CCR1 and CCR5 promote hepatic fibrosis in mice

Hepatic fibrosis develops as a response to chronic liver injury and almost exclusively occurs in a proinflammatory environment. However, the role of inflammatory mediators in fibrogenic responses of the liver is only poorly understood. We therefore investigated the role of CC chemokines and their receptors in hepatic fibrogenesis. The CC chemokines MIP-1α, MIP-1β, and RANTES and their receptors CCR1 and CCR5 were strongly upregulated in 2 experimental mouse models of fibrogenesis. Neutralization of CC chemokines by the broad-spectrum CC chemokine inhibitor 35k efficiently reduced hepatic fibrosis, and CCR1- and CCR5-deficient mice displayed substantially reduced hepatic fibrosis and macrophage infiltration. Analysis of fibrogenesis in CCR1- and CCR5-chimeric mice revealed that CCR1 mediates its profibrogenic effects in BM-derived cells, whereas CCR5 mediates its profibrogenic effects in resident liver cells. CCR5 promoted hepatic stellate cell (HSC) migration through a redox-sensitive, PI3K-dependent pathway. Both CCR5-deficient HSCs and CCR1- and CCR5-deficient Kupffer cells displayed strong suppression of CC chemokine–induced migration. Finally, we detected marked upregulation of RANTES, CCR1, and CCR5 in patients with hepatic cirrhosis, confirming activation of the CC chemokine system in human fibrogenesis. Our data therefore support a role for the CC chemokine system in hepatic fibrogenesis and suggest distinct roles for CCR1 and CCR5 in Kupffer cells and HSCs.     

siRNA-mediated knockdown of connective tissue growth factor prevents N-nitrosodimethylamine-induced hepatic fibrosis in rats

Hepatic fibrosis is a dynamic process that involves the interplay of different cell types in the hepatic tissue. Connective tissue growth factor (CTGF) is a highly profibrogenic molecule and plays a crucial role in the pathogenesis of hepatic fibrosis. The aim of the present investigation was three-fold. First, we studied the expression of CTGF in the cultured hepatic stellate cells using immunohistochemical technique. Second, we induced hepatic fibrosis in rats through serial intraperitoneal injections of N-nitrosodimethylamine (NDMA; dimethylnitrosamine, DMN) and studied the upregulation of CTGF and TGF-beta1 during hepatic fibrogenesis. Third, we downregulated CTGF expression using CTGF siRNA and examined the role of CTGF siRNA to prevent the progression of NDMA-induced hepatic fibrosis. The results depicted strong staining of CTGF in the transformed hepatic stellate cells in culture. Serial administrations of NDMA resulted in activation of hepatic stellate cells, upregulation of CTGF and TGF-beta1 both at mRNA and protein levels and well-developed fibrosis in the liver. Immunostaining, Western blot analysis, semiquantitative and real-time RT-PCR studies showed downregulation of CTGF and TGF-beta1 after treatment with CTGF siRNA. The results of the present study demonstrated that CTGF gene silencing through siRNA reduces activation of hepatic stellate cells, prevents the upregulation of CTGF and TGF-beta1 gene expression and inhibits accumulation of connective tissue proteins in the liver. The data further suggest that knockdown of CTGF upregulation using siRNA has potential therapeutic application to prevent hepatic fibrogenesis.     

Pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis

Liver fibrosis is a complex pathological process controlled by a variety of cells, mediators and signaling pathways. Hepatic stellate cells play a central role in the development of liver fibrosis. In chronic liver disease, hepatic stellate cells undergo dramatic phenotypic activation and acquire fibrogenic properties. This review focuses on the pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis. They enter the cell cycle under the influence of various triggers. The “Initiation” phase of hepatic stellate cells activation overlaps and continues with the “Perpetuation” phase, which is characterized by a pronounced inflammatory and fibrogenic reaction. This is followed by a resolution phase if the injury subsides. Knowledge of these pathophysiological mechanisms paved the way for drugs aimed at preventing the development and progression of liver fibrosis. In this respect, impairments in intracellular signaling, epigenetic changes and cellular stress response can be the targets of therapy where the goal is to deactivate hepatic stellate cells. Potential antifibrotic therapy may focus on inducing hepatic stellate cells to return to an inactive state through cellular aging, apoptosis, and/or clearance by immune cells, and serve as potential antifibrotic therapy. It is especially important to prevent the formation of liver cirrhosis since the only radical approach to its treatment is liver transplantation which can be performed in only a limited number of countries.     

