Characterization of bone marrow mesenchymal stromal cells in aplastic anaemia

Global microRNA profiling of bone marrow-MSC derived extracellular vesicles identifies miRNAs associated with hematopoietic dysfunction in aplastic anemia

Recently, we have reported that extracellular vesicles (EVs) from the bone marrow mesenchymal stromal cells (BM-MSC) of aplastic anemia (AA) patients inhibit hematopoietic stem and progenitor cell (HSPC) proliferative and colony-forming ability and promote apoptosis. One mechanism by which AA BM-MSC EVs might contribute to these altered HSPC functions is through microRNAs (miRNAs) encapsulated in EVs. However, little is known about the role of BM-MSC EVs derived miRNAs in regulating HSPC functions in AA. Therefore, we performed miRNA profiling of EVs from BM-MSC of AA (n = 6) and normal controls (NC) (n = 6) to identify differentially expressed miRNAs. The Integrated DEseq2 analysis revealed 34 significantly altered mature miRNAs, targeting 235 differentially expressed HSPC genes in AA. Hub gene analysis revealed 10 HSPC genes such as IGF-1R, IGF2R, PAK1, PTPN1, etc., which are targeted by EV miRNAs and had an enrichment of chemokine, MAPK, NK cell-mediated cytotoxicity, Rap1, PI3k-Akt, mTOR signalling pathways which are associated with hematopoietic homeostasis. We further showed that miR-139-5p and its target, IGF-1R (hub-gene), might regulate HSPC proliferation and apoptosis, which may serve as potential therapeutic targets in AA. Overall, the study highlights that AA BM-MSC EV miRNAs could contribute to impaired HSPC functions in AA.

Elevated senescence in the bone marrow mesenchymal stem cells of acquired aplastic anemia patients: A possible implication of DNA damage responses and telomere attrition

BACKGROUND

Bone marrow mesenchymal stem cells (BM-MSC) are an integral part of the BM niche that is essential to maintain hematopoietic homeostasis. In aplastic anemia (AA), a few studies have reported phenotypic defects in the BM-MSC, such as reduced proliferation, imbalanced differentiation, and apoptosis; however, the alterations at the molecular level need to be better characterized. Therefore, the current study aims to identify the causative factors underlying the compromised functions of AA BM-MSC that might eventually be contributing to the AA pathobiology.

METHODS

We performed RNA sequencing (RNA-Seq) using the Illumina platform to comprehend the distinction between the transcriptional landscape of AA and control BM-MSC. Further, we validated the alterations observed in senescence by Senescence- associated beta-galactosidase (SA -β-gal) assay, DNA damage by γH2AX staining, and telomere attrition by relative telomere length assessment and telomerase activity assay. We used qRT-PCR to analyze changes in some of the genes associated with these molecular mechanisms.

RESULTS

The transcriptome profiling revealed enrichment of senescence-associated genes and pathways in AA BM-MSC. The senescent phenotype of AA BM-MSC was accompanied by enhanced SA -β-gal activity and elevated expression of senescence associated genes TP53, PARP1, and CDKN1A. Further, we observed increased γH2AX foci indicating DNA damage, reduced telomere length, and diminished telomerase activity in the AA BM-MSC.

CONCLUSION

Our results highlight that AA BM-MSC have a senescent phenotype accompanied by other cellular defects like DNA damage and telomere attrition, which are most likely driving the senescent phenotype of AA BM-MSC thus hampering their hematopoiesis supporting properties as observed in AA.

Irisin protected hemopoietic stem cells and improved outcome of severe bone marrow failure

Acquired aplastic anemia (AA) is a bone marrow failure (BMF) disease, characterized by fatty bone marrow (BM) and BM hypocellularity resulted from auto-immune dysregulated T cells-mediated destruction of BM haemopoietic stem cells (HPSC). The objective of this study was to investigate potential therapeutic effect of irisin, a molecule involved in adipose tissue transition, on AA mouse model. Our results showed that the concentration of irisin in serum was lower in AA patients than in healthy controls, suggesting a role of irisin in the pathogenesis of AA. In the AA mice, irisin administration prolonged the survival rate, prevented or attenuated peripheral pancytopenia, and preserved HPSC in the BM. Moreover, irisin also markedly reduced BM adipogenesis. In vitro results showed that irisin increased both cell proliferation and colony numbers of HPSC. Furthermore, our results demonstrated that irisin upregulated the expression of mitochondrial ATPase Inhibitory Factor 1 (IF1) in HPSC, inhibited the activation of mitochondrial fission protein (DRP1) and enhanced aerobic glycolysis. Taken together, our findings indicate novel roles of irisin in the pathogenesis of AA, and in the protection of HPSC through stimulation of proliferation and regulation of mitochondria function, which provides a proof-of-concept for the application of irisin in AA therapy.

Mesenchymal Stem Cells in Acquired Aplastic Anemia: The Spectrum from Basic to Clinical Utility

Aplastic anemia (AA), a rare but potentially life-threatening disease, is a paradigm of bone marrow failure syndromes characterized by pancytopenia in the peripheral blood and hypocellularity in the bone marrow. The pathophysiology of acquired idiopathic AA is quite complex. Mesenchymal stem cells (MSCs), an important component of the bone marrow, are crucial in providing the specialized microenvironment for hematopoiesis. MSC dysfunction may result in an insufficient bone marrow and may be associated with the development of AA. In this comprehensive review, we summarized the current understanding about the involvement of MSCs in the pathogenesis of acquired idiopathic AA, along with the clinical application of MSCs for patients with the disease. The pathophysiology of AA, the major properties of MSCs, and results of MSC therapy in preclinical animal models of AA are also described. Several important issues regarding the clinical use of MSCs are discussed finally. With evolving knowledge from basic studies and clinical applications, we anticipate that more patients with the disease can benefit from the therapeutic effects of MSCs in the near future.

Differences in the Differentiation Potential and Relative Levels of Gene Expression in the Bone Marrow-Derived Fibroblast Colony-Forming Units in Patients during the Onset of Aplastic Anemia Depending on the Disease Severity

The differentiation potential of individual clones of fibroblast CFU (CFU-F) was studied and the relative expression level of genes was analyzed in the culture of CFU-F from the bone marrow in patients with non-severe and severe forms of aplastic anemia at the onset of the disease. The differentiation potential of CFU-F clones was determined by the relative expression of marker genes using quantitative PCR. In aplastic anemia, the ratio of CFU-F clones with different differentiation potential changes, but the molecular mechanisms of this phenomenon are different in non-severe and severe aplastic anemia. In the culture of CFU-F in non-severe and severe aplastic anemia, the relative expression level of genes associated with the maintenance of the hematopoietic stem cell in the bone marrow niche changes, but the decrease in the expression of immunoregulatory genes occurs in severe form only, which may reflect differences in the pathogenesis of non-severe and severe aplastic anemia.

