Aglaia Dimitrakopoulou

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal hematopoietic stem (HSCs) and/or progenitor cells disorders. The established dependence of MDS progenitors on the hypoxic bone marrow (BM) microenvironment turned scientific interests to the transcription factor hypoxia-inducible factor 1 (HIF-1). HIF-1 facilitates quiescence maintenance and regulates differentiation by manipulating HSCs metabolism, being thus an appealing research target. Therefore, we examine the aberrant HIF-1 stabilization in BMs from MDS patients and controls (CTRLs). Using a nitroimidazole–indocyanine conjugate, we show that HIF-1 aberrant expression and transcription activity is oxygen independent, establishing the phenomenon of pseudohypoxia in MDS BM. Next, we examine mitochondrial quality and quantity along with levels of autophagy in the differentiating myeloid lineage isolated from fresh BM MDS and CTRL aspirates given that both phenomena are HIF-1 dependent. We show that the mitophagy of abnormal mitochondria and autophagic death are prominently featured in the MDS myeloid lineage, their severity increasing with intra-BM blast counts. Finally, we use in vitro cultured CD34+ HSCs isolated from fresh human BM aspirates to manipulate HIF-1 expression and examine its potential as a therapeutic target. We find that despite being cultured under 21% FiO2, HIF-1 remained aberrantly stable in all MDS cultures. Inhibition of the HIF-1α subunit had a variable beneficial effect in all <5%-intra-BM blasts-MDS, while it had no effect in CTRLs or in ≥5%-intra-BM blasts-MDS that uniformly died within 3 days of culture. We conclude that HIF-1 and pseudohypoxia are prominently featured in MDS pathobiology, and their manipulation has some potential in the therapeutics of benign MDS.

Myelodysplastic syndromes (MDS) encompass a very heterogeneous group of clonal hematopoietic stem cell differentiation disorders with malignant potential and an elusive pathobiology. Given the central role of metabolism in effective differentiation, we performed an untargeted metabolomic analysis of differentiating myeloid lineage cells from MDS bone marrow aspirates that exhibited n = 10 and G2, n = 4) and age matched controls (n = 5). Following myeloid lineage cell isolation, untargeted mass spectrometry-based metabolomics analysis was performed. Data were processed and analyzed using Metabokit. Enrichment analysis was performed using Metaboanalyst v4 employing pathway-associated metabolite sets. We established a bioenergetic profile coordinated by the Warburg phenomenon in both groups, but with a massively different outcome that mainly depended upon its group mitochondrial function and redox state. G1 cells are overwhelmed by glycolytic intermediate accumulation due to failing mitochondria, while the functional electron transport chain and improved redox in G2 compensate for Warburg disruption. Both metabolomes reveal the production and abundance of epigenetic modifiers. G1 and G2 metabolomes differ and eventually determine the MDS clinical phenotype, as well as the potential for malignant transformation.