Clinical course of sly syndrome (mucopolysaccharidosis type VII)

Advanced piperazine-containing inhibitors target microbial β-glucuronidases linked to gut toxicity

The gut microbiome plays critical roles in human homeostasis, disease progression, and pharmacological efficacy through diverse metabolic pathways. Gut bacterial β-glucuronidase (GUS) enzymes reverse host phase 2 metabolism, in turn releasing active hormones and drugs that can be reabsorbed into systemic circulation to affect homeostasis and promote toxic side effects. The FMN-binding and loop 1 gut microbial GUS proteins have been shown to drive drug and toxin reactivation. Here we report the structure-activity relationships of two selective piperazine-containing bacterial GUS inhibitors. We explore the potency and mechanism of action of novel compounds using purified GUS enzymes and co-crystal structures. Our results establish the importance of the piperazine nitrogen placement and nucleophilicity as well as the presence of a cyclohexyl moiety appended to the aromatic core. Using these insights, we synthesized an improved microbial GUS inhibitor, UNC10206581, that potently inhibits both the FMN-binding and loop 1 GUS enzymes in the human gut microbiome, does not inhibit bovine GUS, and is non-toxic within a relevant dosing range. Kinetic analyses demonstrate that UNC10206581 undergoes a slow-binding and substrate-dependent mechanism of inhibition similar to that of the parent scaffolds. Finally, we show that UNC10206581 displays potent activity within the physiologically relevant systems of microbial cultures and human fecal protein lysates examined by metagenomic and metaproteomic methods. Together, these results highlight the discovery of more effective bacterial GUS inhibitors for the alleviation of microbe-mediated homeostatic dysregulation and drug toxicities and potential therapeutic development.

Hematopoietic Stem Cell Transplantation for Storage Disorders: Present Status

Storage disorders are a group of inborn errors of metabolism caused by the defective activity of lysosomal enzymes or transporters. All of these disorders have multisystem involvement with variable degrees of neurological features. Neurological manifestations are one of the most difficult aspects of treatment concerning these diseases. The available treatment modalities for some of these disorders include enzyme replacement therapy, substrate reduction therapy, hematopoietic stem cell transplantation (HSCT) and the upcoming gene therapies. As a one-time intervention, the economic feasibility of HSCT makes it an attractive option for treating these disorders, especially in lower and middle-income countries. Further, improvements in peri-transplantation medical care, better conditioning regimens and better supportive care have improved the outcomes of patients undergoing HSCT. In this review, we discuss the current evidence for HSCT in various storage disorders and its suitability as a mode of therapy for the developing world.

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.

Disease characteristics, effectiveness, and safety of vestronidase alfa for the treatment of patients with mucopolysaccharidosis VII in a novel, longitudinal, multicenter disease monitoring program

BACKGROUND

Mucopolysaccharidosis VII (MPS VII) is an ultra-rare, autosomal recessive, debilitating, progressive lysosomal storage disease caused by reduced activity of β-glucuronidase (GUS) enzyme. Vestronidase alfa (recombinant human GUS) intravenous enzyme replacement therapy is an approved treatment for patients with MPS VII.

METHODS

This disease monitoring program (DMP) is an ongoing, multicenter observational study collecting standardized real-world data from patients with MPS VII (N ≈ 50 planned) treated with vestronidase alfa or any other management approach. Data are monitored and recorded in compliance with Good Clinical Practice guidelines and planned interim analyses of captured data are performed annually. Here we summarize the safety and efficacy outcomes as of 17 November 2022.

RESULTS

As of the data cutoff date, 35 patients were enrolled: 28 in the Treated Group and seven in the Untreated Group. Mean (SD) age at MPS VII diagnosis was 4.5 (4.0) years (range, 0.0 to 12.4 years), and mean (SD) age at DMP enrollment was 13.9 (11.1) years (range, 1.5 to 50.2 years). Ten patients (29%) had a history of nonimmune hydrops fetalis. In the 23 patients who initiated treatment prior to DMP enrollment, substantial changes in mean excretion from initial baseline to DMP enrollment were observed for the three urinary glycosaminoglycans (uGAGs): dermatan sulfate (DS), -84%; chondroitin sulfate (CS), -55%; heparan sulfate (HS), -42%. Also in this group, mean reduction from initial baseline to months 6, 12, and 24 were maintained for uGAG DS (-84%, -87%, -89%, respectively), CS (-70%, -71%, -76%, respectively), and HS (+ 3%, -32%, and - 41%, respectively). All adverse events (AEs) were consistent with the known vestronidase alfa safety profile. No patients discontinued vestronidase alfa. One patient died.

CONCLUSIONS

To date, the DMP has collected invaluable MPS VII disease characteristic data. The benefit-risk profile of vestronidase alfa remains unchanged and favorable for its use in the treatment of pediatric and adult patients with MPS VII. Reductions in DS and CS uGAG demonstrate effectiveness of vestronidase alfa to Month 24. Enrollment is ongoing.

Humanistic burden of mucopolysaccharidoses: a systematic literature review

OBJECTIVE

To systematically review the literature and summarize the health-related quality-of-life (HRQoL) of patients undergoing treatment for mucopolysaccharidoses (MPS), a rare, hereditary lysosomal storage disorder.

METHODS

A systematic review was performed in accordance with PRISMA guidelines to identify research studies that describe the humanistic burden of MPS. A comprehensive literature search was conducted in EMBASE, MEDLINE, and eligible conferences were screened to include applicable abstracts.

RESULTS

Of 870 identified articles, 15 studies reported the HRQoL burden of patients with MPS undergoing or with a history of ERT and/or HSCT. These studies include patients of MPS I (n = 2), MPS II (n = 4), MPS IV (n = 6), MPS VI (n = 1), and subtype not mentioned (n = 2). Although the quality-of-life of MPS patients is influenced by time of diagnosis, pain, cognitive involvement, severity of disease, mobility, dependence, and time of treatment initiation, the HRQoL scores of MPS patients across all the scales were below the median reference population scores across all dimensions. This is seen in comparison to healthy participants but also in comparison to patients with other chronic illnesses. The multi-organ involvement, neurological impairment, pain, and morbidity associated with the condition not only affects activity of daily living but also affects social functioning, emotional status, employment status among adults, and school functioning among children.

CONCLUSIONS

This systematic literature review revealed the substantial humanistic burden of individuals affected by MPS as well as caregivers. Significant variation in HRQoL scores was observed, however studies indicate that the quality-of-life of MPS patients is influenced primarily by severity of disease (MPS type and phenotype), and then by time of diagnosis, pain, cognitive involvement, mobility, dependence, and time of treatment initiation. Further studies are needed to assess the global humanistic burden of MPS, particularly in MPS III, VI, VII, and IX subtypes, in adults, and for a longer follow-up period. Considering the vast array of HRQoL assessment tools available and used in this study, researchers should also consider using scales with condition-specific measures to ensure appropriate estimates of effectiveness.

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.

Self-complementary AAV vector therapy for treating corneal cloudiness of mucopolysaccharidosis type VII (MPS VII)

PURPOSE

To design a novel efficacious scAAV-Gusb viral vector for treating Mucopolysaccharidosis Type VII (MPS VII) caused by a mutation in the β-Glu gene (Gusb allele).

