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Results for “Intestinal Barrier Function”

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PubMed2006

Absence of bacterially induced RELMbeta reduces injury in the dextran sodium sulfate model of colitis.

Although inflammatory bowel disease (IBD) is the result of a dysregulated immune response to commensal gut bacteria in genetically predisposed individuals, the mechanism(s) by which bacteria lead to the development of IBD are unknown. Interestingly, deletion of intestinal goblet cells protects against intestinal injury, suggesting that this epithelial cell lineage may produce molecules that exacerbate IBD. We previously reported that resistin-like molecule beta (RELMbeta; also known as FIZZ2) is an intestinal goblet cell-specific protein that is induced upon bacterial colonization whereupon it is expressed in the ileum and colon, regions of the gut most often involved in IBD. Herein, we show that disruption of this gene reduces the severity of colitis in the dextran sodium sulfate (DSS) model of murine colonic injury. Although RELMbeta does not alter colonic epithelial proliferation or barrier function, we show that recombinant protein activates macrophages to produce TNF-alpha both in vitro and in vivo. RELMbeta expression is also strongly induced in the terminal ileum of the SAMP1/Fc model of IBD. These results suggest a model whereby the loss of epithelial barrier function by DSS results in the activation of the innate mucosal response by RELMbeta located in the lumen, supporting the hypothesis that this protein is a link among goblet cells, commensal bacteria, and the pathogenesis of IBD.

Animals↗

PubMed2000

Innervation of the cavernous body of the human efferent tear ducts and function in tear outflow mechanism.

The lacrimal sac and nasolacrimal duct are surrounded by a wide cavernous system of veins and arteries comparable to a cavernous body. The present study aimed to demonstrate the ultrastructure of the nervous tissue and the localisation of neuropeptides involved in the innervation of the cavernous body, a topic not previously investigated. Different S-100 protein antisera, neuronal markers (neuron-specific enolase, anti-200 kDa neurofilament), neuropeptides (substance P, neuropeptide Y, calcitonin gene-related peptide, vasoactive intestinal polypeptide) and the neuronal enzyme tyrosine hydroxylase were used to demonstrate the distribution pattern of the nervous tissue. The ultrastructure of the innervating nerve fibres was also examined by means of standard transmission electron microscopy. The cavernous body contained specialised arteries and veins known as barrier arteries, capacitance veins, and throttle veins. Perivascularly, the tissue was rich in myelinated and unmyelinated nerve fibres in a plexus-like network. Small seromucous glands found in the region of the fundus of the lacrimal sac were contacted by nerve fibres forming a plexus around their alveoli. Many nerve fibres were positive for S-100 protein (S 100), neuron-specific enolase (NSE), anti-200 kDa neurofilament (RT 97), calcitonin gene-related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY). Vasoactive intestinal polypeptide (VIP) immunoreactivity was only demonstrated adjacent to the seromucous glands. Both the density of nerve fibres as well as the presence of various neuropeptides emphasises the neural control of the cavernous body of the human efferent tear ducts. By means of this innervation, the specialised blood vessels permit regulation of blood flow by opening and closing the lumen of the lacrimal passage as effected by the engorgement and subsidence of the cavernous body, at the same time regulating tear outflow. Related functions such as a role in the occurrence of epiphora related to emotional responses are relevant. Moreover, malfunction in the innervation of the cavernous body may lead to disturbances in the tear outflow cycle, ocular congestion or total occlusion of the lacrimal passages.

Adult↗

PubMed1983

Further research into the possibility of salmonella-free fattening and slaughter of pigs.

