Identification and expression of the epithelial Muc1 mucin in normal feline tissues

Differential expression of glycans in the urothelial layers of horse urinary bladder

BACKGROUND

Urothelium is a multilayer epithelium covering the inner surface of the urinary bladder that acts as a blood-urine barrier and is involved in maintaining the wellbeing of the whole organism. Glycans serve in the maturation and differentiation of cells and thus play a key role in the morphology and function of the multilayered epithelium. The aim of the present study was to examine the glycoprotein pattern of the horse urinary bladder urothelium by lectin histochemistry.

METHODS

The study involved urinary bladders from four horse stallions. Tissue sections were stained with a panel of eleven lectins, in combination with saponification and sialidase digestion (Ks).

RESULTS

Basal cells displayed high-mannose N-glycans (Con A), α2,6-linked sialic acid (SNA), and O-linked sialoglycans with sialic acids linked to Galβl,3GalNAc (T antigen) (KsPNA) and terminal N-acetylgalactosamine (Tn antigen) (KsSBA). The young intermediate cells expressed terminal N-acetylglucosamine (GlcNAc) (GSA II), galactose (GSA I-B₄), T- and Tn antigens (PNA, SBA). The mature intermediate cells showed additional high-mannose N-glycans, O-linked sialoglycans (sialyl-T antigen, sialyl-Tn antigen), α2,6- and α2,3-linked sialic acid (MAL II), α1,2-linked fucose (UEA I), and GlcNAc (KsWGA). The latter residue marked the boundary with the overlying surface layer. Few Con A positive intermediate cells were seen to cross the entire urothelium thickness. The surface cells showed additional glycans such as T antigen and sialic acids linked to GalNAc binding DBA (KsDBA). Few surface cells contained α1,3-linked fucose (LTA), whereas some other cells displayed intraluminal secretion of mucin-type glycans terminating with GalNAcα1,3(LFucα1,2)Galβ1,3/4GlcNAcβ1 (DBA). The luminal surface expressed the most complex glycan pattern in the urothelium because only α1,3-linked fucose lacked among the demonstrated glycans.

CONCLUSIONS

This study showed that the glycan pattern becomes more complex from the basal to surface layer of the urothelium and that surface cells could modify the composition of urine via the secretion of glycoproteins.

Detection of Epithelial Cell Adhesion Molecule in Feline Normal and Tumor Cell Lines and Tissues With Selected Commercial Anti-human EpCAM Antibodies

Epithelial cell adhesion molecule (EpCAM) is a transmembrane protein expressed at intercellular junctions in epithelial cells. As an epithelial biomarker, it used for immunologic-based capture of epithelial-derived circulating tumor cells (CTCs) in human patients with different carcinomas. EpCAM expression has not been described in normal or neoplastic epithelial tissues in cats. Our goal was to find a commercial antibody that recognizes surface EpCAM expression for CTC detection. We tested two anti-human EpCAM antibodies, designated for use with flow cytometry, for detection of surface EpCAM expression on feline cell lines derived from normal mammary and renal epithelia and mammary and oropharyngeal squamous cell carcinomas in cats. Only one of the antibodies, a goat polyclonal antibody, labeled normal and neoplastic feline mammary epithelial cells and oropharyngeal squamous cell carcinoma cells; no labeling was observed for normal feline kidney epithelial cells. At low dilution, this antibody immunohistochemically stained the intercellular junctions of normal pancreatic, intestinal and mammary epithelium, as well as neoplastic mammary epithelium in feline tissues; however, oral mucosa, skin, and an oropharyngeal squamous cell carcinoma showed no positive immunostaining. The antibody only weakly bound feline squamous cell carcinoma cell lines under static adhesion. Our results indicate that EpCAM is expressed in specific epithelia in cats but is variably expressed in feline mammary tumors and oropharyngeal squamous cell carcinoma. A higher avidity cross-reactive or feline-specific antibody will be required to further investigate EpCAM expression in normal and neoplastic feline tissue or for detecting CTCs in the blood of tumor-bearing cats.

