient (SCID) and nonobese diabetic/SCID (NOD/SCID) mice following intravenous transplantation. Accumulated data from gene marking and cell purification experiments indicate that the engrafting cells (defined as SCID-repopulating cells or SRC) are biologically distinct from and more primitive than most cells that can be assayed in vitro. Here we demonstrate through limiting dilution analysis that the NOD/SCID xenotransplant model provides a quantitative assay for SRC. Using this assay, the frequency of SRC in cord blood (CB) was found to be 1 in 9.3 × 105 cells. This was significantly higher than the frequency of 1 SRC in 3.0 × 106 adult BM cells or 1 in 6.0 × 106 mobilized peripheral blood (PB) cells from normal donors. Mice transplanted with limiting numbers of SRC were engrafted with both lymphoid and multilineage myeloid human cells. This functional assay is currently the only available method for quantitative analysis of human hematopoietic cells with repopulating capacity. Both CB and mobilized PB are increasingly being used as alternative sources of hematopoietic stem cells in allogeneic transplantation. Thus, the findings reported here will have important clinical as well as biologic implications.

Download Full-text

Enrichment of Rabbit Primitive Hematopoietic Cells via MACS Depletion of CD45+ Bone Marrow Cells

Magnetochemistry ◽

10.3390/magnetochemistry7010011 ◽

2021 ◽

Vol 7 (1) ◽

pp. 11

Author(s):

Jaromír Vašíček ◽

Andrej Baláži ◽

Miroslav Bauer ◽

Andrea Svoradová ◽

Mária Tirpáková ◽

...

Keyword(s):

Bone Marrow ◽

Mononuclear Cells ◽

Bone Marrow Cells ◽

Quantitative Polymerase Chain Reaction ◽

Hematopoietic Cells ◽

Hematopoietic Stem ◽

Stem And Progenitor Cells ◽

Rabbit Bone ◽

Hematopoietic Disorders ◽

Novel Strategy

Hematopoietic stem and progenitor cells (HSC/HPCs) of human or few animal species have been studied for over 30 years. However, there is no information about rabbit HSC/HPCs, although they might be a valuable animal model for studying human hematopoietic disorders or could serve as genetic resource for the preservation of animal biodiversity. CD34 marker is commonly used to isolate HSC/HPCs. Due to unavailability of specific anti-rabbit CD34 antibodies, a novel strategy for the isolation and enrichment of rabbit HSC/HPCs was used in this study. Briefly, rabbit bone marrow mononuclear cells (BMMCs) were sorted immunomagnetically in order to remove all mature (CD45+) cells. The cells were depleted with overall purity about 60–70% and then cultured in a special medium designed for the expansion of CD34+ cells. Quantitative Polymerase Chain Reaction (qPCR) analysis confirmed the enrichment of primitive hematopoietic cells, as the expression of CD34 and CD49f increased (p < 0.05) and CD45 decreased (p < 0.001) at the end of culture in comparison to fresh BMMCs. However, cell culture still exhibited the presence of CD45+ cells, as identified by flow cytometry. After gating on CD45− cells the MHCI+MHCII−CD38+CD49f+CD90−CD117− phenotype was observed. In conclusion, rabbit HSC/HPCs might be isolated and enriched by the presented method. However, further optimization is still required.

Download Full-text

Primitive hematopoietic cells in murine bone marrow express the CD34 antigen

Blood ◽

10.1182/blood.v88.10.3774.bloodjournal88103774 ◽

1996 ◽

Vol 88 (10) ◽

pp. 3774-3784 ◽

Cited By ~ 65

Author(s):

F Morel ◽

SJ Szilvassy ◽

M Travis ◽

B Chen ◽

A Galy

Keyword(s):

