Repeated administration of low-dose cisplatin in mice induces fibrosis

Human umbilical cord blood mononuclear cells protect against renal tubulointerstitial fibrosis in cisplatin-treated rats

Currently, there is no effective method to prevent renal interstitial fibrosis after acute kidney injury (AKI). In this study, we established and screened a new renal interstitial fibrosis rat model after cisplatin-induced AKI. Our results indicated that rats injected with 4 mg/kg cisplatin once a week for two weeks after firstly administrated with 6.5 mg/kg loading dose of cisplatin could set up a more accurate model reflecting AKI progression to renal interstitial fibrosis. Then, we investigated the effects and possible mechanisms of human umbilical cord blood mononuclear cells (hUCBMNCs) on renal tubular interstitial fibrosis after cisplatin-induced AKI. In rats injected with hUCBMNCs for four times, level of matrix metalloproteinase 7 (MMP-7) in serum and urine, urinary albumin/creatinine ratio, tubular pathological scores, the relative collagen area of the tubulointerstitial region, endoplasmic reticulum dilation and the mitochondrial ultrastructural damage were significantly improved. The level of reactive oxygen species, α-smooth muscle actin (α-SMA), [NOD]-like pyrin domain containing protein 3 and cleaved-Caspase 3 in renal tissue decreased significantly. However, in rats injected with hUCBMNCs for two times, no significant difference was discovered in MMP-7 levels and urinary albumin/creatinine ratio. Although expression of α-SMA and the percentage areas of collagen staining in tubulointerstitial tissues were ameliorated in rats injected with hUCBMNCs for two times, the effects were significantly weaker than those in rats injected with hUCBMNCs for four times. Taken together, our study constructed a highly efficient, duplicable novel rat model of renal fibrosis after cisplatin-induced AKI. Multiple injections of hUCBMNCs may prevent renal interstitial fibrosis after cisplatin-induced AKI.

Human umbilical cord blood mononuclear cells protect against renal tubulointerstitial fibrosis in cisplatin-treated rats

Currently, there is no effective method to prevent renal interstitial fibrosis after acute kidney injury (AKI). In this study, we established and screened a new renal interstitial fibrosis rat model after cisplatin-induced AKI. Our results indicated that rats injected with 4 mg/kg cisplatin once a week for two weeks after firstly administrated with 6.5 mg/kg loading dose of cisplatin could set up a more accurate model reflecting AKI progression to renal interstitial fibrosis. Then, we investigated the effects and possible mechanisms of human umbilical cord blood mononuclear cells (hUCBMNCs) on renal tubular interstitial fibrosis after cisplatin-induced AKI. In rats injected with hUCBMNCs for four times, level of matrix metalloproteinase 7(MMP-7)in serum and urine, urinary albumin/creatinine ratio, tubular pathological scores, the relative collagen area of the tubulointerstitial region, endoplasmic reticulum dilation and the mitochondrial ultrastructural damage were significantly improved. The level of reactive oxygen species, α-smooth muscle actin (α-SMA), [NOD]-like pyrin domain containing protein 3 and cleaved-Caspase 3 in renal tissue decreased significantly. However, in rats injected with hUCBMNCs for two times, no significant difference was discovered in MMP-7 levels and urinary albumin/creatinine ratio. Although expression of α-SMA and the percentage areas of collagen staining in tubulointerstitial tissues were ameliorated in rats injected with hUCBMNCs for two times, the effects were significantly weaker than those in rats injected with hUCBMNCs for four times. Taken together, our study constructed a highly efficient, duplicable novel rat model of renal fibrosis after cisplatin-induced AKI. Multiple injections of hUCBMNCs may prevent renal interstitial fibrosis after cisplatin-induced AKI.

The Predictive Role of the Biomarker Kidney Molecule-1 (KIM-1) in Acute Kidney Injury (AKI) Cisplatin-Induced Nephrotoxicity

Acute kidney injury (AKI) following platinum-based chemotherapeutics is a frequently reported serious side-effect. However, there are no approved biomarkers that can properly identify proximal tubular injury while routine assessments such as serum creatinine lack sensitivity. Kidney-injury-molecule 1 (KIM-1) is showing promise in identifying cisplatin-induced renal injury both in vitro and in vivo studies. In this review, we focus on describing the mechanisms of renal tubular cells cisplatin-induced apoptosis, the associated inflammatory response and oxidative stress and the role of KIM-1 as a possible biomarker used to predict cisplatin associated AKI.

