[In search of renal stem cells]

The therapeutic potential of stem cell research is very promising. Although arising ethical questions, especially in the field of embryonic stem cells (ES), it is astonishing how, in the last few years, the potential application of stem cells for treating proliferative as well as degenerative diseases, is becoming increasingly evident. It was recently demonstrated that somatic stem cells showed unexpected plasticity similar to ES. In fact, if somatic stem cells are exposed to proper stimuli they can differentiate into a multitude of cell types that may be different from those of the tissue they belong to. In addition, it was recently demonstrated that circulating blood stem cells, probably of bone marrow origin, were recruited at the sites of injury to regenerate or repair damaged tissues. Very little is known about renal stem cells. Although the great capacity of the kidney to regenerate injured nephrons is well established, renal somatic stem cells have yet to be identified. The question we are now faced with is whether renal stem cells exist and, if they do exist, where do they reside. In the attempt to answer this question, the present review will focus on the achievements both in the fields of somatic stem cells and renal embryogenesis and in the field of renal repair and regeneration mechanisms.