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| 2008 JASN IMPACT FACTOR 7.505 | HOME AUTHOR INFO EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP | |||
| CURRENT ISSUE | ARCHIVES | JASN Express | ONLINE SUBMISSION | |
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| 2008 JASN IMPACT FACTOR 7.505 | HOME AUTHOR INFO EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP | |||
| CURRENT ISSUE | ARCHIVES | JASN Express | ONLINE SUBMISSION | |
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Special Feature: ASN Renal Research Report |
Abstract
In the spring of 2004, the Board of Advisors and the Council of the American Society of Nephrology believed it necessary to conduct a series of research retreats to steer priorities appropriately in an era of limited resources. In this regard, retreats were conducted by five working groups in areas that were identified to require distinct attention: acute renal failure, diabetic nephropathy, hypertension, transplantation, and uremic cardiovascular toxicity. The goal of each retreat was to join experts, both within and outside the renal community, to identify areas of basic science and clinical research that should receive highest priority in the next five years. The five retreat summaries with their individual listings of research priorities allow for the distillation of three overriding recommendations that strongly emanate from them:
In December 1998 and February 1999, the American Society of Nephrology (ASN), in collaboration with the Council of the American Kidney Societies, conducted two strategic planning meetings that brought together experts in various disciplines of nephrology to provide a summary of the status, needs, and priorities for renal research in the ensuing years. The timing of the report reflected the now fulfilled expectation that the National Institutes of Health budget was to grow generously, in fact double, over the subsequent five years. Several initiatives outlined in these reports were taken under advisement by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) leadership and served as guides for requests for application (RFA); the launch of various new programs, such as the National Kidney Disease Education Program; the initiation of consortia to undertake clinical trials; and the development of centers to study diabetic complications in animal models.
Now in a dramatically altered fiscal environment, in the spring of 2004, the Board of Advisors and the Council of the ASN believed it appropriate to conduct another series of research retreats to similarly steer priorities in an era of more limited resources. In this regard, retreats were conducted by only five (as opposed to 10 in the previous occasion) working groups in areas identified to require distinct attention: acute renal failure (ARF), diabetic nephropathy, hypertension, transplantation, and uremic cardiovascular toxicity. The goal of each retreat was to join experts, both within and outside the renal community, to identify areas of basic science and clinical research that should receive highest priority in the next five years. Primary regard was given to priorities that are likely to translate into discoveries that improve the understanding of the pathogenesis of renal disorders and that improve the outlook of patients who are afflicted with kidney diseases.
Society leaders selected the five areas of interest as we believe that these carry the burden and that their solution provides the best hope in making a dent in reducing kidney disease, which is growing at an alarming rate and is a disabling and costly public health problem. The number of patients in the ESRD program continues to grow, and, in parallel, the cost of such programs has escalated in the past decade. Concurrently, we have recognized, with better measures of renal dysfunction, that there is a significant number of people with various degrees of renal insufficiency, individuals who are at risk for further swelling the ranks of the ESRD population in the coming decade. At this point, diabetes, hypertension, and failed graft function are the three most common causes of initiation of dialysis treatments. Furthermore, it is evident from a number of large clinical trials, as well as from population-based observations, that the presence of even mild renal insufficiency conveys a significant added risk for cardiovascular diseases (CVD) in these patients.
The ASN, along with others who participated in this effort—the National Kidney Foundation, the American Society of Pediatric Nephrology, the American Society of Transplantation, the American Society of Hypertension, and the Kidney Council of the American Heart Association—as well as the entire renal research community hope that this article, drawing from the wisdom and expertise of numerous participants (see Appendix) will provide a helpful guide to the leaders of the NIDDK and the National Heart, Lung, and Blood Institute (NHLBI), to whom we respectfully submit this report, as they plan the allocation of resources in the coming years.
Acute Renal Failure
Introduction
ARF remains a vexing and significant clinical problem. Hospitalizations for ARF have dramatically increased in the past two decades. ARF may also be a precursor to ESRD as approximately 13% of patients with ARF proceed to ESRD over a 3-yr period. ARF during hospitalization represents an independent high risk for mortality, particularly for patients who require renal replacement therapies. In the past two decades, understanding of the pathophysiology and mechanisms of renal dysfunction has been greatly enhanced by focused investigations related to the pathobiology of this disorder. This knowledge has led to the limited development of preventive and therapeutic advances. However, barring a few successes, most clinical trials of new modalities or interventions have been unsuccessful. Despite the progress made in the fundamental biology of this disease, characterization of human ARF has been lacking. In most instances, an abrupt decline in kidney function is secondary to an injury that leads to a functional or structural change in the kidney. Therefore, in the absence of an accepted definition for ARF, we use the term acute kidney injury (AKI) to reflect the entire spectrum of this disease. AKI is a complex disorder that comprises multiple causative factors and occurs in a variety of settings with varied clinical manifestations ranging from a minimal elevation in serum creatinine to anuric renal failure.
The goals of the ARF retreat were to:
To accomplish these goals, retreat participants were divided into several working groups. The deliberations and recommendations of these working groups follow.
Recommendations
Classification and Stratification Group.
This group acknowledged difficulties with the term "acute renal failure," considered multiple alternatives, and reached a consensus for the term "acute kidney injury." However, they recognized that other societies and organizations have a vested interest in this field and that others should be consulted to reach a consensus for terminology that would be accepted worldwide.
The highest priorities are to:
To this end, the group believed that a consensus conference, with representation from various societies and organizations, should be organized.
Additional priorities are to:
Biomarkers Group.
The Food and Drug Administration (FDA) representative in this group expressed great interest in biomarkers and surrogates as a way of expediting the drug development process. He cited the Critical Path Initiative, issued by the FDA in the spring of 2004, which stated, "Additional biomarkers (quantitative measures of biologic effects that provide informative links between mechanism of action and clinical effectiveness) and additional surrogate markers (quantitative measures that can predict effectiveness) are needed to guide product development." This was accompanied by a provocative statement that, "In some cases, datamining and analysis, with possibly a single additional clinical trial, may be all that is necessary to confirm the surrogacy of a particular marker." He also cited Dr. Robert Temple, a senior clinical regulator at the FDA, who defined a surrogate end point as a laboratory measure or a physical sign used as a substitute for a clinically meaningful end point.
