Histochemistry and morphology of porcine mast cells

Pot-bellied Vietnamese pig with visceral mast cell tumors and mastocytemia

An approximately 12-year-old female Vietnamese Pot-Bellied Pig was presented to the Mississippi State College of Veterinary Medicine Food Animal Service for anorexia of 2 days duration. On physical examination, the patient appeared depressed and lethargic with significantly pale mucus membranes, open mouth breathing, and nostril flaring. On abdominal palpation, the abdomen was tense and uncomfortable. A complete blood count (CBC) and chemistry profile were performed. The CBC revealed significant anemia and mild leukocytosis characterized by mild neutrophilia with a left shift. Mast cells were rarely observed. Hematocrit = 8.1% (RI 22-50), RBC = 1.25 × 10⁶ /μL (RI 3.6-7.8), WBC = 19.85 × 10³ /μL (RI 5.2-17.9), Neutrophils = 15.08 × 10³ /μL (RI 0-11.4), and Bands = 0.993 × 10³ /μL (RI 0-0.019). The chemistry profile was unremarkable with a mildly elevated BUN and slightly decreased total protein and albumin (BUN = 39 mg/dL [RI 4.2-15.1], total protein = 6.2 g/dL [RI 6.6-8.9], and albumin = 2.5 g/dL [RI 3.6-5.0]). An abdominal ultrasound revealed numerous hypoechoic nodules diffusely scattered throughout the hepatic parenchyma. An FNA of one of the hepatic nodules was performed. A mild suppurative component and numerous variably granulated mast cells were observed. A presumptive cytologic diagnosis of mast cell tumor was made. Histopathology was performed, confirming the cytologic interpretation.

Modern Imaging Technologies of Mast Cells for Biology and Medicine (Review)

Mast cells play an important role in the body defense against allergens, pathogens, and parasites by participating in inflammation development. However, there is evidence for their contributing to the pathogenesis of a number of atopic, autoimmune, as well as cardiovascular, oncologic, neurologic, and other diseases (allergy, asthma, eczema, rhinitis, anaphylaxis, mastocytosis, multiple sclerosis, rheumatoid arthritis, inflammatory gastrointestinal and pulmonary diseases, migraine, etc.). The diagnosis of many diseases and the study of mast cell functions in health and disease require their identification; so, the knowledge on adequate imaging techniques for mast cells in humans and different species of animals is of particular importance. The present review summarizes the data on major methods of mast cell imaging: enzyme histochemistry, immunohistochemistry, as well as histochemistry using histological stains. The main histological stains bind to heparin and other acidic mucopolysaccharides contained in mast cells and stain them metachromatically. Among these are toluidine blue, methylene blue (including that contained in May-Grünwald-Giemsa stain), thionin, pinacyanol, and others. Safranin and fluorescent dyes: berberine and avidin - also bind to heparin. Longer staining with histological dyes or alcian blue staining is needed to label mucosal and immature mast cells. Advanced techniques - enzyme histochemistry and especially immunohistochemistry - enable to detect mast cells high-selectively using a reaction to tryptases and chymases (specific proteases of these cells). In the immunohistochemical study of tryptases and chymases, species-specific differences in the distribution of the proteases in mast cells of humans and animals should be taken into account for their adequate detection. The immunohistochemical reaction to immunoglobulin E receptor (FcεRI) and c-kit receptor is not specific to mast cells, although the latter is important to demonstrate their proliferation in normal and malignant growth. Correct fixation of biological material is also discussed in the review as it is of great significance for histochemical and immunohistochemical mast cell detection. Fluorescent methods of immunohistochemistry and a multimarker analysis in combination with confocal microscopy are reported to be new technological approaches currently used to study various mast cell populations.

Protective effects of metallothionein and vitamin E in the trunk kidney and blood of cadmium poisoned Ctenopharyngodon idellus

Cadmium (Cd), a substance with one of the most critical health hazard indices, can cause damage to both the blood and kidneys and accumulates in the body at last. The present work studied the toxicological effects of Cd and the therapeutic effects of metallothionein (MT) and vitamin E (VE) on the trunk kidney and blood of freshwater grass carp (Ctenopharyngodon idellus). Grass carp were divided into three groups: Cd + phosphate-buffered saline (PBS) group, Cd + VE group, and the Cd + MT group. Fish were injected with CdCl₂ on the first day and then VE, MT, or PBS was administered 4 days post-injection. Fish not injected with Cd were used as a negative control. The blood and trunk kidney amassed Cd and suffered severe damage in the forms of organ toxicity cytotoxicity, and immunotoxicity. However, the MT reduced the Cd content in the trunk kidney and blood and partially stabilized the damaged organs. Treatment with VE, however, only demonstrated weaker protection against on Cd-induced toxicity. The results indicate that exogenous MT may play an essential role in restoring homeostasis of the Cd-poisoned urinary and circulatory system and that it may help eliminate Cd in aquatic animals.

