Cellules souches embryonnaires : une nouvelle source pour les cellules rénales ?

In the absence of leukemia inhibitory factor (LIF) mouse embryonic stem (ES) cells give rise to embryoid bodies (EBs) that can differentiate into all 3 lineages including mesoderm from which kidney is derived. The generation of ES cell-derived progenitors offers potential for regenerative therapies. Since brachyury denotes mesoderm specification, we used a mouse ES cell-line with GFP knocked into the functional brachyury locus as well as lac-Z in the ROSA26 for use in cell selection and lineage tracing. Culture conditions were optimized (4 days, 10ng/ml Activin-A) to generate maximal numbers of renal progenitor populations identified by expression of the specific combination for renal progenitors : Brachyury, Cadherin-11, WT-1, Pax-2, Wnt-4, CD133, CD24 and Oct-4. LacZ/Brachy/GFP+ cells and LacZ/Brachy/GFP- cells were further selected by FACS. 5 days after injection into embryonic kidney explants in organ culture, LacZ/Brachy/GFP+ cells localized into blastemal cells of the nephrogenic zone while LacZ/T/GFP- cells incorporated in the ureteric bud. After a single injection into developing live newborn mouse kidneys, co-localization studies showed that the LacZ/Brachy/GFP+ cells were stably integrated into proximal tubules for 7 months without teratoma formation. LacZ/Brachy/GFP- cells got incorporated in different kind of tubules, preferentially in the collecting duct, but 12. 5% of the mice developed teratomas. It is concluded that defined differentiation of ES cells into EBs with Activin-A and selection for Brachyury expression provides a means to isolate and purify renal proximal tubular progenitor cells with the potential for safe use in regenerative therapies