ABSTRACT
In order to gain a deeper understanding of bladder function, it is necessary to study the time-dependent response of the bladder wall. The present study evaluated and compared the viscoelastic behaviors of normal and spinal cord injured (SCI) rat bladder wall tissue using an established rat model and planar biaxial stress relaxation tests. Bladders from normal and spinalized (3 weeks) rats were subjected to biaxial stress (either 25 or 100 kPa in each loading direction) rapidly (in 50 ms) and subsequently allowed to relax at the constant stretch levels in modified Kreb's solution (in the absence of calcium; with no smooth muscle tone) for 10,000 s. We observed slower and therefore less stress relaxation in the SCI group compared to the normal group, which varied with the stress-level. These experimental results were fitted (r2 > 0.98) to a reduced relaxation function. Furthermore, biochemical assays revealed that the collagen content of SCI rat bladders was significantly (p < 0.05) lower by 43%, while the elastin content was significantly (p < 0.001) higher by 260% than that of normal bladders. These results suggest that SCI and the associated urologic functional changes induce profound tissue remodeling, which, in turn, provided the structural basis for the alterations in the complex, time-dependent mechanical behavior of the urinary bladder wall observed in the present study.
Subject(s)
Collagen/metabolism , Elastin/metabolism , Models, Biological , Spinal Cord Injuries/physiopathology , Urinary Bladder, Neurogenic/physiopathology , Urinary Bladder/physiopathology , Adaptation, Physiological , Animals , Anisotropy , Computer Simulation , Elasticity , Female , Rats , Rats, Sprague-Dawley , Spinal Cord Injuries/complications , Stress, Mechanical , Tensile Strength , Thoracic Vertebrae/physiopathology , Urinary Bladder, Neurogenic/etiology , ViscosityABSTRACT
OBJECTIVES: To study the safety and efficacy of intravesically administered capsaicin, a C-fiber afferent neurotoxin, in patients with interstitial cystitis (IC). METHODS: A pilot study of intravesical capsaicin therapy was performed on 5 female patients diagnosed with IC using NIDDK criteria. Patients were evaluated with cystoscopy and CMG on initial presentation. Bladder capacity, urinary histamine, PGE2 and substance P were measured before and after treatment. A symptom score, visual analogue pain score and frequency/nocturia charts were completed before treatment and weekly thereafter by each patient. Topical anesthesia (30 mls of 0.5% bupivacaine) was instilled intravesically for 30 minutes prior to each treatment with capsaicin. The initial instillation consisted of vehicle (1% ethanol in normal saline) and subsequent weekly instillations of capsaicin in increasing concentrations (10, 50, 100, and 250 uM solutions in 1% ethanol) were given as tolerated by the patient. RESULTS: Four out of 5 of the patients experienced subjective improvement in both symptom and pain score. Bladder capacity improved in 1 patient and symptoms of frequency and nocturia improved in 2 patients. Urinary histamine and PGE2 revealed no trend between before and after treatment; however, 3 out of 5 of the patients did have a trend to decreased substance P. No complications were noted during the course of this study. CONCLUSIONS: Intravesical capsaicin is a safe and promising treatment for interstitial cystitis. A potential mechanism of action is desensitization of bladder C-fiber afferents which presumably initiate painful sensations in IC patients. Low dose intravesical capsaicin therapy represents a potential treatment option for interstitial cystitis.
