Bone Marrow Hematopoietic Stem Cells Research Articles

Flow Cytometry Analysis of Murine Bone Marrow Hematopoietic Stem and Progenitor Cells and Stromal Niche Cells

Flow Cytometry Analysis of Murine Bone Marrow Hematopoietic Stem and Progenitor Cells and Stromal Niche Cells

Murine fetal bone marrow does not support functional hematopoietic stem and progenitor cells until birth

While adult bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs) and their extrinsic regulation is well studied, little is known about the composition, function, and extrinsic regulation of the first HSPCs to enter the BM during development. Here, we functionally interrogate murine BM HSPCs from E15.5 through P0. Our work reveals that fetal BM HSPCs are present by E15.5, but distinct from the HSPC pool seen in fetal liver, both phenotypically and functionally, until near birth. We also generate a transcriptional atlas of perinatal BM HSPCs and the BM niche in mice across ontogeny, revealing that fetal BM lacks HSPCs with robust intrinsic stem cell programs, as well as niche cells supportive of HSPCs. In contrast, stem cell programs are preserved in neonatal BM HSPCs, which reside in a niche expressing HSC supportive factors distinct from those seen in adults. Collectively, our results provide important insights into the factors shaping hematopoiesis during this understudied window of hematopoietic development.

Frizzled-6 promotes hematopoietic stem/progenitor cell mobilization and survival during LPS-induced emergency myelopoiesis

SummaryEmergency hematopoiesis involves the activation of bone marrow hematopoietic stem/progenitor cells (HSPCs) in response to systemic inflammation by a combination of cell-autonomous and stroma-dependent signals and leads to their release from bone marrow and migration to periphery. We have previously shown that FZD6 plays a pivotal role in regulating HSPC expansion and long-term maintenance. Now we sought to better understand the underlying mechanisms. Using lipopolysaccharide (LPS)-induced emergency granulopoiesis as a model, we show that failed expansion was intrinsic to FZD6-deficient HSPCs but also required a FZD6-deficient environment. FZD6-deficient HSPCs became more strongly activated, but their mobilization to peripheral blood was impaired and they were more susceptible to inflammatory cell death, leading to enhanced release of pro-inflammatory cytokines in the marrow. These studies indicate that FZD6 has a protective effect in the bone marrow to prevent an overactive inflammatory response and further suggest that mobilization improves HSPC survival during bone marrow inflammation.

Endocytosis of the thrombopoietin receptor Mpl regulates megakaryocyte and erythroid maturation in mice.

Dnm2fl/fl Pf4-Cre (Dnm2Plt–/– ) mice lacking the endocytic GTPase dynamin 2 (DNM2) in platelets and megakaryocytes (MKs) develop hallmarks of myelofibrosis. At the cellular level, the tyrosine kinase JAK2 is constitutively active but decreased in expression in Dnm2Plt–/– platelets. Additionally, Dnm2Plt–/– platelets cannot endocytose the thrombopoietin (TPO) receptor Mpl, leading to elevated circulating TPO levels. Here, we assessed whether the hyperproliferative phenotype of Dnm2Plt–/– mice was due to JAK2 constitutive activation or to elevated circulating TPO levels. In unstimulated Dnm2Plt–/– platelets, STAT3 and, to a lower extent, STAT5 were phosphorylated, but their phosphorylation was slowed and diminished upon TPO stimulation. We further crossed Dnm2Plt–/– mice in the Mpl–/– background to generate Mpl–/–Dnm2Plt–/– mice lacking Mpl ubiquitously and DNM2 in platelets and MKs. Mpl–/– Dnm2Plt–/– platelets had severely reduced JAK2 and STAT3 but normal STAT5 expression. Mpl–/– Dnm2Plt–/– mice had severely reduced bone marrow MK and hematopoietic stem and progenitor cell numbers. Additionally, Mpl–/– Dnm2Plt–/– mice had severe erythroblast (EB) maturation defects, decreased expression of hemoglobin and heme homeostasis genes and increased expression of ribosome biogenesis and protein translation genes in spleen EBs, and developed anemia with grossly elevated plasma erythropoietin (EPO) levels, leading to early fatality by postnatal day 25. Mpl–/– Dnm2Plt+/+ mice had impaired EB development at three weeks of age, which normalized with adulthood. Together, the data shows that DNM2-dependent Mpl-mediated endocytosis in platelets and MKs is required for steady-state hematopoiesis and provides novel insights into a developmentally controlled role for Mpl in normal erythropoiesis, regulating hemoglobin and heme production.

