Melatonin protects bone marrow mesenchymal stem cells against iron overload‐induced aberrant differentiation and senescence

Bone marrow mesenchymal stem cells (BMSCs) are an expandable population of stem cells which can differentiate into osteoblasts, chondrocytes and adipocytes. Dysfunction of BMSCs in response to pathological stimuli contributes to bone diseases. Melatonin, a hormone secreted from pineal gland, has been proved to be an important mediator in bone formation and mineralization. The aim of this study was to investigate whether melatonin protected against iron overload‐induced dysfunction of BMSCs and its underlying mechanisms. Here, we found that iron overload induced by ferric ammonium citrate (FAC) caused irregularly morphological changes and markedly reduced the viability in BMSCs. Consistently, osteogenic differentiation of BMSCs was significantly inhibited by iron overload, but melatonin treatment rescued osteogenic differentiation of BMSCs. Furthermore, exposure to FAC led to the senescence in BMSCs, which was attenuated by melatonin as well. Meanwhile, melatonin was able to counter the reduction in cell proliferation by iron overload in BMSCs. In addition, protective effects of melatonin on iron overload‐induced dysfunction of BMSCs were abolished by its inhibitor luzindole. Also, melatonin protected BMSCs against iron overload‐induced ROS accumulation and membrane potential depolarization. Further study uncovered that melatonin inhibited the upregulation of p53, ERK and p38 protein expressions in BMSCs with iron overload. Collectively, melatonin plays a protective role in iron overload‐induced osteogenic differentiation dysfunction and senescence through blocking ROS accumulation and p53/ERK/p38 activation.     

Expression of the melanoma cell adhesion molecule in human mesenchymal stromal cells regulates proliferation,differentiation, and maintenance of hematopoietic stem and progenitor cells

The melanoma cell adhesion molecule defines mesenchymal stromal cells in the human bone marrow that regenerate bone and establish a hematopoietic microenvironment in vivo. The role of the melanoma cell adhesion molecule in primary human mesenchymal stromal cells and the maintenance of hematopoietic stem and progenitor cells during ex vivo culture has not yet been demonstrated. We applied RNA interference or ectopic overexpression of the melanoma cell adhesion molecule in human mesenchymal stromal cells to evaluate the effect of the melanoma cell adhesion molecule on their proliferation and differentiation as well as its influence on co-cultivated hematopoietic stem and progenitor cells. Knockdown and overexpression of the melanoma cell adhesion molecule affected several characteristics of human mesenchymal stromal cells related to osteogenic differentiation, proliferation, and migration. Furthermore, knockdown of the melanoma cell adhesion molecule in human mesenchymal stromal cells stimulated the proliferation of hematopoietic stem and progenitor cells, and strongly reduced the formation of long-term culture-initiating cells. In contrast, melanoma cell adhesion molecule-overexpressing human mesenchymal stromal cells provided a supportive microenvironment for hematopoietic stem and progenitor cells. Expression of the melanoma cell adhesion molecule increased the adhesion of hematopoietic stem and progenitor cells to human mesenchymal stromal cells and their migration beneath the monolayer of human mesenchymal stromal cells. Our results demonstrate that the expression of the melanoma cell adhesion molecule in human mesenchymal stromal cells determines their fate and regulates the maintenance of hematopoietic stem and progenitor cells through direct cell-cell contact.     

基质细胞衍生因子1对骨髓间充质干细胞的趋化作用

骨髓干细胞主要由造血干细胞和间充质干细胞组成,其中骨髓间充质干细胞除具有自我更新和多向分化的潜能外,更具有很强的可塑性,在一定的诱导条件下能向多细胞分化,且其相对容易获得,成为近年来研究的热点.许多体内外试验证实,细胞因子可以影响移植细胞的微环境,进而影响骨髓干细胞的动员、迁移及分化.基质细胞衍生因子1是一类对免疫细胞有趋化作用的小分子蛋白,属于CXC趋化因子之一,具有广泛的生物学活性,对骨髓干细胞亦有趋化作用,现就SDF-1对骨髓间充质干细胞的趋化作用作一综述.     

