Multicenter clinical trial of recombinant human insulin-like growth factor I in patients with acute renal failure

The role of IGFBP-1 in the clinical prognosis and pathophysiology of acute kidney injury

The ability to predict progression to severe acute kidney injury (AKI) remains an unmet challenge. Contributing to the inability to predict the course of AKI is a void of understanding of the pathophysiological mechanisms of AKI. The identification of novel prognostic biomarkers could both predict patient outcomes and unravel the molecular mechanisms of AKI. We performed a multicenter retrospective observational study from a cohort of patients following cardiac surgery. We identified novel urinary prognostic biomarkers of severe AKI among subjects with early AKI. Of 2,065 proteins identified in the discovery cohort, insulin-like growth factor binding protein 1 (IGFBP-1) was the most promising. We validated IGFBP-1 as a prognostic biomarker of AKI in 213 patients. In addition, we investigated its role in the pathophysiology of AKI using a murine model of cisplatin-induced AKI (CIAKI). Urinary IGFBP-1 concentration in samples collected from patients with stage 1 AKI following cardiothoracic surgery was significantly higher in patients who progressed to severe AKI compared with patients who did not progress beyond stage 1 AKI (40.28 ng/ml vs. 2.8 ng/ml, P < 0.0001) and predicted the progression to the composite outcome (area under the curve: 0.85, P < 0.0001). IGFBP-1 knockout mice showed less renal injury, cell death, and apoptosis following CIAKI, possibly through increased activation of the insulin growth factor receptor 1. IGFBP-1 is a clinical prognostic biomarker of AKI and a direct mediator of the pathophysiology of AKI. Therapies that target the IGFBP-1 pathways may help alleviate the severity of AKI.NEW & NOTEWORTHY The ability to predict progression to severe AKI remains an unmet challenge. Early prognostic biomarkers of AKI hold promise to improve patient outcomes by early implementation of clinical therapy, as well as unravel the pathophysiological mechanisms of AKI. Here, we present a novel urinary biomarker, IGFBP-1, that predicts the progression to severe AKI following cardiac surgery. In addition, we show that IGFBP-1 mice are protected against CIAKI, suggesting a mechanistic role for IGFBP-1 in AKI.

Impaired microvascular circulation in distant organs following renal ischemia

Mortality in acute kidney injury (AKI) patients remains very high, although very important advances in understanding the pathophysiology and in diagnosis and supportive care have been made. Most commonly, adverse outcomes are related to extra-renal organ dysfunction and failure. We and others have documented inflammation in remote organs as well as microvascular dysfunction in the kidney after renal ischemia. We hypothesized that abnormal microvascular flow in AKI extends to distant organs. To test this hypothesis, we employed intravital multiphoton fluorescence imaging in a well-characterized rat model of renal ischemia/reperfusion. Marked abnormalities in microvascular flow were seen in every organ evaluated, with decreases up to 46% observed 48 hours postischemia (as compared to sham surgery, p = 0.002). Decreased microvascular plasma flow was found in areas of erythrocyte aggregation and leukocyte adherence to endothelia. Intravital microscopy allowed the characterization of the erythrocyte formations as rouleaux that flowed as one-dimensional aggregates. Observed microvascular abnormalities were associated with significantly elevated fibrinogen levels. Plasma flow within capillaries as well as microthrombi, but not adherent leukocytes, were significantly improved by treatment with the platelet aggregation inhibitor dipyridamole. These microvascular defects may, in part, explain known distant organ dysfunction associated with renal ischemia. The results of these studies are relevant to human acute kidney injury.

Urine metabolites for preoperative prediction of acute kidney injury after coronary artery bypass graft surgery

OBJECTIVE

Acute kidney injury is a common complication after on-pump coronary artery bypass grafting. Prediction of acute kidney injury remains a challenge. Our study aims to identify a panel of urine metabolites for preoperative warning of acute kidney injury after on-pump coronary artery bypass grafting.

METHODS

A total of 159 patients undergoing isolated on-pump coronary artery bypass grafting were enrolled from July 7, 2017, to May 17, 2019. Preoperative urine samples were analyzed with the approach of liquid chromatography-mass spectrometry-based urine metabolomics. The study end point was the episode of acute kidney injury within 48 hours postoperatively. The predictive performance was determined by the area under the curve and calibration curve. The results were validated using bootstrap resampling.

RESULTS

The acute kidney injury (n = 55) and nonacute kidney injury (n = 104) groups showed significant different metabolic profiling. A total of 28 metabolites showed significant differences between the acute kidney injury and nonacute kidney injury groups. A metabolite panel of 5 metabolites (tyrosyl-gamma-glutamate, deoxycholic acid glycine conjugate, 5-acetylamino-6-amino-3-methyluracil, arginyl-arginine, and L-methionine) was discovered to have a good predicting performance (area under the curve, 0.89; 95% confidence interval, 0.82-0.93), which is higher than the clinical factor-based model (area under the curve, 0.63; 95% confidence interval, 0.53-0.72). Internal validation by bootstrap resampling showed an adjusted area under the curve of 0.88, and the calibration curve demonstrated good agreement between prediction and observation in the probability of postoperative acute kidney injury. Decision curve analysis revealed a superior net benefit of the metabolite model over the traditional clinical factor-based model.

CONCLUSIONS

We present 5 urine metabolites related to acute kidney injury after coronary artery bypass grafting. This metabolite model may serve as a preoperative warning of acute kidney injury after on-pump coronary artery bypass grafting.

Cardiac effects of renal ischemia

Mortality in acute kidney injury (AKI) remains very high, yet the cause of death is often failure of extrarenal organs. We and others have demonstrated remote organ dysfunction after renal ischemia. The term "cardiorenal syndrome" was first applied to the "cross talk" between the organs by the National Heart, Lung, and Blood Institute of the National Institutes of Health, and the clinical importance is being increasingly appreciated. Nevertheless, more information is needed to effectively address the consequences of renal injury on the heart. Since AKI often occurs in patients with comorbidities, we investigated the effect of renal ischemia in the setting of existing cardiac failure. We hypothesized that the cardiac effects of renal ischemia would be significantly amplified in experimental cardiomyopathy. Male Sprague-Dawley rats with preexisting cardiac and renal injury due to low-dose doxorubicin were subjected to bilateral renal artery occlusion. Cardiac structure and function were examined 2 days after reperfusion. Loss of functional myocardial tissue with decreases in left ventricular pressure, increases in apoptotic cell death, inflammation, and collagen, and greater disruption in ultrastructure with mitochondrial fragmentation were seen in the doxorubicin/ischemia group compared with animals in the groups treated with doxorubicin alone or following ischemia alone. Systemic inflammation and cardiac abnormalities persisted for at least 21 wk. These results suggest that preexisting comorbidities can result in much more severe distant organ effects of acute renal injury. The results of this study are relevant to human AKI.NEW & NOTEWORTHY Acute kidney injury is common, expensive, and deadly, yet morbidity and mortality are often secondary to remote organ dysfunction. We hypothesized that the effects of renal ischemia would be amplified in the setting of comorbidities. Sustained systemic inflammation and loss of functional myocardium with significantly decreased systolic and diastolic function, apoptotic cell death, and increased collagen and inflammatory cells were found in the heart after renal ischemia in the doxorubicin cardiomyopathy model (vs. renal ischemia alone). Understanding the remote effects of renal ischemia has the potential to improve outcomes in acute kidney injury.