This group recommended that the highest priority is to standardize and/or discover biomarkers to:
To accomplish this task, the group strongly suggested that a biomarker core facility be established to facilitate validation and standardization of putative biomarkers that are currently under investigation and that form the nexus for discovery of new biomarkers. The aims of such a project would include:
Preventive and Therapeutic Intervention Studies Group.
This group considered input from industry and the FDA as being critical to advancing preventive and therapeutic strategies for ARF. An industry representative believed that it was critical that the community agree on a definition that will provide a commercially viable indication. In other words, physicians in practice would view intervention as providing tangible benefit. The treatment paradigm for AKI should be aligned with critical illnesses such as stroke and myocardial infarction, for which the treatment window is defined in hours rather than days. The major difficulty of arriving at an end point is that the currently used end point of mortality is often influenced by nonrenal factors.
The group considered all of the potential difficulties and barriers in designing a clinical trial. The major difficulty with a therapeutic trial after renal failure is established is that the intervention may be too late to make a difference. The major difficulty with a preventive trial is that the event rate is generally low, requiring huge patient populations per study. Therefore, designing a preventive trial, limited to a patient group at high risk for developing ARF, seems to be an appropriate starting point. An additional advantage of this strategy is that most animal studies have been targeted at studying mechanisms and therefore have been preventive in nature. The group identified high-risk patients who undergo cardiothoracic vascular surgery as the most appropriate subjects for an initial observational or therapeutic trial. The primary objective of such a trial would be to establish a network of centers with a broad spectrum of experience and diverse populations of patients with AKI. Thus, the highest priority for this group was the establishment of a clinical trial network to:
In Vitro and In Vivo Systems Group.
Unfortunately, most animal models do not seem to be applicable to the treatment of human ARF. However, it is noted that in human studies, treatments are used after the establishment of ARF, whereas in most of the animal studies, mechanisms were examined and treatments were initiated before induction of ARF. Nonetheless, the consensus was that one model is unlikely to fit all exigencies.
In view of these facts, the group believed that the highest priority should be given to the development of complex models of ARF that better reflect the human setting. Investigators who are developing such models should be further encouraged to pursue this course.
Collaborative Network Group.
This group, similar to the Preventative Therapeutic Intervention Studies Group, believed that a permanent, collaborative network would facilitate productive research, including cross-sectional and longitudinal observational studies, single and multicenter interventional studies, and health services–related research. The following barriers were identified:
Because of these difficulties and because there are several very important gaps in our knowledge in the natural history and epidemiology of acute renal injury, this group believed that the highest priority at this time is to develop a registry/data repository to address the following critically important gaps in knowledge about clinical AKI:
Proposal
The steering committee of the ARF retreat has proposed and the Acute Renal Failure Advisory Group has endorsed the establishment of an Acute Kidney Injury Clinical Initiative (AKI-CI) that would address many of the priorities identified in the retreat. The goal of this proposal is to establish a collaborative network of investigators and centers that are dedicated to advancing knowledge and developing refined approaches for the recognition, prevention, and treatment of AKI that will ultimately improve the care and outcomes of patients who are afflicted with this disorder. The network would consist of collaborating investigators from approximately 10 participating centers initially on the basis of (but not exclusively) existing networks (PICARD, VA dialysis study, etc.). The participating centers will use a common definition, staging system, and protocol to identify patients who are at high risk for AKI and established criteria to recognize when AKI has occurred. All centers would contribute a set of common data elements to a pooled database, obtain timed biologic samples that are stored in a repository and are available for assessment, and participate in studies designed either to reduce the vulnerability of patients to AKI or to intervene to improve outcomes. The network will be flexible to accommodate the spectrum of clinical and translational research as well as to capitalize on the expertise of specific participating centers. The network will be scalable to meet the needs of different projects and will be financially responsible, with the ultimate goal of becoming self-supportive. The infrastructure for the network will require three interdependent core functions.
Core A: Biomarker Core.
A Biomarker Core will evaluate, develop, and explore biomarkers using modern techniques. This core will feature expertise with established techniques and develop an interactive core biomarker facility. Core A would focus on standardizing the best techniques for:
The data from Core A would be interpreted in the context of clinical data that had been collected and analyzed independently by Core B. This core will include a biostatistics capability that will facilitate validation of the predictive diagnostic characteristics of individual and panels of biomarkers, as well as explore innovative technologies to monitor candidate biomarkers. Core A will provide new knowledge of biomarkers in AKI that will ultimately lead to a clinically relevant definition of this disorder on the basis of pathobiologic alterations and will evolve as a resource for future validation and discovery. This core will be supported by a biologic sample repository that will receive samples from the collaborating centers.
Core B: Registry Core.
A Registry Core will develop a registry of patients with AKI. Patient data for both cross-sectional and longitudinal studies of AKI will be obtained. In conjunction with Core C, this core will identify participating centers with specific expertise for particular subsets of patients (e.g., cardiovascular surgery, community and academic hospital) that will facilitate broad enrollment of patients. It will also select centers to participate with Core C in specific cohort or interventional studies in the future.
Core B will be designed to assess the practicality of obtaining data, ascertaining the most relevant data elements and the frequency of collection, to allow valid and accurate assessment of patient characteristics and process factors to determine the course of the disease.
Core B will provide four key functions:
This core will be supported by a registry coordination center equipped to facilitate data acquisition and provide statistical support for rapid ongoing analysis. Reporting of results will be widely disseminated to provide new knowledge to direct the design and implementation of clinical trials and ultimately identify best practices for development of evidence based practice guidelines.
Core C: Clinical Studies Core.
The Clinical Studies Core has two objectives:
To achieve these objectives, Core C has five functions:
This core would be supported by a clinical trials coordinating center responsible for organization, education, facilitation, and evaluation of participating sites to maximize acquisition of patients, maintain data flow, and minimize intercenter variability in protocol implementation and data collection. This core extends and amplifies the database of Core B and provides biologic samples for Core A that are specifically timed to coincide with potential therapeutic interventions.
As shown in Figure 1, a well-coordinated and integrated AKI-CI built on the foundation of these three cores will build a network of centers that are responsible for developing:
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A group of collaborating centers will be identified to enroll patients and to conduct three specific projects concurrently. Core B will collect and analyze cross-sectional and longitudinal data across the entire spectrum of AKI in hospitalized patients (intensive care unit and non–intensive care unit). Core C will initially focus on a subset of high-risk patients (e.g., cardiac surgery) to delineate critical risk factors or events that may lead to AKI and to obtain samples before and after the potential AKI inducing event for biomarkers to help define appropriate points for diagnosis and initiation of preventive or therapeutic interventions. Samples from all patients who are entered into this cohort study will be provided to Core A for analysis of existing biomarkers and potential discovery of new indicators of injury or recovery. In the first phase of this endeavor, each core will focus on establishing essential infrastructure, adding coordination with participating centers to obtain data that will be used to inform and design studies to be carried out in subsequent years. An ongoing AKI-CI will benefit patients, both at risk and with established AKI, and will provide new insights into this complex, multifaceted disease.
