Autosomal dominant polycystic kidney disease in the fetus

Long-Term Outcomes in Patients with Very-Early Onset Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Long-term clinical outcomes in children with very-early onset (VEO; diagnosis in utero or within the first 18 months of life) autosomal dominant polycystic kidney disease (ADPKD) are currently not well understood. We conducted a longitudinal retrospective cohort study to assess the association between VEO status and adverse clinical outcomes.

METHODS

Seventy patients with VEO-ADPKD matched (by year of birth, sex and race/ethnicity) to 70 patients with non-VEO-ADPKD who participated in research at the University of Colorado were studied. Kaplan-Meier survival analysis was performed. The predictor was VEO status, and outcomes were progression to end-stage renal disease (ESRD), development of hypertension, progression to estimated glomerular filtration rate (eGFR <90 ml/min/1.73 m2), glomerular hyperfiltration (eGFR ≥140 ml/min/1.73 m2) and height-adjusted total kidney volume (htTKV) measured by MRI ≥600 ml/m.

RESULTS

Median follow-up was until 16.0 years of age. There were only 4 ESRD events during the follow-up period, all in the VEO group (p < 0.05). VEO patients were more likely to develop hypertension (hazard ratio, HR 3.15, 95% CI 1.86-5.34; p < 0.0001) and to progress to eGFR <90 ml/min/1.73 m2 (HR 1.97, 95% CI 1.01-3.84; p < 0.05) than non-VEO patients. There was no difference between groups in the development of glomerular hyperfiltration (HR 0.89, 95% CI 0.56-1.42; p = 0.62). There were only 7 patients who progressed to htTKV ≥600 ml/m, 4 in the VEO group and 3 in the non-VEO group (p < 0.01).

CONCLUSIONS

Several clinical outcomes are worse in patients with VEO-ADPKD compared to non-VEO ADPKD. Children with VEO-ADPKD represent a particularly high-risk group of ADPKD patients.

Placental mesenchymal dysplasia and fetal renal-hepatic-pancreatic dysplasia: androgenetic-biparental mosaicism and pathogenesis of an autosomal recessive disorder

Androgenetic-biparental mosaicism (ABM) denotes an embryo in which a subset of cells contains a diploid chromosomal complement derived entirely from the father. Such embryos have a high incidence of placental mesenchymal dysplasia (PMD) and paternal imprinting disorders because the androgenetic cells have pangenomic paternal uniparental disomy. Uniparental disomy also poses a theoretical risk for paternally transmitted autosomal recessive disorders, if both chromosomes of each autosomal pair are identical (isodisomy). We present the 1st example of a recessive disorder, renal-hepatic-pancreatic dysplasia, in a pregnancy complicated by PMD and ABM. Androgenetic-biparental mosaicism was demonstrated in fetal DNA, extracted from multiple organs, by quantitative polymerase chain reaction-based methods that detected allelic imbalances at the differentially methylated SNRPN locus (chromosome 15); polymorphic short tandem repeat microsatellite markers located on chromosomes 4, 7, 8, 13, 18, and 21; and single nucleotide polymorphisms on chromosomes 1 and 19. Laser capture microdissection was performed to isolate specific placental and renal cell populations and document selective enrichment of androgenetic cells in the stroma of PMD and the epithelium of renal cysts. Mutational analysis of coding sequences did not reveal any mutations in NPHP3, a ciliopathy gene implicated in some cases of renal-hepatic-pancreatic dysplasia. Nonetheless, the fetal phenotype and laser capture data support the model of a paternally transmitted autosomal recessive disorder, which occurred because of ABM.

