Pragmatic Trial of Hospitalization Rate in Chronic Kidney Disease.

BACKGROUND: Despite the availability of effective therapies for patients with chronic kidney disease, type 2 diabetes, and hypertension (the kidney-dysfunction triad), the results of large-scale trials examining the implementation of guideline-directed therapy to reduce the risk of death and complications in this population are lacking. METHODS: In this open-label, cluster-randomized trial, we assigned 11,182 patients with the kidney-dysfunction triad who were being treated at 141 primary care clinics either to receive an intervention that used a personalized algorithm (based on the patient's electronic health record [EHR]) to identify patients and practice facilitators to assist providers in delivering guideline-based interventions or to receive usual care. The primary outcome was hospitalization for any cause at 1 year. Secondary outcomes included emergency department visits, readmissions, cardiovascular events, dialysis, and death. RESULTS: We assigned 71 practices (enrolling 5690 patients) to the intervention group and 70 practices (enrolling 5492 patients) to the usual-care group. The hospitalization rate at 1 year was 20.7% (95% confidence interval [CI], 19.7 to 21.8) in the intervention group and 21.1% (95% CI, 20.1 to 22.2) in the usual-care group (between-group difference, 0.4 percentage points; P = 0.58). The risks of emergency department visits, readmissions, cardiovascular events, dialysis, or death from any cause were similar in the two groups. The risk of adverse events was also similar in the trial groups, except for acute kidney injury, which was observed in more patients in the intervention group (12.7% vs. 11.3%). CONCLUSIONS: In this pragmatic trial involving patients with the triad of chronic kidney disease, type 2 diabetes, and hypertension, the use of an EHR-based algorithm and practice facilitators embedded in primary care clinics did not translate into reduced hospitalization at 1 year. (Funded by the National Institutes of Health and others; ICD-Pieces ClinicalTrials.gov number, NCT02587936.).

Impact of chronic kidney disease and end-stage renal disease on outcomes after complex endovascular and open aortic aneurysm repair.

OBJECTIVE: Chronic kidney disease (CKD) and end-stage renal disease are traditionally associated with worse outcomes after endovascular aortic repair (EVAR) and open aneurysm repair (OAR) of abdominal aortic aneurysms (AAAs). However, there needs to be more data on complex AAA repair involving the aorta's visceral segment. This study stratifies complex AAA repair outcomes by CKD severity and dialysis dependence. METHODS: All patients undergoing elective OAR and fenestrated/branched EVAR (F-BEVAR) for complex AAA with preoperative renal function data captured by the Vascular Quality Initiative between January 2003 and September 2020 were analyzed. Patients were stratified by CKD class as follows: normal/mild (CKD 1 and 2), moderate (CKD class 3a), moderate to severe (CKD 3b), severe (CKD class 4 and 5), and dialysis. Only patients with clamp sites above one of the renal arteries were included for complex OAR. For F-BEVAR, patients with proximal landing zones below zone 5 (above celiac artery) were included, and distal landing zones between zones 1 and 5 were excluded. Primary outcomes were perioperative and 1-year mortality. Predictors of mortality were identified by Cox multivariate regression models. RESULTS: We identified 7849 elective complex AAA repairs: 4230 (54%) complex OARs and 3619 (46%) F-BEVARs. Most patients were White (89%) and male (74%), with an average age of 72 ± 8 years. The patients who underwent F-BEVAR were older and had more comorbidities. Elective F-BEVAR for complex AAA started in 2012 and increased from 1.4% in 2012 to 58% in 2020 (P < .001). The OAR cohort had more perioperative complications, but less 1-year mortality. The normal/mild CKD cohort had the highest 1-year survival compared with other groups after both complex OAR and F-BEVAR. On Cox regression analysis, when compared with CKD 1-2, worsening CKD stage (CKD 3b: hazard ratio [HR], 2.5; 95% confidence interval [CI], 1.82-3.40; P < .001; CKD 4-5: HR, 1.9; 95% CI, 1.16-3.26; P = .011; and dialysis: HR, 4.4; 95% CI, 2.53-7.72; P < .001) were independently associated with 1-year survival after F-BEVAR. After complex OAR, worsening CKD stage but not dialysis was associated with 1-year mortality compared with CKD 1-2 (CKD 3b: HR, 1.6; 95% CI, 1.13-2.35; P = .009; CKD 4-5: HR, 3.4; 95% CI, 2.03-5.79; P < .001). CONCLUSIONS: CKD severity is an essential predictor of perioperative and 1-year mortality after complex AAA repair, irrespective of the treatment modality, which may reflect the natural history of CKD. Consideration should be given to raising the threshold for elective AAA repair in patients with moderate to severe CKD and end-stage renal disease, given the high 1-year mortality rate.

