Zebrafish In-Vivo Screening for Compounds Amplifying Hematopoietic Stem and Progenitor Cells: - Preclinical Validation in Human CD34+ Stem and Progenitor Cells.

The identification of small molecules that either increase the number and/or enhance the activity of human hematopoietic stem and progenitor cells (hHSPCs) during ex vivo expansion remains challenging. We used an unbiased in vivo chemical screen in a transgenic (c-myb:EGFP) zebrafish embryo model and identified histone deacetylase inhibitors (HDACIs), particularly valproic acid (VPA), as significant enhancers of the number of phenotypic HSPCs, both in vivo and during ex vivo expansion. The long-term functionality of these expanded hHSPCs was verified in a xenotransplantation model with NSG mice. Interestingly, VPA increased CD34+ cell adhesion to primary mesenchymal stromal cells and reduced their in vitro chemokine-mediated migration capacity. In line with this, VPA-treated human CD34+ cells showed reduced homing and early engraftment in a xenograft transplant model, but retained their long-term engraftment potential in vivo, and maintained their differentiation ability both in vitro and in vivo. In summary, our data demonstrate that certain HDACIs lead to a net expansion of hHSPCs with retained long-term engraftment potential and could be further explored as candidate compounds to amplify ex-vivo engineered peripheral blood stem cells.

In Vivo Chemical Screen in Zebrafish Embryos Identifies Regulators of Hematopoiesis Using a Semiautomated Imaging Assay.

Hematopoietic stem and progenitor cells (HSPCs) generate all cell types of the blood and are crucial for homeostasis of all blood lineages in vertebrates. Hematopoietic stem cell transplantation (HSCT) is a rapidly evolving technique that offers potential cure for hematologic cancers, such as leukemia or lymphoma. HSCT may be autologous or allogenic. Successful HSCT depends critically on the abundance of engraftment-competent HSPCs, which are currently difficult to obtain in large numbers. Therefore, finding compounds that enhance either the number or the activity of HSPCs could improve prognosis for patients undergoing HSCT and is of great clinical interest. We developed a semiautomated screening method for whole zebrafish larvae using conventional liquid handling equipment and confocal microscopy. Applying this pipeline, we screened 550 compounds in triplicate for proliferation of HSPCs in vivo and identified several modulators of hematopoietic stem cell activity. One identified hit was valproic acid (VPA), which was further validated as a compound that expands and maintains the population of HSPCs isolated from human peripheral blood ex vivo. In summary, our in vivo zebrafish imaging screen identified several potential drug candidates with clinical relevance and could easily be further expanded to screen more compounds.

Adoptive transfer of allogeneic regulatory T cells into patients with chronic graft-versus-host disease.

BACKGROUND AIMS: Mouse models indicate that adoptive transfer of regulatory T cells (Treg) may suppress graft-versus-host-disease (GvHD) while preserving graft-versus-leukemia reactions. We aimed to develop a protocol for the efficient isolation and in vitro expansion of donor-derived Treg and to establish the proof-of-concept for the clinical application of ex vivo-generated Treg preparations in five patients with otherwise treatment-refractory chronic GvHD (cGvHD). METHODS: Allogeneic Treg were isolated from unstimulated leukapheresis products of the corresponding human leukocyte antigen-matched donors by use of clinical-grade magnetic-activated bead sorting. To increase the amount and purity, Treg were cultivated for 7-12 days and infused after a median time of 35 months after allogeneic hematopoietic cell transplantation. RESULTS: Final products contained Treg with a median purity of 84.1% CD4(+)CD25(high)CD127(low)FOXP3(+)of CD45(+) cells and a mean quantity of 2.4 × 10(6) Treg per kg body wt. All isolated cell products showed in vitro suppressive activity. On transfusion, two of five patients showed a clinical response with improvement of cGvHD symptoms. The other three patients showed stable cGvHD symptoms for up to 21 months. In four of five patients, increased counts of Treg were detectable on Treg transfusion, immunosuppressive treatment could be reduced and suppression of CD69 activation marker expression on T-effector cells was observed. However, one patient had development of malignant melanoma and another patient had Bowen skin cancer 4 months and 11 months after Treg transfusion, respectively. CONCLUSIONS: We demonstrate a feasible and reproducible approach of isolating functional Treg in high quantity and purity for clinical application and show opportunities and risks of adoptive Treg transfer into patients with cGvHD.

Allogeneic stem cell transplantation for the treatment of refractory scleromyxedema.

