Urothelial cells in vitro
Monolayer cultures
Isolated normal human urothelial (NHU) cells can be maintained in low calcium (0.09mM), serum-free culture as finite lifespan cell lines. These cell lines can be kept in a highly proliferative state through multiple serial passages. The cultures can be induced to stratify by increasing the exogenous calcium concentration of the medium to near physiological (2mM), but do not spontaneously express markers associated with terminal urothelial cytodifferentiation. Although our emphasis is on human urothelium, by adapting our methods, we are also able to grow normal urothelial cells from porcine and bovine bladders, which we can obtain from abattoir sources.
Gene Manipulation
The phenotype of the NHU cells can be modified by genetic manipulation to overexpress normal or cancer oncogenes. We can also abrogate normal gene function by transducing dominant negative gene variants or using siRNA to knockdown or silence target gene expression. We use amphotropic retroviral transduction as the most efficient method of introducing genetic material into NHU cells to produce stable sublines. We have also used lentivirus to produce uroplakin 2 reporter urothelial cell lines that fluoresce green when induced to differentiate.
Immortalisation
Although NHU cells can be immortalised by introduction of immortalising viral genes (eg HPV16 E6) or overexpression of hTERT, we have found that these cell lines lose the capacity to differentiate and are therefore of only limited use as surrogates of the finite NHU cell lines.
Cancer-derived established cell lines
We also carry a number of well-characterised established human bladder carcinoma-derived cell lines that originate from different grades and stages of cancer. These cell lines are useful as they retain features that reflect the grades and stages of the cancers from which they were derived.
Organ cultures
Intact normal human urothelial tissues maintained at an air-liquid interface in organ culture show an initial period of repair and regeneration, after which the urothelium exhibits a differentiated phenotype that may be maintained in culture for at least 18 weeks. This provides a model for investigating epithelium:stroma interactions during tissue regeneration and homeostasis.
We are also able to develop 3D urothelial tissues by combining NHU or bladder cancer cell lines with de-epithelialised stromal tissues to form reconstituted organoids. These are maintained as organ cultures and give insight into normal and malignant processes, including cancer invasion.
Glossary
finite lifespan - limited lifespan and after a certain number of cell divisions the cells will senesce (stop dividing)