Chronic effects of repeated low-dose cisplatin treatment in mouse kidneys and renal tubular cells

Cisplatin is a commonly used chemotherapeutic drug for cancer treatment, but its nephrotoxicity may lead to the deterioration of renal function. Previous work has been focused on cisplatin-induced acute kidney disease, whereas the mechanism of chronic kidney disease after cisplatin chemotherapy is largely unknown. In the present study, we have characterized the mouse model of chronic kidney defects induced by repeated low-dose cisplatin treatment. We have also established a relevant cell culture model. In the animal model, C57 mice were given weekly injection of 8 mg/kg cisplatin for 4 wk. This led to a sustained decline of kidney function. These mice showed loss of kidney mass, interstitial fibrosis, continued activation of inflammatory cytokines, and appearance of atubular glomeruli. In the cell model, the BUMPT mouse proximal tubular cell line was treated four times with 1-2 μM cisplatin, resulting in low levels of apoptosis and the expression of fibrosis proteins and profibrotic factors. These data suggest that repeated treatment with low-dose cisplatin causes long-term renal pathologies with characteristics of chronic kidney disease.

Capillary rarefaction is more closely associated with CKD progression after cisplatin, rhabdomyolysis, and ischemia-reperfusion-induced AKI than renal fibrosis

Acute kidney injury (AKI) is a strong independent predictor of mortality and often results in incomplete recovery of renal function, leading to progressive chronic kidney disease (CKD). Many clinical trials have been conducted on the basis of promising preclinical data, but no therapeutic interventions have been shown to improve long-term outcomes after AKI. This is partly due to the failure of preclinical studies to accurately model clinically relevant injury and long-term outcomes on CKD progression. Here, we evaluated the long-term effects of AKI on CKD progression in three animal models reflecting diverse etiologies of AKI: repeat-dose cisplatin, rhabdomyolysis, and ischemia-reperfusion injury. Using transdermal measurement of glomerular filtration rate as a clinically relevant measure of kidney function and quantification of peritubular capillary density to measure capillary rarefaction, we showed that repeat-dose cisplatin caused capillary rarefaction and decreased renal function in mice without a significant increase in interstitial fibrosis, whereas rhabdomyolysis-induced AKI led to severe interstitial fibrosis, but renal function and peritubular capillary density were preserved. Furthermore, long-term experiments in mice with unilateral ischemia-reperfusion injury showed that restoration of renal function 12 wk after a contralateral nephrectomy was associated with increasing fibrosis, but a reversal of capillary rarefaction was seen at 4 wk. These data demonstrate that clear dissociation between kidney function and fibrosis in these models of AKI to CKD progression and suggest that peritubular capillary rarefaction is more strongly associated with CKD progression than renal fibrosis.

Dynamic signature of lymphangiogenesis during acute kidney injury and chronic kidney disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected syndromes with significant attributable morbidity and mortality. The disturbing trend of increasing incidence and prevalence of these clinical disorders highlights the urgent need for better understanding of the underlying mechanisms that are involved in pathogenesis of these conditions. Lymphangiogenesis and its involvement in various inflammatory conditions is increasingly recognized while its role in AKI and CKD remains to be fully elucidated. Here, we studied lymphangiogenesis in three models of kidney injury. Our results demonstrate that the main ligands for lymphangiogenesis, VEGF-C and VEGF-D, are abundantly present in tubules at baseline conditions and the expression pattern of these ligands is significantly altered following injury. In addition, we show that both of these ligands increase in serum and urine post-injury and suggest that such increment may serve as novel urinary biomarkers of AKI as well as in progression of kidney disease. We also provide evidence that irrespective of the nature of initial insult, lymphangiogenic pathways are rapidly and robustly induced as evidenced by higher expression of lymphatic markers within the kidney.

Found in Translation: Reasons for Optimism in the Pursuit to Prevent Chronic Kidney Disease After Acute Kidney Injury

Purpose of review:

The current review will discuss on the progress of studying the transition phase between acute kidney injury (AKI) and chronic kidney disease (CKD) through improved animal models, common AKI and CKD pathways, and how human studies may inform different translational approaches.

Sources of information:

PubMed and Google Scholar.

Methods:

A narrative review was performed using the main terms “acute kidney injury,” “chronic kidney disease,” “end-stage renal disease,” “animal models,” “review,” “decision-making,” and “translational research.”

