Surgical Model for Single-Staged Tissue-Engineered Urothelial Tubes in Minipigs
July 5th, 2024
Tissue-engineered implants for reconstructive surgery rarely progress beyond preclinical trials due to laborious ex vivo culturing, which includes complex and expensive scaffold components. Here, we present a single-staged procedure designed for urinary diversion with an accessible collagen-based tubular scaffold containing autologous micrografts.
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.
Overview
This study presents a novel single-staged procedure for urinary diversion using a collagen-based tubular scaffold embedded with autologous micrografts. The method aims to simplify the tissue-engineering process, which often faces challenges in preclinical trials due to complex scaffold requirements.
Key Study Components
Area of Science
- Tissue engineering
- Reconstructive surgery
- Urology
Background
- Tissue-engineered implants often fail to progress beyond preclinical trials.
- Current methods involve complex and costly scaffold components.
- There is a need for more accessible and efficient surgical procedures.
- Collagen-based scaffolds can provide a biocompatible solution for urinary diversion.
Purpose of Study
- To develop a simplified surgical procedure for urinary diversion.
- To utilize a collagen-based scaffold that incorporates autologous micrografts.
- To evaluate the feasibility and effectiveness of the new method.
Methods Used
- Preparation of a collagen-based scaffold with minced mucosal micrografts.
- Standard surgical techniques for bladder segment excision and scaffold implantation.
- Post-operative evaluation through endoscopy and CT imaging.
- Histological analysis of the scaffold tissue after six weeks.
Main Results
- The tubular scaffold remained patent and unobstructed after six weeks.
- No signs of host rejection or infection were observed.
- Histological evaluations showed a stratified luminal epithelium of urothelial origin.
- Remnants of the reinforcing biomaterials were still visible after six weeks.
Conclusions
- The single-staged procedure is a viable alternative for urinary diversion.
- Collagen-based scaffolds with autologous micrografts can enhance surgical outcomes.
- This method may facilitate the transition of tissue-engineered implants into clinical practice.
Frequently Asked Questions
Executive Industry Relevance
Biopharma R&D faces persistent challenges in developing reliable, scalable tissue-engineered solutions for reconstructive urology, where graft availability and host compatibility are critical. This single-staged collagen-based scaffold model in minipigs provides a reproducible platform for evaluating autologous tissue integration and short-term in vivo performance. The approach supports predictive confidence in scaffold-host interactions and informs translational risk for future clinical applications.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables mechanistic interrogation of scaffold integration and tissue regeneration in a controlled large-animal model.
- Supports biological de-risking by using autologous tissue to minimize immunogenicity and rejection risk.
- Facilitates functional target validation for urothelial tissue engineering strategies.
Screening & Assay Development
- Provides a standardized workflow for preparing and implanting tissue-engineered constructs with quantitative post-implantation readouts.
- Enables reproducible assessment of scaffold patency, epithelialization, and host response using imaging and histology.
- Supports downstream screening of biomaterial modifications or cell sources in a validated preclinical context.
Translational & Preclinical Research
- Aligns with disease-relevant reconstructive needs by modeling urinary diversion in a physiologically relevant system.
- Enables continuity from scaffold design through in vivo validation, supporting risk-adjusted advancement decisions.
- Provides translational insight into scaffold durability, host integration, and infection risk over a defined observation period.
Pipeline & Workflow Integration
This model bridges early discovery and preclinical validation by enabling hypothesis-driven testing of tissue-engineered scaffolds in a large-animal system.
- Discovery Biology: Supports hypothesis testing on scaffold-host integration and tissue regeneration mechanisms.
- Screening: Delivers quantitative outputs such as conduit patency and epithelial coverage for comparative analysis.
- Analytics: Utilizes endoscopy, CT imaging, and histology to generate reproducible, decision-enabling data.
- Translational Research: Provides a platform for evaluating clinical feasibility and biomaterial performance in a relevant anatomical context.
- Enterprise Reuse: Establishes a reusable workflow for iterative scaffold optimization and cross-program benchmarking.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in tissue-engineered construct performance and host compatibility.
- Operational Value: Standardizes scaffold preparation and implantation for reproducible, scalable studies.
- Strategic Value: Informs go/no-go decisions for advancing scaffold technologies toward clinical translation.
- Portfolio Impact: Enables risk-adjusted prioritization of tissue engineering programs based on in vivo performance data.
Implementation Considerations
- Requires surgical expertise in large-animal models and tissue handling.
- Demands access to imaging modalities and histological analysis infrastructure.
- Necessitates cross-team standardization of scaffold fabrication and implantation protocols.
- Adaptation to other anatomical sites or species may require protocol modifications.
- Short-term observation limits assessment of long-term scaffold durability and function.