Upregulation of AKR1C1 in mesenchymal stromal cells promotes the survival of acute myeloid leukaemia cells

The leukaemic bone marrow microenvironment, comprising abnormal mesenchymal stromal cells (MSCs), is responsible for the poor prognosis of acute myeloid leukaemia (AML). Therefore, it is essential to determine the mechanisms underlying the supportive role of MSCs in the survival of leukaemia cells. Through in silico analyses, we identified a total of 271 aberrantly expressed genes in the MSCs derived from acute myeloid leukemia (AML) patients that were associated with adipogenic differentiation, of which aldo-keto reductase 1C1 (AKR1C1) was significantly upregulated in the AML-MSCs. Knockdown of AKR1C1 in the MSCs suppressed adipogenesis and promoted osteogenesis, and inhibited the growth of co-cultured AML cell lines compared to the situation in wild- type AML-derived MSCs. Introduction of recombinant human AKR1C1 in the MSCs partially alleviated the effects of AKR1C1 knockdown. In addition, the absence of AKR1C1 reduced secretion of cytokines such as MCP-1, IL-6 and G-CSF from the MSCs, along with inactivation of STAT3 and ERK1/2 in the co-cultured AML cells. AKR1C1 is an essential factor driving the adipogenic differentiation of leukaemic MSCs and mediates its pro-survival effects on AML cells by promoting cytokine secretion and activating the downstream pathways in the AML cells.     

再生障碍性贫血患者骨髓间充质干细胞成脂和成骨分化能力的变化

目的 通过观察再生障碍性贫血(再障)患者间充质干细胞(MSCs)成脂肪和成骨能力的变化,研究骨髓MSCs成脂分化的异常在再障患者红髓脂肪化中的作用.方法 分离培养再障患者及正常人的骨髓,观察其一般生物学特性,并在体外诱导其向脂肪、成骨细胞分化,同时用RT-PCR方法检测成脂肪、成骨特异基因的表达时间,比较再障患者和正常对照MSCs向脂肪细胞、成骨分化能力的不同.结果 原代培养7 d,再障组贴壁细胞克隆形成率为(19.30±4.77)/(5×105 MNCs),较正常对照组明显降低(47.72±3.46)/(5×105 MSCs)(P＜0.05).在培养初期,再障组MSCs与正常对照MSCs增殖能力相似,但在连续传8代后,其增殖能力降低.再障组MSCs体外诱导成脂滴早,诱导分化的脂肪细胞leptin(瘦素)基因表达早.再障组MSCs体外诱导成骨形成钙化结节少,碱性磷酸酶活性低,诱导的成骨细胞osteocalcin(骨钙素)基因表达晚.结论 再障患者MSCs成脂分化能力增强而成骨分化能力降低,可能在再障的病程中起一定作用.     

Chromosomal aberrations in bone marrow mesenchymal stroma cells from patients with myelodysplastic syndrome and acute myeloblastic leukemia

OBJECTIVE: Bone marrow mesenchymal stroma cells (BMSC) are key components of the hematopoietic microenvironment. The question of whether BMSC from patients with hematological disorders have cytogenetic abnormalities is discussed controversially, some studies indicating that they are cytogenetically normal and others providing evidence of their aberrations. PATIENTS AND METHODS: We performed standard and molecular cytogenetic analyses of both hematopoietic cells and BMSC from 31 patients with myelodysplastic syndrome (MDS, n = 18) and acute myeloid leukemia (AML, n = 13) and 7 healthy individuals. Mononuclear cells were isolated from fresh bone marrow aspirates at the time of initial diagnosis for cytogenetic analysis of hematopoietic cells (HC) and selection of BMSC. RESULTS: Clonal cytogenetic aberrations were observed in HC from 8 (44%) MDS and 8 (61%) AML patients. Cytogenetic analyses of BMSC were successfully performed in 27 of the 31 cases. Structural chromosomal aberrations, including t(1;7), t(4;7), t(7;9), t(7;10), t(7;19), t(15;17), and others, were detectable in BMSC from 7 of 16 (44%) MDS and 6 of 11 (54%) AML patients. The breakpoints of chromosomes in BMSC were typical for leukemia aberrations. Two patients showed clonal chromosomal markers. CONCLUSIONS: BMSC from MDS and AML patients show chromosomal abnormalities. Although the majority of cytogenetic aberrations in BMSC were not clonal and differed from chromosomal markers in HC from the same individual, detection of typical chromosomal changes in BMSC suggests enhanced genetic susceptibility of these cells in MDS/AML. This may indicate potential involvement of BMSC in the pathophysiology of MDS/AML.     