Effect of Interleukin-6 Gene Deletion on Radiation-Induced Mouse Hematopoietic Injury and Relative Mechanism

To study the effect of interleukin-6 (IL-6) gene deletion on radiation-induced hematopoietic injury in mice and relative mechanism. Before and after whole body 60Co γ-ray irradiation, it was analyzed and compared that the difference of peripheral hemogram, bone marrow hematopoietic stem and progenitor cells conts in IL-6 gene knockout (IL-6-/-) and wild-type (IL-6+/+) mice and serum IL-6 and G-CSF expression levels in above- mentioned mouse were detected. Moreover, 30 days survival rate of IL-6-/- and IL-6+/+ mice after 8.0 Gy γ-ray irradiation were analyzed. IL-6 levels in serum of IL-6+/+ and IL-6-/- mice were respectively (98.95±3.85) pg/ml and (18.36±5.61) pg/ml, which showed a significant statistical differences (P<0.001). There were no significant differences of peripheral blood cell counts and G-CSF level in serum between IL-6+/+ and IL-6-/- mice before irradiation (P>0.05). However, the number of leukocytes, neutrophils, lymphocytes, monocytes, platelets in peripheral blood and G-CSF level in serum of IL-6-/- mice were significantly decreased at 6 h after 8.0 Gy γ-ray irradiation compared with that of IL-6+/+ mice. On days 30 after 8.0 Gy γ-ray irradiation, the survival rate of IL-6+/+ and IL-6-/- mice was 62.5% and 12.5%, and the mean survival time of dead mice was 16.0±1.0 and 10.6±5.3 days, respectively. On days 14 after 6.5 Gy γ-ray irradiation, bone marrow nucleated cells in IL-6+/+ and IL-6-/- mice were respectively (10.0±1.2)×106 and (8.3±2.2)×106 per femur. Compared with IL-6+/+ mice, the proportion of Lin-Sca-1-c-kit+ (LK) in bone marrow of IL-6-/- mice had no significant change (P>0.05), but the proportion of Lin-Sca-1+c-kit+ (LSK) was significantly decreased (P<0.05). IL-6 plays an obvious role in regulating hematopoietic radiation injury, and IL-6 deficiency can inhibit the radiation-induced increase of endogenous G-CSF level in serum, aggravates the damage of mouse hematopoietic stem cells（HSC） and the reduction of mature blood cells in peripheral blood caused by ionizing irradiation, resulting in the shortening of the survival time and significant decrease of the survival rate of mice exposed to lethal dose radiation.

An experimental study on the effect of preoperative autologous blood donation on bone marrow hematopoiesis and hematopoietic stem cells.

To evaluate the effect of autologous blood transfusion (ABT) on hematopoietic stem cells through the observation of the changes in the number and activity of bone marrow CD34+ cells after preoperative autologous blood donation (PABD). Rabbit bone marrow specimens were collected preoperatively (T2), 6 h postoperatively (T3), and 24 h postoperatively (T4). Next, the percentages of CD34+ cells, the cell cycle, and the relative expression of telomeric DNA were measured in each group of rabbits. Peripheral blood specimens were collected before PABD (T1) and at T4 to measure reticulocytes. At T3 and T4, the percentages of CD34+ cells and the expressions of telomeric DNA were significantly higher, and the percentages of cells in the G1 phase were significantly lower in each experimental group compared with those in the blank control group (group A) (P<0.05). Compared with the surgical blood collection group (group C), the CD34+ cells and the expressions of telomeric DNA were significantly higher, and the percentages of cells in the G1 phase were significantly lower in the preoperative autologous whole blood group (group D) and the preoperative autologous blood component group (group E) (P<0.05). Compared with group D, the CD34+ cells and the expressions of telomeric DNA were significantly lower, and the percentages of cells in the G1 phase were significantly higher in group E (P<0.05). At T4, the reticulocyte percentages in the surgery group (group B) and group C were significantly higher than in group E and group D, and the reticulocyte percentages in group E were higher than in group D (P<0.05). This study's findings indicated that ABT suppressed bone marrow hematopoiesis, while autologous blood component transfusion had less of an effect than that of whole blood transfusion. Therefore, PABD blood component transfusion would be superior to autologous whole blood transfusion.

