THE BLADDER DOES NOT APPEAR TO HAVE A DYNAMIC SECRETED CONTINUOUS MUCOUS GEL LAYER

Mechanisms and strategies to enhance penetration during intravesical drug therapy for bladder cancer

Bladder cancer (BCa) is one of the most prevalent cancers worldwide. The effectiveness of intravesical therapy for bladder cancer, however, is limited due to the short dwell time and the presence of permeation barriers. Considering the histopathological features of BCa, the permeation barriers for drugs to transport across consist of a mucus layer and a nether tumor physiological barrier. Mucoadhesive delivery systems or mucus-penetrating delivery systems are developed to enhance their retention in or penetration across the mucus layer, but delivery systems that are capable of mucoadhesion-to-mucopenetration transition are more efficient to deliver drugs across the mucus layer. For the tumor physiological barrier, delivery systems mainly rely on four types of penetration mechanisms to cross it. This review summarizes the classical and latest approaches to intravesical drug delivery systems to penetrate BCa.

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.

Surface Shave: Revealing the Apical-Restricted Uroglycome

This study aimed to investigate the highly differentiated urothelial apical surface glycome. The functions of the mammalian urothelium, lining the majority of the urinary tract and providing a barrier against toxins in urine, are dependent on the correct differentiation of urothelial cells, relying on protein expression, modification, and complex assembly to regulate the formation of multiple differentiated cell layers. Protein glycosylation, a poorly studied aspect of urothelial differentiation, contributes to the apical glycome and is implicated in the development of urothelial diseases. To enable surface glycome characterization, we developed a method to collect tissue apical surface N- and O-glycans. A simple, novel device using basic laboratory supplies was developed for enzymatic shaving of the luminal bladder urothelial surface, with subsequent release and mass spectrometric analysis of apical surface O- and N-glycans, the first normal mammalian urothelial N-glycome to be defined. Trypsinization of superficial glycoproteins was tracked using immunolabeling of the apically expressed uroplakin 3a protein to optimize enzymatic release, without compromising the integrity of the superficial urothelial layer. The approach developed for releasing apical tissue surface glycans allowed for comparison with the N-glycome of the total porcine bladder urothelial cells and thus identification of apical surface glycans as candidates implicated in the urothelial barrier function. Data are available in MassIve: MSV000087851.

The glycobiology of uropathogenic E. coli infection: the sweet and bitter role of sugars in urinary tract immunity

Urinary tract infections (UTI) are among the most prevalent infectious diseases and the most common cause of nosocomial infections, worldwide. Uropathogenic E. coli (UPEC) are responsible for approximately 80% of all UTI, which most commonly affect the bladder. UPEC colonize the urinary tract by ascension of the urethra, followed by cell invasion, and proliferation inside and outside urothelial cells, thereby causing symptomatic infections and quiescent intracellular reservoirs that may lead to recurrence. Sugars, or glycans, are key molecules for host–pathogen interactions, and UTI are no exception. Surface glycans regulate many of the events associated with UPEC adhesion and infection, as well as induction of the host immune response. While the bacterial protein FimH binds mannose‐containing host glycoproteins to initiate infection and UPEC‐secreted polysaccharides block immune mechanisms to favour intracellular replication, host glycans on the urothelial surface and on secreted glycoproteins prevent or limit infection by inhibiting UPEC adhesion. Given the importance of glycans during UTI, here we review the glycobiology of UPEC infection to highlight fundamental sugar‐mediated processes of immunological interest for their potential clinical applications. Interdisciplinary approaches incorporating glycomics and infection biology may help to develop novel non‐antibiotic‐based therapeutic strategies for bacterial infections as the spread of antimicrobial‐resistant uropathogens is currently threatening modern healthcare systems.

Preclinical Evaluation of Intravesical Cisplatin Nanoparticles for Non-Muscle-Invasive Bladder Cancer

