Amelioration of clinical disease following bone marrow transplantation in fucosidase-deficient dogs

Rare forms of hypomyelination and delayed myelination

Hypomyelination is defined by the evidence of an unchanged pattern of deficient myelination on two MRIs performed at least 6 months apart in a child older than 1 year. When the temporal criteria are not fulfilled, and the follow-up MRI shows a progression of the myelination even if still not adequate for age, hypomyelination is excluded and the pattern is instead consistent with delayed myelination. This can be mild and nonspecific in some cases, while in other cases there is a severe delay that in the first disease stages could be difficult to differentiate from hypomyelination. In hypomyelinating leukodystrophies, hypomyelination is due to a primary impairment of myelin deposition, such as in Pelizaeus Merzabcher disease. Conversely, myelin lack is secondary, often to primary neuronal disorders, in delayed myelination and some condition with hypomyelination. Overall, the group of inherited white matter disorders with abnormal myelination has expanded significantly during the past 20 years. Many of these disorders have only recently been described, for many of them only a few patients have been reported and this contributes to make challenging the diagnostic process and the interpretation of Next Generation Sequencing results. In this chapter, we review the clinical and radiologic features of rare and lesser known forms of hypomyelination and delayed myelination not mentioned in other chapters of this handbook.

Emerging cellular themes in leukodystrophies

Leukodystrophies are a broad spectrum of neurological disorders that are characterized primarily by deficiencies in myelin formation. Clinical manifestations of leukodystrophies usually appear during childhood and common symptoms include lack of motor coordination, difficulty with or loss of ambulation, issues with vision and/or hearing, cognitive decline, regression in speech skills, and even seizures. Many cases of leukodystrophy can be attributed to genetic mutations, but they have diverse inheritance patterns (e.g., autosomal recessive, autosomal dominant, or X-linked) and some arise from de novo mutations. In this review, we provide an updated overview of 35 types of leukodystrophies and focus on cellular mechanisms that may underlie these disorders. We find common themes in specialized functions in oligodendrocytes, which are specialized producers of membranes and myelin lipids. These mechanisms include myelin protein defects, lipid processing and peroxisome dysfunction, transcriptional and translational dysregulation, disruptions in cytoskeletal organization, and cell junction defects. In addition, non-cell-autonomous factors in astrocytes and microglia, such as autoimmune reactivity, and intercellular communication, may also play a role in leukodystrophy onset. We hope that highlighting these themes in cellular dysfunction in leukodystrophies may yield conceptual insights on future therapeutic approaches.

Fucosidosis in a Chinese boy: a case report and literature review

Fucosidosis is a rare lysosomal storage disease, resulting from a deficiency in an alpha-l-fucosidase enzyme. There are fewer than 120 cases of this disease worldwide and very few reported in Chinese children. Here, we report a Chinese boy presenting with psychomotor regression, dermatological abnormality, dysostosis multiplex, and classic changes observed with head magnetic resonance imaging. He was diagnosed with fucosidosis, with a previously reported homozygous mutation of c.393(exon2)T > A, p.Tyr131Stop, in the FUCA1 gene. Increasing awareness of fucosidosis will help in the early diagnosis of this disease and could shed light on the therapeutic role of hematopoietic stem cell transplantation, which may be effective in early stages of the disease.

Fucosidosis-Clinical Manifestation, Long-Term Outcomes, and Genetic Profile-Review and Case Series

Fucosidosis is a neurodegenerative disorder which progresses inexorably. Clinical features include coarse facial features, growth retardation, recurrent upper respiratory infections, dysostosis multiplex, and angiokeratoma corporis diffusum. Fucosidosis is caused by mutations in the FUCA1 gene resulting in α-L-fucosidase deficiency. Only 36 pathogenic variants in the FUCA1 gene are related to fucosidosis. Most of them are missense/nonsense substitutions; six missense and 11 nonsense mutations. Among deletions there were eight small and five gross changes. So far, only three splice site variants have been described—one small deletion, one complete deletion and one stop-loss mutation. The disease has a significant clinical variability, the cause of which is not well understood. The genotype–phenotype correlation has not been well defined. This review describes the genetic profile and clinical manifestations of fucosidosis in pediatric and adult cases.

The Role of Hematopoietic Cell Transplant in the Glycoprotein Diseases

The glycoprotein disorders are a group of lysosomal storage diseases (α-mannosidosis, aspartylglucosaminuria, β-mannosidosis, fucosidosis, galactosialidosis, sialidosis, mucolipidosis II, mucolipidosis III, and Schindler Disease) characterized by specific lysosomal enzyme defects and resultant buildup of undegraded glycoprotein substrates. This buildup causes a multitude of abnormalities in patients including skeletal dysplasia, inflammation, ocular abnormalities, liver and spleen enlargement, myoclonus, ataxia, psychomotor delay, and mild to severe neurodegeneration. Pharmacological treatment options exist through enzyme replacement therapy (ERT) for a few, but therapies for this group of disorders is largely lacking. Hematopoietic cell transplant (HCT) has been explored as a potential therapeutic option for many of these disorders, as HCT introduces functional enzyme-producing cells into the bone marrow and blood along with the engraftment of healthy donor cells in the central nervous system (presumably as brain macrophages or a type of microglial cell). The outcome of HCT varies widely by disease type. We report our institutional experience with HCT as well as a review of the literature to better understand HCT and outcomes for the glycoprotein disorders.

Canine Models of Inherited Musculoskeletal and Neurodegenerative Diseases

Mouse models of human disease remain the bread and butter of modern biology and therapeutic discovery. Nonetheless, more often than not mouse models do not reproduce the pathophysiology of the human conditions they are designed to mimic. Naturally occurring large animal models have predominantly been found in companion animals or livestock because of their emotional or economic value to modern society and, unlike mice, often recapitulate the human disease state. In particular, numerous models have been discovered in dogs and have a fundamental role in bridging proof of concept studies in mice to human clinical trials. The present article is a review that highlights current canine models of human diseases, including Alzheimer's disease, degenerative myelopathy, neuronal ceroid lipofuscinosis, globoid cell leukodystrophy, Duchenne muscular dystrophy, mucopolysaccharidosis, and fucosidosis. The goal of the review is to discuss canine and human neurodegenerative pathophysiologic similarities, introduce the animal models, and shed light on the ability of canine models to facilitate current and future treatment trials.

