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.

Gene therapies for mucopolysaccharidoses.

Current specific treatments for mucopolysaccharidoses (MPSs) include enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT). Both treatments are hampered by several limitations, including lack of efficacy on brain and skeletal manifestations, need for lifelong injections, and high costs. Therefore, more effective treatments are needed. Gene therapy in MPSs is aimed at obtaining high levels of the therapeutic enzyme in multiple tissues either by engrafted gene-modified hematopoietic stem progenitor cells (ex vivo) or by direct infusion of a viral vector expressing the therapeutic gene (in vivo). This review focuses on the most recent clinical progress in gene therapies for MPSs. The various gene therapy approaches with their strengths and limitations are discussed.

Actin Cytoskeleton Polymerization and Focal Adhesion as Important Factors in the Pathomechanism and Potential Targets of Mucopolysaccharidosis Treatment.

The main approach used in the current therapy of mucopolysaccharidosis (MPS) is to reduce the levels of glycosaminoglycans (GAGs) in cells, the deposits considered to be the main cause of the disease. Previous studies have revealed significant differences in the expression of genes encoding proteins involved in many processes, like those related to actin filaments, in MPS cells. Since the regulation of actin filaments is essential for the intracellular transport of specific molecules, the process which may affect the course of MPSs, the aim of this study was to evaluate the changes that occur in the actin cytoskeleton and focal adhesion in cells derived from patients with this disease, as well as in the MPS I mouse model, and to assess whether they could be potential therapeutic targets for different MPS types. Western-blotting, flow cytometry and transcriptomic analyses were employed to address these issues. The levels of the key proteins involved in the studied processes, before and after specific treatment, were assessed. We have also analyzed transcripts whose levels were significantly altered in MPS cells. We identified genes whose expressions were changed in the majority of MPS types and those with particularly highly altered expression. For the first time, significant changes in the expression of genes involved in the actin cytoskeleton structure/functions were revealed which may be considered as an additional element in the pathogenesis of MPSs. Our results suggest the possibility of using the actin cytoskeleton as a potential target in therapeutic approaches for this disease.

Intraparenchymal convection enhanced delivery of AAV in sheep to treat Mucopolysaccharidosis IIIC.

BACKGROUND: Mucopolysaccharidosis IIIC (MPSIIIC) is one of four Sanfilippo diseases sharing clinical symptoms of severe cognitive decline and shortened lifespan. The missing enzyme, heparan sulfate acetyl-CoA: α-glucosaminide-N-acetyltransferase (HGSNAT), is bound to the lysosomal membrane, therefore cannot cross the blood-brain barrier or diffuse between cells. We previously demonstrated disease correction in MPSIIIC mice using an Adeno-Associated Vector (AAV) delivering HGSNAT via intraparenchymal brain injections using an AAV2 derived AAV-truetype (AAV-TT) serotype with improved distribution over AAV9. METHODS: Here, intraparenchymal AAV was delivered in sheep using catheters or Hamilton syringes, placed using Brainlab cranial navigation for convection enhanced delivery, to reduce proximal vector expression and improve spread. RESULTS: Hamilton syringes gave improved AAV-GFP distribution, despite lower vector doses and titres. AAV-TT-GFP displayed moderately better transduction compared to AAV9-GFP but both serotypes almost exclusively transduced neurons. Functional HGSNAT enzyme was detected in 24-37% of a 140g gyrencephalic sheep brain using AAV9-HGSNAT with three injections in one hemisphere. CONCLUSIONS: Despite variabilities in volume and titre, catheter design may be critical for efficient brain delivery. These data help inform a clinical trial for MPSIIIC.

Changes in Corneal Clouding Over Time in Patients With Mucopolysaccharidosis.

