Damaging effects of gliadin on three-dimensional cell culture model

AIM: To evaluate the effects of gliadin on the oxidative environment in the "in vivo-like" model of a three-dimensional cell culture system. METHODS: LoVo cell line (intestinal adenocarcinoma) multicellular spheroids were treated with digested gliadin (with albumin used as a control). Spheroid volumes, cell viability and morphology, lactate dehydrogenase (LDH) release, content of reduced glutathione (GSH) and activity of GSH-related enzymes were examined. The data were statistically analyzed using the Student's t-test (P<0.05). was considered statistically significant. RESULTS: Gliadin reduced cell viability (from 20% to 60%) and led to morphological alterations characterized by apoptotic findings and cytoskeletal injuries. LDH activity increased. The content of GSH reduced (-20% vs controls), and activity of GSH-related enzymes was significantly inhibited. CONCLUSION: Gliadin treatment induces an imbalance in the antioxidative mechanism of cells cultured by the three-dimensional technique. This alteration may explain the cell damage directly caused by gliadin and the subsequent morphological abnormalities.     

Chinese medicinal compound delisheng has satisfactory anti-tumor activity, and is associated with up-regulation of endostatin in human hepatocellular carcinoma cell line HepG2 in three-dimensional culture

AIM： TO investigate the multicellular resistance of human hepatocellular carcinoma HepG2 cells in three-dimensional culture to delisheng, 5-fluorouracil and adriamycin, and the possible molecular mechanisms of delisheng.
METHODS： Human hepatocellular carcinoma HepG2 cells were cultured with a liquid overlay technique. After the formation of multicellular spheroids, morphology was analyzed by phase contrast microscopy, scanning electron microscopy and transmission electron microscopy. Sensitivity of HepG2 cells to delisheng, 5-fluorouracil and adriamycin was investigated by Ml-I- assay in multicelluar spheroids and monolayers. Vascular endothelial growth factor （VEGF） and endostatin expression were analyzed in multicellular spheroids treated with delisheng, 5-fluorouracil, adriamycin and negative control PBS, with immunohistochemical staining.
RESULTS： Multicellular spheroids exhibited structural characteristics somewhat different to those in monolayers. The cells in three-dimensional cell culture turned out to be less sensitive to delisheng, 5-fluorouracil and adriamycin than the cells cultured in monolayer. This showed that delisheng had a satisfactory cells inhibition ratio compared to 5-fluorouracil and adriamycin. Immunohistochemical staining showed that VEGF and endostatin expression was positive during growth as multicellular spheroids, and endostatin expression in spheroids with treatment of delisheng was higher than that with 5-fluorouracil, adriamycin and PBS （139.35 ± 7.83, 159.23 ± 10.34, 162.83 ± 3.47 and 148.48 ± 11.06, P 〈 0.05）.
CONCLUSION： Chinese medicine compound delisheng has satisfactory anti-tumor activity in HepG2 cells in three-dimensional culture, and the effects are associated with up-regulation of endostatin.     

Early effects of gliadin on enterocyte intracellular signalling involved in intestinal barrier function

BACKGROUND AND AIMS: Despite the progress made in understanding the immunological aspects of the pathogenesis of coeliac disease (CD), the early steps that allow gliadin to cross the intestinal barrier are still largely unknown. The aim of this study was to establish whether gliadin activates a zonulin dependent enterocyte intracellular signalling pathway(s) leading to increased intestinal permeability. METHODS: The effect of gliadin on the enterocyte actin cytoskeleton was studied on rat intestinal epithelial (IEC-6) cell cultures by fluorescence microscopy and spectrofluorimetry. Zonulin concentration was measured on cell culture supernatants by enzyme linked immunosorbent assay. Transepithelial intestinal resistance (Rt) was measured on ex vivo intestinal tissues mounted in Ussing chambers. RESULTS: Incubation of cells with gliadin led to a reversible protein kinase C (PKC) mediated actin polymerisation temporarily coincident with zonulin release. A significant reduction in Rt was observed after gliadin addition on rabbit intestinal mucosa mounted in Ussing chambers. Pretreatment with the zonulin inhibitor FZI/0 abolished the gliadin induced actin polymerisation and Rt reduction but not zonulin release. CONCLUSIONS: Gliadin induces zonulin release in intestinal epithelial cells in vitro. Activation of the zonulin pathway by PKC mediated cytoskeleton reorganisation and tight junction opening leads to a rapid increase in intestinal permeability.     

