Aortic abnormalities in males with Alport syndrome

A comprehensive review of Alport syndrome: definition, pathophysiology, clinical manifestations, and diagnostic considerations

Alport syndrome, a rare genetic disorder affecting around 1 in 50,000 individuals, primarily presents as microscopic hematuria and chronic kidney disease (CKD) with associated extrarenal complications. The Alport syndrome results from mutations in COL4A3, COL4A4, and COL4A5 genes, disrupting the formation of the α3-α4-α5 chain in the collagen IV network. The etiology involves X chromosome-related, autosomal dominant, autosomal recessive, and digenic inheritance patterns. The disease primarily manifests as kidney involvement, featuring persistent hematuria, proteinuria, and a progressive decline in renal function. Hearing loss, ocular abnormalities, and extrarenal manifestations further contribute to its complexity. Genotype-phenotype correlations are relatively evident, with distinct presentations in X-linked, autosomal recessive, and autosomal dominant cases. Diagnosis relies on urinalysis, histologic examination, and genetic testing with advancements in next-generation sequencing aiding identification. Although no specific treatment exists, early diagnosis improves outcomes, emphasizing the importance of genetic testing for prognosis and familial screening. The purpose of this review is to advance knowledge and enhance understanding of Alport syndrome.

Identification of Variants of Uncertain Significance in the Genes Associated with Thoracic Aortic Disease in Russian Patients with Nonsyndromic Sporadic Subtypes of the Disorder

Nonsyndromic sporadic thoracic aortic aneurysm (nssTAA) is characterized by diverse genetic variants that may vary in different populations. Our aim was to identify clinically relevant variants in genes implicated in hereditary aneurysms in Russian patients with nssTAA. Forty-one patients with nssTAA without dissection were analyzed. Using massive parallel sequencing, we searched for variants in exons of 53 known disease-causing genes. Patients were found to have no (likely) pathogenic variants in the genes of hereditary TAA. Six variants of uncertain significance (VUSs) were identified in four (9.8%) patients. Three VUSs [FBN1 c.7841C>T (p.Ala2614Val), COL3A1 c.2498A>T (p.Lys833Ile), and MYH11 c.4993C>T (p.Arg1665Cys)] are located in genes with "definitive" disease association (ClinGen). The remaining variants are in "potentially diagnostic" genes or genes with experimental evidence of disease association [NOTCH1 c.964G>A (p.Val322Met), COL4A5 c.953C>G (p.Pro318Arg), and PLOD3 c.833G>A (p.Gly278Asp)]. Russian patients with nssTAA without dissection examined in this study have ≥1 VUSs in six known genes of hereditary TAA (FBN1, COL3A1, MYH11, NOTCH1, COL4A5, or PLOD3). Experimental studies expanded genetic testing, and clinical examination of patients and first/second-degree relatives may shift VUSs to the pathogenic (benign) category or to a new class of rare "predisposing" low-penetrance variants causing the pathology if combined with other risk factors.

Multidisciplinary and multidimensional approaches to transplantation in children with rare genetic kidney diseases

In this review, we describe the multidisciplinary, multidimensional care required to optimize outcomes for pediatric transplant recipients with rare genetic kidney diseases. Transplant success, recipient survival, and improvement in quality of life depend on collaboration between patients, families, and a team of specialists with medical, as well as nonmedical expertise. A multidisciplinary transplant team composed of experts from medicine, surgery, nursing, nutrition, social services, transplant coordination, psychology, and pharmacology, is now standard in most transplant centers and is critical to the success of a transplant. In addition to these professionals, other specialists, such as cardiologists, urologists, geneticists, metabolic disease specialists, occupational therapists, case management, child life, chaplain, and palliative care services, have a crucial role to play in the preparation, surgery, and follow-up care, especially when a pediatric patient has a rare genetic disorder leading to renal involvement, and the need for transplantation. In order to describe this multidisciplinary care, we divide the genetic renal diseases into five subgroups-metabolic and tubular disorders, glomerular diseases, congenital anomalies of the kidney and urinary tract, ciliopathies including cystic diseases, and miscellaneous renal conditions; and describe for each, the need for care beyond that provided by the standard transplant team members.

Ascending aortic aneurysm and histopathology in Alport syndrome: a case report

BACKGROUND

Alport syndrome (AS) is caused by mutations in type IV collagen genes that typically target and compromise the integrity of basement membranes in kidney, ocular, and sensorineural cochlear tissues. Type IV and V collagens are also integral components of arterial walls, and whereas collagenopathies including AS are implicated in aortic disease, the incidence of aortic aneurysm in AS is unknown probably because of underreporting. Consequently, AS is not presently considered an independent risk factor for aortic aneurysm and more detailed case studies including histological evidence of basement membrane abnormalities are needed to determine such a possible linkage.

CASE PRESENTATION

Here, we present unique histopathological findings of an ascending aortic aneurysm collected at the time of surgery from an AS patient wherein hypertension was the only other known risk factor.

CONCLUSIONS

The studies reveal classical histological features of aortic aneurysm, including atheroma, lymphocytic infiltration, elastin disruption, and myxoid degeneration with probable AS association.

