Stromal β-catenin overexpression contributes to the pathogenesis of renal dysplasia

Abstract

Renal dysplasia, the leading cause of renal failure in children, is characterized by disrupted branching of the collecting ducts and primitive tubules, with an expansion of the stroma, yet a role for the renal stroma in the genesis of renal dysplasia is not known. Here, we demonstrate that expression of β-catenin, a key transcriptional co-activator in renal development, is markedly increased in the expanded stroma in human dysplastic tissue. To understand its contribution to the genesis of renal dysplasia, we generated a mouse model that overexpresses β-catenin specifically in stromal progenitors, termed β-cat(GOF-S) . Histopathological analysis of β-cat(GOF) (-S) mice revealed a marked expansion of fibroblast cells surrounding primitive ducts and tubules, similar to defects observed in human dysplastic kidneys. Characterization of the renal stroma in β-cat(GOF) (-S) mice revealed altered stromal cell differentiation in the expanded renal stroma demonstrating that this is not renal stroma but instead a population of stroma-like cells. These cells overexpress ectopic Wnt4 and Bmp4, factors necessary for endothelial cell migration and blood vessel formation. Characterization of the renal vasculature demonstrated disrupted endothelial cell migration, organization, and vascular morphogenesis in β-cat(GOF) (-S) mice. Analysis of human dysplastic tissue demonstrated a remarkably similar phenotype to that observed in our mouse model, including altered stromal cell differentiation, ectopic Wnt4 expression in the stroma-like cells, and disrupted endothelial cell migration and vessel formation. Our findings demonstrate that the overexpression of β-catenin in stromal cells is sufficient to cause renal dysplasia. Further, the pathogenesis of renal dysplasia is one of disrupted stromal differentiation and vascular morphogenesis. Taken together, this study demonstrates for the first time the contribution of stromal β-catenin overexpression to the genesis of renal dysplasia. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Stromal beta-catenin activation impacts nephron progenitor differentiation in the developing kidney and may contribute to Wilms tumor

“…In normal kidney development, Wnt/β-catenin signaling regulates multiple aspects of nephrogenesis, including nephron progenitor renewal, mesenchymal-to-epithelial transition, ureteric bud progenitor renewal and differentiation of the interstitium Boivin et al, 2016;Park et al, 2007;Sarin et al, 2014;Marose et al, 2008;Karner et al, 2011;Ramalingam et al, 2018). Which of these processes is perturbed in WT is still unclear.…”

Proliferation control of kidney interstitial cells

“…6A,B). Reduction in 5 activation of feedback inhibitors can be interpreted as evidence of reduced Wnt/b-catenin 6 signaling, which would be unanticipated considering the proliferative phenotype of Smad4 IC . We 23 Smads modulate the Wnt signaling pathway in a number of developmental and disease contexts interactions in the interstitium we generated a primary cell line.…”

“…Data to this point indicate that Smad4 is required for Wnt/b-catenin feedback inhibition in 1 interstitial cells. To test if Smad4 is required for the expression of the Wnt/b-catenin antagonist 2 Apcdd1, we generated a series of cell lines using the same approach as described for the 3-1 line CreERT2 cassette is recombined into this locus, Smad4 can be deleted by transient tamoxifen 6 treatment. Hprt is located on the X chromosome, and therefore only male mice of 7 Hprt CreERT2 ;Smad4;R26R genotype were used for cell line derivation.…”

“…2G) in Smad4 IC mice. The lack of expression of α-SMA in the abundant interstitial cells of 6 the medulla suggests that Smad4 is required for their differentiation.…”

“…Kidneys were vibratome 5 sectioned and whole mount immunofluorescence staining was performed as described above. 6 Click-it chemistry was subsequently performed on sections according to the manufacturer 7 protocol (ThermoFisher) followed by imaging with a laser scanning confocal microscope. EdU In vitro proliferation analysis 14 Cells were cultured for 5 days at 37°C followed by treatment with CHIR (50nM, 100nM, 15 250nM, 500nM, and 1uM) or CHIR (1uM) with FH535 (15uM) or TGFβ1 (5ng/ml) in 2% serum 16 media for 24hr.…”