Figure 6.

BMP7 and FGF2 promote expansion of the stromal progenitor cell population. Whole kidneys were isolated at 11.5 dpc and grown for 48 hr in culture containing 10% FBS in the absence (A,C,E,G,I) or in the presence of both BMP7 and FGF2 (B,D,F,H,J). After culture, explants were processed for whole-mount in situ hybridization or stained in X-gal. (A) Pax2 is expressed in the ureter and in the condensed mesenchyme. (B) A similar expression pattern is observed in the treated kidneys. WT1 is expressed in the condensed mesenchyme associated with the tips of the branching ureter in both control (C) and treated kidneys (D). X-gal staining for the Bmp7^lacZ allele also shows a similar expression pattern in both the control (E) and treated (F) explants. In all cases the expanded rind of cells in the periphery of the kidney do not express any of these markers of induced mesenchyme (arrow). The stromal precursor marker BF2 (G), however, is expressed in this expanded population of cells (H). Sections through G and H reveal that BF2 is expressed throughout the expanded region of mesenchyme cells (arrow, I,J). The apparent BF2 signal in the nephrogenic mesenchyme is attributable to the layer of stromal progenitor cells that encompasses the entire explant (G,H).