Vertebral and Basilar Artery Dissection in a Patient With Alport Syndrome

Basilar artery occlusion (BAO) is a rare cause of stroke associated with significant morbidity and mortality. It is most frequently thromboembolic in nature, but may be caused by vertebral artery dissection. We present a case of BAO in a 36-year-old woman with Alport syndrome. She was treated with emergent thrombectomy via the right vertebral artery with return to baseline neurological status. Her clinical status deteriorated later the same day and she was found to have re-occlusion. Repeat thrombectomy was complicated by persistent re-occlusion requiring 7 passes to achieve reperfusion. Unfortunately, her neurological exam remained poor and she was transitioned to comfort care, expiring on admission day 3. An autopsy demonstrated acute dissection of the left vertebral artery, basilar artery, and bilateral posterior cerebral arteries. Alport syndrome is a type IV collagenopathy most known for causing kidney disease. It may also be associated with vascular fragility as type IV collagen forms a significant component of the vascular basement membrane. There are reports of aortic, coronary, and cervical dissections, but few reports of intracranial dissections in patients with Alport syndrome. While iatrogenic dissection cannot be ruled out, the histological findings in this case are most consistent with spontaneous arterial dissection as the cause of her initial neurologic presentation. This highlights the need for further investigation into the relationship between Alport syndrome and vascular fragility and should alert clinicians to the possibility of intracranial dissection in patients with AS.

Bullous Pemphigoid in X-linked Alport Syndrome

Skin lesions in X-linked Alport syndrome (XLAS) are rarely observed. Bullous pemphigoid (BP) is caused by autoantibodies against BP180, also called α1 (XVII) chain, in the basement membrane zone (BMZ). A 48-year-old man with XLAS developed tense blisters. A skin biopsy showed a cleft between the basal cell layer and dermis, with the infiltration of neutrophils and eosinophils. α1 (XVII) staining was positive on the epidermal side of α2/5 (IV) staining. Oral prednisolone improved his symptoms gradually. Abundant tense blisters on the palms and soles might suggest an important role of the α5 (IV) chain in the integrity of BMZ.

Alport Syndrome and Oral Mucous Membrane Pemphigoid: An Interesting Case

Alport syndrome (AS) is a hereditary progressive glomerular disease associated with sensorineural hearing loss and ocular abnormalities. It is attributed to the altered structure and the subsequent dysfunction of the glomerular basement membrane (GBM) due to the mutated type IV collagen a3/a4/a5 chains. It may emerge either as an X-linked disease, the most common, or as an autosomal disease, both recessive and dominant. A female patient, 26 years old, came in 2023 to the Department of Oral Medicine/ Pathology, Dental School, Aristotle University of Thessaloniki, complaining about pain and a burning sensation in her right cheek. Her medical history revealed the diagnosis of Alport syndrome in 2016 and kidney transplantation in 2022 with extensive post-transplantation drug administration. The clinical examination revealed an ulcer, partially covered by a pseudomembrane, on the oral mucosa of the right cheek, surrounded by an erythematous border. A biopsy was taken, and the histopathological examination showed the oral manifestation of mucous membrane pemphigoid. After communicating with the attending nephrologist, the prescription of methylprednisolone was decided, and the lesions receded. The differential diagnosis included both AS-induced pemphigoid and drug-induced pemphigoid. The thorough medical history, detailed clinical investigation, lesion biopsy, and collaboration of different dental and medical specialties constitute necessary prerequisites for a successful treatment, even in immunosuppressed patients.

The genetic landscape and clinical implication of pediatric Moyamoya angiopathy in an international cohort

Pediatric Moyamoya Angiopathy (MMA) is a progressive intracranial occlusive arteriopathy that represents a leading cause of transient ischemic attacks and strokes in childhood. Despite this, up to now no large, exclusively pediatric MMA cohort has been subjected to systematic genetic investigation. In this study, we performed molecular karyotyping, exome sequencing and automated structural assessment of missense variants on a series of 88 pediatric MMA patients and correlated genetic, angiographic and clinical (stroke burden) findings. The two largest subgroups in our cohort consisted of RNF213 and neurofibromatosis type 1 (NF1) patients. While deleterious RNF213 variants were associated with a severe MMA clinical course with early symptom onset, frequent posterior cerebral artery involvement and higher stroke rates in multiple territories, NF1 patients had a similar infarct burden compared to non-NF1 individuals and were often diagnosed incidentally during routine MRIs. Additionally, we found that MMA-associated RNF213 variants have lower predicted functional impact compared to those associated with aortic disease. We also raise the question of MMA as a feature of recurrent as well as rare chromosomal imbalances and further support the possible association of MMA with STAT3 deficiency. In conclusion, we provide a comprehensive characterization at the genetic and clinical level of a large exclusively pediatric MMA population. Due to the clinical differences found across genetic subgroups, we propose genetic testing for risk stratification as part of the routine assessment of pediatric MMA patients.

Col4a3-/- Mice on Balb/C Background Have Less Severe Cardiorespiratory Phenotype and SGLT2 Over-Expression Compared to 129x1/SvJ and C57Bl/6 Backgrounds

Alport syndrome (AS) is a hereditary renal disorder with no etiological therapy. In the preclinical Col4a3^-/- model of AS, disease progression and severity vary depending on mouse strain. The sodium-glucose cotransporter 2 (SGLT2) is emerging as an attractive therapeutic target in cardiac/renal pathologies, but its application to AS remains untested. This study investigates cardiorespiratory function and SGLT2 renal expression in Col4a3^-/- mice from three different genetic backgrounds, 129x1/SvJ, C57Bl/6 and Balb/C. male Col4a3^-/- 129x1/SvJ mice displayed alterations consistent with heart failure with preserved ejection fraction (HFpEF). Female, but not male, C57Bl/6 and Balb/C Col4a3^-/- mice exhibited mild changes in systolic and diastolic function of the heart by echocardiography. Male C57Bl/6 Col4a3^-/- mice presented systolic dysfunction by invasive hemodynamic analysis. All strains except Balb/C males demonstrated alterations in respiratory function. SGLT2 expression was significantly increased in AS compared to WT mice from all strains. However, cardiorespiratory abnormalities and SGLT2 over-expression were significantly less in AS Balb/C mice compared to the other two strains. Systolic blood pressure was significantly elevated only in mutant 129x1/SvJ mice. The results provide further evidence for strain-dependent cardiorespiratory and hypertensive phenotype variations in mouse AS models, corroborated by renal SGLT2 expression, and support ongoing initiatives to develop SGLT2 inhibitors for the treatment of AS.

