Normal Adult Bone Marrow Research Articles

Normal Bone Marrow and Non-neoplastic Systemic Hematopoietic Disorders in the Adult.

This article provides an overview of the imaging appearances of normal adult bone marrow with an emphasis on magnetic resonance imaging. We also review the cellular processes and imaging features of normal developmental yellow-to-red marrow conversion and compensatory physiologic or pathologic red marrow reconversion. Key imaging features that differentiate between normal adult marrow, normal variants, non-neoplastic hematopoietic disorders, and malignant marrow disease are discussed, as well as posttreatment changes.

Whole Genome Bisulfite Sequencing of 63 Primary AML Samples Identifies a Unique DNA Hypermethylation Signature for Mutant IDH1/2 Cases That Is Different from That of TET2 Mutant AML

Mutations in IDH1, IDH2, and TET2 occur in more than 30% of AML patients, and are thought to contribute to leukemogenesis by disrupting TET2-mediated DNA demethylation, either directly or indirectly. While IDH1/2 and TET2 mutations are both predicted to result in hypermethylation, the specific methylation changes associated with these mutations are poorly understood. Additionally, we recently showed that CpG island (CGI) hypermethylation is common across virtually all AML subtypes, and it has been yet unclear whether IDH or TET2 hypermethylation is distinct from these 'generic', AML-associated changes. To investigate genome-wide methylation in IDH and TET2 mutated AML samples, we performed whole genome bisulfite sequencing (WBGS) on 15 primary AML samples with canonical IDH mutations (IDH1R132C, N=6; IDH1R132G, N=1; IDH2R140Q, N=7; and IDH2R172K, N=1) and 9 samples with biallelic loss-of-function mutations in TET2. These data were analyzed with WGBS data from primary CD34+ hematopoietic stem/progenitor cells (HSPCs) from 6 normal adult bone marrow donors, and 39 additional primary AML samples (representing 9 AML mutational categories) to define the methylation phenotypes specifically associated with IDH and/or TET2 mutations. Differential methylation analysis of each AML subtype vs. HSPCs identified a mean of 8,622 (53,73-13,773) AML-associated Differentially Methylated Regions (DMRs) in each mutational category (mean size: 986 bp), of which 6% to 97% were hypermethylated in the AML samples vs. HSPCs. IDH-mutant AML samples were the most hypermethylated subtype, with 97% of the 6,392 identified DMRs having increased methylation compared to HSPCs. The TET2-mutant samples were hypermethylated at fewer loci, representing 71% of the 5,892 identified DMRs vs HSPCs. Analysis of all AML subtypes demonstrated that 55% (16,275/29,534) of identified DMRs were shared across multiple subtypes, with more pronounced overlap among hypermethylated DMRs (>70%). To distinguish mutation-specific changes in IDH and TET2 mutated AMLs from commonly hypermethylated loci across AML subtypes, we conducted a joint analysis of either IDH or TET2 mutant AMLs with data from all other AML samples and normal HSPCs. We performed hierarchical clustering of the methylation values at each DMR, and used the clustering topology to identify DMRs where the single outlier branch represented either the IDH or TET2 AML samples. We identified 2,024 DMRs (mean size: 998 bp) specific to IDH mutant AML samples, of which 100% were hypermethylated with respect to normal HSPCs (mean DMR b value of 0.60 vs 0.35 in HSPCs). IDH outlier DMRs were enriched for functional genomic elements relative to the set of commonly hypermethylated loci, including CGIs (65% of DMRs; 2.4-fold enrichment) and potential enhancers marked by H3K27ac in HSPCs (82% of DMRs; 1.4-fold enrichment); overlap with promoter regions was reduced (20% of DMRs; 0.77-fold decrease). Outlier analysis of TET2 mutated samples demonstrated that most changes were also present in other AML types, with only 93 unique DMRs (mean size 552 bp), and a subtler hypermethylation phenotype (83% of DMRs were hypermethylated, with a mean b value of 0.51 vs. 0.32 in HSPCs). TET2 DMRs were also enriched for overlap with CGIs with respect to background, but to a lesser extent than IDH outliers (52% of DMRs; 1.9-fold). Intersection of IDH and TET2-associated DMRs showed that TET2-specific DMRs represented a subset of IDH hypermethylated regions, with 60% of TET2 DMRs overlapping a DMR independently identified in the IDH samples. Conversely, the vast majority of IDH outliers (97%) were identified only in IDH mutated AMLs. This comprehensive, genome-wide analysis demonstrates that IDH mutations result in a clear hypermethylation phenotype in primary AML samples that is far more expansive than the observed TET2-associated methylation changes. IDH-specific methylation changes were enriched for CGIs located outside of promoters and were distinct from the AML-associated CGI hypermethylation that occurs in other AML subtypes. TET2 mutations were associated with far fewer hypermethylated DMRs, and only a small fraction of mutation-specific changes occurred in bothIDH and TET2 samples. Our results demonstrate that the methylation phenotypes of IDH and TET2 mutant AML samples do not phenocopy, and suggest that IDH-associated hypermethylation must have a TET2-independent component. Disclosures No relevant conflicts of interest to declare.

Crucial Role of Increased Arid3a at the Pre-B and Immature B Cell Stages for B1a Cell Generation.

