Effective treatment of alpha-mannosidosis by allogeneic hematopoietic stem cell transplantation

Stem cells as potential therapeutics for hearing loss

Hearing impairment is a global health problem. Stem cell therapy has become a cutting-edge approach to tissue regeneration. In this review, the recent advances in stem cell therapy for hearing loss have been discussed. Nanomaterials can modulate the stem cell microenvironment to augment the therapeutic effects further. The potential of combining nanomaterials with stem cells for repairing and regenerating damaged inner ear hair cells (HCs) and spiral ganglion neurons (SGNs) has also been discussed. Stem cell-derived exosomes can contribute to the repair and regeneration of damaged tissue, and the research progress on exosome-based hearing loss treatment has been summarized as well. Despite stem cell therapy's technical and practical limitations, the findings reported so far are promising and warrant further investigation for eventual clinical translation.

Hearing loss in inherited metabolic disorders: A systematic review

Inherited metabolic disorders (IMDs) have been observed in individuals with hearing loss (HL), but IMDs are rarely the cause of syndromic HL. With early diagnosis, management of HL is more effective and cortical reorganization is possible with hearing aids or cochlear implants. This review describes relationships between IMDs and HL in terms of incidence, etiology of HL, pathophysiology, and treatment. Forty types of IMDs are described in the literature, mainly in case reports. Management and prognosis are noted where existing. We also describe IMDs with HL given age of occurrence of HL. Reviewing the main IMDs that are associated with HL may provide an additional clinical tool with which to better diagnose syndromic HL.

Use of the Bruininks-Oseretsky test of motor proficiency (BOT-2) to assess efficacy of velmanase alfa as enzyme therapy for alpha-mannosidosis

Objectives

Alpha-mannosidosis is a rare autosomal recessive lysosomal storage disorder resulting from deficient lysosomal alpha-mannosidase activity. Clinical manifestations include progressive balance disorders, immune deficiency, skeletal abnormalities and cognitive deficits beginning in early childhood. Enzyme replacement therapy with recombinant human alpha-mannosidase (velmanase alfa) is scheduled for clinical development in the US beginning in 2020 and has been approved in the EU for treatment of non-neurological manifestations in cases of mild to moderate disease. This study assessed effects of velmanase alfa on fine and gross motor proficiency in children and adults.

Methods

Integrated Bruininks-Oseretsky (BOT-2) test of Motor Proficiency data from velmanase alfa clinical trials was stratified by age for 14 adults and 19 children treated for up to 4 years.

Results

Patients showed global developmental delays at baseline. For the combined adult and pediatric group there was a statistically significant increase (improvement) in BOT-2 total point score of 13% (p = .035, 95% CI 1.0, 25.0) from baseline to last observation. When stratified by pediatric versus adult patients, there was improvement in BOT-2 total point score in patients <18 years (mean percent increase from baseline to last observation 23%) compared to adults (mean decrease of −0.7%). Subtest analysis of individual BOT-2 items captured some improvement following velmanase alfa treatment in pediatric patients.

Conclusions

There was limited ability to assess the BOT-2 change responses in adults. Pediatric patients showed stability or improvement in scaled scores relative to healthy peers, indicating continued skill acquisition, which may increase independence and contribute to improved patient quality of life.

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Alpha-mannosidosis patients have global developmental delay, requiring assistance with many activities of daily living.

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BOT-2 is used to assess improvements in functional capacity in children and young adults.

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Pediatric patients showed stability or improvement in BOT-2 scaled scores relative to healthy peers, indicating continued skill acquisition.

Intellectual functioning in alpha-mannosidosis

Alpha-mannosidosis is a rare inherited metabolic disorder (OMIM #248500) caused by mutations in the enzyme α-mannosidase encoded by the gene MAN2B1. Patients have distinct physical and developmental features, but only limited information regarding standardized cognitive functioning of patients has been published. Here we contribute intellectual ability scores (IQ) on 12 patients with alpha-mannosidosis (ages 8-59 years, 10 males, 2 females). In addition, a pooled analysis was performed with data collected from this investigation and 31 cases obtained from the literature, allowing a comprehensive analysis of intellectual functioning in this rare disease. The initial and pooled analyses show that patients with alpha-mannosidosis have variable degrees of intellectual disability but show decline in IQ with age, particularly during the first decade of life. Patients treated with hematopoietic stem cell transplantation tend to show stabilized cognitive abilities.

