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Poor translation from animal studies to human clinical trials is one of the main hurdles in the development of new drugs. Here, we used precision-cut kidney slices (PCKS) as a translational model to study renal fibrosis and to investigate whether inhibition of tyrosine kinase receptors, with the selective inhibitor nintedanib, can halt fibrosis in murine and human PCKS. We used renal tissue of murine and human origins to obtain PCKS. Control slices and slices treated with nintedanib were studied to assess viability, activation of tyrosine kinase receptors, cell proliferation, collagen type I accumulation, and gene and protein regulation. During culture, PCKS spontaneously develop a fibrotic response that resembles in vivo fibrogenesis. Nintedanib blocked culture-induced phosphorylation of platelet-derived growth factor receptor and vascular endothelial growth factor receptor. Furthermore, nintedanib inhibited cell proliferation and reduced collagen type I accumulation and expression of fibrosis-related genes in healthy murine and human PCKS. Modulation of extracellular matrix homeostasis was achieved already at 0.1 μM, whereas high concentrations (1 and 5 μM) elicited possible nonselective effects. In PCKS from human diseased renal tissue, nintedanib showed limited capacity to reverse established fibrosis. In conclusion, nintedanib attenuated the onset of fibrosis in both murine and human PCKS by inhibiting the phosphorylation of tyrosine kinase receptors; however, the reversal of established fibrosis was not achieved.

Chronic kidney disease (CKD) is associated with renal fibrosis, a pathological process that is characterized by excessive accumulation of extracellular matrix proteins resulting in loss of organ architecture and function. Currently, renal transplantation and dialysis are the sole treatment options for advanced CKD, yet these therapies have limited impact on fibrogenesis. Even though antifibrotic therapies are being developed, the search for effective antifibrotic drugs is being hampered by the lack of appropriate cell and animal models to study renal fibrosis. In vitro models lack cellular heterogeneity whereas in vivo models do not fully reflect human pathology. Precision-cut tissue slices, prepared from human or rodent tissue, provide a unique ex vivo model system that captures the complexity of organs, and they are widely used for ADME/Tox drug testing. Moreover, precision-cut kidney slices (PCKS) have been recently established as a useful model to study renal fibrosis. This review summarizes the currently available models for renal fibrosis, describes the wide array of possibilities with PCKS and shows its role in the search for antifibrotic drugs. (C) 2016 Elsevier B.V. All rights reserved.

Chronic kidney disease is a major health concern, and experimental models bridging the gap between animal studies and clinical research are currently lacking. Here, we evaluated precision-cut kidney slices (PCKSs) as a potential model for renal disease. PCKSs were prepared from human cortical tissue obtained from tumor nephrectomies and cultured up to 96 hours. Morphology, cell viability, and metabolic functionality (ie, uridine 5'-diphospho-glucuronosyltransferase and transporter activity) were determined to assess the integrity of PCKSs. Furthermore, inflammatory and fibrosis-related gene expressions were characterized. Finally, to validate the model, renal fibrogenesis was induced using transforming growth factor beta 1 (TGF-beta 1). Preparation of PCKSs induced an inflammatory tissue response, whereas long-term incubation (96 hours) induced fibrogenesis as shown by an increased expression of collagen type 1A1 (COL1A1) and fibronectin 1 (FN1). Importantly, PCKSs remained functional for more than 48 hours as evidenced by active glucuronidation and phenolsulfonphthalein uptake. In addition, cellular diversity appeared to be maintained, yet we observed a clear loss of nephrin messenger RNA levels suggesting that our model might not be suitable to study the role of podocytes in renal pathology. Moreover, TGF-beta 1 exposure augmented fibrosis, as illustrated by an increased expression of multiple fibrosis markers including COL1A1, FN1, and alpha-smooth muscle actin. In conclusion, PCKSs maintain their renal phenotype during culture and appear to be a promising model to investigate renal diseases, for example, renal fibrosis. Moreover, the human origin of PCKSs makes this model very suitable for translational research.

Animal models are a valuable tool in preclinical research. However, limited predictivity of human biological responses in the conventional models has stimulated the search for reliable preclinical tools that show translational robustness. Here, we used precision-cut kidney slices (PCKS) as a model of renal fibrosis and investigated its predictive capacity for screening the effects of anti-fibrotics. Murine and human PCKS were exposed to TGF&beta, or PDGF pathway inhibitors with established anti-fibrotic efficacy. For each treatment modality, we evaluated whether it affected: (1) culture-induced collagen type I gene expression and interstitial accumulation, (2) expression of markers of TGF&beta, and PDGF signaling, and (3) expression of inflammatory markers. We summarized the outcomes of published in vivo animal and human studies testing the three inhibitors in renal fibrosis, and drew a parallel to the PCKS data. We showed that the responses of murine PCKS to anti-fibrotics highly corresponded with the known in vivo responses observed in various animal models of renal fibrosis. Moreover, our results suggested that human PCKS can be used to predict drug efficacy in clinical trials. In conclusion, our study demonstrated that the PCKS model is a powerful predictive tool for ex vivo screening of putative drugs for renal fibrosis.