Key findings:

The last decade has shown much progress in the study of AKI, including evidence of a pathophysiological link between AKI and CKD. We are now in a phase of redesigning animal models and discovering mechanisms that can replicate the pathological conditions of the AKI-to-CKD continuum. Translating these findings into the clinic is a barrier that must be overcome. To this end, current efforts include prediction of AKI onset and maladaptive repair, detecting patients susceptible to the progression of chronic maladaptive repair, and understanding shared signaling mechanisms between AKI and CKD.

Limitations:

This is a narrative review of the literature that is partially influenced by the knowledge, perspectives, and experiences of the authors and their research background.

Implications:

Overall, this new knowledge from the AKI-to-CKD continuum will help bridge the discontinuity that exists between animal models and patients, resulting in more effective translational biomarkers and therapeutics to test in known AKI pathologies thereby preventing the chronicity of kidney injury progression.

A Simple Ex Vivo Semiquantitative Fluorescent Imaging Utilizing Planar Laser Scanner: Detection of Reactive Oxygen Species Generation in Mouse Brain and Kidney

Objective:

Oxidative stress plays an important role in the onset of many neuronal and peripheral disorders. We examined the feasibility of obtaining semiquantitative fluorescent images of reactive oxygen species (ROS) generation in mouse brain and kidney utilizing a planar laser scanner and dihydroethidium (DHE).

Methods:

To investigate ROS generation in brain, sodium nitroprusside was injected into the striatum. Dihydroethidium was injected into the tail vein. After DHE injection, tissue slices were analyzed utilizing a planar laser scanner. For kidney study, cis-diamminedichloroplatinum [II] (cisplatin) was intraperitoneally administrated into mice.

Results:

Clear and semiquantitative fluorescent images of ROS generation in the mouse brain and kidney were obtained. Furthermore, the fluorescence intensity was stable and not affected by fading. Sodium nitroprusside induced approximately 6 times the fluorescence accumulation in the brain. Cisplatin caused renal injury in all mice, and in comparison with control mice, more than 10 times fluorescence accumulation was observed in the renal medulla with tubular necrosis and vacuolization.

Conclusions:

We successfully obtained ex vivo semiquantitative fluorescent images of ROS generation utilizing a planar laser scanner and DHE. This simple method is useful for ROS detection in several ROS-related animal models and would be applicable to a variety of biochemical processes.

Recent Advances in Models, Mechanisms, Biomarkers, and Interventions in Cisplatin-Induced Acute Kidney Injury

Cisplatin is a widely used chemotherapeutic agent used to treat solid tumours, such as ovarian, head and neck, and testicular germ cell. A known complication of cisplatin administration is acute kidney injury (AKI). The development of effective tumour interventions with reduced nephrotoxicity relies heavily on understanding the molecular pathophysiology of cisplatin-induced AKI. Rodent models have provided mechanistic insight into the pathophysiology of cisplatin-induced AKI. In the subsequent review, we provide a detailed discussion of recent advances in the cisplatin-induced AKI phenotype, principal mechanistic findings of injury and therapy, and pre-clinical use of AKI rodent models. Cisplatin-induced AKI murine models faithfully develop gross manifestations of clinical AKI such as decreased kidney function, increased expression of tubular injury biomarkers, and tubular injury evident by histology. Pathways involved in AKI include apoptosis, necrosis, inflammation, and increased oxidative stress, ultimately providing a translational platform for testing the therapeutic efficacy of potential interventions. This review provides a discussion of the foundation laid by cisplatin-induced AKI rodent models for our current understanding of AKI molecular pathophysiology.

Multiscale Mathematical Model of Drug-Induced Proximal Tubule Injury: Linking Urinary Biomarkers to Epithelial Cell Injury and Renal Dysfunction

Drug-induced nephrotoxicity is a major cause of acute kidney injury, and thus detecting the potential for nephrotoxicity early in the drug development process is critical. Various urinary biomarkers exhibit different patterns following drug-induced injury, which may provide greater information than traditional biomarkers like serum creatinine. In this study, we developed a multiscale quantitative systems pharmacology model relating drug exposure to proximal tubule (PT) epithelial cell injury and subsequently to expression of multiple urinary biomarkers and organ-level functional changes. We utilized urinary kidney injury molecule-1 (Kim-1), alpha glutathione S-transferase, albumin (αGST), glucose, and urine volume time profiles as well as serum creatinine and histopathology data obtained from rats treated with the nephrotoxicant cisplatin to develop the model. Although the model was developed using single-dose response to cisplatin, the model predicted the serum creatinine response to multidose cisplatin regimens. Further, using only the urinary Kim-1 response to gentamicin (a nephrotoxicant with a distinctly different injury time course than cisplatin), the model detected and predicted mild to moderate PT injury, as confirmed with histopathology, even when serum creatinine was unchanged. Thus, the model is generalizable, and can be used to deconvolute the underlying degree and time course of drug-induced PT injury and renal dysfunction from a small number of urinary biomarkers, and may provide a tool to determine optimal dosing regimens that minimize renal injury.

