Evaluation of the Relationship between Clonal Hematopoiesis and Severe COVID-19 Disease in Rhesus Macaques

Abstract Clinical manifestations of infection with the novel SARS-CoV-2 in humans are widely varied, ranging from asymptomatic to COVID-19 respiratory failure and multiorgan damage. Profound inflammation is the hallmark of severe COVID-19 disease, and commonly does not occur until the second week of infection. Although risk factors for this late hyperinflammatory disease have been identified, most notably age and pre-existing co-morbidities, even within high-risk groups the specific factors leading to severe COVID-19 illness remain elusive. Acquired somatic mutations in hematopoietic stem and progenitor cells (HSPCs), termed clonal hematopoiesis (CH), are associated with advanced age, and loss of function (LOF) mutations in certain genes, most commonly DNMT3A and TET2, have been linked to a marked hyperinflammatory phenotype as well as clonal expansion of mutant HSPCs. Given the similar age range of frequent CH and severe COVID-19 disease, the presence of CH could impact the risk of severe COVID-19. Several human cohort studies have suggested this relationship may exist, but results to date are conflicting. Rhesus macaques (RM) have been established as a model for SARS-CoV infection and are being utilized to test therapies and vaccine development, but up to now, macaques have not been reported to develop late hyperinflammatory COVID-19 disease. We have created a robust RM model of CH by introducing LOF TET2 mutations into young adult HSPC via CRISPR/Cas9 followed by autologous transplantation, recapitulating the clonal expansion and hyperinflammatory phenotype. Thus, we hypothesized that macaques with CH could develop severe late COVID-19 disease and be utilized as a model to study disease pathophysiology or test therapeutic approaches. Macaques with either engineered (n=2) or natural CH (n=1) along with age-matched transplanted controls (n=3) were inoculated with SARS-CoV-2 and monitored clinically and via laboratory studies until 12 days post-inoculation (dpi). Macaques normally clear infection and symptoms within 3-5 days of infection. No significant differences in clinical symptoms and blood counts were noted, however, an aged animal with natural DNMT3A CH died on 10 dpi. IL-6 levels were somewhat higher in sera of the CH animals until 12 dpi, and in BAL, mean concentrations of MCP-1, IL-6, IL-8 and MIP-1b were consistently higher in CH macaques compared to controls. Interestingly, we found the median copy number of subgenomic SARS-CoV-2 RNA was higher at every timepoint in the CH group as compared with the control group, in both upper and lower respiratory samples. Lung sections from euthanasia at 10 or 12 dpi showed evidence of mild inflammation in all animals. However, in the immunohistochemical analysis, the viral antigen was detected in the lung tissues of all three animals in the CH group even at the time of autopsy, whereas only one animal of three controls had detectable viral antigen. Although the striking inflammation and serious disease have not been observed, data so far provide evidence of potential pathophysiological differences with or without CH upon SARS-CoV-2 infection. We continue to expand sample size and conduct further analyses to draw a solid conclusion, but we believe this model may be of benefit to understand the relationship between COVID-19 disease and CH. Disclosures No relevant conflicts of interest to declare.

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Aging, hematopoiesis, and the myelodysplastic syndromes

Blood Advances ◽

10.1182/bloodadvances.2017009852 ◽

2017 ◽

Vol 1 (26) ◽

pp. 2572-2578 ◽

Cited By ~ 12

Author(s):

Stephen S. Chung ◽

Christopher Y. Park

Keyword(s):

Myelodysplastic Syndromes ◽

Bone Marrow Failure ◽

Hematologic Malignancies ◽

Relative Increase ◽

Extrinsic Factors ◽

Hematopoietic Stem ◽

Clonal Hematopoiesis ◽

Increased Risk ◽

The Many ◽

The Relationship

Abstract The aging hematopoietic system undergoes numerous changes, including reduced production of red blood cells and lymphocytes as well as a relative increase in the production of myeloid cells. Emerging evidence indicates that many of these changes are due to selection pressures from cell-intrinsic and cell-extrinsic factors that result in clonal shifts in the hematopoietic stem cell (HSC) pool, resulting in predominant HSC clones that exhibit the functional characteristics associated with HSC aging. Given the recent descriptions of clonal hematopoiesis in aged populations, the increased risk of developing hematologic malignancies in individuals with clonal hematopoiesis, and the many similarities in hematopoietic aging and acquired bone marrow failure (BMF) syndromes, such as myelodysplastic syndromes (MDS), this raises significant questions regarding the relationship between aging hematopoiesis and MDS, including the factors that regulate HSC aging, whether clonal hematopoiesis is required for the development of MDS, and even whether BMF is an inevitable consequence of aging. In this article, we will review our current understanding of these processes and the potential intersections among them.

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Analysis of TCR Vgamma and Vdelta Repertoire and Clonality of T Cells in MDS Patients.

