犬舌黏膜与颊黏膜组合移植重建尿道的实验研究

目的 探讨犬舌黏膜与颊黏膜组合移植替代尿道的可行性和有效性. 方法杂种雌犬7只,平均体质量13 kg,剥离尿道黏膜4 cm×1 cm,取2 cm×1 cm舌侧面黏膜和颊黏膜各1条,拼接后移植至尿道内,恢复尿道黏膜的连续性.术后留置硅胶导尿管1周,拔除尿管后观察排尿情况.1.5～12.0个月后行逆行尿道造影检测实验犬尿道通畅情况,并用10 F尿管证实有无狭窄.随后处死实验犬,测定移植物长度并行病理组织学检查,观察舌黏膜与颊黏膜组合移植至尿道后组织学改变情况. 结果7只实验犬均存活,排尿通畅6只,发生尿道狭窄1只;无尿瘘.移植手术前后舌黏膜和颊黏膜拼接长度分别为(4.00±0.15)和(3.75±0.23)cm,差异有统计学意义(P＜0.05).排尿通畅犬移植黏膜存活良好;舌黏膜与颊黏膜交界处愈合良好,无狭窄发生;光镜下见鳞状上皮呈连续分布,拼接移植黏膜的鳞状上皮与尿道的移行上皮区分明显,移植黏膜的鳞状上:皮有渐被尿道移行上皮替代的趋势.结论 犬舌黏膜和颊黏膜组合移植可替代尿道黏膜并恢复尿道的连续性.     

Evaluation of stretched electrospun silk fibroin matrices seeded with urothelial cells for urethra reconstruction

Background

We investigated the feasibility of urethral reconstruction using stretched electrospun silk fibroin matrices.

Materials and methods

A novel electrospun silk fibroin matrix was prepared. The structure of the material was assessed by scanning electron microscopy and a porosity test. Canine urothelial cells were isolated, expanded, and seeded onto the material for 1 wk to obtain a tissue-engineered graft. The tissue-engineered graft was assessed using hematoxylin and eosin staining and scanning electron microscopy. A dorsal urethral mucosal defect was created in nine female beagle dogs. In the experimental group, tissue-engineered mucosa was used to repair urethra mucosa defects in six dogs. No substitute was used in the three dogs of the control group. Retrograde urethrography was performed at 1, 2, and 6 mo after grafting. The urethral grafts were analyzed grossly and histologically.

Results

Scanning electron microscope and a porosity test revealed that the material had a three-dimensional porous structure. Urothelial cells grew on the material and showed good biocompatibility with the stretched silk fibroin matrices. Canines implanted with tissue-engineered mucosa voided without difficulty. Retrograde urethrography revealed no signs of stricture. Histologic staining showed gradual epithelial cell development and stratified epithelial layers at 1, 2, and 6 mo. The canines in the control group showed difficulty in voiding. Retrograde urethrography showed urethra stricture. Histologic staining showed that no or only one layer of epithelial cells developed. A severe inflammatory reaction was also observed in the control group.

Conclusions

Stretched electrospun silk fibroin matrices have good biocompatibility with urothelial cells, which could prove to be a potential material for use in urethra reconstruction.     

Treatment of urethral defects: skin, buccal or bladder mucosa, tube or patch? An experimental study in dogs

PURPOSE: We studied 3 graft materials and 2 urethroplasty techniques in 24 adult male mongrel dogs. MATERIALS AND METHODS: The animals were divided into 2 equal groups. In group 1 a 4 cm. segment of perineal urethra was excised and tubed urethroplasty was performed using free full-thickness skin, buccal and bladder mucosa grafts in 4 dogs each. In group 2 a 4 cm. urethral strip was excised and onlay urethroplasty was performed using the same graft materials in 4 dogs each. Retrograde urethrography was done and the animals were sacrificed at week 12. Autopsy specimens were calibrated with a 10Fr catheter. Hematoxylin and eosin stained sections were examined. Masson's trichrome stain was used to determine the extent of fibrosis. RESULTS: Urethral stricture was diagnosed by radiology and confirmed by calibration in 8 of the 12 dogs (66%) in group 1 but in only 1 of the 12 (8%) in group 2 (p <0.004). Buccal mucosa grafts were associated with the lowest stricture rate of 12%, followed by 37% for bladder mucosa and 62% for skin (p <0.2). There was no difference in neovascularization among the 3 grafts. Graft shrinkage was less than 10% for buccal mucosa compared with 20% to 40% for skin and bladder mucosa. The shrinkage rate was similar for the onlay and tube techniques. The intensity of chronic inflammation and fibrosis was highest in the skin grafts. Circumferential fibrosis was noted in association with tubed urethroplasty but not with the onlay technique. CONCLUSIONS: The theoretical advantages of buccal mucosal grafts were pathologically demonstrated. When possible, grafts should be used as an onlay rather than as a complete tube.     

