Abstract
Bladder epithelium is not only a simple defence against infections, but it is also a specialized tissue regulating complex bladder functions and playing an active role in the pathogenesis of many bladder diseases. There is strong evidence that different chronic inflammatory bladder diseases, such as recurrent urinary tract infection (UTI), chemical or radiation cystitis and painful bladder syndrome/interstitial cystitis (PBS/IC), can be pathophysiologically linked in the first step of the disease to the loss of the glycosaminoglycan (GAG) mucous layer independently of the original cause of the inflammatory process. The aim of this article is to review the current evidence on the clinic applications of GAGs in urology, with particular emphasis on the therapeutic use of hyaluronic acid (HA) and chondroitin sulphate (CS). A comprehensive electronic literature search was conducted in May 2011 using the Medline database. Three studies supported the decrease of the rate of recurrent UTIs by restoring the GAG layer, showing a significant reduction of UTI rates and a prolonged median time to recurrence after HA intravesical instillations in women with recurrent UTI. We provide higher level evidence by reporting a prospective, randomized, double-blind, placebo-controlled study on the use of intravesical HA and CS in women with recurrent UTIs. A significant reduction of 77% in the UTI rate per patient per year versus placebo was observed at the end of the study. Nine studies were published between 2002 and 2011 on the use of HA and CS to treat PBS/IC. Three of them evaluated the use of GAGs bladder instillation to prolong the effects of bladder hydrodistension. In the other six studies the efficacy of HA bladder instillations to reduce symptoms score was assessed. Preliminary studies support data on the role of HA–CS in detrusor overactivity, nonbacterial cystitis and urological malignancies. Few data are available regarding the mode of action of HA–CS or its effectiveness in the management of bladder diseases. The major issue in interpreting the available evidence regarding HA–CS is that most of the reported studies are nonrandomized and without a control arm. HA–CS may be considered for further studies, including randomized, controlled trials with adequate power.
Introduction
Bladder epithelium (BE), also known as ‘transitional epithelium’ or ‘urothelium’, is not only a simple defence against infections, but it is also a specialized tissue regulating complex bladder functions and playing an active role in the pathogenesis of many bladder diseases.
Evidence suggests that the urothelium has two main active functions [Arms and Vizzard, 2011; Kanai, 2011; Clemens 2010]: ‘afferent’ function, which informs the central nervous system on local stimuli and therefore is involved in the control of the micturition reflex, pain reflex, and cardiovascular reflex modulation; ‘efferent’ (or paracrine) function, which is linked to the release of mediators, such as substance P and tachykinins, provoking smooth muscle contraction and local inflammation.
BE is coated by a thick layer of glycosaminoglycans (GAGs) that acts as a nonspecific anti-adherence factor and a nonspecific defence mechanism against infection and found in urine irritants (e.g. urea and potassium). GAGs are long, linear and highly negative charged heterogeneous polysaccharides composed of a variable number of repeating disaccharide units.
There are two main types of GAGs: nonsulphated GAGs, that is, hyaluronic acid (HA), and sulphated GAGs, that is, heparan sulphate and heparin, chondroitin sulphate (CS), dermatan sulphate, and keratan sulphate. With the exception of HA, GAGs are usually covalently attached to a protein core, forming an overall structure that is referred to as a proteoglycan [Lilly and Parsons, 1990].
There is strong evidence that different chronic inflammatory bladder diseases, such as recurrent urinary tract infection (UTI), chemical or radiation cystitis, and painful bladder bladder syndrome (PBS)/interstitial cystitis (IC) can be pathophysiologically linked in the first step of the disease to the loss of the GAGs mucous layer independently of the original cause of the inflammatory process [Iavazzo et al. 2007].
A cascade of events starting from a GAG injury that fails to heal may lead to chronic bladder epithelial damage and neurogenic inflammation [Geppetti et al. 2008].
