Potentiation of biological effects of mesenchymal stem cells in ischemic conditions by melatonin via upregulation of cellular prion protein expression

Mesenchymal stem cells (MSCs) are promising candidates for stem cell‐based therapy in ischemic diseases. However, ischemic injury induces pathophysiological conditions, such as oxidative stress and inflammation, which diminish therapeutic efficacy of MSC‐based therapy by reducing survival and functionality of transplanted MSCs. To overcome this problem, we explored the effects of melatonin on the proliferation, resistance to oxidative stress, and immunomodulatory properties of MSCs. Treatment with melatonin enhanced MSC proliferation and self‐renewal via upregulation of cellular prion protein (PrP^C) expression. Melatonin diminished the extent of MSC apoptosis in oxidative stress conditions by regulating the levels of apoptosis‐associated proteins, such as BCL‐2, BAX, PARP‐1, and caspase‐3, in a PrP^C‐dependent manner. In addition, melatonin regulated the immunomodulatory effects of MSCs via the PrP^C‐IDO axis. In a murine hind‐limb ischemia model, melatonin‐stimulated MSCs improved the blood flow perfusion, limb salvage, and vessel regeneration by lowering the extent of apoptosis of affected local cells and transplanted MSCs as well as by reducing infiltration of macrophages. These melatonin‐mediated therapeutic effects were inhibited by silencing of PrP^C expression. Our findings for the first time indicate that melatonin promotes MSC functionality and enhances MSC‐mediated neovascularization in ischemic tissues through the upregulation of PrP^C expression. In conclusion, melatonin‐treated MSCs could provide a therapeutic strategy for vessel regeneration in ischemic disease, and the targeting of PrP^C levels may prove instrumental for MSC‐based therapies.     

Melatonin protects chronic kidney disease mesenchymal stem cells against senescence via PrPC‐dependent enhancement of the mitochondrial function

Although mesenchymal stem cell (MSC)‐based therapy is a treatment strategy for ischemic diseases associated with chronic kidney disease (CKD), MSCs of CKD patients undergo accelerated senescence, with decreased viability and proliferation upon uremic toxin exposure, inhibiting their utility as a potent stem cell source for transplantation therapy. We investigated the effects of melatonin administration in protecting against cell senescence and decreased viability induced by pathophysiological conditions near the engraftment site. MSCs harvested from CKD mouse models were treated with H₂O₂ to induce oxidative stress. CKD‐derived MSCs exhibited greater oxidative stress‐induced senescence than normal‐mMSCs, while melatonin protected CKD‐mMSCs from H₂O₂ and associated excessive senescence. The latter was mediated by PrP^C‐dependent mitochondrial functional enhancement; melatonin upregulated PrP^C, which bound PINK1, thus promoting mitochondrial dynamics and metabolism. In vivo, melatonin‐treated CKD‐mMSCs survived longer, with increased secretion of angiogenic cytokines in ischemic disease engraftment sites. CKD‐mMSCs are more susceptible to H₂O₂‐induced senescence than normal‐mMSCs, and melatonin administration protects CKD‐mMSCs from excessive senescence by upregulating PrP^C and enhancing mitochondrial function. Melatonin showed favorable therapeutic effects by successfully protecting CKD‐mMSCs from related ischemic conditions, thereby enhancing angiogenesis and survival. These results elucidate the mechanism underlying senescence inhibition by melatonin in stem cell‐based therapies using mouse‐derived CKD‐mMSCs.     

Bone marrow mesenchymal stromal cells non-selectively protect chronic myeloid leukemia cells from imatinib-induced apoptosis via the CXCR4/CXCL12 axis

Background

Residual chronic myeloid leukemia disease following imatinib treatment has been attributed to the presence of quiescent leukemic stem cells intrinsically resistant to imatinib. Mesenchymal stromal cells in the bone marrow may favor the persistence and progression of leukemia by preserving the proliferation and self-renewal capacities of the malignant progenitor cells.

Design and Methods

BV173 or primary chronic myeloid leukemia cells were co-cultured with human mesenchymal stromal cells and imatinib-induced cell death was then measured. The roles of pro-and anti-apoptotic proteins and chemokine CXCL12 in this context were evaluated. We also studied the ability of BV173 cells to repopulate NOD/SCID mice following in vitro exposure to imatinib and mesenchymal stromal cells.