Predicting renal function response to renal artery stenting.

OBJECTIVE: The Cardiovascular Outcomes in Renal Atherosclerotic Lesions Trial found no benefit of renal artery stenting (RAS) over medical therapy, although it was underpowered to detect a benefit among patients with chronic kidney disease (CKD). A post hoc analysis demonstrated improved event-free survival after RAS for patients whose renal function improved by 20% or more. A significant obstacle to achieving this benefit is the inability to predict which patients' renal function will improve from RAS. The objectives of the current study were to identify predictors of renal function response to RAS. METHODS: The Veteran Affairs Corporate Data Warehouse was queried for patients who underwent RAS between 2000 and 2021. The primary outcome was improvement in renal function (estimated glomerular filtration rate [eGFR]) after stenting. Patients were categorized as responders if the eGFR at 30 days or greater after stenting increased by 20% or more compared with before stenting. All others were nonresponders. RESULTS: The study cohort included 695 patients with a median follow-up of 7.1 years (interquartile range, 3.7-11.6 years). Based on postoperative change in eGFR, 202 stented patients (29.1%) were responders, and the remainder (n = 493 [70.9%]) were nonresponders. Before RAS, responders had a significantly higher mean serum creatinine, lower mean eGFR, and higher rate of decline of preoperative GFR in the months before stenting. After stenting, responders had a 26.1% increase in eGFR, compared with before stenting (P < .0001), which remained stable during follow-up. In contrast, nonresponders had a progressive 5.5% decrease in eGFR after stenting. Logistic regression analysis identified three predictors of renal function response to stenting: (1) diabetes (odds ratio [OR], 0.64; 95% confidence interval [CI], 0.44-0.91; P = .013), (2) CKD stages 3b or 4 (OR, 1.80; 95% CI, 1.26-2.57; P = .001), and (3) rate of decline in preoperative eGFR per week before stenting (OR, 1.21; 95% CI, 1.05-1.39; P = .008). CKD stages 3b and 4 and the rate of decline in preoperative eGFR are positive predictors of renal function response to stenting, whereas diabetes is a negative predictor. CONCLUSIONS: Based on our data, patients in CKD stages 3b and 4 (eGFR 15-44 mL/min/1.73 m2) are the only subgroups with a significant probability of improved renal function after RAS. The rate of decline of preoperative eGFR over the months before stenting is a powerful discriminator of patients who are most likely to benefit from RAS. Specifically, patients with a more rapid decrease in eGFR before stenting have a significantly greater probability of improved renal function with RAS. In contrast, diabetes is a negative predictor of improved renal function, so interventionalists should be circumspect about RAS in diabetic patients.

Chronic kidney disease impacts outcomes after abdominal aortic aneurysm repair.

OBJECTIVE: Chronic kidney disease (CKD) and end-stage renal disease are traditionally associated with worse outcomes after endovascular and open repair of abdominal aortic aneurysm (AAA). This study stratifies outcomes of AAA repair by approach, CKD severity, and dialysis dependence. METHODS: All patients undergoing elective infrarenal open aneurysm repair (OAR) and endovascular aortic repair (EVAR) with preoperative renal function data captured by the Vascular Quality Initiative between January 2003 and September 2020 were analyzed. Patients were stratified by CKD class as follows: CKD stages 1 and 2, CKD stage 3a, CKD stage 3b, CKD stages 4 and 5, and dialysis. Primary outcomes were perioperative and 1-year mortality. Predictors of survival were identified by Cox multivariate regression models. RESULTS: In total, 53,867 elective AAA repairs were identified: 5396 (10%) OARs and 48,471 (90%) EVARs. Most patients were White (90%) and male (81%), with a mean age of 73 ± 9 years. Patients who underwent EVAR were older and had more comorbidities. The use of elective EVAR for AAA increased from 52% in 2003 to 91% in 2020 (P < .001). The OAR cohort had more perioperative complications and short-term mortality. The CKD 1 and 2 group had the highest 1-year survival compared with the other groups after both OAR and EVAR. On Cox regression analysis, after EVAR, compared with CKD 1 and 2, worsening CKD stage (CKD 3a: hazard ratio [HR], 1.25; 95% confidence interval [CI], 0.93-1.68; P = .13; CKD 3b: HR, 1.74; 95% CI, 1.23-2.45; P < .050; CKD 4-5: HR, 3.23; 95% CI, 2.13-4.88; P < .001), and dialysis (HR, 4.48; 95% CI, 1.90-10.6; P < .001) were independently associated with worse 1-year survival rates. After OAR, compared with CKD 1 and 2, worsening CKD stage (CKD 3a: HR, 1.08; 95% CI, 0.96-1.20; P = .20; CKD 3b: HR, 1.60; 95% CI, 1.41-1.81; P < .001; CKD 4-5: HR, 2.85; 95% CI, 2.39-3.41; P < .001), and dialysis (HR, 3.79; 95% CI, 3.01-4.76; P < .001) were independently associated with worse 1-year survival rates. CONCLUSIONS: Regardless of the treatment approach, CKD severity is an important predictor of perioperative and 1-year mortality rates after infrarenal AAA repair and may reflect the natural history of CKD. Open repair is associated with high perioperative mortality risk in patients with CKD stages 4 and 5, as well as end-stage renal disease. Individualization of patient decision-making is especially important in patients with a glomerular filtration rate of less than 45 and perhaps consideration should be given to raising the threshold for elective AAA repair in these patients. Further studies focusing on appropriate size threshold for repair in these patients may be warranted.

