T-cell suppression mediated by mesenchymal stem cells is deficient in patients with severe aplastic anemia

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.

Umbilical Cord Blood-Derived Cells Can Reconstruct Hematopoiesis in an Aplastic Anemia Animal Model

Objectives

To explore the efficacy and the mechanism of the umbilical cord-derived cells combined with cyclosporine A (CsA) in treating aplastic anemia (AA) in mice.

Methods

Immune-mediated AA model mice were treated with CsA + UC mesenchymal stem cells (UC-MSC), CsA + umbilical cord blood regulatory T cells (UCB-Treg), UC-MSC, UCB-Treg, CsA alone, or blank control, respectively (n = 9 mice/group). CsA and the cell infusion was administered on d0. Routine peripheral blood testing was performed once weekly; bone marrow colony culture, bone marrow cell flow cytometry, peripheral blood T cell subsets, and serum inflammatory cytokines tests were performed on d14. Transcriptome sequencing was performed for cells from CsA + UC-MSC, CsA + UCB-Treg, and CsA groups to detect the possible related genes. Gene function cluster and signal pathway enrichment analysis were also performed.

Results

Blank control mice died due to pancytopenia within 21 days, whereas mice in other groups survived for >28 days. On d14, the CsA + UC-MSC and CsA + UCB-Treg groups had higher white blood cell (WBC) counts than the other groups (p < 0.05), along with higher burst-forming unit (BFU) and colony-forming unit-granulocyte, macrophage (CFU-GM) counts (p < 0.01). The CsA + UC-MSC group had the highest BFU count (p < 0.01). The CsA + UC-MSC and CsA + UCB-Treg groups exhibited the highest bone marrow CD34+ cell proportion (9.68% ± 1.35% and 8.17% ± 0.53%, respectively; p < 0.01). Tumor necrosis factor (TNF)-α and interleukin (IL)-2 levels in the CsA + UC-MSC group (p < 0.05) and TNF-α, interleukin-2, and interferon (INF)-γ levels in the CsA + UC-Treg group (p < 0.01) were lower than those in the CsA group. Compared with CsA treatment, CsA + UC-MSC significantly downregulated the histone methylation pathway (p < 0.05), whereas CsA + UCB-Treg significantly upregulated energy metabolism processes (p < 0.05). Treatment with CsA + UC-MSC upregulated superoxide dismutase activity compared with CsA + UCB-Treg treatment.

Conclusions

Adding UC-MSC or UCB-Treg to CsA markedly enhanced the reconstruction of hematopoiesis in AA mice, with UC-MSC eliciting greater efficiency than UCB-Treg. Accordingly, the addition of these cells could further improve immune abnormalities.

Reduced regulatory effects of bone marrow-derived mesenchymal stem cells on activated T lymphocytes and Th1/Th2 cytokine secretion in children with aplastic anemia

Acquired aplastic anemia (AA) is a recognized immune-mediated disorder and abnormally activated T lymphocyte-mediated bone marrow destruction is considered to be its main pathogenesis. Whether abnormal activation of T lymphocytes would also damage bone marrow-derived MSCs remains to be further studied. The aim of this study was to analyze the extent of T lymphocyte activation and the levels of Th1/Th2 cytokines of AA patients, and to explore the immunomodulatory effects of BM-MSCs on IL-2-stimulated T lymphocyte activation and cytokine production in vitro by means of transwell co-culture assay and flow cytometry measurement. The intermediate (CD25+) activated T cells were dominant in peripheral blood, while the early (CD69+) and late (HLA-DR+) activated T cells were predominant in bone marrow. Severe AA patients have an obviously higher proportion of CD3+CD8+CD69+ T cells than NSAA cases. The levels of IL-2 and IL-6 in AA patients were slightly elevated and INF-γ was mildly decreased in comparison with normal individuals. BM-MSCs derived from AA could not effectively inhibit the IL-2-induced activation of T cells with higher proportions of CD25+CD3+CD4+, CD69+CD3+CD4+ and CD25+CD3+CD8+ T cells after co-culture, and they showed a decreased ability to balance the Th1/Th2 cytokine production. Moreover, they had less robust osteogenic differentiation and more prone to adipogenic differentiation. We concluded that abnormally excessive T cell activation accompanied by abnormal cytokine secretion may impair the function of BM-MSCs in children with aplastic anemia.

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.

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.

Aplastic Anemia as a Roadmap for Bone Marrow Failure: An Overview and a Clinical Workflow

In recent years, it has become increasingly apparent that bone marrow (BM) failures and myeloid malignancy predisposition syndromes are characterized by a wide phenotypic spectrum and that these diseases must be considered in the differential diagnosis of children and adults with unexplained hematopoiesis defects. Clinically, hypocellular BM failure still represents a challenge in pathobiology-guided treatment. There are three fundamental topics that emerged from our review of the existing data. An exogenous stressor, an immune defect, and a constitutional genetic defect fuel a vicious cycle of hematopoietic stem cells, immune niches, and stroma compartments. A wide phenotypic spectrum exists for inherited and acquired BM failures and predispositions to myeloid malignancies. In order to effectively manage patients, it is crucial to establish the right diagnosis. New theragnostic windows can be revealed by exploring BM failure pathomechanisms.

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.

Current insights into the treatments of severe aplastic anemia in China

Recently, several studies have been conducted to generate considerable evidence regarding unique treatments for severe aplastic anemia (SAA) in China. Haploidentical donor hematopoietic stem cell transplantation (HID-HSCT) showed an overall survival rate (80.3-86.1%) comparable to those with immunosuppressive therapy (IST) and matched related donor (MRD)- and matched unrelated donor (MUD)-HSCT. Failure-free survival of HID-HSCT was also comparable (76.4-85.0%) to those of MRD- and MUD-HSCT and better than IST in patients < 40 years. Although these results are promising, HID-HSCT should be regarded as a salvage therapy when young patients fail to respond to IST. Porcine anti-human lymphocyte immunoglobulin (pALG) showed similar or superior overall response at 6 months compared to rabbit anti-human thymocyte immunoglobulin (rATG) (64.0-79.4% in the pALG-group vs.48.1-64.7% in the rATG-group) as a first-line IST. Promising hematological response (28.4-33.3%) was observed in patients with refractory AA following infusion of the mesenchymal stromal cells (MSCs) derived from the bone marrow of allogeneic donors. pALG can replace rATG as an immunosuppressive drug and MSCs infusion can be used as a second-line treatment for refractory SAA. We believe that this review contributes to refine the global practices for SAA treatment.