A Process for the Design and Development of Novel Bone Morphogenetic Protein-7 (BMP-7) Mimetics With an Example: THR-184

Growth Factors have been evaluated as therapeutic targets for the treatment of a broad spectrum of diseases. Because they are proteins with pleiotropic effects, the quest to harness their beneficial effects has presented challenges. Most Growth Factors operate at the extracellular-receptor level and have natural feedback mechanisms that modulate their effects. As proteins, they are difficult and expensive to manufacture. Frequently proteins must be administered parenterally, may invoke an immune response, and may be neutralized by naturally occurring inhibitors. To circumvent these limitations, we have undertaken an effort to develop mimetics for the Bone Morphogenetic Protein (BMP) signaling pathway effects that incorporate the beneficial effects, eliminate the deleterious effects, and thereby create effective drug-like compounds.To this end, we have designed and tested a family of small peptide BMP mimetics. The design used the three-dimensional structure of BMP-7 to identify likely active surface regions. Lead sequences were then optimized based on in vitro assays that examine the selective binding to BMP receptors, demonstrate the phosphorylation of Smad-1,5,8, detect anti-apoptosis and anti-inflammation, and block the epithelial to mesenchymal transition (EMT) in renal tubular epithelial cells. These sequences were further optimized using in vivo assays of the attenuation of acute kidney injury in a rat-model of unilateral clamp ischemic reperfusion. This process uses a Structure Variance Analysis algorithm (SVA) to identify structure/activity relationships. One member of this family, THR-184, is an agonist of BMP signaling and a potent antagonist of TGFβ signaling. This small peptide mimetic inhibits inflammation, apoptosis, fibrosis and reverses epithelial to mesenchymal transition (EMT) by regulating multiple signaling pathways involved in the cellular injury of multiple organs. Its effects have been shown to control Acute Kidney Injury (AKI). THR-184 has progressed through phase I and II clinical trials for the prevention of Cardio-Vascular Surgery (CVS) associated AKI. This work provides a roadmap for the development of other growth factor mimetics and demonstrates how we might harness their therapeutic potential.

[Therapeutics for acute tubular necrosis in 2020]

Acute kidney injury is a major cause of in-hospital morbidity and mortality because of the serious nature of the underlying illnesses and the high incidence of complications. The two major causes of acute kidney injury that occur in the hospital are prerenal disease and acute tubular necrosis. Acute tubular necrosis has a histological definition, even if a kidney biopsy is rarely performed. Kidney injuries occurring during acute tubular necrosis are underlined by different pathophysiological mechanisms that emphasize the role of hypoxia on the tubular cells such as apoptosis, cytoskeleton disruption, mitochondrial function and the inflammation mediated by innate immune cells. The microcirculation and the endothelial cells are also the targets of hypoxia-mediated impairment. Repair mechanisms are sometimes inadequate because of pro-fibrotic factors that will lead to chronic kidney disease. Despite all the potential therapeutic targets highlighted by the pathophysiological knowledge, further works remain necessary to find a way to prevent these injuries.

Current Status of Novel Biomarkers for the Diagnosis of Acute Kidney Injury: A Historical Perspective

Acute kidney injury (AKI) is a common and serious medical condition associated with significant increases in morbidity, mortality, and cost of care. Because of the high incidence and poor outcomes associated with AKI, there has been significant interest in the development of new therapies for the prevention and treatment of the disease. A lack of efficacy in drug trials led to the concern that AKI was not being diagnosed early enough for an effective intervention and that a rise in serum creatinine itself is not a sensitive-enough marker. Researchers have been searching for novel biomarkers that can not only assess a decline in kidney function but also demonstrate structural damage to the kidney and at time points earlier than increases in serum creatinine measurements allow. Over the past 10 years, there have been 3300 new publications and hundreds of new biomarkers investigated, yet concern still remains regarding AKI biomarker performance. The AKI biomarkers are yet to be widely utilized in clinical practice, leading some to question whether AKI biomarkers will ever reach their initial promise. However, we believe that biomarkers are an important part of current and future AKI research and clinical management. In this review, we compare the historical contexts of acute myocardial ischemia and AKI biomarker development to illustrate the progress that has been made within AKI biomarker research in a relatively short period of time and also to point out key differences between the disease processes that have been barriers to widespread AKI biomarker adoption. Finally, we discuss potential paths by which biomarkers can lead to appropriate AKI treatment responses that lower morbidity and mortality.

Potential targeted therapy and diagnosis based on novel insight into growth factors, receptors, and downstream effectors in acute kidney injury and acute kidney injury-chronic kidney disease progression

Acute kidney injury (AKI) is defined as a rapid decline in renal function and is characterized by excessive renal inflammation and programmed death of resident cells. AKI shows high morbidity and mortality, and severe or repeated AKI can transition to chronic kidney disease (CKD) or even end-stage renal disease (ESRD); however, very few effective and specific therapies are available, except for supportive treatment. Growth factors, such as epidermal growth factor (EGF), insulin-like growth factor (IGF), and transforming growth factor-β (TGF-β), are significantly altered in AKI models and have been suggested to play critical roles in the repair process of AKI because of their roles in cell regeneration and renal repair. In recent years, a series of studies have shown evidence that growth factors, receptors, and downstream effectors may be highly involved in the mechanism of AKI and may function in the early stage of AKI in response to stimuli by regulating inflammation and programmed cell death. Moreover, certain growth factors or correlated proteins act as biomarkers for AKI due to their sensitivity and specificity. Furthermore, growth factors originating from mesenchymal stem cells (MSCs) via paracrine signaling or extracellular vesicles recruit leukocytes or repair intrinsic cells and may participate in AKI repair or the AKI-CKD transition. In addition, growth factor-modified MSCs show superior therapeutic potential compared to that of unmodified controls. In this review, we summarized the current therapeutic and diagnostic strategies targeting growth factors to treat AKI in clinical trials. We also evaluated the possibilities of other growth factor-correlated molecules as therapeutic targets in the treatment of AKI and the AKI-CKD transition.

Prediction Efficiency of Postoperative Acute Kidney Injury in Acute Stanford Type A Aortic Dissection Patients with Renal Resistive Index and Semiquantitative Color Doppler

Objectives

This study is aimed to evaluate the efficiency in early prediction of postoperative persistent acute kidney injury (PAKI) after surgery in acute Stanford type A aortic dissection (AAAD) patients by using Doppler renal resistive index (RRI) and semiquantitative color (SQC) Doppler grade, respectively.