Liver Regeneration by Hematopoietic Stem Cells: Have We Reached the End of the Road?

The liver is the organ with the highest regenerative capacity in the human body. However, various insults, including viral infections, alcohol or drug abuse, and metabolic overload, may cause chronic inflammation and fibrosis, leading to irreversible liver dysfunction. Despite advances in surgery and pharmacological treatments, liver diseases remain a leading cause of death worldwide. To address the shortage of donor liver organs for orthotopic liver transplantation, cell therapy in liver disease has emerged as a promising regenerative treatment. Sources include primary hepatocytes or functional hepatocytes generated from the reprogramming of induced pluripotent stem cells (iPSC). Different types of stem cells have also been employed for transplantation to trigger regeneration, including hematopoietic stem cells (HSCs), mesenchymal stromal cells (MSCs), endothelial progenitor cells (EPCs) as well as adult and fetal liver progenitor cells. HSCs, usually defined by the expression of CD34 and CD133, and MSCs, defined by the expression of CD105, CD73, and CD90, are attractive sources due to their autologous nature, ease of isolation and cryopreservation. The present review focuses on the use of bone marrow HSCs for liver regeneration, presenting evidence for an ongoing crosstalk between the hematopoietic and the hepatic system. This relationship commences during embryogenesis when the fetal liver emerges as the crossroads between the two systems converging the presence of different origins of cells (mesoderm and endoderm) in the same organ. Ample evidence indicates that the fetal liver supports the maturation and expansion of HSCs during development but also later on in life. Moreover, the fact that the adult liver remains one of the few sites for extramedullary hematopoiesis—albeit pathological—suggests that this relationship between the two systems is ongoing. Can, however, the hematopoietic system offer similar support to the liver? The majority of clinical studies using hematopoietic cell transplantation in patients with liver disease report favourable observations. The underlying mechanism—whether paracrine, fusion or transdifferentiation or a combination of the three—remains to be confirmed.

Epigenetic Memories in Hematopoietic Stem and Progenitor Cells.

The recent development of next-generation sequencing (NGS) technologies has contributed to research into various biological processes. These novel NGS technologies have revealed the involvement of epigenetic memories in trained immunity, which are responses to transient stimulation and result in better responses to secondary challenges. Not only innate system cells, such as macrophages, monocytes, and natural killer cells, but also bone marrow hematopoietic stem cells (HSCs) have been found to gain memories upon transient stimulation, leading to the enhancement of responses to secondary challenges. Various stimuli, including microbial infection, can induce the epigenetic reprogramming of innate immune cells and HSCs, which can result in an augmented response to secondary stimulation. In this review, we introduce novel NGS technologies and their application to unraveling epigenetic memories that are key in trained immunity and summarize the recent findings in trained immunity. We also discuss our most recent finding regarding epigenetic memory in aged HSCs, which may be associated with the exposure of HSCs to aging-related stresses.

SAT196 - Restoring bone marrow hematopoietic stem cells (BM-HSC) reserve augments regression of fibrosis and regeneration in animal model of cirrhosis

SAT196 - Restoring bone marrow hematopoietic stem cells (BM-HSC) reserve augments regression of fibrosis and regeneration in animal model of cirrhosis

COVID-19 vaccination antibody responses in patients with aplastic anaemia and paroxysmal nocturnal haemoglobinuria

COVID-19 vaccination antibody responses in patients with aplastic anaemia and paroxysmal nocturnal haemoglobinuria

Hyaluronic acid–GPRC5C signalling promotes dormancy in haematopoietic stem cells

Bone marrow haematopoietic stem cells (HSCs) are vital for lifelong maintenance of healthy haematopoiesis. In inbred mice housed in gnotobiotic facilities, the top of the haematopoietic hierarchy is occupied by dormant HSCs, which reversibly exit quiescence during stress. Whether HSC dormancy exists in humans remains debatable. Here, using single-cell RNA sequencing, we show a continuous landscape of highly purified human bone marrow HSCs displaying varying degrees of dormancy. We identify the orphan receptor GPRC5C, which enriches for dormant human HSCs. GPRC5C is also essential for HSC function, as demonstrated by genetic loss- and gain-of-function analyses. Through structural modelling and biochemical assays, we show that hyaluronic acid, a bone marrow extracellular matrix component, preserves dormancy through GPRC5C. We identify the hyaluronic acid–GPRC5C signalling axis controlling the state of dormancy in mouse and human HSCs.