Pathogenesis of aplastic anemia

Aplastic anemia (AA) is a rare and life-threatening bone marrow failure (BMF) that results in peripheral blood cytopenia and reduced bone marrow hematopoietic cell proliferation. The symptoms are similar to myelofibrosis, myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) making diagnosis of AA complicated. The pathogenesis of AA is complex and its mechanism needs to be deciphered on an individualized basis. This review summarizes several contributions made in trying to understand AA pathogenesis in recent years which may be helpful for the development of personalized therapies for AA.

Insights into Inflammatory Priming of Adipose-Derived Mesenchymal Stem Cells: Validation of Extracellular Vesicles-Embedded miRNA Reference Genes as A Crucial Step for Donor Selection

Mesenchymal stem cells (MSCs) are promising tools for cell-based therapies due to their homing to injury sites, where they secrete bioactive factors such as cytokines, lipids, and nucleic acids, either free or conveyed within extracellular vesicles (EVs). Depending on the local environment, MSCs’ therapeutic value may be modulated, determining their fate and cell behavior. Inflammatory signals may induce critical changes on both the phenotype and secretory portfolio. Intriguingly, in animal models resembling joint diseases as osteoarthritis (OA), inflammatory priming enhanced the healing capacity of MSC-derived EVs. In this work, we selected miRNA reference genes (RGs) from the literature (let-7a-5p, miR-16-5p, miR-23a-3p, miR-26a-5p, miR-101-3p, miR-103a-3p, miR-221-3p, miR-423-5p, miR-425-5p, U6 snRNA), using EVs isolated from adipose-derived MSCs (ASCs) primed with IFNγ (iASCs). geNorm, NormFinder, BestKeeper, and ΔCt methods identified miR-26a-5p/16-5p as the most stable, while miR-103a-rp/425-5p performed poorly. Our results were validated on miRNAs involved in OA cartilage trophism. Only a proper normalization strategy reliably identified the differences between donors, a critical factor to empower the therapeutic value of future off-the-shelf MSC-EV isolates. In conclusion, the proposed pipeline increases the accuracy of MSC-EVs embedded miRNAs assessment, and help predicting donor variability for precision medicine approaches.

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.

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.

Cyclosporin A inhibits adipogenic differentiation and regulates immunomodulatory functions of murine mesenchymal stem cells

Aplastic anemia (AA) is generally considered as an immune-mediated bone marrow failure syndrome. Several studies show that bone marrow mesenchymal stem cells (BM-MSCs), as key cellular components of the bone marrow microenvironment, are also involved in the pathogenic mechanism of AA. Cyclosporin A (CsA) is a classic immunosuppressive drug for AA, and it specifically inhibits mammalian T cells by preventing activation of transcription factors involved in cytokine gene expression. However, little is known about the effect of CsA on the BM-MSCs. In this study, murine BM-MSCs were stimulated in the presence of CsA. Further, we found that CsA could inhibit murine BM-MSC proliferation and promote BM-MSC apoptosis, what's more CsA could inhibit adipogenic differentiation. Our study also showed that CsA could inhibit interleukin-6 expression in BM-MSCs, while promoting programmed death-ligand 2 expression. In conclusion, our results proposed that CsA may exert an effect on regulating the bone marrow environment by influencing BM-MSCs, which have a beneficial effect on treating AA.

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.

Immunosuppressive function of mesenchymal stem cells from human umbilical cord matrix in immune thrombocytopenia patients

Human umbilical cord matrix/Wharton's Jelly (hUC)-derived mesenchymal stem cells (MSC) have been shown to have marked therapeutic effects in a number of inflammatory diseases and autoimmune diseases in humans based on their potential for immunosuppression and their low immunogenicity. Currently, no data are available on the effectiveness of UC-MSC transplantation in immune thrombocytopenia (ITP) patients. It was the objective of this study to assess the effect of allogeneic UC-MSCs on ITP patients in vitro and in vivo. Peripheral blood mononuclear cells (PBMCs) and bone marrow mononuclear cells (BM-MNCs) from ITP patients and healthy controls were co-cultured with UC-MSCs for three days and seven days, respectively. Flow cytometry and ELISA were applied to assess the various parameters. In PBMCs from ITP patients, the proliferation of autoreactive T, B lymphocytes and destruction of autologous platelets were dramatically suppressed by UC-MSCs. UC-MSCs not only suppressed co-stimulatory molecules CD80, CD40L and FasL expression but also in shifting Th1/Th2/Treg cytokines profile in ITP patients. UC-MSCs obviously reversed the dysfunctions of megakaryocytes by promoting platelet production and decreasing the number of living megakaryocytes as well as early apoptosis. In addition, the level of thrombopoietin was increased significantly. Our clinical study showed that UC-MSCs play a role in alleviating refractory ITP by increasing platelet numbers. These findings suggested that UC-MSCs transplantation might be a potential therapy for ITP.

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.

