Vacuolated villous epithelium of the small intestine of young pigs

C/EBPα Epigenetically Modulates TFF1 Expression via mC-6 Methylation in the Jejunum Inflammation Induced by a Porcine Coronavirus

Porcine epidemic diarrhea virus (PEDV) is an emerging coronavirus which causes acute diarrhea and destroys gastrointestinal barrier function in neonatal pigs. Trefoil factor 1 (TFF1) is a protective peptide for maintaining the integrity of gastrointestinal mucosa and reducing intestinal inflammation. However, its role in protecting intestinal epithelium against PEDV infection is still unclear. In this study, we discovered that TFF1 expression was activated in the jejunum of pigs with PEDV infection and TFF1 is required for the growth of porcine intestinal epithelial cells. For instance, inhibited cell proliferation and cell arrest were observed when TFF1 is genetically knocked-out using CRISPR-Cas9. Additionally, TFF1 depletion increased viral copy number and PEDV titer, along with the elevated genes involved in antiviral and inflammatory cytokines. The decreased TFF1 mRNA expression is in line with hypermethylation on the gene promoter. Notably, the strong interactions of protein-DNA complexes containing CCAAT motif significantly increased C/EBPα accessibility, whereas hypermethylation of mC-6 loci decreased C/EBPα binding occupancies in TFF1 promoter. Overall, our findings show that PEDV triggers the C/EBPα-mediated epigenetic regulation of TFF1 in intestine epithelium and facilitates host resistance to PEDV and other Coronavirus infections.

Secretory IgA N-glycans contribute to the protection against E. coli O55 infection of germ-free piglets

Mucosal surfaces are colonized by highly diverse commensal microbiota. Coating with secretory IgA (SIgA) promotes the survival of commensal bacteria while it inhibits the invasion by pathogens. Bacterial coating could be mediated by antigen-specific SIgA recognition, polyreactivity, and/or by the SIgA-associated glycans. In contrast to many in vitro studies, only a few reported the effect of SIgA glycans in vivo. Here, we used a germ-free antibody-free newborn piglets model to compare the protective effect of SIgA, SIgA with enzymatically removed N-glycans, Fab, and Fc containing the secretory component (Fc-SC) during oral necrotoxigenic E. coli O55 challenge. SIgA, Fab, and Fc-SC were protective, whereas removal of N-glycans from SIgA reduced SIgA-mediated protection as demonstrated by piglets' intestinal histology, clinical status, and survival. In vitro analyses indicated that deglycosylation of SIgA did not reduce agglutination of E. coli O55. These findings highlight the role of SIgA-associated N-glycans in protection. Further structural studies of SIgA-associated glycans would lead to the identification of those involved in the species-specific inhibition of attachment to corresponding epithelial cells.

A simplified method of preparation of mammalian intestine samples for scanning electron microscopy

Due to strong tissue hydration and complex architecture of the mucous membrane, appropriate preparation of inhomogeneous gastrointestinal tissues, especially from the intestine, for scanning electron microscopy is still a challenge and requires constant improvement of preparation techniques. In this article, we describe a simplified method of preparation of small intestinal mucosa tissues for observations in a scanning electron microscope. We emphasized the most important points in the preparation process that, when ignored, may result in formation of numerous artifacts and the inability to analyze the samples reliably. The developed technique facilitates proper animal tissue sampling in the field conditions, reducing the time of tissue collection and sample preparation as well as the total process costs. The fixative of choice, that is, buffered formalin, fixes, and stiffens the processed tissues properly, which is especially important in preservation of long, highly hydrated intestinal villi without shrinkage artifacts. The method described has been successfully used in comparative studies of the development of small intestines in mammals (pigs, mice, rats), reptiles, and birds (hens).