At a pig-fattening farm in the south-western Veluwe which was infected with salmonellas it was sought to achieve salmonella-free fattening in a specially adapted piggery. The test piggery was thoroughly cleaned and disinfected and measures were taken to exclude birds, insects and rodents. An attempt was also made to obtain salmonella-free piglets. Clean clothing, special footwear and disinfectants were used when entering the piggery. During the experiment an infection was detected in the test piggery caused by the same salmonella serotypes as had only been found immediately before the test at the breeding farm. Other salmonella serotypes occurring at the fattening farm did not find their way into the test piggery, and therefore it can be concluded that after the pigs had been brought in all the hygienic barriers functioned adequately. The test showed that the hygienic measures taken had a beneficial effect on growth performance, even though salmonellas were not entirely excluded. After fattening the pigs were slaughtered in two groups. The first group was slaughtered in the usual way, but with the second group extra care was taken with the individual singeing of the carcasses and the careful removal of the intestines. Tests on the carcasses showed that 46% of the pigs in the first group were contaminated with salmonellas as against only 7% in the second. From this it can be concluded that slaughter need not lead to further contamination by salmonellas present in the intestines; indeed, carefully carrying out the slaughter process can even reduce the contamination of the surface of pig carcasses by salmonellas.

Abattoirs↗

PubMed2004

The immune-enhancing enteral agents arginine and glutamine differentially modulate gut barrier function following mesenteric ischemia/reperfusion.

BACKGROUND: Immune-enhancing enteral diets have been shown to improve patient outcome. One contributing mechanism may be via maintenance of gut barrier function. While recent data has shown that glutamine is beneficial, arginine may be harmful. We therefore hypothesized that the immune-enhancing agents, glutamine and arginine, differentially modulate gut barrier function. METHODS: At laparotomy, rats had jejunal sacs filled with 10 mmol/L glutamine, arginine, fructose, or magnesium sulfate (osmotic control) followed by 60 minutes of superior mesenteric artery occlusion and 2 hours of reperfusion. Jejunum was harvested for histology, deconvolution microscopy, F:G actin, ATP, and permeability measurements. RESULTS: Glutamine and fructose minimized mucosal injury compared with controls and arginine. Deconvolution microscopy confirmed that glutamine and fructose preserved the actin cytoskeleton but there was disruption by arginine which correlated with F:G actin ratios and tissue ATP levels. Permeability was enhanced by arginine compared with the other groups. CONCLUSION: Arginine resulted in worsened mucosal injury, disruption of the actin cytoskeleton, decreased tissue ATP and enhanced permeability compared with glutamine which appeared protective. The immune-enhancing agent arginine results in breakdown of gut barrier function which may have important implications for critically injured patients.

Actins↗

PubMed1998

Signal transduction pathways involved in enterohemorrhagic Escherichia coli-induced alterations in T84 epithelial permeability.

Enterohemorrhagic Escherichia coli (EHEC) infection is associated with watery diarrhea and can lead to complications, including hemorrhagic colitis and the hemolytic-uremic syndrome. The mechanisms by which these organisms produce diarrheal disease remain to be elucidated. Changes in T84 epithelial cell electrophysiology were examined following EHEC infection. T84 cell monolayers infected with EHEC O157:H7 displayed a time-dependent decrease in transepithelial resistance. Increases in the transepithelial flux of both [3H]mannitol and 51Cr-EDTA accompanied the EHEC-induced decreases in T84 resistance. Altered barrier function induced by EHEC occurred at the level of the tight junction since immunofluorescent staining of the tight-junction-associated protein ZO-1 was disrupted when examined by confocal microscopy. Decreased resistance induced by EHEC involved a protein kinase C (PKC)-dependent pathway as the highly specific PKC inhibitor, CGP41251, abrogated the EHEC-induced drop in resistance. PKC activity was also increased in T84 cells infected with EHEC. Calmodulin and myosin light chain kinase played a role in EHEC-induced resistance changes as inhibition of these effector molecules partially reversed the effects of EHEC on barrier function. These studies demonstrate that intracellular signal transduction pathways activated following EHEC infection link the increases in T84 epithelial permeability induced by this pathogen.

Calmodulin↗

PubMed1987

Cellular retinoid-binding proteins.

