[Establishment and Evaluation Strategy of an in vitro Cell Model of Bone Marrow Microenvironment Injury in Mouse Acute Graft-Versus-Host Disease].

OBJECTIVE: To establish a mesenchymal stem cell（MSC）-based in vitro cell model for the evaluation of mouse bone marrow acute graft-versus-host disease (aGVHD). METHODS: Female C57BL/6N mice aged 6-8 weeks were used as bone marrow and lymphocyte donors, and female BALB/c mice aged 6-8 weeks were used as aGVHD recipients. The recipient mouse received a lethal dose (8.0 Gy,72.76 cGy/min) of total body γ irradiation, and injected with donor mouse derived bone marrow cells (1×107/mouse) in 6-8 hours post irradiation to establish a bone marrow transplantation (BMT) mouse model (n=20). In addition, the recipient mice received a lethal dose (8.0 Gy,72.76 cGy/min) of total body γ irradiation, and injected with donor mouse derived bone marrow cells (1×107/mouse) and spleen lymphocytes (2×106/mouse) in 6-8 hours post irradiation to establish a mouse aGVHD model (n=20). On the day 7 after modeling, the recipient mice were anesthetized and the blood was harvested post eyeball enucleation. The serum was collected by centrifugation. Mouse MSCs were isolated and cultured with the addition of 2%, 5%, and 10% recipient serum from BMT group or aGVHD group respectively. The colony-forming unit-fibroblast（CFU-F) experiment was performed to evaluate the potential effects of serums on the self-renewal ability of MSC. The expression of CD29 and CD105 of MSC was evaluated by immunofluorescence staining. In addition, the expression of self-renewal-related genes including Oct-4, Sox-2, and Nanog in MSC was detected by real-time fluorescence quantitative PCR（RT-qPCR). RESULTS: We successfully established an in vitro cell model that could mimic the bone marrow microenvironment damage of the mouse with aGVHD. CFU-F assay showed that, on day 7 after the culture, compared with the BMT group, MSC colony formation ability of aGVHD serum concentrations groups of 2% and 5% was significantly reduced （P < 0．05）; after the culture, at day 14, compared with the BMT group, MSC colony formation ability in different aGVHD serum concentration was significantly reduced （P < 0．05）. The immunofluorescence staining showed that, compared with the BMT group, the proportion of MSC surface molecules CD29+ and CD105+ cells was significantly dereased in the aGVHD serum concentration group (P < 0.05), the most significant difference was at a serum concentration of 10% （P < 0．001, P < 0.01）. The results of RT-qPCR detection showed that the expression of the MSC self-renewal-related genes Oct-4, Sox-2, and Nanog was decreased, the most significant difference was observed at an aGVHD serum concentration of 10% （P < 0.01,P < 0．001,P < 0．001）. CONCLUSION: By co-culturing different concentrations of mouse aGVHD serum and mouse MSC, we found that the addition of mouse aGVHD serum at different concentrations impaired the MSC self-renewal ability, which providing a new tool for the field of aGVHD bone marrow microenvironment damage.

Multiple Myeloma Derived Extracellular Vesicle Uptake by Monocyte Cells Stimulates IL-6 and MMP-9 Secretion and Promotes Cancer Cell Migration and Proliferation.

Multiple Myeloma (MM) is an incurable haematological malignancy caused by uncontrolled growth of plasma cells. MM pathogenesis is attributed to crosstalk between plasma cells and the bone marrow microenvironment, where extracellular vesicles (EVs) play a role. In this study, EVs secreted from a panel of MM cell lines were isolated from conditioned media by ultracentrifugation and fluorescently stained EVs were co-cultured with THP-1 monocyte cells. MM EVs from three cell lines displayed a differential yet dose-dependent uptake by THP-1 cells, with H929 EVs displaying the greatest EV uptake compared to MM.1s and U266 EVs suggesting that uptake efficiency is dependent on the cell line of origin. Furthermore, MM EVs increased the secretion of MMP-9 and IL-6 from monocytes, with H929 EVs inducing the greatest effect, consistent with the greatest uptake efficiency. Moreover, monocyte-conditioned media collected following H929 EV uptake significantly increased the migration and proliferation of MM cells. Finally, EV proteome analysis revealed differential cargo enrichment that correlates with disease progression including a significant enrichment of spliceosome-related proteins in H929 EVs compared to the U266 and MM.1s EVs. Overall, this study demonstrates that MM-derived EVs modulate monocyte function to promote tumour growth and metastasis and reveals possible molecular mechanisms involved.