Donor variability among anti-inflammatory pre-activated mesenchymal stromal cells

Therapeutic mesenchymal stromal cells (MSCs) are attractive in part due to their immunomodulatory properties, achieved by their paracrine secretion of factors including prostaglandin E2 (PGE2). Despite promising pre-clinical data, demonstrating clinical efficacy has proven difficult. The current studies were designed to develop approaches to pre-induce desired functions from naïve MSCs and examine MSC donor variability, two factors contributing to this disconnect. MSCs from six human donors were pre-activated with interleukin 1 beta (IL-1β) at a concentration and duration identified as optimal or interferon gamma (IFN-γ) as a comparator. Their secretion of PGE2 after pre-activation and secondary exposure to pro-inflammatory molecules was measured. Modulation of tumor necrosis factor alpha (TNF-α) secretion from M1 pro-inflammatory macrophages by co-cultured pre-activated MSCs was also measured. Our results indicated that pre-activation of MSCs with IL-1β resulted in upregulated PGE2 secretion post exposure. Pre-activation with IL-1β or IFN-γ resulted in higher sensitivity to induction by secondary stimuli compared to no pre-activation. While IL-1β pre-activation led to enhanced MSC-mediated attenuation of macrophage TNF-α secretion, IFN-γ pre-activation resulted in enhanced TNF-α secretion. Donor variability was noted in PGE2 secretion and upregulation and the level of improved or impaired macrophage modulation.

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.

Platelet-Derived Growth Factor-BB Protects Mesenchymal Stem Cells (MSCs) Derived From Immune Thrombocytopenia Patients Against Apoptosis and Senescence and Maintains MSC-Mediated Immunosuppression

: Immune thrombocytopenia (ITP) is characterized by platelet destruction and megakaryocyte dysfunction. Mesenchymal stem cells (MSCs) from ITP patients (MSC-ITP) do not exhibit conventional proliferative abilities and thus exhibit defects in immunoregulation, suggesting that MSC impairment might be a mechanism involved in ITP. Platelet-derived growth factor (PDGF) improves growth and survival in various cell types. Moreover, PDGF promotes MSC proliferation. The aim of the present study was to analyze the effects of PDGF-BB on MSC-ITP. We showed that MSC-ITP expanded more slowly and appeared flattened and larger. MSC-ITP exhibited increased apoptosis and senescence compared with controls. Both the intrinsic and extrinsic pathways account for the enhanced apoptosis. P53 and p21 expression were upregulated in MSC-ITP, but inhibition of p53 with pifithrin-α markedly inhibited apoptosis and senescence. Furthermore, MSCs from ITP patients showed a lower capacity for inhibiting the proliferation of activated T cells inducing regulatory T cells (Tregs) and suppressing the synthesis of anti-glycoprotein (GP)IIb-IIIa antibodies. PDGF-BB treatment significantly decreased the expression of p53 and p21 and increased survivin expression in MSC-ITP. In addition, the apoptotic rate and number of senescent cells in ITP MSCs were reduced. Their impaired ability for inhibiting activated T cells, inducing Tregs, and suppressing the synthesis of anti-GPIIb-IIIa antibodies was restored after PDGF-BB treatment. In conclusion, we have demonstrated that PDGF-BB protects MSCs derived from ITP patients against apoptosis, senescence, and immunomodulatory defects. This protective effect of PDGF-BB is likely mediated via the p53/p21 pathway, thus potentially providing a new therapeutic approach for ITP.

SIGNIFICANCE

Immune thrombocytopenia (ITP) is characterized by platelet destruction and megakaryocyte dysfunction. Platelet-derived growth factor (PDGF) improves growth and survival in various cell types and promotes mesenchymal stem cell (MSC) proliferation. PDGF-BB protects MSCs derived from ITP patients against apoptosis, senescence, and immunomodulatory defects. This protective effect of PDGF-BB is likely mediated via the p53/p21 pathway, thus potentially providing a new therapeutic approach for ITP.

Intravenous infusion of allogeneic mesenchymal stromal cells in refractory or relapsed aplastic anemia

BACKGROUND AIMS

For patients with aplastic anemia (AA) who are refractory to anti-thymocyte globulin (ATG) and cyclosporine, a second course of immunosuppression is successful in only one-fourth to one-third of cases.

METHODS

We conducted a phase 1/2 study to evaluate the addition of two to five weekly intravenous infusions of allogeneic unrelated non-human leukocyte antigen-matched bone marrow-derived mesenchymal stromal cells (MSCs) (median, 2.7 × 10(6) cells/kg/infusion; range, 1.3-4.5) to standard rabbit ATG and cyclosporine in nine patients with refractory or relapsed AA.

RESULTS

After a median follow-up of 20 months, no infusion-related adverse event was observed, but four deaths occurred as the result of heart failure and bacterial or invasive fungal infections; only two patients achieved partial hematologic responses at 6 months. We failed to demonstrate by fluorescence in situ hybridization or variable number tandem repeat any MSC engraftment in patient marrow 30, 90 or 180 days after infusions.

CONCLUSIONS

Infusion of allogeneic MSCs in AA is safe but does not improve clinical hematologic response or engraft in recipient bone marrow. This study was registered at clinicaltrials.gov, identifier: NCT01297972.

Therapeutic effects of transplantation of bone marrow mesenchymal stem cells on ConA-induced acute liver injury in mice

AIM: To assess the therapeutic action of bone marrow mesenchymal stem cells (BMMSCs) on concanavalin A (ConA)-induced acute liver injury in mice.

METHODS: BMMSCs were isolated from bone tissues of C57BL/6 mice, cultured, identified, and labeled with CM-Dil in vitro. C57BL/6 mice were injected with different doses of ConA to find the optimal concentration to generate a mouse model of ConA-induced hepatitis. C57BL/6 mice were randomly divided into groups I-IV and a control group. Groups I-IV were injected with CM-Dil labeled BMMSCs at 1 × 10⁵, 5 × 10⁵, 1 × 10⁶, and 1 × 10⁷, respectively. The control group was injected with PBS. Serum levels of liver enzymes [alanine transaminase (ALT) and aspartate transaminase (AST)], cytokines [tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and interleukin-4 (IL-4)], histopathology, and localization of BMMSCs were investigated at 24 h after injection.

RESULTS: We collected cells in line with the characteristics of BMMSCs, and the rate of CM-Dil labeling was over 90%. With increasing doses of ConA, the severity of liver injury increased, and 15 mg/kg was the optimal dose for inducing acute liver injury in C57BL/6 mice. Serum levels of ALT, AST, TNF-α, IFN-γ, IL-4 and Knodell score were significantly reduced in groups II and III as compared with the control group (P < 0.05). Injected CM-Dil labeled BMMSCs were located in the liver of ConA-injected mice, but were not detected in the heart, lung or spleen.

