Porcine Bladder Replacement with a Bilayer Silk Fibroin Enhanced Prosthetic Reservoir: A Feasibility Study

Abstract

Introduction: The creation of synthetic reservoirs for bladder replacement has been limited by challenges of interfacing synthetic materials and native tissue. We sought to overcome this challenge by utilizing a novel bilayer silk fibroin scaffold (BLSF) as an intermediary toward the development of an acellular prosthetic reservoir. Methods: Under institutionally approved protocols, 3D-printed reservoirs were implanted in six juvenile female pigs after cystectomy. BLSF was attached to the in situ prosthetic reservoir serving as an intermediary to native ureteral and urethral tissue anastomoses. Our first protocol allowed four pigs to be survived up to 7 days, and the second protocol allowed two pigs to be survived for up to 1 year. At the first sign of functional decline or the end of the study period, the animals were euthanized, and kidneys, ureters, prosthetic bladder, and urethra were harvested en bloc for histopathology analysis. Results: The first two pigs had anastomotic urine leaks because of design flaws resulting in early termination. The third pig had acute renal failure resulting in early termination. The artificial bladder design was modified in subsequent iterations. The fourth pig survived for 7 days and, upon autopsy, had intact urethral and ureteral anastomoses. The fifth and sixth pigs survived for 11 and 12 weeks, respectively, before they were sacrificed because of failure to thrive. One animal developed an enteric fistula. The other animal had an intact anastomosis, and the BLFS was identified at the ureteral and urethral anastomoses on histopathologic analysis. Conclusions: Replacing the porcine bladder with a prosthetic bladder was achieved for up to 3 months, the second longest survival period for a nonbiologic bladder alternative. BLSF was used for the first time to create an interface between synthetic material and biologic tissue by allowing ingrowth of urothelium onto the acellular alloplastic bladder.

Keywords: alloplastic; artificial bladder; prosthetic; synthetic bladder; urinary diversion.

FIG. 1.

Artificial bladder version 1. Volume 230 mL (Designed by Richard Ewers in 1999).

FIG. 2.

Artificial bladder version 2. Volume 160 mL. Reservoir was anchored to the anterior abdominal wall through anchoring loops. Silk scaffold was applied to urethral port. Also, silk scaffolds were tubularized to provide a “tunnel” through which the ureters were passed.

FIG. 3.

Artificial bladder version 3. Volume 170 mL. Silk graft applied around both the ureteral and urethral ports. Reservoir anchored to the anterior abdominal wall through anchoring loops.

FIG. 4.

Artificial bladder version 4. Volume 52 mL.

FIG. 5.

Preimplantation (cystectomy completed).

FIG. 6.

Postimplant for bladder version 2, trial 3.

FIG. 7.

On the left, the 5 mm stapler is demonstrated. On the right, the common sheath of the stapled Wallace ureteroureteral anastomosis is shown.

FIG. 8.

(Left) Ureteral stents were passed into the artificial bladder and up each ureter; note the preplaced sutures aid in securing the common sheath to the silk scaffold, which in turn encircles the ureteral port. (Right) Completed ureteral attachment to the prosthesis.

FIG. 9.

Artificial bladder version 4 as it was implanted in pigs 5 and 6. Arrows point to the ureters with stents in place.

FIG. 10.

Autopsy findings for trial 3. Urethral and bilateral ureteral anastomoses are intact.

FIG. 11.

(Left image) Fluoroscopic images demonstrating appropriate position of both ureteral stents (arrows) and (right image) Cope loop urethral catheter (arrow).

FIG. 12.

Ureteroscopic views. Left—common Wallace sheath of the anastomosed ureters (arrow points to the staple line). Middle–right ureter. Right–left ureter.

FIG. 13.

Shown is an endoscopic view with a flexible ureteroscope, which is used to perform cystoscopy. Arrow points to the ureteral opening (stents have been removed). Encrustation that developed within the lumen of the prosthetic bladder is seen layering at the bottom of the screen.

FIG. 14.

Ultrasound comparison at 2, 5, and 6 weeks. Stable parenchymal thickness is shown.

FIG. 15.

(A) Endoscopic view from within prosthetic bladder looking at the ureteral port. (B, C) Luminal appearance of the ureteral anastomosis. (D) The common sheath of both ureters just proximal to the anastomosis.

FIG. 16.

Trial 6, prosthetic bladder version 4 with the explanted kidneys, ureters, and urethra en bloc.

FIG. 17.

Histopathology analysis in pig 6 at 12 weeks. (A) Photomicrograph showing representative section of the ureteral anastomosis with remnant of silk mesh (green arrow) in the mucosal surface. (B) Photomicrograph shows representative section of the urethral anastomosis with silk mesh material (green arrow) deep within the fibromuscular wall with no significant inflammatory response. (C) Section of ureteral anastomosis showing normal urothelial mucosa (blue arrow) with mild chronic inflammation (black arrow).