Methods

84 AAAD patients received Sun's surgical management, and 67 patients were enrolled. RRI and SQC Doppler grade were evaluated by ultrasonography, respectively, at 6 hours after surgery. Serum creatinine (sCr) was recorded before operation and at 24 hours, 48 hours, and 72 hours after operation. AKI grade was evaluated according to the classifications of the Acute Kidney Injury Network (AKIN). PAKI is defined as persistent oliguria and/or sCr elevation after 3 days. RRI and SQC Doppler grade were compared, respectively, between the PAKI and non-PAKI groups. Potential predictors were first tested by univariate logistic regression analysis, and a multivariate model was identified to determine the independent predictive ability of RRI and SQC Doppler grade for the PAKI. Receiver operating characteristic (ROC) analysis was performed to compare the diagnostic accuracy between RRI and SQC Doppler grade in early prediction of PAKI by using AKIN classifications as the reference standard.

Results

Of a total of 67 patients enrolled during the study period, 21 (31.3%) patients suffered from PAKI and 8 (11.9%) patients required dialysis. There are significant differences in RRI (0.80 ± 0.09 vs. 0.70 ± 0.05, P=0.002) and SQC Doppler grade (x²=12.193, P=0.007) between the 2 groups with and without PAKI. Univariate analysis showed that RRI, SQC Doppler grade, length of stay in ICU, time of CPB, and length of stay in hospital were significant predictors of PAKI. RRI and the SQC Doppler grade remained independent predictors of PAKI. Area under the curve (AUC) of RRI was 0.855 (95% CI, 0.74–0.96) with cutoff value 0.725 (sensitivity 90.9% and specificity 71.1%), AUC of SQC Doppler grade was 0.642 (95% CI, 0.49–0.79) with cutoff value grade 2 (sensitivity 50% and specificity 73.3%).

Conclusion

Both postoperative RRI and SQC Doppler grade are independent predictors for PAKI after surgery in AAAD patients. Both postoperative RRI and SQC Doppler grade can be obtained rapidly by bedside ultrasound, which is a good tool for early prediction for postoperative PAKI.

Hepcidin - Potential biomarker of contrast-induced acute kidney injury in patients undergoing percutaneous coronary interventions

PURPOSE

Contrast-induced acute kidney injury (CI-AKI) is a common and potentially serious complication of percutaneous coronary interventions (PCI). In this study, we tested the hypothesis whether serum and urinary hepcidin could represent early biomarkers of CI-AKI in patients with normal serum creatinine undergoing PCI. In addition, we assessed serum and urinary neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, eGFR and serum creatinine in these patients.

METHODS

Serum and urinary hepcidin and NGAL, serum cystatin C, were evaluated before, and after 2, 4, 8, 24 and 48 h after PCI using commercially available kits. Serum creatinine was assessed before, 24 and 48 h after PCI.

RESULTS

We found a significant rise in serum hepcidin as early as after 4 and 8 h when compared to the baseline values. Serum NGAL increased after 2, 4 and 8 h, and in urinary NGAL after 4, 8 and 24 h after PCI. We found a significant fall in urinary hepcidin after 8 and 24 h after PCI. Serum cystatin C increased significantly 8 h after PCI, reaching peak 24 h after PCI and then decreased after 48 h. The prevalence of CI-AKI was 8%. Urine hepcidin was significantly lower 8 and 24 h after PCI in patients with CI-AKI, while serum and urine NGAL were significantly higher in patients with CI-AKI.

CONCLUSIONS

Our findings suggest that serum hepcidin might be an early predictive biomarker of ruling out CI-AKI after PCI, thereby contributing to early patient risk stratification. However, our data needs to be validated in large cohorts with various stages of CKD.

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.

Renal regeneration after acute kidney injury

Acute kidney injury is common and associated with negative renal and patient outcomes. The human kidney has a real but limited regeneration capacity. Understanding renal regeneration may allow us to manipulate this process and thus develop therapeutic weapons to improve patients' outcome. In the first part of this paper we discuss the clinical factors associated with renal recovery: baseline patient particularities, acute kidney injury characteristics and the medical approach taken in the short and long-term. In the second part, the cellular and molecular mechanisms underlying renal regeneration are explored. The immune system seems to have an important role, first promoting inflammation and then tissue healing. Other players, such as cellular senescence, mitochondrial dysfunction, renal haemodynamics and metabolic reprogramming also have a role in renal regeneration. We aim to develop a short review of renal regeneration, offering a holistic view of this process.

Goal-directed therapy in patients with early acute kidney injury: a multicenter randomized controlled trial

OBJECTIVES

Acute kidney injury is associated with many conditions, and no interventions to improve the outcomes of established acute kidney injury have been developed. We performed this study to determine whether goal-directed therapy conducted during the early stages of acute kidney injury could change the course of the disease.

METHODS

This was a multicenter prospective randomized controlled study. Patients with early acute kidney injury in the critical care unit were randomly allocated to a standard care (control) group or a goal-directed therapy group with 8h of intensive treatment to maximize oxygen delivery, and all patients were evaluated during a period of 72h. ClinicalTrials.gov: NCT02414906.

RESULTS

A total of 143 patients were eligible for the study, and 99 patients were randomized. Central venous oxygen saturation was significantly increased and the serum lactate level significantly was decreased from baseline levels in the goal-directed therapy group (p=0.001) compared to the control group (p=0.572). No significant differences in the change in serum creatinine level (p=0.96), persistence of acute kidney injury beyond 72h (p=0.064) or the need for renal replacement therapy (p=0.82) were observed between the two groups. In-hospital mortality was significantly lower in the goal-directed therapy group than in the control group (33% vs. 51%; RR: 0.61, 95% CI: 0.37-1.00, p=0.048, number needed to treat=5).

CONCLUSIONS

Goal-directed therapy for patients in the early stages of acute kidney injury did not change the disease course.

Treatment of Patients with Cardiac Surgery Associated-Acute Kidney Injury

Members of the Acute Dialysis Quality Initiative (ADQI) participated in a 3-day conference in Vicenza in May 2007 to evaluate the available literature on this topic and draft consensus recommendations for research studies in this area. This report summarizes the available evidence and describes the key questions that will need to be addressed with the goal of standardizing the care of patients with cardiac surgery-associated acute kidney injury (CSA-AKI) and improving outcomes.

Angiotensinogen as a biomarker of acute kidney injury

Early recognition of acute kidney injury (AKI) is critical to prevent its associated complications as well as its progression to long term adverse outcomes like chronic kidney disease. A growing body of evidence from both laboratory and clinical studies suggests that inflammation is a key factor contributing to the progression of AKI regardless of the initiating event. Biomarkers of inflammation are therefore of interest in the evaluation of AKI pathogenesis and prognosis. There is evidence that the renin angiotensin aldosterone system is activated in AKI, which leads to an increase in angiotensin II (Ang II) formation within the kidney. Ang II activates pro-inflammatory and pro-fibrotic pathways that likely contribute to the progression of AKI. Angiotensinogen is the parent polypeptide from which angiotensin peptides are formed and its stability in urine makes it a more convenient marker of renin angiotensin system activity than direct measurement of Ang II in urine specimens, which would provide more direct information. The potential utility of urinary angiotensinogen as a biomarker of AKI is discussed in light of emerging data showing a strong predictive value of AKI progression, particularly in the setting of decompensated heart failure. The prognostic significance of urinary angiotensinogen as an AKI biomarker strongly suggests a role for renin-angiotensin system activation in modulating the severity of AKI and its outcomes.

