Metformin inhibits chronic kidney disease‐induced DNA damage and senescence of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are promising source of cell‐based regenerative therapy. In consideration of the risk of allosensitization, autologous MSC‐based therapy is preferred over allogenic transplantation in patients with chronic kidney disease (CKD). However, it remains uncertain whether adequate cell functionality is maintained under uremic conditions. As chronic inflammation and oxidative stress in CKD may lead to the accumulation of senescent cells, we investigated cellular senescence of CKD MSCs and determined the effects of metformin on CKD‐associated cellular senescence in bone marrow MSCs from sham‐operated and subtotal nephrectomized mice and further explored in adipose tissue‐derived MSCs from healthy kidney donors and patients with CKD. CKD MSCs showed reduced proliferation, accelerated senescence, and increased DNA damage as compared to control MSCs. These changes were significantly attenuated following metformin treatment. Lipopolysaccharide and transforming growth factor β1‐treated HK2 cells showed lower tubular expression of proinflammatory and fibrogenesis markers upon co‐culture with metformin‐treated CKD MSCs than with untreated CKD MSCs, suggestive of enhanced paracrine action of CKD MSCs mediated by metformin. In unilateral ureteral obstruction kidneys, metformin‐treated CKD MSCs more effectively attenuated inflammation and fibrosis as compared to untreated CKD MSCs. Thus, metformin preconditioning may exhibit a therapeutic benefit by targeting accelerated senescence of CKD MSCs.     

Immune modulation by mesenchymal stem cells

Mesenchymal stem cells (MSCs) can be derived from various adult tissues with multipotent and self‐renewal abilities. The characteristics of presenting no major ethical concerns, having low immunogenicity and possessing immune modulation functions make MSCs promising candidates for stem cell therapies. MSCs could promote inflammation when the immune system is underactivated and restrain inflammation when the immune system is overactivated to avoid self‐overattack. These cells express many immune suppressors to switch them from a pro‐inflammatory phenotype to an anti‐inflammatory phenotype, resulting in immune effector cell suppression and immune suppressor cell activation. We would discuss the mechanisms governing the immune modulation function of these cells in this review, especially the immune‐suppressive effects of MSCs.     

The Chemokine CCL3 Promotes Experimental Liver Fibrosis in Mice

Liver fibrosis is associated with infiltrating immune cells and activation of hepatic stellate cells. We here aimed to investigate the effects of the CC chemokine CCL3, also known as macrophage inflammatory protein-1α, in two different fibrosis models. To this end, we treated mice either with carbon tetrachloride or with a methionine- and choline-deficient diet to induce fibrosis in CCL3 deficient and wild-type mice. The results show that the protein expression of CCL3 is increased in wild-type mice after chronic liver injury. Deletion of CCL3 exhibited reduced liver fibrosis compared to their wild-type counterparts. We could validate these results by treating the two mouse groups with either carbon tetrachloride or by feeding a methionine- and choline-deficient diet. In these models, lack of CCL3 is functionally associated with reduced stellate cell activation and liver immune cell infiltration. In vitro, we show that CCL3 leads to increased proliferation and migration of hepatic stellate cells. In conclusion, our results define the chemokine CCL3 as a mediator of experimental liver fibrosis. Thus, therapeutic modulation of CCL3 might be a promising target for chronic liver diseases.     

Immunomodulation of activated hepatic stellate cells by mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) have been reported to prevent the development of liver fibrosis in a number of pre-clinical studies. Marked changes in liver histopathology and serological markers of liver function have been observed without a clear understanding of the therapeutic mechanism by which stem cells act. We sought to determine if MSCs could modulate the activity of resident liver cells, specifically hepatic stellate cells (SCs) by paracrine mechanisms using indirect cocultures. Indirect coculture of MSCs and activated SCs led to a significant decrease in collagen deposition and proliferation, while inducing apoptosis of activated SCs. The molecular mechanisms underlying the modulation of SC activity by MSCs were examined. IL-6 secretion from activated SCs induced IL-10 secretion from MSCs, suggesting a dynamic response of MSCs to the SCs in the microenvironment. Blockade of MSC-derived IL-10 and TNF-alpha abolished the inhibitory effects of MSCs on SC proliferation and collagen synthesis. In addition, release of HGF by MSCs was responsible for the marked induction of apoptosis in SCs as determined by antibody-neutralization studies. These findings demonstrate that MSCs can modulate the function of activated SCs via paracrine mechanisms provide a plausible explanation for the protective role of MSCs in liver inflammation and fibrosis, which may also be relevant to other models of tissue fibrosis.     

