Nephron generation in kidney cortices through injection of pretreated mesenchymal stem cell-differentiated tubular epithelial cells.

Transplantation of artificially treated metanephroi or pluripotent stem cell-injected blastocyst-derived whole kidneys will be established in the near future as a useful therapeutic method for renal failure. We have attempted in vivo nephron generation for kidney repair by exploiting cellular interactions via conditioned media (CMs). In a previous report, we showed stimulative cross-talks between vascular endothelial cells (VECs) and tubular epithelial cells (TECs) on cell proliferation and morphological changes, the differentiation of mesenchymal stem cells (MSCs) into TECs by TEC-CM, and nephron generation from TECs or MSCs in rat subcutaneous spaces. In this study adding collecting duct cells (CDCs) and their CM, we demonstrate the suppressive actions of CDC-CM against VECs and TECs, in addition to stimulative cross-talks between VECs and TECs, during the above changes. Furthermore, CDC-CM, similar to TEC-CM, caused differentiation of MSCs into TECs. Thus, we injected CDC-CM-induced MSC-differentiated TECs into rat kidney cortices. The pretreatment of cells in 3-dimensional culture using a small amount of gel complex before implantation triggered the generation of much more nephron-like structures, compared to the implantation of non-pretreated cells. Our method of injecting pretreated TECs into kidney cortices might have applications for repairing dysfunctional kidney tissue.