METHODS

β-Glu expression of single-stranded AAV-Gusb (ssAAV-Gusb) and self-complementary AAV (scAAV-Gusb) vectors are tested with cultured murine Gusb fibroblasts. The scAAV-Gusb vector was chosen in further studies to prolong the life span and treat corneal pathology of Gusb mice via intrahepatic injection of neonates and intrastromal injection in adults, respectively. Corneal pathology was studied using HRT2 in vivo confocal microscope and histochemistry in mice corneas.

RESULTS

Both ssAAV-Gusb and scAAV-Gusb vectors expressed murine β-Glu in cultured Gusb fibroblasts. The scAAV-Gusb vector had higher transduction efficiency than the ssAAV-Gusb vector. To prolong the life span of Gusb mice, neonates (3 days old) were administered with scAAV-Gusb virus via intrahepatic injection. The treatment improves the survival rate of Gusb mice, prolonging the median survival rate from 22.5 weeks (untreated) to 50 weeks (treated). Thereafter, we determined the efficacy of the scAAV-Gusb virus in ameliorating corneal cloudiness observed in aged Gusb mice. Both corneal cloudiness and stroma thickness decreased, and there was the presence of β-Glu enzyme activity in the Gusb corneas receiving scAAV-Gusb virus associated with morphology change of amoeboid stromal cells in untreated to characteristic dendritic keratocytes morphology after 4-12 weeks of scAAV-Gusb virus injection.

CONCLUSION

Intrahepatic injection of scAAV-Gusb is efficacious in prolonging the life span of Gusb mice, and intrastromal injection can ameliorate corneal phenotypes. Both strategies can be adapted for treating other MPS.

Comparative dose effectiveness of intravenous and intrathecal AAV9.CB7.hIDS, RGX-121, in mucopolysaccharidosis type II mice

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal disease caused by iduronate-2-sulfatase (IDS) deficiency, leading to accumulation of glycosaminoglycans (GAGs) and the emergence of progressive disease. Enzyme replacement therapy is the only currently approved treatment, but it leaves neurological disease unaddressed. Cerebrospinal fluid (CSF)-directed administration of AAV9.CB7.hIDS (RGX-121) is an alternative treatment strategy, but it is unknown if this approach will affect both neurologic and systemic manifestations. We compared the effectiveness of intrathecal (i.t.) and intravenous (i.v.) routes of administration (ROAs) at a range of vector doses in a mouse model of MPS II. While lower doses were completely ineffective, a total dose of 1 × 109 gc resulted in appreciable IDS activity levels in plasma but not tissues. Total doses of 1 × 1010 and 1 × 1011 gc by either ROA resulted in supraphysiological plasma IDS activity, substantial IDS activity levels and GAG reduction in nearly all tissues, and normalized zygomatic arch diameter. In the brain, a dose of 1 × 1011 gc i.t. achieved the highest IDS activity levels and the greatest reduction in GAG content, and it prevented neurocognitive deficiency. We conclude that a dose of 1 × 1010 gc normalized metabolic and skeletal outcomes, while neurologic improvement required a dose of 1 × 1011 gc, thereby suggesting the prospect of a similar direct benefit in humans.

A de novo homozygous missense mutation of the GUSB gene leads to mucopolysaccharidosis type VII identification in a family with twice adverse pregnancy outcomes due to non-immune hydrops fetalis

Non-immune hydrops fetalis (NIHF) is a common and severe manifestation of many genetic disorders. The ultrasound is an ideal method for diagnosing hydrops fetalis during pregnancy. Since most NIHFs do not have an identifiable cause, determining the underlying etiology remains a challenge for prenatal counseling. Due to advancements in exome sequencing, the diagnostic rates of NIHF have recently increased. As reported here, DNA was extracted from the amniotic fluid of a pregnant woman who was prenatally diagnosed with a NIHF type of unclear origin. Amniocentesis sampling demonstrated a normal female karyotype and copy number variation(CNVs) without alterations. Tri-whole exome sequencing (WES) was conducted to identify possible causative variants. In the fetus, a de novo genetic mutation was identified as a homozygous form. The mutation was located on the glucuronidase beta (GUSB) gene: NM_000181.3: c.1324G > A; p. Ala442Thr; Chr7:65439349, which leads to mucopolysaccharidosis type VII. This mutation was inherited from the parents and was first reported to be related to NIHF. We conclude that the use of WES is beneficial for NIHF cases whose prognosis has not been explained by standard genetic testing.

Mucopolysaccharidosis type VII (Sly syndrome) - What do we know?

Mucopolysaccharidosis type VII (MPS VII) is an ultra-rare, life-threatening, progressive disease caused by genetic mutations that affect lysosomal storage/function. MPS VII has an estimated prevalence of <1:1,000,000 and accounts for <3% of all MPS diagnoses. Given the rarity of MPS VII, comprehensive information on the disease is limited and we present a review of the current understanding. In MPS VII, intracellular glycosaminoglycans accumulate due to a deficiency in the lysosomal enzyme that is responsible for their degradation, β-glucuronidase, which is encoded by the GUSB gene. MPS VII has a heterogeneous presentation. Features can manifest across multiple systems and can vary in severity, age of onset and progression. The single most distinguishing clinical feature of MPS VII is non-immune hydrops fetalis (NIHF), which presents during pregnancy. MPS VII usually presents within one month of life and become more prominent at 3 to 4 years of age; key features are skeletal deformities, hepatosplenomegaly, coarse facies, and cognitive impairment, although phenotypic variation is a hallmark. Current treatments include hematopoietic stem cell transplantation and enzyme replacement therapy with vestronidase alfa. Care should be individualized for each patient. Development of consensus guidelines for MPS VII management and treatment is needed, as consolidation of expert knowledge and experience (for example, through the MPS VII Disease Monitoring Program) may provide a significant positive impact to patients.

Growth patterns in patients with mucopolysaccharidosis VII

Objective

This study assessed growth patterns in patients with mucopolysaccharidosis (MPS) VII before enzyme replacement therapy.

Methods

Height, weight, and body mass index (BMI) measurements and Z-scores from patients from three clinical studies were compared with those from CDC healthy population growth charts. Relationships with age/sex and history of non-immune hydrops fetalis (NIHF) were assessed by linear regression and ANOVA, respectively.

Results

Among 20 enrolled patients with MPS VII, height Z-scores were near normal until 1 year of age but declined thereafter, particularly among males. There was no consistent pattern in weight Z-score. BMI Z-scores were above normal and increased slightly with age among males and were slightly below normal among females. Male patients with a history of NIHF had greater declines in height and weight Z-scores over time versus males without history of NIHF. There was no clear effect of NIHF history on height and weight Z-scores in female patients.

Conclusions

In patients with MPS VII, declines in height Z-score began early in life, particularly among males, while changes in BMI varied by sex. Patients with MPS VII and a history of NIHF had greater declines in height Z-score with age than did patients without a history of NIHF.Clinical trial registration: This retrospective analysis included patients enrolled in an open-label phase 2 study (UX003-CL203; ClinicalTrials.gov, NCT02418455), a randomized, placebo-controlled, blind-start phase 3 study (UX003-CL301; ClinicalTrials.gov, NCT02230566), or its open-label, long-term extension (UX003-CL202; ClinicalTrials.gov, NCT02432144). Requests for individual de-identified participant data and the clinical study report from this study are available to researchers providing a methodologically sound proposal that is in accordance with the Ultragenyx data sharing commitment. To gain access, data requestors will need to sign a data access and use agreement. Data will be shared via secured portal. The study protocol and statistical analysis plan for this study are available on the relevant clinical trial registry websites with the tabulated results.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Meaningful changes for efficacy outcomes in patients with chronic rhinosinusitis with nasal polyps

Objective

Nasal Polyp Score (NPS) and Nasal Congestion Score (NCS) are commonly used clinical trial endpoints to determine improvements in response to treatment in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). However, limited information is available on within-patient meaningful change thresholds (MCTs) and between-group minimal important differences (MIDs) for NPS and NCS, which would aid interpretation of results.