Histochemical Study of Heparin-positive Mast Cells in the Terminal Part of Porcine Ductus Choledochus and Papilla Duodeni Major

The study presented in detail the localization and density of mast cells (MCs) in the intramural part of the common bile duct (CBD) and in the major duodenal papilla (MDP) of domestic swine. MCs' density (number/mm(2) ) in different layers of both of the duct and papilla was evaluated after toluidine blue staining. Their number was higher in the lamina propria mucosae than in the tunica muscularis of the studied structures. The localization of berberine-positive, (heparin containing) MCs and the ratio between them and toluidine blue-positive MCs with γ-ma metachromasia was also established. Ratios of heparin-containing MCs in comparison with all toluidine blue-positive MCs were found as follows: ductus choledochus - 32% in the subglandular connective tissue of lamina propria mucosae in the intramural part of the duct; m. sphincter ductus choledochus - 31% in the circular and 0.06% in the longitudinal muscle layer; subserosa - 59%; papilla duodeni major - 0.03% in the subepithelial connective tissue and 34% in the subglandular connective tissue of lamina propria mucosae, respectively. The established large difference in heparin-positive MCs in both the subepithelial and subglandular connective tissues of CBD and MDP, respectively, is an evidence for the existence of mucosal and connective tissue MCs.

The thymus and skin wound healing in Xenopus laevis adults

The capacity to heal wounds without scars is generally lost during the development in vertebrates. To explore the involvement of cells of the adaptive immune system in a scar-like tissue based repair, we studied the thymus in 15-month-old Xenopus after skin incisional wounding. After injury, the organ size significantly increased and marked changes in structure and TNF-α immunoreactivity were detected in the medullary microenvironment when the granulation tissue was present in the repair area. Most of the lymphocytes present in this wound connective tissue were found to be immunoreactive to specific T cell markers. Thymic mucocyte-like cells and epithelial cysts increased in number, the myoid cells acquired a faster turnover and associated in large clusters, blood vessels were dilated and corpuscles similar to mammalian Hassall's bodies were formed in medulla. A higher number of stronger medullary TNF-α immunoreactive cells, i.e., dendritic, epithelial, granular basophilic and myoid cells were also induced after wounding. With progression of healing the thymus gradually returned to histochemical patterns of controls. Our results suggest that during the scar-based skin repair of Xenopus adults the activity of the thymus may be stimulated and associated with the T lymphocyte infiltration observed into injured granulation tissue.

The porcine innate immune system: an update

Over the last few years, we have seen an increasing interest and demand for pigs in biomedical research. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of their anatomy, genetics, and physiology, and often are the model of choice for the assessment of novel vaccines and therapeutics in a preclinical stage. However, the pig as a model has much more to offer, and can serve as a model for many biomedical applications including aging research, medical imaging, and pharmaceutical studies to name a few. In this review, we will provide an overview of the innate immune system in pigs, describe its anatomical and physiological key features, and discuss the key players involved. In particular, we compare the porcine innate immune system to that of humans, and emphasize on the importance of the pig as model for human disease.

Porcine intestinal mast cells. Evaluation of different fixatives for histochemical staining techniques considering tissue shrinkage

Staining of mast cells (MCs), including porcine ones, is critically dependent upon the fixation and staining technique. In the pig, mucosal and submucosal MCs do not stain or stain only faintly after formalin fixation. Some fixation methods are particularly recommended for MC staining, for example the fixation with Carnoy or lead salts. Zinc salt fixation (ZSF) has been reported to work excellently for the preservation of fixation-sensitive antigens. The aim of this study was to establish a reliable histological method for counting of MCs in the porcine intestinum. For this purpose, different tissue fixation and staining methods that also allow potential subsequent immunohistochemical investigations were evaluated in the porcine mucosa, as well as submucosa of small and large intestine. Tissues were fixed in Carnoy, lead acetate, lead nitrate, Zamboni and ZSF and stained subsequently with either polychromatic methylene blue, alcian blue or toluidine blue. For the first time our study reveals that ZSF, a heavy metal fixative, preserves metachromatic staining of porcine MCs. Zamboni fixation was not suitable for histochemical visualization of MCs in the pig intestine. All other tested fixatives were suitable. Alcian blue and toluidine blue co-stained intestinal goblet cells which made a prima facie identification of MCs difficult. The polychromatic methylene blue proved to be the optimal staining. In order to compare MC counting results of the different fixation methods, tissue shrinkage was taken into account. As even the same fixation caused shrinkagedifferences between tissue from small and large intestine, different factors for each single fixation and intestinal localization had to be calculated. Tissue shrinkage varied between 19% and 57%, the highest tissue shrinkage was found after fixation with ZSF in the large intestine, the lowest one in the small intestine after lead acetate fixation. Our study emphasizes that MC counting results from data using different fixation techniques can only be compared if the respective studyimmanent shrinkage factor has been determined and quantification results are adjusted accordingly.

