Mucopolysaccharidosis enzyme production by bone marrow and dental pulp derived human mesenchymal stem cells

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.

Hurler Syndrome: Orofacial Clinical Findings

Hurler syndrome (HS) belongs to the category of mucopolysaccharidosis (MPS), a spectrum of rare genetic disorders of the mucopolysaccharides metabolism. This syndrome is due to a defect in α-iduronidase, an enzyme responsible for the degradation of the glycosaminoglycans (GAGs) heparin and dermatan sulfate. Intra and extracellular accumulation of these non-metabolized substances may lead to multisystemic dysfunction, with severe stomatognathic involvement that may often need treatment. The aim of this article is to present the heterogeneity of orofacial and radiographic findings observed in two patients with HS with long-term follow-up, who were referred to our Stomatology department.

A kaleidoscopic view of extracellular vesicles in lysosomal storage disorders

Extracellular vesicles (EVs) are a heterogeneous population of stable lipid membrane particles that play a critical role in the regulation of numerous physiological and pathological processes. EV cargo, which includes lipids, proteins, and RNAs including miRNAs, is affected by the metabolic status of the parental cell. Concordantly, abnormalities in the autophagic-endolysosomal pathway, as seen in lysosomal storage disorders (LSDs), can affect EV release as well as EV cargo. LSDs are a group of over 70 inheritable diseases, characterized by lysosomal dysfunction and gradual accumulation of undigested molecules. LSDs are caused by single gene mutations that lead to a deficiency of a lysosomal protein or lipid. Lysosomal dysfunction sets off a cascade of alterations in the endolysosomal pathway that can affect autophagy and alter calcium homeostasis, leading to energy imbalance, oxidative stress, and apoptosis. The pathophysiology of these diseases is very heterogenous, complex, and currently incompletely understood. LSDs lead to progressive multisystemic symptoms that often include neurological deficits. In this review, a kaleidoscopic overview will be given on the roles of EVs in LSDs, from their contribution to pathology and diagnostics to their role as drug delivery vehicles. Furthermore, EV cargo and surface engineering strategies will be discussed to show the potential of EVs in future LSD treatment, both in the context of enzyme replacement therapy, as well as future gene editing strategies like CRISPR/Cas. The use of engineered EVs as drug delivery vehicles may mask therapeutic cargo from the immune system and protect it from degradation, improving circulation time and targeted delivery.

Mucopolysaccharidosis Type VI, an Updated Overview of the Disease

Mucopolysaccharidosis type VI, or Maroteaux-Lamy syndrome, is a rare, autosomal recessive genetic disease, mainly affecting the pediatric age group. The disease is due to pathogenic variants of the ARSB gene, coding for the lysosomal hydrolase N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). The enzyme deficit causes a pathological accumulation of the undegraded glycosaminoglycans dermatan-sulphate and chondroitin-sulphate, natural substrates of ASB activity. Intracellular and extracellular deposits progressively take to a pathological scenario, often severe, involving most organ-systems and generally starting from the osteoarticular apparatus. Neurocognitive and behavioral abilities, commonly described as maintained, have been actually investigated by few studies. The disease, first described in 1963, has a reported prevalence between 0.36 and 1.3 per 100,000 live births across the continents. With this paper, we wish to contribute an updated overview of the disease from the clinical, diagnostic, and therapeutic sides. The numerous in vitro and in vivo preclinical studies conducted in the last 10-15 years to dissect the disease pathogenesis, the efficacy of the available therapeutic treatment (enzyme replacement therapy), as well as new therapies under study are here described. This review also highlights the need to identify new disease biomarkers, potentially speeding up the diagnostic process and the monitoring of therapeutic efficacy.

Impaired neural differentiation of MPS IIIA patient induced pluripotent stem cell-derived neural progenitor cells

