Basis of sialic acid heterogeneity in ulcerative colitis

The Histochemical Alterations of Mucin in Colorectal Carcinoma Quantified by Two Efficient Algorithms of Digital Image Analysis

The practical use of knowledge on the diagnostic-prognostic role of polysaccharide components of mucins in colorectal cancer (CRC) has been difficult, due to the number of histochemical (HC) reaction types, as well as lack of standard methods of computer-assisted analysis of tissue expression of these molecules. Using two algorithms of digital image analysis (by application of Image-Pro Premier and our originally designed program Filter HSV), we evaluated the expression of polysaccharides in tissue samples of CRC patients (n = 33), and fragments of normal colorectal tissue from the same patients (control) using periodic acid Schiff reaction (PAS) (neutral mucins) and alcian blue staining (AB) (acidic mucins). Our results indicate lower expression of the PAS+ and AB+ mucins in CRC, as compared to the control samples. The higher expression of PAS+ polysaccharides was detected in flat tumors than in protruded CRC, while higher AB+ mucins expression was a feature of mucinous CRC subtypes. Positive correlation between mutual PAS+ and AB+ expression, as well as correlations with glucose concentration (PAS+ mucins), and hemoglobin level (AB+ mucins) were observed exclusively in unchanged colorectal samples (control). Both algorithms of digital image analysis (smart segmentation and Filter HSV) work properly and can be used interchangeably in daily practice of pathologists, as useful tools of quantitative evaluation of HC reaction in both normal and cancerous tissues.

Could Mycobacterium avium subspecies paratuberculosis cause Crohn's disease, ulcerative colitis…and colorectal cancer?

Infectious agents are known causes of human cancers. Schistosoma japonicum and Schistosoma mansoni cause a percentage of colorectal cancers in countries where the respective Schistosoma species are prevalent. Colorectal cancer is a complication of ulcerative colitis and colonic Crohn’s disease, the two main forms of idiopathic inflammatory bowel disease (IIBD). Mycobacterium avium subspecies paratuberculosis (MAP), the cause of a chronic intestinal disease in domestic and wild ruminants, is one suspected cause of IIBD. MAP may therefore be involved in the pathogenesis of IIBD-associated colorectal cancer as well as colorectal cancer in individuals without IIBD (sporadic colorectal cancer) in countries where MAP infection of domestic livestock is prevalent and MAP’s presence in soil and water is extensive. MAP organisms have been identified in the intestines of patients with sporadic colorectal cancer and IIBD when high magnification, oil immersion light microscopy (×1000 total magnification rather than the usual ×400 total magnification) is used. Research has demonstrated MAP’s ability to invade intestinal goblet cells and cause acute and chronic goblet cell hyperplasia. Goblet cell hyperplasia is the little-recognized initial pathologic lesion of sporadic colorectal cancer, referred to as transitional mucosa, aberrant crypt foci, goblet cell hyperplastic polyps or transitional polyps. It is the even lesser-recognized initial pathologic feature of IIBD, referred to as hypermucinous mucosa, hyperplastic-like mucosal change, serrated epithelial changes, flat serrated changes, goblet cell rich mucosa or epithelial hyperplasia. Goblet cell hyperplasia is the precursor lesion of adenomas and dysplasia in the classical colorectal cancer pathway, of sessile serrated adenomas and serrated dysplasia in the serrated colorectal cancer pathway, and of flat and elevated dysplasia and dysplasia-associated lesions or masses in IIBD-associated intestinal cancers. MAP’s invasion of intestinal goblet cells may result in the initial pathologic lesion of IIBD and sporadic colorectal cancer. MAP’s persistence in infected intestines may result in the eventual development of both IIBD-associated and sporadic colorectal cancer.