Uncovering the cellular and omics characteristics of natural killer cells in the bone marrow microenvironment of patients with acute myeloid leukemia.

BACKGROUND: Acute myeloid leukemia (AML) is a highly heterogeneous hematologic malignancy and the most frequently acute leukemia of stem cell precursors and the myeloid derivatives in adult. Longitudinal studies have indicated the therapeutic landscape and drug resistance for patients with AML are still intractable, which largely attribute to the deficiency of detailed information upon the pathogenesis. METHODS: In this study, we compared the cellular phenotype of resident NK cells (rAML-NKs, rHD-NKs) and expanded NK cells (eAML-NKs, eHD-NKs) from bone marrow of AML patients (AML) and healthy donors (HD). Then, we took advantage of the co-culture strategy for the evaluation of the in vitro cytotoxicity of NK cells upon diverse tumor cell lines (e.g., K562, Nalm6, U937). With the aid of RNA-sequencing (RNA-SEQ) and bioinformatics analyses (e.g., GOBP analysis, KEGG analysis, GSEA, volcano plot), we verified the similarities and differences of the omics features between eAML-NKs and eHD-NKs. RESULTS: Herein, we verified the sharp decline in the content of total resident NK cells (CD3-CD56+) in rAML-NKs compared to rHD-NKs. Differ from the expanded eHD-NKs, eAML-NKs revealed decline in diverse NK cell subsets (NKG2D+, CD25+, NKp44+, NKp46+) and alterations in cellular vitality but conservations in cytotoxicity. According to transcriptomic analysis, AML-NKs and HD-NKs showed multifaceted distinctions in gene expression profiling and genetic variations. CONCLUSIONS: Collectively, our data revealed the variations in the cytobiological and transcriptomic features between AML-NKs and HD-NKs in bone marrow environment. Our findings would benefit the further development of novel biomarkers for AML diagnosis and NK cell-based cytotherapy in future.

Intra-bone marrow injection with engineered Lactococcus lactis for the treatment of metastatic tumors: Primary report.

Bone marrow has the capacity to produce different types of immune cells, such as natural killer cells, macrophages, dendritic cells (DCs) and T cells. Improving the activation of immune cells in the bone marrow can enhance the therapy of bone metastases. Previously, we designed an engineered probiotic Lactococcus lactis, capable of expressing a fusion protein of Fms-like tyrosine kinase 3 ligand and co-stimulator OX40 ligand (FOLactis), and proved that it can induce the activation and differentiation of several immune cells. In this research, we successfully establish mouse models of bone metastasis, lung metastasis and intraperitoneal dissemination, and we are the first to directly inject the probiotics into the bone marrow to inhibit tumor growth. We observe that injecting FOLactis into the bone marrow of mice can better regulate the immune microenvironment of tumor-bearing mice, resulting in a tumor-suppressive effect. Compared to subcutaneous (s.c.) injection, intra-bone marrow (IBM) injection is more effective in increasing mature DCs and CD8+ T cells and prolonging the survival of tumor-bearing mice. Our results confirm that IBM injection of FOLactis reprograms the immune microenvironment of bone marrow and has remarkable effectiveness in various metastatic tumor models.

Metabolomics profile and machine learning prediction of treatment responses in immune thrombocytopenia: A prospective cohort study.