Large animal models contribute to the development of therapies for central and peripheral nervous system dysfunction in patients with lysosomal storage diseases

Lysosomal storage diseases (LSDs) are a group of 70 monogenic disorders characterized by the lysosomal accumulation of a substrate. As a group, LSDs affect ~1 in 5000 live births; however, each individual storage disease is rare, limiting the ability to perform natural history studies or to perform clinical trials. Perhaps in no other biomedical field have naturally occurring large animal (canine, feline, ovine, caprine, and bovine) models been so essential for understanding the fundamentals of disease pathogenesis and for developing safe and effective therapies. These models were critical for the development of hematopoietic stem cell transplantation in α- and β- mannosidosis, fucosidosis, and the mucopolysaccharidoses; enzyme replacement therapy for fucosidosis, the mucopolysaccharidoses, and neuronal ceroid lipofuscinosis; and small molecule therapy in Niemann-Pick type C disease. However, their most notable contributions to the biomedical field are in the development of gene therapy for LSDs. Adeno-associated viral vectors to treat nervous system disease have been evaluated in the large animal models of α-mannosidosis, globoid cell leukodystrophy, GM1 and GM2 gangliosidosis, the mucopolysaccharidoses, and neuronal ceroid lipofuscinosis. This review article will summarize the large animal models available for study as well as their contributions to the development of central and peripheral nervous system dysfunction in LSDs.

Companion animal models of neurological disease

Clinical translation of novel therapeutics that improve the survival and quality of life of patients with neurological disease remains a challenge, with many investigational drug and device candidates failing in advanced stage clinical trials. Naturally occurring inherited and acquired neurological diseases, such as epilepsy, inborn errors of metabolism, brain tumors, spinal cord injury, and stroke occur frequently in companion animals, and many of these share epidemiologic, pathophysiologic and clinical features with their human counterparts. As companion animals have a relatively abbreviated lifespan and genetic background, are immunocompetent, share their environment with human caregivers, and can be clinically managed using techniques and tools similar to those used in humans, they have tremendous potential for increasing the predictive value of preclinical drug and device studies. Here, we review comparative features of spontaneous neurological diseases in companion animals with an emphasis on neuroimaging methods and features, illustrate their historical use in translational studies, and discuss inherent limitations associated with each disease model. Integration of companion animals with naturally occurring disease into preclinical studies can complement and expand the knowledge gained from studies in other animal models, accelerate or improve the manner in which research is translated to the human clinic, and ultimately generate discoveries that will benefit the health of humans and animals.

Sensorimotor and Neurocognitive Dysfunctions Parallel Early Telencephalic Neuropathology in Fucosidosis Mice

Fucosidosis is a lysosomal storage disorder (LSD) caused by lysosomal α-L-fucosidase deficiency. Insufficient α-L-fucosidase activity triggers accumulation of undegraded, fucosylated glycoproteins and glycolipids in various tissues. The human phenotype is heterogeneous, but progressive motor and cognitive impairments represent the most characteristic symptoms. Recently, Fuca1-deficient mice were generated by gene targeting techniques, constituting a novel animal model for human fucosidosis. These mice display widespread LSD pathology, accumulation of secondary storage material and neuroinflammation throughout the brain, as well as progressive loss of Purkinje cells. Fuca1-deficient mice and control littermates were subjected to a battery of tests detailing different aspects of motor, emotional and cognitive function. At an early stage of disease, we observed reduced exploratory activity, sensorimotor disintegration as well as impaired spatial learning and fear memory. These early markers of neurological deterioration were related to the respective stage of neuropathology using molecular genetic and immunochemical procedures. Increased expression of the lysosomal marker Lamp1 and neuroinflammation markers was observed throughout the brain, but appeared more prominent in cerebral areas in comparison to cerebellum of Fuca1-deficient mice. This is consistent with impaired behaviors putatively related to early disruptions of motor and cognitive circuits particularly involving cerebral cortex, basal ganglia, and hippocampus. Thus, Fuca1-deficient mice represent a practical and promising fucosidosis model, which can be utilized for pathogenetic and therapeutic studies.

Ocular findings in a patient with fucosidosis

Purpose

To describe the ocular findings in a patient with fucosidosis, a rare inborn lysosomal storage disease.

Observations

A 14 year-old female presented with angiokeratomas corporis diffusum, coarse facial features, poor verbal skills, hearing impairment and mild developmental delay. A lysosomal storage enzyme screen confirmed absent activity of α-l-fucosidase consistent with a diagnosis of fucosidosis. Her eye exam was remarkable for telangiectatic vessels in the inferior conjunctiva and mild corneal stromal haze bilaterally. Spectral domain–optical coherence tomography scans of the macula and a full-field electroretinogram were normal.

Conclusions and importance

We describe the findings in a 14 year-old patient with fucosidosis and review the systemic and ocular manifestations of this rare lysosomal storage disease.

A mouse model for fucosidosis recapitulates storage pathology and neurological features of the milder form of the human disease

Fucosidosis is a rare lysosomal storage disorder caused by the inherited deficiency of the lysosomal hydrolase α-L-fucosidase, which leads to an impaired degradation of fucosylated glycoconjugates. Here, we report the generation of a fucosidosis mouse model, in which the gene for lysosomal α-L-fucosidase (Fuca1) was disrupted by gene targeting. Homozygous knockout mice completely lack α-L-fucosidase activity in all tested organs leading to highly elevated amounts of the core-fucosylated glycoasparagine Fuc(α1,6)-GlcNAc(β1-N)-Asn and, to a lesser extent, other fucosylated glycoasparagines, which all were also partially excreted in urine. Lysosomal storage pathology was observed in many visceral organs, such as in the liver, kidney, spleen and bladder, as well as in the central nervous system (CNS). On the cellular level, storage was characterized by membrane-limited cytoplasmic vacuoles primarily containing water-soluble storage material. In the CNS, cellular alterations included enlargement of the lysosomal compartment in various cell types, accumulation of secondary storage material and neuroinflammation, as well as a progressive loss of Purkinje cells combined with astrogliosis leading to psychomotor and memory deficits. Our results demonstrate that this new fucosidosis mouse model resembles the human disease and thus will help to unravel underlying pathological processes. Moreover, this model could be utilized to establish diagnostic and therapeutic strategies for fucosidosis.

Associations between neurologic dysfunction and lesions in canine fucosidosis

Canine fucosidosis in English Springer spaniels is the only animal model of the neurovisceral lysosomal storage disease fucosidosis available for preclinical therapeutic trials. For this reason, it is crucial to identify critical time points in disease progression, and if there are particular lesions associated with specific aspects of neurologic dysfunction. Historical records of 53 canine fucosidosis cases from 1979 to 2009 containing a neurologic dysfunction score assessing motor, behavioral and sensory dysfunction were interrogated by statistical analysis. Motor and behavioral dysfunction scores assessing gait deficits and apprehensive behavior first significantly increased at 12-17 months, and increased at each 6-month interval thereafter. Sensory dysfunction scores, assessing hearing loss, balance and vision deterioration, did not significantly increase until 18-23 months, and coincided with a rapid decline in neurologic function. Regression analysis incorporating published neuropathology data, measured by image analysis, identified neuroinflammation and apoptotic cell death as significant informative predictors of increasing neurologic dysfunction. These findings indicate that the level of neuropathology required to induce consistent and conspicuous clinical signs in canine fucosidosis is reached by approximately 12 months of age in the absence of other disease processes. Significant association between neuroinflammation and apoptotic cell death also suggests that specifically targeting these lesions combined with enzyme replacement in future studies may reduce disease burden in fucosidosis. Overall, examining this historical clinical data to identify associations between the extent of neuropathology and degree of clinical dysfunction provides a useful reference tool for monitoring disease and evaluating therapeutic trials conducted in canine fucosidosis.

