The use of scanning electron microscopy in the study of the intestinal villi

Contributions of the microbiome to intestinal inflammation in a gut-on-a-chip

The intestinal microbiome affects a number of biological functions of the organism. Although the animal model is a powerful tool to study the relationship between the host and microbe, a physiologically relevant in vitro human intestinal system has still unmet needs. Thus, the establishment of an in vitro living cell-based system of the intestine that can mimic the mechanical, structural, absorptive, transport and pathophysiological properties of the human intestinal environment along with its commensal bacterial strains can promote pharmaceutical development and potentially replace animal testing. In this paper, we present a microfluidic-based gut model which allows co-culture of human and microbial cells to mimic the gastrointestinal structure. The gut microenvironment is recreated by flowing fluid at a low rate (21 μL/h) over the microchannels. Under these conditions, we demonstrated the capability of gut-on-a-chip to recapitulate in vivo relevance epithelial cell differentiation including highly polarized epithelium, mucus secretion, and tight membrane integrity. Additionally, we observed that the co-culture of damaged epithelial layer with the probiotics resulted in a substantial responded recovery of barrier function without bacterial overgrowth in a gut-on-a-chip. Therefore, this gut-on-a-chip could promote explorations interaction with host between microbe and provide the insights into questions of fundamental research linking the intestinal microbiome to human health and disease.

Establishment and Application of Peristaltic Human Gut-Vessel Microsystem for Studying Host-Microbial Interaction

Intestinal floras influence a lot of biological functions of the organism. Although animal model are strong tools for researches on the relationship between host and microbe, a physiologically relevant in vitro human gut model was still required. Here, a novel human gut-vessel microfluidic system was established to study the host–microbial interaction. Peristaltic motion of the cells on the chip was driven by a pneumatic pump. When intestinal epithelial cells (Caco2) were co-cultured with vascular endothelial cells (HUVECs) on the peristaltic microfluidic chip, Caco2 showed normal barrier and absorption functions after 5 days cultivation, which generally took 21 days in static Transwell models. Intestinal microvilli and glycocalyx layer were seen after 4 days cultivation, and Lactobacillus casei was successfully co-cultured for a week in the intestinal cavity. A model for intestinal damage and inflammatory responses caused by E. coli was set up on this chip, which were successfully suppressed by Lactobacillus casei or antibiotic. In summary, this human gut-vessel microfluidic system showed a good potential for investigating the host–microbial interaction and the effect and mechanism of microbiome on intestinal diseases in vitro.

White Scours in Piglets; II. Scanning Electron Microscopy of the Mucosa of the Small Intestine

The mucosa of the small intestine of clinically normal piglets and of piglets with white scours was investigated, using a scanning electron microscope. No new findings on the rough villous pattern of the small intestinal mucosa could be added to those obtained with the stereomicroscope. In the high range of magnification, however, the surface of the different villous forms showed features that could barely be seen with the stereomicroscope. The findings indicate that in general the microstructure of the villous surface differs in the various types of villi.

Contributions of microbiome and mechanical deformation to intestinal bacterial overgrowth and inflammation in a human gut-on-a-chip

A human gut-on-a-chip microdevice was used to coculture multiple commensal microbes in contact with living human intestinal epithelial cells for more than a week in vitro and to analyze how gut microbiome, inflammatory cells, and peristalsis-associated mechanical deformations independently contribute to intestinal bacterial overgrowth and inflammation. This in vitro model replicated results from past animal and human studies, including demonstration that probiotic and antibiotic therapies can suppress villus injury induced by pathogenic bacteria. By ceasing peristalsis-like motions while maintaining luminal flow, lack of epithelial deformation was shown to trigger bacterial overgrowth similar to that observed in patients with ileus and inflammatory bowel disease. Analysis of intestinal inflammation on-chip revealed that immune cells and lipopolysaccharide endotoxin together stimulate epithelial cells to produce four proinflammatory cytokines (IL-8, IL-6, IL-1β, and TNF-α) that are necessary and sufficient to induce villus injury and compromise intestinal barrier function. Thus, this human gut-on-a-chip can be used to analyze contributions of microbiome to intestinal pathophysiology and dissect disease mechanisms in a controlled manner that is not possible using existing in vitro systems or animal models.

Effect of rutin against gastric esophageal reflux in experimental animals

CONTEXT

The present study was undertaken to elucidate the effect of rutin against gastric esophageal reflux in experimental animals.

METHODS

Groups of rats, fasted overnight received normal saline (3 ml/kg, sham control) or esophagitis control (3 ml/kg, normal saline) or pantoprazole (30 mg/kg) or rutin (50 and 100 mg/kg) were subjected to pylorus and forestomach ligation. Animals were sacrificed after 12 h and scrutinized physiologically (gastric pH, total acidity, free acidity and esophagitis index), biochemically (TBAR's, SOD, catalase, GSH and protein carbonyl) and morphologically. The esophageal tissues were also inquested for the presence of proinflammatory (IL-2 and IL-1β) and immunoregulatory (IL-4 and IL-6) cytokines.

RESULTS

The results demonstrated momentous physiological, biochemical and morphological protection imparted by rutin. The rutin also restored the altered levels of proinflammatory and immunoregulatory cytokines, which further strengthens the implication of rutin in GERD.

CONCLUSION

The beneficial effects as observed in the current experiment could be accredited to the antioxidant and anti-inflammatory (through inhibition of COX and LOX) property of rutin.

Analysis of the expression of p53 during the morphogenesis of the gastroesophageal mucosa of Gallus gallus domesticus (Linnaeus, 1758)

Ontogenesis comprises a series of events including cell proliferation and apoptosis and resulting in the normal development of the embryo. Protein p53 has been described as being involved in the development of several animal species. The aim of this study was to analyze the expression of protein p53 during the morphogenesis of the gastroesophageal mucosa of Gallus gallus domesticus and to correlate it with the histogenesis of structures present in this tissue. We used 24 embryos (at 12-20 days of incubation) and the thymus of two chickens. Immunohistochemical analysis was performed with the ABC indirect method. The expression of p53 in the gastroesophageal mucosa increased during the formation of the organ, mainly at the stages during which tissue remodeling and cell differentiation began. In the esophagus at stages 42 and 45, we observed immunoreactive (IR) cells in the surface epithelium and in early esophageal glands. In the proventriculus at stages 39-45, IR cells were present in the epithelial mucosa and rarely in the proventricular glands. In the gizzard after stage 42, we found IR cells mainly in the medial and basal epithelial layers of the mucosa and especially within the intercellular spaces that appeared at this phase and formed the tubular gland ducts. Thus, protein p53 occurs at key stages of development: in the esophagus during the remodeling of esophageal glands, in the proventriculus during the differentiation of the epithelium of the mucosa and in the gizzard during the formation of tubular glands.

[Early fetal development of the small intestine mucosa in cattle (Bos primigenius taurus)]

The development of the bovine small intestine was examined in 24 embryos and fetuses by light microscopic, scanning and transmission electron microscopic methods. Special reference was paid to the genesis of the epithelium and particularly of the villi intestinales. The primitive intestine consists of one layer of epithelial cells surrounded by mesenchym and tunica serosa. The fetal intestine (up to the 24th week of gestation) shows all the morphologic structures of the adult. In small intestine the development of cryptae and villi intestinales starts before the 7th week of gestation and progresses with a proximo-distal gradient. Epithelial proliferation that gives rise to primary epithelial villi makes epithelium become temporarily stratified. Finger-like secondary villi develop by proliferation of the mesenchym. In addition to this process mucosal folds occur in duodenum giving rise to villi by segmentation. At the same time the differentiation of epithelium starts. The fetal small intestine, like many other fetal tissues displays masses of glycogen.

The effect of an elemental diet with and without gluten on disease activity in dermatitis herpetiformis

Elemental diets are reported to decrease activity of patients with dermatitis herpetiformis. We tested the hypothesis that gluten, given in addition to an elemental diet, is responsible for the intestinal abnormalities, cutaneous immunoreactant deposition, and skin disease activity in dermatitis herpetiformis. At entry eight patients with dermatitis herpetiformis, who were consuming unrestricted diets, were stabilized on their suppressive medications at dosage levels that allowed individual lesions to erupt. Six patients were then given an elemental diet plus 30 of gluten for 2 weeks, followed by the elemental diet alone for 2 weeks. Conversely, two patients received an elemental diet alone for 2 weeks followed by an elemental diet plus gluten during the final 2 weeks. Small bowel biopsies, skin biopsies, and clinical assessments were done at 0, 2, and 4 weeks. Suppressive medication dose requirement decreased over the 4 weeks by a mean of 66%. Six of eight subjects significantly improved clinically during the gluten-challenge phase of the elemental diet and all were improved at the end of the study. The amount of IgA in perilesional skin did not change significantly, but the amount of C3 increased in five of seven evaluable subjects after gluten challenge. Circulating anti-gluten and anti-endomysial antibodies were not significantly affected by the diets. All subjects completing evaluable small bowel biopsies (seven of seven) demonstrated worsening of their villus architecture (by scanning electron microscopy and intraepithelial lymphocyte counts) during gluten challenge and improvement (six of six subjects) after 2 weeks of elemental dietary intake. We conclude that 1) there is a significant improvement in clinical disease activity on an elemental diet, independent of gluten administration, 2) small bowel morphology improves rapidly on an elemental diet, and 3) complement deposition but neither IgA deposition nor circulating antibody levels correlate with gluten intake. It seems likely that dietary factors other than gluten are important in the pathogenesis of the skin lesions in dermatitis herpetiformis.

Effect of soy protein on calves' intestinal absorptive ability and morphology determined by scanning electron microscopy

Neonatal calves were fed whole milk (control) or one of three milk replacers with one-third of the total protein supplied by casein, Promocaf (a commercial soy protein concentrate), or an experimental soy flour. Xylose absorption was studied at 3 and 8 wk after a 12-h fast. Urine was collected for 5 h, and jugular blood was sampled at 0, 2.5, and 5 h after administration of xylose. Urinary excretions of xylose at 8 wk were 3.4, 5.3, 7.8, and 21.3% of xylose administered, respectively, for calves fed Promocaf, soy flour, casein, and milk. Increases in plasma xylose 2.5 h after administration were 7.7, 21.3, 31.8, and 46.5 mg/dl. Calves were sacrificed at 12 or 14 wk and duodenal tissues sampled for scanning electron microscopy. Micrographs revealed normal intestinal morphology with long, round, tapering villi when milk was fed. Casein feeding produced shorter, broader villi than did feeding whole milk. Abnormalities included absence of villi and short, blunted, convoluted villi on mucosal surfaces of calves fed soy proteins. Reduced surface area for intestinal absorption probably resulted from villous atrophy in calves with abnormal mucosae. Impairment of absorptive ability appears to be associated with morphological changes in intestinal structure.

Gluten-sensitive enteropathy: sequence of villous regrowth as viewed by scanning electron microscopy

Small-intestinal biopsy specimens from five children with gluten-sensitive enteropathy (GSE) were studied by scanning electron microscopy (SEM) before dietary treatment and sequentially after removal of gluten from the the diet. Compared with biopsy specimens from patients without evidence of villous atrophy, these specimens showed marked architectural changes. In patients with total villous atrophy observed by light microscopy, absent villi and prominent crypts were observed by SEM. Patients with subtotal villous atrophy had the first stages of villous formation characterized by semicircular ridge formation. Biopsy specimens obtained from the five patients with GSE after dietary treatment demonstrated a sequence of changes characterizing villous repair. The earliest change consisted of semicircular elevations of cells around the crypts. Unequal cellular repletion around the crypts and migration of the cells led to the formation of parallel ridges. Increased cell proliferation resulted in thickening and twisting of the ridges to form convoluted ridges. Increased complexity of the ridges appears to lead to the formation of cerebriform ridges, and septation at various points in the ridges results in the formation of mitten-like villi. In biopsy specimens from patients with villous atrophy from other causes, similar reparative changes were seen by SEM. Scanning electron microscopy is a useful adjunct to the light microscopic and dissecting microscopic assessment of small intestine biopsy specimens, and may be more sensitive tan light microscopy in documenting early morphologic response to dietary treatment for gluten-sensitive enteropathy.

Scanning electron microscopy, autolysis, and irradiation as techniques for studying small intestinal morphology

Examination of autolysed control mouse small intestine using scanning electron microscopy has revealed details of the connective tissue components of the mucosa. The cores of the villi are seen collapsed across the intervillous basin. Crypts of Lieberkuhn are seen as tubular channels stretching down from the intervillous basin. Sometimes the crypts are split in two by a connective tissue septum. The mouths of the crypts of Lieberkuhn are, in general, arranged in double rows between the single rows of villi. The ratio of number of crypts to numbers of villi was calculated as 5.01:1. This is close to the figure of 4.53:1, as quoted by Smith & Jarvis (1980) who used differential interference contrast microscopy to investigate the crypt to villus ratio. After radiation, the severe drop in the number of crypt mouths can be clearly seen by the combination of autolysis and scanning electron microscopy: the rows of crypt mouths between the villi have been lost, and many crypt mouths have been occluded by stromal tissue. The arrangement of the crypt mouths and the observation of mucosal abnormalities after irradiation have led to the postulation that cells leaving the crypt mouths move in a spiral manner towards and then up the villous surface: this postulated movement might imply an asymmetry in some properties of enterocytes. The use of scanning electron microscopy in conjugation with autolysis and irradiation has thus forced a critical re-examination of the relationships between crypts and villi.

Multinucleate giant enterocytes in small intestinal villi after irradiation

Scanning electron microscopy of the small intestine of the mouse 5 days after X- or neutron irradiation has revealed the formation of giant cells on the villus surface. Correlative light microscopy and transmission electron microscopy have shown that these giant cells are syncytial in nature. Characteristic features of lipid inclusions and apical microvilli suggest tha these syncytia are giant enterocytes. It has also been shown that these giant cells are in contact with the connective tissue core of the villus and have a close contact with the normal enterocytes, thus maintaining mucosal integrity. It is postulated that radiation damage has caused incomplete separation during mitosis and that attempted division occurs outside the crypts of Lieberkuhn.

Toxoplasma Gondii: scanning electron microscope studies on the small intestine of infected and uninfected cats

The mucosal surfaces of villi from the small intestine of cats infected with Toxoplasma gondii were studied with the scanning electron microscope and compared with those from uninfected control cats. In uninfected cats villi were predominantly leaf shaped and were lined with ridges; goblet cell openings could be seen. The enterocytes had a hexagonal surface outline and were dome-shaped. Infected cats had both normal and abnormal villi. Injured villi were shortened and attained a broad leaf shape, often with blunt edges. Enterocytes containing oocysts were enlarged, and microvilli were resolvable only on these surfaces. Ruptured cells from which parasite discharge had occurred were seen. Oocysts were observed and possessed a smooth coat.

Crohn's disease: a scanning electron microscopic study

A scanning electron microscopic study of Crohn's disease was done using surgically resected specimens. Grossly normal resection margins as well as nonulcerated portions from diseased areas were selected for study. Scanning electron microscopic findings in Crohn's disease included changes in villous size and shape, villous fusion and epithelial bridge formation, goblet cell hypertrophy and hyperplasia, and increased secretion of mucus. These changes were marked in involved areas, and many were also present in six of seven margins of resection available for study in the ileal group. The abnormalities found in grossly normal margins of resection suggest a more widespread involvement than can be appreciated by gross and light microscopic examination of the specimen. Formation of the increased coat of mucus observed may be stimulated by a number of agents and could contribute to an enhanced barrier function in areas of early involvement in Crohn's disease, thereby decreasing the uptake of toxic or antigenic macromolecules. A decrease in bacterial superinfections would also be facilitated. Later lesions, with severe villous changes and hypersecretion of mucus, may favor the uptake of toxic and antigenic macromolecules as well as aid in the establishment of bacterial superinfections.