Protease-activated receptor 2 exacerbates cisplatin-induced nephrotoxicity

Acute kidney injury (AKI) is associated with hypercoagulability. Tissue factor/factor VIIa complex and factor Xa in the coagulation cascade activate protease-activated receptor 2 (PAR2). Previously, we have shown that PAR2-mediated inflammation aggravates kidney injury in models of diabetic kidney disease and adenine-induced renal fibrosis. However, the role of PAR2 in AKI remains unclear. To clarify the role of PAR2, we administered cisplatin, one of the most common causal factors of AKI, to wild-type and PAR2-deficient mice. The expression levels of tissue factor and PAR2 were significantly increased in the kidneys of mice that were administered cisplatin. A lack of PAR2 corrected the levels of plasma blood urea nitrogen and creatinine as well as ameliorated the acute tubular injury score in the kidney. A lack of PAR2 corrected the infiltration of neutrophils and the gene expression levels of proinflammatory cytokines/chemokines in these mouse kidneys. Similarly, apoptotic markers, such as cleaved caspase-3-positive area and Bax/Bcl2 ratio, were attenuated via PAR2 deletion. Thus, elevated PAR2 exacerbates cisplatin nephrotoxicity, and targeting PAR2 is a novel therapeutic option that aids in the treatment of patients with cisplatin-induced AKI.

N-acetylcysteine ameliorates cisplatin-induced renal senescence and renal interstitial fibrosis through sirtuin1 activation and p53 deacetylation

The mechanism underlying the development of chronic kidney disease (CKD) after acute kidney injury (AKI) remains unclear. Maladaptive repair has been considered an important mechanism of CKD post AKI. Renal tubular cells under maladaptive repair have characteristics of premature senescence. These premature senescent cells can generate profibrotic factors that promote organ fibrosis. The purpose of this study was to investigate whether cisplatin induces premature renal senescence and the role of premature renal senescence in the progression of CKD post AKI. As oxidative stress is a major cause of senescence, we further evaluated whether antioxidant therapy could protect renal tubular cells from cisplatin-induced premature senescence and retard the progression of CKD post AKI. The molecular mechanism of this protection was also investigated. We found that cisplatin induced premature renal senescence in vitro and in vivo. In a multiple-cisplatin-treatment murine model, renal interstitial fibrosis was accompanied by premature renal senescence. N-acetylcysteine (NAC), an antioxidant, attenuated premature senescence and decreased renal fibrosis, and its effects were dependent on sirtuin1 (SIRT1) activation and p53 deacetylation. These results indicate that cisplatin can induce premature renal senescence, which is associated with the development of CKD post cisplatin-induced AKI. SIRT1 activation and p53 deacetylation might be identified as potential targets for attenuating premature renal senescence and retarding the progression of CKD post AKI.

Moderate aging does not exacerbate cisplatin-induced kidney injury or fibrosis despite altered inflammatory cytokine expression and immune cell infiltration

Aging is a risk factor for certain forms of kidney injury due to normal physiological changes, but the role of aging in cisplatin-induced kidney injury is not well defined in humans or animal models of the disease. To improve on current knowledge in this field, we treated 8- and 40-wk-old FVB/n mice with one high dose of cisplatin as a model of acute kidney injury or with repeated low doses of cisplatin (7 mg/kg cisplatin once a week for 4 wk) as a clinically relevant model of chronic kidney disease to determine if aging exacerbates cisplatin-induced kidney injury. Levels of acute kidney injury were comparable in 8- and 40-wk-old mice. In 40-wk-old mice, fibrotic markers were elevated basally, but treatment with cisplatin did not exacerbate fibrosis. We concluded that this may be the result of a decreased inflammatory response in 40-wk-old cisplatin-treated mice compared with 8-wk-old mice. Despite a decreased inflammatory response, the level of immune cell infiltration was greater in 40-wk-old cisplatin-treated mice than 8-wk-old mice. Our data highlight the importance of examining age as a risk factor for cisplatin-induced kidney injury.