The effects of intracisternal enzyme replacement versus sham treatment on central neuropathology in preclinical canine fucosidosis

BACKGROUND

Fucosidosis results from lack of α-L-fucosidase activity, with accumulation of fucose-linked substrates in the nervous system and viscera leading to progressive motor and mental deterioration, and death. The naturally occurring dog model of fucosidosis was used to evaluate the neuropathological responses to partial enzyme replacement, and substrate reduction in early disease following treatment with recombinant canine α-L-fucosidase delivered through cerebrospinal fluid.

METHODS

Neuropathology in both treated (n = 3) and untreated fucosidosis-affected (n = 3) animals was evaluated with immunohistochemistry, image analysis, manual quantification and gene expression analysis and compared with unaffected age-matched controls (n = 3) in an extension of our previous biochemical report on the same cohort. Data were analyzed by ANOVA.

RESULTS

Quantification demonstrated a consistent trend to reduction in vacuolation, pyramidal neuron loss, astrocytosis, microgliosis, perivascular storage, apoptosis, oligodendrocyte loss, and hypomyelination throughout the central nervous system of enzyme treated animals compared to placebo-treated, age-matched affected controls. Key lesions including lysosomal expansion in neurons of deep cortex, astrocytosis in cerebral cortex and medulla, and increased lysosomal membrane associated protein-1 (LAMP-1) gene expression were ameliorated in treated animals. There was no change in spheroid formation and loss of Purkinje cells, but Purkinje cell vulnerability to apoptosis was reduced with treatment.

CONCLUSIONS

Despite reduced severity of fucosidosis neuropathology with partial enzyme replacement, more complete and sustained biochemical correction is required to halt neuropathological processes in this large animal model of lysosomal storage disease.

Delivering drugs to the central nervous system: an overview

Developing therapies for the brain is perhaps the greatest challenge facing modern medicine today. While a great many potential therapies show promise in animal models, precious few make it to approval or are even studied in human patients. The particular challenges to the translation of neurotherapeutics to the clinic are many, but a major barrier is difficulty in delivering therapeutics into the brain. The goal of this workshop was to present ways to deliver therapeutics to the brain, including the limitations of each method, and describe ways to track their delivery, safety, and efficacy. Solving the problem of delivery will aid translation of therapeutics for patients suffering from neurodegeneration and other disorders of the brain.

Late diagnosis of fucosidosis in a child with progressive fixed dystonia, bilateral pallidal lesions and red spots on the skin

Fucosidosis is a rare lysosomal storage disease. A 14-year-old girl is presented, with recurrent infections, progressive dystonic movement disorder and mental retardation with onset in early childhood. The clinical picture was also marked by mild morphologic features, but absent dysostosis multiplex and organomegaly. MRI images at 6.5 years of age were reminiscent of pallidal iron deposition ("eye-of-the-tiger" sign) seen in neurodegeneration with brain iron accumulation (NBIA) disorders. Progressively spreading angiokeratoma corporis diffusum led to the correct diagnosis. This case extends the scope of clinical and neuroradiological manifestations of fucosidosis.

Advances and pitfalls of cell therapy in metabolic leukodystrophies

Leukodystrophies are a group of disorders characterized by myelin dysfunction, either at the level of myelin formation or maintenance, that affect the central nervous system (CNS) and also in some cases, to a lesser extent, the peripheral nervous system (PNS). Although these genetic-based disorders are generally rare, all together they have a significant impact in the society, with an estimated overall incidence of 1 in 7,663 live births. Currently, there is no cure for leukodystrophies, and the development of effective treatments remains challenging. Not only leukodystrophies generally progress very fast, but also most are multifocal needing the simultaneous targeting at multiple sites. Moreover, as the CNS is affected, the blood-brain barrier (BBB) limits the efficacy of treatment. Recently, interest on cell therapy has increased, and the leukodystrophies for which metabolic correction is needed have become first-choice candidates for cell-based clinical trials. In this review, we present and discuss the available cell transplantation therapies in metabolic leukodystrophies including fucosidosis, X-linked adrenoleukodystrophy, metachromatic leukodystrophy, Canavan disease, and Krabbe's disease. We will discuss the latest advances of cell therapy and its pitfalls in this group of disorders, taking into account, among others, the limitations imposed by reduced cell migration in multifocal conditions, the need to achieve corrective enzyme threshold levels, and the growing awareness that not only myelin but also the associated axonopathy needs to be targeted in some leukodystrophies.

Treatment of canine fucosidosis by intracisternal enzyme infusion

The blood brain barrier is the major obstacle to treating lysosomal storage disorders of the central nervous system such as canine fucosidosis. This barrier was overcome by three, monthly injections of recombinant canine α-l-fucosidase enzyme were given intracisternally. In dogs treated from 8 weeks of age enzyme reached all areas of central nervous system as well as the cervical lymph node, bone marrow and liver. Brainstem and spinal cord samples from regions adjacent to the injection site had highest enzyme levels (39-73% of normal). Substantial enzyme activity (8.5-20% of normal controls) was found in the superficial brain compared to deeper regions (2.6-5.5% of normal). Treatment significantly reduced the fucosyl-linked oligosaccharide accumulation in most areas of CNS, liver and lymph node. In the surface and deep areas of lumbar spinal cord, oligosaccharide accumulation was corrected (79-80% reduction) to near normal levels (p<0.05). In the spinal meninges (thoracic and lumbar) enzyme activity (35-39% of normal control) and substrate reduction (58-63% affected vehicle treated samples) reached levels similar to those seen in phenotypically normal carriers (p<0.05).The procedure was safe and well-tolerated, treated (average 16%) dogs gained more weight (p<0.05) and there was no antibody formation or inflammatory reaction in plasma and CSF following treatments. The capacity of early ERT to modify progression of biochemical storage in fucosidosis is promising as this disease is currently only amenable to treatment by bone marrow transplantation which entails unacceptably high risks for many patients.

Fucosidosis in a domestic shorthair cat

This paper documents the first reported case of fucosidosis in a cat. The cat presented with signs of forebrain and cerebellar dysfunction and a magnetic resonance imaging scan of the brain suggested a degenerative or metabolic disease process. A fine needle aspirate of grossly normal lymph nodes revealed vacuolated lymphocytes and a renal biopsy of an irregular shaped kidney identified vacuolated tubular epithelial cells. A white cell lysosomal enzyme screen revealed negligible α-fucosidase activity. Fucosidosis should be considered in the differential diagnosis of young cats with cerebellar dysfunction and must be added to the list of lysosomal storage diseases affecting the cat.