A number of specific carrier proteins for members of the vitamin A family have been discovered. Two of these proteins bind all-trans-retinol and are found within cells important in vitamin A metabolism or function. These two proteins have considerable sequence homology and have been named cellular retinol-binding protein (CRBP) and cellular retinol-binding protein, type II (CRBP [II]). A third intracellular protein, cellular retinoic acid-binding protein (CRABP) also is structurally similar but binds only retinoic acid. Although retinol appears to be bound quite similarly by the two retinol-binding proteins, subtle differences are apparent that appear to be related to the different functions of the two proteins. That, coupled with the specific cellular locations of the two proteins, suggests their roles. Cellular retinol-binding protein appears to have several roles, including (1) delivering retinol to specific binding sites within the nucleus and (2) participating in the transepithelial movement of retinol across certain blood-organ barriers. In contrast, CRBP (II) appears to be involved in the intestinal absorption of vitamin A and, in particular, may direct retinol to a specific esterifying enzyme, resulting in the production of fatty acyl esters of retinol that are incorporated into chylomicrons for release to the lymph. Like CRBP, CRABP can deliver its ligand retinoic acid to specific binding sites within the nucleus, sites different from those for retinol. The nuclear binding of retinol and retinoic acid may be part of the mechanism by which vitamin A directs the state of differentiation of epithelial tissue.

Amino Acid Sequence↗

PubMedDate not supplied

[Functional state of the immunological system and of the gastrointestinal tract in children with a food allergy].

A group of 37 children suffering from bronchial asthma of an atopic and combined genesis and also from allergy attended by skin manifestations have been examined. The general immunologic system has been shown to be strongly imbalanced which manifested in hypo-, hyper- or dysimmunoglobulinemia and in IgE accumulation by the blood. Most of the children showed increased permeability of the epithelial barrier of the intestine by food antigens, that was associated with appearance in the blood of agglutinating antibodies to food proteins. In addition, most of the children had dyskinesia of the biliary tract and intestine as well as altered microecology of the gastrointestinal tract.

Agglutinins↗

PubMed1996

Morphologic changes in intestinal mucosa with urinary contact--effects of urine or disuse?

PURPOSE: To evaluate the morphological changes induced in bypassed ileal and colonic segments and the influence of the urine on the mucosal histology. MATERIALS AND METHODS: In a rat model, an isolated ileocolonic segment was used for construction of an ileocolocystoplasty or an exteriorized blind loop. Sham-operated animals were used for control. RESULTS: In ileal mucosa, villi and microvilli were better preserved when exposed to urine than when deprived of contact with luminal content. Numerical reduction of microvilli was found in colonic mucosa deprived of luminal content. In colonic mucosa exposed to urine some areas were denuded of microvilli and showed blebs. Findings of intact tight junctions in all specimens implied that an important morphological requirement of maintained epithelial barrier function is present in mucosa deprived of normal luminal stimulation and also after contact with urine. The intracellular ultrastructural changes in both colon and ileum were similar in the 2 groups. However, there were more solitary ribosomes lying free in the mucosa exposed to urine, indicating depressed or arrested protein synthesis. CONCLUSIONS: Mucosa in contact with urine seems to maintain surface characteristics better than mucosa deprived of luminal stimulation, indicating that factors present in the urine may be important for the epithelial cell physiology. Certain intracellular changes were found more often in mucosa exposed to urine, but there were no major differences. The changes noticed may indicate enterocyte adaptation to a new physiologic environment.

Animals↗

PubMed2006

Surface modification and initial adhesion events for intestinal epithelial cells.