Mesenchymal stem cells and immunomodulation: current status and future prospects

The unique immunomodulatory properties of mesenchymal stem cells (MSCs) make them an invaluable cell type for the repair of tissue/ organ damage caused by chronic inflammation or autoimmune disorders. Although they hold great promise in the treatment of immune disorders such as graft versus host disease (GvHD) and allergic disorders, there remain many challenges to overcome before their widespread clinical application. An understanding of the biological properties of MSCs will clarify the mechanisms of MSC-based transplantation for immunomodulation. In this review, we summarize the preclinical and clinical studies of MSCs from different adult tissues, discuss the current hurdles to their use and propose the future development of pluripotent stem cell-derived MSCs as an approach to immunomodulation therapy.     

Immunomodulation: The next target of mesenchymal stem cell-derived exosomes in the context of ischemic stroke

Ischemic stroke(IS) is the most prevalent form of brain disease, characterized by high morbidity, disability, and mortality. However, there is still a lack of ideal prevention and treatment measures in clinical practice. Notably, the transplantation therapy of mesenchymal stem cells(MSCs) has been a hot research topic in stroke. Nevertheless, there are risks associated with this cell therapy, including tumor formation, coagulation dysfunction, and vascular occlusion. Also, a growing number of st...     

Chemokines in tissue fibrosis

Fibrosis or scarring of diverse organs and tissues is considered as a pathologic consequence of a chronically altered wound healing response which is tightly linked to inflammation and angiogenesis. The recruitment of immune cells, local proliferation of fibroblasts and the consecutive accumulation of extracellular matrix proteins are common pathophysiological hallmarks of tissue fibrosis, irrespective of the organ involved. Chemokines, a family of chemotactic cytokines, appear to be central mediators of the initiation as well as progression of these biological processes. Traditionally chemokines have only been considered to play a critical role in orchestrating the influx of immune cells to sites of tissue injury. However, within the last years, further aspects of chemokine biology including fibroblast activation and angiogenesis have been deciphered in tissue fibrosis of many different organs. Interestingly, certain chemokines appear to mediate common effects in liver, kidney, lung, and skin of various animal models, while others mediate tissue specific effects. These aspects have to be kept in mind when extrapolating data of animal studies to early human trials. Nevertheless, the further understanding of chemokine effects in tissue fibrosis might be an attractive approach for identifying novel therapeutic targets in chronic organ damage associated with high morbidity and mortality. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.     

Differential Induction of Ly6G and Ly6C Positive Myeloid Derived Suppressor Cells in Chronic Kidney and Liver Inflammation and Fibrosis

CD11b⁺Gr1⁺ myeloid derived suppressor cells (MDSC) are known to be very potent suppressors of T cell immunity and can be further stratified into granulocytic MDSC and monocytic MDSC in mice based on expression of Ly6G or Ly6C, respectively. Here, using these markers and functional assays, we aimed to identify whether MDSC are induced during chronic inflammation leading to fibrosis in both kidney and liver and whether additional markers could more specifically identify these MDSC subsets. In an adenine-induced model of kidney inflammation/fibrosis suppressive Ly6G^pos MDSC were induced. The suppressive function within the Ly6G⁺ MDSC population was exclusively present in IFNγRβ expressing cells. In contrast, in chronic inflammation in the liver induced by bile duct ligation, suppressive capacity was exclusively present in the Ly6C^pos MDSC subset. Gene expression analyses confirmed the differential origins and regulation of those MDSC subsets. Additionally, depletion of MDSC in either kidney or liver fibrosis enhanced fibrosis markers, indicating a protective role for MDSC in organ fibrosis. Thus, our data demonstrate that during liver inflammation and kidney fibrosis MDSC with similar function arise bearing a distinct marker profile and arising from different cell populations.     