Pkd1-inactivation in vascular smooth muscle cells and adaptation to hypertension

Autosomal dominant polycystic kidney disease (ADPKD) is a multisystem disorder characterized by renal, hepatic and pancreatic cyst formation and cardiovascular complications. The condition is caused by mutations in the PKD1 or PKD2 gene. In mice with reduced expression of Pkd1, dissecting aneurysms with prominent media thickening have been seen. To study the effect of selective disruption of Pkd1 in vascular smooth muscle cells (SMCs), we have generated mice in which a floxed part of the Pkd1 gene was deleted by Cre under the control of the SM22 promotor (SM22-Pkd1(del/del) mice). Cre activity was confirmed by X-gal staining using lacZ expressing Cre reporter mice (R26R), and quantitative PCR indicated that in the aorta Pkd1 gene expression was strongly reduced, whereas Pkd2 levels remained unaltered. Histopathological analysis revealed cyst formation in pancreas, liver and kidneys as the result of extravascular Cre activity in pancreatic ducts, bile ducts and in the glomerular Bowman's capsule. Remarkably, we did not find any spontaneous gross structural blood vessel abnormalities in mice with somatic Pkd1 gene disruption in SMCs or simultaneous disruption of Pkd1 in SMCs and endothelial cells (ECs). Extensive isometric myographic analysis of the aorta did not reveal differences in response to KCl, acetylcholine, phenylephrin or serotonin, except for a significant increase in contractility induced by phenylephrin on arteries from 40 weeks old Pkd1(del/+) germ-line mice. However, SM22-Pkd1(del/del) mice showed significantly reduced decrease in heart rate on angiotensin II-induced hypertension. The present findings further demonstrate in vivo, that adaptation to hypertension is altered in SM22-Pkd1(del/del) mice.

Incompletely penetrant PKD1 alleles mimic the renal manifestations of ARPKD

Autosomal dominant polycystic kidney disease (ADPKD), caused by mutation in PKD1 or PKD2, is usually an adult-onset disorder but can rarely manifest as a neonatal disease within a family characterized by otherwise typical ADPKD. Coinheritance of a hypomorphic PKD1 allele in trans with an inactivating PKD1 allele is one mechanism that can cause early onset ADPKD. Here, we describe two pedigrees without a history of cystic kidney disease that each contain two patients with onset of massive PKD in utero. The presentations were typical of autosomal recessive PKD (ARPKD) but they were not linked to the known ARPKD gene, PKHD1. Mutation analysis of the ADPKD genes provided strong evidence that both families inherited, in trans, two incompletely penetrant PKD1 alleles. These patients illustrate that PKD1 mutations can manifest as a phenocopy of ARPKD with respect to renal involvement and highlight the perils of linkage-based diagnostics in ARPKD without positive PKHD1 mutation data. Furthermore, the phenotypic overlap between ARPKD and these patients resulting from incomplete penetrant PKD1 alleles support a common pathogenesis for these diseases.

Determinants of renal disease variability in ADPKD

In common with other Mendelian diseases, the presentation and progression of autosomal dominant polycystic kidney disease (ADPKD) vary widely in the population. The typical course is of adult-onset disease with ESRD in the 6th decade. However, a small proportion has adequate renal function into the 9th decade, whereas others present with enlarged kidneys as neonates. ADPKD is genetically heterogeneous, and the disease gene is a major determinant of severity; PKD1 on average is associated with ESRD 20 years earlier than PKD2. The majority of PKD1 and PKD2 mutations are likely fully inactivating although recent studies indicate that some alleles retain partial activity (hypomorphic alleles). Homozygotes for such alleles are viable and in combination with an inactivating allele can result in early-onset disease. Hypomorphic alleles and mosaicism may also account for some cases with unusually mild disease. The degree of phenotypic variation detected in families indicates that genetic background influences disease severity. Genome-wide association studies are planned to map common variants associated with severity. Although ADPKD is a simple genetic disease, fully understanding the phenotypic variability requires consideration of influences at the genic, allelic, and genetic background level, and so, ultimately, it is complex.