Various causes, such as autoimmune diseases, chronic bacterial infections, chemicals including Calmette–Guérin exposure, may be considered in the early stage of urothelial GAG loss. The loss of the watertight function of the urothelium would allow both the normal and abnormal (i.e. metabolites of cytotoxic drugs or toxic substances excreted in urine) constituents of urine to come into direct contact with the subepithelial layers causing inflammation and delayed healing of the damaged urothelial layer and GAGs.
The activation of the peptide-containing fibres in the suburothelium is responsible for neuronal hypersensitivity that leads to allodynia with increased frequency, nocturia, urgency and pain during filling.
According to these theories, the early repair of the GAG layer by HA and CS might avoid the chronic evolution of bladder inflammation. The restoration of the GAG layer has recently become the main aim of new therapies for the treatment of chronic cystitis and PBS/IC.
The aim of this article is to review the current evidence on the clinic applications of GAGs in urology, with particular emphasis on the therapeutic use of HA and CS.
A comprehensive electronic literature search was conducted in May 2011 using the Medline database, through either PubMed or Ovid as a search engine, to identify all publications relating to HA, CS, GAG replacement treatment, intravesical administration and bladder disease in urology. Both experimental and clinical research studies were considered. English language articles were included for review, and non-English articles were included if they provided additional, relevant information.
The search was conducted using a free-text protocol that included the following terms: hyaluronic acid, chondroitin sulphate, glycosaminoglycan replacement treatment, intravesical administration and bladder disease.
Recurrent UTIs
UTIs are very common in women and they represent one of the most formidable challenges in clinical practice, given their high prevalence, frequent recurrence and myriad of associated morbidities in the setting of rapidly evolving antimicrobial resistance. According to the European Association of Urology guidelines [Naber et al. 2001], recurrent UTIs are defined as at least three episodes of uncomplicated infection documented by urine culture with the isolation of greater than 103 colony-forming units/ml. It is estimated that approximately 20% of patients with UTI will develop a second infection within 6 months [Foxman et al. 2002; Foxman, 2000].
Low-dose antimicrobial therapy may be used to prevent recurrent UTIs in affected women but it generates antimicrobial resistance and side effects. Thus, nonantimicrobial prevention strategies are welcomed.
Damage of the urothelial GAGs layer may facilitate bacterial adherence and infection development [Parsons et al. 1994].
A comparative analysis of studies on recurrent urinary tract infections.
PCS, prospective cohort studies; RCT, randomized controlled trial; UTI, urinary tract infection.
Constandinides and colleagues first supported the decrease in the rate of recurrent UTIs by restoring the GAG layer [Constandinides et al. 2004]. They showed a significant reduction in the UTI rates per patient, both in number of infections per year (from 4.3 to 0.3, p < 0.001) and prolonged median time to recurrence (from 96 to 498 days, p < 0.001) after HA intravesical instillations in 40 women with recurrent UTI.
Lipovac and colleagues evaluated the efficacy of nine HA bladder instillations over 6 months in 20 women with a history of recurrent UTI [Lipovac et al. 2007]. Their status was assessed prospectively but compared with a retrospective review of patients’ charts. The number of infections per year per patient was significantly reduced (from 4.99 ± 0.92 to 0.56 ± 0.82, p > 0.001) and the mean time to recurrence (from 76.7 ± 24.6 to 178.3 ± 25.5 days, p > 0.001) was prolonged significantly. Nevertheless 65% of patients were free of recurrences until the end of study (47.6 weeks).
It should be noted that, despite providing encouraging results, no control group was included in both these early studies.
More recently, our group was able to provide a higher level of evidence by reporting a prospective, randomized, double-blind, placebo-controlled study on the use of intravesical HA and CS in women with recurrent UTIs [Damiano et al. 2011]. A significant reduction of 77% (mean difference, 95% confidence interval, 73.2–80.8, p = 0.0002) in the UTI rate per patient per year versus placebo (−86.6 ± 47.6% versus −9.6 ± 24.6%) was observed at the end of the study. Moreover, mean time to UTI recurrence was significantly prolonged (185.2 ± 78.7 versus 52.7 ± 33.4 days, p < 0.001) after treatment with HA–CS compared with placebo. Overall urinary symptoms and quality of life measured by questionnaires significantly improved compared with placebo. Finally, serious adverse events were not observed in this study.
