Cardiac disease in patients with mucopolysaccharidosis: presentation, diagnosis and management

Consensus-based expert recommendations on the management of MPS IVa and VI in Saudi Arabia

BACKGROUND

Mucopolysaccharidosis type IVa (Morquio A syndrome) and mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome) are rare inherited lysosomal storage diseases associated with significant functional impairment and a wide spectrum of debilitating clinical manifestations. These conditions are thought to have higher-than-average prevalence rates in Saudi Arabia due to high rates of consanguineous marriage in the country. There are several unmet needs associated with the management of these diseases in Saudi Arabia.

MAIN BODY

The aim of this manuscript is to contextualize unmet management needs and provide recommendations to optimize diagnosis, multidisciplinary care delivery, and local data generation in this disease area. An expert panel was assembled comprising seven consultant geneticists from across Saudi Arabia. The Delphi methodology was used to obtain a consensus on statements relating to several aspects of mucopolysaccharidosis types IVa and VI. A consensus was reached for all statements by means of an online, anonymized voting system. The consensus statements pertain to screening and diagnosis, management approaches, including recommendations pertaining to enzyme replacement therapy, and local data generation.

CONCLUSION

The consensus statements presented provide specific recommendations to improve diagnostic and treatment approaches, promote multidisciplinary care and data sharing, and optimize the overall management of these rare inherited diseases in Saudi Arabia.

Cardiac Manifestations in Inherited Metabolic Diseases

Inherited metabolic diseases (IMDs) stem from genetic defects affecting enzyme function within specific metabolic pathways, collectively constituting rare conditions with an incidence of less than 1/100,000 births. While IMDs typically manifest with multisystemic symptoms, cardiac manifestations are common, notably hypertrophic cardiomyopathy. Additionally, they can lead to dilated or restrictive cardiomyopathy, as well as noncompacted left ventricular cardiomyopathy. Rhythm disturbances such as atrioventricular conduction abnormalities, Wolff-Parkinson-White syndrome, and ventricular arrhythmias, along with valvular pathologies and ischemic coronary issues, are also prevalent. This study aims to provide a narrative review of IMDs associated with cardiac involvement, delineating the specific cardiac manifestations of each disorder alongside systemic symptoms pivotal for diagnosis.

Causes of death in mucopolysaccharidoses

Mucopolysaccharidoses are inherited metabolic diseases caused by mutations in genes encoding enzymes required for degradation of glycosaminoglycans. A lack or severe impairment of activity of these enzymes cause accumulation of GAGs which is the primary biochemical defect. Depending on the kind of the deficient enzyme, there are 12 types and subtypes of MPS distinguished. Despite the common primary metabolic deficit (inefficient GAG degradation), the course and symptoms of various MPS types can be different, though majority of the diseases from the group are characterized by severe symptoms and significantly shortened live span. Here, we analysed the frequency of specific, direct causes of death of patients with different MPS types, the subject which was not investigated comprehensively to date. We examined a total of 1317 cases of death among MPS patients, including 393 cases of MPS I, 418 cases of MPS II, 232 cases of MPS III, 45 cases of MPS IV, 208 cases of MPS VI, and 22 cases of MPS VII. Our analyses indicated that the most frequent causes of death differ significantly between MPS types, with cardiovascular and respiratory failures being predominant in MPS I, MPS II, and MPS VI, neurological deficits in MPS III, respiratory issues in MPS IV, and hydrops fetalis in MPS VII. Results of such studies suggest what specific clinical problems should be considered with the highest priority in specific MPS types, apart from attempts to correct the primary causes of the diseases, to improve the quality of life of patients and to prolong their lives.

Cardiac manifestations in inherited metabolic diseases

Inherited metabolic diseases (IMD) are caused by the functional defect of an enzyme, of genetic origin, that provokes a blockage in a specific metabolic pathway. Individually, IMD are considered rare diseases, with an incidence of less than 1/100,000 births. The symptoms are usually multisystemic, but frequently include cardiac manifestations. Of these, the most common are cardiomyopathies, especially hypertrophic cardiomyopathy. In addition, they can cause dilated or restrictive cardiomyopathy and non-compacted cardiomyopathy of the left ventricle. Characteristic signs also include rhythm alterations (atrio-ventricular conduction disturbances, Wolff-Parkinson-White syndrome or ventricular arrhythmias), valvular pathology and ischaemic coronary pathologies. The aim of this study is to present a narrative review of the IMD that may produce cardiac involvement. We describe both the specific cardiac manifestations of each disease and the systemic symptoms that guide diagnosis.

Evaluation of aortic elasticity properties in mucopolysaccharidosis patients; effect of enzyme replacement therapy (ERT) on aortic stiffness

OBJECTIVES

We aimed to cardiologically evaluate the consequences of glycosaminoglycan (GAG) accumulation in the large vessels of patients with mucopolysaccharidosis (MPS).

METHODS

The left ventricular wall thickness, left ventricular mass (LVmass) were evaluated and aortic annulus diameter (AA), aortic sinus valsalva diameter (SV), sinotubular junction diameter (STJ), systolic aortic diameter (ADs), diastolic aortic diameter (ADd) body indices were obtained by dividing by the surface area. Aortic distensibility and stiffness index were obtained using aortic strain. Ejection fraction, mitral E and A velocities, mitral early diastolic tissue velocity (e'), E/A ratio, and E/e' ratio were evaluated.

RESULTS

The LVED-i, LVmass-i, AA-i, SV-i, STJ-i, ADs-i, and ADd-i values were significantly higher in the MPS group. While the E and e' velocities and E/A ratio were significantly low in the MPS group, the A velocity and E/e' ratio were significantly high. While the stiffness index, SBP, and PP values were significantly higher in the MPS group, the aortic strain and distensibility were significantly lower. There was a correlation between the stiffness index and the aortic strain, distensibility, SBP, PP, and ventricular function. Cardiac function, aortic diameter, and aortic elasticity characteristics were similar between patients with MPS who received ERT and those who did not.

CONCLUSIONS

In the MPS group, aortic elasticity properties were impaired, and aortic stiffness increased. ERT has positive effects on cardiac function, aortic diameter, and aortic stiffness in MPS patients. An increased LVmass-i and impaired ventricular geometric structure in patients with MPS may be associated with increased aortic stiffness.

Dental Profile of Brazilian Patients with Rare Skeletal Genetic Disorders: Clinical Features and Associated Factors

The aim of this study is to compare the dental profiles of Brazilian patients with rare genetic skeletal disorders and normotypical patients. A cross-sectional study was carried out with 210 individuals aged between 2 and 54 years old [105 with rare diseases (Mucopolysaccharidosis/MPS n = 27 and Osteogenesis Imperfecta/OI n = 78) and 105 without rare diseases] and their parents/caregivers. The parents/caregivers answered a questionnaire about individual aspects of their child and the dental profile was identified from questions related to dental history and the presence/absence of dental problems. The patients' oral cavity was also examined by three examiners for dental caries, malocclusion, gingivitis, and dental anomalies. The average age of individuals with a rare disease was 14.1 years (±12.2) and the median was 9.5 years. Participants who had already used the public health system (SUS) dental care services had a 2.24 times higher chance of belonging to the group with a rare disease (OR = 2.24; 95% CI: 1.07-4.89). Patients with rare diseases are 14.86 times more likely to have difficulty receiving dental treatment (OR = 14.86; 95% CI: 5.96-27.03) and 10.38 times more likely to have one or more dental problems (OR = 10.38; 95% CI: 1.95-35.17). Individuals with rare disorders have a greater history of difficulty in accessing dental treatment, using the SUS, and were diagnosed with more dental problems compared to normotypical individuals.