Incompletely penetrant PKD1 alleles suggest a role for gene dosage in cyst initiation in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) caused by mutations in PKD1 is significantly more severe than PKD2. Typically, ADPKD presents in adulthood but is rarely diagnosed in utero with enlarged, echogenic kidneys. Somatic mutations are thought crucial for cyst development, but gene dosage is also important since animal models with hypomorphic alleles develop cysts, but are viable as homozygotes. We screened for mutations in PKD1 and PKD2 in two consanguineous families and found PKD1 missense variants predicted to be pathogenic. In one family, two siblings homozygous for R3277C developed end stage renal disease at ages 75 and 62 years, while six heterozygotes had few cysts. In the other family, the father and two children with moderate to severe disease were homozygous for N3188S. In both families homozygous disease was associated with small cysts of relatively uniform size while marked cyst heterogeneity is typical of ADPKD. In another family, one patient diagnosed in childhood was found to be a compound heterozygote for the PKD1 variants R3105W and R2765C. All three families had evidence of developmental defects of the collecting system. Three additional ADPKD families with in utero onset had a truncating mutation in trans with either R3277C or R2765C. These cases suggest the presence of incompletely penetrant PKD1 alleles. The alleles alone may result in mild cystic disease; two such alleles cause typical to severe disease; and, in combination with an inactivating allele, are associated with early onset disease. Our study indicates that the dosage of functional PKD1 protein may be critical for cyst initiation.

Mediation of angiotensin II-induced Ca2+ signaling by polycystin 2 in glomerular mesangial cells

Ca(+) influx across the plasma membrane is a major component of mesangial cell (MC) response to vasoconstrictors. Polycystin 2 (PC2), the protein product of the gene mutated in type 2 autosomal dominant polycystic kidney disease, has been shown to function as a nonselective cation channel in a variety of cell types. The present study was performed to test the hypothesis that PC2 and its binding partners constitute a Ca(2+)-permeable channel and contribute to ANG II-induced Ca(2+) signaling in MCs. Western blot and immunocytochemistry showed PC2 expression in cultured human MCs. The existence of PC2 in MCs was further confirmed by immunohistochemsitry in rat kidney sections. Coimmunoprecipitation displayed a selective interaction of PC2 with canonical transient receptor potential (TRPC) proteins TRPC1 and TRPC4. Cell-attached patch-clamp experiments revealed that ANG II-induced membrane currents were enhanced by overexpression of pkd2 but significantly inhibited by knock down of pkd2, 30 microM Gd(3+) (a PC2 channel blocker), and dominant-negative pkd2 mutant (pkd2-D511V). Corresponding to the increase in channel currents, ANG II stimulation increased expression of PC2 on the cell surface of MCs and interaction with TRPC1 and TRPC4. Furthermore, ANG II-induced MC contraction was significantly reduced in pkd2-knocked down MCs. These data suggest that PC2 selectively assembles with TRPC1 and TRPC4 to form channel complexes mediating ANG II-induced Ca(2+) responses in MCs.

Autosomal Dominant Polycystic Kidney Disease: Time for a Change?

Diagnosis and treatment of autosomal dominant polycystic kidney disease (ADPKD) is rapidly changing. Cellular pathways that involve the polycystins are being mapped and involve the primary cilium, intracellular calcium and cAMP regulation, and the mammalian target of rapamycin (mTOR) pathway. With the use of new imaging approaches, earlier diagnosis of hepatic cystic disease is possible, and measurement of kidney and cystic growth as well as kidney blood flow is possible over relatively short periods. PKD gene type, gender, proteinuria, and the presence of hypertension relate to the rate of kidney growth in ADPKD. On the basis of risk factors for progression to ESRD and the pathogenic roles that intracellular cAMP and mTOR play in cystogenesis, novel therapies are now being tested, including maximal inhibition of the renin-angiotensin system, inhibition of renal intracellular cAMP using vasopressin V2 receptor antagonists, and somatostatin analogues, as well as inhibitors of mTOR. This review addresses the current understanding of the pathogenesis and the natural history of ADPKD; accuracy and reliability of diagnostic approaches in utero, childhood, and adulthood; the value of reliable magnetic resonance imaging to measure disease progression early in the course of ADPKD; and novel therapeutic approaches that are being evaluated in ADPKD.

