Objective To investigate the deposition of urinary crystals and the growth
characteristics of urothelial cells on a collagen sponge, as a preliminary
step in engineering urothelial autologous grafts.
Materials and methods Collagen sponges were exposed to a continuous flow of
urine at pH 5.3 and 6.3 for 1 week, The sponges were examined microscopica
lly for crystal deposition and analysed for their calcium content. Two cell
lines, RT112, derived from a well-differentiated transitional cell carcino
ma, and UROtsa, an immortalized urothelial cell line, were seeded on the co
llagen sponges. Cells were cultured for 6, 12 and 21 days. The pattern of g
rowth was analysed by histology and immunostaining with a pan-cytokeratin a
ntibody. Growth was assayed to quantify cell proliferation on the sponges,
Results No crystals were evident on any of the collagen sponges. Calcium de
position was negligible at pH 5,3. Although calcium levels were measurable
at pH 6,3, the levels were very low, Both cell lines attached and grew in a
stratified manner on the collagen sponge, RT112 forming a layer 6-8 cells
thick, and UROtsa a layer 4-6 cells thick; cell proliferation was maximal a
t 5-10 days. The sponge remained easy to handle after 3 weeks in culture,
Conclusion These findings show that collagen sponges support the growth and
stratification of urothelial cells, and indicate that the collagen sponge
is a suitable substrate for developing urothelial autologous grafts.