肝纤维化自发逆转过程中肝星状细胞上p75的表达

目的　确定低亲和力神经生长因子受体(p75 )在肝纤维化自发逆转过程中的表达分布。方法　四氯化碳诱导的肝纤维化大鼠在去除诱导因素后,应用免疫组化技术动态观察在肝纤维化自发逆转过程中第7,2 0和30d时p75表达的变化,以及肝纤维化病理组织学分级。结果　p75主要在肝星状细胞(HSC)表达,随着肝纤维化的逆转,p75表达减少(P <0 .0 5 )。p75的表达与活化HSC的变化呈相关性(r =0 .89,P <0 .0 1)。结论　p75在HSC有表达,因此,p75可能参与肝纤维化自发逆转的发生。     

T regulatory cell chemokine production mediates pathogenic T cell attraction and suppression

T regulatory cells (Tregs) control immune homeostasis by preventing inappropriate responses to self and nonharmful foreign antigens. Tregs use multiple mechanisms to control immune responses, all of which require these cells to be near their targets of suppression; however, it is not known how Treg-to-target proximity is controlled. Here, we found that Tregs attract CD4⁺ and CD8⁺ T cells by producing chemokines. Specifically, Tregs produced both CCL3 and CCL4 in response to stimulation, and production of these chemokines was critical for migration of target T cells, as Tregs from Ccl3^–/– mice, which are also deficient for CCL4 production, did not promote migration. Moreover, CCR5 expression by target T cells was required for migration of these cells to supernatants conditioned by Tregs. Tregs deficient for expression of CCL3 and CCL4 were impaired in their ability to suppress experimental autoimmune encephalomyelitis or islet allograft rejection in murine models. Moreover, Tregs from subjects with established type 1 diabetes were impaired in their ability to produce CCL3 and CCL4. Together, these results demonstrate a previously unappreciated facet of Treg function and suggest that chemokine secretion by Tregs is a fundamental aspect of their therapeutic effect in autoimmunity and transplantation.     

大鼠骨髓间质干细胞体内诱导肝星状细胞的凋亡

背景:骨髓间质干细胞治疗肝纤维化的疗效己得到很多实验的证实,但其机制仍不明确.目的:实验观察骨髓间质干细胞移植后肝星状细胞的凋亡情况,初步探讨骨髓间质干细胞治疗肝纤维化的机制.方法:连续8周皮下注射CCl_4诱导大鼠肝纤维化.造模成功后,20只大鼠随机分为实验组及对照组,每组10只.实验组经尾静脉注射骨髓间充质干细胞,对照组经尾静脉注射DMEM培养液.于移植前,移植后第3,7天分别处死大鼠,取其肝脏行羟脯氨酸的检测,苏木精-伊红染色及masson染色,免疫组织化学检测α-SMA及α-SMA+TUNEL双染反映肝星状细胞活化及其凋亡情况.结果与结论:造模8周后,大鼠肝脏羟脯氨酸含最明显升高,病理呈进展性肝纤维化表现.移植7 d后,实验组大鼠肝脏羟脯氨酸含量明显降低,肝纤维化有所缓解,而对照组的肝纤维化程度继续加重.免疫组织化学显示,CCl_4注射8周后,α-SMA阳性细胞大量增生,移植后第7天,实验组α-SMA阳件细胞明显少于对照组(P＜0.05).移植后第3天,实验组肝星状细胞凋亡明显较对照组增加(P＜0.05).结果提示,骨髓间质干细胞移植有治疗肝纤维化的作用.骨髓间质干细胞诱导肝星状细胞凋亡可能是其治疗肝纤维化的主要机制之一.     

