Down-regulation of Dicer1 promotes cellular senescence and decreases the differentiation and stem cell-supporting capacities of mesenchymal stromal cells in patients with myelodysplastic syndrome

Immune-monitoring of myelodysplastic neoplasms: Recommendations from the i4MDS consortium

Advancements in comprehending myelodysplastic neoplasms (MDS) have unfolded significantly in recent years, elucidating a myriad of cellular and molecular underpinnings integral to disease progression. While molecular inclusions into prognostic models have substantively advanced risk stratification, recent revelations have emphasized the pivotal role of immune dysregulation within the bone marrow milieu during MDS evolution. Nonetheless, immunotherapy for MDS has not experienced breakthroughs seen in other malignancies, partly attributable to the absence of an immune classification that could stratify patients toward optimally targeted immunotherapeutic approaches. A pivotal obstacle to establishing "immune classes" among MDS patients is the absence of validated accepted immune panels suitable for routine application in clinical laboratories. In response, we formed International Integrative Innovative Immunology for MDS (i4MDS), a consortium of multidisciplinary experts, and created the following recommendations for standardized methodologies to monitor immune responses in MDS. A central goal of i4MDS is the development of an immune score that could be incorporated into current clinical risk stratification models. This position paper first consolidates current knowledge on MDS immunology. Subsequently, in collaboration with clinical and laboratory specialists, we introduce flow cytometry panels and cytokine assays, meticulously devised for clinical laboratories, aiming to monitor the immune status of MDS patients, evaluating both immune fitness and identifying potential immune "risk factors." By amalgamating this immunological characterization data and molecular data, we aim to enhance patient stratification, identify predictive markers for treatment responsiveness, and accelerate the development of systems immunology tools and innovative immunotherapies.

Mesenchymal Stromal Cell Senescence Induced by Dnmt3a -Mutant Hematopoietic Cells is a Targetable Mechanism Driving Clonal Hematopoiesis and Initiation of Hematologic Malignancy

Clonal hematopoiesis (CH) can predispose to blood cancers due to enhanced fitness of mutant hematopoietic stem and progenitor cells (HSPCs), but the mechanisms driving this progression are not understood. We hypothesized that malignant progression is related to microenvironment-remodelling properties of CH-mutant HSPCs. Single-cell transcriptomic profiling of the bone marrow microenvironment in Dnmt3a R878H/+ mice revealed signatures of cellular senescence in mesenchymal stromal cells (MSCs). Dnmt3a R878H/+ HSPCs caused MSCs to upregulate the senescence markers SA-β-gal, BCL-2, BCL-xL, Cdkn1a (p21) and Cdkn2a (p16), ex vivo and in vivo . This effect was cell contact-independent and can be replicated by IL-6 or TNFα, which are produced by Dnmt3a R878H/+ HSPCs. Depletion of senescent MSCs in vivo reduced the fitness of Dnmt3a R878H/+ hematopoietic cells and the progression of CH to myeloid neoplasms using a sequentially inducible Dnmt3a ; Npm1 -mutant model. Thus, Dnmt3a -mutant HSPCs reprogram their microenvironment via senescence induction, creating a self-reinforcing niche favoring fitness and malignant progression.

Statement of Significance

Mesenchymal stromal cell senescence induced by Dnmt3a -mutant hematopoietic stem and progenitor cells drives clonal hematopoiesis and initiation of hematologic malignancy.

Age-Related Alterations in Mesenchymal Stem Cell Function: Understanding Mechanisms and Seeking Opportunities to Bypass the Cellular Aging

Undoubtedly, mesenchymal stem cells (MSCs) are the most common cell therapy candidates in clinical research and therapy. They not only exert considerable therapeutic effects to alleviate inflammation and promote regeneration, but also show low-immunogenicity properties, which ensure their safety following allogeneic transplantation. Thanks to the necessity of providing a sufficient number of MSCs to achieve clinically efficient outcomes, prolonged in vitro cultivation is indisputable. However, either following long-term in vitro expansion or aging in elderly individuals, MSCs face cellular senescence. Senescent MSCs undergo an impairment in their function and therapeutic capacities and secrete degenerative factors which negatively affect young MSCs. To this end, designing novel investigations to further elucidate cellular senescence and to pave the way toward finding new strategies to reverse senescence is highly demanded. In this review, we will concisely discuss current progress on the detailed mechanisms of MSC senescence and various inflicted changes following aging in MSC. We will also shed light on the examined strategies underlying monitoring and reversing senescence in MSCs to bypass the comprised therapeutic efficacy of the senescent MSCs.

Engagement of Mesenchymal Stromal Cells in the Remodeling of the Bone Marrow Microenvironment in Hematological Cancers

Mesenchymal stromal cells (MSCs) are a subset of heterogeneous, non-hematopoietic fibroblast-like cells which play important roles in tissue repair, inflammation, and immune modulation. MSCs residing in the bone marrow microenvironment (BMME) functionally interact with hematopoietic stem progenitor cells regulating hematopoiesis. However, MSCs have also emerged in recent years as key regulators of the tumor microenvironment. Indeed, they are now considered active players in the pathophysiology of hematologic malignancies rather than passive bystanders in the hematopoietic microenvironment. Once a malignant event occurs, the BMME acquires cellular, molecular, and epigenetic abnormalities affecting tumor growth and progression. In this context, MSC behavior is affected by signals coming from cancer cells. Furthermore, it has been shown that stromal cells themselves play a major role in several hematological malignancies' pathogenesis. This bidirectional crosstalk creates a functional tumor niche unit wherein tumor cells acquire a selective advantage over their normal counterparts and are protected from drug treatment. It is therefore of critical importance to unveil the underlying mechanisms which activate a protumor phenotype of MSCs for defining the unmasked vulnerabilities of hematological cancer cells which could be pharmacologically exploited to disrupt tumor/MSC coupling. The present review focuses on the current knowledge about MSC dysfunction mechanisms in the BMME of hematological cancers, sustaining tumor growth, immune escape, and cancer progression.

