Urethral dysfunction in diabetic rats

PURPOSE: We investigated the effects of diabetes mellitus (DM) on urethral relaxation mechanisms during reflex bladder contractions in rats. MATERIALS AND METHODS: Five weeks after streptozotocin injection (65 mg/kg intraperitoneally) the effects of DM on urethral relaxation mechanisms were evaluated by simultaneous recordings of intravesical pressure under isovolumetric conditions and urethral perfusion pressure (UPP) using urethane anesthesia. RESULTS: In diabetic rats the UPP nadir during urethral relaxation and intravesical pressure thresholds for inducing urethral relaxation were significantly higher (199% and 92%, respectively) than in normal rats, while baseline UPPs were not significantly different. The mean rate and amplitude of high frequency oscillations of urethral striated muscle in diabetic rats were also significantly lower (17% and 64%, respectively) compared with normal rats. Following alpha-bungarotoxin treatment to eliminate striated muscle sphincter contractions intravenous administration of L-arginine (200 mg/kg) [corrected] , the substrate of nitric oxide (NO) synthase, decreased the UPP nadir (36% and 22%, in diabetic and normal rats) as well as intravesical pressure thresholds (49% and 22%, respectively). The effect was greater (61% to 126%) in diabetic rats than in normal rats. In each group of rats the effect of L-arginine was inhibited by Nomega-nitro-L-arginine (100 mg/kg intravenously) [corrected], a NO synthase inhibitor. CONCLUSIONS: During reflex bladder contractions streptozotocin induced diabetic rats exhibited smooth and striated muscle dysfunctions of the urethral outlet. L-arginine therapy, which could augment urethral smooth muscle relaxation by increasing NO production, may be useful for partially restoring the urethral relaxation mechanism in DM.     

The distribution of neuronal and inducible nitric oxide synthase in urethral stricture formation

PURPOSE: The distribution of neuronal (n) and inducible (i) nitric oxide synthase (NOS) may have a role in the maintenance of normal urethral spongiosum and during the development of spongiofibrosis in urethral stricture disease. MATERIALS AND METHODS: Eight normal and 33 strictured human bulbar urethras were studied by histological and immunohistochemical techniques for the neuronal markers S-100, nNOS and iNOS. The smooth muscle-to-collagen ratio was calculated by morphometric analysis of Masson's trichrome sections. Immunohistochemical staining patterns of the neuronal markers in normal urethral tissue was compared to that in urethral stricture tissue with spongiofibrosis. RESULTS: The smooth muscle-to-collagen ratio was significantly lower in the strictured urethra compared to that in the control group (p = 0.001). In the strictured bulbar urethra nNOS immunoreactivity was decreased compared to that in normal urethral tissue. The severity of spongiofibrosis corresponded to the loss of nNOS immunoreactivity. iNOS immunoreactivity was found in strictured urethral epithelium and spongiosal tissue, whereas the control group was nonimmunoreactive to iNOS. CONCLUSIONS: Urethral stricture formation is a fibrotic process associated with significant changes in NOS metabolism. Abnormal collagen synthesis following urethral trauma may be stimulated by inappropriate iNOS activity. A functional nerve supply to the urethral spongiosum seems to be crucial in the maintenance of the unique ultrastructure of the urethral spongiosum.     

Age‐related properties of the tumour vasculature in renal cell carcinoma

Study Type – Aetiology (case series)
Level of Evidence 4 What’s known on the subject? and What does the study add? Little is known about the impact of vascular ageing on the angiogenic features of clear cell renal cell carcinoma, a disease in which antiangiogenic therapy currently has a well established role. It is also rather surprising that this question has not been raised in a disease context where patients’ age may differ by several decades. We provide the first glimpse in to the related vasclar changes, including morphology and some of the molecular features.

OBJECTIVE

To assess whether ageing processes influence angiogenesis in renal cell carcinoma (RCC) we carried out a pilot study of vascular properties in a series of archival primary kidney tumours in patients of different ages.