Multisystem Involvement in a Pediatric Patient With Suspected Mucopolysaccharidosis: A Case Report

Mucopolysaccharidoses (MPS) are a group of inherited metabolic disorders characterized by the deficiency or malfunction of lysosomal enzymes responsible for glycosaminoglycan (GAG) degradation. We present the case of an 11-year-old male with a history of calcified mitral valve, rheumatic heart disease, and growth hormone deficiency who presented with dyspnea on exertion. Physical examination revealed dysmorphic facial features, short stature, and suboptimal weight and height parameters. Magnetic resonance imaging (MRI) of the brain showed cystic lesions in the white matter and corpus callosum, hydrocephalus, and cerebral atrophy, suggestive of MPS. This case highlights the importance of considering MPS in the differential diagnosis of patients with multisystemic involvement and the utility of advanced imaging techniques like MRI in guiding diagnosis and management. A multidisciplinary approach involving cardiology, endocrinology, genetics, and neurology is crucial for comprehensive management and improving patient outcomes. Early diagnosis and intervention are essential in optimizing the quality of life for patients with MPS.

Lentiviral Gene Therapy for Mucopolysaccharidosis II with Tagged Iduronate 2-Sulfatase Prevents Life-Threatening Pathology in Peripheral Tissues But Fails to Correct Cartilage

Deficiency of iduronate 2-sulfatase (IDS) causes Mucopolysaccharidosis type II (MPS II), a lysosomal storage disorder characterized by systemic accumulation of glycosaminoglycans (GAGs), leading to a devastating cognitive decline and life-threatening respiratory and cardiac complications. We previously found that hematopoietic stem and progenitor cell-mediated lentiviral gene therapy (HSPC-LVGT) employing tagged IDS with insulin-like growth factor 2 (IGF2) or ApoE2, but not receptor-associated protein minimal peptide (RAP12x2), efficiently prevented brain pathology in a murine model of MPS II. In this study, we report on the effects of HSPC-LVGT on peripheral pathology and we analyzed IDS biodistribution. We found that HSPC-LVGT with all vectors completely corrected GAG accumulation and lysosomal pathology in liver, spleen, kidney, tracheal mucosa, and heart valves. Full correction of tunica media of the great heart vessels was achieved only with IDS.IGF2co gene therapy, while the other vectors provided near complete (IDS.ApoE2co) or no (IDSco and IDS.RAP12x2co) correction. In contrast, tracheal, epiphyseal, and articular cartilage remained largely uncorrected by all vectors tested. These efficacies were closely matched by IDS protein levels following HSPC-LVGT. Our results demonstrate the capability of HSPC-LVGT to correct pathology in tissues of high clinical relevance, including those of the heart and respiratory system, while challenges remain for the correction of cartilage pathology.

Clinical manifestations and genetic mutation analysis of patients with mucopolysaccharidosis type VII in China

OBJECTIVE

This study aimed to explore the clinical and genetic features of Chinese patients with mucopolysaccharidosis type VII (MPS VII), thereby improving early detection, disease management, and patient outcomes.

METHODS

A retrospective review of medical records for five patients presenting with coarse facial features, rib protrusion, chest deformities, and scoliosis was conducted. Exome sequencing was employed to identify causative genetic mutations.

RESULTS

The study comprised five patients (four males, one female) with disease onset at six months of age (range: 0-1.5 years). Common symptoms included coarse facial features, skeletal abnormalities, delayed motor and language development, and intellectual disability. Approximately 80% of the patients exhibited multiple skeletal dysplasias, enlarged adenoids or tonsils, and snoring; 60% had hernias; 40% reported hearing loss and hepatosplenomegaly. Less frequent manifestations were short stature, valvular heart disease, non-immune hydrops fetalis, and corneal opacity. All patients demonstrated elevated urine glycosaminoglycans levels and absent β-glucuronidase activity in leukocytes. Exome sequencing identified compound heterozygous mutations in the GUSB gene in all four tested patients, uncovering seven mutations in total, three of which were novel (c.189G > A, c.869C > T, and c.1745 T > C). Furthermore, prenatal diagnosis through chorionic villus sampling in subsequent pregnancies of one patient's mother revealed both fetuses had normal β-glucuronidase activity and no disease-causing mutations in the GUSB gene.

CONCLUSION

The study's patients all presented with classic symptoms of MPS VII due to β-glucuronidase deficiency, with three new pathogenic mutations identified in the GUSB gene. Genetic counseling and prenatal testing were highlighted as crucial for disease prevention.

Caries assessment and salivary microbial analysis in patients diagnosed with mucopolysaccharidosis

BACKGROUND AND OBJECTIVES

Mucopolysaccharidosis (MPS) is a group of lysosomal storage disorders that cause the deposition of polysaccharides in cells. This causes systemic and oral manifestations, which can be observed clinically and radiographically. The present study aimed to assess dental caries, the effect of salivary pH, and the change of microflora on teeth in patients diagnosed with MPS.

MATERIALS AND METHODS

The study included children affected with mucopolysaccharidosis (n = 50) and healthy children (n = 50) in the control group between 3 and 15 years of age. The pH of saliva and decayed, missing, and filled teeth/decayed extracted and filled teeth index were noted and recorded. For the microbial analysis, saliva was inoculated into blood agar, MacConkey agar, Candida CHROMagar, and Mitis Salivarius agar, then inspected for colony-forming units, which were counted and recorded based on the colony characteristics and gram staining.

STATISTICAL ANALYSIS

Intergroup comparison of the test parameters was done using the Mann-Whitney test. P < 0.05 was considered statistically significant.

RESULTS

The results showed significantly higher total microbial load (P = 0.00008), streptococcus viridans species (P = 0.00001), and Candida species (P = 0.0038) in the study group. The caries incidence was also higher in the study group for both primary (P = 0.0096) and permanent dentition (P = 0.0251), and salivary pH was more acidic (P = 0.00001) in the patients diagnosed with MPS.

INTERPRETATION AND CONCLUSION

Patients diagnosed with MPS have a higher microbial load, more acidic saliva, and subsequently, a higher caries incidence than normal healthy children. Hence, regular dental evaluation, prevention, and treatment must be integrated into their health-care regimen.

Combining angiotensin receptor blockade and enzyme replacement therapy for vascular disease in mucopolysaccharidosis type I

Vascular involvement in the genetic disorder mucopolysaccharidosis type I (MPS I) has features of atherosclerotic disease near branch points of arterial vasculature, such as intimal thickening with disruption of the internal elastic lamina, and proliferation of macrophages and myofibroblasts. Inflammatory pathways are implicated in the pathogenesis of vascular disease in MPS I animal models, evidenced by cytokines like CD18 and TGF-β within arterial plaques. The angiotensin II-mediated inflammatory pathway is well studied in human atherosclerotic coronary artery disease. Recent work indicates treatment with the angiotensin receptor blocker losartan may improve vascular MPS I disease in mouse models. Here, we combined losartan with the standard therapy for MPS I, enzyme replacement therapy (ERT), to measure effects on cytokines in serum and aortic vasculature. Each treatment group (losartan, ERT, and their combination) equally normalized levels of cytokines that were largely differential between normal and mutant mice. Some cytokines, notably CD30 ligand, Eotaxin-2, LIX, IL-13, IL-15, GM-CSF, MCP-5, MIG, and CCL3 showed elevations in mice treated with ERT above normal or mutant levels; these elevations were reduced or absent in mice that received losartan or combination therapy. The observations suggest that losartan may impact inflammatory cascades due to MPS I and may also blunt inflammation in combination with ERT.