Methods

Data from phase 3 placebo-controlled trials of omalizumab in patients with CRSwNP (POLYP 1 and POLYP 2) were used to estimate MCTs and MIDs for both NPS and NCS using anchor-based methods. Sino-Nasal Outcome Test-22 (SNOT-22) and SNOT-22 Sino-Nasal Symptoms Subscale (SNSS) scores were used as anchors (≥0.35 correlation with NPS and NCS). Within- and between-group differences in NPS and NCS change scores were used to estimate MCTs and MIDs, respectively. Identified MCTs were used in unblinded responder analyses to compare the proportions of patients per treatment group achieving a meaningful improvement.

Results

MCTs and MIDs were estimated at -1.0 and -0.5 for NPS and -0.50 and -0.35 for NCS, respectively, and were consistent across studies. Overall, 57.0% of patients achieved the MCT in NPS with omalizumab vs 29.9% with placebo (p < 0.0001). Similarly, 58.9% of patients achieved the MCT in NCS with omalizumab vs 30.7% with placebo (p < 0.0001). Group differences in mean change were statistically significant and exceeded the estimated MIDs.

Conclusions

Meaningful change estimates for NPS and NCS could be used to assess response to treatment for patients with chronic rhinosinusitis with nasal polyps.Trial registration: POLYP1: clinicaltrails.gov NCT03280550; registered September 12, 2017; https://clinicaltrials.gov/ct2/show/NCT03280550). POLYP2 (clinicaltrials.gov NCT03280537; registered September 12, 2017; https://clinicaltrials.gov/ct2/show/NCT03280537).

Neurological Disease Modeling Using Pluripotent and Multipotent Stem Cells: A Key Step towards Understanding and Treating Mucopolysaccharidoses

Despite extensive research, the links between the accumulation of glycosaminoglycans (GAGs) and the clinical features seen in patients suffering from various forms of mucopolysaccharidoses (MPSs) have yet to be further elucidated. This is particularly true for the neuropathology of these disorders; the neurological symptoms are currently incurable, even in the cases where a disease-specific therapeutic approach does exist. One of the best ways to get insights on the molecular mechanisms driving that pathogenesis is the analysis of patient-derived cells. Yet, not every patient-derived cell recapitulates relevant disease features. For the neuronopathic forms of MPSs, for example, this is particularly evident because of the obvious inability to access live neurons. This scenario changed significantly with the advent of induced pluripotent stem cell (iPSC) technologies. From then on, a series of differentiation protocols to generate neurons from iPSC was developed and extensively used for disease modeling. Currently, human iPSC and iPSC-derived cell models have been generated for several MPSs and numerous lessons were learnt from their analysis. Here we review most of those studies, not only listing the currently available MPS iPSC lines and their derived models, but also summarizing how they were generated and the major information different groups have gathered from their analyses. Finally, and taking into account that iPSC generation is a laborious/expensive protocol that holds significant limitations, we also hypothesize on a tempting alternative to establish MPS patient-derived neuronal cells in a much more expedite way, by taking advantage of the existence of a population of multipotent stem cells in human dental pulp to establish mixed neuronal and glial cultures.

Dose-dependent effects of enzyme replacement therapy on skeletal disease progression in mucopolysaccharidosis VII dogs

Mucopolysaccharidosis (MPS) VII is an inherited lysosomal storage disorder characterized by deficient activity of the enzyme β-glucuronidase. Skeletal abnormalities are common in patients and result in diminished quality of life. Enzyme replacement therapy (ERT) for MPS VII using recombinant human β-glucuronidase (vestronidase alfa) was recently approved for use in patients; however, to date there have been no studies evaluating therapeutic efficacy in a large animal model of MPS VII. The objective of this study was to establish the effects of intravenous ERT, administered at either the standard clinical dose (4 mg/kg) or a high dose (20 mg/kg), on skeletal disease progression in MPS VII using the naturally occurring canine model. Untreated MPS VII animals exhibited progressive synovial joint and vertebral bone disease and were no longer ambulatory by age 6 months. Standard-dose ERT-treated animals exhibited modest attenuation of joint disease, but by age 6 months were no longer ambulatory. High-dose ERT-treated animals exhibited marked attenuation of joint disease, and all were still ambulatory by age 6 months. Vertebral bone disease was recalcitrant to ERT irrespective of dose. Overall, our findings indicate that ERT administered at higher doses results in significantly improved skeletal disease outcomes in MPS VII dogs.

Synthesis of Uronic Acid 1-Azasugars as Putative Inhibitors of α-Iduronidase, β-Glucuronidase and Heparanase

1-Azasugar analogues of l-iduronic acid (l-IdoA) and d-glucuronic acid (d-GlcA) and their corresponding enantiomers have been synthesized as potential pharmacological chaperones for mucopolysaccharidosis I (MPS I), a lysosomal storage disease caused by mutations in the gene encoding α-iduronidase (IDUA). The compounds were efficiently synthesized in nine or ten steps from d- or l-arabinose, and the structures were confirmed by X-ray crystallographic analysis of key intermediates. All compounds were inactive against IDUA, although l-IdoA-configured 8 moderately inhibited β-glucuronidase (β-GLU). The d-GlcA-configured 9 was a potent inhibitor of β-GLU and a moderate inhibitor of the endo-β-glucuronidase heparanase. Co-crystallization of 9 with heparanase revealed that the endocyclic nitrogen of 9 forms close interactions with both the catalytic acid and catalytic nucleophile.

[Inborn error of metabolism and allogenic hematopoietic cell transplantation: Guidelines from the 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.

Proteomics identifies novel biomarkers of synovial joint disease in a canine model of mucopolysaccharidosis I

Mucopolysaccharidosis I is a lysosomal storage disorder characterized by deficient alpha-L-iduronidase activity, leading to abnormal accumulation of glycosaminoglycans in cells and tissues. Synovial joint disease is prevalent and significantly reduces patient quality of life. There is a critical need for improved understanding of joint disease pathophysiology in MPS I, including specific biomarkers to predict and monitor joint disease progression, and response to treatment. The objective of this study was to leverage the naturally-occurring MPS I canine model and undertake an unbiased proteomic screen to identify systemic biomarkers predictive of local joint disease in MPS I. Synovial fluid and serum samples were collected from MPS I and healthy dogs at 12 months-of-age, and protein abundance characterized using liquid chromatography tandem mass spectrometry. Stifle joints were evaluated postmortem using magnetic resonance imaging (MRI) and histology. Proteomics identified 40 proteins for which abundance was significantly correlated between serum and synovial fluid, including markers of inflammatory joint disease and lysosomal dysfunction. Elevated expression of three biomarker candidates, matrix metalloproteinase 19, inter-alpha-trypsin inhibitor heavy-chain 3 and alpha-1-microglobulin, was confirmed in MPS I cartilage, and serum abundance of these molecules was found to correlate with MRI and histological degenerative grades. The candidate biomarkers identified have the potential to improve patient care by facilitating minimally-invasive, specific assessment of joint disease progression and response to therapeutic intervention.

