Child and caregiver perspectives on access to psychosocial and educational support in pediatric chronic kidney disease: a focus group study.

BACKGROUND: Children with chronic kidney disease (CKD) generally have worse educational and psychosocial outcomes compared with their healthy peers. This can impair their ability to manage their treatment, which in turn can have long-term health consequences through to adulthood. We attempted to capture the experiences of children with CKD and to describe the perspectives of their parents and caregivers on access to educational and psychosocial support. METHODS: Children with CKD (n = 34) and their caregivers (n = 62) were sampled via focus groups from pediatric hospitals in Australia, Canada, and the USA. Sixteen focus groups were convened and the transcripts were analyzed thematically. RESULTS: We identified four themes: disruption to self-esteem and identity (emotional turmoil of adolescence, wrestling with the sick self, powerlessness to alleviate child's suffering, balancing normality and protection); disadvantaged by lack of empathy and acceptance (alienated by ignorance, bearing the burden alone); a hidden and inaccessible support system (excluded from formal psychological support, falling behind due to being denied special considerations); and building resilience (finding partners in the journey, moving towards acceptance of the illness, re-establishing childhood). CONCLUSIONS: Children with CKD and their caregivers encountered many barriers in accessing psychosocial and educational support and felt extremely disempowered and isolated as a consequence. Improved availability and access to psychosocial and educational interventions are needed to improve the wellbeing and educational advancement of children with CKD. A higher resolution version of the Graphical abstract is available as Supplementary information.

Perspectives of Clinicians on Shared Decision Making in Pediatric CKD: A Qualitative Study.

RATIONALE & OBJECTIVE: Clinical decision-making priorities may differ among children, their parents, and their clinicians. This study describes clinicians' perspectives on shared decision making in pediatric chronic kidney disease (CKD) and identifies opportunities to improve shared decision making and care for children with CKD and their families. STUDY DESIGN: Semistructured interviews. SETTING & PARTICIPANTS: Fifty clinicians participated, including pediatric nephrologists, nurses, social workers, surgeons, dietitians, and psychologists involved in providing care to children with CKD. They worked at 18 hospitals and 4 university research departments across 11 countries (United States of America, Canada, Australia, People's Republic of China, United Kingdom, Germany, France, Italy, Lithuania, New Zealand, and Singapore). ANALYTICAL APPROACH: Interview transcripts were analyzed thematically. RESULTS: We identified 4 themes: (1) striving to blend priorities (minimizing treatment burden, emphasizing clinical long-term risks, achieving common goals), (2) focusing on medical responsibilities (carrying decisional burden and pressure of expectations, working within system constraints, ensuring safety is foremost concern), (3) collaborating to achieve better long-term outcomes (individualizing care, creating partnerships, encouraging ownership and participation in shared decision making, sensitive to parental distress), and (4) forming cumulative knowledge (balancing reassurance and realistic expectations, building understanding around treatment, harnessing motivation for long-term goals). LIMITATIONS: Most clinicians were from high-income countries, so the transferability of the findings to other settings is uncertain. CONCLUSIONS: Clinicians reported striving to minimize treatment burden and working with children and their families to manage their expectations and support their decision making. However, they are challenged with system constraints and sometimes felt the pressure of being responsible for the child's long-term outcomes. Further studies are needed to test whether support for shared decision making would promote strategies to establish and improve the quality of care for children with CKD.

Patient and caregiver perspectives on blood pressure in children with chronic kidney disease.