Novel Therapies for Alport Syndrome

Alport syndrome (AS) is a hereditary kidney disease associated with proteinuria, hematuria and progressive kidney failure. It is characterized by a defective glomerular basement membrane caused by mutations in type IV collagen genes COL4A3/A4/A5 which result in defective type IV collagen α3, α4, or α5 chains, respectively. Alport syndrome has three different patterns of inheritance: X-linked, autosomal and digenic. In a study of CKD of unknown etiology type IV collagen gene mutations accounted for the majority of the cases of hereditary glomerulopathies which suggests that AS is often underrecognized. The natural history and prognosis in patients with AS is variable and is determined by genetics and environmental factors. At present, no preventive or curative therapies exist for AS. Current treatment includes the use of renin-angiotensin-aldosterone system inhibitors which slow progression of kidney disease and prolong life expectancy. Ramipril was found in retrospective studies to delay the onset of ESKD and was recently demonstrated to be safe and effective in children and adolescents, supporting that early initiation of Renin Angiotensin Aldosterone System (RAAS) blockade is very important. Mineralocorticoid receptor blockers might be favorable for patients who develop "aldosterone breakthrough." While the DAPA-CKD trial suggests a beneficial effect of SGLT2 inhibitors in CKD of non-metabolic origin, only a handful of patients had Alport in this cohort, and therefore conclusions can't be extrapolated for the treatment of AS with SGLT2 inhibitors. Advances in our understanding on the pathogenesis of Alport syndrome has culminated in the development of innovative therapeutic approaches that are currently under investigation. We will provide a brief overview of novel therapeutic targets to prevent progression of kidney disease in AS. Our review will include bardoxolone methyl, an oral NRf2 activator; lademirsen, an anti-miRNA-21 molecule; sparsentan, dual endothelin type A receptor (ETAR) and angiotensin 1 receptor inhibitor; atrasentan, oral selective ETAR inhibitor; lipid-modifying agents, including cholesterol efflux transporter ATP-binding cassette A1 (ABCA1) inducers, discoidin domain receptor 1 (DDR1) inhibitors and osteopontin blocking agents; the antimalarial drug hydroxychloroquine; the antiglycemic drug metformin and the active vitamin D analog paricalcitol. Future genomic therapeutic strategies such as chaperone therapy, genome editing and stem cell therapy will also be discussed.

Fibrillar Collagen Variants in Spontaneous Coronary Artery Dissection

IMPORTANCE

Spontaneous coronary artery dissection (SCAD) is an increasingly recognized nonatherosclerotic cause of acute myocardial infarction enriched among individuals with early-onset myocardial infarction but is of unclear etiology.

OBJECTIVE

To assess which genes contribute to the development of SCAD.

DESIGN, SETTING, AND PARTICIPANTS

To prioritize genes influencing risk for SCAD, whole-exome sequencing was performed among individuals with SCAD in the discovery and replication cohorts from a tertiary care hospital outpatient specialty clinic, and gene set enrichment analyses were also performed for disruptive coding variants. All patients were sequentially enrolled beginning July 2013. Aggregate prevalence of rare disruptive variants for prioritized gene sets was compared between individuals with SCAD with population-based controls comprising 46 468 UK Biobank participants with whole-exome sequencing. Complementary mice models were used for in vivo validation. Analysis took place between June 2020 and January 2021.

MAIN OUTCOMES AND MEASURES

The frequency and identity of rare genetic variants in individuals with SCAD.

RESULTS

Of 130 patients, 109 (83.8%) were female (26 of 32 [81.2%] in the discovery cohort and 83 of 98 [84.7%] in the replication cohort) with mean (SD) age at first SCAD event of 48.41 (8.76) years in the discovery cohort and 47.74 (10.09) years in the replication cohort. Across all patients with SCAD, rare disruptive variants were found within 10 collagen genes (COL3A1, COL5A1, COL4A1, COL6A1, COL5A2, COL12A1, COL4A5, COL1A1, COL1A2, and COL27A1) were 17-fold (P = 1.5 × 10-9) enriched among individuals with SCAD compared with a background of 2506 constrained genes expressed in coronary artery. Furthermore, compared with individuals from the UK Biobank, individuals with SCAD were 1.75-fold (P = .04) more likely to carry disruptive rare variants within fibrillar collagen genes. Complementary mice models haploinsufficient for Col3a1 or Col5a1, the 2 most common collagen gene variants identified in SCAD cases, demonstrated increased risk of arterial dissection and increased size of arterial diameters especially in female mice, with resulting changes in collagen fibril organization and diameter.

CONCLUSIONS AND RELEVANCE

Unbiased gene discovery in patients with SCAD with independent human and murine validation highlights the role of the extracellular matrix dysfunction in SCAD.

A Case of Alport Syndrome Associated with Recurrent Stanford Type B Aortic Dissections

Alport syndrome is often characterized by renal dysfunction and hearing loss due to abnormalities in type IV collagen production. In this study, we report a rare case of recurrent aortic dissections that developed in a young patient with Alport syndrome over a short period. We discuss the associations between Alport syndrome and aortic dissection with a literature review and emphasize the need for regular follow-up of patients with Alport syndrome for early detection of aortic disease.