Mesenchymal stromal cell senescence in haematological malignancies

Acute myeloid leukaemia (AML), chronic lymphocytic leukaemia (CLL), and multiple myeloma (MM) are age-related haematological malignancies with defined precursor states termed myelodysplastic syndrome (MDS), monoclonal B-cell lymphocytosis (MBL), and monoclonal gammopathy of undetermined significance (MGUS), respectively. While the progression from asymptomatic precursor states to malignancy is widely considered to be mediated by the accumulation of genetic mutations in neoplastic haematopoietic cell clones, recent studies suggest that intrinsic genetic changes, alone, may be insufficient to drive the progression to overt malignancy. Notably, studies suggest that extrinsic, microenvironmental changes in the bone marrow (BM) may also promote the transition from these precursor states to active disease. There is now enhanced focus on extrinsic, age-related changes in the BM microenvironment that accompany the development of AML, CLL, and MM. One of the most prominent changes associated with ageing is the accumulation of senescent mesenchymal stromal cells within tissues and organs. In comparison with proliferating cells, senescent cells display an altered profile of secreted factors (secretome), termed the senescence-associated-secretory phenotype (SASP), comprising proteases, inflammatory cytokines, and growth factors that may render the local microenvironment favourable for cancer growth. It is well established that BM mesenchymal stromal cells (BM-MSCs) are key regulators of haematopoietic stem cell maintenance and fate determination. Moreover, there is emerging evidence that BM-MSC senescence may contribute to age-related haematopoietic decline and cancer development. This review explores the association between BM-MSC senescence and the development of haematological malignancies, and the functional role of senescent BM-MSCs in the development of these cancers.

Bone Marrow Microenvironment as a Source of New Drug Targets for the Treatment of Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease with one of the worst survival rates of all cancers. The bone marrow microenvironment is increasingly being recognised as an important mediator of AML chemoresistance and relapse, supporting leukaemia stem cell survival through interactions among stromal, haematopoietic progenitor and leukaemic cells. Traditional therapies targeting leukaemic cells have failed to improve long term survival rates, and as such, the bone marrow niche has become a promising new source of potential therapeutic targets, particularly for relapsed and refractory AML. This review briefly discusses the role of the bone marrow microenvironment in AML development and progression, and as a source of novel therapeutic targets for AML. The main focus of this review is on drugs that modulate/target this bone marrow microenvironment and have been examined in in vivo models or clinically.

Aryl hydrocarbon receptor signaling pathway plays important roles in the proliferative and metabolic properties of bone marrow mesenchymal stromal cells

Bone marrow mesenchymal stromal cells (BMMSCs) are widely sourced and easily amplified in vitro; thus, they have a great potential in the treatment of hemopathies. Recent findings suggested that BMMSCs express the aryl hydrocarbon receptor (AHR). However, few studies have reported on the regulation of proliferative behaviors and metabolism by AHR in BMMSCs. In the present study, we found that activating AHR reduced the proliferation of BMMSCs and enhanced their mitochondrial function, whereas inhibiting AHR exerted the opposite effects. This study may provide the basis for further unveiling the molecular mechanisms and therapeutic potential of AHR in BMMSCs.

Nature or Nurture? Role of the Bone Marrow Microenvironment in the Genesis and Maintenance of Myelodysplastic Syndromes

Myelodysplastic syndrome (MDS) are clonal haematopoietic stem cell (HSC) disorders driven by a complex combination(s) of changes within the genome that result in heterogeneity in both clinical phenotype and disease outcomes. MDS is among the most common of the haematological cancers and its incidence markedly increases with age. Currently available treatments have limited success, with <5% of patients undergoing allogeneic HSC transplantation, a procedure that offers the only possible cure. Critical contributions of the bone marrow microenvironment to the MDS have recently been investigated. Although the better understanding of the underlying biology, particularly genetics of haematopoietic stem cells, has led to better disease and risk classification; however, the role that the bone marrow microenvironment plays in the development of MDS remains largely unclear. This review provides a comprehensive overview of the latest developments in understanding the aetiology of MDS, particularly focussing on understanding how HSCs and the surrounding immune/non-immune bone marrow niche interacts together.

Oncogenic KrasG12D Activation in the Nonhematopoietic Bone Marrow Microenvironment Causes Myelodysplastic Syndrome in Mice

The bone marrow microenvironment (BMME) is key player in regulation and maintenance of hematopoiesis. Oncogenic RAS mutations, causing constitutive activation of multiple tumor-promoting pathways, are frequently found in human cancer. So far in hematologic malignancies, RAS mutations have only been reported to occur in hematopoietic cells. In this study, we investigated the effect of oncogenic Kras expression in the BMME in a chimeric mouse model. We observed that an activating mutation of Kras in the nonhematopoietic system leads to a phenotype resembling myelodysplastic syndrome (MDS) characterized by peripheral cytopenia, marked dysplasia within the myeloid lineage as well as impaired proliferation and differentiation capacity of hematopoietic stem and progenitor cells. The phenotypic changes could be reverted when the BM was re-isolated and transferred into healthy recipients, indicating that the Kras^G12D -activation in the nonhematopoietic BMME was essential for the MDS phenotype. Gene expression analysis of sorted nonhematopoietic BM niche cells from Kras^G12D mice revealed upregulation of multiple inflammation-related genes including IL1-superfamily members (Il1α, Il1β, Il1f9) and the NLPR3 inflammasome. Thus, pro-inflammatory IL1-signaling in the BMME may contribute to MDS development. Our findings show that a single genetic change in the nonhematopoietic BMME can cause an MDS phenotype. Oncogenic Kras activation leads to pro-inflammatory signaling in the BMME which impairs HSPCs function. IMPLICATIONS: These findings may help to identify new therapeutic targets for MDS.