Blood ◽

10.1182/blood.v114.22.4833.4833 ◽

2009 ◽

Vol 114 (22) ◽

pp. 4833-4833

Author(s):

SuXia Geng ◽

Xin Du ◽

Yangqiu Li ◽

Jianyu Weng ◽

Liye Zhong ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Clonal Expansion ◽

Refractory Anemia ◽

Rt Pcr ◽

Hematopoietic Stem ◽

Discriminative Value ◽

Skew Distribution

Abstract Abstract 4833 Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis and frequent progression to acute myeloid leukemia. The pathophysiology of these syndromes remains poorly explained. The immune system also seems to contribute to the progressive cytopenias observed in MDS in some cases. We investigated the frequency and the discriminative value of TCR gamma and delta CDR3 clonality using RT-PCR and genescan technique in 40 MDS patients (24 male, 16 female),which included refractory anemia(n=1), refractory anemia with with ringed sideroblasts(n=6), refractory anemia with excess of blasts I (n=16)and II (n=17) respectively. The median age was 60 years (range 15-84).The results showed that 35(87.5%) MDS patients expressed all three TCR Vgamma subfamilies. Four(10%) and one(2.5%) MDS patients expressed two and one TCR Vgamma subfamilies respectively. Clonal expansion of T cells in some Vgamma subfamilies could be identified in 31 patients. The clonal expansion of Vgamma2 subfamily were identified most frequently. All the Vdelta subfamilies were absent in 2 MDS patients. The remaining 38 (95%) MDS cases expressed 0-6 Vdelta subfamilies. Vdelta1 and Vdelta2 were expressed most frequently followed by Vdelta8. While only 3(7.5%) patients expressed Vdelta5 subfamilies. Clonal expansion of Vdelta T cells were found in all MDS patients. The most frequent clonal expansion T cell was Vdelta3. In addition, 12 patients expressed monoclonal T cell Vdelta subfamily. Monoclonal expanded T cells were found in Vdelta3, Vdelta4, Vdelta6, Vdelta7 and Vdelta8 subfamilies. In summary,we found that MDS patients showed TCR Vgamma and delta skew distribution and clonal expansion. The absent of TCR Vdelta subfamily was more evident than TCR Vgamma subfamily. These findings provided further evidence that T cell mediated immune processes were a feature of MDS. Disclosures No relevant conflicts of interest to declare.

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A Modified HIV1-Based Lentiviral Vector Can Transduce Rhesus Hematopoietic Repopulating Cells as Efficiently as An SIV Vector in An Autologous Transplantation Model.

Blood ◽

10.1182/blood.v114.22.692.692 ◽

2009 ◽

Vol 114 (22) ◽

pp. 692-692

Author(s):

Naoya Uchida ◽

Phillip W Hargrove ◽

Kareem Washington ◽

Coen J. Lap ◽

Matthew M. Hsieh ◽

...

Keyword(s):

