Adaptive differentiation promotes intestinal villus recovery

Loss of differentiated cells to tissue damage is a hallmark of many diseases. In slow-turnover tissues, long-lived differentiated cells can re-enter the cell cycle or transdifferentiate to another cell type to promote repair. Here, we show that in a high-turnover tissue, severe damage to the differentiated compartment induces progenitors to transiently acquire a unique transcriptional and morphological postmitotic state. We highlight this in an acute villus injury model in the mouse intestine, where we identified a population of progenitor-derived cells that covered injured villi. These atrophy-induced villus epithelial cells (aVECs) were enriched for fetal markers but were differentiated and lineage committed. We further established a role for aVECs in maintaining barrier integrity through the activation of yes-associated protein (YAP). Notably, loss of YAP activity led to impaired villus regeneration. Thus, we define a key repair mechanism involving the activation of a fetal-like program during injury-induced differentiation, a process we term "adaptive differentiation."

Effect of apitherapy in piglets with preweaning diarrhea

This study was designed to examine the therapeutic effect of honeybee (Apis mellifera L.) venom in piglets with bacterial diarrhea Comparison between bee venom- and drug-treated groups was our main concern in the present study. Preweaning piglets were assigned to treated and non-treated control groups. In the treated group, 47 piglets were acupunctured with the worker honeybee once a day for three consecutive days. Two acupoints, GV-1 (Jiao-chao) and ST-25 (Hai-men), were selected for apitherapy. In the control group, 44 piglets were intramuscularly injected with a standard dose of a known antibacterial drug, colistin sulfate (300,000 IU/kg of body weight), and an antidiarrheal drug (berberine, 2 ml/kg) once a day for three consecutive days. At post-treatment, 90.9% of the control piglets and 93.6% of piglets in the treated group recovered from bacterial diarrhea. Bee acupuncture therapy did not show any side effects such as allergy, intoxication, hemorrhage or infection. It is concluded that bee venom therapy was effective in controlling bacterial diarrhea in preweaning piglets.

Comparative histopathology of intestinal infections

Intestinal infections are characterized by a range of histologic changes. Some examples (moving progressively deeper into the tissue from the intestinal lumen) are: 1) Enterotoxigenic E. coli infections are characterized by layers of E. coli adherent to villous epithelium, usually with little or no apparent structural damage to the mucosa. 2) The term enteropathogenic E. coli infection designates a disease characterized by E. coli attached intimately to the epithelial cell surface membrane with effacement of brush border microvilli. 3) Rotavirus infections are characterized by destruction of villous epithelial cells. Parvovirus infections are characterized by destruction of crypt epithelial cells. 4) Some intracellular infections with Campylobacter-like organisms are characterized by epithelial cell hyperplasia. 5) Hemorrhagic colitis in humans, caused by enterohemorrhagic E. coli strains, is characterized by mucosal hemorrhage and edema indicative of vascular necrosis. 6) Most of these lesions are accompanied by some degree of inflammation. Neurophils and lymphocytes mediate some of the structural and functional changes characteristic of these infections. Some changes are mediated directly by microbial products. Additional examples of the complexity of these diseases are: 1) Edema disease of swine is characterized both by adherent E. coli and vascular necrosis (each process mediated by a different bacterial virulence attribute). 2) Rotavirus infections are characterized both by destruction of villous epithelial cells and compensatory hyperplasia of crypt epithelial cells. 3) There is suggestive evidence that enterohemorrhagic E. coli infections may involve: a) destruction of epithelial brush border by attaching-effacing E. coli, b) neutrophil mediated epithelial cell destruction, c) Shiga-like toxin mediated epithelial cell destruction and d) Shiga-like toxin mediated vascular necrosis which in turn causes ischemic damage to epithelium.

Trichostrongylus colubriformis: epithelial cell kinetics in the small intestine of infected rabbits

Epithelial cell kinetic parameters were compared in intestines of control and Trichostrongylus colubriformis infected rabbits using a microdissection and metaphase accumulation technique in regions of gut with heavy (proximal site) and small (distal site) burdens of worms. In control animals, the cell production rates were respectively 4.3 cells/crypt/hr in the proximal region and 3.7 cells/crypt/hr in the distal one; and the influx of cells onto villi were respectively 67.5 cells/hr and 37.4 cells/hr. In the parasitized rabbits, in the main site of infection, a fourfold increase was recorded in the cell proliferation rate and in the influx of cells onto villi. In the region distal to the main site of infection, the same parameters were twice the control values, although only a low number of T. colubriformis were recovered from this part of gut. These large modifications in the epithelial renewal probably underlies the morphological and enzymological changes previously described in both parts of the T. colubriformis infected gut.

