Botulinum toxin type A: a novel approach to the treatment of recurrent urethral strictures

Pharmacotherapy of urethral stricture

Urethral stricture is characterized by the chronic formation of fibrous tissue, leading to the narrowing of the urethral lumen. Despite the availability of various endoscopic treatments, the recurrence of urethral strictures remains a common challenge. Postsurgery pharmacotherapy targeting tissue fibrosis is a promising option for reducing recurrence rates. Although drugs cannot replace surgery, they can be used as adjuvant therapies to improve outcomes. In this regard, many drugs have been proposed based on the mechanisms underlying the pathophysiology of urethral stricture. Ongoing studies have obtained substantial progress in treating urethral strictures, highlighting the potential for improved drug effectiveness through appropriate clinical delivery methods. Therefore, this review summarizes the latest researches on the mechanisms related to the pathophysiology of urethral stricture and the drugs to provide a theoretical basis and new insights for the effective use and future advancements in drug therapy for urethral stricture.

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.

An update on best practice in the diagnosis and management of post-prostatectomy anastomotic strictures

Postprostatectomy vesicourethral anastomotic stenosis (VUAS) remains a challenging problem for both patient and urologist. Improved surgical techniques and perioperative identification and treatment of risk factors has led to a decline over the last several decades. High-level evidence to guide management is lacking, primarily relying on small retrospective studies and expert opinion. Endourologic therapies, including dilation and transurethral incision or resection with or without adjunct injection of scar modulators is considered first-line management. Recalcitrant VUAS requires surgical reconstruction of the vesicourethral anastomosis, and in poor surgical candidates, a chronic indwelling catheter or urinary diversion may be the only option. This review provides an update in the diagnosis and management of postprostatectomy VUAS.

Advances in urethral stricture management

Urethral stricture/stenosis is a narrowing of the urethral lumen. These conditions greatly impact the health and quality of life of patients. Management of urethral strictures/stenosis is complex and requires careful evaluation. The treatment options for urethral stricture vary in their success rates. Urethral dilation and internal urethrotomy are the most commonly performed procedures but carry the lowest chance for long-term success (0–9%). Urethroplasty has a much higher chance of success (85–90%) and is considered the gold-standard treatment. The most common urethroplasty techniques are excision and primary anastomosis and graft onlay urethroplasty. Anastomotic urethroplasty and graft urethroplasty have similar long-term success rates, although long-term data have yet to confirm equal efficacy. Anastomotic urethroplasty may have higher rates of sexual dysfunction. Posterior urethral stenosis is typically caused by previous urologic surgery. It is treated endoscopically with radial incisions. The use of mitomycin C may decrease recurrence. An exciting area of research is tissue engineering and scar modulation to augment stricture treatment. These include the use of acellular matrices or tissue-engineered buccal mucosa to produce grafting material for urethroplasty. Other experimental strategies aim to prevent scar formation altogether.

Urethral Strictures and Stenoses Caused by Prostate Therapy

The number of patients with prostate cancer and benign prostatic hyperplasia is on the rise. As a result, the volume of prostate treatment and treatment-related complications is also increasing. Urethral strictures and stenoses are relatively common complications that require individualized management based on the length and location of the obstruction, and the patient's overall health, and goals of care. In general, less invasive options such as dilation and urethrotomy are preferred as first-line therapy, followed by more invasive substitution, flap, and anastomotic urethroplasty.

Impact of botulinum toxin A injection on esophageal anastomosis in a rabbit model

PURPOSE

The management of esophageal atresia is established, but the rate of postoperative complications remains high. We focused on a new, recently reported method of esophageal elongation using botulinum toxin type A (BTX-A) and evaluated the efficacy of BTX-A injection around esophageal anastomoses with tension in a rabbit model.

METHODS

Twenty rabbits aged 8-10 weeks and weighing 1.27-1.72 kg underwent resections of the esophagus measuring 1.5 cm long using an anterior cervical approach. Esophagoesophagostomies were performed after intramural administration of Xeomin™ (3 U/body) in the BTX-A group and saline in the control group. Morphological and histological evaluations were examined on postoperative day 14.

RESULTS

Six rabbits in each group survived. The BTX-A group showed significantly less postoperative anastomotic stricture and less fibrosis than the control group. Changes in wall thickness on both sides of the anastomotic areas were equivalent between the two groups, and no muscle fracturing was observed.

CONCLUSION

Local administration of BTX-A for esophagoesophagostomy significantly reduced postoperative anastomotic stricture with less fibrosis than that observed in the control group. Reduced anastomotic tension with BTX-A presumably contributed to better anastomotic healing. Determining the optimum dose of BTX-A is necessary for clinical application.

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.

Posterior urethral complications of radical prostatectomy

The incidence of vesicourethral anastomotic stenosis following radical prostatectomy has fallen over the past two decades, but it remains a relatively common complication of this procedure. Options for management include endoscopic and surgical approaches. These options are briefly discussed in this review and a management algorithm is proposed.