Molecular Basis, Diagnostic Challenges and Therapeutic Approaches of Alport Syndrome: A Primer for Clinicians

Alport syndrome is a genetic and hereditary disease, caused by mutations in the type IV collagen genes COL4A3, COL4A4 and COL4A5, that affects the glomerular basement membrane of the kidney. It is a rare disease with an underestimated prevalence. Genetic analysis of population cohorts has revealed that it is the second most common inherited kidney disease after polycystic kidney disease. Renal involvement is the main manifestation, although it may have associated extrarenal manifestations such as hearing loss or ocular problems. The degree of expression of the disease changes according to the gene affected and other factors, known or yet to be known. The pathophysiology is not yet fully understood, although some receptors, pathways or molecules are known to be linked to the disease. There is also no specific treatment for Alport syndrome; the most commonly used are renin–angiotensin–aldosterone system inhibitors. In recent years, diagnosis has come a long way, thanks to advances in DNA sequencing technologies such as next-generation sequencing (NGS). Further research at the genetic and molecular levels in the future will complete the partial vision of the pathophysiological mechanism that we have, and will allow us to better understand what is happening and how to solve it.

Multidisciplinary Management of Alport Syndrome: Current Perspectives

Alport syndrome is a multisystem disorder that universally affects the kidney and frequently involves the inner ear and the eye. Over the course of a lifetime, addressing the health care needs of a person with Alport syndrome and their family entails the services of primary providers, nephrologists, genetic counselors, audiologists, ophthalmologists, transplant physicians, kidney dieticians, and social workers as well as other healthcare professionals. This article attempts to provide context and guidance regarding the multidisciplinary care of Alport syndrome based on the natural history of the condition.

Analysis of the contribution of 129 candidate genes to thoracic aortic aneurysm or dissection of a mixed cohort of sporadic and familial cases in South China

Thoracic aortic aneurysm or dissection (TAAD) is a group of life-threatening complex diseases after symptomatic onset with genetic heterogeneity accounting for approximately 20% of cases. Previously, we identified 40 rare variants in 11 TAAD-related core genes among 70 TAAD patients by next-generation sequencing. In this study, we further analyzed the variants in the disease-causing genes in 129 cases of sporadic TAAD and 22 familial cases by whole-exome sequencing. A total of 116 variants in 47 TAAD-related genes were identified, 64.7% (75/116) of which occurred in sporadic TAAD without syndromes, and among these genes, FBN1 was the most common TAAD-related gene. Of the 26.7% (31/116) that were pathogenic or likely pathogenic, almost one third were from sporadic cases without syndromes involving FBN1, SMAD3, SMAD6, MYH11, TGFBR1, MYLK, LOX and LTBP3. Interestingly, the novel VUS (variant of uncertain significance) *879Glu in MCTP2 occurred in two unrelated probands with sporadic acute aortic dissection without a bicuspid aortic valve. Furthermore, more than one variant was detected in 24 patients, and 70.8% (17/24) occurred in sporadic cases. Younger individuals were more likely to carry P/LP (pathogenic or likely pathogenic) variants and harbor more variants. P/LP carriers seem to have a larger aortic diameter, lower D-dimer levels, and a shorter ICU length of stay but longer hospitalization time. In conclusion, we expanded the candidate gene profile of TAAD, especially for sporadic cases without syndromic features. VUSs need further clarification.

Long-term outcome among females with Alport syndrome from a single pediatric center

BACKGROUND

Alport syndrome (AS) is a multisystem condition which can result in progressive kidney disease, hearing loss, and ocular changes. X-linked inheritance is observed in 85% of affected individuals. As a result, most prior studies have focused on males. Girls with AS can also be symptomatic although historically thought to have few clinical manifestations in childhood. The objective of the study was to describe the clinical presentation and course of females with AS.

METHODS

A single-center retrospective study of all young females with AS between January 1, 1987, and May 20, 2019. Subjects were identified using ICD-9/10 diagnosis codes for AS, familial hematuria, or nephritis. Clinical data were extracted by retrospective chart review.

RESULTS

Thirty-six female patients were included in the analysis. Mean age at presentation was 5.58 ± 3.0 years, and mean follow-up was 5.9 ± 3.9 years. Twenty-nine patients (80%) had a family history of AS. At end of the follow-up period, gross hematuria was observed in 15 patients (42%), 20 (56%) developed proteinuria, and 2 (6.7%) had an estimated glomerular filtration rate (eGFR) < 90 ml/min/1.73m² with one patient developing stage 5 chronic kidney disease. Four of the twenty-seven (14.8%) who underwent audiologic testing had an abnormal exam.

CONCLUSIONS

Known family histories of AS or gross hematuria were the most common reasons for the initial presentation in our cohort. Development of proteinuria, eGFR < 90 ml/min/1.73m², and abnormal audiology exam are not exceptional findings, suggesting that close monitoring of young females into adulthood is warranted.

