Treatment of Severe Aplastic Anemia with Porcine Anti-Human Lymphocyte Globulin

2020 ◽  
Vol 26 (22) ◽  
pp. 2661-2667
Author(s):  
Qi Lv ◽  
Zhang Huiqin ◽  
Xiao Na ◽  
Liu Chunyan ◽  
Shao Zonghong ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Aplastic Anemia ◽  
Bone Marrow Failure ◽  
New Product ◽  
Therapeutic Effects ◽  
First Line ◽  
Bone Marrow Failure Syndrome ◽  
Hematopoietic Stem

Aplastic anemia (AA) is a bone marrow failure syndrome characterized by pancytopenia. Decreased numbers of hematopoietic stem cells and impaired bone marrow microenvironment caused by abnormal immune function describe the major pathogenesis of AA. Hematopoietic stem cell transplantation and immunesuppressive therapy are the first-line treatments for AA. Porcine anti-lymphocyte globulin (p-ALG) is a new product developed in China. Several studies have shown that p-ALG exhibited good therapeutic effects in AA.

scholarly journals Mesenchymal Stem Cell Benefits Observed in Bone Marrow Failure and Acquired Aplastic Anemia

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Vivian Fonseca Gonzaga ◽  
Cristiane Valverde Wenceslau ◽  
Gustavo Sabino Lisboa ◽  
Eduardo Osório Frare ◽  
Irina Kerkis
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Aplastic Anemia ◽  
Blood Cells ◽  
Bone Marrow Failure ◽  
White Blood Cells ◽  
First Line ◽  
Hematopoietic Stem ◽  
Total Bone Marrow ◽  
Hematopoietic Niche

Acquired aplastic anemia (AA) is a type of bone marrow failure (BMF) syndrome characterized by partial or total bone marrow (BM) destruction resulting in peripheral blood (PB) pancytopenia, which is the reduction in the number of red blood cells (RBC) and white blood cells (WBC), as well as platelets (PLT). The first-line treatment option of AA is given by hematopoietic stem cell (HSCs) transplant and/or immunosuppressive (IS) drug administration. Some patients did not respond to the treatment and remain pancytopenic following IS drugs. The studies are in progress to test the efficacy of adoptive cellular therapies as mesenchymal stem cells (MSCs), which confer low immunogenicity and are reliable allogeneic transplants in refractory severe aplastic anemia (SAA) cases. Moreover, bone marrow stromal cells (BMSC) constitute an essential component of the hematopoietic niche, responsible for stimulating and enhancing the proliferation of HSCs by secreting regulatory molecules and cytokines, providing stimulus to natural BM microenvironment for hematopoiesis. This review summarizes scientific evidences of the hematopoiesis improvements after MSC transplant, observed in acquired AA/BMF animal models as well as in patients with acquired AA. Additionally, we discuss the direct and indirect contribution of MSCs to the pathogenesis of acquired AA.

Regulation of Hematopoietic Stem Cells by Interferons and by DNA Methylation: Implications for Bone Marrow Failure

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. SCI-20-SCI-20
Author(s):  
Margaret A. Goodell
Keyword(s):  
Dna Methylation ◽  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Bone Marrow Failure ◽  
Stem Cell Differentiation ◽  
Primary Myelofibrosis ◽  
Differentiation Potential ◽  
Hematopoietic Stem