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by antibody-mediated platelet destruction and impaired platelet production. The mechanisms underlying ITP and biomarkers predicting the response of drug treatments are elusive. We performed a metabolomic profiling of bone marrow biopsy samples collected from ITP patients admission in a prospective study of the National Longitudinal Cohort of Hematological Diseases. Machine learning algorithms were conducted to discover novel biomarkers to predict ITP patient treatment responses. From the bone marrow biopsies of 91 ITP patients, we quantified a total of 4494 metabolites, including 1456 metabolites in the positive mode and 3038 metabolites in the negative mode. Metabolic patterns varied significantly between groups of newly diagnosed and chronic ITP, with a total of 876 differential metabolites involved in 181 unique metabolic pathways. Enrichment factors and p-values revealed the top metabolically enriched pathways to be sphingolipid metabolism, the sphingolipid signalling pathway, ubiquinone and other terpenoid-quinone biosynthesis, thiamine metabolism, tryptophan metabolism and cofactors biosynthesis, the phospholipase D signalling pathway and the phosphatidylinositol signalling system. Based on patient responses to five treatment options, we screened several metabolites using the Boruta algorithm and ranked their importance using the random forest algorithm. Lipids and their metabolism, including long-chain fatty acids, oxidized lipids, glycerophospholipids, phosphatidylcholine and phosphatidylethanolamine biosynthesis, helped differentiate drug treatment responses. In conclusion, this study revealed metabolic alterations associated with ITP in bone marrow supernatants and a potential biomarker predicting the response to ITP.

Biology and Therapeutic Properties of Mesenchymal Stem Cells in Leukemia.

This comprehensive review delves into the multifaceted roles of mesenchymal stem cells (MSCs) in leukemia, focusing on their interactions within the bone marrow microenvironment and their impact on leukemia pathogenesis, progression, and treatment resistance. MSCs, characterized by their ability to differentiate into various cell types and modulate the immune system, are integral to the BM niche, influencing hematopoietic stem cell maintenance and functionality. This review extensively explores the intricate relationship between MSCs and leukemic cells in acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia, and chronic lymphocytic leukemia. This review also addresses the potential clinical applications of MSCs in leukemia treatment. MSCs' role in hematopoietic stem cell transplantation, their antitumor effects, and strategies to disrupt chemo-resistance are discussed. Despite their therapeutic potential, the dual nature of MSCs in promoting and inhibiting tumor growth poses significant challenges. Further research is needed to understand MSCs' biological mechanisms in hematologic malignancies and develop targeted therapeutic strategies. This in-depth exploration of MSCs in leukemia provides crucial insights for advancing treatment modalities and improving patient outcomes in hematologic malignancies.

CD200 genotype is associated with clinical outcome of patients with multiple myeloma.

Immune dysfunction in patients with MM affects both the innate and adaptive immune system. Molecules involved in the immune response pathways are essential to determine the ability of cancer cells to escape from the immune system surveillance. However, few data are available concerning the role of immune checkpoint molecules in predicting the myeloma control and immunological scape as mechanism of disease progression. We retrospectively analyzed the clinical impact of the CD200 genotype (rs1131199 and rs2272022) in 291 patients with newly diagnosed MM. Patients with a CD200 rs1131199 GG genotype showed a median overall survival (OS) significantly lower than those with CC+CG genotype (67.8 months versus 94.4 months respectively; p: 0.022) maintaining significance in the multivariate analysis. This effect was specially detected in patients not receiving an autologous stem cell transplant (auto-SCT) (p < 0.001). In these patients the rs1131199 GG genotype negatively influenced in the mortality not related with the progression of MM (p: 0.02) mainly due to infections events.

Y-box binding protein 1 in small extracellular vesicles reduces mesenchymal stem cell differentiation to osteoblasts-implications for acute myeloid leukaemia.

