The effect of the somatostatin analogue lanreotide on the prevention of urethral strictures in a rabbit model

Effect of Nintedanib on healing and fibrosis in rats with experimentally induced urethral injury

AIM

We aimed to determine the effectiveness of Nintedanib treatment, which has known antifibrotic effect, in preventing fibrosis after urethral trauma.

MATERIAL AND METHODS

Twenty-three adult Sprague-Dawley rats were divided randomly into 3 different groups: Sham, Urethral injury group (UI) and Urethral injury+ Nintedanib (UI+N). The urethral injury model was made with a pediatric urethrotome knife. Nintedanib was administered at a dose of 50mg/kg by oral gavage for 14 days at the same time every day. After 14 days of treatment, all rats were performed penectomy under general anesthesia. Urethral tissue was evaluated histopathologically (congestion, inflammatory cell infiltration and spongiofibrosis) and immunohistochemically (transforming growth factor (TBF) Beta-1 and vascular endothelial growth factor receptor 2 (VEBFR2)).

RESULTS

Histopathological findings: Group UI had higher scores in all categories (congestion, inflammatory cell infiltration, and spongiofibrosis), followed by Group UI+N and Group Sham, respectively. A statistically significant difference was found between Group UI and Group UI+N in terms of the scores of histopathological parameters (p<0.05). Immunohistochemical findings: Group UI had higher scores in both categories, followed by Group UI+N and Group Sham, respectively. A statistically significant difference was found between Group UI and Group UI+N in TGF Beta-1 and VEGF scores (p<0.05).

CONCLUSION

We found that Nintedanib administration after urethral trauma reduced inflammation and fibrosis histologically and immunohistochemically. The positive effect of Nintedanib on inflammation and fibrosis after urethral trauma reported in this animal study is encouraging for a potential clinical human application.

Mesenchymal Stem Cell-Derived Exosomes Induced by IL-1β Attenuate Urethral Stricture Through Let-7c/PAK1/NF-κB-Regulated Macrophage M2 Polarization

Background

Urethral stricture is a clinical challenge for both patients and clinicians. Post-traumatic urethral stricture is associated with formation of scar tissue caused by excessive inflammation. The aim of this study is exploring potential therapeutic strategies for this condition.

Methods

In vivo experiments on New Zealand rabbits and in vitro experiments on THP-1 monocytes and urethral fibroblasts were performed to investigate the effects on post-traumatic urethral stricture of exosomes isolated from IL-1β-treated mesenchymal stem cells (Exo-MSCs^IL-1β) and the role of macrophage M2 polarization in this process. Additionally, related signaling and mechanism behind were explored.

Results

In a New Zealand rabbit model of post-traumatic urethral stricture, injection of Exo-MSCs^IL-1β significantly reduced urethral stricture and collagen fiber accumulation compared with Exo-MSCs. Addition of Exo-MSCs^IL-1β to THP-1 monocytes in vitro induced M2 macrophage polarization, which, in turn, inhibited activation of urethral fibroblasts and synthesis of collagen. Mechanistically, Exo-MSCs^IL-1β were found to contain high levels of the microRNA let-7c, and luciferase reporter assays showed that let-7c interacted with the 3'UTR of PAK1 mRNA. Transfection of THP-1 cells with a let-7c mimic downregulated PAK1 expression and inhibited activation of the NF-κB signaling pathway.

Conclusion

These results support a role for let-7c-containing Exo-MSCs^IL-1β in reducing urethral stricture via inhibition of PAK1-NF-κB signaling, M2 macrophage polarization, and differentiation of urethral myofibroblasts.

Effect of Mitomycin - C and Triamcinolone on Preventing Urethral Strictures

Urethral stricture is a common disease with high recurrence rate. Several manipulations were defined to prevent the recurrence but the results were disappointing. This study aimed to evaluate the efficacy of triamcinolone and mitomycin-C on urethral stricture formation and their effect on inhibition of urethral fibrosis. A total of 24 New Zealand rabbits were divided into 3 groups. Urethras of rabbits were traumatized with pediatric resectoscope. Resection area was irrigated with 10mL saline, swapped with a cotton wool soaked with 0.5mg/mL MMC and injected by 40mg triamcinolone in groups 1, 2 and 3 respectively. Retrograde urethrogram was performed at 28^th day of procedure and the urethra was removed for histopathologic evaluation. There were significant differences in urethral diameters and in lumen reduction rate between the control and study groups (p<0.001). Compared to control group, all treatment groups showed mild fibrosis, less collagen bundle irregularity, and lower numbers of fibroblasts (p=0.003). The Tunnel assay showed that the number of apoptotic cells in the submucosal connective tissue was quantitatively higher in control groups (p=0.034). In the view of efficacy and safety, MMC and triamcinolone have the potential to replace the use of stents, clean intermittent catheterization, or long term catheters following internal urethrotomy. There were no statistically significant differences between two agents in terms of preventing urethral stricture formation in the present study. Mitomycin C and triamcinolone decreased the recurrence rates of urethral stricture.