CONCLUSION: The therapeutic efficacy of BMMSCs for ConA-induced hepatitis is defined. It is possible that BMMSCs migrate to the inflammatory sites and reduce the production of TNF-α, IFN-γ and IL-4 to alleviate liver injury induced by ConA.

Decreased circulating Th22 and Th17 cells in patients with aplastic anemia

BACKGROUND

Aplastic anemia (AA) is an immune-mediated disorder and mainly related to active destruction of hematopoietic cells by effector T lymphocytes. T helper (Th) 22 cells characterized as a novel subset of CD4+ T cells participate in the pathogenesis of autoimmune and hematological diseases. However, the role of Th22 subset in AA remains unknown.

METHODS

31 untreated AA patients and 30 healthy controls were included in this study. The percentages of Th22, Th17 and pure Th17 cells in peripheral blood were detected by flow cytometry. ELISA to measure interleukin (IL)-22 and IL-17A plasma levels and qRT-PCR for the mRNA levels of Th22 and Th17 related molecules were performed.

RESULTS

The proportions of Th22, pure Th17, Th17 cells and plasma levels of IL-22 were significantly lower in untreated AA patients than those in normal controls. A positive correlation was found between Th22 and pure Th17 cells in AA. Moreover, percentages of Th22 cells correlated positively with reticulocyte counts and percentages. In addition, STAT3/STAT5 mRNA expression ratio was elevated in AA patients.

CONCLUSION

Together, our results showed Th22 cells correlating with clinical characteristics of AA patients, indicating a possible role of Th22 immune response in the pathogenesis and therapeutic intervention of AA.

Bottlenecks in the Efficient Use of Advanced Therapy Medicinal Products Based on Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) have been established as promising candidate sources of universal donor cells for cell therapy due to their contributions to tissue and organ homeostasis, repair, and support by self-renewal and multidifferentiation, as well as by their anti-inflammatory, antiproliferative, immunomodulatory, trophic, and proangiogenic properties. Various diseases have been treated by MSCs in animal models. Additionally, hundreds of clinical trials related to the potential benefits of MSCs are in progress. However, although all MSCs are considered suitable to exert these functions, dissimilarities have been found among MSCs derived from different tissues. The same levels of efficacy and desired outcomes have not always been achieved in the diverse studies that have been performed thus far. Moreover, autologous MSCs can be affected by the disease status of patients, compromising their use. Therefore, collecting information regarding the characteristics of MSCs obtained from different sources and the influence of the host (patient) medical conditions on MSCs is important for assuring the safety and efficacy of cell-based therapies. This review provides relevant information regarding factors to consider for the clinical application of MSCs.

The complex pathophysiology of acquired aplastic anaemia

Immune-mediated destruction of haematopoietic stem/progenitor cells (HSPCs) plays a central role in the pathophysiology of acquired aplastic anaemia (aAA). Dysregulated CD8(+) cytotoxic T cells, CD4(+) T cells including T helper type 1 (Th1), Th2, regulatory T cells and Th17 cells, natural killer (NK) cells and NK T cells, along with the abnormal production of cytokines including interferon (IFN)-γ, tumour necrosis factor (TNF)-α and transforming growth factor (TGF)-β, induce apoptosis of HSPCs, constituting a consistent and defining feature of severe aAA. Alterations in the polymorphisms of TGF-β, IFN-γ and TNF-α genes, as well as certain human leucocyte antigen (HLA) alleles, may account for the propensity to immune-mediated killing of HSPCs and/or ineffective haematopoiesis. Although the inciting autoantigens remain elusive, autoantibodies are often detected in the serum. In addition, recent studies provide genetic and molecular evidence that intrinsic and/or secondary deficits in HSPCs and bone marrow mesenchymal stem cells may underlie the development of bone marrow failure.

The diagnosis and treatment of aplastic anemia: a review

Aplastic anemia is a rare disorder characterized by suppression of bone marrow function resulting in progressive pancytopenia. A trigger-related abnormal T cell response facilitated by some genetic predisposition has been postulated as the pathogenetic mechanism leading to the overproduction of bone marrow-inhibiting cytokines. Immuno-mediated pathogenesis is confirmed by the response to immunosuppressive treatment (IST) (cyclosporin A+ATG), which represents the first-choice therapy for patients <40 years when a matched sibling donor (MSD) is not available for transplant. MSD hematopoietic stem cell transplantation (HSCT) is associated with cure in ~90 % of patients. IST up-front provides an overall survival (OS) rate of above 90 %, but a response rate of about 60 %. Front-line matched unrelated donor (MUD) appears to be a viable option in children with similar OS and event-free survival to that in MSD HSCT. MUD HSCT post-IST failure proved to be a very good rescue strategy. Haploidentical donors/cord blood transplants or alternative immunosuppressive therapies, such as alemtuzumab, may represent valid tools for resistant/relapsing cases. New promising strategies, such as eltrombopag, are now under investigation. Patients should be offered an accurate diagnostic work-up in order to rule out other underlying disorders, primarily constitutional marrow failures, which may require different approaches.

Characterization of bone marrow mesenchymal stromal cells in aplastic anaemia

In aplastic anaemia (AA), haemopoietic activity is significantly reduced and generally attributed to failure of haemopoietic stem cells (HSC) within the bone marrow (BM). The regulation of haemopoiesis depends on the interaction between HSC and various cells of the BM microenvironment, including mesenchymal stromal cells (MSC). MSC involvement in the functional restriction of HSC in AA is largely unknown and therefore, the physical and functional properties of AA MSC were studied in vitro. MSC were characterized by their phenotype and ability to form adherent stromal layers. The functional properties of AA MSC were assessed through proliferative, clonogenic and cross-over culture assays. Results indicate that although AA MSC presented typical morphology and distinctive mesenchymal markers, stromal formation was reduced, with 50% of BM samples failing to produce adherent layers. Furthermore, their proliferative and clonogenic capacity was markedly decreased (P = 0·03 and P = 0·04 respectively) and the ability to sustain haemopoiesis was significantly reduced, as assessed by total cell proliferation (P = 0·032 and P = 0·019 at Week 5 and 6, respectively) and clonogenic potential of HSC (P = 0·02 at Week 6). It was concluded that the biological characteristics of AA MSC are different from those of control MSC and their in vitro haemopoiesis-supporting ability is significantly reduced.