T Cells ◽

Blood Cells ◽

Conflicts Of Interest ◽

Lentiviral Vector ◽

Autologous Transplantation ◽

Vector System ◽

Transduction Efficiency ◽

Large Animal ◽

Hematopoietic Stem ◽

Cd34 Cells

Abstract Abstract 692 HIV1-based vectors transduce rhesus hematopoietic stem cells poorly due to a species specific block by restriction factors, such as TRIM5αa which target HIV1 capsid proteins. The use of simian immunodeficiency virus (SIV)-based vectors can circumvent this restriction, yet use of this system precludes the ability to directly evaluate HIV1-based lentiviral vectors prior to their use in human clinical trials. To address this issue, we previously developed a chimeric HIV1 vector (χHIV vector) system wherein the HIV1-based lentiviral vector genome is packaged in the context of SIV capsid sequences. We found that this allowed χHIV vector particles to escape the intracellular defense mechanisms operative in rhesus hematopoietic cells as judged by the efficient transduction of both rhesus and human CD34+ cells. Following transplantation of rhesus animals with autologous cell transduced with the χHIV vector, high levels of marking were observed in peripheral blood cells (J Virol. 2009 Jul. in press). To evaluate whether χHIV vectors could transduce rhesus blood cells as efficiently as SIV vectors, we performed a competitive repopulation assay in two rhesus macaques for which half of the CD34+ cells were transduced with the standard SIV vector and the other half with the χHIV vector both at a MOI=50 and under identical transduction conditions. The transduction efficiency for rhesus CD34+ cells before transplantation with the χHIV vector showed lower transduction rates in vitro compared to those of the SIV vector (first rhesus: 41.9±0.83% vs. 71.2±0.46%, p<0.01, second rhesus: 65.0±0.51% vs. 77.0±0.18%, p<0.01, respectively). Following transplantation and reconstitution, however, the χHIV vector showed modestly higher gene marking levels in granulocytes (first rhesus: 12.4% vs. 6.1%, second rhesus: 36.1% vs. 27.2%) and equivalent marking levels in lymphocytes, red blood cells (RBC), and platelets, compared to the SIV vector at one month (Figure). Three to four months after transplantation in the first animal, in vivo marking levels plateaued, and the χHIV achieved 2-3 fold higher marking levels when compared to the SIV vector, in granulocytes (6.9% vs. 2.8%) and RBCs (3.3% vs. 0.9%), and equivalent marking levels in lymphocytes (7.1% vs. 5.1%) and platelets (2.8% vs. 2.5)(Figure). Using cell type specific surface marker analysis, the χHIV vector showed 2-7 fold higher marking levels in CD33+ cells (granulocytes: 5.4% vs. 2.7%), CD56+ cells (NK cells: 6.5% vs. 3.2%), CD71+ cells (reticulocyte: 4.5% vs. 0.6%), and RBC+ cells (3.6% vs. 0.9%), and equivalent marking levels in CD3+ cells (T cells: 4.4% vs. 3.3%), CD4+ cells (T cells: 3.9% vs. 4.6%), CD8+ cells (T cells: 4.2% vs. 3.9%), CD20+ cells (B cells: 7.6% vs. 4.8%), and CD41a+ cells (platelets: 3.5% vs. 2.2%) 4 months after transplantation. The second animal showed a similar pattern with higher overall levels (granulocytes: 32.8% vs. 19.1%, lymphocytes: 24.4% vs. 17.6%, RBCs 13.1% vs. 6.8%, and platelets: 14.8% vs. 16.9%) 2 months after transplantation. These data demonstrate that our χHIV vector can efficiently transduce rhesus long-term progenitors at levels comparable to SIV-based vectors. This χHIV vector system should allow preclinical testing of HIV1-based therapeutic vectors in the large animal model, especially for granulocytic or RBC diseases. Disclosures: No relevant conflicts of interest to declare.

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Targeting FVIII Expression to Platelets Induces Immune Tolerance in Hemophilia A Mice with or without Pre-Existing Anti-FVIII Immunity,

Blood ◽

10.1182/blood.v118.21.4170.4170 ◽

2011 ◽

Vol 118 (21) ◽

pp. 4170-4170

Author(s):

Yingyu Chen ◽

Erin L. Kuether ◽

Jocelyn A. Schroeder ◽

Robert R. Montgomery ◽

David W. Scott ◽

...

Keyword(s):

Gene Therapy ◽

Immune Response ◽

Immune Tolerance ◽

Hemophilia A ◽

Conflicts Of Interest ◽

High Titer ◽

Control Group ◽

Hematopoietic Stem ◽

Therapy Strategy ◽

Inhibitory Antibodies

Abstract Abstract 4170 Our previous studies have shown that targeting FVIII expression to platelets (2bF8) can correct murine hemophilia A phenotype even in the presence of inhibitory antibodies. In the present study, we wanted to explore 1) whether platelets containing FVIII can act as an immunogen; and 2) whether platelet-derived FVIII can induce immune tolerance in a hemophilia A mouse model. To investigate whether platelets containing FVIII can act as an immunogen in hemophilia A mice, we infused transgenic mouse platelets with a level of platelet-FVIII of 6 mU/108 platelets to naïve FVIIInull mice weekly for 8 weeks. These platelets were between 30 to 50% of total platelets upon infusion and the levels of platelet-FVIII in the infused animals were 0.11 ± 0.01 mU/108 platelets (n = 6) one week after infusion. No anti-FVIII inhibitory antibodies were detected in the infused mice during the study course. All animals developed inhibitors following further challenged with recombinant human FVIII (rhFVIII) at a dose of 50 U/kg by intravenous injection weekly for 4 weeks, indicating that infusion of platelets containing FVIII does not trigger immune response in hemophilia A mice. To explore whether platelet-derived FVIII will act as an immunogen in the presence of primed spleen cells (from mice already producing inhibitory antibody), we co-transplanted splenocytes from highly immunized FVIIInull mice and bone marrow (BM) cells from 2bF8 transgenic mice into 400 cGy sub-lethal irradiated FVIIInull recipients. We monitored the levels of inhibitory antibodies in recipients for up to 8 weeks and found that inhibitor titers declined with time after transplantation. We then challenged co-transplantation recipients with rhFVIII and found that inhibitor titers in the control group co-transplantat of FVIIInull BM cells increased 103.55 ± 64.83 fold (n = 4), which was significantly more than the group receiving 2bF8 transgenic BM cells (14.34 ± 18.48, n = 5) (P <.05). The inhibitor titers decreased to undetectable in 40% of 2bF8 transgenic BM cells co-transplantation recipients even after rhFVIII challenge, indicating immune tolerance was induced in these recipients. To further explore the immune response in the lentivirus-mediated platelet-derived FVIII gene therapy of hemophilia A mice, we transduced hematopoietic stem cells from pre-immunized FVIIInull mice with 2bF8 lentivirus (LV) followed by syngeneic transplantation into pre-immunized lethally irradiated FVIIInull recipients and monitored the levels of inhibitor titers in recipients. After full BM reconstitution, platelet-FVIII expression was sustained (1.56 ± 0.56 mU/108platelets, n = 10), but inhibitor titers declined with time, indicating that platelet-derived FVIII does not provoke a memory response in FVIIInullmice that had previously mounted an immune response to rhFVIII. The t1/2 of inhibitor disappearance in 2bF8 LV-transduced recipients (33.65 ± 11.12 days, n = 10) was significantly shorter than in untransduced controls (66.43 ± 22.24 days, n = 4) (P <.01). We also transplanted 2bF8 LV-transduced pre-immunized HSCs into 660 cGy sub-lethal irradiated naïve FVIIInull mice. After BM reconstituted, recipients were assessed by platelet lysate FVIII:C assay and tail clip survival test to confirm the success of genetic therapy. Animals were then challenged with rhFVIII. Only 2 of 7 2bF8 LV-transduced recipients developed inhibitory antibodies (55 and 87 BU/ml), while all untransduced control developed high titer of inhibitors (735.50 ± 94.65 BU/ml, n = 4). In conclusion, our results demonstrate that 1) platelets containing FVIII are not immunogenic in hemophilia A mice; and 2) platelet-derived FVIII may induce immune tolerance in hemophilia A mice with or without pre-existing inhibitory antibodies. This tolerance induction would add an additional significant benefit to patients with platelet-derived FVIII gene therapy strategy because protein infusion could be administered in some special situations (e.g. surgery in which a greater levels of FVIII may be required) with minimized risk of inhibitor development. Disclosures: No relevant conflicts of interest to declare.