Cooperation between KDM6B overexpression and TET2 deficiency in the pathogenesis of chronic myelomonocytic leukemia.

Loss-of-function TET2 mutations are recurrent somatic lesions in chronic myelomonocytic leukemia (CMML). KDM6B encodes a histone demethylase involved in innate immune regulation that is overexpressed in CMML. We conducted genomic and transcriptomic analyses in treatment naïve CMML patients and observed that the patients carrying both TET2 mutations and KDM6B overexpression constituted 18% of the cohort and 42% of patients with TET2 mutations. We therefore hypothesized that KDM6B overexpression cooperated with TET2 deficiency in CMML pathogenesis. We developed a double-lesion mouse model with both aberrations, and discovered that the mice exhibited a more prominent CMML-like phenotype than mice with either Tet2 deficiency or KDM6B overexpression alone. The phenotype includes monocytosis, anemia, splenomegaly, andincreased frequencies and repopulating activity of bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs). Significant transcriptional alterations were identified in double-lesion mice, which were associated with activation of proinflammatory signals and repression of signals maintaining genome stability. Finally, KDM6B inhibitor reduced BM repopulating activity of double-lesion mice and tumor burden in mice transplanted with BM-HSPCs from CMML patients with TET2 mutations. These data indicate that TET2 deficiency and KDM6B overexpression cooperate in CMML pathogenesis of and that KDM6B could serve as a potential therapeutic target in this disease.

Bioinformatics analysis of molecular pathways and key candidate biomarkers associated with human bone marrow hematopoietic stem cells (HSCs) micro-array gene expression data

An identification of the molecular properties of glioma stem cells (GSCs) has led studies in clinical use, stem cell identification, and highly-effective usage. The GSE32719 contains a total expression of 54,676 genes of healthy human bone marrow HSCs in 14 young (20–31 years), 5 middle (42–61 years), and a lot of old (65–85 years) age groups. The researchers of this study described age-related changes in the human HSC population, using the gene expression profile of significance analysis to discover differentially expressed genes (DEGs) between each age group. The DEGs were subjected to significantly enriched biological processing that decoded the increase and functional decline in the HSC population. The GSE dataset analysis was conducted by the GEOquery package in Bioconductor. Using the Biobase and gplots packages, 453 DEGs were screened. DEGs analyses were conducted by gene ontology (GO) pathway enrichment and Kyoto Encylopedia of Genes and Genomes (KEGG) enrichment analysis. The Hippo signaling pathway was observed to be significant using the GO pathway enrichment analysis, which was previously reported as an effective pathway in cancers, including AML. A protein-protein interaction (PPI) network was constructed; then based on that, a subnetwork module analysis for the Hippo signaling pathway was made. Additionally, the GO pathway enrichment analysis revealed ‘cellular process’, ‘cellular metabolic process’, ‘metabolic process’, ‘biogenesis’, and ‘vasculogenesis biological processes’, which are involved in a wide of biological activities such as metabolic regulation, cell growth, and proliferation. Our findings offer silico evidence for candidate genes, such as the UBC, PTK2, and TCF7L2, that may be promising biomarkers for the translation approach associated with HSC population age-related diseases.

Bone marrow hematopoiesis drives multiple sclerosis progression

Multiple sclerosis (MS) is a Tcell-mediated autoimmune disease of the central nervous system (CNS). Bone marrow hematopoietic stem and progenitor cells (HSPCs) rapidly sense immune activation, yet their potential interplay with autoreactive Tcells in MS is unknown. Here, we report that bone marrow HSPCs are skewed toward myeloid lineage concomitant with the clonal expansion of Tcells in MS patients. Lineage tracing in experimental autoimmune encephalomyelitis, a mouse model of MS, reveals remarkable bone marrow myelopoiesis with an augmented output of neutrophils and Ly6Chigh monocytes that invade the CNS. We found that myelin-reactive Tcells preferentially migrate into the bone marrow compartment in a CXCR4-dependent manner. This aberrant bone marrow myelopoiesis involves the CCL5-CCR5 axis and augments CNS inflammation and demyelination. Our study suggests that targeting the bone marrow niche presents an avenue to treat MS and other autoimmune disorders.

