Novel treatment for neuronopathic lysosomal storage diseases--cell therapy/gene therapy

Most lysosomal storage diseases (LSD) exhibit neurological symptoms and there has been limited success in their treatment. Innovative treatments employing novel therapy or gene therapy may offer the prospect of improvement. Recent attempts to treat the neurological forms of LSD include neural stem cell therapy, mesenchymal stem cell therapy, hematopoietic stem cell therapy and gene therapy. Additional approaches have included substrate deprivation/chaperone therapy for the treatment of LSD. This article reviews these new technologies, discusses recent progress, and suggests their possible application.     

Treatment of patients with lysosomal storage diseases]

A problem of management of patients with lysosomal storage diseases in own experience with over 100 children with such diseases has been discussed. Symptomatic therapy of carpal tunnel syndrome, Pudenz valves, splenectomies, plasty of hernia, locomotive rehabilitation and various forms of cooperation with patients' families have been used in the treatment. An attempt of the treatment of the storage diseases with implantation of fetal membranes has been undertaken in view of the fact, that such membranes are the source of deficit enzyme.     

Hematopoietic stem cell gene therapy for Niemann-Pick disease and other lysosomal storage diseases

Of the various gene therapy approaches under investigation for the treatment of genetic diseases, hematopoietic stem cell-mediated gene therapy has attracted the most interest. Enriched populations of hematopoietic stem cells can be obtained from diseased individuals, genetically modified to express normal gene products, and then transplanted back into these individuals without the risk of graft versus host disease. Following transplantation and engraftment, hematopoietically-derived cells can repopulate various sites of pathology and express the normal gene product in vivo. Such a procedure has been accomplished in several mouse models of human genetics diseases, leading to partial or complete correction of the disease phenotype, and current efforts are now focused on adapting the success of murine systems to larger animals, including man. This review will focus on the use of hematopoietic stem cell-mediated gene therapy for the treatment of lysosomal storage disorders, and discuss recent data obtained in the laboratory using a murine knock-out mouse model of Types A and B Niemann-Pick disease (NPD).     

Stop-codon read-through for patients affected by a lysosomal storage disorder

Lysosomal storage disorders are a group of inherited diseases that can result in severe and progressive pathology due to a specific lysosomal dysfunction. Current treatment strategies include bone-marrow transplantation, substrate reduction, chemical-chaperone and enzyme-replacement therapy. However, each of these treatments has its limitations. Enhanced stop-codon read-through is a potential alternative or adjunct therapeutic strategy for treating lysosomal-storage-disorder patients. Premature stop-codon mutations have been identified in a large cohort of patients with a lysosomal storage disorder, making stop-codon read-through a possible treatment for this disease. In lysosomal-storage-disorder cells (mucopolysaccharidosis type I, alpha-L-iduronidase deficient), preclinical studies have shown that gentamicin induced the read-through of premature stop codons, resulting in enzyme activity that reduced substrate storage.     

Gene therapy for inherited diseases using heamatopoietic stem cells--gene therapy for patients with chronic granulomatous disease

