Cardiac Valve Defects Research Articles

Lymphatic endothelial-cell expressed ACKR3 is dispensable for postnatal lymphangiogenesis and lymphatic drainage function in mice.

Atypical chemokine receptor ACKR3 (formerly CXCR7) is a scavenging receptor that has recently been implicated in murine lymphatic development. Specifically, ACKR3-deficiency was shown to result in lymphatic hyperplasia and lymphedema, in addition to cardiac hyperplasia and cardiac valve defects leading to embryonic lethality. The lymphatic phenotype was attributed to a lymphatic endothelial cell (LEC)-intrinsic scavenging function of ACKR3 for the vascular peptide hormone adrenomedullin (AM), which is also important during postnatal lymphangiogenesis. In this study, we investigated the expression of ACKR3 in the lymphatic vasculature of adult mice and its function in postnatal lymphatic development and function. We show that ACKR3 is widely expressed in mature lymphatics and that it exerts chemokine-scavenging activity in cultured murine skin-derived LECs. To investigate the role of LEC-expressed ACKR3 in postnatal lymphangiogenesis and function during adulthood, we generated and validated a lymphatic-specific, inducible ACKR3 knockout mouse. Surprisingly, in contrast to the reported involvement of ACKR3 in lymphatic development, our analyses revealed no contribution of LEC-expressed ACKR3 to postnatal lymphangiogenesis, lymphatic morphology and drainage function.

Biallelic loss-of-function variants in PLD1 cause congenital right-sided cardiac valve defects and neonatal cardiomyopathy.

Congenital heart disease is the most common type of birth defect, accounting for one-third of all congenital anomalies. Using whole-exome sequencing of 2718 patients with congenital heart disease and a search in GeneMatcher, we identified 30 patients from 21 unrelated families of different ancestries with biallelic phospholipase D1 (PLD1) variants who presented predominantly with congenital cardiac valve defects. We also associated recessive PLD1 variants with isolated neonatal cardiomyopathy. Furthermore, we established that p.I668F is a founder variant among Ashkenazi Jews (allele frequency of ~2%) and describe the phenotypic spectrum of PLD1-associated congenital heart defects. PLD1 missense variants were overrepresented in regions of the protein critical for catalytic activity, and, correspondingly, we observed a strong reduction in enzymatic activity for most of the mutant proteins in an enzymatic assay. Finally, we demonstrate that PLD1 inhibition decreased endothelial-mesenchymal transition, an established pivotal early step in valvulogenesis. In conclusion, our study provides a more detailed understanding of disease mechanisms and phenotypic expression associated with PLD1 loss of function.

Comparative Serum Analyses Identify Cytokines and Hormones Commonly Dysregulated as Well as Implicated in Promoting Osteolysis in MMP-2-Deficient Mice and Children.

Deficiency of matrix metalloproteinase 2 (MMP-2) causes a complex syndrome characterized by multicentric osteolysis, nodulosis, and arthropathy (MONA) as well as cardiac valve defects, dwarfism and hirsutism. MMP-2 deficient (Mmp2–/–) mice are a model for this rare multisystem pediatric syndrome but their phenotype remains incompletely characterized. Here, we extend the phenotypic characterization of MMP-2 deficiency by comparing the levels of cytokines and chemokines, soluble cytokine receptors, angiogenesis factors, bone development factors, apolipoproteins and hormones in mice and humans. Initial screening was performed on an 8-year-old male presenting a previously unreported deletion mutation c1294delC (Arg432fs) in the MMP2 gene and diagnosed with MONA. Of eighty-one serum biomolecules analyzed, eleven were upregulated (>4-fold), two were downregulated (>4-fold) and sixty-eight remained unchanged, compared to unaffected controls. Specifically, Eotaxin, GM-CSF, M-CSF, GRO-α, MDC, IL-1β, IL-7, IL-12p40, MIP-1α, MIP-1β, and MIG were upregulated and epidermal growth factor (EGF) and ACTH were downregulated in this patient. Subsequent analysis of five additional MMP-2 deficient patients confirmed the upregulation in Eotaxin, IL-7, IL-12p40, and MIP-1α, and the downregulation in EGF. To establish whether these alterations are bona fide phenotypic traits of MMP-2 deficiency, we further studied Mmp2–/– mice. Among 32 cytokines measured in plasma of Mmp2–/– mice, the cytokines Eotaxin, IL-1β, MIP-1α, and MIG were commonly upregulated in mice as well as patients with MMP-2 deficiency. Moreover, bioactive cortisol (a factor that exacerbates osteoporosis) was also elevated in MMP-2 deficient mice and patients. Among the factors we have identified to be dysregulated in MMP-2 deficiency many are osteoclastogenic and could potentially contribute to bone disorder in MONA. These new molecular phenotypic traits merit being targeted in future research aimed at understanding the pathological mechanisms elicited by MMP-2 deficiency in children.