Airway and Anaesthetic Management of Adult Patients with Mucopolysaccharidoses Undergoing Cardiac Surgery

Background: Mucopolysaccharidoses (MPSs) are rare congenital lysosomal storage disorders due to a deficiency of enzymes metabolising glycosaminoglycans, leading to their accumulation in tissues. This multisystem disease often requires surgical intervention, including valvular cardiac surgery. Adult MPSs have complex airways making anaesthesia risky. Methods: We report novel three-dimensional (3D) modelling airway assessments and multidisciplinary peri-operative airway management. Results: Five MPS adults underwent cardiac surgery at the national MPS cardiac centre (type I = 4, type II = 1; ages 20, 24, 33, 35, 37 years; two males, three females). All had complex airway abnormalities. Assessments involved examination, nasendoscopy, imaging, functional studies, 3D reconstruction, virtual endoscopy, virtual reality and simulation using computerised, physical modelling. Awake oral fibre-optic intubation was achieved via airway conduit. Staged extubation was performed on the first post-operative day under laryngo-tracheoscopic guidance. The post-operative period involved chest physiotherapy and occupational therapy. All patients had safe intubation, ventilation and extubation. Four had good cardiac surgical outcomes, one (MPS type I; age 35 years) was inoperable due to endocarditis. None had post-operative airway complications. Conclusions: Expertise from cardiovascular-heart team, multidisciplinary airway management, use of novel techniques is vital. Traditional airway assessments are insufficient, so ENT input, radiology and computerised methods to assess and simulate the airway in 3D by collaboration with clinical engineering is essential.

Natural history of cardiac findings in mucopolysaccharidosis type I: report from an international registry

Mucopolysaccharidosis type I is an inborn error of glycosaminoglycan catabolism with phenotypes ranging from severe (Hurler syndrome) to attenuated (Hurler-Scheie and Scheie syndromes). Cardiovascular involvement is common and contributes significantly to morbidity and mortality. We conducted a retrospective analysis of the prevalence and natural history of cardiac abnormalities in treatment-naïve individuals enrolled in the international Mucopolysaccharidosis Type I Registry. Interrogation of echocardiography data (presence of cardiac valve regurgitation and/or stenosis; measurements of left ventricular chamber dimensions in diastole and systole, diastolic left ventricular posterior wall and interventricular septal thicknesses and ventricular systolic function (shortening fraction)) showed that mitral regurgitation was the most common and earliest finding for individuals with both severe (58.3%, median age 1.2 years) and attenuated (74.2%, median age 8.0 years) disease. Left-sided valve stenosis was also common in individuals with attenuated disease (mitral 30.3%; aortic 25%). Abnormal ventricular wall and septal thickness (Z-scores ≥2) were observed early in both phenotypes. Z-scores for diastolic left ventricular posterior wall and interventricular septal thicknesses increased with age in the severe phenotype (annualised slopes of 0.2777 [p = 0.037] and 0.3831 [p = 0.001], respectively); a similar correlation was not observed in the attenuated phenotype (annualised slopes of -0.0401 [p = 0.069] and -0.0029 [p = 0.875], respectively). Decreased cardiac ventricular systolic function (defined as shortening fraction <28%) was uncommon but, when noted, was more frequent in infants with the severe phenotype. While cardiac abnormalities occur early in both severe and attenuated mucopolysaccharidosis type I, the pattern of valve dysfunction and progression of ventricular abnormalities vary by phenotype.

Molecular Mechanisms in Pathophysiology of Mucopolysaccharidosis and Prospects for Innovative Therapy

Mucopolysaccharidoses (MPSs) are a group of inborn errors of the metabolism caused by a deficiency in the lysosomal enzymes required to break down molecules called glycosaminoglycans (GAGs). These GAGs accumulate over time in various tissues and disrupt multiple biological systems, including catabolism of other substances, autophagy, and mitochondrial function. These pathological changes ultimately increase oxidative stress and activate innate immunity and inflammation. We have described the pathophysiology of MPS and activated inflammation in this paper, starting with accumulating the primary storage materials, GAGs. At the initial stage of GAG accumulation, affected tissues/cells are reversibly affected but progress irreversibly to: (1) disruption of substrate degradation with pathogenic changes in lysosomal function, (2) cellular dysfunction, secondary/tertiary accumulation (toxins such as GM2 or GM3 ganglioside, etc.), and inflammatory process, and (3) progressive tissue/organ damage and cell death (e.g., skeletal dysplasia, CNS impairment, etc.). For current and future treatment, several potential treatments for MPS that can penetrate the blood-brain barrier and bone have been proposed and/or are in clinical trials, including targeting peptides and molecular Trojan horses such as monoclonal antibodies attached to enzymes via receptor-mediated transport. Gene therapy trials with AAV, ex vivo LV, and Sleeping Beauty transposon system for MPS are proposed and/or underway as innovative therapeutic options. In addition, possible immunomodulatory reagents that can suppress MPS symptoms have been summarized in this review.

Evaluation of cardiac findings in mucopolysaccharidosis

PURPOSE

Mucopolysaccharidoses (MPS) are a group of rare genetic diseases and heart involvement is one of the important conflicts in most types, which may cause serious complications. We used M-Mode and two-dimensional speckle tracking echocardiography (2D-STE) to explore cardiovascular involvements in MPS patients.

METHOD

The present cross-sectional study investigated the frequency of cardiac involvements in MPS patients. Included participants were MPS types I, II, III, IV, and VI who underwent specialized echocardiography exams to assess valvular function, systolic and diastolic function, left ventricular ejection fraction (LVEF), and global longitudinal strain (GLS).

RESULTS

35 patients were enrolled in this study. The total mean age of patients was 9.58 ± 5.11 years and 71.4% were male. Type IV (40%) and type III (31.4%) were the most frequent MPS. Although LVEF did not differ notably among MPS types, GLS was significantly different (p = 0.029). Mitral regurgitation was observed remarkably more in MPS type III (p = 0.001) while mitral stenosis was more common in type III (p = 0.007). There was a significant association between LVEF and GLS (β= -0.662; p = 0.025) and between LVEF and MPS type (β = 1.82; p = 0.025) when adjusted for GLS.

CONCLUSION

Cardiac complications are very common and are one of the most important causes of death in MPS patients. 2D-STE seems to be superior to M-Mode for detection of early and subclinical cardiac dysfunction in MPS patients.

Valvular heart disease and cardiomyopathy: reappraisal of their interplay

Cardiomyopathies and valvular heart diseases are typically considered distinct diagnostic categories with dedicated guidelines for their management. However, the interplay between these conditions is increasingly being recognized and they frequently coexist, as in the paradigmatic examples of dilated cardiomyopathy and hypertrophic cardiomyopathy, which are often complicated by the occurrence of mitral regurgitation. Moreover, cardiomyopathies and valvular heart diseases can have a shared aetiology because several genetic or acquired diseases can affect both the cardiac valves and the myocardium. In addition, the association between cardiomyopathies and valvular heart diseases has important prognostic and therapeutic implications. Therefore, a better understanding of their shared pathophysiological mechanisms, as well as of the prevalence and predisposing factors to their association, might lead to a different approach in the risk stratification and management of these diseases. In this Review, we discuss the different scenarios in which valvular heart diseases and cardiomyopathies coexist, highlighting the need for an improved classification and clustering of these diseases with potential repercussions in the clinical management and, particularly, personalized therapeutic approaches.

Mucopolysaccharidosis Type I: The Importance of Early Diagnosis for Adequate Treatment

Mucopolysaccharidoses are rare lysosomal storage disorders in which glycosaminoglycans accumulate in tissues, causing multiorgan dysfunction. Mucopolysaccharidosis type I is an autosomal recessive disease caused by a deficiency of the enzyme alpha-L-iduronidase, resulting in the accumulation of dermatan and heparan sulfate. Early diagnosis is crucial for early treatment and improved outcomes. We report the case of a female child with classic clinical features who was diagnosed early which allowed hematopoietic stem cell transplantation and slowed disease progression. She presented at birth with linea alba and umbilical and inguinal hernias. Since the first months of life, she had recurrent respiratory infections. At nine months, a motor delay was noticed, and at 20 months, craniosynostosis was corrected with surgery. Coarse facial features, thoracolumbar kyphosis, and hepatomegaly prompted a urinary glycosaminoglycan study at 22 months, which showed elevated levels. Alfa-L-iduronidase activity in dried blood spot testing was low, compatible with mucopolysaccharidosis type I. Molecular testing of gene IDUA, performed for genetic counseling, revealed the pathogenic variants c.1205G>A (p.Trp402Ter) and c.1598C>G (p.Pro533Arg) in compound heterozygosity. At 26 months, her development quotient was average for her age. She started enzyme replacement therapy at 29 months and underwent hematopoietic stem cell transplantation at 33 months, which softened the coarse features, reduced respiratory infections, and improved hepatomegaly. However, at age five, her development quotient was 76 (mean = 100, standard deviation = 15). This intellectual impairment might have been prevented with an earlier diagnosis and treatment.