Bone marrow failure (BMF), the inability to regenerate the differentiated cells of the blood, has a number of genetic and environmental etiologies, such as mutation of telomere-associated protein genes and immune-related aplastic anemia. Recently, mutations in DNA methyltransferase 3A (DNMT3A) have been found to be associated with approximately 15% of cases of primary myelofibrosis (MF), which can be a cause of BMF. The role of DNMT3A more broadly in hematopoiesis, and specifically in BMF, is currently poorly understood. DNMT3A is one of two de novo DNA methylation enzymes important in developmental fate choice. We showed that Dnmt3a is critical for normal murine hematopoiesis, as hematopoietic stem cells (HSCs) from Dnmt3a knockout (KO) mice displayed greatly diminished differentiation potential while their self-renewal ability was markedly increased1, in effect, leading to failure of blood regeneration or BMF. Combined with loss of Dnmt3b, HSCs exhibited a profound differentiation block, mediated in part by an increase of stabilized b-catenin. While we did not initially observe bone marrow pathology or malignancy development in mice transplanted with Dnmt3a KO HSCs, when we aged a large cohort of mice, all mice succumbed to hematologic disease within about 400 days. Roughly one-third of mice developed frank leukemia (acute lymphocytic leukemia or acute myeloid leukemia), one-third developed MDS, and the remainder developed primary myelofibrosis or chronic myelomonocytic leukemia. The pathological characteristics of the mice broadly mirror those of patients, suggesting the Dnmt3a KO mice can serve as a model for human DNMT3A-mutation associated disease. Strikingly, bone marrow of mice with different disease types exhibit distinct DNA methylation features. These will findings and the implications for disease development will be discussed. We are currently investigating the factors that drive different outcomes in the mice, including stressors such as exposure to interferons. We have hypothesized that HSC proliferation accelerates the Dnnmt3a-associated disease phenotypes. We have previously shown that interferons directly impinge on HSCs in the context of infections. Interferons activate HSCs to divide, generating differentiated progeny and cycling HSCs. Repeated interferon stimulation may permanently impair HSC function and bias stem cell output. When combined with loss of Dnmt3a, interferons may promote BMF. We will discuss broadly how external factors such as aging and infection may collaborate with specific genetic determinants to affect long-term hematopoiesis and malignancy development. Reference: Challen GA, Sun D, Jeong M, et al. Dnmt3a is essential for hematopoietic stem cell differentiation. Nat Genet 2012; 44: 23-31 Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

DNA Microarray Analysis of GPI-Negative Hematopoietic Stem Cells in Paroxysmal Nocturnal Hemoglobinuria Patients.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1048-1048
Author(s):  
Kazuhiko Ikeda ◽  
Tsutomu Shichishima ◽  
Yoshihiro Yamashita ◽  
Yukio Maruyama ◽  
Hiroyuki Mano
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Hematopoietic Stem Cell ◽  
Paroxysmal Nocturnal Hemoglobinuria ◽  
Bone Marrow Failure ◽  
Data Set ◽  
Hematopoietic Stem ◽  
Pnh Clone

Abstract Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematological disorder which is manifested by complement-mediated hemolysis, venous thrombosis, and bone marrow failure. Deficiencies of glycosylphosphatidylinositol (GPI)-anchored proteins, due to mutations in the phosphatidylinositol glycan-class A (PIG-A) gene, contribute to complement-mediated hemolysis and affect all hematopoietic lineages in PNH. However, it is unclear how a PNH clone with a PIG-A gene mutation expands in bone marrow. Although some genes, including the Wilms’ tumor gene (Shichishima et al, Blood, 2002), the early growth response gene, anti-apoptosis genes, and the gene localized at breakpoints of chromosome 12, have been reported as candidate genes that may associate with proliferations of a GPI-negative PNH clone, previous studies were not intended for hematopoietic stem cell, indicating that the differences in gene expressions between GPI-negative PNH clones and GPI-positive cells from PNH patients remain unclear at the level of hematopoietic stem cell. To identify genes contributing to the expansion of a PNH clone, here we compared the gene expression profiles between GPI-negative and GPI-positive fractions among AC133-positive hematopoietic stem cells (HSCs). By using the FACSVantage (Becton Dickinson, San Jose, CA) cell sorting system, both of CD59+AC133+ and CD59− AC133+ cells were purified from bone marrow mononuclear cells obtained from 11 individuals with PNH. Total RNA was isolated from each specimen with the use of RNeasy Mini column (Qiagen, Valencia, CA). The mRNA fractions were amplified, and were used to generate biotin-labeled cDNAs by the Ovation Biotin system (NuGEN Technologies, San Carlos, CA). The resultant cDNAs were hybridized with a high-density oligonucleotide microarray (HGU133A; Affymetrix, Santa Clara, CA). A total of >22,000 probe sets (corresponding to >14,000 human genes) were assayed in each experiment, and thier expression intensities were analyzed by GeneSpring 7.0 software (Silicon Genetics, Redwood, CA). Comparison between CD59-negative and CD59-positive HSCs has identified a number of genes, expression level of which was statistically different (t-test, P <0.001) between the two fractions. Interestingly, one of the CD59− -specific genes isolated in our data set turned out to encode a key component of the proteasome complex. On the other hand, a set of transcriptional factors were specifically silenced in the CD59− HSCs. These data indicate that affected CD59-negative stem cells have a specific molecular signature which is distinct from that for the differentiation level-matched normal HSCs. Our data should pave a way toward the molecular understanding of PNH.