PATIENTS AND METHODS

A cohort of patients with RCC was identified restrospectively, with an age range of 35–84 years. Paraffin‐embedded, formalin‐fixed sections of surgical tumour specimens were stained for endothelial (CD31, von Willebrand factor [vWF]), pericyte (alpha smooth muscle actin [SMA]) and leucocytic (CD45) markers, as well as for proliferative (Ki67) and angiogenic activity (tumour endothelial markers [TEMs], delta‐like 4 [Dll4], Dll1, endothelial nitric oxide synthase [eNOS]). Vascular properties were compared between patients above and below 65 years of age.

RESULTS

Microvascular density (MVD) within capillary hot spots was generally higher in patients with non‐metastatic clear‐cell RCC (ccRCC; n= 21) than in those with metastatic RCC (mRCC; n= 9). Patients with ccRCC who were more than 65 years old showed significantly higher MVD than their younger (<65 years) counterparts. There were dividing (Ki67‐positive) endothelial and mural cells in both small (<20 µm) capillary and large (>20 µm), pre‐capillary vessels, suggesting the involvement of both angiogenic and remodelling/arteriogenic processes. Tumour endothelial markers (TEM1, TEM7, TEM8), Notch ligands (Dll1, Dll4), and other molecular characteristics (eNOS) were analysed. Age‐related differences were observed in the frequency of pre‐capillary vessels expressing Dll1, which was significantly higher in tumours of younger patients (<65 years), while eNOS was more prevalent among capillaries associated with ccRCC in older patients (>65 years).

CONCLUSIONS

The results of the present study suggest that age influences the structural and molecular properties of the tumour vasculature in ccRCC. We postulate that vascular ageing could also be relevant in the context of anti‐angiogenic therapy.     

Nitric oxide synthase in the external urethral sphincter of the sheep: immunohistochemical and functional study

PURPOSE: We studied the distribution of neuronal nitric oxide synthase (nNOS) and the effects of nitric oxide (NO) modulating drugs on contractile function of the external urethral sphincter of lambs. Gender differences were evaluated. MATERIALS AND METHODS: Longitudinal and transverse sections of the external urethral sphincter from 10 female and 10 male lambs were studied using reduced nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry and nNOS immunocytochemistry. Isometric contractile responses to electrical field stimulation were recorded from external urethral sphincter preparations from 47 female and 45 male lambs and the effects of NO modulating drugs were evaluated. RESULTS: We detected nNOS in the sarcolemma of some but not all striated fibers, where nNOS seems to be concentrated at the neuromuscular junction. In addition, nNOS was present in nerve fibers and intramural ganglia. The density of innervation decreased toward the distal part of the external urethral sphincter and was higher in male preparations. No significant functional effects of the NOS inhibitor NG-nitro-L-arginine (10 mM.) or the NO donors diethylamine and spermine NONOate (Sigma Chemical Co., St. Louis, Missouri) (5 mM. each) on external urethral sphincter isometric contractility were found in either gender. CONCLUSIONS: Despite the evidence for nNOS at the sarcolemma and nerve fibers of the external urethral sphincter the physiological relevance of these immunohistochemical findings remains to be determined.     

Giant prostatic urethral calculus associated with urethrocutaneous fistula

Urethral stones in men are rare clinical entity and most of them migrate from the urinary bladder. Urethral stones are rarely formed primarily in the urethra and are usually associated with urethral strictures or diverticula. We report a 41-year-old man with giant prostatic urethral stone (5.9x3.2x2.8 cm) associated with a urethrocutaneous fistula. The etiological factors, pathogenesis, clinical presentation, complications and management of giant urethral calculi are reviewed.     

Biodegradable urethral stents seeded with autologous urethral epithelial cells in the treatment of post‐traumatic urethral stricture: a feasibility study in a rabbit model

OBJECTIVE

To evaluate the adhesion and growth of rabbit urethral epithelial cells (UECs) on a biodegradable unbraided mesh urethral stent, and to assess the feasibility and effect of the cell‐seeded urethral stent for treating post‐traumatic urethral stricture (PTUS) in a rabbit model.

