Mast cell tryptase levels in normal canine tissues

Expression of Carboxypeptidase A3 and Tryptase as Markers for Lymph Node Metastasis of Canine Cutaneous Mast Cell Tumors

Detection of metastatic mast cell tumors (MCTs) in lymph nodes is a critical factor for treatment, prognosis, and clinical management. Presence/absence of mast cells in the lymph nodes cannot be used as a sole parameter to determine metastasis due to the inability to differentiate neoplastic from non-neoplastic/inflammatory mast cells. While cytologic and histopathologic classifications for assessment of metastatic MCTs based on the numbers and distribution of mast cells have been developed, inconsistency between the clinical interpretation of these grading schemes and actual metastatic status occurs. The aim of this study is to identify a novel diagnostic tool to accurately predict overt metastatic mast cell tumors in lymph nodes. We investigated the possibility of using RT-qPCR to detect mRNA expression of mast cell-specific genes in lymph nodes with different stages of MCT metastatic classification. We are able to establish a highly sensitive and discriminating RT-qPCR measuring Carboxy peptidase A3 (CPA3) and tryptase mRNA expression and identify the cut-off values with high sensitivity and specificity for overt metastatic MCTs in lymph nodes. An area of future interest would be to expand our analysis of the extent to which cut-off values for these markers in correctly identifying disease status, as well as predicting clinical outcomes and survival times. This would offer valuable information regarding the practical applicability of this technique and may enable us to improve our standards of detection metastasis, including possibility of molecular analysis of cytologic specimens obtained from suspicious nodes subjected to surgical excision.

Tumor⁻Microenvironment Interaction: Analysis of Mast Cell Populations in Normal Tissue and Proliferative Disorders of the Canine Prostate

Mast cells (MCs) are involved in angiogenesis, tissue remodeling and immunomodulation in several human and animal tumors, although their exact role is still controversial. Since no information is available in canine prostate carcinoma (PC) and normal prostate tissues, the aims of this study were to evaluate the possible correlations between MC distribution, molecular expression and microvessel density (MVD) in normal prostatic tissue and proliferative disorders of the canine prostate. All samples (6 normal, 15 benign prostate hyperplasia-BPH, 8 PC) were stained with Toluidine Blue and immunohistochemically evaluated for tryptase, c-Kit (CD117) and CD31. Mast cell density (MCD) and MVD were quantified by the hot-spot method. MCD was significantly increased in periglandular/peritumoral areas, when compared with intraglandular/intratumoral areas, in all groups (p = 0.03). C-Kit expression was strongly associated with PC (ρ = 0.75 p = 0.03), whereas positive correlation between tryptase and c-Kit expression (ρ = 0.64 p = 0.01) was observed in periglandular areas of BPH. MVD showed a correlation with MCD in BPH (ρ = 0.54 p = 0.04). Our data support the importance of c-Kit in regulating MC proliferation. The predominant location of MCs in peritumoral areas of canine PC was similar to the human counterpart, in which PC cells are supposed to produce substances attracting MCs to the tumor microenvironment.

The extended substrate recognition profile of the dog mast cell chymase reveals similarities and differences to the human chymase

Human chymase (HC) constitutes a major granule protease in one of the two human mast cell (MC) types. The main biological role of this haematopoietic serine protease is probably not yet known, although it has been implicated in a large number of functions. Dogs, like humans, have only one chymase. This enzyme is closely related to its human homologue, and the MC subtypes of human and dog appear to be similar as well. Therefore, the functions of the dog chymase (DC) may closely reflect the functions of the HC. Moreover, dogs may serve as good models for studies of human MC functions and MC-related diseases. To reveal functional similarities and differences between the DC and HC, we have determined the extended cleavage specificity of the DC by substrate phage display. This method allows the simultaneous permutation of primed and unprimed substrate positions. The DC was found to have very similar preferences to its human counterpart for substrate positions P1, P3, P4 and P3', whereas their preferences differ at positions P2, P1' and P2'. Therefore, the HC and DC may have co-evolved with a substrate where positions P1, P3, P4 and P3' are conserved between dogs and humans, whereas positions P2 and P1' are not and P2'differs to a minor extent. The differences observed between these two enzymes suggest that results obtained from dog models cannot be directly extrapolated to human clinical settings but need to be evaluated carefully concerning potential differences in substrate preferences.

The role of mast cells in atopy: what can we learn from canine models? A thorough review of the biology of mast cells in canine and human systems

Mast cell research has largely focused on the role of these cells in the early phase of allergic reactions. However, their involvement may well extend beyond this stage, and even reach across nonallergic conditions. Mast cells from different sources have helped advance our knowledge of their biology. Although in vitro and in vivo research in this area has mainly focused on humans, such studies are limited by the extent to which cells from certain human tissues and/or human patients can be collected or studied. While rodents also provide valuable models with which to further our understanding of the behaviour of mast cells and their contribution to allergy, reported differences between human and murine mast cells, and, in some instances, the limitations of in vivo rodent models of mast cell-mediated allergic conditions, preclude their use. In this review, we introduce a relatively unknown mast cell population, that of the dog. Canine mast cells display many phenotypic and functional similarities with their human counterparts, and dogs develop spontaneous and induced allergic diseases that share clinical and pathophysiological features with the human condition. Therefore, the use of canine cells can shed light on the general role of mast cells, particularly in relation to allergic diseases given the potential of in vivo dog models within this field. Here we provide a detailed review of the data reported from in vitro and in vivo studies of canine mast cells, and compare them with results obtained in human systems. We also highlight direct evidence of the mast cell contribution to canine atopy. We conclude that the dog offers useful in vitro and in vivo models in which to investigate mast cell behaviour, and that its use should be considered when undertaking studies aimed either at elucidating the role of mast cells in health and disease, or at prescreening novel therapies prior to entry into man.

