Bone Marrow Subpopulations Research Articles

Evaluation of the Immunosafety of Cucurbit[n]uril In Vivo.

Cucurbiturils are a family of macrocyclic oligomers capable of forming host-guest complexes with various molecules. Due to noncovalent binding to drug molecules and low toxicity, cucurbiturils has been extensively investigated as potential carriers for drug delivery. However, the immune system's interactions with different drug carriers, including cucurbiturils, are still under investigation. In this study, we focused on cucurbiturils' immunosafety and immunomodulation properties in vivo. We measured blood counts and lymphocyte subpopulations in blood, spleen, and bone marrow, and assessed the in vivo toxicity to spleen and bone marrow cells after intraperitoneal administration to BALB/c mice. When assessing the effect of cucurbit[6]uril on blood parameters after three intraperitoneal injections within a week in laboratory animals, a decrease in white blood cells was found in mice after injections of cucurbit[6]util, but the observed decrease in the number of white blood cells was within the normal range. At the same time, cucurbit[7]uril and cucurbit[8]uril did not affect the leukocyte counts of mice after three injections. Changes in the number of platelets, erythrocytes, and monocytes, as well as in several other indicators, such as hematocrit or erythrocyte volumetric dispersion, were not detected. We show that cucurbiturils do not have immunotoxicity in vivo, with the exception of a cytotoxic effect on spleen cells after сucurbit[7]uril administration at a high dosage. We also evaluated the effect of cucurbiturils on cellular and humoral immune responses. We founded that cucurbiturils in high concentrations affect the immune system in vivo, and the action of various cucurbiturils differs in different homologues, which is apparently associated with different interactions in the internal environment of the body.

Single Cell Analysis Identifies Expression of PD-L2 on Human Bone Marrow Hematopoietic Stem Cells

The identification of specific and reliable markers for human hematopoietic stem cells (HSCs) is crucial to enable their prospective isolation allowing the investigation of unique physiological HSC functions within the blood cell hierarchy. Despite significant advancements in identification of surface markers for human bone marrow HSC isolation, the enriched populations remain heterogeneous. Here we applied single cell CITE-Seq (cellular indexing of transcriptomes and epitopes) of FACS-enriched hematopoietic stem and progenitor cells (HSPCs) to decipher differentiation hierarchies and to identify markers of most immature populations. We FACS-isolated over 60.000 high-quality human bone marrow HSPCs by sorting CD34 + and CD34 +CD38 - cells from 15 different healthy donors. These were subjected to scCITE-Seq using the BD Rhapsody system with a targeted gene panel comprising 600 most relevant genes of early HSC differentiation and 50 antibodies. To validate differentially expressed surface marker genes, we performed extensive in vitro and in vivo studies of FACS-purified subpopulations of human bone marrow and mobilized peripheral blood samples (mPB) from healthy donors. Our multi-omics based single HSPC profiling indicated Programmed death ligand 2 (PD-L2 / CD273) as a surface marker expressed on the most immature HSCs within the hematopoietic compartment defined as CD34 +CD38 -CD45RA -CD90 +. Prospective FACS-based isolation allowed a deeper understanding of transcriptomic differences depending on PD-L2 positivity. A transcriptomic principal component analysis of CD273 hi and CD273 low expressing HSCs isolated pairwise from four healthy donors proved distinct clustering accompanied by discriminative molecular signatures. Stem cell genes as HOPX, MLLT3 and MPL were enriched in CD273 hi HSCs, and CDK6 was downregulated, further validating our single-cell analysis. The differential expression of stem cell genes was validated at protein level. Single cell tracking using video-microscopy confirmed a delayed entry into cell cycle in CD273 hi HSCs, suggesting deeper quiescence of these cells. Furthermore, their mitochondrial potential was reduced. In vivo transplantations of both populations in immunocompromised NSGs are ongoing and will reveal the long-term repopulation potential of CD273 hi HSCs. Multiple in vitro differentiation assays demonstrated CD273 positivity to be associated with an increased stem cell phenotype with higher expression of EPCR (CD201) and CD90 in liquid culture, a delayed differentiation and high capability of generating multipotent colonies. Interestingly, CD273 surface expression was strongly upregulated in HSCs upon in vitro culture. Since PD-L2 is known as a ligand for the Programmed death receptor 1 (PD1), we investigated the immunomodulating function of PD-L2 expressing HSPCs by establishing an allogeneic lymphocyte reaction assay. In addition to their stem cell-like characteristics, PD-L2 expressing HSPCs mediated diminished T cell proliferation in allogeneic co-culture settings. Furthermore, cytokine profiling of co-culture supernatants indicated increased secretion of anti-inflammatory cytokines (IL-10 and TGF-β1), accompanied by reduced secretion of pro-inflammatory cytokines (IL-17A) and a diminished expression of the pro-inflammatory receptor CD69 on CD8 + T cells. These findings showed that CD34 + cells isolated from mobilized peripheral blood of healthy donors possess immunomodulating capabilities, and that PD-L2 expression indicates an immunocompromising HSC phenotype. In conclusion, this study demonstrates differential surface expression of PD-L2 within the most immature human HSCs. PD-L2 expression is associated with HSC quiescence and delayed in vitro differentiation. Furthermore, these results provide valuable insights into the immunomodulating features of HSCs expressing PD-L2.