BACKGROUND: More than 50% of children with chronic kidney disease (CKD) have uncontrolled hypertension, increasing their long-term risk of cardiovascular disease and progression to kidney failure. Children receiving medications or dialysis may also experience acute blood pressure fluctuations accompanied by debilitating symptoms. We aimed to describe the perspectives of children with CKD and their parental caregivers on blood pressure to inform patient-centered care. METHODS: Secondary thematic analysis was conducted on qualitative data from the Standardized Outcomes in Nephrology-Children and Adolescents initiative, encompassing 16 focus groups, an international Delphi survey and two consensus workshops. We analyzed responses from children with CKD (ages 8-21 years) and caregivers (of children ages 0-21 years) pertaining to blood pressure. RESULTS: Overall, 120 patients and 250 caregivers from 22 countries participated. We identified five themes: invisibility and normalization (reassured by apparent normotension, absence of symptoms and expected links with CKD), confused by ambiguity (hypertension indistinguishable from cardiovascular disease, questioning the need for prophylactic intervention, frustrated by inconsistent messages and struggling with technical skills in measurement), enabling monitoring and maintaining health (gaging well-being and preventing vascular complications), debilitating and constraining daily living (provoking anxiety and agitation, helpless and powerless and limiting life activities) and burden of medications (overwhelmed by the quantity of tablets and distress from unexpected side effects). CONCLUSIONS: For children with CKD and their caregivers, blood pressure was an important heath indicator, but uncertainty around its implications and treatment hampered management. Providing educational resources to track blood pressure and minimizing symptoms and treatment burden may improve outcomes in children with CKD.

Establishing core outcome domains in pediatric kidney disease: report of the Standardized Outcomes in Nephrology-Children and Adolescents (SONG-KIDS) consensus workshops.

Trials in children with chronic kidney disease do not consistently report outcomes that are critically important to patients and caregivers. This can diminish the relevance and reliability of evidence for decision making, limiting the implementation of results into practice and policy. As part of the Standardized Outcomes in Nephrology-Children and Adolescents (SONG-Kids) initiative, we convened 2 consensus workshops in San Diego, California (7 patients, 24 caregivers, 43 health professionals) and Melbourne, Australia (7 patients, 23 caregivers, 49 health professionals). This report summarizes the discussions on the identification and implementation of the SONG-Kids core outcomes set. Four themes were identified; survival and life participation are common high priority goals, capturing the whole child and family, ensuring broad relevance across the patient journey, and requiring feasible and valid measures. Stakeholders supported the inclusion of mortality, infection, life participation, and kidney function as the core outcomes domains for children with chronic kidney disease.

Drug-induced tubulointerstitial nephritis: hypersensitivity and necroinflammatory pathways.

More than 250 drugs carry a small but important dose-independent risk of initiating a delayed-type hypersensitivity reaction that leads to acute tubulointerstitial nephritis (TIN). Clinical manifestations are often non-specific, making epidemiological studies challenging. In severe cases, if cessation of the offending drug is not followed by a prompt improvement in renal function, corticosteroid therapy appears to enhance renal recovery rates. Other drugs, classified as potential nephrotoxins, may induce dose-dependent acute tubular necrosis. Studies over the past decade have identified a unique form of tubular cell death called "necroptosis" that is accompanied by a specific and significant interstitial inflammatory response to certain insults, including some nephrotoxins. Insights into the molecular basis of this necroinflammatory pathway have emerged. There is still a paucity of pediatric data on these two distinct types of drug-induced TIN. Early recognition is essential to minimize the risk of chronic kidney damage.

Identifying Important Outcomes for Young People With CKD and Their Caregivers: A Nominal Group Technique Study.

RATIONALE & OBJECTIVE: Chronic kidney disease (CKD) has wide-ranging and long-term consequences for young people and their families. The omission of outcomes that are important to young people with CKD and their caregivers limits knowledge to guide shared decision making. We aimed to identify the outcomes that are important to young people with CKD and their caregivers. STUDY DESIGN: We used the nominal group technique whereby participants identified and ranked outcomes and explained their priorities. SETTINGS & PARTICIPANTS: Young people with CKD (stages 1-5, dialysis, or transplantation) and their caregivers were purposively sampled from 6 centers across Australia, the United States, and Canada. ANALYTICAL APPROACH: Importance scores were calculated (scale of 0-1), and qualitative data were analyzed thematically. RESULTS: 34 patients (aged 8-21 years) and 62 caregivers participated in 16 groups and identified 48 outcomes. The 5 highest ranked outcomes for patients were survival (importance score, 0.25), physical activity (0.24), fatigue (0.20), lifestyle restrictions (0.20), and growth (0.20); and for caregivers, kidney function (0.53), survival (0.28), infection (0.22), anemia (0.20), and growth (0.17). 12 themes were identified reflecting their immediate and current priorities (wanting to feel normal, strengthening resilience, minimizing intrusion into daily life, imminent threats to life, devastating family burdens, and seeking control over health) and considerations regarding future impacts (protecting health/development, remaining hopeful, concern for limited opportunities, prognostic uncertainty, dreading painful and invasive procedures, and managing expectations). LIMITATIONS: Only English-speaking participants were recruited. CONCLUSIONS: Kidney function, infection, survival, and growth were the highest priorities for patients with CKD and their caregivers. Young people with CKD also prioritized highly the outcomes that directly affected their lifestyle and sense of normality, while caregiver's highest priorities concerned the long-term health of their child, current health problems, and the financial and family burdens of caring for a child with CKD.