Use of a Targeted Urine Proteome Assay (TUPA) to identify protein biomarkers of delayed recovery after kidney transplant

PURPOSE

Development of delayed graft function (DGF) following kidney transplant is associated with poor outcomes. An ability to rapidly identify patients with DGF versus those with immediate graft function (IGF) may facilitate the treatment of DGF and the research needed to improve prognosis. The purpose of this study was to use a Targeted Urine Proteome Assay to identify protein biomarkers of delayed recovery from kidney transplant.

EXPERIMENTAL DESIGN

Potential biomarkers were identified using the Targeted Urine Proteome (MRM) Assay to interrogate the relative DGF/IGF levels of expression of 167 proteins in urine taken 12-18 h after kidney implantation from 21 DGF, 15 SGF (slow graft function), and 16 IGF patients. An iterative Random Forest analysis approach evaluated the relative importance of each biomarker, which was then used to identify an optimum biomarker panel that provided the maximum sensitivity and specificity with the least number of biomarkers.

CONCLUSIONS AND CLINICAL RELEVANCE

Four proteins were identified that together distinguished DGF with a sensitivity of 77.4%, specificity of 82.6%, and AUC of 0.891. This panel represents an important step toward identifying DGF at an early stage so that more effective treatments can be developed to improve long-term graft outcomes.

Design of Clinical Trials in Acute Kidney Injury: Lessons from the Past and Future Directions

Acute kidney injury (AKI) is a common condition with multiple etiologies and variable clinical findings and pathologic manifestations. AKI is associated with serious adverse clinical outcomes, including the development of de novo chronic kidney disease, accelerated progression of pre-existing chronic kidney disease, end-stage kidney disease, and increased mortality. Past research has advanced our understanding of the pathophysiology, epidemiology, and outcomes of AKI significantly, however, little progress has been made in the development of evidence-based interventions for its prevention and treatment. In this review, we discuss key considerations in the design of clinical trials in AKI and highlight significant methodologic limitations that precluded many past studies from determining the effectiveness of preventive and therapeutic strategies for this common and serious condition.

Acute kidney injury in the perioperative period and in intensive care units (excluding renal replacement therapies)

Acute kidney injury (AKI) is a syndrome that has progressed a great deal over the last 20 years. The decrease in urine output and the increase in classical renal biomarkers, such as blood urea nitrogen and serum creatinine, have largely been used as surrogate markers for decreased glomerular filtration rate (GFR), which defines AKI. However, using such markers of GFR as criteria for diagnosing AKI has several limits including the difficult diagnosis of non-organic AKI, also called "functional renal insufficiency" or "pre-renal insufficiency". This situation is characterized by an oliguria and an increase in creatininemia as a consequence of a reduction in renal blood flow related to systemic haemodynamic abnormalities. In this situation, "renal insufficiency" seems rather inappropriate as kidney function is not impaired. On the contrary, the kidney delivers an appropriate response aiming to recover optimal systemic physiological haemodynamic conditions. Considering the kidney as insufficient is erroneous because this suggests that it does not work correctly, whereas the opposite is occurring, because the kidney is healthy even in a threatening situation. With current definitions of AKI, normalization of volaemia is needed before defining AKI in order to avoid this pitfall.

Significance of Cystatin C for Early Diagnosis of Contrast-Induced Nephropathy in Patients Undergoing Coronary Angiography

Background

Contrast-induced nephropathy is acute kidney injury caused by contrast medium exposure. Serum creatinine is the clinical diagnostic standard, but it does not yield quick results. The serum level of cystatin C is stable and it can reflect renal function sensitively. The study aimed to assess the usefulness of cystatin C for early diagnosis of contrast-induced nephropathy in patients undergoing coronary angiography.

Material/Methods

We included 300 patients who underwent CAG. According to the sCr at 48 h, patients were divided into 2 groups: CIN group and non-CIN group. Their demographics and basal renal function were recorded. Changes in sCr, Cys C, and e GFR were compared at the same time. ROC analysis was used to assess the sensitivity and specificity of Cys C in the early diagnosis of CIN.

Results

Comparison of basal renal function and serum level of Cys C showed no significant differences between the 2 groups. Serum level of Cys C increased significantly at 24 h (p<0.001), and sCr increased significantly at 48 h. ROC analysis showed that the AUC of the change in Cys C between baseline and 24 h was 0.936 (95% CI: 0.879–0.992, p=0.000) and the optimum cut-off level was 0.26 mg/L (sensitivity=89.7% and specificity=95.6%).

Conclusions

The concentration change of Cys C is better than sCr as a biomarker in the early detection of CIN.

Carbamylated Erythropoietin Outperforms Erythropoietin in the Treatment of AKI-on-CKD and Other AKI Models

Erythropoietin (EPO) may be a beneficial tissue-protective cytokine. However, high doses of EPO are associate with adverse effects, including thrombosis, tumor growth, and hypertension. Carbamylated erythropoietin (CEPO) lacks both erythropoietic and vasoconstrictive actions. In this study, we compared the renoprotective, hemodynamic, and hematologic activities and survival effects of identical EPO and CEPO doses in rat models of clinically relevant AKI presentations, including ischemia-reperfusion-induced AKI superimposed on CKD (5000 U/kg EPO or CEPO; three subcutaneous injections) and ischemia-reperfusion-induced AKI in old versus young animals and male versus female animals (1000 U/kg EPO or CEPO; three subcutaneous injections). Compared with EPO therapy, CEPO therapy induced greater improvements in renal function and body weight in AKI on CKD animals, with smaller increases in hematocrit levels and similarly improved survival. Compared with EPO therapy in the other AKI groups, CEPO therapy induced greater improvements in protection and recovery of renal function and survival, with smaller increases in systolic BP and hematocrit levels. Overall, old or male animals had more severe loss in kidney function and higher mortality rates than young or female animals, respectively. Notably, mRNA and protein expression analyses confirmed the renal expression of the heterodimeric EPO receptor/CD131 complex, which is required for the tissue-protective effects of CEPO signaling. In conclusion, CEPO improves renal function, body and kidney weight, and survival in AKI models without raising hematocrit levels and BP as substantially as EPO. Thus, CEPO therapy may be superior to EPO in improving outcomes in common forms of clinical AKI.

Clinical Use of the Urine Biomarker [TIMP-2] × [IGFBP7] for Acute Kidney Injury Risk Assessment

Acute kidney injury (AKI) is a serious complication, commonly occurring in the critically ill population, with devastating short- and long-term consequences. Despite standardization of the definition and staging of AKI, early recognition remains challenging given that serum creatinine level is a marker, albeit imperfect, of kidney function and not kidney injury. Furthermore, the delay in increase in serum creatinine level after loss of glomerular filtration also prevents timely detection of decreased kidney function in patients with AKI. During the past decade, numerous clinical investigations have evaluated the utility of several biomarkers in the early diagnosis and risk stratification of AKI. In 2014, the US Food and Drug Administration approved the marketing of a test based on the combination of urine concentrations of tissue inhibitor of metalloproteinase 2 and insulin-like growth factor binding protein 7 ([TIMP-2] × [IGFBP7]) to determine whether certain critically ill patients are at risk for developing moderate to severe AKI. The optimal role of this biomarker in the diagnosis, management, and prognosis of AKI in different clinical settings requires further clarification. In this perspective, we summarize the biological actions of these 2 cell-cycle arrest biomarkers and present important considerations regarding the clinical application, interpretation, and limitations of this novel test for the early detection of AKI.

