The effect of genetic education on the referral of patients to genetic evaluation: Findings from a national survey of nephrologists.

PURPOSE: The success of genomic medicine hinges on the implementation of genetic knowledge in clinical settings. In novel subspecialties, it requires that clinicians refer patients to genetic evaluation or testing, however referral is likely to be affected by genetic knowledge. METHODS: An online survey was administered to self-identified nephrologists working in the United States. Nephrologists' demographic characteristics, genetic education, confidence in clinical genetics, genetic knowledge, and referral rates of patients to genetic evaluation were collected. RESULTS: In total, 201 nephrologists completed the survey. All reported treating patients with genetic forms of kidney disease, and 37% had referred <5 patients to genetic evaluation. A third had limited basic genetic knowledge. Most nephrologists (85%) reported concerns regarding future health insurance eligibility as a barrier to referral to genetic testing. Most adult nephrologists reported insufficient genetic education during residency (65%) and fellowship training (52%). Lower rating of genetic education and lower knowledge in recognizing signs of genetic kidney diseases were significantly associated with lower number of patients referred to the genetic evaluation (P < .001). Most nephrologists reported that improving their genetic knowledge is important for them (>55%). CONCLUSIONS: There is a need to enhance nephrologists' genetic education to increase genetic testing use in nephrology.

Copy Number Variant Analysis and Genome-wide Association Study Identify Loci with Large Effect for Vesicoureteral Reflux.

BACKGROUND: Vesicoureteral reflux (VUR) is a common, familial genitourinary disorder, and a major cause of pediatric urinary tract infection (UTI) and kidney failure. The genetic basis of VUR is not well understood. METHODS: A diagnostic analysis sought rare, pathogenic copy number variant (CNV) disorders among 1737 patients with VUR. A GWAS was performed in 1395 patients and 5366 controls, of European ancestry. RESULTS: Altogether, 3% of VUR patients harbored an undiagnosed rare CNV disorder, such as the 1q21.1, 16p11.2, 22q11.21, and triple X syndromes ((OR, 3.12; 95% CI, 2.10 to 4.54; P=6.35×10-8) The GWAS identified three study-wide significant and five suggestive loci with large effects (ORs, 1.41-6.9), containing canonical developmental genes expressed in the developing urinary tract (WDPCP, OTX1, BMP5, VANGL1, and WNT5A). In particular, 3.3% of VUR patients were homozygous for an intronic variant in WDPCP (rs13013890; OR, 3.65; 95% CI, 2.39 to 5.56; P=1.86×10-9). This locus was associated with multiple genitourinary phenotypes in the UK Biobank and eMERGE studies. Analysis of Wnt5a mutant mice confirmed the role of Wnt5a signaling in bladder and ureteric morphogenesis. CONCLUSIONS: These data demonstrate the genetic heterogeneity of VUR. Altogether, 6% of patients with VUR harbored a rare CNV or a common variant genotype conferring an OR >3. Identification of these genetic risk factors has multiple implications for clinical care and for analysis of outcomes in VUR.

Molecular regulation and function of FoxO3 in chronic kidney disease.

PURPOSE OF REVIEW: FOXOs are transcription factors that regulate downstream target genes to counteract to cell stress. Here we review the function and regulation of FOXO transcription factors, the mechanism of FOXO3 activation in the kidney, and the role of FOXO3 in delaying the development of chronic kidney disease (CKD). RECENT FINDINGS: Progressive renal hypoxia from vascular dropout and metabolic perturbation is a pathogenic factor for the initiation and development of CKD. Hypoxia and low levels of α-ketoglutarate generated from the TCA cycle inhibit prolyl hydroxylase domain (PHD)-mediated prolyl hydroxylation of FoxO3, thus reducing FoxO3 protein degradation via the ubiquitin proteasomal pathway, similar to HIF stabilization under hypoxic conditions. FoxO3 accumulation and nuclear translocation activate two key cellular defense mechanisms, autophagy and antioxidative response in renal tubular cells, to reduce cell injury and promote cell survival. FoxO3 directly activates the expression of Atg proteins, which replenishes core components of the autophagic machinery to allow sustained autophagy in the chronically hypoxic kidney. FoxO3 protects mitochondria by stimulating the expression of superoxide dismutase 2 (SOD2), as tubular deletion of FoxO3 in mice results in reduced SOD2 levels and profound mitochondrial damage. SUMMARY: Knowledge gained from animal studies may help understand the function of stress responsive transcription factors that could be targeted to prevent or treat CKD.

Patent ductus arteriosus is associated with acute kidney injury in the preterm infant.

