Use of epidermal growth factor and collagen synthesis inhibition as adjuvant to healing of ureteroureteral anastomosis

Paclitaxel inhibits ureteral smooth muscle cell proliferation and collagen production in the absence of cell toxicity

PURPOSE

Urinary tract stricture results from excess collagen deposition at an injured area. Paclitaxel (Sigma-Aldrich®) prevents coronary artery restenosis by inhibiting vascular smooth muscle cell proliferation and collagen production. We evaluated the effects of paclitaxel on ureteral smooth muscle cell proliferation and collagen production.

MATERIALS AND METHODS

Three phases of experiments were done in canine smooth muscle cells. In phase 1 we used proliferation assay to study smooth muscle cells exposed to various concentrations of paclitaxel during 7 days. Phase 2 consisted of 6-day enzyme-linked immunosorbent assay to detect the total amount of type III collagen produced by smooth muscle cells exposed to paclitaxel. In phase 3 we assessed smooth muscle cell membrane damage using a lactate dehydrogenase cytotoxicity assay in which cells were exposed to escalating paclitaxel concentrations for 14 days.

RESULTS

Proliferation studies showed that 10 and 100 nM paclitaxel significantly inhibited ureteral smooth muscle cell proliferation. Enzyme-linked immunosorbent assay revealed significantly decreased type III collagen production at 100 nM. Cytotoxicity testing showed that 1 to 100 nM paclitaxel did not harm smooth muscle cells.

CONCLUSIONS

Paclitaxel effectively inhibits canine ureteral smooth muscle cell proliferation and collagen production without toxicity to smooth muscle cells at concentrations up to 100 nM. These results may ultimately translate into new methods of preventing and treating urinary stricture disease.

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

BACKGROUND AND PURPOSE

Urethral strictures are from periurethral spongiofibrosis that develops as a result of urethral trauma, disease, or iatrogenic injury. The spongy tissue that surrounds the strictured urethra has an altered ratio of collagen, with increased collagen type I relative to type III. We evaluated the ability of a urethral catheter that was coated with halofuginone (HF), a potent type I collagen inhibitor, to prevent spongiofibrosis formation in a rat model.

MATERIALS AND METHODS

HF was coated on silicone catheters and release kinetics were measured. Success of impregnation was evaluated with scanning electron microscopy, serial weights, and drug elution data. Urethral strictures were induced in rats using electrocautery. Half the animals had placement of an HF-coated catheter while the others had uncoated silicone controls. Animals were sacrificed at predetermined time points, and urethral tissue was either processed for staining with Masson trichrome and anti-alpha-1 collagen or digested to determine HF concentration. Serum drug levels were also determined in treated animals. Slides were graded by a pathologist who was blinded to treatment to determine collagen deposition.

RESULTS

HF was coated successfully on silicone catheters. Local urethral concentration of HF was tenfold higher than serum concentration in treated rats. Animals with HF-coated catheters had no new type I collagen deposition after urethral injury. Control animals had increased periurethral collagen type I deposition, typical of urethral stricture formation.

CONCLUSIONS

HF can be coated successfully on silicone catheters. HF successfully inhibits periurethral type I collagen deposition after urethral injury. This may become an important therapy to prevent urethral stricture formation or recurrence after endoscopic therapy.

Collagen Changes in the Ureteropelvic Junction after Failed Antegrade Endopyelotomy

PURPOSE

We evaluated the collagen content and differentiation of the ureteropelvic junction (UPJ) of patients who underwent Anderson-Hynes dismembered pyeloplasty after failure of antegrade endopyelotomy.

MATERIALS AND METHODS

A total of 12 UPJ obstructions were examined more than 12 months after endopyelotomy with both histochemical staining to analyze total collagen content and immunohistochemical staining to analyze collagen types I and III. The specimens were compared with 12 primary UPJ obstructions and 6 normal UPJs. Statistical analysis was performed using Fisher's test and Wilcoxon matched-pairs signed-rank test.

RESULTS

Immunohistochemical staining revealed that collagen type I was located in the interfascicular space and collagen type III in the intrafascicular space in all UPJs. We found more collagen in obstructed than in normal UPJs. Collagen type III was more abundant in secondary than in primary UPJ obstructions (P < 0.01). In obstruction after endopyelotomy, the staining intensity of collagen type III was greater than the intensity of collagen type I (P < 0.01).