Rapid resealing of the mucosal epithelia is imperative following injuries to the small intestine because the mucosa is responsible for the adsorption of nutrients as well as providing a barrier to noxious agents present in the lumen. Tissue engineering may provide a possible solution for treating intestinal erosions, ulcerations, inflammatory bowel disease, and infection. Cell-biomaterial interaction is a critical component in tissue engineering that can determine the success of the tissue construct. Cell-biomaterial interactions can be enhanced by various types of surface modification, which promote integrin ligation leading to increased cell function. In order to relate the effect of surface adhesion molecules to signaling events and macroscopic cell response, an intestinal epithelial cell line, IEC-6, was plated on fibronectin (receptor-mediated) and poly-L-lysine (non-specific) surfaces. Focal adhesion kinase (FAK) phosphorylation, cell spreading, and cell adhesion strength were measured. Results showed increases in FAK phosphorylation generally corresponded to increases in cell spreading and adhesion strength for IEC-6 cells. Therefore, in a simplified system, initial adhesion and signaling mechanisms appeared to correspond to subsequent physical responses in IEC-6 cells relevant to tissue engineering applications.

Animals↗

PubMed2001

[Stimulation of immunoglobulin E formation in chronic pancreatitis by alcohol drinking and exocrine pancreatic insufficiency].

Many patients with chronic pancreatitis (CP) complain of several types of food intolerance despite elimination of fat and alcohol. Since there are no data on serum immunoglobulin E (IgE) concentrations in CP, IgE concentrations in serum were detected in 97 persons with CP and 50 controls. IgE was analyzed by the use of a highly sensitive fluoro-enzyme-immunoassay. In CP, a significantly raised IgE level (mean +/- SEM; 286.1 +/- 49 KU/L; p < 0.0001) was detected compared with controls (65.2 +/- 13 KU/L). CP-patients without alcohol consumption and normal exocrine pancreatic function were found to have only slightly elevated serum IgE values (120.2 +/- 54 KU/L), whereas patients with exocrine insufficiency treated with enzyme supplementation showed an IgE level of 153.7 +/- 51 and exocrine insufficient patients without treatment of 261.0 +/- 173 KU/L (p = 0.01). IgE levels were far more elevated in the corresponding groups with continued alcohol consumption (> 25 g/day). Alcohol consuming patients with CP and normal pancreatic function had a mean serum IgE of 295.0 +/- 114 KU/L, while patients with alcohol consumption and sufficiently treated exocrine pancreatic insufficiency showed a serum IgE of 393.7 +/- 147 KU/L (p = 0.03). Non-enzyme supplemented patients with CP and exocrine pancreatic insufficiency were characterized by approximately 10-fold increased serum IgE (1080.0 +/- 313 KU/L; p = 0.001). Non-allergic, alcohol consuming patients with CP have significantly increased serum IgE values. Since patients without alcohol consumption and normal pancreatic function or sufficiently treated exocrine insufficiency showed clearly lower IgE values than non-compliant patients with manifest exocrine pancreatic insufficiency, these results are compatible with the assumption that a reduced rate of antigen digestion in exocrine pancreatic insufficiency may lead to an increased intestinal antigen load, stimulating an abnormal humoral immune response with IgE production. Alcohol may further contribute to this by damaging the mucosal barrier.

Adult↗

PubMedDate not supplied

Recent developments in short-chain fatty acid metabolism.

Bacterial translocation across the bowel wall has recently been proposed as a major problem in the stressed patient. Consequently, there has been considerable interest in fostering bowel wall integrity as a barrier to bacteria and endotoxin. One postulated means to promote this barrier function has been through the provision of the preferred fuels of the bowel wall. Among these are the short-chain fatty acids (SCFAs) which are found to a limited extent in the diet but are primarily produced through the fermentation of non-digestible carbohydrates by the bacterial flora of the colon. In both animal and human studies, SCFAs have been shown to stimulate intestinal mucosal growth. Because non-digestible carbohydrates, after colonic fermentation, are precursors to SCFAs, similar effects to those found with direct provision of SCFAs may be anticipated. Pectin, beta-glucan, and lactulose are among the many available nonabsorbable carbohydrates that could serve as a source of these trophic stimulants to colonic mucosa. Short-chain fatty acids and their precursors deserve extensive and clinical evaluation to define their ultimate role in human disease.