Senescent Mesenchymal Stem Cells in Myelodysplastic Syndrome: Functional Alterations, Molecular Mechanisms, and Therapeutic Strategies

Myelodysplastic syndrome (MDS) is a group of clonal hematopoietic disorders related to hematopoietic stem and progenitor cell dysfunction. However, therapies that are currently used to target hematopoietic stem cells are not effective. These therapies are able to slow the evolution toward acute myeloid leukemia but cannot eradicate the disease. Mesenchymal stem cells (MSCs) have been identified as one of the main cellular components of the bone marrow microenvironment, which plays an indispensable role in normal hematopoiesis. When functional and regenerative capacities of aging MSCs are diminished, some enter replicative senescence, which promotes inflammation and disease progression. Recent studies that investigated the contribution of bone marrow microenvironment and MSCs to the initiation and progression of the disease have offered new insights into the MDS. This review presents the latest updates on the role of MSCs in the MDS and discusses potential targets for the treatment of MDS.

Cytotoxic Therapy-Induced Effects on Both Hematopoietic and Marrow Stromal Cells Promotes Therapy-Related Myeloid Neoplasms

Therapy-related myeloid neoplasms (t-MNs) following treatment with alkylating agents are characterized by a del(5q), complex karyotypes, alterations of TP53, and a dismal prognosis. To decipher the molecular pathway(s) leading to the pathogenesis of del(5q) t-MN and the effect(s) of cytotoxic therapy on the marrow microenvironment, we developed a mouse model with loss of two key del(5q) genes, EGR1 and APC, in hematopoietic cells. We used the well-characterized drug, N-ethyl-N-nitrosurea (ENU) to demonstrate that alkylating agent exposure of stromal cells in the microenvironment increases the incidence of myeloid disease. In addition, loss of Trp53 with Egr1 and Apc was required to drive the development of a transplantable leukemia, and accompanied by the acquisition of somatic mutations in DNA damage response genes. ENU treatment of mesenchymal stromal cells induced cellular senescence, and led to the acquisition of a senescence-associated secretory phenotype, which may be a critical microenvironmental alteration in the pathogenesis of myeloid neoplasms.

Downregulation of extracellular vesicle microRNA-101 derived from bone marrow mesenchymal stromal cells in myelodysplastic syndrome with disease progression

To evaluate the mechanism underlying the communication between myeloid malignant and bone marrow (BM) microenvironment cells in disease progression, the current study established BM mesenchymal stromal cells (MSCs) and assessed extracellular vesicle (EV) microRNA (miR) expression in 22 patients with myelodysplastic syndrome (MDS) and 7 patients with acute myeloid leukemia and myelodysplasia-related changes (AML/MRC). Patients with MDS were separated into two categories based on the revised International Prognostic Scoring System (IPSS-R), and EV-miR expression in BM-MSCs was evaluated using a TaqMan low-density array. The selected miRs were evaluated using reverse transcription-quantitative PCR. The current study demonstrated that the expression of BM-MSC-derived EV-miR was heterogenous and based on MDS severity, the expression of EV-miR-101 was lower in high-risk group and patients with AML/MRC compared with the control and low-risk groups. This reversibly correlated with BM blast percentage, with which the cellular miR-101 from BM-MSCs or serum EV-miR-101 expression exhibited no association. Database analyses indicated that miR-101 negatively regulated cell proliferation and epigenetic gene expression. The downregulation of BM-MSC-derived EV-miR-101 may be associated with cell-to-cell communication and may accelerate the malignant process in MDS cells.

Phenotype of mesenchymal stem cells from patients with myelodyplastic syndrome maybe partly modulated by decitabine

Mesenchymal stem cells (MSCs) derived from myelodysplastic syndromes (MDSs) have been demonstrated to accelerate the progression of MDS. However, whether the phenotype of MSCs derived from MDS (MDS-MSCs) may be reversed and serve as a potential target for the treatment of MDS remains unclear. The present study investigated the functional alternations of MDS-MSCs following in vitro decitabine-treatment. Primary MSCs were cultured from the bone marrow aspirates of 28 patients with MDS. The impact on the growth of MDS-MSCs treated with decitabine was analyzed using the MTT assay. Changes in the gene expression levels of runt related transcription factor 2 (RUNX2), Sp7 transcription factor (SP7), cyclin dependent kinase inhibitor 1A (CDKN1A) and CD274 in MDS-MSCs following treatment with decitabine were analyzed by reverse transcription-quantitative polymerase chain reaction. The effects of decitabine on apoptosis and the cell cycle were examined using flow cytometry. The effect of decitabine on the immune regulation of MDS-MSCs was tested by the co-culture of MSCs with activated T cells in vitro. The results revealed that proliferation, apoptosis and the mRNA expression levels of RUNX2 and SP7 in MDS-MSCs did not significantly change following treatment with decitabine compared with control MDS-MSCs. However, treatment with decitabine resulted in a smaller population of cells in the G1 phase and an increase in the number of cells in the G2/M phase compared with control MDS-MSCs. This change was associated with decreased expression of CDKN1A in cells treated with decitabine compared with control cells. Notably, the ability of MDS-MSCs treated with decitabine to induce the differentiation of T cells into regulatory T cells was significantly reduced compared with control MDS-MSCs. This was associated with a decreased expression of CD274 in MDS-MSCs treated with decitabine compared with control MDS-MSCs. In conclusion, the phenotype of MSCs derived from patients with MDS was partially reversed by treatment with decitabine, presenting a potential therapeutic intervention.