Identification and analysis of o-acetylated sialoglycoproteins

5-N-acetylneuraminic acid, commonly known as sialic acid (Sia), constitutes a family of N- and O-substituted 9-carbon monosaccharides. Frequent modification of O-acetylations at positions C-7, C-8, or C-9 of Sias generates a family of O-acetylated sialic acid (O-AcSia) and plays crucial roles in many cellular events like cell-cell adhesion, proliferation, migration, etc. Therefore, identification and analysis of O-acetylated sialoglycoproteins (O-AcSGPs) are important. In this chapter, we describe several approaches for successful identification of O-AcSGPs. We broadly divide them into two categories, i.e., invasive and noninvasive methods. Several O-AcSias-binding probes are used for this purpose. Detailed methodologies for step-by-step identification using these probes have been discussed. We have also included a few invasive analytical methods for identification and quantitation of O-AcSias. Several indirect methods are also elaborated for such purpose, in which O-acetyl group from sialic acids is initially removed followed by detection of Sias by several approaches. For molecular identification, we have described methods for affinity purification of O-AcSGPs using an O-AcSias-binding lectin as an affinity matrix followed by sequencing using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF-TOF) mass spectroscopy (MS). In spite of special attention, loss of O-acetyl groups due to its sensitivity towards alkaline pH and high temperature along with migration of labile O-acetyl groups from C7-C8-C9 during sample preparation is difficult to avoid. Therefore there is always a risk for underestimation of O-AcSias.

In situ characterization of O-linked glycans of Muc2 in mouse colon

The characterization of mucus O-linked glycans in the proximal and distal mouse colon was performed by conventional histochemical methods and by lectin histochemistry in combination with enzymatic treatment (PNGase, α1,2 fucosidase, sialidase digestion), with and without prior desulfation. We demonstrated the presence of sialo- and sulfomucins in both the proximal and distal colon of the mouse. In the distal colon the sulfomucins were clearly prevalent, although there were always sialomucins with sialyl residues linked α2,6 to the subterminal galactose. Sialic acid was poorly O-acetylated, especially in the distal colon. The lectin binding pattern indicates a massive presence of fucose α1,2 linked to galactose in O-glycans and smaller quantities of fucose linked α1,6 to N-acetylglucosamine in the core of N-linked glycans. Lectin histochemistry also demonstrated the presence of glycosidic residues of N-acetylglucosamine, N-acetylgalactosamine, and galactose in oligosaccharide chains of highly sulfated mucins.

Tissue quantification of neutral and acid mucins in the mucosa of the colon with and without fecal stream in rats

PURPOSE: To quantify the intensity of the expression of neutral and acids mucins in mucosa of the colon with and without fecal stream and to correlate this with the duration of fecal transit diversion. METHODS: Thirty male Wistar rats were subjected to fecal transit deviation in the left colon by a proximal colostomy and a distal mucous fistula. The animals were divided into three experimental groups, according to whether sacrificing would be performed six, 12 or 18 weeks after surgery. The expression of neutral and acid mucins was evaluated using the histochemical techniques of Periodic Acid Schiff and Alcian Blue, respectively. The tissue mucins expression was quantified by computer-assisted image analysis software (NIS-Elements) in the segments with and without fecal stream. Student's paired t test was used to compare the quantities of mucins in colon with or without fecal stream and variance between the experimental groups by ANOVA and Newman-Keuls post-test, establishing level of signification of 5% (p<0.05). RESULTS: There were significant decreased quantities of acid and neutral mucins in the colon without transit, compared with the colon with fecal stream, independent of the duration of exclusion. There was increased expression of neutral mucins in the colon with fecal stream after 12 and 18 weeks of exclusion. There was no increase in the expression of acid mucins in the colon with transit as the duration of fecal transit exclusion progressed. There was increased production of acid mucins in the animals submitted to diversion of the fecal stream for 18 weeks, compared with those subjected to diversion for 6 and 12 weeks. In the colon without fecal stream, there was increased expression of neutral mucins after 12 and 18 weeks of exclusion. CONCLUSIONS: Deviation of the fecal stream decreased the expression of acid and neutral mucins in the segments without fecal transit, compared with segments with transit. Regardless of the reduced expression of acid and neutral mucins in the segments without fecal stream, their tissue expression increased with increasing duration of intestinal deviation.

Aberrant gastric apomucin expression in ulcerative colitis and associated neoplasia

AIM

To evaluated the presence of gastric metaplasia in colonic mucosa of patients with ulcerative colitis and its relationship with dysplasia/neoplasia.

