Isolated cells from urine are mostly exfoliated renal epithelial cells, which are excreted in a normal process of detaching into urine daily. Therefore, 50 to 200 mL urine has to be collected in the middle stream of the micturition. After consecutive washing and centrifugation steps, the isolated epithelial cells can be taken in culture [62]. More precisely, these cells are squamous cells from the urethra with a defined epithelial phenotype. Urine cell derived iPSCs show similar expression and pluripotency patterns compared to embryonic stem cells or iPSCs from other sources [63]. The collection of urine is noninvasive with no need of medical personnel. This brings very few indispositions for the patient. Urine samples are easily accessible because they are often routinely collected for clinical diagnosis and independent of age or sex. The reprogramming efficiency lies in the range of 0.1 to 4%, which is much higher than that of fibroblasts or blood cells [16]. Urine cells can be frozen and thawed for several times without decreasing the reprogramming efficiency. Nevertheless, they show a reduced reprogramming efficiency after five passages [62].
