Development of a porcine animal model for urethral stricture repair using autologous urothelial cells

Development of male and female models of long urethral strictures in swine

Background

Preclinical animal models which mimic the dimensions of long urethral strictures (>2 cm in length) encountered in the clinic are necessary to evaluate prospective graft designs for urethroplasty. The purpose of this study was to develop both male and female porcine models of long urethral strictures (∼4 cm in length) and characterize histological and functional outcomes of iatrogenic stricture formation between genders.

Methods

Focal, partial thickness urethral injuries were created over 5-6 cm long segments in male and female swine (N = 4 per gender) via electrocoagulation and the degree of stricture formation was monitored for up to 6 weeks by urethroscopy and retrograde urethrography. Animals were sacrificed following stricture confirmation and histological, immunohistochemical, and histomorphometric analyses were performed on strictured and uninjured control urethral segments to profile wound healing responses.

Results

Urethral stricture formation was detected in all female swine by 2 weeks and 100 % of male swine at 3.2 ± 1.8 weeks, post-operatively. The mean length of urethral strictures in both male and female swine was ∼4 cm. Substantial variations in the degree of stricture severity between sexes were observed with males exhibiting significant urethral stenosis and loss of α-smooth muscle actin+ smooth muscle bundles in comparison to controls, while females primarily displayed defects in pan-cytokeratin+ epithelia as well as functional urethral obstruction.

Conclusions

Electrocoagulation injury is sufficient to produce long urethral strictures in male and female swine and the degree of stricture severity and nature of urethral obstruction was observed to be dependent on gender. Animal Protocol: AUP-19-150.

Key message

Novel male and female models of long urethral strictures in swine were created to characterize histological and functional outcomes of iatrogenic stricture formation between genders.

Urethroplasty performed with an autologous urothelium-vegetated collagen fleece to treat urethral stricture in the minipig model

INTRODUCTION AND OBJECTIVE

Tissue-engineered materials in urethral reconstructive surgeries are a promising field for innovative therapy. Collagen matrices increase stability of cell-based implants and can promote viability and proliferation of urothelial cells. In this study, a collagen type I-based cell carrier (CCC) with stratified multi-layer autologous urothelium was used for urethroplasty after induction of urethral stricture in eight minipigs.

MATERIALS AND METHODS

Minipigs underwent surgical procedures to induce urethral stricture by thermocoagulation. Simultaneously, bladder tissue was harvested. Urothelial cells were expanded, labeled with PKH26 and seeded onto CCC in high density. 3 weeks after strictures were induced and verified by urethrography, minipigs underwent urethroplasty using the seeded CCC. Two animals were euthanized after 1, 2, 4, and 24 weeks. Urethras were histologically examined for integration and survival of seeded CCC. In vivo phenotype of multi-layered urothelium matrix constructs was characterized via immunofluorescence staining with pancytokeratin, CK20, p63, E-cadherin and ZO-1.

RESULTS

Seeded CCCs showed excellent stability and suturability after manipulation and application. Transplanted cells were detected using positive PKH26 fluorescence up to 6 months after labeling. Urothelium matrix implants integrated well into the host tissue without sign of inflammation. Animals showed no sign of rejection or stricture recurrence (urethrography) at any time during experimental period. Immunofluorescence analysis confirmed epithelial phenotype, junction formation and differentiation after 2 weeks.

CONCLUSION

CCC can be suitable for urologic reconstructive surgeries and represents a promising option for clinical application. Longer follow-up results are required to exclude re-occurrence of stricture reformation.

Effect of angiotensin II receptor blocker on TGF-β1, MMP-1, and collagen type I and type III concentration in New Zealand rabbit urethral stricture model

Introduction

Urethral stricture is a disease with a high recurrence rate. Angiotensin II via AT1 receptor increases collagen formation through its effects on TGF-β1 and inhibition of collagenase activity. In this study, we evaluated the antifibrotic effect of angiotensin II receptor blocker on urethral stricture formation by creating a urethral stricture model in a male rabbit.