The mesenchymal niche in MDS

Myelodysplastic syndrome (MDS) is characterized by bone marrow failure and a strong propensity for leukemic evolution. Somatic mutations are critical early drivers of the disorder, but the factors enabling the emergence, selection, and subsequent leukemic evolution of these “leukemia-poised” clones remain incompletely understood. Emerging data point at the mesenchymal niche as a critical contributor to disease initiation and evolution. Disrupted inflammatory signaling from niche cells may facilitate the occurrence of somatic mutations, their selection, and subsequent clonal expansion. This review summarizes the current concepts about “niche-facilitated” bone marrow failure and leukemic evolution, their underlying molecular mechanisms, and clinical implications for future innovative therapeutic targeting of the niche in MDS.

Epigenetic changes during aging and their reprogramming potential

The aging process results in significant epigenetic changes at all levels of chromatin and DNA organization. These include reduced global heterochromatin, nucleosome remodeling and loss, changes in histone marks, global DNA hypomethylation with CpG island hypermethylation, and the relocalization of chromatin modifying factors. Exactly how and why these changes occur is not fully understood, but evidence that these epigenetic changes affect longevity and may cause aging, is growing. Excitingly, new studies show that age-related epigenetic changes can be reversed with interventions such as cyclic expression of the Yamanaka reprogramming factors. This review presents a summary of epigenetic changes that occur in aging, highlights studies indicating that epigenetic changes may contribute to the aging process and outlines the current state of research into interventions to reprogram age-related epigenetic changes.

Bone mesenchymal stromal cells exhibit functional inhibition but no chromosomal aberrations in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a myeloproliferative neoplasia characterized by the presence of the Philadelphia (Ph) chromosome in hematopoietic cells (HCs). As one of the most important components of the bone marrow microenvironment (BMM), bone mesenchymal stromal cells (BMSCs) are critical in the development of leukemia and essential in the regulation of hematopoiesis. However, little is known regarding the alterations of BMSCs in CML. The current study performed Cell Counting Kit-8 and colony-forming unit fibroblast assays to evaluate the proliferative ability of BMSCs. The percentage of senescent BMSCs was evaluated by a senescence-associated β-galactosidase staining assay. Subsequently, a long-term culture-initiating cell assay was designed to explore the HC-supporting capacity of the BMSCs. Furthermore, cytogenetics were detected by conventional cytogenetic analysis and fluorescence in situ hybridization analysis. The current results revealed that CML-BMSCs exhibited decreased cell proliferation and impaired HC-support capacity, as well as increased susceptibility to senescence. No chromosomal aberrations, including the absence of the Ph chromosome, were noted in all CML-BMSCs. In conclusion, the current study demonstrated functional inhibition of CML-BMSCs; however, no signs of chromosomal aberrations were observed, thereby providing insight into the changes occurring in the CML-BMM.

Chronic immune response dysregulation in MDS pathogenesis

Chronic innate immune signaling in hematopoietic cells is widely described in myelodysplastic syndromes (MDS), and innate immune pathway activation, predominantly via pattern recognition receptors, increases the risk of developing MDS. An inflammatory component to MDS has been reported for many years, but only recently has evidence supported a more direct role of chronic innate immune signaling and associated inflammatory pathways in the pathogenesis of MDS. Here we review recent findings and discuss relevant questions related to chronic immune response dysregulation in MDS.

Role of MSC-derived galectin 3 in the AML microenvironment

In acute myeloid leukemia (AML), high Galectin 3 (LGALS3) expression is associated with poor prognosis. The role of LGALS3 derived from mesenchymal stromal cells (MSC) in the AML microenvironment is unclear; however, we have recently found high LGALS3 expression in MSC derived from AML patients is associated with relapse. In this study, we used reverse phase protein analysis (RPPA) to correlate LGALS3 expression in AML MSC with 119 other proteins including variants of these proteins such as phosphorylated forms or cleaved forms to identify biologically relevant pathways. RPPA revealed that LGALS3 protein was positively correlated with expression of thirteen proteins including MYC, phosphorylated beta-Catenin (p-CTNNB1), and AKT2 and negatively correlated with expression of six proteins including integrin beta 3 (ITGB3). String analysis revealed that proteins positively correlated with LGALS3 showed strong interconnectivity. Consistent with the RPPA results, LGALS3 suppression by shRNA in MSC resulted in decreased MYC and AKT expression while ITGB3 was induced. In co-culture, the ability of AML cell to adhere to MSC LGALS3 shRNA transductants was reduced compared to AML cell adhesion to MSC control shRNA transductants. Finally, use of novel specific LGALS3 inhibitor CBP.001 in co-culture of AML cells with MSC reduced viable leukemia cell populations with induced apoptosis and augmented the chemotherapeutic effect of AraC. In summary, the current study demonstrates that MSC-derived LGALS3 may be critical for important biological pathways for MSC homeostasis and for regulating AML cell localization and survival in the leukemia microenvironmental niche.