Corneal endothelial cell abnormalities in X-linked Alport syndrome

Background: X-linked Alport syndrome results from the effect of COL4A5 mutations on basement membranes in the kidney, ear and eye. This study investigated individuals with X-linked Alport syndrome for corneal abnormalities.Patients and Methods: Six men and four women from 8 families with genetically-diagnosed X-linked Alport syndrome underwent ophthalmological examination including slit lamp examination and corneal endothelial specular microscopy. Results for corneal microscopy for men and women with X-linked disease were compared separately with the mean values for age- matched normals using the student's t test.Results: Five of the 6 men had end-stage kidney failure, all 6 had a hearing loss, three had lenticonus, and three had a central fleck retinopathy. Two men had a history of recurrent corneal erosions but no evidence of posterior polymorphous corneal dystrophy. None of the four women had kidney failure, but two had a hearing loss, and two had a central fleck retinopathy. One woman, whose son had recurrent corneal erosions, also had erosions, but no features of a posterior polymorphous corneal dystrophy.Corneal specular microscopy demonstrated abnormalities in affected men and women, with larger endothelial cells (p = .0001 in men, p = .004 in women) fewer 6-sided cells (p = .0001, p = .001 respectively) and reduced cell density (p = .03, p = .02 respectively) than normal.Conclusions: Recurrent corneal erosions are common in men and women with X-linked Alport syndrome, but posterior polymorphous corneal dystrophy is rare. The abnormal corneal endothelial cells in affected men and women are consistent with an abnormal Descemet membrane, and the reduced cell density resembles the reduced podocyte numbers found in the Alport glomerulus.

Extracellular matrix, regional heterogeneity of the aorta, and aortic aneurysm

Aortic aneurysm is an asymptomatic disease with dire outcomes if undiagnosed. Aortic aneurysm rupture is a significant cause of death worldwide. To date, surgical repair or endovascular repair (EVAR) is the only effective treatment for aortic aneurysm, as no pharmacological treatment has been found effective. Aortic aneurysm, a focal dilation of the aorta, can be formed in the thoracic (TAA) or the abdominal (AAA) region; however, our understanding as to what determines the site of aneurysm formation remains quite limited. The extracellular matrix (ECM) is the noncellular component of the aortic wall, that in addition to providing structural support, regulates bioavailability of an array of growth factors and cytokines, thereby influencing cell function and behavior that ultimately determine physiological or pathological remodeling of the aortic wall. Here, we provide an overview of the ECM proteins that have been reported to be involved in aortic aneurysm formation in humans or animal models, and the experimental models for TAA and AAA and the link to ECM manipulations. We also provide a comparative analysis, where data available, between TAA and AAA, and how aberrant ECM proteolysis versus disrupted synthesis may determine the site of aneurysm formation.

A review of aneurysm formation, swelling in blood vessel, in the aorta, examines distinctions between two forms of the condition and the role of proteins in the extracellular matrix which surrounds cells of the arterial wall. Rupture of aneurysms in the aorta, the body’s main artery, is a major cause of death. Researchers led by Zamaneh Kassiri at the University of Alberta, Edmonton, Canada, emphasize that aneurysms in the thoracic and abdominal regions of the aorta are distinct conditions with crucial differences in their causes. Disrupted production and assembly of the extracellular matrix and its proteins may underlie thoracic aneurysm formation. Factors triggering the degradation of extracellular matrix proteins may be more significant in abdominal aneurysms. Understanding the differing molecular mechanisms involved could help address the current lack of effective drug treatments for these dangerous conditions.

Genetics of the extracellular matrix in aortic aneurysmal diseases

Aortic aneurysms are morbid conditions that can lead to rupture or dissection and are categorized as thoracic (TAA) or abdominal aortic aneurysms (AAA) depending on their location. While AAA shares overlapping risk factors with atherosclerotic cardiovascular disease, TAA exhibits strong heritability. Human genetic studies in the past two decades have successfully identified numerous genes involved in both familial and sporadic forms of aortic aneurysm. In this review we will discuss the genetic basis of aortic aneurysm, focusing on the extracellular matrix and how insights from these studies have informed our understanding of human biology and disease pathogenesis.

Spontaneous Coronary Artery Dissection: A Rare Manifestation of Alport Syndrome

Alport syndrome (AS) is a genetic disorder due to inheritance of genetic mutations which lead to production of abnormal type IV collagen. AS has been associated with renal, auditory, and ocular diseases due to the presence of abnormal alpha chains of type IV collagen in the glomerulus, cochlea, cornea, lens, and retina. The resulting disorder includes hereditary nephritis, corneal opacities, anterior lenticonus, fleck retinopathy, temporal retinal thinning, and sensorineural deafness. Aortic and aortic valve pathologies have been described as extrarenal manifestations of AS in multiple case reports. One case report described intramural hematoma of the coronary artery. We report the first case of true spontaneous coronary artery dissection (SCAD) with an intimal flap as a very rare manifestation of AS. The patient is a 36-year-old female with history of AS with chronic kidney disease, hypertension, and obesity who presented to the emergency room with acute onset of substernal chest pain radiating to her neck and arms. Troponin was elevated, and ECG showed transient 1 mm ST-segment elevation in the inferior leads. Subsequent coronary angiography revealed localized dissection of the left circumflex artery. Percutaneous coronary angioplasty was performed and her symptoms improved. This case illustrates that SCAD may be a manifestation of AS patients with chest pain.

The Chemical Chaperone, PBA, Reduces ER Stress and Autophagy and Increases Collagen IV α5 Expression in Cultured Fibroblasts From Men With X-Linked Alport Syndrome and Missense Mutations

Introduction

X-linked Alport syndrome (OMIM 301050) is caused by COL4A5 missense variants in 40% of families. This study examined the effects of chemical chaperone treatment (sodium 4-phenylbutyrate) on fibroblast cell lines derived from men with missense mutations.