Animals↗

PubMed2002

Lipopolysaccharide-induced enterocyte-derived nitric oxide induces intestinal monolayer permeability in an autocrine fashion.

Studies indicate that endotoxin (LPS) causes intestinal injury, increases inducible nitric oxide synthase (iNOS) activity, leads to increased NO production, and promotes bacterial translocation (BT). To investigate the mechanism by which LPS causes gut injury and to test the hypothesis that NO produced by enterocytes promotes gut injury in an autocrine fashion, rat intestinal epithelial cell (IEC-6) monolayers were tested. IEC-6 monolayers grown in a bicameral system were incubated with media or with LPS (25 microg/mL) and tested for permeability to phenol red, BT, and nitrate/nitrite (NO2/NO3) production. To determine the direct effect of NO on permeability, monolayers were incubated with the NO donor S-nitroso-acetylpenicillinamide (SNAP; 1 mM) and tested for permeability. Next, the protective effects of two NOS inhibitors (L-NMMA and L-NIL) were tested. Finally, to determine if LPS-induced permeability occurs via a poly (ADP-ribose) synthetase- (PARS) dependent pathway, monolayers incubated with LPS alone or with the PARS inhibitor, INH2BP (100 microM) were tested. LPS significantly increased IEC-6 permeability to phenol red, as well as increased NO2/NO3 by 20-fold (P < 0.001) and increased BT 10-fold (P < 0.001). SNAP mimicked the effect of LPS and significantly increased both permeability to phenol red and BT. Inhibition of iNOS significantly decreased the LPS-induced increase in monolayer permeability and BT (P < 0.05). Monolayers incubated with INH2BP had significantly decreased permeability to phenol red and BT, suggesting that LPS-induced NO production increases monolayer permeability at least in part via a PARS-dependent mechanism. In summary, LPS-induced disruption of monolayer barrier function appears to be related, at least in part, to enterocyte produced NO. This supports the hypothesis that NO produced by LPS-stimulated enterocytes promotes injury in an autocrine fashion and highlights the fact that enterocytes can be a target as well as a producer of NO.

Animals↗

PubMed2002

Physical and psychological stress in rats enhances colonic epithelial permeability via peripheral CRH.

Stress may be a contributing factor in intestinal inflammatory disease; however, the underlying mechanisms have not been elucidated. We previously reported that acute stress altered jejunal epithelial physiology. In this study, we examined both physical and psychological stress-induced functional changes in colonic mucosa. Colonic mucosal tissue from rats subjected to either 2 hr of cold-restraint stress or 1 hr of water-avoidance stress demonstrated altered ionic transport as well as significantly elevated baseline conductance (ionic permeability) and flux of horseradish peroxidase (macromolecular permeability). Intraperitoneal pretreatment with the corticotropin-releasing hormone (CRH) antagonist, a helical CRH(9-41), inhibited the stress-induced abnormalities, while exogenous intraperitoneal administration of CRH, to control rats, mimicked the stress responses and in vitro CRH increased the macromolecular permeability. These results suggest that peripheral CRH mediates stress-induced colonic pathophysiology. We speculate that a stress-induced barrier defect may allow uptake of immunogenic substances into the colonic mucosa, initiating or exacerbating intestinal inflammation.

Animals↗

PubMed2001

[Pancreatitis and nutrition. Significance of the gastrointestinal tract and nutrition for septic complications].