Antiproliferative effects of free and liposome-encapsulated retinoic acid in a squamous carcinoma model: monolayer cells and multicellular tumor spheroids

Summary Antiproliferative effects of free retinoic acid (RA) and liposome-encapsulated RA (RAlp) were compared in a squamous carcinoma system using both monolayer cells and multicellular tumor spheroids (MTS), an in-vivo-like model with three-dimensional histological structure. Initial studies examined the effect of lipid composition on the efficiency of RA encapsulation and on the subsequent toxicity of RAlp to red blood cells. In 5-day growth assays for monolayer cells, RA and RAlp (1 M-0.1 nM) produced similar growth inhibition. In 6-day growth assays for MTS, RAlp was shown to have increased effectiveness. Liposomal uptake by the squamous carcinoma cells was examined by culturing monolayers and MTS with fluorescence-tagged liposomes and examining them under fluorescence microscopy between days 1 and 6. Phagocytosed liposomes were present, but their low levels suggested that other mechanisms of drug delivery such as adsorption, fusion or direct lipid transfer probably occurred for RAlp. Histological examination of MTS showed that RA and RAlp produced similar alterations. In this squamous carcinoma system, liposomes are effective in delivering retinoic acid and in producing biological effects in monolayer cells and within the three-dimensional structure of MTS.Abbreviations MTS multicellular tumor spheroids - SCC squamous cell carcinoma - RA free -all-trans-retinoic acid - RAlp lipo-some-encapsulated RA - PtdCho dimyristoylglycerophosphocholine - PtdGro dimyristoylglycerophosphoglycerol This work was supported in part by M. D. Anderson Annual Campaign Funds and by United States Public Health Service grants CA38751 and CA57166 from the National Cancer InstitutePresent address: Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York; NY 10021, USA     

Structural and functional features of bile canaliculi in adult rat hepatocyte spheroids

Abstract: Spheroids of adult rat hepatocytes are spherical cell aggregates which retain three-dimensional architecture and hepatocyte specific functions. In this study, we investigated the detailed structure and function of bile canaliculi in spheroids. Hepatocytes were prepared from adult rat liver and cultured with epidermal growth factor (50 ng/ml). Hepatocytes formed floating spheroids 4 days after inoculation. The morphology of hepatocyte spheroids was investigated after fluorescent staining for actin using confocal laser scanning microscopy and electron microscopy. To study the function of bile canaliculi, the transcellular transport of fluorescein diacetate was observed. These experiments were performed in a control group and in a group treated with the actin inhibitor cytochalasin B. In a control group, spheroids contained bile canalicular structures which were surrounded by actin filaments. Added fluorescent dye was secreted and pooled in bile canaliculi. Cytochalasin B caused marked distention of bile canaliculi and prominent accumulation of secreted fluorescent dye in dilated bile canaliculi. This phenomenon was based on the impairment of contractile movement of bile canaliculi. These results demonstrate that hepatocyte spheroids maintain functional and morphological peculiarity, and therefore this model may be useful in investigation of the mechanism of bile formation and intrahepatic cholestasis.     

Serum signaling factors and spheroids

Normal epithelial cells grow as a sheet-like structure. Upon malignant transformation, epithelial cells grow as multicell aggregates. Adopted in tissue culture, most tumor cells revert to adherent monolayer. In tissue culture, as early as 1958, anchorage-independent multicellular spheroid cancer cells have been shown to revert to adherent monolayer in response to extracellular serum signaling factors. Such serum signaling factors have not yet been characterized. Recent studies reveal that the conversion of adherent monolayer to multicellular spheroids is also mediated by serum signaling factors such as carcinoembryonal antigen, interferon-gamma, insulin-like growth factor-II, heregulin beta1 and plasmin. The reports provide a new approach to investigate the regulatory system of tumor cell growth pattern as well as the effect of the change in growth pattern on various cellular functions.     

