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Transforming growth factor-β1/Smad3-independent epithelial–mesenchymal transition in type I collagen glomerulopathy

Authors Brodeur AC, Roberts-Pilgrim AM, Thompson KL, Franklin CL, Phillips CL

Received 10 May 2017

Accepted for publication 14 July 2017

Published 31 August 2017 Volume 2017:10 Pages 251—259


Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Colin Mak

Peer reviewer comments 2

Editor who approved publication: Professor Pravin Singhal

Amanda C Brodeur,1–3 Anna M Roberts-Pilgrim,3 Kimberlee L Thompson,1 Craig L Franklin,4 Charlotte L Phillips2,3

1Department of Biomedical Sciences, Missouri State University, Springfield, MO, USA; 2Department of Child Health, University of Missouri, Columbia, MO, USA; 3Department of Biochemistry, University of Missouri, Columbia, MO, USA; 4Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, USA

Abstract: The glomerulofibrotic Col1a2-deficient mouse model demonstrates glomerular homotrimeric type I collagen deposition in mesangial and subendothelial spaces. In this report, we investigate the role of transforming growth factor β1 (TGF-β1) in myofibroblast activation and epithelial–mesenchymal transition (EMT) in this glomerulopathy. Immunohistochemical analyses of glomerular α-sma, desmin, vimentin, and proliferating cell nuclear antigen demonstrated parietal epithelial cell proliferation and EMT in late stages of the glomerulopathy in the Col1a2-deficient mice. Glomerular TGF-β1 RNA and protein were not elevated in 1- and 3-month-old mice as determined by quantitative reverse transcriptase-polymerase chain reaction and protein immunoassay analyses. To investigate further whether TGF-β1 plays a role in the glomerulopathy outside of the 1- and 3-month time periods, the Col1a2-deficient mice were bred with Smad3 knockout mice. If the glomerular fibrosis in the Col1a2-deficient mice is mediated by the TGF-β1/Smad3 transcription pathway, it was hypothesized that the resultant Col1a2-deficient/Smad3-deficient mice would exhibit attenuated glomerular homotrimer deposition. However, the Col1a2-deficient/Smad3-deficient kidneys were similarly affected as compared to age-matched Col1a2-deficient kidneys, suggesting that homotrimeric type I collagen deposition in the Col1a2-deficient mouse is independent of TGF-β1/Smad3 signaling. Deposition of homotrimeric type I collagen appears to be the initiating event in this glomerulopathy, providing evidence that EMT and myofibroblast activation occur following initiation, consistent with a secondary wound-healing response independent of TGF-β1.

Keywords: renal pathology, glomerulofibrosis, myofibroblast, homotrimeric type I collagen

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