Child and Parental Perspectives on Communication and Decision Making in Pediatric CKD: A Focus Group Study.

BACKGROUND & OBJECTIVES: Effective communication and shared decision making improve quality of care and patient outcomes but can be particularly challenging in pediatric chronic disease because children depend on their parents and clinicians to manage complex health care and developmental needs. We aimed to describe the perspectives of children with chronic kidney disease (CKD) and their parents with regard to communication and decision making. STUDY DESIGN: Qualitative study. SETTING & PARTICIPANTS: Children with CKD (n=34) and parents (n=62) from 6 centers across 6 cities in Australia, Canada, and the United States participated in 16 focus groups. ANALYTICAL APPROACH: Transcripts were analyzed thematically. RESULTS: We identified 4 themes: (1) disempowered by knowledge imbalance (unprepared and ill-informed, suspicion of censorship, and inadequacy as technicians), (2) recognizing own expertise (intuition and instinct unique to parental bond, emerging wisdom and confidence, identifying opportunities for control and inclusion, and empowering participation in children), (3) striving to assert own priorities (negotiating broader life impacts, choosing to defer decisional burden, overprotected and overruled, and struggling to voice own preferences), and (4) managing child's involvement (respecting child's expertise, attributing "risky" behaviors to rebellion, and protecting children from illness burden). LIMITATIONS: Only English-speaking participants were recruited, which may limit the transferability of the findings. We collected data from child and parent perspectives; however, clinician perspectives may provide further understanding of the difficulties of communication and decision making in pediatrics. CONCLUSIONS: Parents value partnership with clinicians and consider long-term and quality-of-life implications of their child's illness. Children with CKD want more involvement in treatment decision making but are limited by vulnerability, fear, and uncertainty. There is a need to support the child to better enable him or her to become a partner in decision making and prepare him or her for adulthood. Collaborative and informed decision making that addresses the priorities and concerns of both children and parents is needed.

Uromodulin deficiency alters tubular injury and interstitial inflammation but not fibrosis in experimental obstructive nephropathy.

Human GWAS and Mendelian genetic studies have linked polymorphic variants and mutations in the human uromodulin gene (UMOD) with chronic kidney disease. The primary function of this kidney-specific and secreted protein remains elusive. This study investigated whether UMOD deficiency modified responses to unilateral ureteral obstruction (UUO)-induced kidney injury. Kidneys harvested from groups of wild-type (UMOD+/+) and knockout (UMOD-/-) male mice (n = 7-10 each) were studied on days 7, 14, and 21. Compared to sham kidneys, UMOD protein levels increased 9-13x after UUO and were associated with increased urinary UMOD levels. Kidney KIM-1 protein levels were higher in the UMOD-/- groups at all time-points (4-14x). The UMOD-/- groups also had higher KIM-1 kidney-to-urine relative ratios (5-35x). In vitro studies using KIM-1 expressing 769-P cells showed lower KIM-1 levels in the presence of UMOD protein. Levels of proapoptotic genes and the epithelial cell apoptotic protein marker M30 were significantly lower in the UMOD-/- groups. Both M30 and KIM-1 colocalized with intraluminal UMOD protein deposits. Interstitial inflammation was less intense in the UMOD-/- groups. Renal fibrosis severity (kidney collagen mRNA and protein) was similar in both genotypic groups on days 7, 14, and 21. Our findings suggest a role for UMOD-dependent inhibition of KIM-1 expression and its apoptotic cell scavenging responses during chronic obstruction-associated tubular injury.

