Progenitor Cells Research Articles

Computing hematopoiesis plasticity in response to genetic mutations and environmental stimulations

Cell plasticity (CP), describing a dynamic cell state, plays a crucial role in maintaining homeostasis during organ morphogenesis, regeneration, and trauma-to-repair biological process. Single-cell-omics datasets provide an unprecedented resource to empower CP analysis. Hematopoiesis offers fertile opportunities to develop quantitative methods for understanding CP. In this study, we generated high-quality lineage-negative single-cell RNA-sequencing datasets under various conditions and introduced a working pipeline named scPlasticity to interrogate naïve and disturbed plasticity of hematopoietic stem and progenitor cells with mutational or environmental challenges. Using embedding methods UMAP or FA, a continuum of hematopoietic development is visually observed in wild type where the pipeline confirms a lowproportion of hybrid cells(Phc, with bias range: 0.4∼0.6) on a transition trajectory. UponTet2mutation, a driver of leukemia, or treatment of DSS, an inducer of colitis,Phcis increased and plasticity of hematopoietic stem and progenitor cells was enhanced. We prioritized several transcription factors and signaling pathways, which are responsible forPhcalterations. In silico perturbation suggests knocking out EGR regulons or pathways of IL-1R1 and β-adrenoreceptor partially reversesPhcpromoted byTet2mutation and inflammation.

Pharmacogenomic screening identifies and repurposes leucovorin and dyclonine as pro-oligodendrogenic compounds in brain repair

AbstractOligodendrocytes are critical for CNS myelin formation and are involved in preterm-birth brain injury (PBI) and multiple sclerosis (MS), both of which lack effective treatments. We present a pharmacogenomic approach that identifies compounds with potent pro-oligodendrogenic activity, selected through a scoring strategy (OligoScore) based on their modulation of oligodendrogenic and (re)myelination-related transcriptional programs. Through in vitro neural and oligodendrocyte progenitor cell (OPC) cultures, ex vivo cerebellar explants, and in vivo mouse models of PBI and MS, we identify FDA-approved leucovorin and dyclonine as promising candidates. In a neonatal chronic hypoxia mouse model mimicking PBI, both compounds promote neural progenitor cell proliferation and oligodendroglial fate acquisition, with leucovorin further enhancing differentiation. In an adult MS model of focal de/remyelination, they improve lesion repair by promoting OPC differentiation while preserving the OPC pool. Additionally, they shift microglia from a pro-inflammatory to a pro-regenerative profile and enhance myelin debris clearance. These findings support the repurposing of leucovorin and dyclonine for clinical trials targeting myelin disorders, offering potential therapeutic avenues for PBI and MS.

KAT6B is required for histone 3 lysine 9 acetylation and SOX gene expression in the developing brain

Heterozygous mutations in the histone lysine acetyltransferase geneKAT6B(MYST4/MORF/QKF) underlie neurodevelopmental disorders, but the mechanistic roles of KAT6B remain poorly understood. Here, we show that loss of KAT6B in embryonic neural stem and progenitor cells (NSPCs) impaired cell proliferation, neuronal differentiation, and neurite outgrowth. Mechanistically, loss of KAT6B resulted in reduced acetylation at histone H3 lysine 9 and reduced expression of key nervous system development genes in NSPCs and the developing cortex, including the SOX gene family, in particularSox2, which is a key driver of neural progenitor proliferation, multipotency and brain development. In the fetal cortex, KAT6B occupied theSox2locus. Loss of KAT6B caused a reduction inSox2promoter activity in NSPCs.Sox2overexpression partially rescued the proliferative defect ofKat6b−/−NSPCs. Collectively, these results elucidate molecular requirements for KAT6B in brain development and identify key KAT6B targets in neural precursor cells and the developing brain.

A CADASIL NOTCH3 mutation leads to clonal hematopoiesis and expansion of Dnmt3a-R878H hematopoietic clones

AbstractClonal hematopoiesis (CH) is nearly universal in the elderly. The molecular and cellular mechanisms driving CH and the clinical consequences of carrying clonally derived mutant mature blood cells are poorly understood. We recently identified a C223Y mutation in the extracellular domain (ECD) of NOTCH3 as a putative CH driver in mice. Provocatively, germline NOTCH3 ECD mutations perturbing cysteine numbers cause Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), a type of vascular dementia, suggesting an unexpected link between CADASIL and CH. Here, we formally demonstrated that mouse hematopoietic stem and progenitor cells (HSPCs) expressing CADASIL-related NOTCH3C455R exhibit a proliferative advantage resulting in robust cellular expansion in vivo and in vitro. Co-expression of NOTCH3C455R and Dnmt3aR878H, homologous to a frequent human CH mutation, increased the fitness of NOTCH3C455R HSPCs, demonstrating their functional cooperation. Surprisingly, the presence of NOTCH3C455R hematopoietic cells supported the expansion of Dnmt3aR878H HSPCs in a non-cell autonomous fashion in vivo, strongly suggesting that CADASIL patients and asymptomatic carriers can be highly predisposed to DNMT3AR882H-driven CH. Considering that CADASIL-related NOTCH3 mutations are more frequent in the general population than anticipated (~1 carrier in 400 people), the effect of these NOTCH3 mutations on CH development should be considered.