Five decades of progress in haematopoietic cell transplantation based on the preclinical canine model

The preclinical canine model has proved valuable for the development of principles and techniques of haematopoietic cell transplantation (HCT) applicable to human patients. Studies in random-bred dogs concerning the impact of histocompatibility barriers on engraftment and graft-versus-host disease, the kinetics of immunological reconstitution, the efficacy of various pretransplant conditioning regimens, post-transplantation immunosuppression protocols, treatment of malignant diseases, and graft-versus-tumour effects have advanced HCT from an investigational therapy with uncertain clinical benefit half a century ago to an important treatment choice for thousands of patients treated annually in transplantation centres worldwide. More recent preclinical canine studies have resulted in the clinical translation of non-myeloablative, minimally invasive transplantation protocols that have extended allogeneic HCT to include older human patients with malignant and non-malignant, acquired or inherited haematological disorders, and those with comorbid conditions. Here, we review the contributions of the canine model to modern HCT and describe the usefulness of HCT for the treatment of canine haematological disorders.

Allogeneic haemopoietic stem cell transplantation in children: what alternative donor should we choose when no matched sibling is available?

Allogeneic haemopoietic stem cell transplantation has provided curative therapy for life-threatening malignant and non-malignant diseases in children for over 40 years. Only 25% of children in whom an allograft is indicated have the ideal option of a human leucocyte antigen-identical sibling donor. Substantial advances in the use of alternative donors (unrelated volunteer donors, haploidentical family donors and unrelated umbilical cord blood donors) now make it possible for almost all children to benefit from this life-saving treatment. Each donor choice is associated with distinct advantages and disadvantages, which have greater or lesser importance in different diseases. We review the current status of alternative donor transplantation for haematological malignancies, primary immunodeficiencies, inherited metabolic disorders and bone marrow failure syndromes and outline the current UK consensus donor selection algorithms for these disease groups.

Gene therapy for lysosomal storage diseases (LSDs) in large animal models

Lysosomal storage diseases (LSDs) are inherited metabolic disorders caused by deficient activity of a single lysosomal enzyme or other defects resulting in deficient catabolism of large substrates in lysosomes. There are more than 40 forms of inherited LSDs known to occur in humans, with an aggregate incidence estimated at 1 in 7,000 live births. Clinical signs result from the inability of lysosomes to degrade large substrates; because most lysosomal enzymes are ubiquitously expressed, a deficiency in a single enzyme can affect multiple organ systems. Thus LSDs are associated with high morbidity and mortality and represent a significant burden on patients, their families, the health care system, and society. Because lysosomal enzymes are trafficked by a mannose 6-phosphate receptor mechanism, normal enzyme provided to deficient cells can be localized to the lysosome to reduce and prevent storage. However, many LSDs remain untreatable, and gene therapy holds the promise for effective therapy. Other therapies for some LSDs do exist, or are under evaluation, including heterologous bone marrow or cord blood transplantation (BMT), enzyme replacement therapy (ERT), and substrate reduction therapy (SRT), but these treatments are associated with significant concerns, including high morbidity and mortality (BMT), limited positive outcomes (BMT), incomplete response to therapy (BMT, ERT, and SRT), life-long therapy (ERT, SRT), and cost (BMT, ERT, SRT). Gene therapy represents a potential alternative, albeit with its own attendant concerns, including levels and persistence of expression and insertional mutagenesis resulting in neoplasia. Naturally occurring animal homologues of LSDs have been described in all common domestic animals (and in some that are less common) and these animal models play a critical role in evaluating the efficacy and safety of therapy.

Fucosidosis with angiokeratoma. Immunohistochemical & electronmicroscopic study of a new case and literature review

Fucosidosis is a rare lysosomal storage disease due to alpha-L-fucosidase deficiency. It presents clinically with neurological, skeletal, and cutaneous findings, including mainly angiokeratoma corporis diffusum. Electronmicroscopic examination reveals characteristic electron-lucent cytoplasmic vacuolization present in several cell types of the skin and other tissues. We present here a new patient suffering from fucosidosis with angiokeratoma, whose normal and diseased skin was studied by lightmicroscopy and electronmicroscopy. The salient clinicopathological features of this disease are briefly reviewed.

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.

The status of hematopoietic stem cell transplantation in lysosomal storage disease

Lysosomal storage diseases are a group of disorders which have in common an inherited defect in lysosomal function-in most cases, a missing intralysosomal enzyme. Research into potential treatment options for this group of disorders has focused on enzyme replacement. Over the past two decades, hematopoietic stem cell transplantation has been used with increasing frequency to treat patients with lysosomal storage disease by providing a population of cells with the capacity to produce the missing enzyme. The success of marrow transplantation depends on the specific enzyme deficiency and the stage of the disease. Generally, visceral symptoms can be improved, whereas skeletal lesions remain relatively unaffected. The effect on neurologic symptoms varies. Hematopoietic stem cell transplantation remains a viable treatment option in those lysosomal storage diseases where data supportive of disease stabilization or amelioration are known. Early transplantation is the goal so that enzyme replacement may occur before extensive central nervous system injury becomes evident. When inadequate clinical data are available, the decision to perform transplantation requires experimental data demonstrating that the enzyme in question is both excreted from normal cells and taken up by affected cells as evidenced by elimination of storage material in vitro.

Animal models for mucopolysaccharidoses and their clinical relevance

The mucopolysaccharidoses (MPS) are characterized by the accumulation of glycosaminoglycans (GAG) and result from the impaired function of one of 11 enzymes required for normal GAG degradation. MPS II was the first MPS to be defined clinically in humans and is caused by deficient activity of the enzyme iduronate-2-sulphatase. MPS VI was the first MPS recognized in an animal; since then, all but MPS IIIC and IX have been described as naturally occurring in animals or made by knock-out technology. As in humans, all are inherited as autosomal recessive traits, except for MPS II, which is X-linked. Most animal colonies have been established from single related heterozygous animals, making the affected offspring homozygous for the same mutant allele. Importantly, these models have disease pathology that is similar to that seen in humans, making the animals extremely valuable for the investigation of disease pathogenesis and the testing of therapies. Large animal homologues are similar to humans in natural genetic diversity, approaches to therapy and care, and the possibility of evaluating long-term effects of treatment. Therapeutic strategies for MPS include enzyme replacement therapy, heterologous bone marrow transplantation, and somatic cell gene transfer, all of which have been tested in animals with some success.