Cisplatin-Induced Rodent Model of Kidney Injury: Characteristics and Challenges

Cisplatin is an antitumor drug used in the treatment of a wide variety of malignancies. However, its primary dose-limiting side effect is kidney injury, which is a major clinical concern. To help understand mechanisms involved in the development of kidney injury, cisplatin rodent model has been developed. Given the complex pathogenesis of kidney injury, which involves both local events in the kidney and interconnected and interdependent systemic effects in the body, cisplatin rodent model is indispensable in the investigation of underlying mechanisms and potential treatment strategies of both acute and chronic kidney injury. Cisplatin rodent model is well appreciated and widely used model due to its simplicity. It has many similarities to human cisplatin nephrotoxicity, which are mentioned in the paper. In spite of its simplicity and wide applicability, there are also traps that need to be taken into account when using cisplatin model. The present paper is aimed at giving a concise insight into the complex characteristics of cisplatin rodent model and heterogeneity of cisplatin dosage regimens as well as outlining factors that can severely influence the outcome of the model and the study. Challenges for future research are also mentioned.

Cisplatin Effects in Lung Adenocarcinoma-bearing Mice, Alone and in Combination with Erlotinib

Cisplatin causes nephrotoxicity that can lead to the development of acute kidney injury or chronic kidney disease. However, the current mouse model of cisplatin nephrotoxicity is neither physiologically nor clinically relevant. Our goal was to improve upon these deficits by developing a repeated, low-dose regimen of cisplatin and combining it with a transgenic mouse model of lung adenocarcinoma. This overview details how addressing these deficits have improved our understanding of cisplatin-induced kidney injury.

Association of Urinary Biomarkers of Kidney Injury with Estimated GFR Decline in HIV-Infected Individuals following Tenofovir Disoproxil Fumarate Initiation

BACKGROUND AND OBJECTIVES

Tenofovir disoproxil fumarate (tenofovir) is associated with elevated concentrations of biomarkers of kidney damage and dysfunction in individuals with HIV. The relationship of these kidney biomarkers with longitudinal kidney function decline is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated associations of 14 urinary biomarkers of kidney injury with changes in eGFR among 198 men and women with HIV who initiated tenofovir between 2009 and 2015 in the Multicenter AIDS Cohort Study and Women's Interagency HIV Study. Urinary biomarkers included albumin-to-creatinine ratio, α-1-microglobulin, β-2-microglobulin, cystatin C, kidney injury molecule-1 (KIM-1), IL-18, neutrophil gelatinase-associated lipocalin (NGAL), clusterin, osteopontin, uromodulin, monocyte chemoattractant protein-1, EGF, trefoil factor 3, and chitinase 3-like protein 1. We used multivariable linear mixed-effect models controlling for demographics, traditional kidney disease risk factors, and HIV-related risk factors to evaluate associations of baseline biomarkers with first-year changes in eGFR, and associations of year 1 and first-year change in biomarkers with changes in eGFR from year 1 to year 3. We used the least absolute shrinkage and selection operator method to identify a parsimonious set of biomarkers jointly associated with changes in eGFR.

RESULTS

Median eGFR before tenofovir initiation was 103 (interquartile range, 88-116) ml/min per 1.73 m2. During the first year of tenofovir use, eGFR decreased on average by 9.2 (95% confidence interval, 6.5 to 11.9) ml/min per 1.73 m2 and was stable afterward (decrease of 0.62; 95% confidence interval, -0.85 to 2.1 ml/min per 1.73 m2 per year). After multivariable adjustment, higher baseline β-2-microglobulin, KIM-1, and clusterin were associated with larger first-year eGFR declines, whereas higher baseline uromodulin was associated with a smaller eGFR decline. First-year increase in urinary cystatin C and higher year 1 IL-18 were associated with larger annual eGFR declines from year 1 to year 3. The parsimonious models identified higher pre-tenofovir clusterin and KIM-1, lower pre-tenofovir uromodulin, and higher year 1 IL-18 as jointly associated with larger eGFR declines.

CONCLUSIONS

Urinary biomarkers of kidney injury measured before and after tenofovir initiation are associated with subsequent changes in eGFR in individuals with HIV.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_08_28_CJASNPodcast_18_9_S.mp3.