Tissue-engineered buccal mucosa using silk fibroin matrices for urethral reconstruction in a canine model

Background

To investigate the feasibility of urethral reconstruction using tissue-engineered buccal mucosa (TEBM) with silk fibroin (SF) matrices in a canine model.

Materials and methods

Autologous oral keratinocytes and autologous fibroblasts were isolated, expanded, and seeded onto SF matrices to obtain TEBM. The TEBM was assessed using hematoxylin and eosin staining and scanning electron microscopy. A 5-cm urethral mucosal defect was created in 10 female canines. Urethroplasty was performed using TEBM in five canines in the experimental group and with SF matrices without cells in the five canines in the comparison group. Retrograde urethrography was performed after 6 mo of grafting. The urethral grafts were analyzed grossly and histologically.

Results

The oral keratinocytes and fibroblasts exhibited good biocompatibility with the SF matrices. TEBM could be constructed using SF matrices. The canines implanted with the tissue-engineered mucosa voided without difficulty. The retrograde urethrography revealed no sign of stricture. The histologic staining showed that epithelial cells developed gradually and exhibited stratified epithelial layers at 6 mo. In the comparison group, the canines had difficulty voiding, and the retrograde urethrography showed urethra stricture. The histologic staining showed that one to two layers of epithelial cells developed.

Conclusions

The TEBM using SF matrices could be a potential material for urethra reconstruction.     

Tissue-Engineered Buccal Mucosa Urethroplasty—Clinical Outcomes

Introduction

Whilst buccal mucosa is the most versatile tissue for urethral replacement, the quest continues for an ideal tissue replacement for the urethra when substantial tissue transfer is needed. Previously we described the development of autologous tissue-engineered buccal mucosa (TEBM). Here we report clinical outcomes of the first human series of its use in substitution urethroplasty.

Methodology

Five patients with urethral stricture secondary to lichen sclerosus (LS) awaiting substantial substitution urethroplasty elected to undergo urethroplasty using TEBM, with full ethics committee support. Buccal mucosa biopsies (0.5 cm) were obtained from each patient. Keratinocytes and fibroblasts were isolated and cultured, seeded onto sterilised donor de-epidermised dermis, and maintained at air–liquid interface for 7–10 d to obtain full-thickness grafts. These grafts were used for urethroplasty in a one-stage (n = 2) or a two-stage procedure (n = 3). Follow-up was performed at 2 and 6 wk, at 3, 6, 9, and 12 mo, and every 6 mo thereafter.

Results

Follow-up ranged from 32 to 37 mo (mean, 33.6). The initial graft take was 100%, as assessed by visual inspection. Subsequently, one patient had complete excision of the grafted urethra and one required partial graft excision, for fibrosis and hyperproliferation of tissue, respectively. Three patients have a patent urethra with the TEBM graft in situ, although all three required some form of instrumentation.

Conclusions

Whilst TEBM may in the future offer a clinically useful autologous urethral replacement tissue, in this group of patients with LS urethral strictures, it was not without complications, namely fibrosis and contraction in two of five patients.     

结肠粘膜重建尿道的动物实验与临床应用

目的　探讨结肠粘膜代尿道治疗复杂性前尿道长段狭窄或闭锁的可行性。　方法　 6条雌性杂种成年狗在全麻下切开尿道 ,剥离全段尿道粘膜 ,取相等长度的结肠粘膜替代尿道粘膜 ,12周后将狗处死 ,取尿道组织作病理检查。采用结肠粘膜替代尿道一期尿道成形术治疗 1例复杂性前尿道长段狭窄患者 ,术后 3个月分别行逆行尿道造影 ,尿道镜和尿流率检查。　结果　 6条狗移植于尿道的结肠粘膜全部成活 ,部分腺上皮转变为移行上皮细胞。采用结肠粘膜替代尿道的患者术后排尿通畅 ,移植段尿道无狭窄 ,最大尿流率 30ml/s。　结论　结肠粘膜代尿道是治疗复杂性前尿道长段狭窄或闭锁的一种有效方法 ,可用于不适合应用包皮或膀胱粘膜及颊粘膜时的尿道重建     