PURPOSE: Mucopolysaccharidoses (MPSs) are a rare group of lysosomal storage disorders characterized by the accumulation of incompletely degraded glycosaminoglycans (GAGs) in multiple organ systems, including the eye. Visual loss occurs in MPS predominantly due to corneal clouding. Despite the success of enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) in improving many systemic manifestations of MPS, less is known about their effect on corneal clouding. This study prospectively analyses the effect of both ERT and HSCT on corneal clouding using objective measures over time. METHODS: This is a prospective longitudinal observational study. Corneal clouding was assessed in each participant using slitlamp, digital slit-lamp photographs, and an iris camera (Corneal Opacification Measure [COM] and the Pentacam system). RESULTS: Data were collected for 65 participants: 39 MPS I (Hurler), 5 MPS II (Hunter), 12 MPS IV (Morquio), and 9 MPS VI (Maroteaux-Lamy). Follow-up data are available for 45 participants (29 MPS I, 3 MPS II, 6 MPS IV, and 7 MPS VI). CONCLUSIONS: This study found corneal clouding to be stable in most participants with MPS I, II, IV, and VI over a follow-up period of 5 to 75 months (median of 30 months) when measured with clinical corneal grading systems, graded digital slit-lamp images, and iris camera COMs. For those with Pentacam densitometry measures, there was a progression of corneal clouding, on average, in those with MPS I and MPS VI. There was no apparent difference in progression of corneal clouding between patients who were on ERT, HSCT, or no treatment.

Persistent bone and joint disease despite current treatments for mucopolysaccharidosis types I, II, and VI: Data from a 10-year prospective study.

The mucopolysaccharidosis (MPS) disorders have many potential new therapies on the horizon. Thus, historic control data on disease progression and variability are urgently needed. We conducted a 10-year prospective observational study of 55 children with MPS IH (N = 23), MPS IA (N = 10), non-neuronopathic MPS II (N = 13), and MPS VI (N = 9) to systematically evaluate bone and joint disease. Annual measurements included height, weight, and goniometry. Mixed effects modeling was used to evaluate changes over time. All participants had been treated with hematopoietic cell transplantation and/or enzyme replacement therapy. Height z-score decreased over time in MPS IH, MPS II, and MPS VI, but not MPS IA. Adult heights were 136 ± 10 cm in MPS IH, 161 ± 11 cm in MPS IA, 161 ± 14 cm in MPS II, and 128 ± 15 cm in MPS VI. Adult average BMI percentiles were high: 75 ± 30%ile in MPS IH, 71 ± 37%ile in MPS IA, 71 ± 25%ile in MPS II, and 60 ± 42%ile in MPS VI. Every participant had joint contractures of the shoulders, elbows, hips, and/or knees. Joint contractures remained stable over time. In conclusion, despite current treatments for MPS I, II, and VI, short stature and joint contractures persist. The elevation in average BMI may be related, in part, to physical inactivity due to the ongoing bone and joint disease. Data from this longitudinal historical control study may be used to expedite testing of experimental bone and joint directed therapies and to highlight the need for weight management as part of routine clinical care for patients with MPS.

Neuropsychology assessment and outcomes in adult mucopolysaccharidosis - A systematic review as the first step to service development in a large tertiary Lysosomal Storage Disorders centre.

A systematic review of Randomised Controlled Trials in adult mucopolysaccharidoses (MPSs) was conducted to inform neuropsychology service development at a large tertiary Lysosomal Storage Diseases centre. Studies including psychological endpoints for cognition, mood, and quality of life were reviewed. Forty-eight studies met the inclusion criteria for full text review. Of the 48 studies, 44% (21/48) included adult participants, while psychological endpoints were used in 52% (25/48) for cognition, 11% (5/48) for mood, and 69% (33/48) for quality of life. Five studies included both adult participants and relevant psychological endpoints. Risk of bias ratings were 'high' for two studies, while two studies received a rating of 'some concerns', and the last study a 'low' risk of bias rating. The evidence base for psychological outcomes in adult MPS disorders is limited and insufficient for guiding neuropsychology service development. Data on the psychosocial effects of MPS across the lifespan will be crucial for planning service development and supporting the neuropsychological needs of adult patients and their families.

[Inborn error of metabolism and allogenic hematopoietic cell transplantation: Guidelines from the SFGM-TC]. / Maladie héréditaire du métabolisme et allogreffe de cellules souches hématopoïétiques : indication, modalité et suivi. Recommandations de la SFGM-TC.