Functional characteristics of the porcine colonic epithelium following transportation stress and Salmonella infection

OBJECTIVE

Stressful life events and infections contribute to gut disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We used a pig model to analyse whether this could be linked to altered mediator sensitivity of the epithelial lining.

MATERIAL AND METHODS

Uninfected control pigs or pigs with subclinical Salmonella (S.) typhimurium DT 104 infection were killed either without (ConRest, InfRest) or with prior 8-h transportation (ConTrans, InfTrans). Short-circuit current (I(sc)), tissue conductance (G(t)) and release of mast cell mediators were monitored in isolated colonic epithelia mounted in Ussing chambers. Epithelia were exposed to histamine (100 microM, mucosally), substance P (SP; 1 microM, serosally), calcimycin A23187 (1 microM, serosally) and theophylline (10 mM, bilaterally). Transepithelial flux of histamine and colonic activities of histamine N-methyltransferase (HMT) and diamine oxidase (DAO) were determined.

RESULTS

S. infection decreased baseline I(sc), G(t) and histamine fluxes, while transportation had no effect on these values. Mucosal histamine increased I(sc) only in ConTrans pigs. This was not associated with increased mucosal-to-serosal flux of histamine but with a 2-fold increased DAO activity. Serosal SP increased I(sc) only in transported animals, but the increase was six times higher in ConTrans versus InfTrans pigs. Effectiveness of SP was not dependent on the release of histamine or prostaglandin D2. A23187 and theophylline elicited increases in I(sc) that were not different between treatments.

CONCLUSIONS

Transportation stress facilitates secretory responses of the colonic epithelium to SP and luminal histamine. This is suppressed by subclinical S. infection. Effects of S. infection on porcine colon resemble, in part, the known effects of an oral S. endotoxin application.

Pathology of Trichuris suis infection in pigs fed an inulin- and a non-inulin-containing diet

Pathology of the colon in pigs infected with Trichuris suis and fed an inulin and a non-inulin containing diet was studied to investigate the inflammatory response induced and the influence of inulin on this. Twenty-nine pigs were allocated into four groups (N-7, I-7, N-9 and N/I-9). Groups N-7, N-9 and N/I-9 were given a diet with non-fermentable carbohydrates, and group I-7 was fed a diet including fermentable carbohydrates (inulin). After 2 weeks, all pigs were inoculated with 2000 T. suis eggs. Seven weeks post-infection (p.i.), groups N-7 and I-7 were killed and group N/I-9 changed to inulin diet to study the influence of inulin on already established T. suis. Nine weeks p.i., groups N-9 and N/I-9 were killed. Trichuris suis were collected from the colon for enumeration. Tissues from the colon of each pig were taken for histological and immunohistochemical quantitative and semi-quantitative evaluations of heterophils, eosinophils, mast cells, IgA(+), IgG(+), IgM(+) and CD3(+) cells. The findings were compared with tissues from seven uninfected pigs of the same age. Pigs fed inulin had significantly fewer worms compared with pigs on the non-fermentable carbohydrate diet. The number of inflammatory cells in the colonic mucosa was increased in all T. suis-infected pigs compared with uninfected controls. The numbers of eosinophils, mast cells, IgA(+), IgG(+) and CD3(+) cells were significantly lower in pigs fed inulin than pigs fed non-fermentable carbohydrate. Whether this is a direct effect of inulin or a secondary effect due to the lower parasitic burden in inulin fed pigs is not known.