Significance
It is evident that we have a limited knowledge of the natural history of AKI. Although several new molecular, genomic, and proteomic techniques are available and have been used successfully to characterize the spectrum of disease, from CKD through transplantation, these techniques have yet to be applied to ARF. There are several unanswered questions regarding the role of various factors in the pathogenesis and continuation of injury in human ARF. Recent advances in the availability of new biomarkers specific for tubular injury and new techniques to probe and characterize renal tissue samples provide an opportunity to characterize the human disease and validate the concepts established in animal models of ARF. The establishment of an AKI-CI on the basis of three integrated cores, each of which contributes new knowledge, will catalyze clinical studies and inevitably lead to improvements in patient care, outcomes, and our understanding of the clinical aspects of this intriguing but difficult disorder.
Diabetic Nephropathy
Introduction
Diabetic nephropathy (DN) remains the leading course of progressive renal disease. The care of patients with this disease represents a significant financial burden to the health care system. The recent epidemic of obesity and diabetes in children suggests that DN may become a problem in the coming decades.
The DN retreat was convened to focus on the following two areas:
Each of these groups:
Epidemiology of DN and Biomarker Discovery
What We Know; What We Need to Know.
The natural history of DN remains largely unknown, particularly in ethnic minority populations. The role of metabolic syndrome in either initiating nephropathy or modifying the course of DN is also unclear. Renal function in the individual with diabetes should be considered as part of a spectrum of microvascular and macrovascular complications (cardiovascular, cerebrovascular, and ocular). For generating optimal data on the natural history of DN and the effects of the metabolic syndrome on disease risk and for facilitating the search for nephropathy susceptibility genes and biomarkers, large sample sizes are required. If possible, future studies of DN should take advantage of existing cohorts to leverage the available phenotypes for study of natural history and risk factors for DN. Large, ongoing, observational studies provide a unique opportunity to augment diabetes or obesity studies with novel renal, cardiovascular, or cerebrovascular end points; similarly, cardiovascular observational studies afford the opportunity to add renal components. Established and emergent technologies for phenotyping and biomarker discovery could be used in these cohorts with limited additional cost. Cohorts that are assembled by other institutes should be reviewed as valuable resources for these studies.
Currently available biomarkers are not adequate. Thus, albuminuria, a strong predictor of DN risk and a strong indicator of therapeutic response in clinical trials, is, nonetheless, of insufficient precision to serve adequately as the sole indicator of risk of a protection from DN or as the single entry criterion and/or end point for clinical DN trials. Biomarker research should focus primarily on the early stages of disease to develop risk predictors and, at the same time, gain insight into mechanisms of the genesis of early diabetic renal injury. Biomarkers at later stages that predict the rate of renal functional decline from overt DN to ESRD are of indisputable importance but may not be totally specific to diabetes and may be under separate pathogenic and genetic regulatory control compared with the earlier stages and would be complicated by the influences of therapeutic interventions. Accurate description of these early phenotypes is key. A risk or protection algorithm will need to be derived from albumin excretion rate, family history, and demographic and clinical variables (e.g., HbA1c, BP, ambulatory BP, GFR, retinopathy data, lipids, BMI) in combination with proteomic and genomic data sets. Inclusion of information obtained from cross-sectional or longitudinal renal biopsies in these data sets should be considered carefully. The explosion in the incidence of obesity-related type 2 diabetes among the young (adolescent to young adult), particularly among minority population groups that are known to be highly susceptible to DN complications (black, Hispanic, Native American), has enormous public health consequences as complications develop in these patients. With this looming disaster comes the opportunity and the necessity to use this rapidly growing cohort of patients with type 2 diabetes to develop natural history information and to identify biomarkers. This is critical to select individuals who are at especially high risk for the intensive therapies that are known to influence outcomes. Efforts to do so on a global scale (i.e., treat all patients intensively) would require greater resources.
Research Priorities.
The epidemiology and biomarker groups identified the following priorities:
Priority 1.
To build on existing observational cohorts to:
Priority 2.
An integral component of the epidemiologic studies suggested in Priority 1 would be development of a DN biomarker consortium, in some ways parallel to the animal models consortium. This group should develop efficient study designs; tighten phenotype description; consider analytic strategies; formulate recruitment strategies; establish protocols for uniform biologic materials acquisition and processing, including renal biopsy; and ensure broad availability of valuable repositories of clinical and biologic resources to qualified investigators. Biomarker search strategies should include both supervised (targeted candidate) and unsupervised candidate-generating (e.g., microarray, proteomics, metabolomics) approaches. Candidate pathways include podocyte injury markers and oxidative stress pathways. The goals of Priorities 1 and 2 are development of biomarkers and predictive algorithms to identify patients at risk for renal and cardiovascular complications in early-onset obesity, metabolic syndrome, and type 2 diabetes.
Priority 3.
Recognizing that renal, cardiovascular, and cerebrovascular disease risk is determined by overlapping genetic and environmental risk factors and that the full delineation of risk is determined by multiple effects on multiple organ systems, it is recommended that an "Integrative Systems Biology Workshop on Diabetic Nephropathy" be conducted to bring investigators from multiple disciplines together to discuss novel and complementary approaches to research. The initial focus, for example, could be the use of populations, individuals, cells, and DNA in humans and animal models to explore the potential of glycemic memory on diabetic renal disease.
DN Pathogenesis: Cellular and Animal Models
What We Know; What We Need to Know.
Despite increased knowledge of physiologic and biochemical pathways, the mechanisms that mediate diabetic renal dysfunction continue to be a pressing research need. The basic biology of DN has seen considerable advances in the past 5 yr. A critical question remains to be answered: "What are the distinguishing features (i.e., predictors) of individuals who are susceptible to DN versus those who are resistant?"