Characterization of heart disease in mucopolysaccharidosis type II mice

Mucopolysaccharidosis type II (MPSII) is a progressive lysosomal storage disease caused by mutations in the IDS gene, that leads to iduronate 2-sulfatase (IDS) enzyme deficiency. The enzyme catalyzes the first step of degradation of two glycosaminoglycans (GAGs), heparan sulfate (HS) and dermatan sulfate (DS). The consequences of MPSII are progressively harmful and can lead to death by cardiac failure. The aim of this study was to characterize the cardiovascular disease in MPSII mice. Thus, we evaluated the cardiovascular function of MPSII male mice at 6, 8, and 10 months of age, through functional, histological, and biochemical analyzes. Echocardiographic analyses showed a progressive loss in cardiac function, observed through parameters such as reduction in ejection fraction (46% in control versus 28% in MPS II at 10 months, P < .01) and fractional area change (31% versus 23%, P < .05). Similar results were found in parameters of vascular competence, obtained by echo Doppler. Both aortic dilatation and an increase in pulmonary resistance were observed at all time points in MPSII mice. The histological analyses showed an increase in the thickness of the heart valves (2-fold thicker than control values at 10 months). Biochemical analyzes confirmed GAG storage in these tissues, with a massive elevation of DS in the myocardium. Furthermore, an important increase in the activity of proteases such as cathepsin S and B (up to 5-fold control values) was found and could be related to the progressive loss of cardiac function observed in MPSII mice. In this work, we demonstrated that loss of cardiac function in MPSII mice started at 6 months of age, although its global cardiac capacity was still preserved at this time. Disease progressed at later time points leading to heart failure. The MPSII mice at later times reproduce many of the cardiovascular events found in patients with Hunter's disease.

Cardiac magnetic resonance of hypertrophic heart phenotype: A review

Hypertrophic heart phenotype is characterized by an abnormal left ventricular (LV) thickening. A hypertrophic phenotype can develop as adaptive response in many different conditions such as aortic stenosis, hypertension, athletic training, infiltrative heart muscle diseases, storage disorders and metabolic disorders. Hypertrophic cardiomyopathy (HCM) is the most frequent primary cardiomyopathy (CMP) and a genetical cause of cardiac hypertrophy. It requires the exclusion of any other cause of LV hypertrophy. Cardiac magnetic resonance (CMR) is a comprehensive imaging technique that allows a detailed evaluation of myocardial diseases. It provides reproducible measurements and myocardial tissue characterization. In clinical practice CMR is increasingly used to confirm the presence of ventricular hypertrophy, to detect the underlying cause of the phenotype and more recently as an efficient prognostic tool. This article aims to provide a detailed overview of the applications of CMR in the setting of hypertrophic heart phenotype and its role in the diagnostic workflow of such condition.

Sudden cardiac death in childhood hypertrophic cardiomyopathy

The most prevalent cause of mortality in children with hypertrophic cardiomyopathy (HCM) is sudden cardiac death (SCD), which happens more frequently than in adult patients. Risk stratification tactics have generally been drawn from adult practice, however emerging data has revealed significant disparities between children and adult cohorts, implying the need for pediatric-specific risk stratification methodologies. We conducted an all-language literature search on Medline, Cochrane, Embase, and Google Scholar until October 2021. The following search strings and Medical Subject Heading (MeSH) terms were used: "HCM," "SCD," "Sudden Cardiac Death," and "Childhood Onset HCM." We explored the literature on the risk of SCD in HCM for its epidemiology, pathophysiology, the role of various genes and their influence, associated complications leading to SCD and preventive and treatment modalities. Childhood-onset HCM is linked to significant life-long morbidity and mortality, including a higher SCD rate in children than in adults. The present focus is on symptom relief and avoiding illness-related consequences, but the prospect of future disease-modifying medicines offers an intriguing opportunity to alter disease expression and outcomes in these young individuals. Current preventive recommendations promote implantable cardioverter defibrillator placement based on cumulative risk factor thresholds, although they have been demonstrated to have weak discriminating capacity. This article addresses questions and discusses the etiology, risk factors, and method to risk stratification for SCD in children with HCM.

In vivo adenine base editing corrects newborn murine model of Hurler syndrome

Mucopolysaccharidosis type I (MPS I) is a severe disease caused by loss-of-function mutation variants in the α-L-iduronidase (Idua) gene. In vivo genome editing represents a promising strategy to correct Idua mutations, and has the potential to permanently restore IDUA function over the lifespan of patients. Here, we used adenine base editing to directly convert A > G (TAG>TGG) in a newborn murine model harboring the Idua-W392X mutation, which recapitulates the human condition and is analogous to the highly prevalent human W402X mutation. We engineered a split-intein dual-adeno-associated virus 9 (AAV9) adenine base editor to circumvent the package size limit of AAV vectors. Intravenous injection of the AAV9-base editor system into MPS IH newborn mice led to sustained enzyme expression sufficient for correction of metabolic disease (GAGs substrate accumulation) and prevention of neurobehavioral deficits. We observed a reversion of the W392X mutation in 22.46 ± 6.74% of hepatocytes, 11.18 ± 5.25% of heart and 0.34 ± 0.12% of brain, along with decreased GAGs storage in peripheral organs (liver, spleen, lung and kidney). Collectively, these data showed the promise of a base editing approach to precisely correct a common genetic cause of MPS I in vivo and could be broadly applicable to the treatment of a wide array of monogenic diseases.

Clinical Characteristics of a Patient with Mucopolysaccharidosis Type IVA (Morquio Syndrome)

Mucopolysaccharidosis (MPS) type IVA (Morquio syndrome) is a hereditary lysosomal storage disease caused by deficiency of N-acetylglucosamine-6-sulfate sulfatase. This enzyme deficiency leads to specific glycosaminoglycans (keratan sulfate and chondroitin-6-sulfate) accumulation mainly in the bone and cartilage tissues, as well as in the cardiovascular, respiratory systems, and visual systems. Patients with MPS IVA look healthy at birth, however, they develop typical spine deformities (kyphoscoliosis), pectus carinatum, wrists hypermobility with decreased muscle strength and loss of fine motor skills, valgus deformation of lower limbs during the first years of life. Pathological changes in cardiovascular and respiratory systems, visual and acoustic analyzers can be revealed. Early diagnosis of the disease is crucial for timely initiation of enzyme replacement therapy. Thus, low incidence of the disease and its heterogeneous clinical picture complicates diagnosis. Consequently, patients with MAS IVA often become severely disabled as early as adolescence. Patients with severe form and without treatment die before the age of 30 due to complications of respiratory system diseases, valvular heart apparatus involvement, and cervical myelopathy.

Left-sided valvular heart disease and retinopathy in a 38-year-old woman with attenuated mucopolysaccharidosis: a case report

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders caused by deficient levels and/or activity of glycosaminoglycan (GAG)-degradative enzymes. MPS are characterized by accumulation of the mucopolysaccharides heparan sulfate, dermatan sulfate, keratan sulfate, or chondroitin sulfate in tissues. We report the case of a 38-year-old woman with a history of joint restriction and retinitis pigmentosa who developed bivalvular heart failure requiring surgery. It was not until pathological examination of surgically excised valvular tissue that a diagnosis of MPS I was made. Her musculoskeletal and ophthalmologic symptoms, when placed in the context of MPS I, painted the diagnostic picture of a genetic syndrome that was overlooked until a diagnosis was made in late middle age.

