Glutamate accumulation in myelofibrosis microenvironment rewires mesenchymal stromal cells metabolic and epigenetic profiles.

BACKGROUND: Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by bone marrow (BM) fibrosis, osteosclerosis, and a proinflammatory tumor microenvironment (TME). The interplay between malignant hematopoietic stem cells and mesenchymal stromal cells (MSCs) drives disease progression. Although glutamate has been implicated in various cancers, its contribution to MF pathogenesis remains unclear.
METHODS: High-performance liquid chromatography (HPLC) profiling was performed on sera from MF patients and healthy controls (HCs) to identify alterations in amino acid abundance. The proteomic profiles of MF- and HC-derived MSCs were assessed by mass spectrometry. Functional assays in glutamate- and fumarate-treated MSCs were used to investigate metabolic, epigenetic, and phenotypic changes by HPLC, real-time PCR, flow cytometry, immunofluorescence, and Azan-Mallory staining. The therapeutic potential of metabotropic glutamate receptor 5 (mGluR5) inhibition was evaluated using in vitro and in vivo models.
RESULTS: Glutamate emerged as the most enriched amino acid in MF sera. In MSCs, glutamate supplementation induced intracellular fumarate accumulation, mediated by increased expression of α-ketoglutarate dehydrogenase components and downregulation of fumarate hydratase activity. Fumarate treatment recapitulated an upregulation of oxidative phosphorylation, also enhancing mitochondrial ROS. Both fumarate and glutamate induced epigenetic remodeling, as shown by accumulation of 5-methylcytosine (5mC) and H3K36me2, which was also confirmed in primary MF-MSCs. Glutamate and fumarate induced a senescent phenotype in MSCs, characterized by increased β-galactosidase activity, oxidative stress and SASP-related genes induction. Both metabolites also promoted collagen deposition, supporting their involvement in fibrotic remodeling. Notably, selective inhibition of metabotropic glutamate receptor 5 (mGluR5) by UBP310 or UBP296 attenuated glutamate-driven senescence, reduced fumarate-associated epigenetic changes and limited collagen deposition in vitro and in vivo, supporting a central role for glutamate signaling in stromal dysfunction and fibrotic niche remodeling.
CONCLUSION: This study identifies glutamate as a key metabolic and signaling factor in MF microenvironment. Glutamate rewires MSC metabolism via fumarate accumulation, drives epigenetic reprogramming, and induces senescence and fibrotic transformation. Targeting mGluR5 may therefore represent a promising therapeutic strategy to mitigate MSC dysfunction and bone marrow fibrosis in MF.