In Vivo Models of DN:
Several animal models for both type 1 and type 2 diabetes are available. Initial work has focused on rat models of diabetes, either chemically induced with streptozotocin to model type 1 diabetes or diet-induced in genetically susceptible strains with insulin resistance and obesity to model type 2 diabetes. Because of the multiple advantages that the mouse provides for dissecting out cellular, molecular, and genetic mechanisms, there is now a clear preference among investigators to develop murine models of DN. Mice that receive multiple low doses of streptozotocin develop stable, long-lasting diabetes, and the Akita mouse with an ins2 mutation also mimics type 1 diabetes. The db/db mouse, with a mutated leptin receptor, has insulin resistance and therefore models type 2 diabetes. The main drawback of all available murine models is absence of progressive renal failure. In addition, mouse strain–modifying genes influence diabetogenesis, as is the case with the kk mouse, and renal disease susceptibility. Backgrounds such as dba or rop render mice that are diabetic more susceptible to progressive renal disease.
The establishment of the Animal Models of Diabetes Complications Consortium (AMDCC) has been an important step. The major goal during the present funding period has been to develop an animal model that more truly mirrors human DN, a task that remains in progress. Significant differences in susceptibility to DN exist between different strains of mice. Several noteworthy contributions have been made, including the use of HPLC for a more accurate assessment of mouse blood creatinine and insulin-based measurements of GFR in conscious mice. New transgenic models with gene deletions of decorin, endothelial nitric oxide synthase, or bradykinin receptor type 2 deficiency render diabetic mice more susceptible to progression.
In addition to these rodent models, porcine, canine, and primate models have been developed. All of these models are imperfect, however. Most do not have well-defined genetic backgrounds, and in most, the relationship between diabetes and DN and the type of renal disease that is observed differ from those in humans. Nonetheless, although studies in these species lack the genetic uniformity of inbred mouse strains, their disease may more closely mirror that observed in humans. Progress in dissecting these models in vivo has been suboptimal. Success has been hampered by problems in assessing the impact of hypertension and glycemic control, the lack of standardized measures of urinary albumin excretion and renal function, and the variability in analyzing morphologic parameters. The roles of important clinical variables such as lipid abnormalities, inflammation, and gender effects remain unclear.
In Vitro Studies Related to DN:
Significant progress has been made in studying DN using in vitro approaches. Activation of the intrarenal angiotensin II system and generation of reactive oxygen species (ROS) mediate a variety of pathogenic events. TGF-
has been established firmly as the principal mediator of cell hypertrophy and extracellular matrix production in virtually all cell types in the diabetic kidney. Vascular endothelial growth factor has emerged as another potentially important mediator of albuminuria. A significant area of progress has been the definition of a central role for the podocyte in regulating filtration of albumin, in generating a stable interaction with and support of the glomerular capillary wall, and in producing cytokines that affect glomerular cell function. Loss of podocytes by detachment or apoptosis increasingly seems to be a major event in the development of glomerulosclerosis. The kidney tubulointerstitium is now well recognized as a site of critical hypertrophy and fibrogenesis in progressive DN. However, the hypermetabolic effects of the diabetic milieu on tubular cell growth and function and the role of tubular (or interstitial) cell epithelial-to-mesenchymal transition are not well understood. The diabetic microenvironment in vivo induces nonenzymatic glycation of proteins and matrices; causes glomerular hyperfiltration, hypertension, or capillary dilation; and dysregulates cell metabolism. The impact of these events on cell–cell and cell–matrix interactions merits consideration. Cells that have been exposed to a diabetic microenvironment in vitro retain their diabetes-associated phenotype in long-term culture even after exposure to nondiabetic conditions. Long-term follow-up of the Diabetes Control and Complications Trial [DCCT]/Epidemiology of Diabetes Interventions and Complications Study [EDIC] cohort has documented analogous hyperglycemic "memory" in humans. The cellular basis for hyperglycemic memory is unknown. Thus, the diabetic metabolic state may cause epigenetic effects that produce persisting changes in cellular phenotype and organ function.
Research Priorities.
Animal Models
Priority 1.
The Animal Models of Diabetes Complications Consortium should receive continued support to continue characterization of established models and development of new models of progressive DN that better mimic human DN. As animal models of DN are developed, a common "clean" repository, obviating quarantine, should be established for distribution of animals to the investigative community. Specific goals include:
Priority 2.
Comparative genomics using data from the Animal Models of Diabetes Complications Consortium and human studies (e.g., Family Investigation of Nephropathy of Diabetes Consortium [FIND], EDIC, Genetics of Kidneys in Diabetes [GoKIND]) should be promoted to identify environmental and genetic modifiers, including but not limited to inflammation, hypertension, lipid abnormalities, oxidative stress, single-gene mutations, gender, and strain differences, including quantitative trait loci and differences in global gene expression.
In Vitro Models
Priority 3.
To complement the animal studies, we also recommend further study of the basic cell biology of DN in vitro:
Hypertension
Introduction
Hypertension remains one of the leading causes of renal failure and is clearly a contributor to accelerated loss of renal function in the setting of other forms of renal disease. Likewise, the kidney itself is central to the pathogenesis of hypertension.
The Hypertension retreat targeted the following major areas:
On the basis of previous work in the field, these areas were identified as most promising for discoveries that would promote understanding of disease pathogenesis and provide potential for identifying new approaches for therapy and cardiovascular prevention strategies. The recommendations of the group are outlined below.
The Kidney as a Cause of Hypertension
Many lines of evidence from human genetic studies, physiologic studies, and cross-transplantation experiments highlight the critical role of altered renal excretory function as a final common pathway in the development of chronic hypertension. By extension, subtle abnormalities in kidney function seem to be a common cause of hypertension. However, the precise molecular and cellular pathways that are responsible for these perturbations are not clear, especially in patients with essential hypertension. Accordingly, research that focuses on the kidney as a cause of hypertension is an important area for research emphasis. Results of work in this area should advance strategies for diagnosis, treatment, and prevention of hypertension, a disorder that affects more than 40 million individuals in the United States. Specific areas were believed to be priorities for future investigation.
Priority 1:
Studies on renal ion transporters in hypertension:
Priority 2:
Developmental biology of the kidney in hypertension: Molecular and genetic mechanisms of perinatal programming of renal development;
Interventions to interrupt and compensate for adverse perinatal programming;
Clinical correlates of perinatal programming in later life.