Results

Whilst imatinib induced dose-dependent apoptosis of BV173 cells and primary chronic myeloid leukemia cells, co-culture with mesenchymal stromal cells protected both types of chronic myeloid leukemia cells. Molecular analysis indicated that mesenchymal stromal cells reduced caspase-3 activation and modulated the expression of the anti-apoptotic protein Bcl-XL. Furthermore, chronic myeloid leukemia cells exposed to imatinib in the presence of mesenchymal stromal cells retained the ability to engraft into NOD/SCID mice. We observed that chronic myeloid leukemia cells and mesenchymal stromal cells express functional levels of CXCR4 and CXCL12, respectively. Finally, the CXCR4 antagonist, AMD3100 restored apoptosis by imatinib and the susceptibility of the SCID leukemia repopulating cells to the tyrosine kinase inhibitor.

Conclusions

Human mesenchymal stromal cells mediate protection of chronic myeloid leukemia cells from imatinib-induced apoptosis. Disruption of the CXCL12/CXCR4 axis restores, at least in part, the leukemic cells’ sensitivity to imatinib. The combination of anti-CXCR4 antagonists with tyrosine kinase inhibitors may represent a powerful approach to the treatment of chronic myeloid leukemia.     

Melatonin enhances alkaline phosphatase activity in differentiating human adult mesenchymal stem cells grown in osteogenic medium via MT2 melatonin receptors and the MEK/ERK (1/2) signaling cascade

The goals of this study were to determine (a) if melatonin enhances human adult mesenchymal stem cell (hAMSC) differentiation into osteoblasts as assessed by measuring alkaline phosphatase (ALP) enzyme activity, and (b) identify potential signal transduction pathways that mediate this process. ALP activity significantly increased in hAMSCs following a 10-day incubation in osteogenic medium, relative to hAMSCs incubated in basal growth medium alone. Melatonin (50 nm), added in combination with the osteogenic medium, significantly increased ALP activity relative to osteogenic medium alone. Co-exposure of hAMSCs to osteogenic medium supplemented with melatonin and either pertussis toxin or the melatonin receptor antagonists, luzindole or 4P-PDOT (MT2 receptor selective), inhibited the melatonin-induced increase in ALP activity, indicating the involvement of melatonin receptors, in particular, MT2 receptors. Assessment of melatonin receptor function following exposure to osteogenic medium containing either vehicle or melatonin produced dichotomous results. That is, if the differentiation of hAMSCs into an osteoblast was induced by osteogenic medium alone, then 2-[125I]-iodomelatonin binding and melatonin receptor function increased. However, examination of melatonin receptor function following chronic melatonin exposure, an exposure that resulted in a 50% enhancement in ALP activity, revealed that these receptors were desensitized. This was reflected by a complete loss in specific 2-[125I]-iodomelatonin binding as well as melatonin efficacy to inhibit forskolin-induced cAMP accumulation. Further characterization of the mechanisms underlying melatonin's effects on these differentiation processes revealed that MEK (1/2) and ERK (1/2), epidermal growth factor receptors, metalloproteinase and clathrin-mediated endocytosis were essential while PKA was not. Our results are consistent with a role for melatonin in osteoblast differentiation. If so, then, the decrease in plasma melatonin levels observed in humans during late adulthood may further enhance susceptibility to osteoporosis.     

Effect of co-culture of mesenchymal stem/stromal cells with pancreatic islets on viability and function outcomes: a systematic review and meta-analysis

The maintenance of viable and functional pancreatic islets is crucial for successful islet transplantation from brain-dead donors. To overcome islet quality loss during culture, some studies have co-cultured islets with mesenchymal stem/stromal cells (MSC). However, it is still uncertain if MSC-secreted factors are enough to improve islet quality or if a physical contact between MSCs and islets is needed. Therefore, we performed a systematic review and meta-analysis to clarify the effect of different culture contact systems of islets with MSCs on viability and insulin secretion outcomes. Pubmed and Embase were searched. Twenty studies fulfilled the eligibility criteria and were included in the qualitative synthesis and/or meta-analysis. For both outcomes, pooled weighted mean differences (WMD) between islet cultured alone (control group) and the co-culture condition were calculated. Viability mean was higher in islets co-cultured with MSCs compared with islet cultured alone [WMD = 18.08 (95% CI 12.59–23.57)]. The improvement in viability was higher in islets co-cultured in indirect or mixed contact with MSCs than in direct physical contact (P <0.001). Moreover, the mean of insulin stimulation index (ISI) was higher in islets from co-culture condition compared with islet cultured alone [WMD = 0.83 (95% CI 0.54–1.13)], independently of contact system. Results from the studies that were analyzed only qualitatively are in accordance with meta-analysis data. Co-culture of islets with MSCs has the potential for protecting islets from injury during culture period. Moreover, culture time appears to influence the beneficial effect of different methods of co-culture on viability and function of islets.     