The Lin28b+Let7− axis in fetal/neonatal development plays a role in promoting CD5+ B1a cell generation as a B-1 B cell developmental outcome. Here we identify the Let7 target, Arid3a, as a crucial molecular effector of the B-1 cell developmental program. Arid3a expression is increased at pro-B cell stage and markedly increased at pre-B and immature B cell stages in the fetal/neonatal liver B-1 development relative to that in the Lin28b−Let7+ adult bone marrow (BM) B-2 cell development. Analysis of B-lineage restricted Lin28b transgenic (Tg) mice, Arid3a knockout and Arid3a Tg mice, confirmed that increased Arid3a allows B cell generation without requiring surrogate light chain (SLC) associated pre-BCR stage, and prevents MHC class II cell expression at the pre-B and newly generated immature B cell stages, distinct from pre-BCR dependent B development with MHC class II in adult BM. Moreover, Arid3a plays a crucial role in supporting B1a cell generation. The increased Arid3a leads higher Myc and Bhlhe41, and lower Siglec-G and CD72 at the pre-B and immature B cell stages than normal adult BM, to allow BCR signaling induced B1a cell generation. Arid3a-deficiency selectively blocks the development of B1a cells, while having no detectable effect on CD5− B1b, MZ B, and FO B cell generation resembling B-2 development outcome. Conversely, enforced expression of Arid3a by transgene is sufficient to promote the development of B1a cells from adult BM. Under the environment change between birth to adult, altered BCR repertoire in increased B1a cells occurred generated from adult BM. However, crossed with B1a-restricted VH/D/J IgH knock-in mice allowed to confirm that SLC-unassociated B1a cell increase and CLL/lymphoma generation can occur in aged from Arid3a increased adult BM. These results confirmed that in fetal/neonatal normal mice, increased Arid3a at the pre-B cell and immature B cell stages is crucial for generating B1a cells together with the environment for self-ligand reactive BCR selection, B1a cell maintenance, and potential for development of CLL/Lymphoma in aged mice.

CD200 Is a Marker of LSC Activity in Acute Myeloid Leukemia

Abstract Acute myeloid leukemia (AML) is a hierarchical disease in which the bulk blast population is sustained by a minority population of leukemia stem cells (LSC). Evidence of functional heterogeneity in the LSC compartment, including variable responses to chemotherapy, underscores the importance of examining the entire stem cell compartment in studies of LSC biology. However, there are currently no phenotypic markers that can consistently segregate LSCs within the leukemic blast population. Although LSC activity is most often enriched in the CD34+CD38- cell fraction, LSCs are also frequently detected in other phenotypic fractions, and in some cases are absent from CD34+ fractions. Thus, LSC studies that focus only on CD34+CD38- blasts may miss biologically important clones that are present in other phenotypic cell fractions. To identify novel markers that will enable better enrichment of LSC activity, we examined gene expression data obtained from functionally validated LSC+ and LSC- cell fractions sorted from primary AML samples, and identified CD200 as a candidate cell surface marker for LSCs. In normal adult bone marrow and cord blood samples, CD200 is expressed on >95% of CD34+CD38- cells, and expression decreases on CD34+38+ cells, suggesting that CD200, similar to CD34, is a stem cell marker. Flow cytometric analysis of AML patient samples (n=57) demonstrated that CD200 expression was present on a greater proportion of CD45dim blasts compared to CD45high non-blast populations (69.2% vs 4.5%, p<0.0001) and was significantly higher on CD34+ compared to CD34- cells (RFI 51.7 vs 3.5, p<0.0001). Although CD200 expression correlated with CD34 expression in many cases, some samples with low to no CD34 expression had high CD200 expression on CD45dim blasts, suggesting that CD200 can be used to identify CD34- LSCs. To test whether CD200 can segregate LSC activity within the CD45dim blast population, we sorted 14 primary AML samples into cell fractions based on CD45 and CD200 expression followed by transplantation into cohorts of NSG mice. AML samples were prescreened for leukemic engraftment ability and were selected for sorting if: 1) CD45dim blasts comprised both CD200+ and CD200- cells or 2) the CD200+ fraction was <5% of bulk cells. In 7 of 14 patients, LSC activity was enriched within the CD200+ fraction (CD200+ LSCs). For example, in AML40, in which CD200+ cells constituted only 5% of the bulk, as few as 5000 CD200+ blasts generated a leukemic graft at a mean level of 20.6%, whereas up to 500,000 CD200- blasts generated no graft. Importantly, LSC activity in these samples could not be segregated by CD34/CD38 expression; in contrast, the CD200+ fraction encompassed all cell fractions with LSC activity regardless of CD34/CD38 phenotype. In 1 of 14 patients, LSC activity was present in both the CD200+ and CD200- fractions. In the remaining 6 patients, LSC activity was enriched in the CD200- fraction (CD200- LSCs). In these samples, <3% of the bulk population expressed CD200; in 5 of the 6 samples, CD200+ cells generated multi-lineage (CD19+ B plus CD19‒CD33+ myeloid) rather than leukemic grafts, consistent with the presence of pre-leukemic-HSCs (preL-HSCs) in this cell fraction. In 2 additional AML patient samples that generated multi-lineage rather than leukemic grafts following transplantation of bulk cells, we refined our sorting strategy and were able to separate CD200+ LSCs from CD200+ preL-HSCs as evidenced by mutational analysis of xenografts. High CD200 expression was significantly associated with shorter overall survival in univariate analysis in multiple independent AML cohorts, but was not significant in multivariate analysis due to association with NPM1 mutation. NPM1-mutated samples exhibited low CD200 expression on the bulk cells. Interestingly, 7 of the 9 AML patients with CD200+ LSCs had normal karyotype and NPM1 mutation. Our results demonstrate that a CD200-based sorting strategy can successfully enrich and/or segregate LSC activity, and separate LSCs from preL-HSCs in primary AML patient samples. This will now enable direct functional studies of the biological properties of these related but distinct stem cell populations. Furthermore, CD200 will be a valuable tool for the study of LSCs in the subset of NPM1-mutated AML. Disclosures No relevant conflicts of interest to declare.

Human Non-Hematopoietic CD271pos/CD140alow/neg Bone Marrow Stroma Cells Fulfill Stringent Stem Cell Criteria in Serial Transplantations.