Priority 3:
Renal vascular biology in hypertension:
The Kidney as a Target in Hypertension
Along with its causative role in hypertension, the kidney is a target for damage from chronic elevation of arterial pressure. Moreover, hypertension is a major risk factor for progression of CKD. Loss of kidney function from hypertension leads to a vicious cycle of worsening hypertension and continuing kidney damage. Although the capacity of high BP to injure the kidney is widely recognized, the molecular pathways that are responsible for pressure-dependent injury are not clear. Various human populations, such as black individuals, seem to be more vulnerable to hypertensive kidney damage, but the nature of this apparent genetic susceptibility is unknown.
Priority 1:
Support initiatives to develop and identify more precise methods for assessment and quantification of hypertensive kidney injury:
Priority 2:
Renal hemodynamic and cellular factors in hypertensive kidney injury:
Hypertension in Patients with CKD
More than 20 million people in the United States have CKD, and CKD is a newly recognized risk factor for CVD. This risk is independent of other known risks, including hypertension, hypercholesterolemia, and cigarette smoking. In CKD, there is considerable evidence that inhibitors of the renin-angiotensin-aldosterone system slow progression of CKD. In essential hypertension, BP reduction reduces cardiovascular events. However, there are no studies showing that aggressive control of BP and/or use of renin-angiotensin-aldosterone system antagonists reduces cardiovascular risk in patients with CKD. Although albuminuria also confers significant cardiovascular risk, whether targeted reduction in proteinuria reduces cardiovascular events in CKD is not known. Finally, in the subgroup of CKD patients who develop ESRD, CVD is a major cause of morbidity and mortality. As in CKD, the relationship between hypertension and CVD in patients with ESRD is not clear. For example, studies reveal a J-shaped relationship between BP and mortality in patients with ESRD.
Research Priority.
To address these critically important questions and the gaps in our knowledge, we suggest that priorities be given to support a clinical trials consortium to study patients at various stages of CKD and patients on dialysis (ESRD):
Resource Centers for Hypertension Research
The group suggested that development of resource centers focused on areas of common need in this area would be a cost-efficient mechanism for promoting progress in research on the kidney in hypertension. Examples of such resources include:
Transplantation
Introduction
Renal transplantation is the treatment of choice for patients with ESRD. In the past two decades, the advent of improved immunosuppressive drugs has resulted in a significant improvement in the prevention of acute rejection. The emphasis on this prevention was predicated on the dominant thinking underlying transplantation and immunosuppressive biology that if acute rejection could be avoided, then the patient would keep the graft for as long as necessary, eventually succumbing to a nonrenal death. Recent epidemiologic studies suggest that this may not be the case. Thus, although current immunosuppressive therapies are very powerful and have dramatically decreased and almost eradicated acute rejection episodes, we have seen no progress in ultimate graft survival. This important new recognition strongly suggests that our previous emphasis focused solely on the prevention of acute rejection with immunosuppression does not, in itself, lead to ultimate long-term graft survival.
There are at least two not mutually exclusive explanations for this observation: Either we are not defining "rejection" properly, or there are additional nonimmune processes that lead to ultimate graft loss. With regard to "acute rejection," our definition has been operational, involving a general clinical state and rise in creatinine. By the time a rise in creatinine is evident because of acute rejection, a significant degree of tissue damage has occurred within the kidney. The use of creatinine as an end point therefore may lead to interventions too late, leaving undiagnosed chronic, lingering damage that contributes to the multifactorial state that has been called "chronic rejection." One classic approach to an earlier diagnosis of rejection involves early or routine biopsy. This approach has limitations, and the definition of "rejection" remains controversial. Another approach involves "molecular" diagnosis. A new "holy grail" among transplant nephrologists is that there may be a molecular "signature" evident in the kidney, blood, or urine indicative of rejection. If this molecular event precedes biopsy evidence that precedes clinical definition of rejection, then perhaps therapy can be provided earlier and the ultimate outcome improved. The second possibility is that more than one pathway is leading to ultimate graft loss. Perhaps an immunosuppressive-resistant process is giving rise to ultimate graft loss. It is certain that some of the most potent immunosuppressive agents (that have helped to nearly eradicate acute rejection) themselves contribute to vascular damage and ultimate graft loss. To prevent drug toxicity, newer protocols have decreased immunosuppression to relieve the significant toxicities of steroids and/or calcineurin inhibitors.
The use of immunosuppressant medications is complicated by their systemic side effects. Infection is a well-recognized complication of immunosuppression. However, these medications may also worsen or cause illnesses such as diabetes, hyperlipidemia, and hypertension, thereby contributing to the CVD burden of the transplant recipient. Thus, the major new paradigm in renal transplantation is that more powerful immunosuppression is not the ultimate answer. The search for strategies for induction and maintenance of immune tolerance in humans continues, but at the same time, new investigation as to the immunologic and nonimmunologic causes of graft loss is required.
The Transplant retreat focused on:
Ultimate Graft Loss
What We Know; What We Need to Know.
We know:
However:
Research Priority: To Identify Factors Involved in Chronic Graft Loss.
Progress in this field will clearly require:
Posttransplantation CVD
What We Know; What We Need to Know.
We know:
However, we do not know whether the increase in cardiovascular events posttransplantation is due:
Research Priorities.
Priority 1.
Establish a prospective cohort of renal transplant patients in whom medications, conventional risk factors, cardiovascular outcomes, and graft outcomes are recorded. Patient blood should be banked at defined time points so that nontraditional risk factors and inflammatory mediators may be investigated. This cohort of patients may then be used to ask the following questions:
The identification of nontraditional risk factors may be assessed in this population through the use of banked serum. This registry and blood/serum bank overlaps with some of the needs of the surrogate marker group. The establishment of a single large cohort in which both aims are examined and additional specimens, outlined by the biomarker group, are banked would be more fruitful. This would allow for cross-talk, for example, in the area of graft function and inflammatory mediators, given the increasingly recognized role of inflammation in CVD.
Priority 2.
Determine the effects of intervention on disease progression in the renal transplant population. At present, therapies that are directed at the treatment of cardiovascular risk factors in renal transplant patients are based on the extrapolation of data from the general population. A subset of patients from the initial cohort would be randomized to receive intensive therapy as defined by guidelines such as intense lifestyle modification, BP treated as per JNC VII, target LDL <100, maximization of treatment with angiotensin-converting enzyme inhibitors and/or angiotensin II receptor blockers, erythropoietin therapy and Ca+/PO4– management. The outcomes in these patients would be compared with those who receive standard care. The influence of the care provider, nurse, nurse practitioner, or doctor on outcomes would be examined. The two main outcomes investigated would be cardiovascular outcomes and allograft function.
