ABSTRACT
Differences in the culturing conditions of mesenchymal stem cells used in regenerative medicine may affect their differentiation ability, genome instability, and therapeutic effects. In particular, bone marrow-derived mesenchymal stem cells cultured under hypoxia are known to proliferate while maintaining an undifferentiated state and the use of deferoxamine, a hypoxia mimetic reagent, has proven to be a suitable strategy to maintain the cells under hypoxic metabolic state. Here, the deferoxamine effects were investigated in mesenchymal stem cells to gain insights into the mechanisms regulating stem cell survival. A 12-h deferoxamine treatment reduced proliferation, oxygen consumption, mitochondrial activity, and ATP production. Microarray analysis revealed that deferoxamine enhanced the transcription of genes involved in glycolysis and the HIF1α pathway. Among the earliest changes, transcriptional variations were observed in HIF1α, NUPR1, and EGLN, in line with previous reports showing that short deferoxamine treatments induce substantial changes in mesenchymal stem cells glycolysis pathway. NUPR1, which is induced by stress and involved in autophagy-mediated survival, was upregulated by deferoxamine in a concentration-dependent manner. Consistently, NUPR1 knockdown was found to reduce cell proliferation and increase the proapoptotic effect of staurosporine, suggesting that deferoxamine-induced NUPR1 promotes mesenchymal stem cell survival and cytoprotective autophagy. Our findings may substantially contribute to improve the effectiveness of mesenchymal stem cell-based regenerative medicine.
ABSTRACT
Somatic mutations in the isocitrate dehydrogenase (IDH)1/2 genes endow encoding proteins with neomorphic activity to produce the potential oncometabolite, 2-hydroxyglutarate (2-HG), which induces the hypermethylation of histones and DNA. The incidence of IDH1/2 mutations in cartilaginous tumors was previously shown to be the highest among various types of tumors, except for those in the central nervous system. Mutations have been detected in both benign (enchondromas) and malignant (chondrosarcomas) types of cartilaginous tumors, whereas they have rarely been found in other mesenchymal tumors such as osteosarcomas. To address this unique tumor specificity, we herein examined the effects of IDH1 R132C, which is the most prevalent mutant in cartilaginous tumors, on the differentiation properties of human mesenchymal stem cells (hMSCs). The induction of the IDH1 R132C gene into MSCs markedly increased the amount of 2-HG and up-regulated global histone methylation. The induction of IDH1 R132C promoted the chondrogenic differentiation of hMSCs by enhancing the expression of SOX9 and COL2A1 genes in association with an increase in the active mark (H3K4me3), but disrupted cartilage matrix formation. On the other hand, IDH1 R132C inhibited expression of the ALPL gene in association with an increase in the repressive mark (H3K9me3), and subsequently inhibited the osteogenic properties of hMSCs and human osteosarcoma cells. Since osteogenic properties are an indispensable feature for the diagnosis of osteosarcoma, the inhibitory effects of IDH1 R132C on osteogenic properties may contribute to the lack of osteosarcomas with the IDH1 R132C mutation. These results suggested that IDH1 R132C contributed to the formation of cartilaginous tumors by dysregulating the chondrogenic and osteogenic differentiation of hMSCs via gene-specific histone modulation.