Intestinal changes caused by DL-alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase

Subacute (2 week) oral or intravenous administration of DL-alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), caused diarrhea and frequent emesis as early as 4 to 5 days in dogs (dose greater than or equal to 200 mg/kg/day). Diarrhea also occurred in monkeys after 1 week of treatment with an intravenous dose of 1000 mg/kg/day. Especially evident in the treated dogs with diarrhea were fluid loss, hemoconcentration, and decreased serum sodium and chloride which were findings totally reversible about 2 weeks after cessation of dosing. As a result of treatment with the highest intravenous dosage (1000 mg/kg/day), villous atrophy of the mucosa was observed by light and scanning electron microscopy in the canine small intestine. Transmission electron microscopy demonstrated that the most significant alterations of the canine intestinal tract involved the microvilli of epithelial cells which became shorter and were frequently less numerous or absent along focal areas of the plasma membrane. Intestinal mucosal levels of putrescine, especially in the duodenum and jejunum, were decreased as demonstrated in the monkeys following intravenous treatment with 100, 300, or 1000 mg/kg/day of DFMO. The results of this investigation are consistent with the hypothesis that the inhibition of ODC activity and subsequent altered polyamine metabolism may lead to delayed maturation of the intestinal epithelial cells and the impaired development of their microvilli, causing fluid loss due to reduced absorptive surface area.

Three-dimensional sequential study of the intestinal surface in experimental porcine CV 777 coronavirus enteritis

Summary

The intestinal surface of piglets, experimentally infected with the CV777 coronavirus, was studied at different time intervals using stereo‐microscopy, histology and scanning electron microscopy. Desquamation of epithelial cells was most severe on jejunal villi at the time of onset of clinical signs. It was also seen at 6h after the onset of clinical signs in the ileum. Duodenum and colon remained normal. From 24h after the first clinical signs onwards, villous fusion was seen. The alterations of the mucosal surface are compared to those seen in other enteropathogenic conditions of pigs.

Zusammenfassung

Rasterelektronen‐ und stereomikroskopische Untersuchung der Darmoberfläche nach experimenteller Infektion mit dem porcinen Coronavirus CV777

Die Darmoberfläche von experimentell mit CV 777 infizierten Ferkeln wurde nach bestimmten Zeitintervallen mit Hilfe der Stereo‐ und einfachen Lichtmikroskopie sowie mit dem Raster‐Elektronenmikroskop untersucht. Bei Auftreten der ersten klinischen Symptome sowie sechs Stunden danach war die Desquamation der Epithelzellen des Jejunums am ausgeprägtesten. Ab 24 Stunden nach der Infektion wurde eine Verschmelzung der Zotten untereinander beobachtet. Die Veränderungen der Schleimhautoberfläche werden mit denen bei anderen enteropathogenen Prozessen verglichen.

Résumé

Recherche au microscope électronique à balayage et au stéréomicroscope de la surface intestinale après une infection expérimentale avec le Coronavirus CV 777 du porc

On a examiné la surface intestinale chez des porcelets infectés avec CV 777 à intervalles déterminés au stéréomicroscope, au microscope optique et au microscope électronique à balayage. La desquamation des cellules épithéliales du Jejunum fut la plus marquée au début des premiers symptômes cliniques et six heures après. On a observé un amalgame des villosités dès 24 heures suivant l'infection. Les modifications de la surface de la muqueuse sont comparées à celles recontrées dans d'autres processus entéropathogènes.

Resumen

Estudios con el microscopio electrónico de trazados y con el estereo de la superficie intestinal tras la infección experimental con el virus corona porcino CV 777

Se examinó la superficie intestinal de lechones infectados experimental‐mente con CV 777 tras ciertos intervalos de tiempo con ayuda de la estereo‐microscopía y del microscopio óptico simple, así como con el microscopio electrónico de trazados. Al aparecer los síntomas clínicos primeros y seis horas después era muy manifiesta la descamación de las células epiteliales en el yeyuno. A partir de las 24 horas tras la infección se observó una coalescencia de las vellosidades entre sí. Las modificaciones en la superficie mucosa se comparan con las de los otros procesos enteropatógenos.