A Neonate with Mucopolysaccharidosis Type VII with Intractable Ascites

We report a case of a patient with severe fetal hydrops and refractory ascites, diagnosed as mucopolysaccharidosis type VII (MPS VII) by whole-exome sequencing, and discharged at 5 months of age after long-term ventilatory management. A male neonate was born by emergency cesarean section due to fetal distress at 30 ^1/7 weeks' gestation. Physical examination and X-rays revealed pleural effusion, ascites, and generalized edema, indicating severe fetal hydrops. He underwent tracheal intubation because of respiratory distress that was attributed to massive ascites, pulmonary hypoplasia, and pulmonary hypertension. He received mechanical ventilation and inhaled nitric oxide therapy. Prednisone, octreotide, and a factor XIII preparation were used as the treatment for ascites, and the ascites gradually decreased. He was extubated within 2 months of age. At 4 months of age, the results of whole-exome sequencing of the cord blood showed a compound heterozygous mutation in the GUSB gene, the gene responsible for MPS VII. Enzyme replacement therapy was initiated, and the ascites was resolved. Careful systemic management, including lung-protective respiratory management and the early establishment of nutrition, is important for the long-term survival of infants with fetal hydrops, and early aggressive workup, including whole-genome sequencing for the cause, should be performed in the case of refractory ascites.

Burden of Surgical Treatment for the Management of Cervical Myelopathy in Mucopolysaccharidoses: A Systematic Review

Mucopolysaccharidoses (MPSs) are a rare group of heterogeneous genetic and metabolic disorders, caused by loss of functions of several enzymes that are involved in glycosaminoglycan catabolism. Their progressive accumulations in cells, tissues, and consequently, organs lead to several clinical manifestations, such as musculoskeletal involvement. Indeed, the most common manifestation in the central nervous system is represented by cervical spinal stenosis due to bony alterations or dural thickening. Cervical involvement can commonly cause myelopathy and instability exerting severe symptoms. A prompt diagnosis and treatment of the aforementioned conditions is mandatory to ensure a better quality of life in patients with such debilitating disorders. Nevertheless, a clear consensus about their management (i.e., surgical or not) is still lacking, leading to an inevitable delay. This review aims to investigate and discuss the main causes of myelopathy in patients with mucopolysaccharidoses, available therapeutic strategies, and the impact and role of surgery on the neurological outcome.

Diagnosis and Emerging Treatment Strategies for Mucopolysaccharidosis VII (Sly Syndrome)

Mucopolysaccharidosis VII (MPS VII, Sly syndrome) is an ultra-rare lysosomal disease caused by a deficiency of the enzyme β-glucuronidase (GUS). The diagnosis is suspected based on a range of symptoms that are common to many other MPS types, and it is confirmed through biochemical and molecular studies. Besides supportive treatment, current and emerging treatments include enzyme replacement therapy, hematopoietic stem cell transplantation, and gene therapy. This review summarizes the clinical manifestations, diagnosis, and emerging treatments for MPS VII.

Facial features of lysosomal storage disorders

INTRODUCTION

The use of facial recognition technology has diversified the diagnostic toolbelt for clinicians and researchers for the accurate diagnoses of patients with rare and challenging disorders. Specific identifiers in patient images can be grouped using artificial intelligence to allow the recognition of diseases and syndromes with similar features. Lysosomal storage disorders are rare, and some have prominent and unique features that may be used to train the accuracy of facial recognition software algorithms. Noteworthy features of lysosomal storage disorders (LSDs) include facial features such as prominent brows, wide noses, thickened lips, mouth, and chin, resulting in coarse and rounded facial features.

AREAS COVERED

We evaluated and report the prevalence of facial phenotypes in patients with different LSDs, noting two current examples when artificial intelligence strategies have been utilized to identify distinctive facies.

EXPERT OPINION

Specific LSDs, including Gaucher disease, Mucolipidosis IV and Fabry disease have recently been distinguished using facial recognition software. Additional lysosomal disorders LSDs lysosomal storage disorders with unique and distinguishable facial features also merit evaluation using this technology. These tools may ultimately aid in the identification of specific LSDs and shorten the diagnostic odyssey for patients with these rare and under-recognized disorders.

MPS VII - Extending the classical phenotype

Mucopolysaccharidosis VII (or Sly syndrome) is an autosomal recessive disorder characterised by a deficiency in the enzyme Beta-glucuronidase (GUSB). Partial degradation of glycosaminoglycans (GAGs); chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) results in the accumulation of these fragments in the lysosomes of many tissues, eventually leading to multisystem damage. In some cases, early diagnosis on clinical grounds alone can be difficult due to the extreme variability of the clinical presentation and disease progression. We present a case report of a 31-year-old male patient diagnosed with MPS VII at the age of 28, who multiple specialists saw without suspecting the diagnosis due to the unusual presentation. The patient presented with a history of developmental delay, scoliosis, kyphosis, corneal clouding, abnormal gait, short stature, hearing impairment, slightly coarse facial features and progressive deterioration of fine motor skills since childhood. The patient had inguinal hernia repair at around 12 months, bilateral hearing impairment with a left bone-anchored hearing aid, and spinal surgery. During spinal surveillance MPS VII was suspected by a spinal surgeon with interest in MPS, and the diagnosis confirmed with a deficiency in beta-glucuronidase in leucocytes and marginally elevated urinary GAGs. Next-generation sequencing identified two mutations in the GUSB gene (OMIM 611499), c.526C > T p.(Leu176Phe) and c.1820G > C p.(Gly607Ala). Although the patient exhibited features of the severe form of non-classical manifestations, his metabolic condition has remained reasonably stable, surviving into adulthood with only symptomatic treatment. We present the ever-expanding phenotypic spectrum of this ultra-rare disease.

Misdiagnosis in mucopolysaccharidoses

Mucopolysaccharidosis (MPS) is a group of 13 hereditary metabolic diseases identified in humans (or 14 diseases if considering one MPS type described to date only in mice) in which an enzymatic defect results in the accumulation of glycosaminoglycans (GAG) in the lysosomes of cells. First of all, as a result of GAG storage, the proper functioning of the lysosome is disturbed; then, the cells, and finally, tissue, organs, and the whole organism malfunctions are observed. Due to the rarity, heterogeneity, and multi-systemic and progressive nature of MPS, they present a major diagnostic challenge. Due to the wide variation in symptoms and their similarity to other diseases, MPS is often misdiagnosed, usually as neurological diseases (like autism spectrum disorders, psychomotor hyperactivity, and intellectual disability) or rheumatology and orthopedic disorders (like juvenile idiopathic arthritis, Perthes disease, rickets, and muscular dystrophy). In this review article, we present the problems associated with the possibility of misdiagnosing MPS, discuss what diseases they can be confused with, and suggest ways to reduce these problems in the future.