Dual roles of immunoregulatory cytokine TGF-beta in the pathogenesis of autoimmunity-mediated organ damage

Ample evidence suggests a role of TGF-beta in preventing autoimmunity. Multiorgan inflammatory disease, spontaneous activation of self-reactive T cells, and autoantibody production are hallmarks of autoimmune diseases, such as lupus. These features are reminiscent of the immunopathology manifest in TGF-beta1-deficient mice. In this study, we show that lupus-prone (New Zealand Black and White)F(1) mice have reduced expression of TGF-beta1 in lymphoid tissues, and TGF-beta1 or TGF-beta1-producing T cells suppress autoantibody production. In contrast, the expression of TGF-beta1 protein and mRNA and TGF-beta signaling proteins (TGF-beta receptor type II and phosphorylated SMAD3) increases in the target organs, i.e., kidneys, of these mice as they age and develop progressive organ damage. In fact, the levels of TGF-beta1 in kidney tissue and urine correlate with the extent of chronic lesions that represent local tissue fibrosis. In vivo TGF-beta blockade by treatment of these mice with an anti-TGF-beta Ab selectively inhibits chronic fibrotic lesions without affecting autoantibody production and the inflammatory component of tissue injury. Thus, TGF-beta plays a dual, seemingly paradoxical, role in the development of organ damage in multiorgan autoimmune diseases. According to our working model, reduced TGF-beta in immune cells predisposes to immune dysregulation and autoantibody production, which causes tissue inflammation that triggers the production of anti-inflammatory cytokines such as TGF-beta in target organs to counter inflammation. Enhanced TGF-beta in target organs, in turn, can lead to dysregulated tissue repair, progressive fibrogenesis, and eventual end-organ damage.     

Possible ways of MSCs influence on the ischemic tissue in the case of cardiovascular diseases

Mesenchymal stem cells (MSCs) therapy is a modern and promising approach to the treatment of cardiovascular diseases. The background of MSCs therapeutic usage was their ability to differentiate into cardiomyocytes and neuronal lineage cells. It has been experimentally proven that MSCs transplantation accelerates inflammation in the ischemic region, activates angiogenesis, prevents apoptosis and acts as a protective agent in the areas adjacent to infarction. This reduces the size of the scar and the volume of damaged tissue, restores the functioning of the injured organ, and returns the standard rates of behavioral and neurological reactions of the experimental animals.     

Kallikrein-kinin in stem cell therapy

The tissue kallikrein-kinin system exerts a wide spectrum of biological activities in the cardiovascular, renal and central nervous systems. Tissue kallikrein-kinin modulates the proliferation, viability, mobility and functional activity of certain stem cell populations, namely mesenchymal stem cells(MSCs), endothelial progenitor cells(EPCs), mononuclear cell subsets and neural stem cells. Stimulation of these stem cells by tissue kallikrein-kinin may lead to protection against renal, cardiovascular and neural damage by inhibiting apoptosis, inflammation, fibrosis and oxidative stress and promoting neovascularization. Moreover, MSCs and EPCs genetically modified with tissue kallikrein are resistant to hypoxia- and oxidative stress-induced apoptosis, and offer enhanced protective actions in animal models of heart and kidney injury and hindlimb ischemia. In addition, activation of the plasma kallikrein-kinin system promotes EPC recruitment to the inflamed synovium of arthritic rats. Conversely, cleaved high molecular weight kininogen, a product of plasma kallikrein, reduces the viability and vasculogenic activity of EPCs. Therefore, kallikrein-kinin provides a new approach in enhancing the efficacy of stem cell therapy for human diseases.     