Pulsed focused ultrasound pretreatment improves mesenchymal stromal cell efficacy in preventing and rescuing established acute kidney injury in mice

Animal studies have shown that mesenchymal stromal cell (MSC) infusions improve acute kidney injury (AKI) outcomes when administered early after ischemic/reperfusion injury or within 24 hours after cisplatin administration. These findings have spurred several human clinical trials to prevent AKI. However, no specific therapy effectively treats clinically obvious AKI or rescues renal function once advanced injury is established. We investigated if noninvasive image-guided pulsed focused ultrasound (pFUS) could alter the kidney microenvironment to enhance homing of subsequently infused MSC. To examine the efficacy of pFUS-enhanced cell homing in disease, we targeted pFUS to kidneys to enhance MSC homing after cisplatin-induced AKI. We found that pFUS enhanced MSC homing at 1 day post-cisplatin, prior to renal functional deficits, and that enhanced homing improved outcomes of renal function, tubular cell death, and regeneration at 5 days post-cisplatin compared to MSC alone. We then investigated whether pFUS+MSC therapy could rescue established AKI. MSC alone at 3 days post-cisplatin, after renal functional deficits were obvious, significantly improved 7-day survival of animals. Survival was further improved by pFUS and MSC. pFUS prior to MSC injections increased IL-10 production by MSC that homed to kidneys and generated an anti-inflammatory immune cell profile in treated kidneys. This study shows pFUS is a neoadjuvant approach to improve MSC homing to diseased organs. pFUS with MSC better prevents AKI than MSC alone and allows rescue therapy in established AKI, which currently has no meaningful therapeutic options.

Therapeutic Targets of Human AKI: Harmonizing Human and Animal AKI

The opportunity to make advances in the prevention and treatment of AKI has never been greater than it is today. Major advances have been made in the understanding of the biology of AKI, the design of clinical trials, and the use of diagnostic and prognostic biomarkers. These advances have been supplemented by the coordinated effort of societies, federal agencies, and industry, such that we are poised in the ensuing years to positively address the unrelenting harm that this disorder has created. Over the past decade, major advances have been made in understanding the pathophysiology of AKI, mainly through the study of small animal models. However, translating these findings to human AKI remains a barrier, which is typified by the absence of effective therapeutic agents. The purpose of the Acute Dialysis Quality Initiative (ADQI) XIII was to harmonize human and animal studies and determine what is known about potential therapeutic targets and what gaps in knowledge remain. A series of invited reviews will distill key concepts from this initiative that focus on different pathogenic features of AKI, including hemodynamics, immunity and inflammation, cellular and molecular pathways, progression, and regeneration and repair. This series will convey the status of our knowledge of the pathophysiology of human AKI and propose therapeutic targets for further investigation.

Cardiorenal Syndrome Type 1: Activation of Dual Apoptotic Pathways

Cardiorenal syndrome type 1 (CRS1) pathophysiology is complex, and immune-mediated damage, including alterations in the immune response with monocyte apoptosis and cytokine release, has been reported as a potential mechanism. In this study, we examined the putative role of renal tubular epithelial cell (RTC) apoptosis as a pathogenic mechanism in CRS1. In particular, we investigated the caspase pathways involved in induced apoptosis. We enrolled 29 patients with acute heart failure (AHF), 11 patients with CRS1, and 15 controls (CTR) without AHF or acute kidney injury (AKI). Patients who had AKI prior to the episode of AHF or who had any other potential causes of AKI were excluded. Plasma from different groups was incubated with RTCs for 24 h. Subsequently, cell apoptosis, DNA fragmentation, and caspase-3, -8, and -9 activities were investigated in RTCs incubated with AHF, CRS1, and CTR plasma. A p value <0.5 was considered statistically significant. A quantitative analysis of apoptosis showed significantly higher apoptosis rates in CRS1 patients compared to AHF patients and CTR (p < 0.01). This increase in apoptosis was strongly confirmed by caspase-3 levels (ρ = 0.73). Caspase-8 and -9 were significantly higher in CRS1 patients compared to AHF patients and CTR (p < 0.01). Furthermore, caspase-3 levels showed a significantly positive correlation with caspase-8 (ρ = 0.57) and -9 (ρ = 0.47; p < 0.001). This study demonstrated the significantly heightened presence of dual apoptotic disequilibrium in CRS1. Our findings indicated that apoptosis may have a central role in the mechanism of CRS1, and it could be a potential therapeutic target in this syndrome.

[New KDIGO guidelines on acute kidney injury. Practical recommendations]

The incidence of acute kidney injury (AKI) in critically ill patients is very high and is associated with an increased morbidity and mortality. In 2012 the Kidney Disease: Improving Global Outcome (KDIGO) guidelines were published in which evidence-based practical recommendations are given for the evaluation and management of patients with AKI. The first section of the KDIGO guidelines deals with the unification of earlier consensus definitions and staging criteria for AKI. The subsequent sections of the guidelines cover the prevention and treatment of AKI as well as the management of renal replacement therapy (RRT) in patients with AKI. In each section the existing evidence is discussed and a specific treatment recommendation is given. The guidelines appreciates that there is insufficient evidence for many of the recommendations. As a specific pharmacological therapy is missing, an early diagnosis, aggressive hemodynamic optimization, tight volume control, and avoidance of nephrotoxic drugs are the only interventions to prevent AKI. If renal replacement therapy is required different modalities are available to provide an effective therapy with a low rate of adverse effects.

Derivation and validation of cutoffs for clinical use of cell cycle arrest biomarkers

Background

Acute kidney injury (AKI) remains a deadly condition. Tissue inhibitor of metalloproteinases (TIMP)-2 and insulin-like growth factor binding protein (IGFBP)7 are two recently discovered urinary biomarkers for AKI. We now report on the development, and diagnostic accuracy of two clinical cutoffs for a test using these markers.

Methods

We derived cutoffs based on sensitivity and specificity for prediction of Kidney Disease: Improving Global Outcomes Stages 2–3 AKI within 12 h using data from a previously published multicenter cohort (Sapphire). Next, we verified these cutoffs in a new study (Opal) enrolling 154 critically ill adults from six sites in the USA.

Results

One hundred subjects (14%) in Sapphire and 27 (18%) in Opal met the primary end point. The results of the Opal study replicated those of Sapphire. Relative risk (95% CI) in both studies for subjects testing at ≤0.3 versus >0.3–2 were 4.7 (1.5–16) and 4.4 (2.5–8.7), or 12 (4.2–40) and 18 (10–37) for ≤0.3 versus >2. For the 0.3 cutoff, sensitivity was 89% in both studies, and specificity 50 and 53%. For 2.0, sensitivity was 42 and 44%, and specificity 95 and 90%.