NADPH oxidase signal transduces angiotensin II in hepatic stellate cells and is critical in hepatic fibrosis

Angiotensin II (Ang II) is a pro-oxidant and fibrogenic cytokine. We investigated the role of NADPH oxidase in Ang II-induced effects in hepatic stellate cells (HSCs), a fibrogenic cell type. Human HSCs express mRNAs of key components of nonphagocytic NADPH oxidase. Ang II phosphorylated p47phox, a regulatory subunit of NADPH oxidase, and induced reactive oxygen species formation via NADPH oxidase activity. Ang II phosphorylated AKT and MAPKs and increased AP-1 DNA binding in a redox-sensitive manner. Ang II stimulated DNA synthesis, cell migration, procollagen alpha1(I) mRNA expression, and secretion of TGF-beta1 and inflammatory cytokines. These effects were attenuated by N-acetylcysteine and diphenylene iodonium, an NADPH oxidase inhibitor. Moreover, Ang II induced upregulation of genes potentially involved in hepatic wound-healing response in a redox-sensitive manner, as assessed by microarray analysis. HSCs isolated from p47phox-/- mice displayed a blunted response to Ang II compared with WT cells. We also assessed the role of NADPH oxidase in experimental liver fibrosis. After bile duct ligation, p47phox-/- mice showed attenuated liver injury and fibrosis compared with WT counterparts. Moreover, expression of smooth muscle alpha-actin and expression of TGF-beta1 were reduced in p47phox-/- mice. Thus, NADPH oxidase mediates the actions of Ang II on HSCs and plays a critical role in liver fibrogenesis.     

Cellular targeting of the apoptosis-inducing compound gliotoxin to fibrotic rat livers

Liver fibrosis is associated with proliferation of hepatic stellate cells (HSCs) and their transformation into myofibroblastic cells that synthesize scar tissue. Several studies indicate that induction of apoptosis in myofibroblastic cells may prevent fibrogenesis. Gliotoxin (GTX) was found to induce apoptosis of hepatic cells and caused regression of liver fibrosis. However, the use of apoptosis-inducing drugs may be limited due to lack of cell specificity, with a risk of severe adverse effects. In previous studies, we found that mannose-6-phosphate-modified human serum albumin (M6P-HSA) selectively accumulated in liver fibrogenic cells. The aim of this study therefore was to couple GTX to M6P-HSA and test its pharmacological effects in vitro and in rats with liver fibrosis. The conjugate GTX-M6P-HSA bound specifically to HSCs and reduced their viability. Apoptosis was induced in cultures of human hepatic myofibroblasts (hMFs) and in liver slices obtained from rats with liver fibrosis. In vivo treatment with GTX or GTX-M6P-HSA in bile duct ligated rats revealed a significant decrease in alpha-smooth muscle actin mRNA levels and a reduced staining for this HSC marker in fibrotic livers. In addition, although GTX also affected hepatocytes, GTX-M6P-HSA did not significantly affect other liver cells. In conclusion, we developed an HSC-specific compound that induced apoptosis in human hMFs, rat HSCs, and in fibrotic liver slices. In vivo, both GTX and GTX-M6P-HSA attenuated the number of activated HSCs, but GTX also affected hepatocytes. This study shows that cell-selective delivery of the apoptosis-inducing agent GTX is feasible in fibrotic livers.     