Lesions associated with coccidiosis in nursing piglets

Of 45 piglets with diarrhea, 28 had coccidiosis, with no evidence of concurrent viral infection. Villous atrophy and necrotic enteritis were the characteristic lesions, and were more severe in piglets with combined viral and coccidial infections than with coccidiosis alone. Necrotic enteritis presumably was caused by bacterial invasion of the villous lamina propria at foci denuded of epithelium by coccidia, viruses or both. Consistent lesions associated with coccidia in piglets not infected by other primary enteric pathogens suggest that coccidia are the cause of significant clinical disease in nursing piglets 6 to 15 days old.

Canine parvoviral disease: experimental reproduction of the enteric form with a parvovirus isolated from a case of myocarditis

Five 7-week-old pups and four 4-week-old pups, all seronegative to canine parvovirus, were inoculated intravenously with 1000 haemagglutinating units of canine parvovirus originally isolated from the myocardium of a dog with naturally occurring myocarditis. After three days, pups in both litters became pyrexic, anorectic and depressed, with vomiting and diarrhoea. The 4-week-old pups were killed on day 4, and the 7-week-old pups died or were killed on day 5 post-inoculation. Histological examination showed degeneration and necrosis of intestinal crypt epithelial cells and villous atrophy. All pups had thymic atrophy caused by lymphoid depletion. Peyer's patches, mesenteric lymph node and spleen also had lymphoid depletion. Lymphoid necrosis was present occasionally in these tissues. In the bone marrow, granulocytes and granulocyte and erythroid precursors were depleted. Amphophilic intranuclear inclusion bodies were abundant in crypt epithelial nuclei, less so in myocardial nuclei. Canine parvovirus was isolated from intestinal contents, thymus, spleen, mesenteric lymph node and liver in most pups, but not from kidney or myocardium.

Isospora suis enteritis in piglets

A species of porcine coccidia, Isospora suis, when inoculated into piglets, produced diarrhea, dehydration, weight loss and death. Gross lesions were characterized by a fibrino-necrotic membrane within the jejunum and ileum. Villous atrophy and variable erosion, often with an adhered necrotic membrane, were seen microscopically. Asexual and sexual stages of I. suis were seen within the intestinal epithelium and oocysts were recovered from the feces. The severity of clinical disease and lesions were dose-related.

Cytology of canine cutaneous round cell tumors. Mast cell tumor, histiocytoma, lymphosarcoma and transmissible venereal tumor

Sixty-four canine cutaneous round cell tumors were divided into 25 mast cell tumors, 15 histiocytomas, nine cutaneous lymphosarcomas and 15 transmissible venereal tumors. The final diagnosis was made from cytologic, clinical and histologic findings. Cytologic features were significantly distinctive in mast cell tumor, transmissible venereal tumor, and most cases of histiocytoma and lymphosarcoma to allow a diagnostic opinion. This opinion was supported by subsequent histologic examination. In some instances cytology was considered essential in rendering a diagnostic opinion even though histology was available.

Studies on the pathogenesis of swine dysentery. I. Characterization of the lesions in colons and colonic segments inoculated with pure cultures or colonic content containing Treponema hyodysenteriae

Swine dysentery was induced in pigs and in ligated colonic segments by inoculation of pure cultures of, or colonic contents containing, Treponema hyodysenteriae. The mildest changes, best seen in ligated segments 48 or 72 hours after inoculation, were congestion and leucocytic margination in mucosal capillaries and depletion of mucigen from goblet cells lining the base of the crypts of Lieberkühn. Superficial mucosal necrosis and crypt cell hyperplasia were later changes. Perfusion studies with India ink did not demonstrate occlusive mucosal ischemia in acute swine dysentery. Mucosa with lesions of swine dysentery contained at least 10(5) colony forming units of T. hyodysenteriae per gram. Mucosa without lesions had 10(5) or fewer T. hyodysenteriae per gram. Segments with acute swine dysentery were distended with clear mucoid fluid with electrolyte composition indicative of net colonic secretion. No increase in the concentration of volatile fatty acids was detected in content from intact colons or colonic segments with lesions of acute swine dysentery.

