RESUMEN
Hedgehog (Hh) is an evolutionary conserved signaling pathway that has important functions in kidney morphogenesis and adult organ maintenance. Recent work has shown that Hh signaling is reactivated in the kidney after injury and is an important mediator of progressive fibrosis. Pericytes and fibroblasts have been proposed to be the principal cells that respond to Hh ligands, and pharmacological attenuation of Hh signaling has been considered as a possible treatment for fibrosis, but the effect of Hh inhibition on tubular epithelial cells after kidney injury has not been reported. Using genetically modified mice in which tubule-derived hedgehog signaling is increased and mice in which this pathway is conditionally suppressed in pericytes that express the proteoglycan neuron glial protein 2 (NG2), we found that suppression of Hh signaling is associated with decreased macrophage infiltration and tubular proliferation but also increased tubular apoptosis, an effect that correlated with the reduction of tubular ß-catenin activity. Collectively, our data suggest a complex function of hedgehog signaling after kidney injury in initiating both reparative and proproliferative, prosurvival processes.
Asunto(s)
Lesión Renal Aguda/etiología , Proteínas Hedgehog/metabolismo , Túbulos Renales/metabolismo , Transducción de Señal , Obstrucción Ureteral/complicaciones , Lesión Renal Aguda/genética , Lesión Renal Aguda/metabolismo , Lesión Renal Aguda/patología , Lesión Renal Aguda/prevención & control , Animales , Antígenos/metabolismo , Apoptosis , Proliferación Celular , Supervivencia Celular , Modelos Animales de Enfermedad , Proteínas Hedgehog/antagonistas & inhibidores , Proteínas Hedgehog/genética , Túbulos Renales/efectos de los fármacos , Túbulos Renales/patología , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Macrófagos/metabolismo , Macrófagos/patología , Masculino , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Pericitos/metabolismo , Pericitos/patología , Proteoglicanos/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Transducción de Señal/efectos de los fármacos , Receptor Smoothened , Alcaloides de Veratrum/farmacología , Proteína con Dedos de Zinc GLI1 , beta Catenina/metabolismoRESUMEN
Hedgehog (Hh) is a core signaling pathway implicated in fundamental processes during embryonic kidney development. We previously found that loss-of-function mutations in the transcription factor GLIS2, a putative vertebrate ortholog of Drosophila Ci, cause nephronophthisis type 7 in humans and mice. Kidney tubular cells in Glis2-knockout mice acquire mesenchymal phenotype, but the cellular mechanisms of this transition are unknown. Here, we demonstrate that Glis2 is a functional component of Hh signaling and is necessary to suppress this pathway in the postnatal kidney. In the epithelial compartment, Glis2 opposes Gli1 activity by binding cis-acting regulatory sequences in the 5' flanking regions of Snai1 and Wnt4, thereby inhibiting de-differentiation of tubular cells. We conclude that Glis2 is necessary to inhibit Hh signaling and to maintain the mature tubular epithelial phenotype in the adult kidney. This is the first description of a molecular mechanism that links the Hh signaling pathway to cystic kidney diseases and can open new avenues for the treatment of diverse ciliopathies.