Before seeding, SIS^® was either washed with incubation medium or coated with collagen A, fibronectin, or pronectin. A possible influence of SIS^® itself on the viability of urothelial cells was analysed with conditioned cell culture medium obtained by incubation of SIS^® for 24hours. In addition, untreated SIS^® and a setting without SIS^® were used as controls. Viability of urothelial cells was analysed with the WST-1 assay until day 9. Histology of seeded and unseeded SIS^® specimens was investigated after Papanicolaou staining. To demonstrate urothelial cell adherence on SIS^®, immunohistology was performed with a mixture of monoclonal AE1 and AE3 anticytokeratin antibodies.

Urothelial cells seeded on SIS^® revealed no measurable cell viability. SIS^®-conditioned cell culture medium was cytotoxic for urothelial cells after 24hours. Histology only demonstrated cell nuclei and no cytoplasm both in seeded and unseeded SIS^® specimens, thus indicating porcine DNA. Expression of the cell type-specific marker proteins AE1/AE3 could not be demonstrated.

Since the commercially available SIS^® specimens used contained porcine DNA residues and demonstrated cytotoxic effects on urothelial cells, SIS^® is not suitable for in vitro construction of urothelial cell-matrix implants.

Gerhard Feil^a, Margot Christ-Adler^a, Sabine Maurer^a, Stefan Corvin^a, Hans-Oliver Rennekampff^b, Jutta Krug^a, Jörg Hennenlotter^a, Ursula Kuehs^a, Arnulf Stenzl^a, Karl-Dietrich Sievert<sup>a

a</sup> Department of Urology, University of Tübingen, Tübingen, Germany
^b Department of Plastic, Hand, Reconstructive and Burn Surgery, BG-Unfallklinik, Tübingen, Germany

Accepted 15 May 2006 published online 22 June 2006.