Alterations of mesenchymal stem cells on regulating Th17 and Treg differentiation in severe aplastic anemia

Immune-mediated hematopoietic destruction is a key factor in idiopathic severe aplastic anemia (SAA). With great immunomodulatory functions, mesenchymal stem cells (MSCs) are important for bone marrow niche. While the underlying etiology of immunologic changes in SAA bone marrow remains unknown, dysfunctional MSCs are implicated as a major cause. To provide evidence for their defects in immunomodulation, alterations of SAA MSCs in regulating T cell differentiation were determined. During differentiation from CD4+ T cells into T helper 17 (Th17) cells under polarization conditions, impaired inhibition on IL-17 and IL-1β production was noted when cocultured with SAA MSCs compared to control MSCs (P < 0.05). After stimulation of Th17 activation, the percentage of IL-17-secreting cells was significantly increased in the SAA group (9.1 ± 1.5% vs 6.6 ± 0.4%, P < 0.01). Under regulatory T (Treg) polarization, a higher percentage of CD4+CD25+FoxP3+ Treg cells was detected when cocultured with SAA MSCs compared to control MSCs (8.1 ± 0.5% vs 5.8 ± 0.8%, P < 0.01). Inconsistently, transforming growth factor-β (TGF-β) concentrations in the culture supernatant were decreased and IL-1β concentrations were elevated in the SAA group. Our data indicated impaired inhibition of SAA MSCs on Th17 activation and aberrant regulation of SAA MSCs on Treg differentiation. Increased IL-17 and IL-1β levels with decreased TGF-β levels in the supernatant suggested the potential of SAA MSCs for triggering a hyperinflammatory environment. Dysfunctional MSCs could contribute to the lack of immunoprotection in the bone marrow, which may be associated with SAA.

HIV-1 Tat Protein-Mediated Inflammatory Response Inhibits the Erythroid Hematopoietic Support Function of Bone Marrow Mesenchymal Stem Cells

Although combination antiretroviral therapy is widely used to treat HIV-1 infection, anemia affects the health and quality of life in a large number of these patients. The proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs), as important support cells in the hematopoietic microenvironment, can be affected by HIV-1 Tat protein. In this study, we explored the mechanism underlying the effect of Tat protein on the hematopoietic support function of BMSCs in erythroid commitment. BMSCs were treated with Tat protein or transfected with Tat mRNA and cocultured with hematopoietic stem cells (HSCs) to detect the number of erythroid colony-forming units (CFUs) and the proportion of mature red blood cells from HSCs. Subsequently, the expression level of a series of erythroid hematopoietic support factors and inflammatory factors in BMSCs after Tat treatment were analyzed. Then, the activation effect of Tat on the mitogen-activated protein kinase/nuclear factor kappa-B (MAPK/NF-κB) pathway, which is an important inflammatory response signaling pathway, was evaluated. The results showed that the number of erythroid CFUs and the production of mature red blood cells supported by BMSCs treated with Tat protein were significantly reduced and the expression of a series of erythroid supporting factors of BMSCs were significantly decreased by Tat protein. Tat-treated BMSCs highly express a variety of inflammatory mediators. Moreover, the expression of P38, p-p38, ERK1/2, p-ERK1/2, JNK1/2, p-JNK1/2, NF-κB, and p-NF-κB was significantly upregulated by Tat protein. In conclusion, Tat protein induces the inflammatory response of BMSCs by activating the MAPK/NF-κB pathway to inhibit the erythroid hematopoietic support function of BMSCs.

Extracellular vesicles from bone marrow mesenchymal stromal cells of severe aplastic anemia patients attenuate hematopoietic functions of CD34+ hematopoietic stem and progenitor cells

Mesenchymal stromal cells (MSC) regulate hematopoiesis in the bone marrow (BM) niche and extracellular vesicles (EVs) released by BM-MSC are important mediators of the cross-talk between BM-MSC and hematopoietic stem and progenitor cells (HSPC). We have previously demonstrated that BM-MSC of severe aplastic anemia (SAA) patients have an altered expression of hematopoiesis regulatory molecules. In the present study, we observed that CD34⁺ HSPC when cocultured with BM-MSC EVs from aplastic anemia patients exhibited a significant reduction in colony-forming units (p = .001), cell proliferation (p = .002), and increased apoptosis (p > .001) when compared to coculture with BM-MSC EVs from controls. Collectively, our results highlight that EVs derived from the BM-MSC of SAA patients impair the hematopoiesis supporting function of HSPC.

Functional and Immune Modulatory Characteristics of Bone Marrow Mesenchymal Stromal Cells in Patients With Aplastic Anemia: A Systematic Review

Background

In most patients with aplastic anemia (AA), the diagnosis is limited to a description of the symptoms. Lack of understanding of the underlying pathophysiological mechanisms causing bone marrow failure (BMF), hampers tailored treatment. In these patients, auto-immune cell-mediated destruction of the bone marrow is often presumed to be the causative mechanism. The status of the bone marrow microenvironment, particularly the mesenchymal stromal cell (MSC) component, was recently suggested as a potential player in the pathophysiology of AA. Therefore, functional, and immune modulatory characteristics of bone marrow MSCs might represent important parameters for AA.

Objective

To conduct a systematic review to evaluate in vitro functional properties of MSCs derived from patients with AA compared to healthy controls.

Methods

According to PRISMA guidelines, a comprehensive search strategy was performed by using online databases (Pubmed, ISI Web of Science, Embase, and the Cochrane Library). Studies reporting on phenotypical characterization, proliferation potential, differentiation capacity, immunomodulatory potential, and ability to support hematopoiesis were identified and screened using the Rayyan software tool.

Results

23 articles were included in this systematic review, describing a total of 324 patients with AA and 285 controls. None of the studies identified a significant difference in expression of any MSC surface marker between both groups. However, AA-MSCs showed a decreased proliferation potential, an increased tendency to differentiate into the adipogenic lineage and decreased propensity towards osteogenic differentiation. Importantly, AA-MSCs show reduced capacity of immunosuppression and hematopoietic support in comparison to healthy controls.

Conclusion

We conclude that there are indications for a contribution of MSCs in the pathophysiology of AA. However, the current evidence is of poor quality and requires better defined study populations in addition to a more robust methodology to study MSC biology at a cellular and molecular level. Future studies on bone marrow microenvironment should aim at elucidating the interaction between MSCs, hematopoietic stem cells (HSCs) and immune cells to identify impairments associated with/causing BMF in patients with AA.