Priority 3.
Evaluate pretransplant screening process for CVD. Death as a result of CVD early posttransplantation is a significant cause of graft loss very early posttransplantation. There are no current evidence-based guidelines for the evaluation of CVD pretransplantation. Most programs would claim to use protocols that are more aggressive than would be suggested for the evaluation of CVD by the American College of Cardiology. However, we have no data to suggest that this additional effort and expense is warranted. We therefore would propose to evaluate American College of Cardiology guidelines with aggressive pretransplant evaluation to determine the influence on preventing subsequent cardiovascular events. An important resource that will be available is the cohort of patients followed prospectively by the FAVORIT study. The group recommended that RFA associated with these data examining cardiovascular outcomes and/or graft function/survival would maximize the use of this study.
Resource Centers for Transplant Research
Core A: Clinical Consortium.
The objectives of the clinical consortium are (1) to bring together renal transplant programs and therefore patients who will participate in the studies to evaluate the questions outlined in this proposal, evaluation of donor and recipient factors that contribute to graft loss, evaluation of acute rejection as an end point, determination of putative surrogate markers, evaluation of cardiovascular risk, and the benefit of therapeutic intervention in the transplant patient and (2) to provide the infrastructure necessary for subsequent large multicenter trials developed on the basis of initial findings from the studies outlined in this proposal.
Core B: Biomarker Core.
The purpose of the biomarker core would be to centralize the process for evaluation of putative biomarker. Patients will be enrolled and samples will be collected from those centers involved in the clinical consortium.
Core C: Registry Core.
The establishment of a registry of patients with renal transplants for the evaluation of cardiovascular risk factors and the relationship between CKD and CVD as it pertains to the renal transplant population. The registry will be based on the participation of a large number of centers and will facilitate the enrollment of patients into Cores A and B.
Uremic Cardiovascular Toxicity
Introduction
Despite advances in dialysis, overall mortality among patients with end stage kidney disease remains as high as 23% per year, and cardiac causes account for between 40 and 50% of all deaths. The net result of this burden of CVD is that, when compared with the general population, patients with ESRD have between a 10 and 20 times greater incidence of cardiovascular death. The types of heart disease most commonly seen in ESRD patients are coronary artery disease and left ventricular hypertrophy. The former condition is associated with myocardial infarction and sudden death, and the latter is associated with either diastolic or systolic dysfunction and is also associated with sudden death. There is now also compelling evidence that the incidence and prevalence of heart disease increase as renal function declines. Data accumulating from national epidemiologic studies, regional and community-based epidemiologic studies, and the analysis of randomized clinical trials all suggest that CKD is an important independent risk factor for cardiovascular complications.
There are multiple physiologic derangements that occur in patients with kidney disease and combine to lead to the increased incidence and prevalence of heart disease in this patient group. Among these, hypertension, an abnormal calcium/phosphorus product, vascular calcification, the accumulation of advanced oxidation protein products and advanced glycation end products, the accumulation of inhibitors of nitric oxide such as asymmetric dimethylarginine and phenylacetic acid, the high concentrations of angiotensin II as a factor in cardiac hypertrophy and abnormal remodeling, the accumulation of the amino acid homocysteine, and the problem of inflammation as a pro-atherosclerosis factor are, to name a few, several of the important abnormalities associated with the development of heart disease in this patient population. In addition to these factors, the association of other common abnormalities, which occur in advanced kidney failure such as anemia, can contribute to cardiovascular morbidity and mortality. The aggregate burden of kidney and heart disease exacts an enormous human cost and presents a staggering financial burden as well. The partial dialysis costs of the growing ESRD population in the United States is estimated to be between $20 and $30 billion per year, and with the growth of the number of dialysis patients to as many of 600,000 Americans by 2010, these costs are likely to rise dramatically. The costs associated with cardiovascular risk in patients with earlier stages of CKD are more difficult to quantify but are also likely staggering, given the high prevalence in the US adult population.
The goals of the Uremic Cardiovascular Toxicity retreat were to:
The broad focus topics for the retreat designed in advance by the planning committee were:
Epidemiology of CVD in CKD
Background.
There are excellent epidemiologic data regarding cardiovascular complications in patients who have ESRD and receive renal replacement therapy:
Epidemiologic data available on cardiovascular risk in patients who have CKD and do not receive replacement therapy are comparatively less robust. Emerging data are available from:
Data from the first three sources all suggest that the development of CKD may be an independent risk marker for CVD.
Research Priorities.
Priority 1.
Systemically reanalyze previously conducted randomized clinical trials of cardiovascular interventions that have included patients with CKD.
Priority 2.
Support ancillary studies of CKD cohorts in current National Institutes of Health–funded trials. The analysis of these cohorts’ databases should focus on addressing the following unanswered questions:
The group recognized two caveats in the interpretation of this epidemiologic data:
Pathogenesis of Cardiomyopathy and Atherosclerosis in CKD
Background.
Considerable epidemiologic data associating CVD with the degree of CKD currently exist. However, associative studies cannot indicate whether the degree of renal disease is in effect a sensor of vascular injury or is a direct contributor to the vascular injury process. Although mechanistic data from animal models and human studies relating, for example, hypertension and anemia to the development of left ventricular hypertrophy and alterations in divalent anion and cation metabolism to vascular calcification exist, there are less well-established mechanisms potentially linking CKD to accelerated atherogenesis.
An improved understanding of whether and how the loss of renal function and concomitant changes in hormonal and metabolic responses that are associated with retention of unexcreted uremic solutes or the dialysis process contribute to the atherogenesis is a high priority in kidney disease research. An improved mechanistic understanding is likely to evolve from a combination of basic science and translational studies.
Research Priority.
A research priority is to undertake both animal and human studies to define better the mechanisms whereby kidney dysfunction increases CVD. To this end, the retreat suggested the following two approaches:
45 ml/min or are on dialysis. Interventions targeted for potential kidney disease–specific cardiovascular risk pathways can be used as "probes" to detect changes in biomarkers, cardiovascular risk surrogates, and overt measures of CVD. Several important kidney disease–specific risk pathways were identified as priorities for further translational studies in the context of several potential disease modifiers for the CKD disease process (Table 1).
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Defining Study End Points.