The involvement of mast cells and mast cell proteinases in the intestinal response to equine cyathostomin infection

Cyathostomins (Cyathostominae) are regarded as the most pathogenic equine nematode worldwide. These nematodes are difficult to control in equine populations due to emerging anthelmintic resistance and evasion of encysted larval cyathostomins to regular modern anthelmintics. Mast cells and their proteinases have been shown to play a role in the mammalian immune response to nematode infections. Involvement of mast cells and mast cell proteinases in the equine immune response to cyathostomin infection is proposed. A technique was established to perform immunohistochemical staining using polyclonal rabbit anti-equine mast cell proteinase-1 (eqMCP-1) and anti-equine tryptase on formalin-fixed large intestinal sections, from horses classified as cyathostomin positive and negative at the time of death based upon larval enumeration. Quantitative analysis of antibody labelled mast cells was used to detect mast cell proteinases in equine large intestinal sections positive and negative for cyathostomin larvae. This demonstrated an increase in equine tryptase labelled mucosal and submucosal mast cells in cyathostomin positive horses. This study has established an immunohistochemical technique to demonstrate mast cell proteinases in formalin-fixed large intestinal sections. This technique may be used to determine possible involvement of mast cells and their proteinases in the equine immune response to cyathostomin larvae. Further studies are required to define a specific role.

Optimization of an Acridine Orange-bisbenzimide procedure for the detection of apoptosis-associated fluorescence colour changes in etoposide-treated cell cultures

This study was initiated in order to investigate the possibility of improving fluorescence microscopy as a method for evaluating apoptosis in cells by combining two fluorescent dyes with different staining characteristics. Cells were vitally stained with bisbenzimide (1.3 microM) and Acridine Orange (6.6 microM) and observed using the following filter configuration: excitation 380 nm, beamsplitter 395 nm and longpass filter 397 nm. Control cells exhibited clear blue fluorescent nuclei and red fluorescing lysosomes. In cells treated with etoposide to induce apoptosis, two distinct occurrences were observed: a change in the spectrum of emitted light from bisbenzimide bound to the nuclear region and an increase in lysosomal Acridine Orange fluorescence. The two occurrences together permit a more unbiased detection of apoptosis than most assays. Only one filter set is required for evaluation and the resulting images can be easily evaluated visually or processed further by image analysis.

Tissue-specific expression of mast cell granule serine proteinases and their role in inflammation in the lung and gut

Serine proteinases with trypsin-like (tryptase) and chymotrypsin-like (chymase) properties are major constituents of mast cell granules. Several tetrameric tryptases with differing specificities have been characterized in humans, but only a single chymase. In other species there are larger families of chymases with distinct and narrow proteolytic specificities. Expression of chymases and tryptases varies between tissues. Human pulmonary and gastrointestinal mast cells express chymase at lower levels than tryptase, whereas rodent and ruminant gastrointestinal mast cells express uniquely mucosa-specific chymases. Local and systemic release of chymases and tryptases can be quantified by immunoassay, providing highly specific markers of mast cell activation. The expression and constitutive extracellular secretion of the mucosa-specific chymase, mouse mast cell proteinase-1 (mMCP-1), is regulated by transforming growth factor-beta1 (TGF-beta1) in vitro, but it is not clear how the differential expression of chymases and tryptases is regulated in other species. Few native inhibitors have been identified for tryptases but the tetramers dissociate into inactive subunits in the absence of heparin. Chymases are variably inhibited by plasma proteinase inhibitors and by secretory leucocyte protease inhibitor (SLPI) that is expressed in the airways. Tryptases and chymases promote vascular permeability via indirect and possibly direct mechanisms. They contribute to tissue remodelling through selective proteolysis of matrix proteins and through activation of proteinase-activated receptors and of matrix metalloproteinases. Chymase may modulate vascular tissues through its ability to process angiotensin-I to angiotensin-II. Mucosa-specific chymases promote epithelial permeability and are involved in the immune expulsion of intestinal nematodes. Importantly, granule proteinases released extracellularly contribute to the recruitment of inflammatory cells and may thus be involved in innate responses to infection.

The mast cell in wound healing

This review describes the role of the mast cell in the pathobiology of skin healing. After illustrating its main morphofunctional characteristics, with special reference to the dog and cat, we consider the involvement of the mast cell in the various phases of skin repair. With the aid of a wide array of newly formed or preformed mediators released by degranulation, the activated mast cell controls the key events of the healing phases: triggering and modulation of the inflammatory stage, proliferation of connective cellular elements and final remodelling of the newly formed connective tissue matrix. The importance of the mast cell in regulating healing processes is also demonstrated by the fact that a surplus or deficit of degranulated biological mediators causes impaired repair, with the formation of exuberant granulation tissue (e.g. keloids and hypertrophic scars), delayed closure (dehiscence) and chronicity of the inflammatory stage.

The ACVD task force on canine atopic dermatitis (V): biology and role of inflammatory cells in cutaneous allergic reactions

Numerous inflammatory cells are thought to play a role in the pathogenesis of canine atopic dermatitis (AD) although, in the past, mast cells were considered the most important. However, evidence for this assumption is lacking. In this paper, we review the literature concerning the role of inflammatory cells in allergic reactions and conclude that a complex interplay exists between a wide variety of cell types. Thus, on the basis of the available evidence, the cells that appear to be the most important in the pathogenesis of canine AD are Langerhans' cells and dermal dendritic cells (both responsible for antigen processing and presentation), B-lymphocytes (responsible for reaginic antibody production), allergen-specific helper T-lymphocytes (responsible for cytokine production leading to activation of B-cells and other inflammatory cells) and mast cells (production of inflammatory mediators leading to inflammation).