Abstract
ObjectivesThe aim of this study was to evaluate the role of angiotensin II (AT-II) and its main mediator, transforming growth factor beta 1 (TGF-β1), in the development of feline renal fibrosis.MethodsExpression of marker genes indicating epithelial-to-mesenchymal transition (EMT), profibrotic mediators and matricellular proteins was measured in feline kidney epithelial cells (Crandell Rees feline kidney [CRFK] cells) after incubation with AT-II and/or TGF-β1.ResultsCells incubated with TGF-β1 or the combination of TGF-β1 with AT-II showed clear EMT with more stretched fibroblastic cells, whereas the cells incubated without TGF-β1 and AT-II (control) showed more epithelial cells. Gene expression of collagen type I (COL1), tenascin-C (TNC), trombospondin-1 (TSP-1), connective tissue growth factor (CTGF) and alpha-smooth muscle actin (α-SMA) increased significantly after incubation of the CRFK cells with TGF-β1 or TGF-β1 in combination with AT-II for 12 h. As incubation of the CRFK cells with only AT-II did not show any significant rise in gene expression of the above-mentioned genes, this was further investigated. In contrast to healthy feline kidney tissue, CRFK cells showed almost no expression of the AT-II type 1 (AT1) receptor.Conclusions and relevanceTGF-β1 significantly induced expression of the EMT marker gene α-SMA, profibrotic mediator CTGF, and fibrogenic proteins COL1, TNC and TSP-1 in CRFK cells. The effect of TGF-β1 on myofibroblast formation was also observed by the stretched appearance of the CRFK cells. As CRFK cells expressed almost no AT1 receptors, this cell line proved not suitable for testing the efficacy of drugs that interact with the AT1 receptor. As AT-II stimulates the effects of TGF-β1 in mammals, the results of this study suggest an indirect profibrotic effect of AT-II besides the demonstrated profibrotic effect of TGF-β1 and thus the development of feline renal fibrosis. Modulation of EMT or proliferation of myofibroblasts could serve as a diagnostic tool and a novel therapeutic target to inhibit renal fibrogenesis, and could possibly serve in the therapy of feline renal fibrosis.
Highlights
Chronic kidney disease (CKD) is one of the most common progressive diseases in older cats and the renin– angiotensin–aldosterone system (RAAS) is known to play a key role in the progression of the disease
It was concluded that 1 × 10–6 M angiotensin II (AT-II) and 2.5 ng/ml TGF-β1 were the optimal concentrations for the CRFK cells to show epithelial-to-mesenchymal transition (EMT) without influencing the viability of the cells
Cells incubated with TGF-β1 or a combination of TGF-β1 with AT-II showed clear EMT with more stretched fibroblastic cells, whereas the cells incubated without TGF-β1 and AT-II or with AT-II showed more epithelial cells
Summary
Chronic kidney disease (CKD) is one of the most common progressive diseases in older cats and the renin– angiotensin–aldosterone system (RAAS) is known to play a key role in the progression of the disease. The inevitable consequence of CKD is renal fibrosis, a process that has been studied thoroughly in human medicine, but has still not been completely elucidated because of its complexity. The process in which epithelial cells convert to mesenchymal fibroblasts is called epithelial-to-mesenchymal transition (EMT). The number of fibroblasts formed by this process is small,[6] EMT is responsible for more than just a morphological change of the tubular epithelial cells. EMT induces and inhibits expression of proteins involved in the function of tubular epithelial cells and impairs the repair of damaged tissue by inducing cell cycle arrest,[5] eventually leading to renal fibrosis. Regardless of the aetiology, renal tubulointerstitial fibrosis is recognised as the pathological lesion best correlated with renal function in both humans and cats.[3,7,8,9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