Biochemical and clinical response after umbilical cord blood transplant in a boy with early childhood-onset beta-mannosidosis

BACKGROUND

Deficiency in the enzyme β-mannosidase was described over three decades ago. Although rare in occurrence, the presentation of childhood-onset β-mannosidase deficiency consists of hypotonia in the newborn period followed by global development delay, behavior problems, and intellectual disability. No effective pharmacologic treatments have been available.

METHODS

We report 2-year outcomes following the first umbilical cord blood transplant in a 4-year-old boy with early childhood-onset disease.

RESULTS

We show restoration of leukocyte β-mannosidase activity which remained normal at 2 years posttransplant, and a simultaneous increase in plasma β-mannosidase activity and dramatic decrease in urine-free oligosaccharides were also observed. MRI of the brain remained stable. Neurocognitive evaluation revealed test point gains, although the magnitude of improvement was less than expected for age, causing lower IQ scores that represent a wider developmental gap between the patient and unaffected peers.

CONCLUSION

Our findings suggest that hematopoietic cell transplant can correct the biochemical defect in β-mannosidosis, although preservation of the neurocognitive trajectory may be a challenge.

Alpha-Mannosidosis: Therapeutic Strategies

Alpha-mannosidosis (α-mannosidosis) is a rare lysosomal storage disorder with an autosomal recessive inheritance caused by mutations in the gene encoding for the lysosomal α-d-mannosidase. So far, 155 variants from 191 patients have been identified and in part characterized at the biochemical level. Similarly to other lysosomal storage diseases, there is no relationship between genotype and phenotype in alpha-mannosidosis. Enzyme replacement therapy is at the moment the most effective therapy for lysosomal storage disease, including alpha-mannosidosis. In this review, the genetic of alpha-mannosidosis has been described together with the results so far obtained by two different therapeutic strategies: bone marrow transplantation and enzyme replacement therapy. The primary indication to offer hematopoietic stem cell transplantation in patients affected by alpha-mannosidosis is preservation of neurocognitive function and prevention of early death. The results obtained from a Phase I⁻II study and a Phase III study provide evidence of the positive clinical effect of the recombinant enzyme on patients with alpha-mannosidosis.

Bone health in patients with inborn errors of metabolism

Inborn errors of metabolism encompass a wide spectrum of disorders, frequently affecting bone. The most important metabolic disorders that primarily influence calcium or phosphate balance, resulting in skeletal pathology, are hypophosphatemic rickets and hypophosphatasia. Conditions involving bone marrow or affecting skeletal growth and development are mainly the lysosomal storage disorders, in particular the mucopolysaccharidoses. In these disorders skeletal abnormalities are often the presenting symptom and early recognition and intervention improves outcome in many of these diseases. Many disorders of intermediary metabolism may impact bone health as well, resulting in higher frequencies of osteopenia and osteoporosis. In these conditions factors contributing to the reduced bone mineralization can be the disorder itself, the strict dietary treatment, reduced physical activity or sunlight exposure and/or early ovarian failure. Awareness of these primary or secondary bone problems amongst physicians treating patients with inborn errors of metabolism is of importance for optimization bone health and recognition of skeletal complications.

Hematopoietic cell transplantation for a child with OSTM1 osteopetrosis

HCT prior to onset of neurologic symptoms in children with OSTM1 osteopetrosis does not halt neurologic progression.

Personalized Pharmacoperones for Lysosomal Storage Disorder: Approach for Next-Generation Treatment

Lysosomal storage disorders (LSDs) are a collection of inborn errors of metabolic disorders affected by mutations in lysosome functional genes, commonly acid hydrolases. From the past decades, many approaches like enzyme replacement therapy, substrate reduction therapy are followed to treat these conditions. However, all these approaches have their own limitations. Proof-of-concept studies on pharmacological chaperone therapy (PCT) is now transformed into clinical practice to treat LSDs. Furthermore, it is narrowed with individuals to chaperone sensitive, specific mutations. Hence, personalizing the PCT will be a new direction to combat LSDs. In this review, we have discussed the available clinical strategies and pointed the light on how pharmacological chaperones can be personalized and hopeful to be a next-generation approach to address LSDs.