MicroRNA-21 activates hepatic stellate cells via PTEN/Akt signaling

Activation of hepatic stellate cells is the key event in the liver fibrosis. miRs have been shown to play fundamental role in diverse biological and pathological processes. In the present study, we investigated the fibrogenic role of miR-21 in human hepatic stellate LX-2 cells and explored underlying mechanisms. The results showed that treatment of LX-2 cells with platelet-derived growth factor (PDGF)-BB significantly stimulated α1(I) collagen mRNA synthesis and the protein expression of α-SMA, which are characteristics of activation of hepatic stellate cells and simultaneously increased miR-21 expression. Downregulation of miR-21 expression by transfection of anti-miR-21 into LX-2 cells prevented PDGF-BB-induced LX-2 cell activation. Overexpression of miR-21 expression alone also stimulated LX-2 cell activation, while downregulation of miR-21 expression suppressed LX-2 cell activation. miR-21 also played a role in mRNA expression and activity of matrix metalloproteinase 2 (MMP2) in LX-2 cells. Moreover, overexpression of miR-21 decreased protein expression of PTEN in LX-2 cells, resulting in activation of the Akt. Inhibition of Akt signaling by specific inhibitor LY 294002 blocked miR-21-induced fibrogenic effects in LX-2 cells. In summary, miR-21 is an important mediator in LX-2 cell activation. The fibrogenic effects of miR-21 on LX-2 cell activation are mediated through PTEN/Akt pathway. miR-21 may be a potential novel molecular target for the liver fibrosis.     

Rofecoxib has different effects on chemokine production in colorectal cancer cells and tumor immune splenocytes

Cyclooxygenase-2 (COX-2) is overexpressed in colon tumors. Its main product is the immunosuppressive prostaglandin PGE2 that aids tumor immune escape. In this study, we analyzed mechanisms of action of the COX-2 inhibitor rofecoxib on the immune response to colorectal cancer in an animal model. The murine colorectal cancer cell line MC26, and splenocytes from BALB/c mice immune to irradiated MC26 cells, were incubated with rofecoxib or PGE2. In MC26 cells, 100 nM rofecoxib caused a complete abrogation of PGE2 production and inhibited cell proliferation. Splenocytes from tumor immune mice showed a 300% (P<0.01) increase in proliferation in response to irradiated MC26 cells, amplified to 450% (P<0.01) by 1 microM rofecoxib (n=3). MC26 cells incubated with 1 microM rofecoxib showed increased gene expression of CCL3, CCL5, and CCL20 (P<0.01). enzyme-linked immunosorbent assay tests also showed increased production of CCL5 and CCL20 (P<0.01). PGE2 reversed this effect causing a 40% reduction in chemokine gene expression (n=3). In contrast, splenocytes from naive BALB/c mice stimulated with irradiated MC26 cells had only a marginal chemokine response to rofecoxib. PGE2 caused a 50% down-regulation of CCL5 and CCL20 at the gene level (n=2) and 30% and 40% reduction of CCL3, CCL4, CCL5, and CCL20 at the protein level (n=2). Hence rofecoxib has a 2-fold effect upon the immune response to MC26 cells, by enhancing production of chemokines chemotactic for dendritic cells and also reducing PGE2-mediated inhibition of lymphoproliferation. Together, these may be sufficient for an effective TH1-mediated antitumor response. Rofecoxib may have potential as an addition to existing immunotherapy strategies.     

CCL17-expressing dendritic cells drive atherosclerosis by restraining regulatory T cell homeostasis in mice

Immune mechanisms are known to control the pathogenesis of atherosclerosis. However, the exact role of DCs, which are essential for priming of immune responses, remains elusive. We have shown here that the DC-derived chemokine CCL17 is present in advanced human and mouse atherosclerosis and that CCL17+ DCs accumulate in atherosclerotic lesions. In atherosclerosis-prone mice, Ccl17 deficiency entailed a reduction of atherosclerosis, which was dependent on Tregs. Expression of CCL17 by DCs limited the expansion of Tregs by restricting their maintenance and precipitated atherosclerosis in a mechanism conferred by T cells. Conversely, a blocking antibody specific for CCL17 expanded Tregs and reduced atheroprogression. Our data identify DC-derived CCL17 as a central regulator of Treg homeostasis, implicate DCs and their effector functions in atherogenesis, and suggest that CCL17 might be a target for vascular therapy.     

