High–molecular weight hyaluronan attenuates tubulointerstitial scarring in kidney injury
Xinyi Wang, Swathi Balaji, Emily H. Steen, Alexander J. Blum, Hui Li, Christina K. Chan, Scott R. Manson, Thomas C. Lu, Meredith M. Rae, Paul F. Austin, Thomas N. Wight, Paul L. Bollyky, Jizhong Cheng, Sundeep G. Keswani
Xinyi Wang, Swathi Balaji, Emily H. Steen, Alexander J. Blum, Hui Li, Christina K. Chan, Scott R. Manson, Thomas C. Lu, Meredith M. Rae, Paul F. Austin, Thomas N. Wight, Paul L. Bollyky, Jizhong Cheng, Sundeep G. Keswani
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Research Article Nephrology

High–molecular weight hyaluronan attenuates tubulointerstitial scarring in kidney injury

Abstract

Renal fibrosis features exaggerated inflammation, extracellular matrix (ECM) deposition, and peritubular capillary loss. We previously showed that IL-10 stimulates high–molecular weight hyaluronan (HMW-HA) expression by fibroblasts, and we hypothesize that HMW-HA attenuates renal fibrosis by reducing inflammation and ECM remodeling. We studied the effects of IL-10 overexpression on HA production and scarring in mouse models of unilateral ureteral obstruction (UUO) and ischemia/reperfusion (I/R) to investigate whether IL-10 antifibrotic effects are HA dependent. C57BL/6J mice were fed with the HA synthesis inhibitor, 4-methylumbelliferone (4-MU), before UUO. We observed that in vivo injury increased intratubular spaces, ECM deposition, and HA expression at day 7 and onward. IL-10 overexpression reduced renal fibrosis in both models, promoted HMW-HA synthesis and stability in UUO, and regulated cell proliferation in I/R. 4-MU inhibited IL-10–driven antifibrotic effects, indicating that HMW-HA is necessary for cytokine-mediated reduction of fibrosis. We also found that IL-10 induces in vitro HMW-HA production by renal fibroblasts via STAT3-dependent upregulation of HA synthase 2. We propose that IL-10–induced HMW-HA synthesis plays cytoprotective and antifibrotic roles in kidney injury, thereby revealing an effective strategy to attenuate renal fibrosis in obstructive and ischemic pathologies.

Authors

Xinyi Wang, Swathi Balaji, Emily H. Steen, Alexander J. Blum, Hui Li, Christina K. Chan, Scott R. Manson, Thomas C. Lu, Meredith M. Rae, Paul F. Austin, Thomas N. Wight, Paul L. Bollyky, Jizhong Cheng, Sundeep G. Keswani

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Figure 4

IL-10 antifibrotic effects depend on HA, while its antiinflammatory effects are independent.

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IL-10 antifibrotic effects depend on HA, while its antiinflammatory effe...
(A) HABP-stained kidney tissue images of day 14 post-UUO mice fed with either regular diet or 4-MU–supplemented diet. Scale bar: 50 μm. (B) Images of kidney cortex of mice fed the 4-MU diet, which underwent UUO in the absence or presence of IL-10. Trichrome, α-SMA, and HA staining shows that treatment with IL-10 in the 4-MU diet group did not change the fibrotic phenotype, in contrast to previous results in the regular diet group. However, reduction of F4/80 (a marker of macrophage infiltration) suggested that inhibition of HA synthesis does not affect IL-10 antiinflammatory function. (C) Quantification of data from images of panel B as a percentage or ratio of each stain; **P < 0.01. (D) Relative mRNA levels of hyaluronan synthases (Has1–3) and hyaluronidases (Hyal1–2) of UUO and IL-10–treated UUO kidneys from 4-MU–fed mice; n ≥ 3 per sex per condition; **P < 0.01 for Has1; and *P < 0.05 for Hyal2. (E) Tissue HA concentration (ng/mL/mg) as measured by an ELISA-like assay in UUO kidneys or IL-10–treated UUO kidneys from mice on 4-MU diet showed no significant difference. All data were analyzed with t test for differences between groups; ns = no significant differences among groups.