MATERIAL AND METHODS

Ninety patients with UC were selected. The duration and the extent of disease were registered in all the cases. Biopsies were histologically and immunohistochemically assessed. Crypt distortion, goblet cell depletion, Paneth cell metaplasia and inflammatory activity were graded, as well as dysplasia and invasive neoplasia (absent or present). Monoclonal antibodies against the gastric apomucins MUC5AC (foveolar) and MUC6 (mucopeptic) were used.

RESULTS

Neoplasia was observed in 16 patients, 8 non-invasive (dysplasia) and 8 invasive (adenocarcinoma). MUC5AC and MUC6 were detected in 63 and 16 out the 90 cases, 70.0% and 17.8%, respectively. The staining was patchy for both antibodies, affecting groups of cells more often than isolated cells. The presence of MUC5AC correlated positively with inflammatory activity and goblet cell depletion (R=0.231, p=0.03 and R=0.211, p=0.048, respectively). The expression of MUC6 correlated positively with age (R=0.297, p=0.005), duration of disease (R=0.287, p=0.008), extent of disease (R=0.342, p=0.001), crypt distortion (R=0.276, p=0.01) and the presence of neoplasia (R=0.483, p<0.00). There was no correlation between Paneth cell metaplasia and apomucin expression.

CONCLUSIONS

Our study demonstrates the aberrant expression of gastric apomucins in UC and suggests that MUC5AC is associated with inflammation while MUC6 is related to the presence of neoplasia. The demonstration of metaplastic cell lineages preceding dysplasia supports the biological link between inflammation and neoplasia, MUC6 emerging as a putative biomarker of dysplasia in ulcerative colitis patients.

Altered mucin expression in the gastrointestinal tract: a review

Early studies of changes in mucin expression in disorders of the gastrointestinal tract focused on alterations in the carbohydrate chain. This review briefly considers the various mechanisms by which such alterations may come about: (a) normal variation, (b) sialic acid alterations, (c) defective assembly of carbohydrate side-chains, (d) changed expression of core proteins and (e) epithelial metaplasia. The availability of monoclonal antibodies to mucin core proteins adds a new dimension to mucin histochemistry. It is now possible to offer explanations for traditional mucin histochemical findings on the basis of lineage-specific patterns of mucin core protein expression. Changes in core protein expression are described in inflammatory, metaplastic and neoplastic disorders of the gastrointestinal tract. The possibility that mucin change could be important in the aetiology of some diseases such as ulcerative colitis and H. pylori gastritis is considered. It is more probable, however, that changes in mucin expression are secondary to reprogramming of cellular differentiation and altered cell turnover. As such they may serve as markers to explain pathogenesis and provide novel diagnostic and prognostic information.

Reduction of sialic acid O-acetylation in human colonic mucins in the adenoma-carcinoma sequence

The oligo-O-acetylation of sialic acids found in normal colonic mucins is greatly reduced in colorectal cancer. Mucins prepared from cancer tissue in adenocarcinoma showed this reduction, while normal O-acetylation was detected in resection margin and control cases and total mucin sialic acid content was significantly decreased in cancer vs. control samples. A reduction of the O-acetyl transferase activity catalysing the O-acetylation reaction was also found. A series of cultured human colorectal cell lines derived from the same premalignant adenomatous line, and representative of the adenoma-carcinoma sequence were examined and revealed a depletion of oligo-O-acetylation in the original diploid premalignant line, re-expression in a further premalignant line and reduction in malignant mucinous and adenocarcinoma cell lines. Reduction of sialic acid O-acetylation appears as an early event in the process of malignant transformation in human colorectal cancer.

Histochemical alterations of mucin in normal colon, inflammatory bowel disease and colonic adenocarcinoma

Loss of sialic acid o-acyl substitutions in colonic mucus was studied using specific histochemical techniques in individuals with a variety of large-bowel diseases and in a control population. Changes found included a focal or field (diffuse) loss of side-chain substitutions which were qualitatively similar in all groups studied. The results were tested statistically using a variety of assumptions that field and/or focal loss of o-acyl substitution may be either abnormal or a normal variant. No statistically significant differences in the prevalence of substitutions were detected between normal males and females or between normal individuals aged 0-29 years and 30-80 years. Significant differences were found between ascending and descending colon in both normal individuals and in the non-neoplastic mucosa of patients with cancer. There were also significant differences between the normal descending colon and cases with cancer of the descending colon. These differences seem unlikely to be due to non-specific factors, since for most assumptions there were also differences between colons containing cancer and those from patients with inflammatory bowel disease. In agreement with the work of other investigators, it seems likely that focal loss of o-acetylation results from an acquired gene mutation. It is not clear whether or not this plays a role in carcinogenesis.

