Study on genetic stability in human urothelial cells in vitro

A database on differentially expressed microRNAs during rodent bladder healing

Urinary bladder wound healing relies on multiple biological events that are finely tuned in a spatial-temporal manner. MicroRNAs are small non-coding RNA molecules with regulatory functions. We hypothesized that microRNAs are important molecules in the coordination of normal urinary bladder wound healing. We aimed at identifying microRNAs expressed during bladder wound healing using Affymetrix global array for microRNA profiling of the rodent urinary bladder during healing of a surgically created wound. Results were validated in the rat bladders by real-time PCR (RT-PCR) using three of the differentially expressed (DE) microRNAs. The model was thereafter validated in human cells, by measuring the expression of eight of the DE microRNAs upon in vitro wound-healing assays in primary urothelial cells. Our results indicated that 508 (40%) of all rodent microRNAs were expressed in the urinary bladder during wound healing. Thirteen of these microRNAs (1%) were DE (false discovery rate (FDR) < 0.05, P < 0.05, |logfold|> 0.25) in wounded compared to non-wounded bladders. Bioinformatic analyses helped us to identify target molecules for the DE microRNAs, and biological pathways involved in tissue repair. All data are made available in an open-access database for other researchers to explore.

Urothelial cell senescence is not linked with telomere shortening

The success of regenerative medicine relies in part on the quality of the cells implanted. Cell cultures from cells isolated from bladder washes have been successfully established, but molecular changes and cell characteristics have not been explored in detail. In this work, we analysed the role of telomere shortening in relation to the regenerative potential and senescence of cells isolated from bladder washes and expanded in culture. We also analysed whether bladder washes would be a potential source for attaining stem cells or promoting stem cell proliferation by using two different substrates to support their growth: a feeder layer of growth-arrested murine fibroblasts J2 3T3 cells and a xeno-free human recombinant laminin-coated surface. We found no association between telomere shortening and senescence in urothelial cells in vitro. Urothelial cells had a stable telomere length and expressed mesenchymal stem cells markers but failed to differentiate into bone or adipocytes. Feeder layer showed an advantage to laminin-coated surfaces in respect to proliferative capacity with the expense of risking that feeder layer cells could persist in later passages. This emphasizes the importance of using carefully controlled culture conditions and molecular quality controls before autotransplantation in future clinical settings. In conclusion, urothelial cells isolated by bladder washes show regenerative potential that need further understanding. Senescence in vitro might be due to cellular stress, and if so, further improvements in culture conditions may lead to longer cell life and higher proliferative capacity.