Bone marrow transplantation for infantile ceramidase deficiency (Farber disease)

Acid Ceramidase Deficiency: Bridging Gaps between Clinical Presentation, Mouse Models, and Future Therapeutic Interventions

Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME) are ultra-rare, autosomal-recessive, acid ceramidase (ACDase) deficiency disorders caused by ASAH1 gene mutations. Currently, 73 different mutations in the ASAH1 gene have been described in humans. These mutations lead to reduced ACDase activity and ceramide (Cer) accumulation in many tissues. Presenting as divergent clinical phenotypes, the symptoms of FD vary depending on central nervous system (CNS) involvement and severity. Classic signs of FD include, but are not limited to, a hoarse voice, distended joints, and lipogranulomas found subcutaneously and in other tissues. Patients with SMA-PME lack the most prominent clinical signs seen in FD. Instead, they demonstrate muscle weakness, tremors, and myoclonic epilepsy. Several ACDase-deficient mouse models have been developed to help elucidate the complex consequences of Cer accumulation. In this review, we compare clinical reports on FD patients and experimental descriptions of ACDase-deficient mouse models. We also discuss clinical presentations, potential therapeutic strategies, and future directions for the study of FD and SMA-PME.

Clinical Development of Cell Therapies to Halt Lysosomal Storage Diseases: Results and Lessons Learned

Although cross-correction was discovered more than 50 years ago, and held the promise of drastically improving disease management, still no cure exists for lysosomal storage diseases (LSDs). Cell therapies hold the potential to halt disease progression: either a subset of autologous cells can be ex vivo/ in vivo transfected with the functional gene or allogenic wild type stem cells can be transplanted. However, majority of cell-based attempts have been ineffective, due to the difficulties in reversing neuronal symptomatology, in finding appropriate gene transfection approaches, in inducing immune tolerance, reducing the risk of graft versus host disease (GVHD) when allogenic cells are used and that of immune response when engineered viruses are administered, coupled with a limited secretion and uptake of some enzymes. In the last decade, due to advances in our understanding of lysosomal biology and mechanisms of cross-correction, coupled with progresses in gene therapy, ongoing pre-clinical and clinical investigations have remarkably increased. Even gene editing approaches are currently under clinical experimentation. This review proposes to critically discuss and compare trends and advances in cell-based and gene therapy for LSDs. Systemic gene delivery and transplantation of allogenic stem cells will be initially discussed, whereas proposed brain targeting methods will be then critically outlined.

Sphingolipid lysosomal storage diseases: from bench to bedside

Johann Ludwig Wilhelm Thudicum described sphingolipids (SLs) in the late nineteenth century, but it was only in the past fifty years that SL research surged in importance and applicability. Currently, sphingolipids and their metabolism are hotly debated topics in various biochemical fields. Similar to other macromolecular reactions, SL metabolism has important implications in health and disease in most cells. A plethora of SL-related genetic ailments has been described. Defects in SL catabolism can cause the accumulation of SLs, leading to many types of lysosomal storage diseases (LSDs) collectively called sphingolipidoses. These diseases mainly impact the neuronal and immune systems, but other systems can be affected as well. This review aims to present a comprehensive, up-to-date picture of the rapidly growing field of sphingolipid LSDs, their etiology, pathology, and potential therapeutic strategies. We first describe LSDs biochemically and briefly discuss their catabolism, followed by general aspects of the major diseases such as Gaucher, Krabbe, Fabry, and Farber among others. We conclude with an overview of the available and potential future therapies for many of the diseases. We strive to present the most important and recent findings from basic research and clinical applications, and to provide a valuable source for understanding these disorders.

Interorgan communication by exosomes, adipose tissue, and adiponectin in metabolic syndrome

Adipose tissue plays important roles in regulating whole-body energy metabolism through its storage function in white adipocytes and its dissipating function in brown and beige adipocytes. Adipose tissue also produces a variety of secreted factors called adipocytokines, including leptin and adiponectin. Furthermore, recent studies have suggested the important roles of extracellular vesicles of endosomal origin termed exosomes, which are secreted from adipocytes and other cells in adipose tissue and influence whole-body glucose and lipid metabolism. Adiponectin is known to be a pleiotropic organ-protective protein that is exclusively produced by adipocytes and decreased in obesity. Adiponectin accumulates in tissues such as heart, muscle, and vascular endothelium through binding with T-cadherin, a glycosylphosphatidylinositol-anchored (GPI-anchored) cadherin. Recently, adiponectin was found to enhance exosome biogenesis and secretion, leading to a decrease in cellular ceramides, excess of which is known to cause insulin resistance and cardiovascular disease phenotypes. These findings support the hypothesis that adipose tissue metabolism systemically regulates exosome production and whole-body metabolism through exosomes. This review focuses on intra-adipose and interorgan communication by exosomes, adiponectin-stimulated exosome production, and their dysregulation in metabolic diseases.