Analysis of genotype effects and inter-individual variability in iPSC-derived trisomy 21 neural progenitor cells

Abstract Trisomy of human chromosome 21 (T21) gives rise to Down syndrome (DS), the most frequent live-born autosomal aneuploidy. T21 triggers genome-wide transcriptomic alterations that result in multiple atypical phenotypes with highly variable penetrance and expressivity in individuals with DS. Many of these phenotypes, including atypical neurodevelopment, emerge prenatally. To enable in vitro analyses of the cellular and molecular mechanisms leading to the neurological alterations associated with T21, we created and characterized a panel of genomically diverse T21 and euploid induced pluripotent stem cells (iPSCs). We subsequently differentiated these iPSCs to generate a panel of neural progenitor cells (NPCs). Alongside characterizing genotype effects from T21, we found that T21 NPCs showed inter-individual variability in growth rates, oxidative stress, senescence characteristics, and gene and protein expression. Pathway enrichment analyses of T21 NPCs identified vesicular transport, DNA repair, and cellular response to stress pathways. These results demonstrate T21-associated variability at the cellular level and suggest that cell lines from individuals with DS should not solely be analyzed as a homogenous population. Examining large cohorts of genetically diverse samples may more fully reveal the effects of aneuploidy on transcriptomic and phenotypic characteristics in T21 cell types. A panel of genomically diverse T21 and euploid induced pluripotent stem cells (iPSCs) were created and subsequently differentiated into neural progenitor cells (NPCs). T21 NPCs showed reduced growth, increased oxidative stress, and inter-individual variability in gene and protein expression. This inter-individual variability suggests that studies with large cohorts of genetically diverse T21 samples may more fully reveal the effects of aneuploidy.

Stem cell models of TAFAZZIN deficiency reveal novel tissue-specific pathologies in Barth syndrome

Abstract Barth syndrome (BTHS) is a rare mitochondrial disease caused by pathogenic variants in the gene TAFAZZIN, which leads to abnormal cardiolipin (CL) metabolism on the inner mitochondrial membrane. Although TAFAZZIN is ubiquitously expressed, BTHS involves a complex combination of tissue specific phenotypes including cardiomyopathy, neutropenia, skeletal myopathy, and growth delays, with a relatively minimal neurological burden. To understand both the developmental and functional effects of TAZ-deficiency in different tissues, we generated isogenic TAZ knockout (TAZ-KO) and WT cardiomyocytes (CMs) and neural progenitor cells (NPCs) from CRISPR-edited induced pluripotent stem cells (iPSCs). In TAZ-KO CMs we discovered evidence of dysregulated mitophagy including dysmorphic mitochondria and mitochondrial cristae, differential expression of key autophagy-associated genes, and an inability of TAZ-deficient CMs to properly initiate stress-induced mitophagy. In TAZ-deficient NPCs we identified novel phenotypes including a reduction in CIV abundance and CIV activity in the CIII2&CIV2 intermediate complex. Interestingly, while CL acyl chain manipulation was unable to alter mitophagy defects in TAZ-KO CMs, we found that linoleic acid or oleic acid supplementation was able to partially restore CIV abundance in TAZ-deficient NPCs. Taken together, our results have implications for understanding the tissue-specific pathology of BTHS and potential for tissue-specific therapeutic targeting. Moreover, our results highlight an emerging role for mitophagy in the cardiac pathophysiology of BTHS and reveal a potential neuron-specific bioenergetic phenotype.