Mucopolysaccharidosis: What Pediatric Rheumatologists and Orthopedics Need to Know

Mucopolysaccharidosis (MPS) is a group of disorders caused by the reduced or absent activity of enzymes involved in the glycosaminoglycans (GAGs) degradation; the consequence is the progressive accumulation of the substrate (dermatan, heparan, keratan or chondroitin sulfate) in the lysosomes of cells belonging to several tissues. The rarity, the broad spectrum of manifestations, the lack of strict genotype-phenotype association, and the progressive nature of MPS make diagnosing this group of conditions challenging. Musculoskeletal involvement represents a common and prominent feature of MPS. Joint and bone abnormalities might be the main clue for diagnosing MPS, especially in attenuated phenotypes; therefore, it is essential to increase the awareness of these conditions among the pediatric rheumatology and orthopedic communities since early diagnosis and treatment are crucial to reduce the disease burden of these patients. Nowadays, enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are available for some MPS types. We describe the musculoskeletal characteristics of MPS patients through a literature review of MPS cases misdiagnosed as having rheumatologic or orthopedic conditions.

Drug Repositioning Applied to Cardiovascular Disease in Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are genetic metabolic diseases characterized by defects in the activity of lysosomal hydrolases. In MPS, secondary cell disturbance affects pathways related to cardiovascular disorders. Hence, the study aimed to identify MPS-related drugs targeting cardiovascular disease and select a list of drugs for repositioning. We obtained a list of differentially expressed genes and pathways. To identify drug perturbation-driven gene expression and drug pathways interactions, we used the CMAP and LINCS databases. For molecular docking, we used the DockThor web server. Our results suggest that pirfenidone and colchicine are promising drugs to treat cardiovascular disease in MPS patients. We also provide a brief description of good practices for the repositioning analysis. Furthermore, the list of drugs and related MPS-enriched genes could be helpful to new treatments and considered for pathophysiological studies.

Identification of a novel fusion Iduronidase with improved activity in the cardiovascular system

Background

Lysosomal diseases are a group of over 70 rare genetic conditions in which a protein deficiency (most often an enzyme deficiency) leads to multi-system disease. Current therapies for lysosomal diseases are limited in their ability to treat certain tissues that are major contributors to morbidity and mortality, such as the central nervous system (CNS) and cardiac valves. For this study, the lysosomal disease mucopolysaccharidosis type I (MPS I) was selected as the disease model. In MPS I, mutations in the IDUA gene cause a deficiency of the α-L-iduronidase (IDUA) enzyme activity, leading to disease pathology in tissues throughout the body, including the CNS and cardiac valves. Current therapies have been unable to prevent neurodevelopmental deficits and cardiac valvular disease in patients with MPS I. This study aimed to evaluate the delivery of IDUA enzyme, via a novel gene therapy construct, to target tissues.

Methods

MPS I mice were hydrodynamically injected through the tail vein with plasmids containing either a codon-optimized cDNA encoding the wild-type IDUA protein or one of four modified IDUAs under the control of the liver-specific human α1-antitrypsin (hAAT) promoter. Two modified IDUAs contained a ligand for the CB1 receptor, which is a highly expressed receptor in the CNS. Iduronidase activity levels were measured in the tissues and plasma using an enzyme activity assay.

Results

The modified IDUAs did not appear to have improved activity levels in the brain compared with the unmodified IDUA. However, one modified IDUA exhibited higher activity levels than the unmodified IDUA in the heart (p = 0.0211). This modified iduronidase (LT-IDUA) contained a sequence for a six amino acid peptide termed LT. LT-IDUA was further characterized using a noncompartmental pharmacokinetic approach that directly analyzed enzyme activity levels after gene delivery. LT-IDUA had a 2-fold higher area under the curve (AUC) than the unmodified IDUA (p = 0.0034) when AUC was estimated using enzyme activity levels in the plasma.

Conclusion

The addition of a six amino acid peptide improved iduronidase's activity levels in the heart and plasma. The short length of this LT peptide facilitates its use as fusion enzymes encoded as gene therapy or administered as enzyme replacement therapy. More broadly, the LT peptide may aid in developing therapies for numerous lysosomal diseases.

Modern Approaches to the Management of Children with Mucopolysaccharidosis Type I

This article presents modern data on epidemiology, etiology, and clinical manifestations of mucopolysaccharidosis (MPS) type I in children. MPS develops due to deficiency of particular lysosomal enzyme which determines the disease type. The article considers in details disease's pathogenesis and classification. Evidence-based approaches to diagnosis (differential diagnosis included) are covered, moreover, special attention is paid to pathogenetic, symptomatic, and surgical treatment of MPS.

Mucopolysaccharidoses and the blood-brain barrier

Mucopolysaccharidoses comprise a set of genetic diseases marked by an enzymatic dysfunction in the degradation of glycosaminoglycans in lysosomes. There are eight clinically distinct types of mucopolysaccharidosis, some with various subtypes, based on which lysosomal enzyme is deficient and symptom severity. Patients with mucopolysaccharidosis can present with a variety of symptoms, including cognitive dysfunction, hepatosplenomegaly, skeletal abnormalities, and cardiopulmonary issues. Additionally, the onset and severity of symptoms can vary depending on the specific disorder, with symptoms typically arising during early childhood. While there is currently no cure for mucopolysaccharidosis, there are clinically approved therapies for the management of clinical symptoms, such as enzyme replacement therapy. Enzyme replacement therapy is typically administered intravenously, which allows for the systemic delivery of the deficient enzymes to peripheral organ sites. However, crossing the blood-brain barrier (BBB) to ameliorate the neurological symptoms of mucopolysaccharidosis continues to remain a challenge for these large macromolecules. In this review, we discuss the transport mechanisms for the delivery of lysosomal enzymes across the BBB. Additionally, we discuss the several therapeutic approaches, both preclinical and clinical, for the treatment of mucopolysaccharidoses.

Early Neonatal Cardiac Phenotype in Hurler Syndrome: Case Report and Literature Review

Mucopolysaccharidosis type I (MPS I) is a rare inherited lysosomal disorder caused by deficiency of the α-L-iduronidase enzyme, resulting in the progressive accumulation of glycosaminoglycans (GAGs), which interfere with the normal function of multiple tissues and organs. The clinical phenotype includes characteristic facial features, hepatosplenomegaly, dysostosis multiplex, umbilical and inguinal hernias, progressive cognitive deficits with corresponding hydrocephalus, and neuropathology. Untreated children do not survive into the second decade. The common cardiac phenotype seen in MPS I and other MPS types includes valve thickening and dysfunction, conduction abnormalities, coronary artery disease, and cardiomyopathy—usually seen later in the disease course. A 15-month-old ex-35-weeker who presented with cardiomyopathy and left ventricular failure at the age of three weeks is presented here. Early evaluation and diagnosis with the help of newborn screening (NBS), followed by treatment with enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT), resulted in improvement of his cardiopulmonary status. In MPS I, an early cardiac phenotype is uncommon. Based on the evidence from the literature review for early neonatal cardiac phenotype, we propose that all infants with abnormal newborn screening for MPS I should receive cardiac screening with echocardiogram and NT-proB-type natriuretic peptide (BNP) during the initial evaluation.

Unmet Cardiac Clinical Needs in Adult Mucopolysaccharidoses

The Mucopolysaccharidoses (MPSs) are a group of heterogenous disorders with complex multisystemic presentations. Although Haematopoietic Cell Transplantation (HCT) and Enzyme Replacement Therapy (ERT) have extended the lifespan of individuals affected with MPS well into adulthood, reversal of pre-existing cardiac, skeletal and neurocognitive deficits does not occur, so there are no truly curative treatments available to these patients at present. The medical and surgical management of cardiovascular problems in adults with MPS is complicated by these pre-existing comorbidities, requiring the involvement of multidisciplinary and multispecialty perioperative teams. This review sets out to describe the unmet cardiac needs in adults with MPS disorders including the lack of effective treatments, monitoring guidelines, and the challenges regarding expertise and training, and psychosocial support.