Autophagy in mesenchymal progenitors protects mice against bone marrow failure after severe intermittent stress

The cellular mechanisms required to ensure homeostasis of the hematopoietic niche and the ability of this niche to support hematopoiesis upon stress remain elusive. We here identify Wnt5a in Osterix+ mesenchymal progenitor and stem cells (MSPCs) as a critical factor for niche-dependent hematopoiesis. Mice lacking Wnt5a in MSPCs suffer from stress-related bone marrow (BM) failure and increased mortality. Niche cells devoid of Wnt5a show defective actin stress fiber orientation due to an elevated activity of the small GTPase CDC42. This results in incorrect positioning of autophagosomes and lysosomes, thus reducing autophagy and increasing oxidative stress. In MSPCs from patients from BM failure states which share features of peripheral cytopenia and hypocellular BM, we find similar defects in actin stress fiber orientation, reduced and incorrect colocalization of autophagosomes and lysosomes, and CDC42 activation. Strikingly, a short pharmacological intervention to attenuate elevated CDC42 activation in vivo in mice prevents defective actin-anchored autophagy in MSPCs, salvages hematopoiesis and protects against lethal cytopenia upon stress. In summary, our study identifies Wnt5a as a restriction factor for niche homeostasis by affecting CDC42-regulated actin stress-fiber orientation and autophagy upon stress. Our data further imply a critical role for autophagy in MSPCs for adequate support of hematopoiesis by the niche upon stress and in human diseases characterized by peripheral cytopenias and hypocellular BM.

NFĸB Targeting in Bone Marrow Mesenchymal Stem Cell-Mediated Support of Age-Linked Hematological Malignancies

Mesenchymal stem cells (MSCs) can become dysfunctional in patients with hematological disorders. An unanswered question is whether age-linked disruption of the bone marrow (BM) microenvironment is secondary to hematological dysfunction or vice versa. We therefore studied MSC function in patients with different hematological disorders and found decreased MHC-II except from one sample with acute myeloid leukemia (AML). The patients' MSCs were able to exert veto properties except for AML MSCs. While the expression of MHC-II appeared to be irrelevant to the immune licensing of MSCs, AML MSCs lost their ability to differentiate upon contact and rather, continued to proliferate, forming foci-like structures. We performed a retrospective study that indicated a significant increase in MSCs, based on phenotype, for patients with BM fibrosis. This suggests a role for MSCs in patients transitioning to leukemia. NFĸB was important to MSC function and was shown to be a potential target to sensitize leukemic CD34+/CD38- cells to azacitidine. This correlated with their lack of allogeneic stimulation. This study identified NFĸB as a potential target for combination therapy to treat leukemia stem cells and showed that understanding MSC biology and immune response could be key in determining how the aging BM might support leukemia. More importantly, we show how MSCs might be involved in transitioning the high risk patient with hematological disorder to AML.

Human Acquired Aplastic Anemia Patients' Bone-Marrow-Derived Mesenchymal Stem Cells Are Not Influenced by Hematopoietic Compartment and Maintain Stemness and Immune Properties

Methods

In the current study, we investigated the morphological differences, proliferation capacity, population doubling time (PDT), surface marker profiling, trilineage differentiation potential, and immunosuppressive ability of BM Mesenchymal Stem Cells (BM-MSCs) from untreated aAA patients and in the same number of age- and gender-matched controls.

Results

We observed similar morphology, proliferation capacity, phenotype, trilineage differentiation potential, and immunomodulatory properties of BM-MSCs in aAA patients and control subjects.

Conclusion

Our results confirm that the basic and immunosuppressive properties of BM-MSCs from aAA patients do not differ from normal BM-MSCs. Our data suggest that BM-MSCs from aAA patients might not be involved in disease pathogenesis. However, owing to a smaller number of samples, it is not conclusive, and future studies with more exhaustive investigation at transcriptome level are warranted.

Acquired severe aplastic anaemia: how medical therapy evolved in the 20th and 21st centuries

The progress in aplastic anaemia (AA) management is one of success. Once an obscure entity resulting in death in most affected can now be successfully treated with either haematopoietic stem cell transplantation (HSCT) or immunosuppressive therapy (IST). The mechanisms that underly the diminution of haematopoietic stem cells (HSCs) are now better elucidated, and include genetics and immunological alterations. Advances in supportive care with better antimicrobials, safer blood products and iron chelation have greatly impacted AA outcomes. Working somewhat 'mysteriously', anti-thymocyte globulin (ATG) forms the base for both HSCT and IST protocols. Efforts to augment immunosuppression potency have not, unfortunately, led to better outcomes. Stimulating HSCs, an often-sought approach, has not been effective historically. The thrombopoietin receptor agonists (Tpo-RA) have been effective in stimulating early HSCs in AA despite the high endogenous Tpo levels. Dosing, timing and best combinations with Tpo-RAs are being defined to improve HSCs expansion in AA with minimal added toxicity. The more comprehensive access and advances in HSCT and IST protocols are likely to benefit AA patients worldwide. The focus of this review will be on the medical treatment advances in AA.

Implication of therapeutic outcomes associated with molecular characterization of paediatric aplastic anaemia

Objectives

Severe aplastic anemia is characterized by a hypocellular bone marrow and peripheral cytopenia. Mesenchymal stem cells (MSCs) play a crucial role in haematopoietic stem cells (HSCs) development and the development of microenvironment suitable for hematopoiesis. Molecular characterization of telomere maintenance pathway and gene expression profiling of MSCs can be important for the therapeutic interventions among paediatric aplastic anaemia patients.

Methods

The study involved paediatric aplastic anaemia patients (n = 10) and age matched paediatric healthy donors (n = 8). Peripheral blood samples were collected from the individuals. Average leucocyte telomere length and gene expression of the telomere maintenance genes were determined by quantitative real time PCR. Microarray based gene expression profiles (GSE33812) of MSCs for five paediatric aplastic anaemia patients were analyzed compared to five healthy controls and the data was downloaded from the GEO database.

Results

The telomere length was significantly shorter among paediatric AA patients compared to age matched healthy donors. Interestingly, one subgroup (n = 2) of paediatric AA patients has moderate telomere length comparable to age matched healthy donors. Based on the gene expression analysis of telomere maintenance pathway, TERF2 was significantly downregulated among paediatric patients with shorter telomere length but not among paediatric patients with moderate telomere length. Gene expression profiling of MSCs revealed three differentially expressed genes (GAS2L3, MK167 and TMSB15A) among the patients and was associated with therapeutic outcome.

Conclusion

Telomere length estimation and gene expression patterns of the MSCs and telomere length maintenance pathway may serve as a potential biomarker and could be associated with therapeutic choice of paediatric aplastic anaemia patients.

•

One subgroup of paediatric AA patients has moderate telomere length comparable to age matched healthy donors.

•

TERF2 was differentially downregulated among paediatric patients with shorter telomere length.

•

Differential downregulation of GAS2L3, MK167 and TMSB15A genes in MSCs among the patients with immunosuppressive therapy.

All-trans-retinoic acid shifts Th1 towards Th2 cell differentiation by targeting NFAT1 signalling to ameliorate immune-mediated aplastic anaemia

Severe acquired aplastic anaemia (AA) is a serious disease characterised by autoreactive T cells attacking haematopoietic stem cells, leading to marrow hypoplasia and pancytopenia. Immunosuppressive therapy combined with antithymocyte globulin and ciclosporin can rescue most patients with AA. However, the relapse after ciclosporin withdrawal and the severe side effects of long-term ciclosporin administration remain unresolved. As such, new strategies should be developed to supplement current therapeutics and treat AA. In this study, the possibility of all-trans-retinoic acid (ATRA) as an alternative AA treatment was tested by using an immune-mediated mouse model of AA. Results revealed that ATRA inhibited T-cell proliferation, activation and effector function. It also restrained the Fas/Fasl pathway, shifted Th1 towards Th2 cell development, rebalanced T-cell subsets at a relatively high level and corrected the Th1/Th2 ratio by targeting NFAT1 signalling. In addition, ATRA inhibited Th17 cell differentiation and promoted regulatory T-cell development. Therefore, ATRA was an effective agent to improve AA treatment outcomes.