Cognitive profile and activities of daily living: 35 patients with alpha-mannosidosis

BACKGROUND

Alpha-mannosidosis (OMIM 248500) (AM) is a rare lysosomal storage disease caused by a deficiency of the alpha-mannosidase enzyme. The typical signs consist of hearing impairment, intellectual disabilities, coarse facial features and motor function disturbances. We report on the cognitive function and activities of daily living in patients with AM.

METHODS

Thirty five AM patients, age 6-35 years, were included in the study. As a cognitive function test, we used the Leiter international performance scale-revised (Leiter-R), which consists of two batteries: the visual function and reasoning battery and the memory and attention battery, the latter including a memory screening. Additional two questionnaires, The Childhood Health Assessment Questionnaire (CHAQ) and EQ-5D-5 L, were filled out.

RESULTS

We found IQ in the range of 30-81 in our cohort. The total equivalent age (mental age) was significantly reduced, between 3-9 years old for the visual function and reasoning battery, between 2.3-10.2 years for the memory screening. Data suggested a specific developmental profile for AM with a positive intellectual development until the chronological age 10-12 years, followed by a static or slightly increasing intellectual level. All patients were to varying degrees socially and practically dependent and unable to take care of themselves in daily life.

CONCLUSIONS

Intellectual disability is a consistent finding in patients with alpha-mannosidosis but with extensive variation. We assess that this group of patients has, despite their intellectual disabilities, a potential for continuous cognitive development, especially during childhood and early teenage years. This should be included and supported in the individual educational planning.

Alpha-mannosidosis: a report of 2 siblings and review of the literature

Alpha-mannosidosis is a rare lysosomal storage disorder with a heterogeneous clinical presentation. We describe a set of siblings with alpha-mannosidosis. The older child presented with a severe phenotype with multisystem involvement and had progressive deterioration in her motor and cognitive functioning. She had a poor outcome. The second child has a less severe disease course. He is being managed symptomatically only because of the family's poor socioeconomic circumstances. Therapeutic options in this condition are limited to bone marrow transplant early in the disease course. These disorders, although rare, should be considered in the approach to a child with dysmorphism, developmental delay, skeletal deformities, and visceromegaly.

Successful unrelated bone marrow transplantation in two siblings with alpha-mannosidosis

Alpha-mannosidosis is a rare lysosomal storage disorder with an autosomal recessive inheritance. Deficient alpha-mannosidase activity leads to lysosomal accumulation of mannose-rich oligosaccharides. The disease characterized by mental retardation, skeletal changes, hearing impairment, and recurrent infections. Stem cell transplantation has been shown to be an effective treatment. It works by providing increased levels of α-mannosidase in the localized extracellular milieu to provide improvements in skeletal malformations, neurocognitive, and sensorineural function. In this case report, we describe a pair of siblings with α-mannosidosis who successfully underwent HSCT from matched unrelated donors. In both siblings, enzyme levels reached to normal limits and improvements in clinical symptoms were recognized early after HSCT. We conclude that HSCT should be considered as a therapeutic approach in patients with alpha-mannosidosis before disease-related complications have developed.

Exome sequencing can improve diagnosis and alter patient management

The translation of "next-generation" sequencing directly to the clinic is still being assessed but has the potential for genetic diseases to reduce costs, advance accuracy, and point to unsuspected yet treatable conditions. To study its capability in the clinic, we performed whole-exome sequencing in 118 probands with a diagnosis of a pediatric-onset neurodevelopmental disease in which most known causes had been excluded. Twenty-two genes not previously identified as disease-causing were identified in this study (19% of cohort), further establishing exome sequencing as a useful tool for gene discovery. New genes identified included EXOC8 in Joubert syndrome and GFM2 in a patient with microcephaly, simplified gyral pattern, and insulin-dependent diabetes. Exome sequencing uncovered 10 probands (8% of cohort) with mutations in genes known to cause a disease different from the initial diagnosis. Upon further medical evaluation, these mutations were found to account for each proband's disease, leading to a change in diagnosis, some of which led to changes in patient management. Our data provide proof of principle that genomic strategies are useful in clarifying diagnosis in a proportion of patients with neurodevelopmental disorders.