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Neutropenia Does Not Delay Lymphopoietic Regeneration in NODSCIDcγ−/− Mice

Blood ◽

10.1182/blood.v118.21.4831.4831 ◽

2011 ◽

Vol 118 (21) ◽

pp. 4831-4831

Author(s):

Stefanie Bugl ◽

Stefan Wirths ◽

R Müller Martin ◽

Märklin Melanie ◽

Tina Wiesner ◽

...

Keyword(s):

Bone Marrow ◽

Peripheral Blood ◽

Nk Cell ◽

Conflicts Of Interest ◽

Control Group ◽

Early Event ◽

Wild Type ◽

Hematopoietic Stem ◽

Lymphoid Progenitors ◽

Fate Decision

Abstract Abstract 4831 Introduction: Previously it was demonstrated that lymphopoiesis is rapidly established after transplantation of wild type stem cells into lymphopenic NODSCIDcγ−/− mice. These data were interpreted as evidence for an “empty” preformed lymphopoietic niche being replenished by lymphoid progenitors. We hypothesized that antibody-induced neutropenia might influence early post transplant fate decision to myeloid rather than lymphoid differentiation resulting in delayed lymphoid reconstitution. Materials and Methods: 25,000 flow sorted CD45.2-expressing wild type Lin-/Sca1+/c-Kit+ (LSK) cells from C57BL/6 mice were transplanted into sublethally irradiated B-/T-/NK-cell deficient NODSCIDcγ−/− mice (CD45.1). Three groups of n = 7 mice received anti-Gr1 or anti-1A8 i.p. every 48 h to induce continuous antibody-mediated neutropenia vs. PBS as control. Blood was harvested at regular intervals to monitor the engraftment. After 16, 22, and 34 days, animals were sacrificed and underwent blood and bone marrow analysis. Results: Hematopoietic regeneration started with the emergence of donor-derived monocytes in all groups as well as neutrophils in the control group as early as 9 days after transplantation. On day 14, B cells were to be detected for the first time, followed by T lymphocytes approximately 20 days after transplantation. Besides the fact that neutrophils were undetectable in the antibody treated groups, the peripheral blood revealed no significant changes between the neutropenic mice and the control group at any point of time. At the bone marrow level, an increase of LSK and granulocyte-macrophage progenitors (GMPs) at the expense of megakaryocyte erythrocyte progenitor cells (MEPs) was found in neutropenic mice. Common lymphoid progenitors (CLPs), however, were not significantly different. Conclusions: The engraftment of wild type donor cells after hematopoietic stem cell transplantation into NODSCIDcγ−/− mice started with the production of monocytes and neutrophils. B-lymphocytes were detectable by day 14 after transplantation. The production of T-cells started around day 20. Continuous antibody-mediated neutropenia did not significantly delay lymphoid regeneration. Although the marrow of neutropenic mice displayed increased proliferation of granulocyte progenitors, CLPs were unchanged. We conclude that the detection of donor-derived lymphocytes in the host peripheral blood is a relatively early event after LSK transplantation. Moreover, antibody induced neutropenia is not sufficient to induce sustainable changes in early hematopoietic fate decisions on the bone marrow level. Disclosures: No relevant conflicts of interest to declare.