In This Issue

HomeCirculation ResearchVol. 126, No. 8In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published9 Apr 2020https://doi.org/10.1161/RES.0000000000000339Circulation Research. 2020;126:943is related toNfatc1 Promotes Interstitial Cell Formation During Cardiac Valve Development in ZebrafishA Computational Pipeline to Predict Cardiotoxicityis related toCrystal Clots as Therapeutic Target in Cholesterol Crystal EmbolismCardiotoxicity From the Atom to the Cardiac Rhythm (p 947)Yang et al’s new computational method predicts proarrhythmic tendencies of drugs.Download figureDownload PowerPointCardiotoxicity is a common side effect of otherwise promising drugs that can lead to their removal from the market, or failure to get there. A chief cause of drug-induced arrhythmias is inhibition of the cardiac potassium channel hERG, which interacts with a variety of pharmacological agents. To determine a drug’s effect on hERG, researchers measure the heart’s QT interval—the time taken for ventricles to contract and relax—via electrocardiograms. However, while a number of drugs prolong QT intervals, they don’t all result in severe arrhythmias. Yang and colleagues have thus developed an approach to help differentiate damaging drugs from less risky ones. They show that computational modeling of drug interactions—using the atomic structures of hERG and the candidate drug—as well as the resulting cell and tissue effects can predict a drug’s proarrhythmic potential. The approach was tested with two drugs, doletilide and monofloxacin, both of which block hERG but which differ in arrhythmia risk. Comparing the results of the computer modeling with actual clinical data for the drugs showed tight agreement. This proof-of-principle study now lays the foundation for assessing more drugs and, ultimately, for applying the method as a screening aid during drug development.Nfatc1 in Zebrafish Cardiac Valve Development (p 968)Gunawan et al investigate the role of transcription factor Nfatc1 in heart valve development.Download figureDownload PowerPointBy ensuring the unidirectional flow of blood, the cardiac valves are critical to heart function. In humans, congenital valve defects have been associated with polymorphisms at the gene encoding transcription factor Nfatc1. Furthermore, mice lacking functional Nfatc1 die from cardiac valve defects during embryogenesis. The precise mechanisms by which Nfatc1 mediates valve development, however, are unknown. To investigate Nfatc1 activity, Gunawen and colleagues turned to zebrafish—because their transparent bodies facilitate heart imaging during development. By 96 hours postfertilization, fish that lacked functional Nfatc1 were noticeably different from wild-type controls, showing pericardial edema, retrograde blood flow, and significantly fewer valve interstitial cells (VICs)—fibroblast-like cells that secrete and maintain the extracellular matrix material of the valves. Indeed, fewer VICs was associated with reduced valve ECM. The team went on to show that Nfatc1 regulates the development and proliferation of VICs, in part by the activation of twist1b—a cell lineage determination factor. The work not only uncovers the role of Nfatc1 and twist1b in VIC production, but also highlights zebrafish as useful model organisms for further studies of this process.Crystal Clots in Cholesterol Embolism (p e37)Shi et al examine the formation, composition and dismantling of cholesterol clots.Download figureDownload PowerPointWhen an atherosclerotic plaque ruptures releasing crystals of cholesterol, it’s not the crystals themselves that are the major cause of vessel occlusion, but the cells and molecules that surround them, according to Shi and colleagues’ new findings. The team developed a mouse model of cholesterol crystal embolism (CCE) wherein they inject cholesterol crystals into the animal’s left kidney artery. The animals quickly develop an arterial blockage, infarct, and reduced kidney function—measured by glomerular filtration rate (GFR). The vessel occlusions consisted of typical thrombus components, including platelets, neutrophils, and fibrin, as well as extracellular DNA from dying neutrophils and endothelial cells, the team showed. Inhibition of platelet activation, or the use of anticoagulants prevented vascular obstruction, reduced infarct size and maintained GFR, even though the cholesterol crystals remained. As an alternative to anticoagulants, which cannot be used if patients need arterial surgery, the team examined DNase I treatment as a way to dismantle the clots showing it too decreased vessel occlusion. The work shows that clotting components are the critical factors leading to vessel blockage in CCE, and provides a model system in which to study CCE pathogenesis and treatments. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesNfatc1 Promotes Interstitial Cell Formation During Cardiac Valve Development in ZebrafishFelix Gunawan, et al. Circulation Research. 2020;126:968-984Crystal Clots as Therapeutic Target in Cholesterol Crystal EmbolismChongxu Shi, et al. Circulation Research. 2020;126:e37-e52A Computational Pipeline to Predict CardiotoxicityPei-Chi Yang, et al. Circulation Research. 2020;126:947-964 April 10, 2020Vol 126, Issue 8 Advertisement Article InformationMetrics © 2020 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000339PMID: 32271676 Originally publishedApril 9, 2020 PDF download Advertisement