Multifaceted characterization of the signatures and efficacy of mesenchymal stem/stromal cells in acquired aplastic anemia

Background

Longitudinal studies have verified the pivotal role of mesenchymal stem/stromal cells (MSCs) in the bone marrow microenvironment for hematopoiesis and coordinate contribution to leukemia pathogenesis. However, the precise characteristics and alternation of MSCs during acquired aplastic anemia (AA) remain obscure.

Methods

In this study, we originally collected samples from both healthy donors (HD) and AA patients to dissect the hematological changes. To systematically evaluate the biological defects of AA-derived MSCs (AA-MSCs), we analyzed alterations in cellular morphology, immunophenotype, multi-lineage differentiation, cell migration, cellular apoptosis, and chromosome karyocyte, together with the immunosuppressive effect on the activation and differentiation of lymphocytes. With the aid of whole genome sequencing and bioinformatic analysis, we try to compare the differences between AA-MSCs and HD-derived MSCs (HD-MSCs) upon the molecular genetics, especially the immune-associated gene expression pattern. In addition, the efficacy of umbilical cord-derived MSC (UC-MSC) transplantation on AA mice was evaluated by utilizing survivorship curve, histologic sections, and blood cell analyses.

Results

In coincidence with the current reports, AA patients showed abnormal subsets of lymphocytes and higher contents of proinflammatory cytokines. Although with similar immunophenotype and chromosome karyotype to HD-MSCs, AA-MSCs showed distinguishable morphology and multiple distinct characteristics including genetic properties. In addition, the immunosuppressive effect on lymphocytes was significantly impaired in AA-MSCs. What is more, the cardinal symptoms of AA mice were largely rescued by systemic transplantation of UC-MSCs.

Conclusions

Herein, we systematically investigated the signatures and efficacy of MSCs to dissect the alterations occurred in AA both at the cellular and molecular levels. Different from HD-MSCs, AA-MSCs exhibited multifaceted defects in biological characteristics and alterative molecular genetics in the whole genome. Our findings have provided systematic and overwhelming new evidence for the defects of AA-MSCs, together with effectiveness assessments of UC-MSCs on AA as well.

The Phenotype and Functional Activity of Mesenchymal Stromal Cells in Pediatric Patients with Non-Malignant Hematological Diseases

As the biology of mesenchymal stromal cells (MSCs) in patients with non-malignant hematological diseases (NMHD) is poorly understood, in the current study we performed a basic characterization of the phenotype and functional activity of NMHD-MSCs. Bone marrow (BM) of patients with thalassemia major (TM) possessed a significantly higher number of nucleated cells (BM-MNCs)/mL BM than healthy donors (P < 0.0001), which however did not result in a higher number of colony forming units-fibroblast (CFU-F) per milliliter BM. In contrast, from 1 × 10⁶ BM-MNCs of patients with sickle cell disease (SCD) were generated significantly more CFU-Fs than from TM-BM-MNCs (P < 0.013) and control group (P < 0.02). In addition, NMHD-MSCs expressed significantly lower levels of CD146 molecule, demonstrated an equal proliferation potential and differentiated along three lineages (osteoblasts, chondrocytes and adipocytes) as healthy donors’ MSCs, with exception of TM-MSCs which differentiated weakly in adipocytes. In contrast to other NMHD-MSCs and healthy donors’ MSCs, TM-MSCs demonstrated an impaired in vitro immunosuppressive potential, either. Noteworthy, the majority of the immunosuppressive effect of NMHD-MSCs was mediated through prostaglandin-E2 (PGE2), because indomethacin (an inhibitor of PGE2 synthesis) was able to significantly reverse this effect. Our results indicate therefore that NMHD-MSCs, except TM-MSCs, may be used as an autologous cell-based therapy for post-transplant complications such as graft failure, graft-versus-host disease (GvHD) and osteonecrosis.

Insensitive to PTH of CD8+ T cells regulate bone marrow mesenchymal stromal cell in aplastic anemia patients

Aplastic anemia (AA) is a rare disorder characterized by the suppression of bone marrow function resulting in progressive pancytopenia. The pathogenesis of AA is complex and involves an abnormal hematopoietic microenvironment, hematopoietic stem cell/progenitor cell deficiencies, and immunity disorders. However, the underlying mechanism of the disease is still not fully uncovered. In this research, we collected both donor and patient samples and found suppressed proliferation, abnormal differentiation as well as increased apoptosis of patient mesenchymal stem cells (MSCs). Considering the close relationship of parathyroid hormone (PTH) and MSCs differentiation, further studies showed that although patients maintained normal serum PTH level, their CD8⁺ T cells possessed lower PTH receptors. The insensitive to PTH of patients' CD8⁺ T cells finally lead to reduced expression of key Wnt factors. In all, bone marrow CD8⁺ T cells may play an important role in inducing MSCs adipogenesis and osteogenesis imbalancement.

miR-144-3p Suppresses Osteogenic Differentiation of BMSCs from Patients with Aplastic Anemia through Repression of TET2

Reduced osteogenic capacity of bone marrow mesenchymal stem cells (BMSCs) has been causally linked to the development of aplastic anemia. In this work, we aimed to identify novel microRNAs (miRNAs) that participate in the regulation of differentiation of BMSCs from patients with aplastic anemia. We show that miR-144-3p is significantly upregulated in BMSCs from patients with aplastic anemia relative to control equivalents. Depletion of miR-144-3p significantly enhances osteogenic differentiation of BMSCs from patients with aplastic anemia after culturing in osteogenesis-inducing medium. Conversely, overexpression of miR-144-3p blocks osteogenic differentiation of BMSCs. Mechanistically, miR-144-3p negatively regulates the expression of ten-eleven translocation 2 (TET2) in BMSCs. Reduced TET2 expression is associated with a significant decrease in global 5-hydroxymethyl-cytosine (5hmC) levels and osteogenic gene expression. Knockdown of miR-144-3p elevates the expression of TET2 and total 5hmC levels in BMSCs. Silencing of TET2 inhibits the osteogenic differentiation of BMSCs. Overexpression of TET2 reverses miR-144-3p-mediated inhibition of osteogenesis. In addition, there is a significant negative correlation between the expression of miR-144-3p and TET2 in BMSCs from patients with aplastic anemia. Overall, miR-144-3p impairs the osteogenic capacity of BMSCs from patients with aplastic anemia through repression of TET2. Therefore, the targeting of miR-144-3p may be a therapeutic strategy against aplastic anemia.