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Utility of Telomere in Diagnosis of Bone Marrow Failure Syndromes

Blood ◽

10.1182/blood.v126.23.4793.4793 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4793-4793

Author(s):

Hasan Ahmed Abdel-ghaffar ◽

Hosam Zaghloul ◽

Ahmed El-Waseef ◽

Mohamed El-Naggar ◽

Mohamed Mabed ◽

...

Keyword(s):

Bone Marrow ◽

Telomere Length ◽

Conflicts Of Interest ◽

Bone Marrow Failure ◽

Quantitative Polymerase Chain Reaction ◽

Control Group ◽

Hematopoietic Stem ◽

Relative Telomere Length ◽

Bone Marrow Failure Syndromes ◽

Significant Difference

Abstract Background and aim of the work: Bone marrow failure syndromes (BMFS) includes inherited and acquired conditions. Inherited bone marrow failure includes a number of syndromes; with Fanconi anemia (FA) being the most common one of them. Telomeres are eroded with cell division, but in hematopoietic stem cell, maintenance of their length is mediated by telomerase. Short telomeres can result in instability of cell function where diseases occur. Bone Marrow Failure might be developed due to low telomerase activity or short telomeres. Our study is aiming to evaluate the utility of Real Time Quantitative-Polymerase Chain Reaction (RT-qPCR) in measuring the relative telomere length and its significance in diagnosis and prognosis of patients with BMFS. Materials and methods: The study includes 3 groups: A group of congenital BMF (29 patients), a group of acquired BMF (10 patients) and a third control group (15 cases). The relative telomere length is evaluated for them using RT-qPCR. Results: We have found that there is a significant difference in relative telomere length between congenital group and controls (p=0.001), also a significant difference between acquired group and controls (p= 0.029). However, there is no significant difference between congenital and acquired groups (p= 0.479). There is no significant correlation between the telomere length and the overall survival or prognosis of the patients of BMFS. Conclusion: We conclude that the telomere length is significantly altered in patients with BMFS whether being congenital or acquired compared to the control group. Disclosures No relevant conflicts of interest to declare.

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Clonal Events in Normal Aging Hematopoiesis

Blood ◽

10.1182/blood.v126.23.sci-10.sci-10 ◽

2015 ◽

Vol 126 (23) ◽

pp. SCI-10-SCI-10

Author(s):

Lambert Busque

Keyword(s):