The possibility of gene therapy for inherited diseases with a single gene mutation in Figure 1 had been verified by the successful treatment with bone marrow transplantation. As the gene therapy method and theory has been progressing rapidly, it is expected that gene therapy will overcome the complications of bone marrow transplantation. Of these inherited diseases, chronic granulomatous disease (CGD) is the one of the most expected disease for gene therapy. CGD is an inherited immune deficiency caused by mutations in any of the following four phox genes encoding subunits of the superoxide generating phagocyte NADPH oxidase. It consists of membranous cytochrom b558 composed of gp91 phox and p22 phox, and four cytosolic components, p47 phox, p67 phox, rac p21 and p40 phox, which translocate to the membrane upon activation. In our group study, more than 220 CGD patients has been enrolled. The incidence of CGD patients was estimated as 1 out of 250,000 births. The expected life span of the CGD patients is 25 to 30 years old by the Kaplan Meier analysis. Comparing with the ratio of CGD subtype in US and Europe, that with p47phox deficiency is lower (less than 10%/o vs. 23%) and that of gp91 phox deficiency is higher (more than 75% vs. 60%). Prophylactic administration of ST antibiotics and IFN-gamma and bone marrow transplantation have been successfully employed in our therapeutic strategy. However, it is necessary to develop the gene therapy technology for CGD patients as more promising treatment. In the current study we constructed two retrovirus vectors; MFGS-gp91/293 SPA which contains only the therapeutic gp91 phox gene, a bicistronic retrovirus pHa-MDR-IRES-gp91/PA317 which carries a multi drug resistant gene (MDR1) and the gp91phox gene connected with an internal ribosome entry site (IRES). We demonstrate high efficiency transduction of gp 91 phox to CGD EB virus established cell line with high levels of functional correction of the oxidase by MFGS-gp91 and by pHa-MDR-IRES-gp91, respectively. We also demonstrate sufficient transduction of gp91 phox to CD34+ hematopoietic stem cell from the patients with gp91 phox deficiency by MFGS-gp91/293 SPA. Our current studies suggest that the combination of the 293-SPA packaging system and the bicistronic retrovirus system inserted MDR1 gene make our CGD gene therapy more feasible for clinical application.     

Gene therapy: prospects for glycolipid storage diseases

Lysosomal storage diseases comprise a group of about 40 disorders, which in most cases are due to the deficiency of a lysosomal enzyme. Since lysosomal enzymes are involved in the degradation of various compounds, the diseases can be further subdivided according to which pathway is affected. Thus, enzyme deficiencies in the degradation pathway of glycosaminoglycans cause mucopolysaccharidosis, and deficiencies affecting glycopeptides cause glycoproteinosis. In glycolipid storage diseases enzymes are deficient that are involved in the degradation of sphingolipids. Mouse models are available for most of these diseases, and some of these mouse models have been used to study the applicability of in vivo gene therapy. We review the rationale for gene therapy in lysosomal disorders and present data, in particular, about trials in an animal model of metachromatic leukodystrophy. The data of these trials are compared with those obtained with animal models of other lysosomal diseases.     

Cell therapy for inherited diseases of the hematopoietic system

Cell therapy was born in 1968 with the first allogeneic transplantation of hematopoietic stem cells for two immune deficiency disorders: the Wiskott-Aldrich syndrome and the Severe Combined ImmunoDeficiency (SCID). From this pioneering experience, thousands of patients affected with inherited or acquired diseases of the hematopoietic system have benefited from this therapeutic approach. Unfortunately, immunologic obstacles, represented by the compatibility in the major histocompatibility HLA system, still dictate today important limitations for a larger therapeutic utilization of hematopoietic stem cells (HSC). In this review, we have summarized the difficulties and the scientific advances leading us to improve the clinical results; the therapeutic research's track for primary immunodeficiencies is also discussed.     

Fluorophore-assisted electrophoresis of urinary carbohydrates for the identification of patients with oligosaccharidosis-and mucopolysaccharidosis-type lysosomal storage diseases

Lysosomal storage diseases result from defects in the activity of the lysosomal enzymes that break down macromolecules in the cell. These enzyme defects contribute to over 30 separate storage diseases that result in nearomuscular and intellectual impairment and, in some cases, early childhood death. This report describes a new method for identifying defects in the lysosomal enzymes and in the metabolic pathway that functions in the degradation of complex carbohydrates. The method involves identifying abnormal carbohydrates in the urine of affected patients using fluorescent carbohydrate tags and polyacrylamide gel electrophoresis. Currently, the method can be used as a simple screen for the identification of at least 12 different lysosomal storage diseases using a single electrophoretic procedure. Both oligosaccharidoses and mucopolysaccharidoses (MPS) can be identified, and in many cases the MPS subtype can be determined. In addition, the method can be used to confirm enzymatically the results of the initial screening test. We believe that this method will become extremely useful not only in the diagnosis of these diseases but in the management of patients on therapy.     