Small extracellular vesicles (sEVs) released by acute myeloid leukaemia (AML) cells have been reported to influence the trilineage differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs). However, it remains elusive which biological cargo from AML-sEVs is responsible for this effect. In this study, sEVs were isolated from cell-conditioned media and blood plasma using size-exclusion chromatography and ultrafiltration and characterized according to MISEV2018 guidelines. Our results demonstrated that AML-sEVs increased the proliferation of BM-MSCs. Conversely, key proteins that are important for normal haematopoiesis were downregulated in BM-MSCs. Additionally, we revealed that AML-sEVs significantly reduced the differentiation of BM-MSCs to osteoblasts without affecting adipogenic or chondrogenic differentiation. Next, LC-MS/MS proteomics elucidated that various proteins, including Y-box-binding protein 1 (YBX1), were upregulated in both AML-sEVs and BM-MSCs treated with AML-sEVs. Clinically relevant, we found that YBX1 is considerably upregulated in most paediatric AML patient-derived sEVs compared to healthy controls. Interestingly, sEVs isolated after the downregulation of YBX1 in AML cells remarkably rescued the osteoblastic differentiation of BM-MSCs. Altogether, our data demonstrate for the first time that YBX1 containing AML-sEVs is one of the key players that disrupt the normal function of bone marrow microenvironment by reducing the osteogenic differentiation of BM-MSCs.

The impact of gut microbial signals on hematopoietic stem cells and the bone marrow microenvironment.

Hematopoietic stem cells (HSCs) undergo self-renewal and differentiation in the bone marrow, which is tightly regulated by cues from the microenvironment. The gut microbiota, a dynamic community residing on the mucosal surface of vertebrates, plays a crucial role in maintaining host health. Recent evidence suggests that the gut microbiota influences HSCs differentiation by modulating the bone marrow microenvironment through microbial products. This paper comprehensively analyzes the impact of the gut microbiota on hematopoiesis and its effect on HSCs fate and differentiation by modifying the bone marrow microenvironment, including mechanical properties, inflammatory signals, bone marrow stromal cells, and metabolites. Furthermore, we discuss the involvement of the gut microbiota in the development of hematologic malignancies, such as leukemia, multiple myeloma, and lymphoma.

The prevention effect of pulsed electromagnetic fields treatment on senile osteoporosis in vivo via improving the inflammatory bone microenvironment.

This study aimed to assess PEMF in a rat model of senile osteoporosis and its relationship with NLRP3-mediated low-grade inflammation in the bone marrow microenvironment. A total of 24 Sprague Dawley (SD) rats were included in this study. Sixteen of them were 24-month natural-aged male SD rats, which were randomly distributed into the Aged group and the PEMF group (n = 8 per group). The remaining 8 3-month -old rats were used as the Young positive control group (n = 8). Rats in the PEMF group received 12 weeks of PEMF with 40 min/day, five days per week, while the other rats received placebo PEMF intervention. Bone mineral density/microarchitecture, serum levels of CTX-1 and P1CP, and NLRP3-related signaling genes and proteins in rat bone marrow were then analyzed. The 12-week of PEMF showed significant mitigation of aging-induced bone loss and bone microarchitecture deterioration, i.e. PEMF increased the bone mineral density of the proximal femur and L5 vertebral body and improved parameters of the proximal tibia and L4 vertebral body. Further analysis showed that PEMF reversed aging-induced bone turnover, specifically, decreased serum CTX-1 and elevated serum P1CP. Furthermore, PEMF also dramatically inhibited NLRP3-mediated low-grade inflammation in the bone marrow, i.e. PEMF inhibited the levels of NLRP3, proCaspase1, cleaved Caspase1, IL-1ß, and GSDMD-N. The study demonstrated that PEMF could mitigate the aging-induced bone loss and reverses the deterioration of bone microarchitecture probably through inhibiting NLRP3-mediated low-grade chronic inflammation to improve the inflammatory bone microenvironment in aged rats.

[Research Progress on Effect of Bone Marrow Microenvironment Regulated by IL-6/IL-6R/JAK2/STAT3 Pathway on Biological Behavior of Multiple Myeloma--Review].