IL-15 protects NKT cells from inhibition by tumor-associated macrophages and enhances antimetastatic activity

Vα24-invariant NKT cells inhibit tumor growth by targeting tumor-associated macrophages (TAMs). Tumor progression therefore requires that TAMs evade NKT cell activity through yet-unknown mechanisms. Here we report that a subset of cells in neuroblastoma (NB) cell lines and primary tumors expresses membrane-bound TNF-α (mbTNF-α). These proinflammatory tumor cells induced production of the chemokine CCL20 from TAMs via activation of the NF-κB signaling pathway, an effect that was amplified in hypoxia. Flow cytometry analyses of human primary NB tumors revealed selective accumulation of CCL20 in TAMs. Neutralization of the chemokine inhibited in vitro migration of NKT cells toward tumor-conditioned hypoxic monocytes and localization of NKT cells to NB grafts in mice. We also found that hypoxia impaired NKT cell viability and function. Thus, CCL20-producing TAMs served as a hypoxic trap for tumor-infiltrating NKT cells. IL-15 protected antigen-activated NKT cells from hypoxia, and transgenic expression of IL-15 in adoptively transferred NKT cells dramatically enhanced their antimetastatic activity in mice. Thus, tumor-induced chemokine production in hypoxic TAMs and consequent chemoattraction and inhibition of NKT cells represents a mechanism of immune escape that can be reversed by adoptive immunotherapy with IL-15-transduced NKT cells.     

骨髓间充质干细胞对四氯化碳诱发大鼠肝纤维化的治疗作用的实验研究

目的探讨骨髓间充质干细胞(BMSCs)对四氯化碳诱发大鼠肝纤维化的治疗作用及其对大鼠肝星状细胞凋亡的影响。方法将清洁级Sprague-Dawley大鼠分4组,A组(正常对照组)、B组(模型组)、C组(骨髓间充质干细胞移植组)、D组(水飞蓟素对照组)。另取sprague-Dawley大鼠制备骨髓间充质干细胞。除A组外,均皮下注射四氯化碳8周,完成后C组给予移植诱导后的骨髓间充质干细胞,D组给予水飞蓟素干预后化学发光法检测4组大鼠血清肝纤维化和肝功能指标,大鼠肝脏作组织病理学检查,分离各组大鼠肝星状细胞,流式细胞仪检测活化的肝星状细胞凋亡的变化。结果各组大鼠纤维化及肝功能结果:A、C、D组数据与B组对应数据比较,A组P<0.01,其余2组P<0.05。结论骨髓间充质干细胞能够显著改善四氯化碳所诱发的大鼠肝纤维化并能使肝星状细胞凋亡增加。     

Intrahepatic microbes govern liver immunity by programming NKT cells

The gut microbiome shapes local and systemic immunity. The liver is presumed to be a protected sterile site. As such, a hepatic microbiome has not been examined. Here, we showed a liver microbiome in mice and humans that is distinct from that of the gut and is enriched in Proteobacteria. It undergoes dynamic alterations with age and is influenced by the environment and host physiology. Fecal microbial transfer experiments revealed that the liver microbiome is populated from the gut in a highly selective manner. Hepatic immunity is dependent on the microbiome, specifically the bacteroidetes species. Targeting bacteroidetes with oral antibiotics reduced hepatic immune cells by approximately 90%, prevented antigen-presenting cell (APC) maturation, and mitigated adaptive immunity. Mechanistically, our findings are consistent with presentation of bacteroidetes-derived glycosphingolipids to NKT cells promoting CCL5 signaling, which drives hepatic leukocyte expansion and activation, among other possible host-microbe interactions. Collectively, we reveal a microbial/glycosphingolipid/NKT/CCL5 axis that underlies hepatic immunity.     