Methods

Dermal fibroblast cultures were established from 2 affected men and 3 normals. Proliferation rates were examined, the collagen IV α5 chain localized with immunostaining, and levels of the intra- and extracellular chains quantitated with an in-house enzyme-linked immunosorbent assay. COL4A5 mRNA was measured using quantitative reverse transcriptase polymerase chain reaction. Endoplasmic reticulum (ER) size was measured on electron micrographs and after HSP47 immunostaining. Markers of ER stress (ATF6, HSPA5, DDIT3), autophagy (ATG5, BECN1, ATG7), and apoptosis (CASP3, BAD, BCL₂) were also quantitated by quantitative reverse transcriptase polymerase chain reaction. Measurements were repeated after 48 hours of incubation with 10 mM sodium 4-phenylbutyrate acid.

Results

Both COL4A5 missense variants were associated with reduced proliferation rates on day 6 (P = 0.01 and P = 0.03), ER enlargement, and increased mRNA for ER stress and autophagy (all P values < 0.05) when compared with normal. Sodium 4-phenylbutyrate treatment increased COL4A5 transcript levels (P < 0.01), and reduced ER size (P < 0.01 by EM and P < 0.001 by immunostaining), ER stress (p HSPA5 and DDIT3, all P values < 0.01) and autophagy (ATG7, P < 0.01). Extracellular collagen IV α5 chain was increased in the M1 line only (P = 0.06).

Discussion

Sodium 4-phenylbutyrate increases collagen IV α5 mRNA levels, reduces ER stress and autophagy, and possibly facilitates collagen IV α5 extracellular transport. Whether these actions delay end-stage renal failure in men with X-linked Alport syndrome and missense mutations will only be determined with clinical trials.

Hereditary Influence in Thoracic Aortic Aneurysm and Dissection

Thoracic aortic aneurysm is a potentially life-threatening condition in that it places patients at risk for aortic dissection or rupture. However, our modern understanding of the pathogenesis of thoracic aortic aneurysm is quite limited. A genetic predisposition to thoracic aortic aneurysm has been established, and gene discovery in affected families has identified several major categories of gene alterations. The first involves mutations in genes encoding various components of the transforming growth factor beta (TGF-β) signaling cascade (FBN1, TGFBR1, TGFBR2, TGFB2, TGFB3, SMAD2, SMAD3 and SKI), and these conditions are known collectively as the TGF-β vasculopathies. The second set of genes encode components of the smooth muscle contractile apparatus (ACTA2, MYH11, MYLK, and PRKG1), a group called the smooth muscle contraction vasculopathies. Mechanistic hypotheses based on these discoveries have shaped rational therapies, some of which are under clinical evaluation. This review discusses published data on genes involved in thoracic aortic aneurysm and attempts to explain divergent hypotheses of aneurysm origin.

Alport Syndrome in Women and Girls

Alport syndrome is an inherited disease characterized by progressive renal failure, hearing loss, and ocular abnormalities. Inheritance is X-linked (85%) or autosomal recessive (15%). Many renal physicians think of Alport syndrome as primarily affecting men. However, twice as many women are affected by the X-linked diseases. Affected women are commonly undiagnosed, but 15%-30% develop renal failure by 60 years and often hearing loss by middle age. Half of their sons and daughters are also affected. Autosomal recessive Alport syndrome is less common, but is often mistaken for X-linked disease. Recessive inheritance is suspected where women develop early-onset renal failure or lenticonus. Their family may be consanguineous. The prognosis for other family members is very different from X-linked disease. Other generations, including parents and offspring, are not affected, and on average only one in four of their siblings inherit the disease. All women with Alport syndrome should have their diagnosis confirmed with genetic testing, even if their renal function is normal, because of their own risk of renal failure and the risk to their offspring. Their mutations indicate the mode of inheritance and the likelihood of disease transmission to their children, and the mutation type suggests the renal prognosis for both X-linked and recessive disease. Women with X-linked Alport syndrome should be tested at least annually for albuminuria and hypertension. The "Expert guidelines for the diagnosis and management of Alport syndrome" recommend treating those with albuminuria with renin-angiotensin-aldosterone system (RAAS) blockade (and adequate birth control because of the teratogenic risks of angiotensin converting enzyme inhibitors), believing that this will delay renal failure. Current recommendations are that women with autosomal recessive Alport syndrome should be treated with RAAS blockade from the time of diagnosis. In addition, women should be offered genetic counseling, informed of their reproductive options, and monitored closely during pregnancy for the development of hypertension.

Familial non-syndromal thoracic aortic aneurysms and dissections - Incidence and family screening outcomes

BACKGROUND

Non-syndromal thoracic aortic aneurysm and dissection (ns-TAAD) is a genetic aortopathy, with uncertain incidence. This study documented the incidence of ns-TAAD and outcomes of family screening over 15years.

METHODS

Consecutive series of 2385 patients with aortic disease in prospective registry (2000 to 2014), including 675 undergoing surgery. Diagnosis of ns-TAAD included family history, aortic imaging, tissue pathology and mutation testing. Screening was offered to relatives of ns-TAAD probands, with follow-up for affected individuals.

RESULTS

There were 270 ns-TAAD probands (74% males), including 116 (43%) presenting with aortic dissection. Among surgical cases, a diagnosis of ns-TAAD was established for 116 (17%). Age of probands was 50.4±14.1years, with aortic diameter of 51±12mm. Screening of 581 at-risk relatives identified 216 new ns-TAAD cases (detection rate=37%). Among 71 probands with known family history, screening identified 130 new affected relatives and among 53 probands with no family history, screening identified 86 new affected relatives. Mean age of new affected relatives at diagnosis was 44±18years, with aortic diameter of 42±7mm, including 42 with diameter>50mm. Ten-year mortality was similar for probands without dissection (7.7±3.1%) and new affected relatives (11.4±4.0%) but greater for probands surviving initial dissection (27.6±7.8%, p=0.003).