BACKGROUND: This study aimed to test the hypothesis that a patent ductus arteriosus (PDA) is independently associated with acute kidney injury (AKI) in neonates ≤ 28 weeks gestation. METHODS: Preterm infants with echocardiographic diagnosis of moderate-large PDA at age ≤ 30 days were studied retrospectively. AKI, the primary outcome, was defined and staged according to serum creatinine using Kidney Disease Improving Global Outcomes (KDIGO) neonatal criteria. Its association with the timing and duration of PDA, non-steroidal anti-inflammatory drugs (NSAIDs) and other nephrotoxic exposures, gestational age, and other covariates was evaluated using mixed-effects logistic regression models. RESULTS: Acute Kidney Injury occurred in 49% (101/206) of infants. Moderate-to-large PDA was associated with any-stage AKI (OR 5.31, 95% CI 3.75 to 7.53), stage 1 (mild) AKI (OR 4.86, 95% CI 3.12 to 7.56), and stages 2-3 (severe) AKI (OR 10.9, 95% CI 5.70 to 20.8). NSAID treatment added additional risk for mild AKI (OR 2.45, 95% CI 1.61 to 3.71). Severe AKI was less likely when NSAID treatment was effective (OR 0.45, 95% CI 0.21 to 0.97) but not when ineffective (OR 1.63, 95% CI 0.76 to 3.50). CONCLUSIONS: Moderate-to-large PDA was strongly associated with all stages of AKI in preterm infants ≤ 28 weeks of gestational age. Effective NSAID treatment decreased the risk of severe but not mild AKI. These differential effects reflect the balance between the renal benefits of PDA closure and the risk of NSAID toxicity.

Forkhead box O3 (FoxO3) regulates kidney tubular autophagy following urinary tract obstruction.

Autophagy has been shown to be important for normal homeostasis and adaptation to stress in the kidney. Yet, the molecular mechanisms regulating renal epithelial autophagy are not fully understood. Here, we explored the role of the stress-responsive transcription factor forkhead box O3 (FoxO3) in mediating injury-induced proximal tubular autophagy in mice with unilateral ureteral obstruction (UUO). We show that following UUO, FoxO3 is activated and displays nuclear expression in the hypoxic proximal tubules exhibiting high levels of autophagy. Activation of FoxO3 by mutating phosphorylation sites to enhance its nuclear expression induces profound autophagy in cultured renal epithelial cells. Conversely, deleting FoxO3 in mice results in fewer numbers of autophagic cells in the proximal tubules and reduced ratio of the autophagy-related protein LC3-II/I in the kidney post-UUO. Interestingly, autophagic cells deficient in FoxO3 contain lower numbers of autophagic vesicles per cell. Analyses of individual cells treated with autophagic inhibitors to sequentially block the autophagic flux suggest that FoxO3 stimulates the formation of autophagosomes to increase autophagic capacity but has no significant effect on autophagosome-lysosome fusion or autolysosomal clearance. Furthermore, in kidneys with persistent UUO for 7 days, FoxO3 activation increases the abundance of mRNA and protein levels of the core autophagy-related (Atg) proteins including Ulk1, Beclin-1, Atg9A, Atg4B, and Bnip3, suggesting that FoxO3 may function to maintain components of the autophagic machinery that would otherwise be consumed during prolonged autophagy. Taken together, our findings indicate that FoxO3 activation can both induce and maintain autophagic activities in renal epithelial cells in response to injury from urinary tract obstruction.

Sandwich Technique for Endovascular Repair of Acute Type A Aortic Dissection.

OVERVIEW: To describe a new endovascular procedure for acute type A aortic dissection (TAAD) repair. METHODS: Between 2013 and 2016, 12 patients (average age 54±9.6 years; 10 men) with acute TAAD (mean EURO score 11.4%±3.2%, range 5-17) and unfit for surgery underwent thoracic endovascular aortic repair (TEVAR) with 2 periscope grafts to preserve blood supply to supra-aortic branches plus bypass grafting as needed. If the ascending aorta was dilated to >40 mm, sternotomy was performed to wrap the ascending aorta and reduce its diameter to accommodate the aortic stent-grafts. RESULTS: All patients were successfully treated. Seven patients required bypass grafting, and most of the patients had periscope grafts to the innominate/right common carotid artery and left common carotid artery; only 3 patients had the left subclavian artery preserved. All patients exhibited good hemodynamics and normal pressures after the procedure. The mean procedure time and blood loss were 4.5±1.0 hours and 217±111.5 mL, respectively. Two patients treated emergently died shortly after surgery from multiorgan failure. The average follow-up duration was 17±14.5 months (range 2-42) in the 10 survivors. The remaining patients recovered and none experienced stent-graft thrombosis, stroke, or peripheral artery embolism during follow-up. CONCLUSION: A procedure that combines sandwich/periscope grafting with TEVAR, wrapping of the aorta, and supra-arch bypass grafting can be used to treat patients with acute TAAD.