Range and Heterogeneity of Outcomes in Randomized Trials of Pediatric Chronic Kidney Disease.

OBJECTIVE: To determine the range and heterogeneity of outcomes reported in randomized controlled trials of interventions for children with chronic kidney disease (CKD). STUDY DESIGN: The Cochrane Kidney and Transplant Specialized Register was searched to March 2016. Randomized trials involving children across all stages of CKD were selected. All outcome domains and measurements were extracted from included trials. The frequency and characteristics of the outcome domains and measures were evaluated. RESULTS: From 205 trials included, 6158 different measurements of 100 different outcome domains were reported, with a median of 22 domains per trial (IQR 13-41). Overall, 52 domains (52%) were surrogate, 38 (38%) were clinical, and 10 (10%) were patient-reported. The 5 most commonly reported domains were blood pressure (76 [37%] trials), relapse/remission (70 [34%]), kidney function (66 [32%]), infection (61 [30%]), and height/pubertal development (51 [25%]). Mortality (14%), cardiovascular disease (4%), and quality of life (1%) were reported infrequently. The 2 most frequently reported outcomes, blood pressure and relapse/remission, had 56 and 81 different outcome measures, respectively. CONCLUSIONS: The outcomes reported in clinical trials involving children with CKD are extremely heterogeneous and are most often surrogate outcomes, rather than clinical and patient-centered outcomes such as cardiovascular disease and quality of life. Efforts to ensure consistent reporting of outcomes that are important to patients and clinicians will improve the value of trials to guide clinical decision-making. In our study, non-English articles were excluded.

The impact of small kidneys.

BACKGROUND: Small kidneys due to renal hypodysplasia (RHD) result from a decrease in nephron number. The objectives of this study were to identify clinical variables that determine long-term renal outcome in children with RHD and to define the role of kidney size as a predictor of developing end-stage renal disease (ESRD). METHODS: This was a single-center retrospective cohort analysis. The primary outcome was development of ESRD. We identified 202 RHD cases, with 25 (12%) reaching ESRD at mean age of 8.9 (±6.6) years. RESULTS: Children with RHD with a known genetic syndrome had the smallest kidneys while those with posterior urethral valves (PUV) had the largest kidneys at diagnosis. Cases with bilateral RHD were most likely to develop ESRD. Younger gestational age (OR 0.8, CI 0.69-0.99, p = 0.05), smaller kidney size at diagnosis (OR 0.13, CI 0.03-0.47, p = 0.002), lower best-estimated glomerular filtration rate (eGFR) (OR 0.74, CI 0.58-0.93, p = 0.01), proteinuria (OR 1.03, CI 1.01-1.05, p < 0.001) and high blood pressure (OR 1.02, CI 1.01-1.04, p = 0.01) were associated with development of ESRD, while kidney size at diagnosis was independently associated with ESRD (HR 0.03, CI 0.01-0.72, p = 0.043). CONCLUSIONS: In children with RHD, kidney size at diagnosis predicts the likelihood of developing ESRD.

Overview of the cellular and molecular basis of kidney fibrosis.