South Asian and European colitics show characteristic differences in colonic mucus glycoprotein type and turnover

South Asians in Britain have a high incidence of ulcerative colitis and a low incidence of colorectal cancer. The pattern of mucus production in 12 South Asian and 16 European colitics and a control group of 19 South Asians was studied. Three types of mucin were identified after organ culture of colonic biopsy specimens with a dual label of [3H]-glucosamine and sodium [35S]-sulphate: type A had a high [35S]:[3H] ratio and high incorporation ([3H] dpm/micrograms DNA > 500); type B had a low ratio and high incorporation; and type C had low incorporation but with either high (C1) or low (C2) ratios. European colitic mucins show a significant reduction in the level of sulphation detected by mucin histochemistry with high iron diamine/Alcian blue staining, together with predominantly type B or C2 mucins (low sulphation). South Asian colitics showed histochemically normal patterns of high sulphation and largely type A and C1 mucins (high sulphation). There was no correlation of mucin type with disease activity index in either ethnic group. The appearance of apparently normal mucin in patients with ulcerative colitis may be a useful marker for the identification of a subgroup at low risk of colorectal cancer.

Racial variation in the O-acetylation phenotype of human colonic mucosa

O-acetylated and non-O-acetylated sialoglycoproteins can be distinguished by the mPAS (mild periodic acid-Schiff) histochemical technique. Individual adults show one of three different patterns of staining of large intestinal mucosa: uniformly mPAS-positive, uniformly mPAS-negative, or mPAS-negative with scattered mPAS-positive crypts. To test our hypothesis that these variations are the result of a single autosomal gene (oat) polymorphism, we have studied the frequency of the three patterns of staining in a total of 435 adult colon specimens from six geographically separate populations: British, South African blacks, Icelanders, Japanese, Hong Kong Chinese, and Bahrainis. The distribution of the three types of staining fell into two groups. In Japanese and Chinese, uniformly mPAS-positive cases were much more frequent than uniformly mPAS-negative cases; this distribution differed significantly (chi 2, P < 0.001) from that in non-Sino-Japanese, where the uniformly mPAS-positive phenotype was much less frequently found than the uniformly mPAS-negative phenotype. In neither of the groups did the frequency of the three phenotypes differ significantly from that predicted for a single gene polymorphism by the Hardy-Weinberg law. The variation in staining patterns between populations is consistent with variation in frequency of a single polymorphic autosomal gene (oat) controlling O-acetylation of sialic acid, probably by an O-acetyl transferase enzyme. Loss of function mutation in the high acetylator gene (oata) in a colonic crypt stem cell in heterozygous individuals would account for the scattered discordant crypts. Gene frequencies for a variety of enzymes differ between the Sino-Japanese and non-Sino-Japanese races.(ABSTRACT TRUNCATED AT 250 WORDS)

Colorectal mucin histochemistry in health and disease: a critical review

Neoplastic, inflammatory and regenerative processes affecting colorectal mucosa are associated with alterations in structure of epithelial mucin. This review collates mucin-, lectin-, and immuno-histochemical observations on colorectal mucins and introduces recent molecular genetic insights into the structure of the protein backbone of mucins. The numerous structural modifications uncovered by the various technical approaches have been reduced to a few manageable principles that are of relevance to both researcher and diagnostic pathologist. Particular attention is drawn to the need to appreciate the limited specificities of probes, the confounding influences of anatomical site and genetic factors (necessitating the use of appropriate positive and negative control tissues) and the precise location of secretory material. In the past, insufficient attention has been given to the effects of altered differentiation including metaplasia and differing lineage expression in epithelial disorders of growth. It is likely that certain changes loosely ascribed to goblet cell mucin, such as neo-expression of blood group antigens and anomalous expression of core carbohydrate structures, do not occur at all. Critical examination of available data point to only two consistent and unequivocal changes affecting goblet cell mucin in pathological processes: loss of O-acetyl substituents at sialic acid C4 and C7,8,9 and increased sialylation. Furthermore, there are no neoplasia-specific alterations in mucins documented to date. All neoplasia-associated changes have been described in non-neoplastic lesions also.