Long-term efficacy and safety of vestronidase alfa enzyme replacement therapy in pediatric subjects < 5 years with mucopolysaccharidosis VII

Mucopolysaccharidosis (MPS) VII is an ultra-rare, autosomal-recessive, metabolic disease caused by a deficiency of β-glucuronidase, a lysosomal enzyme that hydrolyzes glycosaminoglycans (GAGs), including dermatan sulfate (DS), chondroitin sulfate, and heparan sulfate (HS). β-glucuronidase deficiency leads to progressive accumulation of undegraded GAGs in lysosomes of affected tissues, which may cause hydrops fetalis, short stature, hepatosplenomegaly, and cognitive impairment. An open-label, multicenter, phase II study was conducted in 8 pediatric subjects <5 years of age with MPS VII. Subjects received the recombinant human β-glucuronidase vestronidase alfa 4 mg/kg by intravenous infusion every other week for 48 weeks (treatment period). Those who completed the 48-week treatment were offered to continue treatment with vestronidase alfa 4 mg/kg for up to 240 weeks or until withdrawal of consent, discontinuation, or study termination (continuation period). The level of GAG excreted in urine (uGAG) above normal has been shown to correlate with disease severity and clinical outcomes in MPS diseases. Therefore, the primary efficacy endpoint of this study was to determine the mean percentage change in uGAG DS excretion from baseline to week 48. Statistically significant reductions in uGAG DS from baseline were observed at each visit (p < 0.0001), with a least square mean (standard error) percentage change of -60% (6.6) at week 4 (first post-baseline assessment) and -61% (6.41) at week 48 (final assessment during treatment period). Secondary efficacy endpoints included change from baseline to week 48 in growth and hepatosplenomegaly. Positive trends were observed toward increased standing height Z-score (mean [standard deviation] at baseline, -2.630 [1.17], n = 8; at week 48, -2.045 [0.27], n = 7) and growth velocity (mean [SD] Z-score at baseline, -2.59 [1.49], n = 4; at week 48, -0.39 [2.10], n = 4; p = 0.27). Hepatomegaly was resolved in 3 of 3 subjects assessed by ultrasound and in 5 of 6 subjects assessed by physical examination; splenomegaly was resolved in 1 of 3 subjects assessed by ultrasound and in 2 of 2 subjects assessed by physical examination. There were no new safety signals identified during this study. Mild-to-moderate infusion-associated reactions occurred in 4 (50%) subjects. In conclusion, long-term vestronidase alfa treatment demonstrated a rapid and sustained reduction in uGAGs, maintained growth, and improved hepatosplenomegaly in pediatric subjects with MPS VII <5 years of age. Trial registration: NCT02418455.

Splicing Modulation as a Promising Therapeutic Strategy for Lysosomal Storage Disorders: The Mucopolysaccharidoses Example

Over recent decades, the many functions of RNA have become more evident. This molecule has been recognized not only as a carrier of genetic information, but also as a specific and essential regulator of gene expression. Different RNA species have been identified and novel and exciting roles have been unveiled. Quite remarkably, this explosion of novel RNA classes has increased the possibility for new therapeutic strategies that tap into RNA biology. Most of these drugs use nucleic acid analogues and take advantage of complementary base pairing to either mimic or antagonize the function of RNAs. Among the most successful RNA-based drugs are those that act at the pre-mRNA level to modulate or correct aberrant splicing patterns, which are caused by specific pathogenic variants. This approach is particularly tempting for monogenic disorders with associated splicing defects, especially when they are highly frequent among affected patients worldwide or within a specific population. With more than 600 mutations that cause disease affecting the pre-mRNA splicing process, we consider lysosomal storage diseases (LSDs) to be perfect candidates for this type of approach. Here, we introduce the overall rationale and general mechanisms of splicing modulation approaches and highlight the currently marketed formulations, which have been developed for non-lysosomal genetic disorders. We also extensively reviewed the existing preclinical studies on the potential of this sort of therapeutic strategy to recover aberrant splicing and increase enzyme activity in our diseases of interest: the LSDs. Special attention was paid to a particular subgroup of LSDs: the mucopolysaccharidoses (MPSs). By doing this, we hoped to unveil the unique therapeutic potential of the use of this sort of approach for LSDs as a whole.

Establishment of Cutoff Values for Newborn Screening of Six Lysosomal Storage Disorders by Tandem Mass Spectrometry

Objective

Lysosomal storage disorders (LSDs) are becoming increasingly important in newborn screening, and tandem mass spectrometry (MS/MS) is widely used in newborn screening for LSDs through measurement of enzymatic activities in dried blood spots (DBSs). Overall, the determination of the cutoff value is important in such screening, and different laboratories have different methods of determining this value; most do not use a fixed cutoff value but rather calculate the corresponding batch cutoff value based on each batch of experimental data. In this study, we used MS/MS to screen for LSDs and sought to find an appropriate method to establish the cutoff value for LSD screening.

Methods

A total of 38,945 samples from newborn blood tablets collected from various maternity hospitals in six cities in Shandong province, including Jinan, Dezhou, Heze, Linyi, Weifang, and Zibo, were tested using a Waters Xevo TQD tandem mass spectrometer; the experimental data were analyzed with MassLynx V4.1. The laboratory used 30% of the median GLA enzyme activity and 20% of the median ABG, ASM, GALC, IDUA, and GAA enzyme activities in every test as the cutoff values for that batch of experiments.

Results

There were 254 suspicious positives in the initial screening test, including one case of Gaucher disease, one of Niemann-Pick disease, 47 of Krabbe disease, four of MPS-I, 21 of Fabry disease, and 180 of Pompe disease. After genetic screening, 11 children were diagnosed, including three with Pompe disease, three with Fabry disease, and five with Krabbe disease. In addition, the enzyme activity cutoff value of this experiment showed seasonal variation, which was initially believed to be related to the ambient temperature, such as the effect of ambient temperature on the human body or the temperature when the blood tablets dried naturally.

Conclusion

Overall, MS/MS can be used in LSD screening, and using different cutoff values in each batch of experiments is feasible. The ambient temperature might be a reason why the enzyme activity cutoff value has seasonal variation. More samples are needed to develop a method of determining cutoff values in laboratories.

Mesenchymal Stem Cell-Based Therapy for Lysosomal Storage Diseases and Other Neurodegenerative Disorders

Lysosomal storage diseases (LSDs) are a group of approximately 50 genetic disorders caused by mutations in genes coding enzymes that are involved in cell degradation and transferring lipids and other macromolecules. Accumulation of lipids and other macromolecules in lysosomes leads to the destruction of affected cells. Although the clinical manifestations of different LSDs vary greatly, more than half of LSDs have symptoms of central nervous system neurodegeneration, and within each disorder there is a considerable variation, ranging from severe, infantile-onset forms to attenuated adult-onset disease, sometimes with distinct clinical features. To date, treatment options for this group of diseases remain limited, which highlights the need for further development of innovative therapeutic approaches, that can not only improve the patients' quality of life, but also provide full recovery for them. In many LSDs stem cell-based therapy showed promising results in preclinical researches. This review discusses using mesenchymal stem cells for different LSDs therapy and other neurodegenerative diseases and their possible limitations.

Delineating the neuropathology of lysosomal storage diseases using patient-derived induced pluripotent stem cells

Lysosomal storage diseases (LSD) are inherited metabolic diseases caused due to deficiency of lysosomal enzymes, essential for the normal development of the brain and other organs. Approximately two-thirds of the patients suffering from LSD exhibit neurological deficits and impose an escalating challenge to the medical and scientific field. The advent of iPSC technology has aided researchers in efficiently generating functional neuronal and non-neuronal cells through directed differentiation protocols, as well as in decoding the cellular, subcellular and molecular defects associated with LSDs using two-dimensional cultures and cerebral organoid models. This review highlights the information assembled from patient-derived iPSCs on neurodevelopmental and neuropathological defects identified in LSDs. Multiple studies have identified neural progenitor cell migration and differentiation defects, substrate accumulation, axon growth and myelination defects, impaired calcium homeostasis and altered electrophysiological properties, using patient-derived iPSCs. In addition, these studies have also uncovered defective lysosomes, mitochondria, endoplasmic reticulum, Golgi complex, autophagy and vesicle trafficking and signaling pathways, oxidative stress, neuroinflammation, blood brain barrier dysfunction, neurodegeneration, gliosis, altered transcriptomes in LSDs. The review also discusses the therapeutic applications such as drug discovery, repurposing of drugs, synergistic effects of drugs, targeted molecular therapies, gene therapy, and transplantation applications of mutation corrected lines identified using patient-derived iPSCs for different LSDs.

