Comparison of angiogenic activity after urethral reconstruction using free grafts and pedicle flap: an experimental study

Single-stage tubular urethral reconstruction using oral grafts is an alternative to classical staged approach for selected penile urethral strictures

Penile urethral strictures have been managed by a staged surgical approach. In selected cases, spongiofibrosis can be excised, a neo-urethral plate created using buccal mucosa graft (BMG) and tubularized during the same procedure, performing a “two-in-one” stage approach. We aim to identify stricture factors which indicate suitability for this two-in-one stage approach. We assess surgical outcome and compare with staged reconstruction. We conducted an observational descriptive study. The data were prospectively collected from two-in-one stage and staged penile urethroplasties using BMG in a single center between 2007 and 2017. The minimum follow-up was 6 months. Outcomes were assessed clinically, radiologically, and by flow-rate analysis. Failure was defined as recurrent stricture or any subsequent surgical or endoscopic intervention. Descriptive analysis of stricture characteristics and statistical comparison was made between groups. Of 425 penile urethroplasties, 139 met the inclusion criteria: 59 two-in-one stage and 80 staged. The mean stricture length was 2.8 cm (single stage) and 4.5 cm (staged). Etiology was lichen sclerosus (LS) 52.5% (single stage) and 73.8% hypospadias related (staged). 40.7% of patients had previous failed urethroplasties in the single-stage group and 81.2% in the staged. The most common stricture locations were navicular fossa (39.0%) and distal penile urethra (59.3%) in the single-stage group and mid or proximal penile urethra (58.7%) in the staged group. Success rates were 89.8% (single stage) and 81.3% (staged). A trend toward a single-stage approach for select penile urethral strictures was noted. We conclude that a single-stage substitution penile urethroplasty using BMG as a “two-in-one” approach is associated with excellent functional outcomes. The most suitable strictures for this approach are distal, primary, and LS-related strictures.

The effect of penile urethral fat graft application on urethral angiogenesis

BACKGROUND

Autologous fat grafts are rich in adipose-derived stem cells, providing optimal soft-tissue replacement and significant quantities of angiogenic growth factor. Although fat grafts (FG) are used in several clinical conditions, the use of FG in urethral repairs and the effects of FG to urethral repairs have not yet been reported.

OBJECTIVE

An experimental study was performed to evaluate the effect of FG on urethral angiogenesis and tissue growth factor (GF) levels.

STUDY DESIGN

Sixteen Wistar albino, adult, male rats were allocated into two groups: the control group (CG) (n = 8) and the experiment group (EG) (n = 8). After anesthetization of all rats, 3-mm vertical incisions were made on the urethras, and then sutured with interrupted 5/0 vicryl sutures. The operations were performed under a stereo dissecting microscope under magnification (×20). In the CG, no additional procedure was performed. In the EG after the same surgical procedure, 1 mm(3) FG was removed from the inguinal region by sharp dissection with a knife. The grafts were trimmed to 1 × 1 mm dimensions on millimeter paper. The FGs were placed on the repaired urethras. The skin was then closed. Samples from urethral and penile skin were taken 21 days after surgery in both groups. Density and intensity of staining with vascular-endothelial GF (VEGF), VEGF-receptor, and endothelial-GF receptor (EGFR) in the endothelial and mesenchymal cells of the penile urethral vessels were immunohistochemically evaluated. Data obtained from immunohistochemical evaluations were analyzed with SPSS 15.0. The P-values lower than 0.05 were considered as significant.

RESULTS

Density of VEGF staining was significantly decreased in the vascular endothelium of the EG compared to the CG (P < 0.05). Density of the EGFR staining was significantly decreased in the vascular endothelium of the EG compared to the CG (P < 0.05) (Table). Intensity of VEGF, VEGF-R and EGFR staining was not significantly different between the two groups. There were no significant differences between groups regarding to VEGFR staining and mesenchymal examination.

DISCUSSION

Decreased density was found in the VEGF staining in the vascular endothelium. This could be explained by the day that the tissues were harvested or because autologous fat grafts might cause decreased growth factor levels, which is contrary to the literature data.

CONCLUSION

Fat grafting has an immunohistochemical effect on the growth factor levels that are related to angiogenesis after urethral repair. It is difficult to make a firm conclusion about the role of fat grafting on urethral healing. Therefore, future studies are needed to see if FG can be used as an alternative to other procedures in order to avoid complications.

The use of a perimeatal-based penile skin flap to cover the repair of a tubularized incised plate urethroplasty: from experimental surgery to clinical practice

OBJECTIVE

To prospectively evaluate the efficacy and safety of a perimeatal-based penile skin flap for neourethral coverage after repair of distal hypospadias with tubularized incised plate urethroplasty (TIPU).

METHODS

In 12 New Zealand white rabbits a ventral urethral defect was created and reconstruction was accomplished with continuous suture. An epithelialized defect-based flap was harvested from the penile skin to cover the repaired defect. The animals were euthanized on the 28th postoperative day and their penises were processed for microscopic examination. In 32 children with distal hypospadias a TIPU was performed. A penile skin flap was created immediately below the distal end of the neourethra and used to cover the urethroplasty.

RESULTS

Histological examinations revealed complete restoration of continuity of the stratified squamous epithelium without evidence of inflammation or fistula formation with full consistency with the underlying papillary reticular and corium. There were no cases of fistula formation. One patient developed meatal stenosis. All patients had a satisfactory cosmetic appearance and excellent functional results.