The common pathogenetic pathway of progressive injury in patients with chronic kidney disease (CKD) is epitomized as normal kidney parenchymal destruction due to scarring (fibrosis). Understanding the fundamental pathways that lead to renal fibrosis is essential in order to develop better therapeutic options for human CKD. Although complex, four cellular responses are pivotal. (1) An interstitial inflammatory response that has multiple consequences-some harmful and others healing. (2) The appearance of a unique interstitial cell population of myofibroblasts, primarily derived from kidney stromal cells (fibroblasts and pericytes), that are the primary source of the various extracellular matrix proteins that form interstitial scars. (3) Tubular epithelial cells that have variable and time-dependent roles as early responders to injury and later as victims of fibrosis due to the loss of their regenerative abilities. (4) Loss of interstitial capillary integrity that compromises oxygen delivery and leads to a vicious cascade of hypoxia-oxidant stress that accentuates injury and fibrosis. In the absence of adequate angiogenic responses, a healthy interstitial capillary network is not maintained. The fibrotic 'scar' that typifies CKD is an interesting consortium of multifunctional macromolecules that not only change in composition and structure over time, but can be degraded via extracellular and intracellular proteases. Although transforming growth factor beta appears to be the primary driver of kidney fibrosis, a vast array of additional molecules may have modulating roles. The importance of genetic and epigenetic factors is increasingly appreciated. An intriguing but incompletely understood cardiorenal syndrome underlies the high morbidity and mortality rates that develop in association with progressive kidney fibrosis.

Cysteamine modulates oxidative stress and blocks myofibroblast activity in CKD.

Therapy to slow the relentless expansion of interstitial extracellular matrix that leads to renal functional decline in patients with CKD is currently lacking. Because chronic kidney injury increases tissue oxidative stress, we evaluated the antifibrotic efficacy of cysteamine bitartrate, an antioxidant therapy for patients with nephropathic cystinosis, in a mouse model of unilateral ureteral obstruction. Fresh cysteamine (600 mg/kg) was added to drinking water daily beginning on the day of surgery, and outcomes were assessed on days 7, 14, and 21 after surgery. Plasma cysteamine levels showed diurnal variation, with peak levels similar to those observed in patients with cystinosis. In cysteamine-treated mice, fibrosis severity decreased significantly at 14 and 21 days after unilateral ureteral obstruction, and renal oxidized protein levels decreased at each time point, suggesting reduced oxidative stress. Consistent with these results, treatment of cultured macrophages with cysteamine reduced cellular generation of reactive oxygen species. Furthermore, treatment with cysteamine reduced α-smooth muscle actin-positive interstitial myofibroblast proliferation and mRNA levels of extracellular matrix proteins in mice and attenuated myofibroblast differentiation and proliferation in vitro, but did not augment TGF-ß signaling. In a study of renal ischemia reperfusion, cysteamine therapy initiated 10 days after injury and continued for 14 days decreased renal fibrosis by 40%. Taken together, these data suggest previously unrecognized antifibrotic actions of cysteamine via TGF-ß-independent mechanisms that include oxidative stress reduction and attenuation of the myofibroblast response to kidney injury and support further investigation into the potential benefit of cysteamine therapy in the treatment of CKD.

Acute kidney injury and its association with in-hospital mortality among children with acute infections.

BACKGROUND: We investigated prevalence of acute kidney injury (AKI) at hospitalization and its association with in-hospital mortality among Ugandan children hospitalized with common acute infections, and predictors of mortality among AKI children. METHODS: We enrolled 2,055 children hospitalized with primary diagnoses of acute gastroenteritis, malaria, or pneumonia. Serum creatinine, albumin, electrolytes, hemoglobin, and urine protein were obtained on admission. Participants were assessed for AKI based on serum creatinine levels. Demographic and clinical data were obtained using a primary care provider survey and medical chart review. Logistic regression was used to determine predictors of in-hospital mortality. RESULTS: A total of 278 (13.5%) of children had AKI on admission; for 76.2%, AKI was stage 2 (98/278) or stage 3 (114/278) defined as serum creatinine >2- or 3-fold above normal upper limit for age, respectively. AKI prevalence was particularly high in gastroenteritis (28.6%) and underweight children (20.7%). Twenty-five percent of children with AKI died during hospitalization, compared to 9.9% with no AKI (adjusted odds ratio (aOR) 3.5 (95% CI, 2.2-5.5)). In-hospital mortality risk did not differ by AKI stage. Predictors of in-hospital mortality among AKI children included primary diagnosis of pneumonia, aOR 4.5 (95% CI, 1.8-11.2); proteinuria, aOR = 2.1 (95% CI, 1.0-4.9) and positive human immunodeficiency virus (HIV) status, aOR 5.0 (95% CI, 2.0-12.9). CONCLUSIONS: Among children hospitalized with gastroenteritis, malaria, or pneumonia, AKI at admission was common and associated with high in-hospital mortality.

