Alterations of the bone marrow stromal microenvironment in adult patients with acute myeloid and lymphoblastic leukemias before and after allogeneic hematopoietic stem cell transplantation

Dynamic evolution of bone marrow adipocyte in B cell acute lymphoblastic leukemia: insights from diagnosis to post-chemotherapy

Adipocyte is a unique and versatile component of bone marrow microenvironment (BMM). However, the dynamic evolution of Bone Marrow (BM) adipocytes from the diagnosis of B cell Acute Lymphoblastic Leukemia (B-ALL) to the post-treatment state, and how they affect the progression of leukemia, remains inadequately explicated. Primary patient-derived xenograft models (PDXs) and stromal cell co-culture system are employed in this study. We show that the dynamic evolution of BM adipocytes from initial diagnosis of B-ALL to the post-chemotherapy phase, transitioning from cellular depletion in the initial leukemia niche to a fully restored state upon remission. Increased BM adipocytes retards engraftment of B-ALL cells in PDX models and inhibits cells growth of B-ALL in vitro. Mechanistically, the proliferation arrest of B-ALL cells in the context of adipocytes-enrichment niche, might attribute to the presence of adiponectin secreted by adipocytes themselves and the absence of cytokines secreted by mesenchymal stem cell (MSCs). In summary, our findings offer a novel perspective for further in-depth understanding of the dynamic balance between BMM and B-ALL.

Molecular Changes in Immunological Characteristics of Bone Marrow Multipotent Mesenchymal Stromal Cells in Lymphoid Neoplasia

Immune system and bone marrow stromal cells play an important role in maintaining normal hematopoiesis. Lymphoid neoplasia disturbs not only development of immune cells, but other immune response mechanisms as well. Multipotent mesenchymal stromal cells (MSCs) of the bone marrow are involved in immune response regulation through both intercellular interactions and secretion of various cytokines. In hematological malignancies, the bone marrow stromal microenvironment, including MSCs, is altered. Aim of this study was to describe the differences of MSCs' immunological function in the patients with acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL). In ALL, malignant cells arise from the early precursor cells localized in bone marrow, while in DLBCL they arise from more differentiated B-cells. In this study, only the DLBCL patients without bone marrow involvement were included. Growth parameters, surface marker expression, genes of interest expression, and secretion pattern of bone marrow MSCs from the patients with ALL and DLBCL at the onset of the disease and in remission were studied. MSCs from the healthy donors of corresponding ages were used as controls. It has been shown that concentration of MSCs in the bone marrow of the patients with ALL is reduced at the onset of the disease and is restored upon reaching remission; in the patients with DLBCL this parameter does not change. Proliferative capacity of MSCs did not change in the patients with ALL; however, the cells of the DLBCL patients both at the onset and in remission proliferated significantly faster than those from the donors. Expression of the membrane surface markers and expression of the genes important for differentiation, immunological status maintenance, and cytokine secretion differed significantly in the MSCs of the patients from those of the healthy donors and depended on nosology of the disease. Secretomes of the MSCs varied greatly; a number of proteins associated with immune response regulation, differentiation, and maintenance of hematopoietic stem cells were depleted in the secretomes of the cells from the patients. Lymphoid neoplasia leads to dramatic changes in the functional immunological status of MSCs.

Allogeneic stem cell transplantation in the treatment of acute myeloid leukemia: An overview of obstacles and opportunities

As an important treatment for acute myeloid leukemia, allogeneic hematopoietic stem cell transplantation (allo-HSCT) plays an important role in reducing relapse and improving long-term survival. With rapid advancements in basic research in molecular biology and immunology and with deepening understanding of the biological characteristics of hematopoietic stem cells, allo-HSCT has been widely applied in clinical practice. During allo-HSCT, preconditioning, the donor, and the source of stem cells can be tailored to the patient’s conditions, greatly broadening the indications for HSCT, with clear survival benefits. However, the risks associated with allo-HSCT remain high, i.e. hematopoietic reconstitution failure, delayed immune reconstitution, graft-versus-host disease, and post-transplant relapse, which are bottlenecks for further improvements in allo-HSCT efficacy and have become hot topics in the field of HSCT. Other bottlenecks recognized in the current treatment of individuals diagnosed with acute myeloid leukemia and subjected to allo-HSCT include the selection of the most appropriate conditioning regimen and post-transplantation management. In this paper, we reviewed the progress of relevant research regarding these aspects.