Stem Cells ◽

Prognostic Significance ◽

Aging Population ◽

Clonal Expansion ◽

Normal Aging ◽

Myeloid Lineage ◽

Hematopoietic Stem ◽

Epigenetic Markers ◽

Clonal Hematopoiesis ◽

Age Related

Chronological aging of the hematopoietic compartment is associated with decreased bone marrow cellularity, reduced lymphopoiesis, increased anemia, a myeloid proliferation bias and an increased incidence of myeloid cancers. Beerman et al. proposed that this age-related myeloid lineage favoritism may be explained by clonal expansion of intrinsically myeloid-biased hematopoietic stem cells with robust self-renewal potential(1). This age-associated clonal expansion was initially suspected by X-chromosome inactivation (XCI) studies performed in the normal aging population, which documented a skewed XCI pattern in a significant proportion of women over 60 year-old(2). More recently, genome wide approaches led several groups to document au augmented prevalence of acquired clonal copy number changes (3,4,5) or clonal somatic mutations with increasing age (6,7,8,9). The most frequently mutated genes are the same as those documented in myeloid cancers, such as TET2, DNMT3A, ASXL1, PPM1D, GNAS, TP53, JAK2 and SF3B1 among others. The prevalence of these age-associated mutations may reach > 10% of older individuals, and is associated with an 11-12 fold increased relative risk of developing hematological malignancies. However, the actual problematic is to define the prognostic significance of these clonal mutations in the aging population. Steensma et al. proposed to consider these mutations as «Clonal Hematopoiesis of Indeterminate Potential (CHIP)»(10). The goal of our research group is to define the oncogenic penetrance of CHIP by applying a precision medicine approach in a large prospective cohort (n=4000) of aging individuals comprised of related and unrelated subjects. The variables under investigation include, clonality by XCI in women, deep sequencing (NGS) of myeloid cancer associated genes, epigenetic markers (5hmC, 5mC), telomere length, blood counts, heritability and outcome. PRELIMINARY RESULTS. XCI analyses Acquired skewing of XCI predominantly affects the myeloid lineage with a prevalence of 41.4% for PMN and is age dependent (r=0.15, P<10-4), in contrast to T cells 22.5%. These results support the idea of an age-associated clonal myeloid expansion. NGS of myeloid gene panel. We documented a prevalence of 17.9% of mutated individuals. Mutations were mainly documented in TET2 and DNMT3A which accounted for 90% of all identified mutations. Other significantly mutated genes included JAK2, ASXL1, CBL, TP53 and KRAS. Double mutations were identified in 2.5% of individuals (14% of the mutated individuals) and half of them had concomitant mutation in TET2 and DNMT3A. Age and XCI skewing was similar between subjects with mutation in TET2 or DNMT3A, but slightly higher in double mutants. Epigenetic markers. Subjects with mutation in TET2 had a significant reduction in 5hmC level that correlated with Variable Allele Frequency (VAF) of the mutation. No specific global epigenetic phenotype was documented in the DNMT3A mutation subgroup. We also documented an age-associated reduction in 5hmC that was independent of acquired mutation in the TET2 gene. Taken together these results indicate that age-associated clonal mutations involves predominantly two genes (TET2 and DNMT3A), suggesting that alteration of epigenetic maintenance is a central to the initiation of clonal dominance. Completion of investigation of the aging cohort and prospective follow-up will help characterize the link between aging hematopoiesis and the development of myeloid cancers. 1. Beerman I, Maloney WJ, Weissmann IL, et al. Stem cells and the aging hematopoietic system. Curr Opin Immunol. 2010;22(4):500-506. 2. Busque L, Mio R, Mattioli J, et al. Non-random X-inactivation patterns in normal females: lyonization ratios vary with age. Blood. 1996;88(1):59-65. 3. Forsberg LA, Rasi C, Razzaghian HR, et al. Age-related somatic structural changes in the nuclear genome of human blood cells. AJHG, 2012;90:217-228. 3. Laurie CC, Laurie CA, Rice K, et al. Detectable clonal mosaicism from birth to old age and its relationship to cancer. Nat Genet. 2012;44(6):642-650. 4. Jacobs KB, Yeager M, Zhou W, et al. Detectable clonal mosaicism and its relationship to aging and cancer. Nat Genet. 2012;44(6):651-658. 5. Busque L, Patel JP, Figueroa ME, et al. Recurrent somatic TET2 mutation in normal elderly individuals with clonal hematopoiesis. Nat Genet. 2012;444(11):1179-1181. 6. Xie M, Lu C, Wang J, et al. Age-related mutations associated with clonal hematopoietic expansion and malignancies. Nat Med. 2014;20(12):1472-1478. 7. Genovese G, Kähler AK, Handsaker RE, et al. Clonal hematopoiesis and blood-cancer risk inferred from blood DNA sequence. N Engl J Med. 2014;371(26):2477-2487. 8. Jaiswal S, Fontanillas P, Flannick J, et al. Age-related clonal hematopoiesis associated with adverse outcomes. N Engl J Med. 2014;371(26):2488-2498. 9.Steensma DP, Bejar R, Jaiswal S, et al. Clonal hematopoiesis of indeterminate potential and its distinction from myelodysplastic syndromes. Blood. 2015;126(1):9-16 Disclosures Busque: Pfizer: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau.

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Clonal Compensation Between Hematopoietic Stem Cells upon Differentiation Deficiency

Blood ◽

10.1182/blood.v128.22.422.422 ◽

2016 ◽

Vol 128 (22) ◽

pp. 422-422

Author(s):