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.

Molecular characterization of a large cohort of Mucopolysaccharidosis patients: Iran Mucopolysaccharidosis RE-diagnosis Study (IMPRESsion)

Mucopolysaccharidoses (MPSs) are rare, heterogeneous inborn errors of metabolism (IEM) diagnosed through a combination of clinical, biochemical, and genetic investigations. The aim of this study was molecular characterization of the largest cohort of Iranian MPS patients (302 patients from 289 unrelated families), along with tracking their ethnicity and geographical origins. 185/289 patients were studied using an IEM-targeted NGS panel followed by complementary Sanger sequencing, which led to the diagnosis of 154 MPS patients and 5 non-MPS IEMs (diagnostic yield: 85.9%). Furthermore, 106/289 patients who were referred with positive findings went through re-analysis and confirmatory tests which confirmed MPS diagnosis in 104. Among the total of 258 MPS patients, 225 were homozygous, 90 harbored novel variants, and 9 had copy number variations. MPS IV was the most common type (34.8%) followed by MPS I (22.7%) and MPS VI (22.5%). Geographical origin analysis unveiled a pattern of distribution for frequent variants in ARSB (c.430G>A, c.962T>C [p.Leu321Pro], c.281C>A [p.Ser94*]), GALNS (c.319G>A [p.Ala107Thr], c.860C>T [p.Ser287Leu], c.1042A>G [p.Thr348Ala]), and IDUA (c.1A>C [p.Met1Leu], c.1598C>G [p.Pro533Arg], c.1562_1563insC [p.Gly522Argfs*50]). Our extensive patient cohort reveals the genetic and geographic landscape of MPS in Iran, which provides insight into genetic epidemiology of MPS and can facilitate a more cost-effective, time-efficient diagnostic approach based on the region-specific variants. This article is protected by copyright. All rights reserved.

Targeting neurological abnormalities in lysosomal storage diseases

Central nervous system (CNS) abnormalities and corresponding neurological and psychiatric symptoms are frequently observed in lysosomal storage disorders (LSDs). The genetic background of individual LSDs is indeed unique to each illness. However, resulting defective lysosomal function within the CNS can transition normal cellular processes (i.e., autophagy) into aberrant mechanisms, facilitating overlapping downstream consequences including neurocircuitry dysfunction, neurodegeneration as well as sensory, motor, cognitive, and psychological symptoms. Here, the neurological and biobehavioral phenotypes of major classes of LSDs are discussed alongside therapeutic strategies in development that aim to tackle neuropathology among other disease elements. Finally, focused ultrasound blood-brain barrier opening is proposed to enhance therapeutic delivery thereby overcoming the key hurdle of central distribution of disease modifying therapies in LSDs.

Description of the molecular and clinical characteristics of the mucopolysaccharidosis type VII Iberian cohort

BACKGROUND

Mucopolysaccharidosis type VII (Sly syndrome) is an ultra-rare neurometabolic disorder caused by inherited deficiency of the lysosomal enzyme β-glucuronidase. Precise data regarding its epidemiology are scarce, but birth prevalence is estimated to vary from 0.02 to 0.24 per 100,000 live births. The clinical course and disease progression are widely heterogeneous, but most patients have been reported to show signs such as skeletal deformities or cognitive delay. Additionally, detection criteria are not standardized, resulting in delayed diagnosis and treatment.

METHODS

We present a cohort of 9 patients with mucopolysaccharidosis VII diagnosed in the Iberian Peninsula, either in Spain or Portugal. The diagnostic approach, genetic studies, clinical features, evolution and treatment interventions were reviewed.

RESULTS

We found that skeletal deformities, hip dysplasia, hydrops fetalis, hepatosplenomegaly, hernias, coarse features, respiratory issues, and cognitive and growth delay were the most common features identified in the cohort. In general, patients with early diagnostic confirmation who received the appropriate treatment in a timely manner presented a more favorable clinical evolution.

CONCLUSIONS

This case series report helps to improve understanding of this ultra-rare disease and allows to establish criteria for clinical suspicion or diagnosis, recommendations, and future directions for better management of patients with Sly syndrome.

The first mucopolysaccharidosis type VII in a Taiwanese girl: A case report and review of the literature

The present study included the first case of mucopolysaccharidosis (MPS) type VII in Taiwan. During pregnancy, the patient was diagnosed with hydrops fetalis and had ascites aspiration 4 times. In the following years, she presented gradually with chronic lung disease, developmental delay, short stature, dysmorphic features of coarse face, macroglossia and pigeon chest with scoliosis. Upon referral at age 4 years, she had corneal clouding, mild limitation of range of motion (ROM) and hepatosplenomegaly. X-ray showed paddle ribs and dysplastic vertebral bodies. MPS was suspected and urine glycosaminoglycans (GAGs) elevated were noted. The leukocyte enzymatic analyses for MPS I, MPS II, MPS IIIB, MPS IVA, and MPS VI were all normal. Afterward, the molecular analysis showed two heterozygous genetic variants of c.104C > A and c.1454C > T in trans in the GUSB gene (NM_000181.4) which were the causes for MPS VII. Then, we checked the leukocyte β-glucuronidase activity for MPS VII and showed extremely low, therefore confirmed the diagnosis. Clinicians should increase the awareness on the early signs of MPS to have a prompt diagnosis and offer the correct treatment like enzyme replacement therapy (ERT) as early as possible.

Progression of vertebral bone disease in mucopolysaccharidosis VII dogs from birth to skeletal maturity

Mucopolysaccharidosis (MPS) VII is a lysosomal storage disorder characterized by deficient β-glucuronidase activity, leading to accumulation of incompletely degraded heparan, dermatan and chondroitin sulfate glycosaminoglycans. Patients with MPS VII exhibit progressive spinal deformity, which decreases quality of life. Previously, we demonstrated that MPS VII dogs exhibit impaired initiation of secondary ossification in the vertebrae and long bones. The objective of this study was to build on these findings and comprehensively characterize how vertebral bone disease manifests progressively in MPS VII dogs throughout postnatal growth. Vertebrae were collected postmortem from MPS VII and healthy control dogs at seven ages ranging from 9 to 365 days. Microcomputed tomography and histology were used to characterize bone properties in primary and secondary ossification centers. Serum was analyzed for bone turnover biomarkers. Results demonstrated that not only was secondary ossification delayed in MPS VII vertebrae, but that it progressed aberrantly and was markedly diminished even at 365 days-of-age. Within primary ossification centers, bone volume fraction and bone mineral density were significantly lower in MPS VII at 180 and 365 days-of-age. MPS VII growth plates exhibited significantly lower proliferative and hypertrophic zone cellularity at 90 days-of-age, while serum bone-specific alkaline phosphatase (BAP) was significantly lower in MPS VII dogs at 180 days-of-age. Overall, these findings establish that vertebral bone formation is significantly diminished in MPS VII dogs in both primary and secondary ossification centers during postnatal growth.