Multiple myeloma (MM) is a malignant disease with abnormal proliferation of clonal plasma cells. The development of the disease shows a vast heterogeneity, which is closely related to the interaction between MM cells and bone marrow microenvironment (BMM). The interleukin-6 (IL-6)/interleukin-6 receptor (IL-6R)/Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway can regulate the transcription of related soluble factors in BMM, promote the proliferation, anti-apoptosis, drug resistance and guide related bone destruction of MM cells. This article reviews the research progress on the effect of BMM regulated by IL-6/IL-6R/JAK2/STAT3 pathway on the biological behavior of MM, in order to provide new research ideas for targeted therapy and precise therapy of MM.

Targeting integrins in drug-resistant acute myeloid leukaemia.

Acute myeloid leukaemia (AML) continues to have a poor prognosis, warranting new therapeutic strategies. The bone marrow (BM) microenvironment consists of niches that interact with not only normal haematopoietic stem cells (HSC) but also leukaemia cells like AML. There are many adhesion molecules in the BM microenvironment; therein, integrins have been of central interest. AML cells express integrins that bind to ligands in the microenvironment, enabling adhesion of leukaemia cells in the microenvironment, thereby initiating intracellular signalling pathways that are associated with cell migration, cell proliferation, survival, and drug resistance that has been described to mediate cell adhesion-mediated drug resistance (CAM-DR). Identifying and targeting integrins in AML to interrupt interactions with the microenvironment have been pursued as a strategy to overcome CAM-DR. Here, we focus on the BM microenvironment and review the role of integrins in CAM-DR of AML and discuss integrin-targeting strategies. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Bitter Taste Receptor Agonist Denatonium Inhibits Stemness Characteristics in Hematopoietic Stem/Progenitor Cells.

Bone marrow microenvironmental stimuli profoundly impact hematopoietic stem cell fate and biology. As G protein-coupled receptors, the bitter taste receptors (TAS2Rs) are key in transmitting extracellular stimuli into an intracellular response, within the oral cavity but also in extraoral tissues. Their expression in the bone marrow (BM)-derived cells suggests their involvement in sensing the BM microenvironmental fluctuation. In the present study, we demonstrated that umbilical cord blood (UCB)-derived CD34+ cells express fully functional TAS2Rs along with the signal transduction cascade components and their activation by the prototypical agonist, denatonium benzoate, significantly modulated genes involved in stemness maintenance and regulation of cell trafficking. The activation of these specific pathways was confirmed in functional in vitro experiments. Denatonium exposure exerted an antiproliferative effect on UCB-derived CD34+ cells, mainly affecting the most undifferentiated progenitor frequency. It also reduced their clonogenicity and repopulating potential in vitro. In addition, the TAS2R signaling activation impaired the UCB-derived CD34+ cell trafficking, mainly reducing the migration toward the chemoattractant agent CXCL12 and modulating the expression of the adhesion molecules CD62L, CD49d, and CD29. In conclusion, our results in UCB-derived CD34+ cells expand the observation of TAS2R expression in the setting of BM-resident cells and shed light on the role of TAS2Rs in the extrinsic regulation of hematopoietic stem cell functions.

The Bone Marrow Microenvironment in Immune-Mediated Inflammatory Diseases: Implications for Mesenchymal Stromal Cell-Based Therapies.

Bone marrow (BM)-derived mesenchymal stromal cells (MSCs) are promising candidates for cell-based therapy for several immune-mediated inflammatory diseases (IMIDs) due to their multiplicity of immunomodulatory and reparative properties and favorable safety profile. However, although preclinical data were encouraging, the clinical benefit demonstrated in clinical trials of autologous MSC transplantation in a number of conditions has been less robust. This may be explained by the growing body of evidence pointing to abnormalities of the bone marrow microenvironment in IMIDs, including impaired MSC function. However, it is not currently known whether these abnormalities arise as a cause or consequence of disease, the role they play in disease initiation and/or progression, or whether they themselves are targets for disease modification. Here, we review current knowledge about the function of the BM microenvironment in IMIDs including multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, and type I diabetes, focusing on MSCs in particular. We predict that an improved understanding of disease-related changes in the bone marrow microenvironment including the role of MSCs in vivo, will yield new insights into pathophysiology and aid identification of new drug targets and optimization of cell-based therapy in IMIDs.