Acid Sphingomyelinase Deficiency Ameliorates Farber Disease

Farber disease is a rare lysosomal storage disorder resulting from acid ceramidase deficiency and subsequent ceramide accumulation. No treatments for Farber disease are clinically available, and affected patients have a severely shortened lifespan. We have recently reported a novel acid ceramidase deficiency model that mirrors the human disease closely. Acid sphingomyelinase is the enzyme that generates ceramide upstream of acid ceramidase in the lysosomes. Using our acid ceramidase deficiency model, we tested if acid sphingomyelinase could be a potential novel therapeutic target for the treatment of Farber disease. A number of functional acid sphingomyelinase inhibitors are clinically available and have been used for decades to treat major depression. Using these as a therapeutic for Farber disease, thus, has the potential to improve central nervous symptoms of the disease as well, something all other treatment options for Farber disease can’t achieve so far. As a proof-of-concept study, we first cross-bred acid ceramidase deficient mice with acid sphingomyelinase deficient mice in order to prevent ceramide accumulation. Double-deficient mice had reduced ceramide accumulation, fewer disease manifestations, and prolonged survival. We next targeted acid sphingomyelinase pharmacologically, to test if these findings would translate to a setting with clinical applicability. Surprisingly, the treatment of acid ceramidase deficient mice with the acid sphingomyelinase inhibitor amitriptyline was toxic to acid ceramidase deficient mice and killed them within a few days of treatment. In conclusion, our study provides the first proof-of-concept that acid sphingomyelinase could be a potential new therapeutic target for Farber disease to reduce disease manifestations and prolong survival. However, we also identified previously unknown toxicity of the functional acid sphingomyelinase inhibitor amitriptyline in the context of Farber disease, strongly cautioning against the use of this substance class for Farber disease patients.

Pathological manifestations of Farber disease in a new mouse model

Farber disease (FD) is a rare lysosomal storage disorder resulting from acid ceramidase deficiency and subsequent ceramide accumulation. No treatments are clinically available and affected patients have a severely shortened lifespan. Due to the low incidence, the pathogenesis of FD is still poorly understood. Here, we report a novel acid ceramidase mutant mouse model that enables the study of pathogenic mechanisms of FD and ceramide accumulation. Asah1tmEx1 mice were generated by deletion of the acid ceramidase signal peptide sequence. The effects on lysosomal targeting and activity of the enzyme were assessed. Ceramide and sphingomyelin levels were quantified by liquid chromatography tandem-mass spectrometry (LC-MS/MS) and disease manifestations in several organ systems were analyzed by histology and biochemistry. We show that deletion of the signal peptide sequence disrupts lysosomal targeting and enzyme activity, resulting in ceramide and sphingomyelin accumulation. The affected mice fail to thrive and die early. Histiocytic infiltrations were observed in many tissues, as well as lung inflammation, liver fibrosis, muscular disease manifestations and mild kidney injury. Our new mouse model mirrors human FD and thus offers further insights into the pathogenesis of this disease. In the future, it may also facilitate the development of urgently needed therapies.

Activity-Based Imaging of Acid Ceramidase in Living Cells

Acid ceramidase (AC) hydrolyzes ceramides into sphingoid bases and fatty acids. The enzyme is overexpressed in several types of cancer and Alzheimer's disease, and its genetic defect causes different incurable disorders. The availability of a method for the specific visualization of catalytically active AC in intracellular compartments is crucial for diagnosis and follow-up of therapeutic strategies in diseases linked to altered AC activity. This work was undertaken to develop activity-based probes for the detection of AC. Several analogues of the AC inhibitor SABRAC were synthesized and found to act as very potent (two-digit nM range) irreversible AC inhibitors by reaction with the active site Cys143. Detection of active AC in cell-free systems was achieved either by using fluorescent SABRAC analogues or by click chemistry with an azide-substituted analogue. The compound affording the best features allowed the unprecedented labeling of active AC in living cells.