Cisplatin nephrotoxicity as a model of chronic kidney disease

Cisplatin (CP)-induced nephrotoxicity is widely accepted as a model for acute kidney injury (AKI). Although cisplatin-induced chronic kidney disease (CKD) in rodent has been reported, the role of phosphate in the cisplatin-induced CKD progression is not described. In this study, we gave a single peritoneal injection of CP followed by high (2%) phosphate diet for 20 weeks. High dose CP (20 mg/Kg) led to high mortality; whereas a lower dose (10 mg/Kg) resulted in a full spectrum of AKI with tubular necrosis, azotemia, and 0% mortality 7 days after CP injection. After consuming a high phosphate diet, mice developed CKD characterized by low creatinine clearance, interstitial fibrosis, hyperphosphatemia, high plasma PTH and FGF23, low plasma 1,25(OH)₂ Vitamin D₃ and αKlotho, and classic uremic cardiovasculopathy. The CP model was robust in demonstrating the effect of aging, sexual dimorphism, and dietary phosphate on AKI and also AKI-to-CKD progression. Finally, we used the CP-high phosphate model to examine previously validated methods of genetically manipulated high αKlotho and therapy using exogenous soluble αKlotho protein supplementation. In this CP CKD model, αKlotho mitigated CKD progression, improved mineral homeostasis, and ameliorated cardiovascular disease. Taken together, CP and high phosphate nephrotoxicity is a reproducible and technically very simple model for the study of AKI, AKI-to-CKD progression, extrarenal complications of CKD, and for evaluation of therapeutic efficacy.

Restoration of E-cadherin by PPBICA protects against cisplatin-induced acute kidney injury by attenuating inflammation and programmed cell death

E-cadherin is a major component of tubular adherent proteins that maintain intercellular contacts and cell polarity in epithelial tissue. It is involved in pathological processes of renal cell carcinoma and fibrotic diseases via epithelial-mesenchymal transition. Although studies have shown E-cadherin is significantly downregulated in acute kidney injury (AKI), its function in AKI is unknown. Here, we evaluated cell damage and inflammation in cisplatin-stimulated tubular epithelial cell lines after disrupting E-cadherin and restoring it with PPBICA, a small molecule identified by high-throughput screening. We also determined the therapeutic potential of restoring E-cadherin in vivo. Results show cisplatin reduced E-cadherin expression both in mouse kidney and proximal tubular epithelial cell lines (mTECs). PPBICA restored E-cadherin levels, which increased cell viability while attenuating programmed cell death. This may be mediated via deactivation of the RIPK1/RIPK3 axis and decreased caspase3 cleavage. In addition, PPBICA suppressed inflammatory response in cisplatin-treated mTECs, which correlated with suppressed NF-κB phosphorylation and promoter activity. In contrast, disruption of E-cadherin promoted cell damage and inflammation. PPBICA failed to further attenuate kidney damage in E-cadherin knockdown cells, indicating that PPBICA protects against mTECs through E-cadherin restoration. We also found that peritoneal injection of PPBICA in mice prevented loss of renal function and tubular damage by suppressing NF-κB-driven renal inflammation and RIPK-regulated programmed cell death. This was driven by restoration of E-cadherin in cisplatin nephropathy. Additionally, PPBICA attenuated cisplatin-induced kidney damage in an established AKI model, indicating its therapeutic potential in the treatment of AKI. In conclusion, E-cadherin plays functional roles in tubule integrity, programmed cell death, and renal inflammation. Our results underscore the potential of E-cadherin restoration as a novel therapeutic strategy for AKI.

Rodent models of AKI-CKD transition

Acute kidney injury (AKI) is a contributing factor in the development and progression of chronic kidney disease (CKD). Despite rapid progresses, the mechanism underlying AKI-CKD transition remains largely unclear. Animal models recapitulating this process are crucial to the research of the pathophysiology of AKI-CKD transition and the development of effective therapeutics. In this review, we present the commonly used rodent models of AKI-CKD transition, including bilateral ischemia-reperfusion injury (IRI), unilateral IRI, unilateral IRI with contralateral nephrectomy, multiple episodes of IRI, and repeated treatment of low-dose cisplatin, diphtheria toxin, aristolochic acid, or folic acid. The main merits and pitfalls of these models are also discussed. This review provides helpful information for establishing reliable and clinically relevant models for studying post-AKI development of chronic renal pathologies and the progression to CKD.

