In Vivo Biocompatibility Testing of a Collagen Cell Carrier Seeded withHuman Urothelial Cells in Rats

Tissue-engineered, matrix-stabilized autologous urothelium is a new option for urethral reconstruction, particularly for patients for whom other autologous grafts are not available. In vitro engineering of urothelial tissue requires biomaterials as cell carriers that increase the stability of cell-based implants. The aim of this study was to investigate a new highly standardized, industrially manufactured bovine collagen type I-based cell carrier (CCC) for its suitability as a carrier matrix for human urothelial cells (HUC). As an in vivo biocompatibility test the behaviour and degradation of these implants was to be proven in a nude rat model. Expanded HUC from tissue biopsies were phenotypically analysed by immuno¬cyto¬chemistry and seeded onto CCC. For in vivo application, CCC was seeded with PKH26-labelled HUC in high density and constructs were implanted onto the rectus abdominis muscle of nude rats. Integration, cell survival, and degradation of the urothelium-matrix-implants were studied after 1, 2, and 4 weeks. Immunohistological characterization of multilayered urothelium-matrix-constructs was performed for AE1/AE3 and p63 (epithelial phenotype), CK20 (differentiation), and E-Cadherin and ZO-1 (junction formation). Immunocytochemical staining showed urothelial character of the isolated cells and the absence of fibroblasts and muscle cells. In twelve nude rats, urothelium-matrix-implants integrated well into the host tissue where no inflammation was observed. Immuno¬fluorescence analysis confirmed epithelial phenotype, adherence and tight junction formation homogeneous multilayer formation of stratified HUC cultures as well as urothelial phenotype and differentiation in vitro the CCC-matrix additionally revealed promising biocompatibility investigated in a nude rat model. Thus, this study demonstrates excellent suitability of CCC as a matrix for urothelial cells and recommends its use in a large animal model with regard to clinical application.