Influence of photoactivated tetra sulphonatophenyl porphyrin and TiO2nanowhiskers on rheumatoid arthritis infected bone marrow stem cell proliferation in vitro and oxidative stress biomarkers in vivo

Besides the lethal effects of photodynamic therapy on neoplasms, herein we report photoactivated TSPP–TiO₂nanocomposites' growth promoting effect on rheumatoid arthritis BMS cells.

Interferon-gamma modification of mesenchymal stem cells: implications of autologous and allogeneic mesenchymal stem cell therapy in allotransplantation

Bone marrow-derived mesenchymal stem cells (MSC) have unique immunomodulatory and reparative properties beneficial for allotransplantation cellular therapy. The clinical administration of autologous or allogeneic MSC with immunosuppressive drugs is able to prevent and treat allograft rejection in kidney transplant recipients, thus supporting the immunomodulatory role of MSC. Interferon-gamma (IFN-γ) is known to enhance the immunosuppressive properties of MSC. IFN-γ preactivated MSC (MSC-γ) directly or indirectly modulates T cell responses by enhancing or inducing MSC inhibitory factors. These factors are known to downregulate T cell activation, enhance T cell negative signalling, alter T cells from a proinflammatory to an anti-inflammatory phenotype, interact with antigen-presenting cells and increase or induce regulatory cells. Highly immunosuppressive MSC-γ with increased migratory and reparative capacities may aid tissue repair, prolong allograft survival and induce allotransplant tolerance in experimental models. Nevertheless, there are contradictory in vivo observations related to allogeneic MSC-γ therapy. Many studies report that allogeneic MSC are immunogenic due to their inherent expression of major histocompatibility (MHC) molecules. Enhanced expression of MHC in allogeneic MSC-γ may increase their immunogenicity and this can negatively impact allograft survival. Therefore, strategies to reduce MSC-γ immunogenicity would facilitate "off-the-shelf" MSC therapy to efficiently inhibit alloimmune rejection and promote tissue repair in allotransplantation. In this review, we examine the potential benefits of MSC therapy in the context of allotransplantation. We also discuss the use of autologous and allogeneic MSC and the issues associated with their immunogenicity in vivo, with particular focus on the use of enhanced MSC-γ cellular therapy.

Downregulated CXCL12 expression in mesenchymal stem cells associated with severe aplastic anemia in children

The mechanisms of idiopathic severe aplastic anemia (SAA) in children are not completely understood. Insufficiency of the bone marrow microenvironment, in which mesenchymal stem cells (MSCs) are an important element, can be a potential factor associated with hematopoietic impairment. In the current study, we studied whether aberrant gene expression could be found in MSCs from children with SAA. Using microarray analysis, two different patterns of global gene expression were detected in the SAA MSCs. Fourteen genes (POLE2, HGF, KIF20A, TK1, IL18R1, KITLG, FGF18, RRM2, TTK, CXCL12, DLG7, TOP2A, NUF2, and TYMS), which are related to DNA synthesis, cytokines, or growth factors, were significantly downregulated. Further, knockdown of gene expression was performed using the small hairpin RNA (shRNA)-containing lentivirus method. We found that knockdown of CXCL12, HGF, IL-18R1, FGF18, or RRM2 expression compelled MSCs from the controls to behave like those from the SAA children, with decreased survival and differentiation potential. Among them, inhibition of CXCL12 gene expression had the most profound effects on the behavior of MSCs. Further experiments regarding re-introduction of the CXCL12 gene could largely recover the survival and differentiation potential in MSCs with inhibition of CXCL12 expression. Our findings suggest that MSCs from children with SAA exhibit aberrant gene expression profiles and downregulation of CXCL12 gene may be associated with alterations in the bone marrow microenvironment.

Enhanced adipogenicity of bone marrow mesenchymal stem cells in aplastic anemia

Fatty bone marrow (BM) and defective hematopoiesis are a pathologic hallmark of aplastic anemia (AA). We have investigated adipogenic and osteogenic potential of BM mesenchymal stem cells (BM-MSC) in 10 AA patients (08 males and 02 females) with median age of 37 years (range: 06 to 79 years) and in the same number of age and sex matched controls. It was observed that BM-MSC of AA patients had a morphology, phenotype, and osteogenic differentiation potential similar to control subjects but adipocytes differentiated from AA BM-MSC had a higher density and larger size of lipid droplets and they expressed significantly higher levels of adiponectin and FABP4 genes and proteins as compared to control BM-MSC (P < 0.01 for both). Thus our data shows that AA BM-MSC have enhanced adipogenicity, which may have an important implication in the pathogenesis of the disease.

Low expression of basic fibroblastic growth factor in mesenchymal stem cells and bone marrow of children with aplastic anemia

BACKGROUND

Our previous experiments with gene chip suggested that basic fibroblastic growth factor (FGF2) levels were lower in mesenchymal stem cell (MSC) from aplastic anemia patients. The purpose of this study was to determine the expression of FGF2 in MSC and in bone marrow of children with aplastic anemia to better understand the role of low FGF2 expression in the pathogenesis of aplastic anemia.

PROCEDURE

MSCs from the bone marrow of aplastic anemia children and control group were cultured in vitro. Growth curves of primary and passage MSC were plotted. FGF2 gene expression in MSCs was detected using quantitative real-time polymerase chain reaction (RT-PCR). FGF2 protein expression in mononuclear cells and FGF2 protein level in extracellular fluid of bone marrow were also investigated.

RESULT

Decreased growth of MSCs from aplastic anemia children was observed after passage 8 in serial subcultivation, and FGF2 gene expression was downregulated. Within the patients' bone marrow, low FGF2 expression was validated both in mononuclear cells and in the extracellular fluid.