间充质干细胞上清对高糖慢性炎症损伤的巨噬细胞表型极化的影响

目的探讨脂肪间充质干细胞(MSCs)培养上清对高糖、炎症环境中巨噬细胞表型的影响及其机制。方法分别以及联合利用高浓度葡萄糖(33 mmol/L)、脂多糖(LPS;1μg/ml)体外处理大鼠腹腔巨噬细胞12 h。依据是否采用MSCs干预分为干预组和非干预组,考察各损伤条件下两组巨噬细胞表型的差异。MSCs干预方法为加入MSCs上清0.5 ml,培养48 h。结果在各非干预组中,与正常条件下相比,各损伤条件下的M1型巨噬细胞比例、M1/M2值和IL-6水平均显著增高,而M2型巨噬细胞比例以及IL-10和PGE2水平均显著降低。MSCs干预后,在LPS和高糖+LPS的损伤条件下,与非干预组相比,干预组的M1型巨噬细胞的比例和M1/M2值均显著降低,而M2型巨噬细胞的比例均增加,ELISA结果也显示,在各损伤条件下,与非干预组相比,干预组的IL-6水平均显著降低,而IL-10和PGE2的水平均显著增加。结论高糖及慢性炎症因素叠加可加剧巨噬细胞向M1促炎表型极化及炎症因子的分泌,MSCs上清作用于损伤的巨噬细胞,促使其向M2抗炎表型极化,同时使炎症因子分泌减少,抗炎因子分泌增多。     

Mimicking the functional hematopoietic stem cell niche in vitro: recapitulation of marrow physiology by hydrogel-based three-dimensional cultures of mesenchymal stromal cells

Background

A culture system that closely recapitulates marrow physiology is essential to study the niche-mediated regulation of hematopoietic stem cell fate at a molecular level. We investigated the key features that play a crucial role in the formation of a functional niche in vitro.

Design and Methods

Hydrogel-based cultures of human placenta-derived mesenchymal stromal cells were established to recapitulate the fibrous three-dimensional architecture of the marrow. Plastic-adherent mesenchymal stromal cells were used as controls. Human bone marrow-derived CD34⁺ cells were co-cultured with them. The output hematopoietic cells were characterized by various stem cell-specific phenotypic and functional parameters.

Results

The hydrogel-cultures harbored a large pool of primitive hematopoietic stem cells with superior phenotypic and functional attributes. Most importantly, like the situation in vivo, a significant fraction of these cells remained quiescent in the face of a robust multi-lineage hematopoiesis. The retention of a high percentage of primitive stem cells by the hydrogel-cultures was attributed to the presence of CXCR4-SDF1α axis and integrin beta1-mediated adhesive interactions. The hydrogel-grown mesenchymal stromal cells expressed high levels of several molecules that are known to support the maintenance of hematopoietic stem cells. Yet another physiologically relevant property exhibited by the hydrogel cultures was the formation of hypoxia-gradient. Destruction of hypoxia-gradient by incubating these cultures in a hypoxia chamber destroyed their specialized niche properties.

Conclusions

Our data show that hydrogel-based cultures of mesenchymal stromal cells form a functional in vitro niche by mimicking key features of marrow physiology.     