Investigating the potential of the secretome of mesenchymal stem cells derived from sickle cell disease patients

Sickle cell disease (SCD) is a monogenic red cell disorder associated with multiple vascular complications, microvessel injury and wound-healing deficiency. Although stem cell transplantation with bone marrow-derived mesenchymal stem cells (BMSC) can promote wound healing and tissue repair in SCD patients, therapeutic efficacy is largely dependent on the paracrine activity of the implanted BM stromal cells. Since in vitro expansion and culture conditions are known to modulate the innate characteristics of BMSCs, the present study investigated the effects of normoxic and hypoxic cell-culture preconditioning on the BMSC secretome, in addition to the expression of paracrine molecules that induce angiogenesis and skin regeneration. BMSCs derived from SCD patients were submitted to culturing under normoxic (norCM) and hypoxic (hypoCM) conditions. We found that hypoxically conditioned cells presented increased expression and secretion of several well-characterized trophic growth factors (VEGF, IL8, MCP-1, ANG) directly linked to angiogenesis and tissue repair. The hypoCM secretome presented stronger angiogenic potential than norCM, both in vitro and in vivo, as evidenced by HUVEC proliferation, survival, migration, sprouting formation and in vivo angiogenesis. After local application in a murine wound-healing model, HypoCM showed significantly improved wound closure, as well as enhanced neovascularization in comparison to untreated controls. In sum, the secretome of hypoxia-preconditioned BMSC has increased expression of trophic factors involved in angiogenesis and skin regeneration. Considering that these preconditioned media are easily obtainable, this strategy represents an alternative to stem cell transplantation and could form the basis of novel therapies for vascular regeneration and wound healing in individuals with sickle cell disease.

Effect of ectopic high expression of transcription factor OCT4 on the "stemness" characteristics of human bone marrow-derived mesenchymal stromal cells

OBJECTIVE

To investigate the effect of ectopic high expression of OCT4 on the stemness characteristics of bone marrow-derived mesenchymal stromal cells (BM-MSCs).

METHODS

BM-MSCs were collected from three de novo acute lymphoblastic leukemia (ALL) and three aplastic anemia patients (AA), which were cultivated by the whole bone marrow adherent method. Surface markers of BM-MSCs were analyzed by flow cytometry (FCM); meanwhile, growth characteristics were observed with a phase contrast microscope, and population doubling time (PDT) was calculated. The optimal generation cells (P4) were used for the subsequent experiments. Recombinant plasmid pcDNA3.1-OCT4 was constructed and transferred into ALL MSCs by liposome transfection. The cells with stable and high expression of OCT4 were selected by G418 resistance screening and subcloning, of which the expression of OCT4 was verified by FCM, cellular immunofluorescence assay (CIFA), and RT-PCR. The expression of stemness-related transcription factors (TFs) (NANOG, SOX2) and the embryonic stem cell (ESC)-related surface markers (SSEA4, TRA-1-60, and TRA-1-81) were analyzed by FCM, RT-PCR, and CIFA. Embryonic body (EB) formation was performed with the above cells, and triembryonic differentiation marker genes were evaluated by RT-PCR.

RESULTS

The primary passage of AA MSCs grew more slowly and had longer PDT (16 days on average) than ALL MSCs (10 days on average). AA MSCs presented the same typical morphology and similar expression levels of specific mesenchymal markers as ALL MSCs, whereas the latter had a much better proliferative capacity in P4 cells (P < 0.05). Besides, the expression levels of surface markers in ALL MSCs were slightly higher than that in AA MSCs in P4, P7, and P10 cells (P < 0.05). Cell lines with stable and high expression of OCT4 were successfully established from ALL MSCs, which were confirmed by CIFA, FCM, and RT-PCR. Compared with untransfected parental MSCs, the mean expression levels of TFs in OCT4 overexpression MSCs were increased from 0.63 ± 0.37% to 39.39 ± 1.85% (NANOG) and from 14.34 ± 2.44% to 91.45 ± 4.56% (SOX2). The average expression levels of ESC surface markers were increased from 3.33 ± 2.35%, 1.59 ± 1.29%, and 1.46 ± 0.86% to 84.98 ± 9.2%, 57.28 ± 6.72%, and 75.88 ± 7.35% respectively for SSEA-4, TRA-1-60, and TRA-1-81, which were confirmed by CIFA analysis. Moreover, the OCT4 overexpression MSCs could form EBs ex vivo and express ectoderm (TUBB3, WNT1), mesoderm (Brachyury, TBX20), and endoderm (SPARC) genes.

CONCLUSION

Ectopic high expression of transcription factor OCT4 in BM-MSCs may drive them to grow as ESC-like cells with "stemness" characteristics. Single OCT4 transfection can upregulate the expression of other stemness-related transcription factors such as NANOG and SOX2.

Effect of nutritional supplement on bone marrow-derived mesenchymal stem cells from aplastic anaemia

Aplastic anaemia (AA) is characterised by pancytopenia resulting from a marked reduction in haemopoietic stem cells (HSC). The regulation of haemopoiesis depends on the interaction between HSC and various cells of the bone marrow (BM) microenvironment, including BM-derived mesenchymal stromal cells (BMSC). The purpose of this study was to analyse the biological effect of nutritional supplement (NS), a dietary supplement consisting of thirty-six compounds: amino acids, nucleotides, vitamins and micronutrients on the BMSC of AA rats. The AA rat model was established by irradiating X-ray (2·5 Gy) and intraperitoneal injections of cyclophosphamide (35 mg/kg; Sigma) and chloramphenicol (35 mg/kg; Sigma). Then AA rats were fed with NS in a dose-dependent manner (2266·95, 1511·3, 1057·91 mg/kg d) by intragastric administration. The effect of NS on the BMSC of AA rats was analysed. As compared with AA rats, NS treatment significantly improved these peripheral blood parameters and stimulated the proliferation of total femoral nucleated cells. NS treatment affected proliferative behaviour of BMSC and suppressed BMSC differentiation to adipocytes. Furthermore, NS treatment of AA rats accelerated osteogenic differentiation of BMSC and enhanced bone mineral density. Co-incubation of HSC with mesenchymal stromal cells and serum from AA rats subjected to high-dose NS markedly improved the yield of CD34+cells. Protein microarray analysis revealed that there were eleven differentially expressed proteins in the NS group compared with the AA rat group. The identified specific NS might be implicated in rehabilitation of BMSC in AA rats, suggesting their potential of nutritional support in AA treatment.

Immunohematology Mesenchymal Stromal Cell-based Therapy: From Research to Clinic

Mesenchymal stromal cells (MSC) are nonhematopoietic cells that can be isolated from several adult and fetal tissues. MSC present specific features as the capacity to support hematopoiesis and to regulate immune response. Thus, the use of MSC as a cell therapeutic product in the field of immune-hematology is of great importance. In this review, we focused on human MSC and discussed their immune-hematologic properties and their translation toward therapeutic clinical applications. Thus, these features hold great promise for cell-based therapy and are of important relevance for the field.