Proton nuclear magnetic resonance spectroscopic detection of oligomannosidic n glycans in alpha-mannosidosis: a method of monitoring treatment

In Alpha-mannosidosis (MIM 248500) the patients accumulate mainly unbranched oligosaccharide chains in the lysosomes in all body tissues, including the brain. With ensuing therapeutic modalities in man (BMT and ERT) non-invasive methods of monitoring the effect of treatment are needed. Paramount is the possible effect of the treatment on the brain, since this organ is regarded as difficult to reach because of the blood-brain barrier. We therefore performed proton nuclear magnetic resonance spectroscopy (MRS) of the brain in two untreated patients, and a 16-year-old patient treated with BMT at the age of 10 to assess whether this non-invasive method could be applied in the monitoring of the accumulation of abnormal chemicals in the brain of patients. We found an abnormal peak that was not present in the treated patient. A similar pattern was also found in MRS of urine from patients, reflecting the concentration of oligosaccharides in serum and tissues. We therefore conclude that MRS can be a useful method to monitor the effect of treatment for Alpha-Mannosidosis.

The effects of early and late bone marrow transplantation in siblings with alpha-mannosidosis. Is early haematopoietic cell transplantation the preferred treatment option?

This article documents both the neurological and physical outcomes of the first published set of siblings undergoing transplantation at differing ages for α-mannosidosis. The older brother, the index case, was diagnosed at the age of 3 years and underwent transplantation at 13 years for the treatment of increasing somatic problems and recurrent infections. The younger brother had undergone transplantation pre-symptomatically at 6 months of age. Their clinical, radiological and developmental outcomes are documented and compared with the previous published cases, with the case for early transplantation being weighted against other potential therapies.

Current international perspectives on hematopoietic stem cell transplantation for inherited metabolic disorders

Inherited metabolic disorders (IMD) or inborn errors of metabolism are a diverse group of diseases arising from genetic defects in lysosomal enzymes or peroxisomal function. These diseases are characterized by devastating systemic processes affecting neurologic and cognitive function, growth and development, and cardiopulmonary status. Onset in infancy or early childhood is typically accompanied by rapid deterioration. Early death is a common outcome. Timely diagnosis and immediate referral to an IMD specialist are essential steps in management of these disorders. Treatment recommendations are based on the disorder, its phenotype including age at onset and rate of progression, severity of clinical signs and symptoms, family values and expectations, and the risks and benefits associated with available therapies such as allogeneic hematopoietic stem cell transplantation (HSCT). This review discusses indications for HSCT and outcomes of HSCT for selected IMD. An international perspective on progress, limitations, and future directions in the field is provided.

Cord blood and bone marrow transplantation in inherited metabolic diseases: scientific basis, current status and future directions

Progressive degeneration of the central nervous system leading to the loss of neuromotor, neurophysiological and cognitive abilities is the fundamental clinical problem in patients with many inherited metabolic diseases (IMD). Worldwide experience shows that morbidity, quality of life, and survival in these patients can be improved by allogeneic haematopoietic stem cell transplantation (HSCT), particularly when performed early in the course of the disease. At present, while available for some conditions, exogenous enzyme replacement therapy is unable to correct cognitive and central nervous system disease because of its inability to cross the blood-brain barrier. In contrast, HSCT allows donor-derived, enzyme-producing cells to migrate to the brain and other organs providing a permanent enzyme replacement therapy. HSCT may also mediate non-hematopoietic cell regeneration or repair. Traditionally, bone marrow has been the graft source for IMD patients. However, in the last 5 years many studies utilizing unrelated donor umbilical cord blood (UCB) as a graft source have demonstrated that UCB provides rapid and increased access to transplantation with favourable outcomes. This review describes preclinical studies and past and present clinical treatment approaches and discusses current controversies and future directions of this promising field.

In utero transplantation of monocytic cells in cats with alpha-mannosidosis

BACKGROUND

Lysosomal storage diseases are devastating illnesses, in large part because of their neurologic consequences. Because significant morbidity occurs prenatally, in utero (IU) therapy is an attractive therapeutic approach.

METHODS

We studied the feasibility and efficacy of IU injections of monocytic cells (derived from normal marrow) in feline alpha-mannosidosis. Heterozygous cats were interbred to produce affected (homozygous) and control (heterozygous and wild-type) offspring. Thirty-seven pregnancies were studied in which fetuses were transplanted intraperitoneally (1x10 cells/kg recipient) at gestational days 27 to 33 and then each week for 2 weeks (term=63 days). After birth, affected kittens were evaluated clinically and pathologically, tissue alpha-mannosidase levels were assayed, and in many studies, the numbers of alpha-mannosidase-containing cells were enumerated. When male donor cells were transplanted into female recipients, engraftment was also quantified using polymerase chain reaction to amplify a Y chromosome-specific sequence.