Allogeneic hematopoietic cell transplantation in Farber disease

BACKGROUND

Farber disease (FD) is a rare, lysosomal storage disorder caused by deficient acid ceramidase activity. FD has long been considered a fatal disorder with death in the first three decades of life resulting either from respiratory insufficiency as a consequence of airway involvement or from progressive neurodegeneration because of nervous system involvement. Peripheral symptoms associated with FD, including inflammatory joint disease, have been described to improve relatively rapidly after hematopoietic cell transplantation (HCT).

AIMS

To evaluate the disease-specific status and limitations in the long-term follow-up after HCT, investigate genotype/phenotype correlations and the benefit of allogeneic HCT in FD patients with nervous system involvement.

PATIENTS AND METHODS

Transplant- and disease-related information of ten FD patients was obtained by using a questionnaire, physicians' letters and additional telephone surveys. ASAH1 gene mutations were identified to search for genotype/phenotype correlations.

RESULTS

After mainly busulfan-based preparative regimens, all patients engrafted with one late graft loss. The inflammatory symptoms resolved completely in all patients. Abnormal neurologic findings were present pre-transplant in 4/10 patients, post-transplant in 6/10 patients. Mutational analyses revealed new mutations in the ASAH1 gene and a broad diversity of phenotypes without a genotype/phenotype correlation. With a median follow-up of 10.4 years, overall survival was 80% with two transplant-related deaths.

CONCLUSION

Allogeneic HCT leads to complete and persistent resolution of the inflammatory aspects in FD patients. It appears to have no beneficial effect on progression of nervous system involvement. New mutations in the acid ceramidase gene were identified. A genotype/phenotype correlation could not be established.

Hematopoietic stem cell transplant does not prevent neurological deterioration in infants with Farber disease: Case report and literature review

Farber disease (FD) is an inherited autosomal recessive disorder of lipid metabolism. The hallmark of the disease is systemic accumulation of ceramide due to lysosomal acid ceramidase deficiency. The involvement of the central nervous system is critical in this disorder leading to rapid deterioration and death within a few years after birth. Efforts to treat patients by hematopoietic stem cell transplant (HSCT) have resulted in favorable results in the absence of neurological manifestations. We report the outcomes of HSCT in two patients with FD who received early HSCT and had neurological deterioration posttransplant. We also present a new understanding of the limitations of HSCT in FD management based on our observations of the clinical course of the two patients after therapy.

Inborn errors of metabolism

Inborn errors of metabolism, also known as inherited metabolic diseases, constitute an important group of conditions presenting with neurologic signs in newborns. They are individually rare but collectively common. Many are treatable through restoration of homeostasis of a disrupted metabolic pathway. Given their frequency and potential for treatment, the clinician should be aware of this group of conditions and learn to identify the typical manifestations of the different inborn errors of metabolism. In this review, we summarize the clinical, laboratory, electrophysiologic, and neuroimaging findings of the different inborn errors of metabolism that can present with florid neurologic signs and symptoms in the neonatal period.

Acid ceramidase deficiency: Farber disease and SMA-PME

Acid ceramidase (ACDase) deficiency is a spectrum of disorders that includes a rare lysosomal storage disorder called Farber disease (FD) and a rare epileptic disorder called spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). Both disorders are caused by mutations in the ASAH1 gene that encodes the lysosomal hydrolase that breaks down the bioactive lipid ceramide. To date, there have been fewer than 200 reported cases of FD and SMA-PME in the literature. Typical textbook manifestations of classical FD include the formation of subcutaneous nodules, accumulation of joint contractures, and development of a hoarse voice. In reality, however, the clinical presentation is much broader. Patients may develop severe pathologies leading to death in infancy or may develop attenuated forms of the disorder wherein they are often misdiagnosed or not diagnosed until adulthood. A clinical variability also exists for SMA-PME, in which patients develop progressive muscle weakness and seizures. Currently, there is no known cure for FD or for SMA-PME. The main treatment is symptom management. In rare cases, treatment may include surgery or hematopoietic stem cell transplantation. Research using disease models has provided insights into the pathology as well as the role of ACDase in the development of these conditions. Recent studies have highlighted possible biomarkers for an effective diagnosis of ACDase deficiency. Ongoing work is being conducted to evaluate the use of recombinant human ACDase (rhACDase) for the treatment of FD. Finally, gene therapy strategies for the treatment of ACDase deficiency are actively being pursued. This review highlights the broad clinical definition and outlines key studies that have improved our understanding of inherited ACDase deficiency-related conditions.