Sialic acid and epithelial differentiation in colorectal polyps and cancer--a morphological, mucin and lectin histochemical study

Loss of O-acetyl substituents from sialic acid expressed in mucin secreted by hyperplastic polyps (21), adenomas (9), a mixed polyp (1) and adenocarcinomas (41) of the colorectum was investigated by mucin histochemistry (diastase PAS and mild PAS) and by lectin histochemistry (Arachis hypogaea or peanut agglutinin) with (nPNA) and without (PNA) prior neuraminidase digestion. Mild PAS and nPNA reactivity were closely correlated, indicating that loss of O-acetyl substituents at C7, C8 and C9 (hence mild PAS positive) and at C4 (hence neuraminidase labile) occur pari passu. These sialic acid alterations were characteristic of mucin secreted by both adenocarcinoma and hyperplastic polyp. The same changes occurred patchily or focally in adenoma. Five "serrated" adenocarcinomas resembled the hyperplastic polyp both morphologically and histochemically. Luminal secretions within cancers were classified as mucin-like (type I) and non-mucin-like (type II). Mild PAS was the most specific technique for mucin-like intraluminal material. However, accumulated luminal secretions (type I or II) and intracytoplasmic lumina were quite specific features of colorectal cancer and could be effectively highlighted by means of dPAS. PNA reactivity without prior neuraminidase digestion showed a distribution unlike nPNA. Whilst PNA expression was more cancer specific than either mPAS or nPNA, it was observed mainly in cancers secreting little or no mucus, thus limiting its value as a tumor marker.

Sialic acid histochemistry and the adenoma-carcinoma sequence in colorectum

A change in sialic acid, notably loss of O acetyl substitution, was studied histochemically in a series of 93 colorectal adenomas that included 14 malignant polyps. Changes in sialic acid were uncommon in adenomas showing mild dysplasia but became increasingly common in moderately and severely dysplastic adenomas and were always present in carcinomatous areas. There was no correlation between a change in sialic acid and either size or villous architecture of benign adenomas. As mucin change often preceded the development of invasive cancer, it could not be used on its own to distinguish between epithelial displacement (pseudoinvasion) and malignant invasion. An abundant luminal accumulation of altered sialic acid in association with an epithelial lining that was non-mucin secreting, however, was specific for cancer. Conversely, the presence of unchanged intracellular or intraluminal O-acetyl sialic acid may help to exclude a diagnosis of malignancy in equivocal cases. The change is not specific for colorectal neoplasms and probably represents a metaplasia to a small intestinal phenotype.

Adherence and surface properties of Tritrichomonas mobilensis, an intestinal parasite of the squirrel monkey

Adherence properties of the potentially enteropathogenic Tritrichomonas mobilensis were studied in vitro. Axenically cultivated trichomonads readily attached to isolated intestinal epithelial cells and mucus of the squirrel monkey. The kinetics and nature of T. mobilensis cytadherence were microscopically evaluated in cell-suspension assay using Chinese hamster ovary (CHO) cells and in microplate hemagglutination assay with human erythrocytes. Adherence of the parasites to target cells was concentration- and time-dependent; it was inhibited by sialic acid (N-acetylneuraminic or N-glycolylneuraminic acid) and sialyllactose. Neither trypsinization of the flagellates nor their exposure to low temperature (4 degrees C) affected their cytadherence capacities. The data indicate the presence of adhesin(s) with lectin properties on T. mobilensis. Agglutination of live protozoa by animal and plant lectins with various carbohydrate-binding specificities as well as the occurrence of an electron-dense cell coat on plasma membrane suggest marked glycosylation of the parasite surface.