Experimental hematology最新文献

{"title":"2030 – STEPWISE INFLAMMATORY REMODELING OF THE HUMAN BONE MARROW NICHE IN CHIP AND MDS","authors":"Borhane Guezguez, Karin Prummel, Kevin Woods, Maksim Kholmatov, Eric Schmitt, Jennifer Trowbridge, Clémence Carron, Thierry Jaffredo, Marc Schmitz, Uwe Platzbecker, Judith Zaugg","doi":"10.1016/j.exphem.2026.105558","DOIUrl":"10.1016/j.exphem.2026.105558","url":null,"abstract":"<div><div>Clonal hematopoiesis of indeterminate potential (CHIP) is a premalignant state that increases the risk of myelodysplastic syndromes (MDSs), yet whether mutant hematopoietic stem and progenitor cells (HSPCs) reprogram the bone marrow (BM) niche before overt disease remains unresolved.</div><div>We analyzed matched BM aspirates and biopsies from 84 individuals in the BoHemE study (NCT02867085), including healthy donors, CHIP carriers, and individuals with MDSs. By integrating single-cell transcriptomics, spatial imaging, mutational profiling, and proteomics, we delineated progressive rewiring of the BM HSPC niche across myeloid evolution and validated key findings in primary BM cocultures and a DNMT3A-driven CHIP mouse model.</div><div>We identify stepwise inflammatory remodeling of the BM niche as an early feature of CHIP that intensifies in MDS. This transition is marked by loss of supportive CXCL12-abundant adipogenic stromal cells and emergence of inflammatory mesenchymal stromal cells (iMSCs), already detectable in CHIP and expanded in MDS. Although iMSCs retain partial HSPC-supporting activity, they acquire inflammatory and pro-angiogenic programs, consistent with vascular remodeling in MDS. In parallel, we define IFN-responsive cytotoxic T cell states enriched across CHIP and MDS that preferentially interact with iMSCs, supporting a feed-forward immune–stromal circuit that amplifies niche inflammation. Functionally, aged and CHIP HSPCs preserve the capacity to activate stromal MSC support, whereas MDS HSPCs fail to do so, and MDS blasts further suppress HSPC support.</div><div>Together, these findings show that disruption of the BM HSPC niche begins at the CHIP stage and advances through coordinated stromal and immune rewiring. They position iMSCs and IFN-responsive T cells as mediators of niche dysfunction and candidate biomarkers and therapeutic entry points for intercepting premalignant myeloid evolution.</div></div><div>Clonal hematopoiesis of indeterminate potential (CHIP) is a premalignant state that increases the risk of myelodysplastic syndromes (MDSs), yet whether mutant hematopoietic stem and progenitor cells (HSPCs) reprogram the bone marrow (BM) niche before overt disease remains unresolved.</div><div>We analyzed matched BM aspirates and biopsies from 84 individuals in the BoHemE study (NCT02867085), including healthy donors, CHIP carriers, and individuals with MDSs. By integrating single-cell transcriptomics, spatial imaging, mutational profiling, and proteomics, we delineated progressive rewiring of the BM HSPC niche across myeloid evolution and validated key findings in primary BM cocultures and a DNMT3A-driven CHIP mouse model.</div><div>We identify stepwise inflammatory remodeling of the BM niche as an early feature of CHIP that intensifies in MDS. This transition is marked by loss of supportive CXCL12-abundant adipogenic stromal cells and emergence of inflammatory mesenchymal stromal cells (iMSCs), already detecta","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105558"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149233289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"2042 – THE LANDSCAPE OF SOMATIC RETROTRANSPOSON MUTATIONS IN HSCS, AND A NOVEL JAK2 SIGNALING PATHWAY TO HNRNPA1 THAT PROTECTS THE HSC GENOME FROM RETROTRANSPOSONS","authors":"Stephen Loughran, Jeremy Deuel, Andrejs Makarovs, Sheidasadat Goosheh, George Winder, Yiran Cao, Sophie Webster, Hisham Mohammed, Jason Carroll, Michael Spencer Chapman, Chiraag Kapadia, Peter Campbell, Elisa Laurenti, Constanze Schneider, Thomas Oellerich, Jyoti Nangalia, Anthony Green","doi":"10.1016/j.exphem.2026.105570","DOIUrl":"10.1016/j.exphem.2026.105570","url":null,"abstract":"<div><div>Retrotransposon (RT) expression requires tight control, particularly in long-lived multipotent stem cells, to prevent deleterious consequences including insertional mutations. Several mechanisms repress RT transcription during development and are thought to persist thereafter. However, many RT-derived sequences have acquired advantageous host functions. Little is known about RT expression and mobility in adult stem cells or about how these processes might be dynamically regulated.