Chronic lung injury and impaired pulmonary function in a mouse model of acid ceramidase deficiency

Farber disease (FD) is a debilitating lysosomal storage disorder (LSD) caused by a deficiency of acid ceramidase (ACDase) activity due to mutations in the gene ASAH1. Patients with ACDase deficiency may develop a spectrum of clinical phenotypes. Severe cases of FD are frequently associated with neurological involvement, failure to thrive, and respiratory complications. Mice homozygous ( Asah1P361R/P361R) for an orthologous patient mutation in Asah1 recapitulate human FD. In this study, we show significant impairment in lung function, including low compliance and increased airway resistance in a mouse model of ACDase deficiency. Impaired lung mechanics in Farber mice resulted in decreased blood oxygenation and increased red blood cell production. Inflammatory cells were recruited to both perivascular and peribronchial areas of the lung. We observed large vacuolated foamy histiocytes that were full of storage material. An increase in vascular permeability led to protein leakage, edema, and impacted surfactant homeostasis in the lungs of Asah1P361R/P361R mice. Bronchial alveolar lavage fluid (BALF) extraction and analysis revealed accumulation of a highly turbid lipoprotein-like substance that was composed in part of surfactants, phospholipids, and ceramides. The phospholipid composition of BALF from Asah1P361R/P361R mice was severely altered, with an increase in both phosphatidylethanolamine (PE) and sphingomyelin (SM). Ceramides were also found at significantly higher levels in both BALF and lung tissue from Asah1P361R/P361R mice when compared with levels from wild-type animals. We demonstrate that a deficiency in ACDase leads to sphingolipid and phospholipid imbalance, chronic lung injury caused by significant inflammation, and increased vascular permeability, leading to impaired lung function.

Deletion of MCP-1 Impedes Pathogenesis of Acid Ceramidase Deficiency

Farber Disease (FD) is an ultra-rare Lysosomal Storage Disorder caused by deficient acid ceramidase (ACDase) activity. Patients with ACDase deficiency manifest a spectrum of symptoms including formation of nodules, painful joints, and a hoarse voice. Classic FD patients will develop histiocytes in organs and die in childhood. Monocyte chemotactic protein (MCP-1; CCL2) is significantly elevated in both FD patients and a mouse model we previously generated. Here, to further study MCP-1 in FD, we created an ACDase;MCP-1 double mutant mouse. We show that deletion of MCP-1 reduced leukocytosis, delayed weight loss, and improved lifespan. Reduced inflammation and fibrosis were observed in livers from double mutant animals. Bronchial alveolar lavage fluid analyses revealed a reduction in cellular infiltrates and protein accumulation. Furthermore, reduced sphingolipid accumulation was observed in the lung and liver but not in the brain. The neurological and hematopoietic defects observed in FD mice were maintained. A compensatory cytokine response was found in the double mutants, however, that may contribute to continued signs of inflammation and injury. Taken together, targeting a reduction of MCP-1 opens the door to a better understanding of the mechanistic consequences of ceramide accumulation and may even delay the progression of FD in some organ systems.

A cross-sectional quantitative analysis of the natural history of Farber disease: an ultra-orphan condition with rheumatologic and neurological cardinal disease features

