RESUMEN
Normal kidney function depends on the proper development of the nephron: the functional unit of the kidney. Reciprocal signaling interactions between the stroma and nephron progenitor compartment have been proposed to control nephron development. Here, we show that removal of hedgehog intracellular effector smoothened (Smo-deficient mutants) in the cortical stroma results in an abnormal renal capsule, and an expanded nephron progenitor domain with an accompanying decrease in nephron number via a block in epithelialization. We show that stromal-hedgehog-Smo signaling acts through a GLI3 repressor. Whole-kidney RNA sequencing and analysis of FACS-isolated stromal cells identified impaired TGFß2 signaling in Smo-deficient mutants. We show that neutralization and knockdown of TGFß2 in explants inhibited nephrogenesis. In addition, we demonstrate that concurrent deletion of Tgfbr2 in stromal and nephrogenic cells in vivo results in decreased nephron formation and an expanded nephrogenic precursor domain similar to that observed in Smo-deficient mutant mice. Together, our data suggest a mechanism whereby a stromal hedgehog-TGFß2 signaling axis acts to control nephrogenesis.
Asunto(s)
Factores de Transcripción Forkhead/metabolismo , Proteínas Hedgehog/metabolismo , Nefronas/embriología , Transducción de Señal/fisiología , Receptor Smoothened/metabolismo , Factor de Crecimiento Transformador beta2/metabolismo , Animales , Factores de Transcripción Forkhead/genética , Proteínas Hedgehog/genética , Ratones , Ratones Noqueados , Nefronas/citología , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Receptor Smoothened/genética , Células del Estroma/citología , Células del Estroma/metabolismo , Factor de Crecimiento Transformador beta2/genética , Proteína Gli3 con Dedos de Zinc/genética , Proteína Gli3 con Dedos de Zinc/metabolismoRESUMEN
Intrinsic ureteropelvic junction obstruction is the most common cause of congenital hydronephrosis, yet the underlying pathogenesis is undefined. Hedgehog proteins control morphogenesis by promoting GLI-dependent transcriptional activation and inhibiting the formation of the GLI3 transcriptional repressor. Hedgehog regulates differentiation and proliferation of ureteric smooth muscle progenitor cells during murine kidney-ureter development. Histopathologic findings of smooth muscle cell hypertrophy and stroma-like cells, consistently observed in obstructing tissue at the time of surgical correction, suggest that Hedgehog signaling is abnormally regulated during the genesis of congenital intrinsic ureteropelvic junction obstruction. Here, we demonstrate that constitutively active Hedgehog signaling in murine intermediate mesoderm-derived renal progenitors results in hydronephrosis and failure to develop a patent pelvic-ureteric junction. Tissue obstructing the ureteropelvic junction was marked as early as E13.5 by an ectopic population of cells expressing Ptch2, a Hedgehog signaling target. Constitutive expression of GLI3 repressor in Ptch1-deficient mice rescued ectopic Ptch2 expression and obstructive hydronephrosis. Whole transcriptome analysis of isolated Ptch2+ cells revealed coexpression of genes characteristic of stromal progenitor cells. Genetic lineage tracing indicated that stromal cells blocking the ureteropelvic junction were derived from intermediate mesoderm-derived renal progenitors and were distinct from the smooth muscle or epithelial lineages. Analysis of obstructive ureteric tissue resected from children with congenital intrinsic ureteropelvic junction obstruction revealed a molecular signature similar to that observed in Ptch1-deficient mice. Together, these results demonstrate a Hedgehog-dependent mechanism underlying mammalian intrinsic ureteropelvic junction obstruction.
Asunto(s)
Proteínas Hedgehog/genética , Hidronefrosis/genética , Proteínas del Tejido Nervioso/genética , Receptor Patched-1/genética , Receptor Patched-2/genética , Transducción de Señal , Obstrucción Ureteral/genética , Proteína Gli3 con Dedos de Zinc/genética , Aldehído Oxidorreductasas/genética , Animales , Linaje de la Célula , Niño , Femenino , Factores de Transcripción Forkhead/genética , Expresión Génica , Proteínas Hedgehog/metabolismo , Humanos , Hidronefrosis/congénito , Hidronefrosis/patología , Hibridación in Situ , Pelvis Renal/embriología , Pelvis Renal/metabolismo , Masculino , Mesodermo/embriología , Mesodermo/metabolismo , Ratones , Ratones Noqueados , Proteínas del Tejido Nervioso/metabolismo , Células Madre/metabolismo , Factores de Transcripción/genética , Transcripción Genética , Transcriptoma , Regulación hacia Arriba , Uréter/embriología , Uréter/metabolismo , Obstrucción Ureteral/congénito , Obstrucción Ureteral/patología , Proteína Gli3 con Dedos de Zinc/metabolismoRESUMEN
The renal stroma is defined as a heterogeneous population of cells that serve both as a supportive framework and as a source of specialized cells in the renal capsule, glomerulus, vasculature, and interstitium. In this chapter, we review published evidence defining what, where, and why stromal cells are important. We describe the functions of the renal stroma andhow stromal derivatives are crucial for normal kidney function. Next, we review the specification of stromal cells from the Osr1+ intermediate mesoderm and T+ presomitic mesoderm during embryogenesis and stromal cell differentiation. We focus on stromal signaling mechanisms that act in both a cell and non-cell autonomous manner in communication with the nephron progenitor and ureteric lineages. To conclude, stromal cells and the contribution of stromal cells to renal fibrosis and chronic kidney disease are described.