Premature senescence activation in DLD-1 colorectal cancer cells through adjuvant therapy to induce a miRNA profile modulating cellular death

Cancer, and particularly colon cancer, is associated with an increasing number of cases resistant to chemotherapy. One approach to overcome this, and to improve the prognosis and outcome of patients, is the use of adjuvant therapy alongside the standard chemotherapy regiment. In the present study, the effect of deuterium-depleted water (DDW) as a potential modulator of adjuvant therapy on DLD-1 colorectal cancer models was assessed. A number of functionality assays were performed, including MTT, apoptosis and autophagy, and mitochondrial activity and senescence assays, in addition to assessing the capacity to modify the pattern of released miRNA via microarray technology. No significant effect on cell viability was identified, but an increase in mitochondrial activity and a weak pro-apoptotic effect were observed in the treated DLD-1 cells cultured in DDW-prepared medium compared with those grown in standard conditions (SC). Furthermore, the findings revealed the capacity of DDW medium to promote senescence to a higher degree compared with SC. The exosome-released miRNA pattern was significantly modified for the cells maintained in DDW compared with those maintained in SC. These findings suggest that DDW may serve as an adjuvant treatment; however, a better understanding of the underlying molecular mechanism of action will be useful for developing novel and efficient therapeutic strategies, in which the transcriptomic pattern serves an important role.

Dicer1 downregulation by multiple myeloma cells promotes the senescence and tumor-supporting capacity and decreases the differentiation potential of mesenchymal stem cells

Bone marrow mesenchymal stem cells (BMMSCs) facilitate the growth of multiple myeloma (MM) cells, but the underlying mechanisms remain unclear. This study demonstrates that the senescence of MM-MSCs significantly increased, as evidenced by a decrease in proliferation and increase in the number of cells positive for senescence-associated β-galactosidase activity. Senescent MM-MSCs displayed decreased differentiation potential and increased tumor-supporting capacity. Dicer1 knockdown in the MSCs of healthy controls promoted cellular senescence and tumor-supporting capacity, while decreasing the differentiation capacity. Dicer1 overexpression in MM-MSCs reversed the effects on differentiation and reduced cellular senescence. In addition, decreased expression of the microRNA-17 family was identified as a favorable element responsible for increasing senescence, with the expression of p21 increased in Dicer1 knockdown cells. Furthermore, we observed decreased expression of miR-93 and miR-20a in MM-MSCs, while upregulation of miR-93/miR-20a decreased cellular senescence, as evidenced by the increased p21 expression. Importantly, we found that myeloma cells could induce the senescence of MSCs from healthy controls, as observed from the decreased expression of Dicer1 and miR-93/miR-20a and increased expression of p21. Overall, MM cells downregulate Dicer1 in MSCs, which leads to senescence; in turn, senescent MSCs promote MM cell growth, which most likely contributes to disease progression.

Distinct protein signatures of acute myeloid leukemia bone marrow-derived stromal cells are prognostic for patient survival

Mesenchymal stromal cells (MSC) support acute myeloid leukemia (AML) cell survival in the bone marrow (BM) microenvironment. Protein expression profiles of AML-derived MSC are unknown. Reverse phase protein array analysis was performed to compare expression of 151 proteins from AML-MSC (n=106) with MSC from healthy donors (n=71). Protein expression differed significantly between the two groups with 19 proteins over-expressed in leukemia stromal cells and 9 over-expressed in normal stromal cells. Unbiased hierarchical clustering analysis of the samples using these 28 proteins revealed three protein constellations whose variation in expression defined four MSC protein expression signatures: Class 1, Class 2, Class 3, and Class 4. These cell populations appear to have clinical relevance. Specifically, patients with Class 3 cells have longer survival and remission duration compared to other groups. Comparison of leukemia MSC at first diagnosis with those obtained at salvage (i.e. relapse/refractory) showed differential expression of 9 proteins reflecting a shift toward osteogenic differentiation. Leukemia MSC are more senescent compared to their normal counterparts, possibly due to the overexpressed p53/p21 axis as confirmed by high β-galactosidase staining. In addition, overexpression of BCL-X_L in leukemia MSC might give survival advantage under conditions of senescence or stress and overexpressed galectin-3 exerts profound immunosuppression. Together, our findings suggest that the identification of specific populations of MSC in AML patients may be an important determinant of therapeutic response.

Dicer reprograms stromal fibroblasts to a pro-inflammatory and tumor-promoting phenotype in ovarian cancer

Inflammation and host stromal activation contribute significantly to ovarian cancer (OC) initiation and malignant progression. However, the complex reciprocal interactions between them are largely unknown. Here, we discovered that the tumor suppressor gene Dicer was paradoxically overexpressed in ovarian tumor stroma, and induced fibroblast activation and stromal inflammation. Dicer transformed normal fibroblasts to a carcinoma-associated fibroblast (CAF)-like state, which was morphologically spread out and functionally activated to fuel tumor invasion and metastasis. Attenuation of Dicer hampered CAF characteristics, diminished stromal inflammation and the role of fibroblasts in supporting tumor growth. Moreover, Dicer drove the expression of an "inflammatory signature" in fibroblasts that could be used to discriminate normal and cancerous stroma and predict the survival of patients with OC. Finally, the nuclear factor κ B (NFκB) signaling was demonstrated to be responsible for Dicer effect on fibroblast activation and stromal inflammation, through microRNA (miR)-6780b. Our study represents the first report that characterizes Dicer expression and function in the tumor stroma, and highlights its pro-metastatic role in this context. Additionally, we suggest that the Dicer-miR6780b-NFκB cascade is an attractive target of choice in stroma-oriented OC therapy.