Mutations in the RNA Component of Telomerase, TERC, in Children with Aplastic Anemia and Myelodysplastic Syndrome: An NMDP Study.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3736-3736
Author(s):  
Joshua J. Field ◽  
Philip J. Mason ◽  
Yvonne J. Barnes ◽  
Allison A. King ◽  
Monica Bessler ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Myelodysplastic Syndrome ◽  
Aplastic Anemia ◽  
Stem Cell Transplant ◽  
Bone Marrow Failure ◽  
Juvenile Myelomonocytic Leukemia ◽  
Cell Transplant ◽  
Bone Marrow Failure Syndrome ◽  
Base Pair Deletion

Abstract Mutations in TERC, the RNA component of telomerase, result in autosomal dominant dyskeratosis congenita (DC), a rare bone marrow failure syndrome. DC is clinically heterogeneous and TERC mutations have been detected in a subset of patients previously diagnosed with idiopathic aplastic anemia (AA) and myelodysplastic syndrome (MDS). Unrecognized TERC mutations are clinically relevant as patients with DC respond poorly to immunotherapy and have an increased risk of complications following conventional conditioning for stem cell transplant (SCT). We aimed to determine the frequency of TERC mutations in pediatric patients with AA and MDS who require a SCT. We obtained 315 blood or bone marrow samples from the National Donor Marrow Program Registry from children under age 18 with bone marrow failure who underwent an unrelated stem cell transplant. We screened these samples for mutations in the TERC gene using direct DNA sequencing. To exclude polymorphisms, we also screened 537 racially diverse healthy controls. The study group was composed of patients with MDS (n=151), AA (n=123), and juvenile myelomonocytic leukemia (JMML) (n=41), which may be difficult to distinguish from MDS. The mean age at the time of transplant was 9 years. We found sequence alterations in the promoter region of TERC in 2 patients. A 2 base pair deletion (-240delCT) was identified in a 4 year-old child with MDS and a 1 year-old child with JMML was found to have a point mutation (-99C→G), which was identified previously in an 18 year-old patient with paroxysmal nocturnal hemoglobinuria and is known to affect the Sp1 binding site. The pathogenicity of this mutation is unclear. In summary, our findings suggest that screening for TERC gene mutations is unlikely to diagnose occult DC in children with severe bone marrow failure who require a stem cell transplant but have no clinical features or history to suggest a familial bone marrow failure syndrome.

Lentiviral FANCA Vectors Pseudotyped with a Modified Prototype Foamy Viral Envelope Corrects Murine Fanca−/− Hematopoietic Stem Cells with Reduced Toxicity.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1677-1677
Author(s):  
Zejin Sun ◽  
Yanzhu Yang ◽  
Yan Li ◽  
Daisy Zeng ◽  
Jingling Li ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Gene Transfer ◽  
Ex Vivo ◽  
Bone Marrow Failure ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Ex Vivo Culture