Stem/Stromal Cells for Treatment of Kidney Injuries With Focus on Preclinical Models

Within the last years, the use of stem cells (embryonic, induced pluripotent stem cells, or hematopoietic stem cells), Progenitor cells (e.g., endothelial progenitor cells), and most intensely mesenchymal stromal cells (MSC) has emerged as a promising cell-based therapy for several diseases including nephropathy. For patients with end-stage renal disease (ESRD), dialysis or finally organ transplantation are the only therapeutic modalities available. Since ESRD is associated with a high healthcare expenditure, MSC therapy represents an innovative approach. In a variety of preclinical and clinical studies, MSC have shown to exert renoprotective properties, mediated mainly by paracrine effects, immunomodulation, regulation of inflammation, secretion of several trophic factors, and possibly differentiation to renal precursors. However, studies are highly diverse; thus, knowledge is still limited regarding the exact mode of action, source of MSC in comparison to other stem cell types, administration route and dose, tracking of cells and documentation of therapeutic efficacy by new imaging techniques and tissue visualization. The aim of this review is to provide a summary of published studies of stem cell therapy in acute and chronic kidney injury, diabetic nephropathy, polycystic kidney disease, and kidney transplantation. Preclinical studies with allogeneic or xenogeneic cell therapy were first addressed, followed by a summary of clinical trials carried out with autologous or allogeneic hMSC. Studies were analyzed with respect to source of cell type, mechanism of action etc.

Divergent effects of AKI to CKD models on inflammation and fibrosis

Chronic kidney disease (CKD) is a condition with significant morbidity and mortality that affects 15% of adults in the United States. One cause of CKD is acute kidney injury (AKI), which commonly occurs secondary to sepsis, ischemic events, and drug-induced nephrotoxicity. Unilateral ischemia-reperfusion injury (UIRI) without contralateral nephrectomy (CLN) and repeated low-dose cisplatin (RLDC) models of AKI to CKD demonstrate responses characteristic of the transition; however, previous studies have not effectively compared the pathogenesis. We demonstrate both models instigate renal dysfunction, inflammatory cytokine responses, and fibrosis. However, the models exhibit differences in urinary excretory function, inflammatory cell infiltration, and degree of fibrotic response. UIRI without CLN demonstrated worsening perfusion and function, measured with ^99mTc-mercaptoacetyltriglycine-3 imaging, and physiologic compensation in the contralateral kidney. Furthermore, UIRI without CLN elicited a robust inflammatory response that was characterized by a prolonged polymorphonuclear cell and natural killer cell infiltrate and an early expansion of kidney resident macrophages, followed by T-cell infiltration. Symmetrical diminished function occurred in RLDC kidneys and progressively worsened until day 17 of the study. Surprisingly, RLDC mice demonstrated a decrease in inflammatory cell numbers relative to controls. However, RLDC kidneys expressed increased levels of kidney injury molecule-1 (KIM-1), high mobility group box-1 ( HMGB1), and colony stimulating factor-1 ( CSF-1), which likely recruits inflammatory cells in response to injury. These data emphasize how the divergent etiologies of AKI to CKD models affect the kidney microenvironment and outcomes. This study provides support for subtyping AKI by etiology in human studies, aiding in the elucidation of injury-specific pathophysiologic mechanisms of the AKI to CKD transition.

Protective Effect of D-Methionine on Body Weight Loss, Anorexia, and Nephrotoxicity in Cisplatin-Induced Chronic Toxicity in Rats

D-methionine is a sulfur-containing amino acid that can act as a potent antioxidant. Anorexia and nephrotoxicity are side effects of cisplatin. The protective effects of D-methionine on cisplatin-induced anorexia and renal injury were investigated. The model of chronic cisplatin administration (5 mg/kg body weight) involved intraperitoneal injection on days 1, 8, and 15 and oral D-methionine (300 mg/kg body weight) coadministration daily for 20 days. On the 21st day of treatment, food intake and body weight in the cisplatin-treated group significantly decreased by 52% and 31%, respectively, when compared with a control group. D-methionine coadministration with cisplatin decreased food intake and body weight by 29% and 8%, respectively. In cisplatin-treated rats, white blood cell, mean corpuscular volume, and platelet values significantly decreased, while mean corpuscular hemoglobin concentration significantly increased by 8.6% when compared with control rats. Cisplatin administration resulted in significantly decreased feeding efficiency, elevated renal oxidative stress, and reduced antioxidative activity. Leukocyte infiltration, tubule vacuolization, tubular expansion, and swelling were observed in the kidneys of cisplatin-treated rats. Oral D-methionine exhibited an antianorexic effect, with improvement in food intake, feeding efficiency, and hematological toxicities, as well as a protective effect against nephrotoxicity by elevated antioxidative activity. D-methionine may serve as a chemoprotectant in patients receiving cisplatin as part of a chemotherapy regimen.