PurposeFarber disease (OMIM 22800) is an ultrarare progressive multisystemic neurodevelopmental storage disorder caused by a deficiency of the lysosomal enzyme acid ceramidase (AC). Hard clinical end points for future clinical trials remain to be defined.MethodsWe quantitatively analyzed published cases with Farber disease (N = 96). The main outcome variables were survival and diagnostic delay. As a potential predictor of survival, the influence of residual AC enzyme activity was investigated. The analysis was performed in compliance with STROBE criteria.ResultsThe median survival period of the study population was 3 years. The median age at disease onset was 3 months, and the median age at diagnosis was 17 months. The median diagnostic delay was 13.75 months. Patients with residual AC activity in fibroblasts at more than 5.1% of the normal level survived significantly longer than patients with residual AC activity below this threshold. In addition, higher residual AC activity was associated with a later onset of symptoms.ConclusionFarber disease onset is in infancy. Diagnostic delay is typically substantial. Our data suggest a phenotype-biomarker association with implications for future clinical and therapeutic trials. In the absence of a prospective multicenter natural-history study protocol, we believe that our modeling approach, based on published case descriptions, is the best and most timely approximation for generalizability.

Inherited Paediatric Motor Neuron Disorders: Beyond Spinal Muscular Atrophy

Paediatric motor neuron diseases encompass a group of neurodegenerative diseases characterised by the onset of muscle weakness and atrophy before the age of 18 years, attributable to motor neuron loss across various neuronal networks in the brain and spinal cord. While the genetic underpinnings are diverse, advances in next generation sequencing have transformed diagnostic paradigms. This has reinforced the clinical phenotyping and molecular genetic expertise required to navigate the complexities of such diagnoses. In turn, improved genetic technology and subsequent gene identification have enabled further insights into the mechanisms of motor neuron degeneration and how these diseases form part of a neurodegenerative disorder spectrum. Common pathophysiologies include abnormalities in axonal architecture and function, RNA processing, and protein quality control. This review incorporates an overview of the clinical manifestations, genetics, and pathophysiology of inherited paediatric motor neuron disorders beyond classic SMN1-related spinal muscular atrophy and describes recent advances in next generation sequencing and its clinical application. Specific disease-modifying treatment is becoming a clinical reality in some disorders of the motor neuron highlighting the importance of a timely and specific diagnosis.

Nervous system involvement in Farber disease

A 30 months-old boy with Farber disease developed nystagmus 12 months after hematopoietic stem cell transplantation (HSCT). At 40 months, gait ataxia was evident, and brain MRI showed increased size of pericerebellar sulci and 4th ventricle. EMG showed denervation in the tongue and upper limb muscles, consistent with motor neuron disease. HSCT improves the peripheral manifestations of Farber disease, but may not prevent the progressive neurological deterioration.

Spinal muscular atrophy associated with progressive myoclonic epilepsy: A rare condition caused by mutations in ASAH1

OBJECTIVE

To present the clinical features and the results of laboratory investigations in three patients with spinal muscular atrophy associated with progressive myoclonic epilepsy (SMA-PME), a rare condition caused by mutations in the N-acylsphingosine amidohydrosilase 1 (ASAH1) gene.

METHODS

The patients were submitted to clinical evaluation, neurophysiologic investigations (that included wakefulness and sleep electroencephalography [EEG], video-polygraphic recording with jerk-locked back-averaging, multimodal evoked potentials, and electromyography), brain magnetic resonance imaging (MRI), biochemical screening, muscle and skin biopsies, and molecular genetic analysis.

RESULTS

The main clinical features were onset in childhood with proximal muscular weakness, generalized epilepsy with absences and myoclonic seizures, cognitive impairment of variable degree; the course was progressive with muscle wasting and uncontrolled epileptic seizures. In one patient, earlier onset before the age of 2 years was associated with a more complex clinical picture, with abnormal eye movements, progressive cognitive impairment, and a more rapid and severe course. EEG/polygraphic data were consistent with PME, demonstrating generalized spike-and-wave discharges, evidence of positive and negative myoclonia, and prominent photosensitivity. In one patient, transcranial magnetic stimulation showed a hyperexcitable motor cortex, whereas somatosensory evoked potentials were unaffected. Possible involvement of the central acoustic and visual pathways was suggested by abnormal auditory and visual evoked potentials. Muscle biopsies showed typical signs of neurogenic damage. Molecular genetic analysis showed mutations of the ASAH1 gene.

SIGNIFICANCE

Our data indicate that SMA-PME associated with ASAH1 mutations is a genetically distinct condition with specific clinical and neurophysiologic features. Further studies are warranted to explore the role of the ASAH1 gene in muscle and brain function.