Docetaxel inhibits urethral stricture formation, an initial study in rabbit model

INTRODUCTION

Urethral stricture, a frequent source of lower urinary tract disorders in men, is still a difficult problem for urologists. Based the anti-restenosis effect of paclitaxel on coronary artery, the role of docetaxel, a semi-synthetic analogue of paclitaxel, in limiting urethral stricture formation was studied.

METHODS

Forty adult New Zealand male rabbits were involved in this study, which were randomly assigned into 3 groups, namely a high dose docetaxel (DH, 0.1 mg/d), a low dose docetaxel (DL, 0.01 mg/d) and a control (C) group, with 16, 16, 8 rabbits in each group, respectively. All animals underwent a 10 mm-long circumferential electrocoagulation of the bulbar urethra with a 13Fr pediatric resectoscope. Drugs were given by urethral irrigation daily and continuous for 28 days. Stricture formation was assessed by retrograde urethrography and videourethroscopy. Urethra pathology was evaluated by hematoxylin and eosin staining and Sirius red staining.

RESULTS

At the end of this study, 15, 14 and 7 rabbits remained for evaluation in DH, DL and C group, respectively. Urethral diameters in DH, DL and C group were (7.17±1.63) mm, (6.55±0.62) mm, (3.23±1.36) mm, with a normal urethral diameter of (9.08±1.29) mm. Lumen reduction in DH, DL and C group were (36.93±11.58)%, (48.03±7.89)% and (84.66±14.95)%, respectively. Statistically difference could be found between every two groups (p<0.05) both in urethral diameters and in lumen reduction, except for compare of urethral diameters between DH and DL group. Histological examination confirmed mass fibrous tissue and collagen content at the stricture sit in C group, whereas less in docetaxel treated rabbits.

CONCLUSIONS

Docetaxel could limit urethral stricture formation, which may be due to inhibition of fibrous tissue and collagen expression. Docetaxel may become a new choice in the prevention of urethral stricture formation.

Comparison of two experimental models for urethral stricture in the anterior urethra of the male rabbit

OBJECTIVE

To compare 2 urethral stricture models and determine the appropriate model for the generation of urethral stricture in rabbits.

METHODS

A total of 28 adult male New Zealand rabbits were included in the present study. They were separated randomly into 3 groups. Urethroscopy was performed using a pediatric resectoscope (13F). In 1 group (10 rabbits), circumferential electrocoagulation of the anterior urethra 2-3 mm long was performed until ulceration of the mucosa occurred. In the second group (10 rabbits), 2-3 mm wide resection from the anterior urethra was performed that was deep enough to expose the periurethral tissue to allow urine leakage from the lumen. The remaining 8 rabbits as the control group underwent only urethroscopy. On the 30th day, retrograde urethrography and urethroscopy were performed to evaluate urethral stricture formation. Histologic examination was done to evaluate the urethral pathologic changes.

RESULTS

According to the urethrography and urethroscopy findings, no rabbits in the electrocoagulation or control group developed urethral stricture; however, significant stricture formation was observed in every case of the electroresection group. Regenerating urothelium at the luminal side of the urethra was seen in 6 rabbits in the electrocoagulation group and 4 showed normal urethra. In the electroresection group, extensive fibrosis that obstructed the urethral lumen and nodular collagen bundles in the urethral wall were seen.

CONCLUSION

The electroresection method is more reliable than the electrocoagulation method in developing urethral stricture in the rabbit model. A 2-3-mm-wide resection from the anterior urethra can successfully generate urethral stricture with respect to electrocoagulation. Electroresection offers an ideal animal model for generating urethral stricture.

Rapamycin inhibits formation of urethral stricture in rabbits

Rapamycin has been reported to inhibit hepatic fibrosis, lung fibrosis, renal fibrosis, and subglottic stenosis. Fibrosis is also involved in urethral stricture. Therefore, we investigated the effect of rapamycin on the inhibition of urethral stricture formation in a rabbit model. First, models of urethral stricture were successfully established by electrocoagulation of the bulbar urethra in adult New Zealand male rabbits. Forty-six model rabbits were randomly assigned to four groups: high-dose rapamycin (R(H), 1.0 mg/day), low-dose rapamycin (R(L), 0.1 mg/day), dimethyl sulfoxide (DMSO) alone (DMSO, solvent control), and normal saline (NS). Urethral stricture was assessed by a retrograde urethrogram and video-urethroscopy. Urethra pathology was evaluated by hematoxylin and eosin and Sirius red staining. After 28 days of treatment, lumen reduction in the R(H), R(L), DMSO, and NS groups was 36.0, 56.5, 69.1, and 82.9, respectively. Comparison of the rapamycin groups (R(H) and R(L)) and control groups (DMSO and NS) indicated significantly less restriction in the rapamycin groups. Histopathological analysis confirmed the presence of fibroblasts and an increase in collagen at the stricture site in the two control groups but not in the R(H) or R(L) groups. These results indicate that rapamycin inhibits experimentally induced urethral stricture formation in rabbits. This effect may be due to its inhibition of fibroblast proliferation and collagen expression.