Immune components in porcine mammary secretions

Immune components present in mammary secretions are reviewed. In swine, the histological structure of the placenta prevents in utero transfer of immunoglobulins and mammary secretions are the sole source of maternal antibody for the neonate. In addition to immunoglobulins, porcine mammary secretions contain significant numbers of maternal cells of various types that may contribute to neonatal immunity, including phagocytes (neutrophils and macrophages), lymphocytes (B and T cells), and epithelial cells. Immunomodulating and/or antimicrobial substances, including lactoferrin, lysozyme, lactoperoxidase, and cytokines, are also present in mammary secretions and may contribute to the protection of the neonate. While the role of immunoglobulins in mammary secretions is well understood, the contribution of cellular components and non-specific immune factors to neonatal immunity remains to be defined.

Small intestinal and pancreatic microstructures are modified by an intraduodenal CCK-A receptor antagonist administration in neonatal calves

The aim of the present study was to investigate the role of CCK on the upper gut and pancreas microstructure and on pancreatic juice secretion in neonatal calves assessed by a repetitive intraduodenal administration of FK480, a CCK-A receptor antagonist, during the first 6 days of life. The experiment was performed on 10 neonatal calves surgically fitted with a pancreatic accessory duct catheter and duodenal cannulas. Calves were sacrificed on day 7 for tissue sampling. Treatment with FK480 resulted in: reduction of preprandial pancreatic juice secretion at days 1-3, smaller size of pancreatic acini and number of cells per acinus, reduction in intestinal crypt depth (except in the duodenal bulb), numerous modifications of intestinal villi length and width, lower mitotic index of crypt cells, and increased number and size of enterocytes with 'empty vacuoles'. In conclusion, the blockade of CCK-A receptors during early life both reduced pancreatic exocrine secretion and induced complex changes in pancreatic microstructure. The influence of CCK on the upper gut microstructure in neonatal calves could be either direct via activation of CCK-A receptors located in the mucosa of the upper gut or indirect by modulation of the secretion of pancreatic juice.

Impact of Yersinia enterocolitica enteritis on disaccharidase activity and small intestinal morphology in colostrum-deprived newborn piglets

The effect of enteritis on the development of the small intestine was examined in newborn, colostrum-deprived piglets infected with a human isolate of Y. enterocolitica (serotype 0:3, biotype 4) soon after birth. The piglets were killed 3 days (n = 6) or 5 days (n = 8) after infection, or antibiotic therapy was commenced on day 5 and the animals killed on day 14 (n = 5). Compared with the non-infected controls, infected animals had reduced mucosal lactase and sucrase, but not maltase activity, while after antibiotic therapy, previously infected piglets had a lower lactase and a higher maltase and sucrase activity. Lactase activity was significantly reduced in the duodenum and jejunum, and mean values were lower in the ileum, but the difference did not reach significance; maltase activity was greater at all ages from the distal jejunum to the mid-ileum; sucrase activity was reduced in all segments up to day 5 but after antibiotic therapy was increased in the jejunum and appeared early in the ileum. Enzyme profiles were more mature along the crypt-villus axis in some segments of the intestine in previously infected piglets. Sodium-potassium-ATPase activity was unchanged. There was a reduced villus height:crypt depth ratio, crypt hyperplasia and increased crypt cell proliferation. Morphological maturation, indicated by loss of vacuoles and location of the nucleus at the base of the enterocyte, proceeded distally from the duodenum to ileum from 3 to 14 days of age when only the ileum remained immature. In infected piglets, there was reduced vacuolation and earlier location of the nucleus at the base of the cell in the distal intestine. Accelerated maturity of specific disaccharidases and enterocyte morphology in infected piglets appears to be due to physical damage to the mucosa resulting in faster proliferation of crypt cells and migration of enterocytes. It is suggested that this may reduce macromolecular internalisation and impair the ability to utilise dietary carbohydrate and may have long-term effects on growth and immunological responses of the gut.