Identity, proliferation capacity, genomic stability and novel senescence markers of mesenchymal stem cells isolated from low volume of human bone marrow

Human bone marrow mesenchymal stem cells (hBM-MSCs) hold promise for treating incurable diseases and repairing of damaged tissues. However, hBM-MSCs face the disadvantages of painful invasive isolation and limited cell numbers. In this study we assessed characteristics of MSCs isolated from residual human bone marrow transplantation material and expanded to clinically relevant numbers at passages 3-4 and 6-7. Results indicated that early passage hBM-MSCs are genomically stable and retain identity and high proliferation capacity. Despite the chromosomal stability, the cells became senescent at late passages, paralleling the slower proliferation, altered morphology and immunophenotype. By qRT-PCR array profiling, we revealed 13 genes and 33 miRNAs significantly differentially expressed in late passage cells, among which 8 genes and 30 miRNAs emerged as potential novel biomarkers of hBM-MSC aging. Functional analysis of genes with altered expression showed strong association with biological processes causing cellular senescence. Altogether, this study revives hBM as convenient source for cellular therapy. Potential novel markers provide new details for better understanding the hBM-MSC senescence mechanisms, contributing to basic science, facilitating the development of cellular therapy quality control, and providing new clues for human disease processes since senescence phenotype of the hematological patient hBM-MSCs only very recently has been revealed.

Impaired Expression of Focal Adhesion Kinase in Mesenchymal Stromal Cells from Low-Risk Myelodysplastic Syndrome Patients

The pathogenic role of mesenchymal stromal cells (MSCs) in myelodysplastic syndromes (MDS) development and progression has been investigated by numerous studies, yet, it remains controversial in some aspects (1, 2). In the present study, we found distinct features of MSCs from low-risk (LR)-MDS stromal microenvironment as compared to those from healthy subjects. At the molecular level, focal adhesion kinase, a key tyrosine kinase in control of cell proliferation, survival, and adhesion process, was found profoundly suppressed in expression and activation in LR-MDS MSC. At a functional level, LR-MDS MSCs showed impaired growth and clonogenic capacity, which were independent of cellular senescence and apoptosis. The pro-adipogenic differentiation and attenuated osteogenic capacity along with reduced SDF-1 expression could be involved in creating an unfavorable microenvironment for hematopoiesis. In conclusion, our experiments support the theory that the stromal microenvironment is fundamentally altered in LR-MDS, and these preliminary data offer a new perspective on LR-MDS pathophysiology.

Premature exhaustion of mesenchymal stromal cells from myelodysplastic syndrome patients

Myelodysplastic syndrome (MDS) predominantly occurs in aging people. Over the past decades, the cellular and molecular pathologies of MDS cells have been intensively investigated. However, how the bone marrow stromal niches are altered during MDS development remains elusive. In this study, we attempted to isolate and characterize mesenchymal stromal cells (MSCs) from 30 MDS patients. We observed that only 9/30 bone marrow aspirations from MDS patients successfully formed a monolayer in vitro, while 17/17 bone marrow aspirations from normal donors (median age 45 years, range: 22-73 years) succeeded in this process. Compared to normal MSCs, the MDS MSCs showed premature exhaustion, including reduced osteogenic differentiation ability, slower passage rate, and extremely limited passage times. These functional defects were associated with downregulation of Osterix and Runx2 genes and increased cell cycle arrest and apoptosis. However, the premature exhaustion of MDS MSCs did not correlate with patients' ages, indicating that natural aging is not the cause of dysfunction in MDS MSCs. Our result provides a strong rational to target prematurely exhausting MSCs in future MDS treatment.

Lenalidomide restores the osteogenic differentiation of bone marrow mesenchymal stem cells from multiple myeloma patients via deactivating Notch signaling pathway

Multiple myeloma (MM) always presents osteolytic bone lesions, resulting from the abnormal osteoblastic and osteoclastic function in patients. MM patients exhibit the impairment of osteogenic differentiation of BMMSCs (bone marrow mesenchymal stem cells) and osteoblast deficiency. Effects of the drug, lenalidomide on the osteoblastic functions and the involved mechanisms remain unexplored. In the present study, it is observed that the osteogenic differentiation of BMMSCs from MM patients (MM-MSCs) is impaired and activation of Notch signaling pathway in MM-MSCs is abnormal. Notch signaling activation inhibits BMMSCs osteogenesis. Knockdown of Notch1 expression and DAPT application reverse the osteogenic differentiation from MM-MSCs. Furthermore, it is shown that the gene expression of Notch signaling molecules, including receptors, ligands and downstream factors are significantly decreased in MM-MSCs following lenalidomide treatment, compared with non-treated MM-MSCs. Taken together, treatment with lenalidomide restores the osteogenic differentiation of MM-MSCs via deactivating Notch signaling pathway.

MicroRNA Regulation of Oxidative Stress-Induced Cellular Senescence

Aging is a time-related process of functional deterioration at cellular, tissue, organelle, and organismal level that ultimately brings life to end. Cellular senescence, a state of permanent cell growth arrest in response to cellular stress, is believed to be the driver of the aging process and age-related disorders. The free radical theory of aging, referred to as oxidative stress (OS) theory below, is one of the most studied aging promoting mechanisms. In addition, genetics and epigenetics also play large roles in accelerating and/or delaying the onset of aging and aging-related diseases. Among various epigenetic events, microRNAs (miRNAs) turned out to be important players in controlling OS, aging, and cellular senescence. miRNAs can generate rapid and reversible responses and, therefore, are ideal players for mediating an adaptive response against stress through their capacity to fine-tune gene expression. However, the importance of miRNAs in regulating OS in the context of aging and cellular senescence is largely unknown. The purpose of our article is to highlight recent advancements in the regulatory role of miRNAs in OS-induced cellular senescence.