舌黏膜尿道成形治疗前尿道狭窄（附80例报告）

目的：研究舌黏膜尿道成形治疗尿道狭窄的有效性和安全性。方法：2006年8月～2008年12月采用舌黏膜尿道成形治疗80例前尿道狭窄,尿道狭窄段2．5～18cm,其中30例为长段尿道狭窄（9～18cm）采用双侧舌黏膜或舌黏膜与颊黏膜或与带蒂包皮拼接尿道成形治疗。尿道成形采用两种术式：保留原尿道板的扩大尿道腔37例;埋藏黏膜条43例。结果：术后随访4～30（平均16．8）个月,7例发生并发症,其中尿瘘4例,再次发生尿道狭窄3例,其余患者排尿通畅,最大尿流率从15．2～54．6（平均28．7）ml／s。结论：舌黏膜是一种修复前尿道狭窄较好的尿道替代物,双侧舌黏膜尿道成形能成功治疗长段、复杂性尿道狭窄。     

尿道背侧颊黏膜镶嵌补片法治疗长段前尿道狭窄

目的 评价颊黏膜尿道背侧镶嵌技术尿道修复重建手术的有效性和安全性.方法 男性前尿道狭窄患者57例.平均年龄36(17～52)岁.尿道狭窄长度平均3.0(2.5～7.0)cm.颊黏膜取材长度平均4.0(3.5～8.0)cm,平均宽度2.3(I.8～2.5)am.57例均有经尿道内窥镜冷切电切手术史,其中1次手术史29例(51%),2次20例(35%),3次8例(14%),行耻骨上膀胱造瘘48例,9例采用尿道扩张维持.手术游离并旋转尿道,并于尿道背侧纵行切开,6-0可吸收线缝合颊黏膜与尿道切缘.保留尿管4周,拔管时行顺行尿道造影.患者排尿困难和尿线变细、尿道造影或尿道镜发现尿道管腔狭窄<16 F确定为尿道狭窄复发.结果 57例手术均成功,平均手术时间135(105150)min.平均随访11.2(1～23)个月.尿道通畅54例(95%),术后2～3个月复发3例(5%),狭窄部位均为远端的颊黏膜与尿道结合部,行尿道内窥镜冷刀切开,定期尿道扩张治疗.伤口感染3例,未发生尿瘘及尿道憩室.患者口腔疼痛持续2～5 d,平均2.3 d.术后无张VI困难、颊部麻木及腮腺导管梗阻等并发症发生,VI腔颊部均未见瘢痕形成.结论 VI腔颊黏膜尿道背侧镶嵌补片修复重建尿道,效果确切、并发症少、狭窄复发率低,是理想的长段前尿道狭窄的修复重建手段.     

Biodegradable urethral stents seeded with autologous urethral epithelial cells in the treatment of post‐traumatic urethral stricture: a feasibility study in a rabbit model

OBJECTIVE

To evaluate the adhesion and growth of rabbit urethral epithelial cells (UECs) on a biodegradable unbraided mesh urethral stent, and to assess the feasibility and effect of the cell‐seeded urethral stent for treating post‐traumatic urethral stricture (PTUS) in a rabbit model.

MATERIALS AND METHODS

Rabbit UECs were collected by biopsy from adult rabbit urethra and seeded onto the outer layer of a mesh biodegradable urethral stent. The growth of UECs in cell‐scaffolds was assessed by scanning electron microscopy, immunohistochemical and fluorescence staining. In all, 32 male New Zealand rabbits were used, with either PTUS or uninjured, as a control group. Cell‐seeded stents were implanted into the rabbits strictured urethra. The histological and immunohistochemical findings were assessed after death at 1, 2, 8, 12 and 24 weeks, respectively. The reconstruction and function were evaluated by urethroscopy and retrograde urethrography.