Abstract Fanconi anemia (FA) is a recessive DNA repair disorder characterized by congenital abnormalities, bone marrow failure, genomic instability, and a predisposition to malignancies. As the majority of FA patients ultimately acquires severe bone marrow failure, transplantation of stem cells from a normal donor is the only curative treatment to replace the malfunctioning hematopoietic system. Stem cell gene transfer technology aimed at re-introducing the missing gene is a potentially promising therapy, however, prolonged ex vivo culture of cells, that was utilized in clinical trials with gammaretroviruses, results in a high incidence of apoptosis and at least in mice predisposes the surviving reinfused cells to hematological malignancy. Consequently, gene delivery systems such as lentiviruses that allow a reduction in ex vivo culture time are highly desirable. Here, we constructed a lentiviral vector expressing the human FANCA cDNA and tested the ability of this construct pseudotyped with either VSVG or a modified prototype foamyvirus (FV) envelope to correct Fanca−/− stem and progenitor cells in vitro and in vivo. In order to minimize genotoxic stress due to extended in vitro manipulations, an overnight transduction protocol was utilized where in the absence of prestimulation, murine Fanca−/− bone marrow cKit+ cells were co-cultured for 16h with FANCA lentivirus on the recombinant fibronectin fragment CH296. Transduction efficiency and transfer of lentivirally expressed FANCA was confirmed functionally in vitro by improved survival of consistently approximately 60% of clonogenic progenitors in serial concentrations of mitomycin C (MMC), irregardless of the envelope that was utilized to package the vector. Transduction of fibroblasts was also associated with complete correction of MMC-induced G2/M arrest and biochemically with the restoration of FancD2 mono-ubiquitination. Finally, to functionally determine whether gene delivery by the recombinant lentivirus during such a short transduction period is sufficient to correct Fanca−/− stem cell repopulation to wild-type levels, competitive repopulation experiments were conducted as previously described. Follow-up of up to 8 months demonstrated that the functional correction were also achieved in the hematopoietic stem cell compartment as evidenced by observations that the repopulating ability of Fanca−/− stem cells transduced with the recombinant lentivirus encoding hFANCA was equivalent to that of wild-type stem cells. Importantly, despite the fact that the gene transfer efficiency into cells surviving the transduction protocol were similar for both pseudotypes, VSVG was associated with a 4-fold higher toxicity to the c-kit+ cells than the FV envelope. Thus, when target cell numbers are limited as stem cells are in FA patients, the foamyviral envelope may facilitate overall greater survival of corrected stem cells. Collectively, these data indicate that the lentiviral construct can efficiently correct FA HSCs and progenitor cells in a short transduction protocol overnight without prestimulation and that the modified foamy envelope may have less cytotoxicity than the commonly used VSVG envelope.

ALDH2 Polymorphism In Japanese Children With Acquired Aplastic Anemia

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3717-3717
Author(s):  
Nozomu Kawashima ◽  
Atsushi Narita ◽  
Xinan Wang ◽  
Yinyan Xu ◽  
Hirotoshi Sakaguchi ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Aplastic Anemia ◽  
Categorical Data ◽  
Japanese Population ◽  
Bone Marrow Failure ◽  
Japanese Children ◽  
Hematopoietic Stem ◽  
Variant Alleles