MATERIALS AND METHODS

Rabbit UECs were collected by biopsy from adult rabbit urethra and seeded onto the outer layer of a mesh biodegradable urethral stent. The growth of UECs in cell‐scaffolds was assessed by scanning electron microscopy, immunohistochemical and fluorescence staining. In all, 32 male New Zealand rabbits were used, with either PTUS or uninjured, as a control group. Cell‐seeded stents were implanted into the rabbits strictured urethra. The histological and immunohistochemical findings were assessed after death at 1, 2, 8, 12 and 24 weeks, respectively. The reconstruction and function were evaluated by urethroscopy and retrograde urethrography.

RESULTS

The cultured UECs adhered to the stent and grew well. Immunohistochemistry showed that the cells were stained positively for cytokeratin. At 4 weeks, vs 2 weeks, the thickness of the papillary projections of the epithelium decreased and inflammatory cell infiltration diminished. At 24 weeks the injured urethra was completely covered by integrated regeneration of three to five layers of urothelium. There was no evidence of voiding difficulty, stricture recurrence or other complications.

CONCLUSIONS

The unbraided mesh biodegradable urethral stent with autologous UECs seemed to be feasible for treating PTUS in the rabbit urethra, and provides a hopeful avenue for clinical application allowing reconstruction of PTUS.     

Predicting urethral area from video-urodynamics in women with voiding dysfunction

AIMS: Mathematical models are useful for developing predictive parameters for characterizing the biomechanics of voiding dysfunction. The goal of this project was to test a one-dimensional steady flow model used to predict the minimum cross-sectional urethral area from urodynamic data. METHODS: Nine adult female subjects underwent video-urodynamic testing. By using Bernoulli's formula and the Torricelli theorem, the minimum urethral area was predicted from pressure and flow rate at the moment of maximum flow rate during voiding. This prediction was compared with the minimum cross-sectional area of the urethra, which was calculated from minimum urethral diameter as measured from fluoroscopy, assuming a circular cross-section. RESULTS: The maximum flow rate during voiding was 14.4 +/- 3.0 mL/sec. Mean bladder, abdominal, and detrusor pressures simultaneous with maximum flow rate were 63 +/- 7, 29 +/- 6, and 33 +/- 6 cm H(2)O, respectively. Mean minimum cross-sectional area of the urethra from fluoroscopy was 8.0 +/- 2.0 mm(2). Mean minimum cross-sectional area of the urethra predicted by the mathematical model was 5.0 +/- 1.0 mm(2) using bladder pressure and 7.0 +/- 2.0 mm(2) using detrusor pressure. There were no significant differences between the three cross-sectional area measures. However, when area predictions were expressed as percentage of fluoroscopic measurements, the estimate from detrusor pressure (97 +/- 13%) was significantly larger than the estimate from bladder pressure (69 +/- 7%). CONCLUSIONS: A steady flow model is accurate enough on average to describe urine flow in the urethra. However, it may not be sufficiently accurate to aid in diagnosis of individuals.     