Conclusions

Urinary [TIMP-2]•[IGFBP7] values of 0.3 or greater identify patients at high risk and those >2 at highest risk for AKI and provide new information to support clinical decision-making.

Clinical Trials Registration

Clintrials.gov # NCT01209169 (Sapphire) and NCT01846884 (Opal).

Biomarkers of AKI: a review of mechanistic relevance and potential therapeutic implications

AKI is a common clinical condition associated with a number of adverse outcomes. More timely diagnosis would allow for earlier intervention and could improve patient outcomes. The goal of early identification of AKI has been the primary impetus for AKI biomarker research, and has led to the discovery of numerous novel biomarkers. However, in addition to facilitating more timely intervention, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Furthermore, AKI biomarkers could also function as molecular phenotyping tools that could be used to direct clinical intervention. This review highlights the major studies that have characterized the diagnostic and prognostic predictive power of these biomarkers. The mechanistic relevance of neutrophil gelatinase-associated lipocalin, kidney injury molecule 1, IL-18, liver-type fatty acid-binding protein, angiotensinogen, tissue inhibitor of metalloproteinase-2, and IGF-binding protein 7 to the pathogenesis and pathobiology of AKI is discussed, putting these biomarkers in the context of the progressive phases of AKI. A biomarker-integrated model of AKI is proposed, which summarizes the current state of knowledge regarding the roles of these biomarkers and the molecular and cellular biology of AKI.

Novel biomarkers for contrast-induced acute kidney injury

Biomarkers of acute kidney injury (AKI) may be classified in 2 groups: (1) those representing changes in renal function (e.g., serum creatinine or cystatin C and urine flow rate) and (2) those reflecting kidney damage (e.g., kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18, etc.). According to these 2 fundamental criteria, 4 subgroups have been proposed: (1) no marker change; (2) damage alone; (3) functional change alone; and (4) combined damage and functional change. Therefore, a new category of patients with “subclinical AKI” (that is, an increase in damage markers alone without simultaneous loss of kidney function) has been identified. This condition has been associated with higher risk of adverse outcomes (including renal replacement therapy and mortality) at followup. The ability to measure these physiological variables may lead to identification of patients at risk for AKI and early diagnosis of AKI and may lead to variables, which may inform therapeutic decisions.

Revisiting the relationship between blood pressure and insulin-like growth factor-1

Conflicting evidence exists on the relationship between blood pressure (BP) and insulin-like growth factor-1 (IGF-1). We reviewed available articles and pooled extrapolated regression coefficients for the association between BP and total IGF-1 as reported in the literature and included additional data from 912 individuals from the general population. We identified 20 studies including 11 704 subjects. We also measured total IGF-1, insulin-like binding protein-3, and BP in 912 black and white men and women from South Africa (aged 20-70 years). When plotting positive and negative weighed regression coefficients (29 data points) against IGF-1, we found a significant positive relationship (r=0.31; P<0.001; n=11 704) intercepting the 0 point at 191 ng/mL IGF-1, suggesting an inverse BP/IGF-1 relationship in low IGF-1 conditions, and a positive relationship in overtly high IGF-1 conditions. In conclusion, our findings suggest that the relationship between BP and IGF-1 is dependent on, or related to, IGF-1 concentrations, as an expression of direct or reverse causality. Low IGF-1 bioavailability (associated with aging and vascular deterioration), resistance to IGF-1, and the complex interplay between IGF-1 and other vasoactive hormones could mask the vasoprotective functions of IGF-1 in cross-sectional studies or could modify their functions in prospective studies.

Uremic toxins impair human bone marrow-derived mesenchymal stem cells functionality in vitro

Mesenchymal stem cells (MSCs) are becoming therapeutic agents of interest in many areas of medicine, including renal diseases and kidney transplantations. However, the effect of uremia on cell properties is still unclear. Therefore, we examined the in vitro influence of uremic toxins, p-cresol (PC) and indoxyl sulfate (IS), on human bone marrow-derived MSC functionality. Cultured MSCs were treated with PC and IS at concentrations corresponding to subsequent stages of chronic kidney disease. Cell viability was characterized by metabolic activity (MTT assay) and proliferation rate (BrdU assay). Apoptosis (Annexin V test) and cell membrane damage (LDH assay) were also tested. MSC secretory properties were determined by measuring cytokine/growth factor levels in media from toxin-treated cells (ELISA). Uremic concentrations of PC and IS resulted in significant inhibition of MSC metabolic activity and proliferation. Toxins did not induce apoptosis, but damaged cell membranes. MSC paracrine activity was also altered - a decrease of VEGF and TGF-β1 levels and an increase in IGF-1 and IL-8 secretion was detected. Presented data indicate a negative influence of uremic toxins on functional characteristics of human bone marrow-derived MSCs. Therefore, their use as autologous therapeutic agents for kidney disease may be questionable and requires further investigations. The observed phenomenon may be attributable to many other MSC therapies, because of the high prevalence of chronic kidney disease in adult population.

Development of an immunoassay for the kidney-specific protein myo-inositol oxygenase, a potential biomarker of acute kidney injury

BACKGROUND

Acute kidney injury (AKI) affects 45% of critically ill patients, resulting in increased morbidity and mortality. The diagnostic standard, plasma creatinine, is nonspecific and may not increase until days after injury. There is significant need for a renal-specific AKI biomarker detectable early enough that there would be a potential window for therapeutic intervention. In this study, we sought to identify a renal-specific biomarker of AKI.

METHODS

We analyzed gene expression data from normal mouse tissues to identify kidney-specific genes, one of which was Miox. We generated monoclonal antibodies to recombinant myo-inositol oxygenase (MIOX) and developed an immunoassay to quantify MIOX in plasma. The immunoassay was tested in animals and retrospectively in patients with and without AKI.

RESULTS

Kidney tissue specificity of MIOX was supported by Western blot. Immunohistochemistry localized MIOX to the proximal renal tubule. Serum MIOX, undetectable at baseline, increased 24 h following AKI in mice. Plasma MIOX was increased in critically ill patients with AKI [mean (SD) 12.4 (4.3) ng/mL, n = 42] compared with patients without AKI [0.5 (0.3) ng/mL, n = 17] and was highest in patients with oliguric AKI [20.2 (7.5) ng/mL, n = 23]. Plasma MIOX increased 54.3 (3.8) h before the increase in creatinine.

CONCLUSIONS

MIOX is a renal-specific, proximal tubule protein that is increased in serum of animals and plasma of critically ill patients with AKI. MIOX preceded the increases in creatinine concentration by approximately 2 days in human patients. Large-scale studies are warranted to further investigate MIOX as an AKI biomarker.

Atorvastatin treatment attenuates renal injury in an experimental model of ischemia-reperfusion in rats

BACKGROUND

Recent studies in animal models have shown that statins can protect against renal failure independent of their lipid-lowering actions, and there is also an association between statin use and improved renal function after suprarenal aortic clamping. We investigated the hypothesis that post-ischemic acute renal failure could be ameliorated with atorvastatin (ATO) treatment and the possible molecular mechanisms in a model of ischemia-reperfusion (IR) in rats.