</div><div>We developed PEAR-TREE, a new tool to detect somatic RT mutations in whole genome sequences from single- hematopoietic stem cell (HSC)-derived colonies. Using PEAR-TREE, we describe the landscape of somatic retrotransposition mutations in HSCs. We provide the first evidence that RTs are active in HSCs, observing 460 somatic mutations derived from retrotransposons within the human HSC population across a lifetime (95% confidence interval 126–1,456). The mouse HSC population acquires 4610 mutations over their shorter lifetime.</div><div>We also explored whether RTs are dynamically regulated during HSC cell division, and detected a diverse range of long interspersed nuclear elements (LINEs), short interspersed nuclear elements (SINEs), and endogenous retrovirus (ERV) mRNAs downregulated by thrombopoietin (THPO) treatment in human and mouse HSCs. We determined that the RNA-binding protein HNRNPA1 is phosphorylated by JAK2 downstream of THPO treatment, and analysis of HSCs from phosphomutant mice indicated that HNRNPA1 phosphorylation accounted for at least one-third of THPO/JAK2-mediated RT mRNA repression. HNRNPA1 phosphorylation also reduced mutations caused by a LINE-1 reporter, and by IAP ERVs.</div><div>This novel THPO/JAK2/HNRNPA1 pathway provides a mechanism that integrates RT repression with cytokine-induced proliferation, protecting the HSC genome although it is most vulnerable to RT-mediated mutations.</div></div><div>Retrotransposon (RT) expression requires tight control, particularly in long-lived multipotent stem cells, to prevent deleterious consequences including insertional mutations. Several mechanisms repress RT transcription during development and are thought to persist thereafter. However, many RT-derived sequences have acquired advantageous host functions. Little is known about RT expression and mobility in adult stem cells or about how these processes might be dynamically regulated.</div><div>We developed PEAR-TREE, a new tool to detect somatic RT mutations in whole genome sequences from single- hematopoietic stem cell (HSC)-derived colonies. Using PEAR-TREE, we describe the landscape of somatic retrotransposition mutations in HSCs. We provide the first evidence that RTs are active in HSCs, observing 460 somatic mutations derived from retrotransposons within the human HSC population across a lifetime (95% confidence interval 126–1,456). The mouse HSC population acquires 4610 mutations over their shorter lifetime.</div><div>We also e","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105570"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149233293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"1015 – NRAS CODON MUTATIONS CONFER DISTINCT DISEASE CHARACTERISTICS IN AML AND EXHIBIT DIFFERENTIAL RESPONSE TO PAN-RAS INHIBITORS.","authors":"Linde Miles, Annabelle Anandappa, Vidushi Trivedi, Megan Bones, Meredith Arterburn, Jahnavi Raval, Rachel Hefner, Ashley Wooten, Robert Bowman, Ross Levine, Daniel Starczynowski","doi":"10.1016/j.exphem.2026.105511","DOIUrl":"10.1016/j.exphem.2026.105511","url":null,"abstract":"<div><div>RAS pathway mutations are present in 10%–20% of acute myeloid leukemia (AML) cases at diagnosis, with <em>NRAS</em> G12/G13 codon mutations predominating, followed by Q61 codon mutations. There is growing interest in understanding and targeting <em>RAS</em> AML mutations, as they are associated with relapse after multiple targeted therapies. We aimed to interrogate <em>NRAS</em> codon-specific differences in synergy with <em>NPM1c</em>, disease development/phenotype, and therapeutic response to promising pan-RAS inhibitors (RASi). We first characterized previously generated Cre-recombinant single- and double-mutant mouse models harboring <em>Npm1c, NrasG12D, NrasG13D</em>, and <em>NrasQ61R</em> mutant alleles. We observed that double-mutant <em>Npm1c/NrasQ61R</em> (<em>NRQ61</em>) exhibited higher white blood cell (WBC) counts and spleen weights compared with <em>Npm1c/NrasG12D</em> (<em>NRG12</em>), with more severe anemia at 12 weeks. Flow cytometric analysis also revealed significant differences between the models. Competitive transplants of wild-type (WT), <em>Npm1c</em>, and <em>NR</em> cells revealed that all <em>NR</em> cells outcompeted WT and <em>Npm1c</em> cells, with <em>NRQ61</em> cells showing the highest clonal fitness. All double-mutant cohorts showed decreased overall survival, suggesting that co-occurring <em>Npm1c</em> and <em>Nras</em> mutations synergize to drive rapid disease development, albeit with different latencies. However, analysis of <em>NR</em> moribund mice revealed significant codon-specific differences in disease phenotype and ability to reconstitute leukemia. Gene expression analysis also revealed codon-specific transcriptional regulation, underscoring the divergent synergies between <em>Npm1c</em> and different <em>Nras</em> codons. Ex vivo testing of <em>NRG12</em> and <em>NRQ61</em> leukemic cells with RASi showed dose-dependent decreases in colonies and multiple HSPC populations, with a more drastic effect on <em>NRG12</em> cells. Finally, in vivo testing found that RASi was able to improve survival in <em>NRG12</em> mice, with more limited effects observed in <em>NRQ61</em> mice. Overall, our findings suggest that there are codon-specific differences in disease latency, overall survival, and RASi therapeutic response in models of AML with distinct <em>Nras</em> codon mutations.</div></div><div>RAS pathway mutations are present in 10%–20% of acute myeloid leukemia (AML) cases at diagnosis, with <em>NRAS</em> G12/G13 codon mutations predominating, followed by Q61 codon mutations. There is growing interest in understanding and targeting <em>RAS</em> AML mutations, as they are associated with relapse after multiple targeted therapies. We aimed to interrogate <em>NRAS</em> codon-specific differences in synergy with <em>NPM1c</em>, disease development/phenotype, and therapeutic response to promising pan-RAS inhibitors (RASi). We first characterized previously generated Cre-recombinant single- and double-","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105511"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149233283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"1001 – HOW T LYMPHOID CELL IDENTITY EMERGES FROM HEMATOPOIETIC MOLECULAR MECHANISMS","authors":"Ellen Rothenberg","doi":"10.1016/j.exphem.2026.105497","DOIUrl":"10.1016/j.exphem.2026.105497","url":null,"abstract":"<div><div>T lymphocytes are not just antigen-recognizing immunologic units. They are notable products of hematopoietic differentiation that combine aspects of highly active effectors with sustained stemness. They have high gene regulatory responsiveness, yet retain exceptionally long-term capacities to proliferate and self-renew, although sustaining a unique core of gene expression that defines their identity as T cells. The ways they manage their exponential amplification potential are instructive as examples to restrain leukemogenesis. They acquire all these properties outside of the bone marrow, during passage through the thymus. The thymus enables this process by delivering strong Notch pathway signals to multipotent hematopoietic precursors until they relinquish alternative potentials and undergo commitment to the T-cell lineage.</div><div>This talk focused on the way the T-cell program emerges from a lymphomyeloid precursor epigenetic and transcriptional regulatory state. The separation of the precursors from the bone marrow and the availability of powerful in vitro culture systems to mimic the thymus have enabled a deep molecular analysis of the underlying mechanisms. Although Notch signaling acts as a catalyst, it is the cell-intrinsic regulatory features that give this widely used signal its specific T-cell program impacts. One key feature is the ensemble of factors that guide T-cell development, which lack a distinctive “master regulator.” All are identical or closely related to transcription factors used in other hematopoietic fates but are pivoted through collaboration to special roles in the T-cell program. A second key feature is the prolonged use of a multipotent progenitor gene regulatory network circuit to set the foundation for activation of the T-cell program. This involves the same regulatory genes that can act as oncogenes if not completely and accurately silenced. Their activity means that T-cell development begins with a competition between two partially opposing gene network circuits within individual cell nuclei that is resolved only when the cells undergo commitment.