Acute Inflammation Redirect Bone Marrow Hematopoietic Stem Cell Cycling and Differentiation Program By Reshaping Their Chromatin Architecture at Long-Term

Background: Acute and persistent inflammation induced by microbial infections/sepsis or by therapeutic interventions, such as whole-body irradiation and CAR-T therapy, triggers a rapid overwhelming immune response in the host. While these responses are well defined in the short-term, the long-term impact of the inflammatory injury on the hematopoietic system still needs to be unveiled. Using a murine model of severe inflammation induced by bacteria P. aeruginosa ( P. aer.) or LPS, our group has previously reported that bone marrow (BM) hematopoietic stem cells (HSC) respond to infections with an aberrant expansion associated with their transitory inability to generate the downstream myeloid progenitors. Such dysfunctions correlated with the suppression of transcription factors governing stem-cell self-renewal and myeloid differentiation. Furthermore, when transplanted into healthy mice, the “inflamed” HSC showed reduced ability to contribute to the myeloid lineage and to engraft at long-term, suggesting that they retain memory of the LPS-mediated insult and maintain long-lasting changes. Thus, we hypothesized that severe inflammation alters the HSC epigenome, reshaping their transcriptional programs and affecting cell fate decisions and differentiation. Methods: We performed time-course experiments in WT mice challenged with a single dose of LPS or PBS, as control, and investigated 1) the kinetics of hematopoietic recovery by flow-cytometric immunophenotypic characterization, including cell-cycle 2) changes in the chromatin landscape of Lin- sorted BM subpopulations identified by the expression of the CD150 and CD48 markers as Long-Term (LT-HSC), Short-Term (ST-HSC), and Multipotent Progenitors (MPP1/2 and MPP3/4) using ATAC-seq. Results: Our studies revealed that the LPS challenge resulted in a significant increase in the cell-cycle of LT-HSC, ST-HSC, MPPs, common myeloid progenitors (CMP), and granulocyte-monocyte progenitors (GMP), which persisted up to 3 days from the inflammatory injury. Immunophenotypic analysis showed that while HSC frequencies returned to baseline at 5 days from LPS, the abundance and cell-cycle of myeloid progenitors and mature cells remained altered. Surprisingly, at 15 days post LPS, the cell-cycle of HSC markedly decreased, and such dysregulation was maintained until our last observation at 30 days from LPS. The pool of BM HSC was severely depleted and associated with exhaustion of T-cells but increased B-cells. GMP and Gr1+Mac1+ cells were also significantly decreased in the BM whereas mature lineages were increased in the peripheral blood, exhibiting high WBC, lymphocytes, and platelet count, neutrophilia, monocytosis, basophilia, and eosinophilia. ATAC-seq analysis revealed prominent differences in the chromatin architecture of the four HSC subpopulations at steady state (PBS). In all of them, LPS induced both i) a transient reorganization of the chromatin in some loci, and ii) the formation of persistently reshaped regions. Deeper investigations into the long-term changed sites revealed that chromatic accessibility was altered in proximity of CTCF-enriched regions fundamental to mediate chromatin reorganization and drive gene expression. Moreover, LPS modified the accessibility of genomic loci involved in the maintenance of HSC stemness and quiescence as well as regulation of their cell-cycle, self-renewal, and cell fate decision. Conclusions: Taken together these results suggest that LPS-mediated acute inflammation has long-lasting effects on HSC epigenetic regulation, influencing their cell-cycle and multilineage decisions. Relevance: The association between the resulting phenotype and the persistency of epigenetically remodeled HSC loci identified here may provide potential insights for future therapeutic approaches to re-direct “inflamed” HSC to a normal differentiation program, thereby enabling an efficient innate host response. Disclosures: No relevant conflicts of interest to declare.

Abnormal adipogenic signaling in the bone marrow mesenchymal stem cells contributes to supportive microenvironment for leukemia development

BackgroundAcute myeloid leukemia (AML) is an aggressive hematological malignancy, associated with unfavorable patient outcome, primarily due to disease relapse. Mesenchymal stem cells (MSCs) residing in the bone marrow (BM) niche are the source of mesenchyma-derived subpopulations, including adipocytes, and osteocytes, that are critical for normal hematopoiesis. This study aimed to characterize BM-derived adipocyte/osteocyte fractions and their crosstalk with AML cells as a potential mechanism underlying leukemogenesis.MethodsBM cell subpopulations derived from primary AML patients were evaluated using humanized ex-vivo and in-vivo models, established for this study. The models comprised AML blasts, normal hematopoietic stem and progenitor cells and mesenchymal stromal subpopulations. ELISA, FACS analysis, colony forming unit assay, whole exome sequencing and real-time qPCR were employed to assess the differentiation capacity, genetic status, gene expression and function of these cell fractions. To explore communication pathways between AML cells and BM subpopulations, levels of signaling mediators, including cytokines and chemokines, were measured using the ProcartaPlex multiplex immunoassay.ResultsThe study revealed deficiencies in adipogenic/osteogenic differentiation of BM-MSCs derived from AML patients, with adipocytes directly promoting survival and clonogenicity of AML cells in-vitro. In whole exome sequencing of BM-MSC/stromal cells, the AHNAK2 gene, associated with the stimulation of adipocyte differentiation, was found to be mutated and significantly under-expressed, implying its abnormal function in AML. The evaluation of communication pathways between AML cells and BM subpopulations demonstrated pronounced alterations in the crosstalk between these cell fractions. This was reflected by significantly elevated levels of signaling mediators cytokines/chemokines, in AML-induced adipocytes/osteocytes compared to non-induced MSCs, indicating abnormal hematopoiesis. Furthermore, in-vivo experiments using a fully humanized 3D scaffold model, showed that AML-induced adipocytes were the dominant component of the tumor microenvironment, providing preferential support to leukemia cell survival and proliferation.ConclusionsThis study has disclosed direct contribution of impaired functional, genetic and molecular properties of AML patient-derived adipocytes to effective protection of AML blasts from apoptosis and to stimulation of their growth in vitro and in vivo, which overall leads to disease propagation and relapse. The detected AHNAK2 gene mutations in AML-MSCs point to their involvement in the mechanism underlying abnormal adipogenesis.AaFEVfq6u-1YqH7bnQ85uaVideo

Prebiotics Modulate Gut Microbiota-mediated T-cell Immunity to Enhance the Inhibitory Effect of Sintilimab in Lewis Lung Adenocarcinoma Model Mice.