Hedgehog signaling indirectly affects tubular cell survival after obstructive kidney injury.

Hedgehog (Hh) is an evolutionary conserved signaling pathway that has important functions in kidney morphogenesis and adult organ maintenance. Recent work has shown that Hh signaling is reactivated in the kidney after injury and is an important mediator of progressive fibrosis. Pericytes and fibroblasts have been proposed to be the principal cells that respond to Hh ligands, and pharmacological attenuation of Hh signaling has been considered as a possible treatment for fibrosis, but the effect of Hh inhibition on tubular epithelial cells after kidney injury has not been reported. Using genetically modified mice in which tubule-derived hedgehog signaling is increased and mice in which this pathway is conditionally suppressed in pericytes that express the proteoglycan neuron glial protein 2 (NG2), we found that suppression of Hh signaling is associated with decreased macrophage infiltration and tubular proliferation but also increased tubular apoptosis, an effect that correlated with the reduction of tubular ß-catenin activity. Collectively, our data suggest a complex function of hedgehog signaling after kidney injury in initiating both reparative and proproliferative, prosurvival processes.

New autophagy reporter mice reveal dynamics of proximal tubular autophagy.

The accumulation of autophagosomes in postischemic kidneys may be renoprotective, but whether this accumulation results from the induction of autophagy or from obstruction within the autophagic process is unknown. Utilizing the differential pH sensitivities of red fluorescent protein (RFP; pKa 4.5) and enhanced green fluorescent protein (EGFP; pKa 5.9), we generated CAG-RFP-EGFP-LC3 mice to distinguish early autophagic vacuoles from autolysosomes. In vitro and in vivo studies confirmed that in response to nutrient deprivation, renal epithelial cells in CAG-RFP-EGFP-LC3 mice produce autophagic vacuoles expressing RFP and EGFP puncta. EGFP fluorescence diminished substantially in the acidic environment of the autolysosomes, whereas bright RFP signals remained. Under normal conditions, nephrons expressed few EGFP and RFP puncta, but ischemia-reperfusion injury (IRI) led to dynamic changes in the proximal tubules, with increased numbers of RFP and EGFP puncta that peaked at 1 day after IRI. The number of EGFP puncta returned to control levels at 3 days after IRI, whereas the high levels of RFP puncta persisted, indicating autophagy initiation at day 1 and autophagosome clearance during renal recovery at day 3. Notably, proliferation decreased in cells containing RFP puncta, suggesting that autophagic cells are less likely to divide for tubular repair. Furthermore, 87% of proximal tubular cells with activated mechanistic target of rapamycin (mTOR), which prevents autophagy, contained no RFP puncta. Conversely, inhibition of mTOR complex 1 induced RFP and EGFP expression and decreased cell proliferation. In summary, our results highlight the dynamic regulation of autophagy in postischemic kidneys and suggest a role of mTOR in autophagy resolution during renal repair.

Low nephron endowment increases susceptibility to renal stress and chronic kidney disease.

Preterm birth results in low nephron endowment and increased risk of acute kidney injury (AKI) and chronic kidney disease (CKD). To understand the pathogenesis of AKI and CKD in preterm humans, we generated potentially novel mouse models with a 30%-70% reduction in nephron number by inhibiting or deleting Ret tyrosine kinase in the developing ureteric bud. These mice developed glomerular and tubular hypertrophy, followed by the transition to CKD, recapitulating the renal pathological changes seen in humans born preterm. We injected neonatal mice with gentamicin, a ubiquitous nephrotoxic exposure in preterm infants, and detected more severe proximal tubular injury in mice with low nephron number compared with controls with normal nephron number. Mice with low nephron number had reduced proliferative repair with more rapid development of CKD. Furthermore, mice had more profound inflammation with highly elevated levels of MCP-1 and CXCL10, produced in part by damaged proximal tubules. Our study directly links low nephron endowment with postnatal renal hypertrophy, which in this model is maladaptive and results in CKD. Underdeveloped kidneys are more susceptible to gentamicin-induced AKI, suggesting that AKI in the setting of low nephron number is more severe and further increases the risk of CKD in this vulnerable population.

Implementation and Feasibility of Clinical Genome Sequencing Embedded Into the Outpatient Nephrology Care for Patients With Proteinuric Kidney Disease.