Critical and honest conversations: the evidence behind the "Choosing Wisely" campaign recommendations by the American Society of Nephrology.

Estimates suggest that one third of United States health care spending results from overuse or misuse of tests, procedures, and therapies. The American Board of Internal Medicine Foundation, in partnership with Consumer Reports, initiated the "Choosing Wisely" campaign to identify areas in patient care and resource use most open to improvement. Nine subspecialty organizations joined the campaign; each organization identified five tests, procedures, or therapies that are overused, are misused, or could potentially lead to harm or unnecessary health care spending. Each of the American Society of Nephrology's (ASN's) 10 advisory groups submitted recommendations for inclusion. The ASN Quality and Patient Safety Task Force selected five recommendations based on relevance and importance to individuals with kidney disease.Recommendations selected were: (1) Do not perform routine cancer screening for dialysis patients with limited life expectancies without signs or symptoms; (2) do not administer erythropoiesis-stimulating agents to CKD patients with hemoglobin levels ≥10 g/dl without symptoms of anemia; (3) avoid nonsteroidal anti-inflammatory drugs in individuals with hypertension, heart failure, or CKD of all causes, including diabetes; (4) do not place peripherally inserted central catheters in stage 3-5 CKD patients without consulting nephrology; (5) do not initiate chronic dialysis without ensuring a shared decision-making process between patients, their families, and their physicians.These five recommendations and supporting evidence give providers information to facilitate prudent care decisions and empower patients to actively participate in critical, honest conversations about their care, potentially reducing unnecessary health care spending and preventing harm.

Investigating mechanisms of chronic kidney disease in mouse models.

Animal models of chronic kidney disease (CKD) are important experimental tools that are used to investigate novel mechanistic pathways and to validate potential new therapeutic interventions prior to pre-clinical testing in humans. Over the past several years, mouse CKD models have been extensively used for these purposes. Despite significant limitations, the model of unilateral ureteral obstruction (UUO) has essentially become the high-throughput in vivo model, as it recapitulates the fundamental pathogenetic mechanisms that typify all forms of CKD in a relatively short time span. In addition, several alternative mouse models are available that can be used to validate new mechanistic paradigms and/or novel therapies. Here, we review several models-both genetic and experimentally induced-that provide investigators with an opportunity to include renal functional study end-points together with quantitative measures of fibrosis severity, something that is not possible with the UUO model.

Mannose receptor 2 attenuates renal fibrosis.

Mannose receptor 2 (Mrc2) expresses an extracellular fibronectin type II domain that binds to and internalizes collagen, suggesting that it may play a role in modulating renal fibrosis. Here, we found that Mrc2 levels were very low in normal kidneys but subsets of interstitial myofibroblasts and macrophages upregulated Mrc2 after unilateral ureteral obstruction (UUO). Renal fibrosis and renal parenchymal damage were significantly worse in Mrc2-deficient mice. Similarly, Mrc2-deficient Col4α3(-/-) mice with hereditary nephritis had significantly higher levels of total kidney collagen, serum BUN, and urinary protein than Mrc2-sufficient Col4α3(-/-) mice. The more severe phenotype seemed to be the result of reduced collagen turnover, because procollagen III (α1) mRNA levels and fractional collagen synthesis in the wild-type and Mrc2-deficient kidneys were similar after UUO. Although Mrc2 associates with the urokinase receptor, differences in renal urokinase activity did not account for the increased fibrosis in the Mrc2-deficient mice. Treating wild-type mice with a cathepsin inhibitor, which blocks proteases implicated in Mrc2-mediated collagen degradation, worsened UUO-induced renal fibrosis. Cathepsin mRNA profiles were similar in Mrc2-positive fibroblasts and macrophages, and Mrc2 genotype did not alter relative cathepsin mRNA levels. Taken together, these data establish an important fibrosis-attenuating role for Mrc2-expressing renal interstitial cells and suggest the involvement of a lysosomal collagen turnover pathway.