Voiding dysfunction following removal of eroded synthetic mid urethral slings

PURPOSE: Voiding dysfunction following genitourinary erosion of synthetic mid urethral slings is not clearly reported. We investigated the incidence of voiding dysfunction in patients following sling excision due to vaginal, urethral or intravesical mesh erosion. MATERIALS AND METHODS: Retrospective review identified 19 patients with genitourinary erosion of polypropylene mesh slings. Comprehensive urological evaluation was performed in all patients, and perioperative and postoperative data were analyzed. Voiding dysfunction was defined as refractory storage symptoms, emptying symptoms and pelvic pain. All subsequent medical and surgical interventions were recorded. RESULTS: In 19 patients a total of 11 vaginal, 7 intravesical and 5 urethral erosions occurred. Mean patient age was 52 years (range 32 to 69) and average followup was 8.4 months (range 3 to 34). Average time from symptom onset to sling removal was 10.1 months (range 1.5 to 38). Of the 19 patients 14 (74%) presented with multiple symptoms. Symptoms varied, including refractory pain, recurrent infections and bladder storage/emptying dysfunction. Urodynamic studies were abnormal preoperatively and postoperatively in 9 of 13 (69%) and 4 of 6 patients (67%), respectively. Following surgery lower urinary tract symptoms resolved completely in only 4 of the 19 patients (21%). Stress incontinence recurred in 8 of the 19 patients (42%). Five patients underwent simultaneous pubovaginal sling, of whom none had recurrent stress urinary incontinence. Only 9 patients (47%) considered themselves dry with no pads following surgery. Four patients required further surgery for refractory voiding symptoms. CONCLUSIONS: Voiding dysfunction is not an uncommon finding after sling excision in the setting of genitourinary erosion. It may cause additional patient morbidity.     

Excitatory effect of propiverine hydrochloride on urethral activity in rats

Objectives: To investigate the effects of the antimuscarinic agent, propiverine, on the bladder and urethra in rats. Methods: A total of 54 female rats were given propiverine, imidafenacin (an antimuscarinic agent), or distilled water by gavage once or twice daily. After 2 weeks, bladder and urethral activity were recorded under urethane anesthesia. In the propiverine group, the changes of bladder and urethral activity before and after intravenous injection of α₁‐adrenergic antagonists (prazosin, silodosin and naftopidil) were also recorded. Furthermore, the leak point pressure after electrical stimulation of abdominal wall muscles was measured in rats with vaginal distension from the control and propiverine groups. Results: Intravesical baseline pressure was significantly lower in the propiverine and imidafenacin groups compared with the control group, whereas the urethral baseline pressure was significantly higher in the propiverine group compared with the control or imidafenacin groups. Intravenous injection of prazosin (an α₁‐receptor antagonist) significantly decreased the urethral baseline pressure in both of the propiverine and control groups. Intravenous injection of silodosin and naftopidil (α_1A‐ and α_1D‐receptor antagonists, respectively) significantly decreased the maximum contraction pressure and the urethral baseline pressure in the propiverine group. The leak point pressure of the propiverine group was significantly higher than that of the control group. Conclusions: An increase of catecholamines after propiverine administration might activate smooth muscle of the proximal urethra via α_1A‐ and α_1D‐adrenergic receptors, as well as activating urethral and pelvic floor striated muscle via the spinal motoneurons.     

Autologous bone‐marrow‐derived mesenchymal stem cell transplantation into injured rat urethral sphincter

Objectives: To evaluate the functional and histological recovery by autologous bone‐marrow‐derived mesenchymal stem cell (BMSC) transplantation into injured rat urethral sphincters. Methods: BMSC were harvested from female Sprague–Dawley retired breeder rats for later transplantation. The cells were cultured, and transfected with the green fluorescence protein gene. The urethral sphincters were injured by combined urethrolysis and cardiotoxin injection. One week after injury, the cultured BMSC were injected autologously into the periurethral tissues. Controls included sham‐operated rats and injured rats injected with cell‐free medium (CFM). Abdominal leak point pressures (LPP) were measured before and after surgery during the following 13 weeks. The urethras were then retrieved for histological evaluation. The presence of green‐fluorescence‐protein‐labeled cells and the regeneration of skeletal muscles, smooth muscles, and peripheral nerves were evaluated by immunohistochemical staining. Results: LPP was significantly reduced in the injured rats. It increased gradually after transplantation, but there was no significant difference between the BMSC and CFM groups. In the BMSC group, transplanted cells survived and differentiated into striated muscle cells and peripheral nerve cells. The proportions of skeletal muscle cells and peripheral nerves in the urethra were significantly greater in the BMSC group compared to the CFM group. Conclusions: Despite a clear trend towards recovery of LPP in BMSC‐transplanted urethras, no significant effect was detected. Further study is required for clinical applications for the treatment of stress urinary incontinence.