Secretion of phosphomannosyl-deficient arylsulphatase A and cathepsin D from isolated human macrophages

The transfer of macrophage-secreted arylsulphatase A (ASA) to enzyme-deficient brain cells is part of the therapeutic concept of bone marrow transplantation in lysosomal storage diseases. Here we have investigated this transfer in vitro. The uptake of (125)I-labelled recombinant human ASA purified from ASA-overexpressing mouse embryonic fibroblasts deficient for mannose 6-phosphate (M6P) receptors in a mouse ASA-deficient astroglial cell line was completely inhibited by M6P. In contrast, when ASA-deficient astroglial cells were incubated with secretions of [(35)S]methionine-labelled human macrophages or mouse microglia, containing various lysosomal enzymes, neither ASA nor cathepsin D (CTSD) were detected in acceptor cells. Co-culturing of metabolically labelled macrophages with ASA-deficient glial cells did not result in an M6P-dependent transfer of ASA or CTSD between these two cell types. In secretions of [(33)P]phosphate-labelled macrophages no or weakly phosphorylated ASA and CTSD precursor polypeptides were found, whereas both intracellular and secreted ASA from ASA-overexpressing baby hamster kidney cells displayed (33)P-labelled M6P residues. Finally, the uptake of CTSD from secretions of [(35)S]methionine-labelled macrophages in rat hepatocytes was M6P-independent. These data indicated that lysosomal enzymes secreted by human macrophages or a mouse microglial cell line cannot be endocytosed by brain cells due to the failure to equip newly synthesized lysosomal enzymes with the M6P recognition marker efficiently. The data suggest that other mechanisms than the proposed M6P-dependent secretion/recapture of lysosomal enzymes might be responsible for therapeutic effects of bone marrow transplantation in the brain.

Four year follow-up of a case of fucosidosis treated with unrelated donor bone marrow transplantation

Fucosidosis is a rare autosomal recessive lysosomal disorder caused by alpha-fucosidase deficiency. We report a child with fucosidosis, second daughter of non-consanguineous parents, for whom biochemical diagnosis followed clinical evidence of the disease in her older sister. Based on previous experiences, the indication to transplant was considered. Since she lacked a matched sibling, an unrelated marrow donor was found. At pre-hematopoietic stem cell transplantation evaluation, first signs of neurological involvement were clinically detectable. MRI showed diffuse hypomyelination and auditory brainstem responses and somatic-sensorial evoked potentials were altered. Visual evoked potentials were normal, tortuosity in the retinal veins and peripapillary hemorrhages were detected. Bone marrow transplantation conditioning was with a regimen of busulphan, thiotepa and cyclophosphamide; in vivo Campath 1G, cyclosporin A and short course methotrexate were given to prevent graft-versus-host disease. The patient engrafted rapidly and her post-transplant course was complicated by moderate graft-versus-host disease, transient episodes of idiopathic thrombocytopenic purpura, repeated septic complications and recurrent episodes of Sweet's syndrome. Sequential short tandem repeat polymorphisms on peripheral blood and bone marrow cells documented the persistence of donor engraftment. Follow-up showed a progressive rise of enzymatic levels. Psychomotor development improved, as confirmed by evaluation of evoked potentials and by MRI scanning.

Lysosomal Storage Diseases

Lysosomal storage disorders (LSDs), over 40 different diseases, are now considered treatable disorders. Only a few short years ago, Lysosomal storage disorders were seen as interesting neurodegenerative disorders without any potential for treatment. Effective treatment strategies such as bone marrow transplantation (BMT), enzyme replacement therapy (ERT), and glycolipid synthesis inhibition have been developed in the last 20 years and continue to be researched and evaluated. Bone marrow transplantation began approximately 15 years ago and has shown benefit for some of the lysosomal storage disorders. In order to be effective, the transplant must be performed early in the course of the disease, before the development of irreversible neurologic damage. Diseases such as Hurler appear to respond to BMT, however, improvement in bone disease is much less vigorous than responses in other organs. Krabbe disease responds if the transplant is performed before irreversible signs of neurologic damage appear. Metachromatic leukodystrophy may respond if the transplant can be performed early enough although peripheral nerve findings appear to progress. Other diseases, eg, GM1- and GM2-gangliosidoses do not appear to be altered by BMT. Despite its high cost, ERT has been very effective treatment for type I (non-neuronopathic) Gaucher disease. Enzyme replacement therapy for other LSDs, including ERT for Fabry and Pompe diseases, which are planned to be imminently introduced, and other enzymes such as for Morquio and Hunter diseases that are in the study phases, may be marketed in the very near future. Glycolipid inhibitors, such as N-butyldeoxynijirimycin (OGS-918), have been effective in reducing the liver and spleen volume in type I Gaucher disease. These oral inhibitors may prove to be important adjuncts to ERT and provide the advantage of being able to cross the blood/brain barrier, which limits enzyme access to brain. Currently, clinical studies are being conducted on patients with type III Gaucher disease and Fabry disease using OGS-918. Other, potentially more specific, glycolipid inhibitors are being developed.

Recombinant canine alpha-l-fucosidase: expression, purification, and characterization

Canine fucosidosis has proven to be an excellent large animal model both for the equivalent human disorder and, in more general terms, for the central nervous system pathology found in many of the lysosomal storage disorders. Most importantly studies in this animal model were among the first to convincingly show that bone marrow transplantation could successfully modify the course of clinical central nervous system disease and to define some of the important parameters for successful treatment. In order to evaluate other, more generally applicable routes to treatment of central nervous system disease in the lysosomal storage disorders we have expressed recombinant canine alpha-l-fucosidase (rcFUC) in Chinese hamster ovary and Madin-Darby canine kidney cells to levels of between 2 and 13 mg/liter of culture medium and purified the enzyme to apparent homogeneity by affinity chromatography on fucosylamine-linked agarose. rcFUC is composed of subunits of M(r) 50 kDa and the native enzyme is a homotrimer of M(r) 156 kDa. Kinetic properties of rcFUC were similar to those of FUC isolated from both human and dog liver. rcFUC was shown to be effective in correcting the storage phenotype of human fucosidosis cells after endocytosis via the mannose-6-phosphate-receptor-mediated pathway. It was also shown to degrade fucosylated storage products isolated from affected dog brain. The availability of large amounts of rcFUC will allow us to explore ways of extending the proven efficacy of enzyme replacement therapy to the treatment of central nervous system pathology using the fucosidosis dog as a model system.

Correction of peripheral lysosomal accumulation in mice with aspartylglucosaminuria by bone marrow transplantation

OBJECTIVE

Bone marrow transplantation has been shown to alleviate symptoms outside the CNS in many lysosomal storage diseases depending on the type and stage of the disease, but the effect on neurological symptoms is variable or still unclear. Aspartylglucosaminuria (AGU) is a lysosomal storage disease characterized by mental retardation, recurrent infections in childhood, hepatosplenomegaly and coarse facial features. Vacuolized storage lysosomes are found in all tissues of patients and uncleaved enzyme substrate is excreted in the urine. The recently generated AGU mouse model closely mimicks the human disease and serves as a good model to study the efficiency of bone marrow transplantation in this disease.

METHODS

Eight-week-old AGU mice were lethally irradiated and transplanted with bone marrow from normal donors. The AGA enzyme activity was measured in the liver and the brain and the degree of correction of tissue pathology was analyzed by light and electron microscopy. Reverse bone marrow transplantation (AGU bone marrow to wild-type mice) was also performed.

RESULTS

Six months after transplantation the AGA enzyme activity was 13% of normal in the liver, but only 3% in the brain. Tissue pathology was reversed in the liver and the spleen, but not in the brain and the kidney. The urinary excretion of enzyme substrate was diminished but still detectable. No storage vacuoles were found in the tissues after reverse transplantation, but subtle excretion of uncleaved substrate was detected in the urine.