CONCLUSIONS

Up to 1 in 6 patients undergoing aortic surgery have features of ns-TAAD, frequently presenting as aortic dissection but at later age than other genetic aortopathies. Family screening identifies affected relatives in up to half of ns-TAAD probands, many of whom already have significant aortic dilatation.

The Expanding Clinical Spectrum of Extracardiovascular and Cardiovascular Manifestations of Heritable Thoracic Aortic Aneurysm and Dissection

More than 30 heritable conditions are associated with thoracic aortic aneurysm and dissection (TAAD). Heritable syndromic conditions, such as Marfan syndrome, Loeys-Dietz syndrome, and vascular Ehlers-Danlos syndrome, have somewhat overlapping systemic features, but careful clinical assessment usually enables a diagnosis that can be validated with genetic testing. Nonsyndromic FTAAD can also occur and in 20%-25% of these probands mutations exist in genes that encode elements of the extracellular matrix, signalling pathways (especially involving transforming growth factor-β), and vascular smooth muscle cytoskeletal and contractile processes. Affected individuals with either a syndromic presentation or isolated TAAD can have mutations in the same gene. In this review we focus on the genes currently known to have causal mutations for syndromic and isolated FTAAD and outline the range of associated extracardiovascular and cardiovascular manifestations with each.

The genetic basis of aortic aneurysm

Gene identification in human aortic aneurysm conditions is proceeding at a rapid pace and the integration of pathogenesis-based management strategies in clinical practice is an emerging reality. Human genetic alterations causing aneurysm involve diverse gene products including constituents of the extracellular matrix, cell surface receptors, intracellular signaling molecules, and elements of the contractile cytoskeleton. Animal modeling experiments and human genetic discoveries have extensively implicated the transforming growth factor-β (TGF-β) cytokine-signaling cascade in aneurysm progression, but mechanistic links between many gene products remain obscure. This chapter will integrate human genetic alterations associated with aortic aneurysm with current basic research findings in an attempt to form a reconciling if not unifying model for hereditary aortic aneurysm.

Supramolecular organization of the α121-α565 collagen IV network

Collagen IV is a family of 6 chains (α1-α6), that form triple-helical protomers that assemble into supramolecular networks. Two distinct networks with chain compositions of α121 and α345 have been established. These oligomerize into separate α121 and α345 networks by a homotypic interaction through their trimeric noncollagenous (NC1) domains, forming α121 and α345 NC1 hexamers, respectively. These are stabilized by novel sulfilimine (-S=N-) cross-links, a covalent cross-link that forms between Met(93) and Hyl(211) at the trimer-trimer interface. A third network with a composition of α1256 has been proposed, but its supramolecular organization has not been established. In this study we investigated the supramolecular organization of this network by determining the chain identity of sulfilimine-cross-linked NC1 domains derived from the α1256 NC1 hexamer. High resolution mass spectrometry analyses of peptides revealed that sulfilimine bonds specifically cross-link α1 to α5 and α2 to α6 NC1 domains, thus providing the spatial orientation between interacting α121 and α565 trimers. Using this information, we constructed a three-dimensional homology model in which the α565 trimer shows a good chemical and structural complementarity to the α121 trimer. Our studies provide the first chemical evidence for an α565 protomer and its heterotypic interaction with the α121 protomer. Moreover, our findings, in conjunction with our previous studies, establish that the six collagen IV chains are organized into three canonical protomers α121, α345, and α565 forming three distinct networks: α121, α345, and α121-α565, each of which is stabilized by sulfilimine bonds between their C-terminal NC1 domains.

Development and pathologies of the arterial wall

Arteries consist of an inner single layer of endothelial cells surrounded by layers of smooth muscle and an outer adventitia. The majority of vascular developmental studies focus on the construction of endothelial networks through the process of angiogenesis. Although many devastating vascular diseases involve abnormalities in components of the smooth muscle and adventitia (i.e., the vascular wall), the morphogenesis of these layers has received relatively less attention. Here, we briefly review key elements underlying endothelial layer formation and then focus on vascular wall development, specifically on smooth muscle cell origins and differentiation, patterning of the vascular wall, and the role of extracellular matrix and adventitial progenitor cells. Finally, we discuss select human diseases characterized by marked vascular wall abnormalities. We propose that continuing to apply approaches from developmental biology to the study of vascular disease will stimulate important advancements in elucidating disease mechanism and devising novel therapeutic strategies.

Perturbations of mechanotransduction and aneurysm formation in heritable aortopathies

Thoracic aortic aneurysm and dissection in young and middle aged patients is increasingly recognised as due to genetic aortopathy. Mutations in multiple genes affecting proteins in the extracellular matrix, microfibrillar structure, the endothelium and cell signalling pathways have been associated with thoracic aortic disease. The TGFß signalling pathway appears to play a key role in mediating abnormal aortic growth and aneurysm formation. A challenge remains in understanding how the many different gene mutations can result in deranged TGFß signalling. This review examines the functional relationships between key structural and signalling proteins, with reference to the need for maintenance of homeostasis in mechanotransduction within the aortic wall. A mechanism, through which perturbations in mechanotransduction, arising from different gene mutations, results in altered TGFß signalling is described.