Sintilimab (Sin) helps the body to restore the anti-tumor response of T lymphocytes. However, in clinical use, the treatment process is more complicated due to adverse effects and different dosing regimens. It is not clear whether prebiotics (PREB) have a potentiating effect on Sin for lung adenocarcinoma, and this study intends to investigate the inhibitory effect, safety and possible mechanism of Sin combined with PREB on lung adenocarcinoma from animal experiments. Lewis lung adenocarcinoma cells were inoculated into the right axilla of mice subcutaneously to prepare the Lewis lung cancer mouse model and treated in groups. The volume of transplanted tumors was measured, the histopathology of the liver and kidney of mice was observed by H&E staining, the levels of ALT, AST, UREA, CREA, WBC, RBC, and HGB in blood were analyzed biochemically; the ratio of T-cell subpopulations in blood, spleen, and bone marrow was detected by flow cytometry, the expression of PD-L1 in tumor tissue was detected by immunofluorescence staining, and 16S rRNA to analyze the diversity of fecal flora. Sin inhibited tumor growth and regulated immune cell homeostasis in lung adenocarcinoma mice, but liver and kidney histopathology showed different degrees of damage after Sin treatment, while the addition of PREB reduced liver and kidney damage in lung adenocarcinoma mice and promoted Sin's regulation of immune cells. In addition, the beneficial effects of Sin were associated with changes in intestinal flora diversity. The mechanism by which Sintilimab combined with prebiotics inhibits tumor volume and regulates immune cell subpopulation balance in lung adenocarcinoma mice may be related to gut microbes.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Background: A growing body of evidence has indicated impaired function or compositional changes of monocytes in inflammatory disorders, such as acute respiratory syndrome and covid-19. In myeloma tumor microenvironment, activation of type I interferon pathway and dysregulated expression of major histocompatibility complex type II genes are observed in classical monocytes, which result in loss of antigen presentation of monocytes. The proportions of BAFF+PD-L1+ monocytes in the bone marrow also correlate with survival of myeloma patients following chimeric antigen-receptor T cell therapy. Nevertheless, the mechanisms underlying PB and BM monocytes defects in myeloma remain poorly addressed, at least in part by the lack of large scale scRNA-seq studies. To resolve the heterogeneous bone marrow and peripheral blood monocyte subpopulations and their transcriptional factors between healthy donors and multiple myeloma patients. Methods: We conducted scRNA-seq on monocytes of 7 newly diagnosed myeloma patients and 12 healthy donors. Specifically, 3 and 5 bone marrow aspirates and 9 and 7 peripheral blood samples of 12 healthy controls and 7 newly diagnosed patients were obtained, respectively. Results: Heterogeneous bone marrow and peripheral blood monocyte subpopulations and their transcriptional factors were resolved. The function characteristics of monocyte were compared between MM patients and healthy donors, which indicated a stress signature induced by multiple myeloma. Furthermore, we identified two monocyte differentiation pathways, and discovered that bone marrow monocyte feature type I IFN-associated differentiation dysregulation in patients with MM as well as dysregulated patterns at transcriptome. Finally, we included 10 MM patients as a validation cohort, by tracking the stress signature over time in those patients undergoing first-line treatment, we founded that the stress signature was partially overcome by antitumor therapy. Conclusion: Our results provided further insight into transcriptional and differentiation changes occurring in the bone marrow and peripheral blood monocytes from patients with multiple myeloma and hint and mechanisms of immune evasion. Encore Abstract - previously submitted to EHA 2023 The research was funded by: This investigation was supported by the International Cooperation Projects of National Natural Science Foundation (grants 81920108006), CAMS Innovation Fund for Medical Sciences (CIFMS) (grants 2022-I2M-1-022), the National Natural Science Foundation (grants 81630007; grants 82270218, 81670202; grants 81900214), and the Atlas of Blood Cell Alliance. Keywords: genomics, epigenomics, and other -omics, microenvironment, multiple myeloma No conflicts of interests pertinent to the abstract.

Identifying Biomarkers for Osteogenic Potency Assay Development.

There has been extensive exploration of how cells may serve as advanced therapy medicinal products to treat skeletal pathologies. Osteoblast progenitors responsible for production of extracellular matrix that is subsequently mineralized during bone formation have been characterised as a rare bone marrow subpopulation of cell culture plasticadherent cells. Conveniently, they proliferate to form single-cell derived colonies of fibroblastoid cells, termed colony forming unit fibroblasts that can subsequently differentiate to aggregates resembling small areas of cartilage or bone. However, donor heterogeneity and loss of osteogenic differentiation capacity during extended cell culture have made the discovery of reliable potency assay biomarkers difficult. Nonetheless, functional osteoblast models derived from telomerised human bone marrow stromal cells have allowed extensive comparative analysis of gene expression, microRNA, morphological phenotypes and secreted proteins. This chapter highlights numerous insights into the molecular mechanisms underpinning osteogenic differentiation of multipotent stromal cells and bone formation, discussing aspects involved in the choice of useful biomarkers for functional attributes that can be quantitively measured in osteogenic potency assays.