Unexpected role of surface transglutaminase type II in celiac disease

BACKGROUND & AIMS: In celiac disease (CD), transglutaminase type II (TG2) has 2 fundamental roles: (1) as the autoantigen recognized by highly specific autoantibodies and (2) the modifier of pathogenic gliadin T-cell epitopes. It follows that inhibition of TG2 might represent an attractive strategy to curb the toxic action of gliadin. Here we studied the validity of this strategy using the organ culture approach. METHODS: Duodenal biopsy specimens from 30 treated patients with CD, 33 untreated patients with CD, and 24 controls were cultured with or without gliadin peptides p31-43, palpha-9, and deamidated palpha-9 for 20 minutes, 3 hours, and 24 hours. In 31 patients with CD and 16 controls, TG2 inhibitor R283 or anti-TG CUB 7402 or anti-surface TG2 (6B9) mAbs were used in cultures. T84 cells were also cultured with or without peptides with or without TG inhibitors. Mucosal modifications after culture were assessed by immunofluorescence, in situ detection of TG activity, confocal microscopy, and fluorescence-activated cell sorter analysis. RESULTS: The enzymatic inhibition of TG2 only controlled gliadin-specific T-cell activation. The binding of surface TG2 contained gliadin-specific T-cell activation and p31-43-induced actin rearrangement, epithelial phosphorylation, and apoptosis, both in organ cultures and T84 cells. CONCLUSIONS: These data indicate a novel and unexpected biological role for surface TG2 in the pathogenesis of CD suggesting a third role for TG2 in CD. These results have a specific impact for celiac disease, with wider implications indicating a novel biologic function of TG2 with possible repercussions in other diseases.     

Hepatocyte dynamics in a three-dimensional rotating bioreactor

BACKGROUND AND AIMS: The use of an artificial liver system with extracorporeal circulation or a three-dimensional bioreactor perfused with liquid culture medium inevitably exposes hepatocytes to fluid mechanical stress (MS). The expression of liver-specific hepatocyte functions seems to be modulated by the magnitude of MS. Nonetheless, few studies have focused on the direct effects of MS on hepatocytes. We subjected hepatocytes to MS using an MS loading device and investigated the effects on the cytoskeleton and hepatocyte dynamics inside three-dimensional scaffolds by monitoring the changes in actin fiber, one of the components of the cytoskeleton. We also assessed the influence of MS on specific hepatocyte functions. METHODS: We subjected hepatocytes to MS by a rotating radial flow bioreactor (RRFB) and examined the effects by comparing the MS-loaded culture cells with cells cultured under stationary conditions without MS loading. The hepatocytes (1 x 10(6)/cm(3)) were seeded on gauze without collagen coating and examined to determine morphological changes after 60 h incubation. Actin filaments in samples from the MS-loaded hepatocyte culture were stained by fluorescein isothiocyanate-labeled phalloidin. RESULTS: Hepatocyte aggregation was observed in the MS-loaded culture, but not in the unloaded stationary culture. Better albumin products were observed in the MS-loaded group than in the stationary culture group at all measurement points. Actin filaments extended toward the scaffold after the start of MS loading incubation and polymerized around the hepatocytes. The hepatocyte aggregation eventually advanced to the formation of spheroids. CONCLUSION: These results suggest that MS-induced polymerization of actin filaments stimulate hepatocyte aggregation and thereby improve hepatocyte-specific function.     

Acquired multicellular-mediated resistance to alkylating agents in cancer.