Intravital Microscopy to Study the Effect of Matrix Metalloproteinase Inhibition on Acute Myeloid Leukemia Cell Migration in the Bone Marrow.

Hematopoiesis is the process through which all mature blood cells are formed and takes place in the bone marrow (BM). Acute myeloid leukemia (AML) is a blood cancer of the myeloid lineage. AML progression causes drastic remodeling of the BM microenvironment, making it no longer supportive of healthy hematopoiesis and leading to clinical cytopenia in patients. Understanding the mechanisms by which AML cells shape the BM to their benefit would lead to the development of new therapeutic strategies. While the role of extracellular matrix (ECM) in solid cancer has been extensively studied during decades, its role in the BM and in leukemia progression has only begun to be acknowledged. In this context, intravital microscopy (IVM) gives the unique insight of direct in vivo observation of AML cell behavior in their environment during disease progression and/or upon drug treatments. Here we describe our protocol for visualizing and analyzing MLL-AF9 AML cell dynamics upon systemic inhibition of matrix metalloproteinases (MMP), combining confocal and two-photon microscopy and focusing on cell migration.

Advances in the pathogenesis of multiple myeloma bone disease. / å¤šå‘æ€§éª¨é«“ç˜¤éª¨ç— å‘ç— æœºåˆ¶çš„ç ”ç©¶è¿›å±•.

Multiple myeloma (MM) is a clonal proliferative malignant tumor of plasma cells in bone marrow. With the aging of population in China, the incidence of MM is on the rise. Multiple myeloma bone disease (MBD) is one of the common clinical manifestations of MM, and 80%-90% of MM patients are accompanied by osteolytic lesions at the time of their first visit to the clinic. MBD not only increases the disability rate of patients, but also severely reduces the physical function of patients due to skeletal lesions and bone-related events. Currently available drugs for treating of MBD are ineffective and associated with side effects. Therefore, it is important to find new therapeutic approaches for the treatment of MBD. It is generally believed that the increased osteoclast activity and suppressed osteoblast function are the main pathologic mechanisms for MBD. However, more and more studies have suggested that soluble molecules in the bone marrow microenvironment, including cytokines, extracellular bodies, and metabolites, play an important role in the development of MBD. Therefore, exploring the occurrence and potential molecular mechanisms for MBD from multiple perspectives, and identifying the predictive biomarkers and potential therapeutic targets are of significance for the clinical treatment of MBD.

Novel Developments in the Treatment of Multiple Myeloma-Associated Bone Disease.

Osteolytic bone disease is present in about 80% of patients with multiple myeloma at the time of diagnosis. Managing bone disease in patients with multiple myeloma is a challenge and requires a multi-faceted treatment approach with medication, surgery, and radiation. The established treatments with intravenous or subcutaneous antiresorptives can cause debilitating adverse events for patients, mainly osteonecrosis of the jaw, which, traditionally, has been difficult to manage. Now, oral surgery is recommended and proven successful in 60-85% of patients. Patients with spinal involvement may benefit from surgery in the form of vertebroplasty and kyphoplasty for pain relief, improved mobility, and reestablished sagittal balance, as well as the restoration of vertebral height. These procedures are considered safe, but the full therapeutic impact needs to be investigated further. Ixazomib, the first oral proteasome inhibitor, increases osteoblast differentiation, and recently published preliminary results in patients treated with Ixazomib maintenance have promisingly shown increased trabecular volume caused by prolonged bone formation activity. Other novel potential treatment strategies are discussed as well.

High NEK2 expression in myeloid progenitors suppresses T cell immunity in multiple myeloma.