Septic complications are an important factor for the morbidity and mortality of acute pancreatitis. The gut has been identified as a source of infection early in the course of the disease allowing intestinal bacteria to translocate into pancreatic necrosis and other organs. Bacterial translocation is promoted by an impaired intestinal mucosal barrier which can be attributed to the reduced oxygen and substrate supply of the intestine during the early systemic response to the pancreatic injury. A rat model of severe acute pancreatitis has been used to confirm the hypothesis that an impaired mucosal barrier can be stabilized by supplying certain nutritients, vitamins and trace elements. Following a discussion of the many aspects of bacterial translocation and gut derived sepsis, the role of the gut and nutrition for the development of septic complications in acute pancreatitis is summarized as follows: Early in the course of acute pancreatitis the gut is a target organ of the primary systemic inflammatory response (SIRS) to pancreatic injury. SIRS-induced gut barrier dysfunction promoting bacterial translocation makes the gut the motor for secondary (septic) complications. As a septic focus the gut becomes a target for therapeutic measures aimed at stabilizing the impaired gut barrier. Nutritive factors demonstrated to improve impaired gut barrier function include early enteral feeding and specific factors like glutamine which are essential for enterocytes and colonocytes in stress. Experimental data are presented to underline the significance of these nutritive factors and subsequent randomized multicenter trials performed to verify the positive experimental results are introduced. The effect of other nutritive factors (e.g. omega-3-fatty acids) has not yet been systemically investigated. Thus, experimental and clinical studies need to be performed for evaluating their effect on bacterial translocation and the disease course in acute pancreatitis.

Animals↗

PubMed2002

[Biopharmaceutical studies on molecular mechanisms of membrane transport].

By incorporating the transporter-mediated or receptor-mediated transport process in physiologically based pharmacokinetic models, we succeeded in the quantitative prediction of plasma and tissue concentrations of beta-lactam antibiotics, insulin, pentazocine, quinolone antibacterial agents, and inaperizone and digoxin. The author's research on transporter-mediated pharmacokinetics focuses on the molecular and functional characteristics of drug transporters such as oligopeptide transporter, monocarboxylic acid transporter, anion antiporter, organic anion transporters, organic cation/carnitine transporters (OCTNs), and the ATP-binding cassette transporters P-glycoprotein and MRP2. We have successfully demonstrated that these transporters play important roles in the influxes and/or effluxes of drugs in intestinal and renal epithelial cells, hepatocytes, and brain capillary endothelial cells that form the blood-brain barrier. In the systemic carnitine deficiency (SCD) phenotype mouse model, juvenile visceral steatosis (jvs) mouse, a mutation in the OCTN2 gene was found. Furthermore, several types of mutation in human SCD patients were found, demonstrating that OCTN2 is a physiologically important carnitine transporter. Interestingly, OCTNs transport carnitine in a sodium-dependent manner and various cationic drugs transport it in a sodium-independent manner. OCTNs are thought to be multifunctional transporters for the uptake of carnitine into tissue cells and for the elimination of intracellular organic cationic drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2006

Multidrug transporters as drug targets.

Transport molecules can significantly affect the pharmacodynamics and pharmacokinetics of drugs. An important transport molecule, the 170 kDa P-glycoprotein (Pgp), is constitutively expressed at several organ sites in the human body. Pgp is expressed at the blood-brain barrier, in the kidneys, liver, intestines and in certain T cells. Other transporters such as the multidrug resistance protein 1 (MRP1) and MRP2 also contribute to drug distribution in the human body, although to a lesser extent than Pgp. These three transporters, and especially Pgp, are often targets of drugs. Pgp can be an intentional or unintentional target. It is directly targeted when one wants to block its function by a modifier drug so that another drug, also a substrate of Pgp, can penetrate the cell membrane, which would otherwise be impermeable. Unintentional targeting occurs when several drugs are administered to a patient and as a consequence, the physiological function of Pgp is blocked at different organ sites. Like Pgp, MRP1 also has the capacity to mediate transport of many drugs and other compounds. MRP1 has a protective role in preventing accumulation of toxic compounds and drugs in epithelial tissue covering the choroid plexus/cerebrospinal fluid compartment, oral epithelium, sertoli cells, intesticular tubules and urinary collecting duct cells. MRP2 primarily transports weakly basic drugs and bilirubin from the liver to bile. Most compounds that efficiently block Pgp have only low affinity for MRP1 and MRP2. There are only a few effective and specific MRP inhibitors available. Drug targeting of these transporters may play a role in cancer chemotherapy and in the pharmacokinetics of substrate drugs.