Abstract B064: Prevalence and clinical relevance of clonal hematopoiesis in metastatic urologic malignancies

Abstract Introduction: Clonal hematopoiesis (CH) is an age-related process whereby hematopoietic progenitor cells with specific mutations gain a proliferative advantage, resulting in populations that can be detected in blood. CH is a major confounder in plasma cell-free DNA (cfDNA) assays that do not profile patient-matched white blood cell (WBC) DNA to distinguish circulating tumor DNA (ctDNA) somatic mutations from those with hematopoietic origin. We aimed to characterize CH in patients with advanced urologic cancers and clarify the potential for CH to interfere with plasma-based tumor genotyping. Methods: We applied error-corrected targeted DNA sequencing (median 2200X) to matched cfDNA and WBC DNA from 301 patients with advanced urothelial cancer (UC) or renal cell carcinoma (RCC) enrolled in a provincial biobank, using a 57 gene panel capturing key CH and urologic cancer genes. CH mutations were defined as those detected in both WBC and cfDNA with a variant allele frequency (VAF) exceeding a 0.25% limit of detection and supported by at least 5 mutant reads. In contrast, ctDNA mutations were required to be exclusively detected in plasma, with a cfDNA VAF ≥5 times the VAF in WBC. Results: 73% (221/301) of patients had ≥1 CH mutation with a VAF above 0.25% (35% of patients had a variant above 2% VAF), and CH- patients were younger than CH+ (RCC: 56 vs 68.5, p<0.01; UC: 63 vs 72, p<0.01). There was no difference in CH prevalence by biological sex. There was no difference in overall survival according to CH status (UC: [CH+] 13 vs [CH-] 16 months, p=0.98; RCC: [CH+] 33 vs [CH-] 49 months, p=0.77), in contrast to the presence of ctDNA mutations which is an established prognostic factor linked with shorter overall survival (UC: [ctDNA+] 10 vs [ctDNA-] 23 months, p<0.01; RCC: [ctDNA+] 15 vs [ctDNA-] 49 months, p<0.01). CH+ patients carried CH mutations most commonly within hematologic malignancy-associated genes (e.g. DNMT3A [58%] and TET2 [26%]), although genes linked to DNA damage response such as TP53 (10%) and ATM (9%) were also mutated. PPM1D was mutated more frequently in UC compared to RCC within CH+ patients (UC: 22%, RCC: 9%, p<0.01), likely attributable to platinum chemotherapy exposure prior to blood collection in 50% of the UC cohort. Importantly, a notable proportion of mutations in UC- or RCC-relevant driver genes originated from CH rather than cancer, including 28% and 65% of mutations falling in TP53 and ATM, respectively. Finally, randomly downsampling sequencing reads from WBC DNA suggested that 500X coverage is sufficient to resolve 90% of CH events with >1% VAF. Conclusion: CH was highly prevalent in patients with advanced urologic malignancies but had no impact on survival in this heterogeneous real-world cohort. CH commonly affected clinically-relevant driver genes that are also altered in solid cancers, potentially causing false-positive genotyping and inflating tumor mutation burden estimates in plasma-only ctDNA assays. Incorporating WBC sequencing to liquid biopsy assays can help correctly identify tumor-originating mutations. Citation Format: Aslı D Munzur, Jack V W Bacon, Francine Fishbein, Gráinne Donnellan, Cecily Q Bernales, Karan Parekh, Gillian Vandekerkhove, David C Müller, Cameron Herberts, Lucia Nappi, Corinne Maurice-Dror, Kim N Chi, Bernhard J Eigl, Christian Kollmannsberger, Maryam Soleimani, Alexander W Wyatt. Prevalence and clinical relevance of clonal hematopoiesis in metastatic urologic malignancies [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B064.

Abstract 4123674: The role of CD34+ PI16+ fibroblast progenitor cells in transplant arteriosclerosis

Background: Transplantation arteriosclerosis is one of the major complications for the mid- and long-term survival of recipients with organ transplantation. Although previous studies suggest that CD34 stem/progenitor cells are involved in this process, the heterogeneity and potential adverse effects of CD34 + SPCs have not been fully determined. Methods and Results: A mouse model of transplant arteriosclerosis was established by using Balb/c, C57BL/6J, CD34-CreERT2, R26-tdTomato, Rosa26-iDTR, CD34-Dre, PI16-CreERT2, CAG-LSL-RSR-tdTomato-2A-DTR mice. Using single-cell RNA-seq and the innovative application of genetic lineage tracing with dual recombinases, we identified a subpopulation of fibroblast progenitor cells marked by high CD34 and PI16 expression. Interestingly, this progenitor cell group gave rise to a distinct chemotactic fibroblast subset. Based on chemokine antibody microarray assay and transcriptome analysis, the subgroup with increased CD34 expression and decreased PI16 expression promoted intimal hyperplasia, acting through the paracrine release of a specific chemokine CCL11 (eotaxin-1). Moreover, the binding of CCL11 to its receptor CCR3 triggered the PI3K-AKT signaling pathway in smooth muscle cells, promoting their proliferation and migration to form neointimal lesions. Overexpression of CCL11 by adeno-associated virus can promote neointimal hyperplasia in vivo, while neutralization of CCL11 or inhibition of receptor CCR3 can alleviate neointimal lesions. Conclusion: Our findings identified CD34 + /PI16 + fibroblast progenitors able to differentiate into specific chemotactic fibroblasts that release chemokines pivotal for neointima formation, implicating a therapeutic potential targeting the chemotactic behavior of these cells.