Vascular endothelial cadherin modulates renal interstitial fibrosis.

BACKGROUND/AIMS: Renal interstitial fibrosis is a final common pathway of all chronic, progressive kidney diseases. Peritubular capillary rarefaction is strongly correlated with fibrosis. The adherens junction protein vascular endothelial cadherin (VE-cadherin) is thought to play a critical role in vascular integrity. We hypothesized that VE-cadherin modulates the renal microcirculation during fibrogenesis and ultimately affects renal fibrosis. METHODS: Unilateral ureteral obstruction (UUO) was used as a renal fibrosis model in VE-cadherin heterozygote (VE+/-) and wild-type (WT) mice, and the kidneys were harvested at days 3, 7, and 14. Peritubular capillary changes and fibrogenesis were investigated. RESULTS: VE+/- mice had lower levels of VE-cadherin protein than WT mice at 3 and 7, but not 14 days after UUO. Vascular permeability was significantly greater in VE+/- mice 7 days after UUO, while peritubular capillary density was not significantly different in VE+/- and WT mice. Interstitial myofibroblast numbers and collagen I and III mRNA levels were significantly higher in VE+/- mice, consistent with a stronger early fibrogenic response. Expression of the pericyte marker neuron-glial antigen 2 was upregulated after UUO, but was not greater in VE+/- mice compared to the WT mice. CONCLUSION: Our data suggest that VE-cadherin controls vascular permeability and limits fibrogenesis after UUO.

Albumin-induced apoptosis of glomerular parietal epithelial cells is modulated by extracellular signal-regulated kinase 1/2.

BACKGROUND: The biological role(s) of glomerular parietal epithelial cells (PECs) is not fully understood in health or disease. Given its location, PECs are constantly exposed to low levels of filtered albumin, which is increased in nephrotic states. We tested the hypothesis that PECs internalize albumin and increased uptake results in apoptosis. METHODS: Confocal microscopy of immunofluorescent staining and immunohistochemistry were used to demonstrate albumin internalization in PECs and to quantitate albumin uptake in normal mice and rats as well as experimental models of membranous nephropathy, minimal change disease/focal segmental glomerulosclerosis and protein overload nephropathy. Fluorescence-activated cell sorting analysis was performed on immortalized cultured PECs exposed to fluorescein isothiocyanate (FITC)-labeled albumin in the presence of an endosomal inhibitor or vehicle. Apoptosis was measured by Hoechst staining in cultured PECs exposed to bovine serum albumin. Levels of phosphorylated extracellular signal-regulated kinase 1 and 2 (p-ERK1/2) were restored by retroviral infection of mitogen-activated protein kinase (MEK) 1/2 and reduced by U0126 in PECs exposed to high albumin levels in culture and apoptosis measured by Hoechst staining. RESULTS: PECs internalized albumin normally, and this was markedly increased in all of the experimental disease models (P<0.05 versus controls). Cultured immortalized PECs also internalize FITC-labeled albumin, which was reduced by endosomal inhibition. A consequence of increased albumin internalization was PEC apoptosis in vitro and in vivo. Candidate signaling pathways underlying these events were examined. Data showed markedly reduced levels of phosphorylated extracellular signal-regulated kinase 1 and 2 (ERK1/2) in PECs exposed to high albumin levels in nephropathy and in culture. A role for ERK1/2 in limiting albumin-induced apoptosis was shown by restoring p-ERK1/2 by retroviral infection, which reduced apoptosis in cultured PECs, while a forced decrease of p-ERK1/2 through inhibition of MEK 1/2 significantly increased albumin-induced PEC apoptosis. CONCLUSIONS: A normal role of PECs is to take up filtered albumin. However, this is increased in proteinuric glomerular diseases, leading to apoptosis through changes in ERK1/2.