Scleromyxedema is a rare disorder of connective tissue with unknown etiology. Its manifestation includes a generalized mucin deposition, which is frequently associated with paraproteinemia. The course of scleromyxedema is progressive and often lethal. As a result of its poorly understood pathogenesis, there is no causative treatment option. The efficacy of cytoreductive agents and autologous stem cell transplantation has been reported, but so far allografting as a treatment option has not yet been documented. Herein, we report on a patient with severe neurologic involvement and refractory course attaining durable remission after receiving an allogeneic hematopoietic cell transplant from an human leukocyte antigen-matched sibling. This case not only illustrates a potential new treatment option for selected patients, but also provides insights into the pathogenesis of this rare disease.

Monitoring of hematopoietic chimerism after transplantation for pediatric myelodysplastic syndrome: real-time or conventional short tandem repeat PCR in peripheral blood or bone marrow?

Quantitative real-time PCR (qPCR) has been proposed as a highly sensitive method for monitoring hematopoietic chimerism and may serve as a surrogate marker for the detection of minimal residual disease minimal residual disease in myelodysplastic syndrome (MDS), until specific methods of detection become available. Because a systematic comparison of the clinical utility of qPCR with the gold standard short tandem repeat (STR)-PCR has not been reported, we retrospectively measured chimerism by qPCR in 54 children transplanted for MDS in a previous study. Results obtained by STR-PCR in the initial study served as comparison. Because the detection limit of qPCR was sufficiently low to detect an autologous background, we defined the sample as mixed chimera if the proportion of recipient-derived cells exceeded .5%. The true positive rates were 100% versus 80% (qPCR versus STR-PCR, not significant), and mixed chimerism in most cases was detected earlier by qPCR than by STR-PCR (median, 31 days) when chimerism was quantified concurrently in peripheral blood and bone marrow. Both methods revealed a substantial rate of false positives (22.7% versus 13.6%, not significant), indicating the importance of serial testing of chimerism to monitor its progression. Finally, we propose criteria for monitoring chimerism in pediatric MDS with regard to the subtypes, specimens, PCR method, and timing of sampling.

CXCR4 blockade and sphingosine-1-phosphate activation facilitate engraftment of haematopoietic stem and progenitor cells in a non-myeloablative transplant model.

Both immunosuppressive and cytoreductive effects of γ-irradiation contribute to engraftment of allogeneic haematopoietic stem and progenitor cells. We hypothesized that a release of host stem and progenitor cells from the niche prior to conditioning would permit engraftment after less intensive conditioning. Administration of AMD3100 and SEW2871 on days -4 to -2 followed by irradiation on day -1 in a non-myeloablative zebrafish transplant model resulted in a reduced radiation minimum dose of 10 Gy from 15 Gy being sufficient for engraftment. Targeting the SDF-1 (CXCL12)/CXCR4- and S1P/S1P1 -axis increased the efficacy of allografting in an experimental transplant model.

The level of residual disease based on mutant NPM1 is an independent prognostic factor for relapse and survival in AML.

Mutations of the NPM1 gene (NPM1mut) are among the most common genetic alterations in acute myeloid leukemia and are suitable for minimal residual disease detection. We retrospectively investigated the prognostic impact of NPM1mut-based minimal residual disease detection from bone marrow for development of relapse by using a newly developed real-time polymerase chain reaction based on locked nucleic acid-containing primers in 174 patients, 155 of whom were treated within prospective protocols. The prognostic value of 5 cutoff values after completion of treatment or after allogeneic transplantation was studied by using cause-specific hazard models. Subsequent validation using cross-validated partial likelihood analysis revealed that an increase of more than 1% NPM1mut/ABL1 was most prognostic for relapse after chemotherapy, whereas an increase of more than 10% NPM1mut/ABL1 was most prognostic for relapse after allogeneic transplantation. Univariate and multivariate analysis of disease-free survival and overall survival revealed a significantly worse outcome in patients with >1% NPM1mut/ABL1 and >10% NPM1mut/ABL1, respectively, which remained significant after adjustment for FLT3-internal tandem duplication status. Our results in a large data set define and optimize cutoff values for early diagnosis of molecular relapse. These results may be especially important for defining triggers for early therapeutic intervention.

Reconstitution of interleukin-17-producing T helper cells after allogeneic hematopoietic cell transplantation.