Abstract 4145876: Prognostic significance of somatic mutations in myeloid cells of men with chronic heart failure – interaction between loss of Y chromosome and clonal hematopoiesis

Introduction: Age-associated clonal hematopoiesis of indeterminate potential (CHIP) has been associated with increased incidence and worse prognosis of chronic heart failure. CHIP is driven by somatic mutations in hematopoietic stem and progenitor cells (HSPC). Mosaic loss of the Y chromosome (LOY), the most common somatic mutation in blood cells of men, also correlates with clonal expansion of myeloid cells, increases with age and was experimentally shown to lead to diffuse cardiac fibrosis and subsequent heart failure in mice. However, the prognostic significance of LOY as well as its potential interaction with CHIP in patients with chronic heart failure is unknown. Aims/Methods: We investigated the prevalence and prognostic significance of the extent of LOY and the two most common CHIP-driver mutations DNMT3A and TET2 in 705 male patients with established chronic heart failure across the entire spectrum of left ventricular ejection fraction. Results: Both, LOY and DNMT3A/TET2 mutations, increased with age, and LOY co-occurred with DNMT3A/TET2 mutations in 27.1% of men at age > 70 years. LOY was an independent predictor of death during 3-years of follow-up across the entire spectrum of left ventricular ejection fraction. The co-occurrence of harboring LOY and DNMT3A/TET2 mutations significantly contributed to the observed increased mortality observed in carriers of DNMT3A/TET2 mutations. The detrimental effect of LOY on prognosis was confirmed in a validation cohort of patients with ischemic heart disease.scRNA sequencing of peripheral blood cells in patients with chronic ischemic heart failure showed increased profibrotic signaling in LOY monocytes with elevated markers of monocyte mediated inflammation and profibrotic cardiac remodeling (S100A8, TLR2, CLEC4D) and reduced expression of TGF-b inhibiting genes (SMAD7, TGIF2). The proinflammatory phenotype of LOY monocytes was further amplified in LOY monocytes of patients simultaneously harboring DNMT3A mutations, who displayed heightened expression of alarmins (S100A8, HMGB2) and interferon signaling related genes (IFNGR1, TRIM56, CD84) compared to patients without CHIP mutations. Conclusion: The age-associated acquisition of somatic mutations in blood cells of men with chronic heart failure is associated with increased mortality, with loss of Y chromosome emerging as an independent predictor of all-cause death across the entire spectrum of left ventricular function.

Abstract 4137414: Uncovering MLKL as a Novel Regulator of Endothelial Cells in the Splenic Niche to Repress Hematopoiesis During Atherosclerosis

Background: Atherosclerosis occurs as lipid and immune cell rich plaques deposit within the arterial wall of the heart. These immune cells are produced from hematopoietic stem and progenitor cells (HSPCs) in the bone marrow (BM) and spleen, a process known as hematopoiesis that is dictated by their microenvironment, including endothelial cells (ECs). Objective: While others have shown adverse remodeling of BM ECs during atherogenesis, whether splenic ECs show a similar dysfunction leading to exacerbated hematopoiesis has not been described. Methods: We analyzed RNA sequencing data from chow fed C57Bl/6 mice and high cholesterol diet (HCD) fed Apoe -/- mouse BM and splenic ECs obtained from published studies, as well as our own. In vivo studies were performed in mice on an atherogenic background ( Apoe -/-& Ldlr -/-) fed a HCD for 4 to 16 weeks. Knockdown of the mixed lineage kinase domain-like protein ( Mlkl KD) was achieved by weekly administration of antisense oligonucleotides (ASOs) or scrambled control (50mg/kg sc.). In vitro studies were performed in primary mouse splenic ECs transfected with siRNA. Results: Pathway analysis revealed remarkable tissue-specific responses to an atherogenic milieu, including dysregulation of Lipid Metabolism, Endocytosis and Cell Death pathways in splenic ECs. Interestingly, we previously showed that the mixed lineage kinase domain-like protein (MLKL) regulates the endocytic trafficking of lipids and cell death in macrophages. Indeed using Mlkl KD Apoe -/- mice, transplantation of Mlkl -/- BM into Ldlr -/- mice or EC-specific Mlkl -/- Apoe -/- mice, we show that loss of MLKL drives myelopoiesis and plaque development through regulation of splenic ECs. Both in vivo and in vitro , silencing Mlkl in splenic but not BM ECs potently increased lipid content and disrupted endocytosis by an accumulation of the multivesicular body marker CHMP4B, which mirror the dysregulated pathways we identified above. Furthermore, co-culture with Mlkl KD splenic ECs increased HSPC activation (pStat5) and myeloid colony formation, an effect that was lost when ECs were pre-treated with the upstream endocytosis inhibitor Dynasore. Conclusions: In conclusion, we establish a novel role for MLKL in regulating the balance of HSPCs, specifically through preservation of splenic, but not BM, ECs that repress hematopoiesis, highlighting the importance of splenic lipid metabolism and endocytosis and its impact on atherogenesis.

