Glycoproteins in the urothelium and in the urine of the epidermal growth factor induced growing urinary tract in rats

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.

Systematic Review to Compare Urothelium Differentiation with Urethral Epithelium Differentiation in Fetal Development, as a Basis for Tissue Engineering of the Male Urethra

BACKGROUND

Tissue-engineered (TE) urethra is desirable in men with urethral disease (stricture or hypospadias) and shortage of local tissue. Although ideally a TE graft would contain urethral epithelium cells, currently, bladder epithelium (urothelium) is widely used, but morphologically different. Understanding the differences and similarities of urothelium and urethral epithelium could help design a protocol for in vitro generation of urethral epithelium to be used in TE grafts for the urethra.

PURPOSE

To understand the development toward urethral epithelium or urothelium to improve TE of the urethra.

METHODS

A literature search was done following PRISMA guidelines. Articles describing urethral epithelium and bladder urothelium development in laboratory animals and humans were selected.

RESULTS

Twenty-nine studies on development of urethral epithelium and 29 studies on development of urothelium were included. Both tissue linings derive from endoderm and although adult urothelium and urethral epithelium are characterized by different gene expression profiles, the signaling pathways underlying their development are similar, including Shh, BMP, Wnt, and FGF. The progenitor of the urothelium and the urethral epithelium is the early fetal urogenital sinus (UGS). The urethral plate and the urothelium are both formed from the p63+ cells of the UGS. Keratin 20 and uroplakins are exclusively expressed in urothelium, not in the urethral epithelium. Further research has to be done on unique markers for the urethral epithelium.

CONCLUSION

This review has summarized the current knowledge about embryonic development of urothelium versus urethral epithelium and especially focuses on the influencing factors that are potentially specific for the eventual morphological differences of both cell linings, to be a basis for developmental or tissue engineering of urethral tissue.

The urothelium: anatomy, review of the literature, perspectives for veterinary medicine

Over time, much knowledge has been accumulated about the active role of the urothelium, principally in rodents and human. Far from being a mere passive barrier, this specialized epithelium can alter the ion and protein composition of the urine, is able to sense and respond to mechanical stimuli such as pressure, and react to mechanical stimuli by epithelial cell communication with the nervous system. Most of the specialized functions of the urothelium are linked to a number of morpho-physiologic properties exhibited by the superficial umbrella cells, including specialized membrane lipids, asymmetric unit membrane particles and a plasmalemma with stiff plaques which function as a barrier to most substances found in urine, thus protecting the underlying tissues. Moreover, the entire mucosa lining the low urinary tract, composed of urothelium and sub-urothelium, forms a functional transduction unit, able to respond to eso- and endogenous physical and chemical stimuli in a manner assuring an adequate functional response. This review will summarize the available information on each area of inquiry from a morpho-functional point of view. Possible considerations pertaining to species of veterinary interest are reviewed as well. The review was prepared consulting the electronic databases PubMed and Cab Abstracts and retrieving all pertinent reports and the relative reference lists, in order to identify any potential additional studies that could be included. Full-length research articles and thematic reviews were considered. Information on the urothelium of some domestic animal species was also included.

Glycosylation of uroplakins. Implications for bladder physiopathology

Urothelium, a specialized epithelium, covers the urinary tract and act not only as a barrier separating its light from the surrounding tissues, but fulfills an important role in maintaining the homeostasis of the urothelial tract and well-being of the whole organism. Proper function of urothelium is dependent on the precise assemble of highly specialized glycoproteins called uroplakins, the end products and differentiation markers of the urothelial cells. Glycosylation changes in uroplakins correlate with and might reflect progressive stages of pathological conditions of the urothelium such as cancer, urinary tract infections, interstitial cystitis and others. In this review we focus on sugar components of uroplakins, their emerging role in urothelial biology and disease implications. The advances in our understanding of uroplakins changes in glycan moieties composition, structure, assembly and expression of their glycovariants could potentially lead to the development of targeted therapies and discoveries of novel urine and plasma markers for the benefit of patients with urinary tract diseases.