Single Cell Transcriptomic Analysis of the Bone Marrow Microenvironment Uncovers a Role for Antigen Presentation Processes in MDS/AML Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Background: Bone marrow (BM) diseases such as myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are characterized by a poor overall survival with allogeneic hematopoietic stem cell transplantation (allo-HSCT) often representing the only curative treatment option. However, patient mortality even after allo-HSCT remains high, mainly due to relapse. Previous studies showed involvement of immune escape processes in relapsed patients via downregulation of human leukocyte antigen class II (HLA-II) genes on leukemic blasts, or T cell exhaustion. Nevertheless, other components of the BM microenvironment (BMME) including mesenchymal stromal cells (MSC), endothelial cells and immune cells from the innate and adaptive immune system might play a role in relapse after allo-HSCT. This role remains unclear and needs further characterization. Therefore, we performed single cell transcriptomic analysis of different subpopulations of the BMME in MDS/AML patients who either achieved a long-term complete remission (CR) or relapsed after allo-HSCT. Methods: Patient BM aspirates were obtained before and after 3-6 months post allo-HSCT after written informed consent, and mononuclear cells were stored in liquid nitrogen. To reduce confounding factors (i.e., pre-conditioning treatment, age, sex, diagnosis, graft versus host disease), "best-matched" patient pairs in CR or relapse were established. Subsequently, 2 pairs of matched CR/relapse patients were chosen for further evaluation (Table 1). From each patient, 6 different BM subpopulations were FACS-sorted to enrich for rare cell populations: hematopoietic stem and progenitor cells (HSPC, CD45dim/CD34+), MSC (CD45-/CD271+), endothelial cells (CD45-/CD31+), monocytes (CD45dim/CD14+), granulocytes (CD45dim/CD11b+), T cells (SSClow/CD45hi/CD3+) and NK cells (SSClow/CD45hi/CD3-/CD56+/CD16+). A maximum number of 5x103 cells from each of these 6 cell populations from a single patient and time point were pooled back together in one lane of a 10X Genomics chip for single cell RNA sequencing library preparation. Data analysis was performed in R. Results: After UMAP clustering, 15 groups of cells could be identified by their conserved expression patterns, recapitulating the different input sorted subpopulations. Gene set enrichment analysis comparing cell types from patients in CR and relapse revealed enrichment in immune related pathways in many clusters from relapsing patients both before and after allo-HSCT. In contrast, this pathway enrichment was only observed in classical monocytes from patients in CR after allo-HSCT. Further gene expression analysis showed that within these pathways, the most significantly differentially expressed genes were HLA class I (HLA-I) and HLA-II genes, as well as the transcription factor STAT1. Of note, STAT1 expression was increased 1.2 to 2.3 fold in several cell types from patients in relapse compared to patients in CR. Similarly, the known STAT1 target genes HLA-A and HLA-C showed a 1.2 to 7.5 fold higher expression in several cell types from relapsed patients. Importantly, upregulations were observed in progenitor cells as well as in lymphocytes both before and after allo-HSCT, suggesting that STAT1 upregulation might trigger HLA-I genes expression and play a role in and/or serve as predictive marker of post-transplant relapse. Interestingly, HLA-II gene enrichment patterns were more heterogeneous. Indeed, before transplantation, genes such as HLA-DRA, HLA-DPB1 or CD74 were upregulated 1.4 to 3.0 fold in most cell types of patients in relapse, while after allo-HSCT a downregulation of 1.5 to 3.5 fold was observed in progenitor cells from patients in relapse, and was even more prominent in classical monocytes showing a 2 to 8 fold downregulation (Figure 1). This observation suggests that by preventing T cell activation via HLA-II antigen presentation, monocytes might also play a role in relapse mechanisms after allo-HSCT. Conclusions: Altogether, our results suggest that antigen presentation processes in the BMME via HLA-I and HLA-II could be involved in relapse mechanisms. Their expression level even before transplantation might be used as a predictor of relapse after allo-HSCT. Further analyses are ongoing to confirm our preliminary findings including functional analyses linking relapse with those observed differences in gene expression. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Somatic Mutations in TP53 Identified in T-Cells of Patients with TP53-mutated AML