Composition of abomasal mucins in hair goats

The mucosal epithelium of the digestive tract is covered by a layer of mucusthat protects against chemical, enzymatic and mechanical damage, and pathogenic microorganisms. We investigated the composition of the mucin in the abomasum of goat kids using histochemistry and immunohistochemistry. We used 6 - 8-month-old goat kids; samples were collected from the cardia, fundus and pylorus regions of the abomasum. Alcian blue (pH.2.5)-PAS, Alcian blue (pH.2.5)-aldehyde fuchsin, phenylhydrazine-PAS histochemical staining methods were used as well as Muc1, Muc2, Muc5ac and Muc6 immunohistochemistry. We found that neutral mucins, carboxylic mucins and N-acetyl sialomucins were present in the stomachs of the kids. Muc1 was expressed in all glandular epithelium cells and was expressed intensely by the mucous neck cells in the fundus. Although Muc2 expression was not observed in the cardia and fundus, weak expression was found in the surface epithelial cells and mucus secreting cells of the pylorus. Muc5ac was expressed intensely in all glandular epithelial cells and in mucous neck cells of the fundus as well as mucus secreting cells in the pylorus. Moderately intense Muc6 expression also was found in the cardia and fundus; it was expressed intensely in the mucus secreting cells of the pylorus.

Prenatal development and histochemical characteristics of gastrointestinal mucins in sheep fetuses

The object of this study was to describe the prenatal development and histochemical properties of mucins in the sheep gastrointestinal tract. To determine changes in the mucin profile, the sections were stained with specific histochemical stains for carbohydrates. While neutral and mixed mucins were observed in the superficial epithelial cells of the abomasal pyloric region, acidic mucins were detected in the secretory ducts and corpus of the glands. Acidic mucins consisted predominantly of sialomucins. In the duodenal villi, the number of goblet cells containing neutral mucins increased toward the end of gestation, whereas Brunner's glands contained acidic mucins until the 95th day of gestation and both acidic and neutral mucins thereafter. The jejunal goblet cells contained either acidic, neutral, or mixed mucins. Goblet cells containing acidic mucins, which were mainly localized to the ileal crypts and villi, mostly contained sulfated mucins. While villi were observed in the proximal colon until the 115th day of gestation, later the typical crypt structure emerged. During the period in which the villi were found in the proximal colon, the goblet cells containing sulphomucins were predominant, whereas the goblet cells containing sialomucins were predominant after the typical crypt structure was formed. In conclusion, gastrointestinal mucins may be involved in the formation of meconium during the prenatal period, and acidic mucins may contribute to the strength of the intestinal barrier against pathogens and digestive enzymes, as the barrier is not fully functional after birth.

Airway Gland Structure and Function

Submucosal glands contribute to airway surface liquid (ASL), a film that protects all airway surfaces. Glandular mucus comprises electrolytes, water, the gel-forming mucin MUC5B, and hundreds of different proteins with diverse protective functions. Gland volume per unit area of mucosal surface correlates positively with impaction rate of inhaled particles. In human main bronchi, the volume of the glands is ∼ 50 times that of surface goblet cells, but the glands diminish in size and frequency distally. ASL and its trapped particles are removed from the airways by mucociliary transport. Airway glands have a tubuloacinar structure, with a single terminal duct, a nonciliated collecting duct, then branching secretory tubules lined with mucous cells and ending in serous acini. They allow for a massive increase in numbers of mucus-producing cells without replacing surface ciliated cells. Active secretion of Cl(-) and HCO3 (-) by serous cells produces most of the fluid of gland secretions. Glands are densely innervated by tonically active, mutually excitatory airway intrinsic neurons. Most gland mucus is secreted constitutively in vivo, with large, transient increases produced by emergency reflex drive from the vagus. Elevations of [cAMP]i and [Ca(2+)]i coordinate electrolyte and macromolecular secretion and probably occur together for baseline activity in vivo, with cholinergic elevation of [Ca(2+)]i being mainly responsive for transient increases in secretion. Altered submucosal gland function contributes to the pathology of all obstructive diseases, but is an early stage of pathogenesis only in cystic fibrosis.