Inherited Metabolic Diseases (IMD) are rare genetic diseases, including both lysosomal and peroxisomal diseases. Lysosomal diseases are related to the deficiency of one or more lysosomal enzymes or transporter. Lysosomal diseases are progressive and involve several tissues with most often neurological damage. Among peroxisomal diseases, X-linked adrenoleukodystrophy (ALD) is a neurodegenerative disease combining neurological and adrenal damage. For these diseases, enzyme replacement therapy (ERT), allogeneic hematopoietic cell transplantation (allo-HCT) and gene therapy represent various possible treatment options, used alone or in combination. The purpose of this workshop is to describe the indications, modalities, and follow-up of allo-HCT as well as the use of ERT peri-transplant. All indications for transplant in these rare diseases are associated with comorbidities and are subject to criteria that must be discussed in a dedicated national multidisciplinary consultation meeting. There are some consensual indications in type I-H mucopolysaccharidosis (MPS-IH) and in the cerebral form of ALD. For other IMDs, no clear benefit from the transplant has been demonstrated. The ideal donor is a non-heterozygous HLA-identical sibling. The recommended conditioning is myeloablative combining fludarabine and busulfan. In MPS-IH, ERT has to be started at diagnosis and continued until complete chimerism and normal enzyme assay are achieved. The pre-transplant assessment and post-transplant follow-up are made according to the published recommendations (PNDS). Standard follow-up is carried out jointly by the transplant and referral teams.

Current and new therapies for mucopolysaccharidoses.

The mucopolysaccharidoses (MPSs) are a subset of lysosomal storage diseases caused by deficiencies in the enzymes required to metabolize glycosaminoglycans (GAGs), a group of extracellular heteropolysaccharides that play diverse roles in human physiology. As a result, GAGs accumulate in multiple tissues, and affected patients typically develop progressive, multi-systemic symptoms in early childhood. Over the last 30 years, the treatments available for the MPSs have evolved tremendously. There are now multiple therapies that delay the progression of these debilitating disorders, although their effectiveness varies according to MPS sub-type. In this review, we discuss the basic principle underlying MPS treatment (enzymatic "cross correction"), and we review the three general modalities currently available: hematopoietic stem cell transplantation, enzymatic replacement, and gene therapy. For each treatment type, we discuss its effectiveness across the MPS subtypes, its inherent risks, and future directions. Long term, we suspect that treatment for the MPSs will continue to evolve, and through a combination of early diagnosis and effective management, these patients will continue to live longer lives with improved outcomes for quality of life.

Gene editing strategies to treat lysosomal disorders: The example of mucopolysaccharidoses.

Lysosomal storage disorders are a group of progressive multisystemic hereditary diseases with a combined incidence of 1:4,800. Here we review the clinical and molecular characteristics of these diseases, with a special focus on Mucopolysaccharidoses, caused primarily by the lysosomal storage of glycosaminoglycans. Different gene editing techniques can be used to ameliorate their symptoms, using both viral and nonviral delivery methods. Whereas these are still being tested in animal models, early results of phase I/II clinical trials of gene therapy show how this technology may impact the future treatment of these diseases. Hurdles related to specific hard-to-reach organs, such as the central nervous system, heart, joints, and the eye must be tackled. Finally, the regulatory framework necessary to advance into clinical practice is also discussed.

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.

Delivery and assessment of a CRISPR/nCas9-based genome editing system on in vitro models of mucopolysaccharidoses IVA assisted by magnetite-based nanoparticles.