Introduction: Genomic characterization of AML has delineated the frequent occurrence of somatic mutations in pre-malignant cell populations characterized as clonal hematopoiesis (CH). AML with mutant TP53 (TP53mt) is associated with an adverse prognosis and resistance to all available therapies. The cell-of-origin in AML with TP53mt is not well established. Delineating the clonal architecture of hematopoiesis in AML with TP53mt could improve understanding of resistance. Recurrent somatic DNMT3A mutations, commonly detected in CH, have been identified in purified hematopoietic stem cells (HSCs) and T-cells of patients (pts) with AML (Shlush, Nature 2014). We hypothesized that somatic TP53mt affect early cells in the hematopoietic hierarchy of AML leading to a dysfunction of multiple hematopoietic compartments including T-cells. Methods: Using whole exome sequencing (WES), we analyzed FACS-sorted bone marrow sub-populations from 39 pts with adverse risk, including 16 (41%) with TP53mt AML. Mononuclear cells were flow-sorted for bulk (CD45dim), and leukemia stem cells (LSCs) (Lin-CD34+CD38-CD123+) from diagnostic samples, whereas post-treatment samples were sorted for therapy residual disease based on patient-specific aberrant phenotype. CD3+ sorting was used to identify T-cells in available samples. Mutations were called using MuTect and Pindel against virtual normal. We used patient-specific primers to validate mutations by digital-droplet PCR (ddPCR). DAb-seq (joint profiling of DNA and proteins in single cells) was used to examine mutations in subpopulations. Results: We found that CD3+ sorted cells harbored, in addition to previously described mutations known to occur in CH, mutations in TP53 at relatively high variant allelic frequencies (VAF) (46%, 14% - 88%), in 5/7 (71%) samples from different pts. These were the exact mutations detected in leukemia sub-populations. These pts had no personal or family history indicative of a Li-Fraumeni Syndrome (LFS). To address whether the observed mutations in sorted CD3+ cells are a result of an imperfect selection and contamination by leukemia cells or whether these are mutations in T-cells, we extracted T-cell receptor (TCR) sequences from WES to use as barcodes for quantifying T-cell fractions in each sample (Bentham, Nature 2021). We found that T-cell diversity, a metric quantifying unique TCR sequences, was significantly higher in sorted CD3+ cells indicating a high fraction of T-cells in these samples (median TCRβ normalized diversity of 23.6 vs 1.1, P=0.005). In order to further corroborate these findings, we resorted to sorting of CD3+, CD33-, CD34- cells from an additional cohort yielding purity >97% (Fig. 1A). Subsequently, we used ddPCR with probes designed for corresponding mutations in TP53 detected in clinical testing for each patient. In highly pure sorted samples with these markers (CD3+, CD33-, CD34-), TP53mt were detected in more than 20% of droplets (range of droplets with TP53mt: 23% - 44%) and were detected in 3/9 (33%) samples from different pts (Figure 1A). Finally, we used DAb-seq for simultaneous capture of DNA genotype and cell surface phenotype in bone marrow cells from 5 pts with TP53mt AML. We identified the TP53 (R280G) mutation in the CD34-, CD3+, CD4+, or CD8+ cell cluster, the same mutation detected by the clinical sequencing assay in 1 patient (Fig. 1B). We had previously shown that T-cells from TP53mut AML have aberrant cytokine secretion with immune dysfunction. T cells from TP53mut AML (N=5) have decreased function vs TP53wt (N=5) (Polyfunctional Strength Index of 6.6 vs 73.5, P=0.01). This result was driven by lower secretion of effector cytokines such as granzyme B, interferon-g and TNF-α in TP53mut. All together, these findings identify multiple mechanisms for immune dysfunction in TP53mt AML. Conclusion: We found TP53mt in a fraction of CD3+, CD34- cells from pts with TP53mt AML, likely T-cells. These mutations are likely somatic given the range of VAFs and lack of family history indicative of LFS. This possibility suggests that TP53mt are early events in AML, occurring in HSCs and expanding in multiple cellular compartments including T-cells. Further evaluations of these findings are ongoing. Given the important role of TP53 in various cellular functions including immunity, alterations of TP53 could be a challenge to therapeutic strategies aimed at reinvigorating T-cells in TP53mt AML. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Quantitative Analysis of B-Cell Subpopulations in Bone Marrow by Flow Cytometry.

Flow cytometry is a technology that rapidly detects and measures physical and chemical characteristics of single cells or particles. It is a powerful tool for many areas of research, in particular, immunology, which allows for simultaneous analysis of different immune cell populations in a tissue. Here we describe the procedures to quantify and/or purify various B fractions in mouse bone marrows by flow cytometry using their signature surface markers. This method is useful to study B-cell development during steady-state or emergency hematopoiesis such as viral infections.

ATF3 Reprograms the Bone Marrow Niche in Response to Early Breast Cancer Transformation.

Cancer is a systemic disease able to reprogram the bone marrow (BM) niche towards a protumorigenic state. The impact of cancer on specific BM subpopulations can qualitatively differ according to the signals released by the tumor, which can vary on the basis of the tissue of origin. Using a spontaneous model of mammary carcinoma, we identified BM mesenchymal stem cells (MSC) as the first sensors of distal cancer cells and key mediators of BM reprogramming. Through the release of IL1B, BM MSCs induced transcriptional upregulation and nuclear translocation of the activating transcription factor 3 (ATF3) in hematopoietic stem cells. ATF3 in turn promoted the formation of myeloid progenitor clusters and sustained myeloid cell differentiation. Deletion of Atf3 specifically in the myeloid compartment reduced circulating monocytes and blocked their differentiation into tumor-associated macrophages. In the peripheral blood, the association of ATF3 expression in CD14+ mononuclear cells with the expansion CD11b+ population was able to discriminate between women with malignant or benign conditions at early diagnosis. Overall, this study identifies the IL1B/ATF3 signaling pathway in the BM as a functional step toward the establishment of a tumor-promoting emergency myelopoiesis, suggesting that ATF3 could be tested in a clinical setting as a circulating marker of early transformation and offering the rationale for testing the therapeutic benefits of IL1B inhibition in patients with breast cancer. Significance: Bone marrow mesenchymal stem cells respond to early breast tumorigenesis by upregulating IL1B to promote ATF3 expression in hematopoietic stem cells and to induce myeloid cell differentiation that supports tumor development.