Physiologic Regulation of Systemic Klotho Levels by Renal CaSR Signaling in Response to CaSR Ligands and pH o.

BACKGROUND: The kidney is the source of sKlotho and kidney-specific loss of Klotho leads to a phenotype resembling the premature multiorgan failure phenotype in Klotho-hypomorphic mice ( kl/kl mice). Klotho and the Ca-sensing receptor (CaSR) are highly expressed in the distal convoluted tubule (DCT). The physiologic mechanisms that regulate sKlotho levels are unknown. METHODS: We measured sKlotho in WT and tubule-specific CaSR -/- (TS-CaSR -/- ) mice treated with calcimimetics, alkali, or acid, and Klotho shed from minced mouse kidneys, and from HEK-293 cells expressing the CaSR and Klotho, in response to calcimimetics, calcilytics, alkalotic and acidic pH, and ADAM protease inhibitors. The CaSR, Klotho, and ADAM10 were imaged in mouse kidneys and cell expression systems using confocal microscopy. RESULTS: The CaSR, Klotho, and ADAM10 colocalize on the basolateral membrane of the DCT. Calcimimetics and HCO 3 increase serum sKlotho levels in WT but not in CaSR -/- mice, and acidic pH suppresses sKlotho levels in WT mice. In minced kidneys and cultured cells, CaSR activation with high Ca, calcimimetics, or alkali increase shed Klotho levels via ADAM10, as demonstrated using the ADAM10 inhibitor GI254023X and siRNA. In cultured cells, the CaSR, Klotho, and ADAM10 form cell surface aggregates that disperse after CaSR activation. CONCLUSIONS: We identify a novel physiologic mechanism for regulation of sKlotho levels by the renal CaSR-ADAM10-Klotho pathway. We show that CaSR activators, including alkali, increase renal CaSR-stimulated Klotho shedding and predict that this mechanism is relevant to the effects of acidosis and alkali therapy on CKD progression.

Spot urinary citrate-to-creatinine ratio is a marker for acid-base status in chronic kidney disease.

Due to multiple compensating mechanisms, the serum bicarbonate concentration is a relatively insensitive marker of acid-base status; especially in chronic kidney disease (CKD). This is a major drawback that impairs the ability to diagnose acid excess or monitor alkali therapy. We postulated that it is more logical to measure the compensatory defense mechanism(s) rather than the defended parameter, which remains normal if the compensation is successful. Therefore, a retrospective cross-sectional study was performed in 1733 stone formers along with a prospective cross-sectional study of 22 individuals with normal kidney function and 50 patients in different stages of CKD. While serum bicarbonate was flat and did not fall below the reference range until near CKD stage 5, citrate excretion (24-hour urinary citrate excretion rate; urinary citrate-to-creatinine ratio, in the retrospective analysis, and spot urinary citrate-to-creatinine ratio in the prospective study) progressively and significantly declined starting from CKD stage 2. Following an acute acid load in 25 participants with a wide range of estimated glomerular filtration rates, the urinary citrate-to-creatinine ratio inversely and significantly associated with acid accumulation, whereas serum bicarbonate did not. We compared changes in serum bicarbonate and urinary citrate-to-creatinine ratio in response to alkali therapy in patients with CKD stage 3 or 4 started on potassium citrate in our kidney stone database. With alkali therapy, there was no change in serum bicarbonate, but the urinary citrate-to-creatinine ratio rose consistently in all patients adherent to potassium citrate therapy. Thus, the urinary citrate-to-creatinine ratio (the defense mechanism) is a potential easily implementable, pragmatic, and a superior parameter to serum bicarbonate (the defended entity) to assess acid-base status, and monitor alkali therapy. Additional studies are needed before a clinical test can be devised.