How benign is hematuria? Using genetics to predict prognosis

Hematuria is a common presenting feature of glomerular disease and is sometimes associated with kidney failure later in life. Where isolated microscopic hematuria occurs in children and young adults, an underlying monogenic disorder, such as Alport syndrome or thin basement membrane nephropathy, is frequently responsible. In this review, these and other diseases, which often present with isolated microscopic hematuria, including hereditary angiopathy, nephropathy, aneurysms, and muscle cramps (HANAC) syndrome, IgA nephropathy, and CFHR5 nephropathy, are discussed together with the associated molecular pathology, clinical features, and prognosis. Genetic testing for these conditions used in clinical practice can provide important diagnostic and prognostic information that is relevant to the patient and their family, particularly when kidney transplantation is considered.

Correlation between number of renal cysts and aortic circumferences measured using autopsy material

Although the presence of renal cysts has been reported to be associated with aortic aneurysm or dissection by imaging studies, an autopsy study has not been performed. Therefore, in our institute, recent consecutive adult autopsy cases (n=108, 64 males and 44 females) were reviewed. The circumferences and atherosclerosis ratios of both thoracic and abdominal aorta were individually measured and graded. The number of renal cysts was scored and graded. Age of subjects along with histories of smoking, hypertension, and diabetes mellitus were confirmed. Multiple linear regression analyses demonstrated that severity of atherosclerosis and the number of renal cysts were correlated with thoracic aortic circumference, while only the number of renal cysts was correlated with abdominal aortic circumference (p<0.05), which was more predominant in female subjects (p<0.05). Microscopically, significantly more dilated renal tubules (by Student's t-test, p<0.05) along with decreased stainability of basement membrane by Periodic acid-Schiff staining and immunostaining of type IV collagen were noted in background renal tissues in cases with numerous renal cysts than in age- and sex-matched controls without renal cysts (n=10 vs. 10). The present study suggests that a syndrome that affects both aorta and renal tubules may exist.

Arteriovenous fistula aneurysms in patients with Alport's

Purpose

Alport's syndrome is a rare but important cause of renal failure. It is characterized by Type IV collagen mutations resulting in connective tissue disorders and renal and cochlear dysfunction. Vascular basement membrane also contains collagen IV and the effect on arteriovenous fistulas (AVFs) is not reported. Anecdotally, we observed a high rate of aneurysm formation in Arteriovenous fistulas (AVF) of patients with Alport's and sought to determine whether this was the case within our population.

Methods

All patients with a diagnosis of Alport's were identified from a contemporaneously maintained database. AVFs formed in patients with Alport's were identified to define the incidence of aneurysms in this group.

Results

A total of 40 patients with a diagnosis of Alport's were identified. Of these, 20 patients had undergone AVF formation, the remainder opting for CAPD as renal replacement or had undergone pre-emptive transplantation. Of the 20 patients identified, 11 had an AVF and of these the rate of aneurysm formation was high (55%).

Conclusions

While this finding of high rate of aneurysmal AVF in Alport's patients is a purely observational finding within our population further population study would be extremely interesting and could support enhanced surveillance or alternative dialysis modalities in Alport's syndrome patients.

Alport syndrome--insights from basic and clinical research

In 1927, Arthur C. Alport first published his description of a triad of symptoms in a family with hereditary congenital haemorrhagic nephritis, deafness and ocular changes. A few years after his death, this group of symptoms was renamed Alport syndrome. To this day, Alport syndrome still inevitably leads to end-stage renal disease and the need for renal replacement therapy, starting in young adulthood. During the past two decades, research into this rare disease has focused on the effects of mutations in collagen type IV and the role of changes in podocytes and the glomerular basement membrane that lead to early kidney fibrosis. Animal models of Alport syndrome also demonstrate the pathogenetic importance of interactions between podocytes and the extracellular matrix. Such models might also help researchers to answer basic questions about podocyte function and the development of fibrosis, and to develop new therapeutic approaches that might be of use in other kidney diseases. In this Review, we discuss the latest basic and clinical research on Alport syndrome, focusing on the roles of podocyte pathology and the extracellular matrix. We also highlight early diagnosis and treatment options for young patients with this disorder.

Lessons on the pathogenesis of aneurysm from heritable conditions

Aortic aneurysm is common, accounting for 1-2% of all deaths in industrialized countries. Early theories of the causes of human aneurysm mostly focused on inherited or acquired defects in components of the extracellular matrix in the aorta. Although several mutations in the genes encoding extracellular matrix proteins have been recognized, more recent discoveries have shown important perturbations in cytokine signalling cascades and intracellular components of the smooth muscle contractile apparatus. The modelling of single-gene heritable aneurysm disorders in mice has shown unexpected involvement of the transforming growth factor-β cytokine pathway in aortic aneurysm, highlighting the potential for new therapeutic strategies.

Ventricular septal defect in a child with Alport syndrome: a case report

Background

Alport syndrome (AS) is a rare inherited disorder characterized by an inflammation of the kidneys and damage to the glomerular capillaries, ultimately leading to renal failure at an early age. To date, rare reports of cardiac involvement in AS have been described, due in the majority of cases to the higher risk of heart conduction abnormalities in these patients, at times requiring implantation of a transcutaneous pacemaker. An increased risk of hypertension is likewise commonly featured.

Case presentation

We report the case of a 17-year-old female affected by a very severe early form of AS. A previously unreported association of the syndrome with congenital heart disease (CHD), (in this case membranous ventricular septal defect), is also reported. A possible pathophysiological mechanism underlying the concomitant manifestation of these two disorders is suggested. Complications implicated in surgical treatment of CHD are described. Clinical and therapeutic management of AS with cardiovascular involvement are discussed, and a short literature review performed.

Conclusions

This first report of a cardiovascular association highlights the possible involvement of collagen mutations in the two pathologies. Even when drug-resistance appears to be responsible for the failure to control secondary hypertension in AS, clonidine may represent a safe, effective option in the normalization of high blood pressure.