Pathogenesis of Acquired Aplastic Anemia and the Role of the Bone Marrow Microenvironment

Aplastic anemia (AA) is characterized by bone marrow (BM) hypocellularity, resulting in peripheral cytopenias. An antigen-driven and likely auto-immune dysregulated T-cell homeostasis results in hematopoietic stem cell injury, which ultimately leads to the pathogenesis of the acquired form of this disease. Auto-immune and inflammatory processes further influence the disease course as well as response rate to therapy, mainly consisting of intensive immunosuppressive therapy and allogeneic hematopoietic cell transplantation. Bone marrow hematopoietic stem and progenitor cells are strongly regulated by the crosstalk with the surrounding microenvironment and its components like mesenchymal stromal cells, also consistently altered in AA. Whether latter is a contributing cause or rather consequence of the disease remains an open question. Overall, niche disruption may contribute to disease progression, sustain pancytopenia and promote clonal evolution. Here we review the existing knowledge on BM microenvironmental changes in acquired AA and discuss their relevance for the pathogenesis and therapy.

Altered Expression of Hematopoiesis Regulatory Molecules in Lipopolysaccharide-Induced Bone Marrow Mesenchymal Stem Cells of Patients with Aplastic Anemia

We have investigated the expression of RNA transcripts of hematopoiesis regulatory molecules, viz., macrophage inflammatory protein (MIP)-1α, tumor necrosis factor (TNF)-α, granulocyte colony-stimulating factor (G-CSF), stromal cell-derived factor (SDF)-1α, stem cell factor (SCF), and transforming growth factor (TGF)-β in lipopolysaccharide-induced bone marrow mesenchymal stem cells (BM-MSCs) and levels of their soluble forms in the culture supernatants of BM-MSCs and BM plasma of patients with acquired aplastic anemia (AA) (n = 29) and controls (n = 29). The BM-MSCs of AA patients as compared to controls had markedly lower expression of MIP-1α transcripts (p < 0.001), higher expression of TNF-α (p < 0.001), G-CSF (p < 0.001), and SDF-1α (p < 0.01) transcripts, and no difference in the expression of SCF and TGF-β transcripts. The culture supernatants of BM-MSCs and BM plasma of AA patients in comparison to controls also had lower levels of MIP-1α (p < 0.01 and p < 0.001, respectively) and higher levels of TNF-α (p < 0.05 for both) and G-CSF (p < 0.05 and p < 0.001, respectively) but with no difference in the levels of SDF-1α and SCF. The levels of TGF-β were although similar in culture supernatants of BM-MSCs of both the groups, but they were significantly lower in BM plasma of the patients than controls (p < 0.001). Our data shows that BM-MSCs of AA patients have altered expression of hematopoiesis regulatory molecules suggesting that they may have a role in the pathogenesis of the disease.

Increased apoptosis and peripheral blood mononuclear cell suppression of bone marrow mesenchymal stem cells in severe aplastic anemia

BACKGROUND

Although immune-mediated pathogenesis is considered an important aspect of severe aplastic anemia (SAA), its underlying mechanisms remain unclear. Mesenchymal stem cells (MSCs) are essential to the formation of specialized microenvironments in the bone marrow (BM), and MSC insufficiency can trigger the development of SAA.

METHODS

To find MSC alterations in the SAA BM, we compared BM MSCs from five children with SAA and five controls. Peripheral blood mononuclear cells (PBMCs) were cocultured with MSCs to evaluate the supportive effects of MSCs on hematopoiesis. Cytometric bead array immunoassay was used to determine cytokine excretion by MSCs. The immune functions of MSCs and their conditioned medium (CM) were evaluated by PBMC proliferation assays.

RESULTS

SAA MSCs were characterized by a high percentage of cells in the abnormal sub-G1 phase of the cell cycle, which suggests an increased rate of apoptosis in SAA MSCs. In comparison with control MSCs, PBMCs cocultured with SAA MSCs displayed significantly reduced PBMC proliferation (P = 0.009). Aberrant cytokine profiles were secreted by SAA MSCs, with increased concentrations of interleukin-6, interferon-γ, tumor necrosis factor-α, and interleukin-1β in the CM. PBMC proliferation assays demonstrated additional immunosuppressive effects of SAA MSCs (P = 0.016) and their CM (P = 0.013).

CONCLUSIONS

Our data revealed increased apoptosis and PBMC suppression of SAA MSCs. The alterations of MSCs may contribute to the formation of functionally abnormal microenvironments in SAA BM.

The Pathophysiology of Acquired Aplastic Anemia: Current Concepts Revisited

Idiopathic acquired aplastic anemia is a rare, life-threatening bone marrow failure syndrome characterized by cytopenias and hypocellular bone marrow. The pathophysiology is unknown; the most favored model is of a dysregulated immune system leading to autoreactive T-cell destruction of hematopoietic stem and progenitor cells in a genetically susceptible host. The authors review the literature and propose that the major driver of acquired aplastic anemia is a combination of hematopoietic stem and progenitor cells intrinsic defects and an inappropriately activated immune response in the setting of a viral infection. Alterations in bone marrow microenvironment may also contribute to the disease process.

Levamisole suppresses adipogenesis of aplastic anaemia-derived bone marrow mesenchymal stem cells through ZFP36L1-PPARGC1B axis

Aplastic anaemia (AA) is a life‐threatening hematopoietic disorder characterized by hypoplasia and pancytopenia with increasing fat cells in the bone marrow (BM). The BM‐derived mesenchymal stem cells (MSCs) from AA are more susceptible to be induced into adipogenic differentiation compared with that from control, which may be causatively associated with the fatty BM and defective hematopoiesis of AA. Here in this study, we first demonstrated that levamisole displayed a significant suppressive effect on the in vitro adipogenic differentiation of AA BM‐MSCs. Mechanistic investigation revealed that levamisole could increase the expression of ZFP36L1 which was subsequently demonstrated to function as a negative regulator of adipogenic differentiation of AA BM‐MSCs through lentivirus‐mediated ZFP36L1 knock‐down and overexpression assay. Peroxisome proliferator‐activated receptor gamma coactivator 1 beta (PPARGC1B) whose 3′‐untranslated region bears adenine‐uridine‐rich elements was verified as a direct downstream target of ZFP36L1, and knock‐down of PPARGC1B impaired the adipogenesis of AA BM‐MSCs. Collectively, our work demonstrated that ZFP36L1‐mediated post‐transcriptional control of PPARGC1B expression underlies the suppressive effect of levamisole on the adipogenic differentiation of AA BM‐MSCs, which not only provides novel therapeutic targets for alleviating the BM fatty phenomenon of AA patients, but also lays the theoretical and experimental foundation for the clinical application of levamisole in AA therapy.