Rong Lu ◽

Lisa Nguyen

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Blood Cell ◽

Cell Tracking ◽

Conflicts Of Interest ◽

Genetically Modified ◽

Cell Types ◽

Clonal Expansion ◽

Hematopoietic Stem ◽

Organ Systems

Abstract In most organ systems, regeneration is a coordinated effort that involves many stem cells, but little is known about how individual stem cells compensate for the functional deficiencies of other stem cells. Functional coordination between stem cells is critically important during disease progression and treatment when a subset of HSCs fail or become malignant. We hypothesize that individual HSCs heterogeneously compensate for specific deficiencies, as recent work from our group and others suggest that HSCs heterogeneously supply blood. To test this hypothesis, we tracked mouse HSCs in vivo using a single-cell tracking technology that we had previously developed. We found that individual HSCs heterogeneously compensate for the lymphopoiesis deficiencies of other HSCs by increasing individual clonal expansion and altering lineage bias. Clonal expansion refers to the increase in clonal progenies. Lineage bias refers to the preferential production of specific blood cell types. This compensation rescues the overall blood supply and influences blood cell types outside of the deficient lineages in distinct patterns. We identified the molecular regulators and signaling pathways associated with this form of HSC coordination using RNA sequencing. Specifically, the STAT3 pathway and NF-B signalingwere activated, and PTEN signaling was inhibited in HSCs during the compensation process. To investigate the dynamics of HSC coordination, we employed a genetically modified mouse model that expresses simian diphtheria toxin (DT) receptor under the control of the CD11b promoter. Monocytes derived from this mouse line can be ablated upon DT administration. We co-transplanted HSCs derived from normal and the genetically modified mice, then conditionally ablated the monocyte population repeatedly, and tracked the temporal responses of individual normal HSCs. Our time-course analysis revealed that a distinct subset of HSC clones produced rapid and persistent responses to the blood perturbations. These clones had not been highly active in the affected lineages prior to the perturbation. We identified several significant temporal profiles that indicate a remarkable heterogeneity in the responses of HSCs to blood system changes. Together, these data suggest that HSC differentiation is coordinated in a deterministic manner during compensation and is independent of the normal differentiation program. Our findings suggest that stem cells interact with each other and form a coordinated cellular network that is robust enough to withstand minor functional disruptions. Individual HSCs distinctly adapt their differentiation program to compensate for deficient HSCs and specifically overproduce undersupplied cell types. The heterogeneity in the compensation activities of individual HSC clones may be essential for maintaining robustness in blood regeneration and suggests that stem cell coordination is a complex process. A better understanding of the clonal level differences in individual HSCs is critically important for identifying the pathogenesis of blood diseases. Exploiting the innate compensation capacity of stem cell networks may improve the diagnosis and treatment of many diseases. For example, the identification of the molecular regulators and pathways involved in HSC compensation can help develop new therapeutic treatments that enhance the innate compensation capacity of stem cells. Disclosures No relevant conflicts of interest to declare.

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FoxM1 Haploinsufficiency Drives Clonal Hematopoiesis

Blood ◽

10.1182/blood-2019-128429 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 726-726

Author(s):

Chunjie Yu ◽

Yue Sheng ◽

Zhijian Qian

Keyword(s):

Cell Cycle ◽

Progenitor Cells ◽

Low Dose ◽

Conflicts Of Interest ◽

Clonal Expansion ◽

Brdu Incorporation ◽

Quiescent State ◽

Dapi Staining ◽

Hematopoietic Stem ◽

Increased Risk

Hematopoiesis is an orchestrated process in which hematopoietic stem cells (HSCs) can self-renew and produce all lineages of blood cells. Majority of HSCs are in a quiescent state with a low growth rate. However, some genetic mutations that occur in HSCs impel HSCs to exit the quiescent state and to proliferate excessively, which enables mutant HSCs to outcompete normal HSCs and leads to clonal expansion of mutant HSCs. Myelodysplastic syndromes (MDSs) as a clonal disease, arise from the expansion of mutant HSCs and are characterized by morphologic dysplasia, ineffective hematopoiesis and an increased risk of transformation to acute myeloid leukemia. FoxM1 is one of transcription factors in the family of Fox ('Forkhead box') proteins. Analysis of public database revealed that the expression level of FOXM1 was decreased significantly in CD34 + cells from a subset of patients with MDS as compared to healthy individuals. Thus, we sought to determine whether haploinsufficiency of FOXM1 contributes to the development of MDS in mice. Our study showed that haploinsufficiency of Foxm1 led to an expansion of hematopoietic stem/progenitor cells in mice. Since FoxM1 has previously been implicated in regulation of cell cycle, we determined the cell cycle status of Foxm1 heterozygous HSCs. By BrdU incorporation assay, we showed that Foxm1 heterozygous HSCs have an increased S phase and G2/M phase as compared to control HSCs from wildtype mice. Additional analysis with Hochest33342/Pyronin-Y staining and Ki67/DAPI staining showed a significant decrease in the number of quiescent (G0) cells in Foxm1 heterozygous HSCs as compared to control HSCs. These results suggest that FoxM1 haploinsufficiency promotes HSCs to exit quiescence and to enter cell cycle, thereby leading to exhaustion of HSCs. To further assess the function of Foxm1 heterozygous HSCs in vivo, we performed competitive repopulation assay. We found that Foxm1 haploinsufficiency HSCs exhibited competitive repopulation advantage in the first and secondary recipient mice, but displayed significantly decreased capacity of repopulation in tertiary recipient mice as compared to control HSCs, suggesting that Foxm1 haploinsufficiency promoted clonal expansion of HSCs, which leads to an exhaustion of HSCs eventually. HSC proliferation can be induced by some specific immune effectors such as Toll-like receptor 4 (TLR4). Lipopolysaccharide (LPS) stimulates HSC proliferation by activating TLR4 signaling pathway. Low dose of LPS treatment over time accelerated the development of MDS in mice. Interestingly, low dose of LPS injection chronically induced defects in hematopoiesis in Foxm1 haploinsufficient mice but not the control wildtype mice. Recipient mice transplanted with Foxm1 heterozygous BM cells but not the control BM cells developed MDS-like disease with cytopenia and a decreased number of hematopoietic stem/progenitor cells after LPS stimulation. Moreover, we found that nearly half of aged Foxm1 haploinsufficient mice (20 months) developed splenomegaly. Analysis of histologic sections in Foxm1 haploinsufficient mice showed that the mice developed hematopoietic dysplasia including dysplastic megakaryocytes with bizarre-shaped nuclei in bone marrow and extramedullary hematopoiesis with accumulation of myeloid cells in spleen. RNA-seq analysis indicated that haploinsufficiency of Foxm1 perturbed multiple stem cell-maintenance mechanisms especially in metabolic processes. Taken together, our studies suggest that Foxm1 haploinsufficiency in mice causes clonal expansion of HSCs and promotes MDS-like disease, which underscores the significant role of FOXM1 downregulation in the initiation and development of human MDS. Disclosures No relevant conflicts of interest to declare.