</div></div><div>T lymphocytes are not just antigen-recognizing immunologic units. They are notable products of hematopoietic differentiation that combine aspects of highly active effectors with sustained stemness. They have high gene regulatory responsiveness, yet retain exceptionally long-term capacities to proliferate and self-renew, although sustaining a unique core of gene expression that defines their identity as T cells. The ways they manage their exponential amplification potential are instructive as examples to restrain leukemogenesis. They acquire all these properties outside of the bone marrow, during passage through the thymus. The thymus enables this process by delivering strong Notch pathway signals to multipotent hematopoietic precursors until they relinquish alternative potentials and undergo commitment to the T-cell lineage.</div><div>This ta","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105497"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149233756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"2008 – SUB-DMR METHYLATION STATES RESOLVE EARLY HEMATOPOIETIC COMMITMENT DECISIONS","authors":"Daniel Lipka, Stephen Krämer, Sina Staeble, Maximilian Schönung, Mark Hartmann, Julia Knoch, Ruzhica Bogeska, Mariam Hakobyan, Natasha Anstee, Jens Langstein, Oliver Muecke, Dieter Weichenhan, Marion Bähr, Monika Helf, Melinda Czeh, Julius Graesel, Charles Imbusch, Benedikt Brors, Simon Haas, Jan-Phlipp Mallm, Michael Milsom","doi":"10.1016/j.exphem.2026.105536","DOIUrl":"10.1016/j.exphem.2026.105536","url":null,"abstract":"<div><div>DNA methylation enforces hematopoietic differentiation, yet high-resolution mapping of dynamic methylation changes during lineage commitment is lacking. Conventional analyses focused on the detection of differentially methylated regions (DMRs) which obscures relevant regulatory dynamics at the level of individual CpGs. We resolved DNA methylation programming at single-CpG resolution using whole genome bisulfite sequencing of 25 hematopoietic cell types, including stem and progenitor cells. This was integrated with single-cell methylome and transcriptome profiling of >550 cells. DMRs were deconvoluted into differentially methylated CpGs (dmCpGs) and clustered based on shared dynamics. We identified >122,000 DMRs forming 28 lineage-specific clusters. dmCpG-level analysis revealed that methylation changes within DMRs follow a highly ordered, stage-specific sequence, consistent with a pseudo-temporal progression correlating with focal demethylation of dmCpGs along differentiation trajectories. This hierarchical organization indicates that DMRs function as modular regulatory units with internal pseudo-temporal structure. Our framework enabled robust classification of single-cell epigenetic states within the hematopoietic stem and progenitor cell (HSPC) compartment, revealing that many of the classical MPP populations are not coherent cell types but rather mixtures of divergent cell states. We observed that early DMR seeding events persisted across mature lineages, revealing an epigenetic memory of lineage trajectory and allowing the identification of early lineage bifurcation points within the HSPC compartment. In summary, we provide a CpG-resolved map of DNA methylation in murine hematopoiesis that redefines DMRs as modular pseudo-temporally structured regulatory elements. This framework reveals a hierarchical epigenetic logic underlying lineage commitment, enabling refined resolution of cellular states.</div></div><div>DNA methylation enforces hematopoietic differentiation, yet high-resolution mapping of dynamic methylation changes during lineage commitment is lacking. Conventional analyses focused on the detection of differentially methylated regions (DMRs) which obscures relevant regulatory dynamics at the level of individual CpGs. We resolved DNA methylation programming at single-CpG resolution using whole genome bisulfite sequencing of 25 hematopoietic cell types, including stem and progenitor cells. This was integrated with single-cell methylome and transcriptome profiling of >550 cells. DMRs were deconvoluted into differentially methylated CpGs (dmCpGs) and clustered based on shared dynamics. We identified >122,000 DMRs forming 28 lineage-specific clusters. dmCpG-level analysis revealed that methylation changes within DMRs follow a highly ordered, stage-specific sequence, consistent with a pseudo-temporal progression correlating with focal demethylation of dmCpGs along differentiation trajectories. This hierarchical