Human bone marrow contains a population of non-hematopoietic stromal stem/progenitor cells (BMSCs), which play a central role for bone marrow stroma and the hematopoietic microenvironment. However, the precise characteristics and potential stem cell properties of defined BMSC populations have not yet been thoroughly investigated. Using standard adherent colony-forming unit fibroblast (CFU-F) assays, we have previously shown that BMSCs were highly enriched in the nonhematopoietic CD271pos/CD140alow/neg fraction of normal adult human bone marrow. In this study, we demonstrate that prospectively isolated CD271pos/CD140alow/neg BMSCs expressed high levels of hematopoiesis supporting genes and signature mesenchymal and multipotency genes on a single cell basis. Furthermore, CD271pos/CD140alow/neg BMSCs gave rise to non-adherent sphere colonies (mesenspheres) with typical surface marker profile and trilineage in vitro differentiation potential. Importantly, serial transplantations of CD271pos/CD140alow/neg BMSC-derived mesenspheres (single cell and bulk) into immunodeficient NOD scid gamma (NSG) mice showed increased mesensphere numbers and full differentiation potential after both primary and secondary transplantations. In contrast, BMSC self-renewal potential decreased under standard adherent culture conditions. These data therefore indicate that CD271pos/CD140alow/neg BMSCs represent a population of primary stem cells with MSC phenotype and sphere-forming capacity that fulfill stringent functional stem cell criteria in vivo in a serial transplantation setting.

Bone marrow adipocytes promote hematopoietic regeneration by secreting SCF

Hematopoietic stem cells (HSCs) reside in a perivascular niche in adult bone marrow in which endothelial cells and LepR+ stromal cells are critical sources of niche factors, including SCF, that promote HSC maintenance. The bone marrow changes after myeloablation but how this affects the composition of the niche is unknown. While adipocytes are rare in normal young adult bone marrow they accumulate after irradiation. We discovered that this reflects increased proliferation by Adipoq-Cre/ER+ stromal cells after irradiation.

Signal characteristics of normal adult bone marrow in whole-body diffusion-weighted imaging.

Knowledge of the signal characteristics of normal adult bone marrow in whole-body diffusion-weighted (DW) images (WB-DWI) is essential for correctly interpreting DW images in clinical practice; however, these factors have not yet been clearly determined. To evaluate the signal characteristics of normal adult bone marrow in WB-DWI, to correlate these characteristics with age and gender, and to determine the causes of these phenomena. Ninety-eight healthy volunteers underwent WB-DWI (b = 0 and 800 s/mm(2)). Two radiologists visually evaluated the signal characteristics of bone marrow in DW images separately. One radiologist measured the apparent diffusion coefficient (ADC) of the thoracic and lumbar vertebrae, bilateral femur (including head, neck, and proximal and distal femoral shaft), bilateral humeral head, ilium, and scapula. The signal characteristics of normal bone marrow were analyzed. The visual evaluation results of DW images indicated that hyperintensity of bone marrow was more frequently seen in women aged 21-50 years (68.4%) than in men aged 21-50 years (3.3%) (P < 0.001), men aged 51-81 years (5.9%) (P < 0.001), and women aged 51-81 years (15.4%) (P = 0.001). However, no statistically significant difference was found between men and women aged 51-81 years (P = 0.565). The ADC of bone marrow was significantly higher in women than in men aged 21-50 years. Bone marrow ADC showed significant negative correlation with age in women but not in men. The signal intensity of bone marrow varies with age and gender in DW images. ADC and the T2 shine-through effect contributed to the bone marrow signal intensity in DW images, and the latter effect may predominate.

Clinical Significance of Bone Marrow Imaging of Appendicular Skeletons By Low-Dose Multi-Detector Computed Tomography in Patients with Bone Marrow Failure Syndrome

Background: Aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH) and myelodysplastic syndrome (MDS) are the heterogeneous group of bone marrow failure syndrome (BMFs). AS they often show profound hypocellular marrow, the diagnosis is often difficult by bone marrow and laboratory examination alone. Red to yellow marrow conversion occurs with age in the appendicular skeleton (AS), where red marrow is converted to yellow marrow until the age of early 20s. Although abnormal distribution of red marrow in appendicular skeleton were previously reported in small series of patients with MDS, leukemia and lymphoma by MRI, no further study has published so far. Here, we examined distribution of red marrow in AS by low-dose multi-detector CT (MDCT) in BMFs patients, and analyzed the relationship between the abnormal medullary pattern in AS and laboratory variables. The relationship between the MDCT pattern and subsequent development of leukemic transformation on survivals was analyzed in patients with BMFs.Patients: We retrospectively reviewed the medical records of 138 untreated patients (AA n=36, PNH n=5, and MDS n=97) with BMFs diagnosed in the Department of Hematology/Oncology at Kameda Medical Center, Kamogawa, Japan, from July 2008 to June 2014. Follow-up MDCTs were evaluated in 28 MDS patients when they were diagnosed as overt AML (MDS/tAML). Retrospective review of clinical and laboratory features including complete blood count, % of bone marrow blast, chromosomal analysis, and International Prognostic Scoring System (IPSS) at diagnosis was performed. WHO classification of patients with MDS was as follows: RCUD (n=21), RARS (n=2), RCMD (n=26), RAEB (n=43), and, MDS unclassified (MDS-U) (n=5). Leukemia-free survival (LFS) and overall survival (OS) were analyzed in 73 patients with MDS who were ≥65 years of age and ineligible for allogeneic stem cell transplantation (allo SCT) by the Kaplan-Meier.CT image acquisition and Image analysis: Non-enhanced CT examinations were performed from the skull to the knees by MDCT scanner (Aquilion 64, Tohshiba, Tokyo, Japan). Bony canal of humeral and femoral bone were visualized by coronal and sagittal axis image reconstruction. Medullary CT density of humerus and femurs were measured and the results were expressed as Hounsfield unit (HU). As the normal adult bone marrow was composed of rich adipocytes and called yellow marrow, it is represented by low density CT value between -30 to -100 HU. The value above -30 HU observed in long bony canals was considered as high density. Medullary pattern of AS were categorized as follows: (1) fatty pattern; showing a low signal density marrow (2) focal pattern; showing abnormally focal high density lesions (3) diffuse pattern; showing uniformly high density marrow.Results: All 36 patients with AA showed a fatty (n=13, 36.1%) or focal (n=23, 63.9%) pattern in medullary AS on MDCT, and none of them showed diffuse pattern. Five patients with PNH showed as follows: fatty/focal/diffuse, 1/3/1. Ninety-seven patients with MDS showed as follows: fatty/focal/diffuse, 24/46/27. Patients with MDS who showed diffuse pattern had a significantly low hemoglobin concentration compared to those with fatty or focal pattern (p=0.03). Among the patients with MDS, most of the patients with RCUD (n=21), RARS (n=2), RCMD (n=26), MDS-U (n=5) showed the fatty or focal pattern (fatty or focal/diffuse pattern; RCUD (18/3), RARS (2/0), RCMD (21/5), MDS-U (5/0)), but approximately half (46%) of patients with RAEB showed diffuse pattern (fatty/focal/diffuse pattern; 7/17/19). In addition, patients with transformed to MDS/tAML showed either focal (n=10, 35.7%) or diffuse (n=18, 64.3%) pattern and none of them showed fatty pattern. In 73 patients with MDS who were ≥65 years of age and ineligible for allo SCT, the group with focal or diffuse pattern had significantly shorter LFS and OS compared to the group with fatty pattern (p=0.01, p=0.05, respectively). Patients with focal pattern in AS showed longer LFS than those with diffuse pattern (p=0.05), but difference was not statistically significant in OS (p=0.22).Conclusions: This study showed that MDCT imaging of the appendicular skeletons provided important information for the diagnosis and prognosis of patients with BM. In patients with MDS, focal or diffuse pattern on MDCT showed negative prognostic impact on LFS and OS, and these patterns appeared to reflect the status of disease. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Clinical and Prognostic Significance of Bone Marrow Imaging of Appendicular Skeletons By Low-Dose Multi-Detector Computed Tomography in Patients with Aplastic Anemia and Myelodysplastic Syndorme