Animals↗

PubMed1999

Myofibroblasts. II. Intestinal subepithelial myofibroblasts.

Intestinal subepithelial myofibroblasts (ISEMF) and the interstitial cells of Cajal are the two types of myofibroblasts identified in the intestine. Intestinal myofibroblasts are activated and proliferate in response to various growth factors, particularly the platelet-derived growth factor (PDGF) family, which includes PDGF-BB and stem cell factor (SCF), through expression of PDGF receptors and the SCF receptor c-kit. ISEMF have been shown to play important roles in the organogenesis of the intestine, and growth factors and cytokines secreted by these cells promote epithelial restitution and proliferation, i.e., wound repair. Their role in the fibrosis of Crohn's disease and collagenous colitis is being investigated. Through cyclooxygenase (COX)-1 and COX-2 activation, ISEMF augment intestinal ion secretion in response to certain secretagogues. By forming a subepithelial barrier to Na(+) diffusion, they create a hypertonic compartment that may account for the ability of the gut to transport fluid against an adverse osmotic gradient. Through the paracrine secretion of prostaglandins and growth factors (e.g., transforming growth factor-beta), ISEMF may play a role in colonic tumorigenesis and metastasis. COX-2 in polyp ISEMF may be a target for nonsteroidal anti-inflammatory drugs (NSAIDs), which would account for the regression of the neoplasms in familial adenomatous polyposis and the preventive effect of NSAIDs in the development of sporadic colon neoplasms. More investigation is needed to clarify the functions of these pleiotropic cells.

Animals↗

PubMed2002

Transport of chitosan microparticles for mucosal vaccine delivery in a human intestinal M-cell model.

Uptake of particulate antigen carrier systems by specialized M-cells of the gut-associated lymphoid tissue is still a limiting step in inducing efficient immune responses after oral vaccination. Although transport of soluble drugs over the epithelial barrier of the gut is extensively studied in vitro by using the Caco-2 cell model, this was for long time not possible for particles due to the absence of M-cells. By co-culturing Caco-2 cells with cultured human B-lymphocytes (Raji-cells), cells which are morphologically and functionally similar to M-cells can be induced. This human M-cells model makes it possible to study the uptake of microparticles for oral vaccine delivery. In this way, chitosan microparticles, which have demonstrated to target the Peyer's patches efficiently in vivo, could be tested in vitro. The development of this M-cells model facilitates the optimization of the microparticles in order to target them even more efficiently to the M-cells in the gut. In this study, the integrity of the human M-cell model was investigated by determining the transepithelial electrical resistance (TEER), 14C-mannitol transport and morphology using scanning electron microscopy. The uptake of particles was investigated by measuring transport of both fluorescently labeled microspheres (Fluospheres) and chitosan microparticles using flowcytometry. No discontinuities or abnormalities could be found in the co-culture. Scanning electron microscopy showed that morphologically different cells were present in the human M-cell model. Both commercially available Fluospheres (size 0.2 microm) and chitosan microparticles (size 1.7 microm) for oral vaccine delivery were transported at a significantly higher amount by the human M-cell model compared to the transport by the Caco-2 cell monoculture. Since chitosan microparticles were proven to be taken up by Peyer's patches in mice as well, this human M-cell model is able to predict the M-cell uptake of microparticles for oral vaccine delivery. This M-cell model is a new tool, which can be used to scan, develop and optimize microparticles for oral vaccine delivery. Since the M-cell uptake can now be studied in vitro, the targeting of these cells can be studied more efficiently and can now be done in cells from human origin.

B-Lymphocytes↗