CONCLUSION

Liver and spleen pathology of AGU was corrected by bone marrow transplantation, but there was no effect on lysosomal accumulation in the CNS and in the kidneys.

Enzyme replacement in murine mucopolysaccharidosis type VII: neuronal and glial response to beta-glucuronidase requires early initiation of enzyme replacement therapy

We have previously shown that mucopolysaccharidosis type VII (MPS VII) mice receiving six weekly injections of recombinant beta-glucuronidase from birth had improved cognitive ability and reduced central nervous system lysosomal storage. However, a single beta-glucuronidase injection at 5 wk of age did not correct neuronal storage. We define the age at which central nervous system storage in MPS VII mice becomes resistant to beta-glucuronidase therapy and determine the effect of enzyme on other tissues by comparing the histology of mice begun on therapy at various times after birth. MPS VII mice received injections on the day of birth and then weekly for 5 wk with 16,000U/g beta-glucuronidase had reduced lysosomal storage in brain. The same therapy begun on d 14 of life or thereafter failed to correct neuronal storage, even when treatment was continued for six doses. Glial responsiveness or accessibility to enzyme also depended on early treatment. In contrast, leptomeningeal, osteoblast, and retinal pigment epithelial storage reduction depended on enzyme dose rather than age at initiation of therapy. Fixed tissue macrophage storage was reduced in all treated MPS VII mice, even those receiving a single dose. These observations indicate that fixed tissue macrophages in MPS VII mice remain sensitive to enzyme replacement therapy well into adulthood although neurons are responsive or accessible to enzyme therapy early in life. Because early initiation of enzyme replacement is important to achieve a central nervous system response, these studies emphasize the importance of newborn screening for lysosomal storage diseases so that early treatment can maximize the likelihood of a favorable therapeutic response.

Bone marrow transplantation as effective treatment of central nervous system disease in globoid cell leukodystrophy, metachromatic leukodystrophy, adrenoleukodystrophy, mannosidosis, fucosidosis, aspartylglucosaminuria, Hurler, Maroteaux-Lamy, and Sly syndromes, and Gaucher disease type III

Over 400 patients with lysosomal and peroxisomal storage diseases have received hematopoietic stem cell transplantation from normal donors. Without treatment, all of these diseases have an inexorable fate leading to central nervous system deterioration and early death. On the other hand, all of the engrafted hosts have had a remarkable positive clinical improvement in response to normalization of previously deficient enzymatic activity. Survival data for those engrafted indicates continued life-span as long as two decades beyond transplantation. The particular diseases treated in this way are included in this article. The specific indications and methods for transplantation are also included in this article.

Bone marrow transplantation does not ameliorate the neurologic symptoms in mice deficient in hypoxanthine guanine phosphoribosyl transferase (HPRT)

The use of bone marrow transplantation (BMT) for the treatment of genetic diseases with neurologic involvement has yielded mixed results. We have employed a mouse model of Lesch-Nyhan disease (LND) to assess the efficacy of BMT in ameliorating the neurologic manifestations of the disease. Adult HPRT-deficient mice exhibit a measurable decrease in striatal dopamine levels and a hypersensitivity to amphetamine. Marrow-ablated adult HPRT-deficient mice were transplanted with marrow from congenic HPRT-expressing mice. BMT altered neither the neurochemical nor the behavioral phenotypes in either HPRT-positive or HPRT-deficient mice. Barring any important species differences, these results suggest that BMT in its present form may not be an effective therapy for Lesch-Nyhan syndrome.

Microglia in cell culture and in transplantation therapy for central nervous system disease

The central nervous system (CNS) is host to a significant population of macrophage-like cells known as microglia. In addition to these cells which reside within the parenchyma, a diverse array of macrophages are present in meningeal, perivascular, and other peripheral locations. The role that microglia and other CNS macrophages play in disease and injury is under intensive investigation, and functions in development and in the normal adult are just beginning to be explored. At present the biology of these cells represents one of the most fertile areas of CNS research. This article describes methodology for the isolation and maintenance of microglia in cell cultures prepared from murine and feline animals. Various approaches to identify microglia are provided, using antibody, lectin, or scavenger receptor ligand. Assays to confirm macrophage-like functional activity, including phagocytosis, lysosomal enzyme activity, and motility, are described. Findings regarding the origin and development of microglia and results of transplantation studies are reviewed. Based on these data, a strategy is presented that proposes to use the microglial cell lineage to effectively deliver therapeutic compounds to the CNS from the peripheral circulation.

Determination of cell origin after marrow transplantation in canines by polymerase chain reaction and quantitation of the ZFY/ZFX genes

BACKGROUND

In order to follow the course of bone marrow engraftment in dogs, and to determine the presence, and percentage, of donor-derived cells in other canine tissues, a simple and fast method of determining cell origin after sex-mismatched bone marrow transplantation was developed.

METHODS

Using universal primers, fragments from genomic DNA corresponding to ZFX and ZFY genes were amplified by polymerase chain reaction. A restriction fragment length polymorphism, combined with densitometric analysis, was then used to distinguish and quantitate ZFY and ZFX sequences. Unknown samples were analyzed against standards of known mixtures of male and female DNA.

RESULTS

Canine ZFY and ZFX genes were clearly resolved after amplification, digestion with HaeIII, and denaturing polyacrylamide gel electrophoresis. Microchimerism could be detected in male and female dog DNA samples derived from a range of fresh and frozen tissues including spleen, testicle, and the central nervous system. The levels of chimerism determined using this method were in either agreement with results obtained by karyotyping or more sensitive, with a detection limit of 0.4% compared with 1-2%.

CONCLUSIONS

Polymerase chain reaction/restriction fragment length polymorphism detection of the ZFY and ZFX genes was found to be simple, accurate, and reliable for assessing engraftment in dogs. When compared with cytogenetic analysis, this method was found to be faster to perform, more capable of detecting lower levels of microchimerism, and useful for detecting donor-derived cells in stored specimens and in tissues other than peripheral blood or bone marrow.

Lysosomal storage diseases of animals: an essay in comparative pathology

A wide variety of inherited lysosomal hydrolase deficiencies have been reported in animals and are characterized by accumulation of sphingolipids, glycolipids, oligosaccharides, or mucopolysaccharides within lysosomes. Inhibitors of a lysosomal hydrolase, e.g., swainsonine, may also induce storage disease. Another group of lysosomal storage diseases, the ceroid-lipofuscinoses, involve the accumulation of hydrophobic proteins, but their pathogenesis is unclear. Some of these diseases are of veterinary importance, and those caused by a hydrolase deficiency can be controlled by detection of heterozygotes through the gene dosage phenomenon or by molecular genetic techniques. Other of these diseases are important to biomedical research either as models of the analogous human disease and/or through their ability to help elucidate specific aspects of cell biology. Some of these models have been used to explore possible therapeutic strategies and to define their limitations and expectations.

