Beta-galactosidase deficiency in the hurler syndrome

Nanoparticles as carriers for drug delivery of macromolecules across the blood-brain barrier

Introduction: Current therapies of neurodegenerative or neurometabolic diseases are, to a large extent, hampered by the inability of drugs to cross the blood-brain barrier (BBB). This very tight barrier severely restricts the entrance of molecules from the blood into the brain, especially macromolecular substances (i.e. neurotrophic factors, enzymes, proteins, as well as genetic materials). Due to their size, physicochemical properties, and instability, the delivery of these materials is particularly difficult.Areas covered: Recent research showed that biocompatible and biodegradable nanoparticles possessing tailored surface properties can enable a delivery of drugs and specifically of macromolecules across the blood-brain barrier by using carrier systems of the brain capillary endothelium (Trojan Horse strategy). In the present review, the state-of-art of nanoparticle-mediated drug delivery of different macromolecular substances into the brain following intravenous injection is summarized, and different nanomedicines that are used to enable the transport of neurotrophic factors and enzymes across the blood-brain barrier into the CNS are critically analyzed.Expert opinion: Brain delivery of macromolecules by an intravenous application using nanomedicines is now a growing area of interest which could be really translated into clinical application if dedicated effort will be given to industrial scale-up production.

Comparison of Endovascular and Intraventricular Gene Therapy With Adeno-Associated Virus-α-L-Iduronidase for Hurler Disease

BACKGROUND

Hurler disease (mucopolysaccharidosis type I [MPS-I]) is an inherited metabolic disorder characterized by deficiency of the lysosomal enzyme α-L-iduronidase (IDUA). Currently, the only therapies for MPS-I, enzyme replacement and hematopoietic stem cell transplantation, are generally ineffective for central nervous system manifestations.

OBJECTIVE

To test whether brain-targeted gene therapy with recombinant adeno-associated virus (rAAV5)-IDUA vectors in an MPS-I transgenic mouse model would reverse the pathological hallmarks.

METHODS

Gene therapy approaches were compared using intraventricular or endovascular delivery with a marker (rAAV5-green fluorescent protein) or therapeutic (rAAV5-IDUA) vector. To improve the efficiency of brain delivery, we tested different applications of hyperosmolar mannitol to disrupt the blood-brain barrier or ependymal-brain interface.

RESULTS

Intraventricular delivery of 1 × 10 viral particles of rAAV5-IDUA with systemic 5 g/kg mannitol co-administration resulted in IDUA expression throughout the brain, with global enzyme activity >200% of the baseline level in age-matched, wild-type mice. Endovascular delivery of 1 × 10 viral particles of rAAV5-IDUA to the carotid artery with 29.1% mannitol blood-brain barrier disruption resulted in mainly ipsilateral brain IDUA expression and ipsilateral brain enzyme activity 42% of that in wild-type mice. Quantitative assays for glycosaminoglycans showed a significant decrease in both hemispheres after intraventricular delivery and in the ipsilateral hemisphere after endovascular delivery compared with untreated MPS-I mice. Immunohistochemistry for ganglioside GM3, another disease marker, showed reversal of neuronal inclusions in areas with IDUA co-expression in both delivery methods.

CONCLUSION

Physiologically relevant biochemical correction is possible with neurosurgical or endovascular gene therapy approaches for MPS-I. Intraventricular or endovascular delivery of rAAV5-IDUA was effective in reversing brain pathology, but in the latter method, effects were limited to the ipsilateral hemisphere.

Lipid composition of whole brain and cerebellum in Hurler syndrome (MPS IH) mice

Hurler syndrome (MPS IH) is caused by a mutation in the gene encoding alpha-L-iduronidase (IDUA) and leads to the accumulation of partially degraded glycosaminoglycans (GAGs). Ganglioside content is known to increase secondary to GAG accumulation. Most studies in organisms with MPS IH have focused on changes in gangliosides GM3 and GM2, without the study of other lipids. We evaluated the total lipid distribution in the whole brain and cerebellum of MPS IH (Idua⁻/⁻) and control (Idua(+/?)) mice at 6 months and at 12 months of age. The content of total sialic acid and levels of gangliosides GM3, GM2, and GD3 were greater in the whole brains of Idua⁻/⁻ mice then in Idua (+/?) mice at 12 months of age. No other significant lipid differences were found in either whole brain or in cerebellum at either age. The accumulation of ganglioside GD3 suggests that neurodegeneration occurs in the Idua⁻/⁻) mouse brain, but not to the extent seen in human MPS IH brain.

