MSCs with upregulated lipid metabolism block hematopoietic stem cell differentiation via exosomal CTP-1A in MDS

Abstract

Background Myelodysplastic syndrome (MDS) is a clonal disorder of hematopoietic stem cells (HSCs), characterized by ineffective hematopoiesis and a high risk of progression to acute myeloid leukemia. Elucidating the mechanism underlying the dysfunction of MDS-HSCs is crucial for exploring the pathogenesis of the syndrome. While previous studies have implicated mesenchymal stem cells (MSCs), a principal component of the bone marrow (BM) microenvironment, in the inhibition of normal hematopoiesis, the precise molecular mechanisms have not been fully elucidated. In this study, we investigated the effects of MSCs from MDS patients on hematopoietic functions of HSCs from a metabolic perspective. Methods MSCs were isolated from BM of MDS patients. The proliferation, apoptosis, differentiation and support for hematopoiesis of these cells were analyzed using CCK-8 assay, FC and induction medium and CFU (colony forming units) assay, respectively. Expression levels of metabolic molecules were used as indicators to screen MSCs with different metabolic pathways and were detected by RT-PCR and Western blotting. Exosome derived from MSCs were isolated from the culture supernatant and confirmed by Transmission Electron Microscope, Dynamic Light Scattering and Western blotting. The effects of these exosomes on HSCs were analyzed using the same methods as those used to assess MSCs function. Results Our findings demonstrated that MDS-MSCs exhibited significant functional impairments, including reduced proliferation, impaired differentiation, diminished support for hematopoiesis, and increased apoptosis. Notably, we observed an upregulation of lipid metabolism in these MSCs, which appears to contribute to their dysfunction. Intriguingly, the aberrant lipid metabolic profile can be effectively reversed by the administration of etomoxir (ETO), an inhibitor of carnitine palmitoyltransferase 1A (CPT-1A). Furthermore, MSCs with enhanced lipid metabolism could transmit this dysfunction to HSCs through the secretion of exosomes that are enriched in CPT-1A. Conclusions We suggest that the MDS BM microenvironment disrupts MSCs metabolism by increasing the expression of CPT-1A, which impairs the ability to support normal HSCs. Interestingly, the suppressive effect is mediated by exosomes rich in CPT-1A, which derived from MSCs. These findings provide novel insights into MDS MSCs-metabolism-Exosome axis in ineffective hematopoiesis and offer new strategies for the treatment of MDS.

1. Introduction

Myelodysplastic syndrome (MDS) arise from a small population of clonal disorder hematopoietic stem cells (HSCs) that characterized by aberrant differentiation, peripheral-blood cytopenia, and frequent progression to acute myeloid leukemia[1, 2]. Researchers have found that MDS show an increased incidence with age, often making it challenging to arrive at the appropriate diagnosis[3, 4]. Consequently, it is essential to explore the key mechanism in MDS so that retard the disease process or cure it for an aging society. In clinic practice, the therapy of this disease could be divided into two aspects. One is epigenic therapy, which uses medicine such as azacitidine, decitabine to target the DNA hypermethylation to relieve symptom, but sometimes it is difficult to achieve a proper response for the patients [5]; Another is allogeneic HSCs transplantation, which treated as the only potentially curative option, but some studies indicate that the limited success of HSCs transplantation is attributed to the altered bone marrow (BM) microenvironment in MDS patients[6].

As one of the important components of BM microenvironment, mesenchymal stem cells (MSCs) can form a unique hematopoietic niche with HSCs [7–9], through secreting chemokine (C-X-C motif) CXCL12 to promote the homing of HSCs to the bone marrow [10], and releasing osteopontin to support HSCs expansion [11]. In addition, as multipotent cells, they can also differentiate into osteoblasts secreted chemokine CXCL12 ligand, stem cell factor (SCF), angiogenin, thrombopoietin