Canine hemorrhagic enteritis: detection of viral particles by electron microscopy

At necropsy, several dogs which died showing symptoms of hemorrhagic diarrhea, had significant lesions of the mucosa that were found especially in the duodenum and upper part of the small bowel. Study of ultrathin sections from the diseased mucosa revealed particles resembling parvoviruses in altered nuclei of cells of the intestinal crypts. Electron microscopic examination of intestinal contents by negative staining has shown the presence of many viral particles which have a diameter of 24 nm and whose profile is consistent with an icosahedral shape. These virions float at a density of 1.43 g/cm3 in cesium chloride and agglutinate rhesus monkey and swine red blood cells at 4 degrees C. A possible etiological role is discussed. This virus is compared with the minute virus of canines and the Feline Panleukopenia virus.

Feline panleukopenia. II. The relationship of intestinal mucosal cell proliferation rates to viral infection and development of lesions

Proliferation rates of small intestinal mucosal cells of noninfected germfree and specific pathogen-free kittens were compared to the incidence of infected cells and microscopic lesions in kittens experimentally infected with panleukopenia virus. Mucosal crypt length, cells per crypt, mitotic index and villous length were greater in specific pathogen-free kittens than in germfree kittens. Crypt cells per unit length and villous length per crypt length ratio were greater in germfree kittens. The cryptal cell proliferation rate of specific pathogen-free kittens was 2.24 times that of germfree kittens. Mucosal crypt length, cell per crypt and villous length were greater in the proximal jejunum than in the midjejunum of kittens within groups. Cell proliferation rates per crypt did not differ between areas of the intestine in kittens within groups. There were more virus-infected cells and lesions in specific pathogen-free kittens than in germfree kittens. The incidence of virus-infected cells and lesions was greater in the proximal jejumum and decreased along the small intestine.

Feline Panleukopenia. I. Pathogenesis in germfree and specific pathogen-free cats

Germfree and specific pathogen-free cats were inoculated panleukopenia vivus. Total leucocyte counts decreased significantly in both germfree and specific pathogen-free cats. Clinical illness was not seen in any germfree cat. Specific pathogen-free cats had anorexia and slight diarrhea 5-6 days after inoculation. None of the cats died. Both germfree and specific pathogen-free cats had thymic involution. No other gross lesions were seen. Tissues for histological virus isolation and immunofluorescence studies were taken daily from days 2 through 6 after inoculation. Virus-infected cells and lesions of panleukopenia were seen in the small intestine of both germfree and specific pathogen-free cats. The incidence of virus-infected cells and lesions was greater in specific pathogen-free cats than in germfree cats.

Experimental feline panleucopenia in the conventional cat

Coventional kittens, 12-27 weeks old, were inoculated with cell-cultured feline panleucopenia virus and killed sequentially between day 3 and day 24 after inoculation. All developed a non-fatal mild disease between days 2 and 9, characterized by lymphopenia, neutropenia, listlessness, depression and the development of neutralizing antibodies to the virus. Small intestinal bacterial counts were reduced during the period of maximal clinical disease, presumably a result of decreased food intake. There was involution of the thymus with marked depletion of lymphocytes between days 3 and 12. Depletion of lymphocytes also characterized the lesions in the lymph nodes between days 3 and 8. At the same time crypt lesions with spotty distribution were in the small intestinal and colonic mucosa. The changes were loss of crypt epithelial cells with compensatory attenuation of the remaining epithelium. Electron microscopically, the number and size of microvilli and secretory granules were reduced but there was no change indicating lethal cell injury. There were no virus particles. The findings point to an early and transient cellular damage by the virus. Intestinal alkaline phosphatase activity disappeared from the luminal surface of the attenuated crypt epithelial cells. Otherwise, intestinal alkaline and acid phosphatase activity were not altered in inoculated cats.

Pathogenesis of digestive tract lesions in duck plague

White Pekin ducklings were inoculated orally with duck plague virus. Tissues from the digestive tract were collected daily after inoculation and examined by light, electron and fluorescent microscopy. There were necrosis and degeneration of stratified squamous epithelium of the esophagus and cloaca, epithelium of intestinal crypt and esophageal submucosal glands, macrophages in the lamina propria, and submucosal fibrocytes and lymphocytes. Submucosal hemorrhages occurred after degeneration and necrosis of lymphocytes, macrophages, fibrocytes and epithelial cells. Viral antigens were detected in all these cells by use of fluorescein-labeled antibodies. With the electron microscope, nucleocapsids were seen in the nuclei, budding through the inner nuclear membrane; enveloped virions were present in cytoplasmic vacuoles of macrophages, epithelial cells and fibrocytes. In lymphocytes, nucleocapsids were also in the nuclei, but karyorrhexis and cytolysis occurred before viral maturation was completed.

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.