Mucopolysaccharidosis IV A (MPS IVA) is a lysosomal disorder caused by mutations in the GALNS gene. Consequently, the glycosaminoglycans (GAGs) keratan sulfate and chondroitin 6-sulfate accumulate in the lysosomal lumen. Although enzyme replacement therapy has shown essential advantages for the patients, several challenges remain to overcome, such as the limited impact on the bone lesion and recovery of oxidative profile. Recently, we validated a CRISPR/nCas9-based gene therapy with promising results in an in vitro MPS IVA model. In this study, we have expanded the use of this CRISPR/nCas9 system to several MPS IVA fibroblasts carrying different GALNS mutations. Considering the latent need to develop more safety vectors for gene therapy, we co-delivered the CRISPR/nCas9 system with a novel non-viral vector based on magnetoliposomes (MLPs). We found that the CRISPR/nCas9 treatment led to an increase in enzyme activity between 5 and 88% of wild-type levels, as well as a reduction in GAGs accumulation, lysosomal mass, and mitochondrial-dependent oxidative stress, in a mutation-dependent manner. Noteworthy, MLPs allowed to obtain similar results to those observed with the conventional transfection agent lipofectamine. Overall, these results confirmed the potential of CRISPR/nCas9 as a genome editing tool for treating MPS IVA. We also demonstrated the potential use of MLPs as a novel delivery system for CRISPR/nCas9-based therapies.

Cell cycle disturbances in mucopolysaccharidoses: Transcriptomic and experimental studies on cellular models.

Mucopolysaccharidoses (MPS) are a group of lysosomal storage diseases caused by defects in genes coding for proteins involved in degradation of glycosaminoglycans (GAGs). These complex carbohydrates accumulate in cells causing their serious dysfunctions. Apart from the physical GAG storage, secondary and tertiary changes may contribute significantly to the pathomechanism of the disease. Among processes which were not systematically investigated in MPS cells to date there is the cell cycle. Here, we studied perturbances in this crucial cellular process in majority of MPS types. Transcriptomic analyses indicated that expression of many genes coding for proteins involved in the cell cycle is dysregulated in all tested MPS cells. Importantly, levels of transcripts of particular genes were changed in the same manner (i.e. either up- or down-regulated) in most or all types of the disease, indicating a common mechanism of the dysregulation. Flow cytometric studies demonstrated that the cell cycle is disturbed in all MPS types, with increased fractions of cells in the G0/G1 phase in most types and decreased fractions of cells in the G2/M phase in all types. We found that increased levels of cyclin D1 and disturbed timing of its appearance during the cell cycle may contribute to the mechanism of dysregulation of this process in MPS. Reduction of GAG levels by either a specific enzyme or genistein-mediated inhibition of synthesis of these compounds improved, but not fully corrected, the cell cycle in MPS fibroblasts. Therefore, it is suggested that combination of the therapeutic approaches devoted to reduction of GAG levels with cyclin D1 inhibitors might be considered in further works on developing effective treatment procedures for MPS.

Mucopolysaccharidosis: A broad review.

Mucopolysaccharidosis (MPS) is a group of genetic disorders with seven types and 13 subgroups which are characterized by an inherent deficiency of the enzymes responsible for the degradation of glycosaminoglycans (GAGs). Defective breakdown of GAG products leads to their widespread accumulation within the lysosomes of various organs involving the eye, central nervous system, skeletal, ocular, nervous, respiratory, cardiac, and the gastrointestinal systems. Clinical spectrum varies from mild systemic and ocular abnormalities with a normal life span to severe phenotype, fatal in the first few months of life. Visual disability due to corneal clouding, retinopathy, and optic nerve involvement causes additional impairment of physical and cognitive functions. Treatment modalities such as bone marrow transplantation and enzyme replacement therapies help in increasing the life span as well as the quality of life of the affected patients. For patients with significant corneal clouding, keratoplasty is the answer. The decision to proceed with keratoplasty is governed by various factors such as the motivation of the patient and his family, other systemic affections and anesthesia concerns. A detailed preoperative counseling should be done regarding the expected visual outcomes in the presence of other ocular comorbidities and the postoperative complication such as graft re-opacification, rejection and glaucoma. Future treatment options such as targeted gene therapy and substrate reduction therapy hold promise to reverse corneal clouding, thereby obviating the need for corneal transplantation. These treatment therapies are still in the experimental stages and human trials are needed to validate their outcomes.

Ex Vivo and In Vivo Gene Therapy for Mucopolysaccharidoses: State of the Art.