Breast cancer molecular subtypes and bone marrow immune system in patient’s prognosis

Backgrоund. Breast cancer molecular subtypes serve as a basis for combined treatment of the disease. Some of them (e. g. triple negative subtype) are prognostically unfavorable. Recently, we’ve demonstrated role of bone marrow B-cells in breast cancer prognosis. Correlation between these parameters (molecular subtypes and bone marrow lymphocyte subpopulations) have not yet studied.Aim. To investigate prognostic role of breast cancer molecular subtypes and to see the relationships between these subtypes and subpopulational composition of bone marrow lymphocytes.Materials and methods. Detailed study of bone marrow has been performed in all 107 patients treated in breast cancer department of N.N. Blokhin National Medical Research Center of Oncology in 2013–2016 years. Distribution of patients according to molecular subtypes were as follows: Luminal A – 36 (33.6 %) pts, Luminal B HER2-negative – 38 (35.5 %), Luminal B HER2-positive – 15 (14 %), subtype with Erb-B2 hyper-expression – 5 (4.4 %), triple negative – 13 (12.1 %). Comparison of molecular subtypes with immunological parameters was done for the following bone marrow B-lymphocyte subpopulations: CD19+, CD19+CD10+, CD19+CD38+, CD19+CD5+. The following survival data were analyzed: overall survival, relapse-free survival, progression-free survival, metastasis-free survival.Results. Breast cancer molecular subtypes were not related to overall survival of patients but influenced relapse-free survival, progression-free survival and metastasis-free survival. There were no correlation between molecular subtypes and bone marrow B-lymphocyte subpopulations CD19, CD19+CD10+, CD19+CD38+. B1-lymphocytes were related to molecular subtypes, the levels of B1 cells were significantly higher in Erb-B2 subtype compared to triple-negative subtype (p = 0.039).Conclusion. Breast cancer molecular subtypes are different in prognosis – relapse-free survival, progression-free survival and metastasis-free survival. The most prognostically unfavorable is triple-negative subtype. There are some relationships of bone marrow subpopulations and molecular subtypes of breast cancer: levels of B1-cells are much higher in Erb-B2 subtype compared to triple negative subtype (p = 0.039).

Cytokine expression by CD163+ monocytes in healthy and Actinobacillus pleuropneumoniae-infected pigs

Distinct monocyte subpopulations have been previously described in healthy pigs and pigs experimentally infected with Actinobacillus pleuropneumoniae (APP). The CD163+ subpopulation of bone marrow (BM), peripheral blood (PB) and lung monocytes was found to play an important role in the inflammatory process. The inflammation is accompanied by elevation of inflammatory cytokines. The aim of the study was to evaluate the contribution of CD163+ monocytes and macrophages to cytokine production during APP-induced lung inflammation.Cytokine production was assessed by flow cytometry (FC) and quantitative PCR (qPCR) in CD163+ monocytes and by qPCR, immunohistochemistry/fluorescence in lungs and tracheobronchial lymph nodes (TBLN). Despite the systemic inflammatory response after APP infection, BM and PB CD163+ monocytes did not express elevated levels of a wide range of cytokines compared to control pigs. In contrast, significant amounts of IL-1β, IL-6, IL-8 and TNF-α were produced in lung lesions and IL-1β in the TBLN. At the protein level, TNF-α was expressed by both CD163+ monocytes and macrophages in lung lesions, whereas IL-1β, IL-6 and IL-8 expression was found only in CD163+ monocytes; no CD163+ macrophages were found to produce these cytokines. Furthermore, the quantification of CD163+ monocytes expressing the two cytokines IL-1β and IL-8 that were most elevated was performed. In lung lesions, 36.5% IL-1β positive CD163+ monocytes but only 18.3% IL-8 positive CD163+ monocytes were found.In conclusion, PB and BM CD163+ monocytes do not appear to contribute to the elevated cytokine levels in plasma. On the other hand, CD163+ monocytes contribute to inflammatory cytokine expression, especially IL-1β at the site of inflammation during the inflammatory process.

Single-cell transcriptomics of LepR-positive skeletal cells reveals heterogeneous stress-dependent stem and progenitor pools.

Leptin receptor (LepR)-positive cells are key components of the bone marrow hematopoietic microenvironment, and highly enrich skeletal stem and progenitor cells that maintain homeostasis of the adult skeleton. However, the heterogeneity and lineage hierarchy within this population has been elusive. Using genetic lineage tracing and single-cell RNA sequencing, we found that Lepr-Cre labels most bone marrow stromal cells and osteogenic lineage cells in adult long bones. Integrated analysis of Lepr-Cre-traced cells under homeostatic and stress conditions revealed dynamic changes of the adipogenic, osteogenic, and periosteal lineages. Importantly, we discovered a Notch3+ bone marrow sub-population that is slow-cycling and closely associated with the vasculatures, as well as key transcriptional networks promoting osteo-chondrogenic differentiation. We also identified a Sca-1+ periosteal sub-population with high clonogenic activity but limited osteo-chondrogenic potential. Together, we mapped the transcriptomic landscape of adult LepR+ stem and progenitor cells and uncovered cellular and molecular mechanisms underlying their maintenance and lineage specification.

Development of a method for the identification of receptor activator of nuclear factor-κB+ populations in vivo