Genotype-phenotype correlations in autosomal dominant and autosomal recessive polycystic kidney disease

The phenotypes that are associated with the common forms of polycystic kidney disease (PKD)--autosomal dominant (ADPKD) and autosomal recessive (ARPKD)--are highly variable in penetrance. This is in terms of severity of renal disease, which can range from neonatal death to adequate function into old age, characteristics of the liver disease, and other extrarenal manifestations in ADPKD. Influences of the germline mutation are at the genic and allelic levels, but intrafamilial variability indicates that genetic background and environmental factors are also key. In ADPKD, the gene involved, PKD1 or PKD2, is a major factor, with ESRD occurring 20 yr later in PKD2. Mutation position may also be significant, especially in terms of the likelihood of vascular events, with 5' mutations most detrimental. Variance component analysis in ADPKD populations indicates that genetic modifiers are important, but few such factors (beyond co-inheritance of a TSC2 mutation) have been identified. Hormonal influences, especially associated with more severe liver disease in female individuals, indicate a role for nongenetic factors. In ARPKD, the combination of mutations is critical to the phenotypic outcome. Patients with two truncating mutations have a lethal phenotype, whereas the presence of at least one missense change can be compatible with life, indicating that many missense changes are hypomorphic alleles that generate partially functional protein. Clues from animal models and other forms of PKD highlight potential modifiers. The information that is now available on both genes is of considerable prognostic value with the prospects from the ongoing genetic revolution that additional risk factors will be revealed.

Prognosis of autosomal dominant polycystic kidney disease diagnosed in utero or at birth

The use of prenatal ultrasonography has resulted in increased numbers of fetuses being diagnosed with autosomal dominant polycystic kidney disease (ADPKD), but the long-term prognosis is still not well-known. Between 1981 and 2006 we followed 26 consecutive children with enlarged hyperechoic kidneys detected between the 12th week of pregnancy and the first day of life (Day 1) as well as one affected parent. Three other fetuses were excluded following the termination of the pregnancy. The mother was the transmitting parent in 16 of the 26 children (ns, p=0.1). Clinical features that presented during follow-up were oligoamnios (5/26), neonatal pneumothorax (3/26), pyelonephritis (5/26), gross hematuria (2/26), hypertension (5/26), proteinuria (2/26) and chronic renal insufficiency (CRI) (2/26). At the last follow-up (mean duration of follow-up: 76 months; range: 0.5-262 months), 19 children (mean age: 5.5 years) were asymptomatic, five (mean age: 8.5 years) had hypertension, two (mean age: 9.7 years) had proteinuria and two (mean age: 19 years) had CRI. Children presenting enlarged kidneys postnatally tended to have more clinical manifestations than their counterparts who did not. Of 25 siblings of the patients, seven had renal cysts; these were detected during childhood in five siblings and in utero in two siblings. In conclusion, prognosis is favourable in most children with prenatal ADPKD, at least during childhood. The sex of the transmitting parent is not a risk factor of prenatal ADPKD. A high proportion of siblings develop early renal cysts. Abnormalities visualized by ultrasonography appear to be associated to more clinical manifestations.

Perinatal assessment of hereditary cystic renal diseases: the contribution of sonography

The aims of this review article were to clarify the steps that may lead to a proper diagnosis of fetal and neonatal renal cystic diseases. All the hereditary cystic diseases are reviewed and a classification is proposed. The various sonographic patterns that can be used to ascertain the diagnosis are also reviewed. Finally, tables with differential diagnoses are presented to help the reader in the work-up of such pathologies.

Defining a link with autosomal-dominant polycystic kidney disease in mice with congenitally low expression of Pkd1

Mouse models for autosomal-dominant polycystic kidney disease (ADPKD), derived from homozygous targeted disruption of Pkd1 gene, generally die in utero or perinatally because of systemic defects. We introduced a loxP site and a loxP-flanked mc1-neo cassette into introns 30 and 34, respectively, of the Pkd1 locus to generate a conditional, targeted mutation. Significantly, before excision of the floxed exons and mc1-neo from the targeted locus by Cre recombinase, mice homozygous for the targeted allele appeared normal at birth but developed polycystic kidney disease with a slower progression than that of Pkd-null mice. Further, the homozygotes continued to produce low levels of full-length Pkd1-encoded protein, suggesting that slight Pkd1 expression is sufficient for renal cyst formation in ADPKD. In this viable model, up-regulation of heparin-binding epidermal growth factor-like growth factor accompanied increased epidermal growth factor receptor signaling, which may be involved in abnormal proliferation of the cyst-lining epithelia. Increased apoptosis in cyst epithelia was only observed in the later period that correlated with the cyst regression. Abnormalities in Na(+)/K(+)-ATPase, aquaporin-2, and vasopressin V2 receptor expression were also identified. This mouse model may be suitable for further studies of progression and therapeutic interventions of ADPKD.