Subclinical kidney injury induced by repeated cisplatin administration results in progressive chronic kidney disease

Cisplatin is used to treat many solid cancers, but its dose-limiting side effect is nephrotoxicity, causing acute kidney injury in 30% of patients. Previously, we have developed a mouse model that better recapitulates the cisplatin dosing regimen humans receive and found that repeated dosing of cisplatin induces interstitial renal fibrosis. Chronic kidney disease is progressive and is characterized by chronic inflammation, worsening interstitial fibrosis, development of glomerulosclerosis, and endothelial dysfunction. To determine if damage caused by repeated cisplatin dosing results in bona fide chronic kidney disease, mice were treated with our repeated dosing regimen and then aged for 6 mo. These mice had progressive, chronic inflammation and worsened interstitial fibrosis compared with mice euthanized after day 24. Mice aged for 6 mo developed glomerular pathologies, and endothelial dysfunction was persistent. Mice treated with only two doses of cisplatin had little inflammation or kidney damage. Thus repeated dosing of cisplatin causes long-term effects that are characteristic of chronic kidney disease. This translational mouse model of cisplatin injury may better represent the 70% of patients that do not develop clinical acute kidney injury and can be used to identify both biomarkers for early injury, as well as novel therapeutic targets for the prevention of cisplatin-induced chronic kidney disease.

FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury

Cisplatin, a widely used cancer therapy drug, induces nephrotoxicity or acute kidney injury (AKI), but the underlying mechanism remains unclear, and renal protective approaches are not available. Fibroblast growth factor (FGF)21 is an endocrine factor that regulates glucose uptake, metabolism, and energy expenditure. However, recent work has also implicated FGF21 in cellular stress response under pathogenic conditions. The role and regulation of FGF21 in AKI are unclear. Here, we show that FGF21 was dramatically induced during cisplatin treatment of renal tubular cells in vitro and mouse kidneys in vivo. The inductive response was suppressed by pifithrin (a pharmacological inhibitor of P53), suggesting a role of P53 in FGF21 induction. In cultured renal tubular cells, knockdown of FGF21 aggravated cisplatin-induced apoptosis, whereas supplementation of recombinant FGF21 was protective. Consistently, recombinant FGF21 alleviated cisplatin-induced kidney dysfunction, tissue damage, and tubular apoptosis in mice. Mechanistically, FGF21 suppressed P53 induction and activation during cisplatin treatment. Together, these results indicate that FGF21 is induced during cisplatin nephrotoxicity to protect renal tubules, and recombinant FGF21 may have therapeutic potential.-Li, F., Liu, Z., Tang, C., Cai, J., Dong, Z. FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury.

Developing better mouse models to study cisplatin-induced kidney injury

Cisplatin is a potent chemotherapeutic used for the treatment of many types of cancer. However, its dose-limiting side effect is nephrotoxicity leading to acute kidney injury (AKI). Patients who develop AKI have an increased risk of mortality and are more likely to develop chronic kidney disease (CKD). Unfortunately, there are no therapeutic interventions for the treatment of AKI. It has been suggested that the lack of therapies is due in part to the fact that the established mouse model used to study cisplatin-induced AKI does not recapitulate the cisplatin dosing regimen patients receive. In recent years, work has been done to develop more clinically relevant models of cisplatin-induced kidney injury, with much work focusing on incorporation of multiple low doses of cisplatin administered over a period of weeks. These models can be used to recapitulate the development of CKD after AKI and, by doing so, increase the likelihood of identifying novel therapeutic targets for the treatment of cisplatin-induced kidney injury.

Bridging translation for acute kidney injury with better preclinical modeling of human disease

The current lack of effective therapeutics for patients with acute kidney injury (AKI) represents an important and unmet medical need. Given the importance of the clinical problem, it is time for us to take a few steps back and reexamine current practices. The focus of this review is to explore the extent to which failure of therapeutic translation from animal studies to human studies stems from deficiencies in the preclinical models of AKI. We will evaluate whether the preclinical models of AKI that are commonly used recapitulate the known pathophysiologies of AKI that are being modeled in humans, focusing on four common scenarios that are studied in clinical therapeutic intervention trials: cardiac surgery-induced AKI; contrast-induced AKI; cisplatin-induced AKI; and sepsis associated AKI. Based on our observations, we have identified a number of common limitations in current preclinical modeling of AKI that could be addressed. In the long term, we suggest that progress in developing better preclinical models of AKI will depend on developing a better understanding of human AKI. To this this end, we suggest that there is a need to develop greater in-depth molecular analyses of kidney biopsy tissues coupled with improved clinical and molecular classification of patients with AKI.