微小RNA-1慢病毒载体介导大鼠骨髓间充质干细胞分化为心肌样细胞的研究

目的通过微小RNA-1(microRNA-1,miR-1)慢病毒载体转染大鼠骨髓间充质干细胞(MSC),探讨miR-1对MSC向心肌细胞分化的影响。方法采用全骨髓贴壁培养法分离培养大鼠MSC并进行流式细胞学鉴定;构建表达miR-1慢病毒载体;将miR-1慢病毒载体转染大鼠MSC(MSCmiR-1)连续培养15d,光镜下观察转染后细胞形态,分别于0、4、6、15dqRT-PCR检测miR-1、心肌相关基因锌指结构蛋白(GATA-4)、肌钙蛋白I(cTnI)、α肌动蛋白(α-actin)的表达;免疫荧光观察cTnI的表达;Western blot检测α-actin的表达。结果原代大鼠MSC呈长梭形、漩涡状生长,流式细胞学检测显示,98%以上细胞表达CD44和CD29,不足1%细胞表达CD45;成功构建miR-1重组慢病毒载体,病毒滴度为3×108 TU/μl;转导miR-1后,MSCmiR-1高表达心肌特异性相关基因GATA-4、α-actin、cTnI,并随时间逐渐增强,转染4d免疫荧光检测可见cTnI在部分MSCmiR-1中表达,于15d时表达最强,Westernblot进一步证实了α-actin在MSCmiR-1中表达。结论转导miR-1至大鼠MSC中可促使其向心肌样细胞的分化。     

Hepatic differentiation capability of rat bone marrow-derived mesenchymal stem cells and hematopoietic stem cells

AIM: To investigate the different effects of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) on hepatic differentiation. METHODS: MSCs from rat bone marrow were isolated and cultured by standard methods. HSCs from rat bone marrow were isolated and purified by magnetic activated cell sorting. Both cell subsets were induced. Morphology, RT-PCR and immunocytochemistry were used to identify the hepatic differentiation grade. RESULTS: MSCs exhibited round in shape after differentiation, instead of fibroblast-like morphology before differentiation. Albumin mRNA and protein were expressed positively in MSCs, without detection of alpha-fetoprotein (AFP). HSCs were polygonal in shape after differentiation. The expression of albumin signal decreased and AFP signal increased. The expression of CK18 was continuous in MSCs and HSCs both before and after induction. CONCLUSION: Both MSCs and HSCs have hepatic differentiation capabilities. However, their capabilities are not the same. MSCs can differentiate into mature hepatocyte-like cells, never expressing early hepatic specific genes, while Thy-1.1(+) cells are inclined to differentiate into hepatic stem cell-like cells, with an increasing AFP expression and a decreasing albumin signal. CK18 mRNA is positive in Thy-1.1(+) cells and MSCs, negative in Thy-1.1(-) cells. It seems that CK18 has some relationship with Thy-1.1 antigen, and CK18 may be a predictive marker of hepatic differentiation capability.     

Down-regulation of FoxM1 inhibits viability and invasion of gallbladder carcinoma cells,partially dependent on inducement of cellular senescence

AIM: To investigate the effect of knockdown of Forkhead box M1 (FoxM1) on the proliferation and invasion capacities of human gallbladder carcinoma (GBC)-SD cells.METHODS: Four FoxM1 shRNAs were transfected into GBC-SD cells with Lipofectamine 2000 to select the appropriate shRNA for down-regulation of FoxM1. A recombinant lentivirus for shFoxM1 (Lv-shFoxM1), which expresses FoxM1-specific shRNA, and a negative control carrying green fluorescent protein, which expresses a scrambled RNA, were constructed. After transfection with the recombinant adenovirus and screened with puromycin, RT-PCR and Western blot were utilized to evaluate the inhibition efficiency. Cell viability was evaluated by MTT assay, and cell migration and invasion were assessed using the Transwell system. Cells were suspended in serum-free medium and seeded into Transwell inserts either uncoated (for migration assay) or coated (for invasion assay) with growth factor-reduced Matrigel. To verify the involvement of FoxM1 in the senescence of tumor cells, staining of senescence β-galactosidase (SA β-gal), the widely used biomarker of cellular senescence, was also performed.RESULTS: After successful transfection of four FoxM1 small interfering RNAs (shRNAs) with Lipofectamine 2000, the shF1822 was selected as the most appropriate shRNA according to its obvious inhibitory effect. The recombinant adenovirus was then constructed with the shF1822 and successfully transfected into the GBC-SD cells, resulting in the significant inhibition of FoxM1 expression at both the mRNA and protein levels, compared with the negative control (P < 0.05). After transfection, down-regulation of FoxM1 significantly inhibited cell viability according to the MTT assay (P < 0.05). In addition, Transwell migration and invasion assays also suggested the suppression of invasion ability of the transfected cells. SA β-gal staining showed that down-regulation of FoxM1 could induce more senescent GBC cells (P < 0.05), suggesting the possible involvement of the senescence process of the FoxM1-deficient cells in GBC.CONCLUSION: FoxM1 is functionally involved in viability of GBC cells, partially dependent on the inducement of cellular senescence, and is a potential target for GBC therapy.     