Mucopolysaccharidosis type IIIA (MPS IIIA) is characterised by a progressive neurological decline leading to early death. It is caused by bi-allelic loss-of-function mutations in SGSH encoding sulphamidase, a lysosomal enzyme required for heparan sulphate glycosaminoglycan (HS GAG) degradation, that results in the progressive build-up of HS GAGs in multiple tissues most notably the central nervous system (CNS). Skin fibroblasts from two MPS IIIA patients who presented with an intermediate and a severe clinical phenotype, respectively, were reprogrammed into induced pluripotent stem cells (iPSCs). The intermediate MPS IIIA iPSCs were then differentiated into neural progenitor cells (NPCs) and subsequently neurons. The patient derived fibroblasts, iPSCs, NPCs and neurons all displayed hallmark biochemical characteristics of MPS IIIA including reduced sulphamidase activity and increased accumulation of an MPS IIIA HS GAG biomarker. Proliferation of MPS IIIA iPSC-derived NPCs was reduced compared to control, but could be partially rescued by reintroducing functional sulphamidase enzyme, or by doubling the concentration of the mitogen fibroblast growth factor 2 (FGF2). Whilst both control heparin, and MPS IIIA HS GAGs had a similar binding affinity for FGF2, only the latter inhibited FGF signalling, suggesting accumulated MPS IIIA HS GAGs disrupt the FGF2:FGF2 receptor:HS signalling complex. Neuronal differentiation of MPS IIIA iPSC-derived NPCs was associated with a reduction in the expression of neuronal cell marker genes βIII-TUBULIN, NF-H and NSE, revealing reduced neurogenesis compared to control. A similar result was achieved by adding MPS IIIA HS GAGs to the culture medium during neuronal differentiation of control iPSC-derived NPCs. This study demonstrates the generation of MPS IIIA iPSCs, and NPCs, the latter of which display reduced proliferation and neurogenic capacity. Reduced NPC proliferation can be explained by a model in which soluble MPS IIIA HS GAGs compete with cell surface HS for FGF2 binding. The mechanism driving reduced neurogenesis remains to be determined but appears downstream of MPS IIIA HS GAG accumulation.

Stem Cell Applications in Lysosomal Storage Disorders: Progress and Ongoing Challenges

Lysosomal storage disorders (LSDs) are rare inborn errors of metabolism caused by defects in lysosomal function. These diseases are characterized by accumulation of completely or partially degraded substrates in the lysosomes leading to cellular dysfunction of the affected cells. Currently, enzyme replacement therapies (ERTs), treatments directed at substrate reduction (SRT), and hematopoietic stem cell (HSC) transplantation are the only treatment options for LSDs, and the effects of these treatments depend strongly on the type of LSD and the time of initiation of treatment. However, some of the LSDs still lack a durable and curative treatment. Therefore, a variety of novel treatments for LSD patients has been developed in the past few years. However, despite significant progress, the efficacy of some of these treatments remains limited because these therapies are often initiated after irreversible organ damage has occurred.Here, we provide an overview of the known effects of LSDs on stem cell function, as well as a synopsis of available stem cell-based cell and gene therapies that have been/are being developed for the treatment of LSDs. We discuss the advantages and disadvantages of use of hematopoietic stem cell (HSC), mesenchymal stem cell (MSC), and induced pluripotent stem cell (iPSC)-related (gene) therapies. An overview of current research data indicates that when stem cell and/or gene therapy applications are used in combination with existing therapies such as ERT, SRT, and chaperone therapies, promising results can be achieved, showing that these treatments may result in alleviation of existing symptoms and/or prevention of progression of the disease. All together, these studies offer some insight in LSD stem cell biology and provide a hopeful perspective for the use of stem cells. Further development and improvement of these stem cell (gene) combination therapies may greatly improve the current treatment options and outcomes of patients with a LSD.

Mucopolysaccharidosis (MPS): Review of the literature and case series of five pediatric dental patients

Patients with MPS present with a plethora of dental manifestations, accompanying behavioral difficulties and medical comorbidities which often dictate the need for treatment in specialist centers. Prevention is therefore mandatory in this high-risk group.

Failures of Endochondral Ossification in the Mucopolysaccharidoses

PURPOSE OF REVIEW

The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders characterized by abnormal accumulation of glycosaminoglycans (GAGs) in cells and tissues. MPS patients frequently exhibit failures of endochondral ossification during postnatal growth leading to skeletal deformity and short stature. In this review, we outline the current understanding of the cellular and molecular mechanisms underlying failures of endochondral ossification in MPS and discuss associated treatment challenges and opportunities.

RECENT FINDINGS

Studies in MPS patients and animal models have demonstrated that skeletal cells and tissues exhibit significantly elevated GAG storage from early in postnatal life and that this is associated with impaired cartilage-to-bone conversion in primary and secondary ossification centers, and growth plate dysfunction. Recent studies have begun to elucidate the underlying cellular and molecular mechanisms, including impaired chondrocyte proliferation and hypertrophy, diminished growth factor signaling, disrupted cell cycle progression, impaired autophagy, and increased cell stress and apoptosis. Current treatments such as hematopoietic stem cell transplantation and enzyme replacement therapy fail to normalize endochondral ossification in MPS. Emerging treatments including gene therapy and small molecule-based approaches hold significant promise in this regard. Failures of endochondral ossification contribute to skeletal deformity and short stature in MPS patients, increasing mortality and reducing quality of life. Early intervention is crucial for effective treatment, and there is a critical need for new approaches that normalize endochondral ossification by directly targeting affected cells and signaling pathways.

