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Myelodysplastic cells in patients re-program mesenchymal stromal cells to establish a transplantable stem cell-niche disease unit.

ABSTRACT: Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid neoplasms with defects in hematopoietic stem/progenitor cells (HSPCs) and possibly the HSPC niche. Here we show that patient-derived mesenchymal stromal cells (MDS MSCs) display a disturbed differentiation program and are essential for the propagation of MDS-initiating lin-CD34+CD38- stem cells in orthotopic xenografts. Overproduction of niche factors such as N-Cadherin, IGFBP2, VEGFA and LIF is associated with the ability of MDS MSCs to enhance MDS expansion. These factors represent putative therapeutic targets to disrupt critical hematopoietic-stromal interactions in MDS. Finally, healthy MSCs adopt "MDS-MSC like" molecular features when exposed to hematopoietic MDS cells, indicative of an instructive remodeling of their microenvironment. This patient-derived xenograft model therefore provides functional and molecular evidence that MDS is a complex disease involving both the hematopoietic and stromal compartments. The resulting deregulated expression of niche factors may well also be a feature of other hematopoietic malignancies.

PROVIDER: EGAS00001000716 | EGA |

REPOSITORIES: EGA

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Project description:Ineffective hematopoiesis is a hallmark of myelodysplastic syndromes (MDS). Hematopoietic alterations in MDS patients strictly correlate with microenvironment dysfunctions, eventually affecting also the mesenchymal stromal cells (MSCs) compartment. Stromal cells are indeed epigenetically reprogrammed to cooperate with leukemic cells and propagate the disease as "tumor unit"; therefore, changes on MSCs epigenetic profile might contribute to the hematopoietic perturbations typical of MDS. Here, we unveil that the histone variant macroH2A1 (mH2A1) regulates the crosstalk between epigenetics and inflammation in MDS-MSCs, potentially affecting their hematopoietic support ability. We show that the mH2A1 splicing isoform mH2A1.1 accumulates in MDS-MSCs, correlating with the expression of the Toll-like receptor 4 (TLR4), an important pro-tumor activator of MSC phenotype associated to a pro-inflammatory behavior. MH2A1.1-TLR4 axis was further investigated in HS-5 stromal cells after ectopic mH2A1.1 overexpression (mH2A1.1-OE). Proteomic data confirmed the activation of a pro-inflammatory signature associated to TLR4 and nuclear factor kappa B (NFkB) activation. Moreover, mH2A1.1-OE proteomic profile identified several upregulated proteins associated to DNA and histones hypermethylation, including S-adenosylhomocysteine hydrolase, a strong inhibitor of DNA methyltransferase and of the methyl donor S-adenosyl-methionine (SAM). HPLC analysis confirmed higher SAM/SAH ratio along with a metabolic reprogramming. Interestingly, an increased LDHA nuclear localization was detected both in mH2A1.1-OE cells and MDS-MSCs, probably depending on MSC inflammatory phenotype. Finally, coculturing healthy mH2A1-OE MSCs with CD34+ cells, we found a significant reduction in the number of CD34+ cells, which was reflected in a decreased number of colony forming units (CFU -Cs). These results suggest a key role of mH2A1.1 in driving the crosstalk between epigenetic signaling, inflammation and cell metabolism networks in MDS-MSCs.

Project description:Ex-vivo expanded mesenchymal stromal cells (MSCs) are increasingly used for paracrine support of hematopoietic stem cell (HSC) regeneration, but inconsistent outcomes have been the huddle for on-going clinical trials. Here, we hypothesized that the heterogeneity in the niche activity of manufactured MSCs can be a parameter for variable outcomes in MSC-based cell therapy. We first screened MSC culture medium and found that serum batches caused larger variations in colony forming unit-fibroblast (CFU-F) content of MSCs than individual donor variations. The culture conditions supporting high (stimulatory) and low (non-stimulatory) CFU-F caused distinct niche activity of MSCs; MSCs under stimulatory condition exhibited higher level expression of cross-talk molecules (Jagged-1 and CXCL-12) and higher support for HSCS during long-term culture than MSCs under non-stimulatory culture. Moreover, the effects of MSCs enhancing hematopoietic engraftment were only visible when HSCs were co-transplanted with MSCs expanded under stimulatory, but not non-stimulatory conditions. However, these differences of MSCs were readily reversed by switching the culture mediums, indicating their distinct functional state, rather than clonal heterogeneity. Accordingly, transcriptomic analysis showed distinct gene set enrichment between the different MSCs and revealed distinct upstream signaling pathways such as inhibition of P53 and activation of ATF4 for MSCs under stimulatory conditions. Taken together, our study shows that the heterogeneity in the niche activity of MSCs can be created during ex-vivo expansion to cause a difference in the hematopoietic engraftment and raise the possibility that MSCs can be pre-screened for more predictable outcomes in clinical trials of MSCs. Total RNA obtained from isolated human mesenchymal stromal cells. To compare stimulatory (SS) serum and non-stimulatory (NSS) serums, MSCs had been maintained in each serum media were sub-cultured for at least two passages before analysis.

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Myelodysplastic cells in patients re-program mesenchymal stromal cells to establish a transplantable stem cell-niche disease unit.

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