Odontoid infiltration and spinal compression in Farber Disease: reversal by haematopoietic stem cell transplantation

Farber disease (FD) is a lysosomal storage disorder caused by accumulation of ceramide in various organs and tissues, most notably the central nervous system, subcutaneous tissues and respiratory tract. We report a girl who developed major destructive bone involvement, which affected the odontoid process and produced spinal compression at 9 years of age. Bone involvement was proven histologically but resolved, as assessed by serial MRI scanning, following matched unrelated donor haematopoietic stem cell transplantation. This transplant resulted in only partial donor chimerism (less than 10 % donor cells in peripheral blood), yet this was sufficient to almost normalize acid ceramidase levels in leukocytes and to produce dramatic improvements in subcutaneous nodules and joint mobility as well as the beneficial effect on the involved bone. Unfortunately, the transplant was rejected after 2 years but the patient was rescued from an aplastic state by successful haploidentical peripheral blood stem cell transplantation and remained a full donor chimera without recurrence of the bone involvement and with steadily improving mobility at the age of 17 years. We describe an FD patient who presented with severe destruction of the odontoid by inflammatory tissue which was reversed after long-term control achieved by allogeneic hematopoietic stem cell transplantation. After extensive literature search, we believe that this is the first report of bony involvement in Farber disease.

Systemic ceramide accumulation leads to severe and varied pathological consequences

Farber disease (FD) is a severe inherited disorder of lipid metabolism characterized by deficient lysosomal acid ceramidase (ACDase) activity, resulting in ceramide accumulation. Ceramide and metabolites have roles in cell apoptosis and proliferation. We introduced a single-nucleotide mutation identified in human FD patients into the murine Asah1 gene to generate the first model of systemic ACDase deficiency. Homozygous Asah1^P361R/P361R animals showed ACDase defects, accumulated ceramide, demonstrated FD manifestations and died within 7–13 weeks. Mechanistically, MCP-1 levels were increased and tissues were replete with lipid-laden macrophages. Treatment of neonates with a single injection of human ACDase-encoding lentivector diminished the severity of the disease as highlighted by enhanced growth, decreased ceramide, lessened cellular infiltrations and increased lifespans. This model of ACDase deficiency offers insights into the pathophysiology of FD and the roles of ACDase, ceramide and related sphingolipids in cell signaling and growth, as well as facilitates the development of therapy.

Spinal muscular atrophy associated with progressive myoclonic epilepsy is caused by mutations in ASAH1

Spinal muscular atrophy (SMA) is a clinically and genetically heterogeneous disease characterized by the degeneration of lower motor neurons. The most frequent form is linked to mutations in SMN1. Childhood SMA associated with progressive myoclonic epilepsy (SMA-PME) has been reported as a rare autosomal-recessive condition unlinked to mutations in SMN1. Through linkage analysis, homozygosity mapping, and exome sequencing in three unrelated SMA-PME-affected families, we identified a homozygous missense mutation (c.125C>T [p.Thr42Met]) in exon 2 of ASAH1 in the affected children of two families and the same mutation associated with a deletion of the whole gene in the third family. Expression studies of the c.125C>T mutant cDNA in Farber fibroblasts showed that acid-ceramidase activity was only 32% of that generated by normal cDNA. This reduced activity was able to normalize the ceramide level in Farber cells, raising the question of the pathogenic mechanism underlying the CNS involvement in deficient cells. Morpholino knockdown of the ASAH1 ortholog in zebrafish led to a marked loss of motor-neuron axonal branching, a loss that is associated with increased apoptosis in the spinal cord. Our results reveal a wide phenotypic spectrum associated with ASAH1 mutations. An acid-ceramidase activity below 10% results in Farber disease, an early-onset disease starting with subcutaneous lipogranulomata, joint pain, and hoarseness of the voice, whereas a higher residual activity might be responsible for SMA-PME, a later-onset phenotype restricted to the CNS and starting with lower-motor-neuron disease.