Similar Biophysical Abnormalities in Glomeruli and Podocytes from Two Distinct Models.

Background FSGS is a pattern of podocyte injury that leads to loss of glomerular function. Podocytes support other podocytes and glomerular capillary structure, oppose hemodynamic forces, form the slit diaphragm, and have mechanical properties that permit these functions. However, the biophysical characteristics of glomeruli and podocytes in disease remain unclear.Methods Using microindentation, atomic force microscopy, immunofluorescence microscopy, quantitative RT-PCR, and a three-dimensional collagen gel contraction assay, we studied the biophysical and structural properties of glomeruli and podocytes in chronic (Tg26 mice [HIV protein expression]) and acute (protamine administration [cytoskeletal rearrangement]) models of podocyte injury.Results Compared with wild-type glomeruli, Tg26 glomeruli became progressively more deformable with disease progression, despite increased collagen content. Tg26 podocytes had disordered cytoskeletons, markedly abnormal focal adhesions, and weaker adhesion; they failed to respond to mechanical signals and exerted minimal traction force in three-dimensional collagen gels. Protamine treatment had similar but milder effects on glomeruli and podocytes.Conclusions Reduced structural integrity of Tg26 podocytes causes increased deformability of glomerular capillaries and limits the ability of capillaries to counter hemodynamic force, possibly leading to further podocyte injury. Loss of normal podocyte mechanical integrity could injure neighboring podocytes due to the absence of normal biophysical signals required for podocyte maintenance. The severe defects in podocyte mechanical behavior in the Tg26 model may explain why Tg26 glomeruli soften progressively, despite increased collagen deposition, and may be the basis for the rapid course of glomerular diseases associated with severe podocyte injury. In milder injury (protamine), similar processes occur but over a longer time.

Relationship of and cross-talk between physical and biologic properties of the glomerulus.

PURPOSE OF REVIEW: Cells and tissues must respond to physical stresses. Cells exist in an elastic environment determined by their matrix, matrix contacts, cell-cell contacts, and cytoskeletal structure. We discuss the determinants of the elastic environment of cells and its potential roles in glomerular disease. RECENT FINDINGS: Control of the mechanical environment is sufficient to induce and maintain the differentiated state of cells including myofibroblasts. New experimental techniques permit precise measurement of the elastic characteristics of normal and diseased tissues and cells, and analysis of cell behavior and cytoskeletal structure in response to mechanical and elastic stimuli. Glomeruli become soft early in the course of several disease models, yet late stages are characterized by increased stiffness and fibrosis with loss of organ function. Work in hepatic fibrosis, arterial disease, and oncology demonstrate that increased collagen crosslinking by lysyl oxidase, an early step in the diseases, can result in a sufficient increase in tissue stiffness to alter cell behavior, leading to disease progression. SUMMARY: The elastic environment of cells and tissues provides essential signals in development, differentiation, and disease. Identifying the mechanisms that determine the mechanical environment of glomerular cells will complement other approaches to reduce pathologic fibrosis and loss of tissue function.

Mechanisms of mechanical signaling in development and disease.

The responses of cells to chemical signals are relatively well characterized and understood. Cells also respond to mechanical signals in the form of externally applied force and forces generated by cell-matrix and cell-cell contacts. Many features of cell function that are generally considered to be under the control of chemical stimuli, such as motility, proliferation, differentiation and survival, can also be altered by changes in the stiffness of the substrate to which the cells are adhered, even when their chemical environment remains unchanged. Many examples from clinical and whole animal studies have shown that changes in tissue stiffness are related to specific disease characteristics and that efforts to restore normal tissue mechanics have the potential to reverse or prevent cell dysfunction and disease. How cells detect stiffness is largely unknown, but the cellular structures that measure stiffness and the general principles by which they work are beginning to be revealed. This Commentary highlights selected recent reports of mechanical signaling during disease development, discusses open questions regarding the physical mechanisms by which cells sense stiffness, and examines the relationship between studies in vitro on flat substrates and the more complex three-dimensional setting in vivo.

Shear stress induces cell apoptosis via a c-Src-phospholipase D-mTOR signaling pathway in cultured podocytes.