METHODS

Twenty-four male Sprague-Dawley rats were divided into three groups: sham, IR, and IR + ATO. ATO was given by a single intraperitoneal injection (10 mg/kg) 30 min before reperfusion in the IR + ATO group. The IR group and sham group received saline vehicle via the intraperitoneal route.

RESULTS

After 24 h of IR, serum creatinine levels were increased in the IR group compared with the sham group (p < 0.001). ATO treatment reduced the elevation of serum creatinine level by 18% (p < 0.05) and significantly increased the creatinine clearance rate (p < 0.001). Concentrations of advanced oxidation protein products and malondialdehyde were reduced in the ATO group, approaching levels observed in sham-group rats. ATO treatment alleviated pathological changes in renal tubular cells. Protein and mRNA levels of intercellular adhesion molecule-1 and monocyte chemotactic protein-1 were reduced significantly.

CONCLUSIONS

These data suggest that direct protection of injured kidneys by ATO was possible even though the drug was injected 30 min before reperfusion, and that ATO may reduce IR injury by anti-inflammatory effects and by reducing oxidation stress.

Nephroscreen™: a diagnostic test for predicting acute renal failure?

Acute renal failure is a frequent and often fatal complication of hospitalized patients. While the risk of acute renal failure among select patient groups is well recognized, physicians currently rely on diagnostic tests such as changes of serum creatinine and indirect assessment of the glomerular filtration rate to diagnose acute renal failure. Although these parameters capture the degree of kidney function lost, they are not warning signs of evolving kidney injury. While the clinical emergence of acute renal failure is sudden, the pathologic changes preceding loss of kidney function are not so sudden. Nephroscreen is a fast and easy-to-use urine enzyme-linked immunosorbent assay test designed to quantify specific pathologic events preceding death of renal proximal tubule cells. It detects acute kidney damage days before serum creatinine rises and may open new avenues to defining acute renal failure as well as treating acute renal failure patients earlier and more effectively.

Heart-kidney crosstalk and role of humoral signaling in critical illness

Organ failure in the heart or kidney can initiate various complex metabolic, cell-mediated and humoral pathways affecting distant organs, contributing to the high therapeutic costs and significantly higher morbidity and mortality. The universal outreach of cells in an injured state has myriad consequences to distant organ cells and their milieu. Heart performance and kidney function are closely interconnected and communication between these organs occurs through a variety of bidirectional pathways. The term cardiorenal syndrome (CRS) is often used to describe this condition and represents an important model for exploring the pathophysiology of cardiac and renal dysfunction. Clinical evidence suggests that tissue injury in both acute kidney injury and heart failure has immune-mediated inflammatory consequences that can initiate remote organ dysfunction. Acute cardiorenal syndrome (CRS type 1) and acute renocardiac syndrome (CRS type 3) are particularly relevant in high-acuity medical units. This review briefly summarizes relevant research and focuses on the role of signaling in heart-kidney crosstalk in the critical care setting.

Repulsive guidance cue semaphorin 3A in urine predicts the progression of acute kidney injury in adult patients from a mixed intensive care unit

BACKGROUNDS

Predicting the development of acute kidney injury (AKI) in the critical care setting is challenging. Although several biomarkers showed somewhat satisfactory performance for detecting established AKI even in a heterogeneous disease-oriented population, identification of new biomarkers that predict the development of AKI accurately is urgently required.

METHODS

A single-center prospective observational cohort study was undertaken to evaluate for the first time the reliability of the newly identified biomarker semaphorin 3A for AKI diagnosis in heterogeneous intensive care unit populations. In addition to five urinary biomarkers of L-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL), IL-18, albumin and N-acetyl-β-d-glucosaminidase (NAG), urinary semaphorin 3A was measured at intensive care unit (ICU) admission.

RESULTS AND CONCLUSION

Three hundred thirty-nine critically ill adult patients were recruited for this study. Among them, 131 patients (39%) were diagnosed with AKI by the RIFLE criteria and 66 patients were diagnosed as AKI at post-ICU admission (later-onset AKI). Eighty-four AKI patients showed worsening severity during 1 week observation (AKI progression). Although L-FABP, NGAL and IL-18 showed significantly higher area under the curve (AUC)-receiver operating characteristic (ROC) values than semaphorin 3A in detecting established AKI, semaphorin 3A was able to detect later-onset AKI and AKI progression with similar AUC-ROC values compared with the other five biomarkers [AUC-ROC (95% CI) for established AKI 0.64 (0.56-0.71), later-onset AKI 0.71 (0.64-0.78), AKI progression 0.71 (0.64-0.77)]. Urinary semaphorin 3A was not increased in non-progressive established AKI, while the other biomarkers were elevated regardless of further progression. Finally, sepsis did not have any impact on semaphorin 3A while the other urinary biomarkers were increased with sepsis. Semaphorin 3A is a new biomarker of AKI which may have a distinct predictive use for AKI progression when compared with other AKI biomarkers.

Acute kidney injury and critical cardiac disease

The field of cardiac intensive care continues to advance in tandem with congenital heart surgery. The survival of patients with critical congenital heart disease is seldom in question. Consequently, the focus has now shifted to that of morbidity reduction and eventual elimination. Acute kidney injury (AKI) after cardiac surgery is associated with adverse outcomes, including prolonged intensive care and hospital stays, diminished quality of life, and increased long-term mortality. Acute kidney injury occurs frequently, complicating 30% to 40% of adult and pediatric cardiac surgeries. Patients who require dialysis are at high risk of mortality, but even minor degrees of postoperative AKI portend a significant increase in mortality and morbidity.

Acute kidney injury after cardiovascular surgery: an overview

Acute kidney injury is a complication of open-heart surgery that carries a poor prognosis. Studies have shown that postoperative renal function deterioration in cardiovascular surgery patients increases in-hospital mortality and adversely affects long-term survival. Identifying individuals at risk for developing AKI and aggressive early intervention is extremely important to optimize outcomes. This paper provides an overview of the etiology, prognostic markers, risk factors, and prevention of AKI and treatments that may favorably affect outcomes.

Sustained activation of EGFR triggers renal fibrogenesis after acute kidney injury

Severe acute kidney injury (AKI) is frequently accompanied by maladaptive repair and renal fibrogenesis; however, the molecular mechanisms that mediate these acute and chronic consequences of AKI remain poorly understood. In this study, we examined the role of epidermal growth factor receptor (EGFR) in these processes using waved-2 (Wa-2) mice, which have reduced EGFR activity, and their wild-type (WT) littermates after renal ischemia. Renal EGFR phosphorylation was induced within 2 days after ischemia, increased over time, and remained elevated at 28 days in WT mice, but this was diminished in Wa-2 mice. At the early stage of postischemia (2 days), Wa-2 mice developed more severe acute renal tubular damage with less reparative responses as indicated by enhanced tubular cell apoptosis, and reduced dedifferentiation and proliferation as compared to WT animals. At the late stage of postischemia (28 days), Wa-2 mice exhibited a less severe renal interstitial fibrosis as shown by reduced activation/proliferation of renal myofibroblasts and decreased deposition of extracellular matrix proteins. EGFR activation also contributed to cell cycle arrest at the G2/M phase, a cellular event associated with production of profibrogenetic factors, in the injured kidney. Collectively, these results indicate that severe AKI results in sustained activation of EGFR, which is required for reparative response of renal tubular cells initially, but eventually leads to fibrogenesis.

