Surgical Model for Single-Staged Tissue-Engineered Urothelial Tubes in Minipigs

To begin, fast a full-grown Gottingen mini pig 12 hours before the surgery. After performing a standard lower midline laparotomy on an anesthetized pig, pull the interperitoneal urinary bladder to the wound. Now, perform prophylactic hemostasis on the anterior bladder wall, and incise the detrusor muscle with diathermia.

Then, cut the inner mucosal layer with scissors to excise a full wall bladder segment. Close the bladder wall with a fast resorbable braided running suture while leaving a proximal opening of one square centimeter. Carefully dissect the mucosal layer of the resected specimen under sterile conditions, and mince the mucosal specimen into one square millimeter micro grafts for scaffold embedding.

Using forceps, place the mucosal particles onto a fitted biodegradable mesh with a one to six expansion ratio. Place the mesh with the micro grafts facing upwards inside a rectangular steel mold filled with collagen solution. After solidification, slide the hydrogel onto a nylon mesh resting on a perforated steel plate, and gently remove the mold.

Expel water from the hydrogel by placing a nylon mesh, and then a steel plate on top of the gel, and then passively compress with a 120-gram weight placed on top of the steel plate for five minutes. After compression, gently remove the weight and the nylon mesh. Now, the graft is ready for surgical handling.

Roll the flattened scaffold around a biodegradable stent with the micro grafts facing the stent, and suture the scaffold in place longitudinally with a slow resorbable monofilament running suture. Fixate an antegrade colonic enema stopper inside the lumen of the stent by suturing the stent to the cap with two or three interrupted non-resorbable sutures. After completing the scaffold, anastomose the tubular construct to the remaining opening on the anterior bladder wall with a slow resorbable monofilament running suture.

Tighten the anastomosis with a purse string suture, and ligate the distal end of the conduit. Harvest a peritoneal flap from the pubovesical ligament, and patch the tubular scaffold longitudinally with a running, slow resorbable monofilament suture. Inject saline via the urethral catheter to confirm the anastomotic patency.

Bluntly dissect a trans fascial channel laterally to the midline next to the caudal mammary gland on the right side. Place the conduit in a subcutaneous pocket and mark the conduit with non-resorbable skin level sutures. After closing the anterior muscle fascia of the abdominal muscle, close the skin with a non-resorbable monofilament running suture.

At the end of six weeks of observation, inspect the conduit lumen by endoscopy for continuity and epithelial lining. Perform contrast enhanced computed tomography to ensure conduit patency. After six weeks of observation, microscopical scaffold tissue evaluation revealed no signs of host rejection or infection, and the tubular scaffold remained patent and unobstructed.

Histological evaluations showed a stratified luminal epithelium of urothelial origin covering the entire scaffold with remnants of the reinforcing biomaterials still visible after six weeks.