Amlexanox provides a potential therapy for nonsense mutations in the lysosomal storage disorder Aspartylglucosaminuria

Aspartylglucosaminuria (AGU) is a lysosomal storage disorder caused by mutations in the gene for aspartylglucosaminidase (AGA). This enzyme participates in glycoprotein degradation in lysosomes. AGU results in progressive mental retardation, and no curative therapy is currently available. We have here characterized the consequences of AGA gene mutations in a compound heterozygous patient who exhibits a missense mutation producing a Ser72Pro substitution in one allele, and a nonsense mutation Trp168X in the other. Ser72 is not a catalytic residue, but is required for the stabilization of the active site conformation. Thus, Ser72Pro exchange impairs the autocatalytic activation of the AGA precursor, and results in a considerable reduction of the enzyme activity and in altered AGA precursor processing. Betaine, which can partially rescue the AGA activity in AGU patients carrying certain missense mutations, turned out to be ineffective in the case of Ser72Pro substitution. The Trp168X nonsense allele results in complete lack of AGA polypeptide due to nonsense-mediated decay (NMD) of the mRNA. Amlexanox, which inhibits NMD and causes a translational read-through, facilitated the synthesis of a full-length, functional AGA protein from the nonsense allele. This could be demonstrated as presence of the AGA polypeptide and increased enzyme activity upon Amlexanox treatment. Furthermore, in the Ser72Pro/Trp168X expressing cells, Amlexanox induced a synergistic increase in AGA activity and polypeptide processing due to enhanced processing of the Ser72Pro polypeptide. Our data show for the first time that Amlexanox might provide a valid therapy for AGU.     

Lysosomal storage diseases: mechanisms of enzyme replacement therapy

Summary Lysosomal diseases result from deficiency of one of the many enzymes involved in the normal, step-wise breakdown of macromolecules. Studies in vitro have shown that cells from enzyme-deficient patients can be corrected by an exogenous supply of the missing enzyme. This occurs by receptor-mediated endocytosis of normal enzyme added to tissue culture medium and also by direct transfer from normal leukocytes during cell-to-cell contact. Immunohistochemical analysis has revealed that these processes have similar pathways of intracellular transport of the acquired enzymes, which ultimately reach mature lysosomes in the recipient cells. Moreover, recent studies suggest that both mechanisms are important in the therapy of lysosomal storage diseases by bone marrow transplantation. Advances in gene technology are likely to improve the successful treatment of these disorders, by facilitating the large scale production of clinically effective proteins and also by enabling the stable and safe introduction of normal lysosomal genes into cells of affected patients.     

Lysosomal Ca(2+) homeostasis: role in pathogenesis of lysosomal storage diseases

Disrupted cellular Ca²⁺ signaling is believed to play a role in a number of human diseases including lysosomal storage diseases (LSD). LSDs are a group of ∼50 diseases caused predominantly by mutations in lysosomal proteins that result in accumulation of macromolecules within the lysosome. We recently reported that Niemann-Pick type C (NPC) is the first human disease to be associated with defective lysosomal Ca²⁺ uptake and defective NAADP-mediated lysosomal Ca²⁺ release. These defects in NPC cells leads to the disruption in endocytosis and subsequent lipid storage that is a feature of this disease. In contrast, Chediak-Higashi Syndrome cells have been reported to have enhanced lysosomal Ca²⁺ uptake whilst the TRPML1 protein defective in mucolipidosis type IV is believed to function as a Ca²⁺ channel. In this review we provide a summary of the current knowledge on the role of lysosomal Ca²⁺ signaling in the pathogenesis of this group of diseases.     

