Sonic hedgehog connects podocyte injury to mesangial activation and glomerulosclerosis
Dong Zhou, Haiyan Fu, Yang Han, Lu Zhang, Shijia Liu, Lin Lin, Donna B. Stolz, Youhua Liu
Dong Zhou, Haiyan Fu, Yang Han, Lu Zhang, Shijia Liu, Lin Lin, Donna B. Stolz, Youhua Liu
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Research Article Nephrology

Sonic hedgehog connects podocyte injury to mesangial activation and glomerulosclerosis

Abstract

Glomerular disease is characterized by proteinuria and glomerulosclerosis, two pathologic features caused by podocyte injury and mesangial cell activation, respectively. However, whether these two events are linked remains elusive. Here, we report that sonic hedgehog (Shh) is the mediator that connects podocyte damage to mesangial activation and glomerulosclerosis. Shh was induced in glomerular podocytes in various models of proteinuric chronic kidney diseases (CKD). However, mesangial cells in the glomeruli, but not podocytes, responded to hedgehog ligand. In vitro, Shh was induced in podocytes after injury and selectively promoted mesangial cell activation and proliferation. In a miniorgan culture of isolated glomeruli, Shh promoted mesangial activation but did not affect the integrity of podocytes. Podocyte-specific ablation of Shh in vivo exhibited no effect on proteinuria after adriamycin injection but hampered mesangial activation and glomerulosclerosis. Consistently, pharmacologic blockade of Shh signaling decoupled proteinuria from glomerulosclerosis. In humans, Shh was upregulated in glomerular podocytes in patients with CKD and its circulating level was associated with glomerulosclerosis but not proteinuria. These studies demonstrate that Shh mechanistically links podocyte injury to mesangial activation in the pathogenesis of glomerular diseases. Our findings also illustrate a crucial role for podocyte-mesangial communication in connecting proteinuria to glomerulosclerosis.

Authors

Dong Zhou, Haiyan Fu, Yang Han, Lu Zhang, Shijia Liu, Lin Lin, Donna B. Stolz, Youhua Liu

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Figure 6

Pharmacologic inhibition of Shh signaling decouples proteinuria from glomerulosclerosis.

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Pharmacologic inhibition of Shh signaling decouples proteinuria from glo...
(A) Experimental design. Red arrow, ADR injection. Green bar, CPN treatment. (B) qPCR analyses reveal that pharmacologic inhibition of Shh signaling repressed Gli1 expression at 5 weeks after ADR injection, compared with the vehicles. *P < 0.05 versus controls, †P < 0.05 versus ADR alone (n = 5–6, Student-Newman-Keuls test). (C) Inhibition of Shh signaling by CPN did not affect albuminuria at 5 weeks after ADR. *P < 0.05 (n = 5–6, Student-Newman-Keuls test). (D) qPCR analyses revealed that inhibition of Shh signaling by CPN did not affect nephrin, podocin, CD2AP, podocalyxin, and WT1 expression at 5 weeks after ADR injection, compared with the vehicles (n = 4–5, Student-Newman-Keuls test). (E and F) Western blot analyses showed that CPN did not affect α-actinin-4 expression at 5 weeks after ADR injection. Representative Western blot (E) and quantitative data (F) are presented (n = 5–6). (G and H) Representative micrographs and quantitation of IF intensity (arbitrary unit) showed α-actinin-4 expression and localization in the glomeruli of mice after various treatments as indicated. Scale bar: 20 μm. *P < 0.05 versus controls, Student-Newman-Keuls test. (I–K) Western blot assays showed that CPN inhibited the expression of fibrosis-related genes, including PDGFR-β, fibronectin, α-SMA, and β-catenin at 5 weeks after ADR injection. Representative Western blot (I) and quantitative data (J and K) are presented. *P < 0.05 versus controls, †P < 0.05 versus ADR alone (n = 5–6, Student-Newman-Keuls test). (L) Representative micrographs showed that CPN did not preserve podocyte integrity but inhibited mesangial activation and glomerulosclerosis. Kidney sections were immunostained for nephrin (red), PDGFR-β (green), and α-SMA or subjected to Masson’s trichrome staining. Arrows indicate positive staining. The yellow arrows denotes α-SMA+ podocytes. Scale bar: 25 μm. (M) Quantitation of IF intensity (arbitrary unit) of PDGFR-β in the glomeruli at 5 weeks after ADR in the absence or presence of CPN. *P < 0.05 versus controls, †P < 0.05 versus ADR alone, Student-Newman-Keuls test. (N) Quantitative determination of glomerulosclerotic score. The percentage of sclerotic area was assessed in 20 glomeruli. *P < 0.05 versus controls, †P < 0.05 versus ADR alone, Student-Newman-Keuls test.