Susceptibility of porcine ileal enterocytes to the cytotoxin of Serpulina hyodysenteriae and the resolution of the epithelial lesions: an electron microscopic study

The cytotoxin from Serpulina hyodysenteriae was injected into ileal loops of eight germ-free pigs, and the effects on the villi were observed after 1, 3, and 18 hours of exposure. The mature vacuolated villus enterocytes of the proximal part of the absorptive villi were most susceptible to the lethal effects of the cytotoxin and were extensively exfoliated. The enterocytes at the base of the villi, the goblet cells, and the follicle-associated epithelium of the dome villi, particularly the M cells, were less affected. As the enterocytes were shed, the villi progressively shortened and the basement membrane became extensively folded. The absorptive villi were markedly stunted at 3 hours, and flattened globlet cells predominated at the site of restitution of the lesion. The myofibroblasts were also damaged, apparently subsequent to the exfoliation of the enterocytes. There was no further damage at 18 hours. The absorptive villi were stunted and were devoid of the large interstitial spaces of the normal lamina propria; the enterocytes were generally columnar, and at the apex of each villus there was an accumulation of goblet cells. There was a preponderance of M cells at the apices of the dome villi. Restitution of the lesions was not as rapid as observed in in vitro systems. The changes observed indicated that as the proximal enterocytes of the absorptive villi were shed, the loss of hydrostatic forces in the lamina propria allowed the myofibroblasts to collapse the villi by progressively retracting the basement membrane. This reduced the surface area to be covered during restitution. Resolution of the lesions was still incomplete after 18 hours.

Studies with enteroaggregative Escherichia coli in the gnotobiotic piglet gastroenteritis model

Two strains of enteroaggregative Escherichia coli of human origin fed to gnotobiotic piglets caused diarrhea or death in the majority of them. Histological examination revealed moderate hyperemia of the distal small intestine and cecum, swelling of small intestinal villi, and layers of aggregated bacteria stacked together in a mucus gel-like matrix overlying intact epithelium. These findings confirm that enteroaggregative E. coli strains produce distinctive intestinal lesions different from those caused by other major categories of diarrheagenic E. coli.

[Lysosomal structures in the intestinal epithelium of mammals during their pre- and postnatal development. A micromorphometric-functional synopsis]

The first lysosomes appear in the stratified embryonic intestinal epithelium during its transition into the simple columnar form. This occurs concurrently with the initial villogenesis. Lysosomes situated basally in the epithelium are presumably the precursor of the first giant lysosomes in the lower small intestine of rodents. Immediately after establishment of the simple configuration a special form of secondary lysosomes can be observed, i.e. glycogenosomes, in the ephemerally existing huge glycogen containing areas. During subsequent fetal intestinal development one observes two events in the epithelial cells, which are the same in principle but differ in one essential point, while they exhibit partially impressive structures. On the one hand there are autophagic degenerative lysosomal processes in the villous epithelium until birth, that lead to a surface without villi in the large intestine, where they occur particularly frequently. On the other hand giant lysosomes originate perinatally in the lower small intestine as well as in the caecum and colon ascendens, in which protein molecules, which were transported by a system of inframicrovillar membranes, are lysosomally degraded, which can be defined as a heterophagic event.

Digestion of the zinc in human milk, cow's milk and a commercial babyfood: some implications for human infant nutrition

1. The digestion of zinc present in human milk, cow's milk and a commercial babyfood was compared, using the piglet as a model for the human infant. 2. In piglets given human milk the pH of stomach contents was approximately 1 and 0.4 units lower than that of animals given respectively cow's milk and babyfood. The pH values of intestinal contents were approximately neutral and did not vary with the type of feed. 3. Hard casein curds were present throughout the stomachs and small intestines of animals fed on cow's milk or babyfood and between 55 and 70% Zn in these digesta samples were recovered in an insoluble form by centrifugation. In contrast, little solid material was observed in the digesta of animals fed on human milk, and 57 and 93% respectively of the Zn in digesta were recovered in a soluble form in the stomach and small intestine. 4. Soluble fractions prepared by centrifugation of digesta were analysed by filtration on Sephadex G-150. After any of the three feeds, soluble Zn in stomach contents was mainly in a low-molecular-weight form. In intestinal samples, however, Zn was present in low- and high-molecular-weight forms. Whilst there were similar amounts of Zn in the low-molecular-weight form in all samples, approximately three times as much of the total intestinal Zn was in a soluble high-molecular-weight form complexed to proteins in the animals fed on human milk compared with those fed on cow's milk or babyfood. 5. Analysis of protein-bound soluble Zn in intestinal samples on SDS-polyacrylamide gels resulted in a similar pattern of proteins for all feeds. Results indicated that at least some of these proteins were derived from intestinal secretions of the piglet. 6. Some implications of these results in respect of the mode of digestion of Zn and its biological availability to the human infant are discussed.

