Halofuginone-coated urethral catheters prevent periurethral spongiofibrosis in a rat model of urethral injury

Standardizing urethral stricture models in rats: a comprehensive study on histomorphologic and molecular approach

PURPOSE

To create a reproducible and standardized urethral stricture model in rats, evaluating both histomorphologic findings and gene expression data. In studies involving experimental animals, more standardization is needed for the creation of a urethral stricture model.

METHODS

Sixteen male rats were randomized into two groups. The Sham group (n:8) underwent only a penoscrotal incision, while the stricture group (n:8) had their urethras exposed through a penoscrotal incision, followed by electrocauterization to the corpus spongiosum. On the 15th day, blood and urethral tissues were harvested for histologic and molecular analyses. Histomorphologic, immunohistochemical, and reverse transcription polymerase chain reaction analyses were performed.

RESULTS

The stricture group exhibited more severe and intense spongiofibrosis, inflammation, epithelial desquamation, and congestion in vascular structures compared to the controls (p < 0.05). The urethral tissue in the stricture group showed an increased ratio of inflammation parameters, including Collagen 1A1, Collagen 3A1, elastin, Transforming growth factor β1, α Smooth muscle actin, Platelet-derived growth factor α, and Platelet-derived growth factor β. Transforming growth factor β1, Platelet-derived growth factor α, and Platelet-derived growth factor β each correlated highly with the other six parameters (r > 0.60, p < 0.05).

CONCLUSION

Developing electrocoagulation-induced urethral stricture in rats is a simple, reliable, inexpensive, and reproducible. Reporting histologic data with qualitative and semi-quantitative scoring will enhance data standardization, aiding reader understanding and analysis. Transforming growth factor β and Platelet-derived growth factor play key roles in fibrosis during stricture development. Incorporating these cytokines in urethral stricture animal model studies can demonstrate successful stenosis creation.

A novel trauma induced urethral stricture in rat model

Urethral stricture (US) is a longstanding disease, while there has not existed a suitable animal model to mimic the condition. We aimed to establish a trauma-induced US animal model to simulate this clinical scenario. A total of 30 rats were equally distributed into two groups, sham and US group. All rats were anesthetized with isoflurane and undergone cystostomy. In the US group, a 2 mm incision was made in the urethra and sutured to induce US. The sham group only make a skin incision on the ventral side of the anterior urethra. 4 weeks later, ultrasound and cystourethrography were performed to evaluate the degree of urethral stricture, pathological examinations were carried out to evaluate the degree of fibrosis. Urodynamic evaluation and mechanical tissue testing were performed to evaluate the bladder function and urethral tissue stiffness. The results showed that the urethral mucosa was disrupted and urethral lumen was stenosed in the US group. Additionally, the US group showed elevated bladder pressure, prolonged micturition intervals and increased tissue stiffness. In conclusion, the rat urethral stricture model induced by trauma provides a closer representation of the real clinical scenario. This model will significantly contribute to advancing research on the mechanisms underlying traumatic urethral stricture.

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.

The use of local therapy in preventing urethral strictures: A systematic review

Background

Urethral stricture disease is a common problem amongst men in Western countries often leading to a decreased quality of life. Current endoscopic treatment procedure shows an unsatisfying stricture recurrence rate which could be improved by addition of local therapies.

Objectives

To provide an overview of both preclinical and clinical studies in order to investigate current level of evidence on the addition of local therapy to improve urethral stricture recurrence rates after endoscopic procedures.

Methods

We performed a literature search in December 2020 and August 2021 using Cochrane, Embase, PubMed, Scopus and Web of Science and identified articles through combinations of search terms for ‘urethral stricture disease’, ‘stricture formation’ and ‘local interventions’. We used the SYRCLE, RoB-2 and ROBINS-I tools to assess risk of bias across included studies. We did not perform a meta-analysis due to methodological differences between studies.

Results

We included 32 articles in the qualitative analysis, 20 of which were preclinical studies and 12 clinical studies. Regarding preclinical articles using an animal model, nearly all interventions showed to have a positive effect on either urethral fibrosis, urethral stricture formation and/or fibrotic protein expression levels. Here, immunosuppressants and chemotherapeutics seemed most promising for possible clinical purposes. Regarding clinical studies, mitomycin-C and hyaluronic acid and carboxymethylcellulose showed positive effects on urethral stricture recurrence rates with low to intermediate risk of bias across studies. However, the positive clinical effects of mitomycin-C and steroids seemed to decrease in studies with a longer follow-up time.