In situ characterization of glycans in the urothelium of donkey bladder: evidence of secretion of sialomucins

The glycoprotein pattern was investigated by lectin histochemistry in the urothelium lining the urinary bladder of the donkey Equus asinus. Tissue sections were stained with a panel of twelve lectins, in combination with saponification and sialidase digestion (K-s). The urinary bladder urothelium has three distinct layers from the basal zone to the lumen consisting of basal, intermediate and superficial cells (umbrella cells). Cytoplasm of basal cells reacted with SNA, PNA, K-s-PNA, GSA I-B4 and Con A showing glycans ending with Neu5Acα2,6Gal/GalNAc, Neu5AcGalβ1,3GalNAc, αGal and with terminal/internal αMan. The cytoplasm of umbrella cells displayed an increase of Neu5AcGalβ1,3GalNAc and the appearance of Neu5AcGalβ1,3GalNAc, Neu5acα2,3Galβ1,4GlcNAc and Neu5AcGalNAc residues (MAL II, K-s-SBA and K-s-HPA staining). Scattered umbrella cells were characterized by glycans terminating with GalNAc binding DBA, SBA and HPA. The mucosa forms folds with a crypt-like appearance where the urothelium shows a different pattern of glycans. The bladder luminal surface stained with K-s-PNA, K-s-DBA, KOH-s-SBA, and K-s-HPA displaying a coating of sialoglycoproteins belonging to O-linked glycans (typical secretory moieties). These findings show that different glycosylation patterns exist along the donkey bladder urothelium, and different sub-populations of umbrella cells are present secreting the sialoglycans which constitute the protective gel layer lining the bladder.

Radiation effects on cellularity, proliferation and EGFR expression in mouse bladder urothelium

This study was designed to determine changes in cell numbers, proliferation (using Ki-67) and EGFR expression in mouse bladder urothelium during the early and late radiation response. Groups of mice were irradiated with a single dose of 20 Gy and assayed 0-360 days later. Urothelial cells were counted. After immunohistochemistry, the absolute and relative numbers of Ki-67(+) and EGFR(+) cells were analyzed. Radiation exposure resulted in a decrease in total urothelial cell numbers to 49% by day 31, with restoration of cellularity by day 180. In contrast, at day 360, an increase in total cell number (143%) was seen. Slightly increased Ki-67 expression was found at days 120 and 180 after treatment, followed by a pronounced elevation at days 240 and 360. Compared to controls, higher EGFR expression was detected up to day 360 after irradiation. A positive correlation was found between total urothelial cells numbers and Ki-67 as well as EGFR expression. Radiation exposure results in an increased urothelial expression of EGFR that precedes urothelial restoration, indicating a contribution of the EGF/EGFR system to urothelial proliferation and differentiation. Further studies are needed to evaluate the impact of EGFR inhibition on radiation effects in the urinary bladder.

Creation of luminal tissue covered with urothelium by implantation of cultured urothelial cells into the peritoneal cavity

PURPOSE

We established the culture condition of seeding urothelial cells onto a scaffold for implantation into the peritoneal cavity and evaluated the histology of implanted urothelial cells.

MATERIALS AND METHODS

In part 1 of the study cultured porcine bladder urothelial cells were seeded onto 3 types of collagen gel made on microporous membrane, including collagen gel with or without cultured porcine bladder fibroblasts, or a feeder layer. The macroscopic and microscopic appearance of the gel with urothelial cells were examined in vitro. As an in vivo study, cultured porcine bladder urothelial cells were seeded onto a collagen gel/sponge matrix with or without cultured fibroblasts, or a feeder layer. Urothelial cell survival on each matrix was evaluated 28 days after implantation onto the omentum or mesentery of nude rats. In part 2 of the study rat urothelial cells were cultured and seeded onto fibrin gel/atelocollagen sponge matrix as an autologous implantation model. After 7 days of cultivation the matrix was folded with urothelial cells inside, implanted onto the mesentery and serially evaluated.

RESULTS

Gel containing cultured fibroblasts was shrunken and basement membrane formation was observed on the gel with cultured fibroblasts or the feeder layer in vitro. Urothelial cells cultured with the feeder layer better survived on the collagen based matrix and formed a hollow-like lumen when implanted into the peritoneal cavity. The regenerated urothelium in an autologous implantation showed the same histological features as normal bladder urothelium.

CONCLUSIONS

Selection of less degradable matrix and formation of basement membrane are critical for survival of implanted urothelial cells. The regenerated urothelium in an autologous implantation model seems to have the similar properties to the normal urothelium.