MUC1 marks collecting tubules, renal vesicles, comma- and S-shaped bodies in human developing kidney tubules, renal vesicles, comma- and s-shaped bodies in human kidney

MUC1 is a transmembrane glycoprotein, apically expressed in most epithelial cells, used in the differential diagnosis of carcinomas and for discrimination of tumors of non-epithelial origin showing epithelioid features. Little attention has been paid so far though, on its possible significance in embryonic tissues. A preliminary study from our group revealed MUC1 expression in the cap mesenchymal cells during human nephrogenesis, suggesting a role for MUC1 in the process of mesenchymal-to-epithelial transition. This study aimed at investigating the expression pattern of MUC1 in various developing structures of human fetal kidney. Expression of MUC1 was examined in kidneys of 5 human fetuses. MUC1 immunoreactivity was detected in ureteric bud tips, in collecting tubules, in cap mesenchymal cells undergoing the initial phases of mesenchymal-to-epithelial transition, in renal vesicles, comma-bodies, and S-shaped bodies. Our previous preliminary report suggested a role for MUC1 in the initial phases of the process of mesenchymal-to-epithelial transition. The present data suggest that MUC1 expression characterizes multiple structures during human nephrogenesis, from the ureteric bud, to the initial phases of mesenchymal-to-epithelial transition and that MUC1 should be added to the genes activated during the process of mesenchymal-to-epithelial transition in the cap mesenchyme of human kidney.

MUC1 in mesenchymal-to-epithelial transition during human nephrogenesis: changing the fate of renal progenitor/stem cells?

BACKGROUND

The development of the human kidney is a complex process requiring interactions between epithelial and mesenchymal cells. The condensed cap mesenchyme is hypothesized to generate a population of stem/progenitor cells that undergo mesenchymal-epithelial transition (MET) originating nephrons. Few immunohistochemical markers are available for detecting cap mesenchymal cells in the early phases of MET.

METHODS

The expression of MUC1 was evaluated in the kidneys, of 4 human foetuses and 2 newborns.

RESULTS

MUC1 immunoreactivity was detected in all the examined kidneys in the cap mesenchyme and in the renal vesicles. Immunostaining for MUC1 in cap mesenchymal cells changed from one nodule to the next: some mesenchymal nodules were negative, some showed MUC1 reactivity in scattered cells, whereas in others, positive cells revealed the presence of a roundish developing epithelial structure.

CONCLUSIONS

Our data clearly indicates, for the first time to the best of our knowledge, immunohistochemical evidence of MUC1 expression during human kidney development. We focused on MUC1 reactivity in the cap mesenchyme. On the basis of these preliminary data, we speculate that MUC1 may be involved in human nephrogenesis and may play a relevant role in MET from the cap mesenchyme to the renal vesicle, changing the fate of renal stem/progenitor cells.

The differences between the localizations of MUC1, MUC5AC, MUC6 and osteopontin in quail proventriculus and gizzard may be a reflection of functional differences of stomach parts

Mucins are high molecular weight glycoproteins which constitute the major component of the mucus layer and are produce by many epithelial tissues in vertebrates. Osteopontin (OPN) is an adhesive phosphorylated glycoprotein that is expressed by a broad range of tissues and cells. Although gastric mucins MUC1, MUC5AC, MUC6 and OPN have been widely used in histological studies and in diagnostic pathology in order to diagnose gastric carcinomas, their localizations in the stomach of quail have not yet been studied. In this study, the localizations of MUC1, MUC5AC, MUC6 and OPN in the proventriculus and gizzard of Japanese quail during the post-hatching period were compared at light microscope levels by applying immunohistochemical methods. In all ages studied, the immunoreactivity of MUC5AC was present in the lining epithelium of both folds and superficial proventricular glands in the proventriculus, whereas MUC1, MUC6 and OPN reactivity was found in the oxynticopeptic cells of profound proventricular glands. In addition, some cells in the fold epithelium of the proventriculus showed a positive reaction to OPN. The immunoreactivity of MUC1 in gizzard was different from that of MUC5AC. Although MUC5AC was expressed in the cells of both the surface epithelium and profound glands of the gizzard, MUC1 was only localized in the profound glands of the gizzard. However, MUC6 and OPN immunoreactivity was absent in the gizzard. The results indicated that the differences between the localizations of MUC1, MUC5AC, MUC6 and OPN in quail proventriculus and gizzard may be a reflection of functional differences of stomach parts. Although the biological significances of the expressions of MUC1, MUC5AC, MUC6 and OPN in the quail stomach remains unknown, these notable glycoproteins may be associated with barrier function, host defence, and/or secretion.