Antineoplastic therapy affects the in vitro phenotype and functionality of healthy human bone marrow-derived mesenchymal stromal cells

AbstractWhile antineoplastic therapies aim to specifically target cancer cells, they may also exert adverse effects on healthy tissues, like healthy hematopoietic stem and progenitor cells (HSPC), leading to hematotoxicity as a common side effect. Mesenchymal stromal cells (MSC) are a major component of the bone marrow (BM) microenvironment, regulating normal hematopoiesis, while their susceptibility to anticancer therapies and contribution to therapy-related hematotoxicity remains largely unexplored. To address this, we investigated the effects of etoposide, temozolomide, 5-azacitidine, and venetoclax on healthy BM-derived MSC functionality. Doses below therapeutic effects of etoposide (0.1–0.25 µM) inhibited cellular growth and induced cellular senescence in healthy MSC, accompanied by an increased mRNA expression of CDKN1A, decreased trilineage differentiation capacity, and insufficient hematopoietic support. Pharmacological doses of 5-azacitidine (2.5 µM) shifted MSC differentiation capacity by inhibiting osteogenic capacity but enhancing the chondrogenic lineage, as demonstrated by histochemical staining and on mRNA level. At the highest clinically relevant dose, neither venetoclax (40 nM) nor temozolomide (100 µM) exerted any effects on MSC but clearly inhibited cellular growth of cancer cell lines and primary healthy HSPC, pointing to damage to hematopoietic cells as a major driver of hematotoxicity of these two compounds. Our findings show that besides HSPC, also MSC are sensitive to certain antineoplastic agents, resulting in molecular and functional alterations that may contribute to therapy-related myelosuppression. Understanding these interactions could be helpful for the development of strategies to preserve BM MSC functionality during different kinds of anticancer therapies.

Abstract 4137935: Adipogenesis in Bone Marrow Niche under Cardiac Stress Worsens Cardiac Function

Background: We have recently reported that repetitive cardiac decompensation with multimorbidity often experienced by patients with heart failure (HF) is attributed to epigenetic modifications of hematopoietic stem cells (HSCs) in the bone marrow (BM). HF reprogrammed HSCs differentiation and altered tissue macrophage homeostasis. These findings demonstrate that the BM can carry an innate immune memory of cardiac stress that may exacerbate HF and predispose other organs to pathology. Aims: Because the stemness of HSCs is mainly regulated by mesenchymal stromal cells (MSCs) in the BM niche, we investigated phenotypic alterations of MSCs under cardiac stress. Methods&Results: Transcriptome analysis of MSCs showed preferential differentiation toward adipocytes in murine pressure overload models. In vitro assays and histological BM sections also support this finding. Furthermore, single-cell RNA sequencing of MSCs demonstrated that the percentage of adipocyte-primed MSCs increased in proportion to the severity of cardiac dysfunction, and also correlated with the frequency of myeloid-lineage progenitor cells. To investigate the influence of adipo-lineage MSCs on HSCs, we conducted BM transplantation supplemented with MSCs from control or HF mice. Recipient mice transplanted with HF-MSCs showed significant increases in myeloid-biased multipotent progenitors in BM and myeloid cells in peripheral blood. Additionally, the number of proinflammatory cardiac macrophages was significantly increased in the HF-MSCs group, promoting cardiac fibrosis and dysfunction. Conclusions: Our results demonstrated that the BM niche could perceive cardiac stress in the form of adipocytic skewing of MSCs in the setting of HF, which changed the differentiation behavior in HSCs and ultimately led to further deterioration of cardiac function through the impaired differentiation of circulating monocytes into cardiac macrophages. Therefore, suppressing the adipocytic differentiation of MSCs could have a novel therapeutic potential to avoid repeated HF events.