CONCLUSION

Our results suggest that the success of antegrade endopyelotomy was impaired by an inflammatory process. This condition determined a shift of collagen differentiation toward type III, which is more fibrous than type I.

Ureteral replacement using small-intestinal submucosa and a collagen inhibitor in a porcine model

PURPOSE

Small-intestinal submucosa (SIS) has been successful as an onlay graft in ureteral repair, but tubularized segment interposition of SIS has been unsuccessful. Our objective was to evaluate whether a type I collagen inhibitor, halofuginone, would prevent stricture formation in tubularized SIS interposition.

MATERIALS AND METHODS

We performed either laparoscopic partial ureteral excision followed by an SIS onlay graft (N = 5) or complete laparoscopic ureteral excision followed by an SIS interposition graft (N = 7) in domestic pigs. Animals received either no (N = 3), low-dose (N = 5), or high-dose (N = 4) halofuginone. Animals had ureteral stenting for 2 weeks after surgery and were permitted to survive for 6 or 9 weeks. An intravenous urogram (IVU) was performed prior to sacrifice. Kidneys were examined grossly and histologically.

RESULTS

One animal that received an onlay graft died of an unrelated illness. The remaining four ureteral onlay animals, including one control and two low-dose and one high-dose pig, had grossly normal kidneys at harvest. The IVU was normal in the control and high-dose animal but showed delayed excretion with mild hydroureteronephrosis in the low-dose animals. Pathologic examination of the SIS site revealed circumferential reepithelialization with inflammation and mild fibrosis. All seven tubularized interposition graft kidneys demonstrated either severe hydroureteronephrosis (N = 5) or renal atrophy (N = 2), and all had complete obstruction on IVU. Pathologic examination revealed a stenotic ureteral lumen with extensive surrounding inflammation and fibrosis.

CONCLUSIONS

An SIS onlay graft was successful in the porcine model of ureteral injury. Halofuginone, a type I collagen inhibitor, did not demonstrate a significant beneficial effect in this technique. Ureteral tubularized interpositions with SIS are unsuccessful and not improved by halofuginone.

Comprehensive evaluation of ureteral healing after electrosurgical endopyelotomy in a porcine model: original report and review of the literature

PURPOSE

Endopyelotomy (EP) has yet to equal the success achieved with open dismembered pyeloplasty. To understand better the ureteral response to EP we performed a timed histopathological evaluation of the porcine ureter after Acucise (Applied Medical, Rancho Santa Margarita, California) EP.

MATERIALS AND METHODS

In 28 domestic pigs bilateral Acucise EPs were performed and bilateral 7Fr stents were placed. The kidneys, ureters and bladder were harvested after EP at 0, 1, 2, 3, 6, 12 and 18 hours, 1, 3 and 5 days, and 1, 2, 4 and 8 weeks. The stents were removed after 4 weeks. The healing area of the ureter was sectioned. Half was fixed in formalin 10%, stained and evaluated by light microscopy. The other half was frozen and reverse transcriptase-polymerase chain reaction was performed to measure steady state levels of epidermal growth factor, transforming growth factor (TGF)-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, keratinocyte growth factor, vascular endothelial growth factor, insulin-like growth factor, platelet derived growth factor, collagen type 1, integrin and fibronectin transcript expression. Immunohistochemistry for actin, desmin and myosin expression was completed. The same studies were applied to the mid portion of the unoperated ureter.

RESULTS

Initial sealing of the ureterotomy defect was by blood clot and periureteral fat. Complete healing of the mucosa was observed at 2 weeks in animals without an associated urinoma. However, in no case did the muscle layer bridge the whole circumference of the ureter despite followup out to 8 weeks. In the operated ureter elevated expression of keratinocyte growth factor, vascular endothelial growth factor, TGF-alpha, TGF-beta 1, TGF-beta 3 and integrin was detected 2 hours after the operation and sustained for 7 to 14 days after the procedure. Immunohistochemistry revealed that most presumed myocytes seen in the defect were actually myofibroblasts. Persistent urinoma formation beyond the first few days appeared to slow the healing process.