Quantitative clinical characteristics of 53 patients with MPS VII: a cross-sectional analysis

PURPOSE

The main purpose of the study was to provide quantitative data regarding survival and diagnostic delay. Mucopolysaccharidosis (MPS) type VII (OMIM 253220) is a progressive neurometabolic disorder caused by deficiency of the lysosomal enzyme β-glucuronidase (GUS). Hard clinical end points have not been quantitatedMethods:We quantitatively analyzed published cases with MPS VII (N = 53/88 with sufficient data). Main outcome measures were onset of disease and survival. The role of biomarkers such as GUS residual enzyme activity and levels of storage material assessed as urinary excretion of glucosaminoglycans (GAG) as potential predictors of clinical outcomes were investigated. The analysis was conducted according to STROBE criteria.

RESULTS

Median survival of the postnatally diagnosed population was up to 360 months . Median age of disease onset was the first day of life; median age at diagnosis was 11 months. Hydrops fetalis was frequent. Patients with residual GUS activity in fibroblasts more than 1.4% or urinary GAG excretion less than 602% of normal survived longer than patients with GUS enzyme activity below or GAG excretion above these thresholds.

CONCLUSION

MPS VII has its disease onset prenatally. In the absence of a prenatal diagnosis, most cases are clinically apparent at birth. Our data corroborate a phenotype-biomarker association in MPS VII. The survival data characterize the natural history with important implications for therapeutic studies.Genet Med advance online publication 06 April 2017.

Cardiovascular Abnormalities in Egyptian Children with Mucopolysaccharidoses

INTRODUCTION

The Mucopolysaccharidoses (MPS) are rare inherited metabolic disorders. They are characterized by the progressive systemic deposition of Glycosaminoglycans (GAGs). GAGs accumulate in the myocardium and the cardiac valves. Enzyme Replacement Therapy (ERT) is available for MPS I, II, and VI. However, ERT does not appear to improve cardiac valve disease in patients with valve disease present at the start of ERT.

AIM

To evaluate the cardiac involvement in Egyptian children with MPS.

MATERIALS AND METHODS

Echocardiograms (ECG) were done for 34 patients. Both quantitative and qualitative Glycosaminoglycans (GAGs) in urine and enzyme assay confirmed the diagnosis. Mitral, tricuspid and aortic valves were evaluated for increased thickness, regurgitation and/or stenosis, left ventricular chamber dimensions, septal and posterior wall thicknesses.

RESULTS

The patients' age ranged from 0.9-16 years (median age 4 years). They included 19 cases of MPS I (55.9%), 3 cases of MPS II (8.8%), 2 cases of MPS III (5.9%), 6 cases of MPS IV (17.6%) and 4 cases of MPS VI (11.8%). Heart murmur was heard in 9 of the participants (9/34) (26%). However, 15 patients (15/34) (44%) revealed cardiac lesions on ECG examinations. Mitral regurge (47%), followed by pulmonary hypertension (40%), were the most frequent findings.

CONCLUSION

The absence of Cardiac murmurs does not exclude the heart involvement. Cardiac valve dysfunction may not be reversible. Regular ECG should be routinely warranted in children with MPS and early ERT are recommended.

Reversal of established bone pathology in MPS VII mice following lentiviral-mediated gene therapy

Severe, progressive skeletal dysplasia is a major symptom of multiple mucopolysaccharidoses (MPS) types. While a gene therapy approach initiated at birth has been shown to prevent the development of bone pathology in different animal models of MPS, the capacity to correct developed bone disease is unknown. In this study, ex vivo micro-computed tomography was used to demonstrate that bone mass and architecture of murine MPS VII L5 vertebrae were within the normal range at 1month of age but by 2months of age were significantly different to normal. The difference between normal and MPS VII BV/TV increased with age reaching a maximal difference at approximately 4months of age. In mature MPS VII bone BV/TV is increased (51.5% versus 21.5% in normal mice) due to an increase in trabecular number (6.2permm versus 3.8permm in normal mice). The total number of osteoclasts in the metaphysis of MPS VII mice was decreased, as was the percentage of osteoclasts attached to bone. MPS VII osteoblasts produced significantly more osteoprotegerin (OPG) than normal osteoblasts and supported the production of fewer osteoclasts from spleen precursor cells than normal osteoblasts in a co-culture system. In contrast, the formation of osteoclasts from MPS VII spleen monocytes was similar to normal in vitro, when exogenous RANKL and m-CSF was added to the culture medium. Administration of murine β-glucuronidase to MPS VII mice at 4months of age, when bone disease was fully manifested, using lentiviral gene delivery resulted in a doubling of osteoclast numbers and a significant increase in attachment capacity (68% versus 29.4% in untreated MPS VII animals). Bone mineral volume rapidly decreased by 39% after gene therapy and fell within the normal range by 6months of age. Collectively, these results indicate that lentiviral-mediated gene therapy is effective in reversing established skeletal pathology in murine MPS VII.