Purpose: Prior clinical trials evaluating cisplatin for non-muscle-invasive bladder cancer (NMIBC) were stopped due to local and systemic toxicity. Currently, there is still a need for improved intravesical therapies, and nanoparticle-based CDDP may be efficacious without the toxicity of free cisplatin observed in the past.Experimental Design: Cisplatin nanoparticles (CDDP NPs) were developed using biocompatible poly(l-aspartic acid sodium salt; PAA), both with and without low and high grafting density of methoxy-polyethylene glycol (PEG). In vitro cytotoxicity studies confirmed activity of CDDP NPs and CDDP solution against a papillary bladder cancer cell line. Local toxicity was assessed by three weekly intravesical administrations of CDDP formulations. CDDP NPs and CDDP solution were evaluated for bladder absorption in murine models 1 and 4 hours after intravesical administration. In vivo efficacy was evaluated in an immunocompetent carcinogen model of NMIBC.Results: CDDP NPs showed decreased local toxicity, as assessed by bladder weight, compared with CDDP solution. Furthermore, >2 μg/mL of platinum was observed in mouse serum after intravesical administration of CDDP solution, whereas serum platinum was below the limit of quantification after intravesical administration of CDDP NPs. CDDP NPs provided significantly increased (P < 0.05) drug levels in murine bladders compared with CDDP solution for at least 4 hours after intravesical administration. In vivo, CDDP NPs reduced cancer cell proliferation compared with untreated controls, and was the only treatment group without evidence of invasive carcinoma.Conclusions: Cisplatin-loaded PAA NPs have the potential to improve intravesical treatment of NMIBC while reducing local and systemic side effects. Clin Cancer Res; 23(21); 6592-601. ©2017 AACR.

The role of the antimicrobial peptide cathelicidin in renal diseases

The balance between the human body and surrounding microorganisms is crucial for homeostasis and health. A disturbance in host-pathogen interactions causes disease. Two important diseases of the kidney and urinary tract are directly caused by bacteria or bacterial toxins: urinary tract infection (UTI) and diarrhea-associated hemolytic uremic syndrome (HUS). In the majority of cases, UTIs are caused by bacteria ascending from the perineum through the urethra to the urinary tract. In contrast, HUS is caused by non-invasive bacteria, such as enterohemorrhagic Escherichia coli, which colonize the gut and do not enter the blood stream. In this latter case, the bacteria release Shiga toxin, which binds to blood cells and thus reaches the target organs, mainly kidneys. Interactions between Shiga toxin, blood cells and endothelial cells in the kidney lead to cell apoptosis and inflammation. Innate immunity and the antimicrobial peptide cathelicidin seem to play important roles in the pathogenesis of both UTI and HUS. Moreover, influencing cathelicidin production and release might offer new therapeutic and prophylactic strategies for both diseases.

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.

From infection to immunotherapy: host immune responses to bacteria at the bladder mucosa

The pathogenesis of urinary tract infection and mechanisms of the protective effect of Bacillus Calmette-Guerin (BCG) therapy for bladder cancer highlight the importance of studying the bladder as a unique mucosal surface. Innate responses to bacteria are reviewed, and although our collective knowledge remains incomplete, we discuss how adaptive immunity may be generated following bacterial challenge in the bladder microenvironment. Interestingly, the widely held belief that the bladder is sterile has been challenged recently, indicating the need for further study of the impact of commensal microorganisms on the immune response to uropathogen infection or intentional instillation of BCG. This review addresses the aspects of bladder biology that have been well explored and defines what still must be discovered about the immunobiology of this understudied organ.

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.

Synthesis and localization of trefoil factor family (TFF) peptides in the human urinary tract and TFF2 excretion into the urine

Trefoil factor family (TFF) peptides promote regeneration and repair processes of mucous epithelia. They also probably play a key role in the remarkable regenerative capacity of the urinary tract epithelia. We have localized TFF1, TFF2, and TFF3 expression systematically in surgical specimens from the urinary tract by reverse transcription with the polymerase chain reaction, Western blot analysis, and immunohistochemistry. Urine samples from patients suffering from nephrolithiasis have been investigated and compared with those of healthy controls. TFF synthesis is detectable along the entire urinary tract epithelia. TFF3 synthesis is the most pronounced followed by TFF1, whereas TFF2 synthesis is occasionally detectable but only in trace amounts. In contrast, TFF2 is the predominant TFF peptide excreted into the urine, and significantly increased urinary TFF2 levels (together with occasionally raised TFF3 levels) have been observed in patients suffering from nephrolithiasis. Thus, we consider that TFF3 plays a major part in regeneration and restitution processes in urinary tract epithelia. TFF2 and probably also TFF3 are candidate biomarkers for nephrolithiasis and possibly other inflammatory conditions of the urinary tract.

Antimicrobial mechanisms of the urinary tract

The urinary tract is a key system to maintain the homeostasis of the human body. It is relatively open to the outside environment, the perineum, a region highly colonized by bacteria. Bacteria can even be found in urine of healthy individuals. Still, urinary tract infections are far less frequent than it could be expected under these conditions. The high resistance against such infections has been observed already more than 100 years ago. Since then, many antimicrobial mechanisms of the urinary tract have been elucidated. Some questions, however, remain challenges for patients, scientists and health care professionals. In this review, we try to summarize the achieved knowledge about mechanisms, maintaining the urinary tract free of infection. In addition, we discuss their relevance and possible clinical application.