Cerebral infarction in Hunter syndrome

Hunter syndrome, or mucopolysaccharidosis type II, is an X-linked recessive disorder resulting from iduronate sulfatase deficiency. Typical manifestations include short stature, mental retardation, hydrocephalus, macroglossia and cardiac valvulopathy. We describe a 21-year-old patient who presented with acute ischemic stroke and evidence of cerebral embolization. The echocardiogram demonstrated thickened mitral and aortic valves as potential sources of emboli. We conclude that ischemic stroke secondary to cardioembolization is a potential complication of Hunter syndrome.

Impaired elastogenesis in Hurler disease: dermatan sulfate accumulation linked to deficiency in elastin-binding protein and elastic fiber assembly

Hurler disease resulting from a deficiency in alpha-L-iduronidase, which causes an accumulation of dermatan sulfate and heparan sulfate glycosaminoglycans, is characterized by connective tissue and skeletal deformations, cardiomyopathy, cardiac valve defects, and progressive coronary artery stenosis. In this report, we present evidence that accumulation of dermatan sulfate but not heparan sulfate moieties is linked to impaired elastic fiber assembly that, in turn, contributes substantially to the development of the clinical phenotype in Hurler disease. Our data suggest that dermatan sulfate-bearing moieties bind to and cause functional inactivation of the 67-kd elastin-binding protein, a molecular chaperone for tropoelastin, which normally facilitates its secretion and assembly into elastic fibers. We demonstrate that, in contrast to normal skin fibroblasts and cells from Sanfilippo disease, which accumulate heparan sulfate, Hurler fibroblasts show reduced expression of elastin-binding protein and do not assemble elastic fibers, despite an adequate synthesis of tropoelastin and sufficient production of a microfibrillar scaffold of elastic fibers. Because cultured Hurler fibroblasts proliferate more quickly than their normal counterparts and the addition of exogenous insoluble elastin reduces their proliferation, we suggest that cell contacts with insoluble elastin play an important role in controlling their proliferation.

Hunter's syndrome. An ultrastructural study of an autopsy case

An autopsy case of a 10-year, 8-month-old boy with Hunter's syndrome is reported with emphasis on the ultrastructural findings of almost all the organs, except the brain. Intracytoplasmic inclusion bodies were observed in various organs as follows: nerve cells and glia in the spinal cord, hepatocytes and Kupffer cells in the liver, sinusoidal endothelium of the spleen, proximal tubules, podocytes and epithelium of Bowman's capsule of the kidney, interstitial fibroblast-like cells among cardiac muscle bundles, cardiac valves and aorta, exocrine and endocrine cells of the pancreas, adrenocortical cells, follicular epithelial cells of the thyroid. Leydig cells of the testis, chondrocytes, fibroblasts and endothelium of capillaries throughout the body. Three types of inclusion bodies were morphologically distinguishable. Type 1: clear vacuole, Type 2: zebra body, Type 3: clear vacuole with a lipid-like lamellar structure. The clear vacuole (Type 1) was thought to represent an accumulation of glycosaminoglycans, and the zebra body (Type 2), probably ganglioside. The type 3 inclusion body might be an intermediate and mixed form of the type 1 and type 2 inclusions. Histochemical study also suggested that the type 3 inclusion body contained glycosaminoglycan and a type of lipid.

Chronic GM1 gangliosidosis presenting as dystonia: I. Clinical and pathological features

Clinical and pathological studies are reported from investigation of a 27-year-old man with GM1 gangliosidosis who experienced a slowly progressive dystonia that began about age 4, primarily affected the face and limbs, and eventually became almost totally incapacitating. There was only mild intellectual deterioration; myoclonus, seizures, and macular cherry-red spots were never observed. Postmortem examination revealed intraneuronal storage, localized predominantly to the basal ganglia, in which neurons contained round, multilamellated inclusions. Golgi studies revealed meganeurites arising from medium spiny neurons. Other areas of the central nervous system appeared relatively unaffected, although small basilar dilatations were observed in scattered cortical pyramidal neurons and Purkinje cell dendrites showed focal swellings. Vacuolated cells of the reticuloendothelial system were observed, including Kupffer cells and histiocytes in the spleen, marrow, and intestinal tract. Biochemical analysis revealed a generalized beta-galactosidase deficiency with specific accumulation of GM1 ganglioside in the basal ganglia.