Primary mesenchymal stromal cells in co-culture with leukaemic HL-60 cells are sensitised to cytarabine-induced genotoxicity, whilst leukaemic cells are protected

Tumour microenvironments are hallmarked in many cancer types. In haematological malignancies, bone marrow (BM) mesenchymal stromal cells (MSC) protect malignant cells from drug-induced cytotoxicity. However, less is known about malignant impact on supportive stroma. Notably, it is unknown whether these interactions alter long-term genotoxic damage in either direction. The nucleoside analogue cytarabine (ara-C), common in haematological therapies, remains the most effective agent for acute myeloid leukaemia, yet one third of patients develop resistance. This study aimed to evaluate the bidirectional effect of MSC and malignant cell co-culture on ara-C genotoxicity modulation. Primary MSC, isolated from patient BM aspirates for haematological investigations, and malignant haematopoietic cells (leukaemic HL-60) were co-cultured using trans-well inserts, prior to treatment with physiological dose ara-C. Co-culture genotoxic effects were assessed by micronucleus and alkaline comet assays. Patient BM cells from chemotherapy-treated patients had reduced ex vivo survival (P = 0.0049) and increased genotoxicity (P = 0.3172) than untreated patients. It was shown for the first time that HL-60 were protected by MSC from ara-C-induced genotoxicity, with reduced MN incidence in co-culture as compared to mono-culture (P = 0.0068). Comet tail intensity also significantly increased in ara-C-treated MSC with HL-60 influence (P = 0.0308). MSC sensitisation to ara-C genotoxicity was also demonstrated following co-culture with HL60 (P = 0.0116), which showed significantly greater sensitisation when MSC-HL-60 co-cultures were exposed to ara-C (P = 0.0409). This study shows for the first time that malignant HSC and MSC bidirectionally modulate genotoxicity, providing grounding for future research identifying mechanisms of altered genotoxicity in leukaemic microenvironments. MSC retain long-term genotoxic and functional damage following chemotherapy exposure. Understanding the interactions perpetuating such damage may inform modifications to reduce therapy-related complications, such as secondary malignancies and BM failure.

Clonal Hematopoiesis of Indeterminate Potential as a Novel Risk Factor for Donor-Derived Leukemia

Hematopoietic stem cell transplantation (HSCT) is a critical treatment modality for many hematological and non-hematological diseases that is being extended to treat older individuals. However, recent studies show that clonal hematopoiesis of indeterminate potential (CHIP), a common, asymptomatic condition characterized by the expansion of age-acquired somatic mutations in blood cell lineages, may be a risk factor for the development of donor-derived leukemia (DDL), unexplained cytopenias, and chronic graft-versus-host disease. CHIP may contribute to the pathogenesis of these significant transplant complications via various cell-autonomous and non-cell-autonomous mechanisms, and the clinical presentation of DDL may be broader than anticipated. A more comprehensive understanding of the contributions of CHIP to DDL may have important implications for the screening of donors and will improve the safety of HSCT. The objective of this review is to discuss studies linking DDL and CHIP and to explore potential mechanisms by which CHIP may contribute to DDL.

Hematopoietic Stem Cell Niche During Homeostasis, Malignancy, and Bone Marrow Transplantation

Self-renewal and multidirectional differentiation of hematopoietic stem cells (HSCs) are strictly regulated by numerous cellular components and cytokines in the bone marrow (BM) microenvironment. Several cell types that regulate HSC niche have been identified, including both non-hematopoietic cells and HSC-derived cells. Specific changes in the niche composition can result in hematological malignancies. Furthermore, processes such as homing, proliferation, and differentiation of HSCs are strongly controlled by the BM niche and have been reported to be related to the success of hematopoietic stem cell transplantation (HSCT). Single-cell sequencing and in vivo imaging are powerful techniques to study BM microenvironment in hematological malignancies and after HSCT. In this review, we discuss how different components of the BM niche, particularly non-hematopoietic and hematopoietic cells, regulate normal hematopoiesis, and changes in the BM niche in leukemia and after HSCT. We believe that this comprehensive review will provide clues for further research on improving HSCT efficiency and exploring potential therapeutic targets for leukemia.

Bone Marrow Multipotent Mesenchymal Stromal Cells in Patients with Diffuse Large B-Cell Lymphoma

In diffuse large B-cell lymphoma, bone marrow involvement is rarely diagnosed. We compared the properties of bone marrow stromal progenitor cells and the concentration of fibroblast CFU in patients with diffuse large B-cell lymphoma without bone marrow involvement and in healthy donors. It was found that the properties of multipotent mesenchymal stromal cells in patients in the debut of the disease differed considerably from those in healthy donors. In particular, the total cell production in patients was significantly higher than in donors. In multipotent mesenchymal stromal cells of patients, some cell parameters were changes; the mean fluorescence intensity of the adhesion molecule ICAM1 on the cell surface was increased. The mean fluorescence intensity of mesenchymal stromal cell markers (HLA-ABC, CD73 and CD90) was significantly elevated. The relative expression of BMP4, MMP2, FGFR1, and ICAM1 genes in mesenchymal stromal cell was reduced, while the expression of FGFR2 gene was enhanced. Despite the absence of proven involvement of the bone marrow, the properties of mesenchymal stromal cells, the components in the stromal microenvironment niche regulating hemopoiesis are altered in patients with diffuse large B-cell lymphoma.