Melatonin reverses H2O2‐induced premature senescence in mesenchymal stem cells via the SIRT1‐dependent pathway

Mesenchymal stem cells (MSCs) represent an attractive source for stem cell‐based regenerative therapy, but they are vulnerable to oxidative stress‐induced premature senescence in pathological conditions. We previously reported antioxidant and antiarthritic effects of melatonin on MSCs against proinflammatory cytokines. In this study, we hypothesized that melatonin could protect MSCs from premature senescence induced by hydrogen peroxide (H₂O₂) via the silent information regulator type 1 (SIRT1)‐dependent pathway. In response to H₂O₂ at a sublethal concentration of 200 μm , human bone marrow‐derived MSCs (BM‐MSCs) underwent growth arrest and cellular senescence. Treatment with melatonin before H₂O₂ exposure cannot significantly prevent premature senescence; however, treatment with melatonin subsequent to H₂O₂ exposure successfully reversed the senescent phenotypes of BM‐MSCs in a dose‐dependent manner. This result was made evident by improved cell proliferation, decreased senescence‐associated β‐galactosidase activity, and the improved entry of proliferating cells into the S phase. In addition, treatment with 100 μm melatonin restored the osteogenic differentiation potential of BM‐MSCs that was inhibited by H₂O₂‐induced premature senescence. We also found that melatonin attenuated the H₂O₂‐stimulated phosphorylation of p38 mitogen‐activated protein kinase, decreased expression of the senescence‐associated protein p16^INK4α, and increased SIRT1. Further molecular experiments revealed that luzindole, a nonselective antagonist of melatonin receptors, blocked melatonin‐mediated antisenescence effects. Inhibition of SIRT1 by sirtinol counteracted the protective effects of melatonin, suggesting that melatonin reversed the senescence in cells through the SIRT1‐dependent pathway. Together, these findings lay new ground for understanding oxidative stress‐induced premature senescence and open perspectives for therapeutic applications of melatonin in stem cell‐based regenerative medicine.     

AMD3100 disrupts the cross-talk between chronic lymphocytic leukemia cells and a mesenchymal stromal or nurse-like cell-based microenvironment: pre-clinical evidence for its association with chronic lymphocytic leukemia treatments

Background

Interactions with the microenvironment, such as bone marrow mesenchymal stromal cells and nurse-like cells, protect chronic lymphocytic leukemia cells from spontaneous and drug-induced apoptosis. This protection is partially mediated by the chemokine SDF-1α (CXCL12) and its receptor CXCR4 (CD184) present on the chronic lymphocytic leukemia cell surface.

Design and Methods

Here, we investigated the ability of AMD3100, a CXCR4 antagonist, to sensitize chronic lymphocytic leukemia cells to chemotherapy in a chronic lymphocytic leukemia/mesenchymal stromal cell based or nurse-like cell based microenvironment co-culture model.

Results

AMD3100 decreased CXCR4 expression signal (n=15, P=0.0078) and inhibited actin polymerization/migration in response to SDF-1α (n=8, P<0.01) and pseudoemperipolesis (n=10, P=0.0010), suggesting that AMD3100 interferes with chronic lymphocytic leukemia cell trafficking. AMD3100 did not have a direct effect on apoptosis when chronic lymphocytic leukemia cells were cultured alone (n=10, P=0.8812). However, when they were cultured with SDF-1α, mesenchymal stromal cells or nurse-like cells (protecting them from apoptosis, P<0.001), chronic lymphocytic leukemia cell pre-treatment with AMD3100 significantly inhibited these protective effects (n=8, P<0.01) and decreased the expression of the anti-apoptotic proteins MCL-1 and FLIP. Furthermore, combining AMD3100 with various drugs (fludarabine, cladribine, valproïc acid, bortezomib, flavopiridol, methylprednisolone) in our mesenchymal stromal cell co-culture model enhanced drug-induced apoptosis (n=8, P<0.05) indicating that AMD3100 could mobilize chronic lymphocytic leukemia cells away from their protective microenvironment, making them more accessible to conventional therapies.

Conclusions

Taken together, these data demonstrate that interfering with the SDF-1α/CXCR4 axis by using AMD3100 inhibited chronic lymphocytic leukemia cell trafficking and microenvironment-mediated protective effects. Combining AMD3100 with other drugs may, therefore, represent a promising therapeutic approach to kill chronic lymphocytic leukemia cells.     

