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 5

Podocyte-specific deletion of Shh decouples proteinuria from glomerulosclerosis at 5 weeks after ADR injection.

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Podocyte-specific deletion of Shh decouples proteinuria from glomerulosc...
(A) Podocyte-specific ablation of Shh did not affect albuminuria at different time points after ADR injection (n = 5–14). Urines were collected from mice at 1, 2, 3, 4, and 5 weeks after ADR injection. (B) qPCR analyses revealed that podocyte-specific loss of Shh did not affect nephrin, podocin, CD2AP, and WT1 expression at 5 weeks after ADR injection (n = 13–15). (C and D) Ablation of Shh did not affect podocyte-specific protein expression. Representative Western blots (C) and quantitative data (D) showed the expression of α-actinin-4 and podocalyxin at 5 weeks after ADR. (E) qPCR analyses revealed that loss of podocyte Shh repressed α-SMA, FSP-1, collagen type I, and collagen type III expression at 5 weeks after ADR injection. *P < 0.05 versus controls (n = 13–15, t test). (F) Representative micrographs showed the expression of actinin-4, nephrin (red), and PDGFR-β (green) in the glomeruli of control and Podo-Shh–/– mice. Scale bar: 25 μm. (G–I) Podocyte-specific ablation of Shh repressed protein expression of fibronectin, α-SMA, β-catenin, and PDGFR-β at 5 weeks after ADR injection. Representative Western blots (G) and quantitative data (H and I) are presented. Numbers (1 through 4) indicate each individual animal in a given group. *P < 0.05 versus controls (n = 10, t test). (J) Representative micrographs showed a decreased glomerulosclerotic lesion and reduced α-SMA expression at 5 weeks after ADR injection in Podo-Shh–/– mice, compared with controls. Glomerulosclerotic lesions were assessed by PAS and Masson’s trichrome staining (MTS). Arrows indicate positive staining. Scale bar: 20 μm. (K) Quantitative determination of glomerulosclerotic score. The percentage of sclerotic area was assessed in 20 glomeruli. *P < 0.05 versus controls, t test.