Cell therapy for kidney injury: different options and mechanisms--kidney progenitor cells.

Background: Since no specific or radical treatments have yet been established for acute kidney injury (AKI), the development of cell transplantation therapy using renal progenitors is desirable as a new therapeutic option for AKI. The recent advances in developmental biology, stem cell biology, and nephrology have led to an increased availability of renal progenitors from multiple sources.

Summary: Four main sources of renal progenitors have been described so far: isolation from (1) embryonic or (2) adult kidneys, (3) directed differentiation of pluripotent stem cells such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), and (4) cellular reprogramming of fully differentiated adult renal cells. Renal progenitors from adult kidneys may not be equivalent to those from embryonic kidneys, and they contain several different cell populations identified by various methods. The methods used for the directed differentiation of ESCs/iPSCs and reprogramming of differentiated adult renal cells into renal progenitors have not been fully established. The therapeutic effects of progenitor cell transplantation in AKI animal models have been examined in a small number of reports using renal progenitors from adult kidneys, while no reports have described the therapeutic potential of renal progenitors from other sources.

Key messages: Renal progenitor transplantation might provide a novel therapeutic strategy for AKI. Further research efforts toward the clinical application of this strategy are needed, including a detailed characterization of embryonic or adult renal progenitors and the development of in vitro expansion methods and therapeutically effective transplantation methods for these cell types. More experience and knowledge should be accumulated regarding the directed differentiation of pluripotent stem cells and cellular reprogramming to generate renal progenitor cells.