Autologous transplantation of lentivector/acid ceramidase-transduced hematopoietic cells in nonhuman primates

Farber disease is a rare lysosomal storage disorder (LSD) that manifests due to acid ceramidase (AC) deficiencies and ceramide accumulation. We present a preclinical gene therapy study for Farber disease employing a lentiviral vector (LV-huAC/huCD25) in three enzymatically normal nonhuman primates. Autologous, mobilized peripheral blood (PB) cells were transduced and infused into fully myelo-ablated recipients with tracking for at least 1 year. Outcomes were assessed by measuring the AC specific activity, ceramide levels, vector persistence/integration, and safety parameters. We observed no hematological, biochemical, radiological, or pathological abnormalities. Hematological recovery occurred by approximately 3 weeks. Vector persistence was observed in PB and bone marrow (BM) cells by qualitative and quantitative PCR. We did not observe any clonal proliferation of PB and BM cells. Importantly, AC-specific activity was detected above normal levels in PB and BM cells analyzed post-transplantation and in spleens and livers at the endpoint of the study. Decreases of ceramide in PB cells as well as in spleen and liver tissues were seen. We expect that this study will provide a roadmap for implementation of clinical gene therapy protocols targeting hematopoietic cells for Farber disease and other LSDs.

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.

Farber disease in a newborn

Farber disease is a rare lysosomal storage disease characterized by a clinical triad including painful joint deformity, subcutaneous nodules and hoarseness, due to progressive granulomatous inflammation. We report the case of an early presentation on a female infant who manifested typical signs 1 week after birth.

In vivo delivery of human acid ceramidase via cord blood transplantation and direct injection of lentivirus as novel treatment approaches for Farber disease

Farber disease is a rare lysosomal storage disorder (LSD) caused by a deficiency of acid ceramidase (AC) activity and subsequent accumulation of ceramide. Currently, there is no treatment for Farber disease beyond palliative care and most patients succumb to the disorder at a very young age. Previously, our group showed that gene therapy using oncoretroviral vectors (RV) could restore enzyme activity in Farber patient cells. The studies described here employ novel RV and lentiviral (LV) vectors that engineer co-expression of AC and a cell surface marking transgene product, human CD25 (huCD25). Transduction of Farber patient fibroblasts and B cells with these vectors resulted in overexpression of AC and led to a 90% and 50% reduction in the accumulation of ceramide, respectively. Vectors were also evaluated in human hematopoietic stem/progenitor cells (HSPCs) and by direct in vivo delivery in mouse models. In a xenotransplantation model using NOD/SCID mice, we found that transduced CD34(+) cells could repopulate irradiated recipient animals, as measured by CD25 expression. When virus was injected intravenously into mice, soluble CD25 was detected in the plasma and increased AC activity was present in the liver up to 14 weeks post-injection. These findings suggest that vector and transgene expression can persist long-term and offer the potential of a lasting cure. To our knowledge, this is the first report of in vivo testing of direct gene therapy strategies for Farber disease.

Farber disease: clinical presentation, pathogenesis and a new approach to treatment

BACKGROUND

Farber Disease is an autosomal-recessively inherited, lysosomal storage disorder caused by acid ceramidase deficiency and associated with distinct clinical phenotypes. Children with significant neurological involvement usually die early in infancy, whereas patients without or only mild neurological findings suffer from progressive joint deformation and contractures, subcutaneous nodules, inflammatory, periarticular granulomas, a hoarse voice and finally respiratory insufficiency caused by granuloma formation in the respiratory tract and interstitial pneumonitis leading to death in the third or fourth decade of live. As the inflammatory component of this disorder is caused by some kind of leukocyte dysregulation, allogeneic hematopoietic stem cell transplantation can restore a healthy immune system and thus may provide a curative option in Farber Disease patients without neurological involvement. Previous stem cell transplantations in two children with severe neurological involvement had resulted in a disappointing outcome, as both patients died of progressive deterioration of their neurological status. As a consequence, stem cell transplantation does not appear to be able to abolish or even reduce the neurotoxic effects of the abundant ceramide storage in the brain.

METHODS

After myeloablative, busulfan-based preparative regimens, four Farber Disease patients without neurological involvement received an allogeneic hematopoietic stem cell transplantation from related and unrelated donors. Stem cell source was BM in three patients and PBSC in one patient; GvHD-prophylaxis consisted of CsA and short course MTX.

RESULTS AND DISCUSSION

In all patients, HSCT resulted in almost complete resolution of granulomas and joint contractures, considerable improvement of mobility and joint motility without relevant therapy-related morbidities. All patients are alive and well at this point with stabile donor cell chimerism and without evidence of chronic GvHD or other late sequelae of stem cell transplantation.