Clinical trials should rely primarily on clinical end points, including measures of cardiovascular and renal function, cardiovascular event rates, renal disease progression rates, and cardiovascular and all-cause mortality rates. Surrogate biomarker end points have value with respect to validating or refuting proposed mechanisms for uremic CVD. They would be especially valuable in smaller pilot studies designed to elucidate a more mechanistic understanding of uremic CVD to more rationally choose agents for larger clinical trials.
Therapies for Atherosclerosis Studies.
There are a number of attractive agents for consideration of atherosclerosis studies in populations with advanced CKD and in patients with CKD and known CVD. Statins are attractive agents, and there are currently at least three large-scale, multicenter, randomized, clinical trials under way comparing statin use with placebo either in the dialysis population or in a combined advanced CKD/dialysis population. A preliminary report from the 4D Trial suggests that there may be limited benefit from statin therapy in dialysis patients, accentuating the pressing need for further research in uremic CVD. Results of these ongoing studies will be extremely valuable to the renal community. There are other potential agents for consideration, including antiplatelet agents, antioxidants, peroxisome proliferator-activated receptor agonists, and possibly anti-inflammatory agents. All-cause mortality is the most appropriate primary end point for these trials, and a higher priority should be placed on larger, relatively well-powered studies that will provide a definitive answer rather than on conducting multiple parallel, less well-powered clinical trials.
Therapies for Cardiomyopathy and Congestive Heart Failure Studies.
There are a number of potential attractive therapeutic agents for study in patients with CKD and known congestive heart failure or for CKD patients who have GFR <45 ml/min at are at high risk for congestive heart failure and cardiomyopathy:
Genetic Risks for CVD in CKD.
Several gene polymorphisms have now been identified as being associated with adverse outcomes in small studies in the ESRD population. There is a need for a global, more holistic, and large population-based study of the relationship of gene polymorphisms to CVD in CKD/ESRD patients.
Clinical Trial Networks and Renal Disease Consortia.
Developing renal disease clinical consortia and/or clinical trial networks will facilitate efficient clinical studies of uremic CVD. A prototypical network has been formed through a concept grant from the NIDDK entitled "The Kidney Disease Research Consortium." This and/or other research consortia can provide access to large numbers of CKD and ESRD patients to perform appropriate clinical trials/studies in a speedy, efficient, and cost-effective manner.
Appendix
Acute Renal Failure Retreat, June 7 to 9, 2004
Planning Committee
Sudhir Shah, MD, Chair
University of Arkansas for Medical Sciences
Wilfred Lieberthal, MD
Amgen, Inc.
Ravindra Mehta, MD
University of California San Diego Medical Center
Bruce Molitoris, MD
Indiana University Department of Medicine
Mark Okusa, MD
University of Virginia Health System
Hamid Rabb, MD
Johns Hopkins University School of Medicine
Kidney Transplant Program
Norman Siegel, MD
Yale University School of Medicine
Robert Star, MD
NIDDK, National Institutes of Health
Unit of Renal Diagnostics and Therapeutics
M.A. Venkatachalam, MD
University of Texas, San Antonio
Participants
Louis Brenner, MD
Genzyme Therapeutics
Lakhmir Chawla, MD
George Washington University Medical Center
Prasad Devarajan, MD
Cincinnati Children’s Hospital Medical Center
University of Cincinnati
Charles Edelstein, MD, PhD
University of Colorado Health Sciences Center
Stuart Goldstein, MD
Texas Children’s Hospital
Andrea L. Harabin, PhD
NIH Division of Lung Diseases
National Heart, Lung, and Blood Institute
Stefan Herget-Rosenthal, MD
Klinik für Nieren- und Hochdruckkrankheiten
Universitätsklinikum Essen
Samuel N. Heyman, MD
Hebrew University, Jerusalem
David Humes, MD
University of Michigan Medical School
John A. Kellum, Jr., MD
University of Pittsburgh
Jon Klein, MD, PhD
University of Louisville
Dheerendra Kommala, MD
Abbott Laboratories
Raul Lombardi, MD
Department of Critical Care Medicine, IMPASA
Bill Macias, MD, PhD
Eli Lilly & Co.
Thomas A. Marciniak, MD
FDA, Division of Cardiorenal Drug Products
Dwight McKinney, MD
Eli Lilly & Co.
Lisa Meier McShane, PhD
National Cancer Institute
Donna L. Mendrick, PhD
Gene Logic Inc.
Patrick Murray, MD
University of Chicago Hospitals and Clinics
Paul Palevsky, MD
University of Pittsburgh School of Medicine
Lorraine Racusen, MD
The Johns Hopkins Medical Institutions
Rebekah S. Rasooly, PhD
NIH/NIDDK
Seymour Rosen, MD
Beth Israel Deaconess Medical Center
Gordon D. Rubenfeld, MD
University of Washington
Robert Safirstein, MD
University of Arkansas
Nancy Seybold
Quartermark Consulting, LLC
John Silva, MD
Silva Consulting Services
Manikkam Suthanthiran, MD
Weill Medical College of Cornell University
Jin Tian, MD
Abbott Laboratories
James Tumlin, MD
Emory University
Scott Van Why, MD
Medical College of Wisconsin
Joel Weinberg, MD
University of Michigan Medical Center
Shannon P. Williams, PhD
Adenosine Therapeutics, LLC
Marsha Wolfson, MD
Amgen, Inc
Anna Zuk, PhD
Genzyme Corporation
Diabetic Nephropathy Research Retreat, November 15 to 16, 2004
Planning Committee
Lisa Satlin, MD, Co-chair
Mount Sinai School of Medicine
John Sedor, MD, Co-chair
Case Western Reserve University
Peter Aronson, MD
Yale School of Medicine
Tomas Berl, MD
University of Colorado Health Sciences Center
Mark Cooper, MD
Baker Medical Research Institute, Australia
Michael Mauer, MD
University of Minnesota
Stephen Rich, PhD
Wake Forest University School of Medicine
H. William Schnaper, MD
Northwestern University School of Medicine
Fuad Ziyadeh, MD
University of Pennsylvania
Participants
Sharon Adler, MD
Harbor-UCLA Medical Center
