AEROSOL TRANSFER OF BLADDER UROTHELIAL AND SMOOTH MUSCLE CELLS ONTO DEMUCOSALIZED COLONIC SEGMENTS FOR PORCINE BLADDER AUGMENTATION IN VIVO: A 6-WEEK EXPERIMENTAL STUDY

PURPOSE: In a pilot study we developed a cell transfer technology for populating demucosalized colonic segments with bladder urothelium. This process was achieved through aerosol transfer of a single cell suspension consisting of bladder urothelial cells, smooth muscle cells and fibrin glue onto demucosalized colonic segments. We further evaluate this new concept in a controlled study. MATERIALS AND METHODS: The study was performed on 20 piglets (20 kg). In all animals 50% of the bladder with excised, and a 10 cm segment of the sigmoid was isolated. Animals were then equally divided into 5 groups of 1) colocystoplasty only, 2) demucosalized colocystoplasty, 3) demucosalized colocystoplasty plus covering of the demucosalized sigmoid with fibrin glue only, 4) aerosol application of fibrin glue with single cell suspension of urothelial cells only to the demucosalized colon, and 5) aerosol application of fibrin glue with urothelial and smooth muscle cells to the demucosalized colon. The 4 corners of the augmented segments were marked with 5-zero polypropylene sutures. Animals were sacrificed 6 weeks later and the surface area of the augmented segment was measured. Segments were submitted to histological and immunohistochemical analysis. RESULTS: The surface area of the augmented segments showed an increase in group 1 animals, stabilization in groups 4 and 5, and marked reduction in groups 2 and 3. On hematoxylin and eosin, and Masson trichrome staining all group 1 animals showed normal colonic epithelium of the augment. All animals in groups 2 and 3 showed excessive scarring with urothelial coverage only at the augment periphery, while the central augment area showed no epithelium. Segments from groups 4 and 5 showed confluent epithelial covering with no fibrosis. There was no evidence of colonic epithelial re-growth in any animal in groups 2 to 5. Cytokeratin 7 and uroplakin III staining demonstrated complete coverage of the augmented segment with urothelium only in groups 4 and 5. CONCLUSIONS: The addition of aerosolized cells of urological origin is a viable augmentation approach that appears to achieve the much sought after inhibition of intrinsic fibrosis and contraction of colonic segments when incorporated into the urinary tract without this cellular component. Moreover, this technique appears to provide a histologically normal, confluent urothelium, which sets the stage for prevention of the well-documented biochemical aberrations inherent in augments containing gastrointestinal epithelium. While successful in this model regardless of the incorporation of urological smooth muscle cells, chronic studies are now warranted to validate the short-term results as well as determine whether the urological mesenchymal population (smooth muscle) will be required to sustain the uroepithelial phenotype in the long term.

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