Kinetics of Central Nervous System Microglial and Macrophage Engraftment: Analysis Using a Transgenic Bone Marrow Transplantation Model

To determine the kinetics of tissue macrophage and microglial engraftment after bone marrow (BM) transplantation, we have developed a model using the ROSA 26 mouse. Transplanted ROSA 26 cells can be precisely identified in recipient animals because they constitutively express β-galactosidase (β-gal) and neomycin resistance. B6/129 F2 mice were irradiated and transplanted with BM from ROSA 26 donors and their tissues (spleen, marrow, brain, liver, and lung) examined at various time points to determine the kinetics of engraftment. Frozen sections from transplanted animals were stained histochemically for β-gal to identify donor cells. At 1, 2, 6, and 12 months posttransplantation, 98% to 100% of granulocyte-macrophage colonies were of donor (ROSA 26) origin determined by β-gal staining and by neomycin resistance. Splenic monocytes/macrophages were 89% donor origin by 1 month confirming quick and complete engraftment of hematopoietic tissues. At this time, only rare ROSA 26 tissue macrophages or microglia were observed. Alveolar macrophage engraftment was evident by 2 months and had increased to 61% of total tissue macrophages at 1 year posttransplantation. The kinetics of liver Kupffer cell engraftment were similar to those seen in the lung. However, donor microglial engraftment remained only 23% of total microglia at 6 months and increased to only 30% by 1 year. Also, donor microglia were predominantly seen at perivascular and leptomeningeal, and not parenchymal, sites. The data show that microglia derive from BM precursors but turn over at a significantly slower rate than other tissue macrophages. No clinical or histological graft-versus-host disease was observed in the recipients of ROSA 26 BM. These kinetics may impact strategies for the gene therapy of lysosomal storage diseases. Because individual donor cells can be identified in situ, the ROSA 26 model should have many applications in transplantation biology including studies of homing and differentiation.

Kinetics of Central Nervous System Microglial and Macrophage Engraftment: Analysis Using a Transgenic Bone Marrow Transplantation Model

To determine the kinetics of tissue macrophage and microglial engraftment after bone marrow (BM) transplantation, we have developed a model using the ROSA 26 mouse. Transplanted ROSA 26 cells can be precisely identified in recipient animals because they constitutively express β-galactosidase (β-gal) and neomycin resistance. B6/129 F2 mice were irradiated and transplanted with BM from ROSA 26 donors and their tissues (spleen, marrow, brain, liver, and lung) examined at various time points to determine the kinetics of engraftment. Frozen sections from transplanted animals were stained histochemically for β-gal to identify donor cells. At 1, 2, 6, and 12 months posttransplantation, 98% to 100% of granulocyte-macrophage colonies were of donor (ROSA 26) origin determined by β-gal staining and by neomycin resistance. Splenic monocytes/macrophages were 89% donor origin by 1 month confirming quick and complete engraftment of hematopoietic tissues. At this time, only rare ROSA 26 tissue macrophages or microglia were observed. Alveolar macrophage engraftment was evident by 2 months and had increased to 61% of total tissue macrophages at 1 year posttransplantation. The kinetics of liver Kupffer cell engraftment were similar to those seen in the lung. However, donor microglial engraftment remained only 23% of total microglia at 6 months and increased to only 30% by 1 year. Also, donor microglia were predominantly seen at perivascular and leptomeningeal, and not parenchymal, sites. The data show that microglia derive from BM precursors but turn over at a significantly slower rate than other tissue macrophages. No clinical or histological graft-versus-host disease was observed in the recipients of ROSA 26 BM. These kinetics may impact strategies for the gene therapy of lysosomal storage diseases. Because individual donor cells can be identified in situ, the ROSA 26 model should have many applications in transplantation biology including studies of homing and differentiation.

Bone Marrow Transplantation in Acid Sphingomyelinase-Deficient Mice: Engraftment and Cell Migration Into the Brain as a Function of Radiation, Age, and Phenotype

Types A and B Niemann-Pick disease (NPD) result from the deficient activity of the lysosomal hydrolase, acid sphingomyelinase (ASM). A long-term goal of our research is to evaluate the effects of bone marrow transplantation (BMT) and hematopoietic stem cell gene therapy (HSCGT) on the NPD phenotype. As an initial step toward this goal, we have undertaken a study aimed at optimizing hematopoietic cell engraftment in acid sphingomyelinase “knock-out” (ASMKO) mice. Several parameters were analyzed, including the effects of radiation and donor cell number on survival and engraftment of newborn and adult animals, the number of donor cells detected in the brain posttransplantation, and the levels of ASM activity achieved in the brain. A total of 202 ASMKO and normal animals were transplanted and studied, and the overall conclusions were: (1) newborn ASMKO animals were more susceptible to radiation-induced mortality than normal animals, (2) at low radiation doses, increasing the donor cell number improved engraftment, while this was less evident at the higher radiation doses, (3) engraftment was easier to achieve in normal as compared with ASMKO animals, (4) among newborn transplants, the number of donor cells detected in the brain was directly correlated with engraftment in the blood, (5) more donor cells were detected in the brains of newborn ASMKO animals as opposed to newborn normal animals, and (6) no donor cells were found in the brains of animals transplanted as adults, including those that were highly engrafted in the blood. These results provide important information regarding the design of future BMT and HSCGT studies in ASMKO mice and other mouse models and demonstrate the potential of altering the NPD phenotype by these therapeutic strategies.

Bone Marrow Transplantation in Acid Sphingomyelinase-Deficient Mice: Engraftment and Cell Migration Into the Brain as a Function of Radiation, Age, and Phenotype

Types A and B Niemann-Pick disease (NPD) result from the deficient activity of the lysosomal hydrolase, acid sphingomyelinase (ASM). A long-term goal of our research is to evaluate the effects of bone marrow transplantation (BMT) and hematopoietic stem cell gene therapy (HSCGT) on the NPD phenotype. As an initial step toward this goal, we have undertaken a study aimed at optimizing hematopoietic cell engraftment in acid sphingomyelinase “knock-out” (ASMKO) mice. Several parameters were analyzed, including the effects of radiation and donor cell number on survival and engraftment of newborn and adult animals, the number of donor cells detected in the brain posttransplantation, and the levels of ASM activity achieved in the brain. A total of 202 ASMKO and normal animals were transplanted and studied, and the overall conclusions were: (1) newborn ASMKO animals were more susceptible to radiation-induced mortality than normal animals, (2) at low radiation doses, increasing the donor cell number improved engraftment, while this was less evident at the higher radiation doses, (3) engraftment was easier to achieve in normal as compared with ASMKO animals, (4) among newborn transplants, the number of donor cells detected in the brain was directly correlated with engraftment in the blood, (5) more donor cells were detected in the brains of newborn ASMKO animals as opposed to newborn normal animals, and (6) no donor cells were found in the brains of animals transplanted as adults, including those that were highly engrafted in the blood. These results provide important information regarding the design of future BMT and HSCGT studies in ASMKO mice and other mouse models and demonstrate the potential of altering the NPD phenotype by these therapeutic strategies.