CONCLUSION

Low FGF2 gene expression in MSCs and low FGF2 protein level in bone marrow of aplastic anemia may involve to pathogenesis of aplastic anemia.

Mesenchymal stem cells from pediatric patients with aplastic anemia: isolation, characterization, adipogenic, and osteogenic differentiation

Aplastic anemia is a syndrome of bone marrow (BM) failure characterized by peripheral pancytopenia and marrow hypoplasia. Its exact pathophysiology is still not clear. Mesenchymal stem cells (MSCs) play an important role in providing the specialized BM microenvironment for hematopoietic stem cells survival and differentiation. MSCs were isolated from BM of five patients with aplastic anemia and five controls. MSCs were characterized by morphology and immunophenotyping. Their viability, proliferative capacity, and adipogenic as well as osteogenic differentiation potentials were assessed. MSCs from aplastic anemia patients and controls shared similar spindle-shaped morphology and surface marker expression. MSCs derived from patients with aplastic anemia showed lower viability (74.2 ± 4.44% vs. 97.0 ± 1.58, p < 0.0001) and slower expansion rate as indicated by smaller population doubling and smaller cumulative population doubling from passages 1 to 4 (0.70 ± 0.22 vs. 2.34 ± 0.84; p = 0.009). Besides, aplastic anemia MSCs had poor capacity to differentiate into adipocytic and osteocytic lineages.

Efficacy and safety of mesenchymal stromal cell treatment from related donors for patients with refractory aplastic anemia

BACKGROUND AIMS

This study evaluated the feasibility, safety and immunological effects of the intravenous administration of mesenchymal stromal cells (MSCs) from a related donor in patients with refractory aplastic anemia (AA).

METHODS

A mean of 6 × 10(5)/kg (range, 5.0-7.1 × 10(5)) MSCs were injected intravenously to 18 patients, including 14 patients with nonsevere AA and four patients with severe AA who were refractory to prior immunosuppressive treatment. The outcomes of patients treated with MSCs were evaluated and compared with a historic control cohort, including 18 patients with refractory AA.

RESULTS

Two patients had injection-related adverse events, including transient fever and headache. No major adverse events were reported during the follow-up period. An immunological analysis revealed an increased proportion of CD4(+)CD25(+) FOXP3(+)regulatory T cells in peripheral mononuclear cells. Following up for 1 year, six of 18 patients (33.3%) achieved a complete response or a partial response to MSC treatment. In six patients, two achieved a complete response including a recovery of three hematopoietic cell lines after MSCs therapy at days 88 and 92, two patients achieved only a red cell recovery with hemoglobin levels >100 g/L at days 30 and 48 and two patients had only a platelet recovery with a platelet count of >60 × 10(9)/L at days 54 and 81. In the control cohort, only one patient (5.56%) achieved a partial response during the follow-up period.

CONCLUSIONS

The data from the present study suggest that treatment with MSCs from a related donor may be a promising therapeutic strategy for patients with refractory AA. The trial has been registered at ClinicalTrials.gov: identifier NCT01305694.

Mesenchymal stem cells in immune-mediated bone marrow failure syndromes

Immune-mediated bone marrow failure syndromes (BMFS) are characterized by ineffective marrow haemopoiesis and subsequent peripheral cytopenias. Ineffective haemopoiesis is the result of a complex marrow deregulation including genetic, epigenetic, and immune-mediated alterations in haemopoietic stem/progenitor cells, as well as abnormal haemopoietic-to-stromal cell interactions, with abnormal release of haemopoietic growth factors, chemokines, and inhibitors. Mesenchymal stem/stromal cells (MSCs) and their progeny (i.e., osteoblasts, adipocytes, and reticular cells) are considered as key cellular components of the bone marrow haemopoietic niche. MSCs may interfere with haemopoietic as well as immune regulation. Evidence suggests that bone marrow MSCs may be involved in immune-mediated BMFS underlying pathophysiology, harboring either native abnormalities and/or secondary defects, caused by exposure to activated marrow components. This review summarizes previous as well as more recent information related to the biologic/functional characteristics of bone marrow MSCs in myelodysplastic syndromes, acquired aplastic anemia, and chronic idiopathic neutropenia.

Mesenchymal stem cell transplantation in multiple sclerosis

Mesenchymal stem cells (MSCs) are pluripotent non-hematopoietic precursor cells that can be isolated from bone marrow and numerous other tissues, culture-expanded to purity, and induced to differentiate in vitro and in vivo into mesodermal derivatives. MSCs exhibit many phenotypic and functional similarities to pericytes. The immunomodulatory, tissue protective, and repair-promoting properties of MSCs demonstrated both in vitro and in animal models make them an attractive potential therapy for MS and other conditions characterized by inflammation and/or tissue injury. Other potential advantages of MSCs as a therapeutic include the relative ease of culture expansion, relative immunoprivilege allowing allogeneic transplantation, and their ability to traffic from blood to areas of tissue allowing intravascular administration. The overall published experience with MSC transplantation in MS is modest, but several small case series and preliminary studies yielded promising results. Several groups, including us, recently initiated formal studies of autologous, culture-expanded, bone marrow-derived MSC transplantation in MS. Although there are several potential safety concerns, to date, the procedure has been well tolerated. Future studies that more definitively assess efficacy also will need to address several technical issues.

Evidence for high translational potential of mesenchymal stromal cell therapy to improve recovery from ischemic stroke

Although ischemic stroke is a major cause of morbidity and mortality, current therapies benefit only a small proportion of patients. Transplantation of mesenchymal stromal cells (MSC, also known as mesenchymal stem cells or multipotent stromal cells) has attracted attention as a regenerative therapy for numerous diseases, including stroke. Mesenchymal stromal cells may aid in reducing the long-term impact of stroke via multiple mechanisms that include induction of angiogenesis, promotion of neurogenesis, prevention of apoptosis, and immunomodulation. In this review, we discuss the clinical rationale of MSC for stroke therapy in the context of their emerging utility in other diseases, and their recent clinical approval for treatment of graft-versus-host disease. An analysis of preclinical studies examining the effects of MSC therapy after ischemic stroke indicates near-universal agreement that MSC have significant favorable effect on stroke recovery, across a range of doses and treatment time windows. These results are interpreted in the context of completed and ongoing human clinical trials, which provide support for MSC as a safe and potentially efficacious therapy for stroke recovery in humans. Finally, we consider principles of brain repair and manufacturing considerations that will be useful for effective translation of MSC from the bench to the bedside for stroke recovery.