Prenatal diagnosis of Hurler's syndrome--biochemical studies on the affected fetus

A prenatal diagnosis of Hurler's syndrome was made in a pregnancy at risk in a family with two affected children. The fetus was diagnosed as having Hurler's syndrome on the basis of a deficiency of alpha-L-iduronidase in the cultured amniotic cells. The glycosaminoglycans (GAG) content in the supernatant of the amniotic fluid was increased about 1.5 fold compared with that in the control, and increases of heparan sulfate and dermatan sulfate were observed on electrophoresis. The diagnosis could be confirmed by the deficiencies of alpha-L-iduronidase in the liver and brain from the affected fetus. GAG content in the liver from the affected fetus was increased approximately 10 fold as compared with that in the control fetal liver, and most of the GAG were degraded. The GAG content was observed to be increased two fold in the brain, and dermatan sulfate, which was not detected in normal fetal brain, was identified. beta-Galactosidase activities in the affected liver and brain were decreased to 30-50% of the control, and an altered hexosaminidase A was also observed in the liver.

Morphological observations in the nervous system of prenatal mucopolysaccharidosis II (M. Hunter)

Light and electron microscopic finding in the nervous system of a 23-week-old fetus are reported, in which MPS II was diagnosed prenatally. The degrees of myelination and neuronal differentiation were similar as in a normal fetus of the same age. A storage of mucopolysaccharides in typical vacuolar inclusion bodies was present throughout the peripheral and central nervous system, mainly in cells of mesenchymal origin. "Zebra" bodies and granulo-membranous bodies, which are thought to represent secondard ganglioside accumulation were only found in the well developed neurons of the spinal cord and spinal ganglia, but not in the poorly developed neurons of the cerebellar and cerebral cortex. Mucopolysaccharide storage in endothelial cells of cerebral bood vessels precedes the appearance of lipid storgae in cerebral neurons.

A new variant mucolipidosis: biochemical investigations on two siblings

Biochemical studies are presented on two siblings with some features of Mucolipidosis III, but with distinctive clinical findings. Levels of beta-galatosidase, alpha-mannosidase, beta-glucuronidase, N-acetyl-beta-glucosaminidase and alpha-fucosidase found in serum from these patients ranged from 10 to 10 times higher than normal. The ratio of heat stable to heat labile serum isoenzymes of N-acetyl-beta-glucosaminidase is considerably greater than normal. An extremely low activity of beta-galactosidase was found in fibroblasts cultured from one patient. Levels of the remaining enzymes were in the low normal range. Similarly, beta-galactosidase levels were low in heart, kidney, liver, spleen and lung of one patient who died during the course of the study. Activities of the remaining enzymes were close to normal. No excessive excretion of mucopolysaccharide was noted, however, changes in distribution of several fractions were found. Mucopolysaccharide labeled with radioactive sulfate was degraded by cultured fibroblasts at a normal rate. In addition to clinical differences, the biochemical studies further demonstrate the uniqueness of these patients.

Generalized gangliosidosis: acid beta-galactosidase deficiency with early onset, rapid mental deterioration and minimal bone dysplasia

This report concerns a 3-month-old girl with rapidly progressive psychomotor retardation, hepatomegaly, vacuolated lymphocytes, minimal bone dysplasia and normal excretion of acid mucopolysaccharides. A deficiency of acid beta-galactosidase was demonstrated in isolated leucocytes and in a liver biopsy. The diagnosis of generalized gangliosidosis due to deficiency of beta-galactosidase was also based on the absence of the enzyme activity from cultured fibroblasts. The diagnosis was confirmed on autopsy at 16 months by typical histology, electron microscopy and biochemistry of the organs. beta-galactosidase deficiency has been demonstrated in various clinical conditions ranging from generalized gangliosidosis with severe mental retardation to clinical pictures resembling Morquio's disease and normal intelligence. The heterogeneity of the clinical manifestations in beta-galactosidase deficiency could be explained by different residual activities of a structurally mutated enzyme towards its various substrates.