The glomerular capillary wall, composed of endothelial cells, the glomerular basement membrane and the podocytes, is continually subjected to hemodynamic force arising from tractional stress due to blood pressure and shear stress due to blood flow. Exposure of glomeruli to abnormal hemodynamic force such as hyperfiltration is associated with glomerular injury and progressive renal disease, and the conversion of mechanical stimuli to chemical signals in the regulation of the process is poorly understood in podocytes. By examining DNA fragmentation, apoptotic nuclear changes and cytochrome c release, we found that shear stress induced cell apoptosis in cultured podocytes. Meanwhile, podocytes exposed to shear stress also stimulated c-Src phosphorylation, phospholipase D (PLD) activation and mammalian target of rapamycin (mTOR) signaling. Using the antibodies against c-Src, PLD(1), and PLD(2) to perform reciprocal co-immunoprecipitations and in vitro PLD activity assay, our data indicated that c-Src interacted with and activated PLD(1) but not PLD(2). The inhibition of shear stress-induced c-Src phosphorylation by PP(2) (a specific inhibitor of c-Src kinase) resulted in reduced PLD activity. Phosphatidic acid, produced by shear stress-induced PLD activation, stimulated mTOR signaling, and caused podocyte hypertrophy and apoptosis.

Kidney Biopsy Utility: Patient and Clinician Perspectives from the Kidney Precision Medicine Project.

Rationale & Objective: Limited data exist on patient perspectives of the implications of kidney biopsies. We explored patients' perspectives alongside those of clinicians to better understand how kidney biopsies affect patients' viewpoints and the clinical utility of biopsies. Study Design: Prospective Cohort Study. Setting & Participants: Patient participants and clinicians in the Kidney Precision Medicine Project, a prospective cohort study of patients who undergo a research protocol biopsy, at 9 recruitment sites across the United States. Surveys were completed at enrollment before biopsy and additional timepoints after biopsy (participants: 28 days, 6 months; clinicians: 2 weeks). Analytical Approach: Kappa statistics assessed prebiopsy etiology concordance between clinicians and participants. Participant perspectives after biopsy were analyzed using a thematic approach. Clinician ratings of clinical management value were compared to prebiopsy ratings with Wilcoxon matched-pairs signed-rank tests and paired t tests. Results: A total of 167 participants undergoing biopsy (124 participants with chronic kidney disease [CKD], 43 participants with acute kidney injury [AKI]) and 58 clinicians were included in this study. CKD participants and clinicians had low etiology concordance for the 2 leading causes of CKD: diabetes (k = 0.358) and hypertension (k = 0.081). At 28 days postbiopsy, 46 (84%) participants reported that the biopsy affected their understanding of their diagnosis, and 21 (38%) participants reported that the results of the biopsy affected their medications. Participants also shared biopsy impressions in free-text responses, including impacts on lifestyle and concurrent condition management. The biopsy positively shifted clinician perceptions of the procedure's clinical management benefits, while perceptions of prognostic value decreased and diagnostic ratings remained unchanged. Limitations: Our study did not have demographic data of clinicians and could not provide insight into postbiopsy experiences for participants who did not respond to follow-up surveys. Conclusions: Participant perspectives of the personal implications of kidney biopsy can be integrated into shared decision-making between clinicians and patients. Enhanced biopsy reports and interactions between nephrologists and pathologists could augment the management and prognostic value of kidney biopsies. Plain-Language Summary: The utility of kidney biopsy is debated among clinicians, and patients' perspectives are even less explored. To address these gaps, we synthesized perspectives from clinicians and patient participants of the Kidney Precision Medicine Project (KPMP). Both before and after biopsy, clinicians were surveyed on how the procedure affected their clinical management, diagnosis, and prognosis. After biopsy, participants shared how the procedure affected their diagnosis, medication, and lifestyle changes. Clinicians and patients shared an appreciation for the biopsy's impact on medical management but diverged in their takeaways on diagnosis and prognosis. These findings highlight the need for greater collaboration between patients and clinicians, particularly as they navigate shared decision-making when considering kidney biopsy.

Calcium-sensing receptor decreases cell surface expression of the inwardly rectifying K+ channel Kir4.1.