Cell therapy with autologous mesenchymal stem cells-how the disease process impacts clinical considerations

The prospective clinical use of multipotent mesenchymal stromal cells (MSCs) holds enormous promise for the treatment of a large number of degenerative and age-related diseases. In particular, autologous MSCs isolated from bone marrow (BM) are considered safe and have been extensively evaluated in clinical trials. Nevertheless, different efficacies have been reported, depending on the health status and age of the donor. In addition, the biological functions of BM-MSCs from patients with various diseases may be impaired. Furthermore, medical treatments such as long-term chemotherapy and immunomodulatory therapy may damage the BM microenvironment and affect the therapeutic potential of MSCs. Therefore, a number of practical problems must be addressed before autologous BM-MSCs can be widely applied with higher efficiency in patients. As such, this review focuses on various factors that directly influence the biological properties of BM-MSCs, and we discuss the possible mechanisms of these alterations.

Effect of kidney-reinforcing, blood-activating and stasis-removing recipes on adhesion molecule expression of bone marrow mesenchymal stem cells from chronic aplastic anemia patients

OBJECTIVE

To explore the effect of kidney-reinforcing, blood-activating and stasis-removing recipes on adhesion molecule expression of bone marrow mesenchymal stem cells (MSCs) from patients with chronic aplastic anemia (CAA).

METHODS

We used three Traditional Chinese Medicine recipes, namely a kidney-reinforcing recipe (KRR), blood-activating and stasis-removing recipe (BASRR), and kidney-reinforcing, blood-activating and stasis-removing recipe (KRBASRR), and a normal saline control to prepare herbal medicine serum in Sprague Dawley rats. Thirty CAA patients were enrolled in the experimental group, including 17 kidney-Yang deficient patients and 13 kidney-Yin deficient patients. Ten healthy individuals were included in the control group. MSCs were isolated from bone marrow samples, and the cell density was observed to measure their proliferation ability by microscopy on days 2, 7, and 14 after isolation. In addition, the expression of adhesion molecules of bone marrow MSCs (CD106, CD49d, CD31 and CD44) were detected by flow cytometry after 48 h of treatment with the four different herbal medicine serums.

RESULTS

The proliferation of MSCs from kidney-Yang deficient and kidney-Yin deficient patients was weaker than that of MSCs from the control group. The expression of all adhesion molecules of bone marrow MSCs from CAA patients was obviously lower than that in the control group (P < 0.01). The expression of CD49d and CD31 in MSCs from patients with a kidney-Yin deficiency was lower than in those with a kidney-yang deficiency (P < 0.05 and P < 0.01, respectively). For kidney-Yang deficient patients, CD31 expression in the KRBASRR group was significantly higher than that in the BASRR group (P < 0.01), while CD44 in the KRBASRR group was significantly higher than that in both KRR and BASRR groups (P < 0.01). For kidney-Yin deficient patients, CD106 and CD49d expression in the KRBASRR group was obviously higher than that in the KRR group (P < 0.05), while CD31 and CD44 expression in the KRBASRR group was significantly higher than that in both KRR and BASRR groups (P < 0.05 and P < 0.01, respectively).

CONCLUSION

The bone marrow microenvironment in CAA patients is abnormal. The effect of KRBASRR may be better than that of KRR and BASRR for kidney-Yang deficient and kidney-Yin deficient patients by improving the expression levels of MSC adhesion molecules.

Differential gene expression profile associated with the abnormality of bone marrow mesenchymal stem cells in aplastic anemia

Aplastic anemia (AA) is generally considered as an immune-mediated bone marrow failure syndrome with defective hematopoietic stem cells (HSCs) and marrow microenvironment. Previous studies have demonstrated the defective HSCs and aberrant T cellular-immunity in AA using a microarray approach. However, little is known about the overall specialty of bone marrow mesenchymal stem cells (BM-MSCs). In the present study, we comprehensively compared the biological features and gene expression profile of BM-MSCs between AA patients and healthy volunteers. In comparison with healthy controls, BM-MSCs from AA patients showed aberrant morphology, decreased proliferation and clonogenic potential and increased apoptosis. BM-MSCs from AA patients were susceptible to be induced to differentiate into adipocytes but more difficult to differentiate into osteoblasts. Consistent with abnormal biological features, a large number of genes implicated in cell cycle, cell division, proliferation, chemotaxis and hematopoietic cell lineage showed markedly decreased expression in BM-MSCs from AA patients. Conversely, more related genes with apoptosis, adipogenesis and immune response showed increased expression in BM-MSCs from AA patients. The gene expression profile of BM-MSCs further confirmed the abnormal biological properties and provided significant evidence for the possible mechanism of the destruction of the bone marrow microenvironment in AA.

The role of mesenchymal stem cells in hematopoietic stem cell transplantation: from bench to bedsides

Mesenchymal stem cells (MSCs) have been shown to be effective in the management of graft-versus-host disease (GVHD) due to their immunomodulatory effects. In addition to prevention and treatment of GVHD, many studies have demonstrated that MSCs can promote hematopoietic engraftment, accelerate lymphocyte recovery, reduce the risk of graft failure, and repair tissue damage in patients receiving hematopoietic stem cell transplantation (HSCT). Bone marrow (BM) has been considered as the traditional source of MSCs, and most of the knowledge concerning MSCs comes from BM studies. However, BM-derived MSCs have several limitations for their clinical application. Fetal-type MSCs can be isolated easier and proliferate faster in vitro as well as possessing a lower immunogenicity. Therefore, fetal-type MSCs, such as umbilical cord-derived MSCs, represent an excellent alternative source of MSCs. MSCs play multiple important roles in HSCT. Nevertheless, several issues regarding their clinical application remain to be discussed, including the safety of use in humans, the available sources and the convenience of obtaining MSCs, the quality control of in vitro-cultured MSCs and the appropriate cell passages, the optimum cell dose, and the optimum number of infusions. Furthermore, it is important to evaluate whether the rates of cancer relapse and infections increase when using MSCs for GVHD. There are still many questions regarding the clinical application of MSCs to HSCT that need to be answered, and further studies are warranted.