RESULTS

The cultured UECs adhered to the stent and grew well. Immunohistochemistry showed that the cells were stained positively for cytokeratin. At 4 weeks, vs 2 weeks, the thickness of the papillary projections of the epithelium decreased and inflammatory cell infiltration diminished. At 24 weeks the injured urethra was completely covered by integrated regeneration of three to five layers of urothelium. There was no evidence of voiding difficulty, stricture recurrence or other complications.

CONCLUSIONS

The unbraided mesh biodegradable urethral stent with autologous UECs seemed to be feasible for treating PTUS in the rabbit urethra, and provides a hopeful avenue for clinical application allowing reconstruction of PTUS.     

Two cases of female urethral reconstruction with acellular porcine urinary bladder matrix

Introduction and hypothesis

Female urethral reconstruction via the traditional routes can be limiting for various reasons. Current literature on the use of acellular biologic grafts derived from viscera for female urethral reconstruction is limited. We present two cases of women with complete loss of their posterior urethra presenting for urethral reconstruction.

Methods

Two cases of urethral reconstruction using acellular porcine urinary bladder matrix (UBM), along with labial fat pad transposition and biologic pubovaginal sling are presented.

Results

In both cases the UBM graft showed successful conversion to what appeared to be normal urethral mucosa. One woman showed significant improvement in continence and the other showed complete continence.

Conclusions

Female urethral reconstruction using acellular porcine UBM is a viable option for patients who have lost a significant portion of their urethra. Both cases demonstrated transition of the graft into the posterior wall of the urethra with significant improvement in continence. Further studies are needed to confirm that acellular porcine UBM can transform to urethral mucosa in women requiring urethral reconstruction.

     

DETECTION OF URETHRAL DIVERTICULA IN WOMEN: COMPARISON OF A HIGH RESOLUTION FAST SPIN ECHO TECHNIQUE WITH DOUBLE BALLOON URETHROGRAPHY

Purpose

We compared a rapid high resolution magnetic resonance imaging (MRI) technique to contrast urethrography for the detection of urethral diverticula in women.

Materials and Methods

During a 19-month interval 13 patients with clinically suspected urethral diverticula were evaluated with MRI and contrast urethrography. All patients were referred by a urologist, and had clinical signs and symptoms suggesting the presence of a urethral diverticulum. Double balloon urethrography was performed in 12 patients and voiding cystourethrography was done in 1. MRI was performed using a fast spin echo T2-weighted pulse sequence and a dedicated pelvic multicoil. Following a sagittal localizer sequence 3 mm. thick axial sections were obtained from the bladder base through the entire urethra. Total imaging time was 15 minutes.

Results

In 7 patients MRI and urethrography were negative for urethral diverticula, and in 3 cystourethroscopy was negative. In 1 patient MRI revealed a vaginal inclusion cyst confirmed by surgery. Three patients had no other studies or procedures performed. In 6 patients MRI was positive for urethral diverticula, including 4 in whom the diverticulum was confirmed at surgery, 1 who declined surgery and 1 who was lost to followup. Of the 4 patients (75%) with a surgically confirmed diverticulum double balloon urethrogram was negative in 3.

Conclusions

MRI is a valuable noninvasive technique for determining the presence of urethral diverticula as well as detecting other abnormalities. In our study MRI had a higher sensitivity for detecting diverticula and a much higher negative predictive rate.     

The tongue as an alternative donor site for graft urethroplasty: a pilot study

PURPOSE: Urethroplasty with a buccal mucosal graft provides excellent clinical results but it may also cause oral complications in some cases. The mucosa covering the lateral and under surface of the tongue is identical in structure with that lining the rest of the oral cavity. We evaluated LMGs for urethroplasty. MATERIALS AND METHODS: From January 2001 to September 2004, 8 men 34 to 65 years old (mean age 46.1) with urethral strictures 1.5 to 4.5 cm long were selected for 1-stage dorsal onlay urethroplasty. The site of the harvest graft was the lateral mucosal lining of the tongue. Postoperatively all patients were followed with urethrography, uroflowmetry, cystourethrography and flexible urethroscopy after 3 and 12 months. Successful reconstruction criteria were peak flow rate greater than 15 ml per second and no need for postoperative urethral dilation. RESULTS: Median followup was 18 months (mean 22.1, range 3 to 47). Seven cases were successful. One patient had a partial urethral stricture. In successful cases cystourethrography revealed no significant graft contractures or sacculations and at flexible urethroscopy LMG was almost indistinguishable from native urethra. There were no pain, esthetic or functional complications at the donor site. CONCLUSIONS: Harvesting the LMG is feasible and easy to perform. Compared with the buccal mucosal graft the LMG seems to be associated with less postoperative pain and a minor risk of donor site complications. These preliminary functional and esthetic data are satisfactory.     