Intraluminal valves: development, function and disease.

ABSTRACTThe circulatory system consists of the heart, blood vessels and lymphatic vessels, which function in parallel to provide nutrients and remove waste from the body. Vascular function depends on valves, which regulate unidirectional fluid flow against gravitational and pressure gradients. Severe valve disorders can cause mortality and some are associated with severe morbidity. Although cardiac valve defects can be treated by valve replacement surgery, no treatment is currently available for valve disorders of the veins and lymphatics. Thus, a better understanding of valves, their development and the progression of valve disease is warranted. In the past decade, molecules that are important for vascular function in humans have been identified, with mouse studies also providing new insights into valve formation and function. Intriguing similarities have recently emerged between the different types of valves concerning their molecular identity, architecture and development. Shear stress generated by fluid flow has also been shown to regulate endothelial cell identity in valves. Here, we review our current understanding of valve development with an emphasis on its mechanobiology and significance to human health, and highlight unanswered questions and translational opportunities.

Perioperative Herzinsuffizienz – Anästhesieführung und Monitoring

Due to the demographic and medical development, the number of patients with heart failure needing anaesthesiological care will continue to grow in the upcoming years. For the optimal care of these patients close coordination between the surgically treating, the cardiology and the anesthesiological department is important. Cardiac function and structural characters, such as cardiac valve defects should be known preoperatively. Thus, the anaesthetic management, intraoperative monitoring, as well as necessary pharmacological interventions can be tailored. Especially in high-risk patients goal directed hemodynamic therapy is useful. For this, in addition to the established monitoring procedures, less invasive monitoring devices areincreasingly used. During an acutehaemodynamic instability, thetransoesophageal echocardiography is gaining importance due to its wide diagnostic evaluation.

Metabolic abnormalities in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder and is known to affect all ethnic groups with a prevalence of 1:400-1:1000 live births. The kidney in ADKPD is characterized by the formation of numerous cysts which progressively expand and eventually destroy normal kidney structure and function. Cysts occur in other organs outside the kidney, most commonly in the liver, pancreas and spleen. Important non-cystic features include intracranial aneurysms and cardiac valve defects. Less well recognized are a range of metabolic abnormalities, which could be involved in cystic disease progression or be associated with other disease complications. In this review, we summarize the literature suggesting that metabolic abnormalities could be important under-recognised and under-treated features in ADPKD.

UDP-glucose Dehydrogenase Polymorphisms from Patients with Congenital Heart Valve Defects Disrupt Enzyme Stability and Quaternary Assembly

Cardiac valve defects are a common congenital heart malformation and a significant clinical problem. Defining molecular factors in cardiac valve development has facilitated identification of underlying causes of valve malformation. Gene disruption in zebrafish revealed a critical role for UDP-glucose dehydrogenase (UGDH) in valve development, so this gene was screened for polymorphisms in a patient population suffering from cardiac valve defects. Two genetic substitutions were identified and predicted to encode missense mutations of arginine 141 to cysteine and glutamate 416 to aspartate, respectively. Using a zebrafish model of defective heart valve formation caused by morpholino oligonucleotide knockdown of UGDH, transcripts encoding the UGDH R141C or E416D mutant enzymes were unable to restore cardiac valve formation and could only partially rescue cardiac edema. Characterization of the mutant recombinant enzymes purified from Escherichia coli revealed modest alterations in the enzymatic activity of the mutants and a significant reduction in the half-life of enzyme activity at 37 °C. This reduction in activity could be propagated to the wild-type enzyme in a 1:1 mixed reaction. Furthermore, the quaternary structure of both mutants, normally hexameric, was destabilized to favor the dimeric species, and the intrinsic thermal stability of the R141C mutant was highly compromised. The results are consistent with the reduced function of both missense mutations significantly reducing the ability of UGDH to provide precursors for cardiac cushion formation, which is essential to subsequent valve formation. The identification of these polymorphisms in patient populations will help identify families genetically at risk for valve defects.