EMT-6 murine mammary tumor sublines highly resistant to cyclophosphamide, cis-diamminedichloro-platinum(II), or N,N',N"-triethylenethiophosphoramide were generated in vivo by sequential treatment of tumor-bearing mice with the respective drugs. Previous studies demonstrated the drug-resistant phenotypes of the sublines were not expressed in vitro when the cells were grown as monolayer cultures. We now show that expression of drug resistance--including patterns of cross-drug resistance observed in vivo--can be fully recapitulated in vitro when the cells are grown under in vivo-like, three-dimensional conditions--namely, as multicellular tumor spheroids. Moreover, the spheroids generated from all of the drug-resistant sublines manifested a much more compact structure. Immediate drug-sensitivity testing of single cells released by trypsin treatment from compact drug-resistant spheroids revealed that such cells lost much of their drug-resistant properties. The results suggest a possible mechanism of acquired drug resistance in tumors based on the response of a cell population (i.e., multicellular or tissue resistance) as opposed to classic (uni)cellular resistance mechanisms.     

Short exposure to millimolar concentrations of ethanol induces apoptotic cell death in multicellular HepG2 spheroids

Purpose: We have shown previously that 1 mM ethanol reduces cell proliferation and increases apoptosis in monolayers of human hepatocellular carcinoma (HepG2) cells. However, in vivo liver tumors are usually three-dimensional and multicellular. The purpose of this study was therefore to determine the effect of ethanol in multicellular tumor spheroids (MCTS) as a model system in vitro. Methods: After the application of 1 mM ethanol for 24 h and 48 h, viable, apoptotic and necrotic cells within MCTS were stained with specific fluorescent dyes, and their amount and distribution within the MCTS were assessed by confocal laser scanning microscopy. To evaluate the effect on HepG2 cell migration and cell proliferation, the outgrowth potential after 1 week in culture was evaluated. Results: As assessed by YO-PRO-1 staining, ethanol increased the number of apoptotic cells from 21.5 units (U) in control spheroids to 364 U and 482.2 U after 24 h and 48 h in ethanol-treated spheroids, respectively (P < 0.001). Merocyanine staining fluorescence increased from 10.7 U in the control to 122 U after 24 h and 293.2 U after 48 h (P < 0.001). Cell viability, as determined by staining with the acetoxymethyl ester of calcein, decreased from 578.5 U in the control to 236 U and 73.4 U after 24 h and 48 h of ethanol exposure respectively (P < 0.001). Necrosis showed an increase from 2 U in control to 24.9 after 24 h and 54 U after 48 h. MCTS treated with ethanol showed almost complete inhibition of outgrowth potential after 1 week in culture, compared to controls (P < 0.005). Conclusions: Small concentrations of ethanol (1 mM) induced apoptosis in HepG2 MCTS with a concomitant inhibition on outgrowth potential, accompanied with a low degree of necrosis. These findings suggest that low concentrations of ethanol may already be sufficient for the treatment of hepatocellular carcinoma. Received: 20 July 1999 / Accepted: 27 November 1999     

Multicellular gastric cancer spheroids recapitulate growth pattern and differentiation phenotype of human gastric carcinomas

BACKGROUND & AIMS: Advanced gastric cancer has a poor prognosis and is largely unresponsive to currently available chemotherapeutic drugs. The development of more effective therapies would be aided by better preclinical models. METHODS: An in vitro multicellular gastric cancer spheroid model was established using the liquid overlay technique and compared with the corresponding xenografts in immunodeficient mice. RESULTS: Twelve of 17 (71%) gastric cancer cell lines reflected growth characteristics of their parental gastric carcinomas in three-dimensional culture. Thus, cell lines derived from peritoneal and pleural carcinomatosis grew as single cells (HSC-39, KATO-II, KATO-III) and cell aggregates (SNU-5, SNU-16). Cell lines representing adenosquamous (MKN-1) and tubular differentiation (MKN-28, MKN-74, N87) formed partly compact multicellular spheroids recapitulating the tumor architecture of the respective original tumor. The differentiated phenotype was lost after subcutaneous implantation of the in vitro spheroids in mice. The degree of morphologic differentiation was reflected by the levels of mucin and constitutive E-cadherin expression. Heterogeneous changes of other adhesion molecules (EpCAM, alpha2beta1, CD44s, Le(x), sLe(x)) were observed. In contrast, cell lines derived from poorly differentiated gastric carcinomas (Hs-746T, RF-1, RF-48) formed fully compact spheroids mimicking the poorly differentiated phenotype, were E-cadherin negative, and showed only CD44s up-regulation. CONCLUSIONS: Recapitulating some complexity of their in vivo counterparts, multicellular gastric cancer spheroids may represent a physiologically valid model for studying the biology of this cancer, and testing new therapeutic strategies.     