骨髓间充质干细胞抗肝纤维化的研究进展

肝纤维化及其终末病变肝硬化已严重危害全球人类健康,虽然慢性肝病的治疗手段和抗肝纤维化药物的研究已取得了很大进展,肝移植依然是最有效的治疗方案,但器官的紧缺却是一个现实问题。目前寻找有效的干预手段进行抗肝纤维化治疗已越来越受到大家的关注。近些年,大量基础及临床研究均证实在一定条件下利用骨髓间充质干细胞(MSCs)可以抑制肝星状细胞活化诱导其凋亡,实现肝纤维化逆转。随着干细胞技术的快速发展,基于骨髓间充质干细胞(MSCs)的细胞疗法在肝纤维化治疗领域的研究与应用已成为一个充满生命力的新方向。本文将对肝纤维化及基于MSCs的治疗机制进展及其应用进行综述。     

Potential advantages of acute kidney injury management by mesenchymal stem cells

Mesenchymal stem cells are currently considered as a promising tool for therapeutic application in acute kidney injury (AKI) management. AKI is characterized by acute tubular injury with rapid loss of renal function. After AKI, inflammation, oxidative stress and excessive deposition of extracellular matrix are the molecular events that ultimately cause the end-stage renal disease. Despite numerous improvement of supportive therapy, the mortality and morbidity among patients remain high. Therefore, exploring novel therapeutic options to treat AKI is mandatory. Numerous evidence in animal models has demonstrated the capability of mesenchymal stem cells (MSCs) to restore kidney function after induced kidney injury. After infusion, MSCs engraft in the injured tissue and release soluble factors and microvesicles that promote cell survival and tissue repairing. Indeed, the main mechanism of action of MSCs in tissue regeneration is the paracrine/endocrine secretion of bioactive molecules. MSCs can be isolated from several tissues, including bone marrow, adipose tissue, and blood cord; pre-treatment procedures to improve MSCs homing and their paracrine function have been also described. This review will focus on the application of cell therapy in AKI and it will summarize preclinical studies in animal models and clinical trials currently ongoing about the use of mesenchymal stem cells after AKI.     

Transforming growth factor-β1-overexpressing mesenchymal stromal cells induced local tolerance in rat renal ischemia/reperfusion injury

BackgroundRegulatory T cells (Tregs) suppress excessive immune responses and play a crucial protective role in acute kidney injury (AKI). The aim of this study was to examine the therapeutic potential of transforming growth factor (TGF)-β1-overexpressing mesenchymal stromal cells (MSCs) in inducing local generation of Tregs in the kidney after ischemia/reperfusion (I/R) injury.MethodsMSCs were transduced with a lentiviral vector expressing the TGF-β1 gene; TGF-β1-overexpressing MSCs (designated TGF-β1/MSCs) were then transfused into the I/R-injured kidney via the renal artery.ResultsMSCs genetically modified with TGF-β1 achieved overexpression of TGF-β1. Compared with green fluorescent protein (GFP)/MSCs, TGF-β1/MSCs markedly improved renal function after I/R injury and reduced epithelial apoptosis and subsequent inflammation. The enhanced immunosuppressive and therapeutic abilities of TGF-β1/MSCs were associated with increased generation of induced Tregs and improved intrarenal migration of the injected cells. Futhermore, the mechanism of TGF-β1/MSCs in attenuating renal I/R injury was not through a direct canonical TGF-β1/Smad pathway.ConclusionTGF-β1/MSCs can induce a local immunosuppressive effect in the I/R-injured kidney. The immunomodulatory activity of TGF-β1–modified MSCs appears to be a gateway to new therapeutic approaches to prevent renal I/R injury.     

Mesenchymal stem cells in inflammation microenvironment accelerates hepatocellular carcinoma metastasis by inducing epithelial-mesenchymal transition

In response to inflammation, mesenchymal stem cells (MSCs) are known to migrate to tissue injury sites to participate in immune modulation, tissue remodeling and wound healing. Tumors apply persistent mechanical and pathological stress to tissues and causes continual infiltration of MSCs. Here, we demonstrate that MSCs promote human hepatocellular carcinoma (HCC) metastasis under the influence of inflammation. The metastasis promoting effect could be imitated with the supernatant of MSCs pretreated with IFNγ and TNFα. Interestingly, treatment of HCC cells with the supernatant leads to epithelial-mesenchymal transition (EMT), an effect related to the production of TGFβ by cytokines stimulated MSCs. Importantly, the levels of MSCs expressing SSEA4 in clinical HCC samples significantly correlated with poor prognosis of HCC, and EMT of HCC was strongly associated with a shorter cancer-free interval (CFI) and a worse overall survival (OS). Therefore, our results suggest that MSCs in tumor inflammatory microenvironment could promote tumor metastasis through TGFβ-induced EMT.     