Single-cell Trajectories and Pseudo-time Analysis Reveal Additional Insights into Rheumatoid Arthritis Disease Progression

As the chicken embryo grows, its increasing metabolic demand drives the development of the cardiovascular system, enabling efficient nutrient delivery through complex molecular and structural formation. Key extracellular matrix (ECM) components, such as hyaluronic acid (HA) and collagen type I alpha 1 (COL1A1), play a crucial role in shaping the biomechanical environment of the heart, particularly the sinoatrial node (SAN). These ECM elements regulate cell adhesion, migration, and the maturation of cardiac progenitor cells (CPCs), essential for the heart's electrical conductivity and rhythmicity. Based on the hypothesis that ECM mechanical properties influence the spatial patterning of conduction-related genes, we analyzed spatial transcriptomics data from chicken hearts at different developmental stages. Collagen-related genes associated with a sturdy ECM showed an increasing trend over time, while soft ECM-related genes responsible for producing proteoglycans and breaking down collagen decreased. Although conduction-related genes did not fully align with ECM trends, intriguing patterns were observed, pointing to potential interactions between ECM remodeling and the construction of the cardiac conduction system. Our findings suggest significant ECM r7emodeling between days 4 and 7, which may influence the heart's structural and functional development.

A noncoding variant confers pancreatic differentiation defect and contributes to diabetes susceptibility by recruiting RXRA

AbstractHuman genetics analysis has identified many noncoding SNPs associated with diabetic traits, but whether and how these variants contribute to diabetes is largely unknown. Here, we focus on a noncoding variant, rs6048205, and report that the risk-G variant impairs the generation of PDX1+/NKX6-1+ pancreatic progenitor cells and further results in the abnormal decrease of functional β cells during pancreatic differentiation. Mechanistically, this risk-G variant greatly enhances RXRA binding and over-activates FOXA2 transcription, specifically in the pancreatic progenitor stage, which in turn represses NKX6-1 expression. Consistently, inducible FOXA2 overexpression could phenocopy the differentiation defect. More importantly, mice carrying risk-G exhibit abnormal pancreatic islet architecture and are more sensitive to streptozotocin or a high-fat diet to develop into diabetes eventually. This study not only identifies a causal noncoding variant in diabetes susceptibility but also dissects the underlying gain-of-function mechanism by recruiting stage-specific factors.

Abstract 4119680: First-in-Man Treatment of Heart Failure by Repeated Intravenous Infusions of a Cardiovascular Cell-Derived Extracellular Vesicle-Enriched Secretome

Background: Most of the effects of intramyocardially transplanted stem cells can be duplicated by the sole administration of their secretome but this approach has not yet been tested in heart failure (HF). Methods: The SECRET-HF phase I trial (NCT05774509) was designed according to a Bayesian optimal interval scheme to assess the effects of repeated intravenous infusions of a cellular secretome in 12 patients with a non-ischemic dilated cardiomyopathy. The main inclusion criteria are severe symptoms (NYHA Class III despite an optimal guideline-directed medical therapy), a reduced left ventricular (LV) ejection fraction (EF ≤40%) and ineligibility for a heart transplant. The Investigational Medicinal Product was derived from human induced pluripotent stem cells reprogrammed from a healthy donor and differentiated in cardiovascular progenitor cells (CPC). Following CPC culture in a dedicated "vesiculation" medium, the conditioned media were collected, filtered, enriched for extracellular vesicles, concentrated by tangential flow filtration and scaled out into glass vials stored at -80°C. Quality controls were implemented throughout the whole process which was conducted according to current Good Manufacturing Practices. Results: Three patients, out of the 4 of the initial low-dose cohort, have now been treated. All had been previously fitted with an automatic internal cardioverter defibrillator (AICD). The secretome was delivered intravenously 3 times, 3 weeks apart, at a dose of 20 x10 9 particles/kg for each infusion. By November, 2024, the follow-up will be 16, 9, 6 and 2 months for each of them (mean: 8 months). So far, none of the treated patients has experienced a dose-limiting toxicity; in particular, there have been no post-treatments ventricular arrhythmia detected by the AICD, no allo-immunization and no inflammation based on the enumeration of lymphocyte subpopulations by flow cytometry. At 6 months, the first patient improved to NYHA Class II with a decrease in echographic LVEDV and LVESV (from 108 mL/m 2 to 87 mL/m 2 and from 80 mL/m 2 to 60 mL/m 2 , respectively) and a concomitant increase in LVEF from 25% to 32%. At 1 month post-treatment, the second patient also reports a symptomatic improvement (NYHA Class II) with an increase in EF from 21% to 28%. Conclusions: This initial experience supports the safety of repeated intravenous administrations of a cardiovascular cellular secretome as a potential noninvasive and user-friendly treatment of severe HF.