RESULTS

We establish methods to transplant cats intraperitoneally while IU using ultrasound guidance, thus, describing a new large animal model for prenatal therapy. We show that the donor monocytic cells engraft and persist (for up to 125 days) in the brain, liver, and spleen, albeit at levels below those needed to alter the clinical or pathological progression of the alpha-mannosidosis.

CONCLUSIONS

This is the first study of monocyte transplantation in a large animal model of a lysosomal storage disorder and demonstrates its feasibility, safety, and promise. Delivering cells IU may be a useful strategy to prevent morbidities before a definitive therapy, such as hematopoietic stem-cell transplantation, can be administered after birth.

Large animal models of neurological disorders for gene therapy

he development of therapeutic interventions for genetic disorders and diseases that affect the central nervous system (CNS) has proven challenging. There has been significant progress in the development of gene therapy strategies in murine models of human disease, but gene therapy outcomes in these models do not always translate to the human setting. Therefore, large animal models are crucial to the development of diagnostics, treatments, and eventual cures for debilitating neurological disorders. This review focuses on the description of large animal models of neurological diseases such as lysosomal storage diseases, Parkinsons disease, Huntingtons disease, and neuroAIDS. The review also describes the contributions of these models to progress in gene therapy research.

Intensive care unit mortality trends in children after hematopoietic stem cell transplantation: a meta-regression analysis

BACKGROUND

There is ongoing discussion whether intensive care unit mortality has decreased over time for children after hematopoietic stem cell transplantation.

OBJECTIVE

To analyze intensive care unit mortality trends in children after hematopoietic stem cell transplantation.

DATA SOURCES

Search of MEDLINE, EMBASE, and Cochrane databases, and a manual review of reference lists.

STUDY SELECTION

Prospective and retrospective cohort studies containing intensive care unit mortality data of children after hematopoietic stem cell transplantation.

DATA EXTRACTION

Mortality statistics and features associated with mortality were abstracted from studies of interest. To assess mortality over time, the median years of inclusion in original studies were included as risk factor. A multiple random-effects meta-regression analysis was conducted to assess the independent contribution of prognostic factors on mortality.

DATA SYNTHESIS

Twenty-three studies were included, reporting on 1101 intensive care unit admissions. Overall intensive care unit mortality was 60% (range, 25%-91%). Once mechanical ventilation was necessary (n = 822), mean intensive care unit mortality was 71% (range, 25%-91%). Over the years, significantly fewer intensive care unit admitted patients received mechanical ventilation (p < 0.001). Univariable analysis in all intensive care unit admitted patients showed a significant decrease in mortality associated with year of inclusion. Mechanical ventilation and pulmonary disease were associated with increased mortality. In the multiple meta-regression analysis, only pulmonary disease remained significantly associated with mortality (odds ratio = 1.21, 95% confidence interval 1.01-1.46 per 10% increase in the number of patients with pulmonary disease in studies). The association between year of inclusion and intensive care unit mortality was less pronounced (odds ratio = 0.92, 95% confidence interval 0.84-1.01).

CONCLUSION

There is a widely held impression that intensive care unit mortality clearly decreased in children after hematopoietic stem cell transplantation. However, characteristics of intensive care unit admitted patients significantly changed over time. After correcting for this, an improvement in intensive care unit survival was less evident. More studies are needed before a true improvement in intensive care unit survival can be confirmed.