Overall, in all above mentioned studies, serious adverse events were not observed.
In contrast to traditional antibiotic therapy, which aims at eradicating pathogens, treatment with HA targets bacterial adherence to the bladder mucosa with the presumption that a damaged GAG layer facilitates bacterial adherence and therefore recurrent UTI, and repair of the GAG layer is capable of preventing adherence.
PBS/IC
PBS/IC is a chronic intermittent clinical syndrome characterized by a constellation of symptoms that include bladder/pelvic pain associated with urinary urgency, frequency and dysuria [van de Merwe et al. 2008].
It has been estimated that approximately 500,000 individuals in the USA have PBS/IC; the vast majority are adult women, only 10% are men [Jones et al. 1997]. It is frequently a diagnosis of exclusion so the average delay in diagnosis is estimated to be 4 years.
The exact aetiology of this disease is still unknown and various hypotheses have been postulated including autoimmune and allergic reactions and occult infection. The most recent one is based on a disorder of the lower urinary dysfunction epithelium [Parsons, 2011]. In other words, the loss of the GAGs ‘water-tight’ function exposes the bladder submucosa to toxic substances present in urine (normal substances such as Na–K–H–Cl and abnormal substances such as cytotoxic drugs and toxins). Once these irritating substances penetrate the bladder wall, a ‘domino-like’ mechanism is activated and the bladder fails to repair the damage.
Many drugs have been proposed for the treatment of PBS/IC, many having anti-inflammatory action. Botulin toxin A is also described on the basis of experimental studies that showed the positive effect on visceral pain [Cervigni et al. 2008].
Comparative analysis on studies on interstitial cystitis.
ICAM-1 (intracellular adhesion molecule-1) is one of the identified cell receptors for hyaluronic acid.
Cmax > 350 ml with 0.9% Na solution is not considered a diagnostic criterion for diagnosis of interstitial cystitis. CCS, case control study; CSI, interstitial cystitis symptom index; ICPI, interstitial cystitis problem index; ICSI, interstitial cystitis symptom index; PCS, prospective cohort study; PST, potassium sensitivity test; PUF, pelvic pain and urgency/frequency symptom scale; RCT, randomized controlled trial; VAS, visual analogue scale.
Leppilahti and colleagues administered four weekly intravesical instillations of 40 mg HA after BH in 11 patients and observed a decrease in urinary frequency (less than 75%) and in a visual analogue scale (VAS) pain score (less than 26%) [Leppilahti et al. 2002]. Ahmad and colleagues and Shao and colleagues used 40 mg HA administered intravesically to prolong the bladder capacity obtained after BH [Shao et al. 2010; Ahmad et al. 2008]. They observed in each study an improvement in mean bladder capacity; 492 ml versus 776 ml after 16 months of follow up in the 23 patients [Ahmad et al. 2008]; +27 ml versus −5 ml in the placebo group after 6 months [Shao et al. 2010].
In the other six studies the efficacy of HA bladder instillations to reduce symptoms score was assessed. Daha and colleagues evaluated the efficacy of 10 weekly instillations of 40 mg HA in 48 patients with clinical symptoms of IC and a previous positive 0.4 M potassium sensitivity test [Daha et al. 2005]. Moreover, they analysed the study population by separating it into two groups: first according to bladder capacity after NaCl cystometry (groups I and II) and then according to bladder capacity reduction rate after a 0.2 M KCl test performed (Ia/IIa ≥ 30% and Ib/IIb < 30%). They found symptom relief (VAS scores improvements of 84% and 87%, groups I and II, respectively) more particularly evident in patients with a higher bladder capacity reduction after 0.2 M KCl solution test (mean reduction in VAS scores, 3 in Ia/IIa group versus 5 in group Ib/IIb).