Conclusion

Although local adjuvant use of mitomycin-C or hyaluronic acid and carboxymethylcellulose may carry clinical potential to improve urethral structure recurrence rates after endoscopic procedures, we believe that a large, well-designed RCT with a yearlong follow-up time is necessary to identify the true clinical value.

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.

Drug-delivering devices in the urinary tract: A systematic review

Objective

: To systematically review the use of drug-eluting stents (DES) and drug-coated balloons (DCB) in urology.

Materials and Methods

The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Scopus, Web of science and Cochrane Library online databases were searched in February 2019. Experimental and clinical studies, which included the placement of a DES or dilatation with DCB for investigating their potential use in the urinary tract for the management of ureteric or urethral pathologies, were included. The primary endpoint was to evaluate the current use of DES and DCB in urology.

Results

A total of 29 articles were included in the systematic review. A total of 10 studies tested DES or DCB containing anti-proliferative agents (paclitaxel, zotarolimus, sirolimus, halofugione). Antibiotic agent-containing DES were tested in nine studies (triclosan, quinolones, teicoplanin, nitrofurantoin, silver sulfadiazine). A total of eight studies investigated the release of anti-inflammatory agents by DES (ketorolac, indomethacin, EW-7197). Another group studied heparin-eluting stents.

Conclusion

Despite the inconclusive outcomes of the three randomised controlled trials, drug-coated/eluting devices constitute a promising field in urology for the prevention of complications associated with conventional stents including pain and encrustation. Pre-clinical in vitro and in vivo studies have shown their ability to mitigate inflammation, inhibit re-stenosis and improve pain as indicated by declined use of anti-inflammatory drugs.

Abbreviations: DES: drug-eluting stents; DCB: drug-coated balloons; DCS: drug-coated stents; HF: halofungione; MCP-1: monocyte chemoattractant protein 1; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses; PTCA: percutaneous transluminal coronary angioplasty; RANTES: regulated on activation, normal T-cell expressed and secreted; RCT: randomised controlled trial; USSQ, Ureteric Stent Symptoms Questionaire.

Scar-modulating agents post urethroplasty: Could phosphodiesterase-5 inhibitors be the answer?

Background:

Phosphodiesterase enzyme inhibitors (PDEIs) are most commonly prescribed by urologists for the treatment of erectile dysfunction. They are also gaining popularity as a treatment for lower urinary tract symptoms, based on their effect on smooth muscles – either vascular smooth muscles or smooth muscles in the urinary tract. For vascular smooth muscles, they cause vasodilation, enhanced microcirculatory haemodynamics through inhibition of platelet aggregation and adhesion, induction of apoptosis of adhesion fibroblasts and a reduction in the scarring process.

Methodology:

We reviewed articles published in English and indexed in the PubMed, Embase and Google Scholar databases, and consulted textbooks. Key search terms used were: urethral stricture, anti-fibrotic, scar-modulating agent, PDEIs, urethral scarring and urethroplasty. We created a synopsis of relevant articles, including original research studies and reviews. Level of evidence: Not applicable.

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.

Amelioration of radiation-induced lung injury by halofuginone: An experimental study in Wistar-Albino rats

To evaluate effects of halofuginone (H) on radiation-induced lung injury (RILI), 60 rats were divided into six groups: Group (G) 1 control, G2 radiotherapy (RT) only, G3 and G4 2. 5 and 5 μg H and G5 and G6 RT + 2.5 and 5 μg H groups, respectively. A single dose of 12 Gy RT was given to both lungs. H was applied intraperitoneally with daily doses, until animals were killed at 6 and 16 weeks after RT. At 6th and 16th weeks of RT, five rats from each group were killed. Lung tissues were dissected for light and electron microscopy. Chronic inflammation, fibrosis and transforming growth factor-beta (TGF)-β scores of all study groups were significantly different at 6th and 16th week ( p < 0.001). Chronic inflammation, fibrosis and TGF-β scores of G2 were higher than G5 and G6 at 6th and 16th weeks of RT. At 16th week, fibrosis and TGF-β scores of G5 were higher than G6 ( p = 0.040 and 0.028, respectively). Electron microscopical findings also supported these results. Therefore, H may ameliorate RILI. The effect of the H was more prominent at higher dose and after long-term follow-up. These findings should be clarified with further studies.

Effect of adipose tissue-derived stem cell injection in a rat model of urethral fibrosis

INTRODUCTION

We sought to evaluate the therapeutic effect of adi-pose tissue-derived stem cells (ADSCs) in a rat model of urethral fibrosis.