Alpha-mannosidosis

Alpha-mannosidosis is an inherited lysosomal storage disorder characterized by immune deficiency, facial and skeletal abnormalities, hearing impairment, and intellectual disability. It occurs in approximately 1 of 500,000 live births. The children are often born apparently normal, and their condition worsens progressively. Some children are born with ankle equinus or develop hydrocephalus in the first year of life. Main features are immune deficiency (manifested by recurrent infections, especially in the first decade of life), skeletal abnormalities (mild-to-moderate dysostosis multiplex, scoliosis and deformation of the sternum), hearing impairment (moderate-to-severe sensorineural hearing loss), gradual impairment of mental functions and speech, and often, periods of psychosis. Associated motor function disturbances include muscular weakness, joint abnormalities and ataxia. The facial trait include large head with prominent forehead, rounded eyebrows, flattened nasal bridge, macroglossia, widely spaced teeth, and prognathism. Slight strabismus is common. The clinical variability is significant, representing a continuum in severity. The disorder is caused by lysosomal alpha-mannosidase deficiency. Alpha-mannosidosis is inherited in an autosomal recessive fashion and is caused by mutations in the MAN2B1 gene located on chromosome 19 (19 p13.2-q12). Diagnosis is made by measuring acid alpha-mannosidase activity in leukocytes or other nucleated cells and can be confirmed by genetic testing. Elevated urinary secretion of mannose-rich oligosaccharides is suggestive, but not diagnostic. Differential diagnoses are mainly the other lysosomal storage diseases like the mucopolysaccharidoses. Genetic counseling should be given to explain the nature of the disease and to detect carriers. Antenatal diagnosis is possible, based on both biochemical and genetic methods. The management should be pro-active, preventing complications and treating manifestations. Infections must be treated frequently. Otolaryngological treatment of fluid in the middle ear is often required and use of hearing aids is invariably required. Early educational intervention for development of social skills is needed and physiotherapy is important to improve bodily function. Orthopedic surgery may be necessary. The long-term prognosis is poor. There is an insidiously slow progression of neuromuscular and skeletal deterioration over several decades, making most patients wheel-chair dependent. No patients manage to be completely socially independent. Many patients are over 50 years of age.

[Neurological presentations of lysosomal diseases in adult patients]

Lysosomal diseases represent a large group of genetic storage disorders characterized by a defect in the catabolism of complex molecules within the lysosome. Effective treatments are now possible for some of them given progresses in bone-marrow transplantation, enzyme replacement therapy and substrate reduction therapy. Neurologists and psychiatrists are concerned by these diseases because they can present in adolescence or adulthood with progressive neuropsychiatric signs. Here we focus on late-onset clinical forms which can be met in an adult neurology or psychiatric department. Lysosomal diseases were classified into 3 groups: (1) leukodystrophies (metachromatic leukodystrophy, Krabbe's disease and Salla's disease); (2) Neurodegenerative or psychiatric-like diseases (GM1 and GM2 gangliosidoses, Niemann Pick type C disease, sialidosis type I, ceroid-lipofuscinosis, mucopolysaccharidosis type III); (3) multisystemic diseases (Gaucher's disease, Fabry's disease, alpha and B mannosidosis, Niemann Pick disease type B, fucosidosis, Schindler/Kanzaki disease, and mucopolysaccharidosis type I and II. We propose a diagnostic approach guided by clinical examination, brain MRI, electrodiagnostic studies and abdominal echography.

Correction of enzyme levels with allogeneic hematopoeitic progenitor cell transplantation in Niemann-Pick type B

Niemann-Pick type B (NP) is an autosomal recessive lysosomal storage disorder with variable phenotypes for which few patients have undergone hematopoietic progenitor cell (HPC) transplantation. We present an 18-month old with NP type B who underwent two allogeneic HPC transplants from her HLA-identical sister. Sphingomyelinase in the peripheral leucocytes and skin fibroblasts was absent at diagnosis. Engraftment failed following initial transplant; therefore a second with the same donor was performed. Engraftment since has been durable; all subsequent sphingomyelinase levels have been normal. Our experience indicates that HPC transplantation for patients with NP type B is feasible and beneficial.

Morphopathological features in tissues of α-mannosidosis guinea pigs at different gestational ages

Alpha-mannosidosis is an inherited metabolic disorder characterized by a reduction in alpha-D-mannosidase and intralysosomal accumulation of undegraded mannose-containing oligosaccharides. The alpha-mannosidosis guinea pig exhibits pathological similarities to its human counterpart, which make it a valuable animal model. To trace the progression of alpha-mannosidosis during foetal development, brain and visceral organs from affected and unaffected guinea pigs at 30, 36, 38, 51 and 65 days of gestation (dg) were examined by light and electron microscopy (term: approximately 68 dg). In the affected brain, distended lysosomes (vacuoles) were scarce up to 38 dg and were seen in few differentiating neuronal cells but mostly in macrophages, pericytes and endothelial cells. At 51 and 65 dg, several vacuoles were observed in some neurones, in many Purkinje cells, pericytes, endothelial and microglial cells, and in few cerebellar internal granule cells. Myelination had started by 51 dg. Non-myelinated axonal spheroids were detected in the brainstem at 65 dg. In the kidney cortex and liver, an increase in vacuolation was noticed between 36 and 65 dg. Some vacuolated cells were also noticed in the lungs and spleen at 51 and 65 dg. Altogether, these histological observations suggest that alpha-mannosidosis is unlikely to affect ontogenesis before the second half of gestation in guinea pigs; however, the morphopathological features recorded during the last quarter of gestation (which may roughly correspond to the period covering near term to 1-2 years of age in human) were clearly noticeable and may have had some impact.