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The Impact of Aging of Hematopoietic Stem and Progenitor Cells (HSPCs) in Non-Human Primates As Interrogated By Genetic Barcode Clonal Tracking

Blood ◽

10.1182/blood.v126.23.1151.1151 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1151-1151

Author(s):

Kyung-Rok Yu ◽

Chuanfeng Wu ◽

Diego Espinoza ◽

Idalia Yabe ◽

Sandhya R. Panch ◽

...

Keyword(s):

Conflicts Of Interest ◽

Clustering Algorithms ◽

Autologous Transplantation ◽

Shannon Index ◽

Post Transplantation ◽

Hematopoietic Stem ◽

Poor Prognostic Factor ◽

Age Related ◽

Close Phylogenetic Relationship ◽

The Impact

Abstract Aging of the hematopoietic system is associated with a number of observations, including diminished regenerative potential, skewed lineage differentiation, increased incidence of anemia, and higher rates of neoplastic transformation. Despite advanced age being a strong poor prognostic factor, an increasing number of older patients are receiving hematopoietic stem and progenitor cell (HSPC) transplantation. Most previous investigations of the effects of aging on hematopoiesis have been obtained in murine models. The rhesus macaque is a powerful model to study human hematopoiesis and aging, based on a close phylogenetic relationship to humans, and similar telomere lengths, lifespans and aging phenotypes. To quantitatively elucidate the age-related changes that compromise hematopoietic function at a clonal level, we applied a genetic barcoding approach to quantitatively track the clonal behavior of HSPCs in young versus old macaques following autologous transplantation. We delivered high diversity barcodes via lentiviral transduction of CD34+ HSPC (detailed in our prior study: Wu et al Cell Stem Cell, 2014), allowing quantitative tracking of the output of thousands of individual HSPC clones labeled by unique barcodes, over time and in various lineages post-transplantation. We successfully transplanted barcoded HSPCs into 2 macaques aged 19 and 25 years, constituting "old" macaques based on an average lifespan in captivity of 20-30 years, and compared results to clonal patterns observed in 5 "young" macaques aged 3-5 years. Both old macaques engrafted promptly, and CD3+ T cells, CD3-CD20+ B cells, CD33+ Granulocytes (Gr), CD3-CD20-CD14+ Monocytes (Mo), and CD3-CD20-CD14-CD16+/or CD56+ NK cells were purified from the peripheral blood monthly following transplantation. In terms of overall polyclonality and diversity (Shannon index), analyzed through 4 months to date, there were no marked differences between the old and young recipients, with thousands of individual clones contributing to hematopoiesis in both sets of animals during the initial post-transplant time period studied. However, there were marked differences in the patterns of clonal lineage relationships between young and old animals, as assessed via pairwise Pearson correlations of all contributing clones as well as clustering algorithms allowing interrogation of patterns of clonal behavior. In both young and old, there was no correlation (i.e. no shared clones and thus no shared progenitors) between lineages at 1m, and clones contributing at 1m did not contribute to any lineage at 3m or later, indicating the existence of short-term, lineage-restricted progenitors in both age groups. By 3m in young animals, B and Gr/Mo became correlated, and by 3-6m, B/T/Mo/Gr multilineage clones appeared and constituted the majority of hematopoietic output. However, in old animals clones contributing to Gr/Mo versus B or T lineages remained almost completely distinct or markedly biased, up to 4m studied to date, without evidence for multi-lineage clones (Fig 1). In both young and old animals, the NK lineage remained clonally distinct, as previously reported for young animals. In summary, we transplanted 2 aged macaques with barcoded CD34+ HSPCs, and discovered a pattern of clonal reconstitution distinct from that in young animals, with persistent unilineage or highly-biased myeloid and B lymphoid progenitors in the aged animals. Longer follow-up will be required to determine if this biased pattern persists, and will be presented. This approach should improve our understanding of disorders of hematopoiesis in the elderly, and help improve transplantation and other therapies in this vulnerable patient population. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

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