Development of a porcine animal model for urethral stricture repair using autologous urothelial cells

OBJECTIVE

To present a versatile large animal model for endoscopic stricture repair using autologous urothelial cells.

MATERIALS AND METHODS

12 male minipigs were used. An artificial stricture model was established using suture-ligation, thermo-coagulation and internal urethrotomy. A vesicostomy served for urinary diversion. Stricture formation was confirmed radiologically and histologically. Autologous urothelial cells were harvested from bladder washings, cultivated and labeled. Internal urethrotomy was done in all, and the cultivated cells were injected into the urethrotomy wound. All animals were sacrificed after 4 or 8 weeks. Immunohistology was done to confirm the presence of autologous urothelial cells within the reconstituted urethra.

RESULTS

Stricture formation was verified with all three methods. Histologically, no significant differences in the severity of stricture development could be observed with regard to the method used. The autologous urothelial cells in the area of the urethrotomy could be detected in the urothelium and the corpus spongiosum until 8 weeks after re-implantation.

CONCLUSIONS

We created a reliable and reproducible porcine model for artificial urethral strictures. Autologous urothelial cells can be implanted into an artificial stricture after urethrotomy. These cells retain their epithelial phenotype and are integrated in the resident urothelium. Further comparative studies are needed to ultimately determine a superior efficacy of this novel approach.

The genetics of osteoarthritis in STR/ort mice

OBJECTIVE

The complex genetics of osteoarthritis (OA) are still poorly defined. To circumvent the problems of genetic and environmental diversity hampering the analysis in humans, we investigated quantitative trait loci (QTL) associated with murine OA in the STR/ort strain which spontaneously develops osteoarthritic changes of the knee joints, overweight and elevated serum cartilage oligomeric matrix protein (COMP) levels.

METHODS

Two hundred and seventy six male F2 intercross (STR/ortxC57BL/6) animals were genotyped using 96 microsatellite markers and phenotyped by analyzing weight, serum COMP levels and osteoarthritic changes of the knee joints. Quantitative trait analyses were performed using the R/qtl software.

RESULTS

Elevated weight, serum COMP levels and osteoarthritic changes of the knee joints in the F2 generation compared to C57BL/6 parental animals confirm Mendelian inheritance. Quantitative trait analyses revealed three weight-, one serum COMP- and one OA-locus.

CONCLUSIONS

The weight-QTL coincide with previously described genes and QTL involved in fatty acid metabolism and offer a plausible explanation for the observed phenotype in STR/ort mice. The exact match of the COMP-QTL and the COMP gene itself suggests a regulatory polymorphism to account for elevated serum levels in STR/ort mice and questions the robustness of serum COMP as a prognostic marker in human knee OA. The newly identified QTL associated with degenerative changes of the knee joints support the concept of OA resulting from a defective chondrocyte metabolism and/or altered apoptosis rate. However, we also discuss the unlikelihood of one QTL being responsible for OA in STR/ort mice and the inherent limitations of microsatellite analyses for complex genetic diseases.

„Tissue engineering“ und Stammzellforschung in der Urologie für den rekonstruktiven bzw. regenerativen Therapieansatz

With the involvement of clinical reconstructive urology in the field of tissue engineering, outstanding results have been achieved in basic research as well as in some clinics. Stem cell research has even opened up possibilities for regenerative aspects. In close cooperation with various disciplines, the Department of Urology at the University of Tübingen investigates different clinical aspects with regard to reconstructive and regenerative urology. The regeneration of the external urethral sphincter requires functionally integrated muscle cells. In addition stricture reconstruction with multilayer urothelium should become less invasive and the re-stricture rate reduced. After the application of differentiating stem cells was proven, the clinical setting needed to be set for legal issues. In addition to the specification of culture media and verification in the animal model, the possibility to harvest omnipotent stem cells out of human testis and to differentiate those into the three germ layers was demonstrated. With the reduced invasiveness of harvesting the urothelium cells by a bladder wash using specific culture fluids, the cell culture was significantly improved enabling successful creation of urothelium by stratification. In addition urothelial cells in a matrix are further improved for endoscopic application. The close cooperation of different disciplines shortens the time to develop therapeutic approaches with a close clinical relationship in reconstructive and regenerative urology.

Stellenwert der Stammzelltherapie für die Behandlung der Belastungsinkontinenz

Parallel to a fundamental change in the therapeutic approach to managing stress incontinence, an increasing number of patients ask for reconstruction of the outer, striated urethral sphincter as therapy for urinary stress incontinence. Regenerative medicine is starting to offer solutions using stem cells as a part of oncological therapy or in reconstructive surgery. In addition to the many auspicious experimental approaches, one published study reports the effective therapeutic use of myogenic stem cells in urinary stress incontinent patients. Before this procedure is adopted into general clinical practice, further studies with validated evaluations and a sound legal basis are needed.

Bioartifizielle Materialien in der Urologie

The scope of our research is the development of polymer-based bioabsorbable stents for urologic applications and in vitro testing of tissue reactions of cultured ureteral and urethral segments induced by implanted polymer stent prototypes. For these purposes a tissue cultivation model was developed using selected techniques of tissue engineering. Essential advantages of degradable over nondegradable urethral stents are elimination of the adverse extraction of epithelialized stents and the potential for recovery of organ-specific functionality. Moreover, the biocompatibility of a degradable urethral stent could potentially reduce the risk of restenosis due to hyperplasia and could be used, even repeatedly, for the treatment of a number of subvesical obstructions. For the treatment of tumor-induced strictures, application of degradable polymer stents coated with cytostatic drugs may be possible. The mechanical effect of the drug-loaded stent as a "place holder" could be complemented by adjuvant or palliative approaches such as local chemotherapy. We have developed and tested in vitro a degradable urethral stent incorporated with the model drug methotrexate for local drug delivery (LDD) by diffusion and during stent degradation.