Autosomal-dominant polycystic kidney disease in infancy and childhood: progression and outcome

BACKGROUND

The natural history of autosomal-dominant polycystic kidney disease (ADPKD) has not been well described in children and infants.

METHODS

The present study analyzed the characteristics of 46 ADPKD children diagnosed before 18 months of life (VEO) and 153 children diagnosed between 18 months of age and 18 years of age (non-VEO).

RESULTS

VEO children had more cysts and larger renal volumes than non-VEO children when adjusted for age. In both VEO and non-VEO children, the presence of signs or symptoms at the time of diagnosis as well as the presence of hematuria or proteinuria at the study visit were associated with larger renal volumes. Children diagnosed early (VEO) or diagnosed due to signs or symptoms were also more likely to have high blood pressure. Two VEO children and no non-VEO children reached end-stage renal disease during follow-up.

CONCLUSION

In contrast to many published case reports suggesting the occurrence of early end-stage renal disease in VEO children, the results of the present study were much more optimistic. Over 90% of the VEO children maintained preserved renal function well into childhood.

Prenatal sonographic patterns in autosomal dominant polycystic kidney disease: a multicenter study

OBJECTIVE

To determine whether a specific prenatal sonographic pattern can be identified for autosomal dominant polycystic kidney disease (ADPKD) and if so whether it would be helpful in orienting complementary analysis, properly counseling parents and adapting pregnancy management.

METHODS

A retrospective multicenter study was conducted in four prenatal diagnostic centers. The records of fetuses with a prenatal ultrasound examination revealing abnormal kidneys and with a final diagnosis of ADPKD were analyzed. Ultrasound analysis included: amount of amniotic fluid, bladder size, renal length, presence or absence of renal cysts and size of renal pelves, and was focused on parenchyma echogenicity and status of corticomedullary differentiation. Postnatal follow-up was reviewed.

RESULTS

Of the 27 patients included in the study, 25 had hyperechogenic renal cortex and 20 had hypoechogenic medulla resulting in increased corticomedullary differentiation (CMD). In six cases, the medulla was hyperechogenic leading to absent or decreased CMD. One patient had normal cortical echogenicity and CMD. Renal cysts were present during the prenatal period in four patients (at 22 weeks in one case and after 30 weeks in three cases). In 12 patients, the cysts appeared after birth (within the first 6 months of postnatal life in 10 cases and by the age of 1 year in two cases). Elevated blood pressure was observed in only two cases and moderate chronic renal failure in one case.

CONCLUSION

We have described the sonographic presentation in fetuses with ADPKD: moderately enlarged hyperechogenic kidneys with increased CMD. Although not specific to ADPKD, these findings should prompt familial screening. Other prenatal sonographic features (absent or decreased CMD and cortical cysts) are less frequent.

Phenotypic heterogeneity in pediatric autosomal dominant polycystic kidney disease at first presentation: a single-center, 20-year review

BACKGROUND

The presentation of autosomal dominant polycystic kidney disease (ADPKD) in childhood provides an insight into comorbidities and potential areas for interventions and investigation.

METHODS

Phenotypic heterogeneity at the time of first presentation was studied with respect to age of diagnosis, mode of presentation, parental inheritance pattern, renal function, associated hypertension, and hyperlipidemia. Fifty-five children (median age of presentation, 8.7 years; 27% < 1 year) with ADPKD from 44 families followed up between March 1983 and March 2003 were reviewed. The diagnosis was based on family history and ultrasound confirmation of cysts. Progression of renal disease was followed over the study period (mean duration of follow-up, 4.9 years).