▪Background: Myelodysplastic syndrome (MDS) and aplastic anemia (AA) comprise a heterogeneous group of bone marrow failure disorders. As both show profound hypocellular marrow with minimal morphological atypia, differentiation of MDS and AA is often difficult by bone marrow and laboratory examination alone. Red to yellow marrow conversion occurs with age in the appendicular skeleton (AS), where red marrow is converted to yellow marrow until the early 20s. Although an abnormal distribution of red marrow in AS has previously been reported in small numbers of patients with MDS, along with leukemia and lymphoma by MRI, there have been no further reports to date. Here, we examined the distribution of red marrow in AS by low-dose multi-detector CT (MDCT) in AA and MDS. We analyzed the relationships between the abnormal medullary pattern in AS and laboratory variables, subsequent development of leukemic transformation, and survival in MDS patients.Patients: We performed low-dose MDCT of the humerus and femur in 103 untreated adult patients with AA (n = 32) and MDS (n = 71). We retrospectively reviewed the medical records of patients with AA and MDS diagnosed in the Department of Hematology/Oncology at Kameda Medical Center, Kamogawa, Japan, from July 2008 to June 2014. A retrospective review of clinical and laboratory features, including complete blood count, % bone marrow blasts, chromosomal analysis, and International Prognostic Scoring System (IPSS), was performed. WHO classification of MDS patients was as follows: RA (n = 22), RARS (n = 2), RCMD (n = 17), RAEB 1 (n = 18), RAEB 2 (n = 11), and MDS unclassified (n = 1). Overall survival (OS) and leukemia-free survival (LFS) were analyzed in 71 MDS patients by the Kaplan–Meier method and differences between curves were calculated by two-sided log-rank test.CT image acquisition and image analysis: Non-enhanced CT examinations were performed from the base of the skull down to the knee joint with an MS-CT scanner (AQUILION 64; Toshiba, Tokyo, Japan). The bony canals of the humeral and femoral bones were visualized by coronal and sagittal axis image reconstruction. The effective radiation dose associated with whole-body MD-CT was 10.1 mSv (ICRP 26). The dose was comparable to whole-body CT (2.4 mSv). Medullary CT density of the humerus and femur were measured and the results are expressed in Hounsfield units (HU). As the normal adult bone marrow was composed of rich adipocytes and called yellow marrow, it is represented by a low-density CT value between –30 and –100 HU. A value above –30 HU observed in long bony canals was considered to indicate a high-density lesion. The medullary pattern of the appendicular skeleton was categorized as follows: (1) fatty, showing a low signal density marrow; (2) focal, showing abnormally focal high-density lesions; (3) diffuse, showing uniformly high-density marrow.Results: All 15 patients with AA showed a fatty (n = 12, 37.5%) or focal (n = 20, 62.5%) pattern in medullary AS on MDCT, and none showed a diffuse pattern. Among the 71 patients with MDS, 22 (30.9%) had a fatty pattern, 32 (45.1%) had a focal pattern, and 17 (23.9%) had a diffuse pattern. Seventeen patients with diffuse infiltration pattern on MDCT had significantly shorter LFS (P < 0.01, P = 0.02) compared to 23 patients with fatty pattern and 32 patients with focal medullary pattern (median LFS: 18 months vs. not reached vs. not reached, respectively). Seventeen patients with a diffuse infiltration pattern on MDCT had significantly shorter OS (P = 0.04) compared to 23 patients with a fatty pattern, but the difference was no significant compared to 32 with a focal medullary pattern (P = 0.15) (median OS: 22 months vs. not reached vs. not reached, respectively). The characteristics of the patients with diffuse pattern did not differ significantly in terms of sex, age, WBC count, platelet count, karyotype, WT1, or IPSS classification from those of patients with a fatty or focal pattern, but patients with a diffuse infiltration pattern on MDCT had a significantly low hemoglobin concentration compared to those with a fatty or focal medullary pattern (P = 0.03).Conclusions: This study showed that MDCT imaging of the appendicular skeleton provided important information for the diagnosis and prognosis of patients with MDS and AA. In patients with MDS, a diffuse pattern on MDCT emerged as an independent negative prognostic indicator on LFS and OS. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Developmental Stage Specific B-Progenitor Expansion in Normal Fetal Bone Marrow Is Absent in Down Syndrome: Implications for Infant ALL