Dysfunctional Bone Marrow Mesenchymal Stem Cells in Patients with Poor Graft Function after Allogeneic Hematopoietic Stem Cell Transplantation

Poor graft function (PGF) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is characterized by defective hematopoiesis. Mesenchymal stem cells (MSCs) have been shown to support hematopoiesis, but little is known about the role of MSCs in the pathogenesis of PGF. In the current prospective case-control study, we evaluated whether the number and function of bone marrow (BM) MSCs in PGF patients differed from those in good graft function (GGF) patients. We found that BM MSCs from PGF patients expanded more slowly and appeared flattened and larger, exhibiting more apoptosis and senescence than MSCs from GGF patients. Furthermore, increased intracellular reactive oxygen species, p-p53, and p21 (but not p38) levels were detected in MSCs from PGF patients. Moreover, the ability of MSCs to sustain hematopoiesis was significantly reduced in PGF patients, as evaluated by cell number, apoptosis, and the colony-forming unit-plating efficiency of CD34⁺ cells. In summary, the biologic characteristics of PGF MSCs are different from those of GGF MSCs, and the in vitro hematopoiesis-supporting ability of PGF MSCs is significantly lower. Although requiring further validation, our study indicates that reduced and dysfunctional BM MSCs may contribute to deficient hematopoiesis in PGF patients. Therefore, improvement of BM MSCs may represent a promising therapeutic approach for PGF patients after allo-HSCT.

Interferon-Gamma Impairs Maintenance and Alters Hematopoietic Support of Bone Marrow Mesenchymal Stromal Cells

Bone marrow (BM) mesenchymal stromal cells (MSCs) provide microenvironmental support to hematopoietic stem and progenitor cells (HSPCs). Culture-expanded MSCs are interesting candidates for cellular therapies due to their immunosuppressive and regenerative potential which can be further enhanced by pretreatment with interferon-gamma (IFN-γ). However, it remains unknown whether IFN-γ can also influence hematopoietic support by BM-MSCs. In this study, we elucidate the impact of IFN-γ on the hematopoietic support of BM-MSCs. We found that IFN-γ increases expression of interleukin (IL)-6 and stem cell factor by human BM-MSCs. IFN-γ-treated BM-MSCs drive HSPCs toward myeloid commitment in vitro, but impair subsequent differentiation of HSPC. Moreover, IFN-γ-ARE-Del mice with increased IFN-γ production specifically lose their BM-MSCs, which correlates with a loss of hematopoietic stem cells' quiescence. Although IFN-γ treatment enhances the immunomodulatory function of MSCs in a clinical setting, we conclude that IFN-γ negatively affects maintenance of BM-MSCs and their hematopoietic support in vitro and in vivo.

Role of the microenvironment in myeloid malignancies

The bone marrow microenvironment (BMM) regulates the fate of hematopoietic stem cells (HSCs) in homeostatic and pathologic conditions. In myeloid malignancies, new insights into the role of the BMM and its cellular and molecular actors in the progression of the diseases have started to emerge. In this review, we will focus on describing the major players of the HSC niche and the role of the altered niche function in myeloid malignancies, more specifically focusing on the mesenchymal stroma cell compartment.

N-acetyl-L-cysteine improves mesenchymal stem cell function in prolonged isolated thrombocytopenia post-allotransplant

Prolonged isolated thrombocytopenia (PT) is a serious complication of allogeneic haematopoietic stem cell transplantation (allo-HSCT). Murine studies and in vitro experiments suggest that mesenchymal stem cells (MSCs) can, not only to support haematopoiesis, but also preferentially support megakaryocytopoiesis in bone marrow (BM). However, little is known about the quantity and function of BM MSCs in PT patients. In a case-control study, we found that BM MSCs from PT patients exhibited significantly reduced proliferative capacities, increased reactive oxygen species and senescence. Antioxidant (N-acetyl-L-cysteine, NAC) treatment in vitro not only quantitatively and functionally improved BM MSCs derived from PT patients through down-regulation of the p38 (also termed MAPK14) and p53 (also termed TP53) pathways but also partially rescued the impaired ability of BM MSCs to support megakaryocytopoiesis. Subsequently, a pilot study showed that the overall response of NAC treatment was obtained in 7 of the enrolled PT patients (N = 10) without significant side effects. Taken together, the results indicated that dysfunctional BM MSCs played a role in the pathogenesis of PT and the impaired BM MSCs could be improved by NAC in vitro. Although requiring further validation, our data indicate that NAC might be a potential therapeutic approach for PT patients after allo-HSCT.

Yin and Yang of mesenchymal stem cells and aplastic anemia

Acquired aplastic anemia (AA) is a bone marrow failure syndrome characterized by peripheral cytopenias and bone marrow hypoplasia. It is ultimately fatal without treatment, most commonly from infection or hemorrhage. Current treatments focus on suppressing immune-mediated destruction of bone marrow stem cells or replacing hematopoietic stem cells (HSCs) by transplantation. Our incomplete understanding of the pathogenesis of AA has limited development of targeted treatment options. Mesenchymal stem cells (MSCs) play a vital role in HSC proliferation; they also modulate immune responses and maintain an environment supportive of hematopoiesis. Some of the observed clinical manifestations of AA can be explained by mesenchymal dysfunction. MSC infusions have been shown to be safe and may offer new approaches for the treatment of this disorder. Indeed, infusions of MSCs may help suppress auto-reactive, T-cell mediated HSC destruction and help restore an environment that supports hematopoiesis. Small pilot studies using MSCs as monotherapy or as adjuncts to HSC transplantation have been attempted as treatments for AA. Here we review the current understanding of the pathogenesis of AA and the function of MSCs, and suggest that MSCs should be a target for further research and clinical trials in this disorder.

[The mechanism of bone marrow-derived mesenchymal stem cells excessive senescence in severe aplastic anemia mouse model]

Objective: To explore the mechanism of excessive senescence in bone marrow-derived mesenchymal stem cells (BM-MSC) of mouse model with severe aplastic anemia (SAA) . Methods: 40 BALB/c mice were randomly assigned to two groups of control (n=20) and AA (n=20) . SAA mouse model was induced by intraperitoneal injection with IFN-γ and intragastric infusion with busulfan. BM-MSC were isolated and cultured from bone marrow of SAA and healthy mice. The cell morphology was observed by inverted microscope and cell cytoskeleton was stained by Rhodamine-Phalloidin; The level of proliferation was analyzed by CCK-8 method, and cell cycle was tested by flow cytometry. Senescence-associated β-galactosidase (SA-β-gal) assay was used to detect senescent BM-MSC; The expression of mTOR protein was detected by Western blot method. Results: BM-MSC from normal mice presented spindle-shaped, clear boundaries and stress fibers were arranged in parallel, neat. while BM-MSCs from SAA mice presented cell volume increases, tiled, ill-shaped and the stress fiber appeared to be disordered. The decreased activity of proliferation [more cells restricted in G(0)/G(1) phase [ (77.461±1.567) % vs (46.045±2.055) %, t=-34.384, P<0.001], increased percentage of SA-β-gal positive cells [ (75±11) % vs (28±8) %, t=15.454, P<0.001] and notably enhanced expression of mTOR of BM-MSC from SAA mice were observed when compared with those from normal mice. Conclusion: This study clarified senescent BM-MSCs from SAA model mice, which could be caused by the excessive activation of mTOR pathway.