RESULTS

A family history of ADPKD was known at presentation in 89%, which precipitated the screening diagnostic imaging in 59% of these children. Maternal inheritance was displayed in 51%, whereas 5% had no known family history of ADPKD. Bilateral renal findings were present in 78%. Hypertension (>95(th) percentile for age) was present in 22%, and hyperlipidemia was present in 54%. Renal function was not significantly diminished in 98% of patients with creatinine clearance > or =3rd percentile for age, and 7% had persistent proteinuria (>150 mg/d). No subjects had hepatic, splenic, or pancreatic cysts on ultrasound scan. A subpopulation of 10 patients had features of ADPKD dating back to prenatal ultrasound scans. All prenatal cases were characterized by bilateral renal findings, 90% had a known family history of ADPKD at the time of presentation, and 89% of these patients displayed maternal inheritance. Follow-up studies showed a persistence of hyperlipidemia despite pharmacotherapeutic treatment of hypertension, infrequent proteinuria, and sustained renal function in most patients.

CONCLUSION

The results of this study show that many children at the time of first presentation have a significant prevalence of modifiable risk factors: hypertension, proteinuria, and hyperlipidemia, in the face of normal renal function. The results also show a unique presentation existing in prenatal subjects.

Prenatal diagnosis and management of abnormalities in the urologic system

We have reviewed the prenatal diagnosis and management of abnormalities in the urologic system. Urologic anomalies may be caused by embryologic aberrations, genetic disease, or a nonrandom association with other structural abnormalities. There is a wide range of prognoses, depending on the cause and the impact of the anomaly on the production of amniotic fluid. Management focuses on obtaining an accurate prenatal diagnosis, providing appropriate counseling, and ensuring the proper surveillance or treatment before and after birth.

Prenatal diagnosis of autosomal dominant polycystic kidney disease (PKD1) presenting in utero and prognosis for very early onset disease

We describe four prenatal diagnoses in a family with autosomal dominant polycystic kidney disease. Two pregnancies were terminated following the detection of enlarged echogenic fetal kidneys with cysts. Histopathological examination confirmed the diagnosis of polycystic kidney disease. Linkage to PKD1 was obtained by the analysis of DNA from relatives in three generations and from paraffin blocks and formalin fixed fetal tissues. Prenatal DNA analysis in subsequent pregnancies identified one unaffected fetus and one fetus carrying the high risk PKD1 allelle. Information on survival and subsequent outcome of PKD cases presenting in utero was requested by this family before prenatal testing was performed. Of 83 reported cases of ADPKD presenting in utero (excluding termination of pregnancy) or in the first few months of life, 43% died before 1 year. Longitudinal follow up of 24 children in two studies showed that 67% of survivors developed hypertension, of whom three had end stage renal failure at a mean age of 3 years.

Autosomal dominant polycystic kidney disease with anticipation and Caroli's disease associated with a PKD1 mutation. Rapid communication

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal hereditary disorder. Clinical expression of ADPKD shows interfamilial and intrafamilial variability. We screened for mutations the 3' region of the PKD1 gene, from exon 43 to exon 46, in a family showing anticipation and Caroli's disease and have found a 28 base pairs deletion in exon 46 (12801del28) and a new DNA variant in exon 43 (12184 C to G conserving Ala 3991) segregating with the disease. The mutation should result in a protein 44 amino acids longer then the wild-type PKD1. This PKD1 mutation manifests as typical adult-onset disease in the father, but in the proband, a 26-year-old man, ADPKD was diagnosed as a newborn and was associated with Caroli's disease at the age of 18 years. A renal biopsy performed in childhood disclosed a predominance of glomerular cysts. Mutation 12801del28 is the first molecular defect associated with Caroli's disease and the PKD1 phenotype. The finding of the same mutation in two different members of the same family with different expression of the disease indicates that the phenotypic variation in ADPKD must be due to modifying factors that may radically affect the course of the disease.