A gain-of-function TBX20 mutation causes congenital atrial septal defects, patent foramen ovale and cardiac valve defects

BackgroundOstium secundum atrial septal defects (ASDII) account for approximately 10% of all congenital heart defects (CHD), and mutations in cardiac transcription factors, including TBX20, were identified as an underlying cause...

Folate rescues lithium-, homocysteine- and Wnt3A-induced vertebrate cardiac anomalies.

Elevated plasma homocysteine (HCy), which results from folate (folic acid, FA) deficiency, and the mood-stabilizing drug lithium (Li) are both linked to the induction of human congenital heart and neural tube defects. We demonstrated previously that acute administration of Li to pregnant mice on embryonic day (E)6.75 induced cardiac valve defects by potentiating Wnt-beta-catenin signaling. We hypothesized that HCy may similarly induce cardiac defects during gastrulation by targeting the Wnt-beta-catenin pathway. Because dietary FA supplementation protects from neural tube defects, we sought to determine whether FA also protects the embryonic heart from Li- or HCy-induced birth defects and whether the protection occurs by impacting Wnt signaling. Maternal elevation of HCy or Li on E6.75 induced defective heart and placental function on E15.5, as identified non-invasively using echocardiography. This functional analysis of HCy-exposed mouse hearts revealed defects in tricuspid and semilunar valves, together with altered myocardial thickness. A smaller embryo and placental size was observed in the treated groups. FA supplementation ameliorates the observed developmental errors in the Li- or HCy-exposed mouse embryos and normalized heart function. Molecular analysis of gene expression within the avian cardiogenic crescent determined that Li, HCy or Wnt3A suppress Wnt-modulated Hex (also known as Hhex) and Islet-1 (also known as Isl1) expression, and that FA protects from the gene misexpression that is induced by all three factors. Furthermore, myoinositol with FA synergistically enhances the protective effect. Although the specific molecular epigenetic control mechanisms remain to be defined, it appears that Li or HCy induction and FA protection of cardiac defects involve intimate control of the canonical Wnt pathway at a crucial time preceding, and during, early heart organogenesis.

Noonan syndrome cardiac defects are caused by PTPN11 acting in endocardium to enhance endocardial-mesenchymal transformation

Noonan syndrome (NS), the most common single-gene cause of congenital heart disease, is an autosomal dominant disorder that also features proportionate short stature, facial abnormalities, and an increased risk of myeloproliferative disease. Germline-activating mutations in PTPN11, which encodes the protein tyrosine phosphatase SHP2, cause about half of NS cases; other causative alleles include KRAS, SOS1, and RAF1 mutants. We showed previously that knock-in mice bearing the NS mutant Ptpn11(D61G) on a mixed 129S4/SvJae X C57BL6/J background exhibit all major NS features, including a variety of cardiac defects, with variable penetrance. However, the cellular and molecular mechanisms underlying NS cardiac defects and whether genetic background and/or the specific NS mutation contribute to the NS phenotype remained unclear. Here, using an inducible knock-in approach, we show that all cardiac defects in NS result from mutant Shp2 expression in the endocardium, not in the myocardium or neural crest. Furthermore, the penetrance of NS defects is affected by genetic background and the specific Ptpn11 allele. Finally, ex vivo assays and pharmacological approaches show that NS mutants cause cardiac valve defects by increasing Erk MAPK activation, probably downstream of ErbB family receptor tyrosine kinases, extending the interval during which cardiac endocardial cells undergo endocardial-mesenchymal transformation. Our data provide a mechanistic underpinning for the cardiac defects in this disorder.

Molecular effects of lithium exposure during mouse and chick gastrulation and subsequent valve dysmorphogenesis