organ","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105536"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149233828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3260 – DEVELOPMENTAL CONTINUITY OF HOXB5+ LONG-TERM HEMATOPOIETIC STEM CELLS REVEALS EARLY LINEAGE BIAS","authors":"Allison Banuelos, Michelle Baez, Leyla Yilmaz, Elle Koren-Sedova, Irving Weissman","doi":"10.1016/j.exphem.2026.105582","DOIUrl":"10.1016/j.exphem.2026.105582","url":null,"abstract":"<div><div>The developmental origins of adult long-term hematopoietic stem cells (HSCs) and the timing at which functional heterogeneity is established remain incompletely understood. Homeobox B5 (Hoxb5) marks definitive long-term HSCs in adult bone marrow, but whether Hoxb5 identifies their developmental precursors has been unknown. Here, we investigated HSC ontogeny from embryonic fetal liver to adult bone marrow using Hoxb5 reporter mice. We found that Hoxb5 expression identifies a subset of fetal liver HSCs with long-term multilineage and serial reconstitution potential, demonstrating that Hoxb5 marks definitive long-term HSCs during development. Genetic lineage tracing further revealed that Hoxb5+ fetal liver HSCs give rise to adult bone marrow HSCs, establishing developmental continuity from fetal life to adulthood. Single-cell transcriptomic analyses demonstrated preservation of core HSC programs across ontogeny, accompanied by a transition from highly proliferative fetal HSCs to predominantly quiescent adult HSCs. Despite this continuity, Hoxb5+ HSCs were heterogeneous. We identified a distinct subset of fetal liver Hoxb5+ HSCs expressing Neogenin-1, a marker of myeloid-biased HSCs. Functional transplantation studies demonstrated that Neogenin-1+ Hoxb5+ HSCs preferentially generated myeloid cells relative to Neogenin-1− Hoxb5+ HSCs, and the frequency of Neogenin-1+ cells progressively increased with age. Together, these findings established Hoxb5 as a marker of definitive long-term HSCs throughout ontogeny and demonstrated that functionally distinct HSC states are established during development and persist into adulthood.</div></div><div>The developmental origins of adult long-term hematopoietic stem cells (HSCs) and the timing at which functional heterogeneity is established remain incompletely understood. Homeobox B5 (Hoxb5) marks definitive long-term HSCs in adult bone marrow, but whether Hoxb5 identifies their developmental precursors has been unknown. Here, we investigated HSC ontogeny from embryonic fetal liver to adult bone marrow using Hoxb5 reporter mice. We found that Hoxb5 expression identifies a subset of fetal liver HSCs with long-term multilineage and serial reconstitution potential, demonstrating that Hoxb5 marks definitive long-term HSCs during development. Genetic lineage tracing further revealed that Hoxb5+ fetal liver HSCs give rise to adult bone marrow HSCs, establishing developmental continuity from fetal life to adulthood. Single-cell transcriptomic analyses demonstrated preservation of core HSC programs across ontogeny, accompanied by a transition from highly proliferative fetal HSCs to predominantly quiescent adult HSCs. Despite this continuity, Hoxb5+ HSCs were heterogeneous. We identified a distinct subset of fetal liver Hoxb5+ HSCs expressing Neogenin-1, a marker of myeloid-biased HSCs. Functional transplantation studies demonstrated that Neogenin-1+ Hoxb5+ HSCs preferentially generated myeloid cells relative to ","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105582"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149233978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3267 – SYSTEMATIC IDENTIFICATION OF SURFACE MARKER TARGETS OF MUTANT HEMATOPOIETIC STEM CELLS IN CLONAL HEMATOPOIESIS","authors":"Camille Chu, Thomas Köhnke, Asiri Ediriwickrema, Ravindra Majeti","doi":"10.1016/j.exphem.2026.105589","DOIUrl":"10.1016/j.exphem.2026.105589","url":null,"abstract":"<div><div>Clonal hematopoiesis (CH) is characterized by the expansion of hematopoietic stem cells (HSCs) carrying somatic mutations in genes such as <em>DNMT3A</em> and <em>TET2</em>. Although CH confers increased risk for hematologic malignancies, including acute myeloid leukemia (AML), it typically occurs years before malignant transformation. Therefore, there is a critical need to detect and characterize CH before disease development for prevention and interception. A limitation is that conventional cell surface markers cannot reliably distinguish wild-type HSCs from mutant HSCs in CH (CH-HSCs). Given the poor prognosis of AML, identifying membrane markers that characterize CH-HSCs would enable preventative therapeutic approaches targeting these cells before malignant transformation.