Bone marrow–derived mesenchymal stem cells attenuate tubulointerstitial injury through multiple mechanisms in UUO model

Current evidence supports the use of bone marrow–derived mesenchymal stem cells (MSCs) for a diverse range of clinical applications, and many studies have shown that MSCs have renal-protective effects, but the mechanism is not well understood. Therefore, in this study, we aim to further identify whether MSCs can attenuate renal fibrosis by decreasing tubulointerstitial injury in a unilateral ureteral obstruction (UUO) model. In this study, we cultured MSCs and then transplanted them into a UUO model through the tail vein. Histology, cell proliferation, peritubular capillary (PTC) loss and myofibroblast markers were examined on days 3, 7 and 14 after surgery. We demonstrated that renal interstitial fibrosis in the MSC group was significantly attenuated compared with the UUO and DMEM groups. Moreover, MSC treatment inhibited the loss of PTCs and increased parenchymal cell proliferation. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by MSC infusion. Furthermore, MSCs attenuated tubulointerstitial infiltration of macrophages in UUO mice. Tubulointerstitial damage plays a very important role in the progression of chronic kidney disease (CKD). PTC loss, macrophage recruitment, and myofibroblast activation are directly correlated with the development of renal tubulointerstitial fibrosis. Our results suggest that MSC infusion in the UUO model is a promising therapeutic strategy for promoting kidney repair.     

Trichostatin a modulates intracellular reactive oxygen species through SOD2 and FOXO1 in human bone marrow‐mesenchymal stem cells

Engraft cells are often exposed to oxidative stress and inflammation; therefore, any factor that can provide the stem cells resistance to these stresses may yield better efficacy in stem cell therapy. Studies indicate that histone deacetylase (HDACs) inhibitors alleviate damage induced by oxidative stress. In this study, we investigated whether regulation of reactive oxygen species (ROS) occurs through the HDAC inhibitor trichostatin A (TSA) in human bone marrow‐mesenchymal stem cells (hBM‐MSCs). Intracellular ROS levels increased following exposure to hydrogen peroxide (H₂O₂), and were suppressed by TSA treatment. Levels of the antioxidant enzyme superoxide dismutase 2 (SOD2) increased following treatment with 200 nM TSA and to a lesser level at 1–5 μM TSA. Cell protective effects against oxidative stress were significantly increased in TSA‐MSCs after treatment with low doses of TSA (50–500 nM) and decreased with high doses of TSA (5–10 μM). Consistent results were obtained with immunoblot analysis for caspase3. Investigation of Forkhead box O1 (FOXO1), superoxide dismutase 2 (SOD2), and p53 levels to determine intracellular signaling by TSA in oxidative stress‐induced MSCs demonstrated that expression of phosphorylated‐FOXO1 and phosphorylated‐SOD2 decreased in H₂O₂‐treated MSCs while levels of p53 increased. These effects were reversed by the treatment of 200 nM TSA. These results suggest that the main function of ROS modulation by TSA is activated through SOD2 and FOXO1. Thus, optimal treatment with TSA may protect hBM‐MSCs against oxidative stress. Copyright © 2014 John Wiley & Sons, Ltd.     