Rare Metabolic and Endocrine Diseases with Cardiovascular Involvement: Insights from Cardiovascular Magnetic Resonance - A Review

The identification of rare diseases with cardiovascular involvement poses significant diagnostic challenges due to the rarity of the diseases, but also due to the lack of knowledge and expertise. Most of them remain underrecognized and undiagnosed, leading to clinical mismanagement and affecting the patients' prognosis, as these diseases are per definition life-threatening or chronic debilitating. This article reviews the cardiovascular involvement of the most well-known rare metabolic and endocrine diseases and their diagnostic approach through the lens of cardiovascular magnetic resonance (CMR) imaging and its prognostic role, highlighting its fundamental value compared to other imaging modalities.

Mucopolysaccharidosis Type IVA: Extracellular Matrix Biomarkers in Cardiovascular Disease

Cardiovascular disease (CVD) in Mucopolysaccharidosis Type IVA (Morquio A), signified by valvular disease and cardiac hypertrophy, is the second leading cause of death and remains untouched by current therapies. Enzyme replacement therapy (ERT) is the gold-standard treatment for MPS disorders including Morquio A. Early administration of ERT improves outcomes of patients from childhood to adulthood while posing new challenges including prognosis of CVD and ERT's negligible effect on cardiovascular health. Thus, having accurate biomarkers for CVD could be critical. Here we show that cathepsin S (CTSS) and elastin (ELN) can be used as biomarkers of extracellular matrix remodeling in Morquio A disease. We found in a cohort of 54 treatment naïve Morquio A patients and 74 normal controls that CTSS shows promising attributes as a biomarker in young Morquio A children. On the other hand, ELN shows promising attributes as a biomarker in adolescent and adult Morquio A. Plasma/urine keratan sulfate (KS), and urinary glycosaminoglycan (GAG) levels were significantly higher in Morquio A patients (p < 0.001) which decreased with age of patients. CTSS levels did not correlate with patients' phenotypic severity but differed significantly between patients (median range 5.45-8.52 ng/mL) and normal controls (median range 9.61-15.9 ng/mL; p < 0.001). We also studied α -2-macroglobulin (A2M), C-reactive protein (CRP), and circulating vascular cell adhesion molecule-1 (sVCAM-1) in a subset of samples to understand the relation between ECM biomarkers and the severity of CVD in Morquio A patients. Our experiments revealed that CRP and sVCAM-1 levels were lower in Morquio A patients compared to normal controls. We also observed a strong inverse correlation between urine/plasma KS and CRP (p = 0.013 and p = 0.022, respectively) in Morquio A patients as well as a moderate correlation between sVCAM-1 and CTSS in Morquio A patients at all ages (p = 0.03). As the first study to date investigating CTSS and ELN levels in Morquio A patients and in the normal population, our results establish a starting point for more elaborate studies in larger populations to understand how CTSS and ELN levels correlate with Morquio A severity.

Quantifying medical manifestations in Hurler syndrome with the infant physical symptom score: associations with long-term physical and adaptive outcomes

BACKGROUND

A physical symptom score (PSS) for the mucopolysaccharidosis (MPS) disorders has been developed to quantitate the somatic burden of disease across multiple organ systems. Studies have demonstrated the sensitivity and its relationship to age, IQ and adaptive functioning of the PSS in older children. With the onset of newborn screening, there is an increased need to characterize the somatic symptoms in the earliest stages of life, especially for young children under 36 months of age. Consequently, a new scale, Infant Physical Symptom Score (IPSS), was developed to score physical symptoms in infants and toddlers.

OBJECTIVE

Part I. To create a measure to quantify somatic burden in patients with MPS disorders under 36 months of age. The IPSS assess outcomes and changes in somatic disease in individuals with MPS disorders diagnosed very early in life. Part II. To determine the relationship between IPSS and other measures to evaluate its validity and utility, a) we evaluated the relationship between the IPSS and PSS in the same patients with MPS I over time to determine if the two scales are measuring the same concepts, and b) we evaluated the association between IPSS and a functional adaptive measure over time with a focus on the age at first treatment (under 36 months) to determine if the IPSS has predictive value.

METHODS

Part I. The Infant Physical Symptom Score (IPSS) for the infant population in MPS disorders was established using data from 39 patients enrolled in the Lysosomal Disease Network longitudinal MPS I study (U54NS065768). All of these patients had Hurler syndrome (MPS IH) and underwent hematopoietic stem cell transplant (HSCT) at the University of Minnesota. Items for the IPSS were selected by reviewing CRFs prepared for the MPS I longitudinal study and examining medical records of these patients prior to HSCT based on the knowledge gained from the development of the PSS. Part II. Of those 39 patients, a subset of 19 were all seen 9 to 12 years post HSCT. Having retrospectively calculated their IPSS prior to HSCT, we categorized them by age at HSCT, and examined their most recent PSS along with Composite and Daily Living Skills scores on the Vineland Adaptive Behavior Scales - Second Edition (VABS-II).

RESULTS AND CONCLUSION

The total score on the IPSS collected prior to transplant differed by patient's age at transplant, as expected in this progressive condition. Those transplanted at ≤12 months of age had a mean score of 7.4, which was significantly lower, suggesting less somatic disease burden, compared to those transplanted at >12 to ≤24 months (mean 11.8) and > 24 to ≤36 months (mean 13.6). Higher IPSS reflects more evidence of somatic disease burden and lower IPSS reflects less evidence of disease burden. Nine to 12 years later, the severity level as measured by the PSS was comparable to severity on the IPSS suggesting that the two scales are measuring similar concepts. Retrospectively calculated pre-transplant IPSS were negatively associated with higher VABS-II Composite scores 9-12 years later (p value-0.015) and to a lesser extent Daily Living Skills scores (p value-0.081). We conclude that the IPSS appears to be a useful approach to quantifying the somatic disease burden of MPS IH patients under 36 months of age.

Pre-operative Considerations in Adult Mucopolysaccharidosis Patients Planned for Cardiac Intervention

Mucopolysaccharidoses (MPS) are rare lysosomal storage diseases characterized by multiorgan involvement and shortened longevity. Due to advances in therapies such as enzyme replacement therapy and haematopoietic stem cell therapy, life expectancy has increased posing newer challenges to patients and health professionals. One such challenge is cardiovascular manifestations of MPS, which can be life limiting and cause reduction in quality of life. Any cardiovascular intervention mandates comprehensive, multi-systemic work-up by specialist teams to optimize outcome. We highlight the importance of multidisciplinary evaluation of adult MPS patients requiring cardiovascular intervention. Clinical assessments and investigations are discussed, with a focus on the cardiac, anesthetic, airway, respiratory, radiological and psychosocial factors.

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a heterogeneous group of disorders that results in the absence or deficiency of lysosomal enzymes, leading to an inappropriate storage of glycosaminoglycans (GAGs) in various tissues of the body such as bones, cartilage, heart valves, arteries, upper airways, cornea, teeth, liver and nervous system. Clinical manifestations can become progressively exacerbated with age and affect their quality of life. Developments in advanced supportive treatment options such as enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT) may have improved patients' life span. Adult MPS patients require specialist clinical surveillance long-term. In many cases, in addition to the MPS-related health problems, they may develop age-related complications. Considering the complexity of their clinical manifestations and lack of guidelines on the management of adult MPS disorders, multispecialty and multidisciplinary teams' care is essential to diagnose and treat health problems that are likely to be encountered. This review presents non-cardiac clinical manifestations, their pathophysiology, management and long-term outcomes in adult MPS patients.