Gupta and colleagues showed that 55% of their study population (20/36) improved after six weekly doses of 40 mg HA, particularly those patients with a positive potassium sensitivity test (PST) [Gupta et al. 2005].
In a prospective, uncontrolled study, Kallestrup and colleagues reported a 65% of positive response rate after four weekly plus two monthly bladder instillations of 40 mg HA in 20 patients with PBS/IC [Kallestrup et al. 2005]. A significant reduction in pain score was noted (a 2.2-fold decrease in pain score after 3 months and 5.2-fold decrease after 3 years). However, after 3 years of therapy, seven patients (35%) were considered again partial responders.
Theoharides and colleagues used dietary supplements to treat 252 patients affected by PBS/IC in an uncontrolled study. They observed a reduction of about 50% in VAS score over 12 months of drug administration (25 male patients, mean VAS score reduced from 7.6 to 3.4; 227 women patients, mean VAS score reduced from 7.91 to 3.97) [Theoharides et al. 2008].
In an open, prospective, unblinded and uncontrolled study Cervigni and colleagues showed an improvement in urinary symptoms after 20 weekly and 3 monthly intravesical instillations of 40 mg HA and CS over 8 months of follow up [Cervigni et al. 2008]. They used many questionnaires to evaluate therapy efficacy in 23 women: IC symptom index (ICSI), IC problem index (ICPI), pelvic pain and urgency/frequency (PUF) symptom scale and VAS score for pain–frequency–urgency; they reported a significant improvement in the mean value of each outcome compared with the pretreatment value (ICSI 13 versus 11; ICPI 11 versus 10; PUF 22 versus 17; VAS pain–frequency–urgency 5 versus 4, 7 versus 5, 6 versus 3, respectively).
Similar results were reported by Riedl and colleagues. They administered 40 mg HA weekly in 126 patients with PBS/IC until recording a symptomatic improvement [Riedl et al. 2008]. Therefore, the average number of instillations for all patients was 12 and the mean VAS symptom score was reduced to 3.5 versus 8.5 from the first treatment.
Finally, although different follow ups and outcomes were used to evaluate treatment efficacy, in each study a therapeutic success was reported. However, some limitations of these studies should be recognized as most were unblinded pilot studies, without a control group. However, the positive results obtained by using HA support the ‘domino-like’ pathophysiological hypothesis and it warrants further multicentre, randomized, placebo-controlled trial to confirm these early findings. Finally, no serious adverse events were recorded in any of these studies.
Idiopathic detrusor overactivity
The International Continence Society defines idiopathic detrusor overactivity (IDO) as involuntary detrusor contractions during the filling phase, without a clear cause [Abrams et al. 2002]. IDO can produce the same storage lower urinary tract symptoms such as frequency, urgency and urge incontinence.
We found only few clinical research and experimental models on GAGs and IDO with conflicting results.
Ferrara observed a higher urinary excretion of GAGs in children affected by enuresis and urinary incontinence than in a control group although in the absence of an urodynamic test [Ferrara et al. 2007]. Siracusano and colleagues performed a urodynamic test in their study population (25 women, 63 years median age, with filling lower urinary tract symptoms [LUTS]) and uroflowmetry in the control group (seven men and seven women, 65 years median age, without LUTS) [Siracusano et al. 2009].
Although Soler and colleagues concluded in their study that urinary GAGs cannot differentiate urothelial damage from recovery because elevated levels of urinary GAGs can result from either condition [Soler et al. 2008], Siracusano and colleagues detected a lower GAGs urinary concentration in LUTS-affected population than in controls and because of this they postulated that a long duration of IDO might generate a chronic subepithelial bladder ischemia, which at the same time damages the epithelium and prevents its regeneration [Siracusano et al. 2008].
Unfortunately there is little clinical evidence to establish whether urinary GAGs excretion is low or high, but IDO might be one of the causes of initial epithelium damage and GAGs loss the supporting process.