骨髓间充质干细胞向肝（样）细胞的分化及其在肝脏疾病的应用

骨髓间充质干细胞在肝脏病理条件或体外诱导分化为有功能的肝（样）细胞以及对受损肝脏的修复作用是目前研究的热点。本文就骨髓间充质干细胞分化潜能及其可能的机制、免疫学特性以及在肝脏疾病的应用研究作系统的综述。     

Melatonin enhances the human mesenchymal stem cells motility via melatonin receptor 2 coupling with Gαq in skin wound healing

Melatonin, a circadian rhythm–promoting molecule, has a variety of biological functions, but the functional role of melatonin in the motility of mesenchymal stem cells (MSCs) has yet to be studied. In a mouse skin excisional wound model, we found that transplantation of umbilical cord blood (UCB)‐MSCs pretreated with melatonin enhanced wound closure, granulation, and re‐epithelialization at mouse skin wound sites, where relatively more UCB‐MSCs which were engrafted onto the wound site were detected. Thus, we identified the signaling pathway of melatonin, which affects the motility of UCB‐MSCs. Melatonin (1 μm ) significantly increased the motility of UCB‐MSCs, which had been inhibited by the knockdown of melatonin receptor 2 (MT₂). We found that Gαq coupled with MT₂ and that the binding of Gαq to MT₂ uniquely stimulated an atypical PKC isoform, PKCζ. Melatonin induced the phosphorylation of FAK and paxillin, which were concurrently downregulated by blocking of the PKC activity. Melatonin increased the levels of active Cdc42 and Arp2/3, and it has the ability to stimulate cytoskeletal reorganization‐related proteins such as profilin‐1, cofilin‐1, and F‐actin in UCB‐MSCs. Finally, a lack of MT₂ expression in UCB‐MSCs during a mouse skin transplantation experiment resulted in impaired wound healing and less engraftment of stem cells at the wound site. These results demonstrate that melatonin signaling via MT₂ triggers FAK/paxillin phosphorylation to stimulate reorganization of the actin cytoskeleton, which is responsible for Cdc42/Arp2/3 activation to promote UCB‐MSCs motility.     

Headway and the remaining hurdles of mesenchymal stem cells therapy for bronchopulmonary dysplasia

ObjectivePreterm infants are at a high risk of developing BPD. Although progression in neonatal care has improved, BPD still causes significant morbidity and mortality, which can be attributed to the limited therapeutic choices for BPD. This review discusses the potential of MSC in treating BPD as well as their hurdles and possible solutions.Data SourcesThe search for data was not limited to any sites but was mostly performed on all clinical trials available in ClinicalTrials.gov as well as on PubMed by applying the following keywords: lung injury, preterm, inflammation, neonatal, bronchopulmonary dysplasia and mesenchymal stem cells.Study SelectionsThe articles chosen for this review were collectively determined to be relevant and appropriate in discussing MSC not only as a potential treatment strategy for curbing the incidence of BPD but also including insights on problems regarding MSC treatment for BPD.ResultsClinical trials regarding the use of MSC for BPD had good results but also illustrated insights on problems to be addressed in the future regarding the treatment strategy. Despite that, the clinical trials had mostly favourable reviews.ConclusionWith BPD existing as a constant threat and there being no permanent solutions, the idea of regenerative medicine such as MSC may prove to be a breakthrough strategy when it comes to treating BPD. The success in clinical trials led to the formulation of prospective MSC‐derived products such as PNEUMOSTEM®, and there is the possibility of a stem cell medication and permanent treatment for BPD in the near future.     

Additional benefit of combined therapy with melatonin and apoptotic adipose‐derived mesenchymal stem cell against sepsis‐induced kidney injury

This study tested whether combined therapy with melatonin and apoptotic adipose‐derived mesenchymal stem cells (A‐ADMSCs) offered additional benefit in ameliorating sepsis‐induced acute kidney injury. Adult male Sprague–Dawley rats (n = 65) were randomized equally into five groups: Sham controls (SC), sepsis induced by cecal‐ligation and puncture (CLP), CLP‐melatonin, CLP‐A‐ADMSC, and CLP‐melatonin‐A‐ADMSC. Circulating TNF‐α level at post‐CLP 6 hr was highest in CLP and lowest in SC groups, higher in CLP‐melatonin than in CLP‐A‐ADMSC and CLP‐melatonin‐A‐ADMSC groups (all P < 0.001). Immune reactivity as reflected in the number of splenic helper‐, cytoxic‐, and regulatory‐T cells at post‐CLP 72 hr exhibited the same pattern as that of circulating TNF‐α among all groups (P < 0.001). The histological scoring of kidney injury and the number of F4/80+ and CD14+ cells in kidney were highest in CLP and lowest in SC groups, higher in CLP‐melatonin than in CLP‐A‐ADMSC and CLP‐melatonin‐A‐ADMSC groups, and higher in CLP‐A‐ADMSC than in CLP‐melatonin‐A‐ADMSC groups (all P < 0.001). Changes in protein expressions of inflammatory (RANTES, TNF‐1α, NF‐κB, MMP‐9, MIP‐1, IL‐1β), apoptotic (cleaved caspase 3 and PARP, mitochondrial Bax), fibrotic (Smad3, TGF‐β) markers, reactive‐oxygen‐species (NOX‐1, NOX‐2), and oxidative stress displayed a pattern identical to that of kidney injury score among the five groups (all P < 0.001). Expressions of antioxidants (GR+, GPx+, HO‐1, NQO‐1+) were lowest in SC group and highest in CLP‐melatonin‐A‐ADMSC group, lower in CLP than in CLP‐melatonin and CLP‐A‐ADMSC groups, and lower in CLP‐melatonin‐ than in CLP‐A‐ADMSC‐tretaed animals (all P < 0.001). In conclusion, combined treatment with melatonin and A‐ADMSC was superior to A‐ADMSC alone in protecting the kidneys from sepsis‐induced injury.     