Surgical Management of Valvular Heart Disease in Mucopolysaccharidoses: A Review of Literature

Mucopolysaccharidoses are extremely rare diseases that are frequently presenting with structural heart problems of the aortic and mitral valve in combination with myocardial dysfunction. In a substantial proportion, this leads to heart failure and is a leading cause of death in these patients. As this glycosaminoglycan degradation defect is associated with other conditions strongly influencing the perioperative risk and choice of surgical technique, multidisciplinary planning is crucial to improve short- and long-term outcomes. The extensive variance in clinical presentation between different impaired enzymes, and further within subgroups, calls for personalised treatment plans. Enzyme replacement therapies and bone marrow transplantation carry great potential as they may significantly abrogate the progress of the disease and as such reduce the clinical burden and improve life expectancy. Nevertheless, structural heart interventions may be required. We reviewed the existing literature of the less than 50 published cases regarding surgical management, technique, and choice of prostheses. Although improvement in therapy has shown promising results in protecting valvar tissue when initiated in infancy, concerns regarding stability of this effect and durability of biological prostheses remain.

Progression of Cardiovascular Manifestations in Adults and Children With Mucopolysaccharidoses With and Without Enzyme Replacement Therapy

Background: Cardiovascular involvement is among the main features of MPS disorders and it is also a significant cause of morbidity and mortality. The range of manifestations includes cardiac valve disease, conduction abnormalities, left ventricular hypertrophy, and coronary artery disease. Here, we assessed the cardiovascular manifestations in a cohort of children and adults with MPS I, II, IV, and VI, as well as the impact of enzyme replacement therapy (ERT) on those manifestations.

Methods: We performed a chart review of 53 children and 23 adults with different types of MPS that had performed echocardiograms from January 2000 until October 2018. Standardized Z scores were obtained for heart chamber sizes according to the body surface area. When available, echocardiographic measurements that were performed before ERT and at least 18 months after that date were used for the assessment of pre- and post-treatment parameters.

Results: Left side valvular disease was a frequent finding, with mitral and aortic thickening being reported in most patients in all four MPS types. Left atrium dilatation was present in 26% of the patients; 25% had increased relative wall thickness; 28% had pulmonary hypertension. The cardiovascular involvement was, in general, more prevalent and more severe in adults than in children, including conduction disorders (40 vs. 16%), mitral stenosis (26 vs. 6%), aortic stenosis (13 vs. 4%), and systolic dysfunction (observed in only one adult patient). ERT promoted a significant reduction of the left ventricular hypertrophy parameters, but failed to improve valve abnormalities, pulmonary hypertension, and left atrial dilatation.

Conclusions: Adult patients with MPS may develop severe cardiovascular involvement, not commonly observed in children, and clinicians should be aware of the need for careful monitoring and timely management of those potentially life-threatening complications. Our results also confirm the impact of long-term ERT on left ventricular hypertrophy and its limitations in reversing other prevalent cardiovascular manifestations.

The regulatory mechanism between lysosomes and mitochondria in the aetiology of cardiovascular diseases

Coordinated action among various organelles maintains cellular functions. For instance, mitochondria and lysosomes are the main organelles contributing to cellular metabolism and provide energy for cardiomyocyte contraction. They also provide essential signalling platforms in the cell that regulate many key processes such as autophagy, apoptosis, oxidative stress, inflammation and cell death. Often, abnormalities in mitochondrial or lysosomal structures and functions bring about cardiovascular diseases (CVDs). Although the communication between mitochondria and lysosomes throughout the cardiovascular system is intensely studied, the regulatory mechanisms have not been completely understood. Thus, we summarize the most recent studies related to mitochondria and lysosomes' role in CVDs and their potential connections and communications under cardiac pathophysiological conditions. Further, we discuss limitations and future perspectives regarding diagnosis, therapeutic strategies and drug discovery in CVDs.

MPS VI associated ocular phenotypes in an MPS VI murine model and the therapeutic effects of odiparcil treatment

Maroteaux - Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a lysosomal storage disease resulting from insufficient enzymatic activity for degradation of the specific glycosaminoglycans (GAG) chondroitin sulphate (CS) and dermatan sulphate (DS). Among the most pronounced MPS VI clinical manifestations caused by cellular accumulation of excess CS and DS are eye disorders, in particular those that affect the cornea. Ocular manifestations are not treated by the current standard of care, enzyme replacement therapy (ERT), leaving patients with a significant unmet need. Using in vitro and in vivo models, we previously demonstrated the potential of the β-D-xyloside, odiparcil, as an oral GAG clearance therapy for MPS VI. Here, we characterized the eye phenotypes in MPS VI arylsulfatase B deficient mice (Arsb^-) and studied the effects of odiparcil treatment in early and established disease models. Severe levels of opacification and GAG accumulation were detected in the eyes of MPS VI Arsb^- mice. Histological examination of MPS VI Arsb^- eyes showed an aggregate of corneal phenotypes, including reduction in the corneal epithelium thickness and number of epithelial cell layers, and morphological malformations in the stroma. In addition, colloidal iron staining showed specifically GAG accumulation in the cornea. Orally administered odiparcil markedly reduced GAG accumulation in the eyes of MPS VI Arsb^- mice in both disease models and restored the corneal morphology (epithelial layers and stromal structure). In the early disease model of MPS VI, odiparcil partially reduced corneal opacity area, but did not affect opacity area in the established model. Analysis of GAG types accumulating in the MPS VI Arsb^- eyes demonstrated major contribution of DS and CS, with some increase in heparan sulphate (HS) as well and all were reduced with odiparcil treatment. Taken together, we further reveal the potential of odiparcil to be an effective therapy for eye phenotypes associated with MPS VI disease.

A Compendium of Information on the Lysosome

For a long time, lysosomes were considered as mere waste bags for cellular constituents. Thankfully, studies carried out in the past 15 years were brimming with elegant and crucial breakthroughs in lysosome research, uncovering their complex roles as nutrient sensors and characterizing them as crucial multifaceted signaling organelles. This review presents the scientific knowledge on lysosome physiology and functions, starting with their discovery and reviewing up to date ground-breaking discoveries highlighting their heterogeneous functions as well as pending questions that remain to be answered. We also review the roles of lysosomes in anti-cancer drug resistance and how they undergo a series of molecular and functional changes during malignant transformation which lead to tumor aggression, angiogenesis, and metastases. Finally, we discuss the strategy of targeting lysosomes in cancer which could lead to the development of new and effective targeted therapies.

Drosophila D-idua Reduction Mimics Mucopolysaccharidosis Type I Disease-Related Phenotypes

Deficit of the IDUA (α-L-iduronidase) enzyme causes the lysosomal storage disorder mucopolysaccharidosis type I (MPS I), a rare pediatric neurometabolic disease, due to pathological variants in the IDUA gene and is characterized by the accumulation of the undegraded mucopolysaccharides heparan sulfate and dermatan sulfate into lysosomes, with secondary cellular consequences that are still mostly unclarified. Here, we report a new fruit fly RNAi-mediated knockdown model of a IDUA homolog (D-idua) displaying a phenotype mimicking some typical molecular features of Lysosomal Storage Disorders (LSD). In this study, we showed that D-idua is a vital gene in Drosophila and that ubiquitous reduction of its expression leads to lethality during the pupal stage, when the precise degradation/synthesis of macromolecules, together with a functional autophagic pathway, are indispensable for the correct development to the adult stage. Tissue-specific analysis of the D-idua model showed an increase in the number and size of lysosomes in the brain and muscle. Moreover, the incorrect acidification of lysosomes led to dysfunctional lysosome-autophagosome fusion and the consequent block of autophagy flux. A concomitant metabolic drift of glycolysis and lipogenesis pathways was observed. After starvation, D-idua larvae showed a quite complete rescue of both autophagy/lysosome phenotypes and metabolic alterations. Metabolism and autophagy are strictly interconnected vital processes that contribute to maintain homeostatic control of energy balance, and little is known about this regulation in LSDs. Our results provide new starting points for future investigations on the disease’s pathogenic mechanisms and possible pharmacological manipulations.