Alteration Analysis of Bone Marrow Mesenchymal Stromal Cells from De Novo Acute Myeloid Leukemia Patients at Diagnosis

Bone marrow (BM)-derived mesenchymal stromal cells (MSCs) frequently display alterations in several hematologic disorders, such as acute lymphoid leukemia, acute myeloid leukemia (AML), and myelodysplastic syndromes. In acute leukemias, it is not clear whether MSC alterations contribute to the development of the malignant clone or whether they are simply the effect of tumor expansion on the microenvironment. We extensively investigated the characteristics of MSCs isolated from the BM of patients with de novo AML at diagnosis (L-MSCs) in terms of phenotype (gene and protein expression, apoptosis and senescence levels, DNA double-strand break formation) and functions (proliferation and clonogenic potentials, normal and leukemic hematopoiesis-supporting activity). We found that L-MSCs show reduced proliferation capacity and increased apoptosis levels compared with MSCs from healthy controls. Longer population doubling time in L-MSCs was not related to the AML characteristics at diagnosis (French-American-British type, cytogenetics, or tumor burden), but was related to patient age and independently associated with poorer patient outcome, as was cytogenetic prognostic feature. Analyzing, among others, the expression of 93 genes, we found that proliferative deficiency of L-MSCs was associated with a perivascular feature at the expense of the osteo-chondroblastic lineage with lower expression of several niche factors, such as KITLG, THPO, and ANGPT1 genes, the cell adhesion molecule VCAM1, and the developmental/embryonic genes, BMI1 and DICER1. L-MSC proliferative capacity was correlated positively with CXCL12, THPO, and ANGPT1 expression and negatively with JAG1 expression. Anyway, these changes did not affect their in vitro capacity to support normal hematopoiesis and to modify leukemic cell behavior (protection from apoptosis and quiescence induction). Our findings indicate that BM-derived MSCs from patients with newly diagnosed AML display phenotypic and functional alterations such as proliferative deficiency that could be attributed to tumor progression, but does not seem to play a special role in the leukemic process.

Mesenchymal stromal cells in myeloid malignancies

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are clonal myeloid disorders characterized by hematopoietic insufficiency. As MDS and AML are considered to originate from genetic and molecular defects of hematopoietic stem and progenitor cells (HSPC), the main focus of research in this field has focused on the characterization of these cells. Recently, the contribution of BM microenvironment to the pathogenesis of myeloid malignancies, in particular MDS and AML has gained more interest. This is based on a better understanding of its physiological role in the regulation of hematopoiesis. Additionally, it was demonstrated as a ‘proof of principle’ that genetic disruption of cells of the mesenchymal or osteoblastic lineage can induce MDS, MPS or AML in mice. In this review, we summarize the current knowledge about the contribution of the BM microenvironment, in particular mesenchymal stromal cells (MSC) to the pathogenesis of AML and MDS. Furthermore, potential models integrating the BM microenvironment into the pathophysiology of these myeloid disorders are discussed. Finally, strategies to therapeutically exploit this knowledge and to interfere with the crosstalk between clonal hematopoietic cells and altered stem cell niches are introduced.

Decoding the Regulatory Landscape of Ageing in Musculoskeletal Engineered Tissues Using Genome-Wide DNA Methylation and RNASeq

Mesenchymal stem cells (MSC) are capable of multipotent differentiation into connective tissues and as such are an attractive source for autologous cell-based regenerative medicine and tissue engineering. Epigenetic mechanisms, like DNA methylation, contribute to the changes in gene expression in ageing. However there was a lack of sufficient knowledge of the role that differential methylation plays during chondrogenic, osteogenic and tenogenic differentiation from ageing MSCs. This study undertook genome level determination of the effects of DNA methylation on expression in engineered tissues from chronologically aged MSCs. We compiled unique DNA methylation signatures from chondrogenic, osteogenic, and tenogenic engineered tissues derived from young; n = 4 (21.8 years ± 2.4 SD) and old; n = 4 (65.5 years±8.3SD) human MSCs donors using the Illumina HumanMethylation 450 Beadchip arrays and compared these to gene expression by RNA sequencing. Unique and common signatures of global DNA methylation were identified. There were 201, 67 and 32 chondrogenic, osteogenic and tenogenic age-related DE protein-coding genes respectively. Findings inferred the nature of the transcript networks was predominantly for 'cell death and survival', 'cell morphology', and 'cell growth and proliferation'. Further studies are required to validate if this gene expression effect translates to cell events. Alternative splicing (AS) was dysregulated in ageing with 119, 21 and 9 differential splicing events identified in chondrogenic, osteogenic and tenogenic respectively, and enrichment in genes associated principally with metabolic processes. Gene ontology analysis of differentially methylated loci indicated age-related enrichment for all engineered tissue types in 'skeletal system morphogenesis', 'regulation of cell proliferation' and 'regulation of transcription' suggesting that dynamic epigenetic modifications may occur in genes associated with shared and distinct pathways dependent upon engineered tissue type. An altered phenotype in engineered tissues was observed with ageing at numerous levels. These changes represent novel insights into the ageing process, with implications for stem cell therapies in older patients. In addition we have identified a number of tissue-dependant pathways, which warrant further studies.

Beyond the Niche: Myelodysplastic Syndrome Topobiology in the Laboratory and in the Clinic

We review the murine and human microenvironment and hematopoietic stem cell niche in the context of intact bone marrow architecture in man and mouse, both in normal and in myelodysplastic syndrome marrow. We propose that the complexity of the hematopoietic stem cell niche can usefully be approached in the context of its topobiology, and we provide a model that incorporates in vitro and in vivo models as well as in situ findings from intact human marrow to explain the changes seen in myelodysplastic syndrome patients. We highlight the clinical application of the study of the bone marrow microenvironment and its topobiology in myelodysplastic syndromes.