Chemotherapy-induced genotoxic damage to bone marrow cells: long-term implications

Mesenchymal stem/stromal cells (MSCs) within the bone marrow (BM) are vitally important in forming the micro-environment supporting haematopoiesis after myeloablative chemotherapy. MSCs are known to be damaged phenotypically and functionally by chemotherapy; however, to the best our knowledge, the persistence of genotoxic effects of chemotherapy on the BM micro-environment has not been studied. We therefore aimed to evaluate genotoxic effects of chemotherapy on the BM both in vitro and in vivo, using the comet and micronucleus assays, focussing on the persistence of DNA lesions that may contribute to complications in the patient. The MSC cell line (HS-5) and primary cord blood mononuclear cells (CBMNCs: a source of undamaged DNA) were exposed to the chemotherapeutic agent cyclophosphamide (CY) within a physiologically relevant in vitro model. CY treatment resulted in significant increases in CBMNC DNA damage at all time points tested (3-48 h exposure). Similarly, HS-5 cells exposed to CY exhibited significant increases in DNA damage as measured by the comet assay, with increased numbers of abnormal cells visible in the micronucleus assay. In addition, even 48 h after removal of 48-h CY treatment, DNA damage remains significantly increased in treated cells relative to controls. In patients treated with chemotherapy for haematological malignancy, highly significant increases in damaged DNA were seen in BM cells isolated from one individual 1 year after completion of therapy for acute leukaemia compared with pretreatment (P < 0.001). Similarly, two individuals treated 7 and 17 years previously with chemotherapy exhibited significant increases of damaged DNA in MSC compared with untreated age- and sex-matched controls (P < 0.05). Unlike haematopoietic cells, MSCs are not replaced following a stem cell transplant. Therefore, long-term damage to MSC may impact on engraftment of either allogeneic or autologous transplants. In addition, persistence of DNA lesions may lead to genetic instability, correlating with the significant number of chemotherapy-treated individuals who have therapy-related malignancies.

Recovery of Donor Hematopoiesis after Graft Failure and Second Hematopoietic Stem Cell Transplantation with Intraosseous Administration of Mesenchymal Stromal Cells

Multipotent mesenchymal stromal cells (MSCs) participate in the formation of bone marrow niches for hematopoietic stem cells. Donor MSCs can serve as a source of recovery for niches in patients with graft failure (GF) after allogeneic bone marrow (BM) transplantation. Since only few MSCs reach the BM after intravenous injection, MSCs were implanted into the iliac spine. For 8 patients with GF after allo-BMT, another hematopoietic stem cell transplantation with simultaneous implantation of MSCs from their respective donors into cancellous bone was performed. BM was aspirated from the iliac crest of these patients at 1-2, 4-5, and 9 months after the intraosseous injection of donor MSCs. Patients' MSCs were cultivated, and chimerism was determined. In 6 out of 8 patients, donor hematopoiesis was restored. Donor cells (9.4 ± 3.3%) were detected among MSCs. Thus, implanted MSCs remain localized at the site of administration and do not lose the ability to proliferate. These results suggest that MSCs could participate in the restoration of niches for donor hematopoietic cells or have an immunomodulatory effect, preventing repeated rejection of the graft. Perhaps, intraosseous implantation of MSCs contributes to the success of the second transplantation of hematopoietic stem cells and patient survival.

Creating artificial lymphoid tissues to study immunity and hematological malignancies

PURPOSE OF REVIEW

The specialized microenvironments of lymphoid tissue affect immune cell function and progression of disease. However, current animal models are low throughput and a large number of human diseases are difficult to model in animals. Animal models are less amenable to manipulation of tissue niche components, signalling pathways, epigenetics, and genome editing than ex vivo models. On the other hand, conventional 2D cultures lack the physiological relevance to study precise microenvironmental interactions. Thus, artificial tissues are being developed to study these interactions in the context of immune development, function, and disease.

RECENT FINDINGS

New bone marrow and lymph node models have been created to, respectively, study microenvironmental interactions in hematopoiesis and germinal center-like biology. These models have also been extended to understand the effect of these interactions on the progression and therapeutic response in leukemia, multiple myeloma, and lymphoma.

SUMMARY

3D in-vitro immune models have elucidated new cellular, biochemical, and biophysical interactions as potential regulatory mechanisms, therapeutic targets, or biomarkers that previously could not be studied in animal models and conventional 2D cultures. Incorporation of advanced biomaterials, microfluidics, genome editing, and single-cell analysis tools will enable further studies of function, driver mutations, and tumor heterogeneity. Continual refinement will help inform the development of antibody and cell-based immunotherapeutics and patient-specific treatment plans.