CONCLUSIONS

Urothelium regenerated rapidly over an iatrogenic ureteral defect despite the absence of a lamina propria. Muscle cell coverage failed to occur completely at 8 weeks. In the initial 8 weeks of the healing process myofibroblasts appear to be prevalent. A persistent urinoma negatively impacts the healing process.

The Use of Halofuginone in Limiting Urethral Stricture Formation and Recurrence: An Experimental Study in Rabbits

PURPOSE

We developed a reproducible animal model for the induction of urethral stricture in the rabbit and evaluated the role of halofuginone in limiting stricture formation.

MATERIALS AND METHODS

A total of 20 New Zealand male rabbits were used in the first phase of the experiment. Bulbar urethral stricture was induced by electrocoagulation. The animals were then randomly assigned to 2 groups of 10 each, which received a diet containing halofuginone or a normal diet. In the second phase electrocoagulation induced stricture was treated with visual internal urethrotomy in 45 rabbits. These rabbits were randomly assigned to 2 groups, namely a halofuginone and a control group.

RESULTS

In the first phase stricture developed in 2 study rabbits (20%) vs 10 controls (100%). In the second phase 37 rabbits were evaluable (8 died). Recurrent stricture was observed in 5 of the 18 study rabbits (27%) vs 14 of the 19 controls (73%).

CONCLUSIONS

Halofuginone is effective in limiting the occurrence of de novo urethral stricture and recurrent stricture after visual internal urethrotomy. This antifibrotic molecule may become an important therapy to treat urethral stricture and/or recurrence following endoscopic manipulation of stricture in humans.

Role of acellular collagen matrix surgisis in the endoscopic management of ureteropelvic junction obstruction

PURPOSE

To investigate the role of acellular collagen matrix (Surgisis during endopyelotomy.

MATERIALS AND METHODS

Nine female pigs (25-35 kg) were enrolled in our protocol. The pigs were categorized as follows. Group I (N = 3) had endopyelotomy + insertion of SIS, Group II (N = 3) creation of UPJ stricture + endopyelotomy + insertion of SIS, and Group III (N = 3) Davis intubated ureterotomy using SIS. The contralateral side served as a control for each group (one pig in each group). In three pigs (two in Group III and one in Group II), Surgisis was treated with India ink prior to insertion at the endopyelotomy site. An endopyelotomy stent (14/8 F x 24 cm) was used to stent the ureteropelvic junction (UPJ) for 4 weeks. Four weeks after the stent was removed, laparoscopic nephroureterectomy was performed, and the animals were euthanized. Histopathologic analysis of the Surgisis-regenerated segment of the UPJ was performed using hematoxylin and eosin, reticular (collagen), smooth muscle actin, and S-100 (nerve) stains.

RESULTS

All animals tolerated the procedure. The mean operative time was 162 minutes. One pig (Group II) developed pyonephrosis; one pig (Group III) developed significant ascites and was sacrificed 2 week before the end of the experiment. Histopathologic analysis showed complete epithelializaton at 8 weeks. Reticular stain demonstrated abundant collagen matrix in the submucosa. Smooth muscle staining revealed myofibroblastic proliferation within the SIS-regenerated tissue adjacent to disorganized smooth muscle cells. India ink-stained SIS-regenerated tissue did not show smooth muscle cells. The S-100 stain did not demonstrate neurons at 8 weeks; however, in three pigs, peristaltic activity was noted across the UPJ.

CONCLUSION

The use of acellular collagen matrix in the endoscopic management of UPJ obstruction is a promising technique. The abundance of myofibroblasts and absence of abundant smooth muscle regeneration indicates a need to investigate the role of growth factors in SIS regeneration of host tissue.

Endoscopic and surgical repair of the ureter

Endoscopy has justified its leading position in ureteral surgery. Recent advances in this field have pushed forward the frontiers and enabled the treatment of difficult ureteral strictures and congenital abnormalities such as megaureter and ureteroceles. The use of the ileum is, however, still the reference for ureteral replacement. An ileal ureter may be performed laparoscopically, but it remains an invasive procedure. In the near future the development of ureteral prostheses could simplify the management of ureteral replacement. For that purpose, and in selected cases, alloplastic ureteral prostheses may already have clinical applications. Bioengineered ureteral prostheses are still at an experimental stage.