Notch-Hes pathway mediates the impaired osteogenic differentiation of bone marrow mesenchymal stromal cells from myelodysplastic syndromes patients through the down-regulation of Runx2

Previous studies have demonstrated that bone marrow mesenchymal stromal cells (BMMSCs) from patients with myelodysplastic syndromes (MDS) display defective proliferative potential and impaired osteogenic differentiation ability. However, the underlying mechanisms are unclear. In the present study, the impaired osteogenic differentiation potential of BMMSCs was found in cases with RARS (83.3%), RCMD (75.0%), RAEB I (44.4%), RAEB II (40%). We also observed that MDS-BMMSCs with impaired osteogenic differentiation potential exhibited accelerate senescence and decreased hematopoietic supporting function. Further, we found that an abnormal activation of Notch-Hes signaling pathway in MDS-BMMSCs. By overexpression of Notch intracellular domain (NICD) in BMMSCs from healthy donors, we confirmed that Notch signaling pathway negatively regulated BMMSCs osteogenesis through inhibition of Runx2 transcriptional activity. Importantly, treatment with DAPT, a γ-secretase inhibitor of Notch signaling reversed the osteogenic differentiation in MDS-BMMSCs. Collectively, we provide evidence that activation of Notch-Hes signaling pathway is involved in the impaired osteogenic differentiation of MDS-BMMSCs and support the concept of a primary BMMSCs defect that might have a contributory effect in MDS pathogenesis.

Gene-expression and in vitro function of mesenchymal stromal cells are affected in juvenile myelomonocytic leukemia

An aberrant interaction between hematopoietic stem cells and mesenchymal stromal cells has been linked to disease and shown to contribute to the pathophysiology of hematologic malignancies in murine models. Juvenile myelomonocytic leukemia is an aggressive malignant disease affecting young infants. Here we investigated the impact of juvenile myelomonocytic leukemia on mesenchymal stromal cells. Mesenchymal stromal cells were expanded from bone marrow samples of patients at diagnosis (n=9) and after hematopoietic stem cell transplantation (n=7; from 5 patients) and from healthy children (n=10). Cells were characterized by phenotyping, differentiation, gene expression analysis (of controls and samples obtained at diagnosis) and in vitro functional studies assessing immunomodulation and hematopoietic support. Mesenchymal stromal cells from patients did not differ from controls in differentiation capacity nor did they differ in their capacity to support in vitro hematopoiesis. Deep-SAGE sequencing revealed differential mRNA expression in patient-derived samples, including genes encoding proteins involved in immunomodulation and cell-cell interaction. Selected gene expression normalized during remission after successful hematopoietic stem cell transplantation. Whereas natural killer cell activation and peripheral blood mononuclear cell proliferation were not differentially affected, the suppressive effect on monocyte to dendritic cell differentiation was increased by mesenchymal stromal cells obtained at diagnosis, but not at time of remission. This study shows that active juvenile myelomonocytic leukemia affects the immune response-related gene expression and function of mesenchymal stromal cells. In contrast, the differential gene expression of hematopoiesis-related genes could not be supported by functional data. Decreased immune surveillance might contribute to the therapy resistance and progression in juvenile myelomonocytic leukemia.

The antisenescence effect of trans-cinnamaldehyde on adipose-derived stem cells

As assuring cell quality is an essential parameter for the success of stem cell therapy, the impact of various senescence-inducing stress signals, and strategies to circumvent them, has been an important area of focus in stem cell research. The aim of this study was to demonstrate the capacity of Trans-cinnamaldehyde (TC) in reversing stress-induced senescence and maintaining the quality of stem cells in a chemically (H2O2)-induced cell senescence model. Because of the availability and the promising application potential in regenerative medicine, adipose-derived stem cells (ADSCs) were chosen for the study. We found that H2O2 treatment resulted in the expression of senescence characteristics in the ADSCs, including decreased proliferation rate, increased senescence-associated β-galactosidase (SA-β-gal) activity, decreased silent mating type information regulation 2 homolog (SIRT1) expression, and decreased telomerase activity. However, TC treatment was sufficient to rescue or reduce the effects of H2O2 induction, ultimately leading to an increased proliferation rate, a decrease in the percentage of SA-β-gal-positive cells, upregulation of SIRT1 expression, and increased telomerase activity of the senescent ADSCs at the cellular level. Moreover, a chemically induced liver fibrosis animal model was used to evaluate the functionality of these rescued cells in vivo. Liver dysfunction was established by injecting 200 mg/kg thioacetamide (TAA) intraperitoneally into Wistar rats every third day for 60 days. The experimental rats were separated into groups: normal group (rats without TAA induction), sham group (without ADSC transplantation), positive control group (transplanted with normal ADSCs), H2O2 group (transplanted with H2O2-induced senescent ADSCs), and H2O2 + TC group (transplanted with ADSCs pretreated with H2O2 and then further treated with TC). In the transplantation group, 1 × 10(6) human ADSCs were introduced into each rat via direct liver injection. Based on the biochemical analysis and immunohistochemical staining results, it was determined that the therapeutic effects on liver fibrosis by the induced senescent ADSCs (H2O2 group) were not as significant as those exerted by the normal ADSCs (the positive control group). However, the H2O2 + TC group showed significant reversal of liver damage when compared to the H2O2 group 1 week posttransplantation. These data confirmed that the TC treatment had the potential to reduce the effects of H2O2-induced senescence and to restore in vivo functionality of the induced senescent ADSCs. It is therefore suggested that TC has potential applications in maintaining the quality of stem cells and could aid in treating senescence-related disorders.