Restoring the barrier of chronically damaged urothelium using chondroitin sulfate glycosaminoglycan-replenishment therapy.

PURPOSE OF REVIEW: This study aims to further understand the physiological mechanism of chondroitin sulfate treatment on the urinary bladder in cases of inflammation, by investigating the effect of chondroitin sulfate therapy on recovery of urothelial barrier in an in-vitro chronic injury model. RECENT FINDINGS: With inflammatory bladder conditions, the urothelial barrier seems decreased. Glycosaminoglycan (GAG) replacement therapy is supposed to help restore this barrier. Clinical studies on inflammatory bladder conditions are complicated because of the heterogeneous patient population, hence the need for preclinical models. SUMMARY: In a model using porcine urothelial cells, functional barrier (TEER) and barrier markers were assessed. Chronic urothelial damage was simulated through protamine sulfate instillations with and without subsequent chondroitin sulfate instillations during 3 days. Chondroitin sulfate instillations significantly improved TEER compared to protamine sulfate treatment only (TEER difference 310 Ω.cm 2 , P  < 0.001). This consistent effect over 3 days resulted in a significant higher mean TEER value in the chondroitin sulfate treated group (difference 1855 Ω.cm 2 , P  < 0.001). Enhanced recovery of chondroitin sulfate and other barrier markers was observed.Chondroitin sulfate therapy shows promise in facilitating the recovery of the urothelial barrier in cases of chronic damage. This preclinical study lends support to the use of clinical GAG replenishment therapy for patients with a chronically impaired urothelium.

Improving the barrier function of damaged cultured urothelium using chondroitin sulfate.

AIMS: To determine whether glycosaminoglycan (GAG) replenishment is able to improve recovery of a deficient urothelial barrier, chondroitin sulfate (CS) instillations were tested using an in vitro model. Porcine urothelial cells (Ucells) were terminally differentiated in culture conditions to construct a urothelial layer with a functional barrier. This layer was damaged to compromise barrier function to simulate a key characteristic of bladder pain syndrome/interstitial cystitis. The functional effect of subsequent treatment with CS was evaluated. METHODS: Primary porcine Ucells were isolated and cultured on inserts. Differentiation of cells was evaluated with immunohistochemical analysis for the presence of umbrella cells, tight junctions and CS. Transepithelial electrical resistance (TEER) measurements were performed to evaluate barrier function. Protamine was used to simulate mild urothelial damage. CS 0.2% (vol/vol), a GAG, was subsequently instilled in the treatment group. The recovery of barrier function was further evaluated with TEER measurements. The Student t test was used for the analysis of results. RESULTS: After induction of differentiation, the Ucells expressed barrier markers and a functional barrier was established (measured by high TEER). TEER decreased significantly after instillation with protamine. CS instillation improved recovery of TEER significantly measured after 7 hours (84% vs 22% in controls). After 24 hours; however, the TEER was comparable in both experimental groups. CONCLUSION: CS instillation improves the recovery of the urothelial barrier after damage in vitro. This functional experiment shows that CS improves recovery of damaged urothelial function, which supports the hypothesis behind the mechanism of action of GAG-replenishment therapy.

Co-administration of transient receptor potential vanilloid 4 (TRPV4) and TRPV1 antagonists potentiate the effect of each drug in a rat model of cystitis.

OBJECTIVE: To investigate transient receptor potential vanilloid 4 (TRPV4) expression in bladder afferents and study the effect of TRPV4 and TRPV1 antagonists, alone and in combination, in bladder hyperactivity and pain induced by cystitis. MATERIAL AND METHODS: TRPV4 expression in bladder afferents was analysed by immunohistochemistry in L6 dorsal root ganglia (DRG), labelled by fluorogold injected in the urinary bladder. TRPV4 and TRPV1 co-expression was also investigated in L6 DRG neurones of control rats and in rats with lipopolysaccharide (LPS)-induced cystitis. The effect of TRPV4 antagonist RN1734 and TRPV1 antagonist SB366791 on bladder hyperactivity and pain induced by cystitis was assessed by cystometry and visceral pain behaviour tests, respectively. RESULTS: TRPV4 is expressed in sensory neurones that innervate the urinary bladder. TRPV4-positive bladder afferents represent a different population than the TRPV1-expressing bladder afferents, as their co-localisation was minimal in control and inflamed rats. While low doses of RN1734 and SB366791 (176.7 ng/kg and 143.9 ng/kg, respectively) had no effect on bladder activity, the co-administration of the two totally reversed bladder hyperactivity induced by LPS. In these same doses, the antagonists partially reversed bladder pain behaviour induced by cystitis. CONCLUSIONS: TRPV4 and TRPV1 are present in different bladder afferent populations. The synergistic activity of antagonists for these receptors in very low doses may offer the opportunity to treat lower urinary tract symptoms while minimising the potential side-effects of each drug.