Development of Poland's Central Bone Marrow Donor Registry Affects Donor Searches for Patients With Hematological Diseases

In the last 10 years, numbers of donors in the case of Polish potential unrelated hematopoietic stem cells (HSC) have increased dynamically, reaching 1,900,000 in 2020 (including donors presented in World Marrow Donor Association as PL6). On the world scale, the share of Polish donors in the global registry increased from 1% in 2010 to about 5% in 2020. The level and range of typing of potential donors has also been improving steadily toward the international "gold standard." At the end of 2020, 92% of Polish resources were at least HLA-A, B, C, DR, DQ high- or intermediate-resolution typed, mostly by way of genomic typing techniques, mostly by way of genomic typing techniques. The Central Bone Marrow Donor Registry (CBMDR) also stands out in terms of the young ages of potential donors. As of 2020, 27.2% of those registered were younger than 30 years of age, and 36.3% were aged between 30 and 40 years. Sixty percent of registered donors were female. The data in question were presented at the World Marrow Donor Association Search & Match Service, ensuring their visibility and accessibility to Polish and international search units and registries. In 2020, donors in Poland were the subject of almost 18,000 search requests from 40 countries, with 271 extended typing requests and more than 7600 confirmatory typing requests. The total number of donations from Polish donors also increased. In 2020, HSC of bone marrow, peripheral blood, or lymphocytes were collected from 1391 donors, as opposed to 94 donors in 2010. The growing number of donors available in the CBMDR means a better chance of a donor being found among Polish resources, without any need to resort to international registers. Although in 2010, just 24% of Polish recipients received HSC from Polish donors, by 2019 the figure was as high as 67%, and reached 63% in 2020. The CBMDR is an example of proper strategy on registry development being implemented in Poland.

Sulfur Amino Acid Supplementation Abrogates Protective Effects of Caloric Restriction for Enhancing Bone Marrow Regrowth Following Ionizing Radiation.

Radiation therapy damages and depletes total bone marrow (BM) cellularity, compromising safety and limiting effective dosing. Aging also strains total BM and BM hematopoietic stem and progenitor cell (HSPC) renewal and function, resulting in multi-system defects. Interventions that preserve BM and BM HSPC homeostasis thus have potential clinical significance. Here, we report that 50% calorie restriction (CR) for 7-days or fasting for 3-days prior to irradiation improved mouse BM regrowth in the days and weeks post irradiation. Specifically, one week of 50% CR ameliorated loss of total BM cellularity post irradiation compared to ad libitum-fed controls. CR-mediated BM protection was abrogated by dietary sulfur amino acid (i.e., cysteine, methionine) supplementation or pharmacological inhibition of sulfur amino acid metabolizing and hydrogen sulfide (H2S) producing enzymes. Up to 2-fold increased proliferative capacity of ex vivo-irradiated BM isolated from food restricted mice relative to control mice indicates cell autonomy of the protective effect. Pretreatment with H2S in vitro was sufficient to preserve proliferative capacity by over 50% compared to non-treated cells in ex vivo-irradiated BM and BM HSPCs. The exogenous addition of H2S inhibited Ten eleven translocation 2 (TET2) activity in vitro, thus providing a potential mechanism of action. Short-term CR or fasting therefore offers BM radioprotection and promotes regrowth in part via altered sulfur amino acid metabolism and H2S generation, with translational implications for radiation treatment and aging.

Defects in Long-Term APC Repopulation Ability of Adult Human Bone Marrow Hematopoietic Stem Cells (HSCs) Compared with Fetal Liver HSCs.

Immunodeficient mice reconstituted with immune systems from patients, or personalized immune (PI) mice, are powerful tools for understanding human disease. Compared with immunodeficient mice transplanted with human fetal thymus tissue and fetal liver-derived CD34+ cells administered i.v. (Hu/Hu mice), PI mice, which are transplanted with human fetal thymus and adult bone marrow (aBM) CD34+ cells, demonstrate reduced levels of human reconstitution. We characterized APC and APC progenitor repopulation in human immune system mice and detected significant reductions in blood, bone marrow (BM), and splenic APC populations in PI compared with Hu/Hu mice. APC progenitors and hematopoietic stem cells (HSCs) were less abundant in aBM CD34+ cells compared with fetal liver-derived CD34+ cell preparations, and this reduction in APC progenitors was reflected in the BM of PI compared with Hu/Hu mice 14-20 wk posttransplant. The number of HSCs increased in PI mice compared with the originally infused BM cells and maintained functional repopulation potential, because BM from some PI mice 28 wk posttransplant generated human myeloid and lymphoid cells in secondary recipients. Moreover, long-term PI mouse BM contained functional T cell progenitors, evidenced by thymopoiesis in thymic organ cultures. Injection of aBM cells directly into the BM cavity, transgenic expression of hematopoietic cytokines, and coinfusion of human BM-derived mesenchymal stem cells synergized to enhance long-term B cell and monocyte levels in PI mice. These improvements allow a sustained time frame of 18-22 wk where APCs and T cells are present and greater flexibility for modeling immune disease pathogenesis and immunotherapies in PI mice.

