RECONSTRUCTIVE UROLOGY

Creation of luminal tissue covered with urothelium by implantation of cultured urothelial cells into the peritoneal cavity
Moriya K, Kakizaki H, Murakumo M, Watanabe S, Chen Q, Nonomura K, Koyanagi T
From the Departments of Urology (KM, HK, MM, QC, KN, TK) and Anatomy (SW), Hokkaido University Graduate School of Medicine, Sapporo, Japan
J Urol. 2003; 170: 2480-5

• Purpose: We established the culture condition of seeding urothelial cells onto a scaffold for implantation into the peritoneal cavity and evaluated the histology of implanted urothelial cells.
• Materials and Methods: In part 1 of the study cultured porcine bladder urothelial cells were seeded onto 3 types of collagen gel made on microporous membrane, including collagen gel with or without cultured porcine bladder fibroblasts, or a feeder layer. The macroscopic and microscopic appearance of the gel with urothelial cells were examined in vitro. As an in vivo study, cultured porcine bladder urothelial cells were seeded onto a collagen gel/sponge matrix with or without cultured fibroblasts, or a feeder layer. Urothelial cell survival on each matrix was evaluated 28 days after implantation onto the omentum or mesentery of nude rats. In part two of the study, rat urothelial cells were cultured and seeded onto fibrin gel/atelocollagen sponge matrix as an autologous implantation model. After 7 days of cultivation the matrix was folded with urothelial cells inside, implanted onto the mesentery, and serially evaluated.
• Results: Gel containing cultured fibroblasts was shrunken and basement membrane formation was observed on the gel with cultured fibroblasts or the feeder layer in vitro. Urothelial cells cultured with the feeder layer better survived on the collagen based matrix and formed a hollow-like lumen when implanted into the peritoneal cavity. The regenerated urothelium in an autologous implantation showed the same histological features as normal bladder urothelium.
• Conclusions: Selection of less degradable matrix and formation of basement membrane are critical for survival of implanted urothelial cells. The regenerated urothelium in an autologous implantation model seems to have the similar properties to the normal urothelium.
  
  
• Editorial Comment
  This paper is a direct continuation of studies initiated by Oberpenning et al (reference 2 in the paper) which demonstrated that urothelial and smooth muscle cell expanded in-vitro and seeded onto an acellular matrix could be used for bladder augmentation in a canine model. The authors report about the outcome of inclusion of a feeder layer for epithelial culture on autologue urothelial cell implantation. Thus, when implanted into the peritoneal cavity cystic tissues with an endoluminal surface covered with regenerated autologous urothelium could be created. Apart from that it is remarkable to note that stromal cells were found expressing alpha-smooth muscle actin and desmin despite the absence of smooth muscle cells seeded to the implanted matrix. Whether this phenomenon is due to homing of bone marrow cells or an unproven differentiation of stromal cells is not known but is worth studying in future projects.
  Despite good looking results with regards to tissue engineered segments of the lower urinary tract in animal models too many questions remain to be solved before we are ready to use tissue engineering in the lower urinary tract on a regular basis. One of the problems, i.e. possible malignancy has been discussed in the paper, because perturbation of the implanted transitional cells was noted which may have been the result of undesirable stromal-epithelial interaction.

Dr. Arnulf Stenzl
Professor and Chairman of Urology
Eberhard-Karls-University Tuebingen
Tuebingen, Germany