Genome-wide promoter DNA methylation dynamics of human hematopoietic progenitor cells during differentiation and aging.

DNA methylation plays an important role in the self-renewal of hematopoietic stem cells and in the commitment to the lymphoid or myeloid lineages. Using purified CD34⁺ hematopoietic progenitor cells and differentiated myeloid cell populations from the same human samples, we obtained detailed methylation profiles at distinct stages of hematopoiesis. We identified a defined set of differentiation-related genes that are methylated in CD34⁺ hematopoietic progenitor cells but show pronounced DNA hypomethylation in monocytes and in granulocytes. In addition, by comparing hematopoietic progenitor cells from umbilical cord blood to hematopoietic progenitor cells from peripheral blood of adult donors we were also able to analyze age-related methylation changes in CD34⁺ cells. Interestingly, the methylation changes observed in older progenitor cells showed a bimodal pattern with hypomethylation of differentiation-associated genes and de novo methylation events resembling epigenetic mutations. Our results thus provide detailed insight into the methylation dynamics during differentiation and suggest that epigenetic changes contribute to hematopoietic progenitor cell aging.

Adipogenic differentiation of human mesenchymal stromal cells is down-regulated by microRNA-369-5p and up-regulated by microRNA-371.

Long-term culture of human mesenchymal stromal cells (MSC) has implications on their proliferation and differentiation potential and we have demonstrated that this is associated with up-regulation of the five microRNAs miR-29c, miR-369-5p, miR-371, miR-499, and let-7f. In this study, we examined the role of these senescence-associated microRNAs for cellular aging and differentiation of MSC. Proliferation was reduced upon transfection with miR-369-5p, miR-371, and miR-499. Adipogenic differentiation was impaired by miR-369-5p whereas it was highly increased by miR-371. This was accompanied by respective gene expression changes of some adipogenic key molecules (adiponectin and fatty acid-binding protein 4 [FABP4]). Furthermore luciferase reporter assay indicated that FABP4 is a direct target of miR-369-5p. Microarray analysis upon adipogenic or osteogenic differentiation revealed down-regulation of several microRNAs albeit miR-369-5p and miR-371 were not affected. Expression of the de novo DNA methyltransferases DNMT3A and DNMT3B was up-regulated by transfection of miR-371 whereas expression of DNMT3A was down-regulated by miR-369-5p. In summary, we identified miR-369-5p and miR-371 as antagonistic up-stream regulators of adipogenic differentiation and this might be indirectly mediated by epigenetic modifications.

Characterization of hematopoietic stem cell subsets from patients with multiple myeloma after mobilization with plerixafor.

BACKGROUND AIMS: Previous studies have demonstrated that the combination of granulocyte-colony-stimulating factor (G-CSF) + plerixafor is more efficient in mobilizing CD34(+) hematopoietic stem cells (HSC) into the peripheral blood than G-CSF alone. In this study we analyzed the impact of adding plerixafor to G-CSF upon the mobilization of different HSC subsets. METHODS: We characterized the immunophenotype of HSC subsets isolated from the peripheral blood of eight patients with multiple myeloma (MM) before and after treatment with plerixafor. All patients were supposed to collect stem cells prior to high-dose chemotherapy and consecutive autologous stem cell transplantation, and therefore received front-line mobilization with 4 days of G-CSF followed by a single dose of plerixafor. Samples of peripheral blood were analyzed comparatively by flow cytometry directly before and 12 h after administration of plerixafor. RESULTS: The number of aldehyde dehydrogenase (ALDH)(bright) and CD34(+) cells was significantly higher after plerixafor treatment (1.2-5.0 and 1.5-6.0 times; both P < 0.01) and an enrichment of the very primitive CD34(+) CD38(-) and ALDH(bright) CD34(+) CD38(-) HSC subsets was detectable. Additionally, two distinct ALDH(+) subsets could be clearly distinguished. The small ALDH(high) subset showed a higher number of CD34(+) CD38(-) cells in contrast to the total ALDH(bright) subpopulation and probably represented a very primitive subpopulation of HSC. CONCLUSIONS: A combined staining of ALDH, CD34 and CD38 might represent a powerful tool for the identification of a very rare and primitive hematopoietic stem cell subset. The addition of plerixafor mobilized not only more CD34(+) cells but was also able to increase the proportion of more primitive stem cell subsets.

Innovative method for quantification of cell-cell adhesion in 96-well plates.

Cell adhesion is an important part of many complex biological processes. It plays crucial roles in cancer, development, and maintenance of stem cell compartment. The measurement of adhesion under experimental conditions might provide important information for cell biology. There are several protocols to measure adhesion, usually based on washing or shaking to remove non-adherent cells. Here, we describe a quantification method based on gravitational force to measure adhesion in a 96-well format. Non-adherent cells are separated and only vital cells are quantified with a colorimetric assay. As example we provide the quantification of cell-cell interaction with blocking function antibodies for CD44, an N-cadherin antagonists and the stromal cell derived factor-1 alpha (SDF-1). This method facilitates fast and reliable measurement of cell adhesion in multiwell format for screening assays.