Although distinct fetal and adult B-cell lineage development has been demonstrated in murine studies, human fetal B-lymphopoiesis remains poorly understood. Previous work from our lab identified a population of PreProB progenitors (CD34+CD19+CD10-) in fetal liver (FL), co-existing with adult-type CD34+CD19+CD10+ ProB progenitors (Roy, A., Cowan G et al. PNAS: 109, 17579-17584; 2012). This supports other work demonstrating a PreProB progenitor population in normal cord blood (Sanz, E., et al. PNAS: 107, 5925-5930; 2010) and suggests that fetal pathways of B-cell development are also likely to be markedly different from adult bone marrow (AdBM) in humans. FL PreProB progenitors give rise solely to B-cells in vitro and display a gene expression pattern of successive activation of B-cell transcription factors as determined by Fluidigm RQ-PCR. In addition, increasing evidence indicates that infant ALL and many cases of childhood ALL arise in fetal life, suggesting that ontogeny-related changes in B-cell development may provide the cellular and microenvironmental context for in utero leukemia initiation.We therefore investigated B-cell development in normal human fetal BM from the onset of BM hematopoiesis in late first trimester. The composition and function of the early lymphoid and committed B-progenitor compartments of fetal BM(12-22 weeks; n=20) were compared with FL (n=25) at the same gestation, paediatric (Paed) BM (n=6) and AdBM (n=7), by multiparameter flow cytometry, differentiation in stromal co-culture assays and clonogenic assays. All stages of B-cell development were demonstrable in human fetal BM. However, there was a significantly higher frequency of B-progenitors in fetal BM (45.8±2.7% of CD34+ cells) compared to FL (10.3±0.97%; p<0.0001), PaedBM (28.2±4.2%; p=0.001) and AdBM (25.8±2.8%; p<0.0001). As in FL, both CD34+CD19+CD10- (PreProB) and CD34+CD19+10+ (ProB) progenitors were identified in fetal BM. PreProB progenitors were significantly higher in fetal BM (21.9±2.3% of CD34+ cells) compared to FL (3.8±0.4%), PaedBM (4.2±0.9%) and AdBM (3.4±0.9%) (p<0.0001 for all). Fetal BM PreProB progenitors gave rise solely to B-cells when co-cultured on MS5 stromal cells with FLT3L, SCF and IL7 in contrast to multilineage output of fetal BM HSC and LMPP cultured under identical conditions. Furthermore, fetal BM Lin-CD10-CD34+ cells cultured in vitro acquire CD19 expression before CD10 expression (n=6) consistent with a unique, fetal-specific B-cell differentiation pathway. The progressive decline in the proportion of PreProB progenitors from 47.8% to 36.8%, 14.8% and 13% of total B-progenitors in fetal BM, FL, PaedBM and AdBM respectively points towards a developmental stage-specific emergence of these progenitors. Finally, the fetal BM B-progenitor: B-cell ratio falls rapidly from ~4:1 at 12 weeks gestation to 1:1 at 18 weeks gestation as mature B-cell production in fetal BM gradually increases. This is consistent with a developmentally-regulated drive to B-progenitor proliferation, at the expense of differentiation, early in the second trimester which might represent a target population vulnerable to leukemic transformation in fetal life. Since children with Down syndrome (DS) do not develop infant ALL, we examined DS fetal BM as they may lack susceptible target cells for leukemic transformation. Consistent with this, PreProB progenitors in DS fetal BM (n=7) were >6-fold lower than normal fetal BM (3.3±0.8% vs. 21.9±2.3% of CD34+ cells; p<0.0001). Furthermore, CD19+ cells with an infant ALL-associated immunophenotype (CD19+CD10-CD20-) are detectable in normal fetal BM mononuclear cells, but are rarely found in DS fetal BM.Conclusion: There is a marked expansion of PreProB progenitors in normal second trimester human fetal BM which is virtually absent in DS fetal BM, in normal PaedBM and in normal AdBM. We suggest that developmentally-regulated, functional and molecular characteristics of these fetal-specific B-progenitors may provide the ‘oncogenic’ cellular context necessary to co-operate with genetic events, such as MLL rearrangements, to induce ALL in infants without DS. DisclosuresNo relevant conflicts of interest to declare.

Repetitive genomic elements and overall DNA methylation changes in acute myeloid and childhood B-cell lymphoblastic leukemia patients.

Aberrant epigenetic regulation is a hallmark of neoplastic cells. Increased DNA methylation of individual genes' promoter regions and decreases in overall DNA methylation level are both generally observed in cancer. In solid tumors, this global DNA hypomethylation is related to reduced methylation of repeated DNA elements (REs) and contributes to genome instability. The aim of the present study was to assess methylation level of LINE-1 and ALU REs and total 5-methylcytosine (5metC) content in adult acute myeloid leukemia (AML) (n = 58), childhood B-cell acute lymphoblastic leukemia (ALL) (n = 32), as the most frequent acute leukemias in two age categories and in normal adult bone marrow and children's blood samples. DNA pyrosequencing and ELISA assays were used, respectively. Global DNA hypomethylation was not observed in leukemia patients. Results revealed higher DNA methylation of LINE-1 in AML and ALL samples compared to corresponding normal controls. Elevated methylation of ALU and overall 5metC level were also observed in B-cell ALL patients. Differences of REs and global DNA methylation between AML cytogenetic-risk groups were observed, with the lowest methylation levels in intermediate-risk/cytogenetically normal patients. B-cell ALL is characterized by the highest DNA methylation level compared to AML and controls and overall DNA methylation is correlated with leukocyte count.