</div><div>To address this gap, we performed a systematic, cell type-specific computational analysis to identify surface markers enriched in CH-HSCs. This analysis integrated multiple independent single-cell RNA sequencing data sets (<em>n</em> = 3) of human HSCs with <em>DNMT3A</em> or <em>TET2</em> mutations. Following rigorous quality control, normalization, and batch correction, we applied a machine learning classifier to define cell populations. Differential gene expression analysis was subsequently performed to compare CH-HSCs to healthy HSCs, with filtering restricted to genes encoding surface proteins scored using the surface protein annotation tool (SPAT) for membrane localization. Through this approach, we identified four high-confidence, statistically significant candidates: CD1A, Fms-related receptor tyrosine kinase 4/vascular endothelial growth factor receptor 3 (FLT4/VEGFR3), cluster of differentiation 267/transmembrane activator and CAML interactor (CD267/TACI), and CD5, which we are currently prospectively validating using flow cytometry. All markers demonstrated consistent enrichment across independent datasets and mutation types. These candidates provide a foundation for therapeutic strategies targeting pre-malignant clones during a therapeutic window before malignant transformation to AML.</div></div><div>Clonal hematopoiesis (CH) is characterized by the expansion of hematopoietic stem cells (HSCs) carrying somatic mutations in genes such as <em>DNMT3A</em> and <em>TET2</em>. Although CH confers increased risk for hematologic malignancies, including acute myeloid leukemia (AML), it typically occurs years before malignant transformation. Therefore, there is a critical need to detect and characterize CH before disease development for prevention and interception. A limitation is that conventional cell surface markers cannot reliably distinguish wild-type HSCs from mutant HSCs in CH (CH-HSCs). Given the poor prognosis of AML, identifying membrane markers that characterize CH-HSCs would enable preventative therapeutic approaches targeting these cells before malignant transformation.</div><div>To address this gap, we performed a systematic, cell type-s","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105589"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149234043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"2003 – MHC II-MEDIATED CD4 T CELL ENGAGEMENT OVERCOMES THE DIFFERENTIATION BLOCK IN ACUTE MYELOID LEUKEMIA","authors":"Inés Simó Vesperinas, Vincent Fregona, Jan Bařinka, Svenja Dannenberg, Andreas Sachse, Maximilian Sprechert, Julian Liebaert, Michael Korenkov, Jan Krönke, Ulrich Keller, Simon Haas","doi":"10.1016/j.exphem.2026.105531","DOIUrl":"10.1016/j.exphem.2026.105531","url":null,"abstract":"<div><div>Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by a block in differentiation and the accumulation of immature leukemic blasts. Current therapies mainly rely on eliminating these cells, rather than restoring normal differentiation. In acute promyelocytic leukemia (APL), differentiation therapy has markedly improved outcomes by directly overcoming the differentiation block. However, these approaches remain limited to a small subset of patients, underscoring the need for novel strategies that restore differentiation across AML subtypes. Building on our findings that MHC class II-mediated antigen presentation by hematopoietic stem and progenitor cells can engage CD4⁺ T cells to induce stem cell differentiation (Hernández-Malmierca et al (2022), <em>Cell Stem Cell</em>), we investigated whether this mechanism can be leveraged to overcome the differentiation block in AML. Using a diverse panel of AML cell lines, we show that enforced interaction between CD4⁺ T cells and leukemic blasts via a crosslinking strategy induces differentiation in multiple AML subtypes. Notably, CD4⁺ T cell engagement elicits context-dependent and heterogeneous T cell states, which are linked to differences in leukemic cell differentiation and survival, suggesting that the qualitative nature of the CD4⁺ T cell response shapes therapeutic outcome. Mechanistically, our data support a multilayered mode of action in which CD4⁺ T cells exert antileukemic effects through direct cell–cell interactions and soluble factors. Finally, we validate MHC II-mediated crosslinking-induced differentiation in primary patient samples, showing that this mechanism is preserved in a physiologically relevant setting and highlighting its translational potential. These findings establish MHC II-mediated CD4⁺ T cell engagement as a promising strategy to overcome the differentiation block in AML.