Mesenchymal stem/stromal cells precondition lung monocytes/macrophages to produce tolerance against allo- and autoimmunity in the eye

Intravenously administered mesenchymal stem/stromal cells (MSCs) engraft only transiently in recipients, but confer long-term therapeutic benefits in patients with immune disorders. This suggests that MSCs induce immune tolerance by long-lasting effects on the recipient immune regulatory system. Here, we demonstrate that i.v. infusion of MSCs preconditioned lung monocytes/macrophages toward an immune regulatory phenotype in a TNF-α–stimulated gene/protein (TSG)-6–dependent manner. As a result, mice were protected against subsequent immune challenge in two models of allo- and autoimmune ocular inflammation: corneal allotransplantation and experimental autoimmune uveitis (EAU). The monocytes/macrophages primed by MSCs expressed high levels of MHC class II, B220, CD11b, and IL-10, and exhibited T-cell–suppressive activities independently of FoxP3⁺ regulatory T cells. Adoptive transfer of MSC-induced B220⁺CD11b⁺ monocytes/macrophages prevented corneal allograft rejection and EAU. Deletion of monocytes/macrophages abrogated the MSC-induced tolerance. However, MSCs with TSG-6 knockdown did not induce MHC II⁺B220⁺CD11b⁺ cells, and failed to attenuate EAU. Therefore, the results demonstrate a mechanism of the MSC-mediated immune modulation through induction of innate immune tolerance that involves monocytes/macrophages.Intravenous administration of mesenchymal stem/stromal cells (MSCs) has emerged as a promising cell-based immunotherapy for autoimmune diseases, graft-vs.-host disease, and transplantation (1–3). A significant body of data from preclinical and clinical studies has demonstrated remarkable immunosuppressive capacities of MSCs in various diseases, but the mechanisms are still difficult to explain.One key observation is that therapeutic benefits of MSC administration in animal models are achieved without significant engraftment of the cells; after i.v. infusion, most MSCs reside transiently within the lung and disappear rapidly with a t_1/2 of approximately 24 h in mice (4, 5). Therefore, direct suppressive effects of MSCs on the immune system are short-lived, and do not explain the long-term therapeutic effects observed with MSCs in clinical and animal studies. In this context, it has been suggested that MSCs trigger a state of immune tolerance, for example, through the induction of regulatory T cells (Tregs) (6, 7).Classically, lymphoid cells such as Tregs have been known to play a major role in regulating immune responses and maintaining immune tolerance. Recently, however, myeloid cells, including monocytes/macrophages, have gained attention as important mediators of immune regulation and tolerance (8, 9). In line with this, a few studies demonstrated that MSCs induce the expansion of myeloid cells with immunosuppressive activity and modulate monocytes/macrophages to an antiinflammatory phenotype, thereby inhibiting excessive inflammatory responses (10–12).However, it is not clear whether the MSC-educated myeloid cells can induce significant immune tolerance to repress adaptive immune responses in a setting of allo- or autoimmunity. Moreover, little is known about the mechanism(s) whereby MSCs induce immune tolerance through myeloid cells.In this study, we demonstrate that i.v. injection of MSCs into naive mice before immune challenge induces a significant immune tolerance in TNF-α–stimulated gene/protein (TSG)-6–dependent manner, and prevents the development of immune responses in two models of allo- and autoimmune ocular inflammation: corneal allotransplantation and experimental autoimmune uveitis (EAU). The MSC-induced tolerance involves a distinct subset of suppressive monocytes/macrophages in the lung, and is transferable independently of FoxP3⁺ Tregs. These data suggest a mechanism of MSCs in regulating adaptive immunity through induction of nonspecific innate tolerance.     