The Ca(2+)-sensing receptor (CaR) regulates salt and water transport in the kidney as demonstrated by the association of gain of function CaR mutations with a Bartter syndrome-like, salt-wasting phenotype, but the precise mechanism for this effect is not fully established. We found previously that the CaR interacts with and inactivates an inwardly rectifying K(+) channel, Kir4.1, which is expressed in the distal nephron that contributes to the basolateral K(+) conductance, and in which loss of function mutations are associated with a complex phenotype that includes renal salt wasting. We now find that CaR inactivates Kir4.1 by reducing its cell surface expression. Mutant CaRs reduced Kir4.1 cell surface expression and current density in HEK-293 cells in proportion to their signaling activity. Mutant, activated Gα(q) reduced cell surface expression and current density of Kir4.1, and these effects were blocked by RGS4, a protein that blocks signaling via Gα(i) and Gα(q). Other α subunits had insignificant effects. Knockdown of caveolin-1 blocked the effect of Gα(q) on Kir4.1, whereas knockdown of the clathrin heavy chain had no effect. CaR had no comparable effect on the renal outer medullary K(+) channel, an apical membrane distal nephron K(+) channel that is internalized by clathrin-coated vesicles. Co-immunoprecipitation studies showed that the CaR and Kir4.1 physically associate with caveolin-1 in HEK cells and in kidney extracts. Thus, the CaR decreases cell surface expression of Kir4.1 channels via a mechanism that involves Gα(q) and caveolin. These results provide a novel molecular basis for the inhibition of renal NaCl transport by the CaR.

Lack of collagen XVIII long isoforms affects kidney podocytes, whereas the short form is needed in the proximal tubular basement membrane.

Collagen XVIII is characterized by three variant N termini, an interrupted collagenous domain, and a C-terminal antiangiogenic domain known as endostatin. We studied here the roles of this collagen type and its variant isoforms in the mouse kidney. Collagen XVIII appeared to be in a polarized orientation in the tubular basement membranes (BMs), the endostatin domain embedded in the BM, and the N terminus residing at the BM-fibrillar matrix interface. In the case of the glomerular BM (GBM), collagen XVIII was expressed in different isoforms depending on the side of the GBM. The orientation appeared polarized here, too, both the endothelial promoter 1-derived short variant of collagen XVIII and the epithelial promoter 2-derived longer variants having their C-terminal endostatin domains embedded in the BM and the N termini at the respective BM-cell interfaces. In addition to loosening of the proximal tubular BM structure, the Col18a1(-/-) mice showed effacement of the glomerular podocyte foot processes, and microindentation studies showed changes in the mechanical properties of the glomeruli, the Col18a1(-/-) glomeruli being ∼30% softer than the wild-type. Analysis of promoter-specific knockouts (Col18a1(P1/P1) and Col18a1(P2/P2)) indicated that tubular BM loosening is due to a lack of the shortest isoform, whereas the glomerular podocyte effacement was due to a lack of the longer isoforms. We suggest that lack of collagen XVIII may also have disparate effects on kidney function in man, but considering the mild physiological findings in the mutant mice, such effects may manifest themselves only late in life or require other compounding molecular changes.

Impact of a chronic kidney disease registry and provider education on guideline adherence--a cluster randomized controlled trial.

BACKGROUND: Low adherence to chronic kidney disease (CKD) guidelines may be due to unrecognized CKD and lack of guideline awareness on the part of providers. The goal of this study was to evaluate the impact of provider education and access to a CKD registry on guideline adherence. METHODS: We conducted a cluster randomized controlled trial at the Louis Stokes Cleveland VAMC. One of two primary care clinics was randomized to intervention. Providers from both clinics received a lecture on CKD guidelines at study initiation. Providers in the intervention clinic were given access to and shown how to use a CKD registry, which identifies patients with CKD and is automatically updated daily. Eligible patients had at least one primary care visit in the last year, had CKD based on eGFR, and had not received renal replacement therapy. The primary outcome was parathyroid hormone (PTH) adherence, defined by at least one PTH measurement during the 12 month study. Secondary outcomes were measurement of phosphorus, hemoglobin, proteinuria, achievement of goal blood pressure, and treatment with a diuretic or renin-angiotensin system blocker. RESULTS: There were 418 and 363 eligible patients seen during the study in the control and intervention clinics, respectively. Compared to pre-intervention, measurement of PTH increased in both clinics (control clinic: 16% to 23%; intervention clinic: 13% to 28%). Patients in the intervention clinic were more likely to have a PTH measured during the study (adjusted odds ratio=1.53; 95% CI (1.01, 2.30); P=0.04). However, the intervention was not associated with a consistent improvement in secondary outcomes. Only 5 of the 37 providers in the intervention clinic accessed the registry. CONCLUSIONS: An intervention that included education on CKD guidelines and access to a CKD patient registry marginally improved guideline adherence over education alone. Adherence to the primary process measure improved in both clinics, but no improvement was seen in intermediate clinical outcomes. Improving the care of patients with CKD will likely require a multifaceted approach including system redesign. CLINICALTRIALS.GOV REGISTRATION NUMBER: NCT00921687.