Optimization of adipose tissue-derived mesenchymal stromal cells transplantation for bone marrow repopulation following irradiation.

BACKGROUNDBone marrow (BM) suppression is one of the most common side effects of radiotherapy and the primary cause of death following exposure to irradiation. Despite concerted efforts, there is no definitive treatment method available. Recent studies have reported using mesenchymal stromal cells (MSCs), but their therapeutic effects are contested.AIMWe administered and examined the effects of various amounts of adipose-derived MSCs (ADSCs) in mice with radiation-induced BM suppression.METHODSMice were divided into three groups: Normal control group, irradiated (RT) group, and stem cell-treated group following whole-body irradiation (WBI). Mouse ADSCs (mADSCs) were transplanted into the peritoneal cavity either once or three times at 5 × 105 cells/200 μL. The white blood cell count and the levels of, plasma cytokines, BM mRNA, and BM surface markers were compared between the three groups. Human BM-derived CD34+ hematopoietic progenitor cells were co-cultured with human ADSCs (hADSCs) or incubated in the presence of hADSCs conditioned media to investigate the effect on human cells in vitro.RESULTSThe survival rate of mice that received one transplant of mADSCs was higher than that of mice that received three transplants. Multiple transplantations of ADSCs delayed the repopulation of BM hematopoietic stem cells. Anti-inflammatory effects and M2 polarization by intraperitoneal ADSCs might suppress erythropoiesis and induce myelopoiesis in sub-lethally RT mice.CONCLUSIONThe results suggested that an optimal amount of MSCs could improve survival rates post-WBI.

Stem Cell Transplantation in the Treatment of Type 1 Diabetes Mellitus: From Insulin Replacement to Beta-Cell Replacement.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that attacks pancreatic β-cells, leading to the destruction of insulitis-related islet β-cells. Islet β-cell transplantation has been proven as a curative measure in T1DM. However, a logarithmic increase in the global population with diabetes, limited donor supply, and the need for lifelong immunosuppression restrict the widespread use of β-cell transplantation. Numerous therapeutic approaches have been taken to search for substitutes of β-cells, among which stem cell transplantation is one of the most promising alternatives. Stem cells have demonstrated the potential efficacy to treat T1DM by reconstitution of immunotolerance and preservation of islet β-cell function in recent research. cGMP-grade stem cell products have been used in human clinical trials, showing that stem cell transplantation has beneficial effects on T1DM, with no obvious adverse reactions. To better achieve remission of T1DM by stem cell transplantation, in this work, we explain the progression of stem cell transplantation such as mesenchymal stem cells (MSCs), human embryonic stem cells (hESCs), and bone marrow hematopoietic stem cells (BM-HSCs) to restore the immunotolerance and preserve the islet β-cell function of T1DM in recent years. This review article provides evidence of the clinical applications of stem cell therapy in the treatment of T1DM.

Induction of functional neutrophils from mouse fibroblasts by thymidine through enhancement of Tet3 activity.

Neutrophils are derived from bone marrow hematopoietic stem cells (HSCs) and are the largest population among circulating white blood cells in humans, acting as the first line of defense against invading pathogens. Whether neutrophils can be generated by transdifferentiation strategies is unknown. Here, we show that thymidine induces the conversion of mouse fibroblasts to neutrophils. Induced neutrophils (iNeus) showed antibacterial effects and did not undergo malignant transformation in vivo. Importantly, iNeu transplantation cured neutropenia in mice in vivo. Mechanistically, thymidine mediates iNeu conversion by enhancing Tet3 activity. Tet3 initiates the expression of the neutrophil fate decision factors Cebpδ and Rfx1 that drive the transdifferentiation of mouse fibroblasts to neutrophils. Therefore, the induction of functional neutrophils by chemicals may provide a potential therapeutic strategy for patients with neutropenia patients and infectious diseases.Fibroblasts; Neutrophils; Thymidine; Transdifferentiation; Tet3.