Endoscopic Repair in 154 Cases of Urethral Occlusion: The Promise of Guided Optical Urethral Reconstruction

Purpose

We determined whether optical urethral reconstruction, with the use of a Benique bougie in the proximal urethra and transrectal digital guidance, is effective for the treatment of long and severe urethral occlusions. However, with some skill the procedure can be done without the bougie for the treatment of short occlusions.

Materials and Methods

During a 9-year period 154 men with complete urethral occlusion underwent core through optical urethrotomy via transrectal digital guidance, using the Benique bougie in 89 (58%). A total of 400 urethrotomies was performed. All lesions were in the posterior urethra except 8 in the pendulous portion. There were 64 war related injuries (41.6%). Combined voiding and retrograde urethrography was not useful to measure the length of the occlusion due to failure of proximal urethral filling. Guided optical urethral reconstruction consisted of optical urethrotomy performed with a Benique bougie introduced proximally through the suprapubic catheter site and into the proximal urethra with the index finger of the operator in the rectum. The same procedure was performed blindly without use of the bougie in 65 patients (42%), and in 43 with lesions shorter than 1 cm. and 4 with multiple annular lesions. We also used the blind technique successfully to reestablish 18 occlusions longer than 1 cm. For optimal epithelialization of the urethral tract we suggest leaving a silicone catheter indwelling for 3 months. No prophylactic antibiotics were given.

Results

Of the patients 54 (35%) were cured after 1 procedure, whereas the remaining 100 (65%) required 1 to 9 additional urethrotomies (mean 3). Patients with an uninstrumented urethra who were treated initially with suprapubic catheterization required 1 to 6 urethrotomies (mean 2), compared to 1 to 10 (mean 3) for those who had undergone a prior procedure. Hematuria occurred in 9% of the patients, symptomatic urinary tract infection in 7% and slight extravasation in 3.2%. One patient had stress incontinence.

Conclusions

Our procedure is effective, simple, safe, repeatable, inexpensive and minimally invasive, and it does not require special or sophisticated guiding instruments, which are necessary for previously described techniques. It can be performed with or without use of a Benique bougie depending on the extent of the lesion and skill of the surgeon. The outcome can be judged from the symptomatic response of the patient, and flow studies and urethrography are not mandatory during routine followup.     

Immunohistochemical analysis of estrogen receptors in the urethra of sexually intact,ovariectomized, and estrogen-substituted ovariectomized sheep

Introduction and hypothesis

Urinary incontinence is prevalent in postmenopausal women and spayed dogs and is associated with decreased estrogen plasma concentrations. The objective of the study was to investigate the expression of estrogen receptors (ER) in the urethra of sexually intact, ovariectomized, and estrogen-substituted ovariectomized ewes.

Methods

Paraffin cross-sections from each urethral quarter were immunohistochemically analyzed. The reactivity of ER was semiquantitatively assessed employing an immunoreactive score (IRS).

Results

In contrast to ERβ, ERα was identified in all urethral compartments; the highest IRS was detected in the epithelium of the distal urethra. The immunoreactivity and distribution of ERα did not differ among groups. Highly significant differences in ERα concentrations were observed between consecutive urethral quarters in each group.

Conclusions

Neither ovariectomy nor ovariectomy and estrogen substitution seem to have a significant effect on overall urethral ERα concentration. The results demonstrate that the precise location of the investigated urethral part is crucial to the reliable evaluation or possible comparison of ERα concentrations.     