Lack of intestinal mucosal toxicity of Triticum monococcum in celiac disease patients

OBJECTIVE: The treatment of celiac disease is based on lifelong withdrawal of foods containing gluten. Unfortunately, compliance with a gluten-free diet has proved poor in many patients (mainly due to its low palatability), emphasizing the need for cereal varieties that are not toxic for celiac patients. In evolutionary terms, Triticum monococcum is the oldest and most primitive cultivated wheat. The aim of this study was to evaluate the toxicity of T. monococcum on small intestinal mucosa, using an in vitro organ culture system. MATERIAL AND METHODS: Distal duodenum biopsies of 12 treated celiac patients and 17 control subjects were cultured for 24 h with T. aestivum (bread) gliadin (1 mg/ml) or with T. monococcum gliadin (1 mg/ml). Biopsies cultured with medium alone served as controls. Each biopsy was used for conventional histological examination and for immunohistochemical detection of CD3 + intraepithelial lymphocytes (IELs) and HLA-DR. Secreted cytokine protein interferon-gamma (IFN-gamma) was measured in the culture supernatant using an enzyme-linked immunoadsorbent assay. RESULTS: Significant morphological changes, HLA-DR overexpression in the crypt epithelium and an increased number of CD3 + IELs, found after bread gliadin exposure, were not observed in celiac biopsies cultured with T. monococcum gliadin. In contrast, with bread gliadin, there was no significant IFN-gamma response after culture with monococcum gliadin. Similarly, biopsies from normal controls did not respond to bread or monococcum gliadin stimulation. CONCLUSIONS: These data show a lack of toxicity of T. monococcum gliadin in an in vitro organ culture system, suggesting new dietary opportunities for celiac patients.     

Hanging-drop multicellular spheroids as a model of tumour angiogenesis

The establishment of a vascular network within tumours is a key step in the progression towards an aggressive, metastatic state, with poor prognosis. We have developed a novel in vitro model to specifically capture the interaction between endothelial cells and solid tumours. Micro-vascularised in vitro tumour constructs were produced by introducing endothelial cells to multicellular spheroids formed in hanging drops. Upon introduction, the endothelial cells migrated into the tumour spheroid, establishing tubular networks and luminal structures. This system relies on the natural pro-angiogenic capacity of multicellular spheroids, and does not require the addition of exogenous angiogenic factors, or use of extracellular-matrix substitutes.     

Differential survival of cell subpopulations in spheroids after treatment with bleomycin

Summary The cytotoxic effect of bleomycin (BLM) on Chinese hamster V79-cells grown as spheroids is compared to that on monolayer cultures in exponential vs. plateau phase of growth. Cells treated as intact spheroids with BLM (50 g/ml for 1 h) are more sensitive than monolayer cultures. Cell subpopulations derived from different zones of the spheroids survive BLM-treatment to different degrees: When treated as single cells in suspension, the formerly outer cells are less affected than the inner cells. Within intact spheroids, however, progressive cellular resistance with increasing distance from the outer rim is found.     