Glycosylation, transport, and complex formation of palmitoyl protein thioesterase 1 (PPT1)--distinct characteristics in neurons

BACKGROUND

Neuronal ceroid lipofuscinoses (NCLs) are collectively the most common type of recessively inherited childhood encephalopathies. The most severe form of NCL, infantile neuronal ceroid lipofuscinosis (INCL), is caused by mutations in the CLN1 gene, resulting in a deficiency of the lysosomal enzyme, palmitoyl protein thioesterase 1 (PPT1). The deficiency of PPT1 causes a specific death of neocortical neurons by a mechanism, which is currently unclear. To understand the function of PPT1 in more detail, we have further analyzed the basic properties of the protein, especially focusing on possible differences in non-neuronal and neuronal cells.

RESULTS

Our study shows that the N-glycosylation of N197 and N232, but not N212, is essential for PPT1's activity and intracellular transport. Deglycosylation of overexpressed PPT1 produced in neurons and fibroblasts demonstrates differentially modified PPT1 in different cell types. Furthermore, antibody internalization assays showed differences in PPT1 transport when compared with a thoroughly characterized lysosomal enzyme aspartylglucosaminidase (AGA), an important observation potentially influencing therapeutic strategies. PPT1 was also demonstrated to form oligomers by size-exclusion chromatography and co-immunoprecipitation assays. Finally, the consequences of disease mutations were analyzed in the perspective of our new results, suggesting that the mutations increase both the degree of glycosylation of PPT1 and its ability to form complexes.

CONCLUSION

Our current study describes novel properties for PPT1. We observe differences in PPT1 processing and trafficking in neuronal and non-neuronal cells, and describe for the first time the ability of PPT1 to form complexes. Understanding the basic characteristics of PPT1 is fundamental in order to clarify the molecular pathogenesis behind neurodegeneration in INCL.

Inflammatory cytokines and the development of pulmonary complications after allogeneic hematopoietic cell transplantation in patients with inherited metabolic storage disorders

Patients with inherited metabolic storage disorders are at a higher risk of developing pulmonary complications after hematopoietic cell transplantation (HCT). This single-center prospective study of 48 consecutive inherited metabolic storage disorder patients was performed to identify risk factors for the development of pulmonary complications after HCT. Before HCT, subjects underwent bronchoalveolar lavage (BAL) for cell count, culture, nitrite levels, and analysis of proinflammatory cytokines and chemokines. The overall incidence of pulmonary complications was 52% (infectious, 23%; noninfectious, 29%) over a period of 4 years. Diffuse alveolar hemorrhage was the most frequent noninfectious complication and occurred in 19% of patients, all of whom had a diagnosis of mucopolysaccharidosis (Hurler and Maroteaux-Lamy syndromes). Levels of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor alpha, macrophage inflammatory protein 1alpha, and granulocyte colony-stimulating factor in BAL fluid samples obtained before HCT were higher in patients with mucopolysaccharidoses than in patients with leukodystrophies. In addition, levels of IL-1beta, IL-6, IL-8, and granulocyte colony-stimulating factor were increased in the BAL fluid of patients who developed noninfectious pulmonary complications compared with those who did not develop pulmonary complications. It is interesting to note that most noninfectious pulmonary complications occurred in patients with mucopolysaccharidoses, especially diffuse alveolar hemorrhage, which occurred exclusively in patients with mucopolysaccharidoses. Higher levels of bronchial proinflammatory cytokines and chemokines may be predictive of the development of subsequent posttransplantation noninfectious complications in patients with mucopolysaccharidoses, especially those with Hurler syndrome. Larger studies will be required to further elucidate etiologic mechanisms and predictive factors.