Stem Cells ◽

Monoclonal Antibody ◽

Bone Marrow ◽

Progenitor Cells ◽

Significant Proportion ◽

Hematopoietic Cells ◽

Full Detail ◽

Hematopoietic Stem ◽

Cd34 Antigen

The CD34 antigen is expressed on most, if not all, human hematopoietic stem cells (HSCs) and hematopoietic progenitor cells, and its use for the enrichment of HSCs with repopulating potential is well established. However, despite homology between human and murine CD34, its expression on subsets of primitive murine hematopoietic cells has not been examined in full detail. To address this issue, we used a novel monoclonal antibody against murine CD34 (RAM34) to fractionate bone marrow (BM) cells that were then assayed in vitro and in vivo with respect to differing functional properties. A total of 4% to 17% of murine BM cells expressed CD34 at intermediate to high levels, representing a marked improvement over the resolution obtained with previously described polyclonal anti-CD34 antibodies. Sixty percent of CD34+ BM cells lacked lineage (Lin) markers expressed on mature lymphoid or myeloid cells. Eighty-five percent of Sca-1+Thy-1(10)Lin- /10 cells that are highly enriched in HSCs expressed intermediate, but not high, levels of CD34 antigen. The remainder of these phenotypically defined stem cells were CD34-. In vitro colony-forming cells, day-8 and -12 spleen colony-forming units (CFU-S), primitive progenitors able to differentiate into B lymphocytes in vitro or into T lymphocytes in SCID mice, and stem cells with radioprotective and competitive long-term repopulating activity were all markedly enriched in the CD34+ fraction after single-parameter cell sorting. In contrast, CD34-BM cells were depleted of such activities at the cell doses tested and were capable of only short-term B-cell production in vitro. The results indicate that a significant proportion of murine HSCs and multilineage progenitor cells express detectable levels of CD34, and that the RAM34 monoclonal antibody is a useful tool to subset primitive murine hematopoietic cells. These findings should facilitate more direct comparisons of the biology of CD34+ murine and human stem and progenitor cells.

Download Full-text

Hematopoietic stem and progenitor cells are present in healthy gingiva tissue

Journal of Experimental Medicine ◽

10.1084/jem.20200737 ◽

2021 ◽

Vol 218 (4) ◽

Author(s):

Siddharth Krishnan ◽

Kelly Wemyss ◽

Ian E. Prise ◽

Flora A. McClure ◽

Conor O’Boyle ◽

...

Keyword(s):

Bone Marrow ◽

Immune Responses ◽

Progenitor Cells ◽

Myeloid Cell ◽

Extramedullary Hematopoiesis ◽

Innate Immune ◽

Innate Immune Cells ◽

Hematopoietic Stem ◽

Effector Cells ◽

Stem And Progenitor Cells

Hematopoietic stem cells reside in the bone marrow, where they generate the effector cells that drive immune responses. However, in response to inflammation, some hematopoietic stem and progenitor cells (HSPCs) are recruited to tissue sites and undergo extramedullary hematopoiesis. Contrasting with this paradigm, here we show residence and differentiation of HSPCs in healthy gingiva, a key oral barrier in the absence of overt inflammation. We initially defined a population of gingiva monocytes that could be locally maintained; we subsequently identified not only monocyte progenitors but also diverse HSPCs within the gingiva that could give rise to multiple myeloid lineages. Gingiva HSPCs possessed similar differentiation potentials, reconstitution capabilities, and heterogeneity to bone marrow HSPCs. However, gingival HSPCs responded differently to inflammatory insults, responding to oral but not systemic inflammation. Combined, we highlight a novel pathway of myeloid cell development at a healthy barrier, defining a gingiva-specific HSPC network that supports generation of a proportion of the innate immune cells that police this barrier.

Download Full-text

In Vitro Murine Hematopoiesis Supported by Signaling from a Splenic Stromal Cell Line

Stem Cells International ◽

10.1155/2018/9896142 ◽

2018 ◽

Vol 2018 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Hong Kiat Lim ◽

Pravin Periasamy ◽

Helen C. O’Neill

Keyword(s):

Bone Marrow ◽

Cell Line ◽

Stromal Cell ◽

Hematopoietic Cells ◽

Model Systems ◽

Hematopoietic Stem ◽

Cell Production ◽

Stromal Cell Line ◽

Reticular Cells

There are very few model systems which demonstrate hematopoiesis in vitro. Previously, we described unique splenic stromal cell lines which support the in vitro development of hematopoietic cells and particularly myeloid cells. Here, the 5G3 spleen stromal cell line has been investigated for capacity to support the differentiation of hematopoietic cells from progenitors in vitro. Initially, 5G3 was shown to express markers of mesenchymal but not endothelial or hematopoietic cells and to resemble perivascular reticular cells in the bone marrow through gene expression. In particular, 5G3 resembles CXCL12-abundant reticular cells or perivascular reticular cells, which are important niche elements for hematopoiesis in the bone marrow. To analyse the hematopoietic support function of 5G3, specific signaling pathway inhibitors were tested for the ability to regulate cell production in vitro in cocultures of stroma overlaid with bone marrow-derived hematopoietic stem/progenitor cells. These studies identified an important role for Wnt and Notch pathways as well as tyrosine kinase receptors like c-KIT and PDGFR. Cell production in stromal cocultures constitutes hematopoiesis, since signaling pathways provided by splenic stroma reflect those which support hematopoiesis in the bone marrow.

Download Full-text