Aberrant composition of chondroitin sulfates in the cartilage-type proteoglycan isolated from the iliac crest of patients with some lysosomal storage diseases

In order to investigate the involvement of cartilage proteoglycans in the pathogenesis of human congenital skeletal disorders, proteoglycans were extracted with 4 M guanidine HCl from the iliac crest cartilage of children with various skeletal diseases; lysosomal storage diseases (group I), osteochondrodysplasias (group II) and controls (group III). The cartilage-type proteoglycan (PG-H) was purified and its chondroitin sulfate moiety was analyzed by digestion with chondroitinase-ABC. In group II and group III, the relative amounts of the unsaturated disaccharide products changed in an age-related manner; decrease (from 50% to 30%) of delta Di-4S with a compensatory increase (from 40% to 60%) of delta Di-6S with increasing age from 0 to 15 years. On the other hand, some cases in group I showed aberrant composition of the disaccharide products; a lower content of delta Di-4S with a correspondingly higher content of delta Di-6S. Patients in group I have clinically similar skeletal disorders, and the extent of the compositional abnormality seems to reflect the severity of the skeletal disorder. Therefore, one may consider that the aberrant composition of the glycosaminoglycans in PG-H is involved in the pathogenesis of the skeletal disorder of lysosomal storage diseases.     

Stemming the tide: glycosphingolipid synthesis inhibitors as therapy for storage diseases

Glycosphingolipids (GSLs) are plasma membrane components of every eukaryotic cell. They are composed of a hydrophobic ceramide moiety linked to a glycan chain of variable length and structure. Once thought to be relatively inert, GSLs have now been implicated in a variety of biological processes. Recent studies of animals rendered genetically deficient in various classes of GSLs have demonstrated that these molecules are important for embryonic differentiation and development as well as central nervous system function. A family of extremely severe diseases is caused by inherited defects in the lysosomal degradation pathway of GSLs. In many of these disorders GSLs accumulate in cells, particularly neurons, causing neurodegeneration and a shortened life span. No effective treatment exists for most of these diseases and little is understood about the mechanisms of pathogenesis. This review will discuss the development of a new approach to the treatment of GSL storage disorders that targets the major synthesis pathway of GSLs to stem their cellular accumulation.     

New therapeutic options for lysosomal storage disorders: enzyme replacement,small molecules and gene therapy

During the last few years, much progress has been made in the treatment of lysosomal storage disorders. In the past, no specific therapy was available for the affected patients, and management consisted solely of supportive care and treatment of complications. Since enzyme replacement therapy has been successfully introduced for patients with Gaucher disease, this principle of treatment has been taken into consideration for other lysosomal storage disorders as well. Clinical trials could demonstrate the clinical benefit of this therapeutic principle in Fabry disease, mucopolysaccharidoses type I, II and VI and in Pompe disease. However, the usefulness of enzyme replacement therapy is limited due to the fact that a given enzyme preparation does not have beneficial effects on all aspects of a disorder in the same degree. Additionally, clinical studies have shown that many symptoms of a lysosomal storage disorder even after long-term treatment are no more reversible. A further novel therapeutic option for lysosomal storage disorders consists of the application of small molecules that either inhibit a key enzyme which is responsible for substrate synthesis (substrate deprivation) or act as a chaperone to increase the residual activity of the lysosomal enzyme (enzyme enhancing therapy). Various gene therapeutic techniques (in vivo and ex vivo technique) have been developed in order to administer the gene that is defective in a patient to the bloodstream or directly to the brain in order to overcome the blood–brain barrier. This review will give an insight into these newly developed therapeutic strategies and will discuss their advantages and limitations.     

Lysosomal acid hydrolases in established lymphoblastoid cell lines,transformed by Epstein-Barr virus,from patients with genetic lysosomal storage diseases

Summary Lysosomal acid hydrolases were determined in established lymphoblastoid cell lines, transformed in vitro by Epstein-Barr virus (EBV) from lymphocyte-rich cell populations isolated from the peripheral blood of patients with genetic lysosomal storage diseases—Hurler syndrome, Scheie syndrome, G_M1-gangliosidosis type 1 and type 2, Tay-Sachs disease, and I-cell disease—and from obligate heterozygotes for these diseases.The respective enzyme activity was undectectable in lymphoblastoid cells from the patients, but not from controls. Obligate heterozygotes could not always be distinguished from controls in lymphoblastoid cells as well as in leukocytes. These results suggest that established lymphoblastoid cell lines are useful material for the enzymatic study of genetic lysosomal storage diseases.