Effect of orally administered probiotic E. coli strain Nissle 1917 on intestinal mucosal immune cells of healthy young pigs

Several beneficial effects of probiotics have been described in studies using rodent disease models and in human patients; however, the underlying mechanisms remained mostly unclear. Only a few studies focused on the effects of probiotics on the intestinal mucosal immune system. Here, we studied the effect of the probiotic strain E. coli Nissle 1917 (EcN) administered orally to young pigs at two concentrations (10(9) and 10(11)CFU/d for 21 days) on the gut-associated lymphatic tissue. This probiotic strain was shown recently to reduce recurrence of inflammation in ulcerative colitis patients. We quantified the number and distribution of intestinal immune cells (granulocytes, mast cells, CD4+, CD8+, CD25+, IgA+ lymphocytes) and the mucosal mRNA expression of cytokines (IFN-gamma, TNF-alpha, TGF-beta, IL-10) and antimicrobial peptides (PR-39, NK-lysin, prepro-defensin-beta 1, protegrins). The number and distribution of cells were highly different between small intestinal and colon segments in all groups, but were not influenced by EcN, except high dose EcN fed pigs (10(11) CFU/d) showing an increase in mucosal CD8+ cells in the ascending colon. The mRNA analysis revealed no changes associated with EcN feeding. In conclusion, according to our analyses EcN has only minor effects on the distribution of mucosal immune cells in the gut of healthy individuals. The well-established preventive effects of EcN might therefore be relate to other mechanisms than simple modulation of immune cell distribution.

Morphological and immunocytochemical investigations on mast cells in porcine ureter

Morphological, morphometric, histochemical and immunocytochemical investigations on mast cells, located in the wall of ureter of 8 months aged pigs were performed. Mast cells were found in all three layers of ureteral wall, but their distribution was irregular and the number unequal. It was established that alcian blue (AB)-positive mast cells were significantly more than toluidine blue (TB)-positive mast cells. A statistically significant smaller number of both AB and TB-stained mast cells were observed in the tunica mucosa. The largest number of mast cells was found in the tunica muscularis. In the adventitia, mast cells were higher in number in the main connective tissue than in the connective tissue near the blood vessels. Mast cells stained with TB showed variably expressed gamma-metachromasia, which was best visible in those situated in the lamina propria of the mucosa. The prevailing parts of mast cells, however, were AB-positive after AB-safranin staining. This was mostly found in mast cells of the tunica muscularis and in mast cells of perivascular location in the tunica adventitia. Immunocytochemically, mast cells were found to be positive for histamine and vasoactive intestinal polypeptide in the muscle coat, and to histamine in the adventitia, as well. On the basis of obtained results it was presumed that the mast cells in porcine ureter most probably took part not only in keeping of local homeostasis, but played also an important role of mobility of smooth muscle cells in the middle layer of ureter on one hand, and, on the other, in the adventitial blood vessels.

Establishment and characterization of continuous hematopoietic progenitors-derived pig normal mast cell lines

Mast cells (MCs) are tissue resident, hematopoietic stem cells-derived elements, distributed throughout the body. They are the pivotal mediating cells of allergic reactions. In addition, in mice, MCs play a critical role in the defense against several pathogens, such as bacteria, parasites and viruses. Whereas the biology of rodent and human MCs has been extensively studied using in vitro derived populations, the role of MCs in pigs has not yet been evaluated, given the very low availability of pure porcine MCs populations. In the present report, we describe an original method to obtain continuous factor-dependent normal pig MCs (PMC) lines from fetal hematopoietic progenitors. These Stem Cell Factor (SCF) and Interleukin-3- (IL-3)-dependent PMC lines retain their capacity to growth after conventional freezing methods and exhibit most of the morphological and biochemical properties of normal, although immature, MCs, including metachromatic granules containing sulfated polysaccharides, the expression of c-kit and high-affinity IgE receptors (FcepsilonRI), and the ability to store histamine that is released upon cross-linking of FcepsilonRI. In vitro derived PMC lines might thus be valuable tools to further investigate the reactivity of these elements towards several parasites frequently encountered in pig, such as, but not limited to, Ascaris suum, Trichinella spiralis or Trichuris suis, or towards antigens derived from these pathogens.

The thymus is a site of mast cell development in chicken embryos

Thymic mast cells were studied by light and transmission electron microscopy in chicken embryos during organogenesis. Mast cells made their first appearance at day 15. At days 16 and 17, there was a burst of mast cell development with a peak of 278 +/- 54 cells/mm(2) at day 16. Then, mast cell density decreased until hatching. During the whole embryonic period, about 80% of mast cells localized to the thymic medulla. In the cortex, they were less numerous, and some rare mast cells could be identified in the capsule and septa. Thymic mast cells could be recognized in association with hematopoietic foci, but frequently they grew independently from areas of hematopoiesis and appeared as single cells interspersed among thymocytes, thymic epithelial cells, and interdigitating cells. They were often recognized in close relationship with the scanty and delicate extracellular matrix of the developing gland. Viewed by electron microscopy, mast cells were relatively small cells, with a few secretory granules. Exocytosis was never seen, but, notably, granules emptied in a piecemeal degranulation fashion. This study demonstrates that the chicken thymus is a site of mast cell development during embryogenesis. The high mast cell density we found suggests a possible role for these cells during thymus organogenesis.