Umbilical cord-derived mesenchymal stem cells for hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is becoming an effective therapeutic modality for a variety of diseases. Mesenchymal stem cells (MSCs) can be used to enhance hematopoietic engraftment, accelerate lymphocyte recovery, reduce the risk of graft failure, prevent and treat graft-versus-host disease, and repair tissue damage in patients receiving HSCT. Till now, most MSCs for human clinical application have been derived from bone marrow. However, acquiring bone-marrow-derived MSCs involves an invasive procedure. Umbilical cord is rich with MSCs. Compared to bone-marrow-derived MSCs, umbilical cord-derived MSCs (UCMSCs) are easier to obtain without harm to the donor and can proliferate faster. No severe adverse effects were noted in our previous clinical application of UCMSCs in HSCT. Accordingly, application of UCMSCs in humans appears to be feasible and safe. Further studies are warranted.

Expression of IL-27, Th1 and Th17 in patients with aplastic anemia

BACKGROUND

Aplastic anemia (AA) is an autoimmune disease and interleukin-27 (IL-27) is an important cytokine involved in the pathogenesis of autoimmune diseases. To date there have been no reports concerning the intrinsic association among IL-27 and Thelper (Th) 1 and Th17 cells in AA.

MATERIALS AND METHODS

Enzyme-linked immunosorbent assay (ELISA) to assay IL-27, interferon gamma (IFN-γ) and IL-17 levels, flow cytometry to measure the percentages of Th1 and Th17 cells among peripheral blood mononuclear cells (PBMCs), real-time reverse transcriptase polymerase chain reaction (PCR) for the mRNA levels of IL-27, IFN-γ, T-bet and IL-17 and retinoid related orphan receptor gamma (RORγt) in PBMCs were performed. In addition, the effect of exogenous rhIL-27 on the differentiation of T cells into Th1 and Th17 cells was investigated in vitro.

RESULTS

Plasma and mRNA levels of IL-27 in PBMCs from AA patients were significantly higher than those in healthy controls. A positive correlation was found between plasma levels of IL27 and IFN-γ. The proportions of Th1 and Th17 cells accompanied by the mRNA expression of RORγt and T-bet were significantly higher in AA patients than in healthy controls. Plasma levels of IL-27 correlated positively with frequencies of Th1 cells in AA patients. Exogenous rhIL-27 could significantly upregulate the frequency of Th1 cells and the mRNA levels of T-bet and IFN-γ and the application of rhIL-27 in vitro could inhibit the expression of RORγt mRNA.

CONCLUSION

The upregulation of IL-27 might cause Th1 differentiation and immune disorders in AA patients. Blocking the expression of IL-27 could therefore be a reasonable therapeutic strategy for AA.

The different immunoregulatory functions of mesenchymal stem cells in patients with low-risk or high-risk myelodysplastic syndromes

Myelodysplastic syndrome (MDS) are a group of progressive, clonal, neoplastic bone marrow disorders characterized by hematopoietic stem cell dysregulation and abnormalities in the immune system. Mesenchymal stem cells (MSC) have gained further interests after the demonstration of an immunoregulatory role. Nevertheless, the immunoregulatory function of MDS bone marrow derived MSC (MDS-MSC) remains poorly defined. In addition, it is not clear whether there are differences in the regulatory functions between low-risk and high-risk MDS-MSC. In this study, we obtain and expand MSC from bone marrow of patients with MDS. Our results show that there are significant differences in the immunoregulatory functions between low-risk and high-risk MDS-MSC. Compare to low-risk MDS-MSC, high-risk MDS-MSC is associated with the presence of increased TGF-β1, higher apoptosis, higher immunosuppressive rate and a poor ability of hematopoietic support. In addition, our results find that there are great differences in the CD4+CD25+Foxp3+Tregs inducible rate between high-risk MDS-MSC and low-risk MDS-MSC. Compared to high-risk MDS-MSC, the inducible rate of CD4+CD25+Foxp3+Tregs of low-risk MDS-MSC is lower. At last, we find that MDS-MSC derived TGF-β1 is largely responsible for the increase in CD4+CD25+Foxp3+Tregs based on knockdown studies. These results elucidate the different immunoregulatory role of MSC in low-risk and high-risk MDS, which may be important for understand the pathogenesis of MDS and the development of novel immunomodulatory strategies for the treatment of MDS.

Impaired immunomodulatory ability of bone marrow mesenchymal stem cells on CD4(+) T cells in aplastic anemia

Aplastic anemia (AA) is a marrow failure syndrome mediated by aberrant T-cell subsets. Mesenchymal stem cells (MSCs) play an important role in maintaining immune homeostasis through modulating a variety of immune cells. However, little is known about the immunomodulation potential of bone marrow MSCs (BM-MSCs) in AA. Here, we reported that BM-MSCs from AA patients were reduced in suppressing the proliferation and clonogenic potential of CD4(+) T cells and the production of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), which was associated with decreased prostaglandin E2 (PGE2). Meanwhile, BM-MSCs from AA patients were defective to promote CD4(+)CD25(+)FOXP3(+) regulatory T cells expansion through reduced transforming growth factor-β (TGF-β). No significant difference between AA and normal BM-MSCs was observed in affecting the production of interleukins (IL)-4, IL-10 and IL-17. Our data indicate that BM-MSCs were impaired in maintaining the immune homeostasis associated with CD4(+) T cells, which might aggravate the marrow failure in AA.