</div></div><div>Acute myeloid leukemia (AML) is an aggressive hematologic malignancy characterized by a block in differentiation and the accumulation of immature leukemic blasts. Current therapies mainly rely on eliminating these cells, rather than restoring normal differentiation. In acute promyelocytic leukemia (APL), differentiation therapy has markedly improved outcomes by directly overcoming the differentiation block. However, these approaches remain limited to a small subset of patients, underscoring the need for novel strategies that restore differentiation across AML subtypes. Building on our findings that MHC class II-mediated antigen presentation by hematopoietic stem and progenitor cells can engage CD4⁺ T cells to induce stem cell differentiation (Hernández-Malmierca et al (2022), <em>Cell Stem Cell</em>), we investigated whether this mechanism can be leveraged to overcome the differentiation block in AML. Using a diverse panel of AML cell lines, we show that enforced interaction between CD4⁺ T cells and leukemic blasts via a crosslinking strategy induces ","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105531"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149234048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"2001 – REVERSAL OF HUMAN BONE MARROW FIBROSIS THROUGH STROMAL-IMMUNE REWIRING AND PDE5A INHIBITION","authors":"Adam Benabid, Martin Grasshoff, Juliette Pearce, Vanessa Klöker, Niclas Flosdorf, Lukas Rösch, Katharina Reimer, Katrin Götz, Pia Wanner, Niklas Lutterbach, Carmen Schalla, Paul Wanek, Lina Schmidt, Mayra Ruiz Tejada Segura, Mohamed Saad, Mehdi Joodaki, James Nagai, Liliane Palm, Susanne Schmitz, Stijn Fuchs, Rebekka Schneider","doi":"10.1016/j.exphem.2026.105529","DOIUrl":"10.1016/j.exphem.2026.105529","url":null,"abstract":"<div><div>Progression of myeloproliferative neoplasms (MPNs) to myelofibrosis (MF) is associated with bone marrow failure and high mortality. Most of the current therapies, such as JAK inhibitors, are not disease modifying, leaving a majority of patients without a curative option. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative therapy available for a subset of MF patients. Remarkably, bone marrow fibrosis resolves in approximately 90% of patients within 1 year post-allo-HSCT, offering a unique clinical paradigm. We generated a single-cell map of immune and stromal populations from 30 control and patient-derived MF bone marrow biopsies before and after allo-HSCT. Adipogenic CXCL12-abundant reticular (Adipo-CAR) cells emerged as the fibrosis-driving stromal subset. Interferon response programs dominated the fibrotic niche, and SPP1<sup>+</sup> macrophages formed a central cellular communication hub. Integrating single-cell and spatial proteomics revealed TGF-β–driven crosstalk between megakaryocytes and Adipo-CARs that rewired after allo-HSCT, preceding histological regression of fibrosis, representing a therapeutic window of opportunity. Single-cell genotyping mapped mutant hematopoietic clones, identified CD93 as a clinically relevant mediator of niche interactions and residual mutant macrophages persisted post-allo-HSCT in a transcriptionally altered state. PDE5A expression in Adipo-CARs tracked fibrosis progression and reversal. Its genetic and pharmacologic targeting reduced fibrosis in vitro and in vivo. Mechanistically, PDE5A inhibition resulted in reduced SMAD phosphorylation. These findings establish a cellular and molecular framework for myelofibrosis reversal in humans, reveal how the bone marrow niche normalizes from fibrosis ahead of histological recovery, and open avenues for disease modifying therapies beyond transplantation.</div></div><div>Progression of myeloproliferative neoplasms (MPNs) to myelofibrosis (MF) is associated with bone marrow failure and high mortality. Most of the current therapies, such as JAK inhibitors, are not disease modifying, leaving a majority of patients without a curative option. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative therapy available for a subset of MF patients. Remarkably, bone marrow fibrosis resolves in approximately 90% of patients within 1 year post-allo-HSCT, offering a unique clinical paradigm. We generated a single-cell map of immune and stromal populations from 30 control and patient-derived MF bone marrow biopsies before and after allo-HSCT. Adipogenic CXCL12-abundant reticular (Adipo-CAR) cells emerged as the fibrosis-driving stromal subset. Interferon response programs dominated the fibrotic niche, and SPP1<sup>+</sup> macrophages formed a central cellular communication hub. Integrating single-cell and spatial proteomics revealed TGF-β–driven crosstalk between megakaryocytes and Adipo-CARs that rewired after al","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105529"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149234070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"2041 – DECODING HUMAN HEMATOPOIESIS ACROSS SCALES USING A HEMATOPOIESIS-IN-A-DISH SYSTEM","authors":"Licyel Lenny Paulas Condori, Juan Rubio-Lara, Olivia Hidajat, Laura Magnani, Emily Calderbank-May, Josephine Gollin, Elisa Laurenti, Nicola Wilson, Bertie Göttgens","doi":"10.1016/j.exphem.2026.105569","DOIUrl":"10.1016/j.exphem.2026.105569","url":null,"abstract":"<div><div>Human hematopoietic stem and progenitor cells (HSPCs) exhibit molecular and functional heterogeneity at the clonal level, yet the mechanisms governing this diversity remain unclear. Studying human HSPC heterogeneity has been limited by the lack of in vitro models that simultaneously support hematopoietic stem cell (HSC) expansion and multilineage differentiation, making it difficult to track downstream lineage decisions within the same system. To address this, over 170 culture conditions were screened to develop a human “hematopoiesis-in-a-dish” (HID) system supporting both HSC self-renewal and multilineage output. Spectral flow cytometry and single-cell RNA sequencing confirmed that the HID system enables dynamic and temporally regulated phenotypic HSC expansion over a 21-day period, alongside consistent expression of multiple differentiation markers. CITE-seq analysis revealed that HID produces 32 distinct populations, spanning HSCs to diverse myeloid and early lymphoid lineages. Furthermore, the HID system supports reproducible HSPC expansion and HSCs capable of long-term engraftment. The cultures can be sampled over time, making the system compatible with lentiviral-based lineage tracing approaches that enable clonal tracking of HSPCs. In addition, to accelerate the identification of conditions that govern lineage choice, we leverage a generative modeling approach that learns from our comprehensive screening dataset (spanning over 97 conditions) to predict cellular outcomes for previously untested conditions. Together, these efforts establish a physiologically relevant in vitro model of human hematopoiesis and provide a framework for mechanistic insights into clonal HSPC heterogeneity.</div></div><div>Human hematopoietic stem and progenitor cells (HSPCs) exhibit molecular and functional heterogeneity at the clonal level, yet the mechanisms governing this diversity remain unclear. Studying human HSPC heterogeneity has been limited by the lack of in vitro models that simultaneously support hematopoietic stem cell (HSC) expansion and multilineage differentiation, making it difficult to track downstream lineage decisions within the same system. To address this, over 170 culture conditions were screened to develop a human “hematopoiesis-in-a-dish” (HID) system supporting both HSC self-renewal and multilineage output. Spectral flow cytometry and single-cell RNA sequencing confirmed that the HID system enables dynamic and temporally regulated phenotypic HSC expansion over a 21-day period, alongside consistent expression of multiple differentiation markers. CITE-seq analysis revealed that HID produces 32 distinct populations, spanning HSCs to diverse myeloid and early lymphoid lineages. Furthermore, the HID system supports reproducible HSPC expansion and HSCs capable of long-term engraftment. The cultures can be sampled over time, making the system compatible with lentiviral-based lineage tracing approaches that enable clonal tracking of HS","PeriodicalId":12202,"journal":{"name":"Experimental hematology","volume":"162 ","pages":"Article 105569"},"PeriodicalIF":2.7,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149234121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}