Mucopolysaccharidosis Type I Diagnosed by Aortic and Mitral Valve Replacement

A 32-year-old developmentally delayed man presenting with dyspnea was found to have severe aortic and mitral valve stenosis. After double valve replacement, unique histologic findings prompted a genetics evaluation, ultimately leading to the diagnosis of mucopolysaccharidosis type I, a rare lysosomal storage disorder with high rates of cardiac manifestations. (Level of Difficulty: Advanced.).

Evaluation of the long-term treatment effects of intravenous idursulfase in patients with mucopolysaccharidosis II (MPS II) using statistical modeling: data from the Hunter Outcome Survey (HOS)

BACKGROUND

Mucopolysaccharidosis II (MPS II; Hunter syndrome) is a rare, life-limiting lysosomal storage disease caused by deficient iduronate-2-sulfatase activity. Enzyme replacement therapy (ERT) with intravenous (IV) idursulfase can stabilize or improve many somatic manifestations, but there remains a need for further analysis of long-term treatment outcomes. Using data from patients with MPS II enrolled in the Hunter Outcome Survey (HOS), mixed modeling was performed to evaluate and predict the effects of IV idursulfase treatment on selected clinical parameters for up to 8 years following treatment start. The modeling population comprised male patients followed prospectively in HOS who had received IV idursulfase for at least 5 years and who had data available for two or more time points (at least one post-ERT). Age at ERT start and time since ERT start were included as covariates.

RESULTS

In total, 481 patients were eligible for inclusion in at least one model. At 8 years post-ERT start, improvement from baseline was predicted for each age group (< 18 months, 18 months to < 5 years and ≥ 5 years at treatment start) in the following parameters: mean urinary glycosaminoglycan levels (percentage changes of > -75% in each group), mean left ventricular mass index (decreases of ~ 1 g/m2) and mean palpable liver size (decreases of > 2 cm). Improvements in mean 6-min walk test distance (increase of > 50 m) and stabilization in percent predicted forced vital capacity and forced expiratory volume in 1 s (decreases of ~ 4 and ~ 9 percentage points, respectively) at 8 years post-ERT start were predicted for patients aged ≥ 5 years at ERT start (these assessments are unsuitable for patients aged < 5 years). Predicted changes over time were similar across the three age groups; however, overall outcomes were most favorable in children aged < 18 months at ERT start.

CONCLUSIONS

These findings suggest that the previously reported positive effects of IV idursulfase on the somatic manifestations of MPS II are predicted to be maintained for at least 8 years following ERT initiation and highlight the value of statistical modeling to predict long-term treatment outcomes in patients with rare diseases.

Hyo-Mental Angle and Distance: An Important Adjunct in Airway Assessment of Adult Mucopolysaccharidosis

Background: Mucopolysaccharidosis (MPS) is a rare congenital lysosomal storage disorder with complex airways. High anterior larynx is assessed by thyromental distance (TMD) nasendoscopy. A simpler method to assess this hyoid bone is described. The distance between the central-hyoid and symphysis of the mandible (hyo-mental distance; HMD) and inclination of this line to the horizontal axis (hyo-mental angle; HMA) in neutrally positioned patients is investigated. Methods: HMA, HMD in MPS, and non-MPS were compared, and their correlation with height and weight were assessed. Results: 50 adult MPS patients (M = 32, F = 18, age range = 19–66 years; mean BMI = 26.8 kg/m²) of MPS I, II, III, IV, and VI were compared with 50 non-MPS (M = 25, F = 25; age range = 22–84 years; mean BMI = 26.5 kg/m²). Mean HMA in MPS was 25.72° (−10 to +50) versus 2.42° (−35 to +28) in non-MPS. Mean HMD was 46.5 (25.7–66) millimeters in MPS versus 41.8 (27–60.3) in non-MPS. HMA versus height and weight showed a moderate correlation (r = −0.4, p < 0.05) in MPS and no significant correlation (r < 0.4, p > 0.05) in non-MPS. HMD versus height and weight showed no correlation (r < 0.4, p > 0.05) in both groups. Conclusions: HMA seems more acute in MPS despite nearly the same HMD as non-MPS, signifying a high larynx, which may be missed by TMD.

Airway Abnormalities in Adult Mucopolysaccharidosis and Development of Salford Mucopolysaccharidosis Airway Score

(1) Background: Mucopolysaccharidoses (MPS) are a heterogeneous group of lysosomal storage disorders caused by the absence of enzymes required for degradation of glycosaminoglycans (GAGs). GAGs deposition in tissues leads to progressive airway narrowing and/or tortuosity. Increased longevity of patients has posed newer problems, especially the airway. This study aims to characterise various airway abnormalities in adult MPS from a regional centre and proposes a method to quantify the severity of the airway disease. (2) Methods: Retrospective analysis by case notes review, clinical examination, endoscopy, cross-sectional imaging, 3-dimensional reconstruction, and physiological investigations were used to assess the airway abnormalities. Quantitative assessment of the airway severity was performed a validated questionnaire of 15 parameters to derive Salford Mucopolysaccharidosis Airway Score (SMAS). (3) Results: Thirty-one adult MPS patients (21M/ 9F; median 26.7 years; range 19–42 years) were reviewed. There were 9 MPS I, 12 MPS II, 2 MPS III, 5 MPS IV, 2 MPS VI, and 1 MPS VII. Airway abnormalities in each MPS type are described. Patients scoring more than 35 on SMAS had some form of airway intervention. The area under curve of 0.9 was noted at a score of 25, so SMAS more than 25 may predict a difficult airway and potential to have complications. Pearson’s correlation between SMAS and height, weight, BMI were poor (p < 0.05). (4) Conclusions: Airway abnormalities in adult MPS are varied and complex. Assessment of the airway should be holistic and include multiple parameters. An objective multidimensional score such as SMAS may help to predict and manage difficult airways warranting further investigation and validation.

Differences in MPS I and MPS II Disease Manifestations

Mucopolysaccharidosis (MPS) type I and II are two closely related lysosomal storage diseases associated with disrupted glycosaminoglycan catabolism. In MPS II, the first step of degradation of heparan sulfate (HS) and dermatan sulfate (DS) is blocked by a deficiency in the lysosomal enzyme iduronate 2-sulfatase (IDS), while, in MPS I, blockage of the second step is caused by a deficiency in iduronidase (IDUA). The subsequent accumulation of HS and DS causes lysosomal hypertrophy and an increase in the number of lysosomes in cells, and impacts cellular functions, like cell adhesion, endocytosis, intracellular trafficking of different molecules, intracellular ionic balance, and inflammation. Characteristic phenotypical manifestations of both MPS I and II include skeletal disease, reflected in short stature, inguinal and umbilical hernias, hydrocephalus, hearing loss, coarse facial features, protruded abdomen with hepatosplenomegaly, and neurological involvement with varying functional concerns. However, a few manifestations are disease-specific, including corneal clouding in MPS I, epidermal manifestations in MPS II, and differences in the severity and nature of behavioral concerns. These phenotypic differences appear to be related to different ratios between DS and HS, and their sulfation levels. MPS I is characterized by higher DS/HS levels and lower sulfation levels, while HS levels dominate over DS levels in MPS II and sulfation levels are higher. The high presence of DS in the cornea and its involvement in the arrangement of collagen fibrils potentially causes corneal clouding to be prevalent in MPS I, but not in MPS II. The differences in neurological involvement may be due to the increased HS levels in MPS II, because of the involvement of HS in neuronal development. Current treatment options for patients with MPS II are often restricted to enzyme replacement therapy (ERT). While ERT has beneficial effects on respiratory and cardiopulmonary function and extends the lifespan of the patients, it does not significantly affect CNS manifestations, probably because the enzyme cannot pass the blood-brain barrier at sufficient levels. Many experimental therapies, therefore, aim at delivery of IDS to the CNS in an attempt to prevent neurocognitive decline in the patients.