METHODS

Eighteen (18) male Sprague-Dawley rats (300‒350 g) were divided into three groups: (1) sham (saline injection); (2) urethral fibrosis group (10 μg transforming growth factor beta 1 (TGF-β1) injection); and (3) ADSCs group (10 μg TGF-β1 injection plus 2 × 10⁵ ADSCs). Rat ADSCs were harvested from rat inguinal fat pads. All study animals were euthanized at two weeks after urethral injection. Following euthanasia, rat urethral tissue was harvested for histologic evaluation. Type I and III collagen levels were quantitated by Western blot analysis.

RESULTS

TGF-β1 injection induced significant urethral fibrosis and increased collagen type I and III expression (p<0.05). Significant decrease in submucosal fibrosis and collagen type I and III expression were noted in the ADSCs group compared with the urethral fibrosis group (p<0.05). TGF-β1 induced fibrotic changes were ameliorated by injection of ADSCs.

CONCLUSIONS

Local injection of ADSCs in a rat model of urethral fibrosis significantly decreased collagen type I and III. These findings suggest that ADSC injection may prevent scar formation and potentially serve as an adjunct treatment to increase the success rate of primary treatment for urethral stricture disease. Further animal and clinical studies are needed to confirm these results.

The effect of rapamycin on TGFβ1 and MMP1 expression in a rabbit model of urethral stricture

PURPOSE

To investigate the effect of rapamycin on TGFβ1 and MMP1 expression in a rabbit model of urethral stricture.

METHODS

Twenty-four adult New Zealand male rabbits underwent an electrocoagulation of the bulbar urethra with a 13Fr pediatric resectoscope. Then rabbits were randomly divided into three groups: (1) normal control group: normal saline (NS), (2) the vehicle control group: dimethyl sulfoxide (DMSO), and (3) the treatment group: effective-dose rapamycin in DMSO (Ra), with 12, 6, and 6 rabbits in each group, respectively. Drugs were given by urethral irrigation daily for 4 weeks. Urethral tissue was harvested for histological and molecular analyses. TGFβ1 and MMP1 expression levels were evaluated by real-time quantitative PCR and immunohistochemistry.

RESULTS

Ten, six, and six rabbits were evaluated finally in Ra, DMSO, and NS group, respectively. Histological examination revealed the distribution of fibrosis and the degree of collagen deposition in the Ra group were smaller and slighter than the two control groups. Collagen content was significantly less in the Ra group than in the DMSO group (P < 0.001) and the NS group (P < 0.001). qRT-PCR analysis showed a higher expression of MMP1 mRNA in the Ra group than in the DMSO group (P < 0.001) and the NS group (P < 0.001). Immunohistochemistry showed the protein levels of MMP1 in the Ra group were significantly increased when compared with the DMSO group (P < 0.01) and the NS group (P < 0.01). On the other hand, no statistical difference could be found between every two groups in both mRNA and protein levels of TGFβ1.

CONCLUSIONS

Rapamycin enhances the expression of MMP1 in a rabbit model of urethral stricture, but has no direct effect on the expression of TGFβ1.

Prevention of stricture recurrence following urethral endoscopic management: what do we have?

OBJECTIVE

Strictures of the urethra are the most common cause of obstructed micturition in younger men and there is frequent recurrence after initial treatment. This review was performed to determine the best strategy for stricture recurrence prevention following urethral endoscopic management.

METHODS

We reviewed the published literature in PubMed, the Cochrane Library, and Google Scholar focusing on this intractable problem regardless of language restrictions. Outcomes of interest included the study methods and the applied strategy's efficacy. The level of evidence and grade of recommendations of included studies were appraised with an Oxford Centre for Evidence-Based Medicine Scale.

RESULTS

Currently, numerous techniques, including catheterization, repeated dilation, brachytherapy, and intraurethral use of various antifibrosis agents, have been employed to oppose the process of wound contraction or regulate the extracellular matrix. But unfortunately, none of these techniques or agents have demonstrated efficacy with enough evidence.

CONCLUSIONS

Although lots of strategies are available, still, we do not have a suitable, single optimum solution for all the conditions. The clinical decision of stricture-recurrence-prevention techniques should be carefully tailored to every individual patient. As the studies are not sufficient, more efforts are warranted to address this interesting but challenging issue.

A scoping review of important urinary catheter induced complications

This study presents a scoping review of the literature on the morbidity and mortality associated with several common complications of urinary catheterization. Data gathered from the open literature were analyzed graphically to gain insights into the most important urinary catheter induced complications. The results reveal that the most significant catheter complications are severe mechanical trauma (perforation, partial urethral damage and urinary leakage), symptomatic bacterial infection, and anaphylaxis, catheter toxicity and hypersensitivity. The data analysis also revealed that the complications with the highest morbidity are all closely related to the mechanical interaction of the catheter with the urethra. This suggests that there is a strong need for urinary catheter design to be improved to minimize mechanical interaction, especially mechanical damage to the urinary tract, and to enhance patient comfort. Several urinary catheter design directions have been proposed based on tribological principles. Among the key recommendations is that catheter manufacturers develop catheter coatings which are both hydrophilic and antibacterial, and which maintain their antibacterial patency for at least 90 days.