Roland Blantz, MD
University of California, San Diego and VASDHC
Erwin Bottinger, MD
Mount Sinai Medical Center
Matthew Breyer, MD
Vanderbilt University
Jon Klein, MD, PhD
University of Louisville
Timothy Lyons, MD
University of Oklahoma Health Sciences Center
William Mitch, MD
University of Texas, Galveston
Jerry Nadler, MD
University of Virginia Health System
Anne Marie Schmidt, MD
Columbia University
Kumar Sharma, MD
Thomas Jefferson University
Roger Wiggins, MD
University of Michigan, Ann Arbor
NIH
Monique Cho, MD
Teresa Jones, MD
Jeff Kopp, MD
Mark Knepper, MD
Robert Nelson, MD, PhD
JDRF
Aaron Kowalski, PhD
Marie Nierras, PhD
Hypertension Research Retreat, November 15 to 16, 2004
Planning Committee
Thomas Coffman, MD, Co-chair
Duke University Medical Center
Stuart Linas, MD, Co-chair
University of Colorado
Peter Aronson, MD
Yale School of Medicine
Tomas Berl, MD
University of Colorado Health Sciences Center
Michael Klag, MD
Johns Hopkins Medical Institute
Luis Gabriel Navar, PhD
Tulane University Health Sciences Center
David Warnock, MD
University of Alabama
Christopher Wilcox, MD, PhD
Georgetown University Medical Center
Participants
Rajiv Agarwal, MD
Indiana University
Chris Baylis, PhD
University of Florida
Philip Darwin Bell, PhD
University of Alabama at Birmingham
Anil Bidani, MD
Loyola University, Chicago
Vito Campese, MD
University of Southern California
Arlene Chapman, MD
Emory University
Lance Dworkin, MD
Brown University
L. Lee Hamm, MD
Tulane Medical Center
Julie Ingelfinger, MD
Harvard University
Donald Kohan, MD
University of Utah Medical Center
Rick Lifton, MD, PhD
Yale University School of Medicine
V. Matti Vehaskari, MD
LSU Health Sciences Center
Susan Wall, MD
Emory University School of Medicine
Matthew Weir, MD
University of Maryland Hospital
NIDDK
Larry Agodoa, MD
Josie Briggs, MD
Chris Ketchum, PhD
Mark Knepper, MD
NHLBI
Winnie Barouch, MD
Jeffrey Cutler, MD
Trairak Pisitkun, MD
Cristina Rabadan-Diehl, MD
Paul Velletri, MD
Transplantation Research Retreat, October 4 to 5, 2004
Planning Committee
Alan Krensky, MD, Co-chair
Stanford University
Barbara Murphy, MD, Co-chair
Mount Sinai Medical Center
Tomas Berl, MD
University of Colorado Health Sciences Center
Jon Bromberg, MD
Mount Sinai School of Medicine
Philip Halloran, MD
University of Alberta
William Harmon, MD
Harvard University
Bruce Kaplan, MD
University of Florida
Mohamed Sayegh, MD
Harvard University
Terry Strom, MD
Harvard University
Flavio Vincenti, MD
University of California, San Francisco
Participants
William Bennett, MD
Legacy Good Samaritan Hospital
Carl Cardella, MD
University of Toronto
Anil Chandraker, MD
Harvard University
Richard Fine, MD
SUNY at Stony Brook School of Medicine
Peter Heeger, MD
Cleveland Clinic Foundation
Donald Hricik, MD
Case Western Reserve University
Bertram Kasiske, MD
University of Minnesota
John Neylan, MD
Wyeth Research
Claudio Rigatto, MD
Saint Boniface General Hospital
Montreal, Canada
David Rothstein, MD
Yale University
Alison Schecter, MD
Mt. Sinai School of Medicine
Manikkam Suthanthiran, MD
Weill Medical College of Cornell University
John Williams, PhD
Genzyme Corporation
NIAID
Nancy Bridges, MD
Kristy Kraemer, PhD
Shiv Prasad, PhD
NIDDK
Cathy Meyers, MD
Tom Hostetter, MD
Roz Mannon, MD
Marva Moxey-Mims, MD
Uremic Cardiovascular Toxicity Research Retreat, October 4 to 5, 2004
Planning Committee
William Henrich, MD, Co-chair
University of Maryland School of Medicine
Jonathan Himmelfarb, MD, Co-chair
Maine Medical Center
Tomas Berl, MD
University of Colorado Health Sciences Center
T. Alp Ikizler, MD
Vanderbilt University Medical Center
George Kaysen, MD, PhD
University of California, Davis
Brian Pereira, MD, MBA
Tufts-New England Medical Center
Participants
John Burkart, MD
Wake Forest University Baptist Medical Center
Alfred Cheung, MD
University of Utah
Christopher Cooper, MD
Medical College of Ohio
Josef Coresh, MD, PhD
Johns Hopkins Bloomberg School of Public Health
Laura Dember, MD
Boston University School of Medicine
Matthew Fenton, PhD
University of Maryland School of Medicine
Rob Foley, MD
University of Minnesota
L. Lee Hamm, MD
Tulane Medical Center
Robert Mak, MD, PhD
Oregon Health Science University
William Mitch, MD
University of Texas, Galveston
Rajiv Saran, MD
University of Michigan
Gerald Schulman, MD
Vanderbilt University Medical Center
Robert Schrier, MD
University of Colorado School of Medicine
James Udelson, MD
Tufts-New England Medical Center
Joseph Vita, MD
Boston University
Whittaker Cardiovascular Institute
NHLBI
Jeffrey Cutler, MD
Acknowledgments
The renal research retreats that form the substance of this report were conceived and organized by the Board of Advisors and the Council of the American Society Nephrology. However, it is the dedicated commitment of the leaders of the five retreats and their steering committees and the input of the participants that ultimately make this report possible. We express our gratitude to all of those individuals.
We acknowledge the support and participation in this effort of the National Kidney Foundation, the American Society of Pediatric Nephrology, the American Society of Transplantation (Transplantation retreat), the American Society of Hypertension (Hypertension retreat), and the Kidney Council of the American Heart Association (Uremic Toxicity and Hypertension retreats).
We also recognize our Executive Director, Dr. Karen Campbell, for oversight of the project; Neysa Matthews for assistance with all of the logistics involved in the organization of the meetings; and Shari Leventhal for assistance in the preparation of this report.
Footnotes
Address correspondence to: Dr. Tomas Berl, University of Colorado Health Sciences Center, Medicine/Renal, 4200 East 9th Avenue, C281, Denver, Colorado 80262. Phone: 303-315-7204; Fax: 303-315-0189; E-mail: tomas.berl{at}uchsc.edu
Published online ahead of print. Publication date available at www.jasn.org.
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