诱导分化的骨髓间充质干细胞不同途径移植治疗慢性肝损伤的研究

目的 探讨诱导分化的骨髓间充质干细胞(MSC)不同途径移植治疗慢性肝损伤的可行性.方法 密度梯度离心法联合贴壁培养分离、扩增骨髓MSC,体外诱导向肝系细胞分化,反转录-聚合酶链反应(RT-PCR)、免疫细胞化学法检测肝系细胞标志,电镜观察超微结构的变化.清洁级Wistar大鼠120只,其中114只建立慢性肝损伤模型(实验组),另6只作为正常对照组.实验组8周内自然死亡12只,将剩余96只根据三种移植途径及体质量分层随机均分为门静脉移植实验组、门静脉移植对照组、脾脏移植实验组、脾脏移植对照组、尾静脉移植实验组和尾静脉移植对照组,各移植实验组移植4',6-二脒基-2'-苯基吲哚(DAPI)标记诱导分化14 d的MSC,观察移植后细胞的迁徙、定位,血清肝功能指标,肝脏组织病理学及移植效果.结果 诱导后第7、14天均检测到甲胎蛋白(AFP)mRNA表达,第14、21天检测到白蛋白(ALB)mRNA、兔抗鼠细胞角蛋白18(CK18)和肝细胞抗原表达.诱导后MSC胞体增大,胞质中含有较多线粒体、粗面内质网、高尔基体、溶酶体和糖原颗粒等.各移植实验组大鼠均发现DAPI标记细胞且丙氨酸转氨酶等肝功能指标及肝脏病变程度均较其移植对照组改善,以脾内移植途径更为显著[(98.13±8.22)U/L比(145.85±15.88)U/L,P＜0.05].结论 诱导分化的骨髓MSC通过三种移植途径均对慢性肝损伤具有修复作用,且脾内移植优于门静脉及尾静脉移植.     

An interaction between hepatocyte growth factor and its receptor (c-MET) prolongs the survival of chronic lymphocytic leukemic cells through STAT3 phosphorylation: a potential role of mesenchymal cells in the disease

Background

Chronic lymphocytic leukemia cells are characterized by an apparent longevity in vivo which is lost when they are cultured in vitro. Cellular interactions and factors provided by the microenvironment appear essential to cell survival and may protect leukemic cells from the cytotoxicity of conventional therapies. Understanding the cross-talk between leukemic cells and stroma is of interest for identifying signals supporting disease progression and for developing novel therapeutic strategies.

Design and Methods

Different cell types, sharing a common mesenchymal origin and representative of various bone marrow components, were used to challenge the viability of leukemic cells in co-cultures and in contact-free culture systems. Using a bioinformatic approach we searched for genes shared by lineages prolonging leukemic cell survival and further analyzed their biological role in signal transduction experiments.

Results

Human bone marrow stromal cells, fibroblasts, trabecular bone-derived cells and an osteoblast-like cell line strongly enhanced survival of leukemic cells, while endothelial cells and chondrocytes did not. Gene expression profile analysis indicated two soluble factors, hepatocyte growth factor and CXCL12, as potentially involved. We demonstrated that hepatocyte growth factor and CXCL12 are produced only by mesenchymal lineages that sustain the survival of leukemic cells. Indeed chronic lymphocytic leukemic cells express a functional hepatocyte growth factor receptor (c-MET) and hepatocyte growth factor enhanced the viability of these cells through STAT3 phosphorylation, which was blocked by a c-MET tyrosine kinase inhibitor. The role of hepatocyte growth factor was confirmed by its short interfering RNA-mediated knock-down in mesenchymal cells.

Conclusions

The finding that hepatocyte growth factor prolongs the survival of chronic lymphocytic leukemic cells is novel and we suggest that the interaction between hepatocyte growth factor-producing mesenchymal and neoplastic cells contributes to maintenance of the leukemic clone.