Abstract Introduction Aplastic anemia is a syndrome of bone marrow failure (BMF) characterized by peripheral pancytopenia and marrow hypoplasia. Injury to hematopoietic cells, such as immune-mediated cytotoxicity, can cause aplastic anemia; the successful treatment of aplastic anemia using immunosuppressive therapy supports this hypothesis. Another proposed mechanism is an intrinsic defect of hematopoietic stem cells, which is the presumed major cause of congenital BMF, but this mechanism has not been definitively established in patients with acquired aplastic anemia. Aldehyde dehydrogenase 2 (ALDH2) deficiency resulting from a Glu504Lys substitution (A allele) is prevalent in the Japanese population: the A allele frequency is nearly 50% in the Japanese population. AA homozygotes show scarce catalysis of aldehydes, and GA heterozygotes display strongly reduced catalysis when compared with GG homozygotes. In patients with Fanconi anemia (FA), the most frequent inherited cause of BMF, progression of BMF was strongly accelerated in carriers of the GA and AA allele, possibly due to endogenous DNA damage caused by aldehydes that could not otherwise be repaired through the FA pathway. We studied the role of ALDH2 polymorphism in Japanese children with acquired aplastic anemia. Patients and Methods Seventy-nine Japanese children younger than 15 years who were referred to the Japanese Red Cross Nagoya First Hospital and Nagoya University Hospital were included in this study. Patients were excluded if they had paroxysmal nocturnal hemoglobinuria, toxic exposure to chemicals, or a clinical diagnosis of congenital BMF. Disease severity was classified based on the criteria of the International Aplastic Anemia Study Group as very severe (n = 10), severe (n = 41) and non-severe (n = 28). ALDH2 Glu487Lys polymorphisms (rs671) and alcohol dehydrogenases 1B (ADH1B) Arg47His polymorphisms (rs1229984) were genotyped with site-specific polymerase chain reaction with confronting two-pair primers. Statistical analysis was performed by Fisher’s exact test for categorical data and by Mann-Whitney U test for non-categorical data. P<0.05 was considered to indicate statistical significance. Results Forty children were genotyped with GG, 29 children with GA, and 10 children with AA. The distribution of the ALDH2 variant alleles in children with acquired aplastic anemia was not significantly different from the reported allele frequencies in the healthy Japanese population (GG = 1141, GA = 941, AA = 217; P = 0.4). However, age at diagnosis was significantly lower in children harboring AA (median 2 years, range 0.83-6 years) when compared with children harboring GG (median 10 years, range 1.6-16 years) and GA (median 10 years, range 1-14 years), respectively (P <0.01). In contrast, other clinical characteristics, including duration of disease onset to disease diagnosis, severity of the disease, and peripheral blood cell counts, were not significantly different among the ALDH2 groups. ADH1B may influence the concentration of aldehydes by catalyzing aliphatic alcohol. The ADH1B polymorphism (A allele) confers substantially higher enzymatic activity than the less active form (G allele), which is prevalent in Japanese, and thus may involve aldehyde toxicity. The distribution of the ADH1B variant alleles was not significantly different from the reported allele frequencies in the healthy Japanese population, and age at diagnosis of aplastic anemia was not significantly different among ADH1B variant allele groups in our cohort. Discussion ALDH2 catalyzes acetaldehyde as well as formaldehyde and other aldehydes, which can be genotoxic via DNA-protein crosslinking. Given that our cohort includes only children (alcohol intake is not a factor), intrinsic aldehydes that are mostly produced during lipid oxidation may damage hematopoietic stem cells, resulting in bone marrow failure. In conclusion, endogenous aldehydes may damage hematopoietic cells, resulting in early onset of disease in children with acquired aplastic anemia as well as in patients with FA. Disclosures: No relevant conflicts of interest to declare.

Comprehensive Analysis of Telomere Biology in Patients with Aplastic Anemia and Hypoplastic Myelodysplastic Syndrome: Further Evidence for a Common Mechanism

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2858-2858
Author(s):  
Anne-Sophie Bouillon ◽  
Monica S. Ferreira ◽  
Benjamin Werner ◽  
Sebastian Hummel ◽  
Jens P. Panse ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Myelodysplastic Syndrome ◽  
Aplastic Anemia ◽  
Bone Marrow Failure ◽  
Common Mechanism ◽  
Telomere Shortening ◽  
Hematopoietic Stem ◽  
Bone Marrow Failure Syndromes ◽  
The Individual