Adult, but not neonatal, human lymphoid progenitors respond to TLR9 ligation by producing functional NK-like cells

Remarkable progress has been made in characterizing factors controlling lineage fate decisions of primitive progenitors that initiate the lymphoid program in bone marrow. However, the understanding of neonatal/adult differences in environmental signals that influence differentiation pathway stability is still incomplete. Our recent findings suggest that Toll-like receptors provide a mechanism for producing cells of the innate immune system from early stages of lymphoid development in mice. We now show that both human early multilymphoid progenitors and more differentiated lymphoid progenitors from normal adult bone marrow express TLR9. Furthermore, they respond to its ligation by upregulating the expression of IL-15Rβ (CD122) and accelerating the production of functional natural killer (NK)-like cells. Proliferation of the presumed equivalent progenitor cells from umbilical cord blood was stimulated by CpG-containing oligonucleotides or herpes simplex virus, but the already robust NK-cell formation was unchanged. This new information adds to other known differences between neonatal and adult lymphoid progenitors and suggests only the latter replenish innate NK-like cells in response to Toll-like receptor agonists.

Bone Marrow Imaging of Appendicular Skeleton by Multi-Detector Computed Tomography in Patients with Aplastic Anemia and Hypoplastic MDS.

Abstract 2817 Background:Myelodysplastic syndrome (MDS) and aplastic anemia (AA) are the heterogeneous group of bone marrow failure disorders. AS both shows profound hypocellular marrow without minimal morphologic atypia, differentiation of MDS and AA is often difficult by bone marrow and laboratory examination alone. Red to yellow marrow conversion is occurs with age in the appendicular skeleton (AS), where red marrow is converted to yellow marrow until the age of early 20s. Although abnormal distribution of red marrow in appendicular skeleton has previously reported in small series of patients with MDS, leukemia and lymphoma by MRI, no further study has published so far. Here, we examined distribution of red marrow in AS by low-dose multi-detector CT (MDCT) in AA and MDS. We analyzed the relationship between the abnormal medullary pattern in AS with laboratory variables, subsequent development of leukemic transformation and survivals MDS patients. Patients:We performed a low-dose MDCT of humerus and femurs in 64 untreated adult patients with AA (N=15) and MDS (N=49). Retrospective review of clinical and laboratory features including complete blood count, % of bone marrow blast, chromosomal analysis, and International Prognostic Scoring System (IPSS) was performed. WHO classification of MDS patients was as follows: RA (N=17), RARS (N=2), RCMD (N=9), RAEB (N=19) and MDS unclassified (N=2). Overall survival (OS) and leukemia-free survival (LFS) were analyzed in 49 MDS patients by the Kaplan-Meier and differences between curves were calculated by two-sided log-rank test. Multivariate analysis was Used to assess the effects of prognostic factors - hemoglobin, platelet, bone marrow blast, cytogenetic abnormalities, IPSS score, WHO classification, and MDCT patterns. CT image acquisition and Image analysis:Non-enhanced CT examinations were performed from the base of skull down to the knee joint by MS-CT scanner (AQUILION 64, Tohshiba, Tokyo, Japan). Bony canal of humeral and femoral bone were visualized by coronal and sagittal axis image reconstruction. The effective radiation dose associated with whole body MD-CT was 10.1 mSv. (ICRP 26). The dose was comparable to whole body CT (2.4 mSv.). Medullary CT density of humerus and femurs were measured and the results were expressed as Hounsfield unit (HU). As the normal adult bone marrow was composed of rich adipocytes and called yellow marrow, it is represented by low density CT value between −30 to −100 HU. The value above −30 HU observed in long bony canals was considered as high density lesions. Medullary pattern of appendicular skeletons were categorized as follows: (1) fatty; showing a low signal density marrow (2) focal; showing abnormally focal high density lesions: (3) diffuse; showing uniformly high density marrow. Results:All 15 patients with AA showed a fatty (N=10, 66%) or focal (N=5, 33%) pattern in medullary AS on MDCT and none of them showed diffuse pattern. Conversion from fatty to focal marrow was observed in 9 of 15 AA patients after successful immunosuppressive treatment. Among the 49 patients with MDS, 15 (31%) had fatty pattern, 21 (43%) had focal pattern, and 13 (27%) had diffuse pattern. Patients with diffuse infiltration pattern on MDCT had a significantly low hemoglobin concentration (p<0.01) and shorter OS (p<0.01) compared to those with fatty or focal medullary pattern. The characteristics of the patients with diffuse pattern did not differ significantly in terms of sex, age, WBC count or karyotype from those of the patients with fatty or focal pattern. Among 13 MDS patients with diffuse pattern, 6 developed AML during their follow-up periods (median, 17 months; range, 2 to 38 months). LFS and OS of 13 patients with diffuse patterns were significantly shorter than that of the 36 patients with fatty and focal patterns (74% vs 19% at 3 years; p<0.01 and 79% vs 40% at 3 years; p<0.01, respectively). On multivariable analysis, diffuse pattern on MDCT was emerged as independently negative prognostic impact on LFS and OS in patients with MDS. Conclusions:This study showed that MDCT imaging of the appendicular skeletons provided important information for the diagnosis and prognosis of patients with MDS and AA. Disclosures:No relevant conflicts of interest to declare.