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.

Effect of botulinum toxin type a on a rat surgical wound model

Objectives

The tension on a wound is one of the important factors that determine the degree of fibrosis and scar formation. We hypothesized that local botulinum toxin type A (Botox) induced paralysis of the musculature subjacent to a surgical wound with a skin defect would minimize the repetitive tensile forces on the surgical wound's edges, and this will result in a decreased fibroplastic response and fibrosis of the wound.

Methods

This is a prospective randomized experimental study. Two distinct surgical wounds were made to the dorsum of 15 adult rats, respectively. One of the 2 wounds was injected with Botox, and the other wound was used as a control, and this was done for all the rats' wounds. We evaluated the wound size, the degree of fibrosis and inflammation, the blood vessel proliferation, the thickness of the wound and the expression of transforming growth factor (TGF)-β1 in the wounds.

Results

There were significant differences of wound size at the 3rd and 4th week between the Botox and control groups (P<0.05). The Botox group showed less infiltration of inflammatory cells than the control group at the 2nd week (P<0.05). The Botox group showed a smaller number of fibroblasts and less fibrosis than the control group at the 4th week (P<0.05). The Botox group showed much strong collagen density than the control group at the 8th week (P<0.05). For the immunohistochemical staining, there was a lower transforming growth factor (TGF)-β1 expression in the Botox group than that of the control group at the 4th week (P<0.05).

Conclusion

The wounds of the Botox-treated group showed a larger wound size, less infiltration of inflammatory cells and less fibrosis, a much greater amount of collagen and a lower expression of TGF-β1 than did the control group. Botox might be used to decrease the fibrosis of a surgical wound without damaging the epithelial growth in situations for which decreased fibrosis is necessary, such as for treating laryngeal, tracheal and nasal stenosis.

Effect of botulinum toxin type a on a rat surgical wound model

OBJECTIVES

The tension on a wound is one of the important factors that determine the degree of fibrosis and scar formation. We hypothesized that local botulinum toxin type A (Botox) induced paralysis of the musculature subjacent to a surgical wound with a skin defect would minimize the repetitive tensile forces on the surgical wound's edges, and this will result in a decreased fibroplastic response and fibrosis of the wound.

METHODS

This is a prospective randomized experimental study. Two distinct surgical wounds were made to the dorsum of 15 adult rats, respectively. One of the 2 wounds was injected with Botox, and the other wound was used as a control, and this was done for all the rats' wounds. We evaluated the wound size, the degree of fibrosis and inflammation, the blood vessel proliferation, the thickness of the wound and the expression of transforming growth factor (TGF)-beta1 in the wounds.

RESULTS

There were significant differences of wound size at the 3rd and 4th week between the Botox and control groups (P<0.05). The Botox group showed less infiltration of inflammatory cells than the control group at the 2nd week (P<0.05). The Botox group showed a smaller number of fibroblasts and less fibrosis than the control group at the 4th week (P<0.05). The Botox group showed much strong collagen density than the control group at the 8th week (P<0.05). For the immunohistochemical staining, there was a lower transforming growth factor (TGF)-beta1 expression in the Botox group than that of the control group at the 4th week (P<0.05).

CONCLUSION

The wounds of the Botox-treated group showed a larger wound size, less infiltration of inflammatory cells and less fibrosis, a much greater amount of collagen and a lower expression of TGF-beta1 than did the control group. Botox might be used to decrease the fibrosis of a surgical wound without damaging the epithelial growth in situations for which decreased fibrosis is necessary, such as for treating laryngeal, tracheal and nasal stenosis.

Botulinum toxin-A to improve urethral wound healing: an experimental study in a rat model

OBJECTIVES

Tensile distracting forces caused by elements such as a muscle pull can cause widening of scars in the tissue during the wound healing process. The aim of the present study was to investigate whether induced immobilization of the urethral muscle using botulinum toxin-A (BTX-A) enhances wound healing and also reduces the amount of scar formation in an experimentally induced urethral injury in a male rat model.

METHODS

Prepubertal male albino rats were divided into 2 groups: 20 rats in the BTX-A group received BTX-A injection treatment during surgery and 10 rats in the control group received 0.9% saline solution injection. The penile skin was incised circumferentially and degloved. To make the urethral injury at a location approximately 15 mm proximal to the external meatus, the urethra was cut transversally with scissors, from the 2-o'clock to the 10-o'clock position and then sutured by a single suture at the 6-o'clock position. To evaluate chronic inflammation and fibrosis, the rats were killed, and the injured portions of the urethras were harvested for histopathologic examination after a follow-up period of 21 days.