Introduction: The diagnosis and management of proteinuric kidney diseases such as focal segmental glomerulosclerosis (FSGS) are challenging. Genetics holds the promise to improve clinical decision making for these diseases; however, it is often performed too late to enable timely clinical action and it is not implemented within routine outpatient nephrology visits. Methods: We sought to test the implementation and feasibility of clinical rapid genome sequencing (GS) in guiding decision making in patients with proteinuric kidney disease in real-time and embedded in the outpatient nephrology setting. Results: We enrolled 10 children or young adults with biopsy-proven FSGS (9 cases) or minimal change disease (1 case). The mean age at enrollment was 16.2 years (range 2-30). The workflow did not require referral to external genetics clinics but was conducted entirely during the nephrology standard-of-care appointments. The total turn-around-time from enrollment to return-of-results and clinical decision averaged 21.8 days (12.4 for GS), which is well within a time frame that allows clinically relevant treatment decisions. A monogenic or APOL1-related form of kidney disease was diagnosed in 5 of 10 patients. The genetic findings resulted in a rectified diagnosis in 6 patients. Both positive and negative GS findings determined a change in pharmacological treatment. In 3 patients, the results were instrumental for transplant evaluation, donor selection, and the immunosuppressive treatment. All patients and families received genetic counseling. Conclusion: Clinical GS is feasible and can be implemented in real-time in the outpatient care to help guiding clinical management. Additional studies are needed to confirm the cost-effectiveness and broader utility of clinical GS across the phenotypic and demographic spectrum of kidney diseases.

Use of mouse hematopoietic stem and progenitor cells to treat acute kidney injury.

New and effective treatment for acute kidney injury remains a challenge. Here, we induced mouse hematopoietic stem and progenitor cells (HSPC) to differentiate into cells that partially resemble a renal cell phenotype and tested their therapeutic potential. We sequentially treated HSPC with a combination of protein factors for 1 wk to generate a large number of cells that expressed renal developmentally regulated genes and protein. Cell fate conversion was associated with increased histone acetylation on promoters of renal-related genes. Further treatment of the cells with a histone deacetylase inhibitor improved the efficiency of cell conversion by sixfold. Treated cells formed tubular structures in three-dimensional cultures and were integrated into tubules of embryonic kidney organ cultures. When injected under the renal capsule, they integrated into renal tubules of postischemic kidneys and expressed the epithelial marker E-cadherin. No teratoma formation was detected 2 and 6 mo after cell injection, supporting the safety of using these cells. Furthermore, intravenous injection of the cells into mice with renal ischemic injury improved kidney function and morphology by increasing endogenous renal repair and decreasing tubular cell death. The cells produced biologically effective concentrations of renotrophic factors including VEGF, IGF-1, and HGF to stimulate epithelial proliferation and tubular repair. Our study indicates that hematopoietic stem and progenitor cells can be converted to a large number of renal-like cells within a short period for potential treatment of acute kidney injury.

Adipose tissue-derived mesenchymal stem cells: a fat chance of curing kidney disease?

Many kidney diseases are associated with inflammation and altered immune response. Mesenchymal stem cells (MSCs) are known for their anti-inflammatory properties and immune modulation. Demonstration that the phenotype and immunosuppressive ability of adipose tissue-derived MSCs are not affected by human kidney disease or uremic serum might have clinical significance if autologous adipose tissue-derived MSCs can be tested to prove their long-term safety and efficacy in treating kidney disease.

Snapshots of nascent RNA reveal cell- and stimulus-specific responses to acute kidney injury.

The current strategy to detect acute injury of kidney tubular cells relies on changes in serum levels of creatinine. Yet serum creatinine (sCr) is a marker of both functional and pathological processes and does not adequately assay tubular injury. In addition, sCr may require days to reach diagnostic thresholds, yet tubular cells respond with programs of damage and repair within minutes or hours. To detect acute responses to clinically relevant stimuli, we created mice expressing Rosa26-floxed-stop uracil phosphoribosyltransferase (Uprt) and inoculated 4-thiouracil (4-TU) to tag nascent RNA at selected time points. Cre-driven 4-TU-tagged RNA was isolated from intact kidneys and demonstrated that volume depletion and ischemia induced different genetic programs in collecting ducts and intercalated cells. Even lineage-related cell types expressed different genes in response to the 2 stressors. TU tagging also demonstrated the transient nature of the responses. Because we placed Uprt in the ubiquitously active Rosa26 locus, nascent RNAs from many cell types can be tagged in vivo and their roles interrogated under various conditions. In short, 4-TU labeling identifies stimulus-specific, cell-specific, and time-dependent acute responses that are otherwise difficult to detect with other technologies and are entirely obscured when sCr is the sole metric of kidney damage.

