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Iron overload (IO) has been reported to contribute to mesenchymal stromal cell (MSC) damage, but the precise mechanism has yet to be clearly elucidated. In this study, we found that IO increased cell apoptosis and lowered cell viability in MSCs, accompanied by extensive mitochondrial fragmentation and autophagy enhancement. All these effects were reactive oxygen species (ROS) dependent. In MSCs with IO, the ATP concentrations were significantly reduced due to high ROS levels and low electron respiratory chain complex (ETC) II/III activity. Reduced ATP phosphorylated AMP-activated protein kinase (AMPK). Activation of AMPK kinase complexes triggered mitochondrial fission. Moreover, gene knockout of AMPK via CRISPR/Cas9 reduced cell apoptosis, enhanced cell viability and attenuated mitochondrial fragmentation and autophagy caused by IO in MSCs. Further, AMPK-induced mitochondrial fragmentation of MSCs with IO was mediated via phosphorylation of mitochondrial fission factor (MFF), a mitochondrial outer-membrane receptor for the GTPase dynamin-related protein 1 (Drp1). Gene knockdown of MFF reversed AMPK-induced mitochondrial fragmentation in MSCs with IO. In addition, MSCs from IO patients with myelodysplastic syndrome (MDS) showed increased cell apoptosis, decreased cell viability, higher ROS levels, lower ATP concentrations and increased mitochondrial fragmentation compared with MSCs from non-IO patients. In addition, iron chelation or antioxidant weakened the activity of the AMPK/MFF/Drp1 pathway in MDS-MSCs with IO from several patients, accompanied by attenuation of mitochondrial fragmentation and autophagy. Taken together, the AMPK/MFF/Drp1 pathway has an important role in the damage to MDS-MSCs caused by IO.

To identify the molecular signatures that predict responses to decitabine (DAC), we examined baseline gene mutations (28 target genes) in 109 myelodysplastic syndrome (MDS) patients at diagnosis. We determined that TP53 mutations predicted complete response (CR), as 10 of 15 patients (66·7%) who possessed TP53 mutations achieved a CR. Univariate and multivariate analyses showed that TP53 mutations are the only molecular signatures predictive of a CR to DAC in MDS. Among the ten patients with TP53 mutations who achieved a CR, nine presented with complex karyotypes due to abnormalities involving chromosome 5 and/or chromosome 7, and eight possessed monosomies. Although TP53 mutations were associated with a higher frequency of CRs, they were not associated with improved survival. Poor outcomes were attributed to early relapses and transformation to acute myeloid leukaemia after CR. Post-DAC therapy patient gene mutation profiles showed that most CR patients exhibited fewer gene mutations after achieving a CR. It seems that suppression of these gene mutations was facilitated by DAC, resulting in a CR. In summary, TP53 mutations might predict decitabine-induced complete responses in patients with MDS. DAC-induced responses may result from partial suppression of malignant clones containing mutated TP53 genes.