Evaluation of the bacterial distribution within the biofilm by denaturing gradient gel electrophoresis in the rat model of urinary catheters

PURPOSE

Most nosocomial urinary tract infections are related to urinary catheters and their biofilm. For the research in this province, animal models are needed to explain the host-pathogen interactions and have an advantage in controlling external interference. This study investigated the validity of the denaturing gradient gel electrophoresis (DGGE) technique for identification of bacteria in a rat model of urinary catheter biofilm.

METHODS

After cutting with aseptic technique, the 24-gauge polyurethane IV catheter was placed in the female rat bladder through the urethra. The catheters were kept in the bladder for 2, 4, or 6 weeks for each group. The genomic DNA was isolated from harvested biofilm of the extracted catheter, and DGGE was performed. The band patterns of DGGE results were analysed, and the sequences were compared using the BLAST from the NCBI.

RESULTS

The results show that Pseudomonas aerusinosa, Escherichia coli, Enterococcus spp., and Corynebacterium sp. were the dominant bacterial species, regardless of the indwelling periods, and other species of bacteria, including Burkholderia and Achromobacter, were identified. The changes in bacterial distribution for the different indwelling periods were non-specific.

CONCLUSIONS

This study using rat model of urinary catheter suggests that DGGE is a useful method in the analysis of the bacterial community in biofilms. Molecular techniques, including DGGE, are valuable to identify fastidious bacteria in the urinary catheter biofilm. This study may be used as fundamental data for studies involving human materials hereafter.

The effect of Halofuginone in the amelioration of radiation induced-lung fibrosis

The lung is one of the most sensitive organs to ionizing radiation, and damage to normal lung tissue remains a major dose limiting factor for patients receiving radiation to the thorax. Radiation induced lung injury (RILI) which is also named as "radiation pneumonpathy" is a continuous process and regarded as the result of an abnormal healing response. It has been shown that transforming growth factor β-1 (TGF-β1) plays an integral role in the radiation induced lung fibrosis formation by promoting the chemoattraction of fibroblasts and their conversion to myofibroblasts. Halofuginone is a, low molecular weight plant derived alkaloid, isolated from the Dichroa febrifuga plant that exhibits antifibrotic activity and inhibition of type I collagen synthesis. Halofuginone has been shown to protect against radiation induced soft tissue fibrosis by virtue of inhibiting various members of TFG-β signaling pathway. By the light of these findings, we hypothesize that Halofuginone may be able to ameliorate the radiation induced lung fibrosis.

Halofuginone infused keratin hydrogel attenuates adhesions in a rodent cecal abrasion model

BACKGROUND

Postoperative adhesion formation continues to be a significant surgical complication, and methods for preventing abdominopelvic adhesions remain limited. Halofuginone (HF) is a type-1 collagen synthesis inhibitor and may enhance the effects of a physical barrier in preventing adhesion formation. We evaluated the effectiveness of a HF infused keratin hydrogel on preventing adhesions in a rat cecal abrasion model.

MATERIAL AND METHODS

Laparotomy and standardized cecal abrasion was performed on 58 retired-breeder Sprague Dawley female rats to induce intra-abdominal adhesions. Rats were randomized to: no treatment; Interceed absorbable adhesion barrier; keratin hydrogel alone; or keratin hydrogel infused with 22 μg/mL of HF. Necropsies were performed at postop d-14 to assess the extent and tenacity of adhesions and grade histologic inflammation and fibrosis using a standard scoring system. Serum, liver, kidneys, and lungs were harvested to evaluate tissue HF concentrations. Protein and drug elution curves were generated to assess the release of HF from the hydrogel.

RESULTS

Treatment with Keratin-HF hydrogel resulted in significantly fewer abdominal adhesions than any other treatment, and significantly less dense adhesions compared with Interceed or keratin hydrogel alone. Subset histologic analysis did not reveal qualitative differences. HF was undetectable in serum and kidneys, and detected at negligible concentrations in liver and lungs. Keratin-HF hydrogel drug release in phosphate-buffered solution (PBS) was sustained over 7 d and correlated with keratin protein degradation.

CONCLUSIONS

Keratin-HF hydrogel is a novel therapeutic agent that may provide a better method for preventing the development of postoperative adhesions using a combined physical barrier and pharmacologic approached.

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.