STEM-10. NEURAL PROGENITOR CELL MARKERS IN IDH MUTANT AND IDHWT GLIOMAS

Abstract INTRODUCTION Single-cell RNA sequencing (scRNA-seq) has helped to elucidate the cellular composition of cancer and its microenvironment. Recent scRNA-seq studies have highlighted the heterogeneity of glioblastoma (GBM). Moreover, single-cell GBM analyses have proposed resemblance of GBM cells to radial glia and outer radial glia, supporting the hypothesis that remnants of developmental tissue get reactivated in cancer. A recent study isolated neural progenitor cells (NPCs) from developing fetal human brain (gestational week 17–19) and classified NPCs based on their expression of THY1, CD24 and EGFR. Ventricular radial glia are THY1- CD24-EGFR+ whereas outer radial glia are THY1- CD24-EGFR-. Early neuron precursors are CD24+THY1-EGFR+ and glial progenitor cells (GPCs) are THY1+EGFR+. GPCs give rise to THY1+EGFR+PDGFRA+ pre-oligodendrocyte progenitor cells. The importance of EGFR in NPCs again highlights the resemblance to glioma. METHODS We aimed to apply the classification above to IDH mutant astrocytoma and oligodendroglioma as well as IDHwt glioblastoma samples. We used three publicly available datasets: Wang (paired 74 IDHwt primary and recurrent samples), Tirosh (6 primary oligodendroglioma samples) and Venteicher (10 primary IDH mutant astrocytoma). RESULTS In IDH mutant astrocytoma, 82.63% of cells express THY1+ (mostly EGFR+PDGFRA+) and 10.76% of cells are THY1-CD24-EGFR+. In oligodendroglioma, 75% of cells are THY1+ (mostly EGFR+PDGFRA+) and 12.07% are THY1-CD24-EGFR+. In IDHwt EGFR amplified primary GBM samples, 87.5% of cells are THY1-CD24-EGFR+. This percentage drops to 70.4% in the recurrent setting. THY1-CD24-EGFR- cells increase from 9.7% to 23.1% at recurrence. In IDHwt EGFRwt primary GBM samples, 48.6% of cells are THY1-CD24-EGFR+ and 44.15% are THY1-CD24-EGFR-. In the recurrent setting, 43.26% of cells are THY1-CD24-EGFR+ and 49.58% are THY1-CD24-EGFR-. CONCLUSION IDH mutant gliomas and IDHwt glioblastoma express different progenitor cell markers and may have a different cell of origin. THY1 is highly expressed in IDH mutant gliomas.

Senolysis potentiates endothelial progenitor cell adhesion to and integration into the brain vasculature

Abstract Background One of the most severe consequences of ageing is cognitive decline, which is associated with dysfunction of the brain microvasculature. Thus, repairing the brain vasculature could result in healthier brain function. Methods To better understand the potential beneficial effect of endothelial progenitor cells (EPCs) in vascular repair, we studied the adhesion and integration of EPCs using the early embryonic mouse aorta–gonad–mesonephros – MAgEC 10.5 endothelial cell line. The EPC interaction with brain microvasculature was monitored ex vivo and in vivo using epifluorescence, laser confocal and two-photon microscopy in healthy young and old animals. The effects of senolysis, EPC activation and ischaemia (two-vessel occlusion model) were analysed in BALB/c and FVB/Ant: TgCAG-yfp_sb #27 mice. Results MAgEC 10.5 cells rapidly adhered to brain microvasculature and some differentiated into mature endothelial cells (ECs). MAgEC 10.5-derived endothelial cells integrated into microvessels, established tight junctions and co-formed vessel lumens with pre-existing ECs within five days. Adhesion and integration were much weaker in aged mice, but were increased by depleting senescent cells using abt-263 or dasatinib plus quercetin. Furthermore, MAgEC 10.5 cell adhesion to and integration into brain vessels were increased by ischaemia and by pre-activating EPCs with TNFα. Conclusions Combining progenitor cell therapy with senolytic therapy and the prior activation of EPCs are promising for improving EPC adhesion to and integration into the cerebral vasculature and could help rejuvenate the ageing brain.