THAP1 modulates oligodendrocyte maturation by regulating ECM degradation in lysosomes

Mechanisms controlling myelination during central nervous system (CNS) maturation play a pivotal role in the development and refinement of CNS circuits. The transcription factor THAP1 is essential for timing the inception of myelination during CNS maturation through a cell-autonomous role in the oligodendrocyte lineage. Here, we demonstrate that THAP1 modulates the extracellular matrix (ECM) composition by regulating glycosaminoglycan (GAG) catabolism within oligodendrocyte progenitor cells (OPCs). Thap1 ^-/- OPCs accumulate and secrete excess GAGs, inhibiting their maturation through an autoinhibitory mechanism. THAP1 controls GAG metabolism by binding to and regulating the GusB gene encoding β-glucuronidase, a GAG-catabolic lysosomal enzyme. Applying GAG-degrading enzymes or overexpressing β-glucuronidase rescues Thap1 ^-/- OL maturation deficits in vitro and in vivo. Our studies establish lysosomal GAG catabolism within OPCs as a critical mechanism regulating oligodendrocyte development.

Tolerance induction and microglial engraftment after fetal therapy without conditioning in mice with Mucopolysaccharidosis type VII

Mucopolysaccharidosis type VII (MPS7) is a lysosomal storage disorder (LSD) resulting from mutations in the β-glucuronidase gene, leading to multiorgan dysfunction and fetal demise. While postnatal enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation have resulted in some phenotypic improvements, prenatal treatment might take advantage of a unique developmental window to penetrate the blood-brain barrier or induce tolerance to the missing protein, addressing two important shortcomings of postnatal therapy for multiple LSDs. We performed in utero ERT (IUERT) at E14.5 in MPS7 mice and improved survival of affected mice to birth. IUERT penetrated brain microglia, whereas postnatal administration did not, and neurological testing (after IUERT plus postnatal administration) showed decreased microglial inflammation and improved grip strength in treated mice. IUERT prevented antienzyme antibody development even after multiple repeated postnatal challenges. To test a more durable treatment strategy, we performed in utero hematopoietic stem cell transplantation (IUHCT) using congenic CX3C chemokine receptor 1-green fluorescent protein (CX3CR1-GFP) mice as donors, such that donor-derived microglia are identified by GFP expression. In wild-type recipients, hematopoietic chimerism resulted in microglial engraftment throughout the brain without irradiation or conditioning; the transcriptomes of donor and host microglia were similar. IUHCT in MPS7 mice enabled cross-correction of liver Kupffer cells and improved phenotype in multiple tissues. Engrafted microglia were seen in chimeric mice, with decreased inflammation near donor microglia. These results suggest that fetal therapy with IUERT and/or IUHCT could overcome the shortcomings of current treatment strategies to improve phenotype in MPS7 and other LSDs.

The future of newborn screening for lysosomal disorders

The goal of newborn screening is to enhance the outcome of individuals with serious, treatable disorders through early, pre-symptomatic detection. The lysosomal storage disorders (LSDs) comprise a group of more than 50 diseases with a combined frequency of approximately 1:7000. With the availability of existing and new enzyme replacement therapies, small molecule treatments and gene therapies, there is increasing interest in screening newborns for LSDs with the goal of reducing disease-related morbidity and mortality through early detection. Novel screening methods are being developed, including efforts to enhance accuracy of screening using an array of multi-tiered, genomic, statistical, and bioinformatic approaches. While NBS data for Gaucher disease, Fabry disease, Krabbe disease, MPS I, and Pompe disease has demonstrated the feasibility of widespread screening, it has also highlighted some of the complexities of screening for LSDs. These include the identification of infants with later-onset, untreatable, and uncertain phenotypes, raising interesting ethical concerns that should be addressed as part of the NBS implementation process. Taken together, these efforts will provide critical, detailed data to help guide objective, ethically sensitive decision-making about NBS for LSDs.

Epidemiology of mucopolysaccharidoses (MPS) in United States: challenges and opportunities

Background

Mucopolysaccharidoses (MPS) are rare, inherited lysosomal storage disorders characterized by progressive multiorgan involvement. Previous studies on incidence and prevalence of MPS mainly focused on countries other than the United States (US), showing considerable variation by country. This study aimed to identify MPS incidence and prevalence in the US at a national and state level to guide clinicians and policy makers.

Methods

This retrospective study examined all diagnosed cases of MPS from 1995 to 2015 in the US using the National MPS Society database records. Data included year of birth, patient geographic location, and MPS variant type. US population information was obtained from the National Center for Health Statistics. The incidence and prevalence rates were calculated for each disease. Incidence rates were calculated for each state.

Results

We obtained information from 789 MPS patients during a 20-year period. Incidence of MPS in the US was found to be 0.98 per 100,000 live births. Prevalence was found to be 2.67 per 1 million. MPS I, II, and III had the highest incidence rate at birth (0.26/100,000) and prevalence rates of 0.70–0.71 per million. Birth incidences of MPS IV, VI, and VII were 0.14, 0.04 and 0.027 per 100,000 live births.

Conclusions

This is the most comprehensive review of MPS incidence and prevalence rates in the US. Due to the large US population and state fragmentation, US incidence and prevalence were found to be lower than other countries. Nonetheless, state-level studies in the US supported these figures. Efforts should be focused in the establishment of a national rare disease registry with mandated reporting from every state as well as newborn screening of MPS.

Open-label phase 1/2 study of vestronidase alfa for mucopolysaccharidosis VII

Vestronidase alfa is an enzyme replacement therapy for mucopolysaccharidosis VII (MPS VII). In this open-label, phase 1/2 study, three subjects with MPS VII received intravenous vestronidase alfa administered every other week (QOW) for 14 weeks (2 mg/kg), followed by 24-week forced-dose titration (1, 4, and 2 mg/kg QOW; 8 weeks each), 36-week continuation (2 mg/kg), and long-term extension (4 mg/kg). Vestronidase alfa was well tolerated and led to dose-responsive, sustained reductions in urinary glycosaminoglycan excretion.

Mucopolysaccharidosis VII in Brazil: natural history and clinical findings

Background

Mucopolysaccharidosis type VII (MPS VII), also known as Sly syndrome, caused by deficiency of the lysosomal enzyme β-glucuronidase, is an ultra-rare disorder with scarce epidemiological data and few publications about natural history and clinical spectrum.

Methods

We conducted a case series report which included retrospective data from all MPS VII patients diagnosed through the “MPS Brazil Network” who were known to be alive in 2020 in Brazil (N = 13). Clinical data were obtained from a review of the medical records and descriptive statistics and variables were summarized using counts and percentages of the total population.

Results

The majority of the patients were from the Northeast region of Brazil. Among the signs and symptoms that raised the clinical suspicion of MPS, coarse face was the most frequent; 58% of the patients had a history of non-immune hydrops fetalis. All the subjects presented short neck and trunk. The majority presented typical phenotypical signs of MPS disorders. They all presented neurodevelopmental delay and cognitive impairment. About half of this cohort had knees deformities. Dysostosis multiplex was identified in almost all patients and cardiomyopathy was less frequent than observed in other types of MPSs. The mean age at diagnosis was 5 years, ranging from 1 to 14 years. Almost all patients (12/13) were homozygous for the c.526C>T (p.Leu176Phe) mutation. A novel variant of the GUSB gene was found, the c.875T>C (p.Leu292Pro), in a compound heterozygous with the c.526C>T (p.Leu176Phe) variant.