Mesenchymal stromal cells of myelodysplastic syndrome and acute myeloid leukemia patients have distinct genetic abnormalities compared with leukemic blasts

Mesenchymal stromal cells (MSCs) are an essential cell type of the hematopoietic microenvironment. Concerns have been raised about the possibility that MSCs undergo malignant transformation. Several studies, including one from our own group, have shown the presence of cytogenetic abnormalities in MSCs from leukemia patients. The aim of the present study was to compare genetic aberrations in hematopoietic cells (HCs) and MSCs of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) patients. Cytogenetic aberrations were detected in HCs from 25 of 51 AML patients (49%) and 16 of 43 MDS patients (37%). Mutations of the FLT3 and NPM1 genes were detected in leukemic blasts in 12 (23%) and 8 (16%) AML patients, respectively. Chromosomal aberrations in MSCs were detected in 15 of 94 MDS/AML patients (16%). No chromosomal abnormalities were identified in MSCs of 36 healthy subjects. We demonstrate herein that MSCs have distinct genetic abnormalities compared with leukemic blasts. We also analyzed the main characteristics of patients with MSCs carrying chromosomal aberrations. In view of these data, the genetic alterations in MSCs may constitute a particular mechanism of leukemogenesis.     

Total body irradiation tremendously impair the proliferation,differentiation and chromosomal integrity of bone marrow-derived mesenchymal stromal stem cells

Total body irradiation (TBI) is frequently used in hematopoietic stem cell transplantation (HSCT) and is associated with many complications due to radiation injury to the normal cells, including normal stem cells. Nevertheless, the effects of TBI on the mesenchymal stromal stem cell (MSC) are not fully understood. Bone marrow-derived MSCs (BM-MSCs) isolated from normal adults were irradiated with 200 cGy twice daily for consecutive 3 days, a regimen identical to that used in TBI-conditioning HSCT. The characteristics, differentiation potential, cytogenetics, hematopoiesis-supporting function, and carcinogenicity of the irradiated BM-MSCs were then compared to the non-irradiated control. The irradiated and non-irradiated MSCs shared similar morphology, phenotype, and hematopoiesis-supporting function. However, irradiated MSCs showed much lower proliferative and differentiative potential. Irradiation also induced clonal cytogenetic abnormalities of MSCs. Nevertheless, the carcinogenicity of irradiated MSCs is low in vitro and in vivo. In parallel with the ex vivo irradiation experiments, decreased proliferative and differentiative abilities and clonal cytogenetic abnormalities can also be found in MSCs isolated from transplant recipients who had received TBI-based conditioning previously. Thus, TBI used in HSCT drastically injury MSCs and may contribute to the development of some long-term complications associated with clonal cytogenetic abnormality and poor adipogenesis and osteogenesis after TBI.     

Comprehensive characterization of mesenchymal stromal cells from patients with Fanconi anaemia

Fanconi anaemia (FA) is an inherited disorder characterized by pancytopenia, congenital malformations and a predisposition to develop malignancies. Alterations in the haematopoietic microenvironment of FA patients have been reported, but little is known regarding the components of their bone marrow (BM) stroma. We characterized mesenchymal stromal cells (MSCs) isolated from BM of 18 FA patients both before and after allogeneic haematopoietic stem cell transplantation (HSCT). Morphology, fibroblast colony‐forming unit (CFU‐F) ability, proliferative capacity, immunophenotype, differentiation potential, ability to support long‐term haematopoiesis and immunomodulatory properties of FA‐MSCs were analysed and compared with those of MSCs expanded from 15 age‐matched healthy donors (HD‐MSCs). FA‐MSCs were genetically characterized through conventional karyotyping, diepoxybutane‐test and array‐comparative genomic hybridization. FA‐MSCs generated before and after HSCT were compared. Morphology, immunophenotype, differentiation potential, ability in vitro to inhibit mitogen‐induced T‐cell proliferation and to support long‐term haematopoiesis did not differ between FA‐MSCs and HD‐MSCs. CFU‐F ability and proliferative capacity of FA‐MSCs isolated after HSCT were significantly lower than those of HD‐MSCs. FA‐MSCs reached senescence significantly earlier than HD‐MSCs and showed spontaneous chromosome fragility. Our findings indicate that FA‐MSCs are defective in their ability to survive in vitro and display spontaneous chromosome breakages; whether these defects are involved in pathophysiology of BM failure syndromes deserves further investigation.