Murine Rankl-/- Mesenchymal Stromal Cells Display an Osteogenic Differentiation Defect Improved by a RANKL-Expressing Lentiviral Vector

Autosomal recessive osteopetrosis (ARO) is a severe bone disease characterized by increased bone density due to impairment in osteoclast resorptive function or differentiation. Hematopoietic stem cell transplantation is the only available treatment; however, this therapy is not effective in RANKL-dependent ARO, since in bone this gene is mainly expressed by cells of mesenchymal origin. Of note, whether lack of RANKL production might cause a defect also in the bone marrow (BM) stromal compartment, possibly contributing to the pathology, is unknown. To verify this possibility, we generated and characterized BM mesenchymal stromal cell (BM-MSC) lines from wild type and Rankl^-/- mice, and found that Rankl^-/- BM-MSCs displayed reduced clonogenicity and osteogenic capacity. The differentiation defect was significantly improved by lentiviral transduction of Rankl^-/- BM-MSCs with a vector stably expressing human soluble RANKL (hsRANKL). Expression of Rankl receptor, Rank, on the cytoplasmic membrane of BM-MSCs pointed to the existence of an autocrine loop possibly activated by the secreted cytokine. Based on the close resemblance of RANKL-defective osteopetrosis in humans and mice, we expect that our results are also relevant for RANKL-dependent ARO patients. Data obtained in vitro after transduction with a lentiviral vector expressing hsRANKL would suggest that restoration of RANKL production might not only rescue the defective osteoclastogenesis of this ARO form, but also improve a less obvious defect in the osteoblast lineage, thus possibly achieving higher benefit for the patients, when the approach is translated to clinics. Stem Cells 2017;35:1365-1377.

In patients with chronic aplastic anemia, bone marrow-derived MSCs regulate the Treg/Th17 balance by influencing the Notch/RBP-J/FOXP3/RORγt pathway

The standard treatment for aplastic anemia (AA) in young patients is a matched sibling hematopoietic stem cell transplant. Transfusion of a chronic AA patient with allogeneic bone marrow–derived mesenchymal stromal cells (BMMSCs) is currently being developed as a cell-based therapy, and the safety and efficacy of such transfusions are being continuously improved. Nevertheless, the mechanisms by which BMMSCs exert their therapeutic effects remain to be elucidated. In this study, mesenchymal stromal cells (MSCs) obtained from bone marrow donors were concentrated and intravenously injected into 15 chronic AA patients who had been refractory to prior immunosuppressive therapy. We showed that BMMSCs modulate the levels of Th1, Th2, Th17 and Treg cells, as well as their related cytokines in chronic AA patients. Furthermore, the percentages of Th1 and Th17 cells among the H-MSCs decreased significantly, while the percentage Treg cells increased. The Notch/RBP-J/FOXP3/RORγt pathway was involved in modulating the Treg/Th17 balance after MSCs were transfused in vitro. Additionally, the role played by transfused MSCs in regulating the Treg/Th17 balance via the Notch/RBP-J/FOXP3/RORγt pathway was further confirmed in an AA mouse model. In summary, in humans with chronic AA, BMMSCs regulate the Treg/Th17 balance by affecting the Notch/RBP-J/FOXP3/RORγt pathway.

Bone Marrow-Derived Mesenchymal Stromal Cells from Patients with Sickle Cell Disease Display Intact Functionality

Hematopoietic cell transplantation (HCT) is the only cure for sickle cell disease (SCD), but engraftment remains challenging in patients lacking matched donors. Infusion of mesenchymal stromal cells (MSCs) at the time of HCT may promote hematopoiesis and ameliorate graft-versus-host disease. Experimental murine models suggest MSC major histocompatibility complex compatibility with recipient impacts their in vivo function, suggesting autologous MSCs could be superior to third-party MSCs for promoting HCT engraftment. Here we tested whether bone marrow (BM)-derived MSCs from SCD subjects have comparable functionality compared with MSCs from healthy volunteers. SCD MSC doubling time and surface marker phenotype did not differ significantly from non-SCD. Third-party and autologous (SCD) T cell proliferation was suppressed in a dose-dependent manner by all MSCs. SCD MSCs comparably expressed indoleamine-2,3-dioxygenase, which based on transwell and blocking experiments appeared to be the dominant immunomodulatory pathway. The expression of key genes involved in hematopoietic stem cell (HSC)-MSC interactions was minimally altered between SCD and non-SCD MSCs. Expression was, however, altered by IFN-γ stimulation, particularly CXCL14, CXCL26, CX3CL1, CKITL, and JAG1, indicating the potential to augment MSC expression by cytokine stimulation. These data demonstrate the feasibility of expanding BM-derived MSCs from SCD patients that phenotypically and functionally do not differ per International Society of Cell Therapy essential criteria from non-SCD MSCs, supporting initial evaluation (primarily for safety) of autologous MSCs to enhance haploidentical HSC engraftment in SCD.

Hematopoietic Stem Cell Regulation by Type I and II Interferons in the Pathogenesis of Acquired Aplastic Anemia

Aplastic anemia (AA) occurs when the bone marrow fails to support production of all three lineages of blood cells, which are necessary for tissue oxygenation, infection control, and hemostasis. The etiology of acquired AA is elusive in the vast majority of cases but involves exhaustion of hematopoietic stem cells (HSC), which are usually present in the bone marrow in a dormant state, and are responsible for lifelong production of all cells within the hematopoietic system. This destruction is immune mediated and the role of interferons remains incompletely characterized. Interferon gamma (IFNγ) has been associated with AA and type I IFNs (alpha and beta) are well documented to cause bone marrow aplasia during viral infection. In models of infection and inflammation, IFNγ activates HSCs to differentiate and impairs their ability to self-renew, ultimately leading to HSC exhaustion. Recent evidence demonstrating that IFNγ also impacts the HSC microenvironment or niche, raises new questions regarding how IFNγ impairs HSC function in AA. Immune activation can also elicit type I interferons, which may exert effects both distinct from and overlapping with IFNγ on HSCs. IFNα/β increase HSC proliferation in models of sterile inflammation induced by polyinosinic:polycytidylic acid and lead to BM aplasia during viral infection. Moreover, patients being treated with IFNα exhibit cytopenias, in part due to BM suppression. Herein, we review the current understanding of how interferons contribute to the pathogenesis of acquired AA, and we explore additional potential mechanisms by which interferons directly and indirectly impair HSCs. A comprehensive understanding of how interferons impact hematopoiesis is necessary in order to identify novel therapeutic approaches for treating AA patients.

The clinical application of mesenchymal stromal cells in hematopoietic stem cell transplantation

Mesenchymal stromal cells (MSCs) are multipotent stem cells well known for repairing tissue, supporting hematopoiesis, and modulating immune and inflammation response. These outstanding properties make MSCs as an attractive candidate for cellular therapy in immune-based disorders, especially hematopoietic stem cell transplantation (HSCT). In this review, we outline the progress of MSCs in preventing and treating engraftment failure (EF), graft-versus-host disease (GVHD) following HSCT and critically discuss unsolved issues in clinical applications.