ObjectivesOsteoclasts are induced by macrophage colony-stimulating factor-1 (CSF-1) and receptor activator of nuclear factor-κB (RANK) ligand (RANKL). Monocyte/macrophage lineages are thought to be osteoclast precursors; however, such cells have not been fully characterized owing to a lack of tools for their identification. Osteoclast precursors express colony-stimulating factor-1 receptor (CSF-1R) and RANK. However, the capacity of conventional methods using anti-RANK antibodies to detect RANK+ cells by flow cytometry is insufficient. Here, we developed a high-sensitivity method for detecting RANK+ cells using biotinylated recombinant glutathione S-transferase-RANKL (GST-RANKL-biotin). MethodsWe sorted sub-populations of mouse bone marrow (BM) or peripheral blood (PB) cells using GST-RANKL-biotin, anti-CSF1R, and anti-B220 antibodies and induced osteoclastogenesis in vitro. ResultsThe frequency of the RANK+ population in BM detected by GST-RANKL-biotin was significantly higher than that detected by anti-RANK antibodies. Although RANK+ cells were detected in both the B220+ and B220− populations, the macrophage lineage was present only in B220−. Unexpectedly, a significantly higher number of osteoclasts was induced in RANK−CSF-1R+ cells than in RANK+CSF-1R+ cells contained in the B220− population. In contrast, the PB-derived B220−RANK+CSF-1R+ population contained a significantly higher frequency of osteoclast precursors than the B220−RANK−CSF-1R+ population. ConclusionsThese results suggest that GST-RANKL-biotin is useful for the detection of RANK+ cells and that RANK and CSF-1R may be helpful indicators of osteoclast precursors in PB.

Oligoclonality and subpopulation structure of bone marrow T-cells in patients with aplastic anaemia

Introduction. The main pathogenetic mechanism of the development of aplastic anemia (AA) is a violation of the immune regulation of hematopoiesis.Aim: to study of the subpopulation composition of T-cells and the repertoire of the T-cell receptor in AA patients.Patients and Methods. The study included AA patients (n = 40) without prior immunosuppressive therapy in 2018–2020. The T-cell subpopulation structure and T-cell receptor Vβ-family (TCR-Vβ) oligoclonality were studied in samples of bone marrow using flow cytometry.Results. We report characteristic properties of T-cell subpopulations of bone marrow in all AA patients: elevated counts of cytotoxic T-cells, effector CD4+ and CD8+ cells, CD4+ memory cells, which may suggest a long-term antigenic stimulation with subsequent activation of these cell subpopulations resulting in hyperexpression of pro-inflammatory cytokines. Diminishing of naive CD4+ and CD8+ cells, regulatory and double negative T-cells may indicate a relaxing control of cytokine-producing T-cells. A relationship has been established between the AA severity and counts of effector, regulatory, double negative and PD-1 positive T-cells. A highest count of potentially cytokine-producing T-cells and lowest count of cells involved in T-cell activity regulation were observed in very severe AA patients. Studies of the TCR-Vβ repertoire revealed oligoclonal expansion in the cytotoxic T-cell subpopulation.Conclusion. Enrichment in selected Vβ families suggests autoreactive T-cell clonality and attests to the immune nature of AA. A dynamic TCR-Vβ repertoire assay may be recommended in the disease monitoring. Flow cytometry helps identify valuable biomarkers for T-cell clone monitoring in AA and a better assessment of the disease progression.

Single-cell profiling reveals the trajectories of natural killer cell differentiation in bone marrow and a stress signature induced by acute myeloid leukemia

SummaryNatural killer (NK) cells are innate cytotoxic lymphoid cells (ILCs) involved in the killing of infected and tumor cells. Among human and mouse NK cells from the spleen and blood, we previously identified by single-cell RNA sequencing (scRNAseq) two similar major subsets, NK1 and NK2. Using the same technology, we report here the identification, by single-cell RNA sequencing (scRNAseq), of three NK cell subpopulations in human bone marrow. Pseudotime analysis identified a subset of resident CD56bright NK cells, NK0 cells, as the precursor of both circulating CD56dim NK1-like NK cells and CD56bright NK2-like NK cells in human bone marrow and spleen under physiological conditions. Transcriptomic profiles of bone marrow NK cells from patients with acute myeloid leukemia (AML) exhibited stress-induced repression of NK cell effector functions, highlighting the profound impact of this disease on NK cell heterogeneity. Bone marrow NK cells from AML patients exhibited reduced levels of CD160, but the CD160high group had a significantly higher survival rate.

SEL24/MEN1703 Provides PIM/FLT3 Downstream Pathway Inhibition in Acute Myeloid Leukemia (AML) Blast Cells: Results of the Pharmacodynamics (PD) Assay in the Dose Escalation Part of First-in-Human Diamond Trial