The use of pedicled appendix graft for substitution of urethra in recurrent urethral stricture

Background: Recurrent posterior urethral strictures after failed urethroplasty may need urethral substitution. Skin or mucosal grafts, currently used for this purpose, have a high complication rate. The authors describe the use of pedicled appendix for posterior urethral substitution. Methods: Two boys with pelvic fracture urethral distraction injuries were treated for recurrent posterior urethral strictures after a failed perineal anastomotic urethroplasty. Through a perineal-transpubic approach the stricture tissue was excised, which resulted in a gap of 5 to 7 cm between the healthy ends. The vermiform appendix was mobilised on its own pedicle and transposed to the perineum; the proximal end of appendix was anastomosed to the prostatic urethra and the distal end (tip discarded) to the bulbar/penile urethra. Omentum was transposed to wrap the anastomosis and fill the dead space. Results: Normal micturition was restored in both patients. No further treatment was required after 1 dilatation in the first case. Both patients are continent. Potency status remains unchanged from the preoperative period with normal erections in 1 case. Follow-up (1 to 3 years) has been satisfactory with no complications. Conclusions: The appendix is a promising organ for posterior urethral replacement. It can be brought to the perineum on its own vascular pedicle.     

CONSTRUCTION OF FEMALE URETHRA USING BUCCAL MUCOSA GRAFT

PURPOSE: We reviewed our experience with buccal mucosa grafts for reconstructing difficult female urethral problems. METHODS AND METHODS: Since 1994, we have used a buccal mucosa graft to reconstruct the urethra in 7 girls 3 to 13 years old. The underlying pathological condition was a fibrotic urethra after previous operations for cloacal exstrophy, cloacal malformation, iatrogenic urethral stricture, and multiple false passages in a previously reconstructed urethra of vaginal mucosa that made clean intermittent catheterization difficult. A full-thickness buccal mucosa graft was tubularized in situ as the neourethra to the base of the clitoris. In patients with cloacal exstrophy and cloacal malformation the bladder neck and urethra were widely exposed transabdominally by splitting the pubic symphysis. The fibrotic mucosa was excised and the tubularized buccal mucosa graft was wrapped with periurethral tissues. Other patients underwent transvaginal surgery in the prone position and the graft was covered with a buttock flap. RESULTS: Patients were followed for 12 to 58 months (mean 34.7). Those with cloacal exstrophy and cloacal malformation had been completely incontinent before urethral reconstruction but all attained complete continence postoperatively. They and the girl who underwent urethral reconstruction for difficult catheterization performed clean intermittent catheterization easily. The patient with urethral stricture voided via the urethra without difficulty. CONCLUSIONS: In select female patients with difficult urethral reconstructive problems a tubularized free graft obtained from the buccal mucosa may be effectively used when local tissue is fibrotic and unsuitable for creating a supple new urethra.     

Oral complications after lingual mucosal graft harvesting for urethroplasty in 110 cases

Study Type – Therapy (case series)
Level of Evidence 4 What’s known on the subject? and What does the study add? Lingual mucosal graft harvesting for urethroplasty is feasible, safe, provides long grafts and is easy to carry out. Most patients have minimal immediate or short‐term donor site complications. The oral complications appeared to be related to the graft length and patient age. Most complications resolved within 1 year. Oral complications after LMGs harvesting were related to the patient’s age at surgery. The children did not experience any persistent complications. Cases of bilateral or longer LMGs were associated with higher complication rates. However, most of these oral complications subsided gradually within 1 year. OBJECTIVE ? This study was to evaluate donor‐site complications of lingual mucosal graft harvesting for substitution urethroplasty. PATIENTS AND METHODS ? 110 patients with anterior urethral strictures or hypospadias underwent lingual mucosal grafts (LMGs) urethroplasty. Dual LMGs were harvested from both sites separately or a long mucosal graft was harvested from one side to other side of tongue in 29 patients (group one); a shorter mucosal graft was harvested from one side of tongue in 81 patients (group two). A standard proforma ( Appendix ) was used for all patients. RESULTS ? The mean follow up time was 22 months (range 6～41). At six months follow‐up, numbness of tongue was reported in 19 patients (17.27%), parageusias in six (5.45%) and slurring of speech in 9 (8.18%). ? Ninety‐six patients were followed up for more than 12 mo. Numbness in operative area of tongue was documented in seven patients (7.29%), parageusias in three (3.13%) and slurred speech in three (3.13%). ? None of these complications occurred in the six pediatric cases (<14 year) with a history of failed hypospadias repair. CONCLUSIONS ? LMGs urethroplasty, as most patients, were satisfied, but there were certain complications that have not been previously described in the literature. ? Most oral complications subsided gradually within the first year.     