Autophagy is a component of epithelial cell fate in obstructive uropathy.

Epithelial cell fate and nephron loss in obstructive uropathy are not fully understood. We produced transgenic mice in which epithelial cells in the nephrons and collecting ducts were labeled with enhanced yellow fluorescent protein, and tracked the fate of these cells following unilateral ureteral obstruction (UUO). UUO led to a decrease in the number of enhanced yellow fluorescent protein-expressing cells and down-regulation of epithelial markers, E-cadherin, and hepatocyte nuclear factor-1beta. Following UUO, enhanced yellow fluorescent protein-positive cells were confined within the tubular basement membrane, were not found in the renal interstitium, and did not express alpha-smooth muscle actin or S100A4, markers of myofibroblasts and fibroblasts. Moreover, when proximal tubules were labeled with dextran before UUO, dextran-retaining cells did not migrate into the interstitium or express alpha-smooth muscle actin. These results indicate that UUO leads to tubular epithelial loss but does not cause epithelial-to-mesenchymal transition that has been shown by others to be responsible for nephron loss and interstitial fibrosis. For the first time, we found evidence of enhanced autophagy in obstructed tubules, including accumulation of autophagosomes, increased expression of Beclin 1, and increased conversion of microtubular-associated protein 1 light chain 3-I to -II. Increased autophagy may represent a mechanism of tubular survival or may contribute to excessive cell death and tubular atrophy after obstructive injury.

Dysregulated expression of CXCR4/CXCL12 in subsets of patients with systemic lupus erythematosus.

OBJECTIVE: CXCR4 is a chemokine with multiple effects on the immune system. In murine lupus models, we demonstrated that monocytes, neutrophils, and B cells overexpressed CXCR4 and that its ligand, CXCL12, was up-regulated in diseased kidneys. We undertook this study to determine whether CXCR4 expression was increased in peripheral blood leukocytes from patients with systemic lupus erythematosus (SLE) and whether CXCL12 expression was increased in kidneys from patients with SLE. METHODS: Peripheral blood leukocytes from 31 SLE patients, 8 normal controls, and 9 patients with rheumatoid arthritis were prospectively analyzed by flow cytometry for CXCR4 expression. Biopsy samples (n = 14) from patients with lupus nephritis (LN) were immunostained with anti-CXCL12 antibody. RESULTS: CD19+ B cells and CD4+ T cells from SLE patients displayed a >2-fold increase (P = 0.0001) and >3-fold increase (P < 0.0001), respectively, in median CXCR4 expression compared with that in controls (n = 7-8). Moreover, CXCR4 expression on B cells was 1.61-fold higher in patients with SLE Disease Activity Index (SLEDAI) scores >10 (n = 8) than in patients with SLEDAI scores ≤10 (n = 16) (P = 0.0008), 1.71-fold higher in patients with class IV LN (n = 5) than in patients with other classes of LN (n = 7) (P = 0.02), and 1.40-fold higher in patients with active neuropsychiatric SLE (NPSLE) (n = 6) than in patients with inactive NPSLE (n = 18) (P = 0.01). CXCL12 was significantly up-regulated in the tubules and glomeruli of kidneys in patients with LN (n = 14), with the percentage of positive cells correlating positively with the severity of LN. CONCLUSION: CXCR4 appears to be up-regulated in multiple leukocyte subsets in SLE patients. The heightened expression of CXCR4 on B cells in active NPSLE and of CXCL12 in nephritic kidneys suggests that the CXCR4/CXCL12 axis might be a potential therapeutic target for SLE patients with kidney and/or central nervous system involvement.

CXCR4/CXCL12 hyperexpression plays a pivotal role in the pathogenesis of lupus.

Among various surface molecules screened, CXCR4 was significantly up-regulated on monocytes, neutrophils, B cell subsets, and plasma cells in multiple murine models of lupus with active nephritis, including B6.Sle1Yaa, BXSB, and MRL.lpr. TLR-mediated signaling and inflammatory cytokines accounted in part for this increase. Increased CXCR4 expression was associated with functional consequences, including increased migration and enhanced B cell survival. Simultaneously, the ligand for CXCR4, CXCL12, was significantly up-regulated in the nephritic kidneys. Treatment with a peptide antagonist of CXCR4 prolonged survival and reduced serum autoantibodies, splenomegaly, intrarenal leukocyte trafficking, and end organ disease in a murine model of lupus. These findings underscore the pathogenic role of CXCR4/CXCL12 in lymphoproliferative lupus and lupus nephritis and highlight this axis as a promising therapeutic target in this disease.