BACKGROUND. SEL24/MEN1703 is a first-in-class, orally available, dual PIM/FLT3 kinase inhibitor investigated in unselected AML patients in the First-in-Human, Dose Escalation (DE) and Cohort Expansion (CE) DIAMOND trial (clinicaltrials.gov identifier: NCT03008187). The study has completed the DE part showing an acceptable safety profile up to the recommended dose (RD), with initial evidence of single agent efficacy1. Preclinical studies conducted in vitro - using a panel of 26 AML cell lines harboring different genetic alterations - and in vivo - in xenograft mouse model bearing MOLM-16 cell line - showed a direct correlation between the activity of SEL24/MEN1703 and the inhibition of S6 phosphorylation (pS6) protein, a downstream target of PIM/FLT3 signaling pathway. AIM. To assess the degree of target engagement and its preliminary correlation with the anti-leukemic effect of SEL24/MEN1703 in samples collected from patients enrolled in the DE part of DIAMOND trial. METHODS. S6 phosphorylation has been longitudinally monitored in the DIAMOND study through an optimized assay for multiparametric analysis of phospho-protein activation. The assay allows a quantitative assessment of pS6 at single cell level among blast cells as well as the identification of blast subpopulations in both peripheral blood (PB) and bone marrow (BM). Blast counts were monitored to assess whether the target engagement did translate into blast count reduction. RESULTS. Two cohorts of patients, treated at 100 mg (one dose level below RD) and 125 mg (RD) were analyzed, for a total of n=9 evaluable patients on PB and n=7 on BM. At screening we observed a heterogeneous positivity for pS6 marker in blast cells (range: 1%-53 %) both in PB and in BM, consistent with the unselected AML patient population recruited in the trial. Overall, 7/9 PB and 4/7 BM samples showed pS6 inhibition in blast cells at the end of the Cycle 1 in comparison with screening (range: 70%-94% and 26%-76% in PB and BM, respectively) (Figure 1). In the cohort treated at 100 mg such strong pathway inhibition did not correlate with blast count reduction. Interestingly, in samples from a patient treated at 125 mg who harbored the highest burden of pS6+ blast cells (>25%), a correlation between pathway inhibition and blast count reduction was observed suggesting that a higher burden of blasts with activated pS6 might be more sensitive to the inhibition of the pathway (Figure 1). CONCLUSIONS. The longitudinal PD assessment through the modulation of pS6 activation by flow cytometry confirmed that meaningful target engagement was achieved, both in PB and BM, in patients treated with SEL24/MEN1703 at 100 and 125 mg. Preliminary data suggest that the FLT3/PIM pathway inhibition might be associated with blast count reduction, particularly in case of high baseline activation of pS6. Longitudinal monitoring of PD will be continued in the CE part of DIAMOND trial. REFERENCES. 1. Solomon et al, EHA 2020 Disclosures Tomirotti: Menarini Ricerche: Current Employment. Bellarosa:Menarini Ricerche: Current Employment. Walter:Genentech: Consultancy; Selvita: Research Funding; StemLine: Research Funding; Daiichi: Consultancy; Celgene: Consultancy, Research Funding; Boston Biomedical: Consultancy; BiVictriX: Consultancy; BioLineRx: Consultancy, Research Funding; Astellas: Consultancy; Arog: Research Funding; Argenx: Consultancy; Aptevo: Consultancy, Research Funding; Amphivena: Current equity holder in publicly-traded company; Amgen: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Seattle Genetics: Research Funding; Race Oncology: Consultancy; Pfizer: Consultancy, Research Funding; New Link Genetics: Consultancy; Macrogenics: Research Funding; Kite: Consultancy; Jazz: Consultancy, Research Funding; ImmunoGen: Research Funding. Ravandi:Abbvie: Consultancy, Honoraria, Research Funding; Orsenix: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria. Brzózka:Ryvu Therapeutics: Current Employment. Baldini:Menarini Ricerche: Current Employment. Salerno:Menarini Richerce: Current Employment. Binaschi:Menarini Ricerche: Current Employment. Laurent:Menarini Ricerche: Current Employment. Pellacani:Menarini Ricerche: Current Employment.

P-257 Deep polychromatic flow cytometry characterization of circulating endothelial cells in metastatic colorectal cancer patients

Circulating endothelial cells (CEC) and their progenitors (EPC) are restricted subpopulations of peripheral blood (PB), cord blood (CB), and bone marrow (BM) cells, involved in the endothelial remodeling and turnover. Both CEC and EPC have been studied as potential biomarkers in colon cancer, but a lack of specificity has limited their clinical application. In this work, a highly sensitive polychromatic flow cytometry method has been applied for CEC characterization, exploring the role of different circulating endothelial cell subpopulations as potential and predictive biomarkers in colorectal cancer patients.

Visualizing HIF-1alpha mRNA in a Sub-Population of Bone Marrow Derived Cells to Predict Retinal Neovascularization

Bone marrow derived progenitor cells and macrophages are known to migrate into the retina in response to inflammation and neovascularization. These migratory cells might play important regulatory roles in the pathogenesis of neovascularization, a common complication observed in diabetic retinopathy (DR), retinopathy of prematurity (ROP) and retinal vein occlusion (RVO). Hypoxia-inducible factor 1 alpha (HIF-1α) has been shown to contribute to the pathogenesis of retinal inflammation and neovascularization. However, contributions of bone marrow derived ‘activated’ cells to neovascularization are largely unknown. We hypothesized that selective visualization of migratory activated cells could be a powerful method to predict the onset of neovascularization and its progression at molecular level. I n this report we described the synthesis of a new hybrid nanoparticle to visualize HIF-1α mRNA selectively in activated macrophages in a mouse model of neovascularization. HIF-1a expression was confirmed in MRC-1 positive macrophages as well as in CD4 positive T-cells and CD19 positive B-cells using single cell RNA sequencing (scRNAseq) data analysis. The imaging probes (AS- or NS-shRNA-lipid) were synthesized by conjugating diacyl-lipids to short hairpin RNA with an anti-sense sequence complimentary to HIF-1α mRNA, and a fluorophore that is quenched by a black-hole quencher (BHQ). We believe that imaging mRNA selectively in activated macrophages could be a powerful method to predict the onset of neovascularization, its progression and response to therapy. Funding Statement: This work was supported by National Institutes of Health grants R01EY029693 (to MIU) and R01EY023397 (to MIU and JSP), a Grant from the Knights Templar Eye Foundation, Inc. (to MIU), NIDDK MICROMouse funding program DK076169 and DK115255 (to MIU), a Grant from BrightFocus Foundation (to MIU) and a Grant from the Carl Marshall Reeves & Mildred Almen Reeves Foundation, Inc. (to JSP), Vanderbilt Diabetes Research and Training Center Core grant (P30 DK020593-34-39), Vanderbilt Vision Research Center NEI Core Grant (P30-EY008126) and an Unrestricted Grant from Research to Prevent Blindness, Inc. Declaration of Interests: None. Ethics Approval Statement: All animal procedures used in this study were approved by the Vanderbilt University Institutional Animal Care and Use Committee and were performed in accordance with the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research.