Biophysical properties of normal and diseased renal glomeruli.

The mechanical properties of tissues and cells including renal glomeruli are important determinants of their differentiated state, function, and responses to injury but are not well characterized or understood. Understanding glomerular mechanics is important for understanding renal diseases attributable to abnormal expression or assembly of structural proteins and abnormal hemodynamics. We use atomic force microscopy (AFM) and a new technique, capillary micromechanics, to measure the elastic properties of rat glomeruli. The Young's modulus of glomeruli was 2,500 Pa, and it was reduced to 1,100 Pa by cytochalasin and latunculin, and to 1,400 Pa by blebbistatin. Cytochalasin or latrunculin reduced the F/G actin ratios of glomeruli but did not disrupt their architecture. To assess glomerular biomechanics in disease, we measured the Young's moduli of glomeruli from two mouse models of primary glomerular disease, Col4a3(-/-) mice (Alport model) and Tg26(HIV/nl) mice (HIV-associated nephropathy model), at stages where glomerular injury was minimal by histopathology. Col4a3(-/-) mice express abnormal glomerular basement membrane proteins, and Tg26(HIV/nl) mouse podocytes have multiple abnormalities in morphology, adhesion, and cytoskeletal structure. In both models, the Young's modulus of the glomeruli was reduced by 30%. We find that glomeruli have specific and quantifiable biomechanical properties that are dependent on the state of the actin cytoskeleton and nonmuscle myosins. These properties may be altered early in disease and represent an important early component of disease. This increased deformability of glomeruli could directly contribute to disease by permitting increased distension with hemodynamic force or represent a mechanically inhospitable environment for glomerular cells.

Role of p115RhoGEF in the regulation of extracellular Ca(2+)-induced choline kinase activation and prostate cancer cell proliferation.

Ca(2+) is a ubiquitous cellular signal which plays a central role in the regulation of cell function. To understand aberrant signaling through the Ca(2+)-sensing receptor (CaR) in prostate cancer cells, we compared expression of CaR signaling components in human nonmalignant prostate epithelial cells and several prostate cancer cell lines, as well as normal human prostate and prostate tumor specimens. We found that levels of the CaR, Gα(12) and p115RhoGEF expression are significantly up-regulated in more tumorigenic prostate cancer cells and prostate tumor specimens. By silencing CaR, Gα(12), p115RhoGEF or choline kinase (ChoK) expression, analyzing the change in lipid profiles, blocking signaling pathways using chemical inhibitors, and co-immunoprecipitating the relevant signaling proteins, we demonstrate that p115RhoGEF, a regulator of G protein signaling (RGS) with GAP activity for Gα(12/13) and with guanine nucleotide exchange activity for the small G protein Rho, plays an important role in the regulation of Ca(o)(2+)-induced ChoK activation and cell proliferation in more tumorigenic prostate cancer cell lines. The results demonstrate an important role of p115RhoGEF in prostate tumorigenesis and provide a potential target of cancer therapeutics.

Genetic disorders of NaCl transport in the distal convoluted tubule.

The distal convoluted tubule (DCT) reabsorbs 5-10% of filtered Na, and is an important site for regulation of Na balance. Additionally, the amount and composition of the tubular fluid that leaves the DCT affects H and K secretion in more distal nephrin segments. Mutations in five genes whose products are expressed in the DCT demonstrate these points and help to define the mechanisms by which the DCT contributes to control of electrolyte balance and volume. Loss of function mutations in the apical thiazide-sensitive NaCl cotransporter and the basolateral K channel Kir4.1, and activating mutations in the Ca-sensing receptor cause a phenotypically similar salt wasting syndrome. Mutation in two recently identified kinases, WNK1 and WNK4 cause a salt-retaining syndrome through increased apical expression of NaCl cotransporter. Recent studies indicate that these genes are important not only for understanding the physiology of the distal nephron, but that they and others may also contribute to blood pressure variation in the general population.

Integrating Patient Priorities with Science by Community Engagement in the Kidney Precision Medicine Project.