CONCLUSION

Allogeneic hematopoietic stem cell transplantation provides a promising approach for Farber Disease patients without neurological involvement.

Sphingolipid metabolism diseases

Human diseases caused by alterations in the metabolism of sphingolipids or glycosphingolipids are mainly disorders of the degradation of these compounds. The sphingolipidoses are a group of monogenic inherited diseases caused by defects in the system of lysosomal sphingolipid degradation, with subsequent accumulation of non-degradable storage material in one or more organs. Most sphingolipidoses are associated with high mortality. Both, the ratio of substrate influx into the lysosomes and the reduced degradative capacity can be addressed by therapeutic approaches. In addition to symptomatic treatments, the current strategies for restoration of the reduced substrate degradation within the lysosome are enzyme replacement therapy (ERT), cell-mediated therapy (CMT) including bone marrow transplantation (BMT) and cell-mediated "cross correction", gene therapy, and enzyme-enhancement therapy with chemical chaperones. The reduction of substrate influx into the lysosomes can be achieved by substrate reduction therapy. Patients suffering from the attenuated form (type 1) of Gaucher disease and from Fabry disease have been successfully treated with ERT.

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.

Lysosomal storage disorders

Although the first description of a lysosomal storage disorder was that of Tay-Sachs disease in 1881, the lysosome was not discovered until 1955, by Christian De Duve. The first demonstration by Hers in 1963 of a link between an enzyme deficiency and a storage disorder (Pompe's disease) paved the way for a series of seminal discoveries about the intracellular biology of these enzymes and their substrates, culminating in the successful treatment of Gaucher's disease with beta-glucosidase in the early 1990s. It is now recognized that these disorders are not simply a consequence of pure storage, but result from perturbation of complex cell signalling mechanisms. These in turn give rise to secondary structural and biochemical changes, which have important implications for therapy. Significant challenges remain, particularly the treatment of central nervous system disease. It is hoped that recent advances in our understanding of lysosomal biology will enable successful therapies to be developed.

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.

Successful hematopoietic stem cell transplantation in Farber disease

Farber disease, a lysosomal storage disorder, has a dismal prognosis leading to death with progressive granulomatous inflammation, even in patients without central nervous system involvement (type 2/3). We report the first successful hematopoietic stem cell transplantations in 2 patients with Farber disease type 2/3, resulting in resolution of symptoms.

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.

Metabolic disorders and mental retardation

The metabolic and anatomical substrate of most forms of mental retardation is not known. Because the basis of normal brain function is not sufficiently understood, the basis of abnormal function is understood poorly. Even in disorders where the fundamental biochemical defect is known, such as phenylketonuria (PKU) and other enzyme defects, the exact basis for brain dysfunction is uncertain. The outcome for treated PKU, galactosemia, homocystinuria, and lysosomal disorders is not yet optimal. The various forms of nonketotic hyperglycinemia often respond poorly to current therapy. Less familiar disorders, with or without seizures, such as deficient synthesis of serine or creatine and impaired glucose transport into the brain, and disorders with variable malformations, such as Smith-Lemli-Opitz (SLO) syndrome and the congenital disorders of glycosylation (CDGs), may initially be thought to be a nonspecific form of developmental delay. Less familiar disorders, with or without seizures and disorders with variable malformations may initially be thought to be a nonspecific form of developmental delay. Simple tests of urine, blood, and cerebrospinal fluid may lead to a diagnosis, accurate genetic counseling, and better treatment. Metabolic brain imaging (magnetic resonance spectroscopy (MRS)) has also helped to reveal biochemical abnormalities within the brain.

Surgical treatment of hand disorders in Farber's disease: a case report

Farber's disease is a rare autosomal recessive disorder caused by a deficiency of acid ceramidase activity whose symptoms include hoarseness, subcutaneous nodules, and painful swollen and contracted joints. This case report focuses on hand abnormalities and surgical treatment of hand disorders in Farber's disease. A 9-year-old girl had occasional painful locking of the metacarpophalangeal joints of the middle fingers and severe tenderness of the dorsal aspect of the wrists. Resection of several nodules within the metacarpophalangeal joint and of a nodule that was firmly attached to the extensor pollicis longus tendon beneath the extensor retinaculum relieved pain and enabled the patient to perform daily activities.

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.