Conclusions

This case series is the biggest data collection of MPS VII patients alive in Latin America. The overall clinical picture of the MPS VII patients is very similar to other MPS disorders, including a spectrum of severity and delayed diagnosis.

The natural history of neurocognition in MPS disorders: A review

MPS disorders are associated with a wide spectrum of neurocognitive effects, from mild problems with attention and executive functions to progressive and degenerative neuronopathic disease. Studies of the natural history of neurocognition are necessary to determine the profile of abnormality and the rates of change, which are crucial to select endpoints for clinical trials of brain treatments and to make clinical recommendations for interventions to improve patients' quality of life. The goal of this paper is to review neurocognitive natural history studies to determine the current state of knowledge and assist in directing future research in all MPS disorders. There are seven different types of MPS diseases, each resulting from a specific enzyme deficiency and each having a separate natural history. MPS IX, will not be discussed as there are only 4 cases reported in the literature without cognitive abnormality. For MPS IH, hematopoietic cell transplant (HCT) is standard of care and many studies have documented the relationship between age at treatment and neurocognitive outcome, and to a lesser extent, neurocognitive status at baseline. However, the mortality and morbidity associated with the transplant process and residual long-term problems after transplant, have led to renewed efforts to find better treatments. Rather than natural history, new trials will likely need to use the developmental trajectories of the patients with HCT as a comparators. The literature has extensive data regarding developmental trajectories post-HCT. For attenuated MPS I, significant neurocognitive deficits have been documented, but more longitudinal data are needed in order to support a treatment directed at their attention and executive function abnormalities. The neuronopathic form of MPS II has been a challenge due to the variability of the trajectory of the disease with differences in timing of slowing of development and decline. Finding predictors of the course of the disease has only been partially successful, using mutation type and family history. Because of lack of systematic data and clinical trials that precede a thorough understanding of the disease, there is need for a major effort to gather natural history data on the entire spectrum of MPS II. Even in the attenuated disease, attention and executive function abnormalities need documentation. Lengthy detailed longitudinal studies are needed to encompass the wide variability in MPS II. In MPS IIIA, the existence of three good natural history studies allowed a quasi-meta-analysis. In patients with a rapid form of the disease, neurocognitive development slowed up until 42 to 47 months, halted up to about 54 months, then declined rapidly thereafter, with a leveling off at an extremely low age equivalent score below 22 months starting at about chronological age of 6. Those with slower or attenuated forms have been more variable and difficult to characterize. Because of the plethora of studies in IIIA, it has been recommended that data be combined from natural history studies to minimize the burden on parents and patients. Sufficient data exists to understand the natural history of cognition in MPS IIIA. MPS IIIB is quite similar to IIIA, but more attenuated patients in that phenotype have been reported. MPS IIIC and D, because they are so rare, have little documentation of natural history despite the prospects of treatments. MPS IV and VI are the least well documented of the MPS disorders with respect to their neurocognitive natural history. Because, like attenuated MPS I and II, they do not show progression of neurocognitive abnormality and most patients function in the range of normality, their behavioral, attentional, and executive function abnormalities have been ignored to the detriment of their quality of life. A peripheral treatment for MPS VII, extremely rare even among MPS types, has recently been approved with a post-approval monitoring system to provide neurocognitive natural history data in the future. More natural history studies in the MPS forms with milder cognitive deficits (MPS I, II, IV, and VI) are recommended with the goal of improving these patients' quality of life with and without new brain treatments, beyond the benefits of available peripheral enzyme replacement therapy. Recommendations are offered at-a-glance with respect to what areas most urgently need attention to clarify neurocognitive function in all MPS types.

Enzyme replacement combinational therapy: effective treatments for mucopolysaccharidoses

INTRODUCTION

Mucopolysaccharidoses (MPS), as a group of inherited lysosomal storage disorders (LSDs), are clinically heterogeneous and characterized by multi-systemic manifestations, such as skeletal abnormalities and neurological dysfunctions. The currently used enzyme replacement therapy (ERT) might be associated with several limitations including the low biodistribution of the enzymes into the main targets, immunological responses against foreign enzymes, and the high cost of the treatment procedure. Therefore, a suitable combination approach can be considered for the successful treatment of each type of MPS.

AREAS COVERED

In this review, we provide comprehensive insights into the ERT-based combination therapies of MPS by reviewing the published literature on PubMed and Scopus. We also discuss the recent advancements in the treatment of MPS and bring up the hopes and hurdles in the futuristic treatment strategies.

EXPERT OPINION

Given the complex pathophysiology of MPS and its involvement in different tissues, the ERT of MPS in combination with stem cell therapy or gene therapy is deemed to provide a personalized precision treatment modality with the highest therapeutic responses and minimal side effects. By the same token, new combinational approaches need to be evaluated by using drugs that target alternative and secondary pathological pathways.

Rational Design, Synthesis, In Vitro, and In Silico Studies of Dihydropyrimidinone Derivatives as β-Glucuronidase Inhibitors

In the current study, a series of dihydropyrimidinone derivatives were rationally designed as β-glucuronidase inhibitors. These designed compounds were successfully synthesized and characterized through various spectroscopic techniques such as IR, 1H-NMR, 13C-NMR, and EI-MS. A structure-activity relationship (SAR) of synthesized derivatives to inhibit β-glucuronidase was also established. In vitro biological evaluations revealed that 4i as the most potent compound in this series has an IC50 value of 31.52 ± 2.54 μM compared to the standard D-saccharic acid 1,4-lactone (IC50 = 41.32 ± 1.82 µM). Also, molecular docking and dynamics studies of the most potent compound are performed to evaluate interactions between the active compound and binding site.

Hip disease in Mucopolysaccharidoses and Mucolipidoses: A review of mechanisms, interventions and future perspectives

The hips are frequently involved in inheritable diseases which affect the bones. The clinical and radiological presentation of these diseases may be very similar to common hip disorders as developmental dysplasia of the hip, osteoarthritis and avascular necrosis, so the diagnosis may be easily overlooked and treatment may be suboptimal. Mucopolysaccharidosis (MPS) and Mucolipidosis (ML II and III) are lysosomal storage disorders with multisystemic involvement. Characteristic skeletal abnormalities, known as dysostosis multiplex, are common in MPS and ML and originate from intra-lysosomal storage of glycosaminoglycans in cells of the cartilage, bones and ligaments. The hip joint is severely affected in MPS and ML. Hip pathology results in limitations in mobility and pain from young age, and negatively affects quality of life. In order to better understand the underlying process that causes hip disease in MPS and ML, this review first describes the normal physiological (embryonic) hip joint development, including the interplay between the acetabulum and the femoral head. In the second part the factors contributing to altered hip morphology and function in MPS and ML are discussed, such as abnormal development of the pelvic- and femoral bones (which results in altered biomechanical forces) and inflammation. In the last part of this review therapeutic options and future perspectives are addressed.

Prenatal mucopolysaccharidosis VII: A novel pathogenic variant identified in GUSB gene

Clinical exome sequencing is a powerful approach to overcome the wide clinical and genetic heterogeneity of mucopolysaccharidosis. These data could be useful for prenatal diagnosis of MPS VII, genetic counseling, and preimplantation genetic testing.