Bone marrow transplantation for lysosomal storage disorders

Bone marrow transplantation for lysosomal storage disorders has been used for the past 25 years. The early allure of a promising new therapy has given way to more realistic expectations, as it has become clear that bone marrow transplantation is not a cure, but merely ameliorates the clinical phenotype. The results in some disorders are more acceptable than in others. Significant challenges have emerged, particularly the poor mesenchymal and neurological responses. Important recent advances in lysosomal biology, both in health and disease, have helped us to better understand the results of bone marrow transplantation, and to rationalize its role in the treatment of lysosomal storage disorders alongside newer therapies. At the same time, they have helped researchers to explore new therapeutic applications of bone marrow cells, such as gene and stem cell therapy.

Neurocognitive and psychotiform behavioral alterations and enhanced hippocampal long-term potentiation in transgenic mice displaying neuropathological features of human alpha-mannosidosis

Mice with alpha-mannosidase gene inactivation provide an experimental model for alpha-mannosidosis, a lysosomal storage disease with severe neuropsychological and psychopathological complications. Neurohistological alterations in these mice were similar to those in patients and included vacuolations and axonal spheroids in the CNS and peripheral nervous system. Vacuolation was most prominent and evenly distributed in neuronal perikarya of the hippocampal CA2 and CA3 regions, whereas CA1 and dentate gyrus were weakly or not affected. Field potential recordings from CA1 region in hippocampal slices showed enhanced theta burst-induced long-term potentiation (LTP) in alpha-mannosidase-deficient mice. Longitudinal assessment in age-matched alpha-mannosidase-deficient and wild-type littermates, using an extended test battery, demonstrated a neurocognitive and psychotiform profile that may relate to the psychopathological alterations in clinical alpha-mannosidosis. Brainstem auditory-evoked potentials and basic neuromotor abilities were not impaired and did not deteriorate with age. Exploratory and conflict tests revealed consistent decreases in exploratory activity and emotional blunting in the knock-out group. alpha-Mannosidosis mice were also impaired in aversively motivated learning and acquisition of signal-shock associations. Acquisition and reversal learning in the water maze task, passive avoidance learning in the step-through procedure, as well as emotional response conditioning in an operant procedure were all impaired. Acquisition or shaping of an appetitive instrumental conditioning task was unchanged. Appetitive odor discrimination learning was only marginally impaired during shaping, whereas both the discrimination and reversal subtasks were normal. We propose that prominent storage and enhanced LTP in hippocampus have contributed to these specific behavioral alterations in alpha-mannosidase-deficient mice.

Allogeneic stem cell transplantation for the treatment of lysosomal and peroxisomal metabolic diseases

This is a review of the clinical responses and prospectus of new therapies following use of allogeneic hematopoietic stem cell transplantation for the treatment of the following disorders: Hurlers syndrome (MPS 1-H), globoid cell leukodystrophy (GLD; Krabbes disease), adrenoleukodystrophy, metachromatic leukodystrophy, Wolmans disease, I-cell disease (mucolipidosis II; MLS-II), alpha-mannosidosis, fucosidosis, Niemann-Pick B/A disease, Slys disease (MPS VII), Gauchers disease (Gaucher-II-III), Battens disease, Farbers disease, Sanfilippo syndrome (MPS-III), Hunters disease (MPS-II), Maroteaux-Lamy syndrome (MPS-VI), and aspartylglucosaminuria (AGU). Over 500 patients with lysosomal and peroxisomal metabolic storage diseases due to deficiency of primary enzymes have been treated with hematopoietic stem cell transplantation since the initial patient was treated a quarter of century ago. Normal enzymatic activity has been robust and continuous over these years without the need for any medication. Proof of principle has been reported for multiple positive effects including that of the reconstruction of the central nervous system. Furthermore, the excellent engraftment rate along with significantly diminished graft-vs-host-disease needs to be emphasized. The genetic diseases enumerated above have remarkable differences from those discussed elsewhere in this issue of Seminars in Immunopathology. Each has a greater genetic heterogeneity. Misdiagnosis resulting in delay of treatment and further decline of function and ultimate quality of life occurs almost all the time. Neonatal screening of these diseases will be mandatory to vastly improve outcomes. Plans are being implemented to use dried blood spots on filter paper, as is commonly done for many other genetic diseases. Many new therapies are being adopted which should enhance positivity and acceptance of treatment by hematopoietic stem cell transplantation.