Activation of TLR2 or TLR4 by endogenous ligands such as high mobility group box 1 (HMGB1) may mediate inflammation causing diabetic kidney injury. We determined whether blockade of HMGB1 signaling by: (1) supra-physiological production of endogenous secretory Receptor for Advanced Glycation End-products (esRAGE), a receptor for HMGB1; (2) administration of HMGB1 A Box, a specific competitive antagonist, would inhibit development of streptozotocin induced diabetic nephropathy (DN). Wild-type diabetic mice developed albuminuria, glomerular injuries, interstitial fibrosis and renal inflammation. Using an adeno-associated virus vector, systemic over-expression of esRAGE afforded significant protection from all parameters. No protection was achieved by a control vector which expressed human serum albumin. Administration of A Box was similarly protective against development of DN. To determine the mechanism(s) of protection, we found that whilst deficiency of TLR2, TLR4 or RAGE afforded partial protection from development of DN, over-expression of esRAGE provided additional protection in TLR2−/−, modest protection against podocyte damage only in TLR4−/− and no protection in RAGE−/− diabetic mice, suggesting the protection provided by esRAGE was primarily through interruption of RAGE and TLR4 pathways. We conclude that strategies to block the interaction between HMGB1 and its receptors may be effective in preventing the development of DN.

Kidney allograft failure due to chronic injury/rejection remains the main cause of graft loss in renal transplant recipients (RTR). Here, we investigated whether specific biomarkers of extracellular matrix (ECM) turnover are associated with allograft function and chronic kidney disease (CKD) stage in RTR. Seventy-eight patients who attended the University Medical Center Groningen for a routine check-up after kidney transplantation were enrolled in the study. Plasma and/or 24h-urine samples were collected and specific matrix-metalloproteinase- generated neo-epitope fragments of collagens were measured by enzyme-linked immunosorbent assay. Our results demonstrated that urinary levels of C3M, a marker for collagen type III degradation, correlated with estimated glomerular filtration rate (eGFR; r = 0.58, p

Chronic kidney disease (CKD) is a major global health concern, and the uremic state is highly associated with fibrogenesis in several organs and tissues. Fibrosis is characterized by excessive production and deposition of extracellular matrix proteins with a detrimental impact on organ function. Another key feature of CKD is the retention and subsequent accumulation of solutes that are normally cleared by the healthy kidney. Several of these uremic retention solutes, including indoxyl sulfate and p-cresyl sulfate, have been suggested to be CKD-specific triggers for the development and perpetuation of fibrosis. The purpose of this brief review is to gather and discuss the current body of evidence linking uremic retention solutes to the fibrotic response during CKD, with a special emphasis on the pathophysiological mechanisms in the kidney.

Activation of the innate immunity through Toll-like receptors (TLRs) has been postulated to play an important role in the pathophysiology of renal allograft dysfunction. TLR2 and TLR4 dynamics in different human post-transplant pathological entities has never been studied. Therefore, we evaluated pre- and post-transplantation protein expression of TLR2 and TLR4 in human kidney biopsies. Human kidney biopsies obtained from living kidney donors and patients with acute tubular necrosis, acute cellular and vascular rejection and interstitial fibrosis/tubular atrophy (IF/TA) were used. Translating results from animal studies to the clinical situation is highly important considering the upcoming clinical studies with TLR inhibitors in human renal transplantation. Hence, the TLR2 and TLR4 expression in healthy mouse and rat kidneys was analyzed and compared with human kidneys. In healthy human kidneys, TLR2 is expressed on the endothelium and Bowman's capsule, while TLR4 is expressed on the endothelium only. No tubular staining was found for both receptors in human kidneys. In contrast to human biopsies, TLR2 and TLR4 expression in rodents was observed on tubular epithelial cells. In all acute rejection human biopsies, increased infiltration of TLR4(+) leukocytes was observed. In conclusion, a discrepancy exists between human and rodent renal TLR expression, which suggests careful attention when translating results from rodent studies to the human situation. Additionally, this study revealed human TLR2 and TLR4 expression dynamics in human biopsies pre- and post-transplantation.