Material and methods

Thirty three male adult rabbits were separated into 3 groups (control, treatment, and sham). Group I consisted of 15 rabbits with urethral stricture that did not undergo any treatment, group II consisted of 15 rabbits with urethral stricture that were treated with a daily dose of 15 mg/kg losartan, given orally. Group III consisted of 3 rabbits with normal urethra and without any treatment. After 1, 2, and 4 weeks, the urethral tissues were collected, processed, and examined for TGF-β1, MMP-1, collagen type I, and collagen type III using enzyme-linked immunosorbent assay. Data were analyzed using 2-way analysis of variance using SPSS version 20.0.

Results

Urethral TGF-β1 concentration in the treatment group was significantly lower during the 2nd and 4th week of observation (p<0.0001), MMP-1 was significantly higher in the 1st, 2nd, and 4th week of observation (p<0.0001), collagen type I was significantly lower during the 2nd (p=0.001) and 4th week (p<0.0001), and collagen type III concentration was significantly lower in the 2nd and 4th week of observation (p<0.0001).

Conclusion

Angiotensin II receptor blocker could limit the progression of urethral stricture. The mechanism may be related to the AT1 blockage that leads to a decrease in TGF-β1 concentration, eventually resulting in lower collagen concentration due to increased MMP-1 activity.

Collagen cell carriers seeded with human urothelial cells for urethral reconstructive surgery: first results in a xenograft minipig model

PURPOSE

Urethral strictures are a common disease of the lower urinary tract in men. At present, the use of buccal mucosa is the method of choice for long or recurrent strictures. However, autologous tissue-engineered grafts are still under investigation for reconstructive urological surgery. The aim of this pilot study was to evaluate the use of human urothelial cells (HUC) seeded on bovine collagen type I-based cell carriers (CCC) in an animal model and to evaluate short-term outcome of the surgical procedure.

METHODS

Four male Göttingen minipigs were used with immunosuppression (cyclosporine A) for this pilot xenograft study. HUC obtained from human benign ureteral tissue were stained by PKH26 and seeded on a collagen cell carrier (CCC). Seven weeks after urethral stricture induction and protective vesicostomy, cell-seeded CCC was implanted in the urethra with HUC luminal and antiluminal, respectively. After two weeks animals were euthanized, urethrography and histological assessment were performed.

RESULTS

Surgery was technically feasible in all minipigs. Stricture was radiologically established 7 weeks after induction. CCC was visible after two weeks and showed good integration without signs of inflammation or rejection. In the final urethrography, no remaining stricture could be detected. Near porcine urothelium, PKH26-positive areas were found even if partially detached from CCC. Although diminished, immunofluorescence with pankeratin, CK20, E-cadherin and ZO-1 showed intact urothelium in several areas on and nearby CCC.

CONCLUSION

Finally, this study demonstrates that the HUC-seeded CCC used as a xenograft in minipigs is technically feasible and shows promising results for further studies.

Collagen--emerging collagen based therapies hit the patient

The choice of biomaterials available for regenerative medicine continues to grow rapidly, with new materials often claiming advantages over the short-comings of those already in existence. Going back to nature, collagen is one of the most abundant proteins in mammals and its role is essential to our way of life. It can therefore be obtained from many sources including porcine, bovine, equine or human and offer a great promise as a biomimetic scaffold for regenerative medicine. Using naturally derived collagen, extracellular matrices (ECMs), as surgical materials have become established practice for a number of years. For clinical use the goal has been to preserve as much of the composition and structure of the ECM as possible without adverse effects to the recipient. This review will therefore cover in-depth both naturally and synthetically produced collagen matrices. Furthermore the production of more sophisticated three dimensional collagen scaffolds that provide cues at nano-, micro- and meso-scale for molecules, cells, proteins and bulk fluids by inducing fibrils alignments, embossing and layered configuration through the application of plastic compression technology will be discussed in details. This review will also shed light on both naturally and synthetically derived collagen products that have been available in the market for several purposes including neural repair, as cosmetic for the treatment of dermatologic defects, haemostatic agents, mucosal wound dressing and guided bone regeneration membrane. There are other several potential applications of collagen still under investigations and they are also covered in this review.