The application of enzyme replacement therapy in vitro and in a mouse model in aspartylglycosaminuria
Year: 2010
Type: dissertation
Abstract: Aspartylglycosaminuria (AGU) is a recessively inherited lysosomal storage disease caused by the deficient activity of lysosomal enzyme, glycosylasparaginase (AGA).The enzyme normally functions in lysosomes in degradation of carbohydrate-protein linkage in glycoproteins.The deficient AGA activity leads to the accumulation of glycoasparagines, mainly aspartylglucosamine (GlcNAc-Asn), in cells resulting in this multisystem disease characterized by slowly progressing psychomotor retardation with shortened life span.There is no disease-specific treatment for AGU, but some other lysosomal storage disorders with similar cause have been treated with enzyme replacement therapy (ERT) using exogenous recombinant enzymes.In this study the applicability of ERT was evaluated in the treatment of AGU.Therefore, a human recombinant glycosylasparaginase was produced and the mechanism of enzyme transfer and capability of an exogenous enzyme to treat AGU in a cell culture and in a mouse model were studied.The human recombinant AGA was transported from cell culture media into the AGU fibroblasts and lymphocytes through mannose 6-phosphate (M6P) receptor-mediated endocytosis.The GlcNAc-Asn storage in AGU lymphocytes was cleared and further accumulation was prevented when intracellular glycosylasparaginase activity in these cells reached 3-4% of the activity in normal lymphocytes.Cell-to-cell contact was needed for the M6P-receptor independent transfer of the enzyme from normal to AGU cells.The recombinant enzyme was biologically active also in the AGU mouse model.The lysosomal storage was cleared in many somatic tissues of adult AGU mice when 70% of normal glycosylasparaginase activity was reached in these tissues.The response to the therapy was dose-dependent.The recombinant enzyme crossed blood-brain barrier (BBB) of adult AGU mice and decrease in GlcNac-Asn storage was detected also in brain.The overall therapeutic effect in new-born animals was similar to the effect in the adult animals, but the therapeutic effect in brain was better when the therapy was initiated before the full development of the BBB.This study sheds light on details involved in ERT of AGU.The results show that ERT might be efficient in treating the somatic tissues of AGU, but more efficient ways to treat the disease in neuronal tissues are needed.The results form a basis for further development of treatment protocols in AGU, but also contribute to research in other diseases with similar cause.
Author: Ulla Dunder
Language: English
Subfield: Genetics (clinical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3097370995