Servicenavigation

Project Details

Back

Projekt Print View

Patient Serum Stimulates Hematopoietic Regeneration

Subject Area Hematology, Oncology
Term from 2012 to 2015
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 208258533
 
Final Report Year 2015

Final Report Abstract

Hematopoietic stress - e.g. after chemotherapy - evokes enormous regenerative potential of the hematopoietic system. The signals that recruit hematopoietic stem and progenitor cells (HSPCs) into cell cycle and that balance self-renewal and differentiation are so far poorly understood. We identified 23 small RNA molecules (miRNAs) that are differentially expressed in serum after chemotherapy. Particularly, miRNA-320c and miRNA-1275 were downregulated, whereas miRNA-3663-3p was upregulated. Inhibition of miRNA-320c seemed to increase HSPC-proliferation in vitro. Metabolomic profiling demonstrated that 44 metabolites were less abundant, whereas three (including 2-hydroxybutyrate and taurocholenate sulphate) increased in serum upon chemotherapy, but no clear effect on HSPCs could be observed in vitro. We therefore anticipated that these factors may act in concert to regulate hematopoiesis, rather than individually. In analogy, we addressed hematopoiesis-stimulating signals in serum of patients with myelodysplastic syndrome (MDS). We developed a mathematical model to simulate different modifications in MDS-initiating cells and systemic feedback signals during disease development. This model indicated that the disease initiating cells must have higher self-renewal rates than normal HSPCs to eventually outgrow healthy hematopoiesis. Experimental validation supported the predictions of our model. We also analyzed epigenetic modification upon in vitro culture of HSPCs. The culture conditions of CD34+ cells, with or without co-cultivation with mesenchymal stromal cells, had relatively little impact on DNA-methylation (DNAm), although proliferation is greatly increased by stromal support. Our results demonstrate that HSPCs acquire high DNAm at specific sites in the genome, and this is relevant for the rapid loss of primitive properties (‘stemness’) during in vitro manipulation. Aberrant hypermethylation in culture expansion was particularly observed in DNMT3A. Subsequently, we focused on DNAm at this region in AML patients and identified aberrant hypermethylation in DNMT3A in about 40% of AML patients. This “epimutation” in DNMT3A is rather mutually exclusive with somatic mutations in DNMT3A. Both modifications have similar sequel on specific splice variants of DNMT3A and seem to evoke similar changes in gene expression profiles (including HOX clusters). We could demonstrate that age-associated DNAm changes in blood, which can be used to track the chronological age of the donor, are cell intrinsically regulated and hardly affected by the hematopoietic environment. Furthermore, we demonstrated that this aging signature is also applicable to cell-free DNA in patient serum. Taken together, we have pursued all lines of research proposed in the initial grant application. However, our research did not give rise to a unique parameter that can be used to reliably expand HSPCs in vitro or in vivo. Our results indicate that epigenetic modifications, reflected in the DNAm pattern, play a central role for regulation of hematopoiesis. Splice variants of DNMT3A seem be involved in this regulatory process and we want to continue this research in the future.

Publications

 
 

Additional Information

© 2024 DFG Disclaimer / Copyright / Privacy Policy

Textvergrößerung und Kontrastanpassung