Cross-talk between farnesoid-X-receptor (FXR) and peroxisome proliferator-activated receptor gamma contributes to the antifibrotic activity of FXR ligands in rodent models of liver cirrhosis

The nuclear receptors farnesoid X receptor (FXR) and peroxisome proliferator-activated receptor (PPAR)gamma exert counter-regulatory effects on hepatic stellate cells (HSCs) and protect against liver fibrosis development in rodents. Here, we investigated whether FXR ligands regulate PPARgamma expression in HSCs and models of liver fibrosis induced in rats by porcine serum and carbon tetrachloride administration and bile duct ligation. Our results demonstrate that HSCs trans-differentiation associated with suppression of PPARgamma mRNA expression, whereas FXR mRNA was unchanged. Exposure of cells to natural and synthetic ligands of FXR, including 6-ethyl chenodeoxycholic acid (6-ECDCA), a synthetic derivative of chenodeoxycholic acid, reversed this effect and increased PPARgamma mRNA by approximately 40-fold. Submaximally effective concentrations of FXR and PPARgamma ligands were additive in inhibiting alpha1(I) collagen mRNA accumulation induced by transforming growth factor (TGF)beta1. Administration of 6-ECDCA in rats rendered cirrhotic by porcine serum and carbon tetrachloride administration or bile duct ligation reverted down-regulation of PPARgamma mRNA expression in HSCs. Cotreatment with 6-ECDCA potentiates the antifibrotic activity of rosiglitazone, a PPARgamma ligand, in the porcine serum model as measured by morphometric analysis of liver collagen content, hydroxyproline, and liver expression of alpha1(I) collagen mRNA, alpha-smooth muscle actin, fibronectin, TGFbeta1, and tissue inhibitor of metalloprotease 1 and 2, whereas it enhanced the expression of PPARgamma and uncoupling protein 2, a PPARgamma-regulated gene, by 2-fold. In conclusion, by using an in vitro and in vivo approach, we demonstrated that FXR ligands up-regulate PPARgamma mRNA in HSCs and in rodent models of liver fibrosis. A FXR-PPARgamma cascade exerts counter-regulatory effects in HSCs activation.     

Directly induced hepatogenic cells derived from human fibroblast ameliorate liver fibrosis

Recently, reprogramming technology has emerged as a fascinating tool to generate specific tissue cells. In this study, we tested the hypothesis that ultrasound‐directed cellular reprogramming can generate fibroblasts into hepatogenic cells. We directly induced human dermal fibroblasts (HDFs) into hepatocyte‐like cells mediated by environmental transition‐guided cellular reprogramming (h/entr) using ultrasound. We confirmed the characteristics of h/entr by the expression levels of hepatocyte specific RNA and proteins. The effects of h/entr on the activation of hepatic stellate cells were analyzed using conditioned medium (CM). h/entr were transplanted into mice with acute liver fibrosis and the therapeutic effects and mechanism of liver fibrosis were determined. h/entr exhibited high levels of hepatocyte specific genes, hepatogenic (hepatocyte growth factor [HGF], colony‐stimulating factor 3 [CSF‐3]) and anti‐inflammatory (interleukin 10 [IL‐10]) factors. h/entr CM suppressed the activation of hepatic stellate cells in vitro. Transplantation of h/entr significantly delayed liver fibrosis and improved liver function. Transplantation of h/entr accelerates liver regeneration, and human albumin expressing h/entr and human Alu gene were detected in the mouse livers. This report suggests that directly induced h/entr could be one of the highly effective therapeutic options for the treatment of liver cirrhotic disease.     

Coagulation status modulates murine hepatic fibrogenesis: implications for the development of novel therapies