Ultrastructure of tight junctions in prostaglandin-exposed rat stomach

The effect of intragastric misoprostol, a synthetic prostaglandin E₁ methyl ester analog, on the morphology of rat stomach was studied by transmission and scanning electron microscopy. Adult male Sprague-Dawley rats received misoprostol at dose levels ranging from 50 to 1000 μg/kg body weight and were sacrificed after 30 min. At all dose levels, normal organelle ultrastructure was maintained in epithelial cells on the surface, within gastric pits, and lining the gastric glands. Quantitative freeze-fracture electron microscopy was used to examine the influence of misoprostol on epithelial-cell tight junctions, major structural components of the mucosal barrier. The numbers of intramembrane fibrils and the depths of the tight-junction complexes did not differ significantly between controls and animals exposed to 1000 μg/kg misoprostol (P<0.05). Therefore, alterations in gastric epithelial tight-junction ultrastructure do not appear to account for the cytoprotective effect of misoprostol.     

藤梨根提取物对大肠癌LoVo细胞增殖的抑制作用及诱导凋亡的影响

目的:研究藤梨根提取物(ethanol extract from radix of actinidia chinensis,EERAC)对人大肠癌LoVo细胞增殖和凋亡的影响.方法:提取藤梨根抗癌有效活性成分(EERAC),按浓度分为4处理组(10、40、160、320mg/L)和空白对照组(0mg/L).各实验组经作用24、48、72h后,进行一般形态学和AO/EB荧光染色观察;MMT法检测细胞增殖的抑制情况;免疫组织化学(immunohistochemistry,IHC)法测定LoVo细胞中凋亡相关基因Bcl-2、Bax、Caspase-3的蛋白表达变化.结果:与空白对照组比较,一般形态学显示EERAC处理组能使细胞密度减低,增殖变慢;细胞逐渐变大,细胞间接触变松,胞浆中颗粒增多,细胞脱壁现象和周围碎片增多;荧光染色观察可见处理组细胞呈橙红色荧光,细胞核出现碎片状或固缩状的凋亡特征学形态改变,凋亡现象与EERAC的浓度呈正相关性;MTT法检测显示,EERAC处理组对LoVo细胞的最佳作用时间为72h,最大抑制率为79.48%,具有浓度和时间的依赖性(P<0.01);IHC检测结果显示EERAC作用LoVo细胞24h后,Bcl-2表达明显减弱,Bax、Caspase-3表达水平明显增高,Bcl-2/Bax比值下降,差异具有统计学意义(P<0.05),其效应与浓度相关.结论:EERAC具有明显抑制LoVo细胞增殖的作用,其机制可能与降低Bcl-2表达,上调Bax、Caspase-3的表达水平,激活线粒体凋亡途径有关.     

全反式维甲酸诱导LoVo细胞分化的动物实验研究

目的：研究经全反式维甲酸（ＡＴＲＡ）诱导分化的结肠癌细胞株（ＬｏＶｏ细胞）在裸鼠体内的致瘤性。方法：将ＡＴＲＡ作用下经５次和１０次传代的ＬｏＶｏ细胞接种于裸鼠皮下,观察移植瘤生长情况。用扫描电镜观察肿瘤细胞的超微结构,用免疫组化法分析肿瘤细胞癌胚抗原（ＣＥＡ）的表达及分泌粘液的性质。结果：经５次传代实验组与对照组裸鼠均有移植瘤形成,但实验组移植瘤生长明显受抑制（Ｐ〈０．０５）。经１０次传代实验组裸     

Endomysial antibody production is not related to histological damage after in vitro gluten challenge

OBJECTIVE: To determine whether in vitro induction of endomysial antibodies is an in vitro marker of coeliac toxicity. DESIGN: To determine whether in vitro endomysial antibodies induced by gliadin incubation correlate with histological damage induced by in vitro gliadin challenge. METHODS: Small-bowel organ cultures from seven patients with treated coeliac disease were incubated in an organ culture system with gliadin; histological damage was morphometrically evaluated and endomysial antibodies were measured in the organ culture supernatant by indirect immunofluorescence. RESULTS: Although incubation with gliadin caused histological damage, there was no detectable production of endomysial antibody. CONCLUSIONS: In vitro, endomysial antibody induction cannot be used as a marker of coeliac toxicity. Endomysial antibodies are not necessary for generating the histological lesion of coeliac disease.