CONCLUSION

The formation of a perimeatal-based skin flap is a simple and safe method of providing additional cover for the constructed neourethra after TIPU, minimizing the fistula rate.

Long-term angiogenic activity of free grafts and pedicle flap in a rabbit urethroplasty model

PURPOSE

We studied the late angiogenic activity of free grafts and a pedicle flap in a rabbit urethroplasty model to determine whether angiogenic activity plays a role in late outcomes of urethral reconstruction in rabbits.

METHODS

Twenty-eight rabbits were randomly divided into five groups according to the method used to bridge a urethral defect as an onlay patch: Control, simple closure of urethral defect (Group O1); free penile skin graft (FPSG, Group A1); buccal mucosal graft (BuMG, Group B1); bladder mucosal graft (BlMG, Group C1); and pedicle penile skin flap (PPSF, Group D1). Angiogenic activity of the patch on postoperative day 84 was assessed by immunohistochemistry.

RESULTS

The angiogenic activity in Groups O1, A1, B1, C1, and D1 was 23.33 ± 4.92 (means ± SD), 42.89 ± 6.52, 55.78 ± 3.46, 53.61 ± 6.17, and 24.11 ± 9.07 vessels per optical field, respectively. There were statistically significant differences (p < .001) between Group O1 and A1 B1, C1, Group A1 and B1, C1, D1, Groups B1 and D1 and Groups C1 and D1, but not between Groups O1 and D1 (p = 1.000) and Groups B1 and C1 (p = .872). The long-term angiogenic activity of all the groups was significantly lower (p < .001) than in the corresponding early groups.

CONCLUSIONS

Although the angiogenic activity of all the groups decreased in the late assessment, the buccal mucosal graft continued to exhibit elevated angiogenesis above bladder or skin (free or pedicle) graft. Therefore, buccal mucosal patch graft might be preferable because of its easier harvesting.

Mechanical stimuli-induced urothelial differentiation in a human tissue-engineered tubular genitourinary graft

BACKGROUND

A challenge in urologic tissue engineering is to obtain well-differentiated urothelium to overcome the complications related to other sources of tissues used in ureteral and urethral substitution.

OBJECTIVE

We investigated the effects of in vitro mechanical stimuli on functional and morphologic properties of a human tissue-engineered tubular genitourinary graft (TTGG).

DESIGN, SETTING, AND PARTICIPANTS

Using the self-assembly technique, we developed a TTGG composed of human dermal fibroblasts and human urothelial cells without exogenous scaffolding. Eight substitutes were subjected to dynamic flow and hydrostatic pressure for up to 2 wk compared to static conditions (n=8).

MEASUREMENTS

Stratification and cell differentiation were assessed by histology, electron microscopy, immunostaining, and uroplakin gene expression. Barrier function was determined by permeation studies with carbon 14-urea.

RESULTS AND LIMITATIONS

Dynamic conditions showed well-established stratified urothelium and basement membrane formation, whereas no stratification was observed in static culture. The first signs of cell differentiation were perceived after 7 d of perfusion and were fully expressed at day 14. Superficial cells under perfusion displayed discoidal and fusiform vesicles and positive staining for uroplakin 2, cytokeratine 20, and tight junction protein ZO-1, similar to native urothelium. Mechanical stimuli induced expression of the major uroplakin transcripts, whereas expression was low or undetectable in static culture. Permeation studies showed that mechanical constraints significantly improved the barrier function compared to static conditions (p<0.01 at 14 d, p<0.05 at 7 d) and were comparable to native urothelium.

CONCLUSIONS

Mechanical stimuli induced in vitro terminal urothelium differentiation in a human genitourinary substitute displaying morphologic and functional properties equivalent to a native urologic conduit.

Dorsal onlay buccal mucosa versus penile skin flap urethroplasty for anterior urethral strictures: results from a randomized prospective trial

PURPOSE

Reconstructive techniques for anterior urethral strictures have not been subjected to a randomized comparison. In a randomized controlled study we compared outcomes of buccal mucosa dorsal onlay vs skin flap dorsal onlay urethroplasty in patients with complex anterior urethral strictures.

MATERIALS AND METHODS

In this prospective study 55 patients with anterior urethral strictures were randomized to undergo buccal mucosa dorsal onlay (27) or penile skin flap (28) urethroplasty. Operative time, hospital stay, short and long-term complications, recurrence rates, and patient satisfaction were compared between the 2 groups.

RESULTS

The number of patients with pendulous, bulbar and bulbopendulous strictures as well as mean stricture length and median followup were comparable between the 2 groups. Mean operative time was significantly higher in the penile flap (224 minutes) vs the buccal mucosa group (162 minutes, p = 0.001). In the penile flap group 6 patients had superficial penile skin necrosis, 1 had extensive skin loss and required skin grafting, and 2 had penile torsion. In the buccal mucosa group 25.6% of patients had minor morbidity which settled by 4 weeks after surgery. There were 9 (34.1%) patients in the penile flap group and 4 (14.8%) in the buccal mucosa group (p = 0.001) who had troublesome post-void dribbling. In the buccal mucosa group 89% and in the penile flap group 65% said they would recommend this procedure to another patient (p = 0.001). The success rate in the buccal mucosa (89.9%) and penile flap (85.6%) groups was similar (p >0.05).

CONCLUSIONS

On intermediate followup dorsal onlay penile skin flap and buccal mucosa urethroplasty provide similar success rates. Compared to buccal mucosa, penile flap procedures are technically complex, associated with higher morbidity and less preferred by patients.