Novel biomarkers for early diagnosis of acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a common and serious problem in critically ill patients. Tests currently used to detect AKI (i.e., serum creatinine, serum urea and various urinary indices) often result in serious delays in detection of clinically relevant injury. This delayed detection translates into a potential missed opportunity for therapeutic interventions at a time when kidney damage may be limitable or reversible. This is also recognized as a potential reason for the poor clinical outcomes often associated with AKI.

OBJECTIVES

To appraise the recent literature characterizing several novel serum and urinary biomarkers, including neutrophil gelatinase-associated lipocalin, IL-18 and kidney injury molecule-1, which are capable of detecting AKI at an earlier phase of injury. Also to discuss the pitfalls of current conventional testing in kidney injury.

METHOD

Narrative literature review.

CONCLUSIONS

These novel biomarkers can detect injury when damage may still be reversible, allow for early risk stratification and/or prognostication, and are associated in early clinical studies with important outcomes such as severity of AKI, need for renal replacement therapy and survival. There is optimism that these novel biomarkers will discriminate the underlying pathophysiology of AKI (i.e., ischemia, sepsis, toxins or multifactorial), discriminate AKI from other renal disease (i.e., chronic kidney disease) and aid in localizing the site of acute injury in the kidney. As such, the future may entail development of an 'AKI biomarker panel' (i.e., analogous to a cardiac or liver enzyme panel) for use in clinical practice.

Semaphorin 3A is a new early diagnostic biomarker of experimental and pediatric acute kidney injury

BACKGROUND

Semaphorin 3A is a secreted protein that regulates cell motility and attachment in axon guidance, vascular growth, immune cell regulation and tumor progression. However, nothing is known about its role in kidney pathophysiology. Here, we determined whether semaphorin3A is induced after acute kidney injury (AKI) and whether urinary semaphorin 3A can predict AKI in humans undergoing cardiopulmonary bypass (CPB).

METHODS AND PRINCIPAL FINDINGS

In animals, semaphorin 3A is localized in distal tubules of the kidney and excretion increased within 3 hr after reperfusion of the kidney whereas serum creatinine was significantly raised at 24 hr. In humans, using serum creatinine, AKI was detected on average only 48 hours after CPB. In contrast, urine semaphorin increased at 2 hours after CPB, peaked at 6 hours (2596±591 pg/mg creatinine), and was no longer significantly elevated 12 hours after CPB. The predictive power of semaphorin 3A as demonstrated by area under the receiver-operating characteristic curve for diagnosis of AKI at 2, 6, and 12 hours after CPB was 0.88, 0.81, and 0.74, respectively. The 2-hour urine semaphorin measurement strongly correlated with duration and severity of AKI, as well as length of hospital stay. Adjusting for CPB time and gender, the 2-hour semaphorin remained an independent predictor of AKI, with an odds ratio of 2.19.

CONCLUSION

Our results suggest that semaphorin 3A is an early, predictive biomarker in experimental and pediatric AKI, and may allow for the reliable early diagnosis and prognosis of AKI after CPB, much before the rise in serum creatinine.

Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)

Acute kidney injury (AKI) is a common and serious problem affecting millions and causing death and disability for many. In 2012, Kidney Disease: Improving Global Outcomes completed the first ever, international, multidisciplinary, clinical practice guideline for AKI. The guideline is based on evidence review and appraisal, and covers AKI definition, risk assessment, evaluation, prevention, and treatment. In this review we summarize key aspects of the guideline including definition and staging of AKI, as well as evaluation and nondialytic management. Contrast-induced AKI and management of renal replacement therapy will be addressed in a separate review. Treatment recommendations are based on systematic reviews of relevant trials. Appraisal of the quality of the evidence and the strength of recommendations followed the Grading of Recommendations Assessment, Development and Evaluation approach. Limitations of the evidence are discussed and a detailed rationale for each recommendation is provided.

Acute kidney injury clinical trial design: old problems, new strategies

Apart from supportive dialysis there are no universally accepted interventions in acute kidney injury (AKI). We have summarized the outcomes of all published randomized, placebo-controlled studies of non-dialysis treatment of AKI. Forty-nine trials were identified, only one of which was in a paediatric population. Sixteen trials had positive outcomes; these trials are not comparable in terms of methodology used or outcomes assessed, and they share many of the problems of the negative trials. We discuss the flaws in clinical trial design that have contributed to poor or uncertain outcomes and propose minimum requirements for future trials. In particular, future trials should incorporate biomarkers specific to the etiology of the AKI, and treatment should match the phase of injury.

Production of hydrogen sulfide from d-cysteine and its therapeutic potential

Accumulating evidence shows that H2S has physiological functions in various tissues and organs. It includes regulation of neuronal activity, vascular tension, a release of insulin, and protection of the heart, kidney, and brain from ischemic insult. H2S is produced by enzymes from l-cysteine; cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase (3MST) along with cysteine aminotransferase. We recently discovered an additional pathway for the production of H2S from d-cysteine. d-Amino acid oxidase provides 3-mercaptopyruvate for 3MST to produce H2S. d-Cysteine protects cerebellar neurons from oxidative stress and attenuates ischemia-reperfusion injury caused in the kidney more effectively than l-cysteine. This review focuses on a novel pathway for the production of H2S and its therapeutic application especially to the renal diseases.

Delayed graft function is not associated with an increased incidence of renal allograft rejection

Delayed graft function (DGF) is considered as a risk factor for renal allograft rejection, but this association might be confounded by diagnostic biases (e.g., higher biopsy frequency in patients with DGF, inclusion of clinically diagnosed rejection episodes, and limited details on the rejection phenotype). This retrospective study including 329 deceased donor transplantations aimed to clarify a causal relationship between DGF and rejection. DGF occurred in 93/329 recipients (28%), whereas immediate graft function (IGF) in 236/329 recipients (72%). The percentage of patients with ≥1 allograft biopsy within the first year post-transplant was similar between the DGF and IGF group (96% vs. 94%; p=0.60). The cumulative one-yr incidence of biopsy-proven clinical (35% vs. 34%; p=0.62) and combined (sub)clinical rejection (58% vs. 60%; p=0.79) was not different between the two groups. Furthermore, there were no differences regarding rejection phenotypes/severities and time frame of occurrence. By multivariable Cox regression analysis, donor-specific HLA antibodies, younger recipient age, and immunosuppressive regimens were independent predictors for clinical rejection, while DGF was not. These results in an intermediate sized, but thoroughly investigated patient population challenge the concept that DGF is a risk factor for rejection and highlights the need for additional studies in this regard.