Chimeric Antigen Receptor for Specific Targeting of Acute Myeloid Leukemia

AbstractAbstract 4225Despite the progress in the treatment of acute myeloid leukemia (AML) achieved in the last decades, a significant number of patients are still refractory to or relapse after conventional chemotherapy regimens. Therefore it is necessary to develop novel alternative approaches. Immunotherapy with T cells genetically modified to express chimeric antigen receptors (CARs) represent a valid option in this sense. CARs are artificial T-cell receptors constituted by a specific antigen-binding domain, and a signaling region, that, upon antigen recognition, leads to T-cell activation, and lysis of the target cells. AML is a potential optimal target for CAR strategy because of the over-expression of a number of surface antigens like CD33, CD123. Since CD33 is also expressed on normal hematopoietic stem/progenitors cells (HSPCs) resulting in a potential severe impairment of normal myelopoiesis, CD123 has recently emerged as new potential attractive molecules based on its differential expression pattern, being still wildly overexpressed by AML population, and at the same time less expressed on HSPCs.Here we describe the in vivo efficacy and the safety of this approach based on Cytokine-Induced-Killers (CIK) cells genetically modified to express CAR molecules specific for the CD33 or CD123 antigen.Once injected into low-level AML engrafted NSG mice (median of hCD45+CD33+ 0.6% before treatment), genetically modify T cells had a potent antitumor effect. Indeed, the bone marrow of control untreated animals or mice treated with un-manipulated CIK cells, was infiltrated by leukemic cells (86% and 81% leukemic engraftment), while in 7/8 anti-CD33-CD28-OX40-ζ and 8/10 anti-CD123-CD28-OX40-ζ treated mice we couldn’t detect any AML cells.Similar results have been obtained when the treatment via T cell injection start when high AML burden has been obtained (median of hCD45+CD33+ 70% before treatment). One week after the last CIK’s injection the level of AML engraftment was 96%, 87%, 0.35% and 0.34% for untreated mice, mice treated with un-manipulated CIK cells and with anti-CD33-CD28-OX40-ζ and anti-CD123-CD28-OX40-ζ transduced CIK-cells respectively. We performed secondary transplantation on the residual AML cells present in these animals and mice were treated again with transduced CIK cells. Residual AML cells were still sensitive to CARs approach, leading once again to an almost complete eradication of the disease (median level of hCD45+CD33+ engraftment was 98%, 0.02% and 0.04% respectively for untreated mice, anti-CD33-CD28-OX40-ζ and anti-CD123-CD28-OX40-ζ transduced CIK-cells).Furthermore, a fundamental issue was to determine the safety profile of such approach against normal hematopoietic precursors.In untreated mice injected with primary cord blood derived CD34+ cells the level of engraftment of hCD45 compartment was 42% whilst in mice treated with un-manipulated, anti-CD33-CD28-OX40-ζ or anti-CD123-CD28-OX40-ζ transduced CIK-cells the levels of human compartment was 40%, 11.7% and 26.3% respectively. Moreover when we consider specifically the CD34+CD38- compartment, enriched in HSC, the level of engraftment was 1.92%, 1.02%, 0.55% and 0.83%. Secondary transplantations are now ongoing to give a more complete profile about the remaining HSC repopulating capability after treatment. To more closely mimic a physiological context, similar experiments are ongoing using mice engrafted with normal adult bone marrow instead of umbilical cord blood.These experiments should offer relevant information concerning the efficacy and safety of the proposed strategy particularly in the context of minimal residual disease in high-risk transplanted AML patients. Moreover CAR approach could be potentially used to treat patients resistant to conventional chemotherapeutic approaches or for whom high dose chemotherapy treatment could not be proposed. Disclosures:No relevant conflicts of interest to declare.

The Hemoglobin-Haptoglobin Receptor (CD163) Is Expressed by a Subpopulation of Erythroid and Granulo-Macrophagic Progenitors and Can Be Stimulated in Vitro and in Vivo by Physiological and Pharmacological Ligands to Stimulate Hematopoiesis

AbstractAbstract 1221The receptor for the hemoglobin (Hb)-haptoglobin (Hp) complex, CD163, is expressed on the surface of a subpopulation of hematopoietic stem/progenitor cells (HPCs) (Matthews et al, 2006). The purpose of the studies presented here were two-fold – to demonstrate that the CD34+CD163+ double positive population could be isolated from normal adult bone marrow cells and these cells were functional as HPCs and, in addition, that these cells could be stimulated in vivo by ligands to CD163 to affect hematopoiesis. To investigate the clonogenic potential of CD34+/CD163+ HPCs, bone marrow CD34+ cells were examined for CD163 co-expression, sorted by fluorescence activated cell sorting (FACS) and plated into colony-forming assays (CFAs). 4.2% ± 1.4% (n=4) of CD34+ cells were found to co-express CD163 and this population consisted of two distinct sub-populations, CD34++ (hi)CD163+ and CD34+(lo)CD163+, each of which represented approximately half of the total CD34+CD163+ population. All three sorted populations (CD34+(all)CD163−, CD34++(hi) CD163+, CD34+(lo)CD163+) were plated into CFAs (n=4) and were assessed for erythroid and myeloid colony formation. The clonogenic efficiency of CD34++(hi)CD163+ had a 2.5-fold increase in the number CFU-E and CFU-GM when compared to both CD34+ (total) CD163− and CD34+(lo) CD163+ cells. In contrast, CD34+(hi an low)CD163+cells produced fewer BFU-E.To determine how the expression of CD163 expression on progenitor cells may play a role in hematopoiesis, we investigated the effects of the natural ligand to CD163 (Hb/Hp) as well as an agonistic antibody to CD163 (TBI 304) on HPCs in vivo. NOD-scid IL2R gammanull (NSG) mice (HuMurine Technologies) were engrafted with human CD34+cells and animals with < 30% human CD45+ cells in the peripheral blood were administered either 2 mg Hb/mouse, or 100 or 500 μg/mouse TBI 304 every 4 days. At study termination (day 14), bone marrow cells (BMC) were examined by flow cytometry and enriched for CD34+ cells for enumeration in CFAs. Hb administration resulted in an increase of human CD34+cells ranging from 4% to 7% of BMC and a corresponding 57% increase in colony-forming cells (CFC) when compared to control (PBS-administered) animals. In contrast, TBI 304 produced a dose dependent decrease in CD34+ and CFC, possibly reflecting a depletion of CD34+/CD163+ cells from overstimulation due to the longer circulating antibody. To investigate this, human CD34+ cell engrafted animals were given a single dose of 10 or 100 μg/mouse of TBI 304 and bone marrow cells were examined on day 7. TBI 304 provided a 3.5-fold increase in human CD34+ cells as well as a 1.8 to 6.7-fold increase in bone marrow erythroid lineage engraftment (huGlyA+, huCD36+ and huCD71+) and a 2-fold increase in erythroid and myeloid colony-forming cells. No overall toxicities were observed with the administration of TBI 304 or Hb.We have demonstrated that CD163 is expressed on a population of CD34+ hematopoietic progenitor cells, these cells have increased hematopoietic progenitor activity in vitro and that administration of physiological or pharmacological agonists of the CD163 receptor can measurably stimulate hematopoiesis in vivo. Disclosures:Matthews:Therapure Biopharma: Employment. Bell:Therapure Biopharma: Employment.

