High Incidence of Vesicoureteral Reflux in Mice With Fgfr2 Deletion in Kidney Mesenchyma

Abstract

Purpose Mice with conditional deletion of fibroblast growth factor receptor 2 (Fgfr2) in metanephric mesenchyme (Fgfr2Mes−/−) have ureteric bud induction abnormalities. Our goal was to determine if Fgfr2Mes−/− mutants developed abnormally positioned ureters predisposing to vesico-ureteral reflux (VUR). Materials and Methods We measured common nephric duct (CND) lengths and assayed for apoptosis in embryonic day (E) 11.5 mice. We performed 3 dimensional (3D) reconstructions of and real time PCR and whole mount in situ hybridization for Fgfr2 in urinary tracts in E15.5 embryos. We performed cystograms followed by 3D reconstructions in postnatal animals. Results Compared with controls, Fgfr2Mes−/− embryos had increased CND lengths (with no differences in apoptosis) indicating cranially displaced ureteric buds. 3-D reconstructions at E15.5 showed low insertions of ureters into the bladder (near bladder necks) in Fgfr2Mes−/− mice. Postnatal Fgfr2Mes−/− mutants had high rates of VUR compared with controls (47.4% vs. 4.0%, p=0.00006). In postnatal mutants with unilateral reflux, the refluxing ureters inserted closer to the bladder neck than non-refluxing ureters. The external ureteral insertional angles at the outer bladder wall (formed by the ureteral insertion points and bladder neck) were greater in mutant refluxing ureters compared to contralateral non-refluxing ureters and to control ureters. At E15.5, Fgfr2 levels were decreased in Fgfr2Mes−/− kidneys compared with controls, but were not statistically different in ureters or bladders. Conclusions Fgfr2Mes−/− mice have ureteric induction abnormalities, associated with abnormal ureteral insertion in the bladder and subsequent VUR, consistent with the Mackie and Stephens hypothesis.

Ureteric Morphogenesis Requires Fgfr1 and Fgfr2/Frs2α Signaling in the Metanephric Mesenchyme

“…19,52 Briefly, image layers were generated from serial hematoxylin and eosin-stained sections by tracing around capsules, developing nephrons by stage (vesicles, comma-shaped bodies, S-shaped bodies, and immature glomeruli), ureteric tissues, ureters, ductus deferens, and urogenital sinuses (Stereoinvestigator, Microbrightfield, VT). The traced layers were then aligned into a stack, rendering a 3D image that could be manipulated to show any of the traced structures (either separately or simultaneously).…”

“…These defects often result in abnormalities of the kidney and urinary tract (hypoplasia, dysplasia, obstructed ureters) and high rates of vesicoureteral reflux. 12,19 Conditional deletion of Fgfr1 and Fgfr2 in the MM (Fgfr1/2…”

Nephric duct insertion is a crucial step in urinary tract maturation that is regulated by aGata3-Raldh2-Retmolecular network in mice

“…According to this model, ureteric buds emerging posterior to the normal sprouting site would insert in the primitive bladder too early, which can lead to ectopically positioned distal ureters and vesico-ureteral reflux. Conversely, ureters emerging at an abnormally anterior site will fail to join the bladder or will join at a later stage than normal, a defect that can result in defective ureter maturation and obstruction (Hains et al, 2010;Kume et al, 2000;Miyazaki et al, 2000;Pope et al, 1999). Recent evidence supports this model and further shows that ureter maturation depends on apoptotic elimination of the common nephric duct (CND), the most caudal segment of the ND (Batourina et al, 2005;).…”

Fgfr2 is integral for bladder mesenchyme patterning and function

“…While Fgf10 affects bladder urothelial cell patterning, no published data exist on Fgfr actions in the developing bladder mesenchyme (9). Although Fgfr2 is expressed in the bladder urothelium and mesenchyme (12), its roles are unclear, as global Fgfr2 deletion results in early embryonic lethality (2).…”