Nasal Mucosa Derived-Mesenchymal Stem Cells from Mice Reduce Inflammation via Modulating Immune Responses

Mesenchymal stem cells (MSCs) have arisen the attention to be a new attractive therapeutic tool treating autoimmune diseases such as allergic rhinitis (AR). AR is a chronic reversible allergic inflammation caused by the excessive activation of T-helper 2 (Th2) cells. Recently, MSCs have been proposed as a new therapy of AR as it can suppress some cytokines to control allogeneic Th2 response and functions. However, how MSCs function to reduce inflammation remains unclear. In this study, we aimed to investigate the role of ectomesenchymal stem cells (ECTO-MSCs) derived from nasal mucosa in eosinophilic inflammation and how it affects some immunoglobulins and cytokines. We used ovalbumin (OVA) as a sensitizer to induce nasal inflammation in mice by both injection and inhalation. In order to obtain deeper insights into the influences of ECTO-MSCs on nasal inflammation, the migration of ECTO-MSCs was assessed, the numbers of eosinophils and sneezing were counted, and several immunoglobulins and cytokines were measured. Here we show the ECTO-MSCs are able to migrate to inflammation site via tail vein injection. Eosinophils and sneezing were suppressed by ECTO-MSCs. Interestingly, IgE, interleukin (IL)-4, IL-5 and IL-10 secreted by Th-2 cells were down-regulated by ECTO-MSCs whereas IgG₂ and IFN-γ were up-regulated. In conclusion, we have observed that ECTO-MSCs are associated with enhanced Th-1 immune response to nasal inflammation and reduced Th-2 immune response. Given the contributions of Th-2 cells to AR, the injection of ECTO-MSCs can be a promising therapy of AR through balancing immune response.     

Local but not systemic administration of mesenchymal stromal cells ameliorates fibrogenesis in regenerating livers

Chronic liver injury leads to the accumulation of myofibroblasts resulting in increased collagen deposition and hepatic fibrogenesis. Treatments specifically targeting fibrogenesis are not yet available. Mesenchymal stromal cells (MSCs) are fibroblast‐like stromal (stem) cells, which stimulate tissue regeneration and modulate immune responses. In the present study we assessed whether liver fibrosis and cirrhosis can be reversed by treatment with MSCs or fibroblasts concomitant to partial hepatectomy (pHx)‐induced liver regeneration. After carbon tetrachloride‐induced fibrosis and cirrhosis, mice underwent a pHx and received either systemically or locally MSCs in one of the two remaining fibrotic/cirrhotic liver lobes. Eight days after treatment, liver fibrogenesis was evaluated by Sirius‐red staining for collagen deposition. A significant reduction of collagen content in the locally treated lobes of the regenerated fibrotic and cirrhotic livers was observed in mice that received high dose MSCs. In the non‐MSC‐treated counterpart liver lobes no changes in collagen deposition were observed. Local fibroblast administration or intravenous administration of MSCs did not ameliorate fibrosis. To conclude, local administration of MSCs after pHx, in contrast to fibroblasts, results in a dose‐dependent on‐site reduction of collagen deposition in mouse models for liver fibrosis and cirrhosis.     

间充质干细胞与肿瘤形成的研究进展

间充质干细胞(Mesenchymal stem cells,MSCs)具有独特的免疫调节作用、自我更新和跨胚层多向分化的潜能,存在于许多组织中并活跃地向组织损伤部位迁移,参与伤口修复。在对肿瘤的信号发生反应后,MSCs不断被招募并成为肿瘤微环境的成分。肿瘤相关MSCs(Tumor-associated MSCs, TA-MSCs)在肿瘤发生、促进、进展和转移中有重要作用。本文对MSCs在调节肿瘤细胞的存活、增殖、迁移、药物抵抗中如何发挥作用,以及MSCs对肿瘤微环境免疫状态的影响作一综述。我们强调了MSCs和其他肿瘤基质细胞之间的复杂关系,特别是炎症细胞可以改变肿瘤微环境的免疫状态,以期通过对TA-MSCs进一步的研究来取得对不同肿瘤类型和肿瘤进展不同阶段中肿瘤相关MSCs功能的更好的理解,并优化MSCs来得到更有效和安全的MSCs为基础的肿瘤治疗。MSCs已被有效用于治疗慢性炎性疾病和慢性损伤,因此,其机制方面的研究还有利于在其他疾病中合理利用MSCs从而达到疾病治疗的目的。