The heart in the Hurler syndrome: gross, histologic and ultrastructural observations in five necropsy cases

Clinical and morphologic features of the cardiovascular system are described in five necropsy patients with the Hurler syndrome. In all five patients the coronary arteries, four cardiac valves, mural endocardium of all four chambers, myocardial walls and aorta were affected in a characteristic manner. All of these sites contained large clear cells known as Hurler cells (readily visible by light microscopy). In addition, granular cells were observed in semi-thin (1 mu) sections and by electron microscopy in the coronary arteries, atrioventricular (A-V) valves and in myocardial interstitium. These latter cells appear to produce collagen in an abnormal way and are probably responsible for the heavy deposits of collagen in the cardiovascular system of patients with the Hurler syndrome. In the cardiac muscle cells, in smooth muscle cells of the coronary arteries and in fibroblasts, wherever located, deposits of acid mucopolysaccharides and glycolipids usually were also observed. The acid mucopolysaccharide deposits were observed easily with light microscopy except in the cardiac muscle cells where they were seen only with electron microscopy. The glycolipid depositis, observed only on examination of 1 mu thick sections or with electron microscopy, have not previously been observed in coronary arteries or in myocardial cells. The infiltration into the heart by these cells and deposits in all five patients resulted in severe narrowing of the extramural coronary arteries, considerable thickening of the cardiac valves (the left-sided more than the right-sided valves), generalized thickening of mural endocardium and "stiffening" of the myocardial walls. Thus, the cardiovascular lesions in the Hurler syndrome are specific and life-threatening.

Spondyloepiphyseal dysplasia, corneal clouding, normal intelligence and acid beta-galactosidase deficiency

A 14-year-old girl with a unique type of progressive spondyloepiphyseal dysplasia, corneal clouding, and no evidence of neurological abnormality, was found to have a remarkable deficiency of acid beta-galactosidase activity in cultured skin fibroblasts and in leucocyte preparations. In fibroblasts, ganglioside GM1 beta-galactosidase activity averaged 7% of the normal mean while asialofetuin beta-galactosidase and 4-methylumbe lifery-beta-galactosidase averaged 1.4% and 3.5%, respectively. Activities for all three substrates in leucocytes from both her parents were close to 50% of the normal mean indicating that the patient is homozygous for a mutation (or mutations) affecting GM1 beta-galactosidase.

Mucopolysaccharidosis: secondarily induced abnormal distribution of lysosomal isoenzymes

Total activities of acid hydrolases in liver of two patients with mucopolysaccharidosis are decreased for beta-galactosidase, alpha-galactosidase, and arylsulfatase A; total activities of four other hydrolases are normal or increased. The isoenzyme distribution of five hydrolases (beta-glucuronidase, alpha-glucosidase, beta- galactosidase, N-acetyl-beta-glucosaminidase, and alpha-galactosidase) is ábnormal in that the isoelectric points (by isoelectric focusing) of these enzymes are more acid than in control liver. Along with the isoenzyme abnormalities different kinds of glycolipids were stored in kidney, liver, and brain. The isoenzyme abnormalities can be reproduced in vitro by addition of chondroitin sulfate to a homogenate of normal liver, suggesting that stable binding occurs between mucopolysaccharides and the hydrolase molecules. After the addition of chondroitin sulfate, the total activity of beta-galactosidase is inhibited, whereas other hydrolases are affected only slightly or not at all.

Early prenatal diagnosis of Hurler's syndrome with termination of pregnancy and confirmatory findings on the fetus

Type I mucopolysaccharidosis was diagnosed in a fetus by assay of the glycosaminoglycans of the amniotic liquor. Results are presented of biochemical and ultrastructural studies on the 18-week abortus. The evidence suggests that the liver is more severely affected than the central nervous system at this stage of gestation, and this finding agrees with the recent demonstration of the underlying enzyme defect of this disorder, with the corollary that many biochemical abnormalities previously noted in gargoylism must be pleiotropic effects of the mutant genotype.

Tay-Sachs disease: prenatal diagnosis

Fifteen pregnant women with a 25 percent risk of delivering a child with Tay-Sachs disease were monitored by amniocentesis and hexosaminidase A assays of amniotic fluid, uncultured amniotic cells, and cultured amniotic cells. Tay-Sachs disease was diagnosed prenatally in six fetuses; the diagnosis was confirmed in one child after birth and in five fetuses after therapeutic abortion. Prenatal diagnosis indicated the absence of Tay-Sachs disease in nine other fetuses; this diagnosis was confirmed postnatally in six, three are still in utero.