Murine mucopolysaccharidosis type VII: long term therapeutic effects of enzyme replacement and enzyme replacement followed by bone marrow transplantation

We demonstrated previously that short term administration of recombinant beta-glucuronidase to newborn mice with mucopolysaccharidosis type VII reduced lysosomal storage in many tissues. Lysosomal storage accumulated gradually after cessation of enzyme replacement therapy. Mice alive at 1 yr of age had decreased bone deformities and less lysosomal storage in cortical neurons. Here we compare the effects of long term enzyme replacement initiated either at birth or at 6 wk of age, and of enzyme administration initiated at birth followed by syngeneic bone marrow transplantation (BMT) at 5 wk of age. Several mice from each treatment group lived to at least 1 yr of age. Liver and spleen samples had beta-glucuronidase levels ranging from 2.4 to 19.8% of normal and showed a parallel decrease in lysosomal storage. The combination of enzyme replacement therapy followed by BMT reduced lysosomal distension in meninges, corneal fibroblasts, and bone when compared with treatment with enzyme alone. Mice treated at birth had less lysosomal storage in some neurons of the brain and the skeletal dysplasia was less severe when compared to mice whose treatment was delayed until 6 wk of age. We conclude that both enzyme replacement alone and early enzyme replacement followed by BMT have long term positive effects on murine mucopolysaccharidosis type VII. In addition, treatment started at birth is far more effective than treatment initiated in young adults.

The mannosidoses and ceroid-lipofuscinoses: experimental studies on two types of storage disease

alpha-Mannosidosis of Angus calves was studied both for its veterinary importance and as a model of analogous human lysosomal storage diseases. This study facilitated a similar study in Australia on Swainsona spp. intoxication of livestock in which the toxic principle was shown to be an indolizidine alkaloid, Swainsonine. These genetic and acquired alpha-mannosidoses are compared with beta-mannosidosis. Collectively the study has helped the understanding of the processes of glycosylation and catabolism of glycoproteins. An experiment of nature involving an alpha-mannosidosis chimeric calf born co-twin to a normal calf helped to define the expectations and limitations of bone marrow transplants in this type of storage disease in humans. The inherited ceroid-lipofuscinoses (Batten disease) were studied in an ovine model. Isolation and analyses of the fluorescent accumulated lipopigment denied the dogma of lipid peroxidation current in the 1970s and 1980s. It was shown that in this, and analogous diseases in humans, the dominantly accumulated species was the very hydrophobic protein, subunit c of mitochondrial ATP synthase. Contrary to the adage that this should reflect a disorder of lysosomal proteolysis, there is accumulating evidence that the primary defect resides in mitochondria. Because of its hydrophobic nature, subunit c forms paracrystaline complexes which appear resistant to proteolysis within the lysosomal apparatus.

Correction of Sanfilippo A skin fibroblasts by retroviral vector-mediated gene transfer

The recent cloning of the sulfamidase gene has made possible the consideration of gene-based therapies for Sanfilippo A syndrome (mucopolysaccharidosis type IIIA), one of the most common of the mucopolysaccharidoses. In this paper, we present the construction of a retroviral vector in which a sulfamidase cDNA is under the transcriptional control of the Moloney murine leukemia virus long terminal repeat. This construct was used to make a high-titer (4 x 10(5) colony-forming units/ml) producer cell line, PA317/LNSSN#19, in the amphotropic packaging cell line PA317. This producer cell line was shown to be helper virus free using an assay for horizontal spread of virus. Virus supernatant from PA317/LNSSN#19 was used to transduce Sanfilippo A fibroblasts, resulting in complete correction of both the enzymatic defect and the storage phenotype as assessed by intracellular accumulation of 35SO4(-)-labeled material. Phenotypic correction was seen even when the levels of viral transduction were low. These results show that gene therapy of the Sanfilippo A syndrome is practicable, although the nature of the disorder suggests that careful consideration needs to be given to the choice of the cellular target for gene transfer.

The molecular defect underlying canine fucosidosis

Fucosidosis is a lysosomal storage disease which affects humans and English springer spaniel dogs. The disease is recessively inherited in both species and results from a deficiency of the enzyme alpha-L-fucosidase. We have recently cloned and sequenced the canine fucosidase gene (EMBL sequence admission number X92448 (cDNA) and X92671-X92678 (individual exonic data)). The gene spans 12 kb and consists of eight exons. SSCP based mutation analysis of affected animals was carried out on the coding region of this gene both with exonic primers, and intronic primer pairs for each exon. A 14 base pair deletion of the cDNA was identified at the 3' end of exon 1 in fucosidosis affected animals. Surprisingly, PCR based genomic cloning of DNA from these animals showed an identical deletion in this DNA, ending at the start of intron 1. This change causes a frameshift and, in consequence, 25 novel codons are transcribed in exon 2 before the first of two adjacent premature stop codons is encountered.

Isolation of the canine alpha-L-fucosidase cDNA and definition of the fucosidosis mutation in English Springer Spaniels

Fucosidosis is a lysosomal storage disorder caused by deficiency of alpha-L-fucosidase. A biochemically and clinically well characterized canine model of fucosidosis exists in a colony of English Springer Spaniels. To facilitate its use as a model for gene therapy and enzyme replacement therapy in lysosomal storage disorders displaying neurological symptoms, isolation of the canine alpha-L-fucosidase cDNA was undertaken. Both the nucleotide sequence and the predicted amino acid sequence of canine fucosidase show high levels of identity with the human and rat sequences. Fucosidosis dogs were found to have a greatly reduced level of alpha-L-fucosidase mRNA when compared with normal dogs by Northern blot analysis. Direct PCR sequencing of products generated from cDNA demonstrated a 14-bp deletion in mRNA from affected dogs. This deletion creates a frameshift mutation and introduces a premature translation termination codon at amino acid position 152 and was shown to correspond to a deletion of the last 14 base pairs of exon 1 of the canine alpha-L-fucosidase gene. Rapid PCR-based screening for the mutation has now been performed on genomic DNA from dogs within the colony, enabling detection of both carriers and homozygotes.

Hematopoietic cell transplantation in fetal lambs with ceroid-lipofuscinosis

Hematopoietic cells from the liver of normal 45-48-day-old fetal lambs (Hb type AA) were transplanted intraperitoneally into 58-60-day-old recipient fetuses (Hb type BB). The recipient fetuses resulted from mating homozygous ceroid-lipofuscinosis affected males with heterozygous, phenotypically normal, females. The sex of the donor fetus was also recorded. At age 2 1/2 months the recipient lambs with ceroid-lipofuscinosis were diagnosed by histopathology of brain biopsies. Monitoring of blood and bone marrow cells showed that an average of 9% of blood cells in ceroid-lipofuscinosis affected recipients were of donor origin. No differences were evident in the clinical course of disease, brain weight, or histopathology of organs between transplanted and non-transplanted lambs with ceroid-lipofuscinosis. Under the conditions of this experiment, transplantation of fetal hematopoietic cells was not beneficial.