Summary.  Background:  There is strong evidence demonstrating that coagulation system activation contributes to wound healing and promotes organ fibrosis. Several epidemiological studies have now shown that prothrombotic status, including carriage of the factor (F)V Leiden mutation, is associated with rapid progression of hepatic fibrosis. Objectives:  To assess the effect of a procoagulant state on progression of hepatic fibrosis in a controlled environment and to test whether anticoagulation could attenuate fibrogenesis. Methods:  We investigated the effects of coagulation status on liver fibrosis development in a mouse model of chronic toxic liver injury. Prothrombotic FV Leiden mutant mice, C57BL/6 control animals and anticoagulated mice were studied after chronic exposure to carbon tetrachloride. Results:  Carriage of the FV Leiden mutation caused a significant increase in hepatic fibrosis. Anticoagulation with warfarin significantly reduced fibrosis progression in wild-type mice but was less effective against the profibrotic FV Leiden mutation. Changes in the fibrosis scores were mirrored by changes in liver hydroxyproline content and hepatic stellate cell activation detected by α-smooth muscle actin expression. Conclusions:  These results demonstrate that coagulation status has a strong influence on hepatic fibrogenesis. It is likely that thrombin signaling through the proteinase-activated receptor 1 (PAR₁) receptor expressed on hepatic stellate cells is responsible for this relationship. These results represent the first reported use of anticoagulation to slow hepatic fibrogenesis and suggest a potential novel anti-fibrotic therapeutic approach for the future.     

Cannabinoid receptor 1 signaling in hepatocytes and stellate cells does not contribute to NAFLD

The endocannabinoid system regulates appetite and energy expenditure and inhibitors of cannabinoid receptor 1 (CB-1) induce weight loss with improvement in components of the metabolic syndrome. While CB-1 blockage in brain is responsible for weight loss, many of the metabolic benefits associated with CB-1 blockade have been attributed to inhibition of CB-1 signaling in the periphery. As a result, there has been interest in developing a peripherally restricted CB-1 inhibitor for the treatment of nonalcoholic fatty liver disease (NAFLD) that would lack the unwanted centrally mediated side effects. Here, we produced mice that lacked CB-1 in hepatocytes or stellate cells to determine if CB-1 signaling contributes to the development of NAFLD or liver fibrosis. Deletion of CB-1 in hepatocytes did not alter the development of NAFLD in mice fed a high-sucrose diet (HSD) or a high-fat diet (HFD). Similarly, deletion of CB-1 specifically in stellate cells also did not prevent the development of NAFLD in mice fed the HFD, nor did it protect mice from carbon tetrachloride–induced fibrosis. Combined, these studies do not support a direct role for hepatocyte or stellate cell CB-1 signaling in the development of NAFLD or liver fibrosis.     

人骨髓间质干细胞对肝星状细胞的体外调控

背景:目前肝纤维化尚没有公认的特效疗法,近年来骨髓间质干细胞应用于肝纤维化的治疗已取得一定效果,但具体机制仍不明确.目的:体外探讨人骨髓间质干细胞对肝星状细胞的调控作用.设计、时间及地点:细胞学体外观察,于2008-06/12在中山大学干细胞与组织工程研究中心、中山大学第三附属医院中心实验室完成.材料:骨髓来源于青年健康志愿者髂骨,入肝星状细胞购自中山大学实验动物中心,人正常肝细胞系L-02购自中山大学实验动物中心.方法:将分离提纯的人骨髓间质干细胞与肝星状细胞在β孔Transwell板上建立上下共培养体系.接种密度均为2×104cells/well.另设L-02代替人骨髓间质干细胞作为阴性对照,单纯培养的肝星状细胞为空白对照,培养72 h.主要观察指标:肝星状细胞形态及免疫细胞化学染色结果,流式细胞仪检测肝星状细胞凋亡情况,Western blot法检测肝星状细胞活化标志α-肌动蛋白的表达.结果:倒置显微镜下活化的肝星状细胞呈扁平状,胞浆内缺乏脂肪滴,α-肌动蛋白位于肝星状细胞胞质内,呈高张力纤维状分布.与L-02+肝星状细胞组、单纯肝星状细胞组比较,骨髓间质干细胞+肝星状细胞共培养组的肝星状细胞凋亡率明显升高(P<0.05),α-肌动蛋白表达水平明显下调.结论:人骨髓间质干细胞可抑制肝星状细胞活化,促进其凋亡,这可能是骨髓间质干细胞抗肝纤维化的作用机制.