Non-specific labelling of mast cells in feline oral mucosa--a potential problem in immunohistochemical studies

Non-specific labelling of mast cells was found to occur in formalin-fixed sections of feline oral mucosa during immunohistochemical procedures. The phenomenon occurred when normal goat, rabbit or mouse serum was applied as a negative control in place of primary antibodies. In addition, with murine isotype-specific negative control reagents, non-specific labelling of mast cells was intense when IgG2b was applied as the primary reagent, but absent or mild when IgGl or IgG2a isotypes were utilized. The non-specific labelling could be eliminated or diminished by reducing the pH of the washing and dilution buffers from 7.4 to 6.0, or by preincubating sections with heparin. The non-specific binding could also be abolished by preincubating sections with heparinase-I. The results suggest that the non-specific binding was mediated by heparin present within feline oral mucosal mast cells. These findings illustrate the importance of the inclusion of adequate control sections in immunohistochemical studies.

The porcine gastrointestinal lamina propria: an appropriate target for mucosal immunisation?

During the course of a lifetime, it has been calculated that we may consume between 100 and 700 tons of food. For the average British citizen, this is likely to include some 550 poultry, 36 pigs, 36 sheep, eight oxen, 10000 eggs and dairy products (milk, butter cheese, etc.) equivalent to 18 tonnes of milk. As if that were not sufficient enough a challenge, the homeostasis within the intestine is further complicated by the presence of 10(5)-10(11) bacteria (pathogenic and non-pathogenic) per gram of mucus and the constant turnover of gut epithelial cells. Given such a magnitude of challenge, which, at least in health is heavily biased in favour of harmless antigens, it can be reasonably hypothesised that the default response of the intestinal mucosal immune system would appear to be set heavily in favour of non-responsiveness and oral tolerance. The purpose of this review is to briefly describe recent progress from studies of the pig that support this hypothesis and to discuss the implications for future mucosal vaccine design.

Histochemical and morphological characteristics of canine cardiac mast cells

Cardiac mast cells have been recently isolated and characterized in humans, however canine cardiac mast cells have not been investigated. The objective of this study is to describe the histological and morphological characteristics of canine cardiac mast cells and examine the potential usefulness of canine models in investigating the role of mast cells in cardiovascular pathology. Canine cardiac mast cells could be easily identified by staining with Toluidine Blue or FITC-avidin. Using Toluidine Blue staining, we demonstrated fewer mast cells in formalin-fixed samples than in specimens fixed in Carnoy's, thus identifying a formalin-sensitive mast cell population in the canine heart. Mast cells were equally distributed in atria and ventricles with approximately 50% showing a perivascular location. Using enzyme-histochemical techniques, we detected tryptase and chymase activity in canine cardiac mast cells. Ultrastructural studies identified mast cells as granular cells with an eccentric non-segmented nucleus. Immunohistochemistry with the macrophage specific antibody AM-3K demonstrated that resident cardiac macrophages were 1.9 times more numerous than mast cells, also showing a predominantly perivascular (60%) location. Perivascular macrophages were more often periarteriolar, whereas perivascular mast cells were more often located along small veins and capillaries. Due to their ability to release cytokines and growth factors and their strategic perivascular location, resident cardiac inflammatory cells, such as mast cells and macrophages, may be important in pathological processes causing myocardial inflammation and fibrosis. Furthermore, mast cell-derived chymase, an important angiotensin II-forming enzyme may have a significant role in regulating the cardiac renin-angiotensin system.

Thyrotropin-releasing hormone immunoreactivity in rat adrenal tissue is localized in mast cells

Pro-thyrotropin-releasing hormone (pro-TRH) has been shown to be present throughout the central nervous system and in several peripheral tissues. In adrenals, TRH immunoreactivity has been reported but not characterized. We show here that two rat pro-TRH-derived peptides, TRH and prepro-TRH[160-169] (Ps4), were detected in extracts of rat adrenal glands by enzyme immunoassay. Endogenous TRH and Ps4 were purified by gel exclusion chromatography and reverse-phase HPLC. Structural identification of each peptide was achieved by chromatographic comparison with synthetic standards. By using the indirect immunofluorescence technique, TRH-immunoreactive cell bodies were found rather widely scattered outside the adrenal, in the brown adipose tissue in which the gland is embedded. These immunofluorescent cells have the typical appearance of mast cells and are metachromatic after histological staining with acidic Toluidine Blue. Our findings suggest that pro-TRH-derived peptides exist in rat mast cells.