RESULTS

On histopathologic evaluation, the control group rats had a more severe fibrotic change in the urethral tissue compared with the BTX-A injected rats, which showed a mild fibrotic change. The mean +/- SD and median fibrosis score was 2.4 +/- 0.5 and 2 in the control group and 1.5 +/- 0.5 and 1 in the BTX-A group, respectively (P < .01 and P < .01, respectively).

CONCLUSIONS

The results of our study have shown that BTX-A prevented increases in collagen content during urethral wound healing.

Hitting below the belt (Bladder): Botulinum treatment of urethral and prostate disorders

Botulinum toxin type A (BTX-A) has been used to treat urethral and prostatic diseases (off-label uses). Injection of BTX-A into the external sphincter of patients with detrusor external sphincter dyssynergia has been shown to successfully lower postvoid residual volumes and detrusor pressures. Average efficacy is 3 to 4 months, but long-term effects on detrusor leak point pressures or renal function are unknown. Injection of BTX-A into the prostate has shown promising short-term results (< or = 12 months) in improving the symptoms, postvoid residual volumes, maximal urinary flow rates, and prostate sizes in patients with benign prostatic hyperplasia. The mechanisms of action and long-term durability of this treatment modality are unknown. Evidence supporting the use of BTX-A in treating detrusor hypocontractility, pelvic floor dysfunction, postpubovaginal sling retention, urethral stricture, prostatitis, and chronic pelvic pain syndrome in men is preliminary and deserves further evaluation.

Intradetrusor injection of botulinum-A toxin in patients with idiopathic and neurogenic detrusor overactivity: Urodynamic outcome and patient satisfaction

PURPOSE

To assess and compare the efficacy of botulinum-A toxin (BTX-A) injections into the detrusor in idiopathic and neurogenic detrusor overactivity (IDO and NDO) resistant to anticholinergic treatment with respect to patient satisfaction.

PATIENTS AND METHODS

In a prospective study, 16 patients with IDO and 14 with NDO resistant to anticholinergic treatment were injected with 500 U of Dysport into the detrusor. Clinical, urodynamic, and satisfaction assessments were performed at baseline and after BTX-A injections.

RESULTS

In IDO as well as in NDO, there was a significant increase in median maximum cystometric capacity (MCC) from 177.5 to 262.5 ml (P<0.0005) and 160 to 270 ml (P=0.001), median bladder compliance from 24.5 to 40.0 ml/cmH2O (P<0.0005) and 25.5 to 44.0 ml/cmH2O (P=0.001) and median PVR from 15 to 80 ml (P=0.001) and 15.0 to 62.5 ml (P=0.001), respectively. Median Pdet max decreased significantly from 49 to 37 cmH2O (P<0.0005) and 48.5 to 37.0 cmH2O (P=0.001), and median Pdet Qmax from 32.0 to 20.0 ml/sec (P<0.0005) and 36.0 to 21.5 ml/sec (P=0.001), respectively. The effect of BTX-A injections lasted for a median time of 5 months in both groups. Median daytime frequency, nocturia, and number of used pads decreased significantly in both groups. More than 80% of the patients were satisfied with the effect of BTX-A.

CONCLUSIONS

Patients with intractable IDO respond to intradetrusor BTX-A with a significant and comparable but temporally limited effect in urodynamic and LUTS parameters as those with NDO. The majority of patients were satisfied with treatment.

Botulinum-A toxin for treatment of overactive bladder without detrusor overactivity: Urodynamic outcome and patient satisfaction

OBJECTIVES

To investigate the effect of botulinum toxin type A bladder injections in the treatment of overactive bladder syndrome in the absence of detrusor overactivity.

METHODS

The subjects were 7 women (average age 61.1 years, range 51 to 79) who presented with overactive bladder symptoms. Their disorder had been refractory to several classic treatment options. Urodynamic examination excluded detrusor overactivity. A total of 300 U BTX-A (Botox) was injected, of which 50 to 75 U was injected as quadrant injections into the external sphincter muscle to avoid the postoperative need for catheterization in the case of high postvoid residual urine volume. For follow-up, complete urodynamic studies were performed, and a bladder diary and validated incontinence questionnaires were given to patients at all visits at 1, 3, and 6 months.

RESULTS

The bladder diaries indicated a clear reduction in daytime frequency and nocturia and a reduction in pad use. The maximal voiding volume increased significantly. The urodynamic examinations showed a significant increase in volume when the first and the strong desire to void were expressed. The maximal bladder capacity increased by 20% in 3 months. In the questionnaires, 5 of the 7 patients reported better urine control after therapy, and 6 would have chosen this therapy again for their condition. The overall satisfaction score (on a scale of 0 to 10) averaged 6.8. No side effects, such as urine retention, occurred.

CONCLUSIONS

Botulinum-A toxin injection has positive effects in treating overactive bladder symptoms without detrusor overactivity. The effects were seen not only in urodynamic measures but also in patient satisfaction.