Cell-Seeded Tubularized Scaffolds for Reconstruction of Long Urethral Defects: A Preclinical Study

Background

The treatment options for patients requiring repair of a long segment of the urethra are limited by the availability of autologous tissues. We previously reported that acellular collagen-based tubularized constructs seeded with cells are able to repair small urethral defects in a rabbit model.

Objective

We explored the feasibility of engineering clinically relevant long urethras for surgical reconstruction in a canine preclinical model.

Design, setting, and participants

Autologous bladder epithelial and smooth muscle cells from 15 male dogs were grown and seeded onto preconfigured collagen-based tubular matrices (6 cm in length). The perineal urethral segment was removed in 21 male dogs. Urethroplasties were performed with tubularized collagen scaffolds seeded with cells in 15 animals. Tubularized constructs without cells were implanted in six animals. Serial urethrography and three-dimensional computed tomography (CT) scans were performed pre- and postoperatively at 1, 3, 6, and 12 mo. The animals were euthanized at their predetermined time points (three animals at 1 mo, and four at 3, 6, and 12 mo) for analyses.

Outcome measurements and statistical analysis

Statistical analysis of CT imaging and histology was not needed.

Results and limitations

CT urethrograms showed wide-caliber urethras without strictures in animals implanted with cell-seeded matrices. The urethral segments replaced with acellular scaffolds collapsed. Gross examination of the urethral implants seeded with cells showed normal-appearing tissue without evidence of fibrosis. Histologically, an epithelial cell layer surrounded by muscle fiber bundles was observed on the cell-seeded constructs, and cellular organization increased over time. The epithelial and smooth muscle phenotypes were confirmed using antibodies to pancytokeratins AE1/AE3 and smooth muscle–specific desmin. Formation of an epithelial cell layer occurred in the unseeded constructs, but few muscle fibers formed.

Conclusions

Cell-seeded tubularized collagen scaffolds can be used to repair long urethral defects, whereas scaffolds without cells lead to poor tissue development and strictures. This study demonstrates that long tissue-engineered tubularized urethral segments may be used for urethroplasty in patients.     

A Balloon-Tipped Catheter for Measuring Urethral Pressures

Background:

Better methods are needed for recording urethral function for complex urologic problems involving the bladder, urethra, and pelvic floor.

Objective:

To evaluate a balloon catheter for recording urethral pressure and function using bench-top testing and evaluation in an animal model.

Methods:

Balloon pressure–recording methods included slightly inflating the balloon with water and placing the pressure transducer on the distal end of the catheter. For bench-top testing, manual procedures and a silastic tube with a restriction were used. In 3 anesthetized dogs, pressure recorded from the skeletal urethral sphincter was induced with electrical stimulation of the sphincter. Anal sphincter pressure was also recorded.

Results:

Bench-top testing showed good pressure recordings, including a confined peak at the tube restriction. Animal tests showed urethral pressure records with rapid responses when electrical stimulation was applied. Peak pressure at the urethral skeletal sphincter was 55.7 ± 15 cmH₂O, which was significantly higher than the peak pressure recorded 2 cm distally in the proximal urethra (3.3 ± 2.3 cmH₂O). Peak anal pressures were smaller and unchanged for the 2 stimulations.

Conclusions:

Balloon-pressure recordings showed rapid responses that were adequate for the tests conducted. In the animal model, high-pressure contractions specific to the skeletal urethral sphincter were shown. Balloon-tipped catheters warrant further investigation and may have applications for the evaluation of detrusor-sphincter dyssynergia after spinal cord injury or for stress urinary incontinence.     

非编织状聚乙醇酸膜片重建兔尿道的实验研究

目的探讨非编织状聚乙醇酸膜片重建兔全层尿道的效果。方法制备1cm×1cm的非编织状PGA膜片。建立新西兰大白兔尿道腹侧1cm全层尿道缺损动物模型,将PGA膜片植入尿道缺损区域,修补尿道缺损。术后1、2、3个月进行尿道造影、大体观察和组织学观察评价尿道重建情况。结果PGA膜片修复新西兰兔全层尿道缺损,9只动物除1只术后1个月发生尿瘘外．其余动物均排尿通畅。组织学检查发现尿道黏膜再生良好,但尿道海绵体区域主要以纤维瘢痕增生为主,未见明显尿道海绵体再生。结论PGA膜片能够修复新西兰大白兔1cm尿道黏膜的缺损,但缺乏尿道海绵体再生。