Abstract Introduction: Acquired aplastic anemia (AA) is typically characterized by pancytopenia and bone marrow (BM) failure mostly due to an autoimmune attack against the hematopoietic stem cell compartment. Thus, AA patients frequently respond to immunosuppressive therapy (IST). Hypoplastic myelodysplastic syndrome (hMDS) frequently mimics clinical and morphological features of AA and proper clinical discrimination of hMDS from AA sometimes remains difficult. Interestingly, some cases of hMDS respond at least partially to IST and on the other hand, AA can clonally evolve to hMDS. Telomeres shorten with each cell division and telomere length (TL) reflects the replicative potential of somatic cells. Whereas it is proposed that TL can to some degree discriminate hereditary subtypes of bone marrow failure syndromes from classical acquired forms, the role of TL for disease pathogenesis in hMDS remains unclear. In this study, we therefore aimed to investigate accelerated TL shortening as a possible (bio-)marker to distinguish hMDS from AA. Patients and Methods: TL of BM biopsies at diagnosis of 12 patients with hMDS and 15 patients with AA treated in the University Hospital Düsseldorf were analyzed. Mean age was 45.2 years in AA patients and 65.2 years in patients with hMDS. Confocal Q-FISH protocol was used for TL measurement as published previously (Blood, 2012). TL analysis was performed in single-blinded fashion. 28 patients (range 18-80 years) with newly diagnosed M. Hodgkin without BM affection were used as controls for linear regression and calculation of age-adapted TL difference. For the analysis of the data, we made use of a recently developed mathematical model of TL distribution on the stem cell level allowing us to extrapolate mean TL shortening per year (TS/y) based on the individual TL distributions of captured BM biopsies. Results: Using the controls to adjust for age, we found that age-adapted TL was significantly shortened both in patients with AA (median: -2.96 kb, range -4.21 to 0.26, p=0.001) and patients with hMDS (median: -2.26, range -3.85 to -0.64, p=0.005). In direct comparison, telomere shortening was more accelerated in patients with AA as compared to hMDS (p=0.048). Next, we analyzed the TL shortening per year (TS/y) based on the individual telomere distribution. Calculating the extrapolated TL shortening per year (TS/y), we found significant increased TS/y in AA patients (mean±SD: 235,8 bp/y±202,9, p=0.001) and hMDS patients (120,5±41,7 bp/y, p=0.0001) compared to controls (37,5±18,9 bp/y). Interestingly, the extrapolated rate of TS/y remained stable at different ages in hMDS patients as observed in healthy controls. In contrast, TS/y in AA patients showed a strong age-dependence with a maximum of TS/y in patients younger than 30 years (R²=0.42, p=0.008). Finally, we set to test whether TS/y can be used to identify AA or hMDS patients. Using 150 bp TS/y as a cut-off (4-fold the mean of controls), we found significantly more AA patients (10/15, 66.7%) had accelerated TL shortening compared to hMDS (1/12, 8.3% p=0.005). Conclusion: We provide first retrospective data on TL in patients with hMDS using confocal Q-FISH. Age-adapted TL is significantly shorter in patients with AA compared to hMDS. Interestingly, telomere shortening per year is both significantly increased in AA as compared to hMDS patients as well as in both groups compared to controls. The rate of telomere shortening TS/y might represent a new marker in patients with bone marrow failure syndromes that allows to discriminate AA from hMDS patients pending prospective validation. Disclosures No relevant conflicts of interest to declare.

scholarly journals The Role of Interferon, Inflammation and Infection in Aplastic Anemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. SCI-34-SCI-34
Author(s):  
Katherine C. MacNamara
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Aplastic Anemia ◽  
Hematopoietic Stem Cell ◽  
Chronic Infection ◽  
Type I ◽  
Bone Marrow Aplasia ◽  
Ifn Gamma ◽  
Hematopoietic Stem