Nonbacterial cystitis
The bladder is often vulnerable to the adverse effects of drugs because of the frequent excretion of drug metabolites in the urine. The term ‘nonbacterial’ also includes cystitis caused by pelvic radiation therapy or by adjuvant chemo-immunotherapy for nonmuscle invasive bladder cancer.
As a matter of fact, up to 54% of the patients undergoing intravesical therapy with chemotherapeutic agents to treat superficial bladder tumours can be affected by nonbacterial cystitis [Drake et al. 1998]. Antimicrobials, anticholinergics, anaesthetics and analgesics are often utilized to relieve patients’ symptoms but they are not able to prevent the chronic progression of the disease.
Sommariva and colleagues performed a prospective study on 55 male patients (age range 54–81 years) to evaluate the use of 8–24 (depending on the time needed to symptoms’ resolution) weekly bladder instillations of 40 mg HA in the treatment of nonbacterial cystitis [Sommariva et al. 2010]. Although a control group was not included and over the first 4 weeks 32 mg of dexamethasone were mixed with HA in order to obtain a stronger anti-inflammatory activity, the authors observed an improvement in VAS score (mean initial value 8.6 versus 1 at the end of the study) and in bladder capacity (from a mean value of 56 to 276 ml) after 16 weeks.
Samper and colleagues evaluated retrospectively the efficacy of bladder instillations of 40 mg of HA to reduce the vesical toxicity (measured by the Radiation Therapy Oncology Group criteria) induced by radiotherapy [Samper et al. 2009]. The study included 95 patients with cervical or endometrial cancer. In 48 of the patients HA was administered 30 min prior to each session of brachytherapy (BT). The authors reported a reduction in acute vesical toxicity after the second session (20.8% HA group versus 40.4% without HA group), the fourth session (10.9% HA group versus 31.9% without HA group) and whole study period (2.08% HA group versus 12.8% without HA group) (p < 0.05). No significant differences between groups with regard to the total number of BT sessions, dose per session, total dose or biological equivalent dose were reported.
Urological malignancies
HA is also one of the major matrix molecules in human malignancies [Tammi et al. 2008]. It is associated with invasion, lymph angiogenesis, angiogenesis and host–tumour interactions and with local involvement (lymphatic nodes and adjacent organs) and distant metastasis (such as bone) [Sironen et al. 2011; Theocharis et al. 2010]. HA may be employed also in the diagnosis and treatment of bladder cancer.
HA and hyaluronidase (HAase) have been reported as possible urinary markers to the diagnosis and follow up of bladder cancer. The enzyme-linked immunosorbent assay-like test to dose urinary excretion of HA-HAase is considered promising test for bladder cancer detection for its high sensitivity and specificity (83% and 78% respectively) [Hautmann, 2004].
In some clinical studies HA is attached with some chemotherapeutic agents to make them less lipophilic and so reduce systemic drug absorption and side effects. Recently, Bassi and colleagues evaluated bladder instillation of paclitaxel conjugated with HA for treatment of bladder carcinoma in situ refractory to bacillus Calmette–Guérin in a phase I study [Bassi et al. 2011]. They did not observe systematic drug absorption or serious adverse events related to drug administration. Although the 60% of study population was disease free at the end of the trial, oncological outcomes did not represent the main endpoint.
Conclusion
Few data are available regarding the mode of action of HA–CS or its effectiveness in the management of bladder diseases. The major issue in interpreting the available evidence regarding HA–CS is that most reported studies are nonrandomized and without a control arm. Thus, this novel therapeutic modality has not been compared with other commonly used therapeutic options in patients with bladder diseases.
HA–CS may be considered for further study, including randomized controlled trials with adequate power. Nevertheless, positive reported findings are very encouraging and may prompt investigators to embark on clinical and experimental trials to better understand the action of GAGs in bladder diseases and to define the role of HA–CS in their management.
Footnotes
Funding
This work received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest statement
The authors declare no conflicts of interest in preparing this article.