The Kidney Precision Medicine Project (KPMP) is a multisite study designed to improve understanding of CKD attributed to diabetes or hypertension and AKI by performing protocol-driven kidney biopsies. Study participants and their kidney tissue samples undergo state-of-the-art deep phenotyping using advanced molecular, imaging, and data analytical methods. Few patients participate in research design or concepts for discovery science. A major goal of the KPMP is to include patients as equal partners to inform the research for clinically relevant benefit. The purpose of this report is to describe patient and community engagement and the value they bring to the KPMP. Patients with CKD and AKI and clinicians from the study sites are members of the Community Engagement Committee, with representation on other KPMP committees. They participate in KPMP deliberations to address scientific, clinical, logistic, analytic, ethical, and community engagement issues. The Community Engagement Committee guides KPMP research priorities from perspectives of patients and clinicians. Patients led development of essential study components, including the informed consent process, no-fault harm insurance coverage, the ethics statement, return of results plan, a "Patient Primer" for scientists and the public, and Community Advisory Boards. As members across other KPMP committees, the Community Engagement Committee assures that the science is developed and conducted in a manner relevant to study participants and the clinical community. Patients have guided the KPMP to produce research aligned with their priorities. The Community Engagement Committee partnership has set new benchmarks for patient leadership in precision medicine research.

Absence of filamin A prevents cells from responding to stiffness gradients on gels coated with collagen but not fibronectin.

Cell types from many tissues respond to changes in substrate stiffness by actively remodeling their cytoskeletons to alter spread area or adhesion strength, and in some cases changing their own stiffness to match that of their substrate. These cell responses to substrate stiffness are linked to substrate-induced changes in the state, localization, and amount of numerous proteins, but detailed evidence for the requirement of specific proteins in these distinct forms of mechanical response are scarce. Here we use microfluidics techniques to produce gels with a gradient of stiffness to show the essential function of filamin A in cell responses to mechanical stimuli and dissociate cell spreading and stiffening by contrasting responses of a pair of human melanoma-derived cell lines that differ in expression of this actin cross-linking protein. M2 melanoma cells null for filamin A do not alter their adherent area in response to increased substrate stiffness when they link to the substrate only through collagen receptors, but change adherent area normally when bound through fibronectin receptors. In contrast, filamin A-replete A7 cells change adherent area on both substrates and respond more strongly to collagen I-coated gels than to fibronectin-coated gels. Strikingly, A7 cells alter their stiffness, as measured by atomic force microscopy, to match the elastic modulus of the substrate immediately adjacent to them on the gradient. M2 cells, in contrast, maintain a constant stiffness on all substrates that is as low as that of A7 cells on the softest gels examined (1000 Pa). Comparison of cell spreading and cell stiffening on the same gradient substrates shows that cell spreading is uncoupled from stiffening. At saturating collagen and fibronectin concentrations, adhesion of M2 cells is reduced compared to that of A7 cells to an extent approximately equal to the difference in adherent area. Filamin A appears to be essential for cell stiffening on collagen, but not for cell spreading on fibronectin. These results have implications for different models of cell protrusion and adhesion and identify a key role for filamin A in altering cellular stiffness that cannot be compensated for by other actin cross-linkers in vivo.

MUPP1 complexes renal K+ channels to alter cell surface expression and whole cell currents.

We previously found that the Ca(2+)-sensing receptor (CaR) interacts with and inactivates the inwardly rectifying K(+) channel Kir4.2 that is expressed in the kidney cortex and that has a COOH-terminal PDZ domain. To identify potential scaffolding proteins that could organize a macromolecular signaling complex involving the CaR and Kir4.2, we used yeast two-hybrid cloning with the COOH-terminal 125 amino acids (AA) of Kir4.2 as bait to screen a human kidney cDNA library. We identified two independent partial cDNAs corresponding to the COOH-terminal 900 AA of MUPP1, a protein containing 13 PDZ binding domains that is expressed in the kidney in tight junctions and lateral borders of epithelial cells. When expressed in human embryonic kidney (HEK)-293 cells, Kir4.2 coimmunoprecipitates reciprocally with MUPP1 but not with a Kir4.2 construct lacking the four COOH-terminal amino acids, Kir5.1, or the CaR. MUPP1 and Kir4.2 coimmunoprecipitate reciprocally from rat kidney cortex extracts. Coexpression of MUPP1 with Kir4.2 in HEK-293 cells leads to reduced cell surface expression of Kir4.2 as assessed by cell surface biotinylation. Coexpression of MUPP1 and Kir4.2 in Xenopus oocytes results in reduced whole cell currents compared with expression of Kir4.2 alone, whereas expression of Kir4.2DeltaPDZ results in minimal currents and is not affected by coexpression with MUPP1. Immunofluorescence studies of oocytes demonstrate that MUPP1 reduces Kir4.2 membrane localization. These results indicate that Kir4.2 interacts selectively with MUPP1 to affect its cell surface expression. Thus MUPP1 and Kir4.2 may participate in a protein complex in the nephron that could regulate transport of K(+) as well as other ions.