Epigenetic inactivation of PLCD1 in chronic myeloid leukemia

PhospholipaseCδ1 (PLCD1), is located at the important tumor suppressor locus 3p22. It encodes an enzyme that mediates regulatory signaling of energy metabolism, calcium homeostasis and intracellular movements. PLCD1 has been studied in some human solid tumors relating to the CpG island methylation of the gene promoter as a functional tumor suppressor. However, no such information is available in chronic myeloid leukemia (CML). In this study, we investigated PLCD1 expression in the CML K562 cell line (0/1) and 15% (2/13) of bone marrow mononuclear cells with CML by using semi-quantitative PCR. The CpG island (CGI) methylation status of the PLCD1 promoter was detected in K562 (0/1) and 56% (23/41) of CML patients by methylation-specific PCR (MSP), but not in the normal adult bone marrow mononuclear cells. Furthermore, the DNA demethylation agent 5'-aza-2'deoxycytidine restored the expression of PLCD1 in K562 cells. Functional studies showed that ectopic expression of PLCD1 in K562 cells was able to dramatically inhibit their colony formation and induce cell cycle G1 arrest, suggesting that PLCD1 acts as a functional tumor suppressor and may serve as a biomarker for possible early detection and prognosis of CML.

A Novel Population of Cells Expressing Both Hematopoietic and Mesenchymal Markers Is Present in the Normal Adult Bone Marrow and Is Augmented in a Murine Model of Marrow Fibrosis

Bone marrow (BM) fibrosis is a feature of severe hyperparathyroidism. Consistent with this observation, mice expressing constitutively active parathyroid hormone (PTH)/PTH-related peptide receptors (PPR) in osteoblasts (PPR*Tg) display BM fibrosis. To obtain insight into the nature of BM fibrosis in such a model, a double-mutant mouse expressing constitutively active PPR and green fluorescent protein (GFP) under the control of the type I collagen promoter (PPR*Tg/GFP) was generated. Confocal microscopy and flow cytometry revealed the presence of a cell population expressing GFP (GFP(+)) that was also positive for the hematopoietic marker CD45 in the BM of both PPR*Tg/GFP and control animals. This cell population was expanded in PPR*Tg/GFP. The existence of cells expressing both type I collagen and CD45 in the adult BM was confirmed by IHC and fluorescence-activated cell sorting. An analysis of total RNA extracted from sorted GFP(+)CD45(+) cells showed that these cells produced type I collagen and PTH/PTH-related peptide receptor and receptor activator for NF-κB mRNAs, further supporting their features of being both mesenchymal and hematopoietic lineages. Similar cells, known as fibrocytes, are also present in pathological fibroses. Our findings, thus, indicate that the BM is a permissive microenvironment for the differentiation of fibrocyte-like cells and raise the possibility that these cells could contribute to the pathogenesis of BM fibrosis.

Functional characteristics of mesenchymal stem cells derived from bone marrow of patients with myelodysplastic syndromes

Mesenchymal stem cells (MSCs) have emerged as excellent candidates for clinical application because of their capabilities of immunomodulatory and supporting hematopoiesis. Nevertheless, it is unclear whether the characteristics of MSCs are altered in diseased states. In this study, we obtained and expanded MSCs from bone marrow of patients with myelodysplastic syndromes (MDS). Our results showed that MSCs derived from MDS (MDS–MSCs) were similar to normal adult bone marrow derived MSCs in morphology, growth property, surface epitopes, and differentiation ability in vitro. In addition, MDS–MSCs had normal karyotype and ultrastructure. However, MDS–MSCs appeared to be impaired in immunomodulatory and supporting hematopoiesis function. Although, MDS–MSCs could express hematopoietic cytokines and support hematopoiesis in long term culture, Real time quantitative polymerase chain reaction showed that the expression of hematopoietic cytokines in MDS–MSCs was much lower than that of normal adult derived MSCs. Moreover, MDS–MSCs showed reduced hematopoiesis support function, as compared to their normal counterparts. Lastly, the capacity of MDS–MSCs to inhibit T lymphocyte activation and proliferation was impaired in vitro. These results indicate that MDS–MSCs have impaired immunomodulatory and hematopoiesis support functions, suggesting their critical role in the pathogenesis of MDS.

ASH 2010 meeting report—Top 10 clinically oriented abstracts in transfusion medicine

ASH 2010 meeting report—Top 10 clinically oriented abstracts in transfusion medicine

Hematopoietic progenitors express embryonic stem cell and germ layer genes

Cell therapy for tissue regeneration requires cells with high self-renewal potential and with the capacity to differentiate into multiple differentiated cell lineages, like embryonic stem cells (ESCs) and adult somatic cells induced to pluripotency (iPSCs) by genetic manipulation. Here we report that normal adult mammalian bone marrow contains cells, with the cell surface antigen CD34, that naturally express genes characteristic of ESCs and required to generate iPSCs. In addition, these CD34+ cells spontaneously express, without genetic manipulation, genes characteristic of the three embryonic germ layers: ectoderm, mesoderm and endoderm. In addition to the neural lineage genes we previously reported in these CD34+ cells, we found that they express genes of the mesodermal cardiac muscle lineage and of the endodermal pancreatic lineage as well as intestinal lineage genes. Thus, these normal cells in the adult spontaneously exhibit characteristics of embryonic-like stem cells.