Interleukin 17A (IL-17)-producing CD4(+) T helper type 17 (Th17) cells have recently drawn attention as possible effector cells of acute graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT) in murine models. Their role after allogeneic HCT in humans is unknown. In this prospective study, Th17, Th1/17, and Th1 cells were quantified in the peripheral blood of 80 patients within the first 3 months after allogeneic HCT using intracellular cytokine staining and flow cytometry. Within the observation period, Th1, Th1/17, and Th17 cells did not reconstitute to levels of healthy control subjects. In contrast to Th1 cells, no further expansion of Th1/17 and Th17 cells was observed during the first month after HCT. Antithymocyte globulin during conditioning significantly reduced the frequency of Th1/17 and Th17 cells but not of Th1 cells. Acute GVHD was not associated with significant changes in the size of the Th1, Th1/17, or Th17 cell subsets. Cytomegalovirus reactivation triggered the expansion of all T helper subsets, and Th1 cells showed the strongest increase. In contrast, no significant changes were found in the T helper cell compartment of patients with bacterial infections compared with time-matched control subjects. In conclusion, quantitative reconstitution of Th1, Th1/17, and Th17 cells is impaired within the first 3 months after HCT, especially when antithymocyte globulin is administered during conditioning. Cytomegalovirus reactivation, but not acute GVHD or bacterial infection, triggered the absolute expansion of these T cell subsets.

Reconstitution of 6-sulfo LacNAc dendritic cells after allogeneic stem-cell transplantation.

BACKGROUND: Infections and acute graft-versus-host disease (GvHD) represent major complications of allogeneic stem-cell transplantation (SCT). Dendritic cells (DCs) display an extraordinary capacity to induce innate and adaptive immune responses. Therefore, they play a crucial role in the elimination of pathogens and in the pathogenesis of acute GvHD. 6-Sulfo LacNAc DCs (slanDCs) are a major subpopulation of human blood DCs with a high proinflammatory capacity. We investigated for the first time the reconstitution of slanDCs in the blood of patients after SCT and the modulation of their frequency by bacterial infection, cytomegalovirus (CMV) reactivation, and acute GvHD. METHODS: The frequency of slanDCs, CD1c myeloid DCs (mDCs), and plasmacytoid DCs (pDCs) in the peripheral blood was quantified by flow cytometry in 80 patients after SCT. To assess individual DC subsets, we used pregating of the HLADRLin subset and antibodies against slanDCs, blood DC antigen 1 (CD1c mDCs), and blood DC antigen 2 (pDCs). RESULTS: SlanDCs showed the slowest reconstitution in the first month after SCT compared with CD1c mDCs and pDCs. Interestingly, in the second and third months after SCT, their percentage steadily increased, and slanDCs were the most abundant DC subset. In addition, we observed a markedly reduced frequency of slanDCs in the blood of patients with bacterial infection, CMV reactivation, or severe acute GvHD. Furthermore, slanDCs showed the most prominent reduction after steroid treatment of acute GvHD. CONCLUSIONS: These results indicate that SCT-associated complications such as bacterial infection, CMV reactivation, and acute GvHD can significantly modulate the frequency of slanDCs.

Sequence polymorphism systems for quantitative real-time polymerase chain reaction to characterize hematopoietic chimerism-high informativity and sensitivity as well as excellent reproducibility and precision of measurement.

Sequence polymorphisms (SPs) can serve as genetic markers for quantitative polymerase chain reactions (qPCR) for chimerism analysis, providing a significantly higher sensitivity compared to short tandem repeat PCR. In this study, a panel of 29 selected markers was evaluated in 317 patients with leukemia and myelodysplastic syndrome, who received allogeneic stem cell transplantation. In total, 5415 posttransplantation samples were analyzed. Recipient genotype discrimination was possible in 96% with a mean number of 2.5 (1-7) informative markers per recipient/donor pair. Marker specific standard dilution series from volunteers' DNA served as standard for quantification of chimerism. Sensitivity of the method was < or =1 x 10-3 (0.1% of recipient cells) in 83.3% of the assays. By this method, it was possible to very accurately detect autologous signals in the range from 0% to 0.5% (95% confidence interval [CI] +/-0.2), from 0.5% to 1% (95% CI +/-0.4), from 1% to 2% (95% CI +/-0.6) and from 2% to 5% (95% CI +/-1.2). Reproducibility of the quantified autologous signals was independent from the amount of DNA. This is the first report on a SP-based chimerism system allowing for the performance of chimerism analyses for virtually all patients with high sensitivity, excellent reproducibility, and precision of measurement.