Lithium (Li) has been associated with cardiac teratogenicity in the developing fetus. We took advantage of the association of therapeutic administration of Li with an increase in heart defects to gain insight into both normal and pathological heart and valve development with GSK-3 inhibition. The objective of this study was to define whether Li mimicry of canonical Wnt/beta-catenin signaling induces cardiac valve defects. Li was administered by a single intraperitoneal injection to the pregnant mouse on embryonic day E6.75, much earlier than heretofore analyzed. On E15.5 developing heart defects were defined by Doppler ultrasound. The embryonic hearts were analyzed for changes in patterning of active canonical Wnt expression and nuclear factor of the activated T cells-c1 (NFATc1), both key regulators of valve development. Li-exposed chick embryos were used to define the early cell populations during gastrulation that are susceptible to GSK-3 inhibition and may relate to valve formation. Li exposure during gastrulation decreased the number of prechordal plate (PP) cells that reached the anterior intestinal portal, a region associated with valve development. Li decreased expression of Hex, an endoderm cardiac inducing molecule, normally also expressed by the PP cells, and of Sox 4 at the anterior intestinal portal and NFAT, critical factors in valvulogenesis. Cells existing already during gastrulation are associated with valve formation days later. The Wnt/beta-catenin signaling in PP cells is normally repressed by Wnt antagonists and Hex is up-regulated. The antagonism occurring at the receptor level is bypassed by Li exposure by its intracellular inactivation of GSK-3 directly to augment Wnt signaling.

Catheter-Based Modification of Heart Valve Diseases: From Experimental to Clinical Application

Efforts to modify cardiac valve defects using catheter-based techniques are increasing at the present time. We present observations on cardiac valve morphology and disease and review the progress being made to address valve defects with these innovative methods. Some new procedures developed through animal experimentation have already been put to use in clinical practice, but the newness of these techniques and the small number of cases in which they have been applied to date precludes an evaluation of their long-term durability. Although at the present time cardiac surgery remains the standard for treating most cases of valve disease, in certain situations a catheter-based treatment might provide a reasonable alternative, even if only temporary, especially for individuals with serious disease who are not suitable candidates for surgery.

Glycogen synthase kinase 3α and 3β have distinct functions during cardiogenesis of zebrafish embryo

BackgroundGlycogen synthase kinase 3 (GSK3) encodes a serine/threonine protein kinase, is known to play roles in many biological processes. Two closely related GSK3 isoforms encoded by distinct genes: GSK3α (51 kDa) and GSK3β (47 kDa). In previously studies, most GSK3 inhibitors are not only inhibiting GSK3, but are also affecting many other kinases. In addition, because of highly similarity in amino acid sequence between GSK3α and GSK3β, making it difficult to identify an inhibitor that can be selective against GSK3α or GSK3β. Thus, it is relatively difficult to address the functions of GSK3 isoforms during embryogenesis. At this study, we attempt to specifically inhibit either GSK3α or GSK3β and uncover the isoform-specific roles that GSK3 plays during cardiogenesis.ResultsWe blocked gsk3α and gsk3β translations by injection of morpholino antisense oligonucleotides (MO). Both gsk3α- and gsk3β-MO-injected embryos displayed similar morphological defects, with a thin, string-like shaped heart and pericardial edema at 72 hours post-fertilization. However, when detailed analysis of the gsk3α- and gsk3β-MO-induced heart defects, we found that the reduced number of cardiomyocytes in gsk3α morphants during the heart-ring stage was due to apoptosis. On the contrary, gsk3β morphants did not exhibit significant apoptosis in the cardiomyocytes, and the heart developed normally during the heart-ring stage. Later, however, the heart positioning was severely disrupted in gsk3β morphants. bmp4 expression in gsk3β morphants was up-regulated and disrupted the asymmetry pattern in the heart. The cardiac valve defects in gsk3β morphants were similar to those observed in axin1 and apcmcr mutants, suggesting that GSK3β might play a role in cardiac valve development through the Wnt/β-catenin pathway. Finally, the phenotypes of gsk3α mutant embryos cannot be rescued by gsk3β mRNA, and vice versa, demonstrating that GSK3α and GSK3β are not functionally redundant.ConclusionWe conclude that (1) GSK3α, but not GSK3β, is necessary in cardiomyocyte survival; (2) the GSK3β plays important roles in modulating the left-right asymmetry and affecting heart positioning; and (3) GSK3α and GSK3β play distinct roles during zebrafish cardiogenesis.

Endothelial to Mesenchymal Transformation in Cardiovascular Tissue Engineering

We envision the use of blood-derived endothelial progenitor cells (EPCs) to repair cardiovascular defects, including cardiac valve defects. To pursue this, we are studying growth and differentiation pathways in normal cardiac valve endothelium. Two of our studies have shown that valve endothelial cells from adult tissue can recapitulate processes that occur during valve development. These pathways involve TGF-β-induced endothelial to mesenchymal transformation (EMT) and VEGF-induced proliferation. In support of the concept of using blood-derived EPCs to create tissue-engineered heart valves, we have shown that EPCs respond, like valve endothelial cells, to VEGF and TGF-b when seeded on 3-dimensional biodegradable scaffolds. We hypothesize that human EPCs, expanded ex vivo, can be induced to behave as valve endothelial cells and thereby manipulated, via tissue engineering processes, to create viable long-lived tissue valve substitutes.

