Background/Purpose : Nephrogenic Systemic Fibrosis (NSF) is a generalized progressive fibrotic disorder that occurs in some patients with renal insufficiency exposed to various gadolinium based contrast agents (GdBCA).  TLR4 and TLR7 signaling has been reported to be necessary for the in vitro establishment of a profibrotic phenotype by the GdBCA Omniscan in normal human macrophages. In this study, we examined the role of TLR4 and TLR7 in the development of NSF-like lesions in vivoin mice with renal failure induced by a high adenine diet following exposure to GdBCA by intratracheal instillation.

Methods:

Chronic renal failure was induced in normal mice and in TLR4 and TLR7 knockout  (TLR4 KO) and (TLR7 KO) mice by ad libitumfeeding of a standard rodent diet supplemented with 3% adenine for 30 days.  Two weekly doses of either the GdBCA Omniscan (100 µL of a 0.5 M solution, corresponding to a 0.05 mmol/kg dose) or an equal volume of normal saline were administered by intratracheal instillation to mice with either normal renal function or with adenine diet-induced chronic renal failure.  Mice were sacrificed 56 days after the final instillation and tissues were isolated for analysis of the severity of tissue fibrosis by histological examination (hematoxyllin/eosin and Masson’s trichrome stains) and by assays of collagen content employing a standard hydroxyproline assay of hydrolyzed tissue samples.

Results: Histopathology studies showed mononuclear cell infiltration and severe peribronchial fibrosis and moderate diffuse interstitial fibrosis in lungs isolated from adenine-fed control (C57BL6/J) mice instilled with Omniscan. In contrast, lungs from adenine-fed TLR4 KO or TLR7 KO mice maintained normal lung histology.  Mice of all three strains with normal renal function instilled with Omniscan and mice with either normal or ablated renal function instilled with saline also demonstrated no fibrosis. Hydroxyproline content was increased ~3 fold in the lungs of Omniscan-instilled wild type mice with adenine diet-induced renal failure. In contrast, the lungs of Omniscan-instilled TLR4 KO and TLR7 KO mice with or without renal failure had normal hydroxyproline levels.

Conclusion:

The present study demonstrates for the first time in vivo that the ability to induce significant tissue fibrosis and increased collagen deposition in mice with adenine induced renal failure exposed to the gadolinium contrast agent Omniscan requires signaling through TLR4 and TLR7.  These results indicate that targeting of TLR signaling could be a valuable strategy to prevent or treat NSF and other TLR-mediated chemically-induced fibrotic disorders.

---

« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/tlr4-and-tlr7-are-required-for-gadolinium-based-contrast-agent-induction-of-dermal-and-pulmonary-fibrosis-in-an-adenine-induced-model-of-chronic-renal-failure/