TMET-01. LIPID METABOLIC PROGRAMS DEFINE GLIOMA STATE IDENTITY, PLASTICITY AND DEPENDENCIES

Abstract Gliomas are lethal malignancies comprised of heterogeneous and dynamic subpopulations of cell states resembling normal neurodevelopmental cell types (radial glia (RG), oligodendrocyte progenitor cell (OPC), neuron progenitor cell (NPC), neuron, etc). While both intrinsic (genetics) and extrinsic (brain environment) cues are coupled to glioma state identity, the functional programs governing glioma cell state and plasticity are unknown. Here we performed a multi-omic interrogation of a large library (n=392) of glioma patient tumors, in vivo orthotopic xenografts and in vitro gliomasphere cultures. Comparisons of matched glioma samples across environments revealed the non-native in vitro environment constrains glioma state diversity specifically enriching for stem-like glioma cell states (RG, immune, vascular). This enrichment was linked to lipid metabolic flexibility, enabling tumors enriched for stem-like states to adapt to various tumor microenvironments. By contrast, “lineage-committed” cell states (OPC, NPC, and neuron) demonstrate restricted lipid metabolism, consequently having a dependence on lipid scavenging from the brain microenvironment for survival. These results connect intra-tumoral heterogeneity and plasticity of glioma to lipid metabolism, leveraging the functional diversity of cellular states to reveal potential therapeutic opportunities.

EXTH-09. GENE MODIFICATION OF HEMATOPOIETIC STEM AND PROGENITOR CELLS FOR IMPROVEMENT OF IMMUNOTHERAPIES FOR MALIGNANT GLIOMAS

Abstract Patients living with high-grade gliomas have a poor survival prognosis. Furthermore, standard of care treatment for these malignant gliomas has not significantly improved in the past decades. Our laboratory previously demonstrated that the combination of two different immunotherapies with HSPCs provided a significant survival benefit in preclinical brain tumor models, however, this therapeutic combination is still not 100% curative. We hypothesized that gene modification of HSPCs could add additional therapeutic benefit to immunotherapies for the treatment of resistant gliomas. Hematopoietic stem and progenitor cells (HSPCs) have been widely used in different clinical settings due to their ability to self-renew and differentiate into all immune cell lineages. In recent years, HSPCs have been the target of a variety of gene editing research efforts to decipher the most effective method for gene modification to use for therapeutic purposes. After comparison with previously established methods, we optimized a protocol for the successful editing of murine HSPCs and human CD34+ cells. Using Cas9 mRNA and sgRNAs in HSPCs, we achieved up to 80% reduction in gene expression. This method is superior to others due to its efficient, quick, inexpensive, and reliable nature. We also showed that, by knocking-down IL-6R in HSPCs, we can drive their differentiation into dendritic cells, while decreasing MDSCs and macrophages. Furthermore, gene-modified HSPCs are also capable of bone marrow reconstitution of lethally irradiated mice. Currently, we are testing whether the combination of gene-modified HSPCs with immunotherapy provides additional survival benefit to unmodified HSPCs with immunotherapy in a resistant murine glioma model.

TMIC-51. NEUROIMMUNE-COMPETENT ORGANOID MODELING OF MICROGLIA/TUMOR INTERACTIONS AND DRUG RESPONSIVENESS

Abstract INTRODUCTION Due to its highly aggressive and infiltrative nature, lack of effective treatment options and localization in the skull base, diffuse intrinsic pontine glioma (DIPG) is universally fatal with less than a year median survival time. Studying how DIPG cells interact with brain cells in its microenvironment, including microglia which is the primary brain immune cell type, may lead to new therapeutic strategies to halt the invasion of DIPG into brain tissue. We developed a clinically relevant human immunocompetent brain organoid-DIPG fusion model for investigating the tumor invasion process at the cellular and molecular levels. METHODS Neuronal progenitor and GFP-labeled myeloid precursor cells were derived from human embryonic stem cells and combined to self-assemble and co-develop over two months into microglia-containing brain organoids (MiCBOs). The development of the MiCBOs as well as the distribution and motility of the microglia within the brain organoid was characterized by confocal and multiphoton microscopy, immunofluorescence staining and Western Blots. Confocal live-cell imaging was used to investigate the invasion of TdTomato-labeled tumor cells into MiCBO. We further performed single-cell RNA-Sequencing (scRNA-Seq) analysis to gain insight into the cell-specific gene expression changes after the confrontation of the MiCBOs with tumor spheroids. RESULTS MiCBOs contain viable, widely distributed and highly motile microglia as well as functionally mature neurons, highly resembling those in the human brain. scRNA-Seq showed distinct gene expression patterns in both microglia and tumor cells after confronting MiCBOs with DIPG spheroids, suggesting candidate signaling pathways between those two cell types. CONCLUSION Our novel MiCBO-DIPG fusion model provides a pathophysiologically-relevant system to elucidate molecular mechanisms underlying cell-cell interactions during tumor invasion in a human brain tissue context. This scalable model can be adapted to drug screening applications to identify therapeutics that modulate neuroimmune/tumor interactions and to establish the therapeutic index for anti-cancer medications.