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Glutamine addicted myeloma cells inhibits osteoblastic differentiation of bone marrow mesenchymal stromal cells limiting asparagine availability.

ABSTRACT: Osteolytic lesions with suppression of osteoblastic (OB) differentiation are hallmarks of multiple myeloma (MM). Most recently, Gln availability has been found to be essential to sustain bone mass formation in murine models. On the other hand, MM cells are Gln-addicted and consume huge amounts of the amino acid, leading to a partial Gln depletion in the bone marrow (BM) plasma. We hypothesize that MM-dependent Gln depletion contributes to the defective OB differentiation characteristic of MM. Conversely, GLS (both KGA and GAC isoforms) and SLC38A2, the gene for the concentrative Gln transporter SNAT2, were induced. Consistent with this conclusion, the activity of SNAT2 was absent in undifferentiated hMSCs but well detectable after 14 days of OB differentiation, when total Gln uptake was also increased. Under the same conditions, OB differentiation markers (RUNX2, COL1A1, ALPL expression and ALPL activity or staining) were significantly induced but their expression was blunted by incubation in low-Gln (0.4 mM) medium or in the presence of the SNAT2 inhibitor MeAIB. The incubation in Gln-free D-MEM suppressed the induction of GLS and SLC38A2 along with OB differentiation, which was restored by the supplementation of Non-Essential Amino Acids (NEAA). Among NEAA, only asparagine (Asn) was able to rescue OB differentiation in the absence of Gln. The determination of intracellular amino acids with MS indicated that OB differentiation was associated with the increase of cell Asn, without significant changes of Gln, glutamate (Glu) or aspartate (Asp). Asparagine Synthetase (ASNS), the Gln-dependent enzyme that accounts for Asn synthesis, was also found induced during OB differentiation of hMSCs. Gene Expression Profiles of primary BM hMSCs and OBs from bone biopsies of both healthy donors and MM patients indicated that GLS, ASNS, and SLC38A2 are more expressed in OBs, while the expression of GLUL, the gene for GS, is higher in undifferentiated hMSCs from healthy donors. Overall, these results indicate that (1) OB differentiation of hMSCs is Gln-dependent; (2) the partial Gln depletion, imposed by Gln-addicted MM cells in the BM microenvironment, contributes to the impairment of osteoblastic differentiation of hMSCs; (3) hindrance of differentiation may depend on the limited availability of intracellular Asn derived from Gln-dependent ASNS. These results support the evidence that Gln addiction of MM cells affects bone microenvironment leading to the inhibition of OB differentiation and, consequently, to the development of MM bone disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE147791 | GEO | 2020/12/01

REPOSITORIES: GEO

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Project description:Endogenous bioelectric signaling via changes in cellular resting potential (Vmem) is a key regulator of patterning during regeneration and embryogenesis in numerous model systems. Depolarization of Vmem has been functionally implicated in de-differentiation, tumorigenesis, anatomical re-specification, and appendage regeneration. However, no unbiased analyses have been performed to understand genome-wide transcriptional responses to Vmem change in vivo. Moreover, it is unknown which genes or gene networks represent conserved targets of bioelectrical signaling across different patterning contexts and species. Here, we use microarray analysis to comparatively analyze transcriptional responses to specific Vmem depolarization. We compare the response of the transcriptome during embryogenesis (Xenopus development), regeneration (Axolotl regeneration), and stem cell differentiation (human mesenchymal stem cells in culture) to identify common networks across model species that are associated with depolarization. Both sub-network enrichment and PANTHER analyses identified a number of key genetic modules as targets of Vmem change, and also revealed important (well-conserved) commonalities in bioelectric signal transduction, despite highly diverse experimental contexts and species. Depolarization regulates specific transcriptional networks across all three germ layers (ectoderm, mesoderm and endoderm) such as cell differentiation and apoptosis, and this information will be used for developing mechanistic models of bioelectric regulation of patterning. Moreover, our analysis reveals that Vmem change regulates transcripts related to important disease pathways such as cancer and neurodegeneration, which may represent novel targets for emerging electroceutical therapies. Whole bone marrow aspirate from a 25 year-old healthy man was purchased from Lonza through their Research Bone Marrow Donor Program, following approved guidelines of informed consent as previously documented (Sundelacruz et al. 2008, 2013b). Aspirate was plated at a density of 10 mL of aspirate per cm2 in control medium (DMEM with 10% fetal bovine serum (FBS), penicillin (100 U/mL), streptomycin (100 mg/mL), and 0.1 mM nonessential amino acids) supplemented with basic fibroblast growth factor (1 ng/mL) (Invitrogen). Cells were maintained in a humidified incubator at 37Â°C with 5% CO2. The hMSCs were isolated on the basis of their adherence to tissue culture plastic and were used for experiments between passages two and four. Undifferentiated hMSCs were cultured in control medium. Osteogenic (OS) differentiation medium consisted of Î±MEM medium supplemented with 10% FBS, penicillin (100 U/mL), streptomycin (100 mg/mL), 10mM Î²-glycerophosphate, 0.05mM L-ascorbic acid-2-phosphate, and 100nM dexamethasone (Sigma-Aldrich). Vmem was depolarized by (1) addition of Na+/K+ - ATPase-inhibitor ouabain (OB, 10 nM; Sigma-Aldrich) to differentiation medium or (2) elevation of extracellular K+ by adding potassium gluconate (High K+, HK, 40 mM; Sigma-Aldrich) to differentiation medium. Depolarization induced by these concentrations of OB and K+ has been confirmed using voltage-sensitive dyes and/or sharp intracellular recordings [(Sundelacruz et al. 2008) and unpublished data]. OS cells were pre-differentiated for three weeks before the addition of OB or HK for an additional three weeks of culture. The depolarizers were added to the differentiation medium and replenished in subsequent media changes.

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Glutamine addicted myeloma cells inhibits osteoblastic differentiation of bone marrow mesenchymal stromal cells limiting asparagine availability.

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