Multiple myeloma (MM) growth is supported by an immune-tolerant bone marrow microenvironment. Here, we find that loss of Never in mitosis gene A (NIMA)-related kinase 2 (NEK2) in tumor microenvironmental cells is associated with MM growth suppression. The absence of NEK2 leads to both fewer tumor-associated macrophages (TAMs) and inhibitory T cells. NEK2 expression in myeloid progenitor cells promotes the generation of functional TAMs when stimulated with MM conditional medium. Clinically, high NEK2 expression in MM cells is associated with increased CD8+ T effector memory cells, while low NEK2 is associated with an IFN-γ gene signature and activated T cell response. Inhibition of NEK2 upregulates PD-L1 expression in MM cells and myeloid cells. In a mouse model, the combination of NEK2 inhibitor INH154 with PD-L1 blockade effectively eliminates MM cells and prolongs survival. Our results provide strong evidence that NEK2 inhibition may overcome tumor immune escape and support its further clinical development.

Spatiotemporal evolution of AML immune microenvironment remodeling and RNF149-driven drug resistance through single-cell multidimensional analysis.

BACKGROUND: The composition of the bone marrow immune microenvironment in patients with acute myeloid leukaemia (AML) was analysed by single-cell sequencing and the evolutionary role of different subpopulations of T cells in the development of AML and in driving drug resistance was explored in conjunction with E3 ubiquitin ligase-related genes. METHODS: To elucidate the mechanisms underlying AML-NR and Ara-C resistance, we analyzed the bone marrow immune microenvironment of AML patients by integrating multiple single-cell RNA sequencing datasets. When compared to the AML disease remission (AML-CR) cohort, AML-NR displayed distinct cellular interactions and alterations in the ratios of CD4+T, Treg, and CD8+T cell populations. RESULTS: Our findings indicate that the E3 ubiquitin ligase RNF149 accelerates AML progression, modifies the AML immune milieu, triggers CD8+T cell dysfunction, and influences the transformation of CD8+ Navie.T cells to CD8+TExh, culminating in diminished AML responsiveness to chemotherapeutic agents. Experiments both in vivo and in vitro revealed RNF149's role in enhancing AML drug-resistant cell line proliferation and in apoptotic inhibition, fostering resistance to Ara-C. CONCLUSION: In essence, the immune microenvironments of AML-CR and AML-NR diverge considerably, spotlighting RNF149's tumorigenic function in AML and cementing its status as a potential prognostic indicator and innovative therapeutic avenue for countering AML resistance.

Bone Marrow Microenvironment Involvement in t-MN: Focus on Mesenchymal Stem Cells.

Therapy-related myeloid neoplasms (t-MN) are a late complication of cytotoxic therapy (CT) used in the treatment of both malignant and non-malignant diseases. Historically, t-MN has been considered to be a direct consequence of DNA damage induced in normal hematopoietic stem or progenitor cells (HSPC) by CT. However, we now know that treatment-induced mutations in HSC are not the only players involved in t-MN development, but additional factors may contribute to the onset of t-MN. One of the known drivers involved in this field is the bone marrow microenvironment (BMM) and, in particular, bone marrow mesenchymal stem cells (BM-MSC), whose role in t-MN pathogenesis is the topic of this mini-review. BM-MSCs, physiologically, support HSC maintenance, self-renewal, and differentiation through hematopoietic-stromal interactions and the production of cytokines. In addition, BM-MSCs maintain the stability of the BM immune microenvironment and reduce the damage caused to HSC by stress stimuli. In the t-MN context, chemo/radiotherapy may induce damage to the BM-MSC and likewise alter BM-MSC functions by promoting pro-inflammatory response, clonal selection and/or the production of factors that may favor malignant hematopoiesis. Over the last decade, it has been shown that BM-MSC isolated from patients with de novo and therapy-related MN exhibit decreased proliferative and clonogenic capacity, altered morphology, increased senescence, defective osteogenic differentiation potential, impaired immune-regulatory properties, and reduced ability to support HSC growth and differentiation, as compared to normal BM-MSC. Although the understanding of the genetic and gene expression profile associated with ex vivo-expanded t-MN-MSCs remains limited and debatable, its potential role in prognostic and therapeutic terms is acting as a flywheel of attraction for many researchers.