Department of Pathophysiology, School of Medicine, National and Kapodistrian University of Athens, 11527 Athens, Greece.
Laboratory of Molecular Genetics, Department of Immunology, Hellenic Pasteur Institute, 11521 Athens, Greece.
Int J Mol Sci. 2021 Apr 15;22(8):4099. doi: 10.3390/ijms22084099.
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.
骨髓增生异常综合征（MDS）是一组异质性的克隆造血干（HSCs）和/或祖细胞疾病。MDS 前体对低氧骨髓（BM）微环境的依赖性已得到证实，这使得科学家们对转录因子缺氧诱导因子 1（HIF-1）产生了兴趣。HIF-1 通过调节 HSCs 代谢来促进静止维持和分化，因此成为一个有吸引力的研究目标。因此，我们检查了 MDS 患者和对照（CTRLs）的 BM 中异常的 HIF-1 稳定。我们使用硝基咪唑-吲哚菁绿缀合物，表明 HIF-1 的异常表达和转录活性是与氧无关的，从而在 MDS BM 中建立了伪缺氧现象。接下来，我们检查了从新鲜 BM MDS 和 CTRL 抽吸物中分离出的分化髓系谱系中的线粒体质量和数量以及自噬水平，因为这两种现象都是 HIF-1 依赖的。我们表明，异常线粒体的噬线粒体和自噬性死亡在 MDS 髓系谱系中明显突出，其严重程度随 BM 内 blast 计数的增加而增加。最后，我们使用从新鲜人 BM 抽吸物中分离的体外培养的 CD34+HSCs 来操纵 HIF-1 表达，并研究其作为治疗靶点的潜力。我们发现，尽管在 21%FiO2 下培养，但所有 MDS 培养物中的 HIF-1 仍然异常稳定。在所有 <5%-BM 内 blast-MDS 中，HIF-1α 亚基的抑制具有可变的有益作用，而在 CTRLs 或≥5%-BM 内 blast-MDS 中则没有作用，后者在培养后 3 天内均均匀死亡。我们得出结论，HIF-1 和伪缺氧在 MDS 病理生物学中突出，其操纵在良性 MDS 的治疗中有一定的潜力。