Proper coronary vascular development and heart morphogenesis depend on interaction of GATA-4 with FOG cofactors.

GATA-family transcription factors are critical to the development of diverse tissues. In particular, GATA-4 has been implicated in formation of the vertebrate heart. As the mouse Gata-4 knock-out is early embryonic lethal because of a defect in ventral morphogenesis, the in vivo function of this factor in heart development remains unresolved. To search for a requirement for Gata4 in heart development, we created mice harboring a single amino acid replacement in GATA-4 that impairs its physical interaction with its presumptive cardiac cofactor FOG-2. Gata4(ki/ki) mice die just after embryonic day (E) 12.5 exhibiting features in common with Fog2(-/-) embryos as well as additional semilunar cardiac valve defects and a double-outlet right ventricle. These findings establish an intrinsic requirement for GATA-4 in heart development. We also infer that GATA-4 function is dependent on interaction with FOG-2 and, very likely, an additional FOG protein for distinct aspects of heart formation.

The vasculopathy of autosomal dominant polycystic kidney disease: Insights from animal models

A 37-year-old white man with autosomal dominant polycystic kidney disease (ADPKD) was admitted to Boston's Beth Israel Hospital with sudden severe headache of two-hour duration. He was unconscious on admission. Emergency angiography revealed a ruptured 15 mm cerebral aneurysm. Emergency surgery to clip the aneurysm was unsuccessful, and the patient died 36 hours after admission. His serum creatinine was 3.2 mg/dL on admission; the rest of his laboratory values were within normal limits. A request for an autopsy was denied. At age 20, the patient and his then 15-year-old sister had abdominal ultrasound examinations that revealed bilateral renal cysts, consistent with the diagnosis of ADPKD. At age 32, the patient had a sudden, relatively severe, acute myocardial infarction (MI). Cardiac catheterization revealed three-vessel disease, and he subsequently underwent a triple coronary artery bypass operation. Throughout his medical course, the patient's blood pressure was in the 120/80 to 140/80 mm Hg range while he was taking lisinopril, 10 mg/day, which was started after his MI. The patient's mother has ADPKD and end-stage renal disease, and she is on hemodialysis. She recently underwent unsuccessful renal transplantation. There is no known family history of cerebral aneurysms. However, the mother had two cerebrovascular accidents and recovered from both. The patient's father had an MI at age 32, but he lived to age 64. A paternal uncle also died at an early age of an MI. The patient's younger sister was later screened for cerebral aneurysms and the test was negative. The patient's two young children have not been screened for ADPKD.

Impaired Elastogenesis in Hurler Disease: Dermatan Sulfate Accumulation Linked to Deficiency in Elastin-Binding Protein and Elastic Fiber Assembly

Hurler disease resulting from a deficiency in alpha-L-iduronidase, which causes an accumulation of dermatan sulfate and heparan sulfate glycosaminoglycans, is characterized by connective tissue and skeletal deformations, cardiomyopathy, cardiac valve defects, and progressive coronary artery stenosis. In this report, we present evidence that accumulation of dermatan sulfate but not heparan sulfate moieties is linked to impaired elastic fiber assembly that, in turn, contributes substantially to the development of the clinical phenotype in Hurler disease. Our data suggest that dermatan sulfate-bearing moieties bind to and cause functional inactivation of the 67-kd elastin-binding protein, a molecular chaperone for tropoelastin, which normally facilitates its secretion and assembly into elastic fibers. We demonstrate that, in contrast to normal skin fibroblasts and cells from Sanfilippo disease, which accumulate heparan sulfate, Hurler fibroblasts show reduced expression of elastin-binding protein and do not assemble elastic fibers, despite an adequate synthesis of tropoelastin and sufficient production of a microfibrillar scaffold of elastic fibers. Because cultured Hurler fibroblasts proliferate more quickly than their normal counterparts and the addition of exogenous insoluble elastin reduces their proliferation, we suggest that cell contacts with insoluble elastin play an important role in controlling their proliferation.

Comparative quantitative research on the composition of myocardial fibers in cardiac defects, cardiac valve defects and in hypertension

Comparative quantitative research on the composition of myocardial fibers in cardiac defects, cardiac valve defects and in hypertension