Enzyme replacement therapy (ERT) and allogeneic hematopoietic stem cell transplantation (HSCT) are standard treatments for some mucopolysaccharidoses. Nevertheless, ERT is not curative, and HSCT is associated with significant mortality and morbidity, leaving a substantial disease burden of brain and skeletal manifestations. To overcome these limitations, different gene therapy (GT) strategies are under preclinical and clinical development. Data from ex-vivo GT clinical trials have demonstrated encouraging biochemical and early clinical outcomes. In-vivo GT, based on local brain delivery or systemic intravenous injections, resulted in biochemical and clinical stabilization of the disease.

Limited diagnostic facilities impeding the therapeutic approach of Mucopolysaccharidosis in Bangladesh: a case report.

In resource-constrained settings, mucopolysaccharidosis (MPS) is a rare hereditary metabolic illness that frequently remains undiagnosed. We present a scenario that illustrates the challenges in diagnosing and managing MPS because of test inaccessibility, and we propose potential approaches to minimize the hurdles. We recommend that physicians anticipate a rare genetic disease, such as MPS, based on the clinical history findings from routine radiological investigations. Additionally, stakeholders should perform risk stratification and implement screening tests as soon as possible to ensure that patients are effectively enrolled in treatment programs.

The landscape of Mucopolysaccharidosis in Southern and Eastern European countries: a survey from 19 specialistic centers.

BACKGROUND: Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by defects in genes coding for different lysosomal enzymes which degrade glycosaminoglycans. Impaired lysosomal degradation causes cell dysfunction leading to progressive multiorgan involvement, disabling consequences and poor life expectancy. Enzyme replacement therapy (ERT) is now available for most MPS types, offering beneficial effects on disease progression and improving quality of life of patients. The landscape of MPS in Europe is not completely described and studies on availability of treatment show that ERT is not adequately implemented, particularly in Southern and Eastern Europe. In this study we performed a survey analysis in main specialist centers in Southern and Eastern European countries, to outline the picture of disease management in the region and understand ERT implementation. Since the considerable number of MPS IVA patients in the region, particularly adults, the study mainly focused on MPS IVA management and treatment. RESULTS: 19 experts from 14 Southern and Eastern European countries in total responded to the survey. Results outlined a picture of MPS management in the region, with a high number of MPS patients managed in the centers and a high level of care. MPS II was the most prevalent followed by MPS IVA, with a particular high number of adult patients. The study particularly focused on management and treatment of MPS IVA patients. Adherence to current European Guidelines for follow-up of MPS IVA patients is generally adequate, although some important assessments are reported as difficult due to the lack of MPS skilled specialists. Availability of ERT in Southern and Eastern European countries is generally in line with other European regions, even though regulatory, organizational and reimbursement constrains are demanding. CONCLUSIONS: The landscape of MPS in Southern and Eastern European countries is generally comparable to that of other European regions, regarding epidemiology, treatment accessibility and follow up difficulties. However, issues limiting ERT availability and reimbursement should be simplified, to start treatment as early as possible and make it available for more patients. Besides, educational programs dedicated to specialists should be implemented, particularly for pediatricians, clinical geneticists, surgeons, anesthesiologists and neurologists.

Damage of the cardiovascular system in lysosomal storage disease - mucopolysaccharidosis.

The analysis of literature data reflecting the issues of the pathology of the cardiovascular system in mucopolysaccharidosis are presented. It was found out that heart and vessels damage is one of the cardinal signs of this pathology, often leading to death. Cardiac pathology is recorded in all types of mucopolysaccharidosis, but it is most significant for patients with three clinical variants of Hurler syndrome, Hunter, and Maroteaux-Lamy syndromes. Typical signs of damage to the cardiovascular system in mucopolysaccharidosis are thickening of the valves with the development of their dysfunction (while the severity of damage to the left-sided valves is more pronounced), myocardial hypertrophy, conduction disturbance, coronary artery disease, arterial hypertension. Many researchers emphasize the difficulties of clinical and functional examination of the cardiovascular system in patients with mucopolysaccharidosis, which is due to the presence of physical and intellectual limitations in patients, ands a gradual increase in symptoms. For the treatment of cardiovascular pathology at mucopolysaccharidosis, medical and surgical methods are used, including enzyme replacement therapy and stem cell transplantation.