Bone marrow failure (BMF) syndromes are a group of acquired and inherited diseases characterized by failed production of blood and immune cells, and profound bone marrow aplasia. Acquired BMF, including severe aplastic anemia (SAA), has been linked to radiation, chemical exposure, and infection, and the precise mechanisms of disease likely differ on a case-by-case basis. Inflammation and immune-mediated destruction of the marrow is a key driver of SAA, thus disease management centers on immunosuppressive therapy (IST) and, especially in young patients, bone marrow transplantation (BMT). However, not all patients are good transplant candidates and IST responsiveness varies, therefore, more specific treatments are necessary. HSC loss is a key feature of SAA, though it has been unclear if inflammation depletes HSCs directly or does so through the microenvironment. Interferons (IFNs) are proteins produced in response to microbial infections that play key roles in limiting pathogen spread and eradicating infections. While transient inflammatory responses and IFN production are often necessary for appropriate host defense, elevated levels of IFN-gamma (IFNγ) have long been associated with BMF syndromes, and type I IFNs (alpha and beta) are well documented to cause bone marrow aplasia during viral infection 1. In models of infection and inflammation IFNs can activate HSCs to proliferate and differentiate, but can also impair proliferation, and in both cases result in restricting HSC self-renewal 2-5. The precise mechanisms whereby IFNs mediate SAA and whether IFNs act directly on HSCs have remained elusive. In a mouse model of SAA driven by T cell-derived IFNγ we found that IFNγ-dependent HSC loss was associated with reduced marrow stromal cells, but a marked preservation of bone marrow-resident macrophages (MΦs) 6. Our data were consistent with findings from SAA patient marrow that also demonstrates MΦ persistence, despite significant reductions in nearly all other stromal and hematopoietic cell types 7. Moreover, we found that IFNγ was necessary for the maintained pool of MΦs. Depleting MΦs using Clodronate-loaded liposomes, or abrogating IFNγ signaling specifically in MΦs was shown to rescue HSCs and reduce SAA-associated mortality. Targeting MΦs during SAA improved thrombocytopenia, increased BM megakaryocytes, preserved platelet-primed HSCs, and increased the platelet-repopulating capacity of transplanted HSCs 6. During SAA IFNγ and MΦs were required for elevated levels of particular chemokines in the bone marrow, including CCL3, CCL4, and CCL5, which were further identified as downstream targets for mitigating SAA pathogenesis. The identification of MΦ function as a key determinant of IFNγ-dependent HSC loss in SAA furthers our understanding of disease pathogenesis and illustrates an important role for the microenvironment in SAA. These studies may reveal potential therapeutic strategies to complement current treatments for SAA that avoid generalized immunosuppression and potentially improve long-term outcomes. Smith JN, Kanwar VS, MacNamara KC. Hematopoietic Stem Cell Regulation by Type I and II Interferons in the Pathogenesis of Acquired Aplastic Anemia. Frontiers in immunology. 2016;7:330. Baldridge MT, King KY, Boles NC, Weksberg DC, Goodell MA. Quiescent haematopoietic stem cells are activated by IFN-gamma in response to chronic infection. Nature. 2010;465(7299):793-797. de Bruin AM, Demirel O, Hooibrink B, Brandts CH, Nolte MA. Interferon-gamma impairs proliferation of hematopoietic stem cells in mice. Blood. 2013;121(18):3578-3585. MacNamara KC, Jones M, Martin O, Winslow GM. Transient activation of hematopoietic stem and progenitor cells by IFNgamma during acute bacterial infection. PLoS One. 2011;6(12):e28669. Matatall KA, Jeong M, Chen S, et al. Chronic Infection Depletes Hematopoietic Stem Cells through Stress-Induced Terminal Differentiation. Cell reports. 2016;17(10):2584-2595. McCabe A, Smith JNP, Costello A, Maloney J, Katikaneni D, MacNamara KC. Hematopoietic stem cell loss and hematopoietic failure in severe aplastic anemia is driven by macrophages and aberrant podoplanin expression. Haematologica. 2018;103(9):1451-1461. Park M, Park CJ, Jang S, et al. Reduced expression of osteonectin and increased natural killer cells may contribute to the pathophysiology of aplastic anemia. Appl Immunohistochem Mol Morphol. 2015;23(2):139-145. Disclosures No relevant conflicts of interest to declare.

scholarly journals Generation of Dyskeratosis Congenita-like Hematopoietic Stem Cells through the Stable Inhibition of DKC1

2021 ◽  
Author(s):  
Carlos Carrascoso-Rubio ◽  
Hidde A. Zittersteijn ◽  
Laura Pintado-Berninches ◽  
Beatriz Fernández-Varas ◽  
M. Luz Lozano ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Bone Marrow Failure ◽  
Clinical Manifestations ◽  
Dyskeratosis Congenita ◽  
Bone Marrow Failure Syndrome ◽  
Hematopoietic Stem ◽  
Human Cd34 ◽  
Cd34 Cells

Abstract Dyskeratosis congenita (DC) is a rare telomere biology disorder, which results in different clinical manifestations, including severe bone marrow failure. To date, the only curative treatment for bone marrow failure in DC patients is allogeneic hematopoietic stem cell transplantation. However due to the toxicity associated to this treatment, improved therapies are recommended for DC patients. Here we aimed at generating DC-like human hematopoietic stem cells in which the efficacy of innovative therapies could be investigated. Because X-linked DC is the most frequent form of the disease and is associated with an impaired expression of DKC1, we have generated DC-like hematopoietic stem cells based on the stable knock-down of DKC1 in human CD34 + cells with lentiviral vectors encoding for DKC1 short hairpin RNAs. At a molecular level, DKC1 -interfered CD34 + cells showed a decreased expression of TERC, as well as a diminished telomerase activity and increased DNA damage, cell senescence and apoptosis. Moreover, DKC1 -interfered human CD34 + cells showed defective clonogenic ability and were incapable of repopulating the hematopoiesis of immunodeficient NSG mice. The development of DC-like hematopoietic stem cells will facilitate the understanding of the molecular and cellular basis of this inherited bone marrow failure syndrome, and will serve as a platform to evaluate the efficacy of new hematopoietic therapies for DC.

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