Pathogenesis of diarrhoea caused by astrovirus infections in lambs

Experimental infection of 2-day-old gnotobiotic lambs with lamb astrovirus produced mild diarrhoea after an incubation period of about 48 hours. No other clinical symptoms developed. Infection was studied by immunofluorescent and histological examination of tissues from the lambs. Astroviruses infected only mature villus epithelial cells and subepithelial macrophages in the small intestine, where they produced partial villus atrophy. Infected enterocytes were replaced with cuboidal cells from the crypts, and the lesion gradually healed by 5 days after infection. No serological relationship was detected by immunofluorescence between lamb astrovirus antigen in gut sections and antisera to either calf or human astrovirus.

The ultrastructure of the neonatal pig colon

The neonatal pig colon has several unique structural and developmental features. At birth it has a variable population of epithelial cells which in their arrangement on villus-like protrusions and in their capability for protein uptake into large preformed supranuclear vacuoles closely resemble neonatal ileal cells. Such villus-like protrusions and vacuolated cells are not present in the 2-day-old piglet. On the first day after birth absorptive epithelial cells which lack supranuclear vacuoles transiently accumulate a large number of lipid droplets, each separated from the cytoplasm only by a proteolipid interface. None of the much smaller lipid droplets bounded by a unit membrane of the smooth endoplasmic reticulum and characteristic of normal small intestinal fat uptake were ever seen in these cells. Very few of the large lipid drops remain on the second day after birth. This initial capacity of the colon for protein and lipid uptake never reappears. The pattern of colonic amino acid transport also changes markedly in the first four days of independent life and this may be correlated with the observation that the absorptive cells at birth have microvilli which are twice the length of those on similar cells at and after two days old. These morphological results are discussed in terms of implied functional changes in the neonatal period.

Adherence of enteropathogenic Escherichia coli to intestinal epithelium in vivo

Two porcine strains of enteropathogenic Escherichia coli, one possessing K88 antigen and one lacking K88, were orally inoculated into conventional neonatal piglets. Athough both strains caused severe diarrhea, only the K88-possessing strain was able to proliferate in the anterior small intestine. Both K88-possessing and K88-lacking strains were found in large numbers in the posterior small intestine and, using fluorescent antibodies and scanning and transmission electron microscopy, were found adhering to the epitheial surface in these regions. The presence of an unusual surface structure on the bacterial cell of the K88-lacking strain was described.

Age-dependent resistance to transmissible gastroenteritis of swine. III. Effects of epithelial cell kinetics on coronavirus production and on atrophy of intestinal villi

Coronavirus titers in small intestine, degree of villous atrophy and apparent rates of regeneration of intestinal villi were compared in newborn, 3-week-old and adult pigs for 1 week after they were exposed to the transmissible gastroenteritis virus of swine. The response within the newborn group was homogeneous, resulting in high virus titers, maximal villous atrophy and comparatively slow regeneration. In general, virus titers were lower, villous atrophy was less severe and regeneration more rapid in both older groups than in the newborn pigs. However, the response varied greatly in the older groups. The 3-week-old group was divided into two populations. The major population had low virus titers and developed partial villous atrophy, whereas the minor population had marked villous atrophy and virus titers comparable to those of the newborn pigs. These observations support the hyposthesis that the accelerated replacement of villous epithelium in the small intestine of pigs during the first 3 weeks contributes to the innate age-dependent resistance to transmissible gastroenteritis. The accelerated replacement of villous epithelial cells in older pigs contributes to resistance in two ways. The increased proliferative capacity of crypt epithelium results in a more rapid regeneration of atrophic villi; and the comparatively young villous absorptive cells resulting from accelerated replacement produce less virus per cell than the older ones of the newborn pig.