Scanning electron microscopic studies of ileal epithelial cells in suckling rats

The ileal epithelial cells containing the tubulo-vacuolar systems and supranuclear vacuoles in suckling rats were investigated with scanning electron microscopy, using specimens treated with osmium-thiocarbohydrazide-osmium staining methods, and critical point drying and cracking. The cracked surface of the apical cytoplasm is seen as irregular and small hollows and pores of the anastomosing and branching tubulo-vacuolar system. The cracked surface of the supranuclear vacuoles shows the ellipsoidal structures. Numerous pores of various size and irregular shape are present on the apical inner surface of the supranuclear vacuole. These pores are clearly the openings from the tubulo-vacuolar system to the supranuclear vacuole. Some small pores are visible on the inner lateral surface of the supranuclear vacuole, especially near the nucleus. They are probably the pathways of the absorbed materials from the supranuclear vacuole into the lateral cytoplasm. Usually, the inclusions of the supranuclear vacuole reveal the globes or coarse and sponge-like networks.

Scanning electron microscopy of the small intestine of a normal unsuckled calf and a calf with enteric colibacillosis

Sections of the small intestine were taken under general anaesthesia from a normal calf and from a calf with enteric colibacillosis and examined by scanning electron and light microscopy. In the normal calf villi were long and oval throughout the intestine and in the challenged calf there was villous stunting and fusion in the distal small intestine.

Scanning electron microscopy of the duodenal mucosa of chickens infected with Eimeria acervulina

The morphology of the duodenal mucosal surface of chickens infected with Eimeria acervulina has been studied on days 5, 6, 8 and 11 post-infection and compared with that of the normal duodenal mucosa using the scanning electron microscope. The normal duodenum possessed tall, spatulate villi with horizontally-arranged surface clefts upon which a regular pattern of hexagonal absorptive cells and goblet cell mouths was superimposed. A maximum degree of villous atrophy was shown on day 5 post-infection, the villi being thickened and flattened with frequent adhesions and fusions between them. The general effects of the disease together with the physical presence of intracellular parasites caused considerable changes in size and shape of the cell apices. By day 8 the mucosa was clearly recovering, with a normal pattern of somewhat thickened and truncated villi beginning to re-appear and by day 11 post-infection the mucosa had regained an outwardly normal morphological pattern. The mucosal changes are discussed in relation to similar changes which occur in diseases of the alimentary tract of other animals, including man.

Scanning electron microscopy of the duodenal mucosa of lambs infected with Trichostrongylus colubriformis

Duodenal mucosae of uninfected lambs and lambs inoculated at least 16 days earlier with 85000–140000 Trichostrongylus colubriformis larvae were examined with the scanning electron microscope. Normal duodenum had tall spatulate villi with surface folds upon which goblet cells and a regular pattern of hexagonal enterocytes were seen. Micro villi on normal enterocytes were closely packed and imparted a granular surface texture. In heavily infected areas of gut the villi were atrophic, the mucosa sometimes being composed of irregular masses and ridges, with crypt mouths, often surrounded by collars of cells, opening into the surface. More severely affected mucosae were flat, with protuberant collars of cells surrounding crypt mouths. There were rounded bodies, interpreted as sloughing enterocytes, or inflammatory cells, on the mucosal surface. Apices of enterocytes were domed and microvilli were sparse and irregular. Micro-organisms were numerous on cell surfaces